[The medial epicondyle of the humerus, an anatomical study].

A large variation in the shape of the medial epicondyle is encountered. This study was performed to investigate any role of the shape of medial humeral epicondyle in the etiology of osteoarthritis in the elbow, which can lead to cubital tunnel syndrome. A total of 71 humerus from 36 cadaveric specimens (mean age 75, ranging from 52 to 93) were used to study the morphological characterization of the medial humeral epicondyle. The specimens were divided into four types according to the index of medial epicondylar breadth and medial epicondylar length. A correlation was found between the angle of inclination of the sulcus nervi ulnaris and osteophyte formation in the medial epicondyle. This finding suggested that Type 2 (wider type) and 3 (longer type) might each contribute to the onset of osteoarthritis, resulting in cubital tunnel syndrome. However, we found some cases of Type 1 (wider and longer type) with a large angle and only minor osteophyte formation, suggesting that a large inclination angle of the sulcus nervi ulnaris alone was not an independent factor in osteophyte formation. Moreover from our results of measuring the distance between the tip of the medial epicondyle and the medial edge of the anterior medial collateral ligament origin, we concluded that medial epicondylectomy (King's method) without damaging this ligament should be performed at a point approximately 20% of the overall width of the medial epicondyle from the tip of the medial epicondyle.