eMedicine - Multidirectional Glenohumeral Instability : Article by Daniel C Wnorowski

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Multidirectional Glenohumeral Instability

Article Last Updated: Mar 5, 2007

Multidirectional instability (MDI) is a relatively common, generally bilateral, atraumatic condition affecting shoulder function. MDI is caused by generalized capsular laxity—that is, insufficiency of the static ligament constraints. There is excessive mobility of the glenohumeral joint in all directions, although there may be a predominance of 1 direction, typically anteroinferior or posteroinferior.

History of the Procedure

The history of MDI of the shoulder is neither as colorful nor as ancient as that of traumatic shoulder instability. Whereas traumatic shoulder dislocation and its treatment can be traced back to Egyptian times, MDI was acknowledged as a real entity only as recently as 1980, when it was first described in detail by Neer and Foster. Although Perthes and Bankart, in 1906 and 1923, respectively, described the essential lesion of recurrent traumatic glenohumeral dislocations (ie, detachment of the labrum and inferior glenohumeral ligament from the glenoid), the role of generalized capsular laxity in glenohumeral instability was not appreciated until 1980.

Problem

A patient with symptomatic MDI may complain of instability symptoms but often presents only with pain. Initial treatment is conservative, focusing on strengthening the dynamic components of shoulder stability—the rotator cuff and the scapular stabilizers. A conservative approach is often successful; however, when rehabilitation fails, surgical management may be undertaken to enhance static stabilization by tightening the shoulder capsule, historically via an open procedure, but arthroscopic management is evolving rapidly. The prognosis for MDI is generally good.

Frequency

The prevalence of MDI of the shoulder in the general population is not known. Traumatic shoulder instability is a much more common surgical indication.

Etiology

Shoulder instability has been classified by Hawkins and colleagues (1990), as well as others, in various ways, including direction (eg, anterior, posterior), degree (dislocation vs subluxation), etiology (eg, traumatic, atraumatic, overuse), and chronology (eg, acute, recurrent, fixed). For this article, 2 major categories are especially useful (Matsen et al, 1990, 1994; Hawkins and Bokor, 1990):

Pathophysiology

Physicians must thoroughly understand basic shoulder biomechanics to understand MDI, to make the diagnosis in appropriate cases, and to prescribe a proper treatment plan. The most well-written, simple, understandable, concise, and readable summary of shoulder stability is that of Matsen et al (1994). Review of the text of Matsen et al is encouraged; highlights of this text are summarized in this section.

The shoulder is unlike other joints in the body in that for it to meet the demands for extreme motion, osseous- and ligamentous-based stability is sacrificed. Matsen et al describe the following concepts, which contribute to the stability of the shoulder joint: balance, concavity compression, superior stability, adhesion-cohesion, glenohumeral suction cup, limited joint volume, and capsuloligamentous constraints.

Balance refers to the passage of the net joint-reaction forces on the humeral head through the center of the glenoid fossa. An analogy is made to a golf ball on a tee. The key components of balance include alignment of the humerus with the glenoid center line, facilitated by the surface arcs and areas of the glenoid and humeral head and by the muscles that position these 2 bones relative to each other—namely, the rotator cuff and scapular positioners. Factors that affect balance stability include loss of glenoid surface area, scapular malalignment, and muscle imbalance or weakness (eg, rotator cuff dysfunction).

The concept of concavity compression refers to the stabilizing effect of the depth of the concave glenoid fossa on translation of the convex humeral head. This is augmented by (1) the increased thickness of the glenoid articular cartilage at the periphery of the glenoid relative to its center, (2) the glenoid labrum, and (3) the compressive force of an appropriately functioning rotator cuff. Factors that affect this component include deficiencies of glenoid concavity (congenital flatness); labral hypoplasia, attrition, or tearing; and rotator cuff dysfunction.

Superior stability refers specifically to the superior-inferior component of glenoid concavity, which resists proximal migration of the humeral head within the glenoid. Coupled with the compressive function of the rotator cuff, even with a torn supraspinatus, this component can resist the upward pull of the deltoid. Factors that affect such superior stability include a deficient superior glenoid and the biceps–labral anchorage.

Adhesion–cohesion is a mechanism by which fluid on coated surfaces provides an intrinsic adherence between the surfaces. This may be affected by changes in the fluid chemistry (secondary to inflammatory disease), loss of smoothness of the surfaces (secondary to degenerative disease), and alterations in the contact areas.

The glenohumeral suction-cup effect depends upon the tendency for matched concave and convex surfaces with a flexible periphery to center and stabilize after expressing any intervening air and fluid, thereby forming a seal. Deficiencies of the glenoid labrum or of the margin of the glenoid can adversely affect this stabilizing mechanism.

The limited joint volume mechanism reflects the fact that the normal glenohumeral joint is really a potential space, contains minimal fluid, and has an inherent negative pressure. A sealed joint ensures an increase in this negative pressure with attempted distraction, thus increasing the joint reactive force independent of other muscular forces. Joint puncture by any means, increase in joint fluid secondary to trauma or inflammation, and laxity of the capsule (increasing joint volume) all contribute to the loss of this stabilizing mechanism.

Matsen et al stress that the aforementioned components provide midrange stability. Midrange stability refers to stability in the mid range of motion (ROM), where the ligaments and capsule provide little tension-dependent static stability. These factors act independently of the capsuloligamentous restraints. The capsule serves as a passive leash that can restrain glenohumeral motion within a given ROM. The insertion of the capsule upon the glenoid labrum provides continuity for the concavity mechanisms described above. The glenohumeral ligaments are ideally positioned thickenings within the capsule that serve to check large forces encountered within the capsule during specific arm positions and activities.

Numerous studies (O'Connell et al, 1990; Ovesen and Nielsen, 1986; Turkel et al, 1981) have elucidated the role of the capsuloligamentous complex in the static stabilization of the shoulder, and it has been shown that the inferior glenohumeral ligament is clearly the most crucial component.

The value of the dynamic supports of shoulder stability (ie, rotator cuff, scapular stabilizers) cannot be overstated. The proper compressive function of the rotator cuff is essential for glenohumeral stability and remains the primary focus of rehabilitative management for this problem. Deficits of shoulder proprioceptive function have been reported in MDI (Kirkley et al, 2001).

Clinical

The diagnosis of MDI is highly clinical. Suggestive history and physical examination findings are the basis of a diagnosis of MDI. Imaging studies, including plain radiographs, magnetic resonance imaging (MRI), and MRI-arthrography, may be of marginal help. Examination under anesthesia (EUA) and arthroscopic findings are highly supportive.

The patient with MDI most often presents with complaints of a generalized painful or sore shoulder, which is usually worse with activity or with certain arm positions. Instability symptoms perceived by the patient, such as dislocation, subluxation, or functional symptoms (eg, catching, locking), are less commonly reported than pain. In fact, some patients may not appreciate or describe any actual sense of instability. Symptoms may follow a roller coaster pattern and may be aggravated by overhead activity, carrying objects at the side, overuse, or injury. These symptoms are relieved by rest and support of the arm. Nocturnal pain is variable.

The patient usually denies a history of frank traumatic dislocation but may describe subluxation or looseness, even with activities of daily living (ADL). This history should provoke suspicion of and search for a multidirectional pattern of laxity, particularly if bilateral or posterior. The combination of posterior and inferior laxity is classic, according to Neer and Foster (1980).

An athletic history may be contributory. Patients with a predisposition to MDI who are engaged in sports that are stressful to the shoulder girdle, such as swimming, throwing, or racquet sports, may have a difficult time with consistent high activity levels.

Perhaps one of the most confusing presentations is that of concomitant impingement. Not uncommonly, a patient with MDI may complain chiefly of pain with overhead use, especially if there is involvement with overhead athletics, such as throwing, volleyball, swimming, or racquet sports. Pain, in this case, may be minimal with the arm at the side. Tibone et al (1986) have shown that therapeutic management directed at the diagnosis of impingement and rotator cuff pathology in patients participating in overhead activities may be unsuccessful. Underlying instability always must be considered in those who report a painful shoulder, especially in the younger patient who is involved in vigorous activities above the shoulder.

Impingement symptoms (ie, pain with the arm at 90° or more) may be secondary to glenohumeral hypermobility and superior humeral head translation, regardless of acromial arch architecture.

A notable highlight of MDI on examination is the bilaterality of physical findings. Although active ROM (AROM) may be guarded, there are no passive limits. A good stability examination yields underlying glenohumeral hyperlaxity if adequate relaxation can be achieved. The pathognomonic feature of MDI is demonstration of the sulcus sign—the hallmark of the inferior component of the capsular laxity. Again, with adequate relaxation, a patient examiner demonstrates laxity beyond the normal limits with anterior and posterior testing. Grade may be variable, and anterior and posterior components need not be symmetrical.

If the patient is unable to relax, an EUA may be required to demonstrate increased glenohumeral anterior and posterior translation, as well as inferior translation (ie, sulcus sign). More often than not, these findings are symmetrical.

Examination of the labrum (eg, labral grind test, superior labrum anterior and posterior lesion [SLAP] test) also may reveal positive findings, with or without true labral anatomic abnormalities. Furthermore, apprehension testing also may be positive, usually in the direction of the chief component of instability. For example, anterior apprehension findings in the external rotation and abducted position may suggest a predominant anterior-inferior MDI pattern, with or without positive relocation, crank, or fulcrum tests.

Indications for surgical treatment of MDI include the presence of persistent symptoms to a disabling degree and failure of conservative management, including a supervised rehabilitation program and a trial of activity modification or restriction.

A reasonable trial of conservative treatment is 3 to 6 months. Any patient for whom conservative management has failed may be counseled regarding the option of surgical treatment. The following points must be considered:

A thorough discussion of the relevant anatomy is included in the discussion of surgical techniques available for MDI, both open and arthroscopic (see Open surgical technique and Arthroscopic surgical technique in the Treatment, Surgical therapy section). The reader is also urged to read the Complications section, especially with regard to precautions necessary when working close to the axillary nerve.

According to Neer and Foster (1980), contraindications to the surgical management of MDI include willful, habitual, or voluntary shoulder instability; collagen connective tissue disorders (eg, Ehlers-Danlos syndrome, Marfan syndrome); and lack of a trial of, or noncompliance with, a supervised rehabilitation program.

Imaging Studies

Diagnostic Procedures

Medical therapy

Neer and Foster (1980) stressed the importance of conservative management before surgery. In their original case series, the patients they selected for surgery had symptoms and disability for 1 year and had also undergone a trial of rotator cuff and deltoid rehabilitation that failed. Furthermore, Neer and Foster carefully excluded patients with emotional problems (now referred to as intentional, habitual, and willful voluntary dislocators).

Many patients respond positively to a supervised vigorous shoulder-conditioning program. Supervision is essential, at least initially, to ensure both compliance and effective instruction in the proper execution of an exercise program. Exercises should address all portions of the rotator cuff. A low-resistance, high-repetition, subimpingement range, isotonic cuff-strengthening program works well with use of stretch cords or hand weights. These exercises are most beneficial when performed 3-5 times per week.

Isokinetic equipment is useful but not essential; this equipment is helpful for interval testing to assess progress. The most important factor is to teach the patient the value of a persistent, ongoing effort at shoulder-girdle strengthening (ie, strengthening for life). Many patients initially do well with their exercise program but then lose discipline when symptoms subside—with recurrences subsequently following. Most patients learn to return to conditioning exercises when symptoms return.

In addition to a strengthening program, activity modification is necessary to eliminate, or at least reduce, pain and instability symptoms. Avoidance of unnecessary overhead motions (eg, throwing, racquet sports, swimming), side carrying and lifting, and pushing and pulling may be required. Work modifications also may be considered.

Anti-inflammatory medications or analgesics may help during exacerbations of MDI. Steroid injections have a limited place in the nonoperative treatment of MDI but may be helpful in the treatment of secondary impingement syndrome. Narcotic medications have no place in the management of MDI.

A reasonable duration for conservative treatment is 3 to 6 months; any patient in whom conservative treatment has failed may be counseled regarding the option of surgical treatment. The following points must be considered:

Surgical therapy

Open surgical management

The landmark paper on MDI was that of Neer and Foster, published in 1980. Not only did this classic paper facilitate widespread recognition of the MDI problem that was previously believed to be rare relative to unidirectional instability, but it also described a capsulorrhaphy to address the pathologic capsular laxity associated with MDI. Of the 32 patients in their study, 31 (97%) had satisfactory results following the inferior capsular shift procedure with no recurrent instability, no significant postoperative pain, full strength, and full return to activity. However, this was a preliminary study; by today's standards, ROM was questionable, with satisfactory defined as ROM within 10° of elevation and 40° of rotation of the contralateral side.

A biomechanical study by Wang et al (2001) of joint reactive forces and glenohumeral translations in a cadaveric model has reported that the inferior capsular shift is superior to a unidirectional anterior capsular repair in reproducing more normal forces, kinematics, and mechanics.

In a follow-up report by Neer and Foster (1985), the longevity of the results of the inferior capsular shift procedure for MDI was documented in larger numbers of patients with longer follow-up.

Other reports of the use of the inferior capsular shift procedure for MDI were published early in the learning curve. Recurrence rates consistently were reported at 10% or less (Marberry, 1988; Brems and Bergfeld, 1991; Altchek et al, 1991; Lebar and Alexander, 1992). However, average loss of motion has remained variable, with the best cited as only 6° of elevation loss and 3° of external rotation loss in a series of active-duty naval personnel at 28 months (Lebar and Alexander), and only 5° and 4° of external rotation loss at 0° and 90° of abduction, respectively, at 36 months (Altchek et al). Postoperative ROM obviously varies from patient to patient and surgeon to surgeon, and it is likely to also be a function of the rehabilitation program.

The classic Neer-type inferior capsular shift has been modified by making the shift in the glenoid side, rather than the humeral side, and by applying it to patients with a predominantly anterior-inferior instability pattern. In 42 shoulders, of which 90% had a concomitant Bankart repair and 50% had generalized ligamentous laxity, 4 (9.5%) had recurrent instability (Altchek et al). Interestingly, 3 of these 4 (7.1% of 42) had recurrent posterior instability. However, in the successful category, motion loss was relatively small, averaging only 5° of external rotation, with no more than 5° of elevation loss.

The classic humeral side inferior capsular shift procedure has been applied to lesser degrees of MDI as well. The procedure has also held up well in patients who are very active. Bigliani et al (1994) reviewed 63 patients, in whom a combined total of 68 inferior capsular shifts had been performed. Most were performed primarily for anterior-inferior instability, excluding combined anterior and posterior patholaxity and associated glenoid fractures. These patients were athletic, including 31 throwers, and 21 (30.9%) of these surgeries also included a Bankart procedure. Results were good to excellent in 94% of the cases, with 92% of patients able to return to their previous sports. However, only 75% of the patients were able to return at their previous level of play (only 5 of 10 were elite throwers). Motion loss was less than in Neer and Foster's series, averaging only 7° of lost external rotation. Two patients (3.2%) had redislocations resulting from falls, 1 (1.6%) patient had musculocutaneousnervepalsythat resolved, and 10% of patients had persistent minor clicking.

Arthroscopic management

The use of the arthroscope for treatment of MDI has only recently made the transition from the diagnostic to the operative realm. Snyder's 1994 textbook, Shoulder Arthroscopy, makes no mention of arthroscopic management techniques for MDI, but he describes the diagnostic findings of arthroscopy. Indeed, he states, "If surgery is required for atraumatic laxity, most often an open capsular shift procedure is used." He refers the reader to Neer and Foster's classic paper (1980).

However, various options are evolving for arthroscopic management of MDI. The same basic principles of open surgery apply. The goals are reduction of overall capsular patholaxity anteriorly, posteriorly, and inferiorly; closure of the rotator cuff interval; and minimization of morbidity and risk of complications.

Thermal or radiofrequency (RF) capsular shrinkage has been increasing in popularity, probably because of its technical ease and simplicity relative to traditional open capsulorrhaphy or arthroscopic suture techniques. Abundant basic science research has revealed that RF energy applied to collagen tissues results in shortening proportional to temperature and duration of contact (Hayashi et al, 1996).

Initially based upon laser administration of heat energy to tissues, RF has become a simpler and less costly tool of choice for shrinkage of collagen tissues, and it is rising in popularity for use in the shoulder. RF energy can be administered via either monopolar or bipolar techniques. No clear-cut advantages or disadvantages of one versus the other have yet been demonstrated, with use primarily dictated by surgeon preference (West et al, 2001).

Lopez et al (1988) demonstrated that ultrastructural changes in collagen subjected to RF energy include increased cross-sectional fibril diameter, loss of fibril size variation, and loss of collagen cross-striations, as well as nuclear pyknosis. This is a temperature- and time-dependent process, with most marked effects seen when the temperature is above 65°C, and application is 1 minute or longer (Naseef et al, 1997).

Furthermore, Hecht et al (1998) showed that the area and depth of capsular involvement of tissues subjected to RF heat energy are directly correlated with the power setting (watts) of the application instrument, with marked effects producing inflammation and decreased vascularity. They concluded that RF power settings and heat dissipation via lavage within the arthroscopic fluid environment play major roles in resultant heat application and distribution and, thus, the resultant morphologic changes noted.

But what are the mechanical effects of RF energy on the joint capsule? The lowest strength to failure and the least stiffness was seen at 2 weeks following RF application to sheep capsule, with remodeling to nearly normal properties by 12 weeks (Hecht et al, 1999). Technique—that is, the method of RF application—also makes a difference. A confluent paintbrush pattern of application was compared with a grid (stripes) pattern, and although similar overall amounts of shrinkage were noted, faster healing with better mechanical properties was noted for the grid type of application. In addition, although histologic viability was similar for the 2 types at 12 weeks, the viability of the grid type was superior to that of the paintbrush at 6 weeks (Lu et al, 2000 [Am J Sports Med]).

Results of RF treatment in individuals with MDI of the shoulder are beginning to emerge. A group of 23 consecutive patients treated with thermal capsulorrhaphy, including 2 who had prior open procedures on the opposite shoulder, were evaluated at follow-up of 12 to 22 months (Ceballos et al, 2001). All patients reported Rowe scores above 90/100 (average of 97), all were satisfied, and all but 2 achieved full ROM postoperatively. All patients returned to preoperative activity levels, including the athletes. No neurologic problems were noted.

Karas et al (2001) reported on 27 of 28 patients with a minimal follow-up of 2 years (of 141 patients who had surgery). Ten (7.1%) of these individuals had MDI, and of these 10, 2 (1.4% of 141) had a history of previous open repairs. The overall failure rate was 26%, and 50% of those failures occurred in individuals with posterior instability and 30% occurred in individuals with MDI. Those with anterior patterns fared the best. Overall improvements were noted for pain levels and painless activity above the neck. Eighty-nine percent of the patients said they would have the procedure again. The authors considered their results promising.

Results of arthroscopic suture management of MDI are premature, and long-term follow-up is pending. Snyder (2001) reported on 23 of 24 patients who had a capsular plication for glenohumeral instability in the absence of a Bankart lesion. He notes MDI was present in 8 of the 23 seen for follow-up at an average of more than 24 months. American shoulder and elbow system (ASES) scores improved on average, and Rowe scores were good or excellent in 78% of cases. Snyder termed this technique a promising alternative to open techniques.

Wolf and Durkin (1999) presented their results of suture plication in 20 of 26 patients with average 34-month follow-up (minimum follow-up, 24 mo). With regard to pain, strength, activity, ROM, stability, and overall satisfaction, results were good to excellent in 75% of cases. Workers' compensation claims correlated with unsatisfactory outcome, and 5 patients with recurrent instability required a total of 8 additional surgeries.

Treacy et al (1997) reported their results of an arthroscopic capsular shift for MDI in 26 patients and noted 88% satisfactory results in 24 patients available for review at an average of 52 months (range 28-72 mo). Three patients had postoperative instability. All but 1 of the 24 patients had regained full symmetrical ROM. The authors felt that these results were comparable to the results of open surgery.

A recent review article by Caprise and Sekiya (2006) is worthy of mention and comment. The authors stress that although arthroscopic suture techniques for the treatment of MDI are new and evolving, these methods "have comparable results to open techniques when the multifactorial nature of the disease is recognized and the multiple techniques are used in combination to fully treat all pathology.... The advantages of a less invasive procedure make arthroscopic capsular plication attractive, but it is associated with increased technical difficulty and a steep learning curve." Caprise and Sekiya stress that further research and follow-up are needed, and they emphasize the goal of any surgery for MDI, open or arthroscopic, is "addressing the capsular laxity and redundancy to restore anatomic capsuloligamentous tension without overconstraining the shoulder."

Recent cadaveric studies shed light on the effects of capsular plication on capsular tightness. Gerber et al (2003) studied the effects of selective capsular plications on the range of motion of the shoulder in 8 cadaveric specimens and found predictable patterns of motion loss. Medial to lateral 1-cm plications resulted in significant losses of motion as follows: anterosuperior plication, 30.1° loss of external rotation in adduction; anteroinferior plication,19.4° loss of abduction and 20.6° loss of external rotation; and posterosuperior plication, 16.1° loss of internal rotation in adduction. Furthermore, total anterior and total posterior plication resulted in loss of flexion of 20° and abduction of more than 15°, whereas total anterior plication had a greater than 30° loss of external rotation and total posterior plication had a greater than 20° loss of internal rotation. Finally, total inferior plication resulted in loss of abduction of 27.7°.

Alberta et al (2006) found that in 6 cadaveric specimens that underwent "stretching" of the anteroinferior capsule that resulted in increased external rotation of 23.2° without increased glenohumeral translation, selective anteroinferior plication reduced this external rotation by more than 12°. The center of rotation of the glenohumeral joint was posteriorly and inferiorly shifted, with loss of anterior translation 49-61%, at 15N and 20N loads, respectively. Finally, the capsulolabral "bumper" height more than doubled, from 2.9 mm to 6.4 mm. Such observed restrictions of motion may improve clinical instability but may have consequences for the long-term function of the glenohumeral joint.

Intraoperative details

Author's recommended management

This author currently uses a traditional open surgical approach for moderate to severe MDI and for anteroinferior predominant MDI; uses an arthroscopic plication technique for mild to moderate MDI and for posteroinferior predominant MDI; and no longer uses thermal treatment, mainly in light of reported complications, especially with the risk of axillary nerve injury (see the Complications section).

This discussion of the open surgical technique focuses first on the classic treatment for MDI, followed by modifications. Useful and recommended modifications are in parentheses.

Neer and Foster's (1980) technique emphasized the basic principle of capsular detachment from the humeral neck on the predominant side of instability and then shifting the capsule to the opposite side of the calcar. The goals are to reduce the capsular redundancies on the more-involved approach side and also on the opposite side, while additionally obliterating the axillary pouch. Furthermore, Neer and Foster emphasized the creation of thickenings in the repaired shifted capsule by folding and overlapping capsular flaps. Permanent nonabsorbable sutures are used.

After a thorough EUA to elucidate the dominant direction of instability, the patient is placed in a beach-chair position for a planned anterior approach. If arthroscopy is performed before a planned open anterior approach, it is useful to perform the arthroscopic segment in the beach-chair position as well. If a posterior approach is planned, arthroscopy is best performed in a lateral position, with open surgery continuing via a posterior approach in the same position. In other words, the surgical position should be clear following EUA, with patient position maintained through both the arthroscopic and open portions of the procedure. In this author's experience, arthroscopic findings rarely change the plan following EUA.

For the predominant anterior-inferior pattern of MDI, both anterior and posterior aspects of the shoulder are exposed, and a deltopectoral approach is planned. A 9-cm incision is made from the axillary crease distally to the coracoid proximally. (This is a long incision and is rarely necessary. In fact, an axillary incision [see Images 7-8] measuring more than 4 cm is sufficient in a patient who is slim.) The interval between the deltoid and pectoralis major muscles is identified, as well as the cephalic vein, which then is retracted medially. (Take the vein in any direction it wants to follow). Retract the conjoined tendon medially. (Respect the musculocutaneous nerve, which typically penetrates the conjoined tendon 3-5 cm below the coracoid process.)

The subscapularis tendon is identified. Cauterize the vessels at their lower margins, superficial to the subscapularis. Neer and Foster then recommend dividing the superficial one-half thickness of the subscapularis tendon 1 cm medial to the long head of the biceps, whereas the deeper one-half thickness is left on the capsule for reinforcement. (It is wise to leave slightly more [1.5 cm] lateral subscapularis tendon.)

The medial subscapularis flap is tagged, dissected from its deeper component, and retracted medially. (The lower third of the subscapularis tendon is mostly muscle, with minimal tendon fibers.) The underlying capsule is inspected, and the interval between superior and middle glenohumeral ligaments is closed with nonabsorbable sutures (see Image 9). (This is a constant finding, and the rotator cuff interval closure is essential to reduce inferior glenohumeral translation, but it may be difficult to reach with a very small incision in the axilla.)

Next, a "T"-shaped incision is made in the capsule with the stem of the T aimed at the glenoid, traversing the interval between the middle and inferior glenohumeral ligaments and the top of the T parallel to the humeral anatomic neck (1 cm from its lateral insertion). Two capsular flaps thereby are created, 1 superomedial (SM) and another inferomedial (IM) (see Image 10). During exposure and repair, it is very helpful to tag each flap corner with a long suture to control the flaps.

The proximal-distal incision is gradually extended distally, dividing the IM flap from the inferior humeral neck around to the posterior portion of the neck, while carefully protecting the axillary nerve with a flat retractor. To assist in control of the flap and to aid in visualization, it is helpful to place nonabsorbable sutures at 1-cm intervals in the lateral margin of the IM flap while progressing distally; the sutures will be used in the repair on the way out. Once the dissection reaches the posterior portion of the capsule and humeral neck, it is useful to apply traction to the IM flap in order to test the effect of capsular shortening on posterior capsular tension and to estimate and adjust necessary capsular repair tension.

Using a gauge or curette (a rongeur works well), a shallow groove is then fashioned in the anterior-inferior portion of the humeral neck adjacent to the capsular reflection. Then, the IM flap is advanced in a proximal direction to eliminate the inferior pouch and increase posterior tension. The lateral edge of the IM flap of the capsule is sutured to the remnant lateral capsular tag or adjacent subscapularis stump (using the aforementioned sutures). Once this has been accomplished with the IM flap, any redundant superior portion may be reflected inferiorly to thicken the anterior capsule. Finally, the SM flap is advanced distally and inferiorly and similarly sutured to the superior and anterior lateral capsular remnant and subscapularis stump.

An overlap develops as the SM flap is advanced inferiorly. This overlap serves to further reinforce the anterior tissues (see Image 11). Neer and Foster recommended securing the capsule with the arm in slight forward flexion and at about 10° of external rotation. To avoid overtension, this author secures the repair sutures with the arm in at least 45° of abduction and 45° of external rotation.

The subscapularis tendon is closed at its normal location; avoid shortening anatomically. Matsen et al (1990) has shown that a shortening of 1 cm can theoretically limit rotation by 20°. After the remaining closure is finished, the arm is immobilized at the side in a splint or a sling with a chest pad on neutral flexion and 20° of internal rotation.

For the posterior-inferior predominant instability pattern, a posterior approach may be chosen. A recent trend has been to perform all shifts from the front; the reasoning behind this is that the rotator interval cannot be closed from the back, and reasonable posterior tightening can be obtained from the front. For a posterior approach, according to Neer and Foster, a 10-cm incision is made either horizontally or vertically over the posterior-lateral scapular spine and posterior glenohumeral joint. They recommend detaching the deltoid from the posterior acromion and scapular spine, followed by a vertical split 2-3 cm to expose the underlying external rotators. However, detachment of the deltoid can usually be avoided, as it can be more simply retracted upward.

Similar to the dissection of the subscapularis anteriorly as described above, the infraspinatus is divided near its insertion and peeled medially, leaving some of its fibers on the posterior capsule for reinforcement. The posterior capsule normally is very thin posteriorly; hence, this step is important.

Again, a T-shaped capsulotomy is made, creating SM and IM flaps, dissecting and gradually releasing the IM flap progressively around the inferior humeral neck in an anterior direction while carefully protecting the axillary nerve throughout. A trough is prepared on the posterior-inferior humeral neck. Eventually, the IM flap is advanced and repaired gradually in a superior direction, eliminating both anterior patholaxity and the axillary recess. Then the SM flap is advanced over the top of the IM flap to reinforce and add bulk to the middle posterior capsule. Afterward, the infraspinatus is repaired in an anatomic fashion, followed by the posterior deltoid.

The arm is immobilized in neutral flexion-extension and 10° of external rotation for 6 weeks. This author generally immobilizes the arm in 30°-45° of abduction and 30° of external rotation for 4 weeks, followed by a 1-week transition to the Neer and Foster position, followed by a sling.

Arthroscopic surgical technique

The role of the arthroscope in the evaluation and management of MDI was limited to a diagnostic function even as recently as 1994 (Snyder). However, as with other shoulder applications, operative arthroscopy for MDI is developing and evolving rapidly.

Operative arthroscopy for MDI can be used for either primary or adjunctive functions. Open surgery—namely, the open capsular shift—is predictable, safe, and successful, with a proven track record. Thus, any new arthroscopic approaches must be compared to open surgery with regard to efficacy and safety. The general principles of open surgical treatment must be addressed via arthroscopic means. Furthermore, should arthroscopic approaches prove easier, as well as effective and safe, they must not displace or preempt a routine trial of conservative management before consideration of surgical treatment.

Two arthroscopic procedures that have shown early promise include RF thermal capsular shrinkage and intra-articular suture plication. These techniques are innovative and relatively simple, but long-term results are lacking.

Arthroscopic stabilization of the MDI shoulder can be performed in either the beach-chair or lateral position. A thorough EUA must precede diagnostic arthroscopy. Routine utilitarian portals are established. The posterior portal is made 1.5 cm distal and medial to the posterior-lateral corner of the acromion; the anterior portal is made1.5 cm medial and proximal to the coracoid process, between the long head of the biceps and upper edge of the subscapularis intra-articularly.

Arthroscopic suture repair techniques have been developed by Snyder (2001). He calls this approach "capsular pinch-tuck," or "plication surgery." The arm position is lateral, at 70° abduction and 10° flexion. Two anterior portals in the rotator cuff interval are created, as well as a posterior superior portal. The synovial surfaces are excoriated on the capsule and adjacent areas of the labrum. While the surgeon views from the posterior portal and uses a suture hook through 1 of the anterior portals, a pinch-tuck of capsular tissue is taken 1 cm lateral to the labrum, and the needle and tissue are approximated to the edge of the labrum. The needle is then passed through the labrum (it has now captured both the capsule and labrum). First, a suture relay is passed through the suture hook; then a suture is passed via the relay in the opposite direction out the original cannula. This thus leaves a suture crossing the labrum and also through the capsular fold.

The process is repeated at 1-cm intervals along the labrum in an inferior direction; each suture is tied with an arthroscopic knot pusher by a sliding knot technique (Snyder recommends the Tennessee slider knot). The number of tucks and the extent of anterior, inferior, and posterior tightening are a matter of surgical judgment. Snyder warns that the axillary nerve is at risk with a deep pass through the inferior capsule.

Images 12-18 show posterior plication and are representative. The view is of a right shoulder from the anterosuperior portal, just anterior to the biceps long head, viewing in a posteroinferior direction. The patient is in the lateral decubitus position, with the arm in 5 lb of traction, positioned in 45° of abduction and 20° of forward flexion. The working portal is the typical posterior portal, which is 1.5 cm inferior and 1.5 cm medial to the posterior corner of the acromion.

First, a suture passer device (Spectrum; ConMed Linvatec, Largo, Fla) is placed through the working cannula; it is then initially passed through a pinch of posterior capsule 1 cm from the labrum and then through the posterior labrum itself (see Image 12). Next, using monofilament suture and an all-arthroscopic, knot-tying technique (sliding knot first, backed up by an alternating post, alternating half-hitch technique), a knot is tied, plicating the capsular pinch to the labrum (see Image 13).

The process is repeated, placing a second, slightly more superior suture and knot (see Image 14). Capsular pinches or tucks may vary at the surgeon's discretion, and the number of sutures and the spacing between sutures also may vary (typically 1 cm) (see Images 15-18).

An arthroscopic interval closure is also typically added to reduce inferior laxity; this may be done last, after completion of plication sutures (see Images 19-20).

Regarding RF techniques, either monopolar or bipolar equipment may be utilized. Monopolar tools allow for monitoring of probe tip temperatures, for surgeon feedback. With the arthroscope in the posterior portal, the RF probe is used to shrink the inferior glenohumeral ligaments first, concentrating on the anterior and posterior bands (see Image 21). The area of heat application is gradually expanded proximally, concentrating on the glenohumeral ligaments, and the arthroscope is exchanged with the RF probe as needed.

The target temperature is 65°C, but it is important to visualize the actual capsular shrinkage for prime feedback. A grid pattern is recommended, "painting" in a linear fashion, with lines at right angles, preserving islands of untouched capsule amidst the grid (see Images 22-23). The rotator cuff interval must be included (see Image 24).

The posterior capsule is usually saved for last, as it is the easiest to access. The arthroscope is inserted anteriorly, and the RF probe is placed through the previously made posterior portal to treat the posterior capsule, including the posterior band of the inferior glenohumeral ligament, if not already done (see Image 25).

One must be careful to avoid contact with the labrum, biceps, articular cartilage, and especially the axillary pouch directly inferiorly, to avoid inadvertent thermal damage to the axillary nerve. It is also important to remember that the tissue of the inferior capsule is very thin, and the depth of heating applied via RF energy may easily traverse the capsular layer.

Follow-up

Postoperative rehabilitation

Neer and Foster recommended 6 weeks of postoperative immobilization, followed by heat and gentle assisted exercises. Their goal was for the ROM to be 20° less than the opposite shoulder. They advocated patients perform isometric exercises at 8 weeks postoperatively and progressive resistive exercises beginning at 12 weeks postoperatively. Additionally, Neer and Foster restricted sports and more than 20-lb lifting for 9 months and advised against swimming using back and butterfly strokes, heavy overhead use of the arm, and contact sports for 12 months postsurgery.

Modern protocols for repair of traumatic instability are more aggressive, as the philosophy has shifted in parallel to knee rehabilitation; the focus is on obtaining complete ROM, with earlier institution of rotator cuff strengthening in order to protect the surgical repair. Whether this opinion applies to the MDI-reconstructed shoulder may be debatable. This author has used the same protocol for both types of surgery.

According to Norris (1993), the most common complication of rehabilitation is recurrent instability caused by early motion and return to activity before complete healing. The opposite consideration, slow motion, is of at least equal concern because of the consequence of permanent motion loss and, if severe, iatrogenic arthritis similar to failed Magnuson-Stack and Putti-Platt procedures (incidence reported at 43%) (Norris).

Table 1 lists this author's current protocol for anterior capsular shift repairs. I delay both arthroscopically plicated and thermally treated shoulders relative to a conventional open shift.

Table 1: Postoperative Multidirectional Instability (MDI) Rehabilitation Protocol

General complications of instability repairs apply to any technique of MDI stabilization, open or arthroscopic. Failed repairs can result from errors in diagnosis, failure to address specific pathology (eg, omitting a Bankart repair in favor of a capsulorrhaphy when a labral detachment is present), loose repair, problems with healing (including failure to recognize collagen diseases such as Ehlers-Danlos and Marfan syndromes), postoperative noncompliance, or reinjury, to name a few.

Norris stressed that errors in diagnosis can include treating impingement as primary with decompression, missing secondary impingement caused by instability. This problem is especially common in throwers, swimmers, and other athletes who use overhead arm motions. A high index of suspicion for secondary impingement is required. Overtensioning the tighter side of a multidirectionally loose shoulder does not appear to be a common problem, but it is possible that a shift performed from the anterior side of a posterior predominant MDI pattern may worsen the posterior component, despite correcting the inferior component.

The inferior capsular laxity must be addressed in the MDI shoulder, and this has been discussed above. Failure to satisfactorily correct the inferior capsular laxity, failure to tighten the rotator cuff interval, or failure to adequately support the shoulder postoperatively may lead to recurrent instability. Furthermore, for revision surgery after initial MDI surgery has failed, it is important to be sure that the interval has been repaired, that there are no labral detachments, and that the capsular flaps are firmly secured to the glenoid.

The axillary nerve is at particular risk during the inferior dissection and during development of the inferior flap in both the anterior and posterior open approaches (Loomer and Graham, 1989). The relationship of the nerve with the inferior capsule must also be kept in mind with use of arthroscopic thermal and suture techniques. Some authors advocate exposure and isolation of the axillary nerve during this portion of the procedure. However, dissecting around the axillary nerve, merely to identify it, may paradoxically cause injury. It may be enough to maintain an elevator immediately beneath the inferior capsule while working on the inferior flap. (This author has not seen any axillary nerve injuries in hundreds of repairs, and I have yet to make a specific effort to identify and isolate the nerve.)

In an excellent cadaveric study, Price et al (2004) examined the relationship of the axillary nerve to the inferior capsule as the nerve passes through the quadrangular space, in order to define the risk to this structure from an arthroscopic perspective, specifically in the axillary nerve's relationship to the glenoid rim and inferior glenohumeral ligament (IGHL). The authors used a simulated lateral decubitus position, akin to typical arthroscopic positioning, with the arm in 5-lb traction, in 45° abduction and 20° flexion. The following findings are most relevant. The axillary nerve branches from anterior to posterior. The branch to the teres minor was closest to the rim of the glenoid, and the branch to the anterior deltoid was the farthest, with the branch to the posterior deltoid and the superior lateral cutaneous branch both intermediate in position, the latter closer to the glenoid than the posterior deltoid motor branch.

The axillary nerve was closest to the glenoid rim at the 6 o'clock meridian, averaging a distance of 12.4 mm (11.6-13.2 mm at the 95% confidence interval [CI]) at this site. At 10 mm anterior and posterior to the 6 o'clock meridian, the axillary nerve averaged a distance of 14.5 mm and 13.9 mm, respectively. Furthermore, the nerve was a mere 2.3 mm (1.7-2.9 mm at the 95% CI) from the IGHL at the 6 o'clock meridian, and averaged 2.8 mm at 10 mm anterior and posterior to the 6 o'clock meridian. Limitations of this study were discussed by the authors: they did not replicate capsular abnormalities that may be associated with unstable shoulders (ie, a loose capsule) or the effects of arthroscopic distention, both of which may alter the "normal" relationships defined above. Clinical applications of this work may explain the predominance of sensory deficits with arthroscopic axillary nerve injury. The teres minor must be carefully evaluated, as injury to the teres minor branch of the axillary nerve maybedifficult to discern.

In an interesting in vivo study, Esmail et al (2005) used intraoperative neurophysiologic monitoring to locate and map the axillary nerve and assessed capsuloligament thickness during arthroscopic thermal capsulorrhaphy and/or labral repair for glenohumeral instability. All surgeries were done in the beach-chair position. The authors recorded spontaneous and continuous electromyography (EMG). In 4 of 11 (36%) patients undergoing thermal application, excessive spontaneous neurotonic EMG activity was noted, altering the surgeon's behavior in applying heat, and in 1 of the 4 patients, increased motor latency was also noted, but all patients were without any clinical sequelae. No neurophysiologic abnormalities were noted in any cases of labral repair without thermal treatment. Consistent with the findings of Price et al, these authors mapped the nerve at a distance of 1.0-1.5 cm from the glenoid at the 5 or 7 o'clock meridian. The authors also noted that such monitoring added 15 minutes of surgical timeand$570 for a neurophysiologist per case.

Gryler et al (2001) measured increased temperatures along the course of the axillary nerve in thermal capsulorrhaphy, suggesting the likelihood of thermal-mediated neurologic injury. They utilized 9 cadaveric specimens with 4 thermocouples placed at 7-mm intervals along the axillary nerve within the inferior capsule. Measured temperatures were 42.8°C to 52.2°C from posterior to anterior, but 2 (22%) specimens measured greater than 67° (the set point of the device). In 4 of 9 (44%) specimens, transient readings greater than 50° for 10-second durations were recorded. These levels have been felt to be harmful to nerve tissue (Monafo and Eliasson, 1987; Langberg et al, 1992; Wen et al, 1996). Gryler et al advocated using power settings greater than 25 watts, keeping the probe moving, and using a stripe technique, should thermal management be considered.

The relationship of the axillary nerve to arthroscopically placed capsulolabral sutures has also been studied by Eakin et al (1998). Ten cadaveric shoulders underwent suture placement that mimicked arthroscopic suture plication techniques. Sutures were placed in a simulated lateral decubitus position with the arm in 45° abduction and 20° flexion, with 10-lb traction, through the capsule 1 cm from the glenoid rim, and then through the labrum at anterior (3 or 9 o'clock), anteroinferior (4:30 or 7:30), posteroinferior (4:30 or 7:30), and posterior (3 or 9 o'clock) positions. The average distance of each suture position to the axillary nerve was 16.7 mm (13.7-19.7 mm at the 95% CI) for the anterior sutures, 12.5 mm (10.2-14.8) for the anteroinferior, 14.4 mm (10.9-17.9) for the inferior, 24.1 mm (19.7-28.5) for the posteroinferior, and 32.3 mm (28.4-36.4) for the posterior sutures. The authors noted a statistically significant trend for the axillary nerve to lie closest to the anteroinferiorsuturesand then gradually at farther distances from more posteriorly placed sutures. They concluded that a "safe zone" exists between the common locations of suture placement for arthroscopic plication and the axillary nerve, but they urged caution during anteroinferior and inferior suture placement.

Axillary nerve injuries are not unique to arthroscopic management of shoulder instability. Neer and Foster reported 3 cases of axillary neuropraxia in their landmark presentation of open inferior capsular shift.

Complications of thermal capsulorrhaphy of the shoulder are increasingly being reported. Weber (2001) reported on 15 patients referred to his practice for complications related to this treatment method, including recurrent instability (11), axillary nerve injury (3), adhesive capsulitis (2), and capsular necrosis (2). He advocated salvage of recurrent instability with revision open capsular shift. Weber noted the transient nature of the axillary nerve injuries, but painful neuralgia persisted in 2 cases. The stiff shoulders required subsequent capsular release but failed to gain complete motion at "final follow-up." Capsular necrosis is difficult to treat and may require autografting or allografting for salvage (Warner JP, personal communication, 2001). Weber stressed that these complications are serious but that true rates of complications are unknown and, therefore, the "RF technique" should be used with caution until more data are available.

Miniaci et al (2001) noted a failure rate of 47% and 4 transient axillary nerve problems (3 sensory and 1 motor, all resolving by 9 months) in 19 MDI patients followed for 2 years after monopolar thermal capsulorrhaphy. The authors have abandoned this technique.

Wong and Williams (2001) reported the results of a survey compiled by members of the American Shoulder and Elbow Surgeons, the Arthroscopy Association of North America, and the American Orthopaedic Society for Sports Medicine. The authors focused on recurrence of instability, axillary nerve injury, and the incidence of capsular necrosis following monopolar, bipolar, and laser thermal treatment for glenohumeral instability. Thermal treatment was reported to be used in 14,277 (6%) of 236,015 cases, with most utilizing monopolar RF, where the rates of recurrent instability ranged between 7.1% and 8.4%. Furthermore, between 18% and 33% of patients requiring revison surgery showed evidence of capsular attenuation (33% with laser treatment). The incidence of associated axillary nerve injury was 1.4% (least with laser), with 95% recovering between 2 and 4 months.

Hanypsiak et al (2004) reported 2 cases of proximal long head biceps tendon rupture following thermal capsular capsulorrhaphy, without known direct contact of the thermal probe to the biceps tendon. These patients presented with "blocked forward extension" mechanisms 11 and 14 weeks after the thermal technique, with resultant deformity that suggested biceps rupture. One patient was treated with open tenodesis, the other left alone, and both were asymptomatic at follow-up of 15 months and over 2 years, respectively. The authors theorized that despite lack of known direct thermal insult to the biceps tendon proper, indirect insult might have occurred as a result of heat dispersion within the joint during capsular treatment, because of a secondary inflammatory response weakening the tissues, or from stress transfer to the biceps due to tightening of the posterior capsular tissues. Johnson and Walker (2001) reported 3 cases of long head biceps rupture due to thermal shoulder capsulorrhaphy.

No axillary nerve injuries were reported in either of the suture plication series of Snyder (1994, 2001) and Wolf and Durkin.

A thorough review of the literature is included under surgical management (see Surgical therapy). The review outlines the rationale, development, and results of open and arthroscopic repairs.

In general, patients who have had open capsular shifts do reasonably well. Published studies indicate that recurrence of MDI following surgery is about 10%. Loss of ROM following open capsular shift repair was greater in the early case series than in the later series, particularly for external rotation and abduction. Reported complications are rare.

Good results tend to persist with time as well. Stability does not seem to be lost at later follow-up on individuals with conventional open shift repair.

The long-term follow-up of arthroscopic management of MDI cannot yet be assessed. Advocates of both suture and thermal techniques have reported results that are somewhat less favorable in some cases than those of open surgery at follow-ups of up to 2 years, with recurrence rates of approximately 20-30% (Wolf and Durkin; Snyder, 2001; Karas et al)versus 10% in open repairs (Neer and Foster, 1980; Mayberry, 1988; Brems and Bergfeld; Altchek et al; Lebar and Alexander). However, others have reported similar results at > 4 years (Treacy et al).

Areas of future development in the treatment of MDI likely will parallel the further development of operative shoulder arthroscopy. The trend has been to drift away from open surgery, and it is very likely that this will continue. This trend is driven by patient and surgeon perceptions of less surgical invasiveness and reduced morbidity associated with arthroscopic techniques. However, it remains to be seen whether the effectiveness of arthroscopic management approaches that of the conventional open capsular shift technique, particularly after long-term follow-up. For now, it is wise to advise patients that the results of arthroscopic stabilization for MDI may be discounted relative to open surgery, at least in the long run.

Thermal stabilization is very controversial and may best be avoided. Significant complications, including capsular necrosis, tendon rupture, adhesive capsulitis, and axillary nerve injury, have been reported. The use of this technique has grown rapidly, perhaps because it is relatively easy to perform and because it avoids arthroscopic knot tying. Although basic science studies underscore the apparent effectiveness of thermal stabilization, more work is needed to elucidate its long-term effect on shoulder stability, especially with late clinical follow-up.

Thermal ablation chondroplasty serves as a good example of the need for caution and patience with regard to adoption of new, promising techniques. Reports of significant hyaline cartilage necrosis following thermal ablation of chondral lesions are worrisome, to say the least.

With regard to arthroscopic suture techniques, a paucity of basic science data is available thus far to compare the effectiveness of this stabilization technique with the customary open shift. There are many questions, including where to place sutures, how many sutures to use, whether to use absorbable versus nonabsorbable sutures, how tight the plication should be, and what rehabilitation modifications are necessary. Whether arthroscopic suture techniques can mimic an open shift repair over the long term remains unknown. The possibility of overconstraining the joint must also be considered. Again, more work is needed to support the general use of this approach over its open counterpart.