Shoulder Dislocation in Emergency Medicine Clinical Presentation

Updated: Nov 29, 2018
  • Author: Sharon R Wilson, MD; Chief Editor: Trevor John Mills, MD, MPH  more...
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Presentation

History

Patients with shoulder dislocation generally complain of severe shoulder pain and an associated decreased range of motion of the affected extremity. [5]

Mechanisms of injury are usually traumatic but may vary. Mechanisms may include sports, assaults, falls, seizures, throwing an object, reaching to catch an object, forceful pulling on the arm, reaching for an object, turning over in bed, or combing hair.

Patients may have a history of recurrent ED visits for the same complaint.

Specific mechanisms or historical facts may be suggestive of certain types of dislocations, such as lightning injuries, electrical injuries, and seizure with posterior dislocations; throwing a ball or a punch or forceful pulling of the arm with an anterior dislocation; and axial loading of an extremely abducted arm with inferior dislocation.

Shoulder instability can result from repetitive microtrauma in overhead-throwing athletes, such as baseball, tennis, and volleyball players and swimmers,  as the glenohumeral joint often exceeds its physiologic limit. [18]

Congenital dislocation of the shoulder is a very rare condition, and the dislocation of the glenohumeral joint in infants is usually associated with a fracture or a neurologic problem (eg, brachial plexus injury). If there is no history of trauma or a brachial plexus injury, congenital dislocation should be considered as a possible diagnosis. [13]

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Physical

Anterior shoulder dislocation (95-98% of ED dislocations):

  • Arm is held in slight abduction and external rotation.

  • Shoulder is "squared off" (ie, boxlike) with loss of deltoid contour compared with contralateral side.

  • Humeral head is palpable anteriorly (subcoracoid region, beneath the clavicle).

  • Patient resists abduction and internal rotation and is unable to touch the opposite shoulder.

  • Compare bilateral radial pulses to help rule out vascular injury.

  • In all cases, evaluate the axillary nerve before and after reduction by testing both pinprick sensation in the "regimental badge" area of the deltoid and palpable contraction of the deltoid during attempted abduction. Evaluate sensory and motor function of the musculocutaneous and radial nerves.

Posterior shoulder dislocation (3% of ED shoulder dislocations):

  • Arm is held in adduction and internal rotation.

  • Anterior shoulder is "squared off" and flat with prominent coracoid process. Shoulders may look identical in bilateral dislocation, making it a commonly missed injury.

  • Posterior shoulder is full with humeral head palpable beneath the acromion process.

  • Patient resists external rotation and abduction.

  • Neurovascular deficits are infrequent.

Inferior (luxatio erecta) shoulder dislocation (0.5% of ED dislocations) [19] :

  • Arm is fully abducted with elbow commonly flexed on or behind head.

  • Humeral head may be palpable on the lateral chest wall.

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Causes

Anterior shoulder dislocations usually result from abduction, extension, and external rotation, such as when preparing for a volleyball spike. [18] Falls on an outstretched hand are a common cause in older adults. The humeral head is forced out of the glenohumeral joint, rupturing or detaching the anterior capsule from its attachment to the head of the humerus or from its insertion to the edge of the glenoid fossa. This occurs with or without lateral detachment.

Posterior dislocations are caused by severe internal rotation and adduction. This type of dislocation usually occurs during a seizure, a fall on an outstretched arm, or electrocution. Occasionally, a severe direct blow may cause a posterior dislocation. Bilateral posterior dislocation is rare and almost always results from seizure activity. Misinterpretation of the radiograph appearance of a posterior dislocation may result in misdiagnosis as a soft tissue injury in up to 79% of cases.

Rare, but serious, inferior dislocations (luxatio erecta) may be due to axial force applied to an arm raised overhead, such as when a motorcycle collision victim tumbles to the ground. More commonly, the shoulder is dislocated inferiorly by indirect forces hyperabducting the arm. The neck of the humerus is levered against the acromion and the inferior capsule tears as the humeral head is forced out inferiorly. Luxatio erecta almost always has an associated fracture or soft-tissue injury. One series found 80% of patients to have fracture of the greater tuberosity or tear of the rotator cuff. Neurologic compromise was found in 60% of patients, with the axillary nerve the most commonly injured nerve. Inferior dislocations have the highest incidence (3.3%) of vascular compromise.

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Complications

Complications include shoulder dislocation, soft tisue injuries, nerve injuries, and vascular injuries. [20, 21, 22, 23, 16, 24, 25]

Fractures and soft-tissue injuries

Hill-Sachs lesions occur when the edge of the glenoid causes an impaction fracture in the posterolateral aspect of the humeral head during anterior dislocation and in the anterolateral aspect in posterior dislocation (referred to as a "reverse Hill-Sachs" lesion).

A Bankart lesion is fracture of the anterior rim of the glenoid labrum associated with joint capsule rupture and inferior glenohumeral ligament injury. Significantly displaced anterior or posterior glenoid rim fractures require operative management. Most initial shoulder dislocations produce a Bankart lesion, particularly in younger patients.

Fracture of the greater tuberosity, acromion, coracoid, clavicle, and humeral neck also occur.

Rotator cuff traction injury is most common in elderly patients and in association with inferior dislocations. This is a commonly missed injury, with an average time of 7 months from injury to diagnosis of rotator cuff rupture in patients older than 40 years.

Patients who experience anterior shoulder dislocation are at increased risk for glenohumeral arthropathy. Average overall T1p values on MRI for humeral head cartilage in dislocated shoulders have been shown to be significantly greater than that in control patients. [25]

Nerve injury

Approximately 3% (and higher in some series) of dislocations involve injury to the axillary nerve. Injury may resolve spontaneously or require surgical exploration and possible nerve grafting.

Patients exhibit numbness in the area of the deltoid muscle and weakness with abduction and external rotation.

Axillary nerve injury does not change initial treatment, but pre-reduction and post-reduction neurologic examinations are important.

Radial nerve injury should also be determined. The axillary and radial nerves both arise from the posterior cord. The thumb, wrist, and elbow will be weak on extension, and the dorsal hand will be numb.

Vascular injury

Axillary artery injuries are rare but have been reported to occur with anterior, inferior, and intra-thoracic dislocations. Especially susceptible are older adults with atherosclerotic axillary arteries. Arterial injury may be associated with decreased radial pulse.

Lateral chest wall ecchymosis with associated axillary hematoma and bruit may be noted on physical examination.

Angiography should be considered with any brachial plexus injury.

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