Arthroscopic Treatment of Traumatic Anterior Shoulder Instability

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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

Humeral Avulsion of the Glenohumeral Ligament Lesions.

These are difficult to visualize and repair arthroscopically and may be better suited to an open approach.

Engaging Hill-Sachs Lesions.

These lesions, more than 30% to 40% of the humeral head, are a relative contraindication to arthroscopic anterior stabilization, particularly in combination with anterior glenoid erosion. Rates of recurrence are considerably reduced with open stabilization.⁴⁸ Bone grafting of the humeral head defect has been reported to reduce the risk of recurrence. Arthroscopic remplissage, in which the infraspinatus is tenodesed into the Hill-Sachs defect, can be a potentially useful adjunct if anterior stabilization provides stability, but does not completely limit anterior translation.

TREATMENT OPTIONS

Conservative Management

Nonoperative management typically involves a period of immobilization for a variable duration after closed reduction, followed by physical therapy for strengthening of the rotator cuff and scapular stabilizers. The basis for this treatment strategy, however, is largely anecdotal and the literature regarding the efficacy of these interventions is controversial. Aronen and Regan have advocated a program of immobilization followed by intense rehabilitation.⁴⁹ Twenty military personnel who sustained primary anterior shoulder dislocations were followed for an average of 36 months. All patients participated in an identical treatment regimen, which included a rehabilitation program emphasizing the muscles of internal rotation and adduction, plus rigid restrictions of activities until an asymptomatic stable shoulder was noted. Strength exercises progressed from isometrics to isotonics and isokinetics. The authors reported a success rate of 75%, and concluded that adherence to an aggressive postdislocation rehabilitation program could effectively allow a full return to preinjury activities. There was a 25% recurrence rate, however.

Other studies, however, have failed to corroborate these conclusions. Burkhead and Rockwood ⁵⁰ reported on 140 shoulders that had a diagnosis of traumatic or atraumatic recurrent subluxation and were treated with a specific set of muscle-strengthening exercises. Only 16% of the 74 shoulders that had traumatic subluxation had a good or excellent result from the exercises, compared with 80% of the 66 shoulders that had atraumatic subluxation. Hovelius and associates²²^,²³ have found no correlation between the type or duration of immobilization and the rate of recurrence among 247 patients with primary anterior dislocations who were followed for 10 years. Chalidis and coworkers²⁷ and Kralinger and colleagues³² both reported similar findings, failing to identify any correlation between duration of immobilization and recurrence risk in series of 308 and 241 patients, respectively. Kralinger’s group was also unable to demonstrate any substantial benefit from supervised physical therapy, suggesting that a well-structured home program completed independently by the patient may be equally effective.

Immobilization of the shoulder in external rotation after primary, traumatic anterior shoulder dislocation may be more favorable than conventional sling immobilization to reduce the risk of recurrent instability. MRI studies have demonstrated improved position and coaptation of the Bankart lesion against the glenoid rim with external rotation.⁵²^–⁵⁴ Furthermore, Miller and associates⁵⁵ conducted biomechanical studies in a human cadaveric model and measured the contact force between the Bankart lesion and the glenoid, with the arm in 60 degrees of internal rotation, neutral rotation, and 45 degrees of external rotation. They reported no contact force with the arm in internal rotation, but the contact force increased as the arm passed through neutral rotation and reached a maximum at 45 degrees of external rotation.

Two randomized clinical trials have provided further evidence that immobilization in external rotation may be beneficial. Itoi and coworkers ⁵³^,⁵⁴ presented a series of 40 patients, randomized equally to conventional immobilization in internal rotation versus immobilization in 10 to 30 degrees of external rotation for 3 weeks after the initial dislocation. The recurrence rate was 30% in the internal rotation group and 0% in the external rotation group at a mean of 15.5 months. Recently, a much larger series by the same authors was published,⁵² reporting 2-year follow-up data on 198 patients with a primary anterior dislocation who were randomized to immobilization in internal rotation or external rotation for 3 weeks. Statistical analysis revealed the recurrence risk to be significantly lower in the external rotation group, with a relative risk reduction of 38.2%. When the analysis was restricted to patients younger than 30 years, the effect was even more profound, with a relative risk reduction of 46.1%.

Surgical Stabilization

Whether an open or arthroscopic surgical technique is selected, the goal of surgical stabilization is to restore the native anatomy and therefore requires a repair of the Bankart lesion and retensioning for plastic capsular deformation. The ultimate goal of any surgical intervention is achieving a pain-free stable shoulder while maximally preserving the range of motion of the glenohumeral joint.

Arthroscopic Technique

This procedure can be undertaken under a general anesthetic or regional nerve block with sedation based on patient preference and the experience of the anesthesia team. The risks of neurological sequelae from a regional nerve block are commensurate with the skill and experience of the anesthesiologists. Preoperative nerve blocks can provide for intraoperative muscle relaxation, blood pressure control, and perioperative analgesia.

The lateral decubitus position is the preferred position for anterior stabilization procedures. Care must be taken to ensure complete unencumbered access to the anterior and posterior aspects of the shoulder while the anesthesiologist and equipment are positioned at the foot of the table (Fig. 11-1).

FIGURE 11-1 The lateral decubitus position is preferred, with complete access to the anterior and posterior aspects of the shoulder.

Examination under anesthesia of the involved and contralateral shoulder is critical. With the shoulder in neutral rotation, load shift testing is performed to determine the predominant direction and degree of instability. The Sulcus test is also performed. These typically provide intraoperative confirmation of the preoperative diagnosis and appropriate planning. The arm is then secured in an arm holder that applies 8 to 10 pounds of axial traction in a slightly forward-flexed (10 degrees) and internally rotated position. A second load is attached to the upper arm sleeve, exerting 8 to 10 pounds of distraction towards the ceiling, which promotes better intra-articular visualization and the ability to manipulate tissue in the inferior pouch region. The table can be rotated so that the glenoid is parallel to the floor, which assists in orientation.

Arthroscopy is initiated with a standard posterior portal slightly lateral to the glenohumeral joint line. This initial viewing portal will become a working portal and must be placed lateral to the joint line so that instruments can clear the posterior glenoid rim.

After the joint is entered, dual anterior portals are established at the inferior and superior margins of the rotator interval (Fig. 11-2) using an inside-out technique with a Wissinger rod. The anterior-inferior working portal requires an 8.25-mm cannula to allow for the passage of suture hooks for subsequent repair, and should be created slightly superior to the superolateral border of the subscapularis. Use of a spinal needle to verify a satisfactory angle of approach to the inferior glenoid can be helpful prior to establishing the anterior-inferior working portal. The anterior-superior portal becomes the viewing portal while the posterior portal is converted to a working portal (Fig. 11-3).

FIGURE 11-2 View from posterior portal of right shoulder. Dual anterior cannulae straddle the biceps tendon. HH, humeral head.

FIGURE 11-3 The anterior-superior portal is for viewing while the anterior-inferior and posterior portals become the working portals.

A probe is used via the anterior-inferior portal to complete a comprehensive diagnostic arthroscopy. The inferior capsular pouch and humeral insertion of the ligaments are visualized to confirm the absence of a lesion (Fig. 11-4). If a Hill-Sachs lesion is encountered, the potential for engagement of the humeral head on the anterior glenoid margin should be assessed in the abducted, externally rotated position (Fig. 11-5). If contact occurs, there is concern for potential breakdown of the Bankart repair should this engagement occur postrepair.

FIGURE 11-4 View from anterior-superior portal of a left shoulder. A large HAGL lesion is identified. Muscle fibers of the subscapularis are visible. Arrows indicate the retracted glenohumeral ligament from humeral attachment site. HH, humeral head.

FIGURE 11-5 View from anterior-superior portal of a left shoulder. An engaging Hill Sachs lesion on the glenoid rim is noted as the arm is brought into the abducted, externally rotated position. C, cannula.

Sufficient glenoid bone stock can be confirmed arthroscopically. Measuring from the bare spot, the presumed center of the glenoid, the radius of the glenoid can be measured on the intact posterior glenoid and the bony deficiency calculated comparing the anterior and posterior radii (Fig. 11-6). Bone loss of more than 20% to 25% may necessitate a bony solution.

FIGURE 11-6 View from anterior-superior portal of a left shoulder. Glenoid bone loss can be measured from the bare spot (black arrow), or anatomic center of the glenoid. Blue arrow, radius to posterior glenoid; HH, humeral head; red arrow, radius to anterior glenoid.

Continuing to view from the anterior-superior portal, attention is now directed toward mobilization of the Bankart lesion. A periosteal elevator or radiofrequency device is used to develop the plane between the glenoid and capsulolabral complex. To retension the inferior glenohumeral ligament adequately, a thorough release must be accomplished so that the defect can be closed and the tissue also can be shifted inferior to superior. The capsulolabral complex is completely freed from the glenoid neck when the subscapularis muscle belly can be clearly visualized (Fig. 11-7).

FIGURE 11-7 View from anterior-superior portal of a left shoulder. The inferior glenohumeral ligament (IGHL) has been mobilized and the subscapularis muscle can be seen.

The glenoid neck is prepped with a shaver (burr is rarely needed), and the double-loaded anchors are inserted on to the glenoid face by 1 to 2 mm (Fig. 11-8). Placement on to the glenoid face allows for better bone purchase and facilitates re-creation of the concavity-compression phenomenon, in which the labral bumper is re-established and the glenoid deepened. It is best to approach the glenoid at approximately 45 degrees relative to the articular surface to ensure secure anchor purchase in bone. The position of the first anchor is always guided by the pathology and should be at the level of the inferior aspect of the labral tear. The detached capsulolabral complex should be captured and translated to this anchor to achieve a superior shift of the tissue.