Bending of the distraction site during mandibular distraction osteogenesisin the rabbit: A model for studying segment control and side effects

Purpose: The purpose of this investigation was to develop an animal model f or studying and correcting mandibular distraction side effects. Materials and Methods: Twenty-nine rabbits underwent bilateral mandibular d istraction. Bending of the mandible was accomplished by offsetting a linear distraction by 35 degrees from the occlusal plane (4 screws per distracter ), rotating the anterior segment inferiorly (2 screws per distracter), and removing a 3- or 6-mm wedge of the distraction site. The amount of bite ope ning varied according to the surgical design. Direct measurements, radiogra phs, and histology samples were compared. Results: Linear distraction produced a 4-mm anterior open bite and a Class III malocclusion after 2 weeks of distraction. Segmental rotation produced an 8-mm anterior open bite without complications. Removal of a wedge initia ted rotation of the anterior segment. A large wedge (G mm) produced fibrous union in the distraction site. The amount of bite opening or closure depen ded on the number of surgical screws and position of the distracter. Serial histologic sections showed bone formation at the rotated, triangular distr action site. Conclusion: Bite opening or closure can occur from loss of segment control or by altering surgical design. This information is needed to counter unwan ted side effects or to plan segment rotations. (C) 2001 American Associatio n of Oral and Maxillofacial Surgeons.