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Unique Rodent Model of Distraction Osteogenesis of the Mandible

Buchman, Steven R. MD, FACS*; Ignelzi, Michael A. Jr DDS, PhD; Radu, Caius MD*; Wilensky, Jonathan MD*; Rosenthal, Andrew H. MD*; Tong, Lawrence MD*; Rhee, Samuel T. MD*; Goldstein, Steven A. PhD

Original Articles
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Despite the increasing use of distraction osteogenesis (DO) of the mandible, the molecular mechanisms regulating new bone formation during DO remain poorly understood. The purposes of this study were (1) to establish a unique rodent model of DO capable of outlining parameters for new bone formation at the distraction site and (2) to determine a critical-size defect to differentiate osteogenesis resulting from distraction from conventional fracture healing at the osteotomy site. Adult Sprague–Dawley rats were fitted successfully with this newly developed distraction device. Analyses demonstrated that the device could distract the rat mandible reliably to 5.1 mm with complete union. Acute intersegmental gaps of 2 mm resulted in complete bony union in a manner consistent with fracture healing, whereas 3-mm acute gaps resulted in varying degrees of bony union. Acute intersegmental gaps of 5.1 mm invariably resulted in fibrous nonunion. In summary, the authors have developed a rodent model of DO of the mandible. Their distraction protocols resulted successfully in advancement to 5.1 mm with bony consolidation. Notable fracture healing occurred at immediate intersegmental spaces as large as 3 mm. A gap of 5.1 mm was sufficient to act as a critical-size defect, resulting consistently in fibrous nonunion. These findings validate the effectiveness of this distraction device and establish the critical-size defect of a rat mandible at more than 3 mm. This novel model of DO provides an effective method of examining fundamental mechanisms responsible for new bone formation in the craniofacial skeleton.

An adult rat model of distraction osteogenesis of the mandible successfully resulted in advancement of 5.1 mm with bony consolidation. The titanium and steel devices were well tolerated, and no dental injuries resulted.

*Section of Plastic Surgery, Department of Surgery, and the ‡Orthopaedic Research Laboratory, University of Michigan School of Medicine; and the †Department of Orthodontics and Pediatric Dentistry, University of Michigan School of Dentistry, Ann Arbor, MI.

Received Nov 14, 2001, and

in revised form Jan 28,2002.

Accepted for publication Jan 28, 2002.

Address correspondence and reprint requests to Dr Buchman, Section of Plastic Surgery, F7859 Mott Children's Hospital, 1500 E. Medical Center Drive, University of Michigan Medical Center, Ann Arbor, MI 48109-0219.

Supported in part by grants NIH-5-P60-AR20557 (University of Michigan Multipurpose Arthritis and Musculoskeletal Disease Center), NIH-RO1 DE13014 (Mechanically Guided Tissue Regeneration), NIH R01 HL 60454, and the Carls Foundation.

Buchman SR, Ignelzi Jr MA, Radu C, Wilensky J, Rosenthal A, Tong L, Rhee ST, Goldstein SA. Unique rodent model of distraction osteogenesis of the mandible.

© 2002 Lippincott Williams & Wilkins, Inc.