Reconstruction of Major Articular Osteochondral Defects with OP-1 Treated Allografts and Vascularized Tissue

ABSTRACT

The treatment of articular cartilage and bone defect has been challenging for many years. Autologous osteochondral grafting represents the most physiologic procedure for reconstructing joint defects but is severely limited by the availability of donor material. Allogenic osteochondral grafting differs from the other grafting method in obtaining almost unlimited amounts of material of exact size and form for complex joint reconstructions. An alternative approach that may improve allograft revascularization and incorporation was to combine an autologous muscle flap with an allograft and vascularized osteochondral allografts that have reported excellent long term results. The vascular characteristics of muscle flaps, with their capacity as a source for mesenchymal stem cells, provide the muscle flap with the ability to initiate bone formation and repair in transplanted allografts in response to osteogenic factors. Forty adult New Zealand White rabbits underwent complete resection of the proximal 2/3 of the humerus. The defects were immediately grafted following substance (1) lyophilized osteochondral allografts (n=10); (2) lyophilized osteochondral allograft with a muscle flap filling the bone marrow cavity(n=10); (3) OP-1(Osteogenic protein-1) treated lyophilized osteochondral allografts (n=10); (4) OP-1 treated lyophilized osteochondral allograft with OP-1 injected muscle flap filling the bone marrow cavity(n=0). All the examinations were operated under aseptic conditions, and follow-up evaluations were performed in the 4th, 6th, 8th, 10th, 12th, and 24th week. Range of motion showed no difference between the groups, but more limited in OP-1 treated allograft groups. Under the histologic examination, the groups of lyophilized osteochondral allograft with a muscle filling the bone marrow cavity regenerated more articular cartilage than that of OP-1 treated allograft. These results suggest that using OP-1 treated lyophilized osteochondral allograft with OP-1 injected muscle flap filling the bone marrow cavity could get more organized articular cartilage and bone regeneration.