Plastic Surgery Volume 6: Hand and Upper Extremity (4th Edition) – Peter C. Neligan

9
Bones and joints
Fig. 1.10  Relationship of the radius and ulna at the proximal and distal radioulnar joints. (Reprinted with permission from © Elsevier Inc. All Rights
Reserved.)
Olecranon
Head
Neck
Radial tuberosity
Radius
Anterior surface
Anterior border
Interosseous border
Interosseous
membrane
Styloid process
Styloid process
of ulna
Radius
Ulna
Ulnar notch
of radius
Styloid process
Styloid
process
Area for scaphoid bone
Area for lunate bone
Carpal articular suface
Trochlear notch
Coronoid process
Radial notch of ulna
Ulnar tuberosity
Oblique cord
Oblique cord
Ulnar tuberosity
Ulna
Ulna
Lateral surface
Posterior border
Posterior surface
Anterior border
Anterior surface
Interosseous
membrane
Interosseous
border
Dorsal tubercle
Styloid process
Radius
Right radius and ulna
in supination: anterior view
Right radius and
ulna in pronation:
anterior view
Area for extensor
pollicis brevis and
abductor pollicis
longus muscles
Groove for extensor
digitorum and extensor
indicis muscles
Groove for extensor
pollicis longus muscle
Groove for extensor
carpi radialis longus
and brevis muscles
Coronal section of
radius demonstrates
how thickness of
cortical bone of
shaft diminishes
to thin layer over
cancellous bone
at distal end

10
SECTION I
CHAPTER 1 • Anatomy and biomechanics of the hand
(flexor retinaculum), is such that they make up a strong and
fixed transverse carpal arch (Box 1.3).
The complex motions of the wrist are a product of the sums
of the movements of the carpal bones in various planes and
degrees of rotation relative to one another. The motion of any
one carpal bone is a consequence of several factors. The first
factor is the contour of the bone and the arrangements of
its articular surfaces. The second is the degree of freedom
afforded by intrinsic ligaments, which are ligaments originat­
ing from one carpal bone and inserting on another carpal
bone, and by extrinsic ligaments, which are ligaments arising
from the radius or ulna and attaching to a carpal bone or
bones. This complex set of ligaments and the shape of the
intercarpal and radiocarpal articulations control movement
because no muscles arise or insert on any of the carpal bones
except for the pisiform.
This unique adaptation of nature avoids the need for a
thickly muscled wrist and hand unit. It permits great flexibil­
ity in positioning the hand in space without the need for sets
of muscle agonists and antagonists to control the several
degrees of freedom of movement.
The proximal row of carpal bones is anchored to the radius
by a series of stout palmar ligaments arising primarily from
the radius and by an additional set of stout ligaments arising
from the ulna and the palmar portion of the triangular fibro­
cartilage complex. The triangular fibrocartilage complex sepa­
rates the distal end of the ulna from the ulnar-sided carpal
bones and serves to suspend the distal ulna to the radius at
the distal radioulnar joint. These primary extrinsic palmar
ligaments take the form of an inverted “V” with its apex
pointed distally.
The three most predominant nerves innervating the trian­
gular fibrocartilage complex are the dorsal cutaneous branch
of the ulnar nerve (100%), the medial antebrachial cutaneous
nerve (91%), and the volar branch of the ulnar nerve (73%).
Other nerves play a minor role in the innervation of the tri­
angular fibrocartilage complex: the anterior interosseous
nerve, the posterior interosseous nerve and the palmar branch
of the median nerve.28
Fig. 1.11  X-ray of ulnar positive variance: this patient has ulnar-sided wrist pain
due to ulnar impaction syndrome.
Fig. 1.12  Gilula’s lines showing the greater arc and lesser arc of the carpal bones.
(Reproduced from Hentz VR, Chase RA. Hand Surgery: A Clinical Atlas.
Philadelphia: WB Saunders, 2001.)
BOX 1.2  Clinical pearl: blood supply to the scaphoid
Investigations by Gelberman and Menon have described two main
vessel systems that perfuse the scaphoid via ligamentous
attachments.27 The superficial palmar branch of the radial artery
contributes a volar blood supply that feeds the distal scaphoid. The
dorsal carpal branch of the radial artery contributes a dorsal blood
supply that also primarily feeds the distal scaphoid. Therefore, the
proximal scaphoid is poorly vascularized and is susceptible to
nonunion after proximal pole fracture.
BOX 1.3  Clinical pearl: checking for malrotation
The tubercle of the scaphoid is found at the distal flexion crease of
the wrist joint, lateral to the tendon of the flexor carpi radialis. It is an
important skeletal landmark in evaluating digital malrotations.
Normally, each finger points to the scaphoid tubercle when
individually flexed. A finger that points away from the tubercle may
do so because of destructive flattening of the carpal arch. More
commonly, it may result from malrotation following a metacarpal or
phalangeal fracture (Fig. 1.13).
joint. The pisiform is essentially a floating bone, unimportant
for carpal stability.
All four of the bones in the distal carpal row present articu­
lar surfaces for junction with the metacarpals. The distal
carpal row forms a solid architectural arch with the central
capitate as the keystone. The nature of the articulations of the
distal carpals with one another, and of the carpal ligament

11
Bones and joints
ligament is also composed of dorsal, proximal, and palmar
portions. There is less motion between these two carpal bones.
Disruption of either the scapholunate or lunotriquetral liga­
ments may lead to wrist instability as the normal restraints
on synchronous motion are removed.
Joint motion
The bony anatomy of the hand is presented in Fig. 1.14. Normal
metacarpophalangeal joint motion in the fingers ranges from 0
to 90°. Lateral activity in the metacarpophalangeal joints is
limited by the rein-like collateral ligaments. These ligaments
are loose and redundant when the metacarpophalangeal joints
are in extension, allowing maximal medial and lateral devia­
tion. As the metacarpophalangeal joint is flexed, the cam effect
of the eccentrically placed ligaments and the epicondylar
bowing of the collateral ligaments result in tightening and
strict limitation of lateral mobility (Fig. 1.15). The fingers that
have been fixed in extension during a period of healing have
had the stage set for collateral ligament shrinkage and locking
of the metacarpophalangeal joints in hyperextension.
The proximal interphalangeal joint can be pushed to 110°
of flexion, but extension usually cannot be carried beyond 5°
of hyperextension because of the ligamentous volar plate,
which is an inseparable part of the joint capsule. The medial
and lateral collateral ligaments are a part of the capsule. They
are radially fixed in a manner that allows no medial or lateral
deviation of the joint in any position. The shape of the articular
joint surface also strongly contributes to this stability in lateral
motion.
The distal interphalangeal joints of the fingers can be
pushed into about 90° of flexion before they are limited by the
dorsal joint capsule and extensor mechanism. The distal
interphalangeal joints extend to 30° of hyperextension. There
is no lateral mobility in these joints with the collateral liga­
ments intact. The collateral ligaments of the distal interpha­
langeal joints are simply thickened medial and lateral portions
of the joint capsule.
Dorsally, the extrinsic radiocarpal ligament complex is
thinner and is primarily a condensation of capsular tissues,
except for two stout structures, the dorsal intercarpal ligament
joining the distal pole of the scaphoid and the triquetrum, and
the dorsal radiocarpal ligament. According to work by Viegas,
these two dorsal ligaments form a unique lateral “V” configu­
ration that allows variation in length by changing the angle
of the “V” while maintaining a stabilizing force on the scaph­
oid during wrist range of motion.29
The intrinsic ligaments are broad, stout structures that
link one carpal bone to another, either within the proximal
or distal row, or linking one carpal row to the other. The
two most significant intrinsic ligaments are the scapholunate
ligament and the lunotriquetral ligament. The scapholunate
ligament anchors the scaphoid to the lunate to allow these two
carpal bones to move in synchrony. Berger has subdivided this
U-shaped structure into three regions: dorsal, proximal, and
palmar.30 The dorsal region is thick and controls scapholunate
stability. The proximal portion, composed mainly of fibrocarti­
lage, and the palmar region, with thin and obliquely oriented
fibers, are less important for stability.31 The lunotriquetral
Fig. 1.13  Each finger in correct alignment points to the tubercle of the scaphoid
when flexed individually. (Redrawn after Chase RA. Atlas of Hand Surgery, vol. 1.
Philadelphia: WB Saunders, 1973.)
Scaphoid
Biomechanical concept: joint motion
Brand and Hollister, in their textbook, Clinical Mechanics of the
Hand, discuss how joints move.32 An axis of rotation of a joint
refers to a line fixed to the proximal bone about which the
motion of the distal bone appears to be a pure rotation. For
the simple (hinge type) interphalangeal joints of the fingers,
the motion occurs only in flexion and extension; the axis of
rotation is perpendicular to the sagittal plane and is located in
the distal head of the phalanx proximal to the joint. A related
concept is that of the degrees of freedom of a joint. The
degrees of freedom of a joint are the minimum number of
axes of rotation that can be used to describe completely the
motion of the bone distal to the joint. The wrist as a whole, for
example, has two degrees of freedom (flexion–extension and
radial–ulnar deviation), represented by two nearly
perpendicular axes of rotation.33 The kinematics of more
complex joints such as the thumb carpometacarpal joint34 or
the intercarpal joints35 is still the subject of research and
thought to have at least two degrees of freedom with
nonintersecting, nonperpendicular axes of rotation.

12
SECTION I
CHAPTER 1 • Anatomy and biomechanics of the hand
Fig. 1.14  Bony anatomy of the wrist and hand. (Reprinted with permission from © Elsevier Inc. All Rights Reserved.)
Carpal
bones
Lunate
Triquetrum
Pisiform
Capitate
Hamate and
Hook
Base
Shafts
Head
Base
Shafts
Head
Base
Shafts
Head
Base
Shafts
Tuberosity
Head
Right hand:
anterior (palmar) view
Sesamoid
bones
Lunate
Scaphoid
Capitate
Trapezoid
Trapezium
Triquetrum
Hamate
Base
Shafts
Head
Base
Shafts
Head
Base
Shafts
Head
Base
Shafts
Tuberosity
Head
Right hand:
posterior (dorsal) view
Carpal bones
Metacarpal bones
Proximal phalanges
Middle phalanges
Distal
phalanges
Carpal
bones
Metacarpal bones
Proximal phalanges
Middle phalanges
Distal
phalanges
Carpal
bones
1
2
3
4
5
1
2
3
4
5
Scaphoid
and
Tubercle
Trapezium
and
Tubercle
Trapezoid

13
Bones and joints
interphalangeal joints, therefore, cannot be sacrificed without
creating a lateral instability that is curable only by fusion of
the interphalangeal joints.
Palmar or volar plates are found in the metacarpophalan­
geal and interphalangeal joints where they reinforce the joint
capsules, enhance joint stability, and limit hyperextension.
The plates of the MCP and IP joints are structurally and
functionally similar. The volar plates of the metacarpophalan­
geal joints are the sites of insertion of the intermetacarpal liga­
ments, which limit separation or fanning of the metacarpal
heads. The volar plate is fixed to that portion of the capsule
that originates from the proximal phalanx, and therefore the
plate moves with the proximal phalanx in flexion and exten­
sion. Dorsal to this ligament on each side of the metacarpal
heads are sagittal bands that connect the volar plates to the
tendon of the extensor digitorum and to the extensor expan­
sion. The volar plates to the proximal and distal interphalan­
geal joints are also stout structures that may become scarred
in cases of fracture/dislocation and may ultimately lead to
joint flexion contractures (Box 1.4).
The thumb
The thumb occupies the extreme radial position in the trans­
verse arch of the hand. The column of bones making up the
thumb architectural base comprises the two phalanges, the
metacarpal, and the trapezium. Its formula differs from that
of the remaining digits by virtue of its two named phalanges
rather than three. From a functional point of view, however,
the thumb metacarpal can be compared to a proximal phalanx
and the trapezium to a grossly foreshortened metacarpal. This
suggests that the thumb is a digit recessed by a short meta­
carpal (the trapezium) with the proximal phalanx loosely
syndactylized to the second metacarpal. There is no clear
evidence to support this point of view phylogenetically, but
it seems sensible in understanding the gross anatomy of the
thumb’s architecture. Like the finger metacarpophalangeal
joints, the thumb’s metacarpotrapezial joint has the greatest
degree of freedom of any in the digital rays. The metacarpo­
trapezial joint is a synovial joint separated and distinct from
the general intercarpal joints of the wrist. The trapezium itself
articulates with the trapezoid and scaphoid with ligamentous
restraints that sharply limit trapezial motion in relationship
to the carpus (Fig. 1.16).
The uniquely wide range of thumb motion as compared
with that of the remaining digits is attributable largely to
the joint between the base of the first metacarpal and the
trapezium. In simplest terms, it is described as a biconcave
double saddle joint with a permissively loose capsule. That
In each finger, there is no difference between the radii of
curvature of the ulnar and radial condyles of the middle
phalanx head. Conversely, the radius of curvature of the distal
phalanx ulnar groove is significantly greater than that of the
radial groove. This asymmetry between the distal phalanx
grooves and the middle phalanx results in a translational
component during the flexion of the distal interphalangeal
joint that may contribute to degenerative changes and devel­
opment of arthritis.36
The proximal and distal interphalangeal joints are hinge
joints: any lateral motion is limited in all phases of flexion and
extension by radially oriented collateral ligaments, which are
tight at any angle. The metacarpophalangeal joints, in con­
trast, allow motion through several axes. The capsule, includ­
ing the collateral ligaments and volar plate, is quite lax,
allowing medial and lateral deviation, flexion, extension, and
thereby circumduction and a small degree of distraction. In
the absence of other sources of stabilization, upon cutting
of the collateral ligaments the metacarpophalangeal joint
becomes a flail, unstable mechanism. Nature, fortunately, has
created another source of lateral stability – the interosseous
muscles. By virtue of the selective variable pull, the interossei
normally influence lateral motion in the metacarpophalangeal
joint to the extent allowed by the unyielding collateral liga­
ments. If the collateral ligaments are sacrificed, the interossei
remain the sole source of lateral stability. When there is intrin­
sic (ulnar) paralysis, if the collateral ligaments are sacrificed,
all lateral stability is lost and disastrous ulnar deviation
occurs. At the interphalangeal joints lateral stability is again
dependent on the collateral ligaments, but at this level there
is no second line of defense. The collateral ligaments of the
Fig. 1.15  (A–D) The true collateral ligaments of the metacarpophalangeal joint are
loose in extension but tight in flexion of the joint as a result of the cam effect of the
metacarpal head in relationship to the proximal phalanx. This accounts for the lack
of lateral mobility of the joint when it is flexed. (Redrawn after Chase RA. Atlas of
Hand Surgery, vol. 1. Philadelphia: WB Saunders, 1973.)
Maximum
mobility
Minimum
mobility
Hyperextension
45° Position of rest
Flexion
BOX 1.4  Clinical pearl: check rein ligaments
Check rein ligaments are, in fact, abnormal structures that are found
only after fibrosis of the proximal interphalangeal joint occurs.37 The
volar lateral ridges of the proximal phalanx are termed “assembly
lines” and represent a coalition of the flexor sheath and Cleland’s
and Grayson’s ligaments. Normally, there is no connection between
the volar plate and these assembly lines. However, in the proximal
interphalangeal joint with a flexion contracture, fibrosis has occurred
and stout check rein “ligaments” have formed from the volar plate
that prevent full joint extension.

14
SECTION I
CHAPTER 1 • Anatomy and biomechanics of the hand
or “beak” for insertion of the important anterior oblique car­
pometacarpal ligament, commonly referred to as the “volar
beak” ligament. As in some other joints in the body (e.g., the
shoulder), stability and close coaptation of the joint surfaces
between the trapezium and the first metacarpal are dependent
on the presence of operational muscles and tendons. As noted
above, there is a lot of slack in the joint capsule, allowing a
wide range of motion, including joint distraction of up to
3 mm.42
An important stabilizing capsular ligament for the first
carpometacarpal joint is the anterior oblique carpometacarpal
ligament or volar beak ligament referred to above. It extends
like the leg of a person seated in the trapezial saddle extend­
ing from the “beak” of the first metacarpal to the anterior crest
of the trapezium and adjacent intercarpal ligaments. It retains
the fragment of bone fractured free from the base of the
metacarpal as the metacarpal displaces radially in Bennett’s
fracture. In advanced metacarpotrapezial joint arthritis it
weakens and attenuates, as also does the intermetacarpal liga­
ment, allowing radial subluxation of the metacarpotrapezial
joint.43
The ligament at the radial border of the joint is like a radial
collateral ligament and is referred to as the dorsoradial or
anteroexternal ligament. Thus, the radial side of the joint
support is the right anteroexternal ligament, which inserts
close to but beneath the insertion of the abductor pollicis
longus on the radial base of the first metacarpal. It forms part
of the joint capsule and then attaches to the anterior crest of
the trapezium. Dorsally, one sees the posterior oblique liga­
ment crossing the dorsal joint capsule from the radially
positioned posteroexternal tubercle of the trapezium to attach
to the ulnar base of the first metacarpal.
There is a stout intermetacarpal ligament between the base
of the first metacarpal and the adjacent base of the second
metacarpal, and good evidence that this ligament together
with the anterior oblique ligament is a key to prevention of
radial subluxation of the metacarpotrapezial joint, as seen in
arthroses of the joint.44 Function and range of motion within
the limits imposed by these ligaments are influenced by the
extrinsic and intrinsic muscles of the thumb and the external
forces applied to the thumb. Bettinger and Berger have
updated this ligamentous anatomy to include 16 different
ligaments that are thought to stabilize the trapezium and
trapeziometacarpal joint.45
The first metacarpophalangeal joint differs from other
metacarpophalangeal joints in several respects in both ana­
tomic make-up and function. Generally, the first metacarpo­
phalangeal joint range of motion in flexion and extension, as
well as abduction and adduction, is less than that in the finger
metacarpophalangeal joints. The metacarpal and proximal
phalanx are more stout in order to accommodate to greater
forces normally borne by the thumb in pinching and grasping.
The head of the first metacarpal is different because the radial
articular prominence is larger than the ulnar. The articular
surface of the proximal phalanx is fashioned reciprocally
to match. The collateral ligaments are similar to those of
finger metacarpophalangeal joints. The metacarpophalangeal
portion is taut in flexion and looser in extension. In extension,
the portion of the fanlike collateral ligaments to the palmar
plate is taut; thus, adduction and abduction are limited in
both extension and flexion.46 Some pronation but no supina­
tion is allowed at the metacarpophalangeal joint when it is in
combination allows movements best described as flexion,
extension, adduction, and abduction through infinite combi­
nations that result in circumduction. The thumb rotates as a
cone with its apex at a point where the axes of flexion–
extension and abduction–adduction cross within the carpo­
metacarpal joint.38–40
The first carpometacarpal joint is best described as a double
saddle where one saddle sits atop another, allowing three
degrees of motion: (1) flexion–extension; (2) abduction–
adduction; and (3) medial rotation–lateral rotation.41 As the
thumb rocks along the central ridge of the trapezial saddle in
abduction and adduction, the metacarpal saddle’s extensions
over the trapezial saddle engage the trapezial saddle’s medial
or lateral condylar parts along the central axis. The axis line
is curved in such a way that when the metacarpal is adducted,
it locks into medial rotation, and when it is abducted, it locks
into lateral rotation. This accounts for the sweep of the thumb
in adduction to abduction along the transverse arch of the
metacarpal heads. This mandatory rotation into medial rota­
tion on adduction helps to position the thumb for pulp-to-
pulp opposition of the thumb to the fingers. In neutral position
the axis of the trapezium, represented by its central ridge, sits
at about 60° from a line through the heads of the central stable
second and third metacarpals. The base of the first metacarpal
has a quadrilateral articular surface that is a complementary
match to the articular surface of the trapezium. Its concavity
is slightly exaggerated on the ulnar volar side by a protrusion
Fig. 1.16  The osteoarticular column of the thumb as compared with that of a
finger. The trapezium in this comparison is the equivalent of a foreshortened
metacarpal, and the metacarpotrapezial joint of the fingers. MC metacarpal; PP
proximal phalanx; DP distal phalanx; ROM range of motion. (Redrawn after Chase
RA. Anatomy of the thumb. In: Strickland J (ed.) The Thumb. Edinburgh: Churchill
Livingstone, 1989.)
Hinge
Index finger
Thumb
DP
PP
MC
MC
PP
MP
DP
Trapezium
Scaphoid
Capitate
Hinge
Wide ROM
Limited ROM

15
Muscles and tendons
extension. In supination, the joint locks into a stable position
for secure grasping.
The sturdy fibrocartilaginous volar plate of the metacarpo­
phalangeal joint extends from the palmar base of the proximal
phalanx to the neck of the metacarpal. It regularly incorpo­
rates two sesamoid bones, one medial and one lateral to the
flexor pollicis longus.
The nature of the condyle of the proximal phalanx of the
interphalangeal joint to the thumb is such that, upon flexion
of the joint, pronation of the distal phalanx occurs.
Muscles and tendons
Extrinsic extensors (Video 1.1 )
Extensor muscles lie on the dorsum of the forearm and hand
and are innervated by the radial nerve (Figs. 1.17–1.19). The
brachioradialis is a flexor of the elbow joint but is included
with the extensor muscles because it is supplied by the radial
nerve. The brachioradialis and the extensor carpi radialis
longus originate from the lateral supracondylar ridge of the
humerus. The four superficial extensors (extensor carpi radia­
lis brevis, extensor digitorum communis, extensor digiti
minimi, and extensor carpi ulnaris) originate from the common
extensor tendon which is attached to the supracondylar ridge
and the lateral epicondyle.
The extensors can be divided by function. The extensor
carpi radialis longus and brevis and the extensor carpi ulnaris
serve to extend the wrist. The extensor digitorum communis,
extensor indicis proprius, and the extensor digiti minimi are
finger extensors. Three extrinsic extensors assist in thumb
motion: abductor pollicis longus, extensor pollicis brevis, and
extensor pollicis longus.
Biomechanical concept: muscle structure
Muscles are composed of tissue that can actively contract
under the influence of the brain and spinal cord to produce
hand and finger motion and forces by pulling on bones via
tendons.47,48 Muscle tissue is composed of parallel
arrangements of muscle fibers that can actively shorten and
passively resist stretching, but cannot actively lengthen. The
muscles of the hand anchor to bone at either end, typically by
a short tendon at their origin (proximal end) and a long tendon
at their insertion (distal end). Muscle fibers run along the
length of the muscle attaching to tendon at either end. The
aponeurosis is the transitional region where the contractile
fibers of the muscle interdigitate with the collagen fibers that
form the tendon. Tendons are stout parallel bundles of
collagen fibers that often cross multiple joints of the hand
before inserting into bone. Some tendons of the hand are
atypical as they bifurcate or combine before inserting into
bone to form the extensor mechanism (or extensor hood) of
the fingers. The lumbrical muscle is atypical as it both
originates from and inserts on to tendon (the flexor profundus
tendon and the extensor mechanism, respectively) and has no
direct bony attachment.
Striated muscle fibers are themselves parallel assemblies of
similarly long cells with multiple nuclei containing sarcomeres,
the fundamental contractile unit of muscle tissue. At the
biochemical level, sarcomeres are interdigitated filaments of
f-actin and myosin proteins. Muscle activation and contraction
occur when a neural command causes the release of calcium
ions inside the muscle cell to cause the free end of the myosin
filaments to “ratchet” past the f-actin filaments to increase the
overlap between them by metabolizing adenosine
triphosphate, an important source of energy fueling cellular
processes. The maximal force a muscle can produce is
proportional to the number of parallel muscle fibers that
compose it (physiological cross-sectional area), and the angle
the fibers make with the line of action of the tendons
(pennation angle). Mammalian muscle tissue is considered to
produce a maximal stress of around 35 N/cm2, which is a
remarkable ratio of force per unit weight that is difficult to
match artificially. In addition, the connective tissue that holds
together the muscle fibers grants muscle tissue passive
viscoelastic properties.
The extensor retinaculum prevents bowstringing of tendons
across the wrist (Fig. 1.20). Six extensor compartments exist
(Video 1.1
and Fig. 1.21): (1) abductor pollicis longus and
extensor pollicis brevis; (2) extensor carpi radialis longus and
extensor carpi radialis brevis; (3) extensor pollicis longus; (4)
extensor digitorum communis and extensor indicis proprius;
(5) extensor digiti minimi; and (6) extensor carpi ulnaris.
Extension of the phalanges of the fingers and thumb is
dependent both on long extensors at the metacarpophalangeal
joints and on an interplay between the long extensors and
intrinsic muscles at the interphalangeal joints. The extensor
digitorum is a series of tendons with a common muscle belly
that enters into the central extensor of each of the fingers.
There are intertendinous bridges between these separate
tendons over the dorsum of the hand. Independent long
extensor power is supplied to the index finger through the
extensor indicis and to the little finger through the extensor
digiti minimi. In each case the independent extensor lies on
the ulnar side of the long extensor tendon to these two fingers
from the extensor digitorum (Fig. 1.22).
Biomechanical concept: the extensor mechanism
of the fingers (Fig. 1.23)
The extensor tendons are attached by dorsal expansions or
dorsal hoods (Video 1.2
). These expansions are divided
into three structures. (1) Lateral bands pass on either side of
the proximal phalanx and extend all the way to the distal
phalanx. The lumbrical and dorsal and palmar interossei
muscles contribute to the lateral bands. (2) A single central
slip passes down the middle of the finger, ending at the base
of the middle phalanx. (3) The retinacular ligament runs
obliquely along the middle phalanx, and connects the fibrous
digital sheath on the volar side of the phalanges to the
extensor expansion.
The extensor hood of the fingers is an example of tendons
bifurcating and recombining in an intricate network that results
in complex muscle actions. For example, extensor muscles
can flex the proximal interphalangeal joints, and intrinsic
Text continued on p. 20

16
SECTION I
CHAPTER 1 • Anatomy and biomechanics of the hand
Fig. 1.17  The anatomy of the extensor muscles: superficial to deep. (Reprinted with permission from © Elsevier Inc. All Rights Reserved.)
Superior ulnar collateral artery
(anastomoses distally with
posterior ulnar recurrent artery)
Ulnar nerve
Medial epicondyle of humerus
Olecranon of ulna
Anconeus muscle
Flexor carpi ulnaris muscle
Extensor carpi ulnaris muscle
Triceps brachii muscle
Brachioradialis muscle
Extensor carpi radialis longus muscle
Common extensor tendon
Extensor carpi radialis brevis muscle
Extensor digitorum muscle
Extensor digiti minimi muscle
Abductor pollicis longus muscle
Extensor pollicis brevis muscle
Extensor pollicis longus tendon
Extensor carpi radialis brevis tendon
Extensor carpi radialis longus tendon
Superficial branch of radial nerve
Abductor pollicis longus tendon
Extensor pollicis brevis tendon
Extensor pollicis longus tendon
Anatomical snuffbox
1
2
3
4
5
6
Extensor carpi ulnaris tendon
Extensor digiti minimi tendon
Extensor digitorum tendons
Extensor indicis tendon
5th metacarpal bone
Dorsal branch of ulnar nerve
Extensor retinaculum
(compartments numbered)

17
Muscles and tendons
Fig. 1.18  The anatomy of the extensor muscles: superficial to deep. (Reprinted with permission from © Elsevier Inc. All Rights Reserved.)
Middle collateral branch of
deep brachial artery
Lateral intermuscular septum
Brachioradialis muscle
Extensor carpi radialis longus muscle
Lateral epicondyle of humerus
Common extensor tendon (partially cut )
Extensor carpi radialis brevis muscle
Supinator muscle
Posterior interosseous nerve
Pronator teres muscle (slip of insertion)
Radius
Posterior interosseous nerve
Abductor pollicis longus muscle
Extensor pollicis brevis muscle
Extensor carpi radialis brevis tendon
Extensor carpi radialis longus tendon
1
2
3
4
5
6
Radial artery
1st metacarpal bone
2nd metacarpal bone
1st dorsal
interosseous muscle
5th metacarpal bone
Extensor retinaculum
(compartments numbered)
Extensor digitorum tendons (cut )
Extensor digiti minimi tendon (cut )
Extensor carpi ulnaris tendon (cut )
Anterior interosseous artery (termination)
Extensor indicis muscle
Extensor pollicis longus muscle
Ulna
Posterior interosseous artery
Recurrent interosseous artery
Flexor carpi ulnaris muscle
Anconeus muscle
Olecranon of ulna
Triceps brachii tendon (cut )
Medial epicondyle of humerus
Posterior ulnar recurrent artery
Ulnar nerve
Medial intermuscular septum
Inferior ulnar collateral
(posterior branch)
Superior ulnar collateral
Branches of
brachial artery

18
SECTION I
CHAPTER 1 • Anatomy and biomechanics of the hand
Fig. 1.19  (A,B) The anatomy of the extensor muscles: superficial to deep. (Reprinted with permission from © Elsevier Inc. All Rights Reserved.)
Medial
epicondyle
Note: Anconeus muscle not shown
because it is extensor of elbow
Medial epicondyle
Olecranon
Lateral epicondyle
Common
extensor
tendon
Extensor
digitorum
and extensor
digiti minimi
(cut away)
Interosseous
membrane
Radius
Ulna
Olecranon
Ulna
Extensors of wrist
Extensor carpi
radialis longus
Extensor carpi
radialis brevis
Extensor carpi ulnaris
Extensors of digits
(except thumb)
Extensor digitorum
Extensor digiti minimi
Extensor indicis
Extensors of thumb
Abductor pollicis longus
Extensor pollicis brevis
Extensor pollicis longus
Extensor digitorum
and extensor digiti
minimi tendons (cut)
Extensor
indicis
tendon
Common
extensor
tendon
Lateral
epicondyle
Right forearm:
posterior
(dorsal) views
A
B

19
Muscles and tendons
Fig. 1.20  The extensor retinaculum and extensor compartments. (Reprinted with permission from © Elsevier Inc. All Rights Reserved.)
Posterior (dorsal) view
Extensor carpi ulnaris – Compartment 6
Extensor digiti minimi – Compartment 5
Extensor digitorum
Extensor indicis
Extensor pollicis longus – Compartment 3
Extensor carpi radialis brevis
Extensor carpi radialis longus
Abductor pollicis longus
Extensor pollicis brevis
Radial artery in anatomical snuffbox
Dorsal interosseous muscles
Compartment 4
Compartment 2
Compartment 1
Extensor retinaculum
Abductor digiti
minimi muscle
Intertendinous connections
Transverse fibers of
extensor expansions (hoods)
Cross section of most distal portion of forearm
Extensor retinaculum
Extensor pollicis longus – Compartment 3
Extensor carpi
radialis brevis
Extensor carpi
radialis longus
Compartment 2
Extensor
pollicis brevis
Abductor
pollicis longus
Compartment 1
Extensor digitorum and
extensor indicis
Extensor
digiti minimi
Extensor
carpi
ulnaris
Compartment 4
Compartment 5
Compartment 6
Ulna
Radius
Plane of cross section
shown below
6
5
4
3
2
1

20
SECTION I
CHAPTER 1 • Anatomy and biomechanics of the hand
The extensor pollicis longus inserts on the distal phalanx and
is the primary extensor of the interphalangeal joint. It second­
arily acts to extend and dorsally abduct the other two thumb
joints.
Pronators and supinators
The pronator teres originates from the common flexor origin
and inserts at the midportion of the radius (Fig. 1.24). It is
innervated by the median nerve and is a primary forearm
pronator and a weak forearm flexor. The pronator quadratus
is a short wide muscle that spans transversely across the distal
radius and ulna. It is also innervated by the median nerve and
is a forearm pronator. At the upper border of the pronator
quadratus muscle, the anterior interosseous artery pierces the
interosseous membrane and reaches the back of the forearm,
where it anastomoses with the dorsal interosseous artery (Fig.
1.25). The supinator originates from the lateral epicondyle of
the humerus and inserts on the proximal third of the radius.
It is inn ervated by the deep branch of the radial nerve and is
a primary supinator, assisted by the biceps brachii.
Extrinsic flexors (Video 1.3 )
Flexion of the phalanges into the palm is a complicated motion
representing the sum of actions of the long flexors (profundus
and superficialis) and long extensors (extensor digitorum,
extensor digiti minimi, and extensor indicis), modified and
enhanced by the intrinsic muscles (interossei and lumbricals)
(Figs. 1.26–1.31). The long flexors to the fingers are responsible
for flexion of the interphalangeal joints and are supplements
to active flexion of the metacarpophalangeal joints and the
wrist joint.58
Fig. 1.21  The extensor compartments. (Upper limb cadaver dissection, Stanford
University Division of Plastic Surgery. © 2015 James Chang, Anais Legrand. All
Rights Reserved.)
Extensor carpi radialis brevis
Extensor carpi radialis longus
Extensor pollicis longus
Extensor carpi ulnaris
Extensor digiti minimi
Extensor digitorum
Intertendinous connection
Extensor pollicis brevis
Abductor pollicis longus
Fig. 1.22  Anatomic relations of the extensor digitorum, extensor indicis and
extensor digiti minimi muscles. (Upper limb cadaver dissection, Stanford University
Division of Plastic Surgery. © 2015 James Chang, Anais Legrand. All Rights
Reserved.)
Extensor indicis
Extensor digitorum
Extensor digiti minimi
muscles can simultaneously flex the metacarpophalangeal
joint and extend the interphalangeal joints.49 The effect of each
muscle at each joint, however, may depend on finger posture
and the distribution of tendon tension. Detailed cadaver
studies have shown that, although the change in length of the
different components of the extensor hood is relatively
small,50,51 their spatial orientation varies considerably from one
finger configuration to another, and it has been suggested that
the extensor mechanism may act as a floating net to amplify
tendon forces52,53 or to coordinate joint motion.54,55 However,
the anatomy of the insertion of the extrinsic and intrinsic
muscles is quite complex and shows variations in the
geometry of muscle bellies and insertion tendons.56,57
Each of the three extrinsic muscles to the thumb on its
extensor surface inserts on one of the thumb bones. The
abductor pollicis longus inserts on the metacarpal where it
primarily radially abducts the metacarpal, but since it bridges
the wrist it secondarily radially deviates the wrist. The exten­
sor pollicis brevis inserts on the proximal phalanx, so that it
primarily acts as an extensor of the metacarpophalangeal joint
but acts at the other joints with the abductor pollicis longus.
Biomechanical concept: muscle force production
Muscles can produce force in different ways.59 Concentric
contractions occur when muscle fibers can shorten to induce
tendon stretch, tendon excursion, and/or joint motion.
Eccentric contractions occur when tendon forces overpower
the passive and active force the muscle can produce and the
muscle fibers lengthen during muscle activation. Isometric
contractions occur when the muscle is not allowed to shorten
(calling this state of the muscle a “contraction”, when in reality
it remains the same length, is a historical artifact). The
structural and biochemical properties of the sarcomere make
the exact magnitude of muscle force for a given level of neural
excitation a function of length of the fibers, velocity at which
fibers shorten or lengthen, and its previous activation history.
The force–length relationship of muscle (sometimes called the
Blix curve) indicates that there is an optimal length of the fiber
at which maximal force can be produced, and it drops at
longer or shorter fiber lengths (Fig. 1.32). Thus, the length at
which the muscle is placed in reconstructive surgeries or
tendon transfers can greatly influence the force the muscle
can produce postoperatively. The force–velocity relationship of
muscle indicates that muscle force drops greatly from its
isometric level when muscle fibers shorten rapidly during
concentric contractions, and rises to a plateau almost double
its isometric level when muscle fibers lengthen rapidly during
eccentric contractions (Fig. 1.33).

21
Muscles and tendons
Fig. 1.23  The extensor mechanism of the fingers. (Reprinted with permission from © Elsevier Inc. All Rights Reserved.)
Insertion of central band of extensor
tendon to base of middle phalanx
Triangular aponeurosis
Slips of long
extensor tendon
to lateral bands
Extensor
expansion
(hood)
Long extensor
tendon
Interosseous muscles
Metacarpal bone
Posterior
(dorsal)
view
Insertion on extensor tendon
to base of distal phalanx
Lateral bands
Interosseous
tendon slip
to lateral band
Lumbrical muscle
Part of interosseous tendon
passes to base of proximal
phalanx and joint capsule
Extensor expansion (hood)
Long extensor tendon
Metacarpal bone
Interosseous muscles
Lumbrical muscle
Flexor digitorum
profundus tendon
Lateral band
Central band
Insertion of extensor tendon
to base of middle phalanx
Insertion of extensor
tendon to base
of distal phalanx
Finger in
extension:
lateral view
Collateral
ligaments
Vinculum
breve
Vincula
longa
Flexor digitorum
superficialis tendon
Collateral ligament
Extensor tendon
Insertion of small deep slip of extensor
tendon to proximal phalanx and joint capsule
Attachment of interosseous muscle to
base of proximal phalanx and joint capsule
Insertion of lumbrical
muscle to extensor tendon
Finger in flexion:
lateral view
Palmar ligament (plate)
Flexor digitorum
superficialis tendon (cut)
Collateral ligaments
Flexor digitorum
profundus tendon (cut)
Palmar ligament (plate)
Interosseous muscles
Lumbrical muscle
Note: Black arrows indicate
pull of long extensor tendon;
red arrows indicate pull
of interosseous and
lumbrical muscles; dots
indicate axis of
rotation of joints

22
SECTION I
CHAPTER 1 • Anatomy and biomechanics of the hand
Fig. 1.24  The forearm pronators and supinators. (Reprinted with permission from © Elsevier Inc. All Rights Reserved.)
Right forearm: anterior view
Supinated position
Pronated position
Lateral epicondyle
Medial epicondyle
Lateral epicondyle
Medial epicondyle
Supinator
Pronator teres
Ulna
Radius
Ulna
Radius
Pronator quadratus

23
Muscles and tendons
Selected flexion of one or more of the metacarpophalangeal
joints, or either the proximal or distal interphalangeal joint,
depends on stabilizing fixation of the remainder by flexor–
extensor interplay. Elimination of any single motor element
reduces the selective adaptability of a finger.
As noted above, a muscle may positively influence any
joint between its site of origin and its insertion. The flexor
digitorum profundus muscle originates in the forearm, and
its tendon therefore bridges the wrist joint, the metacarpopha­
langeal joint, the proximal interphalangeal joint, and the distal
interphalangeal joint before it inserts on the distal phalanx. It
may flex any of these joints, depending on the dynamic fixa­
tion of the others. Fixation of the distal interphalangeal joint
converts the profundus tendon into a functional superficialis
tendon by recessing its prime site of action to the proximal
interphalangeal joint. By combined fixation of any of the
joints, the profundus tendon may primarily flex any selected
one.
The flexors are located on the volar side of the forearm and
wrist and are innervated by the median nerve, except the
flexor carpi ulnaris, and the flexor digitorum profundus to the
ring and small fingers, which are innervated by the ulnar
nerve (see Figs. 1.26–1.31). The flexor carpi radialis, flexor
carpi ulnaris, and palmaris longus provide wrist flexion. The
digital flexors (flexor digitorum superficialis, flexor digitorum
profundus, and flexor pollicis longus) pass through the carpal
tunnel to provide dual flexion to the fingers and single flexion
to the thumb (Video 1.3
).
The flexor digitorum superficialis tendon lies palmar
(superficial) to the profundus tendon in the palm.60 It flattens,
then splits at the level of the proximal phalanx, and its two
tails surround the profundus, decussating behind the profun­
dus to insert on the middle phalanx. The flexor digitorum
profundus perforates the flexor digitorum superficialis to run
superficially along the length of the proximal and middle
phalanges to insert at the base of the distal phalanx. The
superficialis and profundus flexors contribute most of the
force for digital flexion. The flexor digitorum profundus of
the index finger is unique in that it has an independent muscle
belly. The flexor pollicis longus inserts at the distal phalanx of
the thumb (Box 1.5).
In the finger and distal palm, the flexor tendons pass
through a fitted fibrous flexor sheath that has thickened areas.
The tendons at this level are surrounded by synovial sheaths.
The flexor pollicis longus is the interphalangeal flexor of the
thumb equivalent to the finger profundi. The flexor digitorum
profundus is the only muscle that flexes the distal interpha­
langeal joint. Testing for profundus function requires observa­
tion of active flexion of the distal interphalangeal joint.
Fig. 1.25  Anatomic relations between the pronator quadratus muscle and the
anterior interosseous artery. (Upper limb cadaver dissection, Stanford University
Division of Plastic Surgery. © 2015 James Chang, Anais Legrand. All Rights
Reserved.)
Anterior interosseous artery
Pronator quadratus
BOX 1.5  Clinical pearl: independent and common flexor muscles
The flexor profundi to the third, fourth, and fifth fingers work from a
common muscle belly. Acting in unison, they fit the architectural
concept of this unit as a stable vise for grasping objects. The
independent function of the index profundus frees the index finger
for use with the thumb to manipulate an object grasped by the
viselike ulnar unit. Independence of action is well developed in the
superficialis muscles and the intrinsic muscles.
Biomechanical concept: the shape of hand
muscles
Many muscles of the hand depart from the simple fusiform
(fish-like) shape seen in most textbooks. Many are flat, while
others have multiple bellies. The interosseous muscles, for
example, are bipennate. That is, a central common tendon is
pulled on by fibers originating in different bones. The opposite
arrangement is also found in muscles like the flexor
superficialis of the fingers, which originate in a short belly that
leads to a tendon that inserts in a second larger belly that
then subdivides into four branches, each with a superficialis
tendon to each finger. While it is possible to find muscle fibers
that fire only when one finger is being flexed,61,62 the degree to
which force production in each belly is independent of the
others is still unknown. Moreover, most extrinsic flexor and
extensor muscles have tendons that are connected by thin
strands of collagen at the level of the metacarpals that prevent
independent motions of the fingers (try to extend the ring
finger with all other fingers flexed). Other muscles such as the
adductor pollicis have a fan-shaped origin where the resultant
force at the insertion tendon depends on the distribution of
force among muscle fibers. Whether or not muscle fibers fire
in synchrony to produce a consistent resultant force, or if the
fibers can be subdivided in functional regions to produce
different resultant forces, is still unknown.
It is intriguing to realize that under certain conditions the
flexor profundus may accentuate extension of the proximal
interphalangeal joint. The profundus pulling primarily at
the distal interphalangeal joint may flex it acutely. In flexing
the distal interphalangeal joint, the insertion of the extensor
mechanism is advanced distally. This advancement, combined
with either a contraction or fixation of the lateral bands, results
in extension of the proximal interphalangeal joint. This effect
is easily aborted by the intact flexor superficialis, whose prime
flexion function is exerted on the proximal interphalangeal
joint. Absence of the superficialis, whether occasioned by
injury or by tendon graft replacement of the profundus only,
results not infrequently in flexion of the distal interphalangeal

24
SECTION I
CHAPTER 1 • Anatomy and biomechanics of the hand
Fig. 1.26  The anatomy of the flexor muscles, from superficial to deep. (Reprinted with permission from © Elsevier Inc. All Rights Reserved.)
Biceps brachii muscle
Brachial artery and median nerve
Lateral antebrachial cutaneous nerve
(terminal musculocutaneous nerve)
Brachialis muscle
Biceps brachii tendon
Radial artery
Bicipital aponeurosis
Ulnar nerve
Triceps brachii muscle
Medial intermuscular septum
Ulnar artery
Medial epicondyle of humerus
Common flexor tendon
Pronator teres muscle
Flexor carpi
radialis muscle
Palmaris longus
muscle
Flexor carpi
ulnaris muscle
Flexor digitorum
superficialis muscle
Superficial
flexor
muscles
Brachioradialis muscle
Extensor carpi
radialis longus muscle
Extensor carpi
radialis brevis muscle
Flexor pollicis longus
muscle and tendon
Radial artery
Median nerve
Palmar carpal ligament
(continuous with
extensor retinaculum)
Thenar muscles
Palmar aponeurosis
Hypothenar muscles
Palmar branch of median nerve
Pisiform
Ulnar artery and nerve
Dorsal branch of ulnar nerve
Palmaris longus tendon
Medial antebrachial cutaneous nerve

25
Muscles and tendons
augmented by the function of its antagonists at each of the
other joints it crosses. For example, a digital flexor tendon aids
in flexing the wrist, but its flexion capability within the digit
at the metacarpophalangeal joints and interphalangeal joints
is increased by wrist extension using wrist extensors, which
in fact are antagonists to the digital flexors at the wrist. This
is the simplified definition of synergistic function – finger
flexion augmented by wrist extension, and vice versa.
Synergistic and antagonistic groups of muscles in hand
function must be considered when functional substitution by
tendon transfers is contemplated. Obviously, certain groups
of muscles have developed functional synergism, which
makes readjustment natural when one group is transferred to
take on the function of the other. Examples of such natural
synergism are the united functions of the wrist flexors and
digital flexors or the wrist extensors and digital flexors.
In its course from forearm to fingers, the digital profundus
flexor crosses the palmar aspect of the wrist joint, the meta­
carpophalangeal joint, and the interphalangeal joints. The
relationship of the tendon to the joint axes is maintained by
retinacular structures, or pulleys. This prevents the bowstring
effect, which would allow the tendon to move away from the
joint axis, changing the moment arm and therefore the force
exerted at that joint by the flexor tendon. The finely balanced
relationship between the flexor muscle–tendon unit at each
joint in the series may be disrupted by such a change. Such
alterations can be compensated for, to some extent, by graded,
proportional changes in the controlled power of antagonists,
but the physiologic balance may be interfered with.
The retinacular system
The large, restraining pulley at the wrist, which serves all
the long digital flexors, is the transverse carpal ligament
(Fig. 1.35). It bridges the volar surface of the carpals from the
pisiform and hook of the hamate medially to the scaphoid
tubercle and trapezium laterally. It confines the nine extrinsic
flexor tendons and the median nerve within the carpal tunnel,
and prevents bowstringing of the flexor tendons at the wrist.
Three pulleys housing the flexor pollicis longus within the
thumb are usually present. The proximal annular pulley is at
the level of the metacarpophalangeal joint arising from the
volar plate and base of the proximal phalanx. The distal
annular pulley is located over the volar plate of the interpha­
langeal joint. Between the two is a single oblique pulley that
originates proximally on the ulnar side of the middle phalanx,
where it also gains fibers from the adductor pollicis before it
extends to the middle one-third of the radial palmar surface
of the middle phalanx. The oblique pulley must be preserved
in order to prevent bowstringing of the flexor pollicis longus
tendon.
Four or five discrete annular pulleys and three cruciate
bands are ordinarily present in the fingers (Fig. 1.36). The
most proximal pulley (A1) begins 0.5 cm proximal to the
metacarpophalangeal joint. It is anchored to the volar plate
and the proximal phalanx. Just distal to it is the second annular
band (A2), which is the largest pulley, extending to nearly the
proximal one-half of the proximal phalanx. The first cruciform
band (C1) lies distal to A2 and well proximal to the proximal
interphalangeal joint. The third annular pulley (A3) lies over
the proximal interphalangeal joint arising from its volar plate.
joint with recurvatum deformity at the proximal interpha­
langeal joint. This can be corrected by fusion of the distal
interphalangeal joint, making the profundus a functional
superficialis, or by tenodesis or capsulodesis of the proximal
interphalangeal joint in mild flexion. It is wise to keep in
mind the innumerable functional circumstances that can be
created by selective interplay of multiple motor forces exerted
through a series of interdependent joints.63
Fig. 1.27  The anatomy of flexor muscles in relation to surrounding neurovascular
elements. (Upper limb cadaver dissection, Stanford University Division of Plastic
Surgery. © 2015 James Chang, Anais Legrand. All Rights Reserved.)
Ulnar nerve
Ulnar artery
Flexor carpi ulnaris
Flexor carpi radialis
Brachioradialis
Palmaris longus
Flexor digitorum
superficialis
Radial artery
Biomechanical concept: moment arms
The moment arm of a tendon about an axis of rotation of a
joint is defined as the shortest distance between the axis of
rotation and the tendon as it crosses the joint (Fig. 1.34). This
distance can vary with joint angle because of the suspension
system of pulleys guiding flexor tendons, and/or the curved
but not circular contour of the joint surfaces guiding extensor
tendons.63 The greater the moment arm, the greater the
excursion of a tendon (and change in length of a muscle) that
accompanies a given angle of rotation of the joint. Similarly,
the moment of force (rotational action) of a tendon force about
an axis of rotation increases with the magnitude of the
moment arm of the tendon. These relationships between
moment arm and tendon excursion/force assume hinge-type
joints without sliding actions, which holds well for most finger
joints. Note that a tendon that crosses a joint with multiple
degrees of freedom (such as the thumb carpometacarpal
joint) will have simultaneous and different actions about each
axis of rotation.
The gross anatomic configuration and function of the extrinsic
digital flexor tendons have been known since antiquity. The
great growth in our knowledge and understanding of func­
tional biomechanics, muscle physiology, tendon nutrition,
and blood supply has influenced the management of problems
involving these important flexor tendons. The long flexor
tendons cross multiple joints. The tendon–muscle unit has an
effect on each joint it crosses, which is altered by the position­
ing of the other joints in the linkage system. Thus, the influ­
ence of the long flexor tendon on one joint in the system is
Text continued on p. 32

26
SECTION I
CHAPTER 1 • Anatomy and biomechanics of the hand
Fig. 1.28  The anatomy of the flexor muscles, from superficial to deep. (Reprinted with permission from © Elsevier Inc. All Rights Reserved.)
Flexor digitorum superficialis
muscle (radial head)
Anterior branch of medial
antebrachial cutaneous nerve
Flexor pollicis longus muscle
Interosseous membrane
Flexor carpi radialis muscle
Ulnar artery and median nerve
Palmaris longus muscle
Flexor digitorum superficialis
muscle (humeroulnar head)
Common interosseous artery
Ulnar nerve
Flexor carpi ulnaris muscle
Basilic vein
Flexor digitorum profundus muscle
Ulna and antebrachial fascia
Anconeus muscle
Posterior antebrachial cutaneous
nerve (from radial nerve)
Palmaris longus muscle
Flexor digitorum superficialis muscle
Median nerve
Ulnar artery and nerve
Flexor carpi ulnaris muscle
Flexor digitorum profundus muscle
Anterior interosseous artery and nerve
(from median nerve)
Ulna and antebrachial fascia
Interosseous membrane and
extensor pollicis longus muscle
Posterior interosseous artery and nerve
(continuation of deep branch of radial nerve)
Palmaris longus tendon
Median nerve
Flexor digitorum superficialis muscle and tendons
Flexor carpi ulnaris muscle and tendon
Ulnar artery and nerve
Dorsal branch of ulnar nerve
Flexor digitorum profundus muscle and tendons
Extensor digitorum tendons (common tendon
to digits 4 and 5 at this level)
Radius
Extensor digiti minimi tendon
Extensor indicis muscle and tendon
Pronator quadratus muscle and interosseous membrane
Extensor carpi ulnaris tendon
Ulna
Antebrachial fascia
Extensor pollicis longus tendon
Extensor carpi radialis brevis tendon
Extensor carpi radialis
longus tendon
Abductor pollicis longus tendon
Superficial branch of radial nerve
Extensor pollicis brevis tendon
Flexor pollicis longus muscle
Brachioradialis tendon
Radial artery
Flexor carpi radialis tendon
Extensor carpi ulnaris muscle
Extensor digiti minimi muscle
Extensor digitorum muscle
Abductor pollicis longus muscle
Extensor carpi radialis
brevis muscle and tendon
Radius
Extensor carpi radialis
longus muscle and tendon
Flexor pollicis longus muscle
Radial artery and superficial
branch of radial nerve
Brachioradialis muscle
Flexor carpi radialis muscle
Extensor carpi ulnaris muscle
Extensor digiti minimi muscle
Extensor digitorum muscle
Extensor carpi radialis brevis muscle
Extensor carpi radialis longus muscle
Deep branch of radial nerve
Supinator muscle
Cephalic vein and lateral antebrachial
cutaneous nerve (from musculocutaneous
nerve)
Brachioradialis muscle
Radius
Radial artery and superficial branch of radial nerve
Pronator teres muscle
Median antebrachial vein

27
Muscles and tendons
Fig. 1.29  The anatomy of the flexor muscles, from superficial to deep. (Reprinted with permission from © Elsevier Inc. All Rights Reserved.)
Note: Brachioradialis muscle not shown
because it is flexor of elbow
Lateral epicondyle
Medial epicondyle
Common flexor tendon
Flexor carpi radialis
Palmaris longus
Flexor carpi ulnaris
Radius
Ulna
Pisiform
Hook of hamate
Palmar aponeurosis (cut)
Right forearm:
anterior (palmar) view

28
SECTION I
CHAPTER 1 • Anatomy and biomechanics of the hand
Fig. 1.30  The anatomy of the flexor muscles, from superficial to deep. (Reprinted with permission from © Elsevier Inc. All Rights Reserved.)
Ulnar nerve
Median nerve
Brachial artery
Medial intermuscular septum
Pronator teres muscle (humeral head)
(cut and reflected )
Flexor carpi radialis and palmaris
longus tendons (cut )
Flexor digitorum superficialis
muscle (humeroulnar head)
Medial epicondyle
Biceps brachii muscle
Brachialis muscle
Lateral antebrachial cutaneous nerve (cut )
(from musculocutaneous nerve)
Radial nerve
Deep branch
Superficial branch
Biceps brachii tendon
Radial recurrent artery
Radial artery
Supinator muscle
Brachioradialis muscle
Pronator teres muscle (cut )
Flexor digitorum superficialis
muscle (radial head)
Anterior ulnar recurrent artery
Ulnar artery
Common interosseous artery
Pronator teres muscle (ulnar head) (cut )
Anterior interosseous artery
Flexor carpi ulnaris muscle
Flexor digitorum superficialis muscle
Ulnar artery
Ulnar nerve and dorsal branch
Median nerve
Palmar branches of median and ulnar nerves (cut )
Pisiform
Deep palmar branch of ulnar artery
and deep branch of ulnar nerve
Flexor retinaculum
(transverse carpal ligament)
Superficial branch of ulnar nerve
Superficial palmar branch
of radial artery
Flexor carpi radialis
tendon (cut )
Palmar carpal ligament
(continuous with extensor
retinaculum) with palmaris
longus tendon (cut and reflected )
Flexor pollicis longus muscle

29
Muscles and tendons
Fig. 1.31  The anatomy of the flexor muscles, from superficial to deep. (Reprinted with permission from © Elsevier Inc. All Rights Reserved.)
Medial epicondyle
Lateral epicondyle
Common flexor tendon
Coronoid process
Interosseous membrane
Radius
Medial epicondyle
Lateral epicondyle
Coronoid process
Interosseous
membrane
Radius
Flexor digitorum superficialis
Flexor digitorum profundus
Flexor pollicis longus
Ulna
Radius
Radius
Flexor digitorum superficialis
tendons (cut away)
Ulna
Right forearm:
anterior (palmar) views

30
SECTION I
CHAPTER 1 • Anatomy and biomechanics of the hand
Fig. 1.32  The Blix curve. The maximal force is plotted on the vertical axis, and the
muscle fiber length is plotted on the horizontal axis. There is an optimal length of
the fiber at which maximal force can be produced, and this drops at longer or
shorter fiber lengths.
0
0.5 Resting length
Resting length
1.5 Resting length
0.5 Fmax
Fmax
Muscle fiber length (normalized to resting fiber length)
Maximal isometric force
(for a given activation level)
Fig. 1.33  The force–velocity curve. The percentage of maximal isometric force is
plotted on the vertical axis, and the relative shortening velocity is plotted on the
horizontal axis. Therefore, muscle force drops from its isometric level when muscle
fibers shorten rapidly during concentric contractions and rises to a plateau almost
double its isometric level when muscle fibers lengthen rapidly during eccentric
contractions.
Relative shortening velocity
(resting lengths/sec)
Percent maximal isometric force
Shortening
Lengthening
100%
180%
-0.8
0.0
0.8
Fig. 1.34  The moment arm is defined as the shortest
distance between the axis of rotation and the tendon as it
crosses the joint.
Pulley
Tendon
Pulley
Phalanx
Joint
axis
Joint
angle
Phalanx
Moment
arm
Tendon
Joint axis
Moment arm
Moment
arm
Moment arm
Moment arm
Fig. 1.35  (A–D) The flexor tendon pulley system for fingers and thumb. (Redrawn
after Chase RA. Atlas of Hand Surgery, vol. II. Philadelphia: WB Saunders, 1984.)
A
C
D
B
Annular
Oblique
A1
A2
C1
A3
C2
A4 C3 A5
Annular
Thumb pulleys
Finger pulleys
A1
A2
C1
A3
C2
A4
C3
A5
Transverse carpal
ligament

31
Muscles and tendons
Fig. 1.36  Orientation of the flexor tendon sheaths, flexor tendons, and pulleys. (Reprinted with permission from © Elsevier Inc. All Rights Reserved.)
Thenar space
Midpalmar space
(Synovial) tendon
sheaths of fingers
Usual arrangement
Intermediate bursa
(communication
between common
flexor sheath [ulnar
bursa] and tendinous
sheath of flexor pollicis
longus [radial bursa])
Flexor digitorum
profundus tendons
1st and 2nd lumbrical muscles
(unipennate)
Common variation
3rd and 4th lumbrical muscles
(bipennate)
Flexor digitorum
superficialis tendons (cut)
Lumbrical muscles: schema
Palmar ligaments (plates)
A2
C2
A3
C3
A4
C4
A5
Tendinous sheath of flexor
pollicis longus (radial bursa)
Common flexor sheath
(ulnar bursa)
Lumbrical muscles
(in fascial sheaths)
(Synovial) tendon sheath
Tendons of
flexor digitorum
superficialis
and profundus
muscles
Note: Flexor digitorum superficialis and
profundus tendons encased in synovial
sheaths are bound to phalanges by fibrous
digital sheaths made up of alternating
strong annular (A) and weaker cruciform (C)
parts (pulleys).
Camper chiasm
A1
C1

32
SECTION I
CHAPTER 1 • Anatomy and biomechanics of the hand
Fig. 1.37  Flexor digitorum superficialis and profundus; lateral view of the hand.
(Upper limb cadaver dissection, Stanford University Division of Plastic Surgery.
© 2015 James Chang, Anais Legrand. All Rights Reserved.)
Flexor digitorum profundus
Flexor digitorum superficialis
Superficial palmar arch
Vinculum breve
Fig. 1.38  The common configuration of the vincula. FDP, flexor digitorum
profundus; FDS, flexor digitorum superficialis. (Redrawn after Chase RA. Atlas of
Hand Surgery, vol. II. Philadelphia: WB Saunders, 1984.)
FDP tendon
Vinculum longus
profundus
FDS tendon
Mesotenon
Vincula brevia
Vinculum brevia
Vinculum longus
superficialis
The second cruciate ligament (C2) is at the base of the middle
phalanx. The fourth annular pulley (A4) lies over the middle
one-third of the middle phalanx, and just distal to it is the
third cruciate (C3). Often it is possible to identify thickening
of the sheath over the distal interphalangeal joint, which,
when present, is designated the fifth annular pulley (A5). The
A2 and A4 pulleys insert directly into bone over the proximal
and middle phalanges, respectively. In contrast, A1, A3 and
A5 are narrower, more flexible, and insert mostly into the
volar plate; additionally, with the cruciate pulleys, they permit
compression without impingement and expansion during
finger flexion and extension, respectively.
The pulleys are strategically placed to maintain the rela­
tionship of the flexor tendons to the axis of each finger joint,
thus preventing the bowstring effect. The A2 and A4 pulleys
are crucial to prevent bowstringing. The gaps between pulleys
allow unrestrained flexion and extension of the joints by
folding and pleating of the thin sheath between pulleys.
The synovial sheaths are closed sacs around the tendons
composed of a visceral layer on the tendon surface and a
parietal layer on the fibrous sheath surface. The thumb syno­
vial sheath is continuous from the wrist to the distal extreme
of the flexor pollicis longus. The digital synovial sheaths for
the index, long, and ring fingers usually start at the level of
the distal palmar crease and extend to the distal interphalan­
geal joints. Often the little-finger sheath extends more proxi­
mally to communicate with a common sheath around the
finger flexors and then across the wrist to the distal forearm,
where tendons pass through the carpal tunnel.
During embryonic development, synovial sacs form where
the flexor tendons are subject to restraint by retinacula. The
tendon invaginates into the sac, creating a two-layered, closed
synovial membrane around the tendon. The tendon carries
its segmental nutrient vessels, and thus with invagination
a mesentery-like mesotenon is formed. As time passes, and
where the tendon has great excursion in relationship to adja­
cent bone, the mesentery refines itself to tiny, flexible bands,
or vincula. At the sites of insertion, where differential motion
between the bone and tendon is least, the mesenteric configu­
ration persists, as it does for flexor tendons in the hand outside
the confining tunnels. The vincula brevia form the residual
mesotenon at the sites of insertion of the profundus and
superficialis tendons on the phalanges (Fig. 1.37). The vincula
longa are the flexible, vessel-carrying bands to each tendon
in the area where the complete mesotenon has disappeared
(Fig. 1.38).
Because the cell population of tendons is sparse, metabolic
demand is low and cells can survive with minimal nutritional
support. The longitudinal blood supply to a tendon comes
from its musculotendinous junction and its insertion site into
bone. The segmental blood supply derives from the meso­
tenon where a mesotenon exists and from the vincula within
the digital sheaths. It is now clear that synovial fluid within
the sheath supplies nutrition to the tendon much as synovial
fluid in a joint supports cartilage. This fact has altered think­
ing about the necessity for adhesion formation to ensure cell
survival within a lacerated tendon stripped of blood supply
or within tendon grafts.
On the basis of the anatomy of the flexor tendons and the
associated synovial and fibrous sheaths, the area traversed
by the tendons is divided into clinically important zones
(Fig. 1.39).
■ Zone 1 is the area traversed by the flexor digitorum
profundus distal to the insertion of the flexor digitorum
superficialis on the middle phalanx.
■ Zone 2 extends from the proximal end of zone 1 to the
proximal end of the digital fibrous sheath.
■ Zone 3 is the area traversed by the flexor tendons in the
palm and is free of fibrous pulleys. It extends, therefore,
from the proximal end of the finger pulley system (Al) to
the distal end of the wrist retinaculum, the transverse
carpal ligament.
■ Zone 4 is the carpal tunnel. It extends from the distal
to the proximal borders of the transverse carpal
ligament.
■ Zone 5 extends from the proximal border of the
transverse carpal ligament to the musculotendinous
junctions of the flexor tendon (Box 1.6).

33
Muscles and tendons
to as the ulnar bursa. Each index, long, and ring finger has a
flexor synovial sheath from the point of insertion of the pro­
fundus tendon to the level of the distal palmar crease in the
palm. The deep space beneath the flexor tendons is divided
into two compartments by the heavy vertical septum from the
palmar fascia to the third metacarpal. Ulnar to the septum is
the midpalmar space, and radial to it lies the thenar space.
The thenar space straddles the adductor pollicis muscle like
two legs extending between the adductor and deep flexors on
the palmar side, and between the adductor and the first dorsal
interosseous on the dorsal side. Infection starting in the digital
synovial sheaths may extend proximally to the deep palmar
spaces.
Intrinsic muscles (Video 1.2 )
Intrinsic muscles arise and insert within the hand (Figs. 1.40
& 1.41). They can be divided into four groups. The thenar
muscles are a group of four muscles consisting of the abductor
pollicis brevis, flexor pollicis brevis, opponens pollicis brevis,
and the adductor pollicis brevis. The abductor pollicis brevis,
opponens pollicis brevis, and superficial head of flexor pollicis
brevis are median-innervated whereas the adductor pollicis
brevis and the deep head of the flexor pollicis brevis are
ulnar-innervated.
The hypothenar muscles are all innervated by the ulnar
nerve. These four muscles include the palmaris brevis, abduc­
tor digiti minimi, flexor digiti minimi brevis, and opponens
digiti minimi.
Lumbricals originate from flexor digitorum profundus
tendons and insert on the radial aspect of the extensor mecha­
nisms, distal to the metacarpophalangeal joint. They contrib­
ute to the flexion of metacarpophalangeal joints and
the extension of the interphalangeal joints (Video. 1.4
). The
index and middle-finger lumbricals are innervated by the
median nerve, whereas the ring and small-finger lumbricals
are innervated by the ulnar nerve. The tiny lumbrical muscles
harmonize function between the lateral band interphalangeal
extensor mechanism and the flexor digitorum profundus.
They have a moving site of origin from the profundus tendon.
As the flexor profundus contracts, the lumbrical origin moves
proximally. At the same time, the lumbrical insertion moves
distally as the extensor is advanced by interphalangeal flexion.
The separation of its insertion and origin makes the lumbrical
more effective in flexing the metacarpophalangeal joint.
Conversely, with a change in balance of power, the lumbrical
tends to pull the profundus distally as it shortens the lateral
bands. This combination of profundus relaxation and lateral
band pull results in extension at the interphalangeal joints.
Despite the fact that lumbricals have the smallest cross-
sectional area in the upper extremity, they have the greatest
number of muscle spindles, which are responsible for gather­
ing proprioceptive input. They play an important role in
the sensory feedback of the distal interphalangeal, proximal
interphalangeal, and metacarpophalangeal joints of the
fingers. Specifically, the lumbrical muscles may be important
for forming a precision pinch comprised by the first three
digits.64
All interossei are ulnar-innervated. There are three volar
muscles and four dorsal muscles. The interossei originate
from the metacarpals and form the lateral bands with the
lumbricals. The interosseous muscles function as ulnar and
A knowledge of the classical anatomy of the synovial sheaths
and potential anatomic spaces in the hand is essential for
proper diagnosis and treatment of serious hand infections.
The flexor tendons are shrouded in synovial sheaths, particu­
larly where there is flexion mobility in the longitudinal arch
of each ray and at the wrist. The synovial sheath of the flexor
pollicis longus generally extends from the flexor insertion to
a point proximal to the wrist flexor retinaculum. The same is
true of the synovial sheath around the little-finger flexors, but
as the little-finger sheath approaches the proximal palm just
distal to the carpal tunnel, it expands to encompass the flexors
of the ring, long, and index fingers. At this point it is referred
Fig. 1.39  Flexor tendon zones are classified for their relevance to flexor tendon
injuries. (Redrawn after Chase RA. Atlas of Hand Surgery, vol. II. Philadelphia: WB
Saunders, 1984.)
Superficialis insert
Proximal A3
Distal A2
Proximal A1
Transverse
carpal ligament
Carpal tunnel
Distal
Zones
I
II
III
IV
V
Middle
Proximal
BOX 1.6  Clinical pearl: examination of extrinsic flexors
The function of the flexor digitorum profundus can be confined by
active flexion of the distal interphalangeal joint. It is the only flexor of
this joint. Since a muscle–tendon unit affects every joint between its
origin and insertion, the flexor digitorum profundus may also flex the
proximal interphalangeal joint. This makes the diagnosis of
superficialis nonfunction more difficult. Each superficialis flexor has
its own muscle belly, and each acts independently of the others.
The profundus flexors are not as independent, since there is a
common muscle for the long, ring, and little finger profundus
tendons, and a variable degree of interconnection between these
and the index finger profundus. The diagnosis of disruption of flexor
digitorum superficialis function is confirmed by check-reining the
profundus by holding the other fingers in extension while the patient
actively attempts to flex the finger whose superficialis is being
tested. Flexion of the finger at the proximal interphalangeal joint
while the distal interphalangeal joint remains loosely extended
confirms the functional integrity of the flexor digitorum superficialis.

34
SECTION I
CHAPTER 1 • Anatomy and biomechanics of the hand
Fig. 1.40  Superficial and deep intrinsic muscles in the hand. (Reprinted with permission from © Elsevier Inc. All Rights Reserved.)
Radial artery and venae comitantes
Flexor carpi radialis tendon
Tendinous sheath of
flexor pollicis longus
(radial bursa)
Median nerve
Palmaris longus tendon and
palmar carpal ligament
Transverse carpal
ligament (flexor
retinaculum)
Thenar muscles
Proper palmar
digital nerves
of thumb
(Synovial)
tendinous
sheath of flexor
pollicis longus
(radial bursa)
Probe in 1st
lumbrical
fascial sheath
Common palmar
digital artery
Proper palmar
digital arteries
Septa from palmar
aponeurosis forming canals
Palmar aponeurosis
(reflected)
Ulnar artery with venae comitantes and ulnar nerve
Flexor carpi ulnaris tendon
Common flexor sheath (ulnar bursa) containing
superficialis and profundus flexor tendons
Pisiform
Deep palmar branch of ulnar artery and deep
branch of ulnar nerve
Superficial branch of ulnar nerve
Palmar digital nerves to 5th finger and
medial half of 4th finger
Median nerve
Common flexor sheath (ulnar bursa)
Superficial palmar arterial and venous arches
2nd, 3rd, and 4th lumbrical muscles (in fascial sheaths)
(Synovial) flexor tendon sheaths of fingers
Anterior (palmar) views
Proper palmar digital nerves of thumb
Fascia over adductor pollicis muscle
1st dorsal interosseous muscle
Probe in dorsal extension of thenar
space deep to adductor pollicis muscle
Thenar space (deep to flexor tendons
and 1st lumbrical muscle)
Septum separating thenar from midpalmar space
Common palmar digital artery
Proper palmar digital arteries and nerves
Ulnar artery
and nerve
Common palmar
digital branches
of median nerve (cut)
Hypothenar
muscles
Common flexor
sheath (ulnar
bursa)
5th finger
(synovial)
tendinous sheath
Probe in
midpalmar space
Midpalmar space
(deep to flexor
tendons and
lumbrical muscles)
Insertion of
flexor digitorum
superficialis tendon
Insertion of flexor digitorum
profundus tendon
Annular and cruciform parts of fibrous sheath
over (synovial) flexor tendon sheaths
Superficial palmar
branch of radial
artery and recurrent
branch of median
nerve to thenar
muscles

35
Muscles and tendons
Fig. 1.41  Superficial and deep intrinsic muscles in the hand. (Reprinted with permission from © Elsevier Inc. All Rights Reserved.)
Pronator quadratus muscle
Ulnar nerve
Ulnar artery and palmar carpal branch
Flexor carpi ulnaris tendon
Palmar carpal arterial arch
Pisiform
Median nerve
Abductor digiti minimi muscle (cut)
Deep palmar branch of ulnar artery
and deep branch of ulnar nerve
Flexor digiti minimi brevis muscle (cut)
Opponens digiti minimi muscle
Deep palmar (arterial) arch
Palmar metacarpal arteries
Common palmar digital arteries
Deep transverse metacarpal ligaments
Radial artery and palmar carpal branch
Radius
Superficial palmar branch of radial artery
Flexor retinaculum (transverse
carpal ligament) (reflected )
Opponens pollicis muscle
Branches of median nerve
to thenar muscles and to 1st
and 2nd lumbrical muscles
Abductor pollicis
brevis muscle (cut )
Flexor pollicis
brevis muscle
Adductor pollicis
muscle
1st dorsal
interosseous muscle
Branches from deep
branch of ulnar nerve
to 3rd and 4th lumbrical
muscles and to all
interosseous muscles
Lumbrical muscles (reflected )
Anterior (palmar) view
Radius
Ulna
Palmar interosseous
muscles (unipennate)
Deep transverse
metacarpal ligaments
Radius
Ulna
Abductor digiti
minimi muscle
Radial artery
Abductor pollicis
brevis muscle
Dorsal interosseous
muscles (bipennate)
Anterior
(palmar) view
Tendinous slips
to extensor
expansions
(hoods)
Note: Arrows indicate action of muscles.
Posterior
(dorsal) view
1
2
3
1
2
3
4

36
SECTION I
CHAPTER 1 • Anatomy and biomechanics of the hand
Both the adductors and the abductors support flexion of the
metacarpophalangeal joint to prevent recurvatum at this joint
on pinching, which may occur with paralysis of either or both
(Froment’s sign). With graded relaxation of the abductors, the
adductor will dominate and pull the thumb against the side
of the hand.
The carpometacarpal joint is a saddle joint with a lax
capsule. This allows a wide range of circumduction motion
and even a small degree of distraction of the joint on traction.
Stability of the thumb root is heavily dependent on the
muscles affecting it. The radial-innervated extensor pollicis
longus and brevis and abductor pollicis longus secure the
metacarpal dorsally. Opposing this to achieve stability are two
groups of intrinsic muscles that, together with the extensor
and dorsal abductor, triangulate the metacarpal. These two
intrinsic groups are the median-innervated palmar abductors
(the abductor pollicis brevis, opponens pollicis, and superfi­
cial head of the flexor pollicis brevis) and the ulnar-innervated
adductors (the adductor pollicis, first dorsal interosseus, and
deep head of the flexor pollicis brevis).
When there is paralysis of any of the three major motor
nerves, thumb stability is compromised. In median nerve
palsy, the positioning muscles of the thenar eminence are lost,
resulting in inability to oppose the thumb for pulp-to-pulp
opposition with other digits. Ulnar nerve palsy results in
adduction weakness and imbalance of the structures influenc­
ing the metacarpophalangeal joint. Radial nerve palsy destroys
extension and dorsal abduction function, with resultant
adduction contracture that becomes fixed after an extended
period of unopposed adduction. The ulnar nerve innervates
the hypothenar muscle group, which serves further to develop
the concavity of the transverse metacarpal arch (Box 1.8).
radial deviators of the fingers as well as flexors of the meta­
carpophalangeal joints and extensors of the interphalangeal
joints. The dorsal interossei act as abductors from the axis of
the hand, which falls in the middle of the long finger. The long
finger moves both radially and ulnarly under the influence of
the second and third dorsal interossei. The abductor digiti
minimi is the dorsal interosseous equivalent of the little finger.
The palmar interossei adduct the fingers to the hand axis.
The pull of all the interossei palmar to the axis of the
metacarpophalangeal joints and dorsal to the interphalangeal
joint axis acts to flex the metacarpophalangeal joints and
extend the interphalangeal joints. The position assumed is
called the “intrinsic plus” posture (Fig. 1.42 & Box 1.7).
With the hand axis or fixed unit in position, the metacarpal
arch is adjusted primarily by the thenar and the hypothenar
muscle groups. The median nerve generally innervates all the
thenar muscles on the radial side of the flexor pollicis longus.
These two and one-half muscles (the abductor pollicis brevis,
opponens pollicis, and superficial head of the flexor pollicis
brevis) are positioning muscles that act to bring the first
metacarpal into palmar abduction, thus increasing the con­
cavity of the transverse metacarpal arch. This in turn prepares
the thumb for proper pulp-to-pulp opposition with the fingers.
The thumb is steadied in position by contraction of the
antagonist muscles to the abductors and the thumb adductor.
Fig. 1.42  All interossei act as prime flexors of the metacarpophalangeal joints
since they pass palmar to the joint axis. Extensions into the lateral bands result in
extension of the interphalangeal joints. (Redrawn after Chase RA. Atlas of Hand
Surgery, vol. 1. Philadelphia: WB Saunders, 1973.)
BOX 1.7  Clinical pearl: examination of intrinsic muscles
Examination of the hand for finger intrinsic function requires little
more than an understanding of the anatomy described above and
its related function. Function of the interossei may be assessed by
asking the patient to adduct and abduct the fingers from the hand
axis in the middle of the long finger. The ability to flex the
metacarpophalangeal joints with the interphalangeal joints extended
(“intrinsic plus” posture) confirms interosseous function. Paralysis is
reflected by clawing of the fingers with hyperextension of the
metacarpophalangeal joints and flexion of the interphalangeal joints
on attempts actively to extend the fingers (“intrinsic minus”).
Lumbrical function is best reflected by having the patient fully flex
the finger (extrinsic flexor function), then move the finger smoothly
into extension at the interphalangeal joints while holding active
flexion at the metacarpophalangeal joint.
Tightness or contracture of the interossei results in inability
actively or passively to flex the interphalangeal joints while the
metacarpophalangeal joint is extended. Inability to flex the
interphalangeal joints may be a result of fixation of the extrinsic
extensor tendons proximal to the metacarpophalangeal joint. Testing
to differentiate these two possible etiologies is done by passively
extending, then passively flexing, the metacarpophalangeal joint
while assessing the degree of passive extension of the
interphalangeal joints. If the interphalangeal joints passively extend
when the metacarpophalangeal joint is extended, the interosseous
muscle and tendon are short. If, by contrast, the interphalangeal
joints extend when the metacarpophalangeal joint is passively
flexed, the extrinsic extensor is adherent proximal to the
metacarpophalangeal joint (Fig. 1.43).

37
Blood supply
(Fig. 1.45). In the hand, it penetrates between the first and
second metacarpal bones, through an arcade in the first dorsal
interosseous muscle, to enter the palm and form the deep
palmar arch. A superficial branch of the radial artery arises
at the level of the distal radius before the artery enters the
“snuffbox” and courses over or through the abductor pollicis
brevis to contribute to the superficial palmar arch. This branch
contributes blood supply to the skin over the thenar area and
the underlying intrinsic muscles of the thumb.
The ulnar artery is the other major branch of the brachial
artery. Soon after the takeoff of the ulnar artery, the common
interosseous artery originates and itself branches into the
anterior and posterior interosseous arteries. The ulnar artery
continues in the forearm under the flexor carpi ulnaris muscle.
At the wrist, it lies radial to the pisiform and ulnar to the hook
of the hamate and travels into the hand through Guyon’s
canal, deep to the palmaris brevis and the hypothenar fascia.
Here it divides into a deep palmar branch and a superficial
palmar branch. The superficial branch becomes the dominant
contributor to the superficial palmar arch. The superficial arch
crosses the palm at the level of the fully abducted thumb. The
deep branch contributes to the deep palmar arch.
In general, the blood supply of the hand is conveniently
divided into palmar vessels, which are subdivided into
a superficial and a deep layer, and a single dorsal layer
(Fig. 1.46).65 For example, the superficial vascular arch and its
branches constitute the superficial group, the deep arch and
the palmar metacarpal branches make up the deep layer, and
the dorsal arch with its dorsal metacarpal branches forms the
dorsal distribution (Box 1.9).
The superficial palmar arch gives rise to three common
digital arteries and multiple branches to intrinsic muscles and
skin. The deep vascular arch lies at the proximal ends of the
metacarpals deep to all the flexor tendons. It arises chiefly
from the radial artery and becomes an arch by anastomosis
with the deep branch of the ulnar artery. The deep arch is the
major source of blood supply to the thumb and to the radial
Blood supply
The vascular inflow to the upper arm and hand is a continu­
ation of the axillary artery to the brachial artery. The brachial
artery is palpable just medial to the biceps tendon at the level
of the elbow. The brachial artery branches into the radial and
ulnar arteries at the bicipital aponeurosis of the elbow (Fig.
1.44). Supplementary arteries in the forearm include the
anterior interosseous artery, the posterior interosseous artery,
and the median artery.
The radial artery continues distally in the forearm between
the brachioradialis and flexor carpi radialis muscles. At the
wrist, the radial artery is located near the styloid process
of the radius, and then travels dorsally, crossing the “ana­
tomic snuffbox” deep to the tendons of the abductor pollicis
longus, extensor pollicis brevis, and extensor pollicis longus
Fig. 1.43  (A,B) Testing for tightness or shortening of the interosseous muscles as a cause of passive extension contracture of the interphalangeal joint. The
metacarpophalangeal joint is passively extended and the interphalangeal joints passively extend. If the cause of extensor tightness at the interphalangeal joint is a result of
long extensor adhesions to the metacarpal, the interphalangeal joints will passively extend on passive flexion of the metacarpophalangeal joint. (Redrawn after Chase RA.
Atlas of Hand Surgery, vol. II. Philadelphia: WB Saunders, 1984.)
Fibrosed
A
Adhesion
B
BOX 1.8  Clinical pearl: dynamics of hand function
The central backbone of the hand is positioned in extension by the
very important extensor carpi radialis brevis and longus. Flexion is
affected by the flexor carpi radialis. All three muscles insert on the
central two metacarpals (the second and third). These key motors
are responsible for positioning the hand axis in preparation for
operation of the adaptive hand elements around it. There are
numerous other modifying motors to adjust the hand axis in the
exact position desired, such as the flexor carpi ulnaris and extensor
carpi ulnaris, which produce ulnar deviation. The fixed unit of the
hand is extended from the radius at the radiocarpal joint. The entire
complex is a beam attached to the ulna by the distal radioulnar
joint, the interosseous membrane, and the proximal radioulnar
articulation. Rotation around the fixed ulna in supination and
pronation is largely under the influence of the median-innervated
pronator teres and pronator quadratus and the radial-innervated
supinator. The biceps and brachioradialis augment supination.

38
SECTION I
CHAPTER 1 • Anatomy and biomechanics of the hand
Fig. 1.44  Upper arm vascular anatomy and surrounding structures. (Reprinted with permission from © Elsevier Inc. All Rights Reserved.)
Anterior view
Deltoid muscle
Coracobrachialis muscle
Short head (cut )
Long head (cut )
Musculocutaneous nerve
Brachialis muscle
Biceps brachii muscle (cut ) and tendon
Lateral antebrachial cutaneous nerve
(from musculocutaneous nerve)
Deep branch
Superficial branch
Supinator muscle
Brachioradialis muscle
Radial artery
Pronator teres muscle (partially cut )
Median nerve
Flexor pollicis longus muscle
Flexor carpi radialis
tendon (cut )
Flexor retinaculum
(transverse carpal
ligament)
Superficial branch
of radial nerve
Recurrent (motor)
branch of
median nerve to
thenar muscles
Common palmar
digital branches
of median nerve
Proper palmar
digitial branches
of median nerve
Intercostobrachial nerve
Medial brachial
cutaneous nerve
Radial nerve
Ulnar nerve
Medial antebrachial
cutaneous nerve
Median nerve
Brachial artery
Bicipital aponeurosis
Humeral head (cut)
Ulnar head
Pronator teres muscle
Flexor carpi radialis muscle (cut)
Humeroulnar head
Radial head
Flexor digitorum
superficialis muscle (cut)
Flexor digitorum profundus muscle
Flexor carpi ulnaris muscle
Ulnar artery and nerve
Dorsal branch of ulnar nerve
Flexor digitorum superficialis tendons (cut)
Deep palmar branch of ulnar artery and deep branch of ulnar nerve
Superficial branch of ulnar nerve
Superficial palmar arch (cut)
Common palmar digital branch of ulnar nerve
Communicating branch of median nerve with ulnar nerve
Proper palmar digital branches of ulnar nerve
Biceps brachii muscle
Radial nerve

39
Blood supply
dorsal arteries are joined by a varying number of vessels
perforating from the deep palmar metacarpal arteries. In fact,
the dominant supply to the dorsal metacarpal arteries may
come from these perforators. Dorsal arteries to the thumb
come from branches of the radial artery before it plunges
through the first dorsal interosseous arcade. Thus, the dorsal
arterial blood supply of the thumb is similar to that of the
fingers (Box 1.11).
Veins generally follow the arterial pattern in the deep
system as venae comitantes. An abundant superficial system
of venous drainage also exists (Fig. 1.47). Ultimately, these
side of the index finger. This blood supply comes from the
first of the four palmar metacarpal arteries. The first metacar­
pal artery is the prime source of blood supply to the radial
and ulnar proper digital arteries of the thumb and the radial
proper digital artery of the index finger. These digital arteries
generally receive collateral branches from the superficial
palmar arch as well. After giving its branch to the index finger,
the first metacarpal artery becomes the primary source of
blood supply to the thumb and is frequently called the prin­
ceps pollicis (Box 1.10).
The dorsal arteries originate proximally from the posterior
interosseous artery and a dorsal perforating branch of the
anterior interosseous artery. These arteries are joined by
branches from the radial and ulnar arteries to form a dorsal
carpal arch. Dorsal metacarpal arteries arise from this arch
and extend distally to the margins of the fingers.66–70 These
Fig. 1.45  The anatomic snuffbox. The superficial branch of the radial nerve can be
palpated by stroking along the extensor pollicis longus. (Upper limb cadaver
dissection, Stanford University Division of Plastic Surgery. © 2015 James Chang,
Anais Legrand. All Rights Reserved.)
Extensor pollicis brevis
Extensor pollicis longus
Abductor pollicis longus
Superficial branch
of radial nerve
BOX 1.9  Clinical pearl: the Allen’s test
This test may be used to assess the competence of the major
arterial contributors to blood supply in the hand and the functional
efficiency of the vascular arches in the hand. Palpate the radial and
ulnar pulses at the wrist and prepare to compress these arteries.
Have the patient make a very tight fist. Compress the arteries and
ask the patient to extend the digits. The hand will be blanched
white. Release pressure on one of the arteries and observe the
return of a red flush on the hand. Normally, the flush is immediate
and progresses across the whole hand without delay. This confirms
the patency of the artery and the competence of circulatory
collaterals through the vascular arches. The test may be performed
to confirm the competence of each of the two major arteries before
surgery or to check their competence after repair, thrombectomy,
manipulation, or injury.
The Allen’s test principle may be used in clinically assessing the
competence of the two proper digital arteries in the fingers. It may
be done by observing return of color after compression of both
arteries and release of one to the digit. Compress one artery, then
the other, and then both to note the individual proper artery
contribution to cutaneous blood supply. The technique may be
useful when one is planning an island pedicle flap from a donor
finger whose digital artery may have been damaged by an injury
proximal to the finger.
BOX 1.10  Clinical pearl: the relative size of digital vessels
Although two digital arteries (radial and ulnar) usually perfuse each
finger, there are differences in the diameter of the radial versus ulnar
digital arteries.66 In the thumb, the ulnar digital artery is usually much
larger. The index finger is similarly ulnar-dominant whereas the small
finger is radial-dominant. The arteries to the middle and ring fingers
do not have appreciable size differences between radial and ulnar
sides. This anatomic variation may be important in finding adequate
vessels for microanastomosis during replantation or
revascularization.
BOX 1.11  Clinical pearl: dorsal metacarpal artery flaps
The dorsal arterial circulation of the hand is the source of multiple
intrinsic hand flaps. The radial artery and the dorsal carpal arch give
off the first and second metacarpal arteries which run in the
intermetacarpal spaces between the thumb and index finger,
and the index finger and middle finger, respectively. The third
metacarpal artery is much smaller and is less reliable for flap
transfer. Although multiple uses and variations have been described,
the simplest method to catalogue these flaps is by artery and by
direction of flow. Therefore, both the first and second dorsal
metacarpal arteries may be used in an anterograde or retrograde
fashion.
The first dorsal metacarpal artery (FDMA) has been found to
originate from the dorsal radial artery, just distal to the extensor
pollicis longus tendon. In a series of 30 hand dissections, 90% of
hands had superficial or fascial FDMAs, 40% of hands had a deep
intramuscular branch, and 30% had both vessels present.67 The
external diameter averaged 1.0–1.5 mm at the largest part. This
vessel can be used to harvest a pedicled island flap of skin from
the dorsum of the index proximal phalanx innervated by a branch of
the radial sensory nerve.68 In the anterograde fashion, this flap may
reach about the dorsum of the radial two-thirds of the hand, and
even to a portion of the volar hand. The reach of the FDMA flap can
be extended distally if designed in a retrograde fashion.69
The second dorsal metacarpal artery (SDMA) was found in 29 of
30 (97%) hands dissected. The origin of this vessel varied, including
from the dorsal carpal arch, radial artery, FDMA, and the posterior
interosseus artery. Once the SDMA reached the index finger
extensor tendons, the vessel passed deep to the tendons and within
the fascia of the second dorsal interosseous muscle. The SDMA
branched and became superficial at the level of the
metacarpophalangeal joints. The pedicle, being more central
than the FDMA, can nearly reach the entire dorsum of the
hand and can also be extended in a retrograde fashion, to reach
the level of the proximal interphalangeal joints of the index and
middle fingers.70

40
SECTION I
CHAPTER 1 • Anatomy and biomechanics of the hand
Fig. 1.46  Hand vascular anatomy and surrounding structures. (Reprinted with permission from © Elsevier Inc. All Rights Reserved.)
Radial artery
Median nerve and palmar branch
Superficial palmar branch of radial artery
Abductor pollicis brevis muscle (cut )
Opponens pollicis muscle
Flexor pollicis brevis muscle
Recurrent (motor) branch of
median nerve to thenar muscles
Proper digital nerves
and arteries to thumb
Adductor pollicis muscle
Branches of median nerve to
1st and 2nd lumbrical muscles
Flexor tendons, synovial
and fibrous sheaths
Ulnar artery and nerve
Palmar carpal ligament (continuous
with extensor retinaculum)
Flexor retinaculum (transverse
carpal ligament)
Deep palmar branch of ulnar artery
and deep branch of ulnar nerve
Superficial branch of ulnar nerve
Common flexor sheath
(ulnar bursa)
Superficial palmar (arterial) arch
Common palmar digital nerves
and arteries
Communicating branch of
median nerve with ulnar nerve
Proper palmar digital nerves
and arteries
Branches of proper palmar
digital nerves and
arteries to dorsum of
middle and distal
phalanges
Radial artery
Median nerve
Superficial palmar branch of radial artery
Deep palmar (arterial) arch and
deep branch of ulnar nerve
Princeps pollicis artery
Proper digital arteries
and nerves of thumb
Distal limit of
superficial palmar arch
Radialis indicis artery
Palmar metacarpal arteries
Common palmar digital arteries
Proper palmar digital arteries
Proper palmar digital nerves from median nerve
Ulnar artery and nerve
Palmar carpal branches of
radial and ulnar arteries
Pisiform
Deep palmar branch of
ulnar artery and deep
branch of ulnar nerve
Branches to hypothenar
muscles
Superficial branch of
ulnar nerve
Hook of hamate
Communicating branch
of median nerve with
ulnar nerve
Proper palmar digital
nerves from ulnar nerve
Deep palmar branch of
ulnar nerve to 3rd and
4th lumbrical, all
interosseous, adductor
pollicis, and deep head
of flexor pollicis brevis
muscles

41
Blood supply
Fig. 1.47  The superficial and deep venous drainage system of the hand and arm. (Reprinted with permission from © Elsevier Inc. All Rights
Reserved.)
Anterior (palmar) view
Posterior (dorsal) view
Cephalic vein
Posterior antebrachial
cutaneous nerve
(from radial nerve)
Lateral antebrachial
cutaneous nerve
(from musculo-
cutaneous nerve)
Accessory
cephalic vein
Median
cephalic vein
Cephalic vein
Median
antebrachial vein
Superficial branch
of radial nerve
Palmar branch
of median nerve
Intercapitular veins
Basilic vein
Anterior branch
and
Posterior branch
of medial
antebrachial
cutaneous
nerve
Median
basilic vein
Bicipital
aponeurosis
Basilic vein
Perforating
veins
Posterior
antebrachial
cutaneous
nerve (from
radial nerve)
Accessory
cephalic
vein
Posterior
branch of
lateral
antebrachial
cutaneous
nerve (from
musculocu-
taneous nerve)
Cephalic vein
Basilic vein
Posterior
branch
of medial
antebrachial
cutaneous
nerve
Palmar branch
of ulnar nerve
Dorsal branch
of ulnar nerve
Palmar carpal
ligament
(continuous
with extensor
retinaculum)
Palmar
aponeurosis
Superficial
transverse
metacarpal
ligament
Proper palmar digital nerves
and palmar digital veins
Dorsal digital nerves and veins
Superficial branch
of radial nerve
Dorsal
venous
network
Dorsal branch
of ulnar nerve
Dorsal
metacarpal
veins
Intercapitular
veins
Extensor
retinaculum
Note: In 70% of cases,
a median cubital
vein (tributary to
basilic vein) replaces
median cephalic
and median basilic
veins

42
SECTION I
CHAPTER 1 • Anatomy and biomechanics of the hand
superficial veins contribute to the cephalic and basilic
veins of the upper extremities. Lymphatic drainage termi­
nates in the axillary, supraclavicular, and subclavicular
nodes.
Peripheral nerves
The peripheral nerves to the upper extremity have anatomic
relationships of great importance to the surgeon. For example,
one needs to know the anatomic availability for nerve block
and sites where nerves are subject to compression or injury.
Sites of particular susceptibility to injury coincide quite accu­
rately with the sites chosen for anesthesia.
With the ability to perform fascicular and group fascicular
repair of nerves in addition to epineurial repair, it is important
for surgeons to understand the generic internal structure of
peripheral nerves. The epineurium is the tubular fibrous
support structure surrounding the entire nerve; it also courses
between the fascicles. Subdivisions consisting of multiple
fascicles within the nerve are covered by epineurium. Each
fascicle is covered by perineurium. Within each fascicle are
separate axons, some myelinated and some unmyelinated.
Motor, sensory, and sympathetic fibers are present within
each peripheral nerve. Blood vessels are found on the epineu­
rial surface and in the internal supporting structure of the
nerve. The internal topography is plexus-like, as described in
detail in the classic monograph by Sunderland.70
The radial nerve arises from the posterior cord of the bra­
chial plexus (C6–8). As the nerve passes the distal humerus,
muscular branches innervate the brachioradialis and extensor
carpi radialis longus muscles (Fig. 1.48). The radial nerve
divides into terminal deep and superficial branches at the
proximal forearm (Fig. 1.49). The deep posterior interosseous
nerve supplies the supinator as well as muscles in all the
extensor compartments: extensor carpi radialis brevis, exten­
sor digitorum communis, extensor digiti minimi, extensor
carpi ulnaris, extensor indicis proprius, extensor pollicis
longus, extensor pollicis brevis, and abductor pollicus longus
muscles. Finally, the deep posterior interosseous nerve termi­
nates to supply carpal joint sensation.
The dorsal or superficial branch of the radial nerve courses
through the forearm in relationship to the brachioradialis
muscle on the radial side of the arm. The superficial branch
of the radial nerve crosses the “anatomic snuffbox” between
the extensor pollicis brevis and the extensor pollicis longus in
the loose subcutaneous tissue. Here it exchanges fibers with
terminal branches of the lateral antebrachial cutaneous nerve.
The area the superficial branch of the radial nerve supplies is
the skin of the dorsum of the hand over the radial two-thirds,
the dorsum of the thumb, and the index, long, and half of the
ring finger proximal to the distal interphalangeal joint.
The median nerve arises from the lateral and medial
cords of brachial plexus (C5–T1) (Fig. 1.50). In the forearm,
muscular branches supply the pronator teres, flexor carpi
radialis, palmaris longus, and flexor digitorum superificialis
muscles. The anterior interosseous branch of the median
nerve innervates the flexor pollicis longus, flexor digitorum
profundus (index and middle finger), and pronator quadratus
muscles, and provides wrist sensation. Proximal to the wrist
and running between the flexor carpi radialis and palmaris
longus tendons, the palmar cutaneous branch provides lateral
palmar sensation (Fig. 1.51). As the median nerve passes
through the carpal tunnel, the recurrent motor branch inner­
vates the thenar muscles (abductor pollicis brevis, opponens
pollicis, and flexor pollicis brevis (superficial head). Sensory
branches supply digital nerves to the thumb, index, and
middle fingers, as well as the radial aspect of the ring finger
(Video 1.5
).
Lastly, the ulnar nerve enters the upper extremity as a
branch of the medial cord of the brachial plexus (C8–T1) (Fig.
1.52). Muscular branches innervate the flexor carpi ulnaris
and flexor digitorum profundus muscles to the ring and small
fingers. The palmar cutaneous branch of the ulnar nerve
provides sensation to hypothenar eminence and medial
portion of the palm. The dorsal branch of the ulnar nerve
courses around the ulnar aspect of the forearm in its distal
one-fourth after branching from the main trunk at a variable
site in the distal one-third of the forearm. It passes from its
position deep to the flexor carpi ulnaris out through the dorsal
fascia to become subcutaneous (Fig. 1.53). This sensory nerve
branches to innervate the ulnar portion of the dorsum of the
hand, the dorsum of the little finger, and at least part of the
dorsum of the ring finger. In contrast, the main sensory branch
forms the ulnar digital nerve to the small finger and the
common digital nerve which divides into the small-finger
radial digital nerve and the ring-finger ulnar digital nerve.
The deep motor branch of the ulnar nerve passes through the
pisohamate and opponens tunnel in company with the deep
branch of the ulnar artery. It courses with the deep vascular
arch across the depths of the palm, giving off motor branches
to the four hypothenar muscles (abductor digiti minimi,
opponens digiti minimi, flexor digiti minimi brevis, and pal­
maris brevis), all the interossei, the two ulnar lumbricals, and
the thumb intrinsics ulnar to the flexor pollicis longus – the
adductor pollicis brevis and the flexor pollicis brevis (deep
head).
Essentially the flexor pollicis longus divides the hand
into a median and ulnar-innervated portion from the motor
standpoint. The ulnar nerve is far less important from the
standpoint of hand sensation but is very important for its
motor innervation of all the hypothenar muscles and interos­
sei. In addition, it innervates the thumb adductor, the deep
head of the flexor pollicis brevis, and the two ulnar lumbri­
cals. Classically, all the intrinsic muscles on the radial side of
the flexor pollicis longus are median nerve-innervated (the
abductor pollicis brevis, opponens, and superficial head of
the flexor pollicis brevis). All other intrinsic muscles in the
hand receive their innervation from the ulnar nerve. The two
tiny radial lumbricals (median nerve innervated) are the only
exceptions to this axiom (Boxes 1.12 & 1.13).
Conclusion
In the human hand, the complicated motor balance at each
joint resulting from contraction, fixation, or relaxation of
opposing muscle groups is worthless in the absence of the
precisely fitted elements in the skeletal architecture. The
skeletal framework with its restraining ligaments is beauti­
fully designed but is useless without proper dynamic motor
tension. The anatomic presence of both architecture and
functioning muscles is only serviceable when there is integrity
Text continued on p. 48

43
Conclusion
Fig. 1.48  The proximal radial nerve wraps posteriorly around the humerus and then proceeds in a dorsal–radial direction distally. (Reprinted with permission from
© Elsevier Inc. All Rights Reserved.)
Posterior view
Suprascapular nerve (C5, 6)
Dorsal scapular nerve (C5)
Supraspinatus muscle
Levator scapulae
muscle (supplied
also by branches
from C3 and C4)
Rhomboid
minor muscle
Rhomboid
major muscle
Infraspinatus muscle
Teres major muscle
Lower subscapular nerve (C5, 6)
Posterior brachial cutaneous nerve
(branch of radial nerve in axilla)
Triceps brachii muscle
Long head
Lateral head
Medial head
Triceps brachii tendon
Medial epicondyle
Olecranon
Anconeus muscle
Extensor digitorum muscle
Extensor carpi ulnaris muscle
Extensor carpi
radialis brevis
muscle
Extensor carpi radialis
longus muscle
Brachioradialis muscle
Brachialis muscle (lateral
part; remainder of muscle
supplied by musculo-
cutaneous nerve)
Lateral intermuscular
septum
Posterior antebrachial
cutaneous nerve
Inferior lateral brachial
cutaneous nerve
Deltoid muscle
Teres minor muscle
Axillary nerve (C5, 6)
Superior lateral brachial
cutaneous nerve
Radial nerve
(C5, 6, 7 , 8, T1)
Inconstant contribution

44
SECTION I
CHAPTER 1 • Anatomy and biomechanics of the hand
Fig. 1.49  The radial nerve in the forearm innervates the extensor muscles and then lends sensibility to the radial dorsal aspect of the hand. (Reprinted with permission from
© Elsevier Inc. All Rights Reserved.)
Posterior view
Radial nerve (C5, 6, 7, 8, T1)
Inconstant contribution
Superficial (terminal) branch
Deep (terminal) branch
Lateral epicondyle
Anconeus muscle
Brachioradialis muscle
Extensor carpi radialis longus muscle
Supinator muscle
Extensor carpi radialis brevis muscle
Extensor carpi ulnaris muscle
Extensor-supinator
group of muscles
Extensor digitorum muscle and
extensor digiti minimi muscle
Extensor indicis muscle
Extensor pollicis longus muscle
Abductor pollicis longus muscle
Extensor pollicis brevis muscle
Posterior interosseous nerve
(continuation of deep branch of
radial nerve distal to supinator muscle)
Superficial branch of radial nerve
From axillary nerve
Superior lateral
brachial cutaneous
nerve
From radial nerve
Inferior lateral
brachial cutaneous
nerve
Superficial branch of
radial nerve and dorsal
digital branches
Posterior brachial
cutaneous nerve
Posterior antebrachial
cutaneous nerve
Cutaneous innervation from
radial and axillary nerves
Dorsal digital nerves

45
Conclusion
Fig. 1.50  The median nerve classically lends sensibility to the palmar aspect and the distal dorsum of the thumb, index, long, and radial half of the ring fingers. Intrinsic
muscles radial to the flexor pollicis longus and the two radial lumbricals receive motor innervation from the median nerve. (Reprinted with permission from
© Elsevier Inc. All Rights Reserved.)
Anterior view
Note: Only muscles innervated by median nerve shown
Musculocutaneous nerve
Median nerve (C5, 6, 7, 8, T1)
Inconstant contribution
Pronator teres muscle (humeral head)
Articular branch
Flexor carpi radialis muscle
Palmaris longus muscle
Pronator teres muscle (ulnar head)
Flexor digitorum superficialis muscle
(turned up)
Anterior interosseous nerve
Flexor pollicis longus muscle
Pronator quadratus muscle
Palmar branch of median nerve
Abductor pollicis brevis
Opponens pollicis
Superficial head of
flexor pollicis brevis
(deep head
supplied by
ulnar nerve)
Thenar
muscles
1st and 2nd
lumbrical muscles
Dorsal branches to
dorsum of middle and
distal phalanges
Medial
Posterior
Lateral
Cords of
brachial
plexus
Medial brachial
cutaneous nerve
Medial antebrachial
cutaneous nerve
Axillary nerve
Radial nerve
Ulnar nerve
Cutaneous
innervation
Palmar view
Posterior (dorsal) view
Proper palmar
digital nerves
Common palmar
digital nerves
Communicating branch
of median nerve with
ulnar nerve
Flexor digitorum profundus muscle
(lateral part supplied by median
[anterior interosseous] nerve;
medial part supplied by ulnar nerve)

46
SECTION I
CHAPTER 1 • Anatomy and biomechanics of the hand
Fig. 1.51  The palmar cutaneous branch of the median nerve travels superficial to
the flexor retinaculum of the hand while the remaining portion of the median nerve
travels deep. (Upper limb cadaver dissection, Stanford University Division of Clinical
Anatomy. © 2015 James Chang, Anais Legrand. All Rights Reserved.)
Flexor digitorum superficialis
Median nerve
Palmar cutaneous
branch
Flexor retinaculum (cut)
BOX 1.12  Clinical pearl: median and ulnar nerve lacerations
The ulnar and median nerves are frequently injured just proximal to
the wrist. The nerves are quite superficial and it is a region where
injuries to all structures are frequent. Median palsy alone results in
anesthesia over the important exploring and manipulating digits (the
thumb, index, and long fingers, and part of the ring finger) on the
palmar surface. The median positioning muscles of the thumb
become paralyzed, resulting in an inability to position the thumb for
pulp-to-pulp opposition with other digits. In addition, the two radial
lumbricals are paralyzed, but this may be barely perceptible
functionally. There is a constant midvolar blood vessel on the
median nerve that helps in its identity and in achieving very accurate
axial rotation to perfect end-to-end opposition.
The ulnar nerve divides into a deep motor branch and a
superficial sensory branch just beyond the pisiform. Occasionally,
stab wounds of the hand result in transection of the motor branch
with no sensory loss. A guide to proper fascicular orientation in the
ulnar nerve is the fact that one can identify that portion destined to
be the deep or superficial branches well above the wrist.
BOX 1.13  Clinical pearl: crowded areas with unyielding boundaries
Flexion and extension motions in the hand occur at two levels, the
wrist and the finger joints. Flexion at these joints would surely create
volar bowstringing at the long flexor tendons unless it were
prevented by fixed retinacular conduits at these points. At the wrist
the flexor retinaculum is the fixed roof of the carpal tunnel. The
fibrous flexor sheath in the digits forms a fitted pulley system with
condensed thickening in the areas of greatest fulcrum responsibility.
At the wrist and in the digital fibrosynovial sheaths, anatomic
structures create full occupancy. Any addition, whether it be more
structures, postinjury or inflammatory swelling of the contents, or
inflammatory tightening of the sheath, sets the stage for an
inflammatory reaction and adhesion formation.
At the wrist, the median nerve passes beneath the flexor
retinaculum and the transverse carpal ligament as the most
superficial structure in this crowded space. It is subject to
compression injury when swelling occurs within the carpal tunnel.
Just proximal to the wrist, the ulnar nerve passes from beneath
the flexor carpi ulnaris along the radial side of the easily palpable
pisiform. At this point the nerve enters a fibromusculofascial space
that is tubular in configuration, crossing the entire length of the
carpus. This is Guyon’s tunnel, which is quite separate from the
carpal tunnel, through which the median nerve and longitudinal
structures to the digits pass. Guyon’s tunnel starts at a hiatus
formed by the distal edge of the volar carpal ligament superficially
and the proximal edge of the transverse carpal ligament deeply. The
pisiform forms the ulnar side of the tunnel, and fibers from the volar
carpal ligament that plunge down to join the underlying transverse
carpal ligament form the radial wall. There is no fibrous roof on the
proximal part of the tunnel until the pisohamate arcade fibers are
encountered distally. The roof of the tunnel, therefore, consists of a
thick layer of fascia continuous with the hypothenar fascia and
generally a part of the palmaris brevis muscle. Through this rather
soft hiatus, the superficial branch of the ulnar artery and the arterial
branches to the palmaris brevis and overlying skin pass, together
with the superficial branches of the ulnar nerve. Within Guyon’s
tunnel the ulnar nerve lies ulnar to the artery, and the division of the
ulnar nerve into its deep motor branch and two superficial branches
is evident. After the superficial branches of the artery and nerve
emerge through the roof of the tunnel, the deep artery and deep
branch of the ulnar nerve enter the pisohamate tunnel beneath the
pisohamate arcade. Although the tunnel of Guyon is devoid of a
thick, fibrous roof, it is nonetheless covered by palmaris brevis
fascia, creating an unyielding space, and its contents are therefore
subject to compression from a variety of causes. Repeated trauma,
as when one uses the heel of the hand to pound objects, may result
in swelling of the tissues and resultant hypertrophy and fibrosis or
hemorrhage in the tunnel, which may squeeze the nerve or artery, or
both. Ganglia, tumors, or displaced bone may cause compression
in the ulnar tunnel, just as occurs with the median nerve in the
carpal tunnel.

47
Conclusion
Fig. 1.52  The ulnar nerve classically gives sensory innervation to the little finger and the ulnar half of the ring finger. All hypothenar muscles, all interossei, the two ulnar
lumbricals, the adductor pollicis, and the ulnar half of the flexor pollicis brevis are usually innervated by the ulnar nerve. (Reprinted with permission from
© Elsevier Inc. All Rights Reserved.)
Ulnar Nerve
Ulnar nerve (C7, 8, T1)
(no branches above elbow)
Inconstant contribution
Medial epicondyle
Articular branch
(behind condyle)
Flexor digitorum profundus
muscle (medial part only;
lateral part supplied by
anterior interosseous
branch of median nerve)
Dorsal branch of ulnar nerve
Flexor carpi ulnaris muscle
(drawn aside)
Palmar branch
Superficial branch
Deep branch
Palmaris brevis
Abductor digiti minimi
Flexor digiti minimi brevis
Opponens digiti minimi
Hypothenar muscles
Common palmar digital nerve
Palmar and dorsal interosseous muscles
Communicating branch of median nerve with
ulnar nerve
3rd and 4th lumbrical muscles (turned down)
Proper palmar digital nerves
(dorsal digital nerves are from dorsal branch)
Dorsal branches to dorsum of middle and distal phalanges
Adductor pollicis muscle
Posterior
(dorsal) view
Flexor pollicis brevis muscle
(deep head only; superficial
head and other thenar muscles
supplied by median nerve)
Palmar view
Cutaneous
innervation
Anterior view
Note: Only muscles innervated
by ulnar nerve shown

48
SECTION I
CHAPTER 1 • Anatomy and biomechanics of the hand
of the central nervous control mechanisms. As a unified inter­
related melding of these elements emerges, hand function
becomes the marvelous adaptable fact that it is in humans. Its
function is modified and further refined by sensory integrity.
Sensation is protective and influential on central motor func­
tion. Moreover, special sensation as it resides in the hand
makes the hand a special sense organ with which human
beings explore their environment. From a practical standpoint,
surgeons need repeatedly to remind themselves of the ana­
tomic basis for diagnosis and management of surgical prob­
lems in the hand.
Fig. 1.53  The dorsal branch of the ulnar nerve. (Upper limb cadaver dissection,
Stanford University Division of Plastic Surgery. © 2015 James Chang, Anais
Legrand. All Rights Reserved.)
Extensor retinaculum
Flexor carpi ulnaris
Dorsal branch of ulnar nerve
1. Bell C. The Hand – Its Mechanism and Vital Endowments as Evincing
Design. London: William Pickering; 1834. This treatise by Sir Charles
Bell is a literary classic that should be read by any student of hand
surgery and anatomy.
5. Bunnell S. Surgery of the Hand. Philadelphia: J. B. Lippincott; 1944.
This is the first edition of the first modern textbook in hand surgery,
written by Sterling Bunnell, widely regarded as the father of American
hand surgery.
17. Berger RA. The gross and histologic anatomy of the scapholunate
interosseous ligament. J Hand Surg. 1996;21:170–178. In this journal
article, Dr. Berger clearly describes the unique anatomy of the
scapholunate interosseous ligament. He discusses clinical implications of
the anatomy for injury patterns and repair/reconstruction.
24. Legueu F, Juvara E. Des aponèvroses de la paume de la main. Bull
Mem Soc Anat Paris. 1892;67:383. In this original manuscript, Legueu
and Juvara perform anatomic dissections to outline the palmar aponeurosis
of the hand. The vertical fibers that bear the authors’ names are described.
These vertical fibers separate the neurovascular and flexor tendon
compartments within the palm.
27. Gelberman RH, Menon J. The vascularity of the scaphoid bone.
J Hand Surg. 1980;5:508–513. The authors perform dye injection studies
to determine the vascular anatomy to the scaphoid. The relative decreased
blood flow to the proximal pole has implications for poor healing of
scaphoid fractures in this region.
Access the complete reference list online at

48.e1
References
References
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2. Duchenne GB. Physiologie des Mouvements. Philadelphia: J. B.
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and Juvara perform anatomic dissections to outline the palmar aponeurosis
of the hand. The vertical fibers that bear the authors’ names are described.
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compartments within the palm.
25. Bojsen-Moller F, Schmidt L. The palmar aponeurosis and the central
spaces of the hand. J Anat. 1974;117:55–68.
26. Gilula LA. Carpal injuries: analytic approach and case exercises. Am
J Radiol. 1979;133:503–517.
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determine the vascular anatomy to the scaphoid. The relative decreased
blood flow to the proximal pole has implications for poor healing of
scaphoid fractures in this region.
28. LaPorte DM, Shar Hashemi S, Lee Dellon A. Sensory innervation of
the triangular fibrocartilage complex: a cadaveric study. J Hand Surg
Am. 2014;39:1122–1124.
29. Viegas SF. The dorsal ligaments of the wrist. Hand Clin. 2001;17:
65–75.
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interosseous ligament. J Hand Surg. 1996;21:170–178.
31. Berger RA, Imeada T, Berglund L, et al. Constraint and material
properties of the subregions of the scapholunate and interosseous
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Mosby-Year Book; 1999.
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An experimental study of radial-ulnar deviation and flexion-
extension. J Bone Joint Surg. 1978;A60:423–431.
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the thumb interphalangeal and metacarpophalangeal joints. Clin
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35. Wolfe SW, Neu C, Crisco JJ. In vivo scaphoid, lunate, and capitate
kinematics in flexion and in extension. J Hand Surg Am. 2000;25:
860–869.
36. Graham KS, Goitz RK, Kaufmann RA. Curvatures of the DIP joints
of the hand. Hand (NY). 2014;9:522–528.
37. Watson HK, Light TR, Johnson TR. Checkrein resection for flexion
contracture of the middle joint. J Hand Surg. 1979;4:67–71.
38. Eaton RG, Littler JW. A study of the basal joint of the thumb. J Bone
Joint Surg. 1969;51A:661–668.
39. Dahhan P, Fischer L, Alliey Y. The trapeziometacarpal articulation.
Anat Clin. 1980;2:43–56.
40. Cooney WP, An KN, Daube JR, et al. Electromyographic analysis of
the thumb: a study of isometric forces in pinch and grasp. J Hand
Surg. 1985;10A:202–210.
41. Kuczynski K. The thumb and the saddle. Hand. 1975;7:120–122.
42. Kuczynski K. Carpometacarpal joint of the human thumb. J Anat.
1974;118:119–126.
43. Tubiana R. The Hand. Vol. II. Philadelphia: W. B. Saunders; 1985.
44. Pagalidis T, Kuczynski K, Lamb DW. Ligamentous stability of the
base of the thumb. Hand. 1981;13:29–36.
45. Bettinger PC, Berger RA. Functional ligamentous anatomy of the
trapezium and trapeziometacarpal joint (gross and arthroscopic).
Hand Clin. 2001;17:151–168.
46. Aubriot JH. The metacarpophalangeal joint of the thumb. In:
Tubiana R, ed. The Hand. Philadelphia: W. B. Saunders; 1981:184.
47. Lieber RL. Skeletal Muscle Structure and Function: Implications for
Rehabilitation and Sports Medicine. Baltimore: Williams and Wilkins;
1992.
48. Enoka RM. Neuromechanics of Human Movement. Champaign, IL:
Human Kinetics; 2001.
49. Garcia-Elias M, An KN, Berglund L, et al. Extensor mechanism of
the fingers: I. A quantitative geometric study. J Hand Surg Am.
1991;16:1130–1140.
50. Hurlbut PT, Adams BD. Analysis of finger extensor mechanism
strains. J Hand Surg Am. 1995;20:832–840.
51. Garcia-Elias M, An KN, Berglund L, et al. Extensor mechanism of
the fingers: II. Tensile properties of components. J Hand Surg Am.
1991;16:1130–1140.
52. Valero-Cuevas FJ, Zajac FE, Burgar CG. Large index-fingertip forces
are produced by subject-independent patterns of muscle excitation.
J Biomech. 1998;31:693–703.
53. Sancho-Bru JL, Perez-Gonzalez A, Vergara-Monedero M, et al. 3-D
dynamic model of human finger for studying free movements. J
Biomech. 2001;34:1491–1500.

48.e2
SECTION I
CHAPTER 1 • Anatomy and biomechanics of the hand
54. Leijnse JN, Bonte JE, Landsmeer JM, et al. Biomechanics of the
finger with anatomical restrictions – the significance for the
exercising hand of the musician. J Biomech. 1992;25:1253–1264.
55. Leijnse JN, Snijders CJ, Bonte JE, et al. The hand of the musician:
kinematics of the bidigital finger system with anatomical
restrictions. J Biomech. 1993;26:1169–1179.
56. Ikebuchi Y, Murakami T, Ohtsuka A. The interosseous and
lumbrical muscles in the human hand, with special reference to the
insertions of the interosseous muscles. Acta Med Okayama.
1988;42:327–334.
57. Zancolli E, Cozzi EP. Atlas of Surgical Anatomy of the Hand. New
York: Churchill Livingstone; 1992.
58. Chase RA. Surgical anatomy of the hand. Surg Clin North Am.
1964;44:1349.
59. Zajac FE. How musculotendon architecture and joint geometry
affect the capacity of muscles to move and exert force on objects: a
review with application to arm and forearm tendon transfer design.
J Hand Surg Am. 1992;17:799–804.
60. Agee J, McCarroll HR, Hollister AM. The anatomy of the flexor
digitorum superficialis relevant to tendon transfers. J Hand Surg
[Br]. 1991;16B:68–69.
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electromyographic recording during force generation. Application
to index finger kinesiologic studies. Am J Phys Med Rehabil.
1997;76:494–501.
62. Stack HG. A study of muscle function in the fingers. Ann R Coll
Surg Engl. 1963;33:307–322.
63. Tubiana R, ed. The Hand. Philadelphia: Saunders; 1981.
64. Wang K, McGlinn EP, Chung KC. A biomechanical and
evolutionary perspective on the function of the lumbrical muscle. J
Hand Surg Am. 2014;39:149–155.
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level. In: Blair WF, ed. Techniques in Hand Surgery. Baltimore:
Williams and Wilkins; 1996:398–406.
66. Earley MJ, Milner RH. Dorsal metacarpal flaps. Br J Plast Surg.
1987;40:333–341.
67. Small JO, Brennan MD. The first dorsal metacarpal artery
neurovascular island flap. J Hand Surg. 1987;13B:136–145.
68. Maruyama Y. The reverse dorsal metacarpal flap. Br J Plast Surg.
1990;43:24–27.
69. Hao J, Liu X, Ge B, et al. The second dorsal metacarpal flap with
vascular pedicle composed of the second dorsal metacarpal artery
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1993;92:501–506.
70. Sunderland S. Nerves and Nerve Injuries. 2nd ed. New York:
Churchill Livingstone; 1978.

SECTION I • Introduction and Principles
2 
Examination of the upper extremity
Ryosuke Kakinoki
SYNOPSIS
■ Physical examination of the upper extremity starts with a detailed and
accurate patient history.
■ Physical examination of the upper extremity consists of inspection,
palpation, measurement of length, girth, and ranges of motion,
assessment of stability, and detailed assessment of the associated
nerve and vascular systems.
■ Thorough understanding of the anatomy, physiology, and biomechanics
of the upper extremity is essential to perform a physical examination
correctly and to make a correct diagnosis of pathologic conditions of
the upper extremity.
■ Examiners must master correct physical examination techniques based
on the anatomy, physiology, and biomechanics.
■ The entire upper extremity should be examined, even if the patient’s
complaint focuses only on the hand.
■ It is essential to master correct techniques of physical examination to
identify the pathologic conditions of patients.
■ Examiners should have their own routine protocol of examination of the
upper extremity so as not to leave a part unexamined.
■ Comparison of the affected upper extremity with the contralateral
unaffected one helps examiners identify pathologic conditions.
■ Imaging modalities such as X-rays, CT or MRI should be
used to confirm the diagnosis drawn from the physical
examinations.
Obtaining a patient history
The patient history can be the most important tool in develop­
ing an accurate diagnosis. The history should not only detail
the patient’s current complaint, but should also document
other elements of the patient’s history which may be of great
significance for interpreting the patient’s current problem
and choosing between treatment options. A patient history
should include information on the patient’s demographics,
current complaint, medical history, allergies, medications, and
socioeconomic status. The time course of the patient history
interview should also be documented.
Patient demographics
The patient’s name, age, occupation, hand dominance, and
hobbies should be documented. Information about previous
injuries or diseases should be obtained regardless of whether
they seem to be related to the patient’s current complaint.
Current complaint
All information on the patient’s current problem, including
symptoms of pain, numbness, tingling (paresthesia), weak­
ness, dislocation, coldness, clumsiness, or poor coordination
and clicking or snapping should be documented. Each
symptom should be characterized according to its location,
intensity, duration, frequency, radiation and associated
symptoms. The patient history should include information
on activities or treatments that aggravate or ameliorate the
symptoms. It is also important to record the time and place at
which the initial injury occurred and the mechanism.
In trauma cases, the following data are especially
important:
1. The time of the injury and the interval between the
injury and the patient’s presentation should be
determined. The interval between an injury and
revascularization of amputated fingers has a great effect
on the outcome of replantation surgery.
2. The environment in which the injury occurred is
important. Whether an injury occurred in a dirty or a
clean environment may determine whether infection is
likely to be present.
3. The mechanism of injury is also important. For example,
information on the posture of the fingers and hand at
the time of a tendon laceration is helpful for locating a
transected tendon stump.
4. Any previous treatment associated with the injury is
documented.
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50
SECTION I
CHAPTER 2 • Examination of the upper extremity
assessment, stability assessment, nerve assessment, and vas­
cular assessment) should be included in the examination
procedure for patients with problems of the upper extremi­
ties. An understanding of the interrelationships among these
elements is helpful for drawing accurate diagnostic conclu­
sions. Repeated physical examinations reveal how symptoms
change over time, which is important for assessing the effec­
tiveness of the treatment.
Inspection
When inspecting the upper extremities, it is essential to
compare the affected extremity with the contralateral extrem­
ity because the latter can be used as a normal reference if the
injury is unilateral.
Discoloration
An abnormal skin color or a change in the color of the
skin of the upper extremity is indicative of a wide variety
of problems. Infections often cause swelling and patches of
redness with proximal streaking. Vascular problems caused
by arterial inflow insufficiency often present as pale colored
and the distal part of the upper limb appears to have shrunk,
whereas those caused by venous outflow insufficiency
present as a purple or dark red discoloration and a swollen
limb. The color of a hematoma can be used to estimate the
interval since the trauma occurred. A fresh hematoma has
purple or blue patches, which then become green and finally
yellow.
Deformity
Fractures, tumors, arthritis, and some infectious conditions
can cause deformities of the upper extremity. Fractures of the
phalanges of the fingers frequently result in angular rotation
or malrotation of the fingers. When the fingers are held up,
the point at which the long axes of the fingers converge cor­
responds with the position of the scaphoid tubercle. However,
the long axis of a malrotated finger deviates from the position
of the scaphoid.
Muscular atrophy
It is important to determine whether atrophied muscles are
innervated by specific peripheral nerves. If the atrophic
muscles are innervated by a specific nerve, the atrophy may
have been caused by a peripheral nerve disorder. Muscular
atrophy may occur under systemic neural or muscular patho­
logical conditions; in most of these cases, the atrophy is
symmetrical in the bilateral extremities. Generally, neurogenic
diseases involve muscles in the distal part of the extremity
and muscular diseases involve the proximal part of the
extremity. The girths of the arm (a portion measured should
be noted, like the arm girth 20 cm distal to the acromion) and
forearm (a portion with the maximum diameter of the forearm)
of both upper extremities should be measured routinely
because this often reveals a loss of muscle mass, which may
not be obvious to the eye.
Trophic changes
Trophic changes are associated with an abnormality of the
sympathetic nervous system. Increased hair growth or
In non-trauma cases, the following data are especially
significant:
1. The time at which symptoms such as pain, abnormal
sensation, swelling or stiffness began and the
subsequent progression of the symptoms is critical.
2. The effects of the symptoms on the patient’s daily life,
hobby or job are unique to that patient.
3. One must also ascertain whether or not the symptoms
are limited to one part of the body.
4. Activities or postures that aggravate or ameliorate the
symptoms are also discussed.
5. The association between time and the intensity of
symptoms must be carefully documented (e.g., whether
pain increases just after waking up in the morning or
during the night).
Medical history
The patient’s health status may influence diagnosis and treat­
ment. Before starting treatment, it is essential to determine
whether the patient has diabetes, or cardiac, pulmonary, and/
or renal disease and whether the patient has a history of
rheumatologic disease. Documentation of the family’s medical
history may be helpful for making an accurate diagnosis and
for choosing an appropriate treatment if the disease is heredi­
tary. Patients and their families should be questioned about
previous problems associated with bleeding and anesthesia.
It is also important to determine the course of any prior
surgery.
Allergies and medications
The patient history should include data on any medications
that the patient is taking. Previous allergic reactions to foods
or medications should be noted. People who are allergic to
shellfish are often allergic to contrast media that contain
iodine.
Social history
The social history includes the patient’s use of tobacco and
alcohol. The amount of tobacco and alcohol used should be
documented. Substance abuse and infection with hepatitis
virus or HIV should also be noted. The patient’s hobbies or
sports should be documented because these activities often
determine the most appropriate treatment.
Physical examination specific to
the hand
Accurate diagnosis of hand problems depends on a system­
atic, careful physical examination. Physical examination
should be performed routinely following a specific protocol.
Even if the patient complains of a problem limited to the
hand, the physical examination should start at the neck and
shoulder region because the hand is suspended by the bones
of the forearm, which connect proximally to the elbow joint,
which in turn is stabilized by the humerus and the shoulder
joint. In addition, numbness of the hand may be associated
with cervical problems. These elements (inspection, palpa­
tion, measurement of range of motion, musculotendinous

51
Physical examination specific to the hand
abnormal perspiration of the hands is often observed in
chronic regional pain syndrome.
Swelling
Swelling can be identified by comparison with the uninvolved
extremity. Localized swelling indicates recent trauma or
inflammation. Diffuse swelling is often caused by infection.
General swelling may originate from a lymphatic or venous
obstruction. Swelling of the dorsum of the hand is also
common.
Skin creases
Disappearance of skin creases is indicative of loss of motion
of the joint under the creases and can be helpful in determin­
ing the validity of a complaint of an inability to move the
fingers or upper extremities. Clear finger creases over joints
that a patient claims he or she is unable to flex or extend
indicate that the patient moves the joint. In such cases, the
patient may be malingering or may have a psychiatric condi­
tion in which he or she cannot recognize motion of the joint.
Palpation
Palpation is a powerful maneuver for identifying masses,
abnormal skin temperature, areas of tenderness, crepitance,
clicking or snapping and effusion. Masses in the deep layer
can be detected by palpation before they emerge as masses
under the skin. When performing palpation, special attention
should be paid to differences in hardness or mobility relative
to that of the surrounding tissue. For example, subtle palpa­
tion can identify a palmar bowstring of a flexor tendon in a
patient who complains of lack of finger flexion after an injury
of the flexor pulleys.
Assessment of musculotendinous function
The integrity of the tendon and the strength of the muscle
should be considered when conducting a musculotendinous
assessment.
Posture
When musculotendinous units are examined, it should be
kept in mind that the muscle strength and ranges of motion
of the hand and digits change depending on the posture of
the wrist, forearm or digits. For example, the range of motion
of the distal interphalangeal (DIP) joint of a finger is less when
the proximal interphalangeal (PIP) joint is passively extended
than when the PIP joint is flexed.
Motion
Both passive and active ranges of motion should be docu­
mented. The range of motion of both the contralateral healthy
limb and the affected limb should be measured and compared.
The range of motion may be affected by the posture of the
adjacent joints. For example, active and passive distal inter­
phalangeal (DIP) joint flexion is limited when the proximal
interphalangeal (PIP) joint of the same finger is extended.
When the wrist joint is flexed, the active range of finger flexion
decreases. The range of motion of a joint should be measured
in a posture that permits maximum motion.
The passive range of motion is measured by holding proxi­
mal and distal to the joint in question and then moving the
joint from one limit of motion to the other in the absence of
any muscular contraction by the patient. A limited range of
passive motion is associated with joint stiffness and/or soft
tissue contracture.
The active range of motion of a joint is that which occurs
when the patient contracts his or her muscles. The active
range of motion is affected by tendon excursion, the posture
of the hand and fingers, nerve function, and muscular strength.
Power
Muscle power is classed according to the Medical Research
Council scale, which ranges from zero to five (0–5) (Table 2.1).1
Grip strength is a good indicator of the global muscle strength
of the upper extremity. Grip strength is measured using a
dynamometer with the shoulder and elbow joints stabilized.
The patient grips the dynamometer with the elbow straight­
ened beside the trunk in the standing position or flexed 90°
in the sitting position. Measurement of pinch grip strengths
includes the average of three grip strength trials on the
affected and unaffected hands using a Jamar pinch gauge in
two different postures. These include a lateral pinch grip
measured between the thumb pulp and the radial aspect of
the second digit, and a thumb–forefinger pinch grip measured
between the tips of the thumb and forefinger. For both grips,
the shoulder is adducted and neutrally rotated, and the
forearm and wrist are in a closely neutral and comfortable
position (Fig. 2.1).
Examination of the muscles of the hand
There are many muscles and tendons in the hand. Muscles,
the origin and insertion of which are both distal to the wrist
joint, are called intrinsic muscles. Muscles extending across
the wrist joint are called extrinsic muscles. Other muscles
often compensate for a nonfunctioning muscle, in which
case the nonfunctioning muscle appears to function. To
evaluate muscle function, each muscle should be evaluated
in a posture or situation in which the cooperative muscles
do not function. For example, the extensor pollicis longus
(EPL) can compensate for impaired thumb adduction. Even
when the thumb adductors do not function because of ulnar
nerve palsy, patients may be able to adduct the thumb using a
functional EPL.
Table 2.1  Medical research council scale
Grade
Physical examination findings
0
No contraction
1
Flicker or trace contraction
2
Active movement with gravity eliminated
3
Active movement against gravity
4
Active movement against gravity and resistance
5
Normal power
(Reproduced with permission from: Seddon HJ. Peripheral Nerve Injuries.
Medical Research Council Special Report Series, 282. London: HMSO; 1954.)

52
SECTION I
CHAPTER 2 • Examination of the upper extremity
fingers except that of the finger to be tested to keep the MP,
PIP, and DIP joints of the other fingers in full extension. The
patient is then asked to flex the finger to be tested. Each finger
is tested individually. The FDS moves when the other fingers
are kept fully extended.
Flexor pollicis longus muscle
The flexor pollicis longus (FPL) inserts on the palmar
surface of the distal phalanx of the thumb and can be tested
by asking the patient to flex the interphalangeal (IP) joint of
the thumb.
Milking test of the finger and thumb flexor tendons (Video 2.14
)
Purpose: To evaluate the continuity and excursion of the
extrinsic flexors of the thumb and fingers. This test and the
dynamic tenodesis test (Video 2.13
) are useful for distin­
guishing nerve palsy from tendon rupture.
Maneuver: The patient is asked to place the dorsum of the
forearm and the hand on a table and to relax. The examiner
pushes down on the musculotendinous junctions of the flexor
tendons around the palmar aspect of the mid-forearm. If the
tendons have normal excursion and no adhesions, the fingers
and thumb flex as the forearm is pushed down.
Extensor pollicis brevis and abductor pollicis longus muscles
The extensor pollicis brevis (EPB) inserts at the dorsal base of
the proximal phalanx of the thumb. It is sometimes connected
to the EPL. The abductor pollicis longus (APL) has several
tendon slips and inserts at the dorsolateral base of the thumb
metacarpal and trapezium. Both tendons pass through the
first dorsal compartment at the wrist (the APL tendon lies
radial to the EPB in the compartment). When the patient
abducts the thumb maximally, the EPB and APL tendons as
well as the EPL tendon merge under the skin over the radio­
dorsal side of the wrist and create the snuffbox. The EPB and
APL tendons are palpable as taut tendons in the radiopalmar
border of the snuffbox. The tendinitis of the EPB and APL at
the radial wrist level is known as de Quervain’s tenosynovitis.
There are two provocative tests for diagnosing de Quervain’s
tenosynovitis.
The presence of abnormal muscles or an abnormal linkage
of tendons should sometimes be considered. The flexion func­
tion of the PIP joint of a finger is generally accepted to be
independent of that of the other fingers because the flexor
digitorum superficialis (FDS) tendon of each finger has its
own muscle belly. The motion of the FDS tendon of the small
finger is often linked to that of the ring and/or the long finger
and the PIP joint flexion of the small finger often coordinates
with that of the ring and/or long fingers.2 The extensor digi­
torum manus brevis is sometimes present in the middle finger
and causes dorsal wrist pain.3
Examination of the extrinsic muscles
Flexor digitorum profundus muscle
The flexor digitorum profundus (FDP) tendons insert on the
palmar surface of the distal phalanx of the fingers. Because
the FDP muscles share a common origin, holding the DIP joint
of a finger in full extension may prevent motion of all FDPs.
Flexor profundus test (Video 2.1
)
Purpose: This test is used to assess the continuity, excursion,
and muscle power of each of the FDP tendons.
Maneuver: The patient’s hand is placed palm up on a table.
The examiner presses down on the proximal and middle
phalanges of the target finger to keep the metacarpophalan­
geal (MP) and PIP joints in extension and asks the patient to
flex the DIP joint. The test should be performed on each finger.
Flexor digitorum superficialis muscle
The flexor digitorum superficialis (FDS) tendons insert on the
proximal half of the palmar surface of the middle phalanx of
the fingers. Because each FDS tendon has its own muscle belly,
its function is independent of the FDS of the adjacent fingers.
Flexor sublimis test (Video 2.2
)
Purpose: This test is used to assess the continuity, excursion,
and muscle power of each of the flexor digitorum superficialis
tendons.
Maneuver: The patient’s hand is placed palm up on a table.
The examiner presses down on the distal phalanges of all
A
B
Fig. 2.1  Lateral pinch (A) and thumb–forefinger tip pinch (B) grips.

53
Physical examination specific to the hand
Extensor indicis proprius muscle
The extensor indicis proprius (EIP) tendon passes through the
fourth extensor compartment at the wrist deep to the EDC
tendon and merges with the ulnar side of the index finger
EDC tendon over the MP joint. The function of the EIP is to
extend the MP joint of the index finger, which is isolated from
the extension of the MP joints of the other fingers. The EIP is
functional if the patient can straighten the index finger com­
pletely when the other fingers are flexed in a fist.
Extensor digiti minimi muscle
The extensor digiti minimi (EDM) tendon passes the fifth
extensor compartment and merges with the ulnar side of the
small finger EDC tendon at the MP joint level. Because the
EDM tendon is usually divided into two tails distally, both
tails of the tendon must be transected when the tendon is
transferred. This tendon is evaluated by asking the patient to
straighten the small finger when the other fingers are flexed
into a fist.
Extensor carpi ulnaris muscle
The extensor carpi ulnaris (ECU) tendon passes through the
sixth extensor compartment and inserts on the dorsal base of
the fifth metacarpal bone. The function of this tendon is ulnar
deviation of a wrist that is held extended. The wrist cannot
be extended dorsally only by the ECU. This tendon is evalu­
ated by asking the patient to make a fist and to lift and deviate
the wrist ulnarly. The tendon is palpable radial to the ulnar
styloid process.
Examination of the intrinsic muscles
Thenar muscles (Video 2.5
)
The thenar muscles cover the thumb metacarpal and consist
of three muscles: the abductor pollicis brevis, the flexor pol­
licis brevis and the opponens pollicis. The muscles move the
thumb into opposition, enabling the thumb to touch the fin­
gertips when the nails are parallel. These muscles are evalu­
ated by asking the patient to place the dorsum of the hand
flat on a table and to raise the thumb until it is perpendicular
to the palm. The patient is then asked to resist a downward
force by the examiner on the thumb.
Adductor pollicis muscle
The adductor pollicis (ADP) muscle arises from the third
metacarpal and inserts to the ulnar base of the proximal
phalanx of the thumb. Some fibers of the ADP extend dorsally
to form an extensor apparatus for the thumb. Together with
the first dorsal interosseous muscle, the ADP approximates
the thumb to the second metacarpal.
Interosseous and lumbrical muscles (Video 2.6
)
The interosseous and lumbrical muscles flex the MP joints and
extend the PIP and DIP joints of the fingers. In addition, four
dorsal interosseous muscles abduct the thumb and the radial
three fingers and three palmar interosseous muscles adduct
the fingers. The second and third dorsal interosseous muscles
are evaluated by asking the patient to place the hand flat on
a table and then to stretch the long finger upward (i.e., to
hyperextend it) and to deviate it radially and ulnarly. Patients
with ulnar nerve palsy cannot do this because of loss of power
Finkelstein test
Purpose: To detect de Quervain’s tenosynovitis.
Maneuver: The patient places the hand on a table with the
thumb up. The examiner pushes down on the proximal
phalanx of the thumb. A patient with de Quervain’s tendinitis
will experience pain or discomfort in the first extensor com­
partment of the wrist.
Eichoff test (Video 2.15
)
Purpose: To detect de Quervain’s tenosynovitis.
Maneuver: The patient is asked to hold the thumb with the
four flexed fingers of the affected hand. The hand is deviated
ulnarly by the examiner. A patient with de Quervain’s teno­
synovitis will experience pain or discomfort in the first exten­
sor compartment of the wrist.
Extensor carpi radialis longus and brevis muscles
The extensor carpi radialis longus (ECRL) and brevis (ECRB)
tendons insert at the dorsal bases of the second and third
metacarpal bones, respectively. The function of these muscles
is to extend the wrist joint. Because the functional axis of the
ECRL deviates radially, the ECRL extends the wrist dorsoradi­
ally. When the ECRB does not function, extension of the wrist
deviates radially because of the intact ECRL tendon. The
extensor digitorum communis (EDC) tendon also may func­
tion as a wrist extensor. To remove the EDC contribution to
wrist extension, the patient is asked to make a fist and then
extend the wrist. Making a fist eliminates EDC function.
Extensor pollicis longus muscle (Video 2.3
)
The extensor pollicis longus (EPL) passes through the third
dorsal compartment, turns radially at the Lister’s tubercle and
inserts at the dorsal base of the distal phalanx of the thumb.
The EPL extends the IP joint of the thumb. The hand is placed
palm down on a table with the thumb adducted. The patient
is asked to lift only the thumb off the surface of the table,
keeping the thumb adducted. The taut EPL tendon is palpable
in the radiodorsal aspect of the wrist.
Clinical tip
The EPL tendon is often connected to the extensor pollicis
brevis (EPB) tendon. Although the EPL tendon is not
functioning, the thumb IP joint can be extended by means of
the force of the EPB tendon. When examining EPL function, one
must eliminate EPB function by stabilizing the thumb MCP joint.
Extensor digitorum communis muscles (Video 2.4
)
The extensor digitorum communis (EDC) tendons pass
through the fourth extensor compartment and insert at the
dorsal base of the middle phalanges of the fingers. They mainly
extend the MP joint, while the intrinsic extensors extend the
PIP and DIP joints. EDC function is examined by asking
the patient to lift the MP joints of four fingers (the index to the
small finger) keeping the PIP and DIP joints flexed.
Extrinsic tightness test
The PIP joint is more easily flexed when the MP joint is kept
extended than when it is flexed, signifying that tightness of
the extrinsic muscles is present.4

54
SECTION I
CHAPTER 2 • Examination of the upper extremity
the situation of FDP tendon repair using a tendon graft, which
is longer than the appropriate length.
Hypothenar muscles
The hypothenar muscles (the abductor digiti minimi, the
flexor digiti minimi, the opponens digiti minimi, and the
palmaris brevis muscle) abduct the small finger, moving it
away from the other fingers.
Assessment of stability
The tightness of the ligaments around a joint, morphology of
the surface of a joint, and musculotendinous balance around
a joint are useful indices of joint stability. The stability of liga­
ments is tested by holding the portions distal and proximal to
the joint and gently moving the joint passively to stress the
ligaments that stabilize the joint. When assessing joint stabil­
ity, the biomechanical and physiological properties of the liga­
ments should be taken into consideration and the stress forces
applied should be appropriate for the ligament in question.
For example, the bilateral collateral ligaments of the finger
metacarpal (MP) joints tighten when the joint is in the flexed
position (Fig. 2.4), whereas those of the PIP joints tighten
when the joints are in an extended position. The lateral insta­
bility of the MP joints is assessed at the fully flexed position,
and the PIP joints should be checked at the neutral position.
It is useful to measure the opening angle of the affected joint
under stress using X-rays and to compare the opening angle
of the affected joint with that of the corresponding healthy
joint of the opposite hand (Fig. 2.5).
Assessment of the stability of wrist joints is complex and
difficult. The stability of the wrist joint is determined by the
stability of the radiocarpal, ulnocarpal, distal radioulnar, and
midcarpal joints. Special tests for assessing the stability of
specific ligaments or imaging tools such as X-rays, CT or MRI
may be helpful in making a diagnosis.
in the interosseous muscles (the Pitres–Testut sign). The first
palmar interosseous and the second dorsal interosseous
muscles are tested by crossing the index and middle fingers
(crossing fingers sign). The patient is asked to cross a flexed
long finger over the index finger or to cross a flexed index
finger over the long finger when the palm and the ring and
little fingers are placed flat on a table. (Finger abduction refers
to movement away from the long finger; finger adduction
refers to movement toward the long finger.)
Intrinsic tightness test (Bunnell)
Purpose: This test assesses the contracture of the interosseous
muscles.
Maneuver: The PIP joint is more easily flexed when the MP
joint is flexed than when it is extended (0 degree extended
position) if tightness of the interosseous muscles is present
(Fig. 2.2).5 The test can be performed using radial and ulnar
deviation of the finger to distinguish between tightness of the
radial and ulnar lateral bands.
Lumbrical-plus test
The lumbrical muscle connects the flexor digitorum profun­
dus tendon and the radial lateral band of each extensor
tendon. The PIP and DIP joints are apt to be extended when
a patient with lumbrical muscle tightness intends to flex a
finger.6 The finger flexion is thus blocked (paradoxical move­
ment of the finger) (Fig. 2.3). This movement is often seen in
Fig. 2.2  Intrinsic tightness test. If there is a tightness of the interosseous muscles,
the PIP joint can be more easily flexed when the MP joint is held flexed than when
the MP joint is extended. (A) The MP joint is extended. (B) The MP joint is flexed.
A
B
Fig. 2.3  Lumbrical muscle tightness test. Because the lumbrical muscle connects
the flexor digitorum profundus tendon and the radial lateral band of the extensor
tendon, the PIP and DIP joint are apt to be extended when the patient intends to flex
the finger (paradoxical movement). (A) Normal, (B) Abnormal, with lumbrical
tightness causing extension of the finger.
A
B

55
Physical examination specific to the hand
Fig. 2.4  The collateral ligament of the MP joint. The proper portion of the
collateral ligament is relaxed when the joint is extended (top) and is tight when the
MP joint is flexed (bottom). The smaller accessory portion has the opposite effect.
Fig. 2.5  Rupture of the radial collateral ligament of the index finger PIP joint. Measure the opening angle of the affected joint under the radial and ulnar stress forces on
X-ray films and compare the angle with that of the corresponding normal joint of the opposite hand. (A) Affected finger. (B) Normal opposite finger.
A
B
Clinical tip
Assessment of the lateral instability of the MP and PIP
joints of fingers.
The straight portions of the bilateral collateral ligaments of the
finger metacarpal (MP) joints tighten when the joint is in
the flexed position, whereas those of the PIP joints tighten
when the joints are in an extended position. The lateral
instability of the MP joints is assessed with the joint in full
flexion, and the PIP joints should be checked with joint in the
neutral position.
Scaphoid shift test (Watson) (Video 2.12
)
Purpose: This test was originally developed to detect loosening
or disruption of the scapholunate interosseous ligament. This
test can also be used to detect a scaphoid fracture or scapholu­
nate advanced collapse (SLAC) arthritis.
Maneuver: When the wrist deviates radially, the scaphoid
rotates palmarly, and the palmar prominence of the tubercle
of the scaphoid thus becomes evident. However, when the
wrist deviates ulnarly, the scaphoid rotates dorsally and
the bony prominence is less evident. The examiner holds the
dorsum of the patient’s hand with his or her fingers and
places his or her thumb onto the radial palmar wrist to palpate
the bony prominence of the scaphoid tubercle. When the
examiner holds the patient’s hand and deviates the wrist
radially and ulnarly, he or she will feel the motion of the bony
prominence under his or her thumb. When the examiner feels
the palmar movement of the bony prominence of the scaphoid
tubercle when moving the patient’s wrist from the ulnar to
the radial deviation, he or she pushes dorsally up on the
tubercle against the force of the palmar movement. If scaph­
olunate ligament insufficiency is present, the examiner will
feel a clunk on the thumb over the distal tubercle.7
Finger extension test
Purpose: To detect the pre-dynamic rotary subluxation of the
scaphoid (dorsal wrist syndrome).8
Maneuver: When being asked to extend the DIP and PIP joints
of all fingers fully, keeping the wrist and the MP joints of all
fingers in a full-flexed position, patients with overloaded
scapholunate ligaments (pre-dynamic rotary subluxation of
the scaphoid) experience pain around the scapholunate joint
in the dorsal wrist.
Triquetrolunate ballottement test and the lunotriquetral
shuck test
Purpose: To evaluate the stability of the lunotriquetral
ligament.