Abducted, hyperextended small finger deformity of nonneurologic etiology.

The abduction and hyperextension deformity of the small finger is usually associated with ulnar nerve palsy. Six patients who sustained an abduction force to their small finger presented with the finger in an abducted and hyperextended position. All patients were neurologically intact and were unable to adduct or flex the finger at the metacarpophalangeal joint. Surgical findings in these patients included rupture of the radial sagittal band, collateral ligament, and junctura tendinum. Sequential division of these structures in cadaveric hands confirmed that all these tissues had to be deficient for this deformity to occur. The traumatic abducted, hyperextended small finger deformity may respond to conservative treatment, but surgery is sometimes necessary.