Measurement of Adult Hill-Sachs Lesions on Magnetic Resonance Arthrography

Introduction Posterosuperolateral compression fractures of the humeral head, eponymously described by Hill and Sachs in 1940, occur in 40-90% of anterior shoulder dislocations and typically occur in conjunction with anterior capsulolabral tears (Bankart and variant lesions). Repairing a Bankart lesion without simultaneously addressing significant Hill-Sachs lesions may result in repeated instability. However, identifying which Hill-Sachs lesions are clinically important remains challenging. Although Hill-Sachs lesion size affects glenohumeral stability, no consensus exists on the best measurement technique. Recently, Kodali et al demonstrated that Hill-Sachs lesions could be measured on two-dimensional computed tomography. However, while depth of lesions could be reliably measured, width was consistently underestimated. Thus, additional work is needed to determine a more accurate and practical method of quantifying Hill-Sachs lesion size. Magnetic resonance (MR) imaging provides improved visualization of intra-articular structures and soft tissues. MR has high sensitivity (96.3%) and high specificity (90.6%) for detecting HillSachs lesions. Furthermore, Probyn et al showed that MR arthrography could detect HillSachs lesions with 100% sensitivity and 93.3% accuracy compared to surgical findings. In this study, we describe two techniques for measuring the volume of Hill-Sachs lesions on MR arthrography that are reproducible and easy to perform.