Distraction osteogenesis

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Distraction osteogenesis

  1. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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 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.
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