The effect of the small and unstable autologous osteochondral graft on repairing the full-thickness large articular cartilage defect in a rabbit model.

We have investigated the effect of the insufficient autologous osteochondral graft on healing of the large articular cartilage defect using a rabbit model. An osteochondral defect, 7 mm in diameter, was made on the patellar groove of the femoral condyle and repaired with two surgical procedures: Group I, the osteochondral fragment as half as the defect was grafted. The graft was unstable and the size of the graft was smaller than the defect. This is a model of the insufficient autologous osteochondral graft to the large articular cartilage defect; Group II, the defect was left empty. At 2, 4, 12, and 24 weeks after the surgery, the specimens were analyzed macroscopically and histologically. To evaluate the microscopic morphology, a histologic grading scale composed of 5 categories was used. In Group I, although the graft sank a little, a grafted cartilage survived and the reparative fibrous tissue filled the defect covering implanted cartilage. In contrast, in Group II, the defect was only partially covered by fibrocartilaginous tissue with a faintly staining matrix. Throughout the entire observed periods, the scores of the repaired cartilage in Group I are significantly higher than those in Group II. Even the half size of osteochondral graft has an effect to reduce the size of the cartilage defect such as the spacer and leads to better healing compared to the cartilage defect untreated. In case that it is hard to transplant an optimal osteochondral graft because of large cartilage lesion, even the small and unstable osteochondral plug should be transplanted.