Posterior Glenohumeral Instability Clinical Presentation

Updated: Jun 29, 2020
  • Author: John P Salvo, Jr, MD, MS; Chief Editor: S Ashfaq Hasan, MD  more...
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A thorough history is invaluable during the clinical assessment of posterior glenohumeral instability. One must determine the type and mechanism of the event that originally caused the instability (major trauma, repetitive minor trauma, or an atraumatic process).

A history of violent trauma, seizures of any etiology, or electrical shock should alert the physician to search for a posterior dislocation. Patients without a history of major trauma typically report painful symptoms initially that diminish over time. These patients commonly report difficulty in performing activities of daily living, including hair combing, shaving, and eating. [38]

Athletic activities that require the arm to be placed in flexion, adduction, and internal rotation commonly cause symptoms of pain and the sense of instability. Common activities include throwing (follow-through), bench press (lockout), swimming (pull-through), and rowing. [20]

Pain is usually limited to the instability episodes, though many patients report posterior joint line pain or vague anterior pain, which may be thought of as one of Neer's causes of nonoutlet impingement. [16] Finally, it is important to determine whether the patient has a voluntary type of instability or a positional type of involuntary instability.


Physical Examination

Physical examination of a posterior glenohumeral dislocation may reveal prominence of the humeral head posteriorly, with flattening of the anterior contour and prominence of the coracoid. These findings can often be quite subtle and often are obliterated by swelling or a large deltoid muscle mass. [39]

External rotation of the arm is significantly limited, while flexion and internal rotation can be remarkably normal. Rowe and Zarins described examination of the shoulder with flexion of both elbows to 90° to demonstrate a fixed humeral internal rotation deformity. [59] Comparison of the external rotation available on both sides reveals the internal rotation deformity on the dislocated side. With the arm extended, the patient's palm also does not turn fully upward on the affected side, despite full forearm supination due to the fixed internal rotation.

Examination maneuvers for posterior instability are not often dramatic. Palpatory examination may reveal tenderness of the posterior joint line and tenderness of the anterior dynamic stabilizers. Range of motion (ROM) is typically normal, though patients sometimes have a loss of external rotation with the arm abducted at 90°. [25] Testing for generalized ligamentous laxity should be performed. Specific tests for posterior instability include the posterior drawer test (see the image below).

Intraoperative examination under anesthesia of a p Intraoperative examination under anesthesia of a patient with atraumatic posterior instability demonstrates, via a posterior drawer test, significant posterior subluxation of the glenohumeral joint.

The posterior apprehension test (ie, the jerk test) also can be used for this purpose. The examination involves applying an axial posterior load onto an arm flexed at 90°, adducted, and internally rotated; it is positive with reproduction of the instability sensation (see the video below). Hawkins and McCormack suggested flexing the arm to recreate the position in which subluxation occurs and stated that a "clunk" occurs as the arm is elevated to 120°. [38]

Physical examination of this patient with atraumatic posterior instability demonstrates significant posterior glenohumeral translation with the jerk test.

A posterior drawer/relocation test, in which pain or apprehension occurs with a posterior directed force and is relieved by reduction, may be the preferred diagnostic maneuver. [60] The extent of translation during diagnostic examination has been graded as follows [49, 50, 51] :

  • +0 - No translation from being centered in the glenoid fossa
  • +1 - Translation noticeable but not up to the glenolabral rim (without a clunk)
  • +2 - Translation of humeral head onto the glenolabral rim (clunking without locking)
  • +3 - Translocation over the glenolabral rim (locking in the subluxated position that reduces without manual reduction)
  • +4 - Translation with complete dislocation (locking in the dislocated position that requires manual reduction)

Examination in the office and under anesthesia involves a thorough evaluation for motion, laxity, and stability. Patients without symptoms may have as much translation as those requiring surgical repair for symptomatic shoulder instability. The need for surgical reconstruction should, therefore, be based on the history and physical examination findings rather than on the magnitude of translation alone.

Finally, evaluation of other potential components of instability—including through the sulcus test (as described by Neer and Foster [17] ), for inferior instability, and through the crank test, for anterior instability—is equally important. [49, 50, 51]