Orthognathic Surgery

391
CHAPTER 13  Standard Analytic Model Planning for Orthognathic Surgery
4
ORTHOGNATHIC SURGERY : ANALYTIC MODEL PLANNING
Data entry form
Patient name:
Surgical date:
Orthodontist:
Surgical wire date:
Final model date:
Dentist:
E
G
N
A
H
C
L
A
C
I
G
R
U
S
Y
R
A
L
L
I
X
A
M
S
T
N
E
M
E
R
U
S
A
E
M
E
L
B
A
T
N
O
S
K
I
R
E
s
r
o
sic
nit
a
e
g
n
a
h
c
la
t
n
o
zir
o
H
L
A
T
N
O
Z
I
R
O
H
Y
R
A
L
L
I
X
A
M
Vertical change at incisors
Midline change at incisors
Cant correction-Total
↑↓ on right
↑↓ on left
Maxillary plane change-Total
Clockwise - counterclockwise
Vertical change at T#3 (right) molar
(Base
cant
plane)
Vertical change at T#314 (left) molar
(Base
cant
plane)
OCCLUSAL EQUILIBRATION/MISSING TEETH
Upper right
Upper left
Lower right
Lower left
1
2
3
5
6 7 8 9 10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
OVERALL SURGICAL PLAN
Le Fort I
2 seg
3 seg
Sagittal splits of mandible
Genioplasty
Septoplasty
Reduction of inferior turbs
Wisdom teeth removal
Anterior neck rejuvenation
Graft required
Iliac
Allograft
HA
Baseline (mm)
Change (mm)
Final
Right #8
Left #9
MAXILLARY VERTICAL
MAX-MIDLINE (Right-side down)
MAX-MIDLINE (Left-side down)
Right #3
Right #8
Left #9
Left #14
#ML
#ML
#6-11
#3-14
MAX TRANSVERSE (Arch width)
MANDIBULAR HORIZONTAL
Baseline (mm)
Change (mm)
Final
Baseline (mm)
Change (mm)
Final
Baseline (mm)
Change (mm)
Final
Baseline (mm)
Change (mm)
Final
Baseline (mm)
Change (mm)
Final
#ML
C
C, The standard orthognathic surgery model-planning data sheet is shown.
Continued
• Figure 13-6, cont’d

392 SECTION 2  Planning, Surgical Technique, & Complications
79.5
79.5
D
Maxillary Horizontal
Baseline (mm)
Change (mm)
Final
Right #8
Left #9
74.5
74.5
5
5
Baseline (horizontal) position of incisors (mm)
96.2
95.8
E
Maxillary Anterior Vertical
Baseline (mm)
Change (mm)
Final
Right #8
Left #9
96.2
95.8
0
0
Baseline (vertical) position of incisors (mm)
D, The EMT is used to measure the baseline horizontal position of the incisors in mil­
limeters. This is the distance between the base of the EMT and the incisal edge of each maxillary central. The
millimeter number is recorded on the data sheet. The desired horizontal surgical change at the maxillary inci­
sors is also written on the data sheet. The final preferred horizontal position of the maxillary incisors, as a result
of model planning, is calculated and recorded. E, The EMT is used to measure the baseline vertical position
of the incisors in millimeters. This is the distance between the base of the EMT and the incisal edge of each
maxillary central incisor. The millimeter number is recorded on the data sheet. The desired vertical surgical
change at the maxillary incisors is also written on the data sheet. The final preferred vertical position of the
maxillary incisors, as a result of model planning, is calculated and recorded.
• Figure 13-6, cont’d

393
CHAPTER 13  Standard Analytic Model Planning for Orthognathic Surgery
89.1
89.7
F
Maxillary Posterior Vertical
Baseline (mm)
Change (mm)
Final
Right #3
Left #14
93.1
91.7
3/1
3/1
Baseline (vertical) position of first molars (mm)
(plane/cant)
43.6
41.1
G
Max-Midline (Right-Side Down)
Baseline (mm)
Change (mm)
Final
#ML 43.6
0
Max-Midline (Left-Side Down)
Baseline (mm)
Change (mm)
Final
#ML 41.1
0
Baseline transverse (midline) position of incisors (mm)
F, The EMT is used to measure the baseline vertical position of each maxillary first
molar. This is the distance between the base of the EMT and the mesiobuccal cusp tip of each maxillary first
molar. The millimeter number is recorded on the data sheet. The desired vertical surgical change at each maxil­
lary first molar is also written on the data sheet. The final preferred vertical position of the maxillary molars, as
a result of model planning, is calculated and recorded. G, The EMT is used to measure the baseline transverse
midline position of each incisor in millimeters. This is an indication of the maxillary dental midline position from
both the right side down and left side down directions. The base measurement is recorded on the data sheet.
The desired transverse change at the maxillary incisor is written on the data sheet. The final preferred transverse
midline position of the maxillary incisor, as a result of model planning, is calculated and recorded.
• Figure 13-6, cont’d

394 SECTION 2  Planning, Surgical Technique, & Complications
A
Remove the maxillary unit from the articulator
Then separate the maxillary cast from its base
B
3–segments?
2–segments?
Use die saw to segment maxilla
• Figure 13-7  The maxillary unit is now removed from the articulator. A, The maxillary cast is separated from its base. This is accom­
plished with the use of a die saw to cut a groove and a knife that is placed into the groove, which is then hit with a hammer. B, If
indicated, segmentation of the maxillary cast is carried out. This is done in accordance with patient-specific needs to correct the maxil­
lary arch form. Segmentation is generally carried out either as two parts (i.e., between the central incisors and then through the hard
palate) or as three parts (i.e., between the lateral incisor and the canine on each side and then through the hard palate). The maxilla is
cut by hand with a die saw instrument.

395
CHAPTER 13  Standard Analytic Model Planning for Orthognathic Surgery
C
3–segment alignment
2–segment alignment
Mandibular cast
A
Wax or clay to position
maxillary cast to base
Maxillary base
Maxillary cast
Maxillary cast is repositioned on maxillary base
according to clinical assessment/surgical plan
NOTE: If occlusal equilibration is required to achieve the preferred articulation, it is completed on the casts
and recorded at this time. The actual occlusal equilibration procedure is completed during surgery.
C, If segmentation of the maxillary cast is required, the cut segments are placed into the corrected arch form
by aligning the segments over the mandibular arch. It is important to maintain a physiologic orientation of the interdental papilla, with
tight contact between the teeth. Ideally, the adjacent roots are also parallel, with minimal divergence. The maxillary segments are secured
together in the corrected arch form with the use of hot glue from a glue gun.
• Figure 13-7, cont’d 
• Figure 13-8  A, The maxillary cast is next repositioned and reoriented on the maxillary base
in accordance with the clinical assessment and the surgical plan. The Erickson Model Table
(EMT) is used to ensure the correct spatial reorientation of the maxillary cast to achieve the
clinical objectives.
Continued

396 SECTION 2  Planning, Surgical Technique, & Complications
79.5
79.5
B
Maxillary Horizontal
Baseline (mm)
Change (mm)
Final
Right #8
Left #9
74.5
74.0
5
5
Maxillary horizontal change at incisal edge (5.0-mm advance)
96.2
95.8
C
Maxillary Anterior Vertical
Baseline (mm)
Change (mm)
Final
Right #8
Left #9
96.2
95.8
0
0
Maxillary vertical change at incisal edge (no change)
B, The EMT is used to accurately reposition the maxilla. For this patient (see Fig. 13-1), the
maxillary horizontal change at the incisal edge is a 5-mm advancement. C, In this case, the EMT also confirms that
no vertical change will occur at the maxillary incisal edge.
• Figure 13-8, cont’d

397
CHAPTER 13  Standard Analytic Model Planning for Orthognathic Surgery
89.1
89.7
D
Maxillary Posterior Vertical
Baseline (mm)
Change (mm)
Final
Right #3
Left #14
93.1
91.7
3/1
3/1
• Maxillary plane change
 3.0 mm vertical (plane) change at right 1st molar
 3.0 mm vertical (plane) change at left 1st molar
• Maxillary cant correction
 1.0 mm vertical (cant) change at right 1st molar
 1.0 mm vertical (cant) change at left 1st molar
Equal change at both tuberosities
to avoid altering in yaw orientation
Check “yaw” effect
at the occlusal level!!
E
D, The EMT is used to accurately reposition the maxilla at the molars. The confirmation of correct positioning at
the mesiobuccal cusp tip of each first molar is essential. The vertical change incorporates the desired three-dimensional roll and pitch
changes. E, When repositioning the maxilla, the EMT is useful to check for any yaw effect. Establishing equal side-to-side changes at both
tuberosity regions is required to avoid a yaw change of the posterior maxilla. The reoriented maxillary unit is placed back onto the articulator
for viewing.
• Figure 13-8, cont’d 
Continued

398 SECTION 2  Planning, Surgical Technique, & Complications
F
Desired A-pt B-pt alteration to enhance aesthetics (3 mm clockwise rotation of maxilla)
NOTE: Before going forward with intermediate splint construction, confirming the
yaw orientation of the maxilla relative to the mandible is essential.
F, The vertical pin on the articulator should remain neutral throughout the process.

• Figure 13-8, cont’d 
Apply Vaseline to maxillary and mandibular teeth
A
B
Use pink acrylic liquid and resin powder
• Figure 13-9  Construction of the intermediate splint. A, Apply a thin coat of Vaseline to the maxillary and mandibular teeth. B, Use pink acrylic
liquid and orthodontic resin powder, and mix them until the mass does not slump.

399
CHAPTER 13  Standard Analytic Model Planning for Orthognathic Surgery
C
Adapt mass to the maxillary occlusal surface
D
• Close articulator until pin touches
• Mandibular occlusal imprint will result
E
Carefully trim soft acrylic with scissors
C, Roll the mixed acrylic mass into a log shape. Adapt the mass to the maxillary occlusal surface. D, Close the
articulator until the vertical pin touches in a neutral location. A mandibular occlusal surface imprint will result. E, Limit “undercuts” from
brackets by carefully trimming the soft acrylic with scissors.
• Figure 13-9, cont’d 
Continued

400 SECTION 2  Planning, Surgical Technique, & Complications
F
Use lathe to trim excess hardened acrylic
Maintain adequate strength!
G
Use Dremel drill (acrylic burr) to trim excess hardened acrylic
F, When the acrylic is dry, use a lathe to trim excess hardened acrylic. Maintain adequate strength of the
splint to prevent bowing or breakage during surgery. G, Use a rotary drill (e.g., a Dremel drill) with an acrylic bur to further trim
excess hardened acrylic.
• Figure 13-9, cont’d

401
CHAPTER 13  Standard Analytic Model Planning for Orthognathic Surgery
Mandibular cast
“Final” occlusion
secured with hot glue
Maxillary unit
Remove maxillary unit from articulator
Separate mandibular cast from plaster base
Articulate mandibular cast to maxillary unit in “final” occlusion
A
B
Replace casts on articulator
Maintain articulator
pin in neutral position
Secure with hot
glue or plaster
Remove plaster
as needed
Secure mandibular cast to base with hot glue
Then separate max/mand casts and confirm “final” occlusion
• Figure 13-10  Construction of the final splint. A, Remove the maxillary unit from the articulator. Separate the mandibular cast from the plaster
base as previously described for the maxillary unit (see Fig. 13-7, A). Next, articulate the mandibular cast with maxillary unit in the final desired
occlusion. Secure the final occlusion with hot glue from a glue gun. B, Secure the mandibular cast back to the base with the use of either hot glue
from a glue gun or white plaster. Maintain the articular pin in a neutral position to achieve this objective. It is generally necessary to remove as least
some plaster from the mandibular base during this process; only then is the hot glue or additional plaster used to secure the mandibular cast back
to the base. The dried glue that secured the occlusion together is now released. The desired occlusion is confirmed to be accurate before the
construction of the final splint.
Continued

402 SECTION 2  Planning, Surgical Technique, & Complications
C
Use clear acrylic liquid and resin powder
D
Adapt mass to the maxillary occlusal surface
E
Trim soft acrylic with scissors
C, Use clear acrylic liquid and orthodontic resin powder for the final splint. Mix the two together until the mass
does not slump. D, Roll the mixed acrylic mass into a log shape. Adapt the mass to the maxillary occlusal surface. E, Close the articula­
tor until the vertical pin touches in a neutral position. The mandibular occlusal surface will imprint into the acrylic as a result. Limit
“undercuts” from the brackets by carefully trimming the soft acrylic with scissors.
• Figure 13-10, cont’d

403
CHAPTER 13  Standard Analytic Model Planning for Orthognathic Surgery
F
Use additional acrylic to place wire
to reinforce palatal aspect of splint as needed
Paper clip wire
G
Drill holes (1.0-mm diameter) in both intermediate and final splints
H
Polish splints on lathe
F, Use additional acrylic to place a metal wire, if needed, to reinforce the palatal aspect of splint. This will prevent
bowing or breakage of splint when segmental osteotomies are carried out and when extensive arch expansion is required. G, Use a lathe and
a rotary drill (e.g., a Dremel drill) to trim excess acrylic from the hardened final splint. Next, place each splint (i.e., intermediate and final) in turn
on the maxillary cast, and determine the best location and direction for each interdental drill hole. Complete 1-mm drill holes with the use of a
rotary drill (e.g., a Dremel). H, Polish the splints on a lathe with the use of a cloth buffing wheel (i.e., pumice and Acrilustre) (Robert Bosch,
1800 W. Central Road, Mt. Prospect, IL).
• Figure 13-10, cont’d

404 SECTION 2  Planning, Surgical Technique, & Complications
A
Intermediate splint
Final splint
Preoperative articulated casts
Maxilla repositioned
Maxilla and mandible repositioned
B
C
Articulated dental casts after analytic model planning
• Figure 13-11  Dental casts on the semi-adjustable
articulator to demonstrate model planning and a view
of the finished splints. A, Intermediate and final splints
finished and ready for use. B, Lateral views of articu­
lated dental casts first mounted in a centric relation
bite and then after maxillary and final mandibular repo­
sitioning. C, Frontal and side views of articulated
dental casts demonstrating model planning. In this
case, note the extent of the maxillary clockwise rota­
tion (3 mm) needed to achieve a preferred A-point to
B-point relationship and also to overcome the procum­
bency of the maxillary incisors.

405
CHAPTER 13  Standard Analytic Model Planning for Orthognathic Surgery
maxillary occlusal plane to the Frankfort plane as measured
via lateral cephalometry. Of the three semi-adjustable artic­
ulators tested, the Whip Mix Quickmount 8800 came
closest to achieving the maxillary occlusal plane (with
respect to the Frankfort plane) as measured via lateral ceph­
alometry; it flattened the occlusal plane by only 2 degrees
(P < .05). The results of the Dentatus and Denar MkII
articulators demonstrated flattening of the occlusal plane by
5 degrees and 6.5 degrees, respectively. Ellis also demon­
strated how commonly used methods of face-bow registra­
tion may erroneously capture the spatial relationship of the
maxilla with the Frankfort horizontal plane.18 This is likely
to be problematic if the surgeon intends to use the Frankfort
horizontal from the patient’s cephalogram as the reference
plane from which facial aesthetic objectives will be planned.
A critical step in model planning is the accurate record­
ing of the relationship (i.e., angle and orientation) between
a designated facial plane and the maxillary occlusal plane. As
stated, capturing this orientation is accomplished with a
face-bow device that is used in the clinic setting. (Note: I
use the #8645 Quick Mount Face-Bow, Whip Mix Prod­
ucts, Louisville, KY.) The face-bow registration is then
transferred to the semi-adjustable articulator for the mount­
ing of the maxillary model. (Note: I use the #8500 Articula­
tor, Whip Mix Products, Louisville, KY.)
I prefer to judge the desired facial (surgical) change (i.e.,
horizontal, vertical, roll, pitch, and yaw) and register the
face bow from the natural head position (NHP) rather than
the Frankfort horizontal plane.
I prefer to use the NHP orientation as it is the same view
from which aesthetics of the face are typically judged by
others at conversational distance. Many clinicians prefer to
plan angular and linear surgical change for the patient’s face
from the Frankfort horizontal plane rather than the NHP.
If this is done, the surgeon should register the face bow as
precisely to the Frankfort line (i.e., the line between the
porion and the orbitale) as possible. He or she should then
meticulously attempt to mount the cast to match the ori­
entation of the maxilla with that of the Frankfort horizontal
plane.
NOTE: The use of a semi-adjustable articulator in
bimaxillary surgery will be more accurate and is therefore
preferred to the use of a simple hinge articulator.
NOTE: The importance of the face-bow semi-
adjustable articulator system to the process of accurately
capturing the occlusal plane with respect to Frankfort
plane orientation is only relevant if the surgeon is
planning facial aesthetic changes according to a strict
cephalometric analysis (i.e. that also depends on
Frankfort plane orientation).
Centric Relation: Definition and Capture
Definition of Centric Relation
In 1987, the definition of CR underwent a change in ter­
minology from being considered a mandibular position in
which the condyles are seated in the most “posterior
presurgical clinical examination, is one of the essential steps
to avoid unintended errors.10,28-35,42,43,49,58,60,64,65,71-76,82
Controversies Surrounding Model
Planning for Orthognathic Surgery
Articulator and Face-Bow Device Options
Face bow devices were developed in conjunction with simple
and semi-adjustable hinge articulators to assist with the reg­
istering of the maxillary arch position in relation to the axis
of the condylar hinge in three planes of space. The mechan­
ics of the face-bow device require a tripod localization. This
includes two posterior references to approximate the tem­
poromandibular joints and then an anterior point to relate
the maxillary cast three dimensionally to a selected horizon­
tal facial reference plane. The posterior reference points that
are generally used are the external auditory canals. The
anterior point is often aligned with the orbitale (i.e.,
the infraorbital rims). Selection of the anterior point (e.g.,
the orbitale) governs the horizontal facial reference plane.
This will in turn affect the steepness of the recorded maxil­
lary occlusal plane on the articulator; this is discussed later
in this chapter.
For orthognathic surgery, analytic model planning typi­
cally involves the use of an articulator that provides an
approximation of the anatomic relationship between the
hinged axis and the incisors. This type of articulator mecha­
nism is designed to approximate the individual’s actual
mandibular autorotation. This is especially important for
bimaxillary surgery, when autorotation of the maxilloman­
dibular complex helps to dictate the position of the maxilla
before the mandibular osteotomies are completed. Marko
conducted research to demonstrate that the mathematical
difference in the horizontal projection achieved when such
advancement is carried out in combination with a maxillary
impaction of 5 mm is significantly affected by the type of
articulator that is used.46 An average error of 2 mm was
found with use of the Galetti articulator (simple hinge),
whereas only 0.2 mm of error occurred with the Hanau
articulator (semi-adjustable).46
O’Malley and Milosevic compared three face-bow semi-
adjustable articulator systems to measure any differences in
the recorded steepness of the occlusal plane that was pro­
duced.52 The three articulators studied were the Dentatus
type ARL; the Denar MkII; and the Whip Mix Quick­
mount 8800. The recorded measurement of the steepness
of the occlusal plane was taken as the angle between the
face-bow bite fork and the horizontal arm of the articulator.
This measurement was then compared with the angle of the

406 SECTION 2  Planning, Surgical Technique, & Complications
Class II mandibular retrognathism) are more likely to invol­
untarily posture the mandible forward during the swallow­
ing technique.32,33
The chin-point guidance technique is accomplished by
using one hand to apply pressure to the subject’s chin and
the other hand to apply counter pressure to their occiput.
This allows the surgeon to apply posterior and superior
“vectored” force to the anterior aspect of the mandible. By
doing so, the condyles will be positioned in a superior-
anterior location within each glenoid fossa (i.e., CR) (see
Fig. 13-2).
Bite Registration Material
The material used to record CR (e.g., soft wax) is also con­
sidered as a potential source for the introduction of error.
Adrien and Schouver studied mandibular model-mounting
errors; they demonstrated that wax can create error and that
the error is directly proportional to the wax’s thickness.2
They suggest that the wax between the approximating teeth
be as thin as possible. In addition, the wax should not be
punctured, because this may result in sliding from CR to
centric occlusion (CO). The wax should also retain its rigid­
ity to avoid the distortion of contact points. The wax bite
must be protected after it is removed from the mouth,
because it is easily deformed. Ideally, it is used without
significant delay to the time that the models are mounted
on the articulator (see Fig. 13-2).
Inaccuracies of Osteotomy Site Measurements
when used in Isolation to Reorient the Maxilla
in Bimaxillary Surgery
The face-bow device is used to spatially orient patients’ dental
models on a semi-adjustable articulator. The belief that mea­
surements may then be made at the equivalent of the Le
Fort I osteotomy site to accurately reposition or reorient the
maxillary cast on the articulator without the use of the
Erickson Model Table is flawed. The errors of this model
surgery and splint-construction approach would then be
further compounded if the surgeon relied on actual Le
Fort I osteotomy site measurements during operation as a
gauge of where to reorient the maxilla without the assistance
of external facial reference landmarks and measure­
ments.13,28,36,40,41,53,56,57,59,69 The use of these methods (i.e.
osteotomy site measurements) to reposition the maxilla in
the dental laboratory before splint fabrication and then
during surgery before plate and screw fixation may work for
uncomplicated movements (e.g., limited horizontal and
vertical repositioning), but it is likely to become grossly
flawed when trying to accomplish complex yaw, pitch, and
roll orientation changes of the midface.
Accuracy of Current Analytic Model-Planning
Techniques to Achieve Desired Results
The Erickson Model Table is a device that is used to
document the baseline three-dimensional orientation of
superior” position to one in which they are placed in the
most “superior anterior” position in the glenoid fossa.72 For
analytic model planning in preparation for orthognathic
surgery, defining the position of the condylar head during
mandibular protrusion and lateral excursions is not critical.
However, it is essential to locate a mandibular position that
is reproducible with the teeth in occlusion. This must be
obtained without the assistance of the patient (i.e., with
fully relaxed masticatory muscles), and it needs to be reli­
ably accomplished both preoperatively in the clinical setting
and intraoperatively with the patient under anesthesia. This
position of the mandible with the teeth in occlusion is
usually registered in wax (i.e., a wax bite) and then trans­
ferred to the articulator. This is an important step for ana­
lytic model planning to be accomplished accurately.
An erroneous inconsistent recording of CR will lead to
the malpositioning of the maxilla or mandible during
surgery. A survey study conducted by Truitt and colleagues
confirmed that 98% of oral and maxillofacial surgeons
define CR as the most posterior superior positioning of the
mandible.79 Interestingly, a majority of the orthodontists
surveyed agree with the surgeons’ definition of CR, but
there was less consistency.79 According to the survey, sur­
geons and orthodontists do agree that dental casts of the
teeth for orthognathic planning should be mounted in CR.
Capturing of Centric Relation
Hellsing and McWilliam used a subtraction technique to
assess the repeatability of the CR recorded with a one-
handed push-back technique.31 They found that the man­
dibular condyles can be seated in a reproducible position,
which is well suited for the registration of CR. Campos and
colleagues compared the swallowing technique with the chin-
point guidance technique with the patient in both upright
and supine body positions and found that both techniques
established a physiologic CR in a reproducible manner.86
Interestingly, when the chin-point guidance method was
used, the work of these authors suggested that reliability was
greater with the patient in the upright, seated patient as
compared with the supine position.
Simon and Nicholls compared the chin-point guidance,
chin-point guidance with ramus support, and bimanual
manipulation techniques.68 They found that there were no
significant differences in the range of mandibular positions
that were observed. Interestingly, their study patients did
not include individuals with jaw deformities. It is known
that patients with specific patterns of jaw deformity (e.g.,
NOTE:  I find the chin-point guidance technique—
when used both preoperatively in the clinic setting and
intra­operatively by the same surgeon—to be both
reliable and convenient for the orthognathic surgery
patient. This is the method that I have adopted and that
I use successfully in clinical practice.

407
CHAPTER 13  Standard Analytic Model Planning for Orthognathic Surgery
the mounted maxillary model on the semi-adjustable
articulator. (Note: I use the Erickson Model Block and
Platform Model Measuring Kit designed by Great Lakes
Orthodontics Products, Tonawanda, NY.) The Erickson
Model Table is then used to assist the three-dimensionally
reposition and reorient the maxillary cast to the desired
facial (surgical) change.19,20 The reoriented maxillary
model on the articulator is then used to construct the inter­
mediate splint. In the operating room, the use of the pre­
fabricated intermediate splint in conjunction with precise
measurements of the anterior vertical dimension of the midface
(e.g., direct vertical measurement from the medial canthus
to the maxillary incisor on each side of face) has eliminated
many of the inaccuracies that were previously experienced
during model planning and surgical execution (see Fig.
13-6, C).20,27,36,40,41,51,53,56,57,66,81
Interestingly, the few studies published in the literature
show a wide range of variation between what was planned
by the clinician before surgery and what is then actually
achieved during operation with reference to the advance­
ment of the maxilla after Le Fort I osteotomy during
bimaxillary surgery. An exception is the study of Gil and
colleagues,28 who completed a retrospective study to evalu­
ate the predictability of maxillary repositioning (i.e., vertical
and horizontal change measured at the maxillary incisors)
after Le Fort I osteotomy during bimaxillary surgery.
They used analytic model-planning techniques, including
the following: 1) face-bow transfer 2) the use of a semi-
adjustable articulator 3) the use of Erickson Model Table
measurements 4) intermediate splint construction and 5)
the use of external facial height reference points during
surgery. A consecutive series of patients (n = 32) were ana­
lyzed, with measurements taken with consistent lateral
cephalometric radiographs before and 1 week after surgery.69
The results indicate less than a 1-mm difference between
the planned and the early postoperative results for both
vertical and horizontal repositioning in all patients.
Stanchina and colleagues also carried out a retrospective
study to measure the accuracy of external reference points
in conjunction with model planning to reposition the
maxilla during bimaxillary surgery.69 The study subjects (n
= 41) showed a surprisingly consistent mean difference
between predicted and achieved vertical repositioning of the
maxilla (0.36 mm; standard deviation, 0.26 mm). Their
success with horizontal repositioning was less accurate. The
mean horizontal variance was 1.4 mm (standard deviation,
1.63 mm).
Review of Key Steps for Successful Analytic Model
Planning and Surgical Execution
1. The direct visual examination of the patient by the surgeon
in the clinic setting. With the use of facial analysis, key
measurements of the individual’s maxilla in relationship
to the upper face (i.e., the forehead, external ears, and
orbits) are recorded. These measurements will confirm
variations from normal and define the surgical objectives
(see Fig. 13-1, H).
2. The use of a face-bow device to record the spatial orientation
of the upper face and condyles with regard to the maxilla.
This is generally done with the use of the external audi­
tory meatus for two of the reference landmarks. The
anterior aspect of the face bow (i.e., the frontal view) is
adjusted to be parallel with the interpupillary line. With
the patient’s head and neck in the NHP, the lateral
aspects of the face bow are then adjusted to orient the
temporal arms to be parallel with the floor (see Fig. 13-3
C and D).
3. The transfer of the spatial orientation of the maxilla to the
semi-adjustable articulator. This is done with the arms of
the face-bow and the upper arm of the articulator paral­
lel to the floor (counter top) (see Fig. 13-4 A).
4. The taking of an accurate CR bite registration of the patient
in the clinic setting. This is then used to orient the dental
models to each other on the semi-adjustable articulator
(see Figs. 13-2 and 13-4, C).
5. The use of the Erickson Model Table in the dental laboratory
to establish the baseline spatial orientation of the maxillary
cast (see Fig. 13-6, C).
6. The use of the Erickson Model Table to accurately reorient
the upper jaw model on the articulator into the desired
surgical position (see Fig. 13-8, A).
7. The fabrication of a splint for use during surgery to achieve
the planned maxillary reorientation (see Fig. 13-9)
8. The use of external facial measurements (e.g., the distance
from the medial canthus to the maxillary incisor) during
operation to establish the baseline vertical position of the
maxilla within the upper face and then to accurately
reorient the upper jaw to achieve surgical objectives (see
Fig 15-18, A).
9. The accurate location of the terminal hinge position of the
condyles during operation. This is done to reproduce
the position of the condyles when taking the CR bite
registration in the clinic setting, and it is essential before
rigid fixation is secured across each osteotomy site
(see Fig 15-37, B).
NOTE:  The reasons for variation between the
planned and actual maxillary advancement in most
published studies remain unclear. This is because the
descriptions of the key steps that they used are generally
not fully described.
COMMENT: The surgeon no longer attempts to
correlate millimeter changes at the Le Fort I osteotomy
site with the expected facial morphologic outcome.
When properly executed, the accuracy of analytic
model-planning techniques as described for precise
orthognathic surgery has been documented. This is
discussed in more detail later in this chapter.

408 SECTION 2  Planning, Surgical Technique, & Complications
Standard Facial Records for
Orthognathic Surgery
• Standardized facial and occlusal view photographs
• Lateral cephalometric radiograph
• Panoramic radiograph
• Alginate impressions of the maxilla and mandible
• CR wax bite registration
• Face-bow registration for transfer to a semi-adjustable
articulator
• Facial measurements taken via a direct visual examina­
tion (Fig. 13-1H).
• Analytic model planning data entry form (Fig. 13-6C)
• Cone-beam computed tomography scanning (patient
specific)
• Full-mouth periapical radiographs (patient specific)
Key Measurements Obtained via Direct
Visual Examination to Define Planned
Maxillary Surgical Change
Face-Bow Registration and Transfer to
the Semi-Adjustable Articulator
An 18-year-old recent high school graduate who presented
to this surgeon for the evaluation of an uncorrected
dentofacial deformity that was characterized as maxillary
deficiency with relative mandibular excess is described.
He is shown to demonstrate the technique of analytic
model planning as typically carried out (see Figs. 13-1,
13-12, and 13-13).
Face-Bow Registration
(see Figs. 13-2, A, through 13-3, G)
• Place soft wax on upper side of the face-bow bite fork.
• The midpoint between the central incisors (interproxi­
mal) should match the center of the bite fork.
• Register the patient’s maxillary occlusion into the soft
wax on the bite fork.
• Horizontal change at incisors
_________ (mm)
• Vertical change at incisors
_________ (mm)
• Midline change at incisors
_________ (mm)
• Maxillary plane change (total)
_________ (mm)
Clockwise—Counterclockwise
• Maxillary cant correction (total)
_________ (mm)
↑ ↓ _____on right
↑ ↓ _____on left
• Vertical change at T#3 (right) molar
(Base + Cant + Plane)
___ + ___ + ___ = ___ (mm)
• Vertical change at T#14 (left) molar
(Base + Cant + Plane)
___ + ___ + ___ = ___ (mm)
The Role of Computer-Aided Software Design
and Model Planning
For a variety of reasons, some patients with complex maxil­
lofacial skeletal deformities undergo treatment that achieves
suboptimal results. Despite the surgeon’s best efforts, it can
be difficult to assess the preferred surgical spatial reorienta­
tion of the jaws for the achievement of ideal facial projec­
tion and symmetry. Although standard analytic model
planning (as described in this chapter) has proven to be
effective for most orthognathic surgical problems, three-
dimensional deformities of pitch, roll, and yaw continue to
confound the ability to achieve predictable results in each
and every patient. The current standard treatment planning
process is also felt to be time consuming and labor intensive,
especially for those clinicians who do not evaluate dentofa­
cial deformities and execute orthognathic surgery as signifi­
cant components of their practice.
Recently, surgeons have begun looking to computer-
aided design and computer-aided modeling software to
assist with the planning and implementation of orthogna­
thic procedures.3-5,7,11,23,24,25,45,47,48,61,67,70,83,84 These technolo­
gies allow clinicians to import two-dimensional computed
tomography data in a digital imaging format at a computer
work station and to then generate a three-dimensional rep­
resentation of the patient’s skeletal and soft-tissue anatomy.
The data set can be used to mill a stereolithographic model,
or it can be manipulated on the computer screen for pur­
poses of analysis and treatment planning. The ability of
virtual model planning (as opposed to analytic model plan­
ning, as described in this chapter) to routinely achieve an
improved end result for the orthognathic patient has yet to
be confirmed. It is also unclear whether the higher costs of
virtual model surgery planning can be offset by savings in
the clinician’s time that would otherwise be required for
analytic model planning.
A successful orthognathic outcome is often judged by the
achievement of a preferred occlusion, an open upper airway,
and enhanced facial aesthetics. Any methods that are proven
to better achieve these objectives over the long term with
efficiency and reliability are welcomed. Unfortunately,
current virtual model surgery planning still requires that
alginate impressions of the maxilla and mandible be taken,
that plaster models be made of the maxillary and mandibu­
lar arches, and that ideal occlusion be hand articulated and
marked by the surgeon into the set final occlusion. If seg­
mental osteotomies are required, the surgeon must also cut
the plaster models and secure them together as required to
achieve the set final position. Furthermore, a computer-
generated surgical splint has not yet been proven to be fully
reliable for complex, double-jaw surgical cases.11 Problems
that remain to be addressed include the following: the iden­
tification of internal reference systems; the making of three-
dimensional measurements; the management of interferences
by metal (orthodontic) hardware; the orientation of com­
puted tomographic models to the NHP; and the necessity
of capturing the computed tomography data while the
patient is in CR.

409
CHAPTER 13  Standard Analytic Model Planning for Orthognathic Surgery
• Place an ear prong in each ear canal, and hold the tem­
poral extensions with even pressure medially, superiorly,
and forward. Tighten the three thumb screws of the
temporal extensions.
• In the frontal view, the face bow is initially adjusted to
be parallel with the pupils and in proximity to the infra­
orbital rims.
• If the orbits are asymmetric (e.g., in a patient with
hemifacial microsomia or the Klippel–Feil anomaly),
do not use the interpupillary line as a frontal reference
plane. Instead, use the NHP as the facial reference
plane.
• In the profile view, the face bow is adjusted to be parallel
with the floor while the patient is in the NHP.
• If the ear canals are asymmetric, do not rely on them
for face-bow orientation. For example, for a patient
with hemifacial microsomia, if the ear canal on one
side is not present or is abnormally located, then
place the face-bow ear prong in the appropriate posi­
tion to approximate the contralateral ear canal. The
face bow should be parallel with the floor while the
patient is in the NHP (i.e., the NHP is the reference
plane).
Or
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A
B
• Figure 13-12  The patient is shown before and just 5 weeks after surgery. At this time, adequate
bone healing has occurred to allow for a return to a more normal diet and physical activity level. The
patient is also returned to the care of his orthodontist. A, Frontal views in repose before and 5 weeks
after surgery. B, Frontal views with smile before and 5 weeks after surgery.
Continued
Text continued on p. 415

410 SECTION 2  Planning, Surgical Technique, & Complications
Orth
r ognathic Surg
r ery; J.C. Posnick
Orth
r ognathic Surg
r ery; J.C. Posnick
Orth
r ognathic Surg
r ery; J.C. Posnick
Orth
r ognathic Surg
r ery; J.C. Posnick
C
D
C, Oblique facial views before and 5 weeks after surgery. D, Profile views before and 5 weeks after surgery.
• Figure 13-12, cont’d

411
CHAPTER 13  Standard Analytic Model Planning for Orthognathic Surgery
E
Prior to orthodontics
Pre surgery
5 weeks after surgery
Le Fort I
Sagittal
splits
A pt.
B pt.
Genioplasty
F
E, Occlusal views before treatment, immediately before surgery, and just 5 weeks after surgery at the time
of splint removal. F, Computed tomography scan views 5 weeks after surgery. The sites of the maxillary, mandibular, and chin oste­
otomies and the location of standard fixation can be seen.
• Figure 13-12, cont’d

412 SECTION 2  Planning, Surgical Technique, & Complications
Orth
r ognathic Sur
u g
r ery; J.C. Posnick
Orth
r ognathic Sur
u g
r ery; J.C. Posnick
Orth
r ognathic Sur
u g
r ery; J.C. Posnick
Orth
r ognathic Sur
u g
r ery; J.C. Posnick
A
B
• Figure 13-13  The same patient is shown before and then 1½ years after surgery. A, Frontal views in repose before and 1½ years after
surgery. B, Frontal view with smile before and 1½ years after surgery.

413
CHAPTER 13  Standard Analytic Model Planning for Orthognathic Surgery
Orth
r ognathic Sur
u g
r ery; J.C. Posnick
Orth
r ognathic Sur
u g
r ery; J.C. Posnick
Orth
r ognathic Sur
u g
r ery; J.C. Posnick
Orth
r ognathic Sur
u g
r ery; J.C. Posnick
C
D
C, Oblique facial views before and 1½ years after surgery. D, Profile views before and 1½ years after surgery.
• Figure 13-13, cont’d 
Continued

414 SECTION 2  Planning, Surgical Technique, & Complications
Prior to orthodontics
Pre surgery
E
5 weeks after surgery
1½ years after surgery
E, Occlusal views before treatment, immediately before surgery, and then 5 weeks and 1½ years after the
completion of treatment.
• Figure 13-13, cont’d

415
CHAPTER 13  Standard Analytic Model Planning for Orthognathic Surgery
• When the casts are dry (≈15 min), remove the alginate
and base former from each stone cast. Measure 30 mm
of base on the mandibular cast and 25 mm of base on
the maxillary cast. Measure up from the following
locations:
• The first molar cusp tip on each side
• The canine cusp tip on each side
• The incisor cusp tip on each side
• Use a model grinder to trim at the 25-mm and 30-mm
circumferential markings, respectively, for the maxillary
and mandibular casts.
• Remove all blebs from the occlusal surface of the dental
casts.
Face-Bow Transfer: The Orientation of
the Dental Casts (Maxilla and Mandible)
on the Semi-Adjustable Articulator
(see Fig. 13-4, A through F)
• Secure the face-bow device to the semi-adjustable articu­
lator. Adjust both the face-bow device and the upper arm
of the articulator to be parallel to the floor and the
counter lap.
• Secure the plastic base plate to the dental articulator.
Place the maxillary cast on the bite-fork component of
the secured face-bow device. Use white plaster to mount
the maxillary cast to the base plate.
• Use the bite-fork support device to prevent the sagging
of the maxillary cast during this process. Let the plaster
initially set (≈15 min), and then remove the face-bow
apparatus and the bite-fork support device.
• Turn the articulator upside down, and secure the man­
dibular cast to the maxillary unit with the use of the CR
wax bite registration taken in the clinic setting. Further
secure the occlusion in CR with two rubber bands to
• Firmly hold the bite fork to the maxillary occlusal
surfaces (through the soft wax). Pressure is applied to
the bite fork by the patient with the use of a thumb
from each hand. When this is accomplished, do the
following:
• Loosely connect the bite fork, (which is held firmly
to the patients maxillary teeth), to the face-bow appa­
ratus, (which is held in place by the clinician), with
the use of the T-screws on the vertical rod.
• In profile and with the patient in the NHP, adjust the
face-bow temporal extensions to closely parallel the
floor.
• Tighten the two T-screws to secure the bite fork to
the vertical rod of the face-bow apparatus.
• Now that the face-bow registration is complete, loosen
the three thumb screws of the temporal extensions to
release the ear prong from each ear canal. Remove the
face bow from the patient for transfer to the semi-
adjustable articulator.
Take Alginate Impressions, Pour the
Impressions in Stone, and Trim the Casts
(see Fig. 13-3, H through K)
• Take accurate alginate impressions of the maxilla and the
mandible.
• Pour the alginate impressions in green stone, and
incorporate at least 30 mm of base. Base formers are
helpful to accomplish adequate base height. To limit air
bubbles, use a vibrator when pouring stone into alginate
impressions.
F
F, Lateral cephalometric views before and after surgery.
• Figure 13-13, cont’d 
NOTE: The use of stone rather than plaster improves
strength, with less porosity and less breakage.

416 SECTION 2  Planning, Surgical Technique, & Complications
compress the maxillary unit and mandibular cast together
through the bite registration.
• Place the plastic base plate onto the dental articulator,
and then use white plaster to mount the mandibular
cast to the base plate. Let the plaster initially set
(≈15 min).
• Cut the rubber bands used to secure the occlusion, and
remove the wax bite.
• Remove the maxillary unit from the articulator. With the
use of a model grinder, trim the maxillary cast, plaster
base and the base plate all as one unit.
• Remove the mandibular unit from the articulator.
With the use of a model grinder, trim the mandibular
cast, the plaster base and the base plate all as one unit.
Placement of Reference Lines on
the Maxillary and Mandibular Units
(see Fig. 13-5, A through E)
• With the use of the Erickson Model Table, “score” two
horizontal reference lines on the maxillary unit and then
on the mandibular unit. Locate the horizontal reference
lines on the maxillary and the mandibular units by doing
the following:
• Place the first horizontal line within the green stone.
• Place the second horizontal line within the white
plaster.
• Ideally, there will be 15 mm to 20 mm of separation
between these lines.
• With the use of a thick, black Sharpie pen, mark the
“scored” horizontal circumferential reference lines on
both the maxillary and mandibular units.
• With the use of a thick, black Sharpie pen, mark the
vertical reference lines on both the maxillary and man­
dibular units. The vertical lines are located perpendicular
to the horizontal lines and in the following places:
• At the cusp tip of each canine
• At the mesiobuccal groove of each first molar
• Between the central incisors (i.e., at the dental midline)
• Posterior at each tuberosity or retromolar area
Use of the Erickson Model Table to
Define the Spatial Orientation of the
Articulator-Mounted Maxillary Unit*
(see Fig. 13-6)
With the use of a thin, black Sharpie pen, locate specific
reference points from which measurements will be made.
Place a dot at the following reference points:
• The cusp tip of each maxillary canine
• The mesiobuccal cusp tip of each maxillary first molar
*The Erickson Model Table maxillary unit measurements that I find useful
are outlined earlier in this chapter. Other measurements can be made in
accordance with the clinician’s preference.
*This is the only Erickson Model Table mandibular unit measurement
that I find useful. Other measurements can be made in accordance with
the clinician’s preference.
• The midpoint of the incisal edge of each maxillary
central incisor
Baseline vertical (maxillary) measurements: With the
model block on its base, use the electronic caliper to
measure the distance (in mm) at the following areas: (see
Fig. 13-6 E and F)
• The incisal edge of each maxillary central incisor
(#8, #9)
• The mesiobuccal cusp tip of each maxillary first molar
(#3, #14)
Baseline horizontal (maxillary) measurements: With the
model block on its end, use the electronic caliper to measure
the distance (in mm) at the following area: (see Fig. 13-6D).
• The incisal edge of each maxillary central incisor
(#8, #9)
Baseline dental midline (maxillary) measurements: With
the model block on its side, use the electronic caliper to
measure the distance (in mm) at the following areas: (see
Fig. 13-6G)
• The dental midline
with the left side of the cast down
• The dental midline
with the right side of the cast down
Use of the Erickson Model Table to
Define the Spatial Orientation of the
Articulator-Mounted Mandibular Unit
Baseline horizontal (mandibular) measurement: With the
model block on its end, use the electronic caliper to measure
the distance (in mm) at the following area:
• The incisal edge of the mandibular central incisors
(#24/#25)*
Separation of the Maxillary Cast from
the Articulator Base (see Fig. 13-7, A)
• Remove the maxillary unit from the articulator. Separate
the maxillary cast from the plaster base over a protective
surface. You may first use the die saw to cut a groove
in between the green stone and the plaster base. Insert
a knife into this groove, and tap the knife with a
hammer.

417
CHAPTER 13  Standard Analytic Model Planning for Orthognathic Surgery
use of the Erickson Model Table. The key millimeter and
angular changes to be confirmed include the following:
• Maxillary (midface) projection
○ Horizontal change at incisors
• Maxillary incisor shown in repose and with smile
○ Vertical change at incisors
• Maxillary plane change (pitch orientation) and cant
correction (roll orientation), which are controlled by
the following:
○ Vertical change at incisors
○ Vertical change at first molars
• Maxillary midline position (yaw orientation)
○ Dental midline change (right side down)
○ Dental midline change (left side down)
• Considerations of lateral tuberosity position (yaw
orientation)
○ Analysis of lateral shift (change) at posterior maxilla
(tuberosity region)
• Soft wax or clay is used in a tripod fashion to facilitate
the initial placement of the maxillary cast back onto the
plaster base on the articulator in the preferred position.
It is generally necessary to trim the stone or plaster before
repositioning. Fine tune the maxilla into the preferred
position with the use of the Erickson Model Table (i.e.,
via horizontal, vertical, and transverse measurements).
After these measurements are confirmed, fully secure the
preferred maxillary position to the plaster base with hot
glue from a glue gun.
• When repositioning the maxilla into the preferred
position, take into consideration the yaw orientation.
Control the yaw orientation to avoid unwanted asym­
metric shifts, which would be visually noticeable in the
cheeks of the midface and at the mandibular angles (see
Chapter 12).
Intermediate Splint Construction for
the Positioning of the Maxilla During
Operation (see Fig. 13-9, A through E)
• With the maxilla secured in the new preferred position
but without any changes yet made to the baseline man­
dibular position, the intermediate (occlusion) splint is
constructed.
• Apply a thin coat of Vaseline to the maxillary and man­
dibular occlusal surfaces with a toothbrush.
• Use pink acrylic liquid and standard acrylic powder. Mix
these until the mass does not slump. Apply Vaseline to
your hands, and roll the mass into a log shape. Adapt
the mass to the maxillary occlusal surface, and close the
articulator until the vertical pin touches. This will result
in an imprint of the mandible occlusal surfaces on the
opposite side.
• Maintain the acrylic just below the level of the base of
the maxillary orthodontic brackets and just above the
base of the mandibular orthodontic brackets. Use sharp
Transverse distance between maxillary molars (#3 to #14)

• Initial
_____ (mm)

• After segmentation
_____ (mm)
Transverse distance between maxillary canines (#6 to #11)

• Initial
_____ (mm)

• After segmentation
_____ (mm)
Segmentation of the Maxilla
(see Fig. 13-7, A, B, and C)
Segmentation and Subsequent Reorientation
of the Maxilla
• Use a die saw to segment the maxilla, as planned (i.e.,
two pieces versus three pieces).
• After the maxilla is segmented, align the segments over
the mandibular arch into the preferred occlusion. Secure
the segments back together with the use of hot glue from
a glue gun.
• Occlusal equilibration may be indicated to achieve
the preferred occlusion (e.g., plunging palatal cusps
on maxillary molars, bicuspid cusp reduction to level
the posterior arch). If so, use a sharp plaster knife to
complete adjustments on the occlusal surfaces of the
maxillary and mandibular casts. Use a red Sharpie pen
to mark the exact locations where enamel adjustments
were made. The actual equilibration is carried out in
the operating room.
• When repositioning the maxillary segments into
occlusion with the mandibular arch, it is essential to
maintain the physiologic positioning of the interden­
tal papilla and the contact points of adjacent teeth at
all interdental osteotomy sites. If dental gaps are
created or if cervical margins are not reasonably
aligned, then periodontal sequelae are more likely.
Measurement of the Maxillary Arch Width
Before and After Segmental Osteotomies
Use of the Erickson Model
Table Measurements to
Reorient the Maxillary Cast
(see Fig. 13-8, A through F)
• The repositioning of the maxilla on the articulator is
meant to accurately match the desired surgical changes.
These changes have been determined in accordance with
the following: 1) the patient’s clinical objectives (i.e., pre­
ferred facial aesthetics and improvements in function)
2) by taking into account any biologic skeletal, dental, or
soft-tissue limitations and 3) the surgeon’s clinical, dental,
and radiographic analyses (see Chapter 12).
• After the key desired adjustments to the midface are
reproduced on the maxillary unit, they are verified with

418 SECTION 2  Planning, Surgical Technique, & Complications
• If segmental osteotomies are planned, maintain at least
3 mm to 4 mm of lingual acrylic behind the incisors to
prevent splint breakage or torque, which may otherwise
occur in the operating room.
Reorientation of the Mandibular
Cast to Register the Final Occlusion
(see Fig. 13-10, A and B)
• Separate the mandibular cast from the plaster base (as
was done for the maxillary cast).
• Articulate the mandibular cast with the maxillary unit in
the desired final occlusion, and secure the occlusion with
hot glue.
• With the vertical articulator pin remaining in a neutral
position, secure the mandibular cast back to plaster base.
This may require the removal of interferences in the
plaster base or the addition of material (e.g., plaster,
hot glue).
• Remove the glue that was used to secure the occlusion,
and confirm the accuracy of the final occlusion.
Final Splint Construction for the
Positioning of the Mandible During
Operation (see Fig. 13-10, C through F)
• Reapply Vaseline to the maxillary and mandibular occlu­
sal surfaces of the teeth with a toothbrush.
• Mix clear acrylic liquid and standard powder. Mix these
until the slumping stops. Vaseline your hands, roll the
acrylic into a log shape, and then adapt and readapt it
as described for intermediate splint construction.
• Trim the final occlusion splint as described for the inter­
mediate splint. Smooth the lingual edges for patient
comfort.
• If segmental osteotomies are planned, maintain at least
3 mm to 4 mm of lingual acrylic behind the incisors to
prevent splint breakage or torque, which may otherwise
occur in the operating room.
NOTE: If greater strength is needed for the
intermediate splint (see Fig. 13-10, F), then reinforce with
a palatal wire (e.g., use a piece of a heavy paper clip) and
additional acrylic.
NOTE: If greater strength is needed for the final
splint (see Fig. 13-10, F), then reinforce with a palatal
wire (e.g., use a piece of a heavy paper clip) and
additional acrylic.
NOTE: When making the intermediate splint,
maintain the vertical pin of the articulator in a neutral
position, unless significant inferior positioning (i.e.,
lengthening) of the maxilla is planned. If so, there are
two options: either take the initial CR bite (in the clinic
setting) with an increased freeway space (this is
equivalent to the clockwise rotation of the mandible
while the condyles remain seated in the fossa) or
lengthen the vertical pin on the articulator (this is also
equivalent to the clockwise rotation of the mandible
while the condyles remain seated in the fossa) before
making the intermediate splint. Either approach can be
used without error as long as the mandibular opening
is limited to temporomandibular joint rotational
movement. If temporomandibular joint transitional
movement occurs, then the splint will no longer reflect
the patient’s CR bite. If the clinician is uncomfortable
with this approach, then a mandible-first approach
to analytic model planning should be used (see
Chapter 14).
scissors to remove gross excess. This will prevent “under­
cuts” of acrylic on the brackets.
• Continuously open and close the articulator until the
acrylic sets (≈10 min). Maintain the vertical pin in a
neutral position and fully closed. This will ensure that
no “undercuts” remain.
Trimming of Hardened Acrylic Intermediate
Splint (see Fig. 13-9, F and G)
• Remove excess buccal (labial) acrylic when looking at the
model from a bird’s-eye view. Use a pencil to mark a line
parallel to and just outside of the maxillary orthodontic
brackets. Draw a similar line outside of the mandibular
brackets. With a lathe and a circular white stone or an
acrylic bur, trim excess acrylic, as marked.
• Prevent lingual ramping by removing excess acrylic in
the region of the mandibular anterior teeth. This limits
interferences that tend to occur as a result of the arc of
rotation of the mandible during mouth opening and
closing.
• When viewing the splint from the side, mark with a
pencil any areas that require further acrylic removal (e.g.,
just below the base of the maxillary orthodontic brackets,
just above the base of the mandibular orthodontic brack­
ets). With a lathe and a circular white stone or an acrylic
bur, trim excess acrylic, as marked.
Finishing of the Prefabricated
Acrylic Splints (see Fig. 13-10, G
and H, and Fig. 13-11, A and B)
• Place each splint in between the maxillary and mandibu­
lar units to determine the ideal location and direction of
each interdental hole placement. Mark these placements
with a pencil.

419
CHAPTER 13  Standard Analytic Model Planning for Orthognathic Surgery
Radiographic Analysis
For each study patient, a presurgical standard cephalometric
radiograph was obtained for later analysis. At 5 weeks after
surgery, a similar standard cephalometric radiograph was
also taken. This was timed to coincide with initial bone
healing and the removal of the surgical splint.
Four landmark points (i.e., the sella, the nasion, the
porion, and the orbitale) that remained unchanged after Le
Fort I advancement were used for this analysis. These points
were used to create a consistent reference line from which
linear measurements (e.g., a change in the horizontal posi­
tion of the maxillary incisors) could be made and compared
before and after maxillary advancement. To confirm the
consistency of the four designated points in the sequential
radiographs, a reference angle between SN and FH was
verified to remain within 0.5 degrees.
On each cephalometric radiograph, a perpendicular ref­
erence line passing through the sella, called the sella perpen­
dicular (S┴), was then dropped. From S┴, a direct linear
measurement was made parallel to the Frankfort horizontal
(FH) plane and extended to the maxillary incisal edge (U1)
(Fig. 13-14).
To accurately access the horizontal advancement of the
maxillary incisors accomplished during the operation and
maintained at 5 weeks, the distance in millimeters from S
┴ to U1 was measured on both the preoperative and the
5-week postoperative lateral cephalogram. The measure­
ments were then adjusted with the use of a metric reference
frame to correct for magnification. Any difference in length
of these two data points corresponds with variations in
the preoperative and postoperative (i.e., at 5 weeks after
surgery) horizontal positions of the maxillary central
incisors.
Comparisons between the planned and actually achieved
(at 5 weeks after surgery) horizontal positions of the maxil­
lary incisors were made with the paired t-test. Statistical
significance was set at P < .05. Associations between the
planned and postsurgical results were investigated with
Pearson’s correlation.
Results
The collected data for all study patients are presented in
Table 13-1. In all cases, the surgically achieved and main­
tained (i.e., at 5 week postoperatively) horizontal advance­
ment measured at the maxillary incisors was within 1.0 mm
of what was planned. There was a strong correlation between
the two data sets (R = 0.96) (Fig. 13-15). With the use of
the absolute measurement values, the mean difference
between the planned and actual 5-week postsurgical hori­
zontal advancement of the maxilla was found to be 0.6 mm
(range, 0.2 to 1.0 mm). According to the paired t-test, this
mean difference was not considered to be statistically
significant (P > .05).
The distribution of the absolute difference in millimeters
between the planned, actually achieved, and then
• Drill holes that are 1 mm in diameter in both the inter­
mediate and final splints at each interdental location for
the ease of passage of the wires through the splint. For
ease of wire passage, the holes are located below the
maxillary orthodontic arch wire.
• Polish the splints on the lathe with a cloth buffing wheel
using pumice (i.e., coarse, medium, and then fine) and
Acrilustre (Vogel Paint and Wax Co. Inc., 1020 Albany
Place, SE; Orange City, Iowa)
Accuracy of the Described Analytic
Model Planning Technique: Review
of Study
A research study was carried out to assess the accuracy of
analytic model planning to achieve the desired maxillary
advancement during bimaxillary orthognathic surgery.54
Material and Methods
A consecutive series of patients (n = 20) who underwent
at a minimum Le Fort I osteotomy with advancement
and sagittal ramus osteotomies of the mandible for the
correction of dentofacial jaw deformities were included
in the study group. The sample consisted of female (n = 9)
and male (n = 11) with a mean age of 21 years (range,
14 to 45 years). All study subjects underwent the following:
1) preoperative and 5-week postoperative lateral cephalo­
metric radiographs of acceptable quality with a metric refer­
ence frame for analysis; 2) consistent presurgical facial
analysis by the surgeon, including millimeter decisions
regarding planned horizontal and vertical repositioning
and three dimensional reorientation (i.e., pitch, roll, and
yaw) of the maxilla; 3) consistent analytic model planning
as described in this chapter 4) the construction of interme­
diate and final splints; 5) the use of the prefabricated inter­
mediate splint to establish the maxillary positioning after
Le Fort I osteotomy and before plate and screw fixation,
and 6) the use of consistent intraoperative landmarks (i.e.,
the distance between the medial canthus and the maxillary
central incisor measured in millimeters with the use of cali­
pers) to confirm vertical orientation.
The determination of the preferred surgical reorientation
of the jaws was based on a combination of the direct visual
examination of the patient in the clinic setting, the analysis
of the lateral cephalometric radiograph, and the analysis of
the profile facial photograph taken in the NHP during the
presurgical office visit. The extent of preferred maxillary
horizontal advancement in millimeters was ultimately
assessed by the surgeon with the patient in the NHP during
the direct visual examination, with all gathered data taken
into account. The fabrication of an intermediate splint to
capture the preferred maxillary horizontal and other vector
movements (i.e., pitch, yaw, and roll) with the use of
consistent analytic model surgery planning methods was
accomplished.

420 SECTION 2  Planning, Surgical Technique, & Complications
• Figure 13-14  Example of lateral cephalometric radiographs and measurements taken in study patients showing maxillary
advancement in millimeters. Lateral cephalometric radiographs A, before and B, after Le Fort I advancement. From Park N,
Posnick JC: Accuracy of analytic model planning in bimaxillary surgery, Int J Oral Maxillofac Surg. 42:807-814, 2013.
B
A
SN
75.8mm
SN
75.8mm
SN
FH
10°
SN
FH
10°
S
S
S
U1
87.4mm
S
U1
78.9mm
maintained maxillary advancement is presented in Table
13-2. For the majority of patients, the difference fell within
0.4 to 0.8 mm. In 17 of the 20 patients (85%), there was
a small undercorrection; in 3 of the 20 patients (15%) there
was a slight overcorrection.
The results of this study confirm that the described method
of analytic model planning in orthognathic surgery is reliable
in achieving the planned level of maxillary advancement in
bimaxillary procedures.
Conclusions
Orthognathic surgery requires a thorough head and neck
examination and precise preoperative dental, radiographic,
and aesthetic preparation. Although clinical decision making
regarding the preferred spatial reorientation of the jaws to
achieve improved function and enhanced facial aesthetics
remains both an art and a science, the technical aspects of
model planning should be precise and consistent. Current
methods of analytic model planning and the use of prefab­
ricated splints represent the standard of care for bimaxillary
and segmental maxillary osteotomies.
• Figure 13-15  Data from study patients undergoing Le Fort I
advancement. The correlation between the planned and actual
advancement at the maxillary incisors is shown (R = correlation coef­
ficient). From Park N, Posnick JC: Accuracy of analytic model planning
in bimaxillary surgery, Int J Oral Maxillofac Surg. 42:807-814, 2013.
Series 1
10
9
8
7
6
5
4
3
2
1
0
0
2
4
6
8
10
12
Le Fort I horizontal advancement
Actual advancement (mm)
Planned advancement (mm)
R0.96

421
CHAPTER 13  Standard Analytic Model Planning for Orthognathic Surgery
TABLE
13-1 
Maxillary Incisor Vertical Change, Plane Change, and Incisor Horizontal Change: Planned and Actual
Horizontal Change
Patient
Planned Vertical
Change
Planned Plane
Change
Planned
(mm)
Actual
(mm)
Difference
(mm)
1
−6
0
+8
+8.5
+0.5
2
−3
−3
+4
+3.2
−0.8
3
−2
0
+6
+5.3
−0.7
4
−3
0
+10
+9.0
−1.0
5
0
0
+10
+9.4
−0.6
6
0
+2
+5
+4.8
−0.2
7
−1
+3
+6
+5.2
−0.8
8
−6
0
+7
+6.2
−0.8
9
+2
+2
+5
+4.8
−0.2
10
0
+3
+8
+7.5
−0.5
11
−3
0
+7
+6.4
−0.6
12
−2
−3
+8
+7.6
−0.4
13
+2
+2
+5
+4.2
−0.8
14
+4
+1
+7
+6.8
−0.2
15
+1
+4
+9
+8.5
−0.5
16
−5
−4
+6
+5.2
−0.8
17
−4
0
+6
+6.5
+0.5
18
−5
−2
+8
+7.2
−0.8
19
+3
0
+8
+8.8
+0.8
20
+
0
+10
+9.1
−0.9
Vertical change: +, maxillary lengthening; −, maxillary shortening. Plane change: +, clockwise rotation; −, counterclockwise rotation of maxillary plane.
TABLE
13-2 
Distribution of Difference Between the Planned and Actual Horizontal Advancement at
the Maxillary Incisors
Difference (mm)
0 to 0.2
+0.2 to 0.4
+0.4 to 0.6
+0.6 to 0.8
+0.8 to 1.0
No. of patients (%)
3 (15%)
1 (5%)
6 (30%)
8 (40%)
2 (10%)
From Park N, Posnick JC: Accuracy of analytic model planning in bimaxillary surgery, Int J Oral Maxillofac Surg. In press 2013.

422 SECTION 2  Planning, Surgical Technique, & Complications
References
orthognathic surgery. Am J Orthod Dentofacial
Orthop 122:142, 2002.
35. Jasinevicius TR, Yellowitz JA, Vaughan GG,
et al: Centric relation definitions taught in 7
dental schools: results of faculty and student
surveys. J Prosthodont 9:87–94, 2000.
36. Johnson DG: Intraoperative measurement of
maxillary repositioning: an ancillary
technique. Oral Surg Oral Med Oral Pathol
60:266, 1985.
37. Keshvad A, Winstanley RB: An appraisal of
the literature on centric relation: part I. J Oral
Rehabil 27:823, 2000.
38. Keshvad A, Winstanley RB: An appraisal of
the literature on centric relation: part II.
J Oral Rehabil 27:1013, 2000.
39. Keshvad A, Winstanley RB: An appraisal of
the literature on centric relation: part III.
J Oral Rehabil 28:55, 2001.
40. Kretschmer WB, Zoder W, Baciut G, et al:
Accuracy of maxillary positioning in
bimaxillary surgery. Br J Oral Maxillofac Surg
47:446–449, 2009.
41. Kwon TG, Mori Y, Minami K, Lee SH:
Reproducibility of maxillary positioning in Le
Fort I osteotomy: a 3-dimensional evaluation.
J Oral Maxillofac Surg 60:287–293, 2002.
42. Landes C, Sterz M: Proximal segment
positioning in bilateral sagittal split
osteotomy: intraoperative controlled
positioning by a positioning splint. J Oral
Maxillofac Surg 61:1423, 2003.
43. Landes C: Proximal segment positioning in
bilateral sagittal split osteotomy: Intraoperative
dynamic positioning and monitoring by
sonography. J Oral Maxillofac Surg 62:22,
2004.
44. Lapp TH: Bimaxillary surgery without the use
of an intermediate splint to position the
maxilla. J Oral Maxillofac Surg 57:57–60,
1999.
45.  Lubbers HT, Jacobsen C, Matthews F, et al:
Surgical navigation in craniomaxillofacial
surgery: expensive toy or useful tool? A
classification of different indications. J Oral
Maxillofac Surg 69:300–308, 2011.
46.  Marko JV: Simple hinge and semi-adjustable
articulators in orthognathic surgery. Am J
Orthod Dentofacial Orthop 90:37–44,
1986.
47.  Maxilim software, Mechelen, Belgium, 2010,
Medicim Medical Image Computing.
Available at Accessed
January 4, 2010.
48.  McCormick SU, Drew SJ: Virtual model
surgery for efficient planning and surgical
performance. J Oral Maxillofac Surg
69:638–644, 2011.
49. Moses JJ, Lo HH: The use of asymmetric yaw
in the correction of lateral facial defects in
hemifacial microsomia deformities: a case
report. Int J Adult Orthodon Orthognath Surg
7(4):229–234, 1992.
50. Nattestad A, Vedtofte P, Mosekilde E: The
significance of an erroneous recording of the
1. 2000 Series Articulator, Whip Mix
Corporation, 361 Farmington Ave, PO Box
17183, Louisville, KY 40217.
2. Adrien P, Schouver J: Methods for minimizing
the errors in mandibular model mounting
on an articulator. J Oral Rehabil 24:929,
1997.
3.  Amira software, Houston, Texas, 2010, TGS.
Available at Accessed January 4,
2010.
4.  Assael LA: Editorial. J Oral Maxillofac Surg
67:2041, 2009.
5.  Bai S, Shang H, Liu Y, et al: Computer-aided
design and computer-aided manufacturing
locating guides accompanied with prebent
titanium plates in orthognathic surgery. J Oral
Maxillofac Surg 70:2419–2426, 2012.
6. Becker CM, Kaiser DA, Schwalm C:
Mandibular centricity: centric relation.
J Prosthet Dent 83:158, 2000.
7. Bell W, Proffit W, White R: Surgical correction
of dentofacial deformities, Philadelphia, 1980,
W.B. Saunders Company.
8.  Bell RB: Computer planning and
intraoperative navigation in orthognathic
surgery. J Oral Maxillofac Surg 69:592–605,
2011.
9. Bryan DC, Hunt NP: Surgical accuracy in
orthognathic surgery. Br J Oral Maxillofac
Surg 31:343–349, 1993.
10. Campos AA, Nathanson D, Rose L:
Reproducibility and condylar position of a
physiologic maxillomandibular centric relation
in upright and supine body position.
J Prosthet Dent 76:282, 1996.
11.  Centenero SAH, Hernandez-Alfaro F: 3D
planning in orthognathic surgery: CAD/CAM
surgical splints and prediction of the soft and
hard tissues results—our experience in 16
cases. J Craniomaxillofac Surg 40:162–168,
2012.
12. Chow TW, Clark RKF, Cooke MS: Errors in
mounting maxillary casts using face-bow
records as a result of an anatomical variation.
J Dent Res 13:277–282, 1985.
13. Cope MR: Measuring changes in maxillary
height during osteotomy surgery. Br J Oral
Maxillofac Surg 32:257, 1994.
14. Cordray FE: Centric relation treatment and
articulator mountings in orthodontics. Angle
Orthod 66:153–158, 1996.
15. Ellis E, III: Accuracy of model surgery:
evaluation of an old technique and
introduction of a new one. J Oral Maxillofac
Surg 48:1161, 1990.
16. Ellis E, III, Tharanon W, Gambrell K:
Accuracy of face–bow transfer: effect on
surgical prediction and postsurgical result.
J Oral Maxillofac Surg 30:362, 1992.
17. Ellis E, III: Bimaxillary surgery using an
intermediate splint to position the maxilla.
J Oral Maxillofac Surg 57:53–56,
1999.
18. Ellis E, III: A comparison of 3 methods of
face-bow transfer recording: Implications for
orthognathic surgery [discussion]. J Oral
Maxillofac Surg 56:640–641, 2001.
19.  Erickson K, Bell WH, Goldsmith DH:
Analytical model surgery. In Bell WH, editor:
Modern practice in orthognathic and
reconstructive surgery, ed 1, Philadelphia, 1992,
Saunders, pp 155–205.
20. Erickson Model Table, Great Lakes
Orthodontics, Ltd, 199 Fire Tower Drive,
Tonawanda, NY 14151-15111.
21. Gateno J, Forrest KK, Camp B: A comparison
of 3 methods of face-bow transfer recording:
Implications for orthognathic surgery. J Oral
Maxillofac Surg 56:635–640, 2001.
22.  Gateno J, Xia J, Teichgraeber J, et al: The
precision of computer-generated surgical
splint. J Oral Maxillofac Surg 61:814, 2003.
23. Gateno J, Teichgraeber JF, Xia JJ: Three-
dimensional surgical planning for maxillary
and midface distraction osteogenesis.
J Craniofac Surg 14:833–839, 2003.
24. Gateno J, Xia JJ, Teichgraeber JF, et al:
Clinical feasibility of computer-aided surgical
simulation (CASS) in the treatment of
complex cranio-maxillofacial deformities.
J Oral Maxillofac Surg 65(4):728–734, 2007.
25.  Gateno J, Xia JJ, Teichgraeber JF: New
3-dimensional cephalometric analysis for
orthognathic surgery. J Oral Maxillofac Surg
69:606–622, 2011.
26.  Gateno J, Xia JJ, Teichgraeber JF: Effect of
facial asymmetry on 2-dimensional and
3-dimensional cephalometric measurements.
J Oral Maxillofac Surg 69:655–662, 2011.
27. Gil JN, Claus JDP, Manfro R, Lima SM, Jr:
Predictability of maxillary repositioning
during bimaxillary surgery: accuracy of a new
technique. Int J Oral Maxillofac Surg
36:296–300, 2007.
28. Gil JN, Campos FE, Claus JD, et al: Medial
canthal region as an external reference point
in orthognathic surgery. J Oral Maxillofac Surg
69:352–355, 2011.
29. Hartzell DH, Maskeroni AJ, Certosimo FC:
Techniques in recording centric relation. Oper
Dent 25:234–236, 2000.
30. Hatzi P, Millstein P, Maya A: Determining the
accuracy of articulator interchangeability and
hinge axis reproducibility. J Prosthet Dent
85:236–245, 2001.
31. Hellsing G, McWilliam JS: Repeatability of
the mandibular retruded position. J Oral
Rehabil 12:1, 1985.
32. Ingervall B: Recording of retruded positions
of mandible in children. A comparison
between registrations in general anaesthesia
and with children awake. Odontol Revy
19(4):413–421, 1968.
33. Ingervall B, Helkimo M, Carlsson GE:
Recording of the retruded position of the
mandible with application of varying external
pressure to the lower jaw in man. Arch Oral
Biol 16:1165–1170, 1971.
34. Jacobson R, Sarver DM: The predictability of
maxillary repositioning in Le Fort I

423
CHAPTER 13  Standard Analytic Model Planning for Orthognathic Surgery
center of mandibular rotation in orthognathic
surgery. J Craniomaxillofac Surg 19:254, 1991.
51. Nishioka GJ, Van Sickels JE: Modified
external reference measurement technique for
vertical positioning of the maxilla. Oral Surg
Oral Med Oral Pathol 64:22, 1987.
52. O’Malley AM, Milosevic A: Comparison of
three face bow/semiadjustable articulator
systems for planning orthognathic surgery. Br
J Oral Maxillofac Surg 38:185–190, 2000.
53. Ong TK, Banks RJ, Hildreth AJ: Surgical
accuracy in Le Fort I maxillary osteotomies.
Br J Oral Maxillofac Surg 39:96–102, 2001.
54.  Park N, Posnick JC: Accuracy of analytic
model planning in bimaxillary surgery. Int J
Oral Maxillofac Surg 42:807–814, 2013.
55. Perez D, Ellis E, III: Sequencing bimaxillary
surgery: mandible first. J Oral Maxillofac Surg
69:2217–2224, 2011.
56. Polido WD, Ellis E, III, Sinn DP: An
assessment of the predictability of the
maxillary surgery. J Oral Maxillofac Surg
48:697–701, 1990.
57. Polido WD, Ellis E, III, Sinn DP: An
assessment of the predictability of the
maxillary repositioning. Int J Oral Maxillofac
Surg 20:349–352, 1991.
58. Politi M, Toro C, Costa F, et al: Intraoperative
awakening of the patient during orthognathic
surgery: a method to prevent the condylar sag.
J Oral Maxillofac Surg 65:109, 2007.
59. Posnick JC, Fantuzzo JJ, Orchin J: Deliberate
operative rotation of the maxillo-mandibular
complex to alter the A-point to B-point
relationship for enhanced facial esthetics.
J Oral Maxillofac Surg 64:1687–1695, 2006.
60. Posnick JC, Nakano P, Taylor M: A modified
occlusal splint to avoid tracheotomy for total
midface osteotomies. Ann Plast Surg
29(3):223–230, 1992.
61.  Quevedo LA, Ruiz JV, Quevedo CA: Using a
clinical protocol for orthognathic surgery and
assessing a 3-dimensional virtual approach:
current therapy. J Oral Maxillofac Surg
69:623–637, 2011.
62. Quick Mount Face-Bow, Whip Mix
Corporation, 361 Farmington Ave, PO Box
17183, Louisville, KY 40217.
63. Rinchuse DJ, Kandasamy S: Articulators in
orthodontics: an evidence-based perspective.
Am J Orthod Dentofacial Orthop 129:299–
308, 2006.
64. Rinchuse DJ, Kandasamy S: Centric relation:
a historical and contemporary orthodontic
perspective. J Am Dent Assoc 137:494–501,
2006.
65. Roth RH: Gnathological considerations for
orthodontic therapy. In McNeill C, editor:
Science and practice of occlusion, Chicago,
1997, Quintessence, pp 502–514.
66. Scarbrough FE, Ghali GE, Smith BR:
Anatomic guidelines for the placement of
external references for maxillary repositioning.
Oral Surg Oral Med Oral Pathol Oral Radiol
Endod 84:465, 1997.
67.  Schendel S, Jacobsen R: Three-dimensional
imaging and computer simulation for
office-based surgery. J Oral Maxillofac Surg
67:2107, 2009.
68. Simon RL, Nicholls JI: Variability of passively
recorded centric relation. J Prosthet Dent
44:21, 1980.
69. Stanchina R, Ellis E, III, Gallo WJ, Fonseca
RJ: A comparison of two measures for
repositioning the maxilla during orthognathic
surgery. Int J Adult Orthodon Orthognath Surg
3:149–154, 1998.
70.  Swennen RJ, Mollemans W, Schutyser F:
Three-dimensional treatment planning of
orthognathic surgery in the era of virtual
imaging. J Oral Maxillofac Surg 67:2080,
2009.
71. Tarantola GJ, Becker IM, Gremillion H: The
reproducibility of centric relation: a clinical
approach. J Am Dent Assoc 128:1245,
1997.
72. The glossary of prosthodontic terms. J Prosthet
Dent 58:713, 1987.
73. The glossary of prosthodontic terms. J Prosthet
Dent 71:40, 1994.
74. The glossary of prosthodontic terms. J Prosthet
Dent 81:39, 1999.
75. The glossary of prosthodontic terms. J Prosthet
Dent 94:10, 2005.
76. Thompson JR: The rest position of the
mandible and its application to analysis and
correction of malocclusion. Angle Orthod
19:162–187, 1949.
77. Troulis MJ, Everett P, Seldin EB, et al:
Development of a three-dimensional
treatment planning system based on
computed tomographic data. Int J Oral
Maxillofac Surg 31(4):349–357, 2002.
78. Turvey T: Sequencing of two-jaw surgery: the
case for operating on the maxilla first. J Oral
Maxillofac Surg 69:2225, 2011.
79. Truitt J, Strauss RA, Best A: Centric relation:
a survey study to determine whether a
consensus exists between oral and maxillofacial
surgeons and orthodontists. J Oral Maxillofac
Surg 67:1058–1061, 2009.
80. Uechi J, Okayama M, Shibata T, et al: A
novel method for the 3-dimensional
simulation of orthognathic surgery by using a
multimodal image-fusion technique. Am J
Orthod Dentofacial Orthop 130:786–798,
2006.
81. Van Sickels JK, Larsen AJ, Triplett RG:
Predictability of maxillary surgery:
a comparison of internal and external
reference marks. Oral Surg 61:542–545,
1986.
82. Wood DP, Elliot RW: Reproducibility of the
centric relation bite registration technique.
Angle Orthod 64:211–220, 1994.
83.  Xia J, Gateno J, Teichgraeber J: New clinical
protocol to evaluate craniomaxillofacial
deformity and plan surgical correction. J Oral
Maxillofac Surg 67:2093, 2009.
84.  Xia JJ, McGrory JK, Gateno J, et al:
A new method to orient 3-dimensional
computed tomography models to the
natural head position: a clinical feasibility
study. J Oral Maxillofac Surg 69:584–591,
2011.
85. Xia JJ, Shevchenko L, Gateno J, et al:
Outcome study of computer-aided surgical
simulation in the treatment of patients with
craniomaxillofacial deformities. J Oral
Maxillofac Surg 69:2014–2024, 2011.
86. Zizelmann C, Hammer B, Gellrich NC, et al:
An evaluation of face bow transfer for the
planning of orthognathic surgery. J Oral
Maxillofac Surg 70:1944–1950, 2012.

424

14
Mandible-First Analytic
Model Planning for
Orthognathic Surgery
JEFFREY C. POSNICK, DMD, MD
• Controversies Surrounding Centric Relation
• Mandible-First Analytic Model Planning
Technique
• Technical Aspects of Executing the
Mandible-First Approach During
Orthognathic Surgery
• Mandible-First Analytic Model Planning:
Step-by-Step Approach
• Case Presentations
• Conclusions
model planning and the use of prefabricated splints con­
tinue to represent the standard of care for bimaxillary and
segmental maxillary osteotomies.6,14,17,52
Despite the benefits of this time-honored model plan­
ning approach, there is the potential for the introduction
of error. For example, if an inaccurate CR bite registration
is obtained from the patient preoperatively. The surgeon’s
ability to obtain an accurate and reproducible bite registra­
tion in CR during the immediate presurgical clinical exami­
nation, during the occlusion of the dental models on the
articulator in the laboratory, and when using the splints in
the operating room is essential to avoid errors when stan­
dard analytic model planning is employed.5,12,13,17-28,32,33,35,36,53
There are specific clinical settings in which the obtaining
of an accurate and reliable CR can be problematic.8,11,34,37,39,52
Examples include the following individuals: 1) those who
are missing a condyle after tumor resection 2) those with
severe atrophy of the condyle after trauma and 3) those
with specific syndromes in which the condyle-ascending
ramus is aplastic (e.g., Treacher Collins syndrome, or hemi­
facial microsomia with Kaban type IIB or III malformation;
see Chapters 27 and 28) (Fig. 14-1) For those patients with
an unreliable CR, a “mandible-first” approach to analytic
model planning is required.
Controversies Surrounding
Centric Relation
Definition of Centric Relation
The definition of CR remains somewhat controversial, and
it is frequently misstated.46-49 In 1987, the definition of CR
underwent a change in terminology from being considered
a mandibular position in which the condyles are seated in
the most “posterior superior” position to one in which the
condyles are placed in the most “superior anterior” position
in the glenoid fossa.45,46 For analytic model planning in
Unlike most surgical procedures, orthognathic surgery
involves not just thorough medical assessment but also
precise preoperative dental, radiographic, and facial aes­
thetic planning. The surgeon also carries out a detailed
face-to-face examination of the patient to determine varia­
tions from normal.
Immediate presurgical records include current dental
impressions of the maxillary and mandibular arches; accu­
rate bite registration in centric relation (CR); a face-bow
registration; and the recording of specific facial measure­
ments, including deviations from normal. The dental
models are placed on a semi-adjustable articulator for
further analysis, and they are then used to complete analytic
model planning.1,2,10,13,15,39,40 Acrylic splints are fabricated
and used intraoperatively to further ensure the reliable exe­
cution of the predetermined reorientation of the maxilla
and mandible to achieve facial aesthetic and functional
objectives.
Although the making of clinical decisions about the pre­
ferred aesthetic repositioning of the jaws remains both an
art and a science (see Chapter 12), the technical aspects of
model planning should be precise and consistent. Analytic

425
CHAPTER 14  Mandible-First Analytic Model Planning for Orthognathic Surgery
Or
Or
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Or
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Or
Or
Or
Or
Or
Or
O ththththththththththththththththth
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g atatatatatatatatatatata hicicicicicicicicici Su
Su
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Su
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S rg
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ry; J.C.
C.
C.
C.
C.
C Pos
os
os
os
os
os
os
o nicicicicicicicicicicici k
A
Kaban type II B
Or
Or
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g atatatatatatatatatatatatatatatatatatatatatatatatatatatatatatatatatatathicicicicicicicicicicicicicicicicicicicicicicicicicicicici Su
Su
Su
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S rg
r ery
ry
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ry
ry
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ry
ry
ry
ry; J.C.
C.
C.
C.
C.
C.
C.
C.
C.
C.
C.
C.
C.
C.
C.
C.
C.
C.
C.
C.
C.
C.
C.
C Pos
os
os
os
os
os
os
os
os
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os
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o nicicicick
B
Kaban type II B
• Figure 14-1  There are specific clinical settings in which obtaining an accurate and reliable centric relation (CR) can be problematic.
Examples include individuals with atrophy of a condylar head (e.g., after a displaced condyle fracture) or those with specific syndromes in
which aplasia of the glenoid fossa and condyle of the ascending ramus is extensive (e.g., Treacher Collins syndrome, hemifacial microsomia
[HFM] with Kaban type IIB or III mandibular malformations). In addition, there are unique circumstances in which patients undergo bimaxil­
lary procedures that require posterior maxillary lengthening to the extent that clockwise rotation of the mandible would result in a translational
movement of the condyles in the glenoid fossa. In these cases, a mandible-first approach to analytic model planning is indicated. Several
clinical examples are shown. A, A 16-year-old boy who had sustained a fracture of the right condyle of the mandible earlier during his
childhood presented as a teenager with facial asymmetry. Complete atrophy of the right condyle had occurred, with a loss of posterior
facial height. For this reason, a stable CR bite registration was not possible. Facial and computed tomography (CT) scan views are shown
to confirm these facts. B, A 14-year-old girl with right-sided HFM and a Kaban type IIB condyle and ascending ramus malformation is
shown. Because of these conditions, obtaining a consistent CR bite registration was not possible. Facial and CT scan views confirm these
findings.
Continued

426 SECTION 2  Planning, Surgical Technique, & Complications
Orth
r ognathic Surg
r ery; J.C. Posnick
C
Kaban type II B
Absent
condyle
D
Kaban type II A
Orth
r ognathic Surg
r ery; J.C. Posnick
C, An 11 year-old-boy who was born with right-sided HFM and a Kaban type IIB condyle and ascending ramus mal­
formation is shown. Because of these conditions, obtaining a consistent CR bite registration was not possible. Facial and CT scan views confirm
these findings. D, A teenage girl with a bilateral form of HFM and a Kaban type IIA condyle and ascending ramus malformation is shown.
Although a stable CR bite registration could be obtained, the correction of the bimaxillary deformity requires significant counterclockwise rotation
of the maxilla, including the lengthening of the posterior facial height of the maxilla. The use of standard maxilla-first analytic model planning
would require clockwise rotation of the mandible to place the intermediate splint to the extent that translational movement of the condyles in
the glenoid fossa would occur. For this reason, a mandible-first approach is required. Facial and CT scan views confirm these findings.
• Figure 14-1, cont’d

427
CHAPTER 14  Mandible-First Analytic Model Planning for Orthognathic Surgery
pressure to the occiput, the clinician is able to apply poste­
rior and superior “vectored” force to the anterior mandible.
This will seat the condyles in a superior-anterior location
within each glenoid fossa (i.e., CR).
Unstable (Unreliable) Centric Relation
Alternative methods to the standard analytic model planning
approach to bimaxillary orthognathic surgery have been
described in an attempt to improve the accuracy and pre­
dictability of outcomes.8,11,34,37,50,52 Recently, surgeons have
also begun looking to computer-aided design and computer-
aided modeling software to assist with the planning and
implementation of orthognathic procedures (see Chapter
13).3,4,7,14,16,18,19,20,29,30,31,38,42,44,54,55,56
The subset of patients in which obtaining an accurate CR
is not feasible are well suited for a “mandible-first” approach.
Common clinical examples of these patients include the
following: 1) those with specific congenital anomalies (e.g.,
hemifacial microsomia with Kaban Type IIB or III malfor­
mations) (Fig. 14-2 and 14-3) 2) those with specific types
of trauma (e.g., after condylar fracture with resorption or
after ankylosis release with condylar resection) 3) those with
specific pathology (e.g., after condylar resection for tumor)
and 4) those with the inability to cooperate in the office
setting (e.g., those with neuropsychiatric disorders that
involve uncontrolled masticatory muscle spasticity).
A mandible-first approach to analytic model planning is
also indicated in unique clinical circumstances in which
significant posterior maxillary lengthening is planned to the
extent that the clockwise rotation of the mandible will
require the translational movement of the condyles in the
glenoid fossa during the use of the intermediate splint (Fig.
14-4). Fortunately, these cases are not common; very few
patients require the actual lengthening of the posterior max­
illary height. Furthermore, those who do generally either
require the closure of baseline posterior open bites (i.e., cases
that involve the failure of the posterior dentition to erupt)
or are undergoing simultanous advancement. For example,
the advantage of the counterclockwise rotation of the maxil­
lary and mandibular planes (i.e., pitch orientation) is fre­
quently seen in the clinical setting of a long face growth
pattern. This counter clockwise rotation is generally accom­
plished via the differential intrusion of the maxilla (i.e.,
anterior more so than posterior). This does not require the
lengthening of the posterior maxillary height or the overall
posterior facial height (see Chapter 21).
Mandible-First Analytic Model
Planning Technique
We prefer to use the mandible-first analytic model planning
technique, in only specific clinical situations (see Fig. 14-1
through 14-4).8,11,34,37,39,52 However, whichever method of
model planning is used, all orthognathic patients require
a thorough clinical history and physical examination. A
preparation for orthognathic surgery, defining the exact
position of each condylar head during mandibular protru­
sion and lateral excursions is not critical. However, it is
essential to locate a mandibular position that is reproducible
with the teeth in occlusion. This must be obtained without
the assistance of the patient (i.e., with fully relaxed mastica­
tory muscles), and it needs to be reliably accomplished both
preoperatively and intraoperatively. This position must also
be transferable to the articulator in the laboratory for model
planning to be accomplished accurately. An erroneous and
inconsistent recording of CR will lead to the malpositioning
of the maxilla or mandible during surgery.
A survey study conducted by Truitt and colleagues con­
firmed that 98% of oral and maxillofacial surgeons define
CR as the most posterior superior seating of the condyle in
the fossa.51 Interestingly, a majority of the orthodontists
surveyed agree with the surgeons’ definition of CR, but
there was less consistency.22,41 According to the survey, sur­
geons and orthodontists do agree that, in preparation for
orthognathic surgery, analytic model planning requires that
casts of the teeth be mounted in CR on a semi-adjustable
articulator.
Capturing Centric Relation
Hellsing and McWilliam used a subtraction technique
to assess the repeatability of CR that is recorded with a one-
handed push-back technique.21 They found that, with the use
of this technique, the mandibular condyles can
be seated in a reproducible position and thus be well suited
for the registration of CR. Campos and colleagues com­
pared the swallowing technique with the chin-point
guidance technique when the patient was in both upright
and supine body positions.3,5,9,15,21 Both techniques were
found to establish physiologic CR in a reproducible manner.
Interestingly, when the chin-point guidance method was
used, the work of these authors suggested that reliability was
greater with the patient in the upright, seated position as
compared with the supine position.
Simon and Nicholls compared the chin-point guidance,
chin-point guidance with ramus support, and bimanual
manipulation techniques.43 They found that there were no
significant differences in the range of mandibular positions
that were observed. Interestingly, their study patients did
not include individuals with jaw deformities. It is known
that patients with specific patterns of jaw deformity (e.g.,
Class II retrognathism) are more likely to involuntarily
posture the mandible forward during the swallowing
technique.
When a reliable CR can be obtained, we find the chin-
point guidance technique—when used both preoperatively
and intraoperatively by the same clinician—to be both reli­
able and convenient for the orthognathic surgery patient.
This is the method that has been adopted by this author,
and it has been used successfully for orthognathic patients
that have a reliable CR. By using one hand to apply pressure
to the subject’s chin and the other hand to apply opposing

428 SECTION 2  Planning, Surgical Technique, & Complications
to make baseline millimeter reference measurements
on both maxillary units and the mandibular unit (see
Chapter 13).
5. The original maxillary cast is then separated from its
plaster base and three-dimensionally repositioned and
reoriented according to the treatment plan. The Erickson
Model Table is used to confirm the correct reorientation.
If segmentation is required, it is completed before the
reorientation of the maxilla to the plaster base (see
Chapter 13). The reorientation of the maxilla takes into
account the preferred horizontal, vertical, transverse
(segmental) midline (yaw), cant (roll), and plane (pitch),
needs (see Chapter 12). The maxillary cast is then secured
to the plaster base with hot glue in the planned treat­
ment position on the articulator (see Chapter 13).
6. The mandibular cast is then separated from its base and
repositioned into the preferred final occlusion to the
reoriented maxillary unit with the use of hot glue.
The mandibular cast is remounted to its plaster base in
the new position on the articulator with hot glue. The
occlusion is released (i.e., the glue that secured the occlu­
sion is removed), and a “maxillary-positioning” splint is
fabricated with acrylic (see Chapter 13).
7. Next, the repositioned (reoriented) maxillary unit is
removed from the articulator and replaced with the
“uncut” second maxillary unit. This indicates the new
mandibular location and the “unoperated” maxillary
position. The “mandibular-positioning” splint is then
fabricated with acrylic.
Technical Aspects of Executing
the Mandible-First Approach
During Orthognathic Surgery
Consider as an example an individual with hemifacial
microsomia and a Kaban type IIB mandibular malforma­
tion ((Fig. 14-2 and 14-3). When using the mandible-first
approach, the “normal” side of the ramus of the mandible
is split sagittally in the usual way (i.e. sagittal ramus oste­
otomy of mandible). The distal mandible is then placed into
its treatment-planned final position with the use of the
prefabricated “mandibular-positioning” splint, and inter­
maxillary fixation (IMF) is established. To fully mobilize the
distal mandible and secure it into the new occlusion, it may
be necessary to 1) complete an ipsilateral coronoidectomy,
2) excise portions of the rudimentary (ipsilateral) mandible,
or 3) both.
After the distal mandible is in the splint and secured with
IMF, the proximal segment on the “normal” side is seated
into the terminal hinge position. Rigid internal fixation
(e.g., bicortical screws) is then established across the ramus
osteotomy site (see Chapter 15).
The deficient portion of the ipsilateral mandible is con­
structed with the use of a bone graft (e.g., a costochondral
graft). The neocondyle is seated in the glenoid fossa. Once
in place, fixation of the graft is achieved to the distal
maxillofacial and focused dental assessment is also com­
pleted with particular emphasis on the accurate documenta­
tion of the following: 1) any maxillary occlusal cant (i.e.,
role orientation) 2) the maxillary and mandibular dental
midline positions relative to the facial midline (i.e.,
yaw orientation) 3) any disproportions in vertical facial
height 4) any disproportions in the horizontal projection of
each jaw and 5) any advantage to the alteration of the maxil­
lary or mandibular planes (i.e., pitch orientation); (see
Chapter 12).
The basic technical aspects of mandible-first analytic
model planning include the following:
1. To register the bite in a patient with a unilateral “free-
floating” condyle–glenoid fossa relationship (e.g., Kaban
type IIB or III hemifacial microsomia, the absence of the
condyle after tumor resection or trauma), the mandible
is manipulated with the “normal” condyle placed reliably
in the terminal hinge position and with the “abnormal”
(i.e., contralateral) condyle seated in its most posterior-
superior position. This will demonstrate the maximum
mandibular deformity. A wax bite registration is taken
in this position.
2. A face-bow registration is obtained. Care is taken to
accurately reproduce the patient’s existing maxillary
plane (pitch orientation), cant (role orientation), and
midline (yaw orientation) in relationship to the upper
face. If the cranial base and the external auditory canals
have essentially normal morphology, this is accomplished
in a traditional fashion with the use of the standard face-
bow technique, which involves placing an earpiece in
each ear canal. If the patient’s ear canals are abnormally
formed or positioned (e.g., in a patient with hemifacial
microsomia with external auditory canal atresia), adjust­
ments are made by using references to the parallelism of
the floor and the morphology of the orbits. When doing
so, the earpieces maybe placed against the patient’s cheek
skin (rather than in the dysmorphic or absent external
auditory canal). The patient’s head and neck are posi­
tioned by the operator in the natural head position for
the face-bow registration (see Chapters 12 and 13).
3. Two maxillary and one mandibular alginate impressions
are taken. The three dental impressions are poured in
green die stone. The first maxillary cast is mounted onto
the articulator in the standard fashion with white plaster
and the use of the face-bow registration for orientation.
The wax bite registration is then used to articulate the
maxillary and mandibular casts to each other. The man­
dibular cast is then mounted on the articulator in the
standard fashion, also with the use of white plaster (see
Chapter 13).
4. The first maxillary mounting is removed, and the second
maxillary cast is mounted. This is accomplished with the
use of the original bite registration against the already
mounted mandibular cast. Vertical and horizontal refer­
ence lines are created on each maxillary and mandibular
unit (see Chapter 13). The Erickson Model Table is used

429
CHAPTER 14  Mandible-First Analytic Model Planning for Orthognathic Surgery
mandible with an extended titanium plate and screws. The
IMF is released, and the occlusion is confirmed to be accu­
rate and reproducible into the splint.
The “mandibular-positioning” splint is removed, and the
maxillary (Le Fort I) osteotomy is performed. After down-
fracture and disimpaction (including segmentation, if indi­
cated), the “maxillary-positioning” splint is used to achieve
the treatment-planned maxillary reorientation. Plate and
screw fixation is secured across the maxillary osteotomy sites
in the usual manor (see Chapter 15). The IMF is released,
and an accurate and reproducible occlusion is confirmed.
The splint is either removed or left in place, depending on
the patient’s clinical healing needs.
Mandible-First Analytic Model
Planning: Step-by-Step Approach
1. Obtain a wax bite registration with the normal (unaf­
fected) condyle seated in the terminal hinge position
and with the abnormal (hypoplastic) condyle posi­
tioned as posterior and superiorly against the skull base
as possible.
2. Use the face-bow device to register the relationships of
the maxilla, glenoid fossa, and the skull base while the
patient is in the natural head position (NHP). Use a
modified technique if ear canals and the orbital sym­
metry are abnormal.
3. Take alginate impressions (two maxillary, one
mandibular).
4. Pour alginate impressions in green die stone with a
25- to 30-mm base.
5. Mount the first maxillary cast onto the articulator base
plate with the use of white plaster and the face-bow
recording.
6. Turn the articulator upside down and place the man­
dibular cast onto the already mounted maxillary unit
with the use of the wax bite registration. Mount the
mandible cast onto the articulator base plate with white
plaster.
7. Remove the mounted maxillary unit, and mount the
second maxillary cast onto the articulator base plate
with white plaster and the use of the same CR bite
registration.
8. Mark vertical and horizontal reference lines on all
three units, and take baseline measurements on the first
maxillary unit with the use of the Erickson Model
Table.
9. Perform model surgery on the first maxillary cast
(including segmentation, if indicated). Place the maxilla
in its treatment-planned location. Use the Erickson
Model Table to confirm correct positioning. Secure the
maxillary cast to the articulator (in its new location)
with hot glue.
10. Separate the mandibular cast from the base. Secure the
mandibular cast with hot glue into the optimal final
occlusion against the repositioned maxillary cast.
Secure the mandibular cast with hot glue or plaster
back onto the base plate of the articulator.
11. Release the occlusion (i.e., remove the glue), and fab­
ricate the “maxillary-positioning” splint in the standard
fashion with the use of acrylic.
12. Remove the first maxillary (cut) unit, which is currently
on the articulator, and place the second (uncut) maxil­
lary unit.
13. Fabricate the “mandibular-positioning” splint in the
standard fashion with the use of acrylic. This will be
with the final (cut) mandibular unit and initial (uncut)
maxillary unit.

430 SECTION 2  Planning, Surgical Technique, & Complications
Case Presentations
• CASE 14-1 
Hemifacial Microsomia
A child was born with right-sided hemifacial microsomia
that was manifested by mild hypoplasia of the affected soft
tissues, paresis of the temporal branch of the facial nerve, a
degree of zygoma and orbital hypoplasia, and a Kaban type
IIB mandibular malformation (Fig. 14-2). The right exter-
nal ear was displaced but had acceptable formation. She
underwent orthodontic alignment during early adolescence,
and she was referred to this surgeon when she was 14 years
old. At age 16, after the completion of her orthodontic
preparation, she underwent a maxillary Le Fort I osteotomy
with three-dimensional repositioning (cant correction,
occlusal plane adjustment, midline correction, and vertical
and horizontal adjustments); sagittal split osteotomy of
the left ramus; reconstruction of the right condyle and
ascending ramus with an autogenous costochondral graft;
osseous genioplasty (horizontal advancement and asymme-
try correction); and intranasal procedures (septoplasty, and
inferior turbinate reduction).
Or
Or
Or
Or
Or
Or
O thththththththththththththth
r ogn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
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gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
g atatatatatatatatatatatatathicicicicicic Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
S rg
r ery
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry; J.C.
C.
C.
C.
C.
C.
C Pos
os
os
os
os
os
os
os
os
os
os
os
os
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os
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os
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o nicicicicicicicick
Or
Or
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Orthththththththththththththththththththththtr ogn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
g atatatatatatatatatatatatatatatatatatathicici Su
Surg
r ery
ry
ry
ry; J.C.
C.
C.
C.
C.
C Pos
os
os
os
os
os
os
os
os
os
osnicicicick
Or
Or
Orthththththththth
r ogn
gn
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gn
g atatatatatatatatatatatatatatatatatathicicicicicicicicici Su
Su
Su
Su
Su
Su
Su
Su
Su
Surg
r ery
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry; J.C.
C.
C.
C.
C.
C.
C.
C.
C.
C Pos
os
os
os
os
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os
os
os
os
os
o nicicicicicick
Or
Or
Or
Or
Or
Or
Orththththththth
r ogn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
g atatatatatatatatatatatatatatatatatatatatatatatatatatatatatata hicicicicicicicicicicicicicicici Su
Su
Surg
r ery
ry
ry; J.C.
C.
C.
C.
C.
C.
C.
C.
C.
C.
C.
C.
C.
C.
C Pos
os
os
os
os
os
os
os
os
os
os
os
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os
os
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osnicicick
A
B
• Figure 14-2  A 14-year-old girl who was
born with right-sided hemifacial microso­
mia and a Kaban type IIB condyle and
ascending ramus malformation was fol­
lowed longitudinally without treatment
intervention until skeletal maturity. Facial
asymmetry demonstrated no progression
during this time frame. During the adult
dentition and with orthodontic dental
decompensation complete, she under­
went single-stage reconstruction that
included a maxillary Le Fort I osteotomy a
left-sided sagittal split ramus osteotomy;
right mandible reconstruction with costo­
chondral graft septoplasty and inferior
turbinate reduction. Improvements in the
inferior border of mandible symmetry after
surgery have been documented. However,
significant soft-tissue asymmetry in the
pre-auricular cheek region remains. Fat
grafting is an option to consider. A, Frontal
views in repose before and after recon­
struction. B, Frontal views with smile
before and after reconstruction.

431
CHAPTER 14  Mandible-First Analytic Model Planning for Orthognathic Surgery
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
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Or
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Or
Or
Orththththththththththththththththththththththththththththththththtr ogn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
g atatatatatatatatatatatatatatatatatatatatatatatatatatatatatatatatatatatathicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicici Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
S rg
r ery
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry; J.C.
C.
C.
C.
C.
C Pos
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
o nicicicicici k
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Orththththththththththththththththththththththththth
r ogn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
g atatatatatatatatatatatatatatatatatatatatatatatatatatathicicicicicicicicicicicicicicic Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Surg
r ery
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
r ; J.C.
C.
C Pos
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
osnicicicicick
Or
Or
Or
Or
Or
Orththththththththththththththththththththththththththththththththtr ogn
gn
gn
gn
gn
g atatatatatatatatatatatatatatatatata hicicicicicicicici Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Surg
r ery
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry; J.C.
C.
C.
C.
C.
C.
C.
C.
C.
C.
C.
C.
C.
C.
C.
C.
C.
C.
C.
C.
C.
C Pos
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
o nicicicicicicicicicicicicicicicicicicicici k
Or
Or
Or
Or
O thththth
r ogn
gn
gn
g atatata hicic Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
S rg
r ery
ry
ry
ry
ry
ry
ry
ry; J.C.
C.
C.
C.
C.
C.
C.
C.
C.
C.
C.
C.
C.
C.
C.
C.
C.
C.
C Pos
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
o nicicicicicicicicicicicicicicicicicicicicicicicicick
C
D
E
C, Right oblique facial views before and after reconstruction. D, Left oblique
facial views before and after reconstruction. E, Occlusal views before and after reconstruction.
• Figure 14-2, cont’d 
Continued

432 SECTION 2  Planning, Surgical Technique, & Complications
“Mandible-first” analytic model planning
Maxilla used as stable platform—to reconstruct mandible
Mandible repositioned
with interim splint
Maxilla repositioned
with final splint
Articulated
dental casts
F
G
Inferior border of mandible asymmetry improved after surgery
F, Articulated dental casts that indicate “mandible-first” analytic model planning. G, Lateral cephalometric radiographs
before and after reconstruction.
• Figure 14-2, cont’d

433
CHAPTER 14  Mandible-First Analytic Model Planning for Orthognathic Surgery
• CASE 14-2 
Hemifacial Microsomia
A child was born with right-sided hemifacial microsomia,
which was manifested by moderate hypoplasia of the right-
sided soft tissues, displacement and deformity of the exter-
nal ear, anomalous external auditory canals, and a Kaban
type IIB mandibular malformation (Fig. 14-3). Left-sided
macrosomia repair was carried out during childhood.
During the late mixed dentition, the patient was referred to
this surgeon for evaluation (see Fig. 28-15). After orthodon-
tic preparation, he underwent a maxillary Le Fort I oste-
otomy in two segments with three-dimensional repositioning
(horizontal advancement, vertical shortening, transverse
expansion, dental midline shift, occlusal plane change,
and cant correction); sagittal split osteotomy of the left
ramus; reconstruction of the right condyle and ascending
ramus of the mandible with an autogenous costochondral
graft; osseous genioplasty (advancement and asymmetry
correction); an intranasal procedure (septoplasty and
inferior turbinate reduction); and bilateral otoplasty
(set-back).
• Figure 14-3  A child who was born with
hemifacial microsomia of the right side of
face and a type IIB condyle and ascending
ramus malformation was followed longitu­
dinally without treatment intervention until
skeletal maturity (see Fig. 28-15). Facial
asymmetry demonstrated no progression
during this time frame. During the adult
dentition and with orthodontic dental
decompensation complete, the patient
underwent single-stage reconstruction
that included a maxillary Le Fort I osteot­
omy a left-sided sagittal split ramus oste­
otomy; right mandibular reconstruction
with costochondral graft osseous genio­
plasty septoplasty, inferior turbinate reduc­
tion, and bilateral otoplasty (ear set-back).
A, Facial views in repose before and after
reconstruction. B, Facial views with smile
before and after reconstruction.
Or
Or
Or
Or
Or
Orththththththththththththththththththththtr ogn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
g atatatatatatatatatatatatatatatatatatatatatatatathicicicicicicicicicicicicicicicicicic Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
S rg
r ery
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry; J.C.
C.
C.
C.
C.
C.
C.
C.
C Pos
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
osnicicick
Or
Or
Or
Or
Or
Or
Or
Or
Orththththththththththththththththth
r ogn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
g atatatatatatatatatatatatatatatatatatatathicicicicic Su
Su
Su
Su
Su
Su
Su
Surg
r ery
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry; J.C.
C.
C.
C.
C.
C.
C.
C.
C.
C.
C.
C Pos
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
osnicicicicicicicicicicicicicicicicicicicicicicicicick
Or
Or
Or
Or
Or
Or
Or
Or
Orththththththththththththththththththth
r ogn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gnatatatatatatatatatatatatatatatathicicicicicicicicicicicicicicicicicicicici Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Surg
r ery
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry; J.C.
C.
C.
C.
C.
C.
C. Pos
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
osnicicicicicicicicicicick
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
O thththththththththththththththththth
r ogn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
g atatatatatatatatatatatatatata hicicicicicicicic Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
S rg
r ery
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry; J.C.
C.
C.
C.
C.
C.
C.
C.
C.
C.
C.
C. Pos
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
o nicicicicicicicicicicicicicicicicicicici k
A
B
Continued

434 SECTION 2  Planning, Surgical Technique, & Complications
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
O thththththththththththththththththththththththththtr ogn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
g atatatatatatatatatathicicicicicicicicicicicicicicicicicicicicicicicicicicicicic Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
S rg
r ery
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry; J.C.
C.
C.
C.
C.
C.
C.
C.
C.
C.
C.
C.
C.
C.
C.
C.
C.
C.
C.
C.
C Pos
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
o nicicicicicicicicicicicicicicicicicicicicicicicicicicicick
Or
Or
Or
Or
Or
Orththththththththththththththththththththththththththth
r ogn
gn
gn
gn
gn
gn
gn
gn
gn
gn
g atatatatatatatatatatathicicicicicicicicicicic Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
S rg
r ery
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry; J.C.
C.
C.
C.
C.
C.
C.
C.
C.
C.
C.
C. Pos
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
osnicicicicicicicicicicicicicicicicicicicicicicicicicicicick
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
O hthththththththththththththththththththththththththththththththththtr ogn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
g atatatatatatatatatatatatatatatatatatatatatatatatata hicicicicicicicicicicicicicicicicicicicicicicicicicicicicic Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
S rg
r ery
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry; J.C.
C.
C.
C.
C.
C.
C.
C Pos
os
os
os
os
os
os
os
os
os
o nicicici k
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
O thththththththththththththththththththththththth
r ogn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gnatatatatatatatatatatatatatatatatatathicicicicicicicicicicicicicicic Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Surg
r ery
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry; J.C.
C.
C.
C.
C.
C Pos
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
o nicicicicici k
C
D
E
Pre surgery
After treatment
C, Left facial oblique views before and after reconstruction. D, Right oblique facial views before
and after reconstruction. E, Occlusal views before surgery and after the completion of treatment.
• Figure 14-3, cont’d

435
CHAPTER 14  Mandible-First Analytic Model Planning for Orthognathic Surgery
F
G
“Mandible-first” analytic model planning.
The maxilla is used as stable platform—to reconstruct mandible
Mandible repositioned
Maxilla repositioned
Articulated
dental casts
F, Illustrations of the presenting anatomy and the reconstructive procedures that were carried out. G & H, Articu­
lated dental casts that indicate “mandible-first” analytic model planning.
• Figure 14-3, cont’d 
Continued
Part F modified by an original illustration by Bill Winn.

436 SECTION 2  Planning, Surgical Technique, & Complications
“Mandible-first” analytic model planning
Maxilla used as stable platform—to reconstruct mandible
Mandible repositioned
Maxilla repositioned
Articulated dental casts
H
I
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
O ththththththththththththththththththththth
r ogn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gnatatatatatatatatatatatatatata hicicicicicicicicici Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
Surg
r ery
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry; J.C.
C.
C.
C.
C.
C.
C.
C.
C.
C Pos
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
osnicicicicicicicicicicicicicicicicicicicicicick
J
I, Lateral computed tomography scan views before and after reconstruction. J, Frontal facial and computed
tomography scan views after reconstruction.
• Figure 14-3, cont’d

437
CHAPTER 14  Mandible-First Analytic Model Planning for Orthognathic Surgery
• CASE 14-3 
Hemifacial Microsomia
A child was born with an asymmetric bilateral form of
hemifacial microsomia that was manifested by moderate
hypoplasia of the affected soft tissues (including the muscles
of mastication), bilateral microtia, atresia of the external
auditory canals, and mild bilateral hypoplasia of the zygomas
and the orbits. Bilateral asymmetric Kaban type IIA man-
dible malformations were present (Fig. 14-4). The patient’s
previous surgeries included multiple external ear recon-
structive procedures by another surgeon, including the
placement of autogenous costochondral grafts. She also
underwent an attempt to open the left external auditory
canal by another surgeon, but this was aborted after facial
nerve concerns. Mandibular reconstruction was attempted
twice (when the patient was 7 and 11 years old) by another
surgeon with the use of distraction osteogenesis techniques,
but this had limited results. The previous procedures created
intraoral and facial scarring, and a 15-mm anterior open-
bite malocclusion remained.
At 14 years old, the patient was referred to this surgeon
for evaluation (see Fig. 28-16). After additional orthodontic
preparation, she underwent maxillary Le Fort I osteotomy;
bilateral coronoidectomies; bilateral sagittal ramus osteoto-
mies (with autogenous iliac corticocancellous interposi-
tional bone grafts); osseous genioplasty (advancement and
shortening); and intranasal procedures (septoplasty and
inferior turbinate reduction). The described mandible-first
analytic model planning technique was used.
• Figure 14-4  A girl was born with a
bilateral form of hemifacial microsomia
and Kaban type IIA condyle and ascend­
ing ramus malformations (see Fig. 28-16).
When she was 7 and 11 years old (and at
another institution), she underwent bilat­
eral distraction osteogenisis of the man­
dible. The procedures were unsuccessful.
She also underwent bilateral external ear
reconstruction with a suboptimal result.
The patient wore external hearing aids.
Earlier orthodontic treatment was carried
out (at another institution) including four
bicuspid extractions. After presenting to
this surgeon when she was 15 years old,
the patient underwent reconstruction that
included a Le Fort I osteotomy bilateral
ramus osteotomies with interpositional
grafting; osseous genioplasty; septo­
plasty, inferior turbinate reduction, and
nasal floor recontouring. A, Profile facial
and computed tomography scan views
at the time of referral to this surgeon.
B, Frontal views with smile before and
after reconstruction.
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
Or
O thththththththththththththththththtr ogn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
gn
g atatatatatatatatatatatatatathicicicicicicicicicicicicicici Su
Su
Su
Su
Su
Su
Su
Su
Su
Su
S rg
r ery
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry
ry; J.C.
C.
C.
C. Pos
os
o nicicicick
A
Distraction osteogenesis effects on
mandibular ramus/angle
Unfavorable A-pt. to B-pt. relationship
Or
Or
Or
Or
Or
Or hththththththththththththththththththth
r ogn
gn
gn
gn
gn
gn
gn
gn
gn
gn
g atatatatatatathici Su
Su
Su
Surg
r ery
ry
ry
r ; J.C.
C Pos
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
osnicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicicick
Or
Or
Or
Or
Or
Orththththththththththththththththththththththththththththththththththththththththththththththththththththththththth
r ogn
gn
gn
gn
gn
gn
gn
gn
gn
gn
g atata hicicicicic Su
Su
Surg
r ery; J.C.
C.
C Pos
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
os
osnicicicicici k
B
Continued

438 SECTION 2  Planning, Surgical Technique, & Complications
Orth
r ognathic Surg
r ery; J.C. Posnick
Orth
r ognathic Surg
r ery; J.C. Posnick
C
Pre surgery with 4 bicuspid extractions
After treatment
D
C, Oblique facial views before and after reconstruction. D, Occlusal views after ortho­dontic decompensation (i.e., four
bicuspid extractions) and then 1 year after the completion of treatment.
• Figure 14-4, cont’d

439
CHAPTER 14  Mandible-First Analytic Model Planning for Orthognathic Surgery
“Mandible-first” analytic model planning
Maxilla used as stable platform—to reconstruct mandible
Mandible repositioned
Maxilla repositioned
Articulated
dental casts
E
F
E, Articulated dental casts that indicate “mandible-first” analytic model planning. F, Lateral cephalometric
radiographs before and after reconstruction.
• Figure 14-4, cont’d 
clinical settings in which the obtaining of an accurate and
reliable bite registration can be problematic. For these
patients, a mandible-first approach to analytic model planning
for the achievement of accurate and reliable results is
required.
Conclusions
During model planning in preparation for orthognathic
surgery, the introduction of error can occur when obtaining
the bite registration in the clinical setting. There are specific
References
1. 2000 Series Articulator, Whip Mix
Corporation, 1 Farmington Ave, PO Box
17183, Louisville, KY 40217.
2. Adrien P, Schouver J: Methods for minimizing
the errors in mandibular model mounting on
an articulator. J Oral Rehabil 24:929, 1997.
3.  Amira software, Houston, Texas, 2010, TGS.
Available at Accessed
January 4, 2010.
4.  Assael LA: Editorial. J Oral Maxillofac Surg
67:2041, 2009
5. Becker CM, Kaiser DA, Schwalm C:
Mandibular centricity: centric relation.
J Prosthet Dent 83:158, 2000.
6. Bell W, Proffit W, White R: Surgical
correction of dentofacial deformities, ed 6,
Philadelphia, 1980, W.B. Saunders
Company, pp 155–199.
7.  Bell RB: Computer planning and
intraoperative navigation in orthognathic
surgery. J Oral Maxillofac Surg 69:592–605,
2011.
8. Buckley MJ, Tucker MR, Fredette SA: An
alternative approach for staging simultaneous
maxillary and mandibular osteotomies. Int J
Adult Orthodon Orthognath Surg 2:75,
1987.