BIOLOGICAL AND PHYSICAL-PROPERTIES OF AUTOGENOUS VASCULARIZED FIBULAR GRAFTS IN DOGS

The biological and biomechanical properties of normal fibulae, fibulae that had had a sham operation, and both vascularized and non-vascularized autogenous grafts were studied in dogs at three months after the operation. The study was designed to quantify and correlate changes in these properties in orthotopic, stably fixed, weight-bearing grafts and to provide a baseline for additional studies of allografts. The grafts were eight centimeters long and internally fixed. The mechanical properties of the grafts were studied by torsional testing. Metabolic turnover of the grafts was evaluated by preoperative labeling of the dogs with 3H-tetracycline for resorption of bone mineral and with 3H-proline for turnover of collagen. Cortical bone area and porosity were measured. Postoperative formation of bone was evaluated by sequential labeling with fluorochrome. The vascularized grafts resembled the fibulae that had had a sham operation and those that had not had an operation with regard to the total number of osteons and the remodeling process, as measured both morphometrically and metabolically. The vascularized grafts were stronger and stiffer than the non-vascularized grafts and were not different from the bones that had had a sham operation. In contrast, the non-vascularized grafts were smaller, weaker, less stiff, and more porotic, had fewer osteons, and demonstrated increased turnover and resorption compared with the vascularized grafts, the bones that had had a sham operation, and the bones that had not had been operated on. The data suggest that, in the early postoperative period, vascularized bone grafts resemble bones that have had a sham operation and those that have not been operated on and that they maintain their strength and stiffness better than non-vascularized grafts at least during the first three months after the operation. They are not dependent on the host bed for revascularization and maintenance of structural properties, and they may be useful in difficult clinical circumstances when the blood supply is compromised. It should be emphasized, however, that these observations were made early in the postoperative period and that non-vascularized grafts may provide a functional construct after sufficient time.