The internal brachial ligament versus the arcade of Struthers: an anatomical study

Management of the distal part of the medial intermuscular septum and the internal brachial ligament (both described by Struthers in 1854), the medial head of the triceps, and the "arcade of Struthers" (a concept created by Kane et al. in 1973) is still unclear regarding anterior transposition of the ulnar nerve because of anatomical controversies. Dissection of the medial aspect of 30 arms was performed. The internal brachial ligament was found in 22 of 30 cases (73 percent). It separated from the medial septum at an average distance of 11.5 cm above the medial epicondyle, ran medially and then anterior to the ulnar nerve, and finally joined back at the septum at an average distance of 8.2 cm. In the other 27 percent of cases, the ulnar nerve traveled down the arm, passing entirely posterior to the septum. When the internal brachial ligament was present, it always supported the origin of the most superficial layer of the medial head of the triceps, from the inferior border of the teres major to its fusion back to the septum. This layer appeared as an oblique muscular curtain covering the medial aspect of the ulnar nerve. No local thickening was found in the brachial fascia covering these muscular fibers. Muscular fibers were not observed medial to the nerve when the internal brachial ligament was absent. This anatomical study confirms the descriptions of the internal brachial ligament made by Struthers. Foranatomical reasons, the authors propose cancelling the concept of the arcade of Struthers.