Electrodiagnostic examination of the supinator--a more dorsal approach: a brief report

Examination of the supinator muscle of the forearm may be useful in suspected lesions of the 5th and 6th cervical nerve roots, the upper trunk of the brachial plexus, or the radial nerve. It is critical in localizing the level of involvement in a patient with possible posterior interosseous nerve injury. The traditional techniques in the electrodiagnostic examination of this muscle have approached the muscle from the volar aspect, just radial to the insertion of the biceps tendon, medial to the brachioradialis, through the extensor carpi radialis longus/brevis, between the radial wrist extensors and extensor digitorum communis, or through the extensor digitorum communis. These approaches have the inherent risk of piercing vessels and/or nerves. After reviewing the pertinent anatomy in standard textbooks, magnetic resonance imaging, and a cadaver, we developed a more dorsal approach in the examination of the supinator. Examination of 20 patients by staff, fellows, and residents at our institution resulted in consistent, accurate needle placement, with no complications. We describe a more dorsal approach in the examination of the supinator muscle in the forearm.