Shoulder instability: State of the Art

Abstract

The mobility of the glenohumeral joint in multiple anatomic planes is not without consequence as recurrent instability is common, particularly among young, active individuals. Throughout midranges of shoulder motion, stability is conferred primarily by the compression-cavity effect of the rotator cuff as muscular contractions maintain the humeral head centred in the glenoid cavity. At extremes of shoulder motion (flexion and abduction), derangements of capsule-ligamentous complex, glenoid and glenoid labrum drive a pathophysiological cascade that manifests clinically as recurrent anterior, unidirectional instability. In the setting of bone loss <25% of the inferior glenoid diameter, arthroscopic Bankart repair using proper technique yields reliable clinical results. Additionally, much is now known about the extent to which attritional glenoid bone loss, related commonly to repeated dislocation events, affects the predicted success of certain treatment approaches. The preponderance of existing literature supports performing a bone grafting procedure for cases in which the osseous defect comprises >25% of the glenoid width, with the Latarjet procedure being favoured among recent authors. A growing body of evidence has elucidated the consequence of humeral head defects (the Hill-Sachs lesion) as a predictor of recurrent instability. Thus, the concept of ‘bipolar bone loss’ has emerged as a critical concept in the surgical treatment of recurrent shoulder instability. Surgeons should adopt a treatment paradigm that focuses on the relationship between both osseous defects—glenoid and humeral head—and incorporates a surgical tactic to appropriately address each lesion.