Illustration depicting an osseous avulsion of the lateral ulnar collateral ligament (LUCL) at its insertion on the crista supinatoris. A = annular ligament, P = posterolateral aspect of the joint capsule, RCL = radial collateral ligament, H = distal part of the humerus, and R = radius. (Reproduced with permission of Kari Visscher, MD)
Intraoperative image of a Monteggia-variant fracture following open reduction and internal fixation of the ulna. The white arrow points to a displaced fractured crista supinatoris fragment, as visualized through the Boyd interval. With hypersupination, the radial head (r) is posteriorly dislocated and the ulnohumeral joint (black arrow) is subluxated secondary to posterolateral rotatory instability. The radial head is congruent with the lesser sigmoid notch of the proximal radioulnar joint, but traumatic avulsion of the annular ligament from its dorsal attachment is present.
Cadaveric dissection through the Kocher interval between the extensor carpi ulnaris (ECU) and anconeus. The fascia of the extensor carpi ulnaris has been excised, and its muscle belly has been mobilized anteriorly. The deep fascia (D) of the extensor carpi ulnaris is in close apposition with the lateral ulnar collateral ligament. The tip of the hemostat inserted through the Kaplan interval, between the extensor digitorum communis (EDC) and extensor carpi radialis brevis and along the radiocapitellar joint, is seen hooked around the deep fascia of the extensor carpi ulnaris and the capsular thickening representing the lateral ulnar collateral ligament. Fibers of the supinator muscle are seen overlying the distal portion of the lateral ulnar collateral ligament and its insertion on the crista supinatoris (C). These muscle fibers need to be elevated to adequately visualize a crista supinatoris fracture. A = annular ligament and E = lateral epicondyle.