Musculotendinous variations about the medial humeral epicondyle.

Anatomical variations in the musculofascial structures about the region of the medial humeral epicondyle were evaluated in 104 extremities in sixty-four cadavers. This study demonstrated presence of an Osborne's band in 77%, of some degree of ulnar subluxation in 25%, of an epitrochlearis anconeus muscle in 11%, the ulnar nerve beneath the medial head of the triceps in 24%, the medial head of the triceps within the floor of the cubital tunnel in 28%, the presence of a rudimentary supracondylar process in 1.5%, and a high origin of the pronator teres in 17% of the cadavers. There was a significant association between the presence of an epitrochlearis anconeus muscle and the ulnar nerve being completely covered by the medial head of the triceps muscle (p less than .001). There was a significant relationship between the presence of the medial head of the triceps in the cubital tunnel and ulnar nerve subluxation (p.001). The high origin of the pronator teres may provide a proximal site for "double crush" syndromes of the median nerve.