Medial and Lateral Distal Femoral Condyle Osseous and Articular Cartilage Topography to Determine Graft Matching

OBJECTIVES: Osteochondral allograft transplantation (OAT) for osteochondral defects of the knee typically matches donor laterality and condyle to the recipient defect location. This study aimed to compare subchondral osseous and articular cartilage surface topography between medial femoral condyle (MFC) and lateral femoral condyle (LFC) donor grafts. METHODS: Human femoral hemi-condyles (11 MFC and 6 LFC) were divided into 2 groups: MFC donor to MFC defect (MM) and LFC donor to MFC defect (LM). Computed tomography images were exported into point-cloud models using Mimics software. Articular cartilage and subchondral bone were individually segmented, creating two distinct point clouds. Circular articular cartilage defects (15 mm diameter and 25 mm diameter) were created in the MFC samples at 3 locations (0°, 45° posterior, and 90° posterior. Medial and lateral donor models were virtually placed into the MFC defect model so that articular surfaces were flush. Distance of articular surface between donor and defect and resulting osseous mismatch were calculated (Figure 1). RESULTS: Mean articular surface mismatch was <0.5 mm in both groups, suggesting similar surface matching. Group LM exhibited greater osseous mismatch than Group MM for both 15 mm defects (mean least distance: 0.91 ± 0.45 mm, 0.74 ± 0.20 mm, P = 0.04) and for 25 mm defects (mean least distance: 1.05 ± 0.39 mm, 0.74 ± 0.16 mm, P < .01). Osseous mismatch between groups in the 25 mm defect became significant at 0° (MM, 0.66 ± 0.36 mm and LM, 1.10 ± 1.00 mm, P < .01) and at 45° (MM, 0.76 ± 0.15 mm and LM, 1.06 ± 0.47 mm, P = 0.05). CONCLUSION: LFC donor grafts provide acceptable cartilage surface matching for MFC defects but have greater osseous mismatch than MFC grafts. This mismatch increases with increasing graft size. The implications of subchondral bone mismatch are yet to be determined.