Direct recording of local pressure in the radial tunnel during passive stretch and active contraction of the supinator muscle.

The radial tunnel syndrome is recognized as on cause of lateral elbow pain. This investigation demonstrated pressures of 40--50 mmHg exerted on the posterior interosseus herve by the edge of the superficial supinator muscle during passive stretch of the supinator muscle. During active muscle contraction caused by tetanic nerve stimulation, the pressure was about four times greater. Intermittent nerve compression of this magnitude might well cause nerve injury and thus explain the pain and local nerve tenderness observed in patients with the radial tunnel syndrome.