Dụng Cụ Chỉnh Hình Và Chân Tay Giả Trong Phục Hồi Chức Năng (Ấn Bản Thứ 3)

642
Section III  Prostheses in Rehabilitation
strength is generally good. He has good balance and endur­
ance for walking with the prosthesis. He has gradually
increased his prosthesis wear time and activity level. He
works a 5-hour day in agriculture. Today he returns to ther­
apy for a scheduled followup appointment. He complains of
discomfort in the distal end and loss of stability in the socket.
As you observe his gait, the prosthesis appears to be a little
short. Assessment of the residual limb reveals erythema on
the distal end and on the distal aspect of the patella.
Questions to Consider
• What changes have occurred since his last visit? Has he
made changes to sock ply or footwear? Has he gained or
lost weight?
• Is this an alignment- or fit-related issue? When does
the pain occur in the gait cycle? Does the pain increase
throughout the day?
• Is the interface worn out? How old is the interface now?
How long should it be expected to last? Are there thin
areas in the interface that might indicate excessive pres­
sure and premature wear?
Recommendations
You find that his weight and footwear have not changed.
He is wearing the same single-ply sock with which he
began his prosthetic use. His gel liner is still in excel­
lent condition and should be expected to last for about a
year of constant wear. Consideration of all the informa­
tion indicates that the limb has changed since the initial
fitting. As his pain is worst at midstance and increases
proportionally with his time spent weight bearing, the
conclusion is that the limb is too far distal in the socket.
He should increase the number of socks that he is wearing
by one ply until the limb is seated correctly in the socket.
This will also address the length of the prosthesis which
had appeared too short.
In experimenting with sock ply, J. W. went from initially
wearing a single sock to six plies, but he found this number
of socks created a new set of problems. He was then feel­
ing excessive pressure on the tibial tubercle and proximal
aspect of the fibular head. During loading response he was
unable to regulate his knee flexion because of pain on the
anterodistal aspect of the tibia. Despite good suspension,
he was also starting to scuff his toe during swing phase. All
these symptoms indicate that he is now too far out of the
socket. This position decreases the control of the tibia and
allows the socket to flex and extend beyond the position of
the limb, leading to excessive pressure on the ends of the
bones. It also positions the bony prominences of the limb in
areas that do not have adequate reliefs. Removal of several
sock plies is the correct intervention, as this will allow him
to seat further in the socket and increase comfort and stabil­
ity. When J. W. wore four-ply socks, the comfort and control
of the prosthesis were restored.
CASE EXAMPLE 2
An Older Woman with Amputation Related to Vascular Disease
Prosthetic Prescription
G. R. is a 76-year-old woman with type 2 diabetes and
peripheral vascular disease. G. R. sustained an abrasion at
the lateral malleolus of the right leg. The skin abrasion failed
to heal and developed into a stage 4 nonhealing wound.
Circulation at the lower leg was markedly impaired. After
several months of multiple failed therapies to improve cir­
culation and promote wound healing, the right leg was
amputated below the knee 2 months ago. G. R. is 5′4″ tall
and weighs 204 lb (92.5 kg). Prior to the problems with her
leg, she was living independently and caring for her hus­
band, who is significantly disabled. The transtibial ampu­
tation wound site is completely healed. Her physician is
recommending that she begin bearing weight on the limb
as tolerated. She has been using a wheelchair for mobility in
the house, but she is able to stand on her left leg with sup­
port of a standard walker. She is concerned that she will not
be able to do her chores around the house and the shopping
even after she receives her prosthesis.
Questions to Consider
• What are the G. R.'s goals for the prosthesis? Will she be
a functional ambulator? Will the prosthesis be used only
for standing and transfers?
• Will she require assistance with activities of daily living
and care for her husband?
• What are the main design goals for her prosthesis? What
system will allow her to don the prosthesis independently?
Which will require the least maintenance and most reliable
function?
Recommendations
Evaluating G. R.'s candidacy for a prosthesis will involve
assessing her risk-to-benefit ratio as a bipedal ambulator
against the negative health effects of prolonged sitting. Her
motivation to ambulate is clear in her expressed desire to
continue to care for her husband. Her ability to stand on
one leg is a fortuitous sign, even if her balance is impaired
at this point. Her knee ROM is within normal limits. If her

Chapter 23  Transtibial Prosthetics
643
skin integrity is good and her right knee extensors are four
of five, she will likely be a good prosthetic candidate.
Her prosthesis should be easy to put on, as she will not
have assistance available. Her limb has ample soft tissue
based on her weight and etiology, although her diabetes puts
her at risk for fragile skin and delayed healing. The most
appropriate interface for her will be one that most effectively
reduces shear. A silicone elastomer cushion liner in a TSB
socket will work well for her. A sealing sleeve and expul­
sion valve will utilize suction as a means of suspension, thus
minimizing pistoning. This prosthesis should allow her to
wear a cotton sock that is easily laundered as she loses limb
volume. The trim lines should be set higher proximally to
gain as much control as possible for her prosthesis.
Prosthetic Alignment and Fitting: Visit 1
G. R. is seen for delivery of her preparatory prosthesis. She
is instructed on donning the device and she is able to roll on
the gel liner and place her limb into the socket, with mod­
erate effort. Her limb is seated correctly all the way in the
socket. After she rolls the sealing sleeve into position, she
stands at her walker and slowly begins to load the prosthe­
sis. She is comfortable in the socket and a small amount of
air is heard as it is expulsed from the socket through the
valve. The sleeve is rolled down so that a corset stay can be
inserted between the gel liner and the socket. As no areas
were found to have excessive pressure, the corset stay is
removed and the sleeve is rolled back up. Her first steps
are tentative and she is bearing the majority of her weight
through her arms during stance on the prosthetic side. After
some guidance from her therapist, she begins to bear more
weight through the prosthesis. Her strides are asymmetric,
with a very large step on the prosthetic side and a truncated
step on the sound side.
Questions to Consider
• Why is her step length shorter on the sound side? Is the
prosthesis aligned properly? Is her range of hip flexion
and extension within functional limits? Is she stable in
stance?
• What are her goals for ambulation? Does she have suffi­
cient stance stability? Does she have adequate clearance
in swing? Is her gait pattern energy efficient?
Recommendations
The gait pattern she uses is typical of the individual with
recent amputation who is uncertain about weight bear­
ing through a mechanical device. The feeling of instabil­
ity on the prosthesis causes the her to limit stance time on
that side, thereby shortening swing phase on the sound
side. Alternately, the individual is accustomed to bearing
weight unilaterally on the sound side, so the stance time
is increased allowing the prosthesis to move ahead exces­
sively. Weakness of the quadriceps and gluteus minimus
and medius will also impair stance stability. She should be
encouraged to take smaller steps with the prosthesis and
larger steps with her sound limb. She may need further con­
ditioning of her knee extensors and hip abductors to com­
pletely eliminate this asymmetry.
Excessive socket flexion can increase prosthetic step
length, but it also tends to increase the step length on the
sound side as well. Extending the socket makes it more dif­
ficult to advance over the foot during stance and will tend to
shorten step length on the contralateral side.
Prosthetic Fitting and Alignment: Visit 2
G. R. returns for therapy and is complaining about discom­
fort in her socket. Inspection of her skin reveals excessive
pressure, as evidenced by erythema, on her femoral con­
dyles and fibular head. She has been doing a good job man­
aging her sock ply and is now seated correctly in the socket
wearing eight ply. She explains that the tightness she feels
does not get worse during weight bearing.
Questions to Consider
• What changes may have taken place since her last visit?
As her activity level increases, what is the effect on limb
volume? Which areas of the limb are most susceptible to
volume loss?
• What is the source of the erythema? Is there swelling
of the knee? Does the redness appear anywhere else
on the limb? Does it appear to be an allergic reaction
like contact dermatitis? Is her liner clean and in good
condition?
Recommendations
After discussing good hygiene and prosthetic care with
G. R., it is clear that she is washing her gel liner daily with
a mild soap and then rinsing it thoroughly, and that she is
washing her limb every day and patting in dry. She is not
using any lotions that may create buildup in the liner or an
allergic reaction when confined in the warm moist envi­
ronment of the liner. The fit of the socket is assessed next
by probing between the liner and socket with a thin metal
corset stay. This is done in the non–weight-bearing state
as that is when the pressure is occurring. The corset stay
encounters great resistance when passing over the fibular
head and is completely stuck when trying to pass over the
femoral condyles. This indicates excessive pressure over
those bony structures. Although she is wearing the appro­
priate number of socks, they are creating the extra bulk that
makes the socket too tight in those areas. A referral should
be made to her prosthetist so that the socket can be modi­
fied. It is likely that pads can be added in strategic areas that
are more prone to volume loss, such as the area over the calf
muscle and on either side of the tibia. This will take up vol­
ume in the socket and require her to reduce the number of
sock ply that she wears. Following that adjustment, G. R. is
feeling more comfortable in the socket and her skin is free
from irritation.

644
Section III  Prostheses in Rehabilitation
Diagnostic Sockets
Because the fit of the socket is the single most critical fac­
tor in providing a functional prosthesis, great care is taken to
ensure that the fit is optimal. One tool used by prosthetists is a
clear plastic socket that is used during the fitting process and
then discarded, often destroyed, during the fabrication pro­
cess. The diagnostic socket or “check socket” is made from a
translucent plastic so that the prosthetist can inspect the limb
during loading and see the blanching of the skin as the person
goes through various activities of weight bearing. The plastic
is also very amenable to changes in shape and volume simply
by heating the area and deforming the plastic. Extended fit­
tings, during which the individual takes the diagnostic socket
home for a day or more, must be conducted carefully as some
of the materials used for diagnostic sockets are brittle and
can fracture under normal loading conditions. Extended fit­
tings can be quite useful though as the prosthesis will be used
under more realistic conditions and some problems will only
become apparent after spending several hours in the socket.
FINISHING TECHNIQUES
After the prosthetist and the prosthetic wearer are both sat­
isfied with the fit and alignment, the final prosthesis can be
fabricated. The exact finishing technique varies based on the
components that were selected, but the main goal is to pre­
serve the alignment and create a lightweight prosthesis with a
cosmetic appearance. The foot is removed and the ­remainder
of the prosthesis is secured in a vertical alignment jig
(Figure 23-29). The socket is filled with plaster and a pipe that
is held in place by the alignment jig is set into the wet plaster.
After the plaster hardens, the alignment has been captured
and the prosthesis can be removed from the jig. The jig pre­
serves the alignment until the final prosthesis is reassembled.
The prosthetic technician will determine the best method of
fabrication to create the lightest weight prosthesis without
sacrificing structural integrity. Extra alignment devices are
removed during this process. The final limb is assembled with
either endoskeletal or exoskeletal components based on the
individual individual's needs.
Endoskeletal
The term endoskeletal implies that the structure of the prosthe­
sis is located deep inside the prosthetic limb. The exterior of the
prosthesis may consist of passive foam rubber or latex that gives
the prosthesis a realistic appearance and protects the structural
and functional parts that are hidden underneath (Figure 23-30).
This type of prosthesis provides two distinct advantages: adjust­
ability and realistic appearance. Endoskeletal design allows for
the use of modular components that can be adjusted or replaced
quickly and easily when needed. If a single component were
to fail, repair would involve simple removal and replacement
of that component, the same way a tire can be changed on a
car. These modular components can be easily procured as they
are not custom made for the individual. The appearance of the
endoskeletal limb can be quite ­realistic. Virtually any size and
FIGURE  23-28  An example of an energy-return foot with an
integrated dynamic pylon. (Courtesy of Otto Bock Healthcare,
Minneapolis, MN;
b03d8cbbe4dd8ba7acc74ae67aa&detail=3950)
FIGURE 23-29  A prosthetist uses this device to preserve the rela­
tive positions of the foot and socket during fabrication. This allows
the exact alignment of the diagnostic prosthesis to be transferred
to the definitive prosthesis. (From Hosmer/Fillauer, Campbell CA;

EQUIPMENT/ALIGNMENT%20AND%20FITTING%20AIDS/
VERTICAL%20FABRICATING%20JIG.aspx)

Chapter 23  Transtibial Prosthetics
645
shape can be created by shaping soft lightweight foam over the
components. The foam can be coated with a variety of finishes
that provide color and texture and may include lifelike details
such as moles, freckles, pores, and even hair. Premium restora­
tions are nearly indistinguishable from the sound limb.
Exoskeletal
When a more durable and easily cleanable prosthesis is desired
an exoskeletal prosthesis can be fabricated. The socket of an
exoskeletal prosthesis is attached to the foot through an external
composite lamination that is custom shaped for the individual
(Figure 23-31). To create this shape, a wooden ankle block is
first bonded to the socket with rigid foam in the vertical align­
ment jig. The foam is rigid enough to maintain the alignment
between the socket and foot that was preserved in the jig. The
foam and ankle block are then shaped by hand to match the
contralateral side, only a little bit smaller to accommodate the
thickness of the final lamination. The final step is to seal the
foam and laminate the exterior; this final composite covering
provides the structure of the prosthesis as well as the cosmesis.
Exoskeletal prostheses are often heavier than their endoskeletal
counterparts, and are always less adjustable. The advantage of
the exoskeletal system is the durability. The hard surface that
covers the prosthesis is nonporous, chemically inert, and water­
proof, making it easy to clean and virtually indestructible.
GAIT DEVIATIONS
Gait deviations can be caused by improper socket fit, mis­
alignment of the prosthesis or by weakness or other muscu­
loskeletal pathologies of the individual. Careful evaluation
is essential to determine the cause of the deviations and
what can be done to correct them (Readers are referred
to Chapter 5 for a review of the biomechanics of normal
gait). Variations in limb volume or shoe type can introduce
deviations in a prosthetic wearer's gait that had not been
exhibited before. It can be very productive to ask the per­
son if there have been any changes in their routine recently.
Changes in diet, medications, shrinker wear, or activ­
ity level can all effect limb volume. If a shoe with a higher
or lower heel is placed on the prosthesis it will change the
orientation of the socket to the ground. Unless there is a
component that will accommodate the new heel height, the
patent's gait will be adversely affected. Common gait devia­
tions will be reviewed as they occur in the gait cycle in each
individual plane.
Initial Contact
Sagittal
Initial contact should be made with the heel (Figure 23-32). If
contact at the forefoot first there may be either excessive plan­
tarflexion of the prosthetic foot or limitation of the person's
knee extension range of motion (i.e. knee flexion contrac­
ture). Both of these circumstances contribute to a high knee
FIGURE  23-30  A diagram of an endoskeletal prosthesis, in
which the socket and pylon are concealed to within a cosmetic
cover. (Reprinted with permission from: Below Knee Prosthetics,
Prosthetics-Orthotics Program, University of Texas Southwestern
Medical Center at Dallas, TX, 1988, p. 4-11)
FIGURE  23-31  A cross-sectional diagram of an exoskeletal
­prosthesis that transmits weight bearing forces through the ­external
lamination. The lamination gets its shape from the rigid foam
­interior. (Reprinted with permission from: Below Knee Prosthetics,
Prosthetics-Orthotics Program, University of Texas Southwestern
Medical Center at Dallas, TX, 1988, p. 4-10)

646
Section III  Prostheses in Rehabilitation
extension moment during loading response that causes the
knee to move posteriorly. This motion, decimates efficiency
and can damage the knee over time. Every effort should be
made to create a heel strike at initial contact. This includes
therapeutic exercises to increase knee ROM and knee exten­
sor strength; prosthetic alignment changes to accommodate
knee flexion contractures; and proper height and suspension
of the prosthesis. If the prosthesis is too long or does not sus­
pend well, the prosthesis may hit the ground prior to the end
of swing phase.
Frontal
Excessive inversion or eversion of the foot at initial contact
indicates misalignment of the prosthesis. The heel of the
prosthetic foot should be level when it meets the ground.
The lateral border of the heel should contact the surface first;
this is related to the transverse plane alignment of the foot
to accommodate a normal toe-out angle of 5 to 10 degrees.
This lateral heel contact sets up the standard progression of
the ground reaction force up the lateral border of the foot
and then crossing to the medial aspect of the forefoot during
stance phase.
Transverse
The rotation of the prosthesis is fairly consistent throughout
stance phase. The medial border of the foot should be parallel
to the line of progression. Transverse plane rotation at initial
contact is an indicator that the limb is fitting too loosely in the
socket, or that the foot is not directly under the limb. External
motion may be seen with an inset foot, while internal motion
could be a result of an outset foot (Figure 23-33).
Loading Response
Sagittal
Excessive knee flexion moment during loading response is
caused by a foot that is set too far posteriorly, is too dorsi­
flexed, or has a heel that is too rigid. The transition during
loading response should be smooth and controlled, the knee
should bend to approximately 20 degrees of flexion as the
forefoot meets the ground; this moves the limb forward and
aids in shock absorption. Insufficient knee flexion moment
can be caused by a heel that is too soft or a foot that is posi­
tioned too far anteriorly. This can cause the knee to hyperex­
tend leading to pain and inefficiency. Adjustment of the heel
lever length, stiffness, and orientation should be made to pro­
vide the appropriate degree of knee flexion.
Frontal
Rapid loading of the foot during this phase would produce
significant moments at the knee if the foot were not parallel
to the ground at initial contact. The plantar surface of the
FIGURE  23-32  Ideally, initial contact of the prosthesis with the
ground should be at the heel, followed by a controlled flexion of
the knee and foot flat. (diagram courtesy of David A. Knapp, CPO,
Hanger Prosthetics & Orthotics, North Haven, CT)
Loading Response
Midstance
Terminal Stance
Pre-Swing
FIGURE 23-33  The progression of the transfemoral prosthesis during stance phase. Initial ­contact
is made at the heel, and compression of the prosthetic heel simulates controlled lowering of the foot
­during loading response. At midstance, weight bearing forces move anteriorly to the ball of the foot. In
terminal stance, the anterior portion of the prosthetic foot simulates toe extension and the heel rises.
In pre-swing, the individual rolls over the toe and moves into knee flexion for effective ­shortening of
the limb for swing limb clearance. (Diagram courtesy of David A. Knapp, CPO, Hanger Prosthetics
& Orthotics, North Haven, CT)

Chapter 23  Transtibial Prosthetics
647
foot should be level during this phase as viewed in the fron­
tal plane. Some modern prosthetic feet have rearfoot inver­
sion and eversion capabilities and can adapt to the surface
upon weight bearing, which is useful for uneven surfaces.
Be sure to observe the motion as the loading occurs. When
there is motion while ambulating on a flat surface, the
alignment of the foot should be changed to eliminate that
motion.
Transverse
Any rotation of the foot during loading may indicate a loose
or faulty torsion adapter. Rotary moments can be generated
by excessive toe-in or toe-out and the torsion adapters allow
that motion to occur uncontrolled.
Midstance
Sagittal
A choppy or segmented midstance is caused by differences
in the dynamic characteristics between the prosthetic heel
and the prosthetic toe, indicating a lack of stability. The heel
and toe lever arms are adjustable by shifting the socket anteri­
orly to shorten the toe or posteriorly to shorten the heel. The
optimal foot position is one where the forward velocity of the
knee is consistent between loading response and midstance.
The prosthetic foot must accommodate smooth transition of
the ground reaction force from the heel to the forefoot dur­
ing midstance. Over this period, the moment at the knee
changes from a flexion moment to an extension moment.
A steady increase in dorsiflexion should be observed as the
knee moves over the foot.
Frontal
There is a normal and desirable varus moment during mid­
stance. This is because, in order to be most energy efficient
while walking, the body's center of mass does not shift all
the way over the stance foot. The knee should move later­
ally approximately 1 cm during midstance. Shift of the knee
greater than 2 cm indicates an excessive varus moment and
will lead to stress on the medial compartment and lateral lig­
aments of the person's knee. This can be reduced by adduct­
ing the socket or shifting it medially. If the socket does not
move or shifts medially during midstance, the socket is too
far inset (or the foot is too outset) or the socket excessively
adducted. Lateral gapping is a condition where a large gap
occurs during loading between the limb and the lateral wing
of the socket. If a gap larger than 2 cm is observed, the socket
may be too loose and an additional ply of sock should be
added.
Transverse
Rotation that occurs during midstance is typically seen
between the limb and socket and is almost always attribut­
able to poor socket fit. If motion is occurring, the person
may complain of patellar impingement on either the medial
or lateral aspects of the patella. The remedy is often tighten­
ing the socket by adding a ply or two of socks. In cases in
which the socks are insufficient to stabilize the rotation, the
socket should be adjusted by the prosthetist. Pretibial pads
that provide pressure on either side of the tibial crest are an
effective solution to stop rotation.
Terminal Stance
Sagittal
Drop off is the excessive descent of the center of mass during
terminal stance caused by a toe lever that is either too short
or too soft. It is often characterized by diminished heel rise.
This compromises energy efficiency of walking. It occurs at a
point when the body's center of mass is already near the bot­
tom of its sinusoidal path. The toe lever of the prosthetic foot
must have sufficient stiffness to resist dorsiflexion when the
person's entire weight is placed on the ball of the foot. This
is a critical phase of gait when it comes to energy efficiency.
Proper loading of the forefoot promotes knee stability, main­
tains altitude (i.e., level pelvis), and stores energy in the liga­
ments that can be released during swing phase to assist with
limb advancement (Figure 23-34).
Early heel off is an indication that the foot is too plan­
tarflexed or the toe lever is too stiff. The heel should come
off the ground at the point when the swing foot has already
passed anterior to the stance limb. Forward momentum
of the body is impeded by early toe-off and may force the
individual into an anterior lean with the trunk to main­
tain forward progression. The ankle should be set to dorsi­
flex until the swing limb reaches terminal swing so that the
heel remains on the ground until the center of mass has pro­
gressed sufficiently forward. This will preserve step length
and enhance stability.
Frontal
The heel should rise off the ground with the knee breaking
over the point on the foot between the first and second toes.
Any large variance from this position will create instability
and consequently shorten step length. The knee should travel
in a straight line as it flexes; any lateral motion during this
phase will lead to a whip in swing.
Transverse
The toe load is highest during this phase of gait, therefore
there is potential for rotation of the prosthesis due to subopti­
mal alignment. External rotation can be caused by a foot that
is too far outset or had excessive too toe-out. Internal rotation
is caused by an excessively inset or internally rotated foot.
Preswing
Sagittal
As the body weight transfers rapidly to the contralateral limb,
the prosthesis should roll forward over the toe and lift off the
ground. Toe-drag may be a result of a foot that is excessively
plantarflexed or a faulty suspension.
Frontal
The knee should not move medially or laterally during pre­
swing. An externally rotated foot can cause a valgus moment
that pushed the knee medially as the weight is transferred off

648
Section III  Prostheses in Rehabilitation
the prosthesis. This can also be caused by an outset foot or an
excessively adducted socket. Lateral motion during preswing
can be caused by an internally rotated foot, an excessively
inset foot, or an excessively abducted socket.
Transverse
Many of the same factors that lead to instability in the fron­
tal plane can lead to instability in the transverse plane as
well. Appropriate attention to transverse plane alignment
throughout stance phase should help to avoid issues in
­preswing as well.
Swing Phase
Sagittal
The transtibial prosthesis swings passively forward during
swing phase. If sufficient ground clearance is not obtained
the amount of knee flexion should be noted. In cases where
appropriate knee flexion is observed, the suspension of the
prosthesis should be evaluated. A faulty suspension or a plan­
tarflexed foot will reduce swing clearance. The amount of
pistoning varies with the type of suspension used. Motion
exceeding 1cm should be considered excessive. If knee flexion
is observed during swing phase, active and passive motion
should be assessed. Weakness or contracture of the knee
can limit knee motion, as can a tight suspension sleeve or an
aggressive supracondylar wedge. Although suspension and
knee flexion are often adversarial, a balance should be attain­
able that permits enough foot clearance for safe ambulation.
Otherwise, the prosthesis may require shortening.
Frontal
Socket instability during swing is typically caused by either a
faulty suspension or a loose-fitting socket. The weight of the
socket pulls the prosthesis into varus during swing if the limb
is not well seated in the socket. Increasing sock ply and imple­
menting an improved suspension should remedy any swing
phase instability.
Transverse
Rotation during swing phase is often caused by what is known
as a “whip.” When the heel of the prosthetic foot moves medi­
ally in initial swing and then laterally during midswing, it is
referred to as a medial whip. A lateral whip follows the oppo­
site pattern. Whips can be caused by misalignment of the
knee axis at the onset of swing or by irregular loading of the
limb in terminal stance. Alignment of the knee axis in a per­
son using a transtibial prosthesis is determined by the func­
tion of the hip, and should be addressed by strengthening and
ROM exercises. Prosthetic remedies must examine the load­
ing of the prosthesis. Medial whips can be caused by a foot
that is too far inset or externally rotated. Both medial and lat­
eral whips can be caused by a foot that is too plantarflexed.
1/3
10° Excessive Flexion
10° Excessive Extension
1/3
1/3
FIGURE 23-34  Socket angle will affect the magnitude and timing of the ground reaction force through
the knee during stance phase. Optimal alignment (center) varies with specific foot design but will be
approximated by the centerline of the socket falling through the posterior one-third and anterior two
thirds of the foot. (Diagram courtesy of David A. Knapp, CPO, Hanger Prosthetics & Orthotics, North
Haven, CT)

Chapter 23  Transtibial Prosthetics
649
TROUBLESHOOTING
A common problem encountered by individuals with recent
transtibial amputation is application of too few or too many
sock ply. Sock-ply management is a skill that develops as
the indivudal wears the prosthesis more and is conscien­
tious about examining the limb after doffing the prosthe­
sis. The number of socks will eventually become consistent,
but early in the process of limb maturation, a large degree
of variability is common. The correct number of socks may
vary from day to day, or even from hour to hour. There are
a few basic cues that the those new to prosthetic use must
consider to ensure that the limb is in the correct position
within the socket.
The first cue is during donning—the limb should slide into
the socket with some resistance. Although this is a subjective
determination, after a short time the person should recognize
the amount of force needed to fully don the prosthesis with
the correct number of socks. Too few socks allows the limb to
“bottom out” in the socket, where most of the weight-bearing
will occur on the distal end. This leads to pain, instability, and
increased pistoning. Conversely, too many socks prevents the
limb from fully entering the socket; this leads to loss of con­
trol and pressure on bony prominences.
The second cue to the prosthetic wearer is increased pis­
toning, anteroposterior, or medial–lateral motion within the
socket when walking. This can be caused by an insufficient
number of socks.
The final cue is found upon doffing the prosthesis. The
skin should be checked for erythema. Erythema on the distal
aspect of the fibular head or patella indicates that the limb is
too far in the socket and extra ply of socks are needed. If too
many socks are being used, the erythema will appear on the
tibial tubercle or the proximal aspect of the fibular head, as
the limb is not far enough into the socket. In this case, there
may also be signs of verrucose hyperplasia on the distal end of
the limb as a result of the lack of distal contact.
Another common problem that arises with prosthetic
users is caused by inappropriate shoe wear. Although some
prosthetic feet accommodate for the heel height of the shoe,
most do not. Wearing a heel that is too high positions the
limb such that there is a relative excessive flexion of the socket
and actual of the knee joint during stance. A heel that is too
low or going barefoot tends to hyperextend the knee. Proper
foot wear is important for safe ambulation. The prosthe­
sis can be checked by evaluating the top surface of the foot
shell while the prosthesis is free standing on a level surface.
If the top of the foot shell tilts posteriorly, the heel is too low
(Figure 23-35).
In a well-fitting socket, the skin should appear uniform
in color after wearing the prosthesis. Areas of erythema that
fade after 20 minutes are not likely to be problematic. The
skin should be soft and supple, especially on the distal end.
Firm tissue associated with edema is a sign of poor contact
and an effort should be made to create some contact in the
Heel Too Low
Heel Too High
Correct Heel Height
FIGURE 23-35  Heel height of the shoes affects the sagittal plane moments throughout stance. A
heel that is too low for the prosthetic foot creates excessive extensor moment at the knee in mid­
stance, hampering forward progression. A heel that is too high for the prosthetic foot creates a flexion
moment at the knee at midstance, leading to early “drop off” and compromise of stance phase sta­
bility. (Photo courtesy of David A. Knapp, CPO, Hanger Prosthetics & Orthotics, North Haven, CT)

650
Section III  Prostheses in Rehabilitation
area of the firm tissue. The individual may not tolerate much
pressure, but only a small amount of pressure is needed to
push the extra fluid back into circulation. If erythema is
observed over bony prominences, and the person's residual
limb is properly seated in the socket, pressure in those areas
needs to be relieved. Prosthetists can adjust fit of thermo­
plastic sockets by heating and reshaping the areas that need
adjustment. Thermoset sockets, like composites, can only be
adjusted by cutting out fenestrations or by adding padding to
the area around the prominent bone to shift it away from the
socket wall. It is important to note that addition of padding
requires removal of some equivalent sock ply to maintain the
same volume within the socket.
If skin irritation is present, especially over a bony promi­
nence, placing a small mark on the affected areas with lip­
stick before donning the prosthesis will allow the lipstick to
transfer to the socket during ambulation. Once the prosthetic
wearer removes the prosthesis, the lipstick will mark the areas
of excessive contact. Alternatively, a thin flexible steel probe (a
corset stay works exceptionally well) can be inserted between
the socket and the interface to act as a feeler gauge to find
areas of high pressure. The individual should be putting some
weight through the socket during this evaluation. To assess
distal contact in a finished socket, a ball of soft clay, about
the size of a blueberry, can be placed into the bottom of the
socket prior to donning. After the person dons the prosthe­
sis and walks a few steps, the prosthesis should be removed
and the clay examined. The clay should appear compressed.
Postcompression clay thickness of 3 to 5 mm is considered
ideal. Total contact in the socket can be assessed by lightly
powdering the interior surface of the socket with a fine pow­
der like cornstarch and having the individual carefully don
the prosthesis and walk a few steps. Any powder that remains
on the socket's surface after walking indicates that those areas
are not in contact with the residual limb.
The amount of pistoning that is present in a socket
depends upon the socket design and the type of suspension
that is used. If the person is complaining of discomfort while
ambulating but is comfortable while standing, pistoning is the
likely cause of the pain. Pistoning can be assessed by asking
the individual to fully weight bear on the socket and then lift
the prosthesis off the ground while the examiner is palpating
the patella; motion of more than 1 cm should be considered
excessive. Faulty suspension and/or loose socket fit are gener­
ally responsible for pistoning. Wearing the correct ply of sock
and ensuring that the suspension is functioning well should
minimize the motion in the socket to pain-free levels.
There are several patterns of erythema that indicate poor
alignment of the prosthesis. Excessive varus moment on the
limb is suspected when signs of pressure are observed on both
the distolateral and the proximomedial aspects of the limb
together. This pattern can be caused by excessive foot inset or
too much socket adduction. When the erythema is observed
on the distomedial and proximolateral aspects of the limb, an
excessive valgus moment is likely. The foot may be too far out­
set or the socket may be excessively abducted. Anterior distal
pressure accompanied by pressure in the posterior proximal
aspect of the socket may be a result of an excessively long heel
lever arm, excessive dorsiflexion, excessive socket flexion, or
a heel that is too firm. This pattern can also be observed when
an individual wears a shoe that has a higher heel than the
prosthesis can accommodate. Conversely, if the person goes
barefoot, the opposite pattern of pressure will be observed;
erythema on the posterior distal end and the anteroproximal
end. This is the same pattern that can be caused by a toe lever
arm that is too long, an overly plantarflexed foot, or an exces­
sively extended socket.
SPECIALTY PROSTHESES
There are novel prosthetic designs that are intended for use in
specialized activities such as water sports, running, and bicy­
cling. The biomechanical goals of these prosthetic devices
are different from those designed for everyday ambulation.
They must take into account the unique loading and envi­
ronmental exposure requirements that will be encountered.
Running feet, for example, lack a heel spring because sprint­
ing takes place on the toes only; a heel would interfere with
limb motion and add unnecessary weight. Because knee flex­
ion during a sprint may reach beyond 110 degrees, the poste­
rior proximal trim line needs to be lower; and because there
is a great deal more impact force at initial contact, more care
should be given to ensuring that the person and prosthesis are
capable of absorbing the impact slowly in a manner that will
prevent damage to the skin and limb. Running also subjects
the prosthesis to greater tension in swing phase, so the sus­
pension system will be under increased strain. Runners often
use an auxiliary suspension just in case their primary suspen­
sion fails at high speed.
A prosthesis that is designed for swimming includes a lot
more than just the ability to get wet. Attention must be given
to the buoyancy of the device. Neutral buoyancy is preferred
because a prosthesis that floats may inhibit the individual's
ability to keep his or her head above the water surface, and a
prosthesis that sinks could drag the person down with it. Any
water that gets inside the prosthesis should have a quick path
to get back out once the person finishes swimming. A swim­
ming prosthesis can also be fitted with an adjustable ankle
that allows the swimmer to lock the ankle in approximately
70 degrees of plantarflexion, which accommodates the use of
a swim fin. Waterproof components and materials that do not
absorb water are the best choices when designing a swimming
prosthesis so that the individual can also use the device on the
way to and from the swimming area. Any time the prosthe­
sis is used in salt water, it is advised that the the prosthesis be
thoroughly rinsed with fresh water after swimming, even if it
was designed for maritime use.
There are specialized feet for downhill skiing that clip
directly into the ski binding, rock climbing feet that require
no shoes, cycling feet that clip directly into the pedals, and
many other specialized feet for sports and recreational activi­
ties. To save money and time and to avoid carrying several
complete prostheses with them, active prosthetic wearers
can use a quick disconnect adapter to keep one socket and

Chapter 23  Transtibial Prosthetics
651
rapidly switch between different specialty feet. The adapter
ensures that the alignment of the prosthesis is optimal for
each different activity that the specific foot is intended for. It
also provides a light-weight secure and safe connection so the
individual is confident that the prosthesis will not fail. Most
insurance companies will pay for these types of prostheses
when they are shown to be medically necessary.
SUMMARY
Persons with transtibial amputation have the opportunity to
participate in a rehabilitation process that seeks to maximize
function and minimize impairments so that they can partici­
pate as fully as they can in activities of daily living and instru­
mental activities of daily living. An interdisciplinary team
is available to support medical, nursing, social, therapy, and
prosthetic needs of the individual and the team develops a
plan of care that addresses the goals of the persos, family, and
caregivers. Standard and new advances in prosthetics for per­
sons with transtibial amputation offer a wide array of options
that range from prosthesis use for cosmesis and home-bound
ambulator to community ambulator with variable cadence
and intensive athletic involvement. The clinicians dedicated
to enhancing the quality of life of persons with transtibial
amputation evaluate the many variables that come into play
when engaging in a postamputation rehabilitation program
including (a) overall health, functional status, and mobility
skills; (b) prosthetic componentry and technology to assure
the most appropriate and best fitted prosthesis; and (c) mate­
rials and equipment that need to be tailored to the individual
to optimize outcome in the prosthetic rehabilitation pro­
cess. The Medicare K-level standards speak to “potential” to
achieve a level of ambulation and community engagement.
Persons with transtibial amputation should be scheduled for
followup care to assure that the prosthetic prescription pro­
vided at one point in time meets the needs of the individual,
as changes associated with skill progression and advance­
ment occur over time. Therapists, prosthetists, and other
health care providers should advocate on behalf of persons
with amputation for a change in prosthesis as the need arises.
REFERENCES
1. Gailey R, Nash M, Atchley T, et al. The effects of prosthesis mass
on metabolic cost of ambulation in non-vascular trans-tibial
amputees. Prosthet Orthot Int. 1997;21(1):9–16.
2. Green VG. Transtibial amputation: Prosthetic use and func­
tional outcome. Foot Ankle Clin. 2001;6(2):315–327.
3. Centers for Medicare and Medicaid Services, U.S. Department of
Health and Human Services. HCFA Common Procedure Coding
System (HCPCS) 2001. Springfield (VA): U.S. Department of
Commerce, National Technical Information Service; 2001
[Chapter 5.3].
4. Esquenazi A, DiGiacomo R. Rehabilitation after amputation.
J Am Podiatr Med Assoc. 2001;91(1):13–22.
5. Mueller MJ. Comparison of removable rigid dressings and elas­
tic bandages in preprosthetic management of patients with
below-knee amputations. Phys Ther. 1982;62(10):1438–1441.
6. Wu Y, Keagy RD, Krick HJ, et al. An innovative removable rigid
dressing technique for below-the-knee amputation. J Bone Joint
Surg Am. 1979;61(5):724–729.
7. Ladenheim E, Oberti-Smith K, Tablada G. Results of managing
transtibial amputations with a prefabricated polyethylene rigid
removable dressing. J Prosthet Orthot. 2007;19(1):2–4.
8. Witteck F. Some experience with patellar-tendon bearing below-
knee prostheses. Artif Limbs. 1962;6:74–85.
9. Radcliffe CA. The Patellar-Tendon-Bearing Below-Knee Prosthesis.
Berkeley: University of California Biomechanics Laboratory; 1961.
10. Staats T, Lundt J. The UCLA total surface bearing suction below-
knee prosthesis. Clin Prosthet Othot. 1987;118–130.
11. Perry J. Gait Analysis: Normal and Pathological Function.
2 Thorofare, NJ: SLACK; 2010.
12. Pinzur MS, Beck J, Himes R, et al. Distal tibiofibular bone-bridging
in transtibial amputation. J Bone Joint Surg Am. 2008;90:2682–2687.
13. Granata JD, Philbin TM. Distal tibiofibular bone bridging in
transtibial amputation. Curr Orthop Pract. 2010;21:264–267.
14. Sanders JE, Greve JM, Mitchell SB, et al. Material properties of
commonly-used interface materials and their static coefficients of
friction with skin and socks. J Rehabil Res Dev. 1998;35:161–176.
15. Sanders J, Nicholson B, Zachariah S, et al. Testing of elastomeric
liners used in limb prosthetics: classification of 15 products by
mechanical performance. J Rehabil Res Dev. 2004;41:175–186.
16. Fillauer C, Pritham C, Fillauer K. Evolution and development of the
silicone suction socket (3S) for below-knee prostheses. J Prosthet
Orthot. 1989;1:92–103.
17. Kristinsson Ö. The ICEROSS concept: a discussion of a philoso­
phy. The Journal of the International Society for Prosthetics and
Orthoics. J Prosthet Orthot. 1993;17(1):49–55.
18. Ferraro C. Outcomes study of transtibial amputees using ele­
vated vacuum suspension in comparison with pin suspension.
J Prosthet Orthot. 2011;23:78–81.
19. Beil T, Street G. Comparison of interface pressures with
pin and suction suspension systems. J Rehabil Res Dev.
2004;41(6A):821–828.
20. Roberts RA. Suction socket suspension for below-knee
­amputees. Arch Phys Med Rehabil. 1986;67(3):196–199.
21. Grevsten S. Ideas on the suspension of the below-knee prosthe­
sis. Prosthet Orthot Int. 1978;2(1):3–7.
22. Board W, Street G, Caspers C. A comparison of trans-tibial
amputee suction and vacuum socket conditions. Prosthet Orthot
Int. 2001;25:202–209.
23. Biel TL, Street G, Covey S. Interface pressures during ­ambulation
using suction and vacuum-assisted prosthetic sockets. J Rehabil
Res Dev. 2002;39(6):693–700.
24. Goh J, Lee P, Chong S. Comparative study between patellar-tendon-
bearing and pressure cast. J Rehabil Res Dev. 2004;41(3B):491–502.
25. Polhemus. Cobra_Scorpion_brochure.pdf. Available at:
polhemus.com/polhemus_editor/assets/New%20FastSCAN%20
Cobra&Scorpion%20brochure.pdf; 2008. Accessed 12.03.11.
26. Smith DG, Fergason JR. Transtibial amputations. Clin Orthop
Relat Res. 1999;(361):108–115.
27. Lin C, Wu YC, Edwards M. Vertical alignment axis for trans­
tibial prostheses: a simplified alignment method. J Formos Med
Assoc. 2000;99(1):39–44.
28. Compas Overview Pamphlet. 2009. Available at: http://

Overview%20Pamphlet_Low-res.pdf. Accessed 08.03.11.
29. Gard S, Konz R. The effect of a shock-absorbing pylon on the
gait of persons with unilateral transtibial amputation. J Rehabil
Res Dev. 2003;40(2):109–124.

652
24
Transfemoral Prostheses
Richard Psonak
ADVANCES IN TECHNOLOGY
Advances in technology, materials, and prosthetic compo­
nents have had a considerable positive impact on the qual­
ity of life of individuals with transfemoral amputation. In
the past, ambulation wearing a transfemoral prosthesis was
labored and often painful. Only the most physically fit indi­
viduals attempted to run with their prostheses. Now socket
designs better approximate anatomy of the lower limb, sus­
pension systems enhance and maintain intimate residual
limb contact within the socket, and dynamic prosthetic feet
and knee components offer improved, energy-efficient func­
tion. The result has been a significant improvement in quality
of gait, allowing more people with transfemoral amputa­
tion to walk comfortably and naturally with their prostheses.
In addition, athletes with amputations can run in a natural
“step-over-step” pattern with a higher degree of stability and
comfort than previously possible.
This chapter presents information about current socket
designs, suspension systems, and prosthetic knee components
available for individuals with transfemoral amputation. It also
provides the reader with a strategy to assess fit and alignment
of a transfemoral prosthesis as well as explaining the major
user-errors and prosthetic-related reasons for commonly
observed gait deviations.
PROSTHETIC MANAGEMENT AFTER KNEE
DISARTICULATION OR TRANSFEMORAL
AMPUTATION
An amputation proximal to the anatomical knee joint is referred
to as a transfemoral (above knee) amputation. An amputation
through the center of the anatomical knee joint is known as a
knee disarticulation (Figure 24-1). Individuals with knee dis­
articulation present with prosthetic challenges and functional
advantages when compared with those with transfemoral
amputation. The disarticulation residual limb tends to be long
and distally bulbous, a result of the preservation of the femur
and its condyles. Prosthetically, this creates a challenge in don­
ning the prosthesis and cosmetically finishing a knee compo­
nent. The bulbous distal end does, however, enhance prosthetic
suspension. The normal adduction angle of the lower extrem­
ity is more likely to be preserved, and the long lever arm of
the femur facilitates control of the prosthetic knee. Also, as the
proximal component of a weight-bearing joint, the distal femur
tolerates end-bearing pressures within the socket.
In contrast, the transfemoral residual limb varies in length,
depending on how much of the femur has been retained. The
shape of the residual limb is likely to be a tapered cylinder
so that donning a prosthesis is less difficult. Suspension can
be challenging, however, as a result of this cylindrical shape
of the residual limb. The fleshiness of the transfemoral resid­
ual limb presents an opportunity for suction suspension. As
the length of the residual limb decreases, socket suspension
and control of the prosthetic knee (especially stance stability)
become more problematic.
The successful prosthetic management of individuals who
have suffered an amputation above the knee involves provid­
ing a prosthesis that is comfortable in containing the residual
limb, stable during the stance phase of gait, smooth in transi­
tion to the swing phase of gait, and acceptable in appearance.1 In
choosing components for an individual's transfemoral or knee
disarticulation prosthesis, the prosthetic team must ­consider
24
LEARNING OBJECTIVES
On completion of this chapter, the reader will be able to do
the following:
1. Describe the indications for, functional characteristics of,
and advantages and limitations of the most commonly
used transfemoral components and suspension strategies.
2. Compare and contrast the design, fit, and function of the
four most popular transfemoral socket designs: quadri­
lateral, ischial containment, Marlo Anatomical Socket
(MAS), and subischial.
3. Describe the interaction among alignment stability,
mechanical stability, and muscular stability on the control
and function of the prosthetic knee in standing, during
gait, and on uneven surfaces.
4. Describe the key influences that bench, static, and
dynamic alignment have on fit and function of a transfem­
oral prosthesis.
5. Identify the nine items that will cause variations in socket
fit and the quality of transfemoral gait.
6. Recognize and describe the intraindividual and extraindi­
vidual causes of the most common transfemoral gait devi­
ations, and suggest appropriate corrective action.

Chapter 24  Transfemoral Prostheses
653
the interrelationships among the component's weight, func­
tion, cosmesis, comfort, and cost. Often the most functional or
technologically sophisticated components are also the heaviest,
most expensive, most likely to need maintenance, and least cos­
metic. Because of the great variation in physical characteristics,
health, and preferred activities of individuals with transfemo­
ral amputation, no single material, component, or transfemoral
design is appropriate for all persons with amputation. The pref­
erences and needs of each individual must be considered care­
fully, in the context of weight, function, cosmesis, comfort, and
cost, for the optimal prosthetic outcome.
ENERGY EXPENDITURE
An individual with a transfemoral amputation faces con­
siderable energy expenditure when ambulating with a
prosthesis (Box 24-1). The energy cost of gait increases sig­
nificantly as the length of the residual limb decreases.2–6
Fisher and Gullickson report the energy cost of walking
for healthy individuals (mean gait speed: 83 m/min) as
0.063 kcal/min/kg (oxygen consumption/physical effort)
and 0.000764 kcal/m/kg body weight (oxygen cost/energy
required to ambulate).6 Individuals with transtibial ampu­
tation walk 36% more slowly, expending 2% more kilocal­
ories per minute and 41% more kilocalories per meter to
cover a similar distance. For individuals with transfemo­
ral amputation, gait speed is 43% slower, whereas energy
cost is reflected as 5% less kilocalories per minute and 89%
more kilocalories per meter. In other words, the individual
ambulating on a transfemoral prosthesis walks more slowly
to avoid an increase in energy consumption per minute and
is dramatically less efficient in terms of energy expended
over distance (per meter). This increase in energy cost is
manifested as a higher rate of oxygen consumption, ele­
vated heart rate, and notable reduction in comfortable
(self-selected) walking speed.2,5,6
Because of this high energy cost, many older individuals
with high-level transfemoral amputations may be limited in
their ability to become functional community ambulators.
Individuals who wear a prosthesis and have been diagnosed
with vascular disease are often relegated to walking slowly, on
flat terrain, with the assistance of a walker or cane.5,6 Elderly
individuals with bilateral transfemoral amputations rarely
become community ambulators with prostheses, instead
choosing a wheelchair for long-distance mobility.
A
B
FIGURE 24-1  The similarities and differences in prosthetic fit and function between amputations
at transfemoral and knee disarticulation levels are determined, to a large degree, by the length of the
preserved femur. A, The knee disarticulation residual limb is long and bulbous, whereas the trans­
femoral residual limb is a tapered cylinder. B, In a knee disarticulation prosthesis, the center of the
prosthetic knee is generally lower than that of the intact limb, whereas the knee center of most trans­
femoral prostheses matches that of the intact limb.
• Weight of the prosthesis
• Quality of the socket fit
• Accuracy of alignment of the prosthesis
• Functional characteristics of the prosthetic components
BOX 24-1  Prosthetic Features That Affect
Energy Expenditure

654
Section III  Prostheses in Rehabilitation
TRANSFEMORAL SOCKET DESIGNS
Prior to the 1950s, prosthetists typically carved a “plug fit”
socket from a block of wood, which, depending on the skill
of the craftsman, was often uncomfortable and cumbersome
while walking and sitting. The plug socket was crafted to con­
tain the remnant thigh muscles, support body weight at the
groin level (below the ischium), and was often open ended to
eliminate distal limb contact.
Quadrilateral Socket
The traditional quadrilateral (quad) socket, developed at the
University of California at Berkeley in the 1950s, offered a nota­
ble improvement in fit, total contact, function, and remained
the socket design of choice until the mid-1980s. The quad
socket, as its name implies, has four distinct walls fashioned to
contain the thigh musculature. The quad socket was designed
to be a complete above-the-knee prosthetic system that inter­
faces with the individual who wears the prosthesis. The sock­
et's primary functions are to provide for weight-bearing
during the stance phase of gait and to allow the hip and thigh
muscles to function at maximum potential during the stance
phase of gait (Figure 24-2, A).1,7,8 A flat posterior shelf, the
ischial seat, is the primary weight-bearing surface for the
ischium and gluteal muscles. The anterior wall contours cre­
ate a posterior-directed force at the anatomical Scarpa's trian­
gle, which is intended to stabilize the ischium on its prosthetic
seat. As a result, the socket is narrower in its anterior–posterior
dimension than its medial–lateral dimension (Figure 24-3, A).
A
B
C
D
FIGURE 24-2  Comparison of the design of the quadrilateral (quad) socket (A), the ischial-ramal
containment (IRC) socket (B), the Marlo Anatomical Socket (MAS) (C), and subischial socket (D)
from a posterior perspective. The quad socket is designed to have the ischium sitting on the socket
brim (seat). In the IRC socket and the MAS, the ischium sits inside the socket. With the subischial
socket, as the name implies, the socket trim line is below the ischium.

Chapter 24  Transfemoral Prostheses
655
Evolution of Ischial Containment Sockets
The next stage of socket designs evolved in 1970s after
prosthetist Ivan Long took part in a project that evaluated
radiographically the femoral alignment of the transfemo­
ral limb within a quad socket.9 Long observed that many
individuals who wear a quadrilateral socket walk with an
extremely wide base and demonstrated a Trendelenburg
or gluteus medius limp, causing the individual to lean to
the amputated side. He also noted that in most cases the
transected femur was aligned in abduction as opposed
to the normal adduction angle of the sound side femur
(Figure 24-4). The abnormal abduction angle of the femur
was believed to be in part the result of the quad sock­
et's unnaturally wide medial–lateral dimension and nar­
row anteroposterior dimension. The wide medial–lateral
dimension of the quad socket allows the socket to displace
laterally during midstance, thus increasing pressure to the
perineal tissues and decreasing the efficiency of the glu­
teus medius muscle.9,10
Long's socket design was part of a frontal plane align­
ment procedure that became known as “Long's Line.”9,10 Long
believed that by aligning the distal femur over the center of
the knee and through the center of the foot, the wearer of the
prosthesis could bring their residual limb into a normal ana­
tomical position and walk more naturally. Long narrowed the
medial–lateral dimension of his socket design and increased
anteroposterior dimension in an attempt to support the femur
and to prevent lateral shifting of the socket during weight
bearing. According to Long,9,11 an additional advantage of his
design is that the wider anteroposterior dimension enhances
muscle function by providing more room to accommodate
muscle contraction than possible in the crowded anteropos­
terior dimension of the quad socket.
In the 1980s prosthetist John Sabolich expanded upon
Long's concept and developed his contoured anterior
trochanteric-controlled alignment method (CAT-CAM)
socket (see Figure  24-2, B).11–13 His design attempted to
both maintain the femur in an adducted position and con­
trol socket rotation by containing the ischial tuberosity
within the contours of the socket. Since the CAT-CAM
design, a series of sockets have been developed that have
become known as ischial containment or ischial-ramal
containment (IRC) sockets, depending on what anatomy
is contained within the socket.12,13 When comparing the
IRC socket with the quad socket, the most obvious differ­
ence is the narrow medial–lateral dimension that is highly
contoured around the ischial–ramal complex (see
Figure 24-3, B).12
Socket Configuration Influence on Femur Position
The degree to which the prosthetic socket design can influ­
ence the position of the transected femur has been hotly dis­
puted. Orthopedic surgeon Frank Gottschalk developed a
myodesis surgical technique to ensure proper femoral adduc­
tion in a transfemoral residual limb.14 In the journal arti­
cle, “Does socket configuration influence the position of
the femur in above-knee amputation?,” Gottschalk and col­
leagues concluded that the prosthetic socket cannot provide
enough lateral pressure to change the position of the femur.15
The authors indicated that proper anatomical adduction is
achieved only through specific surgical techniques. Most
­practitioners would agree with Gottschalk when he suggests
that “successful prosthetic fitting starts at the time of sur­
gery.”14,15 However, there is also a consensus that indicates
that an intimately contoured socket in optimal alignment
enhances an individual's gait, decreases energy expendi­
ture, increases socket comfort, and improves overall func­
tion.16 Clearly more research is required to understand the
relationship between alignment, socket design, and femoral
adduction.
A
B
C
D
FIGURE 24-3  From a cross-section view of the four different transfemoral sockets designs it is noted
that the quad socket has a narrow anteroposterior dimension (A), the ischial-ramal containment (IRC)
socket (B), and Marlo Anatomical Socket (MAS) (C) have narrow mediolateral dimensions. The
subischial socket (D) has a more oval shape which is consistent with the shape of the proximal thigh.

656
Section III  Prostheses in Rehabilitation
Marlo Anatomical Socket
In the late 1990s, Marlo Ortiz, an engineer-prosthetist from
Mexico, developed a socket configuration that focuses on
providing skeletal support along the medial ischial–ramal
complex (IRC) (see Figure  24-3, C).17 The socket design
became known as the MAS socket (Marlo Anatomical
Socket). The MAS socket attempts to encapsulate the ischial
tuberosity, as well as portions of the ramus, with a distin­
guishable containment buttress that is designed to maximize
socket stabilization (see Figure 24-2, C). The socket features
a low posterior trim line that is said to facilitate the contain­
ment of the ischial–ramal complex without interference from
the gluteus maximus trim lines. The low gluteal trim lines
also allow the prosthetic user to sit directly on the ­gluteus
maximus instead of the posterior socket. External rotation
at the hip is virtually unrestricted, minimizing the need for
a transverse rotation unit (see Figure 24-18) proximal to the
prosthetic knee joint.
Elevated Vacuum Sockets
The latest rendition of transfemoral socket designs has devel­
oped as a result of the ever expanding interest in elevated vac­
uum suspension, also referred to as subatmospheric suspension
(see Figure 24-3, D).18 This socket design is characterized by
lower trim lines (subischial) in comparison to other transfem­
oral socket designs, resulting in substantially increased patient
comfort and range of motion (see Figure 24-2, D). The proxi­
mal socket brim has been lowered as much as two-four inches
FIGURE 24-4  Long noted that for many individuals who wear a quadrilateral socket the transected
femur was aligned in abduction as opposed to the normal adduction angle of the sound side femur (A).
Quad socket wearers typically walk with an unnaturally wide base. Ischial-ramal containment (IRC)
sockets (B) are more naturally designed and aligned to enhance an individual's gait, decrease energy
expenditure, increase socket comfort, and improve function.

Chapter 24  Transfemoral Prostheses
657
below the ischial tuberosity level on transfemoral residual
limbs greater than midlength.19 By utilizing elevated negative
pressure around the distal two-thirds of the residual limb, the
socket no longer requires compression of the proximal resid­
ual limb anatomy to provide weight bearing and stabilization.
As a result of less proximal compression, there is no longer a
need for prominent flares, reliefs, and channels, thus allow­
ing lower trim lines of the socket. The proximal roll on liner
contains the soft tissue of the adductor muscles. Some have
referred to this style of socket as brimless.19
Radcliffe7 suggests that, regardless of socket design, the
primary goals of the transfemoral prosthesis are to achieve
comfort in weight bearing, to provide a narrow base of sup­
port in standing and walking, and to accomplish as close
to normal swing phase function as possible. Mak and col­
leagues indicate that, “For all prosthetic socket designs, the
optimal load distribution should be proportional to the abil­
ity of the body to sustain such stresses.” The authors go on to
summarize that, “The basic principles for socket design vary
from either distributing most of the load over specific load-
bearing areas or more uniformly distributing the load over
the entire limb.”20
RIGID AND FLEXIBLE SOCKET MATERIALS
Most transfemoral sockets are fabricated from various ther­
moplastic or thermosetting resin materials. A rigid socket
consists of a resin-laminated or thermoformed plastic
socket that is intended to have an intimate, total contact
fit over the entire surface of the residual limb. The rigid
socket is durable, easy to clean, and often less bulky and
less expensive to produce than flexible sockets. The disad­
vantage , is that it more difficult to adjust the fit of a rigid
socket, especially for individuals with “bony” or sensitive
residual limbs.
The flexible socket is vacuum formed using any number
of flexible thermoplastic materials.21,22 It is encased in a rigid
frame, which provides support during weight bearing and
helps to maintain socket shape. The flexible socket accommo­
dates to change in muscle shape during contraction and can
be easily modified after initial fabrication to provide relief for
bony prominences. Flexible sockets may also be more com­
fortable to wear, especially in sitting, because there are no hard
edges at the brim to impinge on the groin. Flexible sockets are
especially useful if suction suspension is desired. They are,
however, somewhat less durable, more bulky to wear (requir­
ing a socket and a frame), and more expensive to produce than
rigid sockets.
TRANSFEMORAL SUSPENSION SYSTEMS
Keeping the prosthesis on in its optimal functional position
is more challenging for individuals with transfemoral ampu­
tation than with transtibial amputation. The transfemo­
ral residual limb is fleshy and cylindrical, lacking the bony
prominences that aid in suspending the transtibial prosthesis.
The weight of the transfemoral prosthesis with the addition of
its knee unit creates an additional challenge for adequate sus­
pension. Depending on the nature of the prosthetic wearer's
normal activities, a single system or a combination of several
systems may be chosen.
Traditional Pull-in Suction Suspension
Traditional pull-in suction suspension uses negative air
pressure, skin-to-socket contact, and muscle tension to
hold the socket onto the limb (Figure 24-5).23 A suction
prosthesis can be donned in several ways. One option uses
donning sock (cotton stockinette or similar material), don­
ning sleeve (parachute nylon or similar material), or elas­
tic bandage to pull the residual limb down into the socket.
Once the limb is well seated in the socket, the sock, sleeve,
or elastic wrap is pulled through the valve housing at the
distal socket, and the air expulsion valve is then screwed
into place. This process requires considerable agility and
balance on the part of the wearer. A second option is to
add a lubricant to the skin to facilitate the residual limb
sliding into the socket. The air-expulsion valve is then
“burped,” by pushing or pulling the valve button, to release
any trapped air.
The intimate fit required for suction suspension has sev­
eral additional benefits. The wearer often reports enhanced
prosthetic control and a better proprioceptive sense of the
prosthesis during walking. Because an intimate fit is essential,
suction suspension is inappropriate for patients with recent
FIGURE 24-5  Patient donning a suction socket using a pull sock.
The air expulsion valve has been removed so that the donning sock
can be pulled completely out of the socket.

658
Section III  Prostheses in Rehabilitation
amputation who will continue to lose limb volume or for
those with a history of fluctuating edema or unstable weight.
The high shearing forces associated with donning a suction
socket also may preclude its use for patients with fragile or
sensitive skin, painful trigger points, significant scarring, or
adhesions.
Roll-on Suspension Liners
Growing in popularity as a suspension system is the use of
roll-on liners. These liners are available as an alternative to
the standard suction suspension system. Roll-on liners are
manufactured from various materials, including silicone, ure­
thane, and elastomer. They are produced by several manu­
facturers in a variety of sizes, thicknesses, and tapers.24 Worn
against the skin, roll-on liners are donned by first being
turned inside-out, then rolled directly over the residual limb.
The roll-on suspension liner creates a negative atmospheric
pressure and somewhat adhesive bond to the skin. The liner
can be used for suspension in several different ways: in a shut­
tle lock system, as part of a lanyard system, as a cushion liner
used with an air expulsion valve, or as a vital part of an ele­
vated vacuum socket.
Shuttle Lock Systems
This liner is commonly called a locking liner. It is similar to
the cushion liner except for a distal stabilizing matrix incor­
porated into the liner to prevent elongation. This liner also
has an external distal cap, the center of which a serrated pin
screws into and sticks out approximately 11⁄2 inches. The
pin engages into the shuttle lock, inside the bottom of the
socket, when the individual stands and pushes his or her
limb down into the socket. To remove the prosthesis, the
individual depresses a release button on the medial aspect of
the socket that disengages the serrated pin (Figure 24-6, A).
Lanyard System
This system uses the locking liner, but instead of a locking pin
screwed into the liner's distal cap, a lanyard (strap or cord) is
attached to the cap. This is routed through the distal socket to
pull the residual limb into the socket (see Figure 24-6, B). The
lanyard is then attached to the external lateral aspect of the
socket using Velcro. Many designs maintain suspension and
rotational control by providing suspension distally and stabil­
ity laterally through an additional loop attached to the liner
proximally (Figure  24-7). Some systems utilize a ­ratcheted
strap much like a ski boot binding as a lateral suspension
strap.
Cushion Liner with Air Expulsion Valve
This type of liner is generally referred to as a cushion liner.
After the liner is donned on the residual limb, it is pushed
into the socket, creating a negative pressure environment by
expelling air through the expulsion valve (see Figure 24-6, C).
This process is similar to the traditional skin suction socket
method mentioned previously.
Elevated Vacuum
Elevated vacuum is different than suction suspension.
Both methods use a difference in atmospheric pressure to
suspend and secure the socket to the residual limb. Suction
suspension requires a passive expulsion valve to allow air
to exit from the socket, but only creates a negative pres­
sure differential when the prosthetic limb is unweighted as
when moving into swing phase. With vacuum suspension
the residual limb is continuously under vacuum. A vacuum
pump creates negative pressure to remove air from a sealed
environment between the total surface bearing socket and
a wicked-liner (see Figure  24-6, D). The vacuum cre­
ated by a vacuum pump's removal of air holds the inti­
mately fitting liner firmly to the walls of the socket.25 This
system does not depend on the limb position. An elevated
vacuum of approximately 15 inches Hg between the limb
liner and the socket controls volume fluctuations in the
socket.26,27
Pistoning between the limb, liner, and socket is virtually
eliminated within an elevated vacuum system. Individuals
using vacuum-suspended prostheses report having greater
proprioception and a sense that the prosthesis feels lighter
when using vacuum suspension in comparison to other
types of suspension.25 It has also been suggested that
an elevated vacuum system maintains the volume of the
limb in the socket by improving circulation within the
limb, and may help to heal wounds and improve limb
health.28
The major advantage of roll-on suspension is a signifi­
cant reduction in the amount of friction and shear on the
residual limb.29 The donning procedure is simple, and can
be accomplished while seated. This suspension system has
been useful for individuals with short residual limbs and
those who have experienced discomfort using the tradi­
tional pull-in suction method. The disadvantages of this
system include its expense and durability. Roll-on liners
become worn or torn, and must be replaced two to three
times a year depending on the wearer's activity level. These
types of liners may also increase skin temperature and per­
spiration. Some wearers have experienced rashes or other
types of skin irritation as a result. Wearers who choose this
type of suspension must clean the liners daily to prevent
the buildup of perspiration and bacteria.30,31
Silesian Belt Suspension
A Silesian belt is usually made from leather or lightweight
webbing (Figure 24-8). It is attached to the lateral aspect of
the socket, encircles the pelvis, and then runs through a loop
or buckle on the anterior of the socket. The Silesian belt is
most often used as an auxiliary (backup) for traditional suc­
tion suspension systems. The problem with choosing the
Silesian belt as the sole means of suspension lies in its inabil­
ity to control residual limb rotation within the socket. For
individuals with long residual limbs who are not expected
to be vigorous ambulators, the Silesian belt may provide
adequate suspension.

Chapter 24  Transfemoral Prostheses
659
FIGURE 24-6  Roll-on liners are a popular suspension system. The liner can be used for suspension in at least four different ways. A shuttle
lock system uses a pin that engages into the shuttle lock in the bottom of the socket (A). The lanyard system incorporates a strap or cord into
the liner that is routed through the distal socket and used to pull the residual limb into the socket (B). An air expulsion valve system is similar
to the traditional skin suction socket method. Once the liner is donned, the residual limb is pushed into the socket, expelling air through the
expulsion valve, thus creating a negative pressure environment (C). A vacuum pump (attached to socket) creates negative pressure to remove
air from a sealed environment between the socket and roll-on liner. The vacuum created by a vacuum pump's removal of air holds the inti­
mately fitting liner firmly to the walls of the socket (D).
A
B
C

660
Section III  Prostheses in Rehabilitation
Total Elastic Suspension Belt
The total elastic suspension (TES) belt is typically made
of an elastic neoprene material. The distal sleeve of the
TES belt fits snugly around the proximal half of the thigh
section of the transfemoral prosthesis. The neoprene
belt encircles the waist and attaches in front with Velcro
(Figure 24-9). The TES belt is easy to don, comfortable to
wear and is an excellent auxiliary suspension system. This
system is generally not recommended as a sole source of
suspension for prosthetic users who are active ambulators,
because like the Silesian belt, the TES belt cannot con­
trol residual limb rotation adequately within the socket.
The major disadvantages of the TES system include its
limited durability, ­especially for active ambulators, and
FIGURE 24-7  The lanyard suspension system often incorporates a lat­
eral rotational control loop and strap positioned laterally on the socket.
FIGURE 24-8  Example of Silesian belt suspension. Although the
belt suspends the prosthesis to the pelvis, it cannot fully counter­
act rotary forces between limb and socket during vigorous walking.
FIGURE 24-9  The total elastic suspension belt (TES) is a simple
and comfortable suspension system that is often used as an auxiliary
suspension.

Chapter 24  Transfemoral Prostheses
661
its tendency to retain heat. It is often chosen for individ­
uals with recent ­amputation whose residual limb has not
yet matured to a stable size, for older patients who are
unable to use the pull-in suction or roll-on liners because
of upper-extremity weakness or pain, and for those with
easily irritated skin or adhesions who cannot tolerate suc­
tion. It may also be used as a backup or secondary suspen­
sion system for individuals who use suction suspension
when playing sports or engaging in high-activity leisure
activities.
Pelvic Belt and Hip Joint
For some patients, a pelvic belt and hip joint are used as
a means of suspension (Figure 24-10). Generally, the pel­
vic belt is made of leather and attached to the prosthe­
sis by means of a metal hip joint. Recently, lighter-weight
plastic materials have been used as an alternative to the
metal joint. Whatever the material, the joint center should
be positioned just superior and anterior to the anatomi­
cal greater trochanter. This system not only suspends the
prosthesis but also helps to control rotation and increase
medial-lateral stability of the residual limb within the
socket. Traditionally, this has been the suspension of choice
for those with short residual limbs. The major drawbacks
of this type of suspension are its bulkiness under cloth­
ing, added weight, and tendency to be uncomfortable when
sitting.
FIGURE 24-10  A pelvic belt with hip joint not only suspends the
prosthesis but also helps to control rotation and increases medial
lateral stability of the residual limb within the socket.
CASE EXAMPLE 1
A Grandmother Who Wants to Dance at Her Granddaughter's Wedding
T. F. is a 68-year-old grandmother who wants to attend
her granddaughter's wedding, so she comes into her pros­
thetist's office asking for assistance with her 6-year-old
transfemoral prosthesis. T. F. underwent elective ampu­
tation 6 years ago when she developed osteomyelitis and
nonunion of a comminuted fracture of her left femur after
being hit by a car. Although she was initially deconditioned,
her rehabilitation was quite successful, and she returned
to her home to live independently after a 2-month stay in
a subacute rehabilitation setting. Previously, she smoked
a half pack of cigarettes per day, but she has not smoked
since her injury.
T. F.'s residual limb is relatively short: 41⁄2 inches as mea­
sured from the perineum to the distal end of her residual
limb. She currently wears an endoskeletal prosthesis with
rigid socket and prosthetic socks, a polycentric knee, and
single-axis foot, and ambulates functional distances by using
a straight cane. For suspension she uses a pelvic band with a
leather belt and hip joint, which is typical for those with her
level of amputation. She complains that her prosthesis pis­
tons on her residuum, is heavy and noisy, and pinches her
when she sits. Her major goal is that she be able to “blend
into the ceremony” such that her prosthesis will not be a
distraction. She is also hoping to dance with her son and her
new grandson-in-law at the wedding reception.
Her prosthetist consults with her physician and sug­
gest the fabrication of a new flexible IRC socket in a rigid
frame, but retaining the foot and knee that she has been
wearing. For suspension, the prosthetist recommends
using a roll-on sleeve with a shuttle locking device. This
suspension system will eliminate the metal pelvic band
with leather belt and hip joint as well as improve suspen­
sion and decrease pistoning by means of the locking pin
and high coefficient of friction of the urethane sleeve. The
new socket and suspension system give T. F. better control
of her prosthesis, allowing her to participate in all of the
wedding activities without her cane.
Questions to Consider
• Why was a pelvic band with leather belt and hip joint
used for suspension in T. F.'s initial prosthesis? What are
the pros and cons of this suspension system? Considering
that roll on suspension was not commonly used at the
time of her initial fitting 6 years ago, why did the team
not recommend a TES belt, Silesian belt, or suction
suspension?

662
Section III  Prostheses in Rehabilitation
Knee Disarticulation Considerations
When femoral condyles are not prohibitively bulbous, roll
on sleeves can be used in combination with air expulsion.
Although a pin is not recommended because of space limita­
tions, a lanyard system can be effective. This creates a positive
lock that is engaged even if limb volume changes. When the
femoral condyles are prominent a removable door suspension
design can be used to suspend the prosthesis. This suspen­
sion uses external straps, attached to a door, which can apply
variable pressure proximal to the femoral condyles locking
them in place (Figure 24-11). This suspension system is simi­
lar to the medial opening door occasionally used for Symes
prosthesis.
The stovepipe Pelite liner is another method of suspending
a bulbous residual limb in the knee disarticulation prosthesis.
This suspension method is also similar to a suspension sys­
tem used for Symes amputations. This method, utilizes pads
built up around the femoral condyles that are blended into
the largest circumference of the liner until the limb is more
cylindrical in shape (similar to a stovepipe). A slit is cut over
the medial condyle area to allow the bulbous end of the resid­
ual limb to pass through the narrow section of the liner when
donning.32 This system is easy to fabricate and provides good
suspension and comfortable padding, especially for more
bony limbs.
PROSTHETIC SYSTEMS
A transfemoral prosthesis can be fabricated as either an exo­
skeletal or endoskeletal system. The weight-bearing strength
and cosmetic shape of an exoskeletal prosthesis are provided
by a laminated shell that incorporates the socket, knee–shin
component, and ankle block (Figure 24-12, A). This system
is durable and requires little maintenance but cannot be eas­
ily realigned or adjusted. In the endoskeletal system, weight-
bearing strength comes from an internal pylon that connects
the knee unit to the prosthetic foot (Figure 24-12, B). The
cosmetic shape of the prosthesis is provided by a soft foam
cover, carved to mirror the remaining limb, which is fit over
the socket, knee unit, and pylon. This foam shell is, in turn,
covered by cosmetic stockings or a silicone “skin” to achieve
the desired skin color. The endoskeletal system has two dis­
tinct advantages: the prosthetist is quickly able to adjust pros­
thetic alignment, and easily interchange or replace modular
components. This is particularly helpful as new prosthetic
users become more competent in controlling their knee unit
or when advancing mobility leads to different functional
needs (e.g., involvement in athletic activities). The durability
of the foam and cosmetic coverings may be an issue for some
prosthetic users, especially when work or leisure activities are
physically demanding or occur in harsh environments.
PROSTHETIC KNEE UNITS
The function of the human knee joint is difficult to replicate.
Henschke Mauch, who developed hydraulic guidance sys­
tems for rockets during World War II, turned his considerable
knowledge and creativity to designing a hydraulic prosthetic
knee for veterans with amputations after the war.33 He com­
mented that it was far easier to design a large rocket with a
FIGURE 24-11  Generally, the residual limb of an individual with a
knee disarticulation has prominent femoral condyles. When this is
the case, a removable door suspension or stovepipe liner design can
be used to suspend the prosthesis. This suspension applies variable
pressure proximal to the femoral condyles locking the limb into the
socket.
• Why do you think the team decided to replace T. F.'s
rigid socket with a flexible socket in a rigid frame? What
are the advantages and disadvantages of each type of
socket?
• Why do you think the team decided to retain the poly­
centric knee unit when they replaced her socket and sus­
pension system? Are there other knee units that might
have been appropriate for someone of her age and activ­
ity level? Why or why not?
• Why do you think the team decided to retain the
single axis prosthetic foot when they replaced her
socket and suspension system? Would you have
considered a different prosthetic foot? Why or
why not?

Chapter 24  Transfemoral Prostheses
663
guidance system capable of maneuvering hundreds of miles
than to duplicate the human knee. The anatomical knee is a
modified hinge-type synovial joint. The offset axis of the knee
allows rotation in addition to flexion and extension, practi­
cally making it three joints rolled into one.34 Because most
prosthetic knees function in a single plane of motion, the
action of the anatomical knee is difficult to fully replicate. As
a result, it is more difficult for the individual who is using a
transfemoral prosthesis to walk as efficiently and cosmetically
as someone using a transtibial prosthesis.
Prosthetic knee mechanisms have two primary func­
tions. First, to simulate normal gait, the prosthetic knee must
smoothly flex and extend through the swing phase of gait.
The speed or rate of shin advancement during swing is deter­
mined by the mechanical properties (friction or resistance)
of the prosthetic knee unit. Second, the prosthetic knee must
remain stable as body weight rolls forward over the prosthetic
foot during the stance phase of gait. The major categories of
commonly used prosthetic knee units vary with respect to
how, and to what degree, they accomplish these two tasks.
Various knee units are available in endoskeletal and exoskel­
etal versions.
Single-Axis Knee Units
The single-axis knee simulates a simple hinge and allows
the prosthetic shin to swing freely in flexion and extension.
Stance-phase knee stability is achieved by a combination of
positioning of the knee unit with respect to the weight line
(alignment) and muscular control (activity of hip extensors).
This knee is lightweight, durable, and low maintenance, but
because of its unrestricted movement, it has no inherent
mechanical stability. For this reason, it is not appropriate for
individuals with relatively short residual limbs who lack the
mechanical advantage of a long femoral lever for muscular
control of the knee unit or for those whose stability is compro­
mised for other reasons. Although the rate of advancement of
the shin during swing phase (determined by the friction set­
ting of the knee) can be individualized, cadence responsive­
ness is minimal once the resistance has been set. The shin of
the prosthesis will swing forward at the same rate, regardless
of gait speed. As a result, an audible terminal impact often
occurs as the knee reaches full extension. To run with a
single-axis knee, the individual must use a skipping pattern
on the intact stance limb while waiting for the prosthesis to
complete the swing phase and begin the initial heel contact.
The single-axis knee is primarily for patients with long resid­
ual limbs who can voluntarily stabilize the knee through active
hip extension against the posterior wall of the prosthesis.
Polycentric Knee Units
The single-axis knee has a fixed center of rotation, while
the polycentric knee has a moving center of rotation. Like
the human knee, the polycentric knee rotates around more
than one axis through a four or more bar linkage system
(Figure  24-13). A proximal and posterior location of the
FIGURE 24-13  The single-axis knee has a fixed center of rotation,
while the polycentric knee has a moving center of rotation. Like the
human knee, the polycentric knee rotates around more than one axis
through a four or more bar linkage system. A, The polycentric knee
in the extended position. B, The knee fully flexed.
A
B
FIGURE  24-12  Comparison of the rugged exoskeletal (A)
and the modular endoskeletal (B) transfemoral prosthetic sys­
tems. (Reprinted, with permission, from Otto Bock Health Care,
Minneapolis, MN.)

664
Section III  Prostheses in Rehabilitation
instantaneous center of rotation promotes knee stability dur­
ing the stance phase of gait.35
As the knee unit flexes during swing phase, the polycen­
tric axis of motion leads to relative “shortening” of the dis­
tal prosthesis (shin and foot components), which enhances
toe clearance throughout swing phase.36 It is especially helpful
for individuals with long residual limbs or knee disarticula­
tion because the changing center of rotation allows the shin to
tuck under the thigh when sitting, resulting in a more natural
and cosmetic appearance of thigh and shin lengths. The poly­
centric knee unit's inherent stance phase stability also makes
it an option for individuals who have short residual limbs or
significant weakness of hip extensors. The major disadvan­
tage of the polycentric knee, with its multiple mechanical
joints, is its durability.
WEIGHT-ACTIVATED STANCE CONTROL
KNEE UNITS
The stance control knee has a braking mechanism that is acti­
vated when weight is applied through the knee during the
stance phase of gait (Figure 24-14). The intent of the braking
mechanism is to prevent (or at least reduce) unwanted knee
flexion during stance. The sensitivity of the braking mecha­
nism can be adjusted to match the individual's level of activ­
ity and ability to control the knee voluntarily. If initial contact
is made when the knee is not completely extended, as when
walking on uneven ground, the braking mechanism provides
additional mechanical stability to keep the knee from rapidly
buckling. During swing phase, the weight- activated stance
control knee unit functions like a single-axis knee and has
similar disadvantages. Advancement of the prosthetic shin
occurs at the same rate regardless of changes in gait speed;
minimal cadence responsiveness is present. This type of
knee unit is most often prescribed for individuals who have
recently undergone amputation, and who have short residual
limbs or weakness of hip extensors and would otherwise have
difficulty in actively stabilizing their prosthetic knees.
Manual Locking Knee Units
For patients who must rely on mechanical stability in stance,
the knee of choice is often a manual locking knee. This unit is
basically a single-axis knee with the addition of a locking pin
mechanism (Figure 24-15). The pin automatically locks with
a distinctive click when the knee is fully extended. Individuals
who use a manual locking knee unit walk with their pros­
thetic knees locked in extension. Although a locked knee
provides maximum mechanical stability in stance, it also sig­
nificantly compromises mobility and toe clearance in swing.
The prosthesis is often fit to be slightly shorter than the sound
FIGURE 24-14  A “cut-away” diagram (A) and photo (B) of a stance
control knee unit with extension assist for a transfemoral pros­
thesis. As body weight is shifted on the prosthesis in early stance,
compression of the spring causes the cylindrical brake bushing to
engage and resist the knee flexion moment associated with loading
response. This braking mechanism provides stability even if the knee
is slightly flexed during weight shift. When the knee is unloaded in
late stance/preswing, decompression of the spring leads to “unlock­
ing” of the brake, allowing free knee flexion for limb clearance dur­
ing swing phase. (A, Reproduced, with permission, from Shurr DG,
Michael JW. Prosthetics and Orthotics, 2nd ed. Englewood Cliffs,
NJ: Prentice Hall, 2002. p. 111. B, Courtesy Otto Bock Orthopedic
Industry, Inc., Minneapolis, MN.)
FIGURE  24-15  A manual locking knee provides maximum
stability when the knee is in the locked position. The knee can be
unlocked manually by manipulating a lever and cable system con­
nected to the knee.

Chapter 24  Transfemoral Prostheses
665
side limb to facilitate toe clearance during swing of the pros­
thesis. The prosthetic wearer can manually unlock the knee
by manipulating a pulley or lever system attached to the out­
side of the socket. This unit is often used in the initial training
prosthesis for patients when balance, endurance, or coopera­
tion may be problematic.
Hydraulic Knee Units
Hydraulic knee units are cadence responsive; the forward
progression of the prosthetic shin changes as gait speed
changes. This is because the flow of hydraulic fluid through
narrow channels within the prosthetic knee unit provides a
frictional resistance, which increases with the speed of com­
pression (Figure  24-16). This variable resistance permits a
swing phase that more closely simulates normal gait. As gait
speed increases, the shin of the prosthesis also extends more
rapidly. Little swing-phase delay is experienced in knee exten­
sion as compared with strictly single-axis or polycentric knee
units. This variable cadence characteristic has been help­
ful for both young, active individuals, and older adults with
mobility impairment.37 This enhanced function, however, is
associated with increased weight, higher maintenance needs,
and higher cost. Additionally, with colder temperatures the
knee may initially be slow to respond to changes in cadence
until the hydraulic fluid warms up from typical daily use.
Some manufacturers offer a variation of hydraulic knee
units that allow both variable cadence in swing and mechan­
ical stability in stance (swing and stance [SNS] control).33
Stance control occurs as a result of hydraulic resistance to
knee flexion during weight bearing or by a braking mecha­
nism that is activated by weight bearing through the prosthe­
sis. This feature allows the individual to ambulate with greater
confidence over uneven surfaces and also permits the use of
a more natural step-over-step pattern when negotiating hills
and going down stairs.
Pneumatic Knee Units
Pneumatic knee units offer the prosthetic user a varied
cadence capability, using air pressure dynamics in much the
same way that fluid is used in the hydraulic knee. Because air
is compressible, the channels within the knee can be adjusted
to affect the rate of swing. Pneumatic knees usually weigh less
and are less expensive than their hydraulic counterparts; how­
ever, they provide less precise cadence control and require
just as much maintenance. This is because hydraulic fluid is
denser and has a higher coefficient of viscosity than air.38
Microprocessor Technology
The initial theory of microprocessor knee control was devel­
oped in Japan in the early 1980s. Charles A. Blatchford &
Sons, Ltd, the developer of the Endolite carbon composite
prosthetic system, collaborated with a Japanese electron­
ics company to produce the first commercial application
of microprocessor control in a transfemoral prosthesis.39
The microprocessor swing phase control knee is known as
the Intelligent Prosthesis Plus (IP+). Since then the micro­
processor knee technology has been further developed into
well-known products such as C-Leg (Otto Bock Orthopedic
Industry, Minneapolis, MN), Rheo (Ossur, Iceland), and
Plie (Freedom Innovations, Irvine, CA). Microprocessor
knees are typically equipped with sensors that monitor the
knee position during swing and pressure sensors detecting
and evaluating ground related forces during stance. Sensor
technology is capable of measuring angles, moments, and
pressures at the rate of 50 times per second. Customized
adjustments are commonly made to microprocessor knees
using a laptop or handheld computer (Figure 24-17). Unique
software algorithms determine the phase of gait, then imme­
diately adjust the knee functions to compensate during both
the stance and swing phases of gait.40 Most knee mecha­
nisms provide a stumble recovery feature that limits unin­
tentional bending of the knee that sometimes occurs when
walking on uneven terrain. The microprocessor enables the
patient with transfemoral amputation to move in a natural
way, which makes it easier to navigate down stairs, slopes,
and uneven terrain.41,42 There is also a reported reduction in
energy expenditure and mental concentration required for
ambulation. Microprocessor knees are typically powered by
FIGURE  24-16  Example of a swing and stance, hydraulic, fluid-
controlled knee unit. This type of hydraulic unit is fit inside the knee
frame of an endoskeletal prosthesis or the shin section of an exo­
skeletal knee.

666
Section III  Prostheses in Rehabilitation
rechargeable lithium-ion batteries. In most cases batteries
can be fully charged in approximately 2 hours, and can last
for up to 24 hours when fully charged.
The current disadvantage of microprocessor technology in
prosthetics is the significant expense of such devices. The cost
of an entire prosthesis that incorporates a computerized knee
can be two to three times that of a prosthesis that features a
hydraulic knee.
Next-Generation Knees
Prosthetic knee technology becomes more advanced each
year. The next generation prosthetic knees feature actua­
tors that actively lift and stimulate the users own muscles
for walking up stairs, inclines and ramps. New micropro­
cessor knees provide what is being called “artificial intelli­
gence” features, which allow the systems to anticipate and
direct movement within “the whole state of the respective
human–machine interface.”43 These knees allow patients to
walk with greater efficiency upstairs, backwards, and over
obstacles.44
Additional Components
For individuals who require assistance to initiate knee
extension in early swing phase, an extension aid can be
incorporated into the prosthesis. An extension aid is usu­
ally an internal spring or an elastic strap that recoils from
an elongated position to accelerate the prosthetic shin into
extension during swing (see Figure  24-14, B). Extension
aids may also be useful to control excessive heel rise in early
swing phase.
Torque absorbers (axial rotation devices) are designed
to simulate axial rotation during stance, which would
FIGURE 24-17  Customized stance and swing phase adjustments can be made to the microprocessor
knee using a handheld or laptop computer.

Chapter 24  Transfemoral Prostheses
667
­normally occur in an intact anatomical limb. In the absence
of the ankle and knee joint, significant shearing forces can
occur at the socket–residual limb interface as the prosthetic
user pivots on the prosthesis. Torque absorbers are effec­
tive in reducing shearing, and may be especially useful for
individuals with fragile, sensitive skin, or adherent scars.
They are also often indicated for those involved with sports
or work that requires them to negotiate uneven ground.
Although these units reduce shear to the residual limb and
increase comfort during functional activities, they also add
weight to the prosthesis and are susceptible to mechanical
failure.
Transverse rotation units have been developed to allow
prosthetic wearers to passively rotate the shin section of
their prosthesis passively (Figure 24-18).45 An external but­
ton is pushed to unlock the unit, allowing a full 360 degrees
of rotation. The unit automatically locks once the knee is
moved back into its natural position. This type of device
allows the prosthetic wearer to sit in a crossed-legged posi­
tion, change shoes without having to remove the prosthesis,
and enter and exit automobiles with greater ease.
FIGURE  24-18  A transverse rotation unit is generally installed
between the socket and the prosthetic knee. When the unit is
unlocked, the individual can sit with legs crossed (e.g., to change
shoes without having to remove the prosthesis). (Reprinted, with
permission, from Otto Bock Health Care, Minneapolis, MN.)
CASE EXAMPLE 2
A Young Man with Multiple Trauma as a Result of a Motor Vehicle Accident
C. J. is a 23-year-old man who lost control of his motorcy­
cle on an icy roadway 10 days ago, sustaining moderate head
injury, traumatic amputation of the left lower extremity, and
comminuted fracture of the right femur. On admission, he
was taken to the operating room for debridement and closure
of his amputated limb, and open reduction/internal fixation
of his fractured femur. Initially responsive to pain and voice,
C. J. now fluctuates between level 4 (confused and agitated)
and 6 (confused and appropriate) on the Rancho Los Amigos
Cognitive Scale. C. J. is extremely agitated and combative while
in bed but calms somewhat when seated in a bedside chair. He
repeatedly requests to be allowed to get up to walk but cannot
comprehend the need to limit weight bearing on the fractured
side and doesn't seem to understand that he has lost his left
limb. The rehabilitation team wonders if his cognitive func­
tion will stabilize and advance if he can be upright. After much
discussion and debate, the team decides that C. J.'s residual
limb is healed sufficiently for early fitting with an IRC socket
suspended by a TES belt, with a locking knee and solid-ankle,
cushion-heel (SACH) foot. The team is hopeful that careful
early mobilization into upright posture will reduce his com­
bativeness without compromising his healing residual limb.
When elevated on a tilt table (with a 3-inch lift under the
prosthetic side to maintain the non–weight-bearing status
of the fractured extremity), C. J.'s cognitive function and
behavior improve rapidly. Within several days, he can step
off the tilt table and begin to ambulate, non–weight bearing
on the right, using a walker for short distances with mod­
erate assistance of one therapist. Over the next 3 weeks, he
becomes independent with crutches and continues to use
the locking knee until his fracture site heals enough to
safely tolerate full weight bearing safely. The team antici­
pates that his prosthetic prescription will be significantly
modified as he recovers from his head injury and is better
able to learn to use and control a more advanced knee unit,
prosthetic foot, and methods of suspension.
Questions to Consider
• Why do you think that an ischial containment socket was
selected for C. J.'s initial prosthesis? What are the advan­
tages and disadvantages when compared with a tradi­
tional quadrilateral socket?
• Considering his current cognition and non–weight-
bearing status, what are the advantages and disadvan­
tages of the locking knee unit that the team recommends?
Why do you think that they selected this option from
among the other types of knee units that are available?
• Why do you think that the team recommended a SACH
foot for C. J.'s initial prosthesis? What are the benefits and
tradeoffs of SACH, articulating, and dynamic response feet
for individuals with head injury in C. J.'s situation? (See
Chapter 21 for detailed information about prosthetic feet.)
• Would an extension aide, torque absorber, or transverse
rotational unit be appropriate at this point for C. J.? Why or
why not?
• What are the implications for safety, energy cost, and cos­
mesis of gait when using a locked knee and a SACH foot?
• As C. J. regains cognitive function and the fracture of
his right femur heals, what options might the reha­
bilitation team consider for his next prosthesis, in
terms of socket design, suspension, knee unit, and
prosthetic foot?

668
Section III  Prostheses in Rehabilitation
CHOOSING A PROSTHETIC FOOT
Individuals with transfemoral amputation and knee disar­
ticulation can use the majority of the prosthetic feet and
ankle options that are available (see Chapter 21). For some­
one with transfemoral amputation, one of the important
considerations in choosing a prosthetic foot is its influence
on stability of the prosthetic knee during stance. A foot that
can reach foot flat quickly (e.g., single-axis or multiaxial
foot) is preferable because it enhances stance phase knee
stability. Reaching foot flat quickly is especially important
for individuals who have a short residual limb or weak hip
extensors.
For active individuals, dynamic response feet and those
with flexible keels may have advantages. The energy-
storing capabilities of these prosthetic feet at push-off pro­
mote rapid advancement of the shin section during swing
phase. This enhances the ability of the individual who is
using a transfemoral prosthesis to walk at faster speeds.
Most of these feet are much lighter in weight than the
articulating feet.
GAIT CHARACTERISTICS IN TRANSFEMORAL
PROSTHETICS
Normal ambulation is a result of dynamic symmetric rela­
tionships of the head, spine, and upper and lower extremi­
ties. With a transfemoral amputation, an individual's gait
pattern wearing a prosthesis becomes significantly asym­
metric, regardless of the functional characteristics of the
prosthetic components.46 The more asymmetric the pat­
tern and uneven the cadence, the greater the energy cost
of walking. Asymmetry also increases the demand for
postural adaptation and balance reactions. For patients
with impairment of musculoskeletal and neuromuscu­
lar systems, which are common among those with diabe­
tes or advanced age, the incidence of instability and falls
increases significantly.
In normal gait, the muscles of the hip, knee, and ankle
work in three ways. First, muscle contraction provides
stability during stance by resisting the effects of gravity.
Second, during push-off and early swing phase, they act
to provide propulsion and accelerate the limb. Third, they
also act to decelerate forward progression, especially in
late swing in preparation for subsequent initial contact.
The loss of ankle and knee musculature as a result of trans­
femoral amputation compromises energy efficiency and
quality of gait.
Knee Stability
The most important goal in transfemoral prosthetics is to
obtain optimum knee stability throughout the stance phase
of gait. A prosthetic knee that is unstable or difficult to
c­ontrol during stance is a great danger, and could lead to
a serious fall. Alternately, a knee that is difficult to flex can
cause problems with swing phase clearance, increasing the
relative length of the limb and the likelihood of tripping
and falling.
Three variables influence knee stability during stance:
1. The individual's ability to voluntarily control the knee
using muscular power;
2. The alignment of the knee unit with respect to the
weight line (trochanter-knee-ankle [TKA] line); and,
3. The inherent mechanical stability of the knee unit.
Radcliffe introduced the “zone of voluntary stability” as
an important element in the alignment of the transfemo­
ral prosthesis.47 Radcliff states that the prosthetic knee will
be stable at the critical instant of heel contact if the knee
center is positioned within this zone. Knee stability can be
best understood by visualizing the TKA line,48 representing
body weight in stance (drawn from the greater trochanter to
the ankle of the prosthetic foot), and considering the posi­
tion of the knee with respect to the line (Figure 24-19). The
most appropriate position of the socket, knee, and ankle
components is the one that allows the individual to best
use his or her muscle control with the minimum amount of
alignment stability and still consistently stabilize the knee.
If the prosthetic knee is positioned slightly behind the TKA
line, so that the weight line passes anterior to the knee axis,
the resulting extensor moment provides alignment stabil­
ity during stance so that little muscular power is required.
However, this alignment also increases the muscular effort
and energy required to initiate knee flexion for the swing
phase of gait. If the knee is positioned at or slightly in front
of the TKA line, so that the weight line passes behind the
knee, the resulting flexion moment decreases stance phase
stability, making muscular power much more important.
However, this alignment enhances the ability to flex the
knee to initiate swing phase.
An individual's ability to voluntarily control the pros­
thetic knee is determined by the strength and endurance of
muscles around the hip and by the length of the residual
limb. If stance stability is provided primarily by voluntary
control, hip extensors must be forcefully activated at heel
strike to create an extensor moment at the knee. For an indi­
vidual with a knee disarticulation or long residual limb, the
long bony lever is a distinct advantage: An inverse relation­
ship between length of residual limb and amount of mus­
cular force necessary to control the prosthetic knee exists.
With a long limb, less muscular power is necessary to con­
trol prosthetic knee extension or to initiate flexion in the
early swing phase, and the prosthetic knee can be placed at
or in front of the TKA line. For an individual with a short
residual limb, much more muscular power is necessary to
achieve the same level of control. For this reason, stance
phase stability is provided by using a knee unit with high
mechanical stability or by aligning the knee unit posterior
to the TKA line. Voluntary control is also compromised for
patients with hip flexion contracture, weakness of hip exten­
sors, or physical frailty.
Prosthetists attempt to enhance muscular control by plac­
ing the transfemoral socket in a slight amount of flexion (in
relation to the hip). Slight elongation of the hip extensors
enhance their contractile ability just enough to develop an
effective force (against the posterior wall of the socket) to keep

Chapter 24  Transfemoral Prostheses
669
the prosthetic knee extended (see Figure 24-19).1,38 This also
reduces the individual's tendency to substitute for the weak­
ness of hip extensor muscles with excessive pelvic lordosis.
The amount of initial socket flexion is determined by the ini­
tial available range of motion at the hip joint. In preparation
for initial alignment (bench alignment), the prosthetist sets
the socket in 5 degrees of flexion, in addition to the number of
degrees of flexion contracture that may be present at the hip.
The stability or, conversely, the mobility of the knee is fur­
ther influenced by the mechanical properties of the prosthetic
knee itself. The degree of inherent stability of the knee var­
ies greatly among the different designs of commercially avail­
able prosthetic knees. Because a manually locking knee offers
ultimate mechanical stability, placement with respect to the
weight line and muscular power is of lesser importance. At
the other end of the continuum, a freely moving single-axis
knee offers virtually no mechanical stability; stance phase
stability must come from voluntary control, alignment, or a
combination of the two. The mechanical stability provided
by hydraulic swing and stance, and weight-activated stance
control knee units fall between these extremes. Especially
important is consideration of the contribution of mechanical
stability for individuals with short residual limbs and weak
hip muscles and those who routinely negotiate uneven or
rough terrain.
Pelvic Stability
Because of transfemoral amputation, the direct anatomical
connection between the femur and the ground surface is lost
and closed-chain, medial-lateral stability of the pelvis is signif­
icantly compromised.49–51 The femur, without its distal attach­
ment at the knee, is susceptible to marked lateral displacement
within the socket during weight bearing in the stance phase.
This lateral shift makes it impossible to maintain a horizontal
pelvis, even for individuals with strong hip abductor muscles,
and results in an apparent Trendelenburg sign and compen­
satory gait deviations (Figure 24-20). Pelvic stability is espe­
cially problematic for those with short residual limbs and
those who have developed flexion, abduction, and external
rotation contracture. The design of a quadrilateral socket pri­
marily applies stabilizing forces in the anteroposterior plane
so that there is little to keep the femur from drifting laterally
FIGURE 24-19  The imaginary trochanter-knee-ankle (TKA) line is a useful way to understand the
components of stance phase stability at the knee. A, Alignment stability is at its maximum when the
weight line (W) passes anteriorly to the knee axis. This is often important for prosthetic wearers with
short residual limbs or weak muscles or when initial socket flexion is increased more than the typical
five degrees of preflexion. B, Alignment stability is minimal when the weight line passes through the
center of the knee axis, making additional muscular or mechanical stability necessary. Many pros­
thetic wearers with midlength residual limbs and good muscular power benefit from the enhanced
initiation of swing that this alignment provides. C, No inherent alignment stability is present when
the weight line passes behind the knee axis; all of the stance phase stability must be provided by the
mechanical characteristics of the knee unit or by muscular activity, or both. Prosthetic wearers with
long residual limbs can best manage this alignment.

670
Section III  Prostheses in Rehabilitation
within the socket. As a consequence, the pelvis drops when the
intact limb is in swing phase. To compensate, the prosthetic
wearer often leans or lurches laterally toward the prosthetic
side. This strategy improves swing clearance but also results in
a wide-based, energy-taxing gait. Because the femur is held in
an abnormally abducted position, circumduction of the pros­
thesis during swing is likely to occur. In contrast, the design
of the IRC socket attempts to hold the femur in its normal
adducted position during stance with an upward and medially
directed force along the length of the lateral femur. This strat­
egy enhances the prosthetic wearer's ability to maintain a level
pelvis and improves the quality of functional gait.
EVALUATION OF SOCKET FIT AND ALIGNMENT
Despite all the technological advances in prosthetic knee
units, prosthetic feet, and materials, the single most impor­
tant influence on functional outcome in prosthetics is the
quality of socket fit. The socket is the interface between the
wearer and the prosthesis. It must comfortably contain soft
tissue when the patient is standing or sitting, furnish adequate
relief for bony prominences, distribute stabilizing pressure
to the femur and pelvis, and provide an adequate weight-
bearing surface for the ischial gluteal region.
Transparent diagnostic sockets (test sockets) are rou­
tinely used to assess socket fit.52 These thermoplastic sockets
are molded over the modified positive model of the resid­
ual limb as an interim step in socket fabrication. In the case
of skin suction suspension, the diagnostic socket is donned
without a sock or over a thin nylon sheath so that contact
with tissues and bony prominences can be clearly viewed
(Figure  24-21). Areas of excessive or inadequate pressure
can be detected according to the degree of skin blanching.
To make necessary reliefs or to enhance total contact, cor­
rections to the diagnostic socket are made by reheating the
socket with a hot air gun or torch. The socket may be tried
on and then modified several times before optimal fit and
comfort are achieved. Once proper fit has been established,
the diagnostic socket is filled with plaster or digitized to
create a new, accurate positive model for fabrication of the
definitive socket.
Donning Procedure
The first step in evaluation of socket fit is to ensure that the
socket has been donned properly. If the socket is not posi­
tioned correctly on the residual limb because of being rotated
or only partially donned , its fit cannot be accurately assessed.
Optimally, the socket fits easily but snugly over the residual
limb. If too many plies of prosthetic sock are worn, donning
is difficult and the person will feel as if the residual limb is not
fully down in the socket. If too few plies of sock are worn, the
limb falls more deeply into the socket and the person will feel
medial socket pressure at the pubic ramus as well as a high
degree of distal end pressure.
When suction suspension is used, the socket is slightly
more difficult to don because of the relatively tight total con­
tact fit that is required to maintain suction. Whether elastic
wrap, pull sock, or liquid powder is used, the donning proce­
dure must be consistent each time the prosthesis is donned.
Before the air-escape valve is screwed into place, total con­
tact between skin and socket is evaluated. The skin should
FIGURE  24-20  A, Normally, when weight is borne on the stance
limb the pelvis dips to the swing side because of gravity. Excessive
pelvic dip is prevented by contraction of the gluteus medius, on the
stance side, which is anchored to a femur fixed to the floor through its
distal attachment. B, The femur, without its distal attachment at the
knee, is susceptible to lateral displacement within the socket during
weight bearing. This displacement can make it difficult to maintain
a horizontal pelvis and results in an apparent Trendelenburg sign and
compensatory gait deviations. Pelvic stability is especially problematic
for those with short residual limbs. Lateral stabilization of the pelvis is
maintained by an anatomically aligned and shaped socket which mir­
rors the preamputation adduction angle of the femur.
FIGURE  24-21  Transparent diagnostic sockets are used to visu­
ally evaluate the prosthetic socket fit. Inspection of the skin through
the socket provides information about adequacy of residual limb
containment.

Chapter 24  Transfemoral Prostheses
671
­protrude slightly into the valve housing; however, tissue
should not be taut, bulging, painful, or discolored.
The size of the residual limb of individuals with recent
amputation can vary if adequate volume management has not
been maintained . Inconsistent use of elastic shrinkers or elas­
tic wrapping (Ace wraps) can lead to increased limb circum­
ference. Even small increases in limb size can compromise the
ability to don a prosthetic socket correctly, and can signifi­
cantly alter the quality of functional gait. The importance of
the consistent use of a shrinker or elastic wrap whenever the
prosthesis is not being worn cannot be overemphasized.
Total Contact Fit
Most prosthetic sockets are designed so that total contact is pres­
ent between the skin of the residual limb, the socket interface
(sock and/or roll-on-liner), and the walls of the socket. Total con­
tact fit distributes socket pressure over the entire surface of the
residual limb. Relief areas may be used to reduce pressure over
bony prominences, bone spurs, neuromas, or other pressure-
intolerant areas, but total contact is still the goal. Total contact
also promotes venous return from the tissues of the residual
limb and helps to reduce edema. Wherever contact is inad­
equate, the residual limb is likely to become edematous. Over
time, secondary skin problems are likely to develop as well.
Once the socket has been donned, it may be difficult to
determine if total contact has been achieved or to locate pre­
cise areas of discomfort or excessive pressure. Placing a small
amount of clay or powder or a thin film of lipstick inside
the socket before donning can assist with assessment of fit.
The person dons the socket as usual and then walks (or, if
too uncomfortable, stands) for several minutes. When the
prosthesis is removed, relatively even traces of the substance
should be found on the socks (or skin) of the residual limb.
Alternatively, lipstick can be applied to the sock (or skin for
suction suspension users) over the area of discomfort before
the prosthesis is put on. After donning as usual and wearing
for several minutes, the prosthesis is removed and the inside
of the socket is inspected. Traces of lipstick identify the area
of the socket that requires modification for pressure relief.
Sitting and Kneeling
Most people spend more time sitting than they do stand­
ing or walking. How the prosthesis feels when an individual
using a prosthesis is seated is important. The sitting surface
of the socket should be contoured so that the soft tissue
of the upper posterior thigh is not impinged between the
socket and the seat.53 To be comfortable in sitting and in
kneeling, individuals with transfemoral amputation must
be able to reach at least 90 degrees of hip flexion. If the
anterior wall of the socket is excessively high, the brim
impinges on the abdomen and the anterior superior iliac
spine. For those using pelvic belt and hip joint suspen­
sion, care should be taken to avoid painful pinching of flesh
between the socket and belt.
Another important consideration that relates to standing
and sitting is the suspension of the socket. When a person
wearing a transfemoral prosthesis sits down or stands up,
gaps may occur between the posterior-lateral corner of the
socket brim and the proximal residual limb.53
This lack of total contact causes a loss of the negative
pressure environment required for maintaining proper sus­
pension. One way to help prevent this problem is for the indi­
vidual to maintain control of the prosthesis and not allow the
muscles of the residual limb to go slack within the socket.
The individual should expand the muscles of the residual
limb, by an isometric contraction of the thigh, whenever
going through the motions of sitting down or standing up.54
Evaluating Socket Fit and Brim Contours
The Quadrilateral Socket
For the quad socket, the brim shape is rectangular, with a
narrow anteroposterior dimension (see Figure 24-3, A). The
primary weight-bearing surface, the ischial seat, is located
on the posterior–medial aspect of the brim. The seat should
be widest at the posteromedial corner to adequately support
the ischium and gluteal muscles. It should lie parallel to the
ground. The overall height of the prosthesis is measured as
the distance from this posteromedial corner to the ground
with the knee in full extension. A channel for the adductor
longus tendon is located at the anteromedial corner of the
socket. The anterior brim is higher than the ischial seat as it
moves toward the lateral wall. The contours of the anterior
wall, at the Scarpa's (femoral) triangle, provide a posteriorly
directed force to maintain the ischium on its seat.
The medial wall is a flattened surface that represents the line
of forward progression. The height of the medial brim is usually
the same as that of the ischial seat, fitting well into the groin. It
should not, however, create undue pressure on the perineum or
pubic ramus. For a person in whom an adductor roll has devel­
oped, the medial brim should be flared to accommodate the
extra tissue but not lowered. Excessive lowering of the medial
wall can exacerbate the problem. The primary function of the
lateral wall is to maintain a “normal” femoral adduction angle.
This is often difficult to achieve in the quad socket because
of the wide mediolateral dimension of the design. Pressure is
applied to the limb by flattening the socket along the femoral
shaft. A relief area is usually necessary to accommodate pressure
sensitivity of the distal lateral femur. The lateral wall completely
encases the greater trochanter and fits snugly around the gluteal
muscles as the socket wraps toward the posterior wall.7,8,11
The Ischial–Ramal Containment Socket
A proximal cross section of an IRC socket is more anatomi­
cally contoured in shape rather than rectangular, with a narrow
mediolateral dimension (see Figure 24-3, B and C). This design
more closely resembles the natural shape of the thigh. The brim
of this socket captures more of the adductor muscle complex
than does the quad socket. The ischial tuberosity and the pubic
ramus are contained in a fossa well within the socket. This cre­
ates a bony lock that provides mediolateral stability and reduces
the likelihood of socket rotation on the residual limb. The con­
tour of the posterior socket captures gluteal muscles. No ischial
seat is present because weight bearing occurs predominantly on
the soft tissues of the thigh, gluteal region and medial aspect

672
Section III  Prostheses in Rehabilitation
of the ischium.9–13 Because stability is provided in the medio­
lateral plane, the concave pressure in the Scarpa triangle on the
anterior wall is not as severe in comparison to the quad socket.
The medial wall of the IRC socket incorporates an adduc­
tor complex channel designed to contain all medial tissues.
This minimizes problems with adductor roll pinching. The
lateral socket wall is contoured in adduction, with additional
pressure against the posterior shaft of the femur for added
stability and rotational control. A pocket hollow or fossa is
incorporated into the lateral wall posterior to the greater tro­
chanter for a snug fit against the lateral gluteal muscles.
PROSTHETIC ALIGNMENT
The alignment of a prosthesis is defined as the orientation of
the socket relative to the prosthetic components of the pros­
thesis.55 The prosthetic alignment of a transfemoral prosthe­
sis greatly impacts the comfort and functional characteristics
of the prosthesis. Alignable endoskeletal prosthetic systems
allow the prosthetist to alter the manner in which the pros­
thesis transmits the weight load between the residual limb and
the ground. Optimal prosthetic alignment requires three steps:
bench alignment, static alignment, and dynamic alignment.56
Bench Alignment
Bench alignment is the alignment in which the components of
the prosthesis are assembled according to standards of practice
and manufacturer's guidelines. This step is employed to ensure
knee stability by aligning the prosthetic knee axis in a position
that will promote stability. The load line should pass through
the knee at a position dictated by the knee's kinematics and
the manufacturer's recommendations. The prosthesis is often
assembled in an alignment fixture using a plumb line or laser
line projected on the lateral side of the socket, knee, and foot.
Static Alignment
Static alignment is the alignment that is obtained after an indi­
vidual is comfortably fit in his or her socket and able to stand
transmitting weight onto the prosthesis. Typically, this evalua­
tion is performed with the patient standing within a set of parallel
bars to provide upper extremity support and stability. In addi­
tion to evaluating socket fit, the static examination focuses on: a
level pelvis (to check the height of the prosthesis), knee stability,
and the width of the base of support. The LASAR (laser-assisted
static alignment reference) Posture is a piece of equipment that
can assist the practitioner in examining static alignment.
Height of the Prosthesis
Patients are encouraged to shift weight mediolaterally until
they are comfortable with a symmetric standing position with
relatively equal weight bearing on the prosthesis and intact
limb. The prosthetist or therapist applies a firm downward
force through the iliac crests to ensure equal distribution of
body weight and then visually evaluates the position of the pel­
vis. Ideally the examiner's hands over the iliac crests will be in
the same plane, and the pelvis will be level (Figure 24-22, A).
Another way to evaluate this is by using a hip-leveling guide.
This device, which has a bubble level at its center, is placed
A
B
FIGURE 24-22  The height of the prosthesis should approximate that of the sound limb. A, One
method of checking for adequate prosthetic height is to assess whether the pelvis is level, by compar­
ing the height of the examiner's hands as they rest on the patient's iliac crests. B, A hip-leveling guide
is a device that uses a bubble level to determine if the pelvis is level. If the hips are level, the bubble
is centered. If the pelvis is not level, the bubble moves off center in the direction of the longer limb.

Chapter 24  Transfemoral Prostheses
673
over the individual's iliac crests. If the hips are level, the bubble
will be centered. If the pelvis is not level, the bubble will move
off center in the direction of the longer limb (Figure 24-22, B).
The initial transfemoral prosthesis may be up to one-quar­
ter inch shorter than the intact side to enhance toe clearance
in swing phase. Leg-length discrepancy of more than one-
quarter inch leads to back pain, gait deviation, and higher
energy cost in gait. The examiner can place one or more shims
or boards (cut in various increments of thickness) under the
“short” limb to determine the extent of the discrepancy if the
prosthesis appears to be too short or too long.
Evaluation of Knee Stability
When evaluating knee stability it must be quickly ascer­
tained whether the prosthetic user has a sense of security
with the prosthesis or fears that the knee will buckle under
full weight bearing. The prosthetic user must be able to
easily extend the prosthetic knee and maintain it in a stable
position. Stability of the knee can be altered significantly
if shoes other than those for which the prosthesis has
been aligned are worn (Figure  24-23). Shoes with lower
heels create an extension moment at the knee; the result­
ing stability is often excessive, and can interfere with
the knee flexion that is necessary in late stance and
early swing phase. Shoes with higher heels create a flex­
ion moment at the knee, reducing stance stability and
increasing the likelihood of the knee buckling at mid­
stance. Accommodating higher heels is difficult unless the
­individual uses a prosthetic foot designed specifically for
high heels.
A
B
C
D
FIGURE  24-23  Shoes with differing heel heights affect knee stability for individuals who are
using a transfemoral prosthesis. A, Most prosthetic feet are designed for a standard 3⁄4-inch heel. B,
Decreasing heel height creates an extension moment at the knee, leading to an excessively stable knee.
C, Increasing heel height creates a flexion moment, leading to instability of the prosthetic knee. D,
Special prosthetic feet are made for shoes with high heels.
CASE EXAMPLE 3
Why Should Changing Shoes Be an Issue?
P. O. is 21-year-old man who is learning the hard way about
the effects of improperly changing heel heights. Having
lost his leg just above the knee as the result of a motor
vehicle accident 2 weeks ago, he is fitted with a transfemo­
ral prosthesis, a flexible socket in a rigid frame, TES sus­
pension, weight-activated stance-control knee unit, and
dynamic-response foot while in the hospital. His knee unit
is positioned at the TKA line because of the long lever and
muscular control afforded by his residual limb.
After only a few days of inpatient therapy and education
concerning his prosthesis, P. O. is able to ambulate by using
a straight cane in a fairly symmetrical step-through pattern.
He often attempts to ambulate without aids, but whenever
he does, his physical therapist stops him immediately and
cautions him against varying from the therapy program
until his residual limb is sufficiently healed and tolerant of
full weight bearing on the prosthesis. At this point, he is able
to tolerate up to 3 hours at a time in his prosthesis and is
anxious to begin full-time “all-day” wear.
Despite his need to complete a therapy program, P. O.
discharges himself from the hospital against his physician's
recommendations. Before discharge, he is instructed on
the care of his prosthesis, the accommodation of limb vol­
ume fluctuation, the way to properly negotiate inclines and
stairs, and the impact of changing heel heights. He is also
cautioned to gradually increase his “in prosthesis” time to
minimize risk of skin breakdown or dehiscence of his heal­
ing suture line. P. O. ignores the booklets and instructions
he receives. He wants to “get back to life,” and 2 days after
discharge he wears his favorite pair of high-heeled cowboy
boots to go out partying with his friends. While negotiating
the first step out of his house, his prosthetic knee buckles
and he falls down the next two steps, fracturing the femur of
his residual limb and cracking the frame of his socket. He is
readmitted to the hospital for open reduction internal fixa­
tion and eventually learns to ambulate with a swing-through
pattern, using bilateral axillary crutches. He is discharged
from the hospital after 1 week but is not able to return to

674
Section III  Prostheses in Rehabilitation
Base of Support
The ideal distance between heels during comfortable stance is
relatively narrow, approximating the normal base of individu­
als without amputation (2 to 3 inches). The prosthetic foot and
shoe should lie flat on the ground with relatively equal weight
bearing on medial and lateral borders. This can be assessed
by slipping a piece of paper under both sides of the forefoot
and rearfoot—the distances should be fairly equal. The indi­
vidual must also be able to shift weight comfortably between
the intact and prosthetic limbs. The adequacy of the suspen­
sion system is evaluated by asking the patient to lift the pros­
thetic foot off the ground using a hip-hiking motion. Minimal
pistoning of the residual limb should occur within the socket.
LASAR Posture
The LASAR Posture is a laser platform apparatus used to
visually identify the center of gravity line, or load line, while
an individual is standing in their prosthesis (Figure 24-24).56
The LASAR Posture consists of a platform containing pres­
sure sensors and laser projection system. To measure the load
line, an individual steps onto the force sensor platform with
his or her prosthesis and places their contralateral leg on the
leveling step plate. A laser line is then projected directly on
the patient and prosthesis, whether in the frontal or sagittal
plane, identifying alignment parameters that can be objec­
tively documented.57 The dynamic alignment of the prosthe­
sis can then be optimized based on this static load line.
DYNAMIC ALIGNMENT
Dynamic alignment is the alignment made during basic
ambulation while an individual walks with or without
aids. According to Zahedi and colleagues, dynamic align­
ment is a progressive process in which a practitioner makes
adjustments to the geometrical configuration of the pros­
thesis until an alignment is achieved that is acceptable to
both the individual wearing the prosthesis and the pros­
thetist.55 The goal is to achieve a gait pattern that is safe,
comfortable, cosmetic, and energy efficient. The individ­
ual's ambulatory history, strength, endurance, activity
level, concurrent medical conditions, previous experi­
ence in wearing prostheses, and current goals are just as
important to consider as are the prescribed prosthetic
components.
Dynamic alignment begins with a walk down the length
of the parallel bars. Having an assistant or aid guard or assist
new prosthetic users as they walk is helpful so that the examiner
can focus on gait characteristics. For a complete understand­
ing of the dynamic interaction of patient and prosthesis, gait
must be observed from lateral–sagittal and anterior–posterior
perspectives.
LATERAL–SAGITTAL VIEW
Four key areas evaluated from the lateral perspective are (a)
knee stability throughout stance, (b) transition from initial
heel contact to foot-flat position, (c) symmetry of step length
and step duration, and (d) quality of knee flexion during late
stance and swing phase.
Stability of the knee is the major determinant of safe
ambulation. The new prosthetic wearer must learn to extend
the hip at initial contact (heel strike) to stabilize the prosthetic
knee adequately. Optimally, the knee will extend smoothly,
with little hesitation.
prosthetic use for the next 3 months. He returns to physical
therapy on an outpatient basis to begin the process of pros­
thetic training once again. This time, he is more cautious
and attentive to the instruction and advice of his rehabilita­
tion team. His story now serves as a warning about “what
not to do when you go home” to everyone who attends the
prosthetic clinic that assisted him.
Questions to Consider
• Describe the functional relationships among (a) mechan­
ical stability of P. O's weight-activated stance control
knee, (b) its alignment and position with respect to the
TKA line, and (c) the length of his residual limb. How
might the alignment of his knee unit be adjusted as his
limb heals and is better able to tolerate forces generated
during normal walking?
• What are the advantages of moving the axis of rotation
of the knee unit forward with respect to the TKA line?
Under what conditions would the prosthetist move the
axis of rotation of the knee until it is behind the TKA line?
What would you recommend for P. O. as he begins his
outpatient rehabilitation after his fractured femur heals?
• Why would the rehabilitation team be concerned about
the time P. O. spends in his prosthesis only 2 weeks
after the amputation? What would be an appropri­
ate wearing schedule for someone like P. O. who has
been had an early prosthetic fitting? In what ways
might the team's recommendation about in-prosthesis
time be different as P. O. begins his second period of
rehabilitation?
• Why did P. O.'s weight-activated stance control knee
become unstable when he changed into his cowboy
boots? What forces were acting at the knee at the time
that it buckled? Is there anything he could have done
to counteract the instability associated with higher
heels?
• What would have happened if he had instead put on a
pair of sandals with no heels at all? What types of func­
tional problems might he have encountered during
gait? How might he minimize the effect of changing
to shoes with lower heels and preserve his functional
abilities?
• What is the lesson from P. O.'s situation that should be
conveyed to individuals new to prosthetic use?

Chapter 24  Transfemoral Prostheses
675
Initial contact (heel strike) is the most unstable point in pros­
thetic gait. Stability in stance increases significantly when a foot-
flat position is reached. The transition from initial contact to
foot-flat position should occur relatively quickly and smoothly,
with the goal of reaching a position that promotes knee stability
without obvious “foot slap.” Quality of prosthetic gait and com­
monly occurring gait deviations are discussed later.
Optimally, the prosthesis and intact limb's step lengths are
equal in distance, symmetric in pattern, and even in cadence.
The individual should have little hesitation in initiation of
swing on the prosthesis or intact limb. Asymmetry in step
characteristics impedes the momentum necessary for energy-
efficient forward progression, increasing the work of walking
significantly.
Step length and swing phase function are influenced by
knee flexion during late stance phase. As the patient moves
from midstance into initial swing, a controlled and gradual
knee flexion optimally occurs to provide adequate toe clear­
ance during the swing phase of gait. Knee flexion that occurs
too early compromises stance stability and excessive knee
flexion during swing causes rapid heel rise.
ANTERIOR–FRONTAL VIEW
When viewing gait from an anterior or posterior perspective,
the examiner is most interested in adequacy of suspension,
width of the base of support, control of the pelvis during pros­
thetic stance, and quality and pattern of the prosthetic swing.
Suspension can be effective only if it is donned properly
and fit adequately to the individual. The examiner must deter­
mine if the prosthesis remains in optimal orientation on the
limb through all phases of the gait cycle. Pistoning or rotation
of the prosthesis should be minimal on the residual limb at
any point in the gait cycle, but especially during unweighted
FIGURE 24-24  The LASAR (laser-assisted static alignment reference) Posture is a laser platform
apparatus used to visually identify the center of gravity line, or load line, while an individual is stand­
ing in their prosthesis.

676
Section III  Prostheses in Rehabilitation
swing. Because the distal position of pistoning results in a rel­
ative lengthening of the prosthesis, wearers must use a com­
pensatory strategy to achieve toe clearance. One of the most
common gait deviations observed when suspension is incor­
rectly applied or inadequate is circumduction of the pros­
thetic limb during swing.
Optimally, a normal narrow base of support and swing
path is present with a two-three inch separation between
feet as they alternate between stance and swing. A wide base
increases energy expenditure and results in a less cosmetic
gait pattern.
The pelvis should remain relatively horizontal dur­
ing the prosthetic stance phase with a maximum drop of
5 degrees on the intact swing side for optimal cosmetic and
energy-efficient gait.1,7 For those with short residual limbs
or weakness of hip abductors, a level pelvis is a challenge to
maintain. In these instances, the pelvis drops noticeably to
the side of the intact swing limb during stance on the pros­
thesis. A compensatory pattern, such as lateral trunk bend­
ing, can be used to ensure adequate toe clearance of the
intact swing limb. The frontal plane alignment of socket,
knee, and foot plays a significant role in stabilizing the pel­
vis and trunk.
The line of progression of the prosthetic foot and knee
during swing phase is also assessed. Ideally the foot and knee
move forward in the same plane. If the prosthesis has been
donned improperly, evidence of a medial or lateral whip may
be seen with the foot circumscribing with an inward or out­
ward arc during swing phase (see Figure 24-28). All of these
factors should be considered by the prosthetist through diag­
nostic fittings and dynamic alignment sessions before deliv­
ery of the finished prosthesis.
VARIATIONS IN QUALITY OF GAIT
The pattern and quality of gait with a transfemoral prosthe­
sis can vary a great deal between treatment sessions, espe­
cially for those new to their prosthesis or recently have had
a change in prosthetic components. Most often, these varia­
tions in performance can be traced to intraindividual fac­
tors, rather than to malalignment or dysfunction of the
prosthesis itself. If unrecognized, some of these quite con­
trollable factors can significantly impede progress in gait
training and functional mobility. The most common prob­
lems encountered include inadequate volume control and
edema management, continued shrinkage of the residual
limb as it matures, inappropriate number of sock ply, inap­
propriate heel heights, skin irritation from overuse of a new
prosthesis, improper donning, inadequate suspension, worn
or loose components, and “patient innovation.” Effective
patient education and communication between the pros­
thetic clinical team and the patient can solve many of these
problems.58
Edema and Limb Volume
For a new prosthetic user who is having difficulty with
prosthetic fit and donning, one of the first questions
asked should concern compliance in wearing compression
­garments. An increase in limb circumference after only
15 to 30 minutes without wearing a shrinker or compres­
sive elastic wrap is common. The importance of routine
use of a compressive garment whenever the prosthesis is
not being worn (including overnight while sleeping) can­
not be overstated, especially for those within six months
of amputation. Even in an experienced prosthetic wearer,
limb volume can vary over the course of the day. Adding
or subtracting one or more ply of prosthetic socks at some
point during the day is not unusual. For those who need
the snug fit of suction suspension, edema is a serious prob­
lem that can prevent donning the prosthesis and achieving
suction. In this case, the compression garment or elastic
wrap should be applied for 15 to 20 minutes before don­
ning the prosthesis again.
Maturation and Shrinkage of the Residual Limb
New prosthetic users often experience rapid reduction of
limb volume as their time in the prosthesis increases over
the first few weeks and months after delivery of the pros­
thesis. Although this limb maturation may require several
socket adjustments until limb size stabilizes, it is a natu­
ral and important process that should be supported by the
use of compression whenever the prosthesis is not worn.
The loss of limb volume is usually accommodated by the
need to increase the number of ply of prosthetic socks
being worn to a 15- to 20-ply maximum. When more than
20 plies of sock are worn, intimacy of fit is compromised
and a new socket should be fabricated. Traditionally, the
use of skin suction suspension is not recommended until
limb volume has stabilized. For those using suction sus­
pension who experience further reduction in limb size
(e.g., because of weight loss, increased activity, time in the
socket), the prosthetist can add padding to the socket to
restore the intimate skin-socket fit necessary to restore
suction.
Inappropriate Number of Sock Ply
Because of the normal fluctuation in limb volume, the num­
ber of prosthetic sock ply required for appropriate fit also can
vary from day to day and within the same day. New and expe­
rienced prosthetic users often carry several one-ply socks
with them during the day so that they are prepared should
adjustment become necessary. Individuals wearing too many
ply of sock lose total contact with the distal portion of the
socket, complain of tightness at the proximal socket, and
feel as if the prosthesis is excessively long (this may be mani­
fested as difficulty with toe clearance in swing). Those who
have too few ply of sock experience increasing distal end pres­
sure or discomfort in the perineum because they are seated
too far down in the socket. New prosthetic users should keep
a record of the number of socks and overall ply (thickness)
they wear, as well as the frequency with which they adjust ply
during the day. This helps them to understand the dynamic
nature of limb volume size and enhance proper care of the
residual limb.

Chapter 24  Transfemoral Prostheses
677
Changing Footwear: Improper Heel Heights
All prosthetic feet are designed to be worn with shoes of a
particular heel height (see Figure 24-23). They are avail­
able in various heel heights, ranging from a heel rise of
0 mm for sandals and flats to a 45-mm heel rise for wom­
en's high heels. Matching the heel rise of the prosthetic
foot to the shoes most often worn by the patient is essen­
tial. A heel wedge placed inside the shoe can be used to
accommodate shoes that have a lower heel than what the
foot was designed for. Changing to shoes with significantly
lower heels results in excessive knee stability in stance.
Conversely, a change to shoes with much higher heels
compromises alignment stability of the knee and places
much greater demand on the patient for muscular control
of knee position during stance.
Impact of Overuse
Whether learning to use a training prosthesis for the first
time since amputation or being fit with a new definitive
prosthesis, most prosthetic users benefit from a gradual
break-in period. This strategy allows the skin, soft tissue,
and musculature to grow accustomed to the forces acting
on the residual limb. Failure to adhere to such a plan can
lead to muscle soreness, skin irritation, and, in some cases,
skin breakdown. New users should be advised to increase
the length of time in their prosthesis gradually, carefully
inspecting their skin each time the prosthesis is removed
and wearing an appropriate compression garment when not
in the prosthesis.
Improper Donning
When a prosthesis is not properly oriented on the residual
limb as a result of improper donning technique or incom­
plete donning, it cannot operate efficiently. The wearer may
experience discomfort within the socket or may exhibit vari­
ous gait deviations. Emphasis on developing a careful system­
atic method of donning is essential when working with new
prosthetic wearers. Attention to details when donning the
CASE EXAMPLE 4
Problem Solving When the Prosthesis Suddenly Doesn't Fit
A physical therapist calls a prosthetist colleague one morn­
ing to warn him that T. M., a businessman who 3 years ago
sustained a transfemoral amputation as the result of diabe­
tes, has called complaining about his new prosthesis. T. M.
had been comfortably fit with an IRC socket 9 weeks earlier
without difficulty. However, he now reports that his socket
is too small and he is not getting all the way down into his
prosthesis. He is fearful that the tightness he is experiencing
will cause skin breakdown, a frightening prospect for a per­
son with diabetes. T. M. is wearing a transfemoral prosthesis
with a stance control knee, dynamic response foot, and he is
using a locking roll-on-liner for suspension.
The prosthetist and physical therapist set up an appoint­
ment with the patient for reevaluation in the physical ther­
apy office the next morning. Their goal is to determine why
T. M., who has been wearing his prosthesis in excess of 10
hours a day for 9 weeks, is just now complaining about the
fit. When T. M. enters the clinic, he is obviously experienc­
ing discomfort and is not shifting his weight equally over
the prosthesis during the stance phase of gait. He has cho­
sen to return to using bilateral axillary crutches in an effort
to reduce his discomfort. The prosthetist and physical ther­
apist ask T. M. to take his prosthesis off so that they can
visually check whether any skin damage has occurred. They
find proximal redness and tenderness over the hip adduc­
tors. The prosthetist inspects the prosthesis as the therapist
examines her office notes from the man's last visit.
While watching the patient put on his socket, the physical
therapist recognizes the source of the problem. During T. M's
previous visit she had documented that he was wearing a sin­
gle three-ply sock over a 3-mm roll-on liner. Today he is don­
ning a five- and a three-ply socks over his roll-on liner. When
asked why he has increased the sock ply, T.M. reports that
since he had progressed from a liner-only fit to wearing an
additional three ply in 3 weeks, he thought that by 9 weeks he
should be wearing about eight to nine ply of sock. The pros­
thetist and therapist clarify with him the indicators of need
to increase sock ply. The patient returns to using a three-ply
sock over the liner and returns to the comfort he experienced
before the arbitrary addition of socks. He is relieved to be able
to ambulate once again without his crutches.
Questions to Consider
• What is the typical strategy for managing volume con­
trol and limb shrinkage in the first months following
amputation? Is there a typical rate of maturation of limb
volume that can be predicted? Why or why not? When
might a new user expect that his or her limb will reach a
stable size or volume?
• What are the indicators that an additional sock ply is
necessary in the first months of prosthetic wear? What
must a new prosthetic wearer understand to adjust sock
ply appropriately? How can the therapist or prosthetist
help a new prosthetic wearer master the art of changing
sock ply to adjust prosthetic fit?
• How would T. M.'s complaints about fitting be different
if he were wearing too few prosthetic socks?
• How many sock ply must a new user be wearing before it
is time for the prosthetist to fabricate a new socket? What
other indicators might there be that it is time for a change
in socket or suspension?
• How might improper socket fit (whether too many or too
few socks are worn) affect the prosthetic wearer's stabil­
ity in stance and mobility during swing phase of gait?

678
Section III  Prostheses in Rehabilitation
prosthesis can minimize the frustration, inconvenience, and
discomfort of having to reapply the prosthesis multiple times
until the desired position is achieved.
Inadequate Suspension
Inadequately tightened or badly worn suspension straps,
belts, or Velcro closures should be suspected when the
wearer experiences pistoning of the residual limb within
the socket. The prosthesis drops down slightly when it is
unweighted during swing, resulting in a relatively longer
swing limb and challenging toe clearance. Additionally,
the prosthesis may rotate on the residual limb, leading to
various compensatory gait deviations. New prosthetic users
should be encouraged to assess the adequacy of suspension
carefully and systematically each time they don the pros­
thesis. All prosthetic users must periodically inspect belts,
straps, or Velcro closures for signs of fraying, stretching, or
significant wear, and tear.
Worn or Loosened Components
As for any mechanical device subjected to daily use, the pros­
thesis should be periodically inspected for signs of excessive
wear or loosening of the components. Periodic maintenance
checkups with the prosthetist should be scheduled, especially
if the prosthetic wearer is involved in physically demanding
work or leisure activities. In some circumstances, the pros­
thesis may be misused or abused, increasing the likelihood
of damage to prosthetic components. Fixing a small problem
in the making is much less expensive than having to replace
major components or fabricate a new prosthesis because of
complete mechanical failure.
Patient Innovation
Prosthetic users who do not fully understand the intri­
cate alignment and design specifics of their prostheses may
attempt to modify them. If a patient who has been progress­
ing well in gait training and compliant with compression
strategies suddenly has difficulty with socket fit, patient inno­
vation should be suspected. It may be that padding has been
added or removed from inside the socket. If knee stability has
suddenly changed without any change in footwear, the wearer
may have attempted to fine-tune alignment or knee unit
function. Individuals who have questions about alignment
(including most physical therapists) should not make ran­
dom alignment adjustments, but instead rely on the knowl­
edge, equipment, and skilled experience of the prosthetist if
adjustment is necessary.
QUALITY OF TRANSFEMORAL
PROSTHETIC GAIT
The goal of a well-designed and accurately fit transfemo­
ral prosthesis is an energy-efficient gait in as natural a pat­
tern as possible. Quality of gait is inconsistent early in the
gait-training phase but improves as the individual becomes
more experienced with the prosthesis during therapy.
If gait problems persist, especially if the risk of instability
and falls or skin irritation is present, the source of the prob­
lem should be identified, and an attempt made to correct
it. A number of classic transfemoral prosthetic gait prob­
lems may be the result of prosthetic malalignment. Before
changing alignment or adjusting mechanical settings of the
prosthetic knee or foot, it is wise to rule out patient-related
factors (e.g., hip flexion contracture, weakness, habit) as
potential contributors.
Problems in Early Stance Phase
At initial contact, the prosthetic knee should be fully extended
to position the prosthetic foot appropriately for smooth load­
ing as body weight is transferred onto the prosthesis. As load­
ing occurs, the prosthetic foot rolls smoothly into a foot-flat
position. Problems with either of these functions increase the
risk of instability and shorten the swing time and step length
of the contralateral limb.
Knee Instability: Initial Contact to Midstance
If the prosthetic knee cannot maintain the necessary exten­
sion as the heel strikes the ground, and the prosthesis is
loaded, several possible prosthetic and patient-related fac­
tors should be considered (Figure  24-25). The most com­
mon patient-related problems that lead to knee instability
at initial contact include significant hip flexion contracture
or weakness of hip extensor muscles, which compromise
the patient's ability to stabilize the prosthetic knee by using
FIGURE 24-25  An unstable prosthetic knee during stance phase
often results in a quick, short step taken by the sound limb. The
problem may be caused by patient factors (e.g., hip extensor weak­
ness, hip flexion contracture) or anterior alignment of the pros­
thetic knee.

Chapter 24  Transfemoral Prostheses
679
active hip extension. If strength and range of motion are ade­
quate, four different prosthetic factors might lead to knee
instability:
1. The knee axis may be aligned too far anterior to the
TKA line, promoting a flexion moment.
2. The socket may not have been set in the optimal pre­
flexed position, which places the hip extensor muscles
at a biomechanical advantage for stabilizing the knee.
3. The prosthetic foot may have been aligned in excessive
dorsiflexion.
4. The plantar flexion bumper or SACH heel may be too stiff.
Foot Slap
The speed that the prosthetic forefoot descends to the floor at
heel strike is determined by the stiffness of the heel or plantar
flexion bumper and by how quickly or forcefully the individ­
ual loads the heel of the foot. If the prosthetic foot functions
with an apparent foot slap, two factors should be considered.
The heel cushion or plantar flexion bumper may be too soft
for the user's weight and activity level. Alternatively, those
prosthetic wearers fearful of instability in the early stance
phase may be forcefully driving their heels into the ground
to ensure complete knee extension. For those using a lock­
ing knee component, the ability to reach a foot-flat position
quickly is essential for a smooth transition throughout the
stance phase of gait.
External Rotation of the Prosthetic Foot
One of the gait deviations observed in the frontal plane is
an external rotation of the prosthetic foot at initial contact
and loading response as weight is transferred onto the pros­
thesis. This creates a rotary torque transmitted up the length
of the prosthesis to the residual limb/socket interface, and
can lead to skin irritation and discomfort. The most com­
mon prosthetic cause of this deviation is an excessively firm
heel cushion or plantar flexion bumper. Inappropriate toe-
out alignment of the prosthetic foot must first be ruled out.
When girth of the residual limb is decreasing (for individuals
in whom the whole limb is shrinking as it matures or in any­
one who has recently lost weight), fit within the socket may
be too loose so that the effect of even a small rotary torque
is manifested. Three user-related factors must also be con­
sidered. First, if there is weakness of hip muscles, the wearer
may be unable to maintain the limb in optimal alignment as
transition to stance phase takes place. Second, a wearer who
is fearful of knee instability in early stance may be extending
the prosthetic knee too vigorously at heel strike to ensure full
knee extension has been reached. Third, the shoe may be too
tight for the prosthetic foot.
Problems in Midstance to Late Stance Phase
In early stance phase, the primary goal is to ensure sufficient
stability of the knee while body weight is loaded onto the
prosthesis. In midstance to late stance phase, two additional
but equally important goals must be met: (a) smooth forward
progression of the body over the prosthetic foot and (b) effi­
cient preparation for the upcoming swing phase.
Pelvic Rise
Excessive pelvic elevation during the transition through mid­
stance and terminal stance is often a compensatory strategy
to achieve a smooth progression from foot-flat position to
heel off. The prosthetic wearer may make the classic state­
ment: “I feel as though I am walking up a hill.” The individ­
ual must exert an extra effort, substituting a rise of the pelvis
to roll over the toe-break area of the foot. This is most often
a consequence of inappropriate alignment of the prosthetic
foot, which may be excessively plantarflexed. Alternatively,
the foot may be positioned too far anteriorly with respect to
the knee and socket. Both conditions create a relative increase
in foot length, moving the fulcrum of the third rocker of gait
(toe rocker) farther forward.
Drop-off at Midstance
When relative shortening of the foot is present, the third
rocker is reached prematurely and stability of late stance is
compromised, just as relative lengthening of the prosthetic
foot leads to delayed forward progression and difficulty in
reaching the third rocker of gait. Prosthetic wearers may
sense knee instability and report that they feel like they are
stepping into a hole. A dropping off or lowering of the pelvis
often occurs because rollover occurs too early in the transi­
tion between midstance and terminal stance, rather than dur­
ing terminal stance to preswing. The stride of the swing limb
must be shortened to compensate for lack of stability in late
stance. Most often, this deviation is a consequence of inap­
propriate prosthetic alignment. The prosthetic foot may be
positioned in too much dorsiflexion. If an articulating/axial
foot is used, the dorsiflexion bumper may be worn out or
excessively soft. The durometer of heel cushion on a SACH
foot may be inappropriately soft for the patient's weight or
activity level. Finally, the transfemoral socket may be posi­
tioned too far anteriorly (excessive alignment stability) so that
the weight line falls toward the front of the foot at midstance.
All of these conditions functionally decrease the length of the
prosthetic foot, lead to premature rollover, and instability in
later stance.
Lateral Trunk Bending
A common gait deviation observed in the frontal plane is lat­
eral trunk bending toward the prosthetic side when the pros­
thetic limb is in stance phase. (Figure 24-26). If the lateral
prosthetic wall is not contoured to stabilize the femur in a nat­
ural position of adduction, drift of the femur into an abducted
position causes a drop of the pelvis on the swinging side. An
exaggerated lateral lean toward the stance (prosthetic) side
ensures adequate toe clearance. Lateral trunk bending is used
to avoid discomfort or excessive pressure in the perineum.
This may be a result of a medial wall that is excessively high
or rigid. Excessive pressure occurs when fleshy tissue of an
adductor roll gets pinched between the socket and the pubic
ramus, or when too few prosthetic socks are worn and the
residual limb is positioned too deeply in the prosthesis. Other
possible explanations include a socket that is aligned in exces­
sive initial abduction or a prosthetic foot excessively outset

680
Section III  Prostheses in Rehabilitation
from the midline position. In both instances, the base of sup­
port is functionally wider than normal, and the only effec­
tive way to shift weight onto the prosthetic side is by leaning
laterally. Finally, it is important to understand that it is diffi­
cult to provide lateral stabilization within the socket and align
prosthetic components in the ideal narrow base of support for
individuals with short residual limbs.
Problems in Swing Phase
The functional goal of swing phase is advancement of the
unweighted limb. The prosthetic wearer has two tasks: (a) to
initiate swing with enough hip flexion momentum to achieve
the prosthetic knee flexion that is necessary for toe clearance
and (b) to position the knee in extension in preparation for
initial contact.
Excessive Lumbar Lordosis
Some prosthetic users move into excessive lumbar lordosis
in late stance and into the early swing phase. This may be
the result of an alignment problem: The transfemoral socket
may not have been positioned in an appropriate amount of
initial flexion, especially for patients with a hip flexion con­
tracture. Patients with weakness of hip flexors or abdomi­
nal muscles may compensate by using exaggerated lumbar
motion to initiate hip flexion necessary for a functional
swing. Finally, lumbar lordosis may be a functional compen­
sation for an ineffective femoral lever in those with short
residual limbs.
Excessive Knee Flexion and Heel Rise
Excessive knee flexion/heel rise, a problem that occurs in initial
swing phase, can be observed in the sagittal plane of motion
(Figure 24-27). When the knee of the prosthesis flexes as swing
phase begins, the prosthetic knee continues in flexion with the
foot rising quickly away from the floor. If this heel rise is exces­
sive, it delays extension of the prosthetic knee as the swing
phase progresses. Prosthetic causes of this gait deviation include
inadequate flexion resistance settings in the knee unit, or inad­
equate adjustment of the knee extension aid. Adjustment of
friction or flexion resistance of the knee unit or replacement of
worn extension aids generally solves the problem.
Medial and Lateral Whips
Optimally, forward progression of the prosthetic knee and
foot occurs in the same line of progression, perpendicular
to the floor. A whip occurs when forward progression of the
distal parts of the prosthesis follows an oblique path. Whips
differ from circumducted gait because the thigh advances in
the expected, straight, forward line of progression, whereas
the shin and foot travel in an arcing pattern. Whips are most
easily observed while evaluating gait in the frontal plane. In
a lateral whip (Figure 24-28, A), the prosthetic knee appears
to rotate internally and the foot traces an arc of motion that
moves away from the midline. The possible causes of a lat­
eral whip are the exact opposite of those for a medial whip:
The knee unit may be prepositioned in too much internal
rotation, or the socket may have been positioned in a slightly
internally rotated position during donning.
FIGURE 24-26  Lateral trunk bending over the prosthesis is typi­
cally the result of discomfort or excessive pressure in the perineum.
FIGURE  24-27  Excessive knee flexion/heel rise in early swing
delays the extension of the knee, which is necessary to prepare for
the next initial contact.

Chapter 24  Transfemoral Prostheses
681
In a medial whip (see Figure  24-28, B), the prosthetic
knee appears to rotate externally so that the prosthetic foot
moves in an arc of motion that carries the foot toward mid­
line during swing. For some patients, the heels of the swing
and stance limbs narrowly miss contact at midstance and
midswing. Although this occurs when the prosthetic knee is
aligned in too much external rotation, it also can be the result
of several user-related factors. Medial whips occur when the
prosthesis is donned incorrectly in too much external rota­
tion or when the Silesian belt is worn too tightly and pulls the
socket into external rotation. Medial whips may also be the
consequence of poor purchase between skin and socket for
individuals using suction suspension, especially those with
“flabby” thigh tissue.
Terminal Impact
Excessive terminal impact is a gait deviation observed in the
sagittal plane during terminal swing. The shin of the pros­
thesis moves forward so quickly that the fully extended posi­
tion is reached early, often with an audible or visible impact
against the proximal section of the prosthetic knee. Prosthetic
factors that contribute to this deviation include insufficient
resistance to extension of the knee unit, an excessively strong
extension aid, or worn extension bumper. Prosthetic wear­
ers fearful of knee instability in early stance may choose to
flex the hip forcefully in initial swing to build momentum
for knee extension, then forcefully extend the hip in terminal
swing to snap the knee into full extension in preparation for
initial contact.
Vaulting
If the prosthetic wearer must rise up on the toes during
stance on the nonamputated limb to provide adequate clear­
ance for the prosthesis through midswing (Figure 24-29), sev­
eral possible prosthetic factors should be evaluated. First, the
adequacy and correct application of suspension should be
assessed. Second, if suspension is appropriate, adjustment of
swing resistance in the prosthetic knee should be considered.
Too much resistance to knee flexion and a foot set in exces­
sive plantar flexion may relatively lengthen the prosthesis and
compromise toe clearance in swing. Finally, if suspension and
knee unit friction are appropriate, the height of the prosthe­
sis should be double-checked to determine if the prosthesis
is too long.
FIGURE 24-28  A, In a lateral whip, the shin and foot swing in a lateral arc, as opposed to proceed­
ing straight in the line of progression. The cause of a lateral whip is that the knee is internally rotated.
B, In a medial whip, the opposite occurs. The thigh moves forward as expected, whereas the shin and
foot progress in a medial arc, typically the result of a knee set in excessive external rotation. Most
whips are the consequence of improper donning or suspension.

682
Section III  Prostheses in Rehabilitation
Circumduction During Swing
Optimally, forward progression of the prosthesis during
swing occurs in a straight line with enough knee flexion
for adequate toe clearance (Figure  24-30). If the pros­
thetic knee is maintained in extension, one compensatory
strategy would be to swing the limb in a wide lateral arc.
In this strategy, the peak distance from midline occurs
during midswing, and then the limb moves back toward
midline during terminal swing, in preparation for a nor­
mal heel strike at initial contact. This deviation most eas­
ily observed from a position in front or behind the patient
(frontal plane), is an attempt to compensate for a prosthe­
sis that is functionally or actually too long. Circumstances
that can lead to this compensation are similar to the vault­
ing deviation and include (a) inadequate suspension, in
which the prosthesis pistons downward as a result of the
force of gravity when unweighted during swing and (b)
a prosthetic knee unit that is locked in extension or set with
an excessive friction setting, preventing the knee flexion
necessary during swing phase. The pattern is also adopted
by prosthetic wearers who are nervous about catching their
toe during swing or who are reluctant to use knee flexion
because of anticipated instability in the subsequent early
stance period. Circumduction also can be the result of a
foot set in excessive plantar flexion, which makes the pros­
thesis functionally longer.
Other Issues
Ideally, an individual ambulating with a transfemoral prosthe­
sis walks with a narrow base with minimal sway. There should
be symmetry and evenness in stride length, cadence, and arm
swing so that the gait pattern appears to be as natural as possi­
ble. Excessive side-to-side sway and asymmetry in place of fluid
reciprocal movements increase the work and energy cost of
walking and are obviously different from a normal gait pattern.
Abducted Gait Pattern
In an abducted gait pattern, the prosthesis is held away
from the midline throughout the gait cycle. Functionally,
this is most notable in the stance phase of gait. In initial
contact, the prosthetic foot lands several inches lateral to
the ­normal or ideal foot position, resulting in a wide base
of support and requiring excessive side-to-side sway to
accomplish weight transfer from one limb to the other.
This deviation has a number of possible causes. The length
of the prosthesis may need to be reduced. The socket may
be aligned in a position of too much initial abduction.
Uncomfortable or painful pressure may occur in the groin
area (as in lateral leaning). An abducted gait pattern may
be a compensatory strategy when pelvic instability is a
result of inadequate lateral wall stabilization of the femur
or weakness of hip abductors. The prosthetic wearer may be
attempting to minimize lateral-distal femoral pain within
FIGURE 24-29  Vaulting is a common compensatory strategy for a
prosthesis that is functionally too long. The prosthesis may actually
be too long, have inadequate suspension, excessive friction of the
knee unit, an excessively plantarflexed foot or could be the result of
an acquired habit.
FIGURE 24-30  In a circumduction gait pattern, the entire prosthe­
sis swings in a wide lateral arc (as opposed to a whip where only the
shin section varies from the line of progression) to facilitate toe clear­
ance in swing. Prosthetic causes of circumduction include inadequate
suspension, a locked knee unit, or excessive friction in the knee unit.

Chapter 24  Transfemoral Prostheses
683
the socket. Finally, for those fearful of falling, an abducted
gait pattern may be a habitual movement strategy to mini­
mize feelings of insecurity.
Uneven Step Length and Swing Time
Early in prosthetic training, new prosthetic wearers may be
cautious and reluctant to use the prosthesis to its full capac­
ity. The goal of equal step length and swing time must be
emphasized. Patients gain confidence by practicing single-
limb support on the prosthetic side and performing gait train­
ing exercises that provide appropriate visual, kinesthetic, and
auditory feedback (e.g., equally spaced target marks on the
floor, use of mirrors or videotape). Several possible patient-
related issues or prosthetic problems, or both, should be con­
sidered if gait pattern asymmetry persists. First, the fit of the
socket and condition of the skin should be examined carefully.
Anyone would be reluctant to spend time in weight bearing if
tissue is being pinched or irritated within the socket, if relief
for bony prominences is inadequate, or if an inflamed or open
area or unrecognized neuroma is present. Second, hip flexion
contracture on the prosthetic side may limit excursion in hip
extension in late stance, compromising forward progression
of the opposite swing limb. If fit, skin condition, and range of
motion are adequate, the mechanical and alignment stability
of the knee unit should be reevaluated. A wearer who senses
that the knee cannot provide adequate support in stance will
compensate by shortening stance time to minimize the pos­
sibility of instability . Finally, individuals with impaired pos­
tural responses (poor balance) who are fearful of falling may
decrease the time spent in single-limb support by reducing
step length.
Uneven Arm Swing
Many individuals with amputations demonstrate diminished
or absent reciprocal arm swing when walking with their pros­
theses. They may hold their arms on the prosthetic side stiffly
and relatively still throughout the gait cycle. This is especially
common in a new prosthetic user who has not yet developed
confidence in the stability of the prosthesis as well as someone
with a painful residual limb. This behavior is also observed in
some proficient prosthetic users. The mechanism that under­
lies this alteration in motor behavior is not clearly under­
stood, but it may be related to loss of sensation from the distal
contact between the foot and the ground.
SUMMARY
Advances in technology and improved prosthetic components
have greatly benefited individuals with transfemoral amputa­
tion. This chapter has explained that the successful functional
outcome for individuals needing prosthetic care requires
more than advanced technology. A prosthetic team in which
the prosthetist and physical therapist are key contributors is
necessary. A thorough understanding of the interrelationship
between the prosthesis’ weight, function, cosmesis, comfort,
and cost is also required. Attention to socket design, knee bio­
mechanics, and prosthetic alignment is important in provid­
ing optimal patient care. The prosthetic clinical team's goal is
not merely to present an individual with a prosthetic product
but to provide ongoing comprehensive care that focuses on
the individual's needs, physical condition, and personal goals.
In this way, patients who require a transfemoral prosthesis
have an opportunity to reach their full functional potential.
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1. Radcliffe CW. Functional considerations in the fitting of
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12. Pritham CH. Workshop on teaching materials for above-knee
socket variants. J Prosthet Orthot. 1988;1(1):51–67.
13. Sabolich J. Contoured adducted trochanteric-controlled align­
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Clin Prosthet Orthot. 1985;9:15–26.
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femoral amputation. Prosthet Orthot Int. 1994;18:12–17.
15. Gottschalk FA, Kourosh S, Stills M, et al. Does socket configura­
tion influence the position of the femur in above-knee amputa­
tion? J Prosthet Orthot. 1989;2:94–102.
16. King C. Modern research and the forgotten prosthetic history of
the Vietnam war. J Rehabil Res Dev*. 2009;46(9):xi–xxxvi.
17. Pike A. A new concept in AK socket design. O&P Edge.
2002;1(7):34.
18. Patterson S. Editorial: experiences with negative-pressure socket
design. Acad Today. 2007;3(3):A7–A9.
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course. In: American Orthotic and Prosthetic Association, 93rd
National Assembly. Orlando, FL; September 30, 2010.
20. Mak FT, Zhang M, Boone DA. State-of-the-art research in
lower-limb prosthetic biomechanics-socket interface. J Rehabil
Res Dev. 2001;38(2):161–174.
21. Jendrezejczk DJ. Flexible socket systems. Clin Prosthet Orthot.
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22. Kristinsson O. Flexible above-knee socket made from low den­
sity polyethylene suspended by a weight transmitting frame.
Orthot Prosthet. 1983;37:25–27.
23. Dietzen CJ, Harshburger J, Pidikiti RD. Suction sock sus­
pension for above-knee prostheses. J Prosthet Orthot.
1991;3(2):90–93.
24. Ohio Willow Wood Company. Advanced alpha solutions.
Presented at the Summit Seminars, Mt. Sterling, OH; 2002.
25. Street GM. Vacuum suspension and its effect on the limb.
Orthop Tech. 2007;4:1–4.
26. Gerschutz M. Quantitative evaluation of elevated vacuum sus­
pension system effectiveness under dynamic conditions. In:
American Orthotic and Prosthetic Association, 93rd National
Assembly. Orlando, FL; September 30, 2010.
27. Gerschutz MJ, Denune JA, Colvin JM, Schober G. Elevated vac­
uum suspension influence on lower limb amputee's residual
limb volume at different vacuum pressure settings. J Prosthet
Orthot. 2010;22(4):252–256.
28. Beil T, Street G, Covey S. Interface pressure during ambulation
using suction and vacuum-assisted prosthetic sockets. J Rehabil
Res Dev. 2002;39:693–700.
29. Covey SJ, Muonio J, Street GM. Flow constraint and loading rate
effects on prosthetic liner material and human tissue mechani­
cal response. J Prosthet Orthot. 2000;12(1):15–32.
30. Lake C, Supan TJ. The incidence of dermatological prob­
lems in the silicone suspension sleeve user. J Prosthet Orthot.
1997;9(3):97–106.
31. Haberman LJ, Bedotto RA, Colodney EJ. Silicone-only sus­
pension (SOS) for the above knee amputee. J Prosthet Orthot.
1992;4(2):76–85.
32. Stark G. Overview of knee disarticulation. J Prosthet Orthot.
2004;16(4):130–137.
33. Mauch
Laboratories.
Manual
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Hydraulic Swing-N-Stance Control System. Dayton, OH: Mauch
Laboratories; 1976.
34. Moore KL. Clinical Oriented Anatomy. Baltimore: Williams &
Wilkins; 1980:553.
35. Radcliffe CW. Four-bar linkage prosthetic knee mechanisms:
kinematics, alignment and prescription criteria. Prosthet Orthot
Int*. 1994;18:159–173 36.
36. Gard SA, Childress DS, Uellendahl JE. The influence of four-
bar linkage knees on prosthetic swing-phase floor clearance.
J Prosthet Orthot. 1996;8(2):34–40.
37. Schuch CM. Prosthetic management. In: Bowker JH, Michael JW,
eds. Atlas of Prosthetics: Surgical, Prosthetic, and Rehabilitation
Principles. 2nd ed. St Louis: Mosby; 1992:528–529.
38. Mooney V, Quigley MJ. Above knee amputations: prosthetic
management. In: Bowker JH, ed. Atlas of Limb Prosthetics.
St Louis: Mosby-Year Book; 1981:381–401.
39. Datta D, Howitt J. Conventional versus microchip controlled
swing phase control for transfemoral amputees: user's verdict.
Prosthet Orthot Int. 1998;22:129–135.
40. Otto Bock Orthopedic Industry, Inc. Manual for the 3c100 Otto
Bock C-LEG. Duderstadt, Germany: 1998.
41. Seymour R, Engbertson B, Kott K, et al. Comparison between
C-Leg microprocessor-controlled prosthetic knee and nonmi­
croprocessor control prosthetic knees: a preliminary study of
energy expenditure, obstacle course performance, and quality of
life survey. Prosthet Orthot Int. 2007;31:51–61.
42. Kaufman KR, Levine JA, Brey RH, et  al. Energy expenditure
and activity of transfemoral amputees using mechanical and
microprocessor-controlled prosthetic knees. Arch Phys Med
Rehabil. 2008;89(7):1380–1385.
43. Ossur News. Next Generation of the Power Knee in Early Release
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Controlled Knees: Clinical Evidence and Background Information.
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45. Otto Bock Orthopedic Industry, Inc. Prosthetic Compendium:
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N Am. 1991;2(2):423–432.
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Prosthet Orthot Int. 1977;37:146–160.
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Prosthetic and Orthotic Practice. London: Edward Arnold;
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nants in normal and pathological gait. J Bone Joint Surg.
1953;35A:543–558.
50. Perry J. Gait Analysis: Normal and Pathological Function.
Thorofare, NJ: Slack; 1992.
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displacement of the trunk during normal walking. Gait Posture.
1997;5:233–238.
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thetic practices. Clin Prosthet Orthot. 1985;9(3):11–12.
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knee prosthesis. In Motion. 2001;11(5):14–15.
54. Kahle JT, Highsmith JM. Isometric training helps prevent socket
replacement. In Motion. 2003;13(3):66–67.
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lower-limb prostheses. J Rehabil Res Dev. 1986;23(2):2–19.
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Prostheses. Available at:
ob_us_en/08cat_5.pdf. Accessed January 7, 2011.
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prosthetic services. J Prosthet Orthot. 1989;1(4):242–249.

685
Prosthetic Options for Persons with High-Level and Bilateral
Lower-Limb Amputation
John W. Michael and Milagros Jorge
High-level transfemoral amputation and bilateral amputa­
tion of the lower extremity are the result of trauma or dis­
ease pathology such as peripheral vascular disease because
of health conditions such as diabetes. The twenty-first cen­
tury has started out to be a time of war in many nations
around the globe. The United States and other North
Atlantic Treaty Organization (NATO) countries have
engaged in war and military conflicts. Traumatic ampu­
tation associated with war due to the use of landmines,
improvised explosive devices (IEDs), and combat fire has
resulted in an increase incidence and prevalence of high-
level and bilateral lower-limb amputation.1 Peripheral
vascular disease either primary or diabetes related is the
leading cause of bilateral amputation in the United States.2
Such a significant limb loss presents a substantial challenge
to the patient, the prosthetist, and other rehabilitation pro­
fessionals. Successful prosthesis fitting is often time con­
suming and difficult; however, for many individuals with
high-level or bilateral lower-extremity amputation, pros­
theses can enhance the ability to increase functional inde­
pendence and mobility. This chapter summarizes key
concepts for high-level transfemoral and bilateral lower-
extremity prostheses prescription, fabrication, and reha­
bilitation based on clinical factors, research evidence, and
expected outcomes.
HIGH-LEVEL LOWER-LIMB LOSS
The first part of this chapter focuses on options for patients
with a unilateral high-level lower-limb absence, which is an
amputation at or above the hip joint. Hip disarticulation and
transpelvic and translumbar losses have been estimated to
comprise fewer than 2% of all amputations in the United
States.3 As a result, only those clinicians associated with
specialty centers, such as major trauma hospitals, have the
opportunity to see significant numbers of such cases. Most
prosthetists, therapists, and physicians see only a handful
of patients with such high-level loss in a practice lifetime.
One result of treating each high-level patient as one-of-a-
kind is that many differing approaches can be found in the
literature.
Etiology
Hip disarticulation is a relatively rare amputation. The inci­
dence is reported at 0.5% to 3.0%.3,4 There are three distinct
causes of hip disarticulation: vascular disease, trauma, and
malignancy. Vascular impairment, whether or not associated
with diabetes mellitus, is the most common cause for lower-
limb loss in the industrialized world. Dysvascular symptoms
are generally most pronounced in the distal limb, leading to
nonhealing ulceration, infection, gangrene, and ablation. The
trunk and a portion of the upper thigh are usually spared
even in the presence of severe peripheral vascular disease.
Although rarely, vascular disease at times, leads to high-level
amputation.5 The assumptions about healing, cardiovascular
limitations, and tolerance of activity derived from the experi­
ence with patients with dysvascular amputation do not apply
to those with high-level amputation. Most patients with high-
level amputation are relatively healthy and have reasonable
cardiopulmonary reserves, excellent cognition, and a strong
desire to attempt prosthetic fitting.
The more common cause for hip disarticulation or high-
level lower-limb amputation today is a traumatic injury result­
ing in life-saving emergency medical services and surgical
intervention. In civilian life, within the industrialized countries,
motor vehicle accidents are the most common cause of lower-
extremity amputation. The use of landmines in ­developing
25
LEARNING OBJECTIVES
On completion of this chapter, the reader will be able to do
the following:
1. Discuss the incidence and prevalence of high-level and
bilateral lower-limb amputations.
2. Describe the etiology of high-level and bilateral lower-
limb amputations.
3. Identify the two primary biomechanical limitations of hip
disarticulation and higher-level prostheses.
4. Estimate the relative energy cost of ambulation with high-
level or bilateral limb loss.
5. Describe the prosthetic and rehabilitation needs for per­
sons with high-level and bilateral lower-limb amputation.

686
Section III  Prostheses in Rehabilitation
nations throughout the twentieth century contributed to high-
level limb loss. Although the international community has
banned the practice of placing landmines, many landmines
still exist and continue to inflict trauma that results in high-
level amputation. Military conflicts in Iraq and Afghanistan
and the aggressive rebel tactic of use of IEDs has resulted in
wounded warriors that survive the trauma and are trans­
ported to military hospitals for medical care and rehabilitation.
Military hospitals are aggressively addressing the rehabilita­
tion needs of soldiers with amputation. The Intrepid Center
for Fallen Heroes Fund constructed the Center for the Intrepid
at Brooke Army Medical Center in San Antonio, Texas. The
Center for the Intrepid is a state-of-the-art rehabilitation facil­
ity for wounded warriors. Today, soliders with limb loss may
be able to continue their military careers. The Center for the
Intrepid rehabilitation programs work to maximize the func­
tional abilities of men and women whether they plan to return
to active duty or assume civilian life. Because of the prolonged
U.S. involvement in the Iraq and Afghanistan wars, there are
greater numbers of individuals with hip disarticulations.6
Many high-level amputations are performed for tumor of
the femur, such as osteosarcoma. Fortunately, the frequency
of tumor-related high-level amputation is decreasing with
advances in limb-salvage procedures and more effective che­
motherapy and radiation therapy.7–9 Patients who require
amputation because of tumor can be divided into two groups:
those with benign or fully contained tumors who require no
further oncological intervention and those undergoing che­
motherapy and radiation after amputation. Persons with
benign or fully contained tumors are typically in excellent
physical condition after the amputation, eager to return to
their former lifestyle as much as possible, and ready for early
prosthetic fitting. The benefits of early prosthetic fitting are
well established and are both physical and psychological.10
Early mobilization and single-limb gait training on the con­
tralateral limb with an appropriate assistive device is recom­
mended to reduce the risk of deconditioning, which occurs
even after a few days of hospitalization.11,12 The rehabilitation
and prosthetic management of patients requiring chemother­
apy or radiation therapy may have to be adapted or delayed
depending on the patient's physical condition, energy level,
tolerance of activity, and healing of the surgical site.
Most patients with high-level amputation should be
offered the opportunity for prosthetic fitting and rehabili­
tation. A multidisciplinary team rehabilitation team expe­
rienced in the management of persons with amputation is
essential to assure the most desirable outcomes.12
Biomechanics
Although, historically, loss of the entire lower limb assumed
the use of locked joints in the prosthesis, ample clinical evi­
dence is available that locked prosthetic joints are seldom nec­
essary. Since the 1950s, free-motion hip, knee, and ankle joints
for hip disarticulation and transpelvic prostheses have become
the norm. The Canadian design hip disarticulation prosthe­
sis was introduced by Colin McLaurin,13 and the biomechan­
ics of this prosthesis were clarified by Radcliffe in  1957.14
These  same biomechanical principles are also used in the
functional design of prostheses for patients with higher level
amputation.
In essence, the high-level prosthesis is stabilized by the
ground reaction force (GRF), which occurs during walking.15
For example, when standing quietly in the prosthesis, the
person's weight-bearing line falls posterior to the hip joint,
anterior to the knee joint, and anterior to the ankle joint.
The resultant hip and knee extension moments are resisted
by mechanical hyperextension stops of the prosthetic hip
and knee joints, and the dorsiflexion moment is resisted by
the stiffness of the prosthetic foot (Figure 25-1). This same
principle permits the patient with paraplegia using bilateral
Scott-Craig knee-ankle-foot orthoses to stand without exter­
nal support.16
Ambulation with a high-level prosthesis also relies on
the GRF (Figure  25-2). When an experienced prosthetic
wearer walks with an optimally aligned hip disarticulation
or transpelvic prosthesis, the dynamic gait is surprisingly
smooth and consistent. Patients with hip disarticulation or
transpelvic amputations who have sufficient balance and
strength can learn to walk without any external aids, although
the use of a cane is also common.
The basic functions of the GRF during ambulation with
one type of high-level prosthesis can be summarized as ­follows.
Weight-bearing
line
45°
45°
7E5
0-5 mm
Midfoot
SACH foot
18, 25, 35 mm
A1
10-15 mm
3R36
FIGURE  25-1  Static balance with a high-level lower-limb pros­
thesis is achieved when the GRF passes posterior to the hip joint
and anterior to the knee and ankle joints. The resulting extensor
moments at the hip and knee, and dorsiflexion moment at the ankle,
make the prosthesis stable. Mechanical stops in the prosthetic joints
prevent further movement, and the patient is able to stand without
exertion. SACH, Solid-ankle, cushion-heel. (Courtesy Otto Bock
Orthopedic Industry, Inc., Minneapolis, MN.)

Chapter 25  Prosthetic Options for Persons with High-Level and Bilateral Lower-Limb Amputation
687
At initial contact, as the prosthetic heel touches the ground,
the GRF passes posterior to the ankle axis, the heel cushion
compresses, and the foot is lowered to the ground. At the
same time, an extension moment is created at the prosthetic
knee as the GRF passes anterior to the knee joint axis (see
Figure 25-2, A). By midstance, alignment stability is maximal
as the GRF passes posterior to the prosthetic hip joint axis
and anterior to the prosthetic knee joint axis, just as it does
during quiet standing (see Figure 25-2, B). As forward pro­
gression continues into preswing, the GRF moves posterior
to the knee joint axis, allowing the knee to bend passively
to facilitate swing phase foot clearance while weight is being
shifted onto the opposite limb (see Figure 25-2, C).
Two major biomechanical deficits are inherent with hip
disarticulation and transpelvic prostheses: First, the pros­
thetic limb is always fully extended at midswing because of
the loss of active hip flexion. As a result, the length of the
prosthesis is typically shortened slightly, compared with the
remaining limb, to assist in toe clearance during the swing
phase of gait. The consequence of this strategy, however, is a
second biomechanical deficit—limb length discrepancy.17
Component Selection
The earliest hip disarticulation prosthesis designers insisted
on locking all prosthetic joints. Later, proponents of free-axis
joints for hip disarticulation prostheses advocated the use of
only basic components, such as a single-axis knee and ankle.
In recent years, a strong consensus has emerged that, to meet
the patient's functional needs and goals fully, components
for patients with hip disarticulation and transpelvic amputa­
tions should be selected for the same reasons and with the
same criteria as for those with transfemoral and transtibial
amputation.18,19
Choosing a Prosthetic Foot
All prosthetic feet have been successfully used for high-
level amputations. Nonarticulating designs are often chosen
because of their dependability, durability, and low mainte­
nance; these designs rarely require servicing as a result of wear
and tear. Single-axis feet (which allow the patient to quickly
attain a stable foot-flat position) are used when enhanced
knee stability is a concern. Multiaxial and dynamic response
designs are usually reserved for higher-activity individuals
who appreciate the added mobility of such components.20
Choosing a Prosthetic Knee Unit
The prosthetist selects a particular knee unit on the basis of
the patient's functional needs. Because of the biomechanical
stability of these prostheses, locked knee designs are rarely
necessary. Locked knee designs have two additional draw­
backs: they must be unlocked before sitting, and they may
increase the risk of injury in the event of a fall. When ­stability
A
B
C
FIGURE 25-2  The GRF at initial contact. From loading response through midstance (A) and termi­
nal stance (B) and just prior to preswing (C) of the gait cycle for patients using a unilateral high-level
prosthesis. Once properly aligned, the prosthesis will move in a consistent, predictable fashion and
permit slow but steady ambulation. The patient uses trunk motion to initiate and control prosthetic
movements. (From Van der Waarde T, Michael JW. Hip disarticulation and transpelvic manage­
ment: prosthetic considerations. In Bowker JH, Michael JW [eds], Atlas of Limb Prosthetics: Surgical,
Prosthetic, and Rehabilitation Principles, 2nd ed. St. Louis: Mosby-Year Book, 1992. pp. 539-552.)

688
Section III  Prostheses in Rehabilitation
is a primary concern, stance control or polycentric knees
may be most appropriate. Single-axis knees, when properly
aligned, also work well. The prosthetist might choose a pneu­
matic or hydraulic knee unit to provide fluid swing phase
control for patients who are active and want the ability to
change cadence.19 Most recently, quite encouraging clinical
results have been reported with a microprocessor-controlled,
hydraulic stance and swing control knee, allowing active indi­
viduals to descend stairs foot-over-foot with a hip disarticula­
tion prosthesis for the first time.21
Choosing a Prosthetic Hip Joint
The majority of patients with hip disarticulation benefit from
a free-motion hip joint, although locking joints are still some­
times chosen for those with quite limited ambulation capa­
bilities. Much effort has been made to provide some measure
of active hip flexion motion in these prostheses because that
would reduce or eliminate the key biomechanical deficits
previously noted. In prior decades, modification of the hip
joint by adding a coil spring mechanism that induced hip
flexion when the prosthesis was unweighted was tried with
some success, but maintenance and breakage of the spring
precluded widespread acceptance. More recently, a flexible
carbon fiber thigh “strut” that functions as a leaf spring has
been used clinically in selected cases. Initial reports suggest
that this approach increases cadence and that the improved
swing clearance achieved by better prosthetic hip and knee
flexion eliminates the need to shorten the prosthesis.22 The
use of vertical shock-absorbing shin elements and knees with
stance flexion features is also being explored, with encourag­
ing clinical acceptance.
Torque Absorbers
With the loss of three major biological joints of the lower limb,
a corresponding loss of the body's ability to compensate for
rotary motions inherent in gait occurs. For this reason, many
prosthetists strongly recommend that a torque-­absorbing
device be included in these high-level prostheses. Torque
absorbers typically improve both stride length and comfort by
absorbing transverse forces that would otherwise be transmit­
ted to the socket as skin shear.23,24 Incorporation of a lockable
turntable above the prosthetic knee is also suggested to facili­
tate common daily activities such as dressing and entering an
automobile (Figure 25-3).
Energy Consumption
The major unresolved drawback to prosthetic fitting for those
with high-level amputation is the tremendous increase in
effort required to control a prosthetic limb with passive joints.
Walking with a hip disarticulation or transpelvic prosthesis is
much like controlling a flail biological leg. The concentration
and energy required to ambulate makes short distance ambu­
lation much more practical than distance walking for all but
the most vigorous adult wearers.
Gait studies suggest that the use of a hip disarticulation
prosthesis requires approximately 200% more effort than
unimpaired walking.25 This is approximately the same effort
required when using axillary crutches in single-limb gait.
Because single-limb amputation with crutches tends to be
faster than walking with a hip disarticulation prosthesis, the
relatively high rejection rate of such prostheses is not surpris­
ing. Schnall and colleagues found that kinematic changes and
energy expenditure increased 100% or more during ambula­
tion in persons with hip disarticulation.6
Most rehabilitation professionals believe that any patient
with an amputation who is physically and mentally capable
of prosthetic use should, if interested, be fitted with an ini­
tial prosthesis. This recommendation is particularly true for
those with high-level amputation who may feel “cheated” and
become depressed if their clinical teams do not allow them to
try prosthetic ambulation.
Socket Design
A variety of socket designs have been described in the clini­
cal literature. The most critical factors for successful use are
careful fitting and secure suspension, regardless of which
socket design is selected. For patients with hip disarticulation,
encapsulation of the ascending pubic ramus may add stability,
although not every patient is able to tolerate a proximal trim
A
B
C
D
FIGURE 25-3  A lockable turntable (A) positioned in the prosthesis
above the prosthetic knee (B) makes dressing, entering an automo­
bile, and similar daily tasks much easier for individuals with high-level
amputation (C and D). A torsion adapter absorbs the torque forces
generated during gait and decreases the stress on both the patient's
skin and the prosthetic components. Such ancillary components
should always be considered for patients with high-level amputations.
(Courtesy Otto Bock Orthopedic Industry, Inc., Minneapolis, MN.)

Chapter 25  Prosthetic Options for Persons with High-Level and Bilateral Lower-Limb Amputation
689
line in the perineum.15,26 Flexible thermoplastic or silicone
materials within a rigid laminated frame are more comfort­
able and increasingly popular than the more common hard
plastic sockets (Figure 25-4).27–29
Suspension is achieved by carefully contouring the socket
just proximal to the iliac crests whenever possible. When the
patient is obese or has no ileum, shoulder straps may be nec­
essary to minimize swing phase pistoning of the prosthesis.
The transpelvic socket must fully enclose the gluteal fold
and perineal tissues and completely contain the soft tissues on
the amputated side. Full enclosure provides comfortable weight
bearing on the residual limb tissues despite the absence of hemi­
pelvis. Early transpelvic sockets extended upward to contain the
lower ribs.30 Clinical experience has shown that this may not
always be necessary for relatively muscular or lean individuals.
Failure to contain the transpelvic residuum adequately results
in obvious protrusion where the trim lines are insufficient.
Prosthetists modify the positive plaster model of the transpelvic
residuum to incorporate a diagonally directed compressive force
in the socket design to support and contain transpelvic tissues
and eliminate the risk of perineal shear and tissue breakdown.31
For patients with translumbar amputation, weight bearing
is achieved with a combination of soft tissue compression and
thoracic rib support. Because of the loss of more than half of
the body mass in this amputation, weight-bearing tolerance is
better than might be expected. Designs that allow the patient
to vary the compression by adjustable straps are often useful.32
Patients with translumbar amputation require a socket for
effective seating and wheeled mobility (Figure 25-5). Many
A
B
FIGURE 25-4  A, The interior of a hip disarticulation socket fabri­
cated from flexible silicone rubber. Note the contouring of the proxi­
mal brim to encase the crest of the ileum. B, Thermoplastic sockets
are also used for hip disarticulation prostheses. (From Michael JW.
Component selection criteria: lower limb disarticulations. Clin
Prosthet Orthot 1988;12[3]:99-108.)
FIGURE 25-5  For patients with translumbar amputation, a laminated
adjustable socket provides a stable base for sitting balance and wheeled
stability (left). The socket can be positioned within an outer shell with
bilateral prosthetic limbs (right) for cosmesis in sitting and for limited
prosthetic ambulation. (From Gruman G, Michael JW: Translumbar
amputation: prosthetic considerations. In Bowker JH, Michael JW
[eds], Atlas of Limb Prosthetics: Surgical, Prosthetic, and Rehabilitation
Principles, 2nd ed. St. Louis: Mosby-Year Book, 1992. pp. 563-568.)

690
Section III  Prostheses in Rehabilitation
patients with translumbar amputation successfully progress
to ambulation for short distances with a prosthesis and choose
to wear prosthetic limbs to enhance their cosmetic appear­
ance and self-image. Long-term followup demonstrates posi­
tive prosthetic outcomes; return to work or school is usually
a realistic goal.33 For most patients, polycentric knees provide
sufficient stability for the household ambulation typical of
this population, making locking joints unnecessary.
Rehabilitation Outcomes After High-Level Amputation
Despite the obvious challenges that face patients with high-
level amputation, a substantial percentage are able to manage
a prosthetic device with appropriate training and long-term
followup. Although the rate of prosthetic use varies, the trend
is toward increasing functional use of a prosthesis.6,7,34,35 Using
a multidisciplinary team approach and fitting by an experi­
enced prosthetist are believed to enhance the likelihood of
success and to improve functional outcomes.
BILATERAL LOWER-LIMB LOSS
The loss of both lower limbs complicates the rehabilitation
process, especially if the loss occurs simultaneously.12,36 In
North America, simultaneous bilateral loss is infrequent;
such cases are typically the result of traumatic transportation
or industrial accidents or electrocution. In the developing
world, simultaneous limb loss is more frequent; in areas of
armed conflict and postwar zones, roadside bombs and land­
mines are a major cause.37,38 Fortunately, most patients with
traumatic amputation are healthy and strong and generally
have a good prognosis for the successful use of prostheses.
The major cause of bilateral lower-extremity limb loss
is dysvascular disease. The Centers for Disease Control
reports the number of hospital discharges for nontraumatic
lower-extremity amputation with diabetes as a listed diagno­
sis increased from 45,000 in 1991 to 86,000 in 1996, when
it peaked, and then decreased to 66,000 in 2006. From 1988
to 2006, the number of discharges increased by 20%.39 When
vascular disease affects both limbs, as is often the case,
patients with a single dysvascular amputation face a signifi­
cant risk of eventual bilateral limb loss. An incidence as high
as 50% for contralateral limb loss over a 5-year period has
been reported.36,40 Clinical followup suggests that successful
use of a unilateral prosthesis increases the likelihood of suc­
cess with bilateral artificial limbs. For this reason, early fit­
ting after initial amputation is strongly advocated, even when
amputation of the opposite limb seems imminent.
The rehabilitation of persons with bilateral lower-­extremity
limb loss is similar to the rehabilitation of persons with uni­
lateral amputation.41 One major difference is that using two
artificial limbs is physically more difficult; thus, the pace of
advancement is slower and must be individualized according
to the patient's strength, balance, and ability. Breaking down
complex skills into small incremental tasks that can be more
readily mastered is generally useful. Without the benefit of
a sound limb, patients with bilateral loss can be expected to
walk slowly and cautiously, often with a relatively wide-based
gait that maximizes their sense of stability. Su and colleagues
investigated the gait characteristics of persons with bilateral
transtibial amputations and found that persons with amputa­
tions walked at slower speeds and lower cadences, had shorter
step lengths and wider step widths, and displayed hip hiking
during swing phase.42 Bilateral transfemoral amputees have
even greater energy expenditure and lower rates of full time
prosthetic use for functional ambulation.12
The use of balance aids such as canes are common, but
not universal, in the gait training and mobility ­rehabilitation
­process for persons with bilateral amputation. Environmental
barriers such as ramps, hills, irregular surfaces, and curbs or
stairs present special challenges that must be identified and
overcome. Specific training in sitting down, rising from a
chair, falling in a controlled manner, and recovering from a
fall are all important tasks to be mastered. Transfer with and
without artificial limbs is also an important skill to foster
independence. Persons with bilateral lower-limb amputa­
tion require a wheelchair for mobility for independent toi­
leting in the night and for times when the prosthetic legs
need repair.12
The rehabilitation of persons with bilateral lower-limb
amputation occurs in various phases, including a preop­
erative phases, if time permits, an immediate postoperative
phase, and acute rehabilitation phase. The rehabilitation pro­
cess is patient centered and should be individualized for each
patient, taking into account physical condition, biomechani­
cal loss, and prosthetic needs. The reason for the amputations
influences the pace and level of rehabilitation. Otherwise
healthy individuals who sustain traumatic limb loss may be
able to advance rapidly unless skin trauma is present on the
residual limbs. Early prosthetic fitting is a critical factor in the
long-term successful outcome for functional prosthetic use.12
Energy Cost
The effort required to use a unilateral prosthesis increases in
direct proportion to the level of amputation: the longer the
residual limb, the lower the energy cost of walking with a
prosthesis.43 Saving as much functional limb length as pos­
sible is therefore an axiom in amputation surgery. Although
preservation of the anatomical knee joint is important for
patients with unilateral amputation, it is a critical consider­
ation when bilateral limb loss is present: When at least one
biological knee joint remains, the chances for practical ambu­
lation significantly increase.12,44
Energy cost of ambulation is also related to the reason for
limb loss.45,46 In general, patients with dysvascular amputa­
tion have lower energy reserves and expend more effort
walking than those with traumatic amputation (Figure 25-6).
Long-term use of bilateral transfemoral prostheses is uncom­
mon, but not impossible, for elderly patients with dysvascu­
lar amputation.47 In contrast, a significant number of those
with traumatic bilateral transfemoral amputation success­
fully use prostheses long term.48 Patients with bilateral trans­
tibial ambulation tend to do well with prostheses regardless
of reason for amputation. Interestingly, bilateral transtibial
prostheses require less effort than a unilateral transfemoral