Sonographic assessment of the medial ulnar collateral ligament distal ulnar attachment.

OBJECTIVES: The purpose of this study was to determine whether the long distal attachment of the medial ulnar collateral ligament (MUCL) can be delineated on sonography. METHODS: We used 12 fresh-frozen cadaveric elbows for this study. We performed sonography of the elbow using a coronal-equivalent long-axis view of the MUCL. All sonographic examinations and measurements were performed by a board-certified, fellowship-trained musculoskeletal radiologist. Measurements were performed from the anteroinferior aspect of the medial epicondyle to the sublime tubercle and then from the sublime tubercle to the terminal fibers of the MUCL long ulnar attachment. We then measured the length of the MUCL from its attachment at the medial epicondyle of the humerus to the sublime tubercle and then from the sublime tubercle to the distal extent of its terminal fibers at the ulnar attachment with digital calipers. RESULTS: On sonography, the average length of the MUCL from its humeral attachment to the sublime tubercle (transarticular) was 19.6 mm. The average length of the ulnar attachment was 27.9 mm. The MUCL was thickest (mediolateral dimension) at its humeral attachment and tapered as it coursed distally along the ulnar attachment. The MUCL was clearly identified on sonography and in all anatomic specimens. On gross measurement, the average lengths of the transarticular portion of the MUCL and its ulnar footprint were 21.5 and 30.2 mm, respectively. CONCLUSIONS: We have successfully shown that the distal ulnar attachment of the MUCL can be visualized on high-resolution sonography. This preliminary work provides a framework for developing protocols for diagnosis of injuries to the distal ulnar collateral ligament.