Transplantation of a vascularized rabbit femoral diaphyseal segment: mechanical and histologic properties of a new living bone transplantation model.

A new vascularized bone transplantation model is described, including the anatomy and surgical technique of isolating a rabbit femoral diaphyseal segment on its nutrient vascular pedicle. The histologic and biomechanical parameters of pedicled vascularized femoral autotransplants were studied following orthotopic reimplantation in the resulting mid-diaphyseal defect. Vascularized femur segments were isolated in 10 rabbits on their nutrient pedicle, and then replaced orthotopically with appropriate internal fixation. Postoperative weightbearing and mobility were unrestricted, and the contralateral femora served as no-treatment controls. After 16 weeks, the bone flaps were evaluated by x-ray (bone healing), mechanical testing (material properties), microangiography (quantification of intraosseous vasculature), histology (bone viability), and histomorphometry (bone remodeling). Bone healing occurred by 2 weeks, with further callus remodeling throughout the survival period. Eight transplants healed completely, while two had a distal pseudarthrosis. Microangiography demonstrated patent pedicles in all transplants. Intraosseous vessel densities were comparable to nonoperated (control) femora. We found ultimate strength and elastic modulus to be significantly reduced when compared to normal controls. Viable bone, increased mineral apposition rate, and bone turnover were demonstrated in all transplants. The method described, and the data provided will be of value for the further study of isolated segments of living bone, and in particular, for investigations of reconstruction of segmental bone loss in weight-bearing animal models. This study also provides important normative data on living autologous bone flap material properties, vascularity, and bone remodeling. We intend to use this method and data for comparison in subsequent studies of large bone vascularized allotransplantation. (c) 2008 Wiley-Liss, Inc. Microsurgery, 2008