Progressive enlargement of thoracic ossification of the ligamentum flavum in professional baseball pitchers: a report of two cases.

Both systemic and local factors might influence the development of ossification of the ligamentum flavum (OLF); however, whether specific physical activities play a role in the development of OLF remains unclear. This report presents two cases of thoracic radiculopathy owing to progressive enlargement of thoracic OLF within a few years in Japanese professional baseball pitchers. Two left-handed, Japanese, professional baseball pitchers in their 20s experienced thoracic radiating pain. Mild hypesthesia of the lower thoracic vertebral levels was observed, and an increase in the size of the OLF within a few years was identified in the lower thoracic spine using computed tomography and magnetic resonance imaging. Neither patient exhibited myelopathy and were, therefore, treated conservatively. Both patients were able to return to playing in top condition within 4 months after onset. The findings in these cases suggest that thoracic OLF might increase in size and become exacerbated in certain individuals, such as professional pitchers, who experience repeated, localized, mechanical stress on the thoracic spine, irrespective of age.