HISTOLOGY AND ARTHROSCOPIC ANATOMY OF THE ULNAR COLLATERAL LIGAMENT OF THE ELBOW

The histology and arthroscopic anatomy of the ulnar collateral ligamen t of the elbow were studied in cadaveric specimens. The capsule consis ts of two layers of collagen fibers, with two distinct ligamentous bun dles corresponding to anterior and posterior portions of the ulnar col lateral ligament. The posterior bundle consists of distinct collagen b undles within the layers of the capsule; the anterior bundle consists of a similar thickening within the capsular layers, with an additional ligament complex superficial to the capsular layers. With arthroscopy only the anterior 20% to 30% of the anterior bundle of the ulnar coll ateral ligament could be visualized via the anterior portal. Only the posterior 30% to 50% of the posterior bundle could be seen via the pos terior portals. After sectioning of the anterior bundle, joint instabi lity was noted arthroscopically by an increased opening in the ulnohum eral joint with application of valgus stress. At arthroscopy ulnar col lateral ligament tears may be visualized in part or not at all. To dia gnose a tear or laxity in the ulnar collateral ligament, a demonstrati on of an increase in the opening of the ulnohumeral joint in response to valgus stress is useful.