Biomechanical and histological evaluation of osteochondral transplantation in a rabbit model

Background: Biomechanical and histological properties of osteochondral transplantation have not been extensively examined. Hypothesis: Osteochondral grafts have properties similar to native articular cartilage. Study Design: Controlled laboratory study. Methods: A 2.7 mm (diameter) x 4.0 mm (depth) osteochondral defect was created in 17 New Zealand white rabbit knees. An osteochondral graft, harvested from the contralateral knee, was transplanted into the defect. Eight rabbits were sacrificed each at 6 and 8 weeks. Results: The 12-week grafts (1213.6 +/- 309.0 N/mm) had significantly higher stiffness than the 6-week grafts (483.1 +/- 229.1 N/mm; P < .001) and of normal cartilage (774.8 +/- 117.1 N/mm; P < .003). Stiffness of the 6-week grafts was significantly lower than normal cartilage (P < .036). At all time points, full-thickness defects had significantly lower stiffness than normal cartilage (P < .001). Histologically, transplanted grafts scored significantly higher than the full-thickness defects (P < .001). The defects showed inconsistent, fibrocartilage healing. The grafts demonstrated cartilage viability, yet with a persistent cleft between the graft and host. Conclusions: Osteochondral transplants undergo increased stiffness in the short term, with evidence of structurally intact grafts. Clinical Relevance: Osteochondral transplantation may be a viable treatment option; however, long-term investigation on graft function is necessary.