[Magnetic resonance imaging of glenohumeral instability]

Conventional MR imaging and MR arthrography are established diagnostic imaging modalities for investigating shoulder instability. Since there are currently various surgical shoulder stabilization methods as well as conservative treatment strategies, the role of imaging is to provide diagnostic information to help determine the therapeutic approach. Whereas conventional MR imaging is usually sufficient for the evaluation of acute shoulder injuries due to the presence of a posttraumatic joint effusion, MR arthrography is the imaging modality of choice for chronic shoulder instability. Atraumatic and microtraumatic instability of the shoulder must be distinguished from traumatic instability since clinical findings and secondary or associated injuries differ from those of traumatic instability. Injuries of the IGHL-complex can be reliably diagnosed with MR arthrography. Traumatic anteroinferior luxation causes labroligamentous injuries at the glenoid insertion (Bankart-, Perthes-, ALPSA-, and non-classifiable chronic lesions) and injuries of the IGHL and its humeral insertion (HAGL-, BHAGL-, and floating AIGL-lesions). The type of injury and extent of degenerative changes or scarring that can be assessed with MR arthrography influence the therapeutic approach and in particular the decision between arthroscopic and open surgical methods of stabilization.