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Glenohumeral instability

Department of Radiology, Nuffield Orthopaedic Centre, Oxford, UK

• Normal anatomical variants include: – sublabral foramen – sublabral recess – buford complex – capsular insertions
  
• Shoulder instability includes: – anterior glenohumeral instability: (a) anteroinferior labral tear (i) bankart lesion (iii) anterior labroligamentous periosteal sleeve avulsion lesion (ii) perthes lesion (iv) glenolabral articular disruption lesion (b) extensive anterior labral tear (c) anterosuperior labral tear (d) glenohumeral ligament injury – SLAP lesion – posterior glenohumeral instability – posterior superior glenoid impingement
  

MR arthrography is useful for diagnosing and characterizing labral-ligamentous lesions resulting in glenohumeral instability. The sublabral foramen, sublabral recess and Buford complex are normal variants of the glenoid labrum, which must not be confused with true labral abnormalities. The most common type of glenohumeral instability is anteroinferior instability, characterized by avulsion of the anteroinferior labral-ligamentous complex, which is termed a Bankart lesion. Variants of the Bankart lesion, where the scapular periosteum remains intact, are the anterior labroligamentous periosteal sleeve avulsion (ALPSA) lesion, the Perthes lesion and the glenolabral articular disruption (GLAD) lesion. Anterosuperior labral tears are uncommon and must be differentiated from a normal sublabral foramen. Anterior glenohumeral instability also occurs following injury to the glenohumeral ligaments, most commonly described as humeral avulsion of the inferior glenohumeral ligament (HAGL) lesion. The superior labral anteroposterior (SLAP) lesion is a superior labral tear that extends both anterior and posterior to the bicep tendon attachment. SLAP lesions have a complex classification but the presence and extent of bicep tendon involvement is the most important feature. A SLAP II lesion must be distinguished from a normal sublabral recess. Patterns of injury seen in posterior instability are the reverse of those found following anterior dislocation, with posterior labral tears referred to as a reverse Bankart lesion. Posterior superior glenoid impingement or internal impingement is when the posterosuperior aspect of the glenoid and the humeral head come into contact, causing injury to the interposed rotator cuff and posterosuperior labrum.