Prefabricated vascularized bone flap: A tissue transformation technique for bone reconstruction

In this study, an attempt was made to transform a muscle vascularized pedic le raised on host vessels into a vascularized bone flap, using recombinant human bone morphogenetic protein 2 (rhBMP-2). The purpose of this study was to produce new bone vascularized in nature to increase the survival rate o f the subsequently grafted bone and to fabricate the newly formed bone into the desired shape. Silicone molds in the shape of a rat mandible were used to deliver rat bone matrix impregnated with or without rhBMP-2. A muscle p edicle the same size as the mold,vas raised on the saphenous vessels in the rat thigh and then sandwiched in the center of the silicone molds. The mol ds were sliced in half and each section was filled with rat bone matrix tha t was impregnated either with 25 mug of rhBMP-2 for the experimental group or with diluting material alone for the control group. The sandwiched flaps were then secured by tying them to the adjacent muscles and were harvested at 2 and 4 weeks after surgery. Three and six rats were used in the contro l and experimental groups at each time point, respectively. Bone formation was assessed in the ex. vivo specimens by macroscopic, radiologic, and hist ologic evaluation. Macroscopically, the continuation of the vascular pedicl e was clearly visible for both the control and experimental muscle flaps. H owever, no evidence of muscle-tissue transformation was observed in the con trol flaps, whereas all the flaps treated with rhBMP-2 produced new bone th at replicated the shape of the mold exactly and had saphenous vessels suppl ying the newly formed bone. This study demonstrates that this experimental model has the potential to be therapeutically applied for effective bone re construction.