Experimental study on vascularized island pedicle bone graft: bony fusion between the graft and the recipient floor

To evaluate the process of bony fusion between the recipient floor and the bone graft, where a muscle sleeve has been interposed, an experimental model for a vascularized island pedicle bone graft was prepared using rats. The proximal two thirds of the tibia pedicled with the popliteal artery and vein was collected to be used as a vascularized bone. This was onlay grafted to the femur of the same limb in such a manner that the muscle sleeve was interposed between the bone graft and the recipient floor. The animals subjected to this procedure were designated as the vascularized island pedicle bone graft group (hereafter called group V, n = 32). In another group, vascular pedicles were interrupted by ligation and the animals were subjected to nonvascularized bone graft (hereafter called group N, n = 32). In the third group, an appropriate amount of bone chips was transplanted throughout the length of the grafted floor; then the animals were subjected to additional vascularized island pedicle bone graft (hereafter called group B, n = 13). In groups V and B, the vascularized bone graft formed new bone at the site where the bone graft faced the recipient floor 6 weeks after surgery. Hypertrophy of the bone graft was noted. Bony fusion at the section where a muscle sleeve had been interposed was recognized only in group B. Chondrocytes were found around the free bone graft, suggesting chondrocyte participation in osteogenesis. In group N, the bone graft had been absorbed and no bony fusion was recognized between the bone graft and recipient floor in any of the samples. These findings imply that it is important to minimize the size of the muscle sleeve attached to the vascularized island pedicle bone graft and add free bone chips around the grafted bone to assure bony fusion between a vascularized bone graft and the recipient floor in clinical practice.