PREOPERATIVE CONSIDERATIONS

Multidirectional instability (MDI) of the shoulder is usually an atraumatic condition in which the shoulder demonstrates symptomatic laxity in more than one direction. MDI was first described in 1980 by Neer and Foster.¹ They reported on a group of patients who had pain and laxity in the anterior, posterior, and inferior directions. They successfully eliminated the symptoms in most patients using an open inferior capsular shift procedure based on the humerus. Duncan and Savoie² described the first arthroscopic treatment of MDI in a pilot study using a modification of the Caspari transglenoid capsular shift technique, and many surgeons have expanded and improved on this original idea.

Several reports have been published showing excellent results with arthroscopic treatment of the patient with multidirectional instability. In their initial report, Duncan and Savoie² found that patients showed improvement at 1- to 3-year follow-up. The average postoperative Bankart score was 90 and all had a satisfactory score according to the Neer system.

Wichman and Snyder³ have reported results of arthroscopic capsular shift for MDI in 24 patients with an average age of 26 years and a minimum follow-up of 2 years. Five patients (21%) had an unsatisfactory rating according to the Neer system. Of the unsatisfactory cases, one patient was in litigation for a motor vehicle accident and there were three workers’ compensation cases.

Treacy and Savoie⁴ have reported on 25 patients with MDI of the shoulder who underwent an arthroscopic capsular shift. At an average 5 year follow-up, three patients had episodes of subluxation but none had recurrent dislocation. According to the Neer system, 88% of patients had satisfactory results.

Gartsman⁵ has reported on 47 patients who underwent arthroscopic capsular plication for MDI. Of these patients, 94% had good to excellent results at an average follow-up of 35 months, and 85% of athletes returned to their desired level of participation.

Lyons and colleagues⁶ have shown favorable results with an arthroscopic laser-assisted technique, in which the rotator interval was plicated with multiple sutures. Of 27 shoulders, 26 remained stable at 2-year follow-up, and 86% of athletes returned to their sport at the same level.

McIntyre and associates⁷ have reported results of arthroscopic capsular shift in MDI patients using a multiple suture technique in the anterior and posterior capsules, with 32-month follow-up. Recurrent instability occurred in 1 patient (5%), who was treated successfully with a repeat arthroscopic stabilization; 13 athletes (93%) returned to their previous level of performance.

Hewitt and coworkers⁸ have demonstrated favorable techniques and results in a review article of multidirectional instability of the shoulder using a pancapsular plication suture technique.

Tauro and Carter⁹ have reported preliminary results of a modified arthroscopic capsular shift for anterior and anterior-inferior instability in four patients, with a minimum follow-up of 6 months. No patients developed recurrent instability in this short-term follow-up period.

ANATOMY AND PATHOANATOMY

The underlying pathomechanical derangement is an increase in glenohumeral translation leading to symptoms. Static shoulder stabilizers include the glenohumeral ligaments, bony architecture, labrum, and negative intra-articular pressure. Dynamic stabilizers include the rotator cuff, scapular stabilizers, deltoid, and possibly the biceps brachii.

In MDI patients, there is an increased laxity of the joint capsule. Some patients acquire this laxity with activity and other patients have congenitally lax tissues. The most common surgical finding is a lax inferior capsule. The deficiency of the anterior and posterior pouches will differ among patients. There will be poorly defined bands of the inferior glenohumeral ligament (IGHL) in the anterior pouch, posterior pouch, or both. The rotator interval will exhibit significant laxity and present with a bulged-out appearance. The rotator interval contains the coracohumeral ligament, superior glenohumeral ligament, and joint capsule. A drive-through sign signals the ability to move the arthroscope easily under the humeral head into the axillary pouch and is produced by laterally distracting the humerus. This is a common finding in patients with MDI. Viewing the shoulder from the posterior portal, a skybox view sign is present if the entire posterior sulcus is easily visualized.

It is important while performing the diagnostic arthroscopy in MDI patients to remember that the chronic subluxations can cause significant stress to the labrum, capsule, and rotator cuff tendons, leading to tears, perforations, or partial tears. These lesions must be addressed at the time of the operation.

HISTORY AND PHYSICAL EXAMINATION

A detailed history is extremely important in evaluating all shoulder patients, but is especially true for the patient with MDI. The usual patient will be teenagers or in their 20s. The most common complaint is pain with the activities of daily living in the midrange of function. Athletes present with pain during sporting events as well. The level, timing, and chronicity of pain must be recorded. The activity level of the patient and the specific sport (if any) should be recorded as well. Questions should be directed to determine whether there are symptoms of popping, clicking, subluxation, or dislocations. The number of such episodes needs to be determined, as well as the amount of trauma required to produce the episode. One should note if there has been one or multiple traumatic events, or if the symptoms developed insidiously. Some patients will also give a history of transient neurologic events.

The physical examination starts with visual inspection of the patient. It is extremely important to look at the patient’s posture in the standing and sitting positions. Symptomatic MDI patients will almost always present with a severely protracted shoulder or, occasionally, with the shoulder supported by a sling. Unclothe the shoulder so that see the entire arm, upper chest, scapula, and trapezius can be seen. Again, note the position of the scapula at rest and with attempted active movement. Chronic MDI patients will show scapular kicking or increased protraction with any movement. Ask the patient to abduct and forward-elevate the arm actively. Observe the scapula tracking pattern and repeat this with a forward flexion maneuver as well. Note any scapular dyskinesis that is present preoperatively. General muscle tone should be examined, and note any atrophy of the shoulder girdle. The shoulder may have a squared-off appearance because of the prominence of the acromion secondary to inferior subluxation of the humeral head and disuse atrophy of the deltoid.

Assess shoulder range of motion with the patient sitting, without taking gravity into account, while assessing scapular balance. Check forward flexion, abduction, internal and external rotation (IR-ER) with the arm at the side, and IR-ER with the shoulder in 90 degrees of abduction. Compare the motion with that of the contralateral shoulder.

The next part of the evaluation involves determination of the degree and direction of instability. This is assessed with the patient in the sitting and supine positions. With the patient sitting, place one hand on the proximal humerus and the other hand on the elbow. Apply a load in the anterior, posterior, and inferior directions. A circumduction maneuver can demonstrate subtle instability. Note the degree of shoulder movement in each direction. Check for a sulcus sign in neutral rotation and repeat the test with the arm in external rotation and abduction. Check for a sulcus sign with the shoulder in more than 45 degrees of abduction. With the patient supine, perform a load and shift test in the anterior and posterior directions in varying degrees of shoulder abduction (Cofield test). This can also be performed with the patient on his or her side. Compare the results with the contralateral side. Asymptomatic movement measures laxity. If the maneuver produces pain, then the laxity is considered symptomatic instability. In most MDI patients, the irritated rotator cuff is the source of pain as it compensates for the laxity.

The rotator cuff should be evaluated next. Palpation for swelling and thickening of the tendons may elicit pain. The strength of the rotator cuff should be tested and any pain associated with strength testing should be noted. MDI patients will often develop a rotator cuff tendinitis and exhibit significant pain with manual muscle testing. Preferred tests of the rotator cuff include the Whipple test, supraspinatus stress test, supraspinatus isolation test, external rotation test, and belly press test with the elbow held forward. The Whipple test is performed in 90 degrees of forward flexion and slight adduction. Have the patient resist a downward pressure. The supraspinatus (SS) stress and isolation tests are performed in the scapular plane in 90 degrees of abduction. Have the patient resist a downward pressure with the thumb turned down (SS stress test) and with the thumb turned up (SS isolation test). The supraspinatus stress test will be more painful in patients with posterior superior rotator cuff pathology. The supraspinatus isolation test will be more painful with anterosuperior rotator cuff pathology. If the rotator cuff is weak, check for scapular protraction. If scapular protraction is present and the rotator cuff is weak and painful, check for normalization of shoulder strength with manual scapular stabilization. This is accomplished by stabilizing the inferior pole of the scapula to the chest wall. Next, perform the external rotation test with the arm in slight abduction and 45 degrees of external rotation. Have the patient resist an inward pressure on the hand. The belly press test is performed by placing the hand on the abdomen and maintaining the elbow in front of the body. Have the patient resist an attempt to pull the hand off the abdomen. Rate the patient’s strength according to the standard manual muscle testing system and determine the level of pain associated with the tests. Compare the findings with the contralateral side.

Evaluate the cervical spine for motion and determine whether there are any nerve root compression symptoms.

The vascular status of the arm should be evaluated by performing the Adson test, checking the pulse with the arm abducted to 90 degrees and externally rotated to 90 degrees. In many MDI patients, this will produce transient vascular compromise and a diminished pulse. Manual scapular retraction will relieve pressure and restore a normal pulse. This variation of the Adson or Leffort test demonstrates to the patient that the numbness, tingling, and vascular changes may occur in this condition because of poor scapular control.

Evaluate the range of motion of the other extremities and check for hyperelasticity of the knees, elbows, and metacarpophalangeal joints. Note any and all joints that exhibit hyperextension and/or hypermobility.

DIAGNOSTIC IMAGING

Imaging modalities that are most commonly used are plain radiography and magnetic resonance imaging (MRI). Plain radiographs are often normal, but should be evaluated for any bony deficiency of the glenoid or humeral head. MRI scans are often used in the evaluation of the patient with MDI. An MRI with intra-articular contrast is most helpful. The choice of contrast agent depends on the radiologist, and normal saline appears to be the safest agent used. A typical MRI finding is a large capsular volume. Often, a large axillary fold is noted. The appearance is that of an upside-down bubble in the coronal view, extending inferiorly below the glenoid. One pathognomonic hallmark of MDI, as described by Neer,¹ is bulging of the rotator interval with contrast material. If there is significant rotator interval laxity, one might see the entire intra-articular portion of the biceps tendon silhouette. The underside of the rotator cuff and rotator interval may have space between them and the biceps tendon in the coronal sections. The axial sections will show capsular laxity in the anterior and posterior sides of the joint, usually in the lower sections of the glenoid. Evaluate the scan for any signs of labral degeneration, tears, or malformation. Always try to determine the integrity of the rotator cuff. Evaluate for any cysts in the spinoglenoid notch.

TREATMENT OPTIONS