Poster 173: Evaluation of Radius of Curvature of the Humeral Capitellum in Young Athlete Osteochondritis Dissecans Lesion Sites
Authors: Obilo Chiamaka , Alayleh Amin , Shea Kevin , Chan Charles 
Published: October 2024

Objectives: Elbow Osteochondritis dissecans (OCD) lesions are often seen in young baseball players and gymnasts. Prior studies have suggested that capitellar OCD lesions are frequently found in two distinct and separate locations in these two populations: at 58° and 28° inclination angles from the humeral axis in baseball players and gymnasts respectively. As treatment of OCD lesions with osteochondral allografts and autografts have gained popularity, an increased emphasis has been placed on the utilization of measurements of capitellar radius of curvature (ROC) to minimize articular incongruity or ROC mismatch between the recipient elbow and donor knee. The purpose of this study was to further characterize the coronal-axial ROC in these two distinct locations and potentially identify morphological differences between the two OCD lesion locations. Methods: Elbow MRIs of thirty pediatric patients between the ages of eight and seventeen with no history of elbow injuries were retrospectively studied. Using the radiographic diagnostic viewing software, eUnity, two reviewers measured capitellar ROCs encompassing at least a ten-millimeter plug at both 58° and 28° inclination angles from the humeral axis on coronal-axial elbow MRIs for each patient. Coronal-axial views were established by using the 3D function to orient the axial plane in parallel with the capitellar articular surface and the coronal plane perpendicular to the capitellar surface. 58° and 28° inclination angles from the humeral axis were measured in the sagittal plane, and coronal-axial images were transformed in phase with each inclination angle. For each observer, paired two-tail t-tests were performed to evaluate statistical differences in ROC measurements between the two locations. Inter-observer absolute agreement was examined using the “irr” Intraclass Correlation Coefficient R package. Using a Fisher’s test, p values from the individual observer paired t-tests were combined and reviewed. Results: The Intraclass Correlation Coefficients were 0.886 for the 58° inclination angle and 0.921 for the 28° inclination angle, respectively denoting good and excellent inter-observer reliability. Paired two-tailed t-tests of each observer’s 58° and 28° capitellar ROC measurements yielded p<0.001. The unweighted average t-value of 10.49 with 29 degrees of freedom and the combined Fisher p-value of <0.001 suggest there is a significant difference between the ROC measurements at the 58° and 28° humeral capitellar locations. Average ROC measurements ranged between 13.94mm ± 1.31mm and 14.3mm ± 1.42mm at the 58° capitellar location and 11.7mm ± 1.53mm and 11.76mm ± 1.30mm at the 28° capitellar location. Measurements at the 28° inclination angle from the humeral axis tended to be smaller than those of the 58° inclination angle from the humeral axis. On average the ROC at the 28° inclination was between 2.18mm and 2.50mm smaller than the ROC at the 58° inclination. Conclusions: Prior studies have identified differences in capitellar OCD lesion location between baseball players and gymnasts. This study offers further characterization of both morphologic locations. The capitellar radii of curvature at 58° and 28° inclination angles from the humeral axis statistically differed, as demonstrated by both observer measurements. The ROC at the 28° inclination was on average between 2.18mm and 2.50mm smaller than the ROC at the 58° inclination. Therefore, because of evident ROC differences between these two locations, it may be beneficial to consider anatomic morphologic differences between distinct humeral capitellum regions when selecting graft locations to achieve an optimal osteochondral autograft match. Future research on optimizing donor-to-recipient ROC may improve articular congruity restoration and long-term outcomes.