Abstract
An osteochondral defect greater than 3cm in diameter and 1cm in depth is best managed by an osteochondral allograft.
If there is an associated knee deformity, then an osteotomy is performed. In our series of osteochondral allografts for large post-traumatic knee defects realignment osteotomy is performed about 60% of the time in order to off-load the transplant. To correct varus we realign the proximal tibia with an opening wedge osteotomy. To correct valgus, we realign the distal femur with a closing wedge osteotomy.
Our results with osteochondral allografts for the large osteochondral defects of the knee both femur and tibia, have been excellent in 85% of patients at an average follow-up of 10 years. The Kaplan-Meier survivorship at 15 years is 72%. At an average follow-up of 22 years in 58 patients with distal femoral osteochondral allograft, 13 have been revised (22%). The 15-year survivorship was 84%.
Retrieval studies of 24 fresh osteochondral grafts obtained at graft revision or conversion total knee replacement at an average of 12 years (5 – 25) revealed the following. In the areas where the graft was still intact, the cartilage was of normal thickness and architecture. Matrix staining was normal except in the superficial and upper mid zones. Chondrocytes were mostly viable but there was chondrocyte clusters and loss of chondrocyte polarity. Host bone had extended to the calcified cartilage but variable remnants of dead bone surrounded by live bone persisted. With a stable osseous base the hyaline cartilage portion of the graft can survive for up to 25 years.
