PREFORMED VASCULARIZED BONE-GRAFTS USING POLYETHYLENE CHAMBERS

Previous work has shown that corticocancellous bone chips placed in a titanium chamber with an arteriovenous vascular pedicle will result in a pre-formed vascularized bone graft. The present study was designed to determine whether these grafts can be transferred as an island or free vascularized bone graft, and to examine the material properties of these grafts. Thirty-two male, New Zealand white rabbits were divided into four groups based on the time of sacrifice following the initial chamber implantation. Injected molded cylindrical polyethelyne chambers, measuring 22 mm long and with an 8-mm inner diameter, were used. Corticocancellous bone chips were placed in the chambers and each chamber was implanted in the mid-thigh, with saphenous vessels running through the chamber. The chambers were implanted into the right and left thigh of each animal. To test the hypothesis of the possibility of transferring this graft as an island or free vascularized graft, ligation of the distal vascular pedicle on one side was achieved at re-exploration at 3, 6, 9, and 12 weeks. The contralateral side served as a control in which the vascular pedicle was not ligated. In the controls, bony bridging between the corticocancellous bone chips was observed after 7 weeks. A solid bone graft was present within the chamber by 10 weeks. However, histomorphometric evaluation indicated significant bone resorption. By 13 weeks, resorption progressed to the point where only small islands of bone remained. Ligation of the distal vessels resulted in thrombosis of the vessels within the chamber Necrosis of newly-formed bone was observed in the area adjacent to the vascular thrombosis. By 9 weeks, viable bone was observed within the chamber, despite thrombosis of the vascular pedicle. These findings were most probably due to the development of collateral circulation. This study supports the concept of creating a "molded vascularized bone graft" with a single vascular pedicle.