Experimental model for allograft incorporation and allograft fracture repair

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