Quantitative Anatomic Analysis of the Medial Ulnar Collateral Ligament Complex of the Elbow

BACKGROUND: A more detailed assessment of the anatomy of the entire medial ulnar collateral ligament complex (MUCLC) is desired as the rate of medial elbow reconstruction surgery continues to rise. PURPOSE: To quantify the anatomy of the MUCLC, including the anterior bundle (AB), posterior bundle (PB), and transverse ligament (TL). STUDY DESIGN: Descriptive laboratory study. METHODS: Ten unpaired, fresh-frozen cadaveric elbows underwent 3-dimensional (3D) digitization and computed tomography with 3D reconstruction. Ligament footprint areas and geometries, distances to key bony landmarks, and isometry were determined. A surgeon digitized the visual center of each footprint, and this location was compared with the geometric centroid calculated from the outline of the digitized footprint. RESULTS: The mean surface area of the AB was 324.2 mm(2), with an origin footprint of 32.3 mm(2) and an elongated insertional footprint of 187.6 mm(2) (length, 29.7 mm). The mean area of the PB was 116.6 mm(2) (origin, 25.9 mm(2); insertion, 15.8 mm(2)), and the mean surface area of the TL was 134.5 mm(2) (origin, 21.2 mm(2); insertion, 16.7 mm(2)). The geometric centroids of all footprints could be predicted within 0.8 to 1.3 mm, with the exception of the AB insertion centroid, which was 7.6 mm distal to the perceived center at the apex of the sublime tubercle. While the PB remained relatively isometric from 0° to 90° of flexion (P = .606), the AB lengthened by 2.2 mm (P < .001). CONCLUSION: Contrary to several historical reports, the insertional footprint of the AB was larger, elongated, and tapered. The TL demonstrated a previously unrecognized expansive soft tissue insertion directly onto the AB, and additional analysis of the biomechanical contribution of this structure is needed. CLINICAL RELEVANCE: These findings may serve as a foundation for future study of the MUCLC and help refine current surgical reconstruction techniques.