Glenohumeral Instability: Evaluation with MR Arthrography

Magnetic resonance arthrography is superior to other imaging techniques in evaluation of the glenohumeral joint. Normal variants that can be diagnostic pitfalls include the anterosuperior sublabral foramen, the Buford complex, and hyaline cartilage under the labrum. Anteroinferior dislocation is the most frequent cause of anterior glenohumeral instability and produces a constellation of lesions (anteroinferior labral tear, classic and osseous Bankart lesions, Hill-Sachs lesion). Variants of antero-inferior labral tears include anterior labroligamentous periosteal sleeve avulsion and glenoid labral articular disruption. Anterior glenohumeral instability can also involve tears of the anterior or anterosuperior labrum or the glenohumeral ligaments. Posterior glenohumeral instability can involve a posterior labral tear; posterior capsular stripping or laxity; fracture, erosion, or sclerosis and ectopic ossification of the posterior glenoid fossa; reverse Hill-Sachs lesion; McLaughlin fracture; or posterosuperior glenoid impingement. Superior labral anterior and posterior lesions involve the superior labrum with varying degrees of biceps tendon involvement.