Ball-thrower's fracture of the humerus

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Figure. Frontal (top) and lateral (bottom) digital radiographs of the left humerus of a 20-year-old, left-handed man who had sudden arm pain after throwing a dodgeball.

These radiographs reveal a mildly displaced, comminuted spiral fracture at the distal diaphysis of the left humerus with an associated butterfly fragment (Fig. 1). The patient, a healthy recreational athlete with no prior arm pains, described making an off-balanced but forceful throw that was accompanied by a loud snapping noise.

Figure.

He was neurologically and vascularly intact, distal to the injury. No underlying lesion was identified to suggest a pathological fracture. Test results for serum calcium and thyroid-stimulating and intact parathyroid hormones were all in the normal range; a whole-body bone scan showed no evidence of other lesions. The patient was treated with a hanging cast that was later converted to a functional brace. Bony union was achieved at 11 weeks; no residual deficits were noted.

Fractures of the humeral shaft during a throw are relatively rare. Although they have been reported for various thrown objects, including hand grenades, javelins, shot-puts, cricket balls, stones and snowballs (Am J Sports Med 1998;26:242-6), the items most frequently thrown are balls; hence, the injury's name. The fracture is almost always the result of a full-effort throw that is often accompanied by an audible crack or snap. Ball-thrower's fracture is generally accepted to result from intense torsion upon the humerus during the acceleration phase of the throw.

Interestingly, this fracture rarely occurs in professional pitchers; altered shoulder biomechanics and cortical hypertrophy from years of training may be protective (Am J Sports Med 1998;26:242-6). Because untrained athletes do not experience these changes, the torsional force generated by throwing can exceed bone integrity.

Treatment involves a hanging cast, followed by a functional brace. The radial nerve is not usually involved, but when injured it almost always heals without medical intervention. Surgery is rarely recommended, and recovery is seldom less than excellent.