Spontaneous fractures of the humerus during pitching. A series of 12 cases.

We report the recent occurrence of spontaneous humeral shaft fractures in 12 pitchers. The subjects were interviewed over the telephone using a standard questionnaire. Radiographs and medical records were solicited from their physicians. Their average age was 36 years and they had pitched an average of 11.4 years with an average layoff of 14 years (range, 7 to 24). Mean time between games pitched was 21 days (range, 3 to 56). The average number of pitches before the fracture occurred was 38 (range, 10 to 100). Pain was experienced at some point before the fracture in 75% of the pitchers and 75% of the fractures were spiral. These fractures were most probably spontaneous fractures brought on by accumulated fatigue damage. The period of buildup after a prolonged period of layoff was probably insufficient time for proper bone remodeling to occur in these men. While a large percentage of these men had pain before their injury, suggesting a predisposing stress fracture, there is no doubt that their fractures could still be caused by a sudden torsional load without the presence of a stress fracture.