Optimizing Graft Extraction From the Femoral Condyle for Fresh Osteochondral Allograft Transplantation in Treating Osteochondritis Dissecans of the Capitellum: Best Fit Based on Radius of Curvature.

ABSTRACT

BACKGROUND: Osteochondritis dissecans (OCD) of the capitellum is a common cause of pain and dysfunction in adolescents that engage in repetitive elbow loading. For large, unstable lesions fresh osteochondral allograft transplantation (FOCAT) from the femoral condyle has been described as an effective treatment. Current practice involves significant guesswork in obtaining an appropriately sized graft, with anatomic variations resulting in poor graft fit. No studies currently exist that analyze and identify the best distal femur FOCAT graft site to repair OCD lesions of the capitellum based on the radius of curvature (ROC) and simulated matching. METHODS: Computed tomography scans of the elbow were used to estimate the subchondral bone ROC of capitella in adolescents aged 11 to 21 years. The capitellar location used corresponds to the most commonly reported site of OCD lesions in the elbow. Computed tomography scans of the lower extremity were used to estimate the subchondral bone ROC of 4 potential donor femoral condyle grafts. ROC from distinct regions at the posterior section of both the medial and lateral femoral condyles were measured 2 areas representing 10 mm grafts from the center (MC1 and LC1), and 2 areas estimating 10 mm grafts posterior and adjacent to the physeal scar (MC2 and LC2). Intraobserver and interobserver reliability measurements were preformed to corroborate precision and validate the method. RESULTS: The mean ROC of healthy subchondral bone at the region of the capitellum were OCD lesions most commonly occur was 9.79±1.39 mm. The mean ROC of MC1 was 18.61±2.26 mm. The average ROC of the MC2 was 15.23±1.43 mm. The average ROC of LC1 was 16.47±1.34 mm. The average ROC of LC2 was 18.19±3.09 mm. After 15,000 simulated condyle-to-capitellar site matchings based on these measurements, a good fit graft was achieved at a frequency of 15%. DISCUSSION: No site measured from the femoral condyle demonstrated a subchondral ROC that exactly matched the subchondral ROC of the capitellum at the center location where OCD lesions most commonly occur; of the locations measured, a 10 mm section from MC2 demonstrated the closest match. On the basis of this analysis, extracting a graft from MC2 has the potential to further optimize FOCAT fit to the capitellum. LEVEL OF EVIDENCE Level III.