Imaging description

On non-contrast MRI studies, tears of the lateral ulnar collateral ligament are best seen on coronal proton density fat-suppressed images that have a matrix equal to or greater than 256 × 512. If an MR arthrogram is performed, tears of this ligament are best seen on coronal T1-weighted fat-suppressed images. Normally, the lateral ulnar collateral ligament is seen as a uniformly low-signal intensity. It is attached proximally to the lateral epicondyle and extends distally to insert on the supinator crest of the ulna (Figure 25.1). Disruption or tearing of the lateral ulnar collateral ligament most commonly occurs at its proximal attachment to the lateral epicondyle. More recent research has shown that tearing of the lateral ligamentous complex attachment to the lateral epicondyle (be it the radial collateral ligament or the lateral ulnar collateral ligament) can result in posterolateral rotatory instability of the elbow. In addition, the lateral ulnar collateral ligament can be torn in its midportion, which is also associated with posterolateral rotatory instability of the elbow (Figure 25.2). Lastly, there are those that consider the lateral ligament complex to be a unified single structure (rather than separate radial collateral, lateral ulnar collateral, and annular ligaments) that extends from the lateral humeral epicondyle to attach to the supinator crest and the sigmoid notch. If this is true, then any disruption of this complex may lead to posterolateral rotatory instability at the elbow.