Vascularized Composite Allotransplantation (VCA) has potential for reconstruction of joint defects, but requires life-long immunosuppression (IS), with substantial risks. This study evaluates an alternative, using surgical angiogenesis from implanted autogenous vessels to maintain viability without long-term immunotherapy.
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 (SIEF) flap and a saphenous AV bundle were placed within the transplanted femur and tibia, respectively, to develop a neoangiogenic, autogenous circulation. Ten transplants comprised Group 1. Group 2 (n=9) were no-angiogenesis controls with ligated flaps and AV 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, we assessed bone healing, joint function, bone and cartilage mechanical properties and histology.
Group 1 allotransplants had more robust angiogenesis, better healing, improved mechanical properties and better osteocyte viability than ligated controls (group 2). All 3 groups developed knee joint contractures and arthritic changes. Cartilage thickness and quality were poorer in allograft groups than autotransplant controls.
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.