Background: The medial ulnar collateral ligament (MUCL) is the primary stabilizer against valgus stress on the elbow. The anatomy of the 3 bundles of the MUCL has been well studied in adults, but our review of the English literature found no study evaluating the origin of the MUCL in a large group of asymptomatic, skeletally immature elbows as it relates to the medial epicondylar physis.
Methods: Magnetic resonance T1-coronal images of 44 skeletally immature elbows (ages 5 to 17 y) with no history of fracture were evaluated by 2 independent musculoskeletal radiologists, a board-certified orthopaedic surgeon with fellowship training in pediatric orthopaedics, and an orthopaedic surgery resident. The location of the origin of the anterior bundle of the MUCL (aMUCL) was identified and its distance from the medial epicondylar physis was measured.
Results: All 44 images showed that the aMUCL attached either on or medial to the medial epicondylar physis. The average distance from the origin of the aMUCL to the medial epicondylar physis was 3.1 mm. There was no statistically significant relationship between age and location of the aMUCL insertion relative to the physis (P=0.183).
Conclusions: In the skeletally immature elbow, the aMUCL originates medial to the medial epicondylar physis.
Clinical relevance: Although treatment of medial epicondylar humeral fractures remains controversial, understanding the relationship between the aMUCL and the medial epicondylar physis may be helpful in making decisions regarding fracture management.