Surgical angiogenesis with short-term immunosuppression maintains bone viability in rabbit allogenic knee joint transplantation

BACKGROUND: Vascularized composite allotransplantation has the potential for reconstruction of joint defects but requires lifelong immunosuppression, with substantial risks. This study evaluates an alternative, using surgical angiogenesis from implanted autogenous vessels to maintain viability without long-term immunotherapy. METHODS: Vascularized knee joints were transplanted from Dutch Belted donors to New Zealand White rabbit recipients. Once positioned and revascularized microsurgically, a recipient-derived superficial inferior epigastric fascial flap and a saphenous arteriovenous bundle were placed within the transplanted femur and tibia, respectively, to develop a neoangiogenic, autogenous circulation. There were 10 transplants in group 1. Group 2 (n = 9) consisted of no-angiogenesis controls with ligated flaps and arteriovenous bundles. Group 3 rabbits (n = 10) were autotransplants with patent implants. Tacrolimus was used for 3 weeks to maintain nutrient flow during angiogenesis. At 16 weeks, the authors assessed bone healing, joint function, bone and cartilage mechanical properties, and histology. RESULTS: Group 1 allotransplants had more robust angiogenesis, better healing, improved mechanical properties, and better osteocyte viability than ligated controls (group 2). All three groups developed knee joint contractures and arthritic changes. Cartilage thickness and quality were poorer in allograft groups than in autotransplant controls. CONCLUSIONS: Surgical angiogenesis from implanted autogenous tissue improves bone viability, healing, and material properties in rabbit allogenic knee transplants. However, joint contractures and degenerative changes occurred in all transplants, regardless of antigenicity or blood supply. Experimental studies in a larger animal model with improved methods to maintain joint mobility are needed before the merit of living joint allotransplantation can be judged.