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

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.

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.

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

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.

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

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

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 FoundationThe 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

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

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 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

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

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

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

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

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

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:

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

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

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 obviousCONCLUSION:

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:

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 on

the status of the temporomandibular joint, teeth, periodontal structures, and neurosensory

function. J Oral Maxillofac Surg 1999; 57:1419–25.

5. Guerrero CA, Bell WH, Contasti GI, Rodriguez AM. Mandibular widening by intraoral

distraction osteogenesis. Br J Oral Maxillofac Surg 1997;35:383–92.

6. Morovic CG, Monasterio L. Distraction osteogenesis for obstructive apneas in patients with

congenital craniofacial malformations. Plast Reconstr Surg 2000;105: 2324–30.

7. Judge B, Hamlar D, Rimell FL. Mandibular distraction osteogenesis in a neonate. Arch

Otolaryngol Head Neck Surg 1999;125:1029–32.

8. Dean A, Alamillos F. Mandibular distraction in tempero mandibular joint ankylosis. Plast

Reconstr Surg 1999;104: 2021–31.

9. Makarov MR, Harper RP, Cope JB, Samchukov ML. Evaluation of inferior alveolar nerve

function during distraction osteogenesis in the dog. J Oral Maxillofac Surg 1998;57: 1417–

23.

10. Mommaerts MY. Bone anchored intraoral devices for transmandibular distraction. Br J Oral

Maxillofac Surg 2001;39:8–12.

11. Van Sickels JE. Distraction osteogenesis versus orthognathic surgery. Am J Orthod

Dentofacial Orthop 2000;118: 482–4.

12. Del Santo M, Guerrero CA, Buschang PH, et al. Long-term skeletal and dental effects of

mandibular Symphyseal distraction osteogenesis. Am J Orthod Dentofacial Orthop

2000;118:485–93.

13. Bays RA, Greco JM. Surgically assisted rapid palatal expansion: an outpatient technique with

long term stability. J Oral Maxillofac Surg 1992;50:110–3.

14. Betts NJ, Vanarsdall RL, Barber HD, et al. Diagnosis and treatment of transverse maxillary

deficiency. Int J Adult Orthodon Orthognath Surg 1995;10:75–96.

15. Epker BN, Wolford LM. Surgical-orthodontic expansion of maxilla. In: Epker BN, Wolford LM,

editors. Dentofacial deformities: surgical-orthodontic correction. St. Louis (MO): CV Mosby

Co.; 1980. p. 305–31.

16. Rubio-Bueno P, Padron A, Villa E, Diaz-Gonzalez FJ. Distraction osteogenesis of the

ascending ramus for mandibular hypoplasia. J Oral Maxillofac Surg 2000;58: 593–9.

17. Vu HL, Panchal J, Levine N. Combined simultaneous distraction osteogenesis of the maxilla

and mandible using a single distraction device in hemifacial microsomia. J Craniofac Surg

2001;12:253–8.

18. Rachmiel A, Aizenbud D, Eleftheriou S, et al. Extraoral vs. intraoral distraction osteogenesis

in the treatment of hemifacial microsomia. Ann Plast Surg 2000;45:386–94.

19. Haug RH, Nuveen EJ, Barber JE, Storoe W. An in vitro evaluation of distractors used for

osteogenesis. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 1998;86:648–59.

20. Dolce C, Van Sickels JE, Bays RA, Rugh JD. Skeletal stability after mandibular advancement

with rigid versus wire osteosynthesis. J Oral Maxillofac Surg 2000;58:1219–27.

21. Berger JL, Pangrazio-Kulbersh V, Bacchus SN, Kaczynski R. Stability of bilateral sagittal split

ramus osteotomy: rigid fixation versus transosseous wiring. Am J Orthod Dentofacial Orthop

2000;118:397–403.

22. Van Sickels JE, Dolce C, Keeling S, et al. Technical factors accounting for stability of a

bilateral sagittal split osteotomy advancement: wire osteosynthesis versus rigid fixation.

Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2000;89:19–23

23. Gurstein KW, Sather AH, An KN, Larson BE. Stability after inferior or anterior maxillary

repositioning by Le Fort I osteotomy: a biplaner stereocephalometric study. Int J Adult

Orthodon Orthognathic Surg 1998;13:131–43.

24. Van Sickels JE, Richardson DA. Stability of orthognathic surgery: a review of rigid fixation. Br

J Oral Maxillofac Surg 1996;34:279–85.

25. Heliovaara A, Ranta R, Hukki J, Rintala A. Skeletal stability of Le Fort I osteotomy in patients

with unilateral cleft lip and palate. Scand J Plast Reconstr Surg Hand Surg 2001; 35:43–9.

26. Chow J, Hagg U, Tideman H. The stability of segmentalized Le Fort I osteotomies with

miniplate fixation in patients with maxillary hypoplasia. J Oral Maxillofac Surg 1995;52:

1407–12.

27. Ayliffe PR, Banks P, Martin IC. Stability of the Le Fort osteotomy in patients with cleft lip

and palate. Int J Oral Maxillofac Surg 1995;24:201–7.

28. Polley JW, Figueroa AA. Management of severe maxillary deficiency in childhood and

adolescence through distraction osteogenesis with an external, adjustable rigid distraction

device. J Craniofac Surg 1997;8:181–5.

29. Walker D. Management of severe mandibular retrognathia in the adult patient using

distraction osteogenesis. J Oral Maxillofac Surg 2002;60:1341–6.

30. Williams K, McCarthy J. Osteodistraction: the present and the future. In: Ward-Booth P,

Schendel SA, Hausamen JE, editors. Maxillofacial surgery. New York: Churchill Livingstone;

1999. p. 953.

31. McCormick S. Osteodistraction. In: Sinn D, editor. Selected readings in oral and maxillofacial

surgery. Dallas: Selected Readings in Oral and Maxillofacial Surgery; 1998. p. 1–24.

32. Fischgrund J, Paley D, Suter D. Variables affecting time to bone healing during limb

lengthening. Clin Orthop Relat Res 1994;301:31.

33. Troulis M, Coppe C, O’Neill M, Kaban L. Ultrasound: assessment of the distraction

osteogenesis wound in patients undergoing mandibular lengthening. J Oral Maxillofac Surg

2003;61:1144.

34. McCarthy J, Katzen T, Hopper R, Grayson B. The first decade of mandibular distraction:

lessons we have learned. Plast Reconstr Surg 2002;110:1704.

35. Yu J, Fearon J, Havlik R, et al. Distraction osteogenesis of the craniofacial skeleton. Plast

Reconstr Surg 2004; 114:1e–20e.

36. McCormick S, McCarthy J, Grayson B, et al. The effect of mandibular distraction on the

temporomandibular joint: part 1, a canine study. J Craniofac Surg 1995;6:358.

37. Makarov M, Harper R, Cope J, Samchukov M. Evaluation of inferior alveolar nerve function

during distraction osteogenesis in the dog. J Oral Maxillofac Surg 1998; 56:1417–23.

38. Makarov M, Samchukov M, Cope J. The effect of gradual traction on peripheral nerves. In:

Samchukov ML CJ, Cherkasin A, editors. Craniofacial distraction osteogenesis. St. Louis, MO:

Mosby; 2001.

39. Skoulis T, Vekris M, Terzik J. Effect of distraction osteogenesis on the peripheral nerve:

experimental study in the rat. J Reconstr Surg 1998;14:565.

40. Whitesides L, Meyer R. Effect of distraction osteogenesis on the severely hypoplastic

mandible and inferior alveolar nerve function. J Oral Maxillofac Surg 2004;62:292.

41. Stucki-McCormick S, Fox R, Mizrahi R. Distraction osteogenesis of the craniofacial skeleton.

In: Piecuch J, editor. Oral and maxillofacial knowledge update. Chicago: American

Association of Oral and Maxillofacial Surgeons; 1998. p. 159.

42. Costano F, Troulis M, Glowacki J. Proliferation of massetter myocytes after distraction

osteogenesis of the mandible. J Oral Maxillofac Surg 2001;59:302.

43. Mackool R, Hopper R, Grayson B, et al. Volumetric changes of the medial pterygoid

following distraction osteogenesis of the mandible: an example of the associated soft-tissue

changes. Plast Reconstr Surg 2003;111:1804.

44. Liou E, Polley J, Figueroa A. Distraction osteogenesis: the effects of orthodontic tooth

movement on distracted mandibular bone. J Craniofac Surg 1998;9:564.

45. Cope J, Harper R, Samchukov M. Experimental tooth movement through regenerate

alveolar bone: a pilot study. Am J Orthop Dentofac Orthop 1999;116:501.

46. Taylor T, Stal S. Applications of distraction osteogenesis. Clin Plast Surg 1998;25:553–60 .

47. Ewers R, Schicho K, Wanschitz F, et al. Basic research and 12 years of clinical experience in

computer assisted navigation technology: a review. Int J Oral Maxillofac Surg 2005;34:1–8.

48. Klug C, Schicho K, Ploder O, et al. Point-to-point computer assisted navigation for precise

transfer of planned zygoma osteotomies from the stereolithographic model into reality. J

Oral Maxillofac Surg 2006;64:550–9.

49. Schicho K, Figl M, Seemann R, et al. Accuracy of treatment planning based on

stereolithography in computer assisted surgery. Med Phys 2006. [In press]