Phẫu Thuật Tạo Hình Grabb & Smith’s (Bản Cập Nhật – Kevin C. Chung)

FIGURE 30.6 This patient presented for treatment at 7 years of age. The etiology of her craniofacial anomalies has not been
described. A large part of the problem was the hypoplastic mandible—Pruzansky type IIa. Because adequate bony stock was
present and there was a rudimentary TMJ, internal distractors were placed as diagrammed in Figure 30.5, yielding a total of
31 mm of advancement. A. Mandible contour on lateral X-ray. B. Orientation of the distractor application. C,D. Patient’s
predistraction and postdistraction appearances, respectively, reflecting the significant advancement achieved.
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FIGURE 30.7 Pruzansky grade IIb and above mandibles can be reconstructed using a rib graft to recreate the zygomatic arch
if absent; costochondral rib grafts to recreate the ramus of the mandible, and careful positioning of a cartilaginous cap of the
costochondral graft to serve as a neocondyle within the reconstructed glenoid fossa.
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Timeline
The controversy regarding surgical treatment of the mandible and maxilla in CFM centers around the
questions of intervening in early childhood or waiting until skeletal maturity, with the choice of
distraction osteogenesis or one-stage surgery as a secondary debate. The argument for early intervention
is in part that correcting the mandible in childhood will normalize the patient’s appearance throughout
their childhood, correct some of the soft-tissue contours, and facilitate downward growth of the maxilla,
potentially sparing the child a subsequent surgical procedure to correct the maxilla. These benefits come
at the cost of the increased difficulty of working with the immature mandible bone stock and the
increased likelihood of needing repeat surgery at skeletal maturity to correct for any occlusion changes
that will happen with growth. The alternative is waiting until skeletal maturity and then performing
orthognathic surgery on the developed bony stock, usually comprised of a three-jaw surgery: Le Fort I
osteotomy of the maxilla, BSSO (bilateral sagittal split osteotomy), and asymmetric osseous genioplasty.
Although this is likely to provide a one-stage orthognathic correction, it does not address the soft-tissue
paucity nor the psychological cost to the child in growing up with an uncorrected deformity. Table 30.2
summarizes the basic arguments for earlier or later intervention.
TABLE 30.2
Arguments for Earlier or Later Intervention
Factor
Early Childhood Intervention
Surgery at Skeletal Maturity
Need for revision orthognathic
surgery
High
Low
Soft tissue
Partially addressed during distraction
Must be addressed separately
Psychosocial factors
Provides early improvement prior to school
age
Patient bears burden of deformity until
adolescence
Need for maxillary surgery
Variable based on orthodontic Rx
Almost always
In a study of children with craniofacial anomalies, self-awareness of facial differences began at a mean
age of 3 years and teasing at a mean age of 6, with 43% of individuals 4 years or older reporting teasing. 31
There is also evidence of worse psychological outcomes in children with CFM, 32 lending credence to the
idea of earlier surgery to improve children’s psychosocial development.
Earlier surgery on the mandible also affects the growth of the maxilla, as Kaban et al. showed that
correction of the mandible at an early age and creation of an open bite on the affected side can lead to
responsive downward growth of the maxilla, resulting in an overall level occlusal plane and sparing
patients from the need for Le Fort maxillary osteotomies to level the maxillary occlusal plane in the
future. 27
Choosing distraction versus osteotomy and advancement (with bone grafting, if needed) in a single step
depends on the patient’s age, bone stock, soft tissue, and surgeon preference. It has been thought that by
the virtue of gradually stretching soft tissue with distraction, these forces would be lessened at the end of
the distraction course and thus lead to lower relapse rates. However, a prospective randomized
controlled trial in adults >35 years of age did not show any significant difference in relapse rates for
advancements <10 mm. 33 Whereas 10 mm advancement is a modest distraction distance, differences
between the stability of distraction and orthognathic advancement of the mandible may become apparent
in advancements >10 mm.
One of the other controversial topics in this discussion is the natural growth of the affected mandible,
maxilla, and soft tissues. Although it is clear that the affected tissues do not catch up in growth when
compared with the contralateral side, it is less clear whether it is the relative or absolute size discrepancy
of the affected side that worsens over time. The mandible that has been distracted or reconstructed with a
graft can exhibit growth, albeit at a slower rate than the contralateral side, thus sometimes necessitating a
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revision surgery at maturity if the initial correction was done at a young age.
The overall timeline is as follows:
Infancy (up to 2 years of age)
Correction of macrostomia, clefts, and minor auricular anomalies (pits, accessory appendages)
should be performed early on to improve function and make a dramatic improvement in
appearance.
Distraction of the affected mandible is considered at this early stage for patients with airway
compromise.
Early childhood (to 6 years of age)
Type I: If the deformity is mild, treatment is delayed until skeletal maturity.
Type IIa/IIb: If the aesthetic deformity is severe or airway problems exist, which were not
addressed in infancy, distraction osteogenesis is considered for type IIa and type IIb mandibles
with adequate bone stock.
Type III: The ramus, zygomatic arch, and the temporomandibular articulation is reconstructed
using costochondral grafts at approximately 4 years of age or older, with secondary distraction if
needed to expand the construct once healed.
Late childhood/adolescence (6–16 years of age)
Orthodontic treatment is applied during this period. If the mandible has already been corrected,
orthodontia can help bring the maxilla into occlusion. The goal is to correct the maxilla enough
to avoid a Le Fort I osteotomy in the future.
Adolescence and later (after age 16)
If the mandible has already been operated on:
Once the patient is deemed to be at skeletal maturity, the occlusion and results of
orthodontic treatment are assessed. There is a high likelihood that secondary surgery will be
needed to correct the maxilla, to revise the mandible to account for the unaffected side’s
growth, or to perform an asymmetric genioplasty to restore the chin to the midline.
If the patient has not yet had mandibular surgery (typically type I mandibles or if the decision
was made to delay treatment):
The surgical plan must be customized to each patient, but will usually include:
Sagittal split osteotomy with or without bone graft to address the mandibular vertical
deficiency.
Le Fort I osteotomy, often with impaction on the affected side, to level the occlusal
plane.
Asymmetric osseous genioplasty, to correct the facial asymmetry.
Advanced soft-tissue correction can also be undertaken at this time. Severe soft-tissue deficit is
best addressed by choosing distraction for the mandible: as the bone is expanded, so is the
overlying soft-tissue envelope. For residual defects, an adipofascial free flap or serial fat injection
may be used to correct volume deficiency, depending on the defect size.
Adipofascial free flaps have been associated with ptosis and less predictable volume over time
with patient weight loss or gain. There is currently an increasing trend for serial fat injection to
treat facial soft-tissue deficit because this is less likely to undergo ptosis and patients can be
regrafted with much less morbidity.
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Craniofacial Distraction
The problem of deficient bone stock has long been present in both the pediatric population (e.g.,
hypoplastic mandible in children with CFM or Pierre Robin sequence) and in adults (e.g., bone loss due
to trauma or need of orthognathic surgery with large [>1 cm] advancements). Solutions such as
vascularized bone transfer are often impractical and carry a large donor site burden, and an avascular
graft carries the risks of infection, nonunion, and resorption. Distraction osteogenesis solves this problem
by expanding the existing bone stock along the vector specified by the surgeon, essentially replicating for
bone what tissue expansion has done for the skin. Although it was described earlier, Ilizarov is credited
with proving the concept and establishing its efficacy in long bones. 34 McCarthy and colleagues later
applied these principles to craniofacial scenarios, supporting the clinical efficacy of this technique. 35
The basic principle of distraction osteogenesis consists of an osteotomy across the bone to be distracted
and then carefully controlled separation of the two segments at a rate that promotes bony regeneration to
close the gap. Although details may differ based on surgeon preference and patient age, the basic timeline
is as follows:
Osteotomy and hardware placement
The bone to be distracted is divided into segments with an osteotomy or corticotomy, creating
the distraction zone. The surgeon must ensure that the segments are mobile so that distraction can
take place—an incomplete osteotomy/corticotomy will skew the vector of distraction or cause
hardware failure.
The distractor hardware is placed across the distraction zone aligned with the desired vector of
movement to promote new bone deposition. No distraction takes place at this time, and the
bony segments remain in opposition.
Latency period
Approximately 1 week (5–7 days) is allowed for healing and initial callus formation in the
distraction zone prior to initiation of distraction.
Activation period
The distraction hardware is used to separate the bony segments at some predetermined rate
(usually 0.5 mm twice per day). Faster rates are commonly seen in infants because of their ability
to quickly deposit bone regenerate—the guiding principle here is to set such a rate that
separation of the bony segments will not outpace the deposition of new callus, yet will also not
be so slow so that ossification leading to bony union causes premature end of distraction.
The device is periodically checked for alignment and solid fixation to ensure the desired vector
of distraction is maintained.
Consolidation period
Once the desired amount of travel is achieved, distraction is stopped and the callus formed in
the distraction space ossifies. This period is usually 8 weeks in length, after which time the new
bony construct should be stable and hardware can be removed. However, in infants, the
consolidation period is often shortened to 6 weeks because of rapid bone consolidation.
McCarthy and colleagues examined the histology of the bony generate 36 in the distraction zone, with
later studies providing further detail (Figure 30.8). 37 The healing response is initiated similar to any other
fracture with hematoma formation and inflammatory cell influx during the latency period, producing the
initial callus. Infiltration of fibroblast-like cells and neovascularization are noted after beginning of
activation. Osteogenesis is noted at 2 weeks after activation is started with osteoid deposition and
mineralization, and osteoblasts seen another week later. The basic histologic structure shown in Figure
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30.8 reflects the findings of McCarthy et al., although later studies revealed a more stratified organization
to the generate. The key findings agree in that bony trabeculae start forming along the axis of distraction
with concomitant neovascularization and then continue this process after distraction is stopped until
mature lamellar bone is produced. In an in vitro model, Slack et al. 38 found that skipping the latency
period and starting distraction immediately appears to lead to marked delays in cell proliferation,
alkaline phosphatase activity, osteogenic gene expression, and higher apoptosis at the osteotomy site;
however, the bone volume and quality at the clinical endpoints were unaffected. Of note is that latency
periods are often shortened to 1 day or completely eliminated in infants. Future studies are required to
further investigate the importance, duration, and age-dependence of the latency period.

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FIGURE 30.8 Diagram of the bony generate in the setting of distraction. 36 Central zone is area of mesenchymal proliferation
and collagen deposition. Transition zone has osteoid formation on the scaffold of collagen bundles. Remodeling zone is area of
osteoclast activity and new bone remodeling, leading up to mature bone zone.
The cellular-level processes underlying osteogenesis in this scenario are understandably complex, but one
of the key factors is TGF-B1 (transforming growth factor B1), which peaks during the activation period,
ostensibly inducing deposition of collagen and extracellular matrix necessary for further ossification. 39
TGF-B1 subsequently induced VEGF and FGF, which in turn are key to neovascularization of the bony
generate and fibroblast activity necessary for the process. 40 Bone morphogenic protein, insulin-like
growth factor, and osteonectin/osteopontin also appear to play key roles. 37
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Hardware
A major decision for each distraction case is whether to use internal or external hardware. Applications in
the mandible can use either type with no significant difference in efficacy, whereas others, such as
posterior vault distraction, appear to be better suited for buried (internal) hardware. In general, the
external distractors act similarly to an external fixator with a mechanism for applying a distracting force
between two sets of pins. Each center has its own preference for internal versus external hardware for
mandibular distraction. There are some data that buried devices lead to higher satisfaction with quality of
life and the decision to undergo the procedure in the face of equivalent functional and aesthetic
outcomes. 41 However, internal distraction devices have the disadvantage of requiring a second surgical
procedure for device removal. This is a significant consideration given that injury to the marginal
mandibular nerve with long-term weakness of depressor function of the oral commissure has been
reported in 15% of cases following internal mandibular distraction in patients with Pierre Robin
sequence. 42 One must consider the increased risk of nerve injury following internal distractor placement,
given the need for reentry into the incision for distractor removal when the nerve may be obscured by
scar following the initial procedure. In summary, the guiding principle for hardware choice is to ensure
that fixation will be secure, and the desired vector of distraction will be maintained, with remaining
factors determined by surgeon preference and experience. Table 30.3 shows the general pros and cons of
each design.
TABLE 30.3
KEY DIFFERENCES BETWEEN INTERNAL AND EXTERNAL DISTRACTION HARDWARE
Internal
External
Profile
Lower profile, only the activator arm needs to be
externalized
Bulkier profile, multiple pin sites require more hygienic care
Incisions
Requires a larger incision for the bulky hardware
and wide exposure of the bony for footplate fixation
Smaller stab incisions for pins may reduce external incision burden
if other approach (intraoral) can be used to complete osteotomy
Monitoring
Difficult to assess distraction and hardware
position/security because only the activator arm is
visible
Position and movement of hardware is easily examined; however,
correlation with bone movement is speculative
Adjustments
No adjustments can be made once the hardware is
in place
Vector can be manipulated and multivector distraction can be
carried out
With the establishment of distraction osteogenesis as a clinically effective and safe technique, its
indications have widened. Large early analyses reported pooled complication rates approximating 1 in 3
patients, with markedly lower rates reported by surgeons experienced in the technique. 43 As the
specialty’s collective experience has grown, so has the safety profile, as shown below for the specific
applications.
Figure 30.6 shows the application of internal distraction hardware for mandible distraction. In the same
setting of mandibular distraction, it is easy to appreciate the differences when compared with external
distraction, as shown in Figure 30.9.
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FIGURE 30.9 Mandible distraction using external hardware. An oblique vector addressing the mandibular body is shown in (A)
and a vertical vector addressing a ramus height deficiency is shown in (B).
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Mandibular Distraction
The mandible was the first bone where craniofacial distraction was successfully implemented—it is
accessible, the progress of distraction is easy to assess, and it addresses a significant clinical need.
Mandibular distraction has enabled craniofacial surgeons to address mandibular hypoplasia at a younger
age with less morbidity than traditional methods. It has shown to be effective in infants with Pierre Robin
sequence, Treacher Collins syndrome, and CFM. Patients with these conditions suffering from airway
compromise often find significant improvement after distraction and can be successfully decannulated.
One of the key decisions in mandibular distraction is the choice of vector. This hinges on the morphology
of the patient’s mandible: adequate bony stock in the body with a deficient or absent ramus dictates a
vertical vector (perpendicular to the occlusal plane), whereas the converse (short body but adequate
ramus) dictates a horizontal vector. If both the body and ramus are deficient, an oblique vector can be
chosen. It is important to account for autorotation when distracting with a vertical or oblique vector, as
the extraposterior height will result in anterior movement of the body and increase chin projection. In
unilateral cases, there will also be some correction of the chin point deviation. When performing this in
infants or children who have not yet reached skeletal maturity, the goal should be to achieve
overcorrection as the distracted mandible exhibits slower growth than age-matched controls. 44 One must
also determine whether unilateral or bilateral mandibular distraction is indicated based on the relative
asymmetry of mandibular position relative to the maxilla.
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Monobloc and Le Fort III Distraction
Despite over two decades of experience with monobloc and Le Fort III distraction, 45 in a review of
Monobloc and Le Fort III advancement, it appears there are mixed data regarding the complication
profiles for distraction versus traditional advancement. Monobloc advancements incurred higher
complication rates with distraction, and the opposite was seen in Le Fort III advancements, indicating
that further refinement of these techniques is needed. 46 Nevertheless, for younger children in need of
significant midface advancement, distraction has been 47 and continues to be the preferred method of
midfacial advancement. Both rigid external devices and buried distraction hardware have been
successfully used in this setting.
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Cranial Vault Distraction
Distraction of the cranial vault, and the posterior vault specifically, is a relatively new application of
distraction osteogenesis. The intracranial volume gained by posterior vault distraction is markedly higher
when compared with fronto-orbital advancement, 48 and compared with traditional methods of posterior
vault cranioplasty, the complication rate appears to be comparable. 49 Notably, great care must be paid to
avoid inadvertently injuring the dura with the screws, as the multiple footplates will likely span areas of
variable bone thickness (Figure 30.10). Although the argument exists for distraction to obtain the maximal
possible gain in intracranial volumes, there are not yet enough data to show clear superiority of
distraction to traditional cranioplasty for posterior vault expansion. 33
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FIGURE 30.10 This patient demonstrates the application of posterior cranial vault distraction for correction of brachycephaly
because of bilateral coronal synostosis. Note that internal hardware was used, as is the norm for these cases, with three
distractors placed to stabilize the distracted segment against rotation. A, B. Pre-operative clinical and radiographic
appearance prior to distractor placement. C. Patient appearance at 10 days of distraction at 1 mm per day. D. Radiographic
results of distraction after 40 mm of distraction. E. Patient appearance at 6 months follow up after distractor hardware removal.
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Complications of Distraction Osteogenesis
The complex nature of the deformity and surgical course is associated with complications at any point.
Complications more specific to distraction include hardware problems, soft-tissue ulceration and
breakdown, incorrect distraction vectors, and postdistraction sequelae. The practice of distraction
osteogenesis is heterogeneous because of the varied indications, patient scenarios, hardware types, and
surgeon experience. Accordingly, although there is evidence that surgeon experience is associated with
lower complication rates, complication rates vary widely.
Infectious complications include infection of the hardware, but the more common finding is localized
cellulitis at the pin or activator arm sites, which may be due to poor hygiene. This can often be treated
medically and with improved pin site care. With internal hardware, breakage can occur, leading to
premature distraction termination or repeat surgery for distractor replacement. With external hardware,
distractors can be replaced without requiring repeat surgical procedures. Inappropriate distraction
vectors will lead to poor occlusal outcomes and asymmetry. Cranial distraction has its own unique
complications with dural injury or CSF leaks.
Some of the complications of distractions are less avoidable, such as decreased growth of the distracted
bones or loss of dentition at the site of the osteotomy in cases of mandible distraction. These, as well as
some mild relapse in the year after distraction is complete, appear to be sequelae of the techniques
themselves.
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Questions
1. A new patient shown in the photograph is referred to your clinic by the pediatrician for facial
asymmetry. You tentatively diagnose the patient with CFM and assign which of the following
grades?
a. 1
b. 2a
c. 2b
d. 3
e. 4
f. None of the above
2. During the initial evaluation of a new patient suspected of having CFM, which of the following
testing or imaging modalities are recommended?
I. Echocardiogram
II. Renal ultrasound
III. Cervical spine X-rays
IV. Skeletal survey
a. I only
b. I and II
c. I, II, and III
d. All four are recommended
3. Which of these answers correctly associates a category of mandible hypoplasia seen in the setting
of a patient with CFM, with the correct treatment strategy?
a. Type III, treat at 2 years of age with a costochondral graft to definitively reconstruct the TMJ
b. Type I, treat at 5 to 7 years of age with unilateral sagittal split osteotomy to improve facial
symmetry and contour
c. Type IIb, treat at 5 to 7 years of age with distraction osteogenesis to create a pseudo-TMJ
d. Type III, treat at 2 to 3 years of age with a costochondral graft to reconstruct TMJ and free soft-
tissue transfer to improve facial contour
4. Which of the following is true regarding distraction osteogenesis?
a. Exposure of the bone that is to be distracted is similar for both internal and external hardware
placement, despite different external incision patterns.
b. A latency period is necessary to prevent overly fast distraction.
c. Distraction of a hypoplastic mandibular ramus should not affect chin projection or
asymmetry; an asymmetric genioplasty is always necessary to correct these.
d. The optimal rate of distraction is 0.25 mm twice per day or slower in adults.
e. Distraction osteogenesis has proven efficacy in both long bones of the extremities as well as
the flat bones of the skull.
5. Which of the following is true regarding the treatment of CFM?
a. Distraction of the hypoplastic mandible in early childhood mandates maxillary surgery at
maturity.
b. Distraction of the hypoplastic mandible in early childhood resolves any appearance concerns
until secondary correction is necessary.
c. Correctly executed distraction of the hypoplastic mandible will obviate any need for osseous
genioplasty at maturity.
d. Aside from difference in size, the anatomy of the hypoplastic mandible in CFM is otherwise
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the same.
e. When a costochondral graft is used for ramus reconstruction, a TMJ prosthesis is not
necessary to obtain a functional outcome.
1. Answer: f. The morphology and functional status of the TMJ are key to grading and treatment
planning in a patient with CFM. Without clear information regarding the status of the TMJ, no
definitive grade can be assigned.
2. Answer: c. Cardiac, renal, and cervical spine evaluation is recommended for all CFM patients
because of the high prevalence of associated anomalies in these systems. There is no evidence that
shows any benefit to evaluating the rest of the skeleton aside from the cervical spine.
3. Answer: c. Although there are multiple points of view regarding the specific timing of surgical
intervention for craniofacial macrosomia, certain guidelines are agreed upon. For type III mandibular
hypoplasia, treatment should be considered at 4 years of age and they will likely need revision
procedures after they reach skeletal maturity. Type I mandible hypoplasia is better addressed with
distraction to produce a lower relapse rate and may also require revision in adulthood. Type IIb may
be treated with either distraction and creating of a pseudo-TMJ or a costochondral graft to create a
neo-TMJ. However, type III hypoplasia is not amenable to treatments solely with distraction and
requires bone graft to fabricate an acceptable neomandible and TMJ. Moreover, free soft-tissue
transfer for facial contour would likely be more appropriately performed in a delayed fashion, 6 to
8 months after the bony skeleton reconstruction is in place.
4. Answer: e. Internal and external hardware requires the same osteotomy, but internal hardware
requires much greater periosteal stripping and bony dissection to gain access for securing the
hardware footplates. A latency period is often skipped in very young patients and has been shown to
not significantly alter the final bony generate. Distraction of a mandibular ramus will lead to
autorotation of the mandible on that side, moving the chin toward the contralateral side and
increasing its projection. The most widely used rate of distraction is 0.5 mm twice per day in adults,
with higher rates possible in infants. Distraction osteogenesis has been shown to be an effective
technique in both the extremities (as originally described by Ilizarov) as well as in the bones of the
craniofacial skeleton.
1. Answer: e. Distraction of the hypoplastic mandible in early childhood, coupled with orthodontia,
may often obviate the need for maxillary surgery maturity. Hypothetically, this is due to allowing
the maxilla to resume its normal downward growth on the affected side once the obstruction
presented by the mandible is addressed. Although addressing the mandible in early childhood
improved patients’ appearance as they grow, there is no guarantee the correction will be complete.
Moreover, other associated anomalies (macrostomia, microtia) may continue to cause psychosocial
distress until they are addressed as well. If the size of the affected hemimandible is corrected, the
shape will likely still be asymmetric, with some deviation of the chin, and thus an osseous
genioplasty is often needed at maturity to obtain the best possible result. The anatomy of the
hypoplastic mandible in CFM is different both in terms of altered shape, hypoplasia or lack of
condylar or coronoid processes, as well as displacement of the inferior alveolar foramen superiorly
and the canal buccally.
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References
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Poswillo, D. The aetiology and pathogenesis of craniofacial deformity. Development. 1988;103(suppl):207.
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at this time.
Caron, CJJM, Pluijmers, BI, Wolvius, EB, et al. Craniofacial and extracraniofacial anomalies in craniofacial microsomia: a multicenter study of
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Schaal, SC, Ruff, C, Pluijmers, BI, et al. Characterizing the skull base in craniofacial microsomia using principal component analysis. Int J Oral
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Renkema, RW, Caron, CJJM, Wolvius, EB, et al. Central nervous system anomalies in craniofacial microsomia: a systematic review. Int J Oral
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Marsh, JL, Baca, D, Vannier, MW. Facial musculoskeletal asymmetry in hemifacial microsomia. Cleft Palate J. 1989;26(4):292.
Suzuki, N, Miyazaki, A, Igarashi, T, et al. Relationship between mandibular ramus height and masticatory muscle function in patients with
unilateral hemifacial microsomia. Cleft Palate Craniofac J. 2017;54(1):43.
Zim, DS, Lee, DJ, Rubinstein, DB, Senders, DC. Prevalence of renal and cervical vertebral anomalies in patients with isolated microtia and/or
aural atresia. Cleft Palate Craniofac J. 2017;54(6):664-667.
Keogh, IJ, Troulis, MJ, Monroy, AA, et al. Isolated microtia as a marker for unsuspected hemifacial microsomia. Arch Otolaryngol Head Neck
Surg. 2007;133(10):997-1001.
Rahbar, R, Robson, CD, Mulliken, JB, et al. Craniofacial, temporal bone, and audiologic abnormalities in the spectrum of hemifacial
microsomia. Arch Otolaryngol Head Neck Surg. 2001;127(3):265.
Horgan, JE, Padwa, BL, Labrie, RA, Mulliken, JB. OMENS-Plus: analysis of craniofacial and extracraniofacial anomalies in hemifacial
microsomia. Cleft Palate Craniofac J. 1995;32(5):405.Horgan et al. studied the relationships between varied manifestations of CFM that may be
treated by the craniofacial surgeon and the multiple other developmental anomalies that may be found in these patients.
Meurman, Y. Congenital microtia and meatal atresia; observations and aspects of treatment. AMA Arch Otolaryngol. 1957;66(4):443-463.
Pruzansky, S. Not all dwarfed mandibles are alike. Birth Defects. 1969;4:120.
Kaban, LB, Moses, MH, Mulliken, JB. Surgical correction of hemifacial microsomia in the growing child. Plast Reconstr Surg.
1988;82(1):9.Landmark article modifying the original Pruzansky classification to produce what is currently used to stratify hypoplastic mandibles.
Birgfeld, CB, Luquetti, DV, Gougoutas, AJ, et al. A phenotypic assessment tool for craniofacial microsomia. Plast Reconstr Surg.
2011;127(1):313.
Patel, PK, Novia, MV. The surgical tools: the LeFort I, bilateral sagittal split osteotomy of the mandible, and the osseous genioplasty. Clin
Plast Surg. 2007;34(3):447.This excellent publication lays out the fundamentals of the surgical techniques that are the foundation of correcting the
findings in CFM.
Tiwari, P, Chin, DHL, Cutting, CB, et al. The course of the inferior alveolar nerve in craniofacial microsomia: virtual dissection using three-
dimensional computed tomography image analysis. Plast Reconstr Surg. 2002;109(5):1513.
Luquetti, DV, Brajcich, MR, Stock, NM, et al. Healthcare and psychosocial experiences of individuals with craniofacial microsomia: patient
and caregivers perspectives. Int J Pediatr Otorhinolaryngol. 2018;107:164.
Dufton, LM, Speltz, ML, Kelly, JP, et al. Psychosocial outcomes in children with hemifacial microsomia. J Pediatr Psychol. 2011;36(7):794.
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Fearon, JA. Discussion: an algorithm for managing syndromic craniosynostosis using posterior vault distraction osteogenesis. Plast Reconstr
Surg. 2016;137(5):842e.
Ilizarov, GA. The tension-stress effect on the genesis and growth of tissues. Part I. The influence of stability of fixation and soft-tissue
preservation. Clin Orthop Relat Res. 1989(238):249.
Karp, NS, Thorne, CH, McCarthy, JG, Sissons, HA. Bone lengthening in the craniofacial skeleton. Ann Plast Surg. 1990;24(3):231.This is one of
multiple publications from this very productive group describing their development of the tools and techniques of craniofacial distraction.
Karp, NS, McCarthy, JG, Schreiber, JS, et al. Membranous bone lengthening: a serial histological study. Ann Plast Surg. 1992;29(1):2.
Rachmiel, A, Rozen, N, Peled, M, Lewinson, D. Characterization of midface maxillary membranous bone formation during distraction
osteogenesis. Plast Reconstr Surg. 2002;109(5):1611-1620.
Slack, GC, Fan, KL, Tabit, C, et al. Necessity of latency period in craniofacial distraction: investigations with in vitro microdistractor and
clinical outcomes. J Plast Reconstr Aesthet Surg. 2015;68(9):1206.
Mehrara, B, Rowe, N, Steinbrech, D, et al. Rat mandibular distraction osteogenesis: II. Molecular analysis of transforming growth factor beta-
1 and osteocalcin gene expression. Plast Reconstr Surg. 1999;103(2):536.
Davidson, EH, Sultan, SM, Butala, P, et al. Augmenting neovascularization accelerates distraction osteogenesis. Plast Reconstr Surg.
2011;128(2):406.
Hindin, DI, Muetterties, CE, Lee, JC, et al. Internal distraction resulted in improved patient-reported outcomes for midface hypoplasia. J
Craniofac Surg. 2018;29(1):139.
Steinberg, JP, Brady, CM, Waters, BR, et al. Mid-term dental and nerve-related complications of infant distraction for robin sequence. Plast
Reconstr Surg. 2016;138(1):82e-90e.
Mofid, MM, Manson, PN, Robertson, BC, et al. Craniofacial distraction osteogenesis: a review of 3278 cases. Plast Reconstr Surg.
2001;108(5):1103.
Peacock, ZS, Salcines, A, Troulis, MJ, Kaban, LB. Long-term effects of distraction osteogenesis of the mandible. J Oral Maxillofac Surg.
2018;76(7):1512-1523.
Polley, JW, Figueroa, AA, Charbel, FT, et al. Monobloc craniomaxillofacial distraction osteogenesis in a newborn with severe craniofacial
synostosis: a preliminary report. J Craniofac Surg. 1995;6(5):421.The authors describe their novel application of distraction principles to the complex
monobloc advancement scenario and demonstrate the feasibility of the distraction techniques in these settings.
Knackstedt, R, Bassiri Gharb, B, Papay, F, Rampazzo, A. Comparison of complication rate between LeFort III and monobloc advancement
with or without distraction osteogenesis. J Craniofac Surg. 2018;29(1):144.
Fearon, JA. The Le Fort III osteotomy: to distract or not to distract? Plast Reconstr Surg. 2001;107(5):1091.
Derderian, CA, Wink, JD, McGrath, JL, et al. Volumetric changes in cranial vault expansion: comparison of fronto-orbital advancement and
posterior cranial vault distraction osteogenesis. Plast Reconstr Surg. 2015;135(6):1665.This important study showed that posterior cranial vault
distraction resulted 

in greater intracranial volume gain compared with front-orbital advancement, supporting the growing use of distraction
techniques for cranial vault 

remodeling.
Taylor, JA, Derderian, CA, Bartlett, SP, et al. Perioperative morbidity in posterior cranial vault expansion: distraction osteogenesis versus
conventional osteotomy. Plast Reconstr Surg. 2012;129(4):674e.
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C H A P T E R 3 1
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Orthognathic Surgery
Reza Jarrahy and Thomas D. Willson
Key Points
Orthognathic surgery repositions the maxilla, mandible, or both to correct improper occlusal
relationships and improve facial aesthetics. Patients with clefts and syndromic dentofacial
deformities frequently require orthognathic surgery. Members of the general population without
clefts or congenital facial syndromes, however, may also require orthognathic correction.
Virtual surgical planning (VSP) has largely supplanted traditional dental impression/cast stone
model surgery in developing and executing a treatment plan for orthognathic surgery. Close
collaboration between the orthodontist and surgeon remains critical to successful outcomes.
Skeletal movements significantly impact the position of overlying soft tissues and the overall
appearance of the patient. Movements that expand the face can smooth rhytids and provide support
to otherwise ptotic tissues, resulting in a rejuvenated appearance. In contrast, contraction of the facial
skeleton may decrease soft tissue support and contribute to undesirable aesthetic results.
Following the completion of skeletal movements and rigid fixation of the mobilized jaw segments,
the surgeon must meticulously confirm the final occlusion to ensure it specifically corresponds to the
preoperative plan. Minor misalignments can usually be corrected with postsurgical orthodontics, but
lack of attention to detail can result in persistent malocclusion that may require secondary surgical
correction.
Orthognathic surgery is a discipline that focuses on surgical manipulation of the maxilla and mandible to
optimize the occlusal relationship between the upper and lower jaws. The primary goal of most
orthognathic procedures is to restore function. Malocclusion can result in a variety of functional deficits
of varying severity. These include the development of dental pathology, temporomandibular joint (TMJ)
dysfunction, speech abnormalities, airway obstruction, and problems with deglutition. Surgical
restoration of normal maxillomandibular relationships can successfully correct aberrancies in all of these
areas.
Although the functional impact of jaw surgery is usually the driving force behind orthognathic
procedures, we cannot underestimate the profound effect that surgical movements of the jaws have on
facial aesthetics. Normal dentofacial skeletal relationships help define human standards of beauty and
balance. All surgical planning for orthognathic procedures must therefore consider the aesthetic
implications of specific maneuvers. Similarly, the aesthetic changes that are predictably associated with
certain techniques must be considered when developing the surgical plan.
The most common indication for orthognathic surgery is malocclusion associated with a history of cleft
lip and palate. Up to 25% of cleft lip and palate patients will require orthognathic surgery by the time
they complete adolescence. Similarly, patients with syndromic craniofacial differences, including the
various craniofacial dysostoses, represent another group of patients where the need for orthognathic
surgery is predictably higher than that seen in the general population, where the incidence of jaw surgery
rests at around 2.5%.
Orthognathic surgery is a truly multidisciplinary endeavor. Our best and most stable surgical outcomes
are achieved when surgeon and orthodontist work closely with their patients to develop a unique plan
that is best suited to each individual.
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Dental Anatomy and Jaw Development
A comprehensive review of dental anatomy and physiology is beyond the scope of this chapter, but a
working knowledge of dental development is important for all surgeons who engage in orthognathic
procedures.
Dental development begins in utero. The primary, or deciduous, teeth form during the sixth to eighth
weeks of gestation, and permanent teeth begin development around the 20th week. In an individual with
no dental anomalies, there are a total of twenty deciduous teeth: two central and two lateral incisors, two
canines (or cuspids), and four molars in each of the maxillary and mandibular dental arches. Each
quadrant contains one central incisor, one lateral incisor, one cuspid, and two molars. By comparison, an
adult with complete dentition has thirty-two teeth. The most mesial (anterior) teeth are the central
incisors. These are flanked by the lateral incisors. Distal (posterior) to the lateral incisors are the canine
teeth. They have a single cusp and typically contain a single root. Distal to the canine teeth are the two
bicuspids, or premolars, each with two cusps and a single root (except the first maxillary premolar, which
has two roots). Distal to the premolars are three molars, which have four or five cusps and two or three
roots each.
Shedding of the deciduous teeth begins at around age six with the appearance of the first mandibular
molar. The period when an individual has both deciduous and permanent dentition in place is called the
period of mixed dentition. This period usually lasts until age 12 years, at which time the deciduous teeth
have all typically been lost. The third molars are the last teeth to erupt, late in the second decade of life.
Jaw growth generally proceeds in a cranial to caudal pattern and is mediated by multiple factors,
including dental eruption and movement. The maxilla typically reaches its adult size in the mid-teenage
years. Growth of the mandible typically continues for several years after the maxillary growth has ceased,
as the mandible is usually the last of the bones of the craniofacial skeleton to cease its growth.
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Terminology
In the care of patients requiring orthognathic surgery, clear communication between treating specialists,
including pediatric and adult dentists, orthodontists, prosthodontists, and orthognathic surgeons, is
critical to making an accurate diagnosis and creating an effective treatment plan. Common knowledge of
relevant terminology is a requisite to effective communication between treating specialists. Some of the
more common terms used to discuss dental and oral anatomy are discussed below.
Because the dental arches are U-shaped, terms such as anterior and posterior are not always applicable in
describing the position of dental structures, nor to their movements in orthodontic or orthognathic
interventions. Instead, the terms mesial, meaning toward the midline sagittal plane along the dental arch,
and distal, meaning away from the midline along the dental arch, are used to describe dental positions.
Occlusion is most commonly described using a classification proposed by Edward Angle in the late 19th
century. The nomenclature is based on the relationship between the mesiobuccal cusp of the maxillary
first molar and the buccal groove of the mandibular first molar. In an Angle class I malocclusion, the
mesiobuccal cusp of first maxillary molar aligns with the buccal groove of the mandibular first molar. In
an Angle class II malocclusion, the mesiobuccal cusp of the maxillary first molar is located mesial to the
buccal groove of the mandibular first molar. Patients with class II malocclusion have a retrognathic
appearance, where the mandible appears posteriorly positioned relative to the maxilla. By comparison, in
an Angle class III malocclusion, the mesiobuccal cusp of the maxillary first molar is located distal to the
buccal groove of the mandibular first molar, giving the patient a relatively prognathic appearance.
Overbite, in dental terms, refers to the vertical overlap between the maxillary and mandibular incisors. It
is usually reported either as a percentage of the tooth covered or in millimeters. By comparison, overjet
refers to the space in millimeters between the labial surfaces of the most distal incisor in each arch. A
normal overjet is 2 to 4 mm. When the mandibular incisor is more prominent (e.g., in a prognathic patient
with Angle class III malocclusion), the overjet is referred to as negative.
Retrognathia and prognathia can refer to the position of either jaw, but in common usage, these terms refer
to the position of the mandible relative to the maxilla and help describe the appearance of an individual’s
facial profile. In retrognathia, the mandible appears to be posterior relative to the maxilla. In the prognathic
patient, the mandible appears to be positioned anterior to the maxilla. Note that with either a retrognathic
or prognathic appearance, both of the jaws may actually be malpositioned; the anatomically correct
position of the maxilla and mandible can be specifically determined by cephalometric analysis.
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Cephalometrics
Cephalometry refers to the study and measurement of the bones of the head and the face. In the setting of
orthognathic surgery, cephalometry specifically focuses on measuring the spatial relationships of the
maxilla and mandible to each other, to the upper face, and to the cranial base. Cephalometric analysis has,
and continues to be, foundational in making accurate diagnoses and generating appropriate surgical
plans for patients presenting with malocclusion. 1,2
Historically, cephalometric analysis has been performed manually, using overlay acetate tracings of
lateral cephalograms upon which markings of skeletal and soft tissue landmarks are placed. Once these
landmarks are identified, numerous types of formal analyses can be performed that quantify a myriad of
facial planes and angles to determine the contribution of each jaw to the patient’s deformity. The
orthodontist and surgeon can move the tracings to position the maxilla, mandible, and genioplasty
segment into optimal positions. The sella-nasion-subspinale (SNA) and sella-nasion-supramentale (SNB)
angles are the two most critical measurements in determining the relative positions of the maxilla and
mandible and their relationships to the cranial base. SNA and SNB angles that are less than normal
indicate that the maxilla or mandible, respectively, is positioned more posteriorly than normal relative to
the cranial base; angles that are greater than the norm indicate relative anterior positions.
The cephalometric measurements and movements are then used to guide model surgery, or manipulation
of dental models that are based on impressions taken from the patient’s upper and lower dental arches, as
further described below. The model surgery process yields acrylic splints that capture the new spatial
relationship between the jaws. These splints are used in the operating room, where the surgeon replicates
the same movements made in the dental laboratory to achieve the same occlusion obtained in the model
surgery planning process.
In recent years, however, this manual process has been supplanted by computer-based software systems
that can rapidly and accurately perform an endless number of cephalometric analyses using the same
anatomic landmarks (Figure 31.1). Surgeons are increasingly turning to these digital platforms to render
accurate diagnoses and plan optimal surgical movements via VSP, which is discussed in greater detail
below.
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FIGURE 31.1 Digital cephalometric analysis. Cephalometric landmarks can be labeled on a digital lateral cephalogram.
Multiple detailed analyses of the positions of the upper and lower jaws and the teeth can be instantaneously calculated for use
in surgical planning.
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Patient Evaluation
Cephalometric analysis is critical to making an accurate diagnosis, counseling the patient, and planning
for the most appropriate surgical intervention. However, a thorough history and detailed physical
examination are prerequisites to successful surgical outcomes.
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History
A thorough medical history is important in any surgical patient. General questions should include
inquiry into any underlying medical conditions that may have a negative impact upon surgery, such as
diabetes, connective tissue disease, or autoimmune problems. Medications including steroids and
anticoagulants that may affect wound healing or bleeding and clotting should be noted and managed
perioperatively as appropriate. Any history of adverse reaction to anesthesia should be thoroughly
investigated, as should any prior or current manifestation of cardiac disease, venous thromboembolic
disease, or other disease process that might contribute to the development of potentially life-threatening
complications.
A specific history related to dental and jaw surgery should also be elicited. Previous surgical
interventions, such as mandibular or maxillary distraction, surgically assisted rapid palatal expansion
(SARPE), or fracture repair, can significantly impact treatment planning. Patients should be questioned
about a history of (TMJ) symptoms such as pain, clicking, popping, and trismus. When jaw asymmetries
are noted on physical examination, potential etiologies should be investigated, including syndromic,
neoplastic, or traumatic causes of unilateral mandibular hypoplasia or hyperplasia.
The surgeon should have an open discussion with the patient regarding his or her expectations for
surgical outcomes. Orthognathic surgery is a major undertaking, frequently preceded by months of
orthodontic preparation followed by additional postoperative treatment. The surgery itself results in
weeks of swelling and can dramatically alter a patient’s appearance. The surgeon should describe the
perioperative process in detail, including specific goals of surgery and the potential risks that are inherent
to a surgical procedure of such magnitude.
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Physical Examination
A general physical examination should be performed on every patient before surgery. Specific evaluation
for patients scheduled to undergo orthognathic surgery begins with an objective evaluation of the face,
including analysis of the standard horizontal thirds and vertical fifths of the face. This assessment can
help identify clinical entities such as vertical maxillary excess (VME) or deficiency or transverse
deficiencies because of a narrow or constricted palate. The width of the alar bases should be evaluated, as
maxillary advancement may widen the base of the nose, potentially resulting in an unexpected and
unappreciated alteration in the nasal appearance if this is not addressed during the surgical procedure.
The malar eminence, inferior orbital rim, and pyriform aperture projections are evaluated. Deficiencies in
these areas are a relative indication for maxillary advancement. Soft tissue coverage and contours of the
midface, lower face, and neck are noted. Mentalis strain and lip incompetence should be noted if present,
as these are additional signs of vertical maxillary excess, as is excessive gingival show when smiling (a
gummy smile). The dental midlines of the maxilla and mandible should be noted and any deviation from
the facial midline documented. Any other asymmetries of the maxilla or mandible, particularly those
associated with facial clefting or occlusal cant, should be documented.
Oral evaluation should focus on hygiene and periodontal health. Patients must demonstrate good
hygiene before and during orthodontic preparation to proceed with surgery. Damaged, loose, or missing
teeth should be noted, as should any retained deciduous teeth. If present, the third molars should be
extracted several months before surgery to facilitate safe osteotomies at the time of surgery.
Evaluation of the patient’s profile should note the projection of the forehead, malar eminences, nose,
maxilla, mandible, and chin. An experienced orthognathic surgeon can frequently determine which jaw
or jaws are responsible for the patient’s dentofacial deformity on profile view before confirming the
diagnosis with cephalometric analysis. Careful evaluation of the nose and its spatial relation to the
maxilla is critical, as maxillary movements can potentially change the position of the nose and the
nasolabial angle. Similarly, the predicted postoperative position of the chin should factor into the
presurgical discussion and guide any discussion of the potential need for genioplasty.
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Common Diagnoses
Prognathism
Prognathism technically refers to prominence of either jaw but is generally used to indicate prominence
of the mandible relative to the maxilla. Mandibular prognathism is most often associated with class III
malocclusion. On profile, the patient often demonstrates a strong chin and a long jaw line. Cephalometric
analysis will typically reveal posterior positioning of the maxilla relative to the cranial base (small SNA),
anterior positioning of the mandible compared with the cranial base (large SNB), or both. Treatments
may include maxillary advancement, mandibular setback, or a combination of both procedures (Figure
31.2A–C).
FIGURE 31.2 Relative contributions of maxilla and mandible to retrognathism and prognathism. A–C. Frontal, oblique, and
lateral views, respectively, of a patient with mandibular prognathism and a class III malocclusion with decreased sella-nasion-
subspinale and increased sella-nasion-supramentale. Both jaws are malpositioned. A maxillary advancement and mandibular
setback are both indicated to achieve a normal jaw relationship. D–F. Frontal, oblique, and lateral views, respectively, of a
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patient with mandibular retrognathism and a class II malocclusion with decreased sella-nasion-supramentale. A mandibular
advancement is an appropriate correction.
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Retrognathism
Retrognathism refers to a relative prominence of the maxilla compared with the mandible. Cephalometry
usually shows anterior positioning of the maxilla relative to the cranial base (large SNA), posterior
positioning of the mandible relative to the cranial base (small SNB), or a combination of both. Most
commonly, the retrognathic patient presents with a class II malocclusion because of a small mandible; in
these cases, mandibular advancement is the procedure of choice to correct the condition (Figure 31.2D–F).
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Vertical Maxillary Excess
VME is also known as long face syndrome. Patients with VME have facies that appear long with
excessive gingival show in repose and with smiling. Mentalis strain and lip incompetence are also
frequently seen. Surgical correction involves maxillary impaction with cephalad repositioning of the
maxilla to shorten the midface. The mandible rotates counterclockwise in a compensatory movement.
Resultant changes in chin position should be noted in the preoperative planning phase to determine
whether simultaneous genioplasty is indicated. 3
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Vertical Maxillary Deficiency
In vertical maxillary deficiency, the patient’s lower face appears short, with little or no incisor show on
repose and minimal show with smiling. Appropriate surgical treatment includes downfracture and
caudal repositioning of the maxilla to lengthen the face. 4 Bone grafting to the resultant maxillary gap
ensures a stable result. 5 The mandible compensates with a clockwise rotation, and the chin moves
inferiorly and posteriorly. Again, preoperative planning should include an assessment of the potential
need for genioplasty.
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Maxillary Constriction
Maxillary constriction refers to a deficiency in the transverse dimension of the maxilla. It is commonly
seen in patients with cleft palate. This results in a posterior crossbite on one or both sides of the maxilla.
The condition can be treated, at least in part, with orthodontic palatal expansion. If orthodontic expansion
fails, the palate can be transversely expanded surgically.
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Presurgical Planning
In addition to taking a history, performing a physical examination, and completing a cephalometric
analysis, several additional steps must be taken before performing orthognathic surgery. Initial
preparation for surgery is carried out by an orthodontist, including obtaining dental models,
radiographic records, and composite facial and occlusal photos. Based on the cephalometric analysis, the
planned surgical movements are then executed on traditional models of the teeth or on three-dimensional
(3D) digital renderings. Regardless of the technique used, the process yields splints that index the desired
final positions of the jaws following the orthognathic correction. These splints are used in the operating
room to confirm that the planned movements are precisely replicated in the surgical procedure.
Planning should not only focus exclusively on correction of abnormal values identified in the
cephalometric analysis but also account for the effect of skeletal movements on the overlying soft tissues
to optimize the aesthetic outcomes. 6 Movements that reduce the size of the skeleton, such as maxillary
impactions and maxillary or mandibular setbacks, can have aging effects on the face. When the soft tissue
envelope covers a relatively contracted skeletal framework, deeper creases, more jowling, and an overall
aged appearance may result. By contrast, movements that expand the skeleton tend to flatten creases and
provide greater support to the soft tissues, contributing to a more youthful appearance 7 (Figure 31.3).
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FIGURE 31.3 Impact of skeletal movements on soft tissue support and aesthetics. A,B. The impact of a high Le Fort I
osteotomy and advancement on soft tissue support and facial aesthetics is demonstrated in this 18-year-old patient who
presented with class III malocclusion and prematurely aged appearance characterized by ptotic malar soft tissues, deep
nasolabial folds, marionette lines, and upper lip ptosis. C,D. Her malocclusion is corrected with maxillary advancement, which
also results in a more youthful appearance with improved malar soft tissue support, softening of the perioral skin creases, and
improved upper lip projection.
As noted above, clockwise or counterclockwise autorotation of the mandible secondary to maxillary
movements—and the impact of these movements on chin position—must be considered in the
presurgical plan to achieve balanced facial aesthetics along with a functional postoperative occlusion.
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Orthodontic Preparation
The goal of preoperative orthodontia is to position the teeth, so that at the end of the surgical procedure,
the patient is in a class I malocclusion with optimal dental intercuspation. This requires a considerable
degree of skill on the part of the orthodontist, but also clear communication between the orthodontist and
the surgeon regarding the planned operation. Orthodontic preparation for a single-jaw movement differs
from that for two-jaw surgery; the surgical plan should therefore be clear to all caregivers and the patient
from the outset.
In addition to straightening and appropriately spacing the teeth, the orthodontist is charged with
reversing any natural dental compensations that the patient develops in association with his or her
malocclusion. This includes correcting the aberrant orientation of any proclined or retroclined teeth that
have become malpositioned in the absence of normal anatomic relationships between the upper and
lower dental arches.
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Dental Models and Model Surgery
As practitioners of orthognathic surgery increasingly adapt VSP to their perioperative practices, a
thorough understanding of the fundamentals of traditional model surgery remains requisite to a true
appreciation of the intricacies of jaw surgery and how best to implement VSP platforms in its execution.
Before surgery, the surgeon or the orthodontist will obtain wax-bite registrations and plaster models of
the patient’s presurgical occlusion. These models can be mounted on an articulator, which mimics the
relationship of the maxilla to the cranial base and the relationship of the mandible to the maxilla as it
hinges on the articulator’s joints. In a planned single-jaw surgery, the jaw that is to be cut and moved
during surgery is repositioned on the articulator based on the cephalometric analysis and intended
surgical movement. An acrylic splint that captures the new relationship between the maxillary and
mandibular models is fabricated and brought to the operating room for use in surgery (Figure 31.4).
FIGURE 31.4 Model surgery. A. An articulator is used to mount maxillary and mandibular dental models in their baseline
occlusal relationship (in this case, a class III malocclusion). B. The maxillary model is repositioned to achieve a class I
relationship. The red arrow indicates the vector of movement, simulating a Le Fort I osteotomy and advancement. C. An acrylic
splint is fabricated to capture this new occlusal relationship and will be used in the operating room. D. These images
demonstrate typical steps taken to plan an orthognathic surgery procedure. Preparation begins with cephalometric analysis (i).
The arrow indicates the next step in the process: tracings and planned jaw movements (ii). After the jaw movements are
planned on paper, they are replicated on the mounted dental models (iii). Model surgery results in splint fabrication to facilitate
the actual surgery (iv).
In two-jaw surgery, the model of the jaw that is to receive the first movement is repositioned on the
articulator, again according to the cephalometric analysis and surgical plan. This temporary relationship
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between upper and lower jaws is indexed with an intermediate splint that is used to guide the position of
the first jaw undergoing osteotomy. Once this splint is fabricated, the second jaw to be moved in surgery
is repositioned on the articulator to arrive at the appropriate occlusal relationship. A final splint is then
created based on this occlusion and used to guide the upper and lower jaws into their final desired
positions in the operating room while rigid fixation is obtained.
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Virtual Surgical Planning
Although traditional model surgery has historically allowed surgeons to achieve excellent results, it is a
laborious and time-consuming process. By comparison, the combination of high-resolution maxillofacial
CT scanning, 3D printing, and sophisticated software platforms now allows surgeons to engage in a more
streamlined but equally accurate approach to cephalometric analysis and presurgical planning that
obviates many of the manual components described earlier. As a result, VSP protocols are rapidly
replacing more traditional approaches to orthognathic surgery.
VSP begins with the acquisition of a high-resolution CT scan of the face. These radiographic images are
imported into specialized computer-assisted design software, which generates 3D renderings of the
craniofacial skeleton. Incorporating digital scans of the patient’s dental models into the renderings can
increase the level of detail of the 3D images. The surgeon can perform digital osteotomies on these
renderings, and the positions of the jaws can be subsequently altered to achieve a desired occlusion
(Figure 31.5). A 3D printer can then fabricate splints that capture the new occlusal relationship for use in
the operating room. VSP software can also generate 3D renderings of how the soft tissues of the face may
change as the underlying skeletal components are repositioned, although these renderings are digital
projections only; they should not be used to guide specific patient expectations.
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FIGURE 31.5 Virtual surgical planning for orthognathic surgery. A. The virtual surgical planning summary for this maxilla-first
two-jaw surgery demonstrates the preoperative condition (top), the intermediate position of the jaws (center), and the final
occlusion (bottom). In this case, the maxilla was split and expanded transversely to correct a posterior crossbite, impacted to
correct for vertical maxillary excess, and advanced. Next a bilateral sagittal split osteotomy was used to rotate the mandible in a
counterclockwise direction. A reduction and advancement genioplasty was added to the surgical plan to provide facial balance
and optimize aesthetic results. Cephalometric measurements such as sella-nasion-subspinale and sella-nasion-supramentale
can easily be incorporated into the planning process (B), as can other data such as facial height measurements before and
following planned jaw movements (C).
Although VSP represents a resource that has transformed the process of planning for orthognathic
surgery without any compromise of surgical results, users of this technology must be aware that like any
computer program, VSP outputs are only as good as their inputs. Computer-assisted design software
allows one to make unrestricted movements on a screen, regardless of whether those movements might
be stable or desirable in an actual clinical setting. The surgeon must therefore always rely on his or her
experience and fundamental cephalometric and surgical principles to determine the optimal technique
for each individual patient.
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Surgical Techniques
General Principles
Orthognathic surgery is a true team sport. Active and effective communication between the surgeon and
multiple other specialists is necessary for a successful surgical outcome. Before surgery, the surgeon must
confer with the patient’s orthodontist to confirm that the patient has been adequately prepared for
surgery. On the day of surgery, the surgeon must confirm with the operating room nursing staff that all
necessary equipment is available and in good working order, including powered and manually driven
bone-cutting tools, procedure-specific instruments, and rigid fixation hardware. Ongoing communication
with the anesthesiologist throughout the surgery is of paramount importance. Elective jaw surgery
patients are nasotracheally intubated, preferably with a Ring-Adair-Elwyn (RAE) tube that is secured to
prevent unintentional extubation during surgical manipulation of the jaws. Preoperative antibiotics
covering oral flora are administered intravenously. Hypotensive anesthesia during osteotomies and
maxillary downfracture can help to reduce blood loss.
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Maxillary Osteotomies
Le Fort I
The Le Fort I osteotomy allows for multivector movement of the maxilla. Anterior-posterior, cranial-
caudal, and rotational movements in axial, coronal, and sagittal planes are all possible. This flexibility
permits correction of occlusal cants, midline shifts, and overjet. 8
The medial canthi are marked with ink, and the vertical height of the maxilla between the canthi and the
maxillary dental arch is measured with a caliper. These measurements are important when correcting
occlusal cants or altering the maxillary height (e.g., in cases of maxillary impaction or lengthening). An
upper gingivobuccal sulcus incision is made. The anterior wall of the maxilla is dissected in the
subperiosteal plane with careful preservation of the infraorbital nerve. Lateral dissection continues
around the lateral maxillary walls to the pterygomaxillary buttresses. Subperiosteal dissection of the floor
of the nasal cavity is performed through the pyriform aperture.
When designing the Le Fort osteotomy, the surgeon must note the vertical height of the dental roots to
avoid injury to the teeth. In addition, higher osteotomies that incorporate the upper maxilla and even the
caudal portion of the zygoma into the Le Fort segment can be designed when more soft tissue support is
indicated.
The osteotomies through the medial and lateral buttresses and the anterior maxillary wall are performed
with a reciprocating saw or an ultrasonic bone cutter. The nasal septum is released from the vomer with
either a double-guarded osteotome or the saw blade. Finally, pterygomaxillary osteotomes are used to
create controlled vertical fractures of pterygoid plates and release the Le Fort segment from the skull
base. Downfracture can then be performed (Figure 31.6A).
FIGURE 31.6 Maxillary osteotomies. A. In this cadaver, differential Le Fort I osteotomy levels have been performed for
demonstration purposes. The high osteotomy on the patient’s right will provide increased soft tissue support in the upper
midface if the maxilla is advanced. Regardless of the vertical level, osteotomies are made above the levels of the dental roots to
avoid injury to the teeth. The nasal septum and maxillary sinuses are clearly visible following downfracture. B. In maxilla-first
two-jaw surgery, a bulky intermediate splint is used to index the temporary relationship between the jaws following the Le Fort I
manipulation and before the mandibular movement.
The Le Fort segment is completely mobilized to allow for easy positioning into the splint.
Maxillomandibular fixation (MMF) is obtained using wires or elastics (Figure 31.6B). L-shaped plates
fixed to the medial and lateral buttresses are used to secure the position of the Le Fort segment. During
fixation, the surgeon must ensure that the condyles are properly seated to avoid a postoperative
malocclusion.
Once rigid fixation is achieved, the splint is removed and the new occlusion is evaluated. If the surgery
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was planned as a maxilla-only procedure and the position of the maxilla is consistent with the presurgical
plan, the incision is closed and guiding elastics are placed. The patient is followed closely during the first
few weeks after surgery to monitor stability of the maxillary movement. If the surgery was designed as a
maxilla-first two-jaw manipulation, MMF is reestablished after the appropriate intermediate position of
the maxilla in confirmed and the surgeon proceeds with the mandibular osteotomies.
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Surgically Assisted Rapid Palatal Expansion
In adolescence, transverse maxillary deficiency can usually be corrected orthodontically with palatal
expansion devices. Once the midline palatine suture fuses, however, surgical assistance may be required
to effectively expand the maxilla if correction of posterior crossbite is needed. In these cases, a Le Fort I
osteotomy is then performed as described earlier. The maxilla is then bisected between the roots of the
central incisors and through the hard palate in the midline. Great care must be taken to preserve the
palate mucosa to avoid development of an iatrogenic oronasal fistula. The Le Fort I segment is not rigidly
fixed as in a traditional Le Fort I procedure. Following surgery, a palatal expander is placed and activated
by the orthodontist to correct the transverse deficiency. This approach offers the best correction of
transverse maxillary deficiency with the lowest rate of relapse in skeletally mature patients or in patients
for whom traditional expansion techniques fail.
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Mandibular Osteotomies
Numerous types of mandibular osteotomies have been described for implementation in orthognathic
surgery. The sagittal split osteotomy (SSO) and the vertical ramus osteotomy (VRO) are by far the most
commonly used and are discussed in further detail below. These techniques provide great versatility to
surgeons and consistent, stable results for patients.
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Sagittal Split Osteotomy
SSO is the most common technique used in orthognathic procedures involving the mandible. It is
technically straightforward, can be performed intraorally, and allows for advancement, setback, rotation,
and closure of anterior open bites. Bony overlap between the proximal and distal segments facilitates
stable healing, but the proximity of the inferior alveolar nerve to the osteotomy line contributes to the risk
of permanent sensory changes associated with this approach. 9,10
Surgery begins with an incision in the gingivobuccal sulcus at the level of the first molar that is extended
along the anterior border of the ascending mandibular ramus. Subperiosteal dissection is used to elevate
the soft tissues from the buccal surfaces of the body and ramus, as well as the anterior and lingual
surfaces of the ramus.
The osteotomy begins on the lingual surface of the ramus, above the occlusal plane, to avoid injury to the
inferior alveolar nerve at the level of the lingula. A reciprocating saw or ultrasonic bone cutter is used to
cut the medial ramus. The osteotomy continues across the anterior border of the ramus and along the
external oblique line of the mandible to the first molar, where a vertical cut is made from the oblique line
to the inferior border (Figure 31.7).
FIGURE 31.7 Mandibular osteotomies. A–C. A typical line of corticotomy for the SSO is demonstrated on this skull model from
buccal, lingual, and frontal perspectives. D. This intraoperative photo demonstrates the proximity of the mental nerve exiting its
foramen in a patient undergoing SSO with mandibular advancement. Rigid fixation is achieved with locking titanium alloy plates
and screws.
These bone cuts are corticotomies; once they are made, the sagittal split is completed using osteotomes
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and a mallet. A successful split results in a mandibular segment that contains the buccal plate, ascending
ramus, condyle, and coronoid process (the proximal segment) and a distinct segment that contains the
tooth-bearing portion of the body and symphysis (the distal segment).
Once the proximal and distal segments are mobilized, the mandible is advanced or set back as dictated by
the surgical plan and brought into the prefabricated occlusal splint. 11,12 Rigid fixation is achieved with
either bicortical positional screws or monocortical plates and screws (Figure 31.7D). Again, during
fixation, the surgeon must ensure that the condyles are properly seated in the glenoid fossae. MMF is
released, the occlusion is checked, and guiding elastics are placed as indicated. The incisions are closed in
the surgeon’s preferred fashion.
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Vertical Ramus Osteotomy
In contrast to the SSO, the VRO creates a distal segment that includes the tooth-bearing portion of the
mandible, coronoid process, inferior alveolar nerve, and anterior ramus, and a proximal segment that
includes the mandibular condyle and the posterior ramus. The procedure can be performed via an
external or internal approach, and subperiosteal exposure of the mandible is similar to that of the SSO.
The osteotomy is placed 7 to 8 mm in front of the posterior border of the ramus between the sigmoid
notch and the inferior border of the mandible. Adequate bone stock must be preserved on the posterior
segment to accommodate fixation hardware.
The procedure is of limited utility when mandibular advancement is indicated: significant advancement
creates a long vertical gap between the two segments, increasing the risk of nonunion and relapse.
However, VRO is particularly suited to address horizontal mandibular excess and asymmetries requiring
setback. 13
As with the SSO, occlusion is established intraoperatively using a splint and MMF. Once rigid fixation is
obtained, the patient is taken out of interdental fixation to confirm the position of the jaws. If all is
satisfactory, the incision is closed and guiding elastics are placed.
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