Microvascular transplantation of cryopreserved knee joints

Successful transplantation of cryopreserved complex tissues has not yet been reported. We wanted to test whether microvascular transplantation of cryopreserved knee joints can be achieved in rats. Twenty-five knee joints were cryopreserved and then microsurgically transplanted to the groin of inbred recipient animals. Ten fresh knee joints were transplanted as controls. One week after transplantation, the transplants were evaluated in situ for pedicle patency and tissue perfusion and then harvested for histology. In all surviving rats (n = 21), the cryopreserved knee joints were well perfused immediately after transplantation. At harvest, 14 knee joints appeared viable with a patent pedicle, whereas 6 were questionably viable and demonstrated arterial thrombosis. Histologically, the viable joints revealed an intact bone and cartilage matrix; however, the number of viable chondrocytes and osteocytes was reduced. Additionally, endothelial cell plugs in some areas of the capillary bed led to scattered microinfarctions despite a patent vascular pedicle. The nonperfused transplants showed infarction. In conclusion, we have demonstrated successful microvascular transplantation of cryopreserved knee joints with reduced short-term viability. Long-term studies must determine whether full recovery occurs.