Delayed posterior interosseous nerve palsy.

A rare case of delayed posterior interosseous nerve palsy that developed 39 years after an unreduced anterior dislocation of the radial head is reported. The posterior interosseous nerve was compressed and narrowed at the arcade of Frohse. Radial head resection and release of the arcade was done. The paralysis continued to recover 6 weeks after operation. The nerve, at the arcade of Frohse, was susceptible to compression by the dislocated radial head, especially in the supinated position. Repeated supination and pronation movement over time may have led to developmental changes that caused the delayed nerve palsy.