Throwing fracture of the humeral shaft. An analysis of 90 patients.

Ninety patients with humeral shaft fractures sustained during throwing were analyzed to determine what caused their injuries. All patients were recreational baseball players: 89 were men and 1 was a woman. The average age was 25 years (range, 12 to 43). The throwing style, type of pitch, fielding position, and type of ball used varied; however, the patients sustained their fractures while performing a hard throw in 87 (97%) of the occurrences. The actual courses of the balls thrown ranged from sideways to straight forward. All fractures were external rotation spiral fractures; 25 patients (28%) had a medial butterfly fragment, and 14 patients (16%) had radial nerve palsy. Fractures were most likely to have occurred in the distal half of the humerus, although they occurred frequently in the proximal half in patients in their early teens. We conclude that 1) the fracture can occur at any time during the acceleration phase before ball release, 2) this type of fracture can occur in any recreational baseball player attempting to perform a hard throw, and 3) the cause of this fracture is the throwing action itself.