Morphologic comparison of healing patterns in ethylene oxide-sterilized cortical allografts and untreated cortical autografts in the dog.

Abstract

Full-thickness canine cortical allografts were harvested cleanly, sterilized with ethylene oxide, and stored at 22 degrees C. The sterilized allografts were incorporated into segmental, femoral fracture repairs and evaluated for 6 months. Allografts were compared with untreated cortical autografts, which also were incorporated into segmental, femoral-fracture repairs for 6 months. Sequential fluorochrome labeling at 8, 11, 21, and 24 weeks after surgery made it possible to evaluate retrospectively the time of new bone formation. Morphometric evaluations were made of the numbers of labeled haversian systems, the percentage of labeled bone, and the porosity of the bone. The cortical allografts had bone formation in the proximal and distal portions of the graft, with the greatest activity at 5 to 6 months after surgery. Activity in the center of the allograft was minimal. Cortical autografts had bone formation throughout the graft, with the greatest number of haversian systems labeled at 3 months after surgery. We concluded that cortical allografts heal and remodel more slowly and in a different sequence of events than do cortical autografts.