Physical and biological aspects of repair in dog cortical-bone transplants.

The amount of repair and the time required to accomplish repair of four-centimeter segmental fibular transplants in twenty-one male adult dogs were determined at from two to forty-eight weeks after transplantation by torsional stress testing, microradiography, and tetracycline labeling. The transplanted cortical bone was greatly weakened at from six weeks to six months but was nearly normal at one year. The strength of the transplant appeared to be related to the amount of porosity of the matrix rather than to the quality or completeness of biological repair. Spatially, the repair was ordered rather than random. The initial resorption caused increased porosity which was slowly offset by apposition of new bone, a process which was dependent on general skeletal metabolic activity. Although physical strength was near normal at forty-eight weeks, only 60 per cent of the transplants had been remodeled.