Operative Technique in Plastic Surgery – Kevin C.Chung

TECH FIG 1 • A. Markings for incision. B.
Submandibular approach to expose the mandible.
Note anatomic layers and plane of dissection deep to
the marginal mandibular branch of the facial nerve.
■ A turning arm is attached to the device (preferred is KLS Martin
microZurich with rigid externally removable arm).
■ The device is placed into the field, bringing the turning arm through the
tunnel and skin and positioning the device over the mandible near the angle.
The desired vector is determined, with positioning of the footplates to allow

placement of three screws in each footplate.
■ A line is marked between the footplates, and the device is removed from the
field. This mark is extended into the vertical portion of the osteotomy,
running from the mandibular border to immediately caudal to proximal
condylar process. The mark should be roughly parallel to the posterior ramal
border.
■ The upper extent of the vertical mark is made immediately proximal to the
condylar process.
■ Identify the convexity in the ramus, caudal to the sigmoid notch. Proximal to
the vertical flattening of the convexity is a safe place to orient the horizontal
portion of the osteotomy (this places the osteotomy above the lingula and
tooth buds).
■ The horizontal mark comes off the anterior ramus roughly perpendicular to
the border and intersects the upper extent of the vertical component (see
TECH FIG 2A,B).
■ Generally, the lingula of the ramus is at the halfway point posteriorly and
caudally from the sigmoid notch to the inferior border.
■ Once properly marked, the sagittal saw is used to complete the vertical and
anterior portions of the inverted L, saving the posterior cortex for a few
millimeters anterior to the intersection of the vertical and horizontal limbs
(TECH FIG 2B,C).
■ The sagittal saw is preferred due to the limited kurf compared to the
reciprocating blade.
■ Next, position the device straddling the footplates on either side of the
vertical aspect of the osteotomy near the mandibular border.
■ The device is positioned along the ideal sagittal or slightly oblique vector
(the orientation of the vertical limb of the osteotomy dictates this). Make sure
the device is “zeroed” prior to positioning.
■ If a more vertical vector is planned, the osteotomy needs to be a stair-step
variation of the inverted L.
■ Subsequent to device positioning, place three self-drilling high-profile
screws in each footplate. (Length of the screws will be 5 mm in neonates and
infants, but may be 7 mm in children and skeletally mature individuals.)

TECH FIG 2 • A. Anatomic landmarks for inverted L
osteotomy. Shaded (red) is area of subperiosteal
exposure. Relationship of inferior alveolar nerve and
tooth buds to osteotomy (dashed line) is shown. B.
Inverted L osteotomy, buccal view. C. Posterior lingual
view.
■ Place an Obwegeser elevator underneath the proximal (condylar) segment
for support when placing screws in this segment, to avoid shearing of the
posterior ramus from the condyle.
■ After the device is secured to the mandible, use a mini-osteotome to separate

the posterior cortex near the intersection of the horizontal and vertical limbs
(the portion remaining intact after sagittal saw use).
■ Confirm completion of the osteotomy by activating the turning arm of the
device. If the device turns freely, then the osteotomy is complete. Resistance
may be encountered. Use the mini-osteotome to identify and separate the
unfractured posterior cortex.
■ After confirming osteotomy completion, return the device to the zero
position, and activate the ratchet mechanism (prevents down-turning of the
device, essentially undoing the distraction).
■ Irrigate the operative pocket with saline, and approximate the platysma and
dermis.
■ Note: VSP may be used to optimize osteotomy and device position. This
should allow for the production of operative guides to delineate osteotomy
and device position.
■ A similar procedure is performed on the contralateral side.
■ The contralateral device should be placed along the same vector as the first
operative side.
■ To achieve device symmetry, estimate the proposed vector, place one screw,
center the head, and palpate the rod of each device, rotating the newly
applied device to achieve a parallel vector; then apply the remainder of
screws.
■ If VSP is used, apply footplate drill hole positioning guide, drill the desired
holes, remove, and apply the device.
■ Combined Extraoral-Intraoral Inverted L
Osteotomy
■ The above approach is reliably used in neonates and young children. Older
children and skeletally mature individuals undergoing mandibular distraction
may benefit from a combined extraoral-intraoral approach.
■ The horizontal limb of the inverted L can be difficult to reach from a
submandibular approach in older patients.
■ The extraoral portion of the surgery is similar to neonates and infants, except
that the initial incision migrates lower with increasing age to nearly 1 in.
below the mandibular border in skeletal maturity.

■ To complete intraoral access, be certain the patient has full muscular
relaxation, and place a bite block on the contralateral side.
■ Incise the buccal mucosa with a cuff to the attached gingiva near the first
molar, extending the incision vertically to immediately below the maxillary
occlusal plane.
■ Achieve a subperiosteal plane of dissection; then skeletonize the soft tissue
from the ramus of the mandible on both the buccal and lingual aspects.
■ On the medial aspect of the ramus, identify the lingula (TECH FIG 3).
■ If the extraoral component was performed first, connect the dissection,
creating a single surgical pocket.
■ For those less familiar with the dissection, the intraoral component may be
performed first, so that finding the proper plane from the extraoral approach
is facilitated.
■ Mark the vertical portion of the osteotomy as described above.
■ Under direct visualization, mark the horizontal limb of the inverted L above
the lingula and connect to the markings of the vertical limb.
■ Complete the vertical osteotomy with the sagittal saw.
■ The horizontal osteotomy remains incomplete (save the posterior cortex near
the vertical-horizontal junction).
■ The device can be positioned (as in earlier description) with turning arm
placed either anterior or posterior.
■ Affix device to mandible with self-drilling screws (use the above description
for details).

TECH FIG 3 • Surgical view for intraoral inverted L
osteotomy.
■ Intraoral Inverted L Osteotomy
■ Skeletally mature patients undergoing orthognathic procedures may benefit
from a completely intraoral approach to the ILO.
■ Approach is through a buccal sulcus incision as mentioned in the above
section.
■ Once the mandible is skeletonized and the lingula visualized, mark the
horizontal limb above the lingula and the vertical portion posterior to the
lingula, parallel to the posterior ramal border (TECH FIG 4).
■ The horizontal osteotomy is completed with the reciprocating saw, whereas
the vertical limb is cut with a fan blade oscillating saw.
TECH FIG 4 • Lingual view illustrates relationship of
osteotomy to lingula.
PEARLS AND PITFALLS

Mandibular
anatomy
■ Complete understanding of mandibular anatomy is critical to
perform a safe and effective inverted L osteotomy. This
includes the location of the lingula and tooth buds/teeth.
Facial nerve
anatomy
■ Intimate knowledge of craniocaudal and depth location of
the marginal mandibular nerve is important in accessing the
mandible for extraoral inverted L osteotomy.
Condyle and
proximal segment
relationship
■ Prevention of shear fractures in the proximal segment—
which inadvertently separate the condyle from the ramus—is
key to a successful inverted L osteotomy.
Changes in soft
tissue and bone
anatomy with
growth
■ There are notable differences in marginal mandibular nerve
position, bone anatomy and strength, in the growing
craniofacial skeleton.
POSTOPERATIVE CARE
■ Immediate postoperative care for ILO patients will vary depending on the age
of the patient, indications for the procedure, and the type of skeletal fixation
utilized.
■ Neonates/infants: A mandibular distractor will be applied after the osteotomy,
by providing semirigid fixation across the osteotomy. Bacitracin ointment is
applied to the device exit site. Incisions are covered with Steri-Strips. During
distraction, the patient is fed through an NG tube and kept intubated for a few
days to allow the airway to improve. Timing of extubation is determined by
the surgeon in concert with the multidisciplinary team.
■ Children: At this age, patients are often extubated immediately after surgery,
by virtue of the fact that they have a tracheostomy or are capable of protecting
their airways. Incision care is similar to neonates.
■ Skeletally mature patients: Patients are often undergoing orthognathic
surgery, in which case they will have some form of maxilla-mandibular
fixation (MMF) post-surgery. Most of these patients will have an intraoral
incision, which requires a Peridex rinse daily.
COMPLICATIONS
■ Marginal mandibular nerve—Temporary neuropraxia is common; permanent
palsy is possible when performing extraoral ILO.
■ Inferior alveolar nerve injury—Placement of the vertical or horizontal portion

of the osteotomy in proximity to the lingula can lead to inadvertent damage to
the nerve by the reciprocating, sagittal saw, or Sonopet.
■ Tooth bud injury—Anterior displacement of the vertical portion of the
osteotomy in neonates/children may result in damage to developing dental
structures.
■ Undesired fracture—Neonates are especially susceptible to this occurrence as
their mandibles are thin. Inadvertent fracture of the coronoid process will not
hamper the outcome; however, separation of the condyle from the proximal
segment will cause failure of the operation and requires immediate correction,
by plating the disjoined segments with resorbing fixation in neonates and
titanium in older children.
■ Infection—Extraoral ILO with distractor placement can result in
cellulitis/purulence at the device skin exit site and can generally be treated with
antibiotics/irrigation. In most cases, return to the operating room is not
required.
REFERENCES
1. Chen W, Davidson EH, MacIsaac ZM, Kumar A. Mapping the mandibular
lingula in Pierre Robin sequence: a guide to the inverted-L osteotomy. J
Craniofac Surg. 2015;26(6 suppl):1847-1852.
2. Hwang TJ, Hsu SC, Huang QF, Guo MK. Age changes in location of
mandibular foramen. Zhonghua Ya Yi Xue Hui Za Zhi. 1990;9(3):98-103.
3. Paryab M, Ahmadyar M. Locating mandibular foramen in children with
mandibular retrognathism in mixed dentition. J Dent Res Dent Clin Dent
Prospects. 2015;9(2 suppl):66-71.

39
CHAPTER
Intraoral Vertical Ramus
Osteotomy of the Mandible
Deepak G. Krishnan and Haithem M. Elhadi Babiker
DEFINITION
■ The vertical ramus osteotomy of the mandible performed intraorally is a
popular and simple technique used to achieve mandibular setback in patients
with prognathism or asymmetry.
■ A variation of this technique was described first by Limberg in 1925.1 Many
others have attempted to modify his approach and found that it can be
performed intraorally and can be used to reduce the horizontally excessive
mandibular ramus.
■ A version of the vertical ramus osteotomy performed through a neck incision
was popularized by Caldwell and Letterman in the 1950s.2
■ In 1968, Winstanley performed the first intraoral vertical ramus osteotomy
(IVRO).3 It was the work of Hall and McKenna4 in the 1970s that simplified,
refined, and thus popularized the procedure.
ANATOMY
■ The mandible is the horseshoe-shaped bone that forms the structural
foundation of the lower third of the face. It is the only movable bone of the
skull, articulating with the temporal bones at the temporomandibular joints.
■ It consists of a horizontal curved body and two broad and oblong rami
projecting upward. The alveolar processes of the mandible house and support
the mandibular teeth.
■ The inferior alveolar nerve enters the mandibular foramen on the medial
surface of the ramus near its center.
■ It then runs downward and forward within the body of the mandible and exits
at the mental foramen, which is located on the external surface midway

between the alveolar process and the lower border, in the interval between the
premolar teeth.
FIG 1 • A. Facial aspect of mandible demonstrating a
small anatomic elevation in bone referred to as
antilingula. B. Lingual aspect of mandible
demonstrating position of lingula and the mandibular
foramen.
■ The anteromedial margin of the mandibular foramen is guarded by an upward
tonguelike projection, the lingula.
■ Along its course, the inferior alveolar nerve innervates the mandibular teeth
and associated soft tissue and terminates as the mental nerve, which supplies
sensation to the skin and mucous membrane of the lower lip and chin.
■ The muscles of mastication directly attach to the surface of the mandible. The
masseter and medial pterygoid muscles attach to the lateral and medial surfaces
of the ramus, respectively.
■ These two muscles together form the pterygomasseteric sling, which
straddles the mandibular ramus.
■ The temporalis muscle reaches into the external oblique ridge along the rami

through its tendons and helps with opening and closing of the jaw.
■ The lingual nerve, before reaching the tongue, comes in close contact with the
inner surface of the alveolar border of the mandible in close proximity to the
mandibular third molar tooth.
■ An antilingula or the antilingular prominence is a lateral bony protuberance
that approximately corresponds to the lingula and the entry of the inferior
alveolar nerve into its canal, on the medial aspect of the mandible (FIG 1).
■ This is a useful but not an entirely reliable landmark in this technique.
■ The position of the lingula is posteroinferior relative to the position of the
antilingula. This has been substantiated in cadaver studies.5
PATHOGENESIS AND NATURAL HISTORY
■ Mandibular prognathism is a condition wherein the mandible is positioned
anterior to the maxilla resulting in a malocclusion.
■ In the NHANES study (1989–1994), 0.3% of the US population was reported
to have mandibular prognathism severe enough to require orthodontic-surgical
treatment.
■ About 14% of the youth in the United States have a class III malocclusion.
Roughly a quarter of these patients have an isolated mandibular prognathism,
whereas the remaining three-quarters have a combination of maxillary
deficiency in addition to mandibular protrusion.
■ Often, a midface deficiency is wrongly diagnosed as mandibular
prognathism, whereas in reality upon cephalometric investigation, the
mandibular position may be normal.
■ Mandibular prognathism causes aesthetic concerns, in addition to chewing and
speaking difficulties, leading patients to seek surgical treatment at a younger
age.
■ In cases of severe mandibular prognathism, bimaxillary surgery is the
preferred method of treatment (mandibular setback combined with maxillary
advancement).
■ This is because excessive mandibular setback may result in obstructive sleep
apnea and is also subject to higher rates of relapse.
■ Mandibular growth can occur until late teens and early 20s in young men and
several years past menarche in women.
■ Surgery should be deferred until there is proof of growth cessation.
PATIENT HISTORY AND PHYSICAL FINDINGS

■ Patients typically present during the teenage years.
■ The main functional complaints related to chewing and deglutition, difficulty
with speech and enunciation, and TMJ dysfunction in addition to the aesthetic
concerns. Often, the malocclusion also presents as an open bite.
■ The patients are usually first seen by an orthodontist and eventually referred to
a surgeon when ready for surgery.
■ Orthodontic treatment is usually undertaken for about a year and serves to
align the teeth in the dental arches and remove any dental compensation.
■ Surgery is undertaken when the patient reaches skeletal maturity (girls 16–18
years, boys 18–20 years).
■ When working up for an IVRO, it is useful to note the functional status of the
patient’s temporomandibular joints (TMJs). The IVRO may be preferred in
patients with TMJ dysfunction over a bilateral sagittal split osteotomy (BSSO),
because the condyle seats itself passively in an unloaded position during
healing.
■ Patients with a V-shaped mandible as assessed from a norma basalis are
probably better candidates for an IVRO as opposed to a BSSO for a
mandibular setback (FIG 2).
■ The preoperative workup includes records that replicate the relationship of the
jaws to the skull base, and model surgery to fabricate the surgical splints.
■ Unlike in a BSSO, a splint may not be required in an IVRO in patients with
stable occlusion and orthodontic setup.
■ In the case of double-jaw surgery (Le Fort I advancement combined with a
mandibular procedure) for severe class III malocclusion, however, two
splints are made—an intermediate splint used intraoperatively to position the
maxilla in its final position and a final splint to position the mandible.
IMAGING
■ Lateral cephalometric radiographs are obtained for cephalometric analysis.
■ Panoramic radiographs are obtained to determine the presence and location of
mandibular third molar teeth, level of the inferior alveolar canal.
■ A submentovertex view of the mandible could be used in determining its shape
and flare.
■ A CT scan may be obtained, in case virtual surgical planning is undertaken in
lieu of traditional model surgery.
DIFFERENTIAL DIAGNOSIS

■ Class III skeletal relationship can be due to mandibular prognathism, maxillary
hypoplasia, or a combination of both.
■ Accurate diagnosis is important to determine the appropriate surgery.
■ The diagnosis is confirmed by detailed clinical evaluation combined with
cephalometric analysis.
FIG 2 • U-shaped (A) and V-shaped (B) mandibles as
seen in norma basalis. (Courtesy of Myron R. Tucker,
DDS, Scientific Liaison, OsteoScience Foundation.)
■ Acromegaly and pituitary hyperactivity should be suspected in mandibular
prognathism that presents later in life, and appropriate workup is indicated.
■ Unilateral hyperplasia of the mandible can cause an asymmetric prognathism
and malocclusion. The surgeon should rule out a neoplasm of the mandibular
condylar structures in these cases. Unilateral condylar hyperplasia is an
idiopathic, rare condition that can also cause an asymmetric mandibular
prognathism.
NONOPERATIVE MANAGEMENT
■ Mild class III malocclusion can be treated with orthodontic management
alone.
■ True skeletal class III relationships and asymmetries can be treated only by
surgical intervention, however.
SURGICAL MANAGEMENT

■ The IVRO setback procedure is usually performed during the late teenage
years after the patients have reached skeletal maturity.
■ The main objective of the operation is to reduce the horizontal mandibular
width that contributes to the prognathism and to reposition the mandible
posteriorly to meet the maxilla in a normal class I relationship.
Preoperative Planning
■ The risks, benefits, and complications are discussed with the patient on the day
of surgery.
■ Preoperative photos are obtained for documentation purposes.
■ Lateral cephalometric radiographs are obtained for cephalometric analysis.
■ Panoramic radiographs are obtained to determine the presence and location of
mandibular third molar teeth, level of the inferior alveolar canal.
■ A CT scan may be obtained, in case virtual surgical planning is undertaken in
lieu of traditional model surgery.
Positioning
■ The patient is positioned supine with the arms tucked.
■ He or she is intubated nasally, and the endotracheal tube is secured
appropriately to the forehead.
■ IVRO setback is performed through an intraoral approach.
T E C H N I Q U E S
■ Exposure
■ Cleanse the oral cavity with chlorhexidine or an equivalent antiseptic mouth-
rinse, and place a throat pack.
■ Inject a local anesthetic containing a vasoconstrictor to infiltrate the area of
dissection.
■ Access to the ramus is obtained through a lateral approach.
■ A ramus-exposing incision is made from the level of the occlusal plane to
the level of the first molar tooth (TECH FIG 1A). An adequate cuff of
gingiva (2 to 4 mm) is maintained adjacent to the molar teeth for relaxed
wound closure.

■ It is important to make this incision in that appropriate position. If the
incision is too lateral, it can heal causing a scar band that can cause a
pocket that traps food and makes hygiene difficult to maintain, especially
during the healing phase.
■ A full-thickness mucoperiosteal flap is elevated, exposing the entire lateral
border of the ramus of the mandible. This extends from the inferior border of
the mandible to the sigmoid notch in that plane.
■ The periosteum along the posterior border of the mandible is left
unreleased. There is no exposure on the medial aspect of the mandible.
■ A Bauer retractor is placed in the sigmoid notch, and a second Bauer
retractor is placed at the inferior border.
■ A variant technique uses a Levasseur-Merrill retractor, which is placed at the
posterior border. This, however, requires stripping the periosteum from the
posterior border of the mandible (TECH FIG 1B).
TECH FIG 1 • A. Appropriate incision for exposure of
the mandible. B. Placement of appropriate retractors
and exposure of the lateral ramus.
■ Intraoral Osteotomies
■ This is a two-step procedure—first a superior osteotomy and then an inferior
osteotomy (TECH FIG 2).
Superior Osteotomy
■ The exposed lateral border is inspected and the antilingular prominence is

identified.
■ The antilingula is not always a reliable indicator of where the lingula
would coincide medially. However, staying posterior and inferior to the
antilingula places the cuts in a safe zone, avoiding injury to the inferior
alveolar neurovascular bundle.
■ Using an oscillating saw with an 11.5- × 7-mm blade (TECH FIG 3A), the
surgeon makes an osteotomy outline approximately a centimeter in front of
the posterior border of the mandible.

TECH FIG 2 • Lateral (A) and medial (B) views of the
two-step osteotomy. Appropriate two-step osteotomy
ensures optimal medial pterygoid attachment.

■ A curved Freer elevator is placed at the posterior border to approximately
measure this distance and to ensure that the marking is in the appropriate
position (TECH FIG 3B).
■ Cuts made anterior to the antilingula or too close to it will damage the
mandibular canal and its contents.
■ Following confirmation of the position of the cut, the oscillating saw is now
used to complete the osteotomy (TECH FIG 3C).
■ The cutting edge of the blade is first directed toward the sigmoid notch.
■ Saw movement should never be forced and is directed with a gentle, back
and forth rotational movement of the shaft.
■ The bone is thinner as the blade approaches the sigmoid notch, and its
depth of insertion should be adjusted accordingly (TECH FIG 3D).
Inferior Osteotomy
■ The upper Bauer retractor is removed to make the access easier for the
inferior part of the osteotomy.
■ The inferior cut is made with the same saw blade by directing it inferiorly
within the same cut.
■ The osteotomy is performed anteriorly and inferiorly below the antilingula,
aiming away from the posterior border. This provides a robust proximal
segment on completion of the osteotomy.
Mandible Repositioning
■ After confirming that the osteotomy is complete along the entire ramus, the
mandible is positioned into a class I relationship by separating the proximal
segment and moving it lateral to the distal segment (TECH FIG 4A). An
occlusal splint can be used if needed.
■ Final occlusion is established with maxillomandibular fixation (MMF).
■ Trim the proximal segment with a round bur to allow passive overlap of the
segments.
■ Though the IVRO is usually a bilateral procedure, it is occasionally
performed only unilaterally to correct minor asymmetries and setbacks.
When performed bilaterally, the same steps are repeated on the contralateral
side.
■ Following ramus osteotomies bilaterally, irrigate the wounds, and suction the
oral cavity; remove the throat pack, and establish the planned occlusion, and
secure MMF.

■ Inspect both osteotomies for lateral overlap and passive positioning of the
proximal segment. If the tip of this segment can be palpated in the
submandibular area, it needs to be trimmed (TECH FIG 4B).
■ The wounds are closed with continuous 3-0 chromic in a watertight fashion.
TECH FIG 3 • A. Oscillating saw with an 11.5- × 7-mm
blade. B. A curved Freer elevator is placed at the
posterior border of the mandible to approximately
measure the distance to ensure the osteotomy is in
the appropriate position. C. Oscillating saw in position

for the osteotomy. D. The bone is thinner at the
sigmoid notch.
TECH FIG 4 • A. When the osteotomy is completed,
the proximal segment of the mandible is separated
and moved laterally to overlap the distal segment. B. If
the proximal segment is too prominent and is palpable
in the submandibular area, it is trimmed.
PEARLS AND PITFALLS
Physical
findings
■ Class III skeletal relationship can be caused by mandibular
prognathism, maxillary hypoplasia, or a combination of both. Accurate
diagnosis is critical to determine the appropriate surgery to correct the
deformity.
■ V-shaped mandibles are better suited for setback using the IVRO
technique than are U-shaped mandibles (see FIG 2).
■ IVRO is better suited for mandibular setbacks in patients with pre-
existing TMJ symptoms.
■ IVRO has limited application in mandibular advancements.
Technique
■ Leaving an insufficient cuff of gingiva when making the incision will
lead to difficulty suturing and possible wound dehiscence.

■ Too thick a cuff produces a scar band and a pocket for food impaction.
■ Marking the osteotomy position behind the antilingula is prudent to
avoid the mandibular canal during osteotomy.
■ Alternatively, a 30-degree endoscope can be inserted into the wound to
inspect the position of the planned osteotomy.
■ The saw should be lightly applied and never forced.
■ The saw blade may be too long in areas of thinner mandible when
approaching the sigmoid notch.
■ If the 11.5- × 7-mm blade is too short to complete the osteotomy, there
is a good chance that the planned osteotomy is positioned too far
anteriorly and likely in the mandibular canal.
■ IVRO should not cause mandibular nerve hypoesthesia. If it does, the
cuts violated the canal.
■ Directing the saw anteriorly and inferiorly while making the cut
inferior to the antilingular prominence ensures a robust proximal
segment with a good amount of medial pterygoid attachment.
■ Angled instruments can be used to rigidly fixate IVRO segments. This
is seldom utilized and is generally unnecessary.
POSTOPERATIVE CARE
■ The patient is generally extubated in the operating room and taken to recovery
breathing spontaneously. However, if there are any airway concerns, the patient
may be left intubated and taken to the ICU.
■ MMF is left in place for anywhere from a few days to a few weeks, depending
on operator preference.
■ Most surgeons prefer MMF for at least a few days following the procedure.6
■ Light guiding elastics may be required to help train the occlusion after
removal of rigid interdental wiring.
OUTCOMES
■ Although IVRO is a reliable technique for mandibular setback and closure of
small open bites, it can occasionally be used for mandibular lengthening or
counterclockwise rotation of the mandible.
■ Stripping of masseter and medial pterygoid can lead to a 14% incidence of
open bite at the time of MMF release. This was described as a result of
“condylar sag.”
■ In general, up to 10 mm of mandibular setback is possible with an IVRO. The
magnitude of the setback should not exceed the width of the medial pterygoid

attachment on the proximal segment.
COMPLICATIONS
■ Risks from an IVRO include injury to the inferior alveolar and/or lingual
nerves, condylar sagging and malpositioning, relapse, bleeding including
pseudoaneurysms, infection, and fibrous union.
■ Direct injury to the inferior alveolar nerve may occur while making the
osteotomies, but an indirect injury can also occur if the proximal segment slips
medially and impinges on the nerve bundle.
■ Condylar sagging occurs when the muscles are excessively stripped or when
the osteotomies create a small proximal segment.
■ Significant bleeding can occur if the blade injures the masseteric artery within
the sigmoid notch, or larger vessels like the internal maxillary artery or its
branches in the medial ramus area. Other potential sources of bleeding are the
facial artery and the retromandibular vein. Bleeding can be prevented by
careful surgical technique and protection of the soft tissue.
■ Wound dehiscence and/or infection are a rare complication and are most often
related to poor oral hygiene.
REFERENCES
1. Limberg A. Treatment of the open bite by means of plastic oblique osteotomy
of the ascending rami of the mandible. Dent Cosmos. 1925;67:1191.
2. Caldwell JB, Letterman GS. Vertical osteotomy in the mandibular rami for
correction of prognathism. J Oral Surg. 1954;12:185.
3. Winstanley RP. Subcondylar osteotomy of the mandible and the intraoral
approach. Br J Oral Surg. 1968;6:134.
4. Hall HD, McKenna SJ. Further refinement and evaluation of intraoral vertical
ramus osteotomy. J Oral Maxillofac Surg. 1987;45:684.
5. Aziz SA, Dorfman BJ, Ziccardi VB, Janal M. Accuracy of using the
antilingula as a sole determinant of vertical ramus osteotomy position. J Oral
Maxillofac Surg. 2007;65:859.
6. Hara S, Mitsugi M, Tatemoto Y. Variation of plate fixation for mandibular
advancement with intraoral vertical ramus osteotomy using endoscopically
assisted intraoral rigid or semi-rigid internal fixation. Case series study:
postoperative condylar seating control for mandibular advancement. J
Craniomaxillofac Surg. 2015;43:2015.

40
CHAPTER
Internal Mandibular
Distraction
Michael Alperovich and Roberto L. Flores
DEFINITION
■ Mandibular hypoplasia or an underprojected and diminutive mandible can
have functional consequences including tongue-based airway obstruction, sleep
apnea, reduced intraincisal opening, and malocclusion.1
■ Mandibular hypoplasia can also result in facial disharmony and distressing
aesthetic concerns.2
ANATOMY
■ The normal mandible can be divided into two, symmetric halves from the
midpoint of the mandibular symphysis.
■ Each hemimandible can be subdivided into several segments: the
parasymphysis, body, angle, ramus, and condyle (FIG 1).
■ The symphysis is the midline of the mandible. The parasymphysis is a region
bound by the roots of the mandibular canines. The mandibular body extends
from the mandibular canine roots to the mandibular third molar.
■ The mandibular angle is the triangular region that represents the junction
between the mandibular body and ramus. The mandibular ramus is the vertical
component of the mandible extending from the angle to the sigmoid notch.
■ The mandibular condyle is the portion of posterior mandible extending
cephalad from the sigmoid notch and articulating with the temporomandibular
joint.
■ The Pruzansky-Kaban classification is widely used to define mandibular
deficiency and is most commonly used to classify craniofacial microsomia
severity (FIG 2).3

FIG 1 • Schematic demonstrating the anatomic
subdivisions of the hemimandible.
■ A type I mandible features hypoplasia of the mandibular ramus and condyle
with a normal mandible morphology.
■ A type IIA mandible features reduction in the volume of the body, ramus, and
condyle but has a preserved temporomandibular joint.
■ A type IIB mandible features reduction in the volume of the body, ramus, and
condyle, as well as medial inclination of the ramus displacing the condyle
from the glenoid fossa.
■ A type III mandible features severe ramus reduction or complete absence
with no evidence of a temporomandibular joint.
PATHOGENESIS
■ Mandibular hypoplasia has congenital and acquired causes, with congenital
causes predominating.
■ Craniofacial microsomia and Pierre Robin sequence are the most common
congenital causes followed by Treacher Collins syndrome.4
PATIENT HISTORY AND PHYSICAL FINDINGS

■ Patients with mandibular hypoplasia secondary to craniofacial microsomia can
have malformations in other structures derived from the first and second
branchial arches, including the external ear; midface (zygoma and orbit); facial
nerve, with the marginal mandibular nerve most commonly affected; muscles
of mastication; as well as soft tissue deficiencies.
■ Unilateral craniofacial microsomia patients will present with asymmetric
facies and an upward occlusal cant on the affected side. The ramus is
predominantly affected in craniofacial microsomia.
■ In addition to a hypoplastic mandible, Pierre Robin sequence patients fulfill
the triad of micrognathia, glossoptosis, and airway obstruction.
Retropositioning of the tongue is responsible for airway obstruction and
increased work of breathing. Most patients will also present with a U-shaped
cleft palate.
■ Mandibular hypoplasia in Pierre Robin sequence patients is characterized by
bilateral and symmetric mandibular hypoplasia most severely affecting the
body.
■ Up to 50% of Pierre Robin sequence patients have an associated syndrome,
with Stickler syndrome as the most common.5
■ Pierre Robin sequence patients may present with failure to thrive, feeding
difficulties, developmental delay, reflux, carbon dioxide retention, heart failure,
and desaturations most pronounced in the supine position.
FIG 2 • Pruzansky-Kaban classification of mandibular
deficiency.
IMAGING
■ Preoperative imaging should include a craniofacial CT to evaluate mandibular
morphology including the TMJ and for planning the ideal vector for

mandibular distraction (FIG 3).
■ A Panorex may be obtained to evaluate occlusion and identify the location of
the unerupted tooth buds but is often not necessary if a CT image is obtained.
■ If applicable, dental study models should be obtained for future orthodontic
splint fabrication (ie, correction of any resulting open bite and molding the
newly generated bone).
■ A polysomnogram should be performed to confirm the presence and etiology
of sleep apnea.
■ Bronchoscopy and endoscopy should be performed to identify other potential
causes of obstruction.
DIFFERENTIAL DIAGNOSIS
■ Causes of airway obstruction in addition to retrognathia include the following:
■ Adenoid/tonsillar hypertrophy
■ Bronchial stenosis
■ Bronchomalacia
■ Central sleep apnea
■ Laryngomalacia
■ Subglottic narrowing
■ Tracheomalacia
NONOPERATIVE MANAGEMENT
There is no nonoperative management for mandibular hypoplasia. Airway
compromise associated with retrognathia can be managed through conservative
and invasive techniques.
■ Initial conservative techniques include the following:
■ Prone positioning
■ Supplemental oxygen

FIG 3 • Representative craniofacial CT of a patient with
Pierre Robin sequence and mandibular body deficiency
prior to mandibular distraction.
■ Nasopharyngeal tubes
■ Continuous positive airway pressure
■ Interventional techniques include the following:
■ Intubation
■ Tracheostomy
■ Tongue-lip adhesion
■ Mandibular distraction osteogenesis
■ Intubation stabilizes airway management and can be temporizing prior to more
definitive approaches.
■ Tracheostomy will provide a definitive airway; however, the procedure can
lead to tracheomalacia, chronic pneumonia, laryngeal stenosis, complex
nursing care needs, and impaired psychosocial development.6
■ Tongue-lip adhesion provides less relief to the obstructed airway when
compared to mandibular distraction. It has been associated with lower oxygen
saturation levels and higher apnea-hypopnea indices postoperatively, as well as
higher conversion rates to tracheostomy.7
SURGICAL MANAGEMENT
Preoperative Planning
■ Mandibular distraction has functional indications that include improving lower
jaw position and morphology, correcting tongue-based airway obstruction and
obstructive sleep apnea, obviating the need for tracheostomy, optimizing the
airway for decannulation, treating temporomandibular joint ankylosis, and
lengthening a shortened mandible due to trauma or extirpative surgery.
■ Mandibular distraction has aesthetic indications to treat facial disharmony or
augment a hypoplastic mandible in the absence of a functional deficit.
■ If neonatal distraction is considered, patients need to be evaluated by
otolaryngology, neonatology, genetics, pulmonology, and a pediatrician prior to
surgery.
■ If the patient is an older child (non-neonate) or adult, consultation and
partnership with a craniofacial orthodontist are recommended.

■ In cases in which airway obstruction is a concern, bronchoscopy and
laryngoscopy must be performed by an otolaryngologist to rule out secondary
airway anomalies (tracheomalacia, subglottic stenosis, tracheal rings).8
■ Craniofacial CT is used preoperatively to evaluate the mandibular shape, tooth
bud position, and course of the inferior alveolar nerve and to plan the
distraction vector.
■ Polysomnography preoperatively can help differentiate between central and
obstructive sleep apnea, establish a baseline apnea-hypopnea index, and
confirm retention of carbon dioxide.9
Positioning
■ The patient is positioned supine, endotracheally intubated, and placed on a
horseshoe for maximal maneuverability of the craniofacial region.
■ The entire face and neck are prepped into the field.
Approach
■ Extraoral and intraoral approaches have been described. Only the extraoral
approach will be described below.
■ External and internal distraction devices are used, but this chapter will
exclusively focus on internal distraction devices.10
T E C H N I Q U E S
■ Internal Mandibular Distractor Placement
■ Mark a Risdon incision parallel and 2 cm inferior to the mandibular body.
This distance can be shortened to 1 cm in neonates (FIG 4).
■ Inject weight-based local anesthetic along the planned skin incision; avoid
anesthetic toxicity in the pediatric population.
■ Incision and dissection are extended sharply through skin, subcutaneous
tissue, and platysma. Superior and inferior platysmal flaps are raised to
provide a tension-free, layered final skin closure.
■ Be vigilant to remain inferior to the marginal mandibular nerve; if the nerve
is identified during dissection, it is carefully protected.
■ Preoperative craniofacial CT imaging informs the type and location of the

osteotomy as well as the distraction vector. These factors influence the type
of exposure required. Although there is no consensus on the optimal
osteotomy type, the most popular are body, ramus, inverted L, and transport
distraction.
■ The periosteum is identified and incised along the inferior border of the
mandibular body. Subperiosteal dissection is extended across the entire
buccal surface of the mandible from the proximal ramus through the distal
body. This includes exposure to the coronoid and sigmoid notch if an
inverted-L osteotomy is considered (TECH FIG 1A).
FIG 4 • Risdon incision drawn on a neonate. The chin
is to the left. The ear is superior and to the right. Note
the incision may be drawn 1 cm below the mandibular
border in neonates.
■ If the mandibular deficiency is predominant in the body, the inverted-L
osteotomy is favored. Alternatively, a transverse mandibular body,
mandibular angle, or transverse ramus osteotomy can also be used (TECH
FIG 1B).
■ For the inverted-L osteotomy, a near-complete vertical ramus osteotomy is
performed from the sigmoid notch to the antegonial notch.
Coronoidectomy is performed using a sagittal saw or Kerrison punch
(TECH FIG 1C).

■ A full corticotomy is performed over the buccal surface and the cephalad
and caudal margins of the lingual surface. A bony bridge in the center of
the lingual surface of the mandible is maintained to preserve mandibular
alignment during distractor placement (TECH FIG 1D).
■ If the mandibular deficiency is predominant in the ramus as is commonly
seen in Treacher Collins syndrome, a vertical distraction vector is utilized.
This osteotomy may risk injury to the temporomandibular joint and cause
ankylosis of the joint.
■ A semiburied distraction device is affixed to the lower border of the
mandible (if a horizontal vector is used) with the activation arm exiting
behind the earlobe. The maximum distraction length is determined on a case-
by-case basis with 20 mm favored in infants and 30 mm in older children or
for cases of severe mandibular deficiency.
■ High-profile screws are used to secure the distraction device for ease of
removal after consolidation (TECH FIG 1E).
■ After the device is secured, it is activated for several millimeters to confirm
the absence of resistance. The lingual surface osteotomy is often completed
with device activation alone. Complete osteotomy is confirmed using an
osteotome or suction cannula.
■ Prior to soft tissue closure, the bony edges are returned to apposition and any
intervening soft tissue is removed.
■ The platysma muscle is reapproximated using resorbable suture followed by
closure of the dermis and epidermis.

TECH FIG 1 • A. Wide subperiosteal dissection is
needed to perform an inverted “L” osteotomy. This
includes the distal body, the angle, the ascending
ramus, and sigmoid notch. If a mandibular body
osteotomy is planned, less undermining is required. B.
Inverted “L” osteotomy is drawn. Note the vertical
osteotomy extends from the sigmoid notch to the

antegonial notch. C. Coronoidectomy can be
performed with a sagittal saw or Kerrison punch. D.
The inverted-L osteotomy is made to near completion
with preservation of the lingual cortex just superior to
the mandibular border and inferior to the sigmoid
notch. This narrow bony bridge will maintain anatomic
bony position, while the hardware is placed.
Completion osteotomy is performed after the
hardware is secured. E. High-profile screws may be
used to facilitate placement and removal of hardware.
■ Internal Mandibular Distractor Removal
■ Remove the distraction device 8 weeks following consolidation.
■ Use the prior Risdon incision to access the device while remaining vigilant
of the course of the marginal mandibular nerve and raising platysmal flaps to
maintain a tension-free skin closure.
■ Assess the integrity of the generated bone across the distracted segment by
visual inspection and manual palpation.
■ Removing the device is easiest when the minimum number of high-profile
screws is used initially.
■ As with device placement, reapproximate the platysma muscle first followed
by the dermis and epidermis.
PEARLS AND PITFALLS
Incision
■ At the start of the procedure, raise supraplatysmal skin flaps to close
the platysma muscle as a deeper layer separate from the skin.
Removing tension from the skin closure can improve long-term scar
appearance.
Warning
■ In neonatal distraction, the mandibular bone can be very soft. Gently
incise the periosteum with a 15 blade or when using an elevator as
both instruments can damage the outer cortex.

Technique
■ If using an inverted-L osteotomy, the inferior mandibular osteotomy
should be planned posterior to the antegonial notch to avoid tooth
buds.
Implant
burden
■ Minimize the number of high-profile screws placed to secure the
distractor (four per side) for easier distractor removal after
consolidation.
Theory
■ Premature consolidation is more commonly a result of incomplete
lingual corticotomy. Test the distractor, and confirm the absence of
any resistance before completion of surgery.
Therapeutic
success
■ When performing mandibular distraction to improve the airway,
serial cephalograms and a repeat polysomnogram should be
performed 3 months after completion of distraction.
POSTOPERATIVE CARE
■ A latency period of 5 days is routinely used followed by activation at a rate of
1 mm/d.
■ Serial cephalograms are used to monitor progress with device removal
following 8 weeks of consolidation.
■ If distraction has been performed to relieve airway obstruction, a follow-up
polysomnogram should be performed.
■ In neonatal patients, mandibular distraction can prevent tracheostomy. In
chronically tracheostomy-dependent patients, mandibular distraction can result
in decannulation of the tracheostomy.
■ Overcorrection of the mandible is advised when distraction is performed in a
skeletally immature patient with some studies advocating 40% to 50%
overcorrection.11
OUTCOMES
■ Mandibular distraction has a success rate of 92% to 100%.12
■ Risk factors for failure of mandibular distraction in Pierre Robin sequence
include GERD, need for Nissen fundoplication, and absence of a cleft palate.12
COMPLICATIONS
■ Major complications
■ Marginal mandibular nerve injury
■ Inferior alveolar nerve injury
■ Tooth bud injury

■ Temporomandibular joint ankylosis
■ Death
■ Moderate complications
■ Device failure or fracture
■ Premature consolidation/incomplete osteotomy
■ Device exposure
■ Pin dislodgment
■ Fibrous nonunion
■ Dentigerous cysts secondary to distraction across a tooth follicle
■ Minor complications
■ Marginal mandibular nerve neurapraxia
■ Pin-tract soft tissue infection
■ Unfavorable scars
REFERENCES
1. Singh DJ, Glick PH, Bartlett SP. Mandibular deformities: single-vector
distraction techniques for a multivector problem. J Craniofac Surg.
2009;20(5):1468-1472.
2. Bertin H, Mercier J, Cohen A, et al. Surgical correction of mandibular
hypoplasia in hemifacial microsomia: a retrospective study in 39 patients. J
Craniomaxillofac Surg. 2017;45(6):1031-1038.
3. Mulliken JB, Kaban LB. Analysis and treatment of hemifacial microsomia in
childhood. Clin Plast Surg. 1987;14(1):91-100.
4. Ow AT, Cheung LK. Meta-analysis of mandibular distraction osteogenesis:
clinical applications and functional outcomes. Plast Reconstr Surg.
2008;121(3):54e-69e.
5. van den Elzen AP, Semmekrot BA, et al. Diagnosis and treatment of the Pierre
Robin sequence: results of a retrospective clinical study and review of the
literature. Eur J Pediatr. 2001;160(1):47-53.
6. Gilony D, Gilboa D, Blumstein T, et al. Effects of tracheostomy on well-being
and body-image perceptions. Otolaryngol Head Neck Surg. 2005;133(3):366-
371.
7. Flores RL, Tholpady SS, Sati S, et al. The surgical correction of Pierre Robin
sequence: mandibular distraction osteogenesis versus tongue-lip adhesion.
Plast Reconstr Surg. 2014;133(6):1433-1439.
8. Flores RL, Murage K, Tholpady SS. Incidence of concomitant airway
anomalies when using the University of California, Los Angeles, protocol for

neonatal mandibular distraction. Plast Reconstr Surg. 2013;132(6):1071e-
1072e.
9. Khayat A, Bin-Hassan S, Al-Saleh S. Polysomnographic findings in infants
with Pierre Robin sequence. Ann Thorac Med. 2017;12(1):
25-29.
10. McCarthy JG, Schreiber J, Karp N, et al. Lengthening the human mandible
by gradual distraction. Plast Reconstr Surg. 1992;89(1):1-8.
11. Weichman KE, Jacobs J, Patel P, et al. Early distraction for mild to moderate
unilateral craniofacial microsomia: long-term follow-up, outcomes, and
recommendations. Plast Reconstr Surg. 2017;139(4):
941e-953e.
12. Murage KP, Tholpady SS, Friel M, et al. Outcomes analysis of mandibular
distraction osteogenesis for the treatment of Pierre Robin sequence. Plast
Reconstr Surg. 2013;132(2):419-421.

41
CHAPTER
External Mandibular
Distraction for Micrognathia
Haithem M. Elhadi Babiker
DEFINITION
■ Distraction osteogenesis of the craniofacial skeleton was first attempted by
Snyder in 1972.
■ In 1991, McCarthy et al. published their experience with mandibular
distraction, popularizing the technique.1
■ Mandibular distraction osteogenesis (MDO) can be performed with either an
external or internal technique. Both techniques have been proven to be
successful and safe to lengthen the mandible.2
■ External mandibular distraction involves making a mandibular osteotomy and
applying an external device to slowly and gradually lengthen the mandible.
This technique is used to lengthen the hypoplastic mandible seen in multiple
craniofacial conditions.
ANATOMY
■ The mandible is a unique U-shaped bone with two vertical rami and a
horizontal body. It articulates with the skull at the temporomandibular joints
and is the only movable bone of the facial skeleton.
■ The inferior alveolar nerve enters the mandibular foramen on the medial
aspect of the ascending ramus and then extends within the mandibular body,
exiting at the mental foramen.
■ The lingual nerve is located medial to the ramus in close proximity to the
alveolar process near the third molar.

FIG 1 • A. CT scan showing the bilateral micrognathia in
Pierre Robin sequence (PRS). B. Patient with
hemifacial microsomia (HFM) demonstrating severe
micrognathia. C. Patient with Treacher Collins
syndrome (TCS) exhibiting severe micrognathia (both
mandibular body and ramus), and an anterior open bite.
■ Patients with Pierre Robin sequence (PRS) are characterized by a hypoplastic
mandibular body; the condyle and ramus are generally of normal size (FIG
1A).3
■ Hemifacial microsomia (HFM) is usually unilateral and is classified using a
spectrum of severities from type I to type III (FIG 1B).
■ In Treacher Collins syndrome (TCS), the hypoplasia is similar to that seen in
PRS but also includes a deep antegonial notch and downslanting mandibular
body (steep occlusal plane) associated with an open bite. Some TCS mandibles
may exhibit features similar to HFM (FIG 1C).4
■ Post-traumatic condylar fractures may also lead to mandibular hypoplasia
associated with bilateral TMJ ankylosis.
PATHOGENESIS AND HISTORY
■ Mandibular hypoplasia occurs either as an isolated condition (possibly due to
intrauterine physical growth restriction) or as part of a genetic abnormality.
■ Patients with mandibular hypoplasia present most commonly during the
neonatal period due to obstructive sleep apnea (OSA).
■ HFM is the second most common craniofacial congenital anomaly, with an
incidence of 1/3000 live births.

■ Once a child is born with mandibular micrognathia, the deformity is not
progressive.
PATIENT HISTORY AND PHYSICAL FINDINGS
■ Patients with micrognathia usually present during infancy with tongue-based
OSA, ranging from mild to very severe.2
■ The small mandible pushes on the tongue causing it to fall back and obstruct
the airway.
■ Mild cases present with noisy breathing during sleep.
■ More severe cases present with apneic episodes, cyanotic spells, and feeding
abnormalities.5
■ The child expends most of his or her energy trying to breathe, and hence has
no energy to feed.
■ Poor weight gain and failure to thrive are strong indicators of severe OSA.6
■ Neonates with severe OSA require urgent admission to the neonatal intensive
care unit (NICU) for airway stabilization.
■ Treatment modalities include prone positioning, nasopharyngeal airway,
tongue-lip adhesion, and in very severe cases, tracheostomy.
■ The main objective of mandibular distraction is to avoid a tracheostomy or to
achieve decannulation in patients with a tracheostomy.
IMAGING
■ Lateral cephalometric radiographs can be used to identify the mandibular
micrognathia. In neonates, a lateral skull x-ray at a distance of 72 in. is used to
evaluate the hypoplastic mandible.
■ The best imaging modality is a three-dimensional computed tomography (3D
CT) scan to characterize the mandible and to render a volumetric measurement
of the airway.
■ Low-dose CT scans use very low radiation (comparable to traditional
radiographs) without compromising image quality (FIG 2).
DIFFERENTIAL DIAGNOSIS
■ HFM, 1:3000 live births
■ PRS, 1:14 0007
■ TCS, 1:50 000 live births8
■ Nager syndrome
■ Post-traumatic condylar fractures

■ Stickler syndrome, velocardiofacial syndrome, fetal alcohol syndrome, trisomy
21 and 22, and Kabuki syndrome9
FIG 2 • CT scan showing mandibular micrognathia,
retropositioning of the tongue, and narrow airway stripe.
NONOPERATIVE MANAGEMENT
■ Prone and lateral decubitus positioning.
■ Nasopharyngeal airway, oxygen support, and possible tongue suture.10
■ ICU care and close monitoring is critical to prevent rapid deterioration.
■ A multidisciplinary team comprised of neonatology, otolaryngology,
pulmonology, plastic surgery, and genetics should make the decision regarding
treatment planning.
■ The infant is evaluated with a polysomnography and a
microlaryngoscopy/bronchoscopy, which examines the entire airway and
differentiates lower airway from upper airway problems.
■ Mild cases are treated with conservative measures.
SURGICAL MANAGEMENT
■ Tongue-lip adhesion is advocated by some centers with variable success.6,11
■ Tracheostomy remains the standard in very severe cases of OSA.8,11
■ Mandibular distraction is generally undertaken during the neonatal period.
■ The main objective of the operation is to lengthen the mandible, which pulls

the tongue forward to relieve the tongue-based respiratory obstruction.
■ The main steps of the surgery are as follows:
■ Intraoral incision(s) to expose the posterior aspect of the mandible.
■ Saw or bur to make a corticotomy in the ascending ramus/angle of the
mandible.
■ Self-drilling pins into the mandible proximal and distal to the corticotomy
site.
■ If a rigid external distraction (RED) device is used, place the anterior
mandibular plate and secure it to the mandible with monocortical screws.
■ Use a 5-mm osteotome to convert the corticotomy into an osteotomy to
completely liberate the mandibular segments.
■ Attach the distraction device to the pins.
• If an RED is used, attach the halo component to the anterior mandibular
plate using 25-gauge wire.
■ Close the intraoral wound in watertight fashion.
■ Wait 1 to 3 days (latency period) and then activate the device (activation
period) until the desired final position of the mandible is achieved.
■ Maintain the device in position until the new bone mineralizes (consolidation
period).
■ Remove the distraction device at the end of the consolidation period.
■ The operation is performed bilaterally in cases of PRS, TCS, and Nager
syndrome; or unilaterally in cases of HFM.
■ Selection criteria for mandibular distraction include severe mandibular
micrognathia (maxillomandibular differential of greater than 8 mm),
polysomnogram showing severe OSA, and difficulty with breathing and
feeding.8
Preoperative Planning
■ A 3D CT scan is obtained to delineate the morphology of the mandible, the
position of the inferior alveolar nerve and the teeth follicles.
■ Cephalometric measurements can be obtained from the CT scan to quantify
the mandibular hypoplasia.
Positioning
■ The patient is positioned supine.
■ The procedure is generally performed in conjunction with ENT and
pulmonology to perform the MLB and assist with intubation.

■ The procedure is done under general anesthesia.
■ The patient is intubated nasally; the endotracheal tube is sutured to the nasal
septum and secured appropriately to the forehead (FIG 3).
■ A foam donut stabilizes the head.
Approach
■ Surgery is performed through an intraoral approach with percutaneous
placement of the pins.
FIG 3 • Endotracheal tube secured to the forehead and
sutured to the nasal septum.
T E C H N I Q U E S
■ External Mandibular Distraction With Pins
Exposure and Dissection
■ Inject local anesthetic with vasoconstrictor to infiltrate the area of dissection
in the posterior mandible.
■ Insert a bite block/gauze sponge on the opposite side of dissection to
adequately open the mouth.

■ Expose the area of dissection by placing two Langenbeck retractors to pull
away the cheek.
■ In very small babies, malleable retractors can be used instead. Place a
tongue retractor to protect the tongue.
■ A 3-cm incision is made in the area of the ascending ramus and angle of the
mandible.
■ Sharp dissection is carried through mucosa, muscle, and periosteum to raise
a full-thickness mucoperiosteal flap exposing the entire ascending ramus and
posterior body of the mandible (TECH FIG 1).
■ Dissection is also performed on the lingual aspect of the ramus, while
protecting the inferior alveolar nerve.
■ A malleable retractor is inserted on the medial aspect of the ramus to retract
and protect the neurovascular bundle.
Corticotomy
■ Using an ultrasonic saw (TECH FIG 2A) or a reciprocating saw, a
corticotomy is made at the angle of the mandible.
TECH FIG 1 • Exposure of the posterior aspect of the
mandible. 1: Arrow pointing to the angle of the
mandible.
■ The site of the osteotomy is determined from the CT scan to avoid the teeth

follicles.
■ The direction and orientation of the osteotomy determines the desired vector
of distraction. Distraction can occur in the horizontal, vertical, or oblique
direction (depending on the relationship of the vector to the long axis of the
mandibular body).12
■ A horizontal vector along the long axis of the mandible will lengthen the
mandible in a purely horizontal plane. This is the case of bilateral
micrognathia seen in PRS and TCS patients where most of the deficiency is
in the mandibular body.
■ A vertical vector of distraction is preferred for lengthening a deficient
ramus in a vertical direction as seen in HFM.
■ An oblique vector simultaneously lengthens the body of the mandible and
elongates the ramus.
■ The corticotomy extends from the alveolar process to the inferior border of
the mandible, where the bone is thicker (TECH FIG 2B).
■ The thick inferior mandibular border must be completely cut to prevent a
bad split of the mandible (TECH FIG 2C).
Pin Placement
■ The site of pin placement is determined based on the angle and orientation of
the osteotomy, and the location of tooth follicles.
■ One or two self-drilling and self-tapping pins (40 mm long) are then placed
percutaneously proximal to the corticotomy (TECH FIG 3A).
■ A stab incision is made in the skin immediately below the inferior border of
the mandible to gain access to the bone, and the pins are screwed into the
bone using a manual pin driver (TECH FIG 3B).
■ Ensure that the pins are perpendicular to the bone and advanced far enough
into the bone to engage both cortices (TECH FIG 3C).
■ The skin immediately anterior to the proximal pin/s is retracted posteriorly,
and one or two more pins are drilled distally in a similar fashion. Retraction
of the skin creates redundancy and allows stretching as distraction progresses
and minimizes the scar.
■ The pins are placed parallel to each other with a distance of 3 cm between
them (TECH FIG 3D).

TECH FIG 2 • A. Ultrasonic saw. B. The desired
vector of distraction determines the site and
orientation of the osteotomy. C. Osteotomy extends
along the entire height of the mandible and must
ensure that tooth follicles are avoided.
■ Another option is to use two long pins (120 mm) to penetrate both sides of
the mandible for added stability (transfixed pins; TECH FIG 3E,F).
Placement of the Distraction Device
■ A 5-mm osteotome completes the osteotomy to liberate the two segments of
the mandible (TECH FIG 4A).
■ The intraoral wound is closed with absorbable sutures in a watertight

fashion.
■ The distraction device is then attached to the pins and adjusted using the
activator screwdriver (TECH FIG 4B–D).
■ A uniplanar or multiplanar distraction device can be used depending on the
desired end point of distraction (TECH FIG 4E–G).
TECH FIG 3 • A. Self-drilling, self-tapping
percutaneous pins. B. Manual screwdriver is used to
drive the pins percutaneously into the mandible. C.
Percutaneous pins are placed perpendicular to the
bone and advanced far enough to engage both
cortices. D. Pins are placed parallel with about 3 cm
distance between them. E. Long percutaneous pin
(120 mm). F. The transfixed pin traverses both sides
of the mandible.

TECH FIG 4 • A. Osteotomy of the mandible. B.
Distraction devices of 30 and 45 mm showing the slots
for engaging the pins. C. Distractor device connected
to the pins. D. Activation driver is used for both
activating the device and securing the pins to the
distractor. E. Uniplanar distractor with the activation
arm emerging anteriorly. F. Uniplanar distractor with
the activation arm emerging posteriorly toward the ear.
G. Multiplanar distractor that can lengthen both the
body and ramus of the mandible.

■ External Mandibular Distraction With Rigid
External Device
■ If a RED device is used instead of the pin technique, the same initial steps
are followed.
■ After creation of the corticotomy, the anterior mandibular retention plate is
secured to the menton of the mandible (TECH FIG 5A).
■ A small stab incision is made in the buccal vestibule below the lower
mandibular incisors.
■ A 2-mm Steinmann pin is advanced through this incision in an intraoral to
an extraoral direction to exit through the skin of the chin and create a
passage for the plate (TECH FIG 5B).
■ Ensure that the most anterior portion of the symphysis is captured with the
pin so that the plate rests within a groove in the mandible for added
stability.
■ The T-shaped plate (1.5 mm thickness) is then inserted to follow the passage
created by the pin and exits through the skin (TECH FIG 5C).
■ The plate is bent and adapted to conform to the anterior part of the
mandible overlying the mucosa (TECH FIG 5D).
■ Self-drilling screws are then drilled transmucosally using a cordless driver to
secure the plate to the mandible.
■ Three screws (7 mm in length) are used per side (TECH FIG 5E).
■ The free end of the plate is then bent upward, and a wire loop is inserted
through it (TECH FIG 5F).
■ The halo of the RED device is then applied to the skull using a minimum of
three fixation screws per side (TECH FIG 5G).
■ Ensure that the halo is parallel to the Frankfort horizontal.
■ After wound closure, the halo is secured to the retention plate using 25-
gauge stainless steel wire, which is passed from the slidable loop and through
the eyelet of the activation spindle attached to the horizontal crossbar
assembly.
■ The wire is then twisted securely (TECH FIG 5H,I).

D U

TECH FIG 5 • A. Skull model showing anterior
mandibular retention plate used with the rigid external
distraction (RED) device. B. A cordless drill is used to
drive a 2-mm Steinmann pin through the anterior
mandible to exit through the skin below the chin. C. T-
shaped retention plate is advanced through this
passage created by the pin, capturing the bone of the
symphysis. D. The plate adapted to the anterior
mandible. E. A minimum of three screws per side are
used to secure the plate to the mandible. F. Anterior
mandible plate exiting the skin, with the free end bent
upward for attachment to the halo. G. The halo is
secured to the skull using at least three screws per
side. Ensure parallel placement of the halo to the floor.
H. A 25-gauge wire is used to attach the mandible