Dolph Houben

168 CHAPTER 8 As there were no problems or complications during surgery or in the early post-operative period (0-4 days), we believe the procedure to be technically feasible although clearly complex, requiring experienced surgical teams. The post-operative care of the animals is extremely important, as we have previously experienced in our tibia defect models [16, 25, 32] . Immediate post-operative ambulation was observed following tibia allotransplantation, including full weight bearing after an average of only 4 days. In this feasibility study, the animals were also standing and walking within the first few post-operative days without limitation. Wound problems, including the development of large seromas with infection developed, requiring termination shortly after 2 weeks. Future use of the same animal model will require some modification to reach the target survival period. Wound drainage with both deep and superficial post-operative drains may prevent seroma development, and protection from full weight-bearing, implant failure. Thereafter, some form of protection will be necessary until tissue stability has been achieved. This may include the use of an abdominal sling to suspend the hind limb. The observed complications were unexpected, and we believe avoidable in the future, based upon our prior experience of hind-limb bone allotransplantation in the same porcine model. The pedicled gracilis muscle flap in porcine, has been described in several porcine studies [17, 33] . In our anatomy and feasibility study, we found the same vascularization pattern as described in the literature. We used the anatomy to elevate a pedicled gracilis flap for soft tissue coverage and induction of autologous revascularization of the allogenic knee. In previous studies, bone viability was maintained solely by autogenous AV-bundles. Although this might be true for bone only VCA’s, cartilage is dependent on diffusion as it does not contain its own blood flow, and the knee capsule is dependent on the allogenic microvasculature. The autogenous AV-bundle implantation might therefore not be enough to maintain viability thought-out all tissue types. The gracilis muscle flap was used to stimulate and induce formation of an autogenous neoagenic circulation in all tissue types without the need for life-long immunosuppression. In this, study the allotransplants appeared viable two weeks after transplantation. In future research, a detailed micro angiography of the complete hind-limb should be made to assess neo-angiogenesis arising from the AV-bundles and muscle flap into multiple tissue types. Thereafter, viability can be assessed through histology and molecular analyses. We propose a new whole knee joint allotransplantation model with surgical induced neo- angiogenesis and short-term immunosuppression. Our current surgical technique works, whereas the post-operative care and treatment needs improvement in future studies. This model would provide critical pre-clinical information and allows multiple analyses of the whole knee allotransplant after cessation of immunosuppression and evaluate surgical induced autologous revascularization.