Experimental model for allograft incorporation and allograft fracture repair.

This study describes a rat model of allograft osteotomy healing. An intercalary skeletal defect was created in adult Lewis rats by resecting a 2-cm segment of the femur in the diaphysis, including the periosteum and the cuff of muscle layers. The skeletal defects were replaced with fresh-frozen devascularized intercalary allografts from Sprague-Dawley rats. A transverse osteotomy was made in the middle of the allograft. The osteotomized segments were stabilized with an intramedullary threaded Kirschner wire, which allowed immediate ambulation. Radiographic and histological examination at 4 and 8 weeks revealed a characteristic healing process at three different interfaces. Radiographically, the distal metaphyseal host-donor junction healed faster than the proximal diaphyseal host-donor interface. The osteotomy site did not have evidence of an intramembranous or endochondral repair process. This model can serve as a baseline for assessing allograft incorporation and fracture repair.