Experimental study of vascularized bone grafts in rat : Effect of mechanical loading on bone dynamics

We studied the etiology of postoperative hypertrophy of vascularized bone grafts in a murine experimental model. Syngeneic grafting of revascularized ulna to rat tibia was performed with (group 1) or without (group 2) mechanical loading. The effect of simple overloading on intact bone was studied by segmental resection of the radius (group 3). Bone dynamics were examined by histomorphological measurements. Significant hypertrophy was observed in the early postoperative period in both groups 1 and group 2. After the initial phase, bone growth continued and extensive remodeling was observed in group 1, while marked bone resorption was observed in group 2. Adaptive remodeling was also observed in group 3 after surgery, but was slower than that in groups 1 and 2. Early hypertrophy of vascularized grafts did not correspond to mechanical loading. These results suggest that mechanical loading is the principal factor responsible for remodeling in vascularized bone grafts for their adaptation to a new environment.