Surgery for Atraumatic Instability of the Shoulder.

Last updated Friday, January 28, 2005

Figure 1 - Essential elements of the technique

Figure 2 - Reconstruction of a strong rotator interval capsule

Figure 3 - Posteroinferior capsular recess

Figure 4 - Power burr creating a bony trough in the anteroinferior humeral neck adjacent to the articular surface

Figure 5 - The sutures from the groove are passed through the lateral edge of the capsule

Figure 6 - Fixing the capsule in its advanced position

Figure 7 - Folding the redundant anterior superior capsule over the previous repair to reinforce it

Figure 8 - "Handshake" orthosis

Details of the surgery

Who should consider surgery for atraumatic shoulder instability and in what cases?

The ability of surgery alone to cure atraumatic instability is limited. Usually there is no single lesion that can be repaired. Most of the factors providing midrange stability cannot be enhanced by surgical reconstruction. Problems of poor neuromuscular control or relative glenoid flatness do not have surgical solutions. Even after a snug capsulorrhaphy, the midrange stabilizing mechanisms of balance and concavity compression must be optimized through muscle strengthening and kinematic training. Otherwise, excessive loads will be applied to the surgically tightened glenohumeral capsule, leading to stretching and failure of the surgical reconstruction.

In this light, the indications for surgical treatment of atraumatic instability need to be carefully considered. First, the patient must have major functional problems that are clearly related to atraumatic glenohumeral instability. Second, the patient must clearly understand that good strength and kinematic technique are the primary stabilizing factors for the shoulder rather than capsular tightness. Third, the patient must have participated in a strengthening and training program conscientiously and recognize that strength and proper technique will continue to be major stabilizing factors for the shoulder even after reconstructive surgery is performed. The patient must also recognize that capsulorrhaphy is designed to stiffen the shoulder: the surgery will compromise the range of motion in the hope of gaining stability. If attempts to regain normal range are made early on, instability is likely to recur. Thus the limitations imposed by surgical capsulorrhaphy may be incompatible with the goals of normal or supernormal range of motion. Therefore, gymnasts, dancers, and baseball pitchers may not be good candidates for this surgical procedure. Similarly, this procedure has a limited ability to hold up under the demands of heavy physical labor unless it is accompanied by a superb strength and kinematic rehabilitation program. Finally, the patient must understand that rehabilitation after this procedure is protracted. It is important that the shoulder be immobilized in a brace for a month, during which time muscles get weak and normal kinematics are lost. After this month of immobilization many months are required for the reestablishment of good strength and shoulder kinematics. In spite of the best operative and postoperative management, the success of this procedure in reestablishing normal shoulder function is substantially less than procedures for traumatic instability.

The foregoing is a large amount of very important information that must be understood by the patient considering the surgical procedure. The situation is further complicated by the fact that many patients who present with atraumatic midrange instability are young and may have difficulty understanding and accepting the ramifications of this information. Thus, during the preoperative discussions with young patients it may be important that parents participate actively. We find that many families who present requesting that "the shoulder be fixed" are prepared to work more diligently on the non-operative program after this discussion. We provide detailed information to patients and families interested in the surgical management of atraumatic multidirectional instability.

What are the details of surgery for atraumatic shoulder instability? What is actually done?

The essential elements of the procedure are reconstruction of the rotator interval capsule/coracohumeral ligament mechanism and reduction of the posteroinferior capsular recess. These goals can be accomplished only through an anterior surgical approach. Thus, we usually approach a repair for atraumatic instability from the front, even if the predominant direction of instability appears to be posterior. There are additional advantages of the anterior approach. It is cosmetically superior to the posterior approach. It is accomplished without incising the critical external rotator cuff musculature. Finally, when the capsule is advanced anterosuperiorly on the humeral side, elevation of the arm anteriorly results in additional tightening of the inferior and posterior capsule.

The shoulder is approached through a low anterior axillary incision, entering the deltopectoral groove medial to the cephalic vein. The clavipectoral fascia is divided up to the level of the coracoacromial ligament. The axillary nerve is palpated medially as it courses across the subscapularis and passes inferiorly toward the quadrangular space. The superior edge of the subscapularis is then identified by palpating the rotator interval lateral to the coracoid process and medial to the bicipital groove. The triad of anterior humeral circumflex vessels mark the inferior border of the subscapularis. The subscapularis tendon is sharply and carefully dissected from the subjacent capsule.

A substantial defect in the rotator interval is seen consistently in the AMBRII syndrome. This defect is bordered by the capsule adjacent to the supraspinatus overlying the biceps tendon superiorly, the anterior capsule and subscapularis anteroinferiorly, the coracoid process, and the transverse humeral ligament. This defect is accentuated by pushing the humeral head posteriorly. Sutures of number 2 non-absorbable material are securely placed in the superior edge of the defect and then passed across to the inferior edge of the defect. When these sutures are tied, a strong rotator interval capsule is reconstructed.

The anterior capsule is incised from the humeral neck beginning just below the top of the lesser tuberosity. Traction sutures are placed in the capsule. With the axillary nerve protected and with the arm in adduction and neutral rotation, the anterior inferior and the inferior capsule are incised from the humeral neck. This dissection is continued until superiorly directed traction on the capsular flap causes the capsule to tighten on a finger placed in the posteroinferior capsular recess. Usually this point is reached when the capsule is released just past the inferior (6 o'clock position) on the humeral neck, sectioning the posterior band of the inferior glenohumeral ligament.

After the capsular release, a bony trough is created in the anteroinferior humeral neck adjacent to the articular surface using a power burr. Holes are made in the humeral neck lateral to the groove and sutures are passed through these holes into the groove for reattachment of the capsule securely to bone. With the arm at the side and in neutral rotation and with strong anterior superior traction on the sutures to obliterate the posterior inferior recess, the sutures from the groove are passed through the lateral edge of the capsule. Tying these sutures securely fixes the capsule in its advanced position. This step needs to be accomplished with excellent direct vision to be sure the bites in the capsule are sufficiently inferior to tighten it to the groove and to assure the safety of the axillary nerve. The surgeon must assure that pulling up on these sutures obliterates the posterior inferior recess. If this is not the case, either the inferior capsular release was insufficient or the sutures were not placed sufficiently inferior.

This repair to the groove is continued anteriorly up the humeral neck.

Redundant anterior superior capsule is folded down over the previous repair to reinforce it.

At this point the shoulder is checked to ensure that internal rotation of the abducted arm is limited to 45 degrees below the horizontal, that the posterior drawer is less than 50 percent of the humeral head diameter and that external rotation of the arm at the side is 30 degrees. Excessive internal rotation of the abducted arm indicates the inferior capsule was not advanced sufficiently. Excessive translation on the sulcus test indicates that the rotator interval capsule was insufficiently tightened. Excessive limitation of external rotation indicates that the anterior capsule was tightened too much.

The subscapularis is then repaired to its normal anatomic insertion. After a standard wound closure, the arm is placed in a prefitted "handshake" orthosis with the arm in neutral rotation and slight abduction.

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