Humeral cortical and trabecular changes in the throwing athlete: A quantitative computed tomography study of male college baseball players

Purpose: To examine bone adaptation to the mechanical loading of baseball using quantitative computed tomography. Methods: Quantitative computed tomography was performed on both throwing and nonthrowing humeri of 8 male college baseball players. Quantitative computed tomography geometric variables and volumetric cortical density were measured at each of 5 sites, located at 15%, 25%, 35%, 50%, and 75% of humeral length from distal to proximal. Volumetric trabecular density was measured at the most distal site only. Results: Significant side-to-side differences in favor of the throwing arm were found at all sites for total cross-sectional bone area (8%-17%, P < 0.01), cortical bone area (17%-29%, P < 0.01), and cortical bone thickness (18%-31%, P < 0.05). There were no important differences seen for cortical density; in contrast, trabecular density was significantly different in favor of the throwing arm at the one site measured (38%, P < 0.05). Conclusion: The dominant humerus of baseball players adapts via increases in cortical size and trabecular density.