Anatomic and hemodynamic study of the vascularized pig fibula bone flap model

Despite much interest in studying the pathophysiology of experimental skin and muscle flaps to better understand the pathobiology of flap failure, relatively little has been published in the investigation of vascularized bone flaps. The aim of this study was to develop a suitable vascularized bone flap model in the pig in the hope that this model may prove useful in studying the pathophysiology of vascularized bone tissue transfer. Yorkshire pigs (17-26 kg) were used for all experiments. Anatomic studies revealed that the fibula in the hindlimb was the most suitable bone for investigation as a flap model. Anatomic dissections, radiologic investigations (plain x-rays, angiograms), and morphometric analyses of the fibulae in both hindlimbs of five animals were carried out. In a separate group of pigs (n = 6), the fibula was elevated as a vascularized flap and then blood flow was measured using the 15-microns radioactive microsphere technique. The fibula in the pig is supplied by a branch of the cranial tibial artery, running along an intermuscular septum between the posterior and anterior compartments of the hindlimb accompanied by one or two vena commitans. The bone flap is raised with a cuff of flexor hallucis longus with a length of 9.2 +/- 0.2 cm (mean +/- SEM). Blood flow measurement confirmed that the entire fibula was well vascularized when elevated on its pedicle. Gradient blood flow showed a bimodal distribution, with regions of highest blood flow noted at the proximal and distal ends of the bone flap, in areas where there were greater percentages of cancellous bone. The results of these experiments suggest that the pig fibula may be a suitable model for the study of vascularized bone flap pathophysiology.