The effect of graft sizing on osteochondral transplantation

The goal of this study was to analyze the effect of graft sizing on the histologic property of articular cartilage in autologous osteochondral transplantation.Histologic analysis using an animal model.Eighteen skeletally mature female Japanese white rabbits were used in this study and divided into 2 groups based on the surgical procedure. Group I: A cylindrical fragment (7 mm in diameter and 5 mm in depth) was harvested at the femoral condyle using the Osteochondral Autograft Transfer System (Arthrex, Naples, FL), then precisely returned to the defect from which the fragment was originally harvested. This surgical model supposes that the articular surface geometry of the osteochondral graft exactly matches that of the cartilage lesion; however, the osteochondral graft is not the same size as the defect in this model because of the surrounding gap that corresponds to the blade thickness of the chisel used to take the graft. Group II: A 1-mm larger osteochondral fragment (8 mm in diameter and 5 mm in depth) taken from the contralateral femoral condyle was transplanted to the osteochondral defect made as in group I, achieving a tight fit. Specimens were stained with Safranin-O fast green and analyzed microscopically at 4, 12, and 24 weeks after surgery.In group I, histologic examination revealed an increase in cartilage thickness and cell density during the implantation period. Round and polygonal hypertrophic clusters of chondrocytes with cytoplasmic vacuoles were observed. By contrast, in group II, the thickness of the articular cartilage was almost the same as that of the normal adjacent cartilage with no significant change observed.It is suggested that sizing of the implanted osteochondral fragment plays an important role in preserving the histologic properties of cartilage.This study suggests that osteochondral graft stability may influence the histologic properties of the repaired cartilage. It is preferable to implant the slightly oversized graft into the cartilage lesion in autologous osteochondral transplantation to preserve the histologic properties of cartilage.