CHAPTER 11 Arthroscopic Treatment of Traumatic Anterior Shoulder Instability

The shoulder is one of the most versatile joints in the body, allowing a large functional range of motion in multiple planes. This freedom of motion, however, also renders the joint particularly vulnerable to instability. The shoulder is the most commonly dislocated large joint of the body, with an incidence rate of 0.7% for men and 0.3% for women up to the age of 70 years.¹ Based on a study of over 2000 individuals, Hovelius² reported the prevalence of shoulder dislocation to be 1.7%.

Anterior traumatic dislocation is the most common injury pattern and constitutes 96% of all glenohumeral dislocations.³ Unfortunately, management of the primary anterior shoulder dislocation remains a complex and challenging problem for the orthopedic surgeon. The existing literature has provided conflicting evidence regarding the outcomes of nonoperative management versus immediate surgical stabilization, and decision making is further complicated by variables such as patient age, occupation, functional demands, sports participation, physical characteristics, and family history. Whether nonoperative or surgical stabilization is selected, the goal of the treating physician is to achieve a stable, functional shoulder with full restoration and a painless range of motion.

Although specific recurrence rates following anterior shoulder dislocation remain difficult to determine, there are abundant data supporting the fact that following a traumatic dislocation event, the shoulder is more vulnerable to recurrent instability. Young age at the time of the initial injury is the most consistent and significant prognostic factor for a high risk of recurrent instability episodes. Male gender has also been shown to be independently predictive of recurrent instability. The vast majority of recent studies, however, have failed to show a correlation between the participation in or type of sporting activity and the risk of recurrent instability.⁴^–³²

With the advent and rapid improvement in arthroscopic shoulder techniques, arthroscopic stabilization has become a viable and frequently used procedure to address anterior instability. Compared with the more traditional open stabilization procedures, arthroscopy has conferred the significant advantages of improved visualization and reduced surgical trauma and perioperative pain, as well as the ability to identify and treat associated intra-articular pathology, such as superior labrum anteroposterior (SLAP) tears or glenoid articular defect (GLAD) lesions. In addition, the need to detach and repair the subscapularis is entirely avoided. Despite these advantages, however, failure rates as high as 50% have been reported in midterm case series.⁹^–¹¹ Although the cause of this failure is likely multifactorial, it is clear that meticulous surgical technique and correction of the pathologic anatomy are essential to maximize the likelihood of success.

This chapter will briefly review the pathology and natural history of primary, traumatic anterior shoulder instability. We subsequently review current therapeutic techniques and provide a stepwise approach to the arthroscopic repair of a traumatic anteroinferior labral tear.

PATHOANATOMY

Instability is a pathologic condition of the stabilizing capsuloligamentous complex. Laxity, however, is a physical examination finding and can be a physiologic asymptomatic finding. Various passive and dynamic restraints are responsible for stabilizing the shoulder, and a disruption of any of these, or a combination of these forces, can result in functional instability. An intact anteroinferior glenohumeral labral complex not only provides restraint to anterior humeral head translation in the abducted and externally rotated position, but also deepens the glenoid and provides a bumper effect to the anterior glenoid margin. Negative intra-articular pressure in the setting of an intact capsule also creates a stabilizing suction effect. The concavity-compression effect is critical for glenohumeral stability and is contingent on an intact rotator cuff for dynamic compressive forces.

A traumatic glenohumeral dislocation typically results in damage to the bony and/or soft tissue stabilizers of the joint, although the degree and nature of the injury are highly variable. Most pa tients who sustain a traumatic, anterior dislocation of the shoulder will have an avulsion of the anterior labrum and capsule from the glenoid rim, the classic Bankart lesion, at the time of surgery.⁴ Because the anterior labrum and attached inferior glenohumeral ligament complex are the major passive anterior stabilizers of the shoulder, the high rate of recurrent instability after dislocation may be attributed to failure of the labrum to heal in an anatomic position. Biomechanical studies, however, have demonstrated that an isolated essential Bankart lesion is insufficient to allow for frank glenohumeral dislocation.⁵^–⁸ Associated plastic deformation of the glenohumeral ligaments is a prominent factor in recurrent instability and must be addressed if successful stabilization is to be achieved arthroscopically. In addition to reattaching the labrum to the glenoid, an inferior to superior shift of the anterior capsule is necessary, especially in cases of chronic instability.

A variety of other injuries to the osseous and soft tissue stabilizers of the shoulder joint are frequently encountered after anterior dislocation. The Hill-Sachs lesion (compression fracture of the humeral head), fracture of the greater tuberosity, capsular stretch or tears, superior labral lesions, and tears of the rotator cuff are often seen.¹²^–¹³ Wintzell and colleagues¹⁴^–¹⁸ evaluated a series of 30 patients between the ages of 18 and 30 years with an MRI scan within 3 weeks of the injury and reported an avulsion of the glenohumeral ligaments in 20 patients (66%), a pathologic condition of the labrum in 22 patients (73%), and a combined capsulolabral avulsion in 16 patients (53%).

HISTORY AND PHYSICAL EXAMINATION

A thorough preoperative evaluation is of tantamount importance to the success of the surgical procedure. A careful history and physical examination will help the surgeon determine the direction of instability, degree of functional impairment, likelihood of recurrence, and indications for operative versus nonoperative management.

Subluxation versus frank dislocation events should be distinguished. We have defined frank dislocations as those that require a formal reduction maneuver by medical personnel after a failure to spontaneously reduce with movements of the patient’s arm. The mechanism of injury and number of instability episodes should be identified. Subtle, relatively atraumatic dislocations or subluxations may be suggestive of multidirectional instability caused by pathologic connective tissue. Instability episodes at night, particularly in the setting of recurrent instability, should be noted and can be suggestive of glenoid bone loss. Age, hand dominance, and occupation are important as well in defining patient expectations and risk for recurrence.

Multiple studies have confirmed young age to be the most consistent and significant prognostic factor for a higher risk of recurrent instability.¹⁹^–²⁹ Male gender has also been shown to be independently predictive of recurrent instability. Although conflicting evidence has been reported regarding the correlation of recurrent instability with participation in sporting activities, retrospective series have raised the concern of a potentially increased risk of recurrent dislocation in the athletic population, particularly in those patients participating in shoulder-straining sports.³⁰^–³² In Bankart’s original report,⁴ glenohumeral dislocation was referred to as a condition “peculiar to athletics and epileptics.”

A comprehensive physical examination is essential and begins with the patient sitting. Neck range of motion, Spurling’s, and Adson’s tests should be completed to evaluate for cervical causes of pain or discomfort. Scapulothoracic mechanics and the presence of supraspinatus and/or infraspinatus atrophy should be identified. Primary or secondary scapular winging can present with anterior or posterior instability and must be identified. Significant atrophy may warrant electromyographic studies to evaluate for associated compressive neuropathies or muscular dystrophy. Passive and active glenohumeral range of motion should be assessed. Apprehension in an abducted and externally rotated position is suggestive of anterior instability. Rotator cuff strength and lift-off and belly press tests for subscapularis integrity must be performed. Anterior shoulder dislocations, particularly in older individuals, are frequently accompanied by traumatic rotator cuff tears, which also contribute to pathologic instability. Tests for symptomatic labral pathology should also be performed. Although a myriad of tests have been described, we prefer the active compression (O’Brien’s sign) and resisted supinated external rotation tests.³³^,³⁴ Both have been validated with good sensitivity and specificity for anterior and superior labral lesions. The presence of multidirectional and generalized ligamentous laxity should also be assessed. We examine for a pathologic sulcus sign in the seated position and also examine for Wynne-Davies criteria (e.g., thumb hyperextension, thumb to forearm testing).³⁵ Laxity alone can be a normal finding and does not equate to instability; however, symptomatic laxity would be manifested by actual instability.

Stability should be also be assessed with the patient in the supine position. With the shoulder in neutral rotation and with the head centered on the glenoid, load shift testing can help define the magnitude of anterior and posterior translation. Comparison with the contralateral, uninvolved shoulder is essential to define the degree of physiologic laxity. Jobe’s apprehension and relocation testing is also performed in the supine position. Patients with significant anterior instability will frequently not tolerate testing in the fully abducted and externally rotated position.

DIAGNOSTIC IMAGING

Plain radiographs, including true anteroposterior, scapular Y, and axillary views, are the mainstay of imaging in the setting of traumatic anterior instability. If prereduction radiographs were obtained at the time of a traumatic episode, these should be reviewed to confirm the direction of dislocation. A concentrically reduced joint should be confirmed on scapular Y and axillary images. Anterior translation of the humeral head relative to the glenoid in the resting position is suggestive of insufficiency of anteroinferior stabilizing structures. Associated greater tuberosity fractures are not uncommon and should be identified. Concern for a bony Bankart lesion may be further evaluated with a West Point axillary view. Significant posterior and superior flattening of the humeral head may indicate a Hill-Sachs lesion and can be further evaluated with a Stryker notch view. Large, engaging Hill-Sachs injuries have been associated with an increased rate of recurrence followed isolated arthroscopic anterior stabilization.

Further imaging studies in the setting of a clear history and physical examination may not be necessary. However, computed tomography (CT) is useful in the setting of recurrent instability in which there is concern for glenoid bone loss. An inverted pear configuration, in which the diameter below the glenoid equator is smaller than that above the equator, has been shown to significantly increase the risk of failure after arthroscopic stabilization.³⁶^,³⁷ Magnetic resonance imaging (MRI) is also useful to assess for associated intra-articular pathology. MRI can underestimate the degree of bone loss; in difficult cases, three-dimensional CT is more reliable for quantifying bone deficiencies. Humeral avulsion of the glenohumeral ligament (HAGL), although substantially less common than Bankart lesions, can occur following traumatic dislocation and can be detected on coronal images. These lesions are difficult to stabilize arthroscopically and are more reliably addressed via an open repair. Bankart or anterior labrum periosteal sleeve avulsion (ALPSA) injuries are best visualized on axial images and are manifest by extravasation of synovial fluid into a cleft between the labral complex and bony glenoid margin.^{38, 39} Chondral status, GLAD lesions, rotator cuff integrity, and superior labrum–biceps anchor injury can also be readily assessed on MRI scans.

INDICATIONS

After First-Time Dislocation.

After a first-time dislocation, the risk of recurrence is unacceptably high, usually in the young, male, athletic population. Substantial evidence exists that there is a subset of first-time dislocators who experience a high recurrence rate, with a mean of approximately 67% reported across large series. A number of randomized controlled studies have not only documented a reduced risk of recurrence with early stabilization, but an improved quality of life and durable functional outcome.⁴⁰^–⁴⁶ The risk for progressive, irreversible intra-articular injury with recurrent instability episodes, which may negatively affect subsequent surgical success rates, may also provide a rationale for early surgical stabilization.

Recurrent Anterior Instability.

There can be recurrent anterior instability with failure of nonoperative management, including rehabilitation. Mechanical symptoms, pain, and sensation of anterior instability or apprehension refractory to rehabilitation in the setting of physical examination and imaging studies are consistent with an anteroinferior labral tear.

CONTRAINDICATIONS

Multidirectional Instability.

This can occur with pathologic laxity and poor glenohumeral ligament quality. Arthroscopic anterior stabilization in this setting has a higher rate of documented recurrence and failure compared with open capsular shift procedures.⁴⁷

Large Bony Bankart Lesions.

These can lead to an inverted pear configuration ⁴⁸ and are relative contraindications to arthroscopic anterior stabilization. They are often better reduced and rigidly fixed via an open procedure. Although the definition of a large bony fragment is subjective, a 6-mm-wide or larger fragment will typically compromise 25% or more of the articular surface and has been advocated as a relative indication for an open repair.⁴⁰^–⁴⁷ Note, however, that not all bony Bankart lesions are contraindications to an arthroscopic stabilization. Small lesions can be excised and the capsulolabral complex advanced to the fracture line, or the fragment can be reduced and incorporated into the repair. Favorable results with these techniques have been reported in the literature.⁵¹