Redefining the "Arcade of Struthers".

PURPOSE: To define the anatomy and presence of the arcade of Struthers, its anatomic variations, and potential sites of compression of the ulnar nerve.

METHODS: In 11 fresh specimen dissections, the ulnar nerve was followed from the brachial plexus through the anterior compartment into the posterior compartment through the intermuscular septum and the arcade of Struthers on to the cubital tunnel. The arcade was identified, dissected, measured, and photographed. All anatomic variations were documented.

RESULTS: The arcade of Struthers and intermuscular septum were present in all 11 specimens. The arcade was not merely an opening in the septum nor was it a short band as typically described: the arcade was better described as a fibrous canal with an average length of 5.7 cm. Its openings at either end were 3.9 and 9.6 cm proximal to the medial epicondyle. The structural components of the canal consisted of the fibrous tissue of the intermuscular septum, the internal brachial ligament, the deep fascia of the triceps, and the epimysium of the triceps muscle itself. The ulnar nerve was bound tightly within the entire canal in one case. In all specimens the nerve had an hourglass indentation at the proximal opening of the canal between the intermuscular septum and the internal brachial ligament.

CONCLUSIONS: The arcade of Struthers consists of a fibrous canal. The tightest point is the proximal end of the canal at the intermuscular septum that represents the clinically relevant site of entrapment or compression of the ulnar nerve.