Analysis of magnetic resonance imaging–confirmed soft tissue injury pattern in simple elbow dislocations

Abstract

The elbow is the second most commonly dislocated joint. Stability depends on the degree of soft tissue injury, with 2 proposed patterns, one starting laterally and the other medially. The purpose of this study was to describe the injured structures observed in magnetic resonance images (MRIs) in a prospective cohort of simple elbow dislocations. We evaluated 17 consecutive cases of simple elbow dislocations. Two musculoskeletal radiologists assessed the initial x-ray images and MRIs performed for all elbows. Radiologists evaluated the following soft tissue structures: medial collateral ligament complex (MCL), flexor-pronator muscle mass origin, anterior capsule (AC), posterior capsule, lateral collateral ligament complex (LCL), and extensor muscle mass origin. The radiologists were blinded to the study hypothesis. The initial radiographs in 16 patients showed the dislocation was posterolateral in 12, posterior in 3, and posteromedial in 1. We observed complete AC tear in 12 patients, MCL in 10, and LCL in 9. The inter-rater reliability for the radiologists was 0.70 (substantial) for MRI. In our series after simple elbow dislocation, complete AC tears were most common, followed by MCL and LCL tears. No single mechanism-related soft tissue injury pattern of simple elbow dislocation was observed, and different grades of soft tissue injury exist.