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Glenohumeral Dislocations

The glenohumeral joint (GHJ) is the most commonly dislocated major joint in the body. The lack of intrinsic bony stability in conjunction with its wide range of motion predisposes the joint to dislocations. Anterior dislocations account for 95-97% of all glenohumeral dislocations. Posterior dislocations account for most of the remainder, while inferior and superior dislocations are rare.

Anterior Dislocations

Pathophysiology And Classification

The most common mechanism of injury of anterior dislocations consists of an indirect force transferred tothe anterior capsule from a combination of abduction, extension, and external rotation. In younger individuals, the injury is usually sustained during athletic activities involving rapid movements; a characteristic pathological feature is avulsion of the anteroinferior glenohumeral ligament with capsulolabral detachment (Bankart lesion).65 In older patients, a fall onto the outstretched arm is the more common mechanism of injury and there is often an accompanying rotator cuff tear.53,65

Anterior dislocations can be classified according to the anatomic position of the dislocated humeral head.66 After dislocation, the humeral head can assume a subcoracoid, subglenoid, subclavicular, or intrathoracic position. The subcoracoid (Figure 21) is the most common type of anterior dislocation. The head is displaced anteriorly and rests on the scapular neck inferior to the coracoid process. The second most common type is the subglenoid dislocation, in which the head is anterior and inferior to the glenoid fossa. The subcoracoid and subglenoid types account for 99% of all anterior dislocations. Subclavicular and intrathoracic dislocations are extremely rare and involve the addition of impact forces that push the humeral head medially.



Clinical

Clinical presentation is that of severe pain with the dislocated arm held in slight abduction and external rotation by the opposite extremity. The lateral edge of the acromion process is prominent, and the normally rounded shoulder assumes a "squared-off" appearance. The coracoid process is indistinct, and the anterior shoulder appears full. The patient cannot adduct or internally rotate without pain. A neurovascular examination must be performed to identify associated injuries of the brachial plexus, axillary nerve, radial nerve, or axillary artery. The reported incidence of axillary nerve injuries after anterior glenohumeral dislocation ranges from 5% to 54%, and they are more frequent in patients over 50 years of age.67,68Axillary nerve function can be assessed by testing for sensation over the lateral aspect of the shoulder and by testing motor function of the teres minor and deltoid muscles. Deltoid function can be tested by having the patient attempt shoulder abduction while the examiner simultaneously feels for muscle contraction. Motor testing is recommended, since sensory testing may be inaccurate due to the presence of overlapping cutaneous nerve root dermatomes.

The trauma series of radiographs will confirm the clinical diagnosis and identify the position of the humeral head. Associated fractures may be present in up to 50% of cases. The most common of these is a compression fracture (Figure 22) of the posterolateral aspect of the humeral head caused by forceful impingement against the anterior rim of the glenoid fossa. This defect in the humeral head, or Hill-Sachs deformity, is reported to be present in 11-50% of all anterior dislocations. The actual incidence is probably much higher, since minor compression fractures are difficult to visualize on plain radiographs. A corresponding fracture of the anterior glenoid rim (Bankart's Fracture) is present in approximately 5% of cases.6 Avulsion fractures of the greater tuberosity are present in 10-15% of cases (Figure 23).6,67





Management And Disposition

Perform closed reduction of the dislocation expeditiously because neurovascular complications increase with time.68 It is recommended that radiographic documentation of the type of dislocation and any associated fractures be obtained before attempting reduction. The role of pre-reduction as well as postreduction radiographs have been the subject of several recent studies aimed at reducing radiograph utilization and shortening the time spent in the ED; see the Controversies And Cutting Edge section.

Good muscle relaxation is often the key to a successful reduction. Reductions can also be accomplished without the use of any analgesia if the time from injury to reduction is short or if the dislocation is a recurrent one. Muscle relaxation and analgesia can be achieved through procedural sedation. The intraarticular injection of a local anesthetic agent can be used as an alternative to sedation analgesia. Enter the joint under sterile technique 2 cm inferior to the lateral edge of the acromion using an 18- or 20-gauge needle. Aspirate any associated hemarthrosis and then inject 20 mL of 1% lidocaine over 30 seconds. The patient is then allowed to relax for 15 minutes before reduction is attempted. The published studies to date have all used lidocaine, although it would be reasonable to expect similar results with long acting local anesthetic agents such as bupivicaine. A recent systematic literature review revealed six randomized, controlled trials comparing intravenous sedation to intra-articular lidocaine.69 Outcomes in these studies included success rates, complications, and time spent in the ED.70-75 Although the reduction techniques were not controlled in these studies, none showed a statistical difference in the reduction success rates, which averaged 92% for both the intra-articular lidocaine and intravenous sedation groups.69 Complication rates were quite different, averaging 0.9% in the intra-articular lidocaine group (septic arthritis, abscess, cellulitis, allergy, or failure of reduction) and  16.4% in the intravenous sedation group (potential respiratory depression, cardiac compromise, allergy, or failure of reduction). In two studies, the time spent in the ED was significantly shorter for the intraarticular lidocaine group and there was as much as a 62% cost savings versus the intravenous sedationanalgesia group.71,74

Reduction can be accomplished using various techniques, most of which involve traction, leverage,  or scapular manipulation principles.76 Over a dozen techniques have been described for reducing a shoulder dislocation.69 Most of these have only been described in case series or consecutive prospective cohorts. There is only one randomized trial in the literature which compared the Kocher and Milch techniques; it found no statistical differences in the success rates between the two techniques.77 Due to insufficient data at this time, no specific recommendation can be made regarding the optimal reduction technique.69 The ideal method should be simple, quick, effective, require little assistance, and cause no additional injury to the shoulder. It is wise to be familiar with several techniques of reduction, since none is uniformly successful.

Traction Techniques

Gentle traction in various directions (forward flexion, abduction, overhead, lateral) is used to overcome the muscle spasm that holds the humeral head in its dislocated position.76 In the Stimson technique, the patient is placed prone with the dislocated arm hanging over the edge of the examining table. A 10- or 15-pound weight attached to the wrist or lower forearm provides traction in forward flexion. Reduction usually occurs over 20-30 minutes. Success rates reported with the Stimson method range from 91 to 96%. This is an excellent technique in the busy ED because it saves time and resources.69

In the traction-countertraction method, traction is applied along the abducted arm while an assistant using a folded sheet wrapped across the chest applies counter-traction (Figure 24). The forward elevation maneuver of Cooper and Milch is also simple and safe (Figure 25). The arm is initially elevated 10-20 degrees in forward flexion and slight abduction. Forward flexion is continued until the arm is directly overhead. Abduction is then increased, and outward traction is applied to complete the reduction.78 Reported success rates with this technique range from 70% to 89%.69





Another simple and very effective traction technique with a reported success rate of 97% is the Snowbird technique.79 In this method, the patient is seated in a chair and the affected arm is supported by the patient's unaffected extremity. A three-foot loop of four-inch cast stockinet is then placed along the proximal forearm of the involved extremity with the elbow at 90 degrees. The patient is then assisted or instructed to sit up and the physician's foot is placed in the stockinet loop to provide firm downward traction. The physician's hands remain free to apply any gentle external pressure or rotation as needed until reduction is accomplished.

Leverage Techniques

The most commonly recommended leverage technique is the external rotation method of Liedelmeyer (Figure 26).80With the patient in the supine position, the involved arm is slowly and gently adducted to the side. The elbow is flexed to 90 degrees and slow, gentle external rotation is applied to achieve reduction. Success rates reported with the external rotation method range from 78% to 90%.69



Scapular Manipulation

Scapular manipulation accomplishes reduction by repositioning the glenoid fossa rather than the humeral head. The patient is placed in the prone position with the affected arm hanging off the table as for the Stimson technique. After the application of downward traction (manual or hanging weights), te scapula is manipulated (Figure 27) by rotating the inferior tip medially while simultaneously stabilizing the superior and medial edges with the opposite hand.81 Success rates range from 79% to 96%. McNamara described a seated modification of the scapular method in which traction is applied in the forward horizontal position while an assistant manipulates the scapula.82 Scapular manipulation can be difficult in obese individuals, in whom it is difficult to palpate and grasp the inferior tip of the scapula.



The neurovascular examination must be repeated after any attempt at reduction. It is also generally recommended that radiographs be repeated to confirm reduction and to identify any associated fractures not apparent on pre-reduction films.

Once reduced, immobilize the affected extremity. Discharge patients with adequate analgesia and appropriate follow-up. Primary dislocations and complicated cases (associated fracture, rotator cuff tear, axillary nerve injury) should receive prompt orthopedic follow-up. In uncomplicated cases, immobilize the shoulder for three to six weeks in younger patients and one to two weeks in patients older than 40 years of age.6 If immobilization is used, early initiation of pendular shoulder exercises can help reduce the risk of adhesive capsulitis. This should be followed by a meticulous rehabilitation program aimed at restoring the static and dynamic stabilizers of the glenohumeral joint.6

Complications

Complications include the aforementioned fractures and neurovascular injuries. Most axillary nerve injuries are neuropraxic, and the prognosis for recovery of function is good.68 Rotator cuff tears may be present in 10-15% of cases.83 Rotator cuff tears are more common in primary dislocations in individuals over the age of 40. In this setting, failure to abduct the arm is often initially misdiagnosed as an axillary nerve injury. Most of these individuals require tendon and capsular repair to restore shoulder stability.83 Recurrence is also a common complication after anterior dislocation, especially in patients less than 30 years of age.66

Posterior Dislocation

Pathophysiology

Posterior dislocations are rare and account for 2% of all glenohumeral dislocations.84 The 45-degree angulation of the scapula on the thoracic cage positions the glenoid fossa posterior to the humeral head and serves as a partial buttress against posterior dislocation. Unfortunately, over 50% of posterior dislocations are missed on initial evaluation, and many remain unrecognized for weeks or months.85,86

A posterior dislocation can result from several distinct mechanisms of injury. Convulsive seizures (epileptic or after electrical shock) have been associated with unilateral or bilateral posterior dislocations because the larger and stronger internal rotator muscles (latissimus dorsi, pectoralis major, teres major, subscapularis) overpower the weaker external rotators (teres minor, infraspinatus).85 A posterior dislocation can also occur after a fall onto the outstretched hand with the arm held in flexion, adduction, and internal rotation or after a direct blow to the anterior aspect of the shoulder. Classification (subacromial, subglenoid, subspinous) is based on the final resting position of the humeral head. The subacromial variety accounts for 98% of all posterior dislocations.84

Clinical

Early diagnosis is essential to prevent long-term functional and therapeutic complications. The patient will hold the affected arm across the chest in adduction and internal rotation. The injury can be relatively painless in some cases.85 The normal shoulder contour is replaced by a flat, squared-off appearance and the humeral head may be palpable posteriorly beneath the acromion process. Abduction is severely limited, and external rotation is completely blocked. Failure to diagnose is often due to an over reliance on radiological findings and an under reliance on the clinical examination. The most common misdiagnosis is adhesive capsulitis.84,86

The true or standard AP radiographs can appear deceptively normal with posterior dislocations. The common inability to diagnose posterior dislocation in the frontal plane has led to the description of several characteristic radiographic findings. The humeral head is often profiled in internal rotation and takes on a "light bulb" or "drumstick" appearance (Figure 28). Standard AP films also show loss of the half-moon elliptical overlap of the humeral head and glenoid fossa as well as an increase in the distance between the anterior glenoid rim and the articular surface of the humeral head ("rim sign"). A true AP film will show abnormal overlap of the glenoid fossa with the humeral head (Figure 29). Finally, an impaction fracture (Figure 30) of the anteromedial humeral head (reverse Hill-Sachs deformity) is invariably present. This may produce a curvilinear density on the frontal projection parallel to the articular cortex of the humeral head ("trough sign"). Orthogonal views such as an axillary lateral, transscapular "Y," or apical oblique  (Figure 31) are essential to clinch the diagnosis. These views can identify associated fractures of the humeral head and posterior glenoid rim. CT may be helpful in some instances.87









Management And Disposition

Obtain orthopedic consultation for all patients with posterior dislocations. Closed reduction may be attempted in the ED under procedural sedation. The technique of reduction incorporates axial traction in line with the humerus, gentle pressure on the posteriorly displaced head, and slow external rotation. If this fails, reduction with the patient under general anesthesia is indicated. Once reduced, the shoulder is immobilized in external rotation with slight abduction. 86 Cases that were missed initially and present as a chronic or "locked posterior dislocation" should be discussed with the orthopedist since they often require semi-elective open reduction and internal fixation or arthroplasty.86,87

Complications

The most common complications are associated fractures of the glenoid rim, greater tuberosity, lesser tuberosity, and humeral head. The subscapularis muscle may be avulsed from its insertion site on the lesser tuberosity. Neurovascular injuries are uncommon because the anterior location of the neurovascular bundle protects it from injury. Recurrent posterior dislocations occur in 30% of patients and predispose the joint to degenerative changes.

Inferior Dislocation (Luxatio Erecta)

Pathophysiology


Luxatio erecta is a rare type of glenohumeral dislocation in which the superior aspect of the humeral head is forced below the inferior rim of the glenoid fossa. Less than 1% of all shoulder dislocations are of this variety and the mechanism of injury involves either indirect or direct forces.88,89 Most inferior dislocations result from indirect forces that hyperabduct the affected extremity. This causes impingement of the humeral head against the acromion process. Further levering of the humeral shaft against the acromion ruptures the capsule, dislocating the head inferiorly. Application of a direct axial load to an abducted shoulder can also disrupt the weak inferior glenohumeral ligament and drive the humeral head downward.

Clinical

Typically, the patient presents with the arm locked overhead in 110-160 degrees of abduction. The  elbow is usually flexed with the forearm resting on top of the head. The inferiorly displaced humeral head may be palpable along the lateral chest wall and any attempted movement is very painful. A completed neurovascular examination is essential to evaluate for associated injuries.

Luxatio erecta cases are often mistakenly diagnosed and treated as subglenoid anterior dislocations, since the radiographic features of these two clinical entities are remarkably similar. Standard AP radiographs demonstrate the superior articular surface inferior to the glenoid fossa. In addition, the humeral shaft characteristically lies parallel to the spine of the scapula on the AP view (Figure 32).89 This radiographic feature is useful in distinguishing luxatio erecta from a subglenoid anterior dislocation because the humeral shaft lies perpendicular to the spine of the scapula in the latter. Associated fractures of the acromion, coracoid, clavicle, greater tuberosity, humeral head, and glenoid rim are frequently present.



Management And Disposition

When possible, obtain orthopedic consultation before attempting closed reduction in the ED; it should then be performed under procedural sedation using a traction-countertraction maneuver. Apply traction in line with the humeral shaft while an assistant applies countertraction across the shoulder. Gentle abduction usually reduces the dislocation, and the arm can then be brought down into an adducted position. Multiple attempts may be necessary and occasionally buttonholing of the capsule will prevent closed reduction, necessitating open reduction. A single operator technique has been described by Nho et al.90

Complications

Neuropraxic lesions of the brachial plexus are very common. Aneurysm or thrombosis of the axillary artery as well as thrombosis of the axillary vein have also been associated with luxatio erecta.91,92 Given the proximity of the two structures, arteriography should be strongly considered any time a brachial plexus injury is observed. In a 1990 case report and review of the literature, Mallon et al reported that 12% of cases were associated with rotator cuff tears and 37% of cases had a fracture of some type. Greater tuberosity avulsion fractures occur in 31% of cases, and fractures of the glenoid, acromion, surgical neck, humeral head, and scapular body have also been reported.93 Adhesive capsulitis is a common long-term complication of luxatio erecta.

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Last Modified: 08/16/2017
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