Posterior Glenohumeral Instability: Diagnosis and Management.

Posterior glenohumeral instability can manifest as posterior shoulder pain and dysfunction, particularly among athletes. Repetitive, posteriorly-directed axial loads, as commonly encountered by contact athletes (American football linemen, rugby players), result in microtrauma that can induce posteroinferior labral tears. Alternatively, SLAP tears commonly seen in throwing athletes may propagate in a posteroinferior direction (i.e., a type VIII SLAP tear), owing to a complex pathologic cascade involving glenohumeral capsular contracture and imbalances among the dynamic stabilizing muscles of both the glenohumeral joint and shoulder girdle. The diagnosis of posterior glenohumeral instability is elucidated by a thorough history and physical examination. Posterior shoulder pain is oftentimes insidious in onset. The throwing athlete with posterior glenohumeral instability may complain of diminished control, accuracy, and generalized shoulder discomfort. A number of provocative physical examination maneuvers have been described (Kim test, Jerk test), which load the humeral head against the labral lesion and recreate patients' symptoms. Magnetic resonance imaging and magnetic resonance arthrography can be of value in demonstrating avulsions of the labrum from the posteroinferior glenoid, and computed tomography is useful for quantifying the location and amount of attritional glenoid bone loss, although in contradistinction to anterior glenohumeral instability, clearly defined thresholds that would otherwise guide treatment have not been established. In the absence of substantial bone loss, arthroscopic posterior capsulolabral repair remains the gold standard for the surgical management of symptoms refractory to nonoperative treatment, and excellent clinical outcomes have generally been reported. However, high rates of return to play at the previous level of participation, particularly among throwing athletes, have been less consistently observed. Risk factors for the need for revision stabilization include surgery on the dominant extremity, female sex, and capsulolabral repairs involving either anchorless techniques or the use of less than 4 anchors.