Dolph Houben

157 New surgical technique of whole joint VCA 8 Introduction Management of extensive destruction of the knee joint after infection, trauma, or primary tumors are a difficult problem. In worst-case scenarios, there is a significant loss of bone, cartilage, soft tissue, and an extensor mechanism defect. In these cases, treatment options are either to perform an arthrodesis, amputation or reconstruction [1] . Limb-salvage with joint reconstruction provides a better functional result, an arthrodesis, stability at the expense of motion, and amputation, loss of the limb and function without prosthetic fitting. Current reconstructive options involve the use of prosthetics, cryopreserved allografts, bone transport, alone or in combination. All reconstructive options are associated with significant complication and failure rates [2, 3] . Allotransplantation of knee joints is a relative novel approach to reconstruct large defects of the knee. Vascularized composite allotransplantation of bone and joints has been occasionally performed [4] . After some initial success, subsequent longer-term evaluation of human knee joint allotransplantation demonstrates all to have failed over time. Due to rejection with vascular thrombosis and tissue loss, or infection [1, 5-11] . Experimental models of vascularized knee joint transplantation have been described since 1968 in rodent, lagomorph, feline, and canine [5] . The effect of immunosuppression on vascularized knee allografts has been well described in dogs, demonstrating sustained immunosuppressive therapy to positively effect transplant survival [12] . Life-long drug therapy is clinically associated with the risk of opportunistic infections, diabetes, hypertension and neoplasms, with costs of drugs and monitoring causing a financial burden [1, 3] . The incidence of neoplasms induced by immunosuppressive therapy is estimated to be 4-18% [13] . Joint allotransplantation in a rabbit model using short-term immunosuppression and surgically induced neo-angiogenesis resulted in improved transplant viability, bone healing, and bone properties. Flexion contractures, due in part to the hyperflexed resting stance of the rabbit knee caused functional impairment [14, 15] . An animal joint transplant model better simulating the human knee function would allow a thorough investigation of joint allotransplant feasibility, including bone healing, joint properties, tissue perfusion, as well as systemic and local immune responses. In this feasibly study, we developed a technique permitting whole knee joint allotransplantation in pigs. The method included use of rigid intramedullary locked nail fixation of the femur and tibial segments, microsurgical reconstruction of the transplanted joint blood supply, and angiogenesis from implanted autogenous arteriovenous bundles. The latter, described for bone- only allotransplantation, enables cessation of immunosuppression after development of a robust autogenous blood supply.