Distraction osteogenesis to widen the mandible.

The purpose of this investigation was to elucidate the biology of distraction osteogenesis during mandibular widening. Midsymphyseal vertical interdental osteotomies were performed in nine Macaca mulatta monkeys. After a latency period a tooth-borne appliance was activated at a rate of 0.5 mm twice a day for 7-10 days. The appliance was then stabilized for a period of 4 or 8 weeks. The distraction gap at the inferior portion of the symphysis was bridged completely by new bony trabeculae. Bone formation in the interdental area was apparently related to the surgical technique. Newly formed bony trabeculae were oriented parallel to the direction of distraction. The location of the osteotomy site with an adequate margin of alveolar bone contiguous with the adjacent teeth was necessary for the induction of the distraction osteogenesis. Disproportional movement between superior and inferior portions of the distracted segments was noted.

Reactive changes in the temporomandibular joint after mandibular midline osteodistraction.

The purpose of this study was to evaluate the histologic changes within the condyle in response to mandibular widening using osteodistraction. Mandibular midline osteotomies were made in nine Macaca mulatta monkeys and tooth-borne distraction devices were bonded to the mandibular dentition. Distraction was continued until a 3-5 mm widening was achieved. The appliances were then stabilized for a period of 4 weeks. Non-decalcified sagittal sections of the lateral, middle and medial thirds of the condyles were analyzed. Although three of the seven animals showed no unusual morphology, four others exhibited morphologic differences within the fibrous layer, cartilage layer or bone/cartilage interface. Histologic changes were seen to occur in the fibrous layer, cartilaginous layer and cartilage/bone interface. The severity of these changes were correlated with the likely rotational forces directed at the condyle on the postero-lateral and antero-medial surfaces.

Somatosensory evoked potential monitoring of peripheral nerves during external fixation for limb lengthening and correction of deformity in children.

We undertook a retrospective analysis of 306 procedures on 233 patients, with a mean age of 12 years (1 to 21), in order to evaluate the use of somatosensory evoked potential (SSEP) monitoring for the early detection of nerve compromise during external fixation procedures for limb lengthening and correction of deformity. Significant SSEP changes were identified during 58 procedures (19%). In 32 instances (10.5%) the changes were transient, and resolved once the surgical cause had been removed. The remaining 26 (8.5%) were analysed in two groups, depending on whether or not corrective action had been performed in response to critical changes in the SSEP recordings. In 16 cases in which no corrective action was taken, 13 (81.2%, 4.2% overall) developed a post-operative neurological deficit, six of which were permanent and seven temporary, persisting for five to 18 months. In the ten procedures in which corrective action was taken, four patients (40%, 1.3% overall) had a temporary (one to eight months) post-operative neuropathy and six had no deficit. After appropriate intervention in response to SSEP changes, the incidence and severity of neurological deficits were significantly reduced, with no cases of permanent neuropathy. SSEP monitoring showed 100% sensitivity and 91% specificity for the detection of nerve injury during external fixation. It is an excellent diagnostic technique for identifying nerve lesions when they are still highly reversible.

The effect of sagittal orientation of the distractor on the biomechanics of mandibular lengthening.

PURPOSE: It has been previously demonstrated that distractors placed parallel to the mandible in the transverse plane, without regard to the vector of distraction create lateral displacement tendencies at the appliance-bone interface, leading to potential clinical problems and complications. The purpose of this study was to evaluate the biomechanical effects of linear distractor orientation in the sagittal plane relative to the anatomic axis of the mandible (mandibular plane) and the maxillary occlusal plane. MATERIALS AND METHODS: A 2-dimensional model of the human mandible was generated for computer simulation of osteodistraction. Positional changes of the distal mandibular segment were then analyzed during 10 mm of incremental lengthening based on distractor orientation relative to the maxillary occlusal plane. RESULTS: Distractors placed parallel to the inferior border of the mandible without regard to the maxillary occlusal plane created a vertical translation of the distal bone segment resulting in an anterior open bite. The magnitude of the anterior open bite was proportional to the angle between the vector of distraction and the maxillary occlusal plane, and to the amount of distraction. Placement of the distractors parallel to the maxillary occlusal plane eliminated the tendency for an anterior open bite. CONCLUSIONS: The orientation of the distractors relative to the maxillary occlusal plane is one of the important biomechanical parameters that must be included in preoperative planning for mandibular osteodistraction.

Mandibular distraction osteogenesis: a historic perspective and future directions.

Although orthognathic surgery has gained a generalized acceptance for maxillomandibular deformity correction, several limitations are associated with acute advancement of osteotomized bone segments. Furthermore, large skeletal discrepancies, such as those seen in syndromic patients, require such extensive bone movements that the surrounding soft tissues will not adapt to their new position, resulting in relapse or compromised function and esthetics. Recently, a number of experimental and clinical investigations have demonstrated that gradual mechanical traction of bone segments at an osteotomy site created in the craniofacial region can generate new bone parallel to the direction of traction. This phenomenon, known as distraction osteogenesis, opens up new possibilities in the correction of craniofacial deformities by orthodontists and maxillofacial surgeons. Hence, the purpose of this article is to review the historic development and biologic foundation of mandibular distraction osteogenesis, critically evaluate the current mandibular distraction devices with their clinical applications, and predict the future evolution of mandibular osteodistraction techniques.

Biomechanics of mandibular distractor orientation: an animal model analysis.

PURPOSE: Previous reports suggest that device orientation may be one of the most important parameters affecting the successful application of osteodistraction. However, only computer models or cadaver mandibles have been used to investigate the biomechanical effects of device orientation during mandibular distraction osteogenesis. Therefore, the purpose of this study was to compare two different device orientations during bilateral mandibular osteodistraction in an animal model. MATERIALS AND METHODS: Fifteen skeletally mature beagle dogs underwent 10 mm of bilateral mandibular lengthening by intraoral distraction osteogenesis. The dogs were divided into two groups based on the orientation of the distraction device relative to the mandible when viewed occlusally: either parallel to the body of the mandible (group I) or parallel to the axis of distraction (group II). The effects of device orientation during osteodistraction were then analyzed clinically, radiographically, and by dental cast measurements. RESULTS: Distractors oriented parallel to the body of the mandible caused an increase in the anterior width of the proximal mandibular segments. This lateral displacement of the proximal segments led to several clinical complications, including screw fixation failure and bone resorption under the fixation plates. These effects were minimized when the device was oriented parallel to the axis of distraction. CONCLUSIONS: Device orientation plays an important role when applying distraction osteogenesis in a clinical setting. Although other intrinsic and extrinsic factors affect the success of osteodistraction, the devices should be oriented parallel to the axis of distraction to minimize adverse biomechanical effects during bilateral mandibular lengthening.