The nerve then courses medial to the brachial artery above the level of the medial humeral condyle. This is the second location of possible impingement. A known anatomic variant in this location called a supracondylar spur, simian spur, or supracondylar process, which was described in 1966, attaches to the ligament of Struthers and can result in compression of the nerve at this location. The process arises at the anterior medial aspect of the humerus, approximately 5 cm proximal to the medial humeral condyle. The prevalence is reported to be between 0.1 and 2.7%. This can be readily visualized on ultrasound. Entrapment at this location can cause compression of the brachial artery, compression of the median nerve, or both (1). The ligament of Struthers is not often a visible structure itself but can be identified during ultrasound depending on the body habitus and resolution of the probe.
Fig. 3 Median nerve at the supracondylar level