Introduction: 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 triceps and the “arcade of Struthers” is still unclear with regards to anterior transposition of the ulnar nerve, because of anatomic controversies.

Methods : Dissection of the medial aspect of 30 arms was performed (Institut d’Anatomie, Saints-Pères, Paris), with the medial epicondyle as reference point for measurements.

Results : The internal brachial ligament was found in 22/30 cases (73%). It separated from the medial septum at an average distance of 11.5 ± 1.4 cm, ran medially and then anterior to the ulnar nerve to finally join back the septum at an average distance of 8.2 ± 1.9 cm. In the other 27% of cases, the ulnar nerve travelled 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 triceps, from the inferior border of 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 fibres were not observed medial to the nerve when the internal brachial ligament was absent.

When the distal part of the septum was excised and the neurolysis done, the ulnar nerve was not seen tethered by the internal brachial ligament or the muscular layer originating from it, because these were more highly situated and covered the medial aspect of the nerve.

Discussion : Our results meet the description made by Struthers in the mid XIXth century. We found that this ligament is only present when the ulnar nerve passes from the anterior to the posterior compartment of the arm (73% of cases), and then is equivalent to the small part of the intermuscular septum that runs medial to the nerve.

We found no thickening of the brachial fascia above the ulnar nerve in the mid-arm as described by Kane & al, when they proposed the term of “arcade of Struthers” in 1973. We thus propose to cancel the term of “arcade of Struthers”. The term “intern brachial ligament of Struthers” should be kept, although the very rare ligament in the anterior compartment between the supratrochlear process and the medial epicondyle also bears his name.