Posterior interosseous syndrome revisited.

The question of how the supinator syndrome and the posterior interosseous syndrome are (or are not) related has not been well discussed in the literature. The anatomy of the radial nerve and its innervations is quite variable, as are the etiology, presentation, and clinical findings in the lesions of the posterior interosseous nerve. The present study was based on a retrospective review of the electrodiagnostic records of 12 patients with involvement of the deep radial nerve (posterior interosseous nerve) diagnosed at the EMG lab of New York University Medical Center from 1975 to 1983. Two-thirds of these patients had electrophysiologic abnormalities of the supinator muscle, and in the remainder, the supinator was not involved. All superficial radial nerves had normal evoked mode action potential amplitudes and latencies. We propose that the supinator syndrome is a special case of the posterior interosseous syndrome.