Methods of study: Prospective Controlled Animal Study.

Objectives: Evaluation of the feasibility of embryonal epiphyses transplantation in a xenogeneic model for reconstruction of adult articular cartilage in a rabbit model.

Introduction: Articular cartilage reconstruction has been the goal for many years of orthopaedic research. Current acceptable techniques include the use of allografts, autologous chondrocytes transplantation and osteochondral cylinder grafting. Reconstruction of articular cartilage defects using adult osteochondral allografts is an established clinical procedure, whose principal drawback is lack of lateral integration of the grafts to the surrounding tissue. Autologous chondrocytes transplantation is a sophisticated technique requiring cell culture and a staged operation. Its main draw back is the lack of mechanical strength early on and the prolonged rehabilitation period. This study was conducted in order to evaluate the possibility of using embryonal epiphyses as a cartilage reconstruction tissue.

Methods: A xenogeneic human to rabbit sub-acute osteochondral defect model was designed to evaluate the possibility of allogeneic implantation in humans. The following procedures were performed (n=5): transplantation of: 1. live epiphyses, 2. live epiphyses with autogeneic periosteum, 3. devitalized epiphyses, and 4. devitalized epiphyses with autogeneic articular chondrocytes.

A fifth control group did not receive any implant. Animals were followed for 3 months after transplantation and than sacrificed. The histological specimens were evaluated by image analysis after immuno-histochemical stains were performed (including the following antigens – collagen type II, collagen type I, collagen type III, collagen type X, S-100, alkaline phosphatase, osteocalcin, osteopontin, nitric oxide synthase).

Results: Animals in groups 1 and 2 had a viable reconstruction of the articular surface with little evidence of rejection and without pannus formation. Animals in groups 3 and 4 became severely arthrotic and the graft was resorbed. Nitric oxide synthase accumulation was reduced in group 1 and 2 as compared to groups 3, 4, and 5, indicating a joint preserving function of the epiphyseal grafts.

Discussion: Epiphyseal grafts appear to be a feasible procedure for reconstruction of articular cartilage defects even in a xenogeneic model. The restoration of articular cartilage even with a xenogeneic graft appears to prevent nitric oxide synthesis and the resulting destruction of unafflicted articular cartilage. This is a major pathway leading to secondary osteoarthritis after joint injury. Blocking this pathway might prevent degenerative changes.