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1. DISTRACTION OSTEOGENESIS
Distraction osteogenesis is a relatively new tool that can be used to treat dentofacial
discrepancies. By creating bone, it can be used to lengthen the ramus, both of the mandible
and maxilla. When used within the arch, it creates a space to resolve transverse and anterior–
posterior discrepancies while allowing for the correction of crowded teeth.1–5 Like orthognathic
surgery, it can be used to treat routine skeletal discrepancies6; however, it offers options to
correct discrepancies that are difficult or impossible to achieve with standard orthognathic
procedures.7,8 Furthermore, it appears to offer greater stability for large movements that are
not stable with standard operations.9 Finally, there may be a lesser incidence of sensory deficits
than seen with mandibular surgery to advance the mandible.10
Distraction is frequently done in an outpatient hospital environment and may be more
cost efficient than the more prolonged procedures done on an inpatient basis. It can obviate
the need for bone grafts in large surgical movements of the maxilla and mandible. Its greatest
disadvantage is that it requires close postoperative management and cooperation of patients
and their families. Additionally, the ultimate occlusal result is not as predictable as that with
orthognathic procedures. This necessitates very aggressive post distraction orthodontic
management. Specific skeletal discrepancies that can be treated with distraction can be divided
into segmental deformities and whole-arch deformities.
Segmental deformities
Mandible
Distraction within the corpus of the mandible allows correction of transverse and
anterior–posterior tissues. Intraarch distraction may be done with tooth- or bone-borne
appliances.1-5, 11. Although the arch may be divided anywhere, the symphysis is one of the safer
and more popular regions of the mandible to do distraction in. Symphyseal distraction allows
correction of transverse deficiency of the mandible, allowing an alternative to extraction of
teeth to resolve crowding. Those who advocate bone-borne appliances suggest that with tooth-
borne appliances, there is more tipping and less bodily movement than seen with a bone-borne

2. appliance.11 Advocates of the tooth-borne appliance point to the relatively inexpensive cost
associated with the device.12 In adolescent patients, the maxilla can be expanded by
nonsurgical means, whereas in adults, both the maxilla and mandible are expanded with
surgical techniques.4,5 The patient in Figure 5-1 is a 12-year-old female, who presented with
transverse discrepancies of her maxilla and mandible and severe crowding. She underwent 8
mm expansion of her lower arch, whereas she had a slightly greater amount of expansion of her
upper arch (Figure 5-2). The author’s experience is that the maxilla should be over expanded by
10 to 15% for both nonsurgical processes and surgical-assisted rapid palatal expansion. In
contrast, the mandible does not need to be over expanded. Del Santo and colleagues found
similar results for the lower arch.13 In their study, skeletal expansion in the mandible was
greatest in the intercanine region, but secondary to postsurgical orthodontic movement, where
the greatest increases in dental width were between the first molars and second premolars.
Dressner and colleagues have recently discussed the simultaneous correction of patients with
anterior–posterior discrepancies and dental crowding.1, 2 Segmentalization of the mandible is
tailored to the region where the crowding is the most severe and there is space to make a
corticotomy. Combinations of tooth and hybrid tooth and bone-borne appliances are used and
appear to be indicated when the patient has a deep bite.
A, Maxilla of a 12-year-old patient, with crowding; the appliance is in place. B, Crowding in the lower arch;
the appliance is in place.

3. Maxilla
Like the mandible, both transverse and anterior–posterior segment issues can be
addressed with distraction. Transverse discrepancies of the maxilla have been addressed for
years with surgical-assisted rapid palatal expansion.14–16 The procedure can be done under
general anesthesia or intravenous sedation. It can be used to correct a unilateral or a bilateral
skeletal constriction. Although somewhat controversial, most authors recommend that the
pterygoid plates be fractured in order to allow for posterior expansion.15,16 Others suggest that
the plates do not need to be fractured, especially when having the procedure done as an
outpatient.14 Whereas the majority of maxillary segmental distractions have been used to
address transverse discrepancies, intraarch distraction can be used to resolve crowding with or
without anterior–posterior simultaneous correction. The patient in presented with crowding in
the maxilla and a Class III cuspid and Class I molar. Segmental maxillary distraction was chosen
as an alternative to extractions and advancement of the entire maxillary arch. This allowed
resolution of the crowding while simultaneously correcting the anterior–posterior discrepancy.
An appliance was placed in the maxilla several days prior to surgery. An anterior maxillary
segmental osteotomy was done followed by a two-day latency period. The patient had 0.5 mm
of expansion per day divided into a twice-a-day rhythm for a total of 6 mm of advancement of
the anterior segment. The patient in is a cleft patient with a large anterior–posterior
discrepancy and multiple missing teeth. Her second bicuspids were locked out on the palate.
Segmental distraction was done as a first-phase therapy, to allow the second bicuspids to be
incorporated into the arch. Similar to the previous case, a palatal appliance was placed prior to
surgery. Because of the extensive palatal scarring, vertical incisions were used to maintain a
labial vascular pedicle to the segment. She had a 2-day latency period with a similar rate and
rhythm as was used for the previous case for a total advancement of 8 mm. This allowed space
for the second bicuspids to be brought into the arch. Once the second bicuspids were aligned,
her skeletal discrepancy was treated by conventional orthognathic therapy.

4. Panorex, with appliance in place
Whole-Arch Deformities
Mandible
Ramus
Lengthening of the mandibular ramus is highly unpredictable with orthognathic
procedures, but relatively easily done with distraction.12,17,18 Most authors who have published
results on lengthening of the ramus were treating patients with hemifacial microsomia or
Treacher Collins deformities.17–19 Extraoral appliances have been used to achieve large
advancements, but have the disadvantage of leaving pin tract scars on the face.12 Intraoral
appliances avoid this problem, but are technically more difficult to place.19 Haug and
colleagues showed that intraoral appliances have a mechanical advantage over extraoral
ones.20
Body
Advancement of the mandible beyond 7 mm has shown increasing amounts of instability
when done by a sagittal split osteotomy.21–23 Movements beyond 12 to 15 mm are usually not
possible without extraoral procedures and bone grafts. Additionally, large movements
frequently require a period of maxillomandibular fixation in order to achieve stability.
Distraction presents an alternative choice to advance the mandible in these cases. The patient
was followed over a 4-year period, with increasing mandibular deficiency following an
unsuccessful attempt to advance her mandible and impact her maxilla. Both bone scans and
serial cephalometric radiographs showed that her occlusion was stable. She had symptoms

5. consistent with obstructive sleep apnea. Her mandible was markedly deficient with extremely
small condyles. Although her condyles were small, she did have reasonable protrusive and
excursive function. She was treatment planned for a three-piece Le Fort I osteotomy and
distraction of her mandible to advance it 17 mm at the inferior border. Bone-borne appliances
were placed (Figure 5-10). The extrinsic vector chosen was directed toward the maxillary
occlusal plane. Additional skeletal anchorage was used in both the maxilla and mandible to
allow modification of the primary vector and to resist the intrinsic pull of the suprahyoid
musculature (Figure 5-11). Elastics were placed between the upper and lower skeletal fixation
appliance as the mandible was advanced to create a secondary extrinsic vector. The skeletal
fixation in the mandible was fabricated from four-hole bone plates and fixed with a single
bicortical screw to the genial region below the apices of the teeth. The patient had a 6-day
latency period followed by a 1 mm a day rate of expansion divided into a twice-a-day rhythm.
She was advanced to an end-to-end incisal position to compensate for the procumbance of the
lower incisors following the period of distraction, it was noted that she had a cross-bite and an
open bite on the left side. These were addressed by orthodontics, initiated when the distraction
was discontinued. The internal distractors were left in place for 6 months. When they were
removed, she had a 10 mm augmentation genioplasty done.
Maxilla
Even with rigid fixation, instability of the maxilla is noted when the maxilla is advanced
beyond 7 mm.24, 25 This is particularly true when patients with previously repaired cleft lips
and palates are treated.26–28. Polley and Figueroa have published extensively on distraction of
the maxilla using external devices.29 Modifying the level of the osteotomy can change the
esthetic results. The external distractor system has a tooth-borne component and an external
component (Figure 5-15). Moving the external distractor along an external rod can modify the
vector of movement (Figure 5-16). Furthermore, the internal tooth-borne appliance can be
modified by incorporating an expansion appliance to expand the maxilla (see Figure 5-15). The
procedure is predictable but requires that the patient wear an external framework for 3 months
and frequently a removable facemask for an additional 3 months at night. Intermaxillary
elastics can be used during the period of distraction to modify the primary vector of movement.

6. The maxilla of the patient in Figure 5-17 was advanced 11 mm and the maxillary midline was
shifted to the left. Internal bone-borne appliances have not been used as extensively as
external distracters with tooth-borne appliances. Additionally, there is minimal ability to modify
the bone cuts because of the necessity to place appliances on the maxilla or zygoma. Kebler
and colleagues discussed the use of an internal bone distractor on four cases where they were
able to advance a significant portion of the midface with the maxilla.30. The patient in Figure 5-
18 had a repaired unilateral cleft lip and palate. She had two separate operations in the
posterior pharyngeal region in an attempt to improve the nasal quality to her speech. From the
preoperative cephalometric tracing and mounted models, it was determined that she would
need a primary vector that was forward and down. Secondary vector control would be
accomplished by intermaxillary elastic traction during or shortly after the period of distraction.
Surgery was accomplished as a standard Le Fort I osteotomy. Prior to the osteotomy, care
was taken to place the distractors in the desired vector of distraction. The distractors were
removed and she underwent a full downfracture of the maxilla. The distractors were replaced
and the maxilla was advanced to ensure that the appliances would work and then it was
returned to her preoperative position. Following a 7-day latency period, she underwent
distraction of 1 mm per day with a twice-a-day rhythm. Her maxilla was advanced 8 mm (Figure
5-19). Following the completion of distraction, orthodontics was immediately started. The
distractors were left in place for 6 months (Figure 5-20). Interestingly, she had limited opening
despite physiotherapy, which did not resolve until the distractors were removed. The patient in
Figure 5-21 is also a cleft lip and palate patient. She had a pharyngeal flap and a significant
maxillary deficiency. Prediction tracing and model surgery suggested that she would benefit

7. from a 16 mm maxillary advancement (see Figure 5-21).
Pre operative post operative
Similar to the previous case, this patient had a Le Fort I osteotomy done in an operating
room with the placement of internal distractors. At the time of surgery, an attempt was made
to distract her maxilla the entire distance 16 mm. It was noted that her pharyngeal flap was
very tight and appeared blanched. Her maxilla was returned to its preoperative position. She
had a 6-day latency period and then underwent advancement at 1 mm per day with a twice a-
day rhythm (Figure 5-22). The flap did not appear to restrict the movement during the course of
therapy. Her postoperative course was much more complicated than the patient in Figures 5-18
through 5-20. Because of her limited ability to follow instructions, on several occasions it was
found that her appliance had not been activated as planned. This necessitated multiple
postoperative visits. She is currently in therapy with the distractors in place.
Three dimensional positioning of the maxilla-
The challenge to achieve simultaneous threedimensional maxillary repositioning prompted
us to develop a more predictable, versatile, and stable surgical orthodontic technique for
treatment of selective deformities. We hypothesized that a combination of distraction
osteogenesis, distraction histiogenesis, and individualized lateral maxillary osteotomy designs
would achieve these goals in a single procedure. The maxillary segments would be repositioned
as planned in the sagittal and vertical planes of space by variably designed lateral maxillary

8. osteotomies and transversely by distraction osteogenesis (Figure 20-1). Thus, the best features
of the two techniques
are combined into a single procedure. Nonextraction and extraction orthodontic treatments are
options.
To surgically achieve a maxilla of normal size and proportions mandates variable complex
translational and rotational movements of the jaws. Three-dimensional maxillary deformities
may be associated with crowded anterior teeth, a narrow and tapered arch form, impacted
and/or blocked-out canines, and variable sagittal and vertical maxillary deformities. In the past,
such problems have frequently mandated the use of two- or three-stage surgical techniques
and extraction of premolars. When, however, the planned maxillary repositioning does not
include known problematic unstable maxillary movements (ie, excessive widening or vertical
lengthening) long-term stable positional changes can be expected.
Clinical and Biologic Foundation
The clinical basis for using distraction osteogenesis and histiogenesis in the anterior maxilla is
founded on the need for transverse widening of the crowded, tapered, and constricted anterior
maxilla and associated soft tissues. However, the integrity of the gingival tissue and interdental
papilla in this vital esthetic zone may be compromised by immediate widening in excess of a
few millimeters. In contrast, slow incremental expansion of the anterior segments by
distraction osteogenesis allows adequate stretching of the gingival tissue and periodontal
ligament to widen the anterior maxilla and subsequently reposition the adjacent teeth into the
distraction gap after an appropriate consolidation period. The gingiva responds favorably to
gradual stretching during distraction histiogenesis. The initial mild inflammatory and reactive
changes observed during distraction in the first few weeks of consolidation are followed by
regenerative changes with neohistiogenesis to restore the structural and functional integrity of
the gingiva.19–20
Because many maxillary deformities are, in fact, three-dimensional in nature, treatment
results frequently fall short of the ideal result with the use of osteotomy designs that focus
exclusively on the transverse dimension. In one study, a group of 78 patients were treated by
surgically assisted widening of the maxilla with virtually no consideration of the vertical or
anterior-posterior dimension.19 Current one- or two-stage surgical techniques may not achieve

9. ideal functional, stable, or esthetic results. Moreover, patients may not accept two-step
surgery13 because of the need for two general anesthetics and increased costs.
Surgical Exposure of Osteotomy Sites
The sine qua non of predictable and safe interincisal osteotomies is adequate exposure and
visualization aided by excellent lighting (preferably a headlight or binocular prism loupes) of the
planned interdental osteotomy site (Figure 20-8). A well-oriented radiograph is an essential
part of the preoperative assessment. The incompletely ossified suture line usually seen on a
periapical radiograph provides a means of identifying the planned osteotomy site
intraoperatively. This is visualized through the retracted wound margins after detachment and
retraction of the flap margins to expose the crestal alveolar bone (see Figure 20-8). In most
patients, there is a natural divergence of the central incisor roots that precludes the need for
presurgical orthodontic separation of the incisors. The margins of the superior flap are
undermined subperiosteally to expose the infraorbital nerve, infraorbital rim, anterior and
lateral maxillae, zygomatic crest, and root of the zygoma (Figure 20-9).
Dissection is carried anteriorly to facilitate reflection of the nasal mucoperiosteum from
the lateral and inferior aspects of the piriform aperture and anterior nasal floor. The
mucoperiosteum is detached from the nasal floor, base of the nasal septum, and lateral nasal
walls. The inferior part of the circumvestibular incision in the maxillary midline is undermined
to the crestal alveolar bone to facilitate sectioning of the maxillary cortical bone between the
central incisors.
A horizontal incision is placed opposite the intended osteotomy site 4 to 5 mm above
the level of the mucogingival cuff. The margins of the superior flap are undermined into the
depth of the vestibule and mucosal surface of the upper lip to provide access to the piriform
aperture and floor of the nose.
The anterior maxilla is partially divided into two segments before the lateral maxillary
osteotomies are accomplished with the margins of the mucosa retracted to visualize the labial
osteotomy site. The interdental osteotomy is incompletely accomplished with a fissure bur
extending from the anterior aspect of the nasal floor inferiorly to the crest of the alveolar ridge
Superiorly, the interdental osteotomy is deepened into the spongiosa; more inferiorly, the

10. osteotomy is made through the cortical alveolar bone only (corticotomy). An interincisal
osteotomy is accomplished with the reciprocating saw blade superiorly into the piriform
aperture An osteotome is incrementally tapped into the interradicular area proceeding
superoinferiorly until it partially transects the palatal bone and its tip makes contact with the
nasal floor immediately lateral to the anterior nasal spine (maintained intact) (Figure 20-13).
The osteotome is then malleted into the stable interseptal area between the central incisors to
torque and partially fracture the crestal alveolar bone. Splitting of the anterior maxilla is
facilitated by malleting and manipulating an osteotome into the center of the stable maxilla
Distraction osteogenesis in obstructive sleep apnea syndrome
Principles:
Distraction osteogenesis applies stress to a site of surgically produced bone disruption12 and
uses the body’s natural reparative mechanisms to create new bone.13 Tissue regeneration
occurs by increasing vascularity and recruiting osteoblasts.12 During the surgical procedure, the
bone is sectioned and the distraction device is applied. Distraction osteogenesis then consists of
the following steps13:
• Latency, which represents the interval from surgery to that of the application of distraction
force. During this period of 5 to 7 days, local healing occurs and a callus forms. Latency is
influenced by the age of the patient; the younger the patient, the shorter the latency
required.13
• Distraction, the process in which gradual traction results in new bone formation (the
distraction regenerate). The course is affected by the rate and rhythm (frequency) of distraction
device activation.
• Consolidation is the interval in which the distraction regenerate matures after the
termination of traction. Consolidation is influenced by the ability of the fixation device to
stabilize the new bone formed and the length11 of the distracted bone. Mobility causes
disruption of the new blood vessels, bringing about the failure of the newly formed bone.
Consolidation timing is related to the patient’s age; the younger the patient, the shorter the
healing time.14 The radiographic evaluation during consolidation is used to time the removal of
distraction devices. The appearance of a cortical outline within the regenerate correlates with

11. bone healing.13 Other techniques, such as ultrasonography, are also being investigated as
determinants of consolidated bone.
Responses of Oral Tissues to Distraction Osteogenesis
Bone
Four zones have been identified within the distraction gap during distraction: the central
fibrous zone; a transition zone in which fibroblasts and undifferentiated precursor cells were in
continuity with the osteoblasts; the zone of bone remodeling, which contains increased
numbers of osteoclasts; and mature bone demonstrating evidence of compact cortical bone,
which is similar in appearance to the adjacent nondistracted bone.16 Other investigators have
delineated a similar classification of areas in the distraction gap.17
Temporomandibular Joint
Based on animal studies, significant remodeling of the temporomandibular joint after
distraction osteogenesis does not appear to occur.18 Furthermore, the gradual joint loading
does not appear to exacerbate preexisting disease.11
Inferior Alveolar Nerve
Makarov and colleagues demonstrated that distraction osteogenesis produces minimal
effect on the function of the inferior alveolar nerve in a canine model.19 Others report a range
of neurosensory deficits.20 In the rat model, the safest and fastest rate of distraction was
determined to be 1 mm/d.21 Jaw-jerk reflexes remain intact. Most recently, Whitesides and
Meyer showed that even large mandibular advancements (> 10 mm) can be accomplished
without significantly damaging the inferior alveolar nerve.22
Soft Tissue
A significant advantage of the distraction technique is concomitant expansion of the soft
tissue envelope.17 Muscle and periosteum have been shown experimentally to undergo
elongation and hyperplasia.23 Although it appears that the change in muscle tissue is
dependent on the degree of lengthening, it can be said that there are adaptations in the
sarcomere length, an increased number of myocytes,11–24 and an increase in the volume of

12. the attached muscles.25 Teeth Orthodontic tooth movement can be performed in distracted
bone.26,27
Indication for Maxillomandibular Advancement with Distraction Osteogenesis
Evaluation
The primary evaluation method is the functional clinical assessment in a multidisciplinary
setting. Vital signs, including height and weight to allow calculation of the BMI, are obtained.
Examination includes documentation of facial and other physical parameters, such as
mandibular excursions, maximum interincisal opening, the state of the dentition, the presence
of an occlusal cant, and classification of occlusion. An estimation of tongue volume and
classification of soft palate and temporomandibular joint pathology should be noted.29–46
Nasopharyngoscopy is performed. A review of a recent (within 6 months to 1 year)
polysomnogram is imperative.
Radiographic Assessment
Cephalometric analysis determines skeletal and dental relationships and abnormalities. The
panoramic radiograph is used to provide a view of the position of teeth and to assess for
impacted teeth or bony pathology. The panoramic radiograph is also valuable in the evaluation
of the size and shape of the condyle, body, and mandibular ramus.
Rationale for Selection of the Treatment Modality
Patients are referred to the alternatives to continuous positive airway pressure (CPAP) if
they are intolerant of CPAP, require information about nonsurgical treatments for the disease,
or are considering a surgical procedure owing to impaired quality of life owing to untreated
OSA. If the patient has mild to moderate OSA, the following options are discussed if applicable:
lifestyle changes, dental appliances, weight loss, and nocturnal positional therapy. Owing to the
deficiencies in current data supporting laser-assisted uvuloplasty, UPPP, GA or GAHS,
somnoplasty, sclerotherapy, tongue suspension, and glossoplasty, these procedures are seldom

13. endorsed. MMA is recommended for patients with moderate to severe OSA who has an RDI of
< 70 and a BMI of < 32 kg/m2. Interested patients with a BMI of 40 kg/m2 may obtain a referral
for consultation with a bariatric surgeon. If the RDI is > 70 or the BMI is > 32 kg/m2, MMADO is
advocated.
Technique of Distraction Osteogenesis
Distraction Device

14. Distraction device closed. Distraction device open
A variety of hardware (KLS Martin L.P., Jacksonville, FL) has been investigated for
MMADO. One prototype consists of two titanium miniplates connected by two screws and an
encasement (Figures 38-1 to 38-4). The plates are completely implanted subperiosteally and
secured with monocortical screws. The projecting screw head remains intraorally. Each half-
turn of the screw produces approximately 0.25 mm of distraction. The maximum distraction
obtainable with the device was 25 mm. The device has been designed for versatile applications
and for bimaxillary or monomaxillary placement. In all clinical cases, we have used an intraoral
mandibular distraction application while the maxilla was indirectly advanced via ligation to the
mandibular arch by way of maxillomandibular fixation.
Distraction Protocol
Lateral cephalometric and Panorex radiographs are obtained as soon as possible in the
postoperative period to evaluate for hardware position, prior to patient release from the

15. hospital. Families must be provided with extensive counseling regarding wound care, oral
hygiene, diet, activity, and tracheostomy care. The diet is completely liquid for the period of
distraction and stabilization. 46 After a latency period of 7 days, distraction is initiated at a rate
of 1 mm per day, completed in 0.5 mm cycles twice daily. Progress is monitored by serial lateral
cephalometric radiographs at 1- to 2-week intervals. At the same interval, patients undergo
clinical examination to evaluate stability and assess for infection, occlusal changes, or hardware
malfunction. Once the desired advancement of the maxillomandibular complex is achieved, the
tracheostomy tube is “capped” and a polysomnogram is obtained. If evidence of residual sleep
apnea is demonstrated, jaw advancement is further titrated, guided by repeat
polysomnography in 1 week.29 Once the polysomnogram demonstrates cure of the OSA, the
devices are left in place in a neutral position for stable rigid fixation for a minimum period of 8
weeks. During distraction and consolidation, the use of maxillomandibular elastic traction is
required to achieve the optimal skeletal and occlusal result.34 Distraction device removal is
accomplished after the consolidation phase, under general anesthesia. Maxillomandibular arch
bars are retained for control of the occlusion.
Surgery

16. Distraction device applied and fixated in a bimaxillary fashion. As stated in the text, in all of our
cases, the application was performed only in the mandible while the maxilla was fixed to the
mandible by maxillomandibular fixation.
All surgical procedures were supervised by a single oral and maxillofacial surgery
attending physician. Oral intubation with conversion to tracheostomy is performed, and
maxillary and mandibular circumdental arch bars are placed. A standard Le Fort 1 maxillary
osteotomy is accomplished, and the maxilla is mobilized with full downfracture. The posterior
mandible is approached via a buccal incision similar to that of a sagittal split osteotomy. A full-
thickness mucoperiosteal flap is elevated, and a transverse posterior body osteotomy is
initiated with a reciprocating saw under saline irrigation and completed with an osteotome.
Care is taken to avoid the mandibular nerve by using two fiber handle osteotomes at the same
time, a narrow one at the inferior border of the mandible and the other at the level of the
retromolar trigone. The occlusion is maintained via maxillomandibular arch bar fixation. The
buccal sulcus distraction device is placed transorally and subperiosteally at the time of surgery,
parallel to the inferior border of the mandible. The number of monocortical screws may vary,
but a minimum of three screws are needed on either side of the osteotomy. Device trajectory is
planned for a purely horizontal orientation, but owing to the socket-ball joint in the posterior
aspect of the device, the direction can be corrected with elastic traction from intermaxillary
fixation screws placed at the level of the piriform rim. The device is activated to ensure
separation of the bony segments and is then neutralized into the closed position. Patients

17. selected for this procedure are obese and/or have severe OSA and thus should be admitted to
the intensive care unit because of the potential for airway control in the immediate
postoperative period. Postoperative oral antibiotics are administered for 1 week.
Distraction Osteogenesis in Oral and Maxillofacial Surgery Using Navigation
Technology and Stereolithography
The combination of the surgeon’s Intraoperative view of the patient with additional
computer generated information (eg, preoperative planning) by means of overlay graphics is
commonly known as augmented reality. Based on imaging modalities, mostly computed
tomography (CT) and magnetic resonance imaging, computer assisted navigation technology
displays the positions and movements of surgical instruments relative to the patient and
supports the surgeon’s orientation. The use of this kind of technical setup is widespread and
well established in several fields of medicine.47 Therefore, we also call it the “first generation of
navigation.” A promising further development is the integration of three dimensional
stereolithographic (SL) skull models in a navigation workflow, enabling a new dimension of
“haptic feeling” in the course of preoperative planning. SL models (Figure. 9) are produced on
the basis of CT scans of the patient. A laser beam cures liquid resin layer by layer, leading to a
precise three-dimensional reproduction of the patient’s anatomy. The optimum outcome of a
simulated operation on the SL skull model can be exactly recorded with the point to-point
navigation.48, 49 That is what we denominate the “second generation of navigation.”
Technical Background:

18. Three-dimensional stereolithographic skull model of the patient.
Distraction device in position during simulation surgery on the stereolithographic model.
To support distraction osteogenesis, we applied a similar technical approach for the
planning but were using surgical templates instead of point to- point navigation. Navigation was
used only to optimize preoperative planning, that is, to find out how many turns of the
distractor are required for the desired longitudinal translation of the bone. The “link” between
the patient and the simulated operation on the SL skull model is a simple template that

19. connects the distractor rigidly and in a defined position to the bony structures of the patient
respective to the corresponding parts of the SL skull model. Of course, an identical distractor
must be used at the skull model and at the patient.
Patient
The patient was a 4-year-old female child. The diagnosis was right hemifacial microsomia,
facial asymmetry, and an open bite on the left side. Furthermore, the patient was suffering
from dysplasia of the right auricle (see Figure. 9).
Surgical Treatment
A three-dimensional SL model was manufactured according to the CT scan of the patient,
and a distractor was attached to this model after osteotomy of the mandibular ramus (Figure.
10). To allow for a precise definition of the position of the distractor, we used a template;
therefore, the distractor could be fixed to the patient at a position exactly corresponding to the
position on the SL model in the course of planning. By means of overlay graphics, planes and
lines of symmetry were defined within the CT images on the navigation computer. Then two
navigation sensors were attached to the SL skull: one at the mandible and the other at the
maxilla. These sensors allowed us to follow the distraction process almost in real time. The
distractor was turned until the desired symmetry was achieved. The number of turns required
for this optimum result was the key information for the realization of this plan. Intraoperative
placement of the distractor (using the template) was finalized without any complications. The
distractor was activated to 11.0 mm (1.0 mm per day), beginning from the fifth day after
surgery. The retention phase was 3 months, and then the appliance was removed.
Clinical Outcome

20. Functional and esthetic results were very satisfying and are shown in Figures. 11
(preoperative panoramic radiograph), 12 (distraction device in place), and 13 (2-year follow-
up).
Preoperative panoramic radiograph. Asymmetric
Mandible with shortening of right mandibular ramus.
After 11.0 mm of distraction with the Medicon
(Medicon, Tuttlingen, Germany) ramus distraction device in place.
Two-year follow-up. A slight relapse of mandibular shortening is obvious
CONCLUSION:

21. Management of skeletal deformities in the maxillofacial region has been an important
challenge for medicine and dentistry throughout their evolution as health care sciences.
Distraction osteogenesis (DO), also referred to as osteodistraction, is a surgical technique that
uses the body’s own repairing mechanisms as allies for optimal tissue reconstruction. This
method has gained acceptance and joined the conventional techniques for comprehensive
treatment of patients with skeletal insufficiencies, and its successful application in the
maxillofacial complex has been extensively reported.
References:

22. 1. Dessner S, Razdolsky Y, El-Bialy T, Evans CA. Mandibular lengthening using pre programmed
intraoral tooth borne distraction devices. J Oral Maxillofac Surg 1999;57: 1318– 22
2. Dressner S, Razdolsky Y, El-Bialy T. Surgical and orthodontic considerations for distraction
osteogenesis with ROD appliances. Atlas Oral Maxillofac Surg Clin North Am 2001;9:111–39.
3. Weil TS, Van Sickels JE, Payne CJ. Distraction osteogenesis for correction of transverse
mandibular deficiency: a preliminary report. J Oral Maxillofac Surg 1997;55: 953–60.
4. Kewitt GF, Van Sickels JE. Long-term effect of mandibular midline distraction osteogenesis
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