Operative Technique in Plastic Surgery – Kevin C.Chung

cuff in addition to the branch of the circumflex scapular artery descending
along the lateral scapular border.
■ A right-angled instrument can be used to dissect around the scapula bone at
the planned osteotomy site (TECH FIG 5B).
■ A wedge of bone is then excised with a sagittal saw while the right-angled
instrument is used to protect the vascularized muscle cuff and flap pedicle
(TECH FIG 5C).
■ Further contouring of the osteotomy can be performed with a bur so that
the bone conforms to the arch of the reconstruction plate (TECH FIG 5D).
■ The scapula bone segments are then drilled into a reconstruction plate
(TECH FIG 5E) or a combination of miniplates.
■ The parascapular flap skin and bone are reperfused at the recipient site
following completion of microvascular anastomosis (TECH FIG 5F).

TECH FIG 5 • A. The parascapular osteocutaneous
flap has been divided and is taken to the back table.
B. A right angle retractor is used to dissect between
the vascularized muscle cuff and the scapular bone,
protecting the descending branch of the circumflex
scapular artery. The planned osteotomy site is marked
with purple ink. C. An oscillating saw is used to make

a wedge-shaped osteotomy to enable the bone to
conform to the reconstruction plate. D. Different
methods of performing the wedge osteotomy to
contour the scapular bone to the reconstruction plate.
Once the flap pedicle and muscle cuff are protected,
an oscillating saw can be used to remove a wedge of
bone. This can be freehanded or performed with the
help of a cutting jig. Alternatively, a straight osteotomy
can be performed and a bur can be used to shave the
posterior cortex. This latter method enables controlled,
gradual contouring of the scapular bone until the bone
segments fit together correctly. E. The scapular bone
segments are secured to the locking, reconstruction
plate using monocortical screws. F. The flap is inset
into a segmental mandibular defect and the flap
pedicle is sewn to recipient vessels in the neck
(arrow), resulting in revascularization of the composite
tissue.
■ Reconstruction of Facial Atrophy
■ In addition to being used for segmental reconstruction of the mandible, the
parascapular osteocutaneous flap can also be used as an onlay reconstruction
for severe facial atrophy.
■ The osseous component can be used to augment the jawline, while the soft
tissue is used to balance the contour of the face and establish symmetry
(TECH FIG 6).

TECH FIG 6 • This patient presented with impairment
of left-sided facial growth following removal of a tumor
and adjuvant radiation therapy when she was a young
child. She had loss of soft tissue volume in the left
midface and lower face, in addition to deficiency of the
left mandibular angle and ramus. A. Intraoperative
markings indicate areas of soft tissue and bony
deficiency where the osteocutaneous flap will be used
as an onlay reconstruction. The preauricular incision
was used to develop a pocket for the soft tissue
component of the flap, while the neck incision was
used to develop a space for the osseous component
of the flap and isolate the facial vessels for
microvascular anastomosis. B. Markings for the
osteocutaneous parascapular flap are demonstrated
prior to flap elevation. C. The flap is depicted following
harvest with the vascular pedicle displayed over the
yellow background. D. Postoperative appearance
following flap inset along the left face. E. Preoperative

appearance. F. Appearance 6 weeks after surgery.
PEARLS AND PITFALLS
Patient
positioning
■ Supine positioning with a bump behind the shoulder enables
simultaneous dissection at the recipient and donor sites.
■ Suspension of the arm on the side of the flap being elevated
minimizes pressure points.
Cutaneous
pedicle
dissection
■ While dissecting the cutaneous pedicle of the circumflex scapular
artery from the triangular fossa, preserve the fibrofatty tissue that
surrounds the pedicle.
■ This fatty tissue serves as a sort of mesentery, incorporating small
branches from the circumflex scapular artery at the base of the
septum to the skin paddle. Preservation of this fibrofatty tissue
enhances blood supply to the skin paddle.
Skin paddle
elevation
■ The cutaneous branch of the circumflex scapular artery will usually
arise abruptly just cephalad to the teres major muscle.
■ Dissection should proceed carefully at this level to avoid injury to
the cutaneous blood supply.
Hemostasis
■ The scapular osteotomies usually result in the most bleeding,
typically from contact of the saw with surrounding muscle fibers.
■ Be sure to cauterize any perforating vessels through the
subscapularis muscle as it is divided.
■ Bleeding will usually decrease substantially once the osteotomies are
complete.
Flap
pedicle
dissection
■ The circumflex scapular artery radiates small branches to the
surrounding musculature of the triangular fossa in addition to
branches to the scapular bone.
■ To identify these branches without disrupting them, it helps to spread
through the soft tissue perpendicular to the main axis of the pedicle.
■ This strategy helps the surgeon minimize bleeding and enables him
or her to decide which pedicle branches to preserve and which
pedicle branches to sacrifice.
POSTOPERATIVE CARE
■ Shoulder movement is permitted as tolerated after surgery.

■ As patients progress, they may work on rebuilding shoulder strength and range
of motion.
■ An occupational therapist can be very helpful for creating a graduated program
for the patient.
OUTCOMES
■ Swartz is widely regarded as the first surgeon to popularize the osteocutaneous
scapula flap for mandible reconstruction.9
■ In his series of 26 patients, 21 patients underwent mandibular reconstruction
and there was a 100% flap survival rate.
■ The senior author has also had 100% survival of the osteocutaneous scapular
flap.
COMPLICATIONS
■ The soft tissue elements of the subscapular system carry a robust blood supply.
However, if soft tissue ischemia occurs, local debridement and wound care
may be necessary.
■ Orocutaneous fistulas may occur and can usually be managed with local
wound care.10
■ When scapular osteotomies are performed, there is a risk of ischemia
involving the distal scapula bone beyond the osteotomy site. Swartz described
two patients who experienced nonunion due to bone loss beyond the scapular
osteotomy site.9
■ If multiple osteotomies are being planned, incorporation of both the
circumflex scapular and angular arteries to the lateral scapular bone may be
considered to augment the blood supply and reduce the risk of distal bone
ischemia.1
REFERENCES
1. Urken ML, Bridger AG, Zur KB, Genden EM. The scapular
osteofasciocutaneous flap: a 12-year experience. Arch Otolaryngol Head Neck
Surg. 2001;127:862-869.
2. Disa JJ, Cordeiro PG. Mandible reconstruction with microvascular surgery.
Semin Surg Oncol. 2000;19:226-234.
3. Parthasarathy J. 3D modeling, custom implants and its future perspectives in
craniofacial surgery. Ann Maxillofac Surg. 2014;4:9-18.
4. Valentini V, Gennaro P, Torroni A, et al. Scapula free flap for complex

maxillofacial reconstruction. J Craniofac Surg. 2009;20:1125-1131.
5. Frodel JL Jr, Funk GF, Capper DT, et al. Osseointegrated implants: a
comparative study of bone thickness in four vascularized bone flaps. Plast
Reconstr Surg. 1993;92:449-455.
6. Siebert JW, Longaker MT, Angrigiani C. The inframammary extended
circumflex scapular flap: an aesthetic improvement of the parascapular flap.
Plast Reconstr Surg. 1997;99:70-77.
7. Robb GL. Free scapular flap reconstruction of the head and neck. Clin Plast
Surg. 1994;21:45-58.
8. Gibber MJ, Clain JB, Jacobson AS, et al. Subscapular system of flaps: an 8-
year experience with 105 patients. Head Neck. 2015;37:1200-1206.
9. Swartz WM, Banis JC, Newton ED, et al. The osteocutaneous scapular flap
for mandibular and maxillary reconstruction. Plast Reconstr Surg.
1986;77:530-545.
10. Hyman J, Disa JJ, Cordiero PG, Mehrara BJ. Management of salivary fistulas
after microvascular head and neck reconstruction. Ann Plast Surg.
2006;57:270-273.

36
CHAPTER
Reverse Distraction to
Create a
Temporomandibular Joint
Joseph Lopez and Anand R. Kumar
DEFINITION
■ Distraction osteogenesis is a process of slow bone expansion in which new
bone forms between an osteotomy gap secondary to tension stresses placed
across the bone gap.1
■ Functional remodeling—the process of functional tissue formation—can be
used to create a neocondyle through distraction osteogenesis.
ANATOMY
■ The mandible is composed of seven zones: symphysis, body, dentoalveolar,
angle, ramus, coronoid, and condyle.
■ The mandible articulates with the squamous portion of the temporal bone at
the condyle by forming the temporomandibular joint (TMJ).
■ The TMJ allows rotational and translational movement of the mandible.
■ The TMJ joint is surrounded by several muscles:
■ The masseter muscle, temporalis muscle, medial and lateral pterygoid
muscles elevate or protrude the mandible.
■ The superior portion of lateral pterygoid inserts on the fibrous capsule and
meniscus of the TMJ (stabilizes the meniscus during movement of the
mandible).
■ The inferior portion of the lateral pterygoid inserts on the neck of the condyle
(helps protrude the mandible when contracting).
■ The geniohyoid muscle and the anterior belly of the digastric muscle depress
and retract the mandible.
■ All muscles are innervated by cranial verve V.

■ The TMJ articular surface (articular disc) contains a dense fibrous, connective
tissue known as fibrocartilage (unlike other synovial joints, which contain
hyaline cartilage).
■ The central portion of the TMJ articular disc (fibrocartilage) is avascular,
whereas the periphery is innervated and receives a tributary of blood vessels.
The retrodiskal tissue, which is responsible for the nutrition of the TMJ, are
perfused by branches of the maxillary artery (posterior auricular, anterior
tympanic, and meningeal medial arteries), drained by the temporomandibular
veins, and innervated by the auriculotemporal and posterior auricular nerves.
■ This fibrocartilage material divides the region of the joint into two spaces:
■ The upper joint space extends from the glenoid fossa to the articular
eminence.
■ The lower joint space begins above the insertion of the lateral pterygoid and
then spreads out over the condyle.
■ The upper joint space is involved in translational movement of the mandible
(arthrodial).
■ The lower joint space is involved in rotational movement (ginglymus).
PATHOGENESIS
■ TMJ reconstruction is required in both pediatric and adult populations. The
most common conditions that often require TMJ reconstruction include TMJ
ankyloses after resection arthoplasty, micrognathia/retrognathia (hemifacial
microsomia), and juvenile idiopathic arthritis that can present in both adult and
pediatric patient populations.
■ TMJ ankylosis refers to a pathologic condition in which the mandible is
fused to the cranial fossa by bony or fibrotic tissue. TMJ ankylosis can be
caused by trauma, infection, congenital deformities, idiopathic factors, or
iatrogenic causes.
■ Micrognathia is a congenital condition involving an abnormally small
mandible. It is associated with upper airway obstruction and tends to occur in
conjunction with tongue malposition.
■ Retrognathia is a condition in which there is lack of development of the
mandible; more specifically, it refers to the retruded position of the mandible
in relationship to the maxilla.
■ Juvenile idiopathic arthritis (JIA): JIA is the most common rheumatologic
disease in children of unclear etiology that can commonly affect the TMJ.
■ Other common causes of TMJ pathology include degenerative joint disease,

traumatic injury, rheumatoid arthritis, and TMJ ablation following tumor
resection.
NATURAL HISTORY
■ Distraction osteogenesis for TMJ reconstruction involves moving a segment of
bone, known as the transport disc, slowly away from the host bone into the
defect or future TMJ location (FIG 1).
FIG 1 • A digital image demonstrating the transport disc
in its new simulated position in the region of the newly
generated TMJ joint. Note the vertical vector of
distraction and the largest possible piece of bone used
as the transport disc.
■ The transport disc is formed from the vertical ramus remnant or angle of the
mandible and is slowly moved into the glenoid fossa or neoglenoid fossa
region of the temporal bone.
■ New bone formation (osteogenesis) occurs at the interface between the
transport disc and the host bone. The newly formed bone trailing at the leading
edge of the disc forms the new ramus or condylar neck.
■ Similarly, a fibrocartilagelike structure forms at the disc’s leading edge. This
neofibrocartilage cap becomes the new articular surface.
■ Experimental studies provide support for the remodeling steps described
above:

■ Zhu et al.2 investigated the histomorphologic changes in the newly formed
condyle reconstructed by transport distraction osteogenesis in a nonhuman
primate model. This study found that “bone regeneration was perfect in the
distraction gap between the transport disc and the pre-existing mandible” and
the resulting neocondyle was “similar to the original condyle in appearance
and structure.”
■ Similarly, Hikiji et al.3 investigated articular remodeling capacities of
distraction osteogenesis for TMJ reconstruction in New Zealand white rabbits
and found that after 8 weeks of lengthening, “mature cortical bone” formed
between the transport disc and the host bone mandibular segment. Similarly,
this experimental study found that a collagenous-like structure formed a cap
over the leading edge of the transport segment, suggesting this may
“substitute for an articular disc.”
PATIENT HISTORY AND PHYSICAL FINDINGS
■ Inspection of the head and neck region
■ Assess soft tissue asymmetry or skeletal deformities.
■ Assess ear canals and tympanic membrane for primary benign or malignant
disease.
■ Assess dentition for malocclusion, mobility of teeth or prosthetics, or
mandibular displacement during teeth contact.
■ Assess oral mucosa for periodontal disease, mucosal lesions, or swelling.
■ Assess for overjet, overbite, or open bite.
■ Neurovascular exam
■ Cranial nerves 5 and 7 are checked, particularly examining function of the lip
depressors (marginal mandibular nerve). This is the most common facial
nerve palsy in hemifacial microsomia.
■ Palpation of the head and neck region
■ Palpation of the TMJ region to detect crepitus, clicking, or popping
■ Palpation for swelling or tenderness of the TMJ region
■ Assess TMJ range of motion (ROM). Normal measurements in adults:
• Interincisal opening = 40 to 50 mm
• Lateral interincisal movement greater than 10 mm on each side
• Any restriction in lateral movement, deviation on mouth opening, or
developing of an open bite should be noted.
IMAGING

■ A panoramic radiograph can identify gross fractures, arthritic changes, bone
cysts or tumors, malformation, or bony abnormalities.
■ Computed tomography (CT) provides bone pathology information via
sectional imaging in both the coronal and sagittal planes (taken in both open
and closed joint positions)
■ CT remains the most frequently used modality to image in 2D and 3D the
abnormal bone defect or morphology. The CT can also be used to perform
virtual surgical planning (FIG 2).
■ Magnetic resonance imaging (MRI) provides soft tissue, disc, and bone
pathology information. MRIs are most often used to assess soft tissue and/or
synovial disease.
■ Benefits of MRI vs CT:
■ Absence of ionizing radiation
■ Imaging in multiple planes
■ Adequate soft tissue detail
DIFFERENTIAL DIAGNOSIS
■ Condylar resorption after orthognathic surgery
■ TMJ ankylosis
■ Degenerative joint disease
■ Micrognathia
■ Retrognathia
■ Hemifacial microsomia
■ TMJ resection after pathology
■ Degenerative joint disease of the TMJ
■ Juvenile idiopathic arthritis of the TMJ

FIG 2 • Soft tissue (A), bone 3D CT scan (B), and AP
(C) and oblique (D) bone window 3D CT scans
demonstrating a shortened vertical ramus (type IIB)
mandible with significant distance between the
malshaped condyle and the proposed glenoid fossa
location.
SURGICAL MANAGEMENT
■ The indications for TMJ reconstructions are fairly broad:
■ Tumor resection
■ Degenerative joint disease

■ Ankylosis
■ Congenital anomalies
■ Unrepairable trauma
■ However, the goals are fairly specific:
■ Restoration of normal occlusion and jaw function
■ Pain relief
■ Restoration of mandibular ramus height (condylion to gonion distance)
■ Distraction-based TMJ reconstructions has many benefits:
■ The TMJ is reconstructed with autogenous material that is immunologically
inert and therefore capable of remodeling and growth.
■ A second donor site is not required so as to minimize overall surgical
morbidity.
■ Distraction osteogenesis allows jaw mobility, decreasing the risk of restricted
range of motion.
Preoperative Planning
■ Radiographs of the mandible should be reviewed to determine the size of
distractor needed to form a properly sized defect.
■ An MRI may be useful to evaluate the soft tissue surrounding the TMJ joint.
■ CT is the most useful imaging study to determine the extent of vertical ramus
and transport disk anatomy for securing the hardware (FIG 1).
Positioning
■ The patient is positioned supine on the operating table with the head in
extension using a shoulder roll.
Approach
■ Intraoral approach (preferred approach) with cheek trocar for screw insertion
■ Extraoral/submandibular approach is an alternative.
T E C H N I Q U E S
■ Reverse Distraction for TMJ Reconstruction
Exposure and Osteotomy

■ An intraoral sulcular or submandibular incision is made beneath the angle of
the mandible (TECH FIG 1A,B).
■ Our preference is an intraoral approach in late mixed dentition (9 to 12
years-of-age).
■ A partially completed transverse osteotomy of the vertical ramus remnant is
made to create the transport disc (TECH FIG 1C).
■ The medial periosteum and muscle attachments are left intact so as not to
compromise the transport disc’s blood supply.
■ The superior surface of the transport disc is not adjusted because
postdistraction remodeling will allow for an anatomical articular
pseudosurface to form without direct shaping.
Distractor Placement and Activation
■ A properly sized distractor is chosen and is attached with a single screw
using the percutaneous cheek trocar system or a right angle drill/screw driver
in the inferior attachment plate (TECH FIG 2A,B).
■ The distraction vector is then adjusted to ensure growth into the glenoid
fossa.
■ The remainder of the screws are placed. We prefer 1.5-mm-diameter screws
that are 5 mm in length, with a minimum of three screws on each side of the
osteotomy.
■ After placement of all the screws, the device is activated, and the osteotomy
is partially opened and then completed with an osteotome as needed. Then,
the disc is ready to be mobilized.
■ A separate, single stab incision in the neck region is made to externalize the
activation rod (TECH FIG 1C).

TECH FIG 1 • A. Severe class II bite with an overjet of
more than 10 mm. B. Transoral approach to the
vertical ramus and dissection of the buccal and lingual
surfaces in preparation for the horizontal osteotomy of
the vertical ramus remnant. C. Reciprocating saw
position just prior to beginning the lingual osteotomy.

TECH FIG 2 • A. Use of the transbuccal trocar for
screw placement and the activation rod exit site in the
ipsilateral neck, ensuring a vertical vector. B. Close-up
view of the trocar and activation rod of the internal
distraction device in place. The device is well adapted
to the underlying transport disc. C. The distraction
device is shown in place with the transport disc
activated and displaced cephalad into the region of
the new glenoid fossa. D. Postprocedure CT scans
demonstrating the device in place after vertical ramus
osteotomy but prior to activation during the latency
period of 72 hours after surgery.
■ If simultaneous removal of pathology is necessary (eg, tumor, mass,
ankylosis, or degenerative joint disease resection), a separate preauricular
incision can be created to facilitate the dissection.
■ After a latency period of 72 hours, distraction of 1 mm daily is performed

until completion of distraction (TECH FIG 1D).
■ End points of distraction include symmetric vertical ramus length based on
clinical exam and the creation of an anterior crossbite and posterior open
bite in hemifacial microsomia cases.
■ Distraction is considered complete when the occlusion reaches the desired
final position based on the pathology being treated.
■ Once distraction is no longer needed, the activation rod is removed and the
skin is allowed to close.
■ After a consolidation period of 3 to 4 months, the distractor can be removed
through the original intraoral incision or rarely using a separate
submandibular incision.
PEARLS AND PITFALLS
Indications
■ Tumor resection, degenerative joint disease, ankylosis,
congenital anomalies, and unrepairable TMJ trauma
Goals
■ Restore normal occlusion and jaw function
■ Pain relief
■ Restoration of mandibular ramus height
Distractor
placement
■ Accurate placement and correct distraction vector are crucial
factors that can influence long-term clinical success.
Postoperative
diet
■ Patients should be maintained on soft diet until the
consolidation period is complete, typically 12 wk.
Postoperative
physical
therapy
■ Mouth range-of-motion exercises are crucial to minimize the
risk of joint stiffness after distraction-based TMJ reconstruction.
POSTOPERATIVE CARE
■ Postoperative physical therapy is critical since functional remodeling
continues after removal of the distraction device.
■ Patients are encouraged to open/close the mouth and masticate during the

distraction process.
■ All patients are placed on a soft diet until the consolidation phase is complete.
■ Some surgeons encourage the use of a flat plane TMJ occlusal splint while
sleeping at night for a minimum of 6 months.
OUTCOMES
■ Over the past three decades, only a handful of studies have explored surgical
outcomes after distraction-based TMJ reconstruction.
■ Almost all of the studies have been case series.1–6
■ No high-level evidence studies have been published.
■ In one of the largest series in the literature, Schwartz et al. assessed surgical
outcomes in 12 patients who underwent reverse distraction for TMJ
reconstruction.
■ At an average follow-up of 32 months, all patients demonstrated evidence of
“stable occlusion” with adequate range of motion and no postoperative
symptoms.5
■ Stucki-McCormick6 presented their outcomes in two patients who underwent
transport distraction osteogenesis for TMJ ankylosis and degenerative TMJ
disease.
■ At 18 months follow-up, the interincisal opening of both patients improved
from 6 to 28 mm and from 5 to 45 mm, respectively.
■ None reported pain with mastication at 18 months’ follow-up, and both
patients demonstrated radiographic evidence of neocondyle development.
■ To date, only one study (level III evidence) has compared surgical outcomes in
patients treated with distraction osteogenesis vs arthroplasty for TMJ
reconstruction.
■ Gabbay et al.4 examined nine congenital TMJ bony ankylosis patients, four
of whom underwent distraction osteogenesis and five of whom underwent
arthroplasty reconstruction.
■ Because TMJ ankylosis is prone to relapse, the primary outcome of this study
was the rate of relapse. At 11 months postintervention, the authors found that
TMJ arthroplasty had lower rates of relapse (8% vs 48%) when compared to
distraction osteogenesis.
■ Although distraction osteogenesis patients demonstrated adequate initial
mean incisor openings (27.5 vs 33.4 mm), these patients relapsed to 14.3 mm
by 12.5 months postdistraction.

■ Given the lack of high-level evidence evaluating the role of distraction
osteogenesis in TMJ reconstruction, more studies are necessary to further
elucidate the efficacy of this treatment modality when compared to other
options (ie, arthroplasty, vascularized bone grafts, etc.).
COMPLICATIONS
■ Hardware extrusion
■ Surgical site infection
■ Relapse
■ Facial nerve palsy
■ Seroma/hematoma
■ Fistula
■ Poor wound healing (eg, dehiscence)
REFERENCES
1. Ilazarov G. Clinical application of the tension-stress effect for limb
lengthening. Clin Orthop. 1990;250:8-26.
2. Zhu S, Hu J, Li J, et al. Reconstruction of mandibular condyle by transport
distraction osteogenesis: experimental study in rhesus monkey. J Oral
Maxillofac Surg. 2006;64(10):1487-1492.
3. Hikiji H, Takato T, Matsumoto S, et al. Experimental study of reconstruction
of the temporomandibular joint using a bone transport technique. J Oral
Maxillofac Surg. 2000;58:1270-1277.
4. Gabbay JS, Heller JB, Song YY, et al. Temporomandibular joint bony
ankylosis: comparison of treatment with transport distraction osteogenesis or
the matthews device arthroplasty. J Craniofac Surg. 2006;17:3.
5. Schwartz HC, Relle RJ. Distraction osteogenesis for temporomandibular joint
reconstruction. J Oral Maxillofac Surg. 2008;66(4):718-723.
6. Stucki-McCormick SU. Reconstruction of the mandibular condyle using
transport distraction osteogenesis. J Craniofac Surg. 1997;8:48-52.

37
CHAPTER
Bilateral Sagittal Split
Osteotomy for Mandibular
Deficiency
Stephen B. Baker
DEFINITION
■ The mandible supports the lower 16 teeth, and its position is important for
occlusion, airway function, jawline aesthetics, and facial form.
■ It is a U-shaped bone that has three points of contact: two condylar heads,
which rest in the glenoid fossa of the skull base, and the mandibular teeth,
which are in occlusion with the maxillary teeth.
■ Mandibular growth abnormalities can result in malocclusion as well as other
functional problems such as airway obstruction, articulation difficulty,
masticatory problems, and temporomandibular joint (TMJ) problems.1,2
■ The bilateral sagittal split osteotomy (BSSO) is a procedure that allows
movement of the mandible in an anterior or posterior direction while
maintaining overlap of the osteotomized bone segments.
■ The fact that the proximal and distal osteotomized bone segments overlap
facilitates return to normal jaw strength and function as healing occurs.
■ Dal Pont modification
■ The anterior vertical portion of the sagittal split osteotomy should be made in
the region of the mandibular first molar or slightly anterior.
■ The reason for this recommendation is that the inferior alveolar nerve (IAN)
is more medially positioned within the mandible in this region and therefore
is less at risk of injury during the osteotomy.1
■ Hunsuck modification
■ Hunsuck proposed that the horizontal portion of the BSSO on the medial
ramus did not need to extend through and posterior to the lingula.

■ He proposed correctly that this portion of the osteotomy would split naturally
if the posterior cut did not go posteriorly to the lingula.2
ANATOMY
■ The mandible is divided into several regions: the condyle, ramus, angle, body,
parasymphysis, and the symphysis.
■ The lingula is a triangular bony projection on the medial surface of the
mandible, immediately in front of the mandibular foramen. It provides
attachment for the sphenomandibular ligament.
■ The genial tubercle is on the lingual side of the symphysis and is attached to
the genioglossus and the geniohyoid.
■ In a mandibular advancement, the genial tubercle will bring these two
muscles forward, which may improve the airway as well as tighten submental
laxity.
■ In contrast, posterior positioning may impair the airway and cause submental
fullness.
■ The IAN is a continuation of the third branch of the trigeminal nerve and
enters the mandibular foramen, located on the medial aspect of the ramus. This
nerve travels through the mandible in the inferior alveolar canal before exiting
the mental foramen to become the mental nerve.
■ The mental nerve supplies sensation to the soft tissue of the ipsilateral chin
with a varying degree of cross innervation to the contralateral side.
■ Of note is that the IAN is 4 to 5 mm below the mental foramen before it
ascends to exit the foramen.
Angle Occlusal Classification
■ Class I: Neutro-occlusion
■ Molar relationship: The mesiobuccal cusp of the maxillary first permanent
molar occludes with the mesiobuccal groove of the mandibular first
permanent molar.
■ Canine relationship: The mesial incline of the maxillary canine occludes with
the distal incline of the mandibular canine. The distal incline of the maxillary
canine occludes with the mesial incline of the mandibular first premolar.
■ Mesognathic: normal, straight face profile with flat facial appearance
■ Class II: Disto-occlusion (overjet)
■ Molar relationship: The molar relationship shows the mesiobuccal groove of
the mandibular first molar is distally (posteriorly) positioned when in

occlusion with the mesiobuccal cusp of the maxillary first molar. Usually, the
mesiobuccal cusp of maxillary first molar rests in between the first
mandibular molar and second premolar.
■ Canine relationship: The mesial incline of the maxillary canine occludes
anteriorly with the distal incline of the mandibular canine. The distal surface
of the mandibular canine is posterior to the mesial surface of the maxillary
canine by at least the width of a premolar.
■ Retrognathic: convex facial profile resulting from a mandible that is too
small or maxilla that is too large
■ Class II malocclusion has two subtypes to describe the position of the
anterior teeth:
• Division 1: The molar relationships are like that of class II, and the
maxillary anterior teeth are protruded. Teeth are proclined and a large
overjet is present.
• Division 2: The molar relationships are class II where the maxillary central
incisors are retroclined. The maxillary lateral incisors may be proclined or
normally inclined. Retroclined and a deep overbite exist.
■ Class III: Mesio-occlusion (negative overjet)
■ Molar relationship: The mesiobuccal cusp of the maxillary first permanent
molar occludes distally (posteriorly) to the mesiobuccal groove of the
mandibular first molar.
■ Canine relationship: Distal surfaces of the mandibular canines are mesial to
the mesial surface of the maxillary canines by at least the width of a premolar.
Mandibular incisors are in complete crossbite.
■ Prognathic: concave facial profile with prominent mandible is associated
with class III malocclusion.
PATHOGENESIS
■ Variation in mandibular projection, either prognathia or retrognathia, has a
multitude of etiologies:
■ Heredity
■ Congenital syndromes
■ Endocrine abnormalities
■ Neoplasms
■ Autoimmune disease
■ Trauma
■ It is important to identify the etiology and ensure mandibular growth is stable

prior to performing a surgical correction.
PATIENT HISTORY AND PHYSICAL FINDINGS
■ Dental compensation is the term used to refer to the tendency of teeth to tilt to
decrease occlusal discrepancies. For instance, in a class II occlusion, dental
compensation refers to the tendency of the maxillary anterior teeth to become
retroclined (moving posteriorly) while the mandibular teeth become proclined
(moving anteriorly).
■ The degree of dental compensation is assessed with a lateral cephalometric
radiograph; the degree of dental compensation must be accounted for when
treatment planning for surgery.
■ Surgical procedures are usually planned based on the teeth in an
uncompensated position. In compensated occlusion, the degree of potential
mandibular movement may be underappreciated given the relationship of the
compensated occlusion.
■ Mastication difficulties should be assessed. Dentally uncompensated
retrognathic patients typically have an increased overjet, which compromises
the ability of the incisors to cut and shear foods during mastication.
■ Airway obstruction, primarily in retrognathic patients, should be assessed. It is
important to inquire about any history of snoring or sleep apnea.
■ If sleep apnea has not been diagnosed but is suspected based on the patient’s
history, a sleep study should be obtained. Results should be incorporated into
the treatment plan.
■ If sleep apnea is present, a two-jaw procedure may be indicated in order to
open the airway while correcting the occlusion.
■ Aesthetic considerations of orthognathic surgery are important to consider. In
particular, when treatment planning the correction of a prognathic patient, it is
important to be aware of the soft tissue redundancy and submental fullness that
may result with posterior positioning of the lower jaw.
■ Occasionally, even though the SNB is increased and the SNA is normal, the
aesthetic result may be optimized by correcting the occlusion with upper jaw
advancement to optimize soft tissue draping over the underlying skeletal
relationship.3
■ Many syndromes are associated with mandibular deficiency and should be
identified prior to treatment. Although the treatment may not require technical
modifications, it is important to be aware of any associated syndromes prior to
treatment.

■ Lower third facial asymmetry is not an uncommon finding in patients with
dentofacial deformities.
■ It is important to note whether the asymmetry is due to mandibular deviation,
mandibular asymmetry, or any asymmetry of the chin relative to the mandible.
■ Additionally, there may be maxillary asymmetry associated with mandibular
asymmetry, which requires movement of the upper jaw as well.
■ In patients who are concerned about the aesthetic impact of insufficient
mandibular projection but demonstrate a mild or minimal occlusal abnormality,
advancement of the chin is a treatment option that frequently achieves the
patient’s aesthetic goals without subjecting them to a sagittal split osteotomy.
IMAGING
■ A panoramic radiograph is a two-dimensional representation of the mandible
from condyle to condyle. It is a useful screening tool for any pathology of the
mandible as well as the presence of impacted third molars.
■ A lateral cephalometric radiograph can be used to identify soft tissue and
skeletal cephalometric landmarks to perform cephalometric analyses.
■ Imaging of wrist growth plates is a useful tool to determine whether skeletal
growth is complete or ongoing. Growth plate closure is an indication that
skeletal growth is complete.
■ The cone-beam CT (CBCT) produces three-dimensional radiographic images
of the patient’s face that can be used for computerized treatment planning and
splint fabrication. The technology used in a CBCT allows the image to be
obtained with a far lower dose of radiation compared with traditional CT scan.
■ This image is invaluable in treatment planning for the surgical approach to
correct dentofacial deformities. It also aids in the fabrication of surgical
splints.
■ Nuclear imaging is indicated to assess bone activity. It is nonspecific but is
indicative of bone activity. This allows the clinician to assess the degree of
bone metabolism in the condyles.
■ Useful applications might be to monitor rheumatoid arthritic changes,
fracture healing, neoplastic activity, or condylar hyperplasia.1–3
DIFFERENTIAL DIAGNOSIS
■ Neoplasm: Infrequently, a neoplasm may be the source of excessive
mandibular growth. A neoplastic etiology typically presents as an asymmetric
mandible with the teeth out of occlusion. The rapidity of tumor growth will

produce a mandibular shift that exceeds the ability of the maxillary teeth to
remain in occlusion. Mandibular asymmetries without a crossbite are typically
associated with more chronic processes such as hemifacial microsomia or an
early history of condylar trauma.
■ Trauma: Injury to a condyle before skeletal maturity may stunt growth, leading
to mandibular asymmetry and a crossbite.
■ Autoimmune: Rheumatoid arthritis can cause condylar resorption resulting in
an anterior open bite or mandibular retrognathia. It is important to ensure good
medical control of the disease prior to undertaking surgical correction.
■ Developmental anomalies: Anomalies such as Pierre Robin sequence,
hemifacial microsomia, or congenital syndromes may result in hypoplastic
mandibles. By the time these patients are old enough to be considered for
surgery, the underlying etiology has typically been elucidated and should be
considered when developing the final surgical plan.
■ Endocrine: Acromegaly and other hormone abnormalities can lead to
anomalies of mandibular size and position.
NONOPERATIVE MANAGEMENT
■ In mild cases of mandibular prognathia or retrognathia, it may be possible for
the orthodontist to dentally compensate for the skeletal abnormality and
produce a dental class I occlusion.
■ Occasionally, extraction of premolars may be necessary to create the space
necessary to move the teeth and allow for appropriate dental compensation.
■ A nonsurgical approach to mandibular retrognathia frequently results in the
appearance of a large nose and a weak chin. This occurs because the
orthodontist has to retrocline the maxillary incisors to normalize the dental
overjet. Since the incisors support the upper lip, the lip moves posteriorly as
well as giving the nose an overprojected appearance.
■ If these patients are unhappy with their facial appearance, rhinoplasty and a
genioplasty or chin implant are methods to camouflage the underlying skeletal
discrepancy of the jaws and improve facial proportions.
SURGICAL MANAGEMENT
■ The author performs sagittal split osteotomies after the completion of facial
growth.
■ The goal of this procedure is to anteriorly or posteriorly position the lower jaw.
Additionally, this procedure may be performed to improve mandibular

asymmetry.
■ The main steps of the procedure are as follows:
■ Make incisions in the mandibular mucosa.
■ Perform the osteotomy from the medial ramus down the ascending ramus
along the external oblique bridge to the inferior mandibular cortex.
■ Perform the sagittal split by ensuring the IAN stays within the distal segment.
■ Position the patient’s teeth in a class I occlusion.
■ Verify condylar seating and align the proximal and distal segments with a
bone clamp.
■ Apply rigid fixation with use of the transbuccal trocar.
■ Release the intermaxillary fixation and verify that the patient’s occlusion is in
the desired class I position.
■ Close the mucosa with chromic sutures and the trocar incision with a layered
subcutaneous closure.
■ After the occlusion has been verified and the wounds are closed, heavy elastics
are used to keep the patient’s occlusion stable and immobile.
■ Half of these elastics are removed 1 week postoperatively, and the remaining
elastics are removed 2 weeks postoperatively.
Preoperative Planning
■ Prior to performing mandibular surgery, the patient’s occlusion should be
leveled and aligned by the orthodontist. The anticipated occlusion can be
evaluated by hand in articulating a maxillary and mandibular plaster cast to
verify that the postoperative occlusion will be stable.
■ Additionally, to reduce the complication of an unfavorable split, the
mandibular third molars should be extracted 4 to 6 months prior to the date of
the sagittal split osteotomy.
■ Risks and complications are reviewed with the patient, and include the
following:
■ Injury to the IAN
■ Infection
■ Need for revision surgery
■ Need for removal of titanium fixation
■ Injury to tooth roots
■ Unfavorable split possibly requiring intermaxillary fixation if rigid fixation
cannot be achieved

■ If the maxillary and mandibular plaster casts are placed in the anticipated
position and a stable class I occlusion is achieved, a splint may not be
necessary. However, if the orthodontist desires that the mandible be moved
prior to orthodontic treatment, the resulting occlusion may be unstable and
benefit from a splint to stabilize the mandible while the osteotomy is healing.
In cases in which the occlusion does not “lock in” after the osteotomy, a splint
is recommended and it is our approach to use virtual surgical planning and
CAD/CAM technology to fabricate the surgical splint.4
Positioning
■ The patient is placed supine on the operating room table, the knees are flexed
at 30 degrees with a pillow, and the heels are padded with foam cushions.
■ Pneumatic compression stockings are placed and their function is verified
prior to induction of general anesthesia.
■ Anesthesia is achieved with the nasotracheal tube sutured to the nasal septum
with a 2-0 Prolene mattress suture that is padded on either side of the septum
with Xeroform gauze.
■ The knot for the suture is on the same side as the endotracheal tube, and the
redundant portion of the suture is then circled around the nasotracheal tube
twice before being tied down to secure the tube.
■ A head drape is then placed and secured to the patient’s head with 4- × 4-in.
gauze underneath the anesthesia tubing (FIG 1A,B).
■ The anesthesia tubing is then secured to the head drape using silk tape in a
way that ensures no pressure from the nasotracheal tube is applied to the nasal
ala.
■ Antibiotics and steroids are administered prior to the incision; local anesthesia
is injected prior to prepping and draping the patient (FIG 1C). The epinephrine
takes effect during prepping and draping so that when the incision is made,
blood loss is minimal.
■ We request anesthesia to achieve a mean arterial blood pressure of 55 to 60
mm Hg as long as the patient’s health can tolerate it.
■ Prior to the incision, chlorhexidine oral mouth rinse is placed in the patient’s
mouth and allowed to sit for 5 minutes before removal.
■ Steroid ointment is applied to the lips to reduce swelling after surgery. The
desired blood pressure is verified with anesthesia, and if acceptable, the
procedure begins.

Approach
■ The operative team is given a list of all necessary equipment as well as a
summary of the steps of the operation.
■ Additionally, an image of the Mayo stand with all the instruments and the
position in which they are to be placed is projected on the operating room
computer screen.
■ The instruments are aligned in sequential order so that the scrub nurse can
hand them to the surgeon efficiently.
■ A headlight is extremely helpful in these cases.
■ The tooth-bearing portion of the osteotomy is the distal segment, and the
condylar portion is the proximal segment.
FIG 1 • A,B. A nasotracheal tube is secured with a 2-0
Prolene suture that is tied as a horizontal mattress
through the septum with Xeroform gauze to reduce
pressure necrosis. A surgical towel is then wrapped as
a head drape and secured with silk tape to the head as
shown. The tube is then resecured to the head drape
with gauze padding making sure the endotracheal tube
is not applying pressure to the nasal ala. C. Ten mL of
1% lidocaine with 1/100 000 epinephrine is injected into
each side of the sagittal split site before surgical
draping is performed. The injections are in the mucosal
vestibule from first molar to the ramus. Lidocaine is also
injected in the medial ramus and in the retromolar

trigone.
T E C H N I Q U E S
■ Exposure
■ The Molt mouth prop is placed on the nonoperative side and is opened as far
as possible.
■ A sweetheart retractor pulls the tongue away from the operative side and is
secured to the mouth retractor with a 4- × 4-in. gauze (TECH FIG 1A).
■ The incision is made from the retromolar region to the first molar at least 1
cm from the teeth.
■ This will retract after being incised and will be difficult to close if made
too close to the teeth.
■ A Minnesota retractor is used by the surgeon to retract the cheek while
he/she is making the incision.
■ A periosteal elevator is used to expose, in a subperiosteal plane, the lateral
mandible from external oblique ridge to ascending ramus.
■ The posterior lateral mandible does not need to be exposed because it is not
necessary and impairs the blood supply of the posterior segment.
■ The medial ramus is dissected as well. The anterior portion of the ramus is
dissected to the tip of the coronoid process. Exposure in this dissection is
facilitated by the use of the coronoid notch retractor.
■ A curved periosteal elevator is swept along the inferior border of the
mandible to release muscular attachments that can restrict postosteotomy
positioning of the mandible.
■ Exposure is key to facilitating this procedure.
■ A chained Kocher is clamped to the coronoid process, and the chain is then
pulled posteriorly and clamped to the head drape to retract the mucosal
tissue (TECH FIG 1B).
■ A Seldin retractor is placed medial to the ramus and is lowered toward the
mandibular body until it meets resistance from the mandibular nerve. The
Seldin should be parallel to the occlusal plane and then rotated slightly in a
clockwise direction on the right side (counterclockwise on the left side) to
expose the medial ramus (TECH FIG 1C).

TECH FIG 1 • A. To optimize exposure, a mouth prop
is placed and a sweetheart retractor is then positioned
to pull the tongue medially. These instruments are
secured with surgical gauze. The surgeon now can
use a Minnesota retractor and the free hand for an
instrument. B. Once the incision and initial dissection
has been completed, a Kocher with a chain is
clamped on the coronoid process to retract tissue. The

chain can be clamped to the head drape to eliminate
the need for an assistant. C. A Seldin retractor is
placed between the medial ramus and the soft tissue
parallel to the occlusal plane and then is rotated so its
superior border moves away from the ramus exposing
the bone. The surgeon uses this exposure for the
horizontal medial ramus osteotomy.
■ Osteotomy and Sagittal Split
Video p2-c037_01
Video p2-c037_04
00:00 / 00:00
00:00 / 00:00

■ A reciprocating saw with a short blade is now placed against the medial
ramus to cut the anterior two-thirds of the medial ramus above the
mandibular foramen through the cortical bone (TECH FIG 2A).
■ Once the medial cut is completed, the saw blade is rotated so that the cut
continues in an oblique fashion to the anterior ramus; the cut then continues
along the external oblique ridge down to the inferior border of the
mandible.
■ Ensure that the cortical bone at the inferior mandibular border is cut
completely to generate a smooth split.
■ A mandibular body retractor is used to optimize visualization for the vertical
cut.
■ The retractor can be placed anterior to the location of the vertical cut and
rotated in a counterclockwise fashion so the posterior edge retracts the
cheek tissue away from the area, facilitating visualization while making the
cut.
■ A small osteotome is used to verify that the osteotomy is complete along the
horizontal portion of the medial ramus as well as the inferior mandible at the
anterior portion of the osteotomy (TECH FIG 2B).
Video p2-c037_02
00:00 / 00:00

Video p2-c037_05
■ A small osteotome is tapped along the osteotomy to begin to separate the
segments. It is important not to tap the osteotome too deep to avoid hitting
the IAN.
■ Once the superior portion of the osteotomy is wide enough to fit a Frazier
suction between the edges, a three-prong spreader is placed between the
segments and gradually opened.
■ The surgeon must ensure that the IAN is not in the proximal segment prior
to the split. A sudden split could avulse the nerve if it has not been released
from the inferior alveolar canal in the proximal segment (TECH FIG 2C).
■ Under direct visualization, the osteotomes can be used to complete the split
to avoid the nerve.
■ Alternatively, once the nerve is confirmed to be in the distal segment,
larger fiber-handled osteotomes can be used in tandem to complete the
split. They can be placed in the osteotomy site and rotated to complete the
split.
■ The split is verified by attaching a Kocher to the proximal segment and
moving it independently from the distal segment.
00:00 / 00:00

Video p2-c037_03
00:00 / 00:00

TECH FIG 2 • A. The osteotomy is now made on the
medial ramus. The surgeon should feel the nerve
below the Seldin retractor to ensure the cut is above
the nerve. The osteotomy is made from the medial
ramus obliquely inferior as it then continues down the
ramus and onto the external oblique ridge to the
inferior border of the mandible. B. Osteotomes are
then used to verify the osteotomy at the medial ramus
and the inferior border of the mandible. C. Cadaver
image of IAN in the proximal segment. It is important
prior to completing the osteotomy to verify that the
inferior alveolar nerve is not within the proximal
segment or it may be avulsed during the split. This
image shows the nerve with the proximal segment as
the split is occurring. If this is noted, an osteotome is
used to release the cancellous bone from the inner
cortical bone to release the nerve. If the nerve is not
actually within cancellous bone, it can easily be freed
with a periosteal elevator.
■ Occlusal Correction and Maxillomandibular
Fixation
■ Once both sides of the sagittal split osteotomy are complete, the lower jaw is
placed into the desired occlusion with either a surgical splint or by placing
the patient’s mandible in class I maximum intercuspal position.
■ It is the author’s preference to use many heavy elastic bands for
intermaxillary fixation. Multiple elastics provide solid fixation; if there is
any occlusal shifting, the elastics will return occlusion to the desired
position.
■ Wire stretches and needs to be prestretched prior to making wire loops for
maxillomandibular fixation (MMF). If manipulation of the jaws during
fixation moves the occlusion, wire is not elastic and the occlusion may shift
while rigid fixation is applied.

■ If wire loops are used, it is important that the surgeon periodically verify
the desired occlusion during the fixation process.
■ Avoid excessive torque when applying wire loops because the orthodontic
brackets may loosen or become detached.
Video p2-c037_06
■ The proximal segment is rotated with the condyle seated in the fossa to align
the superior edges of the proximal and distal mandibular segments.
■ A curved Kocher is placed to secure this position by placing it posteriorly
along the osteotomy sites, where there are overlapping bony segments.
■ A small curved hemostat is then placed in the mouth at the area where the
screws will be placed (along the superior border of the mandible posterior to
the second molar).
■ The tip is pushed out toward the skin so the surgeon can palpate where the
trocar incision should be placed (TECH FIG 3A).
■ An incision is then made long enough to accommodate the diameter of the
trocar without avulsing the wound.
■ A slightly longer incision that does not avulse the skin as the trocar is
inserted will be aesthetically superior to a shorter incision that is avulsed as
the trocar is placed through it (TECH FIG 3B).
■ Once the trocar is in place, the trocar cheek retractor is attached (TECH FIG
3C,D).
00:00 / 00:00

TECH FIG 3 • A. A small hemostat is placed in the
mouth adjacent to the location of the screws and is
pushed toward the skin to denote the location of the
trocar incision. B. After the incision is made, a small
hemostat is used to gently spread the tissue to
facilitate the passage of the trocar. C,D. The trocar is
placed through the incision, and then, the surgeon’s

finger is used to keep the tip of the trocar exposed
until the cheek retractor is attached to the trocar.
■ Rigid Fixation
■ The stability of MMF and occlusion is verified prior to fixation.
■ The Kocher is released and the proximal segment is rotated with the
condyle so the superior edges of the segments are aligned.
■ The Kocher is then secured to hold the segments while the position is set
(TECH FIG 4A).
■ Fixation is now applied.
■ A color-coded drill is used to drill holes through the osteotomy for fixation.
■ Irrigation is applied to the drill throughout this process so as to avoid
excessive heat generation (TECH FIG 4B).
■ It is the author’s preference to place three screws in a row at the superior
border, but other patterns are acceptable as long as they do not violate the
IAN or tooth roots.
■ While drilling, there is initial resistance as the drill goes through the outer
cortical bone, a loss of resistance as the drill enters the gap between the
bone segments, a second zone of resistance as the drill goes through the
cortical bone of the distal segment, and then a final loss of resistance as the
drill passes through this bone.
■ The color on the drill as the second loss of resistance occurs is noted, as
this indicates the length of the desired screw (TECH FIG 4C). If one is
uncertain which color corresponds to the loss of resistance, it is
recommended to use the longer length screw.
■ Once three screws are applied in this manner, the same technique is applied
to the opposite side.
■ The stability of MMF and occlusion is periodically checked. Occasionally,
manipulation of the mandible while applying fixation can loosen wire loops
and compromise the occlusion.
■ Any change in occlusion needs to be rectified prior to application of
fixation.

TECH FIG 4 • A. Prior to drilling the fixation holes, the
segments are positioned with the condyle seated and
the superior edges of the segments aligned. A curved
Kocher is placed posteriorly and an assistant
squeezes the Kocher to immobilize the segments
while the fixation is applied. B. The drill is irrigated as
the holes are drilled. C. The drill is color coded, and
each color corresponds to the length of a screw. The
color of the drill as it passes through the cortical bone
of the distal segment (the second loss of resistance) is
noted, and the appropriate size screw is then
selected.
■ Completion
■ Once fixation is applied, MMF is released and the desired occlusion is
verified by rotating the mandible with seated condyles to ensure the desired
intercuspal position has been achieved.

Video p2-c037_07
■ If occlusion is not ideal, the process is repeated until the correct occlusion
has been achieved.
■ If the desired occlusion has been achieved, elastics are placed to provide
MMF and the wounds are irrigated and then closed with 3-0 chromic on an
SH needle.
■ The author typically will close the wound with a running locked suture.
■ The trocar sites are closed with a deep 5-0 Monocryl and transdermal 6-0
Prolene.
■ Prior to extubation, a nasogastric tube is used to empty the stomach.
■ Ice packs are applied to the cheeks in the recovery room, and the head is
elevated.
■ No compression dressing is used.
PEARLS AND PITFALLS
Intraoral
incision
■ A common error is making the intraoral incisions too close to the
teeth.
■ The incision should be made at least 1–1.5 cm from the teeth.
■ Once the mucosa is cut, it retracts, making mucosal closure difficult
at the end of the case.
Incomplete
osteotomy
■ The most likely areas for incomplete osteotomy are at the inferior
border of the mandible of the vertical cut and at the junction of the
00:00 / 00:00

ramus with the posterior horizontal cut that is lingual to the ramus.
■ Each of these areas is verified with an osteotome prior to the split to
decrease the likelihood of an unfavorable split.
Nerve
damage
■ Prior to splitting the segments, it is important to confirm that the
nerve is not within the proximal segment.
■ If a portion of the nerve remains in the proximal segment, a sudden
split could avulse the nerve. If the nerve is noted to be in the proximal
segment, it is not recommended to try to dissect the nerve free from
the cancellous bone. This approach has a high likelihood of nerve
injury.
■ In contrast, use an osteotome to separate the cancellous bone from the
cortical bone in a safe plane. The nerve will remain enveloped within
the cancellous bone and should be minimally traumatized.
Bad split
■ Avoiding a bad split is key to a successful BSSO.
■ Removal of mandibular third molars 6 mo prior to the osteotomy
allows time for the sockets to heal, which decreases the likelihood of a
bad split.
■ If the segments do not appear to be easily separating, the surgeon
should verify that the osteotomies are complete.
■ Do not use excessive force, which increases the chance of an
uncontrolled mandibular split.
■ If a bad split occurs, the segments can be plated to re-establish normal
anatomy, and the proximal and distal segments can then be secured
into the desired position with rigid fixation.
Fixation
■ Be certain the condyles are seated when aligning the proximal
segment during fixation. Verify that occlusion remains in its desired
position during application of fixation.
■ Wire loops may loosen and compromise the result if not corrected
prior to fixation. The author prefers heavy elastics for this reason. If a
shift occurs during fixation, elastics will dynamically reset the
occlusion as opposed to the static nature of a loose wire.
Screw
holes
■ When drilling screw holes, ensure that the drill does not stop and that
the movement is smooth in and smooth out.
■ Never have the drill running without movement.
■ Any small drill whip will enlarge the drill hole and compromise the
holding power of the screw.
MMF
■ Orthodontic brackets may break during the case. If the surgeon loses
the orthodontic surgical lugs, another method of MMF must be
employed.
■ Rather than time-consuming arch bars, the author uses the rapid

screw-anchored MMF sets. The entire arch bar can be used or
individual lugs can be cut and secured with screws as needed.
■ The author does not recommend MMF screws for routine use because
they do not distribute forces as evenly as the screw-anchored MMF
system.
POSTOPERATIVE CARE
■ The patient is placed on a liquid diet for 2 weeks. Feeding is facilitated
through the use of a red rubber catheter and a Toomey syringe to inject full
liquids into the mouth behind the second molars. Instant breakfast, nutrition
drinks, smoothies, and anything blended into a liquid are recommended.
Protein powder and vitamins can be added for additional nutritional
supplementation.
■ Ice packs to cheeks and elevation of the head are recommended for 1 week.
■ Chlorhexidine mouth rinse is used BID for 2 weeks.
■ Gentle tooth brushing with a soft bristle brush can begin as soon as the patient
feels comfortable enough to insert a brush.
■ At the 1-week postoperative appointment, approximately half of the elastics
are removed, and sutures are removed from the trocar incision.
■ Two weeks after surgery, all the elastics are removed and any necessary
guiding elastics are employed. Usually, the orthodontist will dictate the use of
postoperative guiding elastics.
■ After all elastics are removed, the patient begins range-of-motion exercises to
regain normal interincisal opening.
■ The patient is instructed to avoid any contact activity for 10 weeks.
■ A soft mechanical diet is instituted 2 weeks after surgery and is advanced as
tolerated.
■ The patient is told to refrain from firmer foods for 8 weeks.
OUTCOMES
■ The sagittal split osteotomy is a predictable method to correct underlying
mandibular skeletal deformities.
■ Stability of mandibular advancement is greater than that of mandibular
setback.
COMPLICATIONS
■ If a malocclusion intraoperatively or postoperatively is noted due to improper

condyle position during fixation or improper indexing of the splint, fixation
must be removed and reapplied. It is wise to verify splint fit prior to surgery.
■ Paresthesia or anesthesia of the lip may occur from injury to the IAN.
Postoperative sensory disturbances in the lower lip and chin have been reported
to occur in 9% to 85% of operated sides.5 The lack of standardization of
objective methods and time to the evaluation of sensory dysfunction after
BSSO results in a vast range of prevalence of neurosensory disturbance at 1 or
2 years postoperatively (0% up to 85%).6
■ The incidence of bad splits has been shown to be 2.0% per site. The only
predictive factor for a bad split is the removal of third molars at the same time
as BSSO. There is no significant association between bad splits and age, sex,
class of occlusion, or the experience of the surgeon. It has been demonstrated
that doing a BSSO with splitters and separators instead of chisels does not
increase the risk of a bad split and is therefore safe with predictable results.7
REFERENCES
1. Rajchel J, Ellis E III, Fonseca RJ. The anatomical location of the mandibular
canal: its relationship to the sagittal ramus osteotomy. Int J Adult Orthodon
Orthognath Surg. 1986;1:37-47.
2. Hunsuck EE. A modified intraoral sagittal splitting technic for correction of
mandibular prognathism. J Oral Surg. 1968;26:250-253.
3. Rosen HM. Facial skeletal expansion: treatment strategies and rationale. Plast
Reconstr Surg. 1992;89:798.
4. Baker SB, Goldstein JA, Seruya M. Outcomes in computer-assisted surgical
simulation for orthognathic surgery. J Craniofac Surg. 2012;23(2):509-513.
5. Wijbenga JG, Verlinden CR, Jansma J, et al. Long-lasting neurosensory
disturbance following advancement of the retrognathic mandible: distraction
osteogenesis versus bilateral sagittal split osteotomy. Int J Oral Maxillofac
Surg. 2009;38:719-725.
6. Westermark A, Bystedt H, von Konow L. Inferior alveolar nerve function
after mandibular osteotomies. Br J Oral Maxillofac Surg. 1998;36:425-428.
7. Mensink G, Verweij JP, Frank MD, et al. Bad split during bilateral sagittal
split osteotomy of the mandible with separators: a retrospective study of 427
patients. Br J Oral Maxillofac Surg. 2013;51(6):525-529.

38
CHAPTER
Inverted L Osteotomy for
Mandibular Surgery
Raymond J. Harshbarger
DEFINITION
■ Various procedures have been developed to alter the shape and position of the
mandible, including the sagittal split osteotomy, vertical ramus osteotomy, and
inverted L osteotomy (ILO).
■ The ILO allows separation of the proximal condylar bearing segment and the
distal occlusal bearing mandibular segment, for advancement of the distal
segment.
■ Improvements with distal segment advancement:
■ Enhancement of airway space at the tongue base, thus improving breathing
functions
■ Treatment of class II dentofacial deformity, establishing abnormal bite,
chewing, and speaking
ANATOMY
■ The mandible is a ring structure articulating with the skull base at the glenoid
fossa.
■ In addition to bearing responsibility for the foundation of the lower third of the
face, the mandible contains the lower dentition, and the inferior alveolar nerve
transverses the marrow space through the ramus and body.
■ Pertinent features on the lateral (buccal) surface of the mandible include the
anterior/posterior ramus, sigmoid notch, condylar process, and coronoid.
■ Medially, key landmarks include the sigmoid notch, lingua, mandibular
foramen, and position/occlusal surface of molars.
■ The marginal mandibular nerve changes position depending on patient age: in
neonates, the marginal mandibular nerve travels along mandibular border; with

increasing age, the nerve migrates inferiorly. By skeletal maturity, the nerve is
about two fingerbreadths below the mandibular border.
■ The lingula is present along the medial surface of ramus and is halfway from
anterior to posterior ramus and halfway down from sigmoid notch to
mandibular border. It is found 1 to 1.5 cm cephalad to molar occlusal surface,
in skeletally mature individuals.1–3
PATIENT HISTORY AND PHYSICAL FINDINGS
■ Patients who benefit from ILO are generally divided into two groups:
■ Neonates and children:
■ May present with airway obstruction, difficulty feeding, gastroesophageal
reflux, and failure to thrive
■ Physical examination demonstrates micrognathia, glossoptosis, and possible
cleft palate.
■ Skeletally mature patients:
■ May have had a history of obstructive sleep apnea, TMJ disorder (with pain),
and chewing and speaking dysfunction
■ Physical examination demonstrates a sagittal deficiency of the lower third of
the face with class II malocclusion.
IMAGING
■ Computed tomography demonstrates sagittal deficiency of the mandible.
Typically, other components exhibit normal morphology.
■ Operative airway evaluation (rigid and flexible exam) is done to assess
glossoptosis, tongue-based airway obstruction, and prolapsed epiglottis. An
anterior tongue pull and jaw thrust will improve the obstruction.
DIFFERENTIAL DIAGNOSIS
■ Pierre Robin sequence
■ Craniofacial microsomia
■ Treacher Collins
■ Micrognathia
■ Juvenile rheumatoid arthritis
SURGICAL MANAGEMENT
■ Candidates for ILO include patients with sagittal deficiency of the mandibular
body, including neonates, children, and skeletally mature patients. Distraction

may be performed in all three groups. Orthognathic surgery is indicated in
skeletally mature patients; ILO may be chosen over a sagittal split osteotomy,
or vertical ramus osteotomy, especially when dealing with patients who have
asymmetric skeletal findings. With a single-step mandibular advancement,
bone grafts are used to bridge the created gap.
Preoperative Planning
■ Neonates
■ Computed tomography
■ Operative airway (rigid/flexible) evaluation
■ Polysomnography
■ Possible virtual surgical planning with creation of operative cutting and
positioning guides
■ Children and skeletally mature
■ All of the above
■ Placement of orthodontic appliances, with preparatory orthodontics
Positioning
■ Neonates: Supine position, with head on a gel roll, a shoulder roll, neck in
extension, and an oral ET tube that is microcuffed. ET tube should be taped to
the upper lip, brought cephalically, and fixed at the hairline over egg crate foam
with 2-0 silk. Eyes are protected with Tegaderm (FIG 1).
■ Children and skeletally mature patients: Nasal RAE tube sutured at the septum
and at the hairline over egg crate foam with 2-0 silk. A shoulder roll should be
placed, with eyes protected using Tegaderm. The patient’s head should be
placed on a gel roll or foam.
Approach
■ The ILO technique may be approached from either an extraoral or intraoral
incision or both.

FIG 1 • Patient positioning (neonatal) for extraoral
inverted L osteotomy.
T E C H N I Q U E S
■ Extraoral Inverted L Osteotomy
Exposure
■ This technique is commonly used for mandibular distraction osteogenesis.
■ Incision marking is designed to facilitate the osteotomy and protect the
marginal mandibular nerve.
■ In neonates, the neck is placed in extension; palpate the mandibular angle,
marking the incision one finger breadth below the angle. Starting posterior to
anterior at the angle and maintaining one fingerbreadth below the mandibular
border, the incision should be 2.5 cm in length. It may be helpful to dot the
midline of the neck, to view the projected path of each incision, and to
improve symmetry (TECH FIG 1A).
■ In children and skeletally mature patients, a similar approach is used;
however, with increasing age, begin increasing the distance between the

mandibular border and incision placement, migrating caudally to a position
of two fingerbreadths below the border in adults.
■ Vasoconstriction:
■ To protect the marginal mandibular nerve and promote a bloodless field for
surgery, a saline and epinephrine mixture is used. The nerve will then be
responsive during dissection. Despite proper incision placement, the nerve
can be encountered during approach to the mandible. There will be a
greater chance of nerve preservation if it remains active during surgery.
■ Incision and approach in neonates and children undergoing distraction
■ After adequate epinephrine effect, the skin is sharply incised with a 15
blade.
■ Monopolar current on cutting is used to dissect through the fat and
platysma muscle (dissection should be in a straight posterior direction).
■ Look for the submandibular gland and any evidence of the marginal
mandibular nerve. Dissect through the investing fascia of the
submandibular gland, and then begin a cephalad plane of dissection (TECH
FIG 1B).
■ Tenotomy scissors may be used during these steps to help orient the
surgeon, and expose critical structures such as the submandibular gland,
marginal mandibular nerve, and the facial artery/vein.
■ The dissection at this point should be aimed toward the mandibular angle.
This is a “safe zone” to approach the mandible.
■ As the facial vessels are encountered running vertically in the field of
dissection, leave them intact and generally reflect them anteriorly, although
posterior reflection may be performed. Once the mandibular angle is
encountered, use a small toe-in retractor.
■ Incise horizontally just above the mandibular border, and enter the
subperiosteal plane. The lateral surface of the mandible can now be
exposed using a periosteal elevator (the author prefers a small Obwegeser
elevator) (see TECH FIG 1B).
■ Mandibular exposure is complete when all key landmarks are exposed,
including the anterior and posterior ramal borders, proximal portion of
condylar process, and sigmoid notch and body.
Osteotomy
■ The proposed osteotomy can now be marked using a sterile no. 2 pencil.
■ Marking considerations include device footplate position, vector, and