Open Operative Treatment for Anterior Shoulder Instability: When and Why?

Introduction: Arthroscopic treatment of anterior shoulder instability has gained in popularity with advancements in technique. With this minimally invasive procedure, recovery is quicker because the subscapularis is not incised. In addition, associated pathologic conditions can be visualized and treated. Finally, recent studies have demonstrated comparable outcomes between arthroscopic and open repairs. However, open repair is the preferred method when the surgeon lacks the necessary expertise or equipment, or in the presence of large bony defects and soft tissue deficiencies. The various surgical procedures for anterior shoulder instability can be categorized as anatomic or non-anatomic. In anatomic procedures, the surgeon seeks to approximate normal anatomy by reattaching the torn labrum to the glenoid (Bankart procedure), and in the case of excessive capsular laxity, by imbricating the capsule (capsular shift). The goal of non-anatomic procedures is to compensate for soft tissue and bony defects by a checkrein. In the Bristow procedure, the distal aspect of the coracoid process with its conjoined tendon (coracobrachialis and short head of biceps) is transferred through a slit in the subscapularis to the anterior glenoid. This bony transfer is intended to block subsequent dislocation and support anterior capsular structures. The surgical tenodesis of the conjoined tendon prevents the subscapularis tendon from displacing superiorly during abduction and external rotation. In other procedures, the subscapularis tendon can be tightened to limit external rotation by transecting then overlapping the medial and lateral segments (Putti-Platt) or by moving the insertion point laterally and distally (Magnuson-Stack). Non-anatomic procedures can be followed by complications such as marked restriction in external rotation, recurrent dislocation and arthritis. However, in skilled surgical hands and with appropriate indications, these procedures can yield good outcomes. Work-Up/Exam: A thorough history and physical examination preoperatively is essential. This includes ascertaining arm position at time of initial injury, history of recurrence and provocation of symptoms. Mechanical symptoms such as catching or locking may suggest a displaced labral tear or a large osseous defect that is engaging. Instability occurring in midrange or during sleep suggests an osseous defect. Passive and active motion should be compared with the contralateral side. An increase of abduction on the involved side may indicate pathology of the inferior capsule. Strength testing should be performed to assess the irritability and/or integrity of the rotator cuff. Weakness in an older patient following a traumatic dislocation suggests a rotator cuff tear. Positive lift-off or belly-press tests combined with excessive mobility in external rotation suggests failure of the subscapularis. Injuries to the suprascapular and axillary nerves should be ruled out, particularly the axillary nerve which is intimate with the capsule. The integrity and stability of the capsulo-labral complex can be assessed with provocative maneuvers: • the active compression test (pain and/or clicking with resisted forward elevation in slight horizontal adduction and internal rotation vs. external rotation) may suggest a superior labral (SLAP) lesion • the apprehension sign with external rotation and abduction which is relieved by relocation (posterior-directed pressure on the humeral head) can strongly indicates anterior shoulder instability and a Bankart lesion • the sulcus sign (excessive inferior translation) is suggestive of multidirectional instability; if it remains positive in external rotation, there may be a defect of the rotator interval (coracohumeral and superior glenohumeral ligaments) • excessive translation during load and shift maneuvers indicate anterior/posterior instability. Radiographs of the shoulder can demonstrate the direction of instability and osseous lesions such as glenoid fractures and Hill-Sachs lesions. A static anterior subluxation of the humeral head suggests either disruption of the glenoid or a subscapularis rupture. A rotator cuff tear should be suspected in patients with an inferior dislocation. MRI-arthrograms can further elucidate the pathoanatomy of capsulolabral injuries and assist with surgical planning. Three-dimensional CT scans are useful in revealing bone loss. Surgery: Traumatic anterior instability usually consists of a Bankart lesion (avulsion of the anterior labrum from the glenoid) and some degree of capsular injury. Most cases can be successfully managed by either an arthroscopic or an open anatomic capsulolabral repair. However, open repairs are preferred with revision procedures and for multidirectional instability because the capsule must be plicated both anteriorly and posteriorly. Absolute indications for an open approach include substantial bone loss of the glenoid or humeral head (e.g., Hill-Sachs lesion), capsular deficiency, or irreparable rotator cuff lesions, especially of the subscapularis. Major anterior glenoid defects should be reconstructed; an iliac crest bone graft or a coracoid process transfer are two options. Some surgeons recommend adding a coracoid bone block transfer to a standard Bankart repair for athletes participating in collision sports. Hill-Sachs lesions may not require reconstructing unless they are large (greater than 30% of humeral head) or get caught on (engage) the glenoid. Absolute contraindications to open repair include infection and psychogenic or voluntary instability. In cases of coexisting severe arthritis, arthrodesis or arthroplasty may be preferable to open repair. Arthrodesis might also be indicated in cases of instability associated with paralysis. Revision Surgery and Complications: Capsular deficiency is rare but can occur following procedures such as thermal capsulorrhaphy. Bicipital, hamstring and achilles tendon grafts have been used to address the defect. Subscapularis tears or ruptures can occur with recurrent dislocations and surgical procedures as well as in older patients during initial dislocations. Repairs of the subscapularis are less successful than those of the supraspinatus, and may require grafting with tendons such as the pectoralis major. The most common complication of open surgery for anterior instability is recurrence, which can be caused by subsequent traumatic re-injury or faulty surgical technique. Rupture of the subscapularis, failure to recognize and address associated conditions such as bony defects or multidirectional instability will result in poorer outcomes. If a subscapularis rupture goes undetected and un-repaired, the muscle and tendon can retract and adhere to surrounding structures. The axillary nerve, musculocutaneous nerve, and brachial plexus are all at risk. Stiffness can result if tissues are over tightened. As mentioned above, some of the non-anatomic procedures are designed to significantly restrict external rotation. Acceptable range of motion will vary according to occupational requirements: “mild” losses in external rotation will have a greater impact on a throwing athlete. To avoid over constraint, the shoulder should be positioned in 30° of external rotation and 30° of abduction during capsular procedures. Appropriate postoperative rehabilitation can minimize long-term stiffness. Glenohumeral arthrosis can result from over tightening of the anterior structures which drive the humeral head posteriorly, creating shear on the cartilage. Hardware can loosen and migrate. The axillary nerve, musculocutaneous nerve, and brachial plexus are at risk during open surgery. Summary: While arthroscopic capsulolabral repair is becoming the standard of care for the treatment of traumatic anterior shoulder instability, open approaches are still reliable and time-tested which remains the gold standard in many instances. These include bone loss, soft-tissue deficiencies, and some revision situations. A thorough preoperative history and physical exam, an understanding of an individual patient's goals and occupational demands, intraoperative evaluation and surgical skill surgical are essential to optimizing outcomes. Note: I augmented this review with information gleaned from “Treatment of Recurrent Instability,” an article from the University of Washington Department of Orthopaedics and Sports Medicine.