Fracture of the shaft of the humerus secondary to muscular violence.

Fractures of a normal humeral shaft secondary to muscular violence have been uncommonly reported in the literature since the early 1900s. These injuries have been associated with throwing javelins, hand grenades, and baseballs. We report a case of a similar injury occurring in a healthy young amateur baseball pitcher. Pertinent anatomy, pathomechanics, and electromyographic study results are discussed.