EVALUATION OF GROUND CORTICAL AUTOGRAFT AS A BONE-GRAFT MATERIAL IN ANEW CANINE BILATERAL SEGMENTAL LONG-BONE DEFECT MODEL

The recent orthopaedic literature reflects a growing number of bone gr aft substitutes and osteogenic growth factors under investigation in a number of animal models. We attempted to establish a well-controlled, large animal model of a segmental defect in a weight-bearing long bon e by developing a bilateral diaphyseal radial defect model in the cani ne. We also evaluated the effectiveness of ground cortical autograft a s a graft material. Twenty-three adult mongrel dogs underwent bilatera l radial osteotomies with creation of a 2.0-2.5-cm diaphyseal defect o n each side. All dogs received cancellous autograft (CAN) on one side, nine received no graft material (DEF) on the opposite side, and 14 re ceived morselized cortical autograft (CORT) on the opposite side. Radi i were stabilized by external fixation. Animals were followed radiogra phically at 6-week intervals to evaluate the healing process. Thirteen dogs were sacrificed at short-term follow-up (8-12 weeks postsurgery) and 10 at long-term (16-24 weeks). Biomechanical torsion testing to f ailure and histological evaluation were performed on each defect. All CAN radii achieved union (100%) while only one of nine DEF radii (11%) and none of 14 (0%) of CORT radii achieved union. Statistically signi ficant differences in biomechanical parameters between both test group s and their corresponding autograft control radii were found. Histolog y revealed fibrous nonunions in the DEF and CORT radii. These results demonstrate that the bilateral canine radial defect model represents a consistent and reproducible model for bone healing of segmental defec ts in weight-bearing long bones and that ground cortical autograft is an ineffective graft material.