Understanding the medial ulnar collateral ligament of the elbow: Review of native ligament anatomy and function

Abstract

The medial ulnar collateral ligament complex of the elbow, which is comprised of the anterior bundle [AB, more formally referred to as the medial ulnar collateral ligament (MUCL)], posterior (PB), and transverse ligament, is commonly injured in overhead throwing athletes. Attenuation or rupture of the ligament results in valgus instability with variable clinical presentations. The AB or MUCL is the strongest component of the ligamentous complex and the primary restraint to valgus stress. It is also composed of two separate bands (anterior and posterior) that provide reciprocal function with the anterior band tight in extension, and the posterior band tight in flexion. In individuals who fail comprehensive non-operative treatment, surgical repair or reconstruction of the MUCL is commonly required to restore elbow function and stability. A comprehensive understanding of the anatomy and biomechanical properties of the MUCL is imperative to optimize reconstructive efforts, and to enhance clinical and radiographic outcomes. Our understanding of the native anatomy and biomechanics of the MUCL has evolved over time. The precise locations of the origin and insertion footprint centers guide surgeons in proper graft placement with relation to bony anatomic landmarks. In recent studies, the ulnar insertion of the MUCL is described as larger than previously thought, with the center of the footprint at varying distances relative to the ulnar ridge, joint line, or sublime tubercle. The purpose of this review is to consolidate and summarize the existing literature regarding the native anatomy, biomechanical, and clinical significance of the entire medial ulnar collateral ligament complex, including the MUCL (AB), PB, and transverse ligament.

Keywords: Elbow, Anterior bundle, Medial ulnar collateral ligament, Native anatomy, Biomechanics, Valgus stability

Core tip: The anterior bundle of the medial ulnar collateral ligament complex plays a crucial role in elbow stability, specifically as a valgus and rotational constraint. Based on recent studies and our own cadaveric dissections, the ulnar footprint has a broader insertion that is more tapered and elongated than previous considered. A comprehensive understanding of the anatomy and biomechanical properties of the medial ulnar collateral ligament is imperative to optimize reconstructive efforts, and to enhance clinical and radiographic outcomes.