Forearm deformity in patients with hereditary multiple exostoses: factors associated with range of motion and radial head dislocation.

BACKGROUND: There is a high rate of forearm deformity in patients with hereditary multiple exostoses, with many patients developing radial head dislocation associated with ulnar shortening.

METHODS: One hundred and six patients with hereditary multiple exostoses who were fifteen years of age or older were identified with use of a previously compiled database. An independent observer measured flexion and extension of the elbow and wrist as well as supination and pronation of the forearm and recorded the number of exostoses affecting the forearm. Proportional ulnar length was calculated as a percentage of the measured height of the patient ([ulnar length/height] ×100).

RESULTS: Exostoses were identified in 183 (86%) of the 212 forearms that were examined. The distal part of the radius was the most common site and was affected in 73% of the patients. One in seven patients had a dislocated radial head, which was associated with reduced proportional ulnar length (p < 0.001). Both radial head dislocation (p < 0.001) and proportional ulnar length (p < 0.001) were confirmed to be independent risk factors associated with forearm rotation on multivariate regression analysis. In conjunction with other risk factors, both of these factors could be used to predict forearm motion. In addition, a reduced proportional ulnar length was also an independent risk factor for radial head dislocation (p < 0.001).

CONCLUSIONS: Proportional ulnar length could be used as a tool to identify patients who are at risk for diminished forearm motion and radial head dislocation during childhood. Surgical intervention could potentially be offered before deterioration in function and dislocation of the radial head occurs.