Diagnosing Multidirectional Instability of the Shoulder
Appropriately defining the instability pattern is one of the keys to successful patient outcomes in multidirectional instability of the shoulder. It can be difficult to do, however, because of the variability in presentation. The authors review important findings on clinical evaluation, physical exam, and imaging that suggest multidirectional instability.
Matthew D. Williams, MD, and T. Bradley Edwards, MD
The authors have no disclosures relevant to this article.
Multidirectional shoulder instability is a diagnostic and management challenge due to the variability in presentation. [1,2] The classic traumatic unidirectional instability, for example, has a relatively well-defined pattern of disability and shoulder pain in certain glenohumeral positions.
In contrast, multidirectional instability is defined as abnormal glenohumeral translation in more than one direction coupled with variable incidence of associated labral and capsular lesions.
In addition, multidirectional glenohumeral instability must be differentiated from asymptomatic glenohumeral hyperlaxity and glenohumeral hyperlaxity presenting with unidirectional instability. An important distinguishing characteristic is pain and symptoms affecting activity in the face of multidirectional instability.
Appropriately defining the instability pattern is one of the keys to successful patient outcomes in multidirectional instability of the shoulder. The surgeon must also understand the biomechanics of glenohumeral motion and the effects of capsular restraint for operative planning and capsular tightening. [3,4] In addition, the surgeon should note whether the patient has associated labral and capsular lesions; however, these are not pathognomonic of multidirectional instability
Physical therapy and functional exercises are important components in the management of multidirectional shoulder instability.  When surgery is required, arthroscopic stabilization techniques provide direct visualization of the capsulolabral complex and allow the surgeon to address associated lesions and capsular redundancy.
The typical patient presenting with multidirectional instability of the shoulder complains of:
- Pain with activity
Feelings of shoulder instability without associated trauma
Although an acute traumatic event is not required, overuse injury associated with throwing, overhead sports, or contact sports can precipitate symptoms in these patients. Overuse injury produces microtrauma that, over time, can produce glenohumeral lesions. The increasing use of arthroscopy has illustrated that patients suffering with multidirectional instability often have visible traumatic capsulolabral lesions despite the absence of an isolated acute trauma. 
Overhead athletes will often complain of insidious onset of pain that produces:
- Loss of endurance
- Decreased overhead strength or throwing velocity
Patients with multidirectional shoulder instability in one shoulder often present with ligamentous laxity in the contralateral shoulder. Surgical management of both shoulders is rarely indicated.
Voluntary dislocators often present with symptomatic instability or pain and can demonstrate glenohumeral subluxation in the office. Some habitual dislocators can subluxate the glenohumeral joint due to learned muscular control. Voluntary dislocators who have a psychiatric or habitual component are best treated with non-operative measures. However, patients who can voluntarily dislocate their shoulders and do not have a psychiatric undertone are well managed with surgery. 
Patients presenting with recurrent shoulder instability following a stabilization surgery should be carefully evaluated for the presence of multidirectional instability that may have compromised their previous surgical results. Patients suffering from collagen disorders such as Ehlers-Danlos or Marfan’s syndrome will often present with multidirectional shoulder instability. Ehlers-Danlos and Marfan’s can decrease the efficacy of open and arthroscopic soft-tissue shoulder reconstruction procedures.
A complete physical examination for suspected shoulder instability includes an evaluation of:
- Glenohumeral mobility
- Scapular mechanics
- Periscapular strength
- Cervical spine
The presence or absence of generalized ligamentous laxity should be determined by evaluating hyperextension of the elbows, knees, and metacarpophalangeal joints. Following these basic but important components, specific stability tests should be performed to evaluate the stability of the anterior, posterior, and inferior shoulder.
Testing of the anterior shoulder includes:
- Anterior load and shift test
- Anterior apprehension test
- Relocation tests
The load and shift test is performed with the patient in a supine position. The examiner holds the humeral head centered in the joint and then applies an anterior force. The degree of anterior translation of the head across the glenoid face indicates the degree of instability. The test is performed with the arm at the side, with the glenohumeral joint in minimal abduction and neutral rotation. The glenohumeral joint can be moved into varying degrees of abduction and external rotation to assess the superior, middle, and inferior glenohumeral ligaments. 
Anterior apprehension is assessed with the shoulder in 90 degrees of abduction. The arm is gently externally rotated; a positive test is the patient describing a sense of shoulder dislocation. The relocation test is a posteriorly directed force on the abducted and externally rotated shoulder that reduces the feelings of dislocation produced by the apprehension test. Although most patients with multidirectional instability do not have classic apprehension on examination, the examiner should appreciate the spectrum of glenohumeral instability in each patient with a thorough examination.
Posterior shoulder stability may be evaluated with a variety of tests. The jerk test is performed with the patient sitting. The shoulder is flexed to 90 degrees and internally rotated. The elbow is flexed to 90 degrees and pushed posteriorly, with the scapula stabilized. The arm is slowly extended, and the posteriorly subluxed or dislocated glenohumeral joint will reduce with a jerk. The test is positive if the relocation maneuver is associated with pain. 
The Kim test is also performed with the patient sitting. The arm is held in 90 degrees of abduction and the elbow is flexed. An axial and posterior force is applied while elevating the arm to 45 degrees. Pain during this test is consistent with a posteroinferior labral lesion. 
The sulcus test is performed with the arm in adduction. The arm is pulled inferiorly and the gap formed between the undersurface of the acromion and the superior humeral head is measured. A gap greater than 2 cm is suggestive of multidirectional instability (Figure 1).
Figure 1. The sulcus test is performed with the arm in adduction (left). A gap beneath the acromion and apprehension in this patient is suggestive of multidirectional instability (right).
Although the sulcus test does not often produce apprehension or pain, these findings may be observed in patients with multidirectional instability. Pain is a common complaint in patients with multidirectional instability, affecting their ability to compete.
Involvement of the rotator interval in the patient’s instability pattern is evaluated by performing the sulcus test with the arm in 30 degrees of external rotation. If the sulcus decreases in height the rotator interval is intact and does not need to be addressed surgically.
Assessment of the inferior capsule can be performed with the Gagey hyperabduction test. The examiner stands behind the seated patient. The superior scapula is stabilized from above with one arm; the other arm is used to abduct the ipsilateral elbow. Passive abduction greater than 105 degrees indicates inferior laxity. 
Anteroposterior, scapular outlet, and axillary plain radiographs are performed for initial bony evaluation of the unstable shoulder. Anterior and posterior glenoid bone stock is visualized using the glenoid profile view of Bernageau.  Plain radiographs can demonstrate Hill-Sachs lesions or reverse Hill-Sachs lesions and glenoid dysplasia. Positive radiographic findings are more commonly observed in traumatic instability cases. Multidirectional instability is normally associated with a lack of positive radiographic findings.
Magnetic resonance imaging (MRI) or MR-arthrography (MRA) can be performed for evaluation of the capsulolabral structures. An MRA is the gold-standard modality for visualization of the labrum and capsule.
Filling the glenohumeral joint with contrast allows an appreciation of capsular volume, which is increased in patients with multidirectional instability. Frank labral tears due to significant injury and more subtle labral fraying from repetitive microtrauma can be visualized using an MRA.
Imaging is helpful to rule out significant capsulolabral injury and to assess capsular redundancy. Imaging alone, however, is often ineffective at describing the pattern of instability. Physical examination remains the foundation of an appropriate diagnosis to guide treatment.
The primary management of multidirectional shoulder instability is physical therapy and rehabilitation. 
Studies have shown electromyographic differences in muscular firing patterns between normal individuals and patients suffering from multidirectional laxity and instability.  These differences indicate that key stabilizing mechanisms likely fail in patients with multidirectional laxity who push their shoulders toward symptomatic multidirectional instability.
Despite the prevailing recommendation of initial treatment of multidirectional instability with physical therapy, a systematic review of the literature does not demonstrate a conclusive effect of an exercise program for treating multidirectional instability. 
Burkhead and Rockwood  demonstrated improvement with exercise-based treatment. Nyiri et al  evaluated the effect of physical therapy alone versus physical therapy post-capsular shift. They found that exercise therapy alone was ineffective in returning shoulder kinematics to normal in the face of multidirectional instability. Restoration of muscular kinematics similar to normal subjects occurred in the group treated with physical therapy and surgery.
Misamore et al  reviewed 64 patients over a mean 8-year follow-up with multidirectional instability initially managed with rehabilitation. Patients were found more likely to undergo surgery with unilateral involvement, impairment of activities of daily living, and high degrees of laxity. One third of the patients in the study dropped out for surgery within the first 2 years. The study found a poor response to nonoperative management of multidirectional instability in their population of young and athletic patients.
Historically, the open capsular shift was the gold standard for treating multidirectional instability. Neer and Foster  described a reduction of the inferior capsular volume and reinforcement of the capsule and labrum to decrease recurrence. Open capsular shift procedures have recently been discussed for use in revision situations following failed arthroscopic stabilization procedures. 
Arthroscopic techniques are effective in treating multidirectional instability and have become routine practice. When compared with open procedures, arthroscopic capsular shift procedures produce results comparable to open surgery. 
Nineteen patients were treated with arthroscopic stabilization by McIntyre et al.  At an average follow-up of 34 months, 92% returned to previous competition level.
In 2001, Gartsman et al reported on 47 patients treated with arthroscopic stabilization for multidirectional instability. Ninety-four percent rated their outcomes as good or excellent at an average 35 month follow-up. In addition to repair of the capsulolabral lesions, the rotator interval was closed in the face of persistent and excessive humeral head translation. The major operative finding at surgery was increased capsular volume and significant translation of the humeral head anteriorly, inferiorly, and posteriorly. Interestingly, multiple lesions were identified at arthroscopy. These were lesions that may not have otherwise been appreciated with an open procedure and that indicate a multifaceted etiology for multidirectional instability. 
A group of 43 athletic patients with multidirectional instability were treated with arthroscopic stabilization by Baker et al.  Eighty-six percent of their patients were able to return to athletics with little or no limitation (Figure 2).
Figure 2. A 17-year-old patient with bilateral glenohumeral joint laxity presented with pain and feelings of instability. Load and shift, sulcus, and jerk tests were positive. Findings at arthroscopy: Anterior capsulolabral lesion (top left), inferior lesion (middle left), and posterior capsulolabral lesion with capsular redundancy (bottom left). Systematic arthroscopic repair of the lesions: anterior (top right), inferior (middle right), and posterior (bottom right).
Pearls and Pitfalls
- The appropriate treatment of multidirectional shoulder instability hinges on a thorough physical examination and understanding of the pattern of glenohumeral laxity.
Multidirectional glenohumeral instability should be distinguished from asymptomatic glenohumeral hyperlaxity and glenohumeral hyperlaxity presenting with unidirectional instability.
- MRA is the gold-standard imaging modality for multidirectional instability. Large lesions and subtle lesions can be evaluated prior to surgery to direct operative planning.Operative management of multidirectional instability should not be undertaken in the absence of a lesion on MRA without an exhaustive trial of physical therapy.
- Arthroscopic capsular plication and labral repair is our preferred surgical treatment. Arthroscopy allows visualization of the entire joint, the entire capsule, and all associated lesions producing the instability. Additionally, arthroscopy allows the operator to move the shoulder through range of motion while evaluating glenohumeral stability dynamically.
- Labral detachment or tearing from the glenoid is managed with suture anchor fixation to the glenoid in our practice. Isolated simple capsular redundancy is treated with capsular imbrication. Patulous capsules requiring imbrication with concomitant labral tears are treated with capsular shift and labral repair using suture anchor fixation.
- Superior labral tears associated with instability are treated with repair in patients younger than age 40. Patients older than age 40 are treated with concomitant long head of the biceps tenodesis.
- Postoperative physical therapy is a key component of successfully returning normal shoulder kinematics following operative stabilization.
Multidirectional shoulder instability is a multifaceted problem encompassing atraumatic and traumatic etiologies. Pain with overhead activity, decreased endurance, and weakness is often the presenting complaint. These shoulders should be carefully examined, and MRA should be used to assist in delineating underlying lesions.
Appropriate and successful navigation of multidirectional instability requires an appropriate understanding that the instability stems from more than one lesion and requires an ability to work in the anterior, inferior, and posterior glenohumeral joint. Arthroscopic management is the current standard, but it is difficult to perform well. Open surgery should be considered if a surgeon has little arthroscopic experience or in the face of previous failed stabilization procedures.
Matthew D. Williams, MD, is an orthopaedic surgeon with Louisiana Orthopaedic Specialists, Lafayette, Louisiana. T. Bradley Edwards, MD, is an orthopaedic surgeon with Fondren Orthopedic Group and Texas Orthopedic Hospital, Houston, Texas.
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