Anterior Shoulder Dislocation Case File

Anterior Shoulder Dislocation Case File

Eugene C. Toy, MD, Andrew J. Rosenbaum, MD, Timothy T. Roberts, MD, Joshua S. Dines, MD

CASE 1

A 20-year-old, right-hand-dominant male athlete, the star wide receiver on his collegiate football team, had just caught the game-winning touchdown. As his teammates gathered around him to celebrate, they noticed that he was clutching his right shoulder and appeared to be in a great deal of pain. Soon after, in the emergency department (ED), he refused to let anyone move his right arm from its current position of slight abduction and external rotation. The team physician notes that the front of his shoulder appears “full” and that the acromion is prominent in comparison with the contralateral side. He has a strong radial pulse, and sensation to light touch is intact throughout the whole extremity. He refuses a motor exam. An anteroposterior (AP) radiograph of the shoulder is obtained by the ED and is seen in Figure 1–1.

Figure 1–1. AP radiograph of the shoulder.

► What is the most likely diagnosis?

► What abnormalities are seen in the radiograph?

► What other abnormal findings are likely to be noted in this patient?

► What is the best treatment for this patient?

ANSWER TO CASE 1:

Anterior Shoulder Dislocation                              

Summary: A 20-year-old athlete sustained trauma to the right shoulder resulting in obvious deformity and pain, with an AP radiograph of the right shoulder demonstrating a dislocation and osseous defect of the posterolateral aspect of the humeral head.

• Most likely diagnosis: Anteroinferior glenohumeral dislocation
• Radiographic abnormality: These plain films depict a right glenohumeral dislocation and a Hill-Sachs lesion, which is an indentation fracture of the posterolateral humeral head caused by impaction on the anterior glenoid rim after anterior glenohumeral dislocation.
• Associated physical exam findings: Deltoid spasm/dysfunction, positive apprehension and/or crank test, 3+ sulcus sign, rotator cuff tear (especially in older patients), clicking/catching during movement, positive load-shift test, Bankart lesion, and other bony abnormalities of the humerus and/or glenoid rim.
• Best treatment: Prompt closed reduction, if acutely dislocated; nonoperative immobilization in external rotation versus operative Bankart repair (open or arthroscopic), possible bone fragment incorporation, and possible glenoid augmentation, if indicated.

ANALYSIS

Objectives

1. Identify the anatomic structures that serve as stabilizers of the glenohumeral joint.
2. Be familiar with the epidemiology, clinical presentation, and initial management of anterior shoulder dislocations.
3. Understand the clinical indications for operative stabilization procedures.

Considerations

The 20-year-old football player has just sustained his third traumatic anterior shoulder dislocation requiring urgent reduction. Although patients with a history of repeated dislocations may recognize what has happened, a thorough history, exam, and workup should be performed. Special attention must be directed to the patient’s neurovascular exam—both before and after reduction—as the dislocation may cause neurovascular damage. This is more commonly observed in the elderly. The decision of whether to obtain radiographs of the dislocated shoulder or proceed directly to closed reduction is often governed by the unique circumstances of each case. Individuals with a history of dislocations and high pain tolerance may tolerate immediate reductions. Others may need sedation. After the joint is reduced and the reduction confirmed radiographically, the next step should be to investigate the patient’s history of recurrent shoulder dislocations. Factors such as time between events, management of the initial dislocation, and circumstances surrounding each dislocation are especially important. This information will guide both the short-term and long-term management of the patient. The patient described in the vignette would typically be a candidate for further workup and operative stabilization if clinically warranted.

APPROACH TO:

Anterior Shoulder Dislocation                                              

DEFINITIONS

SHOULDER LAXITY: A clinical exam finding referring to the ability of the humeral head to translate on the glenoid. Laxity varies significantly between individuals and is only considered pathologic if it is accompanied with additional symptomatology such as pain.

SHOULDER INSTABILITY: A pathologic state associated with painful, excessive translation of the shoulder. Instability, unlike asymptomatic laxity, should be considered for treatment.

BANKART LESION: The most common sequelae of an anterior shoulder dislocation (up to 85% of cases). Bankart lesions are described as detachment of the anteroinferior labrum from the glenoid rim, accompanied by detachment of the inferior glenohumeral ligament from its glenoid origin. Described as a bony Bankart lesion when the glenoid rim itself fractures in lieu of a labral detachment.

HILL-SACHS LESION: An osteochondral depression in the posterior humeral head caused by impaction of the head on the anterior glenoid during anterior dislocation. If severe, Hill-Sachs lesions may contribute to recurrent instability.

CLINICAL APPROACH

Epidemiology

The glenohumeral joint is the most mobile and most commonly dislocated joint in the human body. Dislocations in the anterior direction are by far the most frequently occurring, representing up to 90% of all shoulder dislocations. Posterior dislocations are significantly less common and may be more insidious in presentation. Rarer still are inferior dislocations (known as luxatio erecta) and superior dislocations.

    The age distribution of anterior dislocations is bimodal in nature. An early peak occurs among men in their second decade of life. Young males are also more likely to have recurrent dislocations: Rates of as high as 90% have been reported in athletes who suffer a dislocation before the age of 20 years. The latter peak represents women in their sixth and seventh decades. Although this population group is less likely to suffer a recurrent dislocation, they experience higher rates of associated injuries such as rotator cuff tears, vascular injuries, and nerve damage.

Anatomy of the Glenohumeral Joint

The glenohumeral joint is a complex array of structures that act together to provide the greatest range of motion of any joint in the human body. These structures can be loosely divided into static and dynamic stabilizers. Static stabilizers passively support the humeral head in the glenoid; they include the congruence between the humeral head and glenoid fossa, the labrum, glenohumeral ligaments, and the joint capsule. Dynamic stabilizers describe the rotator muscles and periscapular musculature.

Static Stabilizers: The glenoid fossa itself engages only a minor proportion of the humeral head, analogous to a golf ball on a tee. The fi brocartilaginous labrum (attached circumferentially to the glenoid rim) helps deepen the glenoid concavity by up to 50%. The anterior inferior attachment of the labrum to the glenoid is tight, whereas the superior attachment is looser and attaches to the long head of the biceps near its origin. Perhaps the most important static stabilizers are the glenohumeral ligaments, particularly the anterior band of the inferior glenohumeral ligament.

A Bankart lesion refers to a traumatic separation of the inferior glenohumeral ligament and labral complex from the glenoid rim. Disruption of this complex is a well-recognized cause of recurrent anterior instability. A bony Bankart lesion refers to avulsion of a portion of the glenoid rim attached to the anteroinferior labral complex during a traumatic anterior dislocation. The glenohumeral ligaments, along with their attachments and specific functions, are listed in Table 1–1. Together, these ligaments act to stabilize the shoulder in different arrays of flexion/extension, abduction/adduction, and internal/external rotation. The joint capsule, aside from providing structural support to the glenohumeral joint, additionally acts to maintain a negative intraarticular pressure that helps “suck” the humeral head down into the glenoid fossa.

Dynamic Stabilizers: Dynamic stabilizers of the glenohumeral joint are the muscles of the shoulder that contract in a highly coordinated fashion to produce smooth, stable movement throughout normal ranges of motion. Specifi cally, these include the rotator cuff muscles (subscapularis, supraspinatus, infraspinatus, and teres minor) as well as the latissimus dorsi, trapezius, pectoralis major, and the long head of the biceps.

Clinical Presentation

The most common clinical presentation of an anterior shoulder dislocation is after an acute traumatic event. Typically, the injury involves one falling on a shoulder that is in extension, external rotation, and abduction (common in athletes like the patient in Case 1). An additional mechanism of injury includes dislocations from direct force to the posterior shoulder, which can also result in anterior dislocation. In older patients or patients with a history of recurrent dislocations, the glenohumeral joint can be extremely unstable and may dislocate with minimal trauma or even during sleep.

Physical Exam: Patients with acutely dislocated shoulders usually have obvious physical deformity on visual inspection. Shoulders will appear “full” anteriorly and may have a visual or palpable depression of the posterior shoulder. Active and passive range of motion is limited by signifi cant pain.

    When presented with a patient who has had multiple episodes of dislocation, there are several bedside maneuvers classically associated with the diagnosis of anterior instability. In the apprehension test, the patient is placed in the supine position and asked to place their arm in a comfortable position. The arm is then gradually externally rotated and abducted by the examiner. A positive test is one in which the patient exhibits apprehension or guards against this shift in position due to the subjective feeling of instability—in other words, the patient anticipates a potential for dislocation and resists further external rotation and abduction. Interestingly, actual pain is usually typically elicited with this maneuver. The relocation test is performed concurrently with a positive apprehension test: When the patient begins to exhibit guarding, a posteriorly applied force should relieve the sensation of impending dislocation.

    The load and shift test can be used to assess both anterior and posterior instability. The examiner applies an axial load on the elbow to drive the humeral head into the glenoid fossa and simultaneously applies an anterior and posterior force on the humeral head with the remaining hand. Translation of the humeral head 0 to 1 cm in either direction is considered mild, whereas translation of greater than 2 cm or translation beyond the glenoid rim is considered severe.

    Finally, the presence of generalized ligamentous laxity should be evaluated. Signs of metacarpophalangeal hyperextension or elbow recurvatum are suggestive of underlying pathologic conditions such as Ehlers-Danlos syndrome and therefore require an appropriate workup if present.

Radiographic Evaluation: A trauma series of a suspected anteriorly dislocated shoulder should be obtained whenever possible. Obtaining an axillary view in the acute setting is often difficult as a result of extreme pain, even after copious narcotic administration. In such instances, a Velpeau axillary radiograph may be obtained by having the patient lean backward over an x-ray cassette and angling the caudally directed beam downward from above the shoulder.

    A pathognomonic radiologic finding for anterior glenohumeral dislocation is the Hill-Sachs lesion, which describes an osteochondral indentation fracture of the posterolateral humeral head. It is caused by the impaction of relatively soft humeral head against the hard glenoid rim after a dislocation and can deepen with recurrent events. These defects can be easily missed on AP radiographs. The Stryker notch view is especially useful in detecting such lesions and is obtained by having the supine patient place the palm of the hand of the affected extremity on the crown of the head and directing the beam toward the coracoid process.

    Magnetic resonance imaging remains the gold standard imaging technique for evaluating soft tissue injuries associated with anterior dislocation and should be obtained when planning an operative stabilization procedure outside.

TREATMENT

Closed Reduction

Closed reduction should be attempted as soon as the patient has been appropriately evaluated and images obtained. Multiple techniques for reduction have been described in the literature. Sedation and/or analgesia serve both to reduce the patient’s discomfort during the reduction as well as to relax the pericapsular musculature, thus allowing for easier reduction. The Stimson technique involves attaching weights to the affected extremity with the patient in the prone position. The gentle traction overcomes muscular spasm over a period of time and allows for reduction to occur. The Hippocratic maneuver and traction-countertraction techniques achieve reduction by combining traction with internal and external rotation movements. The most significant difference between these techniques is the method of countertraction: In the Hippocratic maneuver, the practitioner places his or her foot in the patient’s axilla to stabilize the body while he or she is pulling the affected arm. In the traction-countertraction method, an assistant provides countertraction by pulling on a sheet wrapped around the patient’s body from under the axilla. Postreduction films should always be obtained. If reduction proves extremely difficult and does not occur after multiple attempts, soft tissues are likely interposed between the humeral head and glenoid. In such instances, closed reduction is futile, and urgent operative open reduction should proceed.

    After closed reduction, the shoulder is typically immobilized using a sling or shoulder immobilizer. Some recent literature, however, has failed to clearly demonstrate benefits of immobilization. More commonly agreed on is a gradual rehabilitation, focused on increasing range of motion. Older patients generally are immobilized for shorter periods of time.

Operative Treatment

Absolute indications for operative treatment include failed closed reduction secondary to soft tissue interposition and significant glenoid bone loss. Biomechanical studies have shown that stability decreases exponentially with bone defects of 6 to 7 mm or greater in size.

    Relative indications for operative treatment include those with a history of recurrent dislocations, as well as the initial shoulder dislocation in the young, highly active patient. The question of operative versus nonoperative management of the latter subgroup of patients has been the source of multiple investigations. Studies show an up to 90% recurrence rate in patients younger than 30 years of age managed nonoperatively after their first dislocation.

    The most commonly performed stabilization procedure is repair of the anteroinferior labral/inferior glenohumeral ligament complex, known as the Bankart repair (open or arthroscopic). Other procedures include glenoid cavity deepening, tendon transfers, and capsular shifts. Patients with traumatic dislocations who exhibit unilateral instability and in whom Bankart lesions are present should be considered for surgical intervention—such scenarios are sometimes referenced by the mnemonic TUBS (traumatic, unidirectional, Bankart, surgery). Conversely, the mnemonic AMBRI is sometimes used to describe populations for whom rehabilitation is the preferred initial treatment. AMBRI describes patients with a history of atraumatic dislocations with multidirectional instability, involvement of bilateral shoulders who should be initially treated by rehabilitation; however, if surgery is needed, an inferior capsular shift should be considered. Simply put, TUBS and AMBRI are mnemonics to describe the presentation and treatment of patients at either end of the instability spectrum.

OTHER TYPES OF GLENOHUMERAL DISLOCATION

Posterior glenohumeral dislocations represent up to 15% of all shoulder dislocations. In general, they are less symptomatic in the acute phase and are sometimes found incidentally in the elderly during workup for unrelated pathology. They may also be seen as the sequelae of strong involuntary muscle contractions such as those caused by seizures or electric shock, when the strong pericapsular muscles responsible for internal rotation (latissimus dorsi, pectoralis major, and subscapularis) overpower the relatively weaker external rotators. A reverse Hill-Sachs lesion may be seen on the anteromedial aspect of the humeral head following posterior dislocation.

    Inferior glenohumeral dislocations (luxatio erecta) are exceedingly rare and classically present with a startling, pathognomonic clinical presentation. Luxatio erecta occurs when the arm is forced into a frozen hyperabducted state—sometimes referred to as the “Superman” position because of its likeness to the superhero’s famous flight stance. With the humeral head forced inferiorly, deltoid and other muscular attachments pull the arm into extreme abduction. Neurovascular compromise almost always accompanies this type of dislocation.

COMPREHENSION QUESTIONS

1.1 A 33-year-old rugby player is seen for follow-up after a fi rst-time anterior shoulder dislocation 6 weeks ago while being tackled. The shoulder has remained reduced. On exam, he has a good range of painless active and passive motion. Which of the following is considered a dynamic stabilizer of the glenohumeral joint?

A. Glenoid fossa

B. Anteroinferior labral complex

C. Coracohumeral ligament

D. Subscapularis muscle

E. Anterior band of the inferior glenohumeral ligament

1.2 Which of the following describes a technique for diagnosis of anterior shoulder instability in the patient in Question 1.1?

A. Pivot shift

B. Velpeau axillary

C. Load and shift

D. Stimson maneuver

E. Hippocratic maneuver

1.3 Early radiographs of the patient in Question 1.1 determined the patient to have a small Hill-Sachs lesion. Which of the following radiographs is best suited for visualizing this lesion?

A. West Point

B. Stryker notch

C. Scapular Y

D. AP

E. Axillary

1.4 A 22-year-old amateur wrestler is seen in the ER after a first-time anterior shoulder dislocation. As a result of understaffing, he waits 3 hours for conscious sedation. Appropriate reduction is eventually achieved after 2 manipulation attempts. He is neurovascularly intact and is discharged in a shoulder immobilizer. Which of the following has been shown to be the greatest predictor of future dislocation after a first-time anterior shoulder dislocation?

A. Prolonged reduction

B. Chronic pain with motion after reduction

C. Age at time of first dislocation

D. Tobacco use greater than 1 pack per day

E. Heavy labor occupations

 

ANSWERS

1.1 D. The periscapular musculature stabilizes the glenohumeral joint during and throughout its full range of motion, thus acting as dynamic restraints. The other answers listed are static restraints.

1.2 C. The load and shift test is a bedside examination technique that can aid in the diagnosis of anterior shoulder disability. Because it can be performed in various degrees of arm abduction, it can sometimes aid in identifying the specific deficient structure contributing to anterior shoulder instability.

1.3 B. The Stryker notch view provides an excellent view of the posterolateral humeral head. Hill-Sachs lesions can be easily visualized with other views, however, especially if the defect is large (as seen in Figure 1–1).

1.4 C. Age has been shown to be the most consistent predictor of instability: in young patients < 20 years of age, recurrent rates are reportedly as high as 80% to 90%; in those > 40 years of age, rates drop precipitously to approximately 10% to 15%.

    CLINICAL PEARLS    

► Anterior dislocations of the glenohumeral joint are the most common, representing up to 90% of all shoulder dislocations. ► When a true axillary radiograph cannot be obtained, a Velpeau axillary radiograph should be preformed to evaluate a dislocated glenohumeral joint. ► Urgent closed reduction is critical in the setting of a dislocated shoulder, with a thorough and well-documented neurovascular exam performed. ► Both Bankart and Hill-Sachs lesions are seen concurrently with shoulder dislocations and can contribute to recurrent instability.

REFERENCES

Brown DE, Neumann RD, eds. Shoulder instability. In: Orthopedic Secrets. 3rd ed. Philadelphia, PA: Hanley & Belfus; 2004:107-111. 

Dodson CC, Cordasco FA. Anterior glenohumeral joint dislocations. Orthop Clin North Am. 2008;39: 507-518. 

Lintner SA, Speer KP. Traumatic anterior glenohumeral instability: the role of arthroscopy. J Am Acad Orthop Surg. 1997;5:233-239. 

Piasecki DP, et al. Glenoid bone deficiency in recurrent anterior shoulder instability: diagnosis and management. J Am Acad Orthop Surg. 2009;17:482-493. 

Provencher MT, Ghodadra N, Romea AA. Arthroscopic management of anterior instability: pearls, pitfalls, and lessons learned. Orthop Clin North Am. 2010;41:235-337. 

Sahajpal DT, Zuckerman JD. Chronic glenohumeral dislocation. J Am Acad Orthop Surg. 2008;16: 385-398.

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