Quantitative Analysis of the Medial Ulnar Collateral Ligament Ulnar Footprint and Its Relationship to the Ulnar Sublime Tubercle

Background: The medial ulnar collateral ligament is the major soft tissue restraint to valgus displacement of the elbow. Currently, little has been published regarding the medial ulnar collateral ligament's ulnar footprint. Hypothesis: The medial ulnar collateral ligament has a long attachment onto the ulna and the anatomy of the footprint is consistent. Study Design: Descriptive laboratory study. Methods: The authors studied the morphologic characteristics of the ulnar footprint of the medial ulnar collateral ligament in 10 fresh-frozen cadaveric specimens, 100 osseous specimens, and with 3-dimensional computed tomography in an additional 10 osseous specimens. They measured the length of the anterior band's ulnar attachment and the entire ligament length. They also measured the length of the osseous ridge, which extends distally from the sublime tubercle in both osseous specimens and on computed tomography. Results: The mean length of the medial ulnar collateral ligament was 53.9 mm and the mean length of the ulnar soft tissue footprint was 29.2 mm. The authors identified an osseous ridge that extended distally from the sublime tubercle to just medial to the ulnar insertion of the brachialis muscle tendon. This osseous ridge was present in all osseous and fresh-frozen cadaveric specimens. The mean length of this osseous ridge was 24.5 mm. Conclusion: The medial ulnar collateral ligament has a long attachment along the proximal ulna. The ligament attaches to a previously undescribed ridge of bone located on the medial aspect of the proximal ulna, the medial ulnar collateral ligament ridge. This ridge is present in all skeletal specimens. Clinical Relevance: Injuries to the medial ulnar collateral ligament are common. Published success rates after reconstruction of the medial ulnar collateral ligament are highly variable. The present study illustrates how current reconstruction techniques fail to fully restore the true anatomy of the native ligament. Further studies are needed to investigate this issue.