Multidirectional instability—open inferior capsular shift

Introduction

The open inferior capsular shift operation as described by Neer is a versatile operation that allows adjustment of technique to match identified pathology in patients with glenohumeral instability. Shoulder instability is associated with a wide variety of anatomic lesions involving the labrum, glenohumeral joint capsule, and bony injuries to the glenoid and humeral head. The degree of capsular laxity varies from patient to patient and leads to a spectrum of instability from unidirectional to bidirectional and multidirectional. Surgical treatment of glenohumeral instability is indicated in cases in which conservative treatment modalities have failed.

Evaluation of the patient with shoulder instability begins with a thorough history and physical examination, as with all other pathologic entities. A wide spectrum of patients present with instability whose stories range from atraumatic instability associated with repetitive activities to traumatic injuries. Understanding the onset of symptoms is helpful in determining the cause of instability. Patients who present with pain or symptoms of instability related to repetitive microtrauma are more likely to have capsular pathology, whereas those with traumatic onset are more likely to have associated labral damage as well. Patients with diffuse laxity and hypermobility who are not symptomatic do not require treatment. This trait actually has many advantages in certain sports, such as gymnastics and swimming. Instability by definition indicates a level of symptoms that cause pain or limited function or both. Determining the direction and degree of instability is important in surgical planning. Directionality of instability can be determined based on the position of the arm at which symptoms are experienced (e.g., anterior instability associated with the arm in the throwing position, inferior instability with heavy lifting in the adducted position, and posterior instability with the arm in flexion adduction).

Underlying anatomy in each patient is different, and the natural degree of laxity in each patient will differ. Patients with diffuse ligamentous laxity such as those with Ehlers-Danlos syndrome should be identified preoperatively by examination of multiple joints throughout the body. Beighton signs include laxity in the fingers, as well as knee and elbow hyperextension, and are helpful in evaluating the degree of underlying laxity in a given patient. The patient’s baseline shoulder laxity may be surmised based on careful examination of the contralateral shoulder. Decisions regarding the degree of tightening at the time of surgery are partially based on the perceived quality of the patient’s connective tissues and the degree of laxity noted in that patient.

Conservative treatment for shoulder instability begins with a foundation of pain modalities, gentle stretching, and strengthening exercises followed by a scapular stabilization program, proprioceptive training, and plyometrics. Activity modification may also be a reasonable option in some cases. A reasonable trial of supervised therapy of at least 3 to 6 months is indicated prior to the consideration of surgery. Patients who exhibit voluntary instability of the shoulder have a poor prognosis with surgical management and are best treated nonoperatively with behavioral modification.

The goal of surgery is to reconstruct the glenohumeral anatomy in a balanced fashion avoiding excessive tightening in any one direction (i.e., to obtain a stable yet mobile shoulder without causing stiffness). A traumatic labral tear can occur in a patient with preexisting laxity, and therefore the degree of capsular laxity in patients with labral injuries will vary, requiring the surgeon to adjust the amount of capsular shifting or imbrication required in each case. Because pathoanatomy will vary from case to case, a versatile treatment strategy that allows adjustment of operative technique based on the pathology is paramount.

Treatment principles

The principles of treatment in the management of shoulder instability remain the same whether the surgery is performed open or arthroscopically. The surgeon must strive to identify all pathoanatomy based on history, physical examination, radiographic studies, evaluation under anesthesia, and diagnostic arthroscopy. Surgery can then be performed to repair all damaged structures and reestablish balanced stability of the glenohumeral joint. Characteristic pathoanatomy in patients with multidirectional instability (MDI) includes a patulous capsule, hypoplastic labrum, and a widened rotator interval. Arthroscopic instability repair has gained increasing popularity over the past several decades as techniques and results have improved, and there has been little discussion of the open inferior capsular shift in the literature recently. Most recently, some of the advantages of open instability surgery are being rediscovered. A theoretical advantage of open surgery is the creation of stronger scar tissue than that associated with arthroscopic procedures. Capsular tightening can be performed in a more uniform and balanced fashion by pulling on a released capsule than by the multiple points of imbrication performed arthroscopically. The balanced surgical approach to the capsule described in this chapter can be successfully adapted regardless of the degree or direction of instability encountered and can be combined with other procedures both labral and bony to treat all pathology contributing to instability in that particular patient.

Currently, arthroscopic techniques are ideal for management of labral pathology such as Bankart lesions and can be adapted to treat associated capsular and rotator interval pathology. The open inferior capsular shift offers a versatile and highly effective approach to diffuse capsular laxity and has significant advantages over other described open techniques. The capsular shift procedure described by Neer can be modified to adjust the tightening of the capsule depending on the amount and location of laxity in a particular shoulder. The inferior capsular shift is designed to reduce capsular volume on all sides including anterior, inferior, and posterior through a single approach. It allows overlapping and therefore reinforcement of tissues in the direction of greatest instability with tightening of the capsule inferiorly and on the opposite side. This procedure also avoids asymmetric tightening, which can lead to abnormal joint mechanics and a fixed subluxation in the opposite direction. The operation is laterally based to allow for greater volume decrease compared with medially based or centrally based techniques of the glenohumeral joint, because it is a laterally based truncated cone. This approach also allows treatment of associated labral avulsions anteriorly and rotator interval closure. It does not allow adequate exposure of the superior or posterior labrum, and diagnostic arthroscopy is beneficial prior to open surgery to allow visualization of these structures and repair if needed arthroscopically.

Operative technique

Examination under anesthesia

Examination under anesthesia serves to clarify the direction and degree of instability. This rarely contradicts a preoperative diagnosis but may be helpful, especially in muscular patients who guard on examination in the office. It is also helpful in defining the primary area of instability. The load-shift maneuver allows the surgeon to evaluate the direction and degree of laxity in the affected shoulder. Examination of the contralateral shoulder may be beneficial to determine baseline laxity in that particular patient. The surgeon must be careful to relocate the humeral head in the glenoid prior to each maneuver to maintain the frame of reference. Translation of the humeral head over the glenoid rim is abnormal in any direction. With the arm at the side, the sulcus test, in neutral rotation, will demonstrate laxity in the superior portion of the glenohumeral capsule, including the superior glenohumeral ligament and the rotator interval. Failure of the sulcus sign to improve significantly by placing the shoulder in an externally rotated position is indicative of incompetence of the rotator interval tissue because this should normally tension in external rotation (ER). With the arm in 90 degrees of abduction and neutral rotation, the shoulder can be gently forced anteriorly and posteriorly to test the laxity of the inferior glenohumeral ligament (IGHL) and the anterior posterior capsule. Crepitus on dislocation and relocation is suggestive of labral pathology. If the humeral head locks out of joint, this is suggestive of a Hill-Sachs lesion.

Diagnostic arthroscopy

Diagnostic arthroscopy is of great benefit in identifying pathologic lesions contributing to the patient’s shoulder instability whether arthroscopic or open technique is planned. Magnetic resonance arthrograms are not perfect at identifying all labral pathology. In cases with a traumatic component, visualization of the entire labrum arthroscopically is helpful in planning surgical stabilization. A standard posterior portal is established in the soft spot, and the 30-degree arthroscopic lens is used to perform a systematic evaluation of the glenohumeral joint. The areas of concern include the articular surfaces, labrum, the capsule, and the rotator cuff and biceps tendons. The humeral head is carefully inspected for a Hill-Sachs lesion posterior superiorly. The labrum must be evaluated circumferentially both by visual inspection and tactile examination with a probe. The capsule is inspected for signs of stretching, mid-substance tearing, or tearing from the humeral insertion (humeral avulsion glenohumeral ligament lesion). The drive-through sign describes the ability to easily push the arthroscope between the humeral head and the glenoid, passing the scope from the posterior to the anterior aspect of the glenohumeral joint. The drive-through sign indicates capsular laxity. The arthroscopic hallmarks of MDI include a widened rotator interval, a patulous capsule, and often a hypoplastic labrum. Areas not accessible to open repair such as posterior and superior labral tears must be identified because arthroscopic treatment will be required even if open inferior capsular shift is planned.

Procedure

The success of the capsular shift procedure depends on adequate release of the capsule far enough inferiorly and posteriorly to allow obliteration of the inferior pouch and any associated posterior capsular laxity as well as adequate balanced capsular repair and closure of the lateral aspect of the rotator interval. Understanding and performing several key maneuvers are critical to the success and should help give the surgeon confidence with this operation. Proper takedown of the capsule is critical to avoid bisecting the inferior pouch. The capsular insertion inferiorly on the medial humeral neck is somewhat variable anatomically. Safe techniques with release of both the superior capsular reflection and the more inferior capsular insertion under direct vision are critical in avoiding potential injury to the axillary nerve. Simple guidelines are available to determine the amount of capsular release and amount of shift needed in each individual case. These recommendations depend on the degree of capsular laxity encountered and the functional demands of the patient.

For the open inferior capsular shift, a neurosurgical headrest is used to allow the assistant access to the superior shoulder. A short arm board is built up with sheets to maintain arm position anterior to the anterior axillary line ( Fig. 39.1 ). Local anesthesia is infiltrated in the axilla and the posterior portal site because these areas are not adequately covered by the interscalene block. The table is elevated to position the trunk at a 30-degree angle to the floor, and the table is placed in reverse Trendelenburg during the diagnostic arthroscopy. The table back is then returned to the 30-degree position for the open portion of the case. This maneuver precludes the need to readjust the headrest between the arthroscopic and open portions of the procedure.

The skin incision is made in the deltopectoral interval for muscular men and typically measures 10 cm in line between the coracoid and axillary skin fold. In thin women, a 5- to 6-cm axillary incision can be made in the skin folds. The axillary skin folds can be marked with a needle scratch prior to draping, which allows the incision to be hidden when the arm is at the side ( Fig. 39.2 ). Skin flaps are elevated from the inferior rolled border of the pectoralis major to the clavicle with either incision. A needlepoint cautery is useful for careful dissection while allowing hemostasis. The deltopectoral interval is then developed using blunt and sharp dissection taking the cephalic vein laterally. The clavipectoral fascia is incised along the lateral border of the conjoined tendon, and this structure is retracted medially. Excessive retraction on this structure is avoided to prevent damage to the musculocutaneous nerve. Subacromial and subdeltoid bursal adhesions are released. The anterior humeral circumflex vessels are ligated using 0 polyester sutures. This allows access to the inferior portion of the capsule, and this maneuver has not been associated with avascular necrosis. The sutures are placed 1 cm apart so that the vessels can be cauterized in between and released. Care must be taken to not grasp the joint capsule with this medial suture, because this will allow the subscapularis to be separated from the capsule in later dissection.

The inferior veil (falx) of the coracoacromial ligament is released sharply to the level of the ligament itself to allow clear visualization of the rotator interval. The deep dissection is begun with an incision of the subscapularis tendon 1 cm medial to the lesser tuberosity ( Fig. 39.3 ). The superficial two-thirds of this tendon are dissected off of the capsule using blunt and sharp dissection. This dissection can be tedious, and several maneuvers can be useful to facilitate it. The thickness of the subscapularis can be determined by opening the rotator interval and palpating the thickness of the tendon. The superficial two-thirds can be reliably peeled off of the underlying capsule while leaving some tendinous tissue attached to the capsule for reinforcement ( Fig. 39.4 ). Typically, a pointed Adson clamp is used to spread the subscapularis fibers, which are cut with a long-handled No. 15 blade. During the inferior portion of this dissection, the axillary nerve must be palpated and protected. The tug test as described by Flatow is useful to localize the nerve. The surgeon passes the index finger of the inside hand along subscapularis muscle beneath the conjoined tendon. With the outer hand, the surgeon palpates the axillary nerve on the undersurface of the deltoid muscle lateral to the humerus. By gently tugging back and forth with two hands, the surgeon can be sure which medial structure is indeed the axillary nerve. The ability to tug the nerve medially and feel tension on it laterally assures the surgeon of continuity of the nerve through the axilla. The inferior portion of the subscapularis has a very muscular insertion into the capsule. This can be released using electrocautery, and the plane between the subscapularis and the capsule can be clearly visualized from this inferior portion of the approach ( Fig. 39.5 ). The needlepoint cautery is useful to carefully cut through most of the subscapularis thickness inferiorly until just a few muscle fibers are visible overlying the capsule. These last few fibers are released using a blunt elevator (a round blunt Cobb elevator is preferred). This elevator can then be placed medially to define the plane between the capsule and the subscapularis tendon. The tendon dissection off the capsule can then proceed both from a medial to lateral and lateral to medial direction. Curved Mayo scissors can be used to release the subscapularis tendon from medial to lateral along the inferior portion of the subscapularis tendinous insertion, allowing the curve of the scissors to match the curvature of the humeral head ( Fig. 39.6 ). It is important to free all subscapularis fibers off the capsule so that the capsule is free to be shifted and not tethered by the subscapularis muscle. This also allows a Bankart repair to be performed more easily if this is required. If subscapularis fibers are left attached to the capsule medially at the level of the glenoid, visualization for passage of sutures during the open Bankart repair will be obscured. Suturing the subscapularis to the capsule with the Bankart sutures can potentially tether the subscapularis and limit motion. After release of the subscapularis, the capsule can be clearly visualized.

Capsular release begins at the level of the rotator interval. The capsule is transected 5 mm medial to the stump of the subscapularis tendon ( Fig. 39.7 ). This leaves enough capsule laterally to anchor the repair later during capsular reconstruction. Traction sutures are placed in the medial limb of the capsule during this maneuver. At the inferior border of the subscapularis insertion, it is critical to deviate the incision in the capsule in a hockey-stick fashion laterally along the neck of the humerus, essentially vertical and parallel to the line of the humerus. This avoids amputation of a portion of the inferior pouch. The axillary pouch is now palpated to determine its size. The pouch does have a variable pattern of insertion on the anatomic neck of the humerus. The periosteum and broad capsular insertion are incised vertically along the anterior humerus just distal to the most inferior aspect of the subscapularis stump. Inferior to the subscapularis tendon, the entire capsule can be released from the humerus without leaving a lateral cuff, as the capsular repair will not require suture placement that far inferiorly. The vertical portion of the capsular and periosteal release is carried to the level of the latissimus dorsi tendon insertion ( Fig. 39.8 ). This is done under direct vision with the needlepoint electrocautery. An elevator can then be used to elevate the capsule off the medial anatomic neck, placing the elevator just inferior to the articular reflection of the capsule ( Fig. 39.9 ). This allows any capsular reflection adjacent to the articular surface (usually superior to the elevator) to be incised under direct vision without risk of damage to the axillary nerve. Flexion and external rotation will bring that portion of the neck of the humerus into the surgical field and allow the capsule to be released from the humerus under direct vision ( Fig. 39.10 ). This arm position also reduces tension on the axillary nerve and allows it to fall away from the inferior pouch. Additional traction sutures are placed into the margin of the capsule as more capsule is liberated from the humerus. The more inferior portion of the capsular insertion (that part inferior to the elevator) is cut under direct vision with scissors just superior to the latissimus dorsi tendon. The dissection can be carried posteriorly to the level of the posterior band of the IGHL if needed. The amount of capsular release and amount of shift required will vary from patient to patient. Guidelines for capsular release are the following. The capsule should be released from the anatomic neck of the humerus until traction on the anterior capsule obliterates the inferior pouch and also eliminates posterior subluxation of the glenohumeral joint with the arm in neutral rotation. These two observations at surgery indicate that the inferior and posterior pouches are adequately tightened by anterior tension to allow for a balanced reconstruction of the shoulder joint capsule.