Background
Shoulder dislocation is the most common large-joint dislocation seen in the emergency department (ED). [1] The muscular, ligamentous, and bony anatomy of the shoulder (glenohumeral joint) gives it the most extensive range of motion (ROM) of any joint in the human body. However, this anatomy also makes the glenohumeral joint the most unstable joint in the body.
Anterior dislocations (in which the humeral head is displaced anteriorly in relation to the glenoid), account for as many as 95-98% of shoulder dislocations. [2] The reason is that the muscular and ligamentous support anterior to the humeral head is much less robust than the substantial muscular and bony support afforded posteriorly by the rotator cuff and scapula. Anterior shoulder dislocations may be divided into the following four types:
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Subcoracoid (most common)
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Subglenoid
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Subclavicular (rare)
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Intrathoracic (rare)
Posterior shoulder dislocations are considerably less common, accounting for fewer than 4% of shoulder dislocations. Many posterior shoulder dislocations are initially missed by treating physicians, and diagnosis is delayed in many cases. [1, 3] Failure to diagnose and treat posterior dislocations promptly can result in complications, including recurrent dislocations, avascular necrosis of the humeral head, degenerative disease, and chronic pain.
Inferior glenohumeral dislocation (luxatio erecta humeri) is rare, accounting
Indications
Anterior dislocation
For subcoracoid and subglenoid dislocations, which account for 99% of anterior shoulder dislocations, joint reduction by the ED physician is typically indicated. Subclavicular or intrathoracic dislocations, which are caused by large forces, are not easily corrected and should be referred to an orthopedic surgeon. [8]
Posterior dislocation
For an uncomplicated posterior shoulder dislocation that is diagnosed within 3-6 weeks of injury, reduction in the ED is generally appropriate. After this amount of time, a single atraumatic attempt at relocation in the ED is not absolutely contraindicated, depending on resource availability, but is often futile. Shoulders that have been dislocated posteriorly for that extended period of time often require relocation in the operating room (OR) under general anesthesia. A small humeral head defect is not a contraindication for attempting a closed reduction in the ED. A fracture-dislocation with a nondisplaced lesser tuberosity fracture may be treated with a closed reduction.
Inferior dislocation
In a patient with an inferior glenohumeral dislocation, the presence of brachial plexus injury necessitates prompt atraumatic reduction, with the goal being smooth, uncomplicated, successful reduction on the first attempt.
Contraindications
Anterior dislocation
Standard closed reduction of an anterior shoulder dislocation is contraindicated if prompt surgical consultation is indicated. [8] Contraindications include the following:
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Subclavicular or intrathoracic dislocations
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Associated fractures of the humeral neck - Attempts at reduction may worsen the fracture or result in avascular necrosis
Various neurovascular injuries and common fractures do not prohibit reduction but do call for prompt and atraumatic reduction with avoidance of multiple attempts. These include the following:
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Nerve injuries - The brachial plexus, axillary nerve, or musculocutaneous nerve may be injured; neurapraxias (contusions of the nerve) usually resolve within weeks
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Suspected major arterial injury - Urgent angiography is required
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Common fractures - Hill-Sachs deformity, a compression fracture of the posterolateral aspect of the humeral head, and Bankart fracture, a detachment of the anterior aspect of the glenoid rim, may occur as the result of the dislocating force as the humeral head presses forcefully against the glenoid rim [8] ; avulsion fractures of the greater tuberosity of the humeral head tend to heal well but require immediate orthopedic consultation if the displacement exceeds 1 cm
Posterior dislocation
The following are contraindications for standard closed reduction of a posterior shoulder dislocation:
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Delayed (>3-6 weeks) presentation
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Large humeral head defect
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Displaced or multipart fracture-dislocations - These are treated with open reduction and internal fixation (ORIF) or with arthroplasty
Inferior dislocation
Standard closed reduction of an inferior glenohumeral dislocation is contraindicated in the setting of humeral neck or shaft fractures or in the setting of suspected major vascular injury. The presence of these associated injuries necessitates surgical intervention/open reduction.
Though not a contraindication per se, a “buttonhole deformity” (in which the humeral head becomes trapped in a tear of the inferior capsule) often precludes successful closed reduction, necessitating open reduction.
Technical Considerations
Procedural planning
Clinical assessment determines the type of dislocation present, which guides the approach to reduction (if indicated).
Anterior dislocation
A patient with an anterior shoulder dislocation typically presents with an obvious squared-off shoulder, with the humeral head located inferior and medial to the normal anatomic location. Patients generally hold the injured arm in abduction and resist attempts to adduct or internally rotate the arm. [8] Trying to place the arm into a sling is often futile; patients usually find the position of greatest comfort.
Before any attempts at reduction, the provider should perform a neurovascular examination and assess the probability of a fracture, considering the mechanism of injury and the physical characteristics of the patient. The axillary nerve is the most commonly injured nerve in shoulder dislocations and can be evaluated by testing for sensation in the lateral upper arm and by palpating for contraction of the deltoid muscle while the patient abducts against resistance. The clinician should also look for possible damage to other branches of the brachial plexus.
Arterial injury, though rare in this setting, is also possible and can present with paresthesias, diminished pulse, paleness or coolness of the affected extremity, pain that is out of proportion to the physical findings, or paralysis. [8] Injury to the axillary artery is more common in the elderly population. [9]
Posterior dislocation
Posterior shoulder dislocations usually result from forceful contractions of the internal rotators that occur during seizures or electrical injuries. This mechanism can force the humeral head posteriorly, out of its normal alignment and behind the glenoid. Less commonly, posterior shoulder dislocations follow trauma. The mechanism may be a direct blow to the anterior shoulder or a posteriorly directed force applied through the forward-flexed arm.
A complete neurovascular examination should be performed for these dislocations as well, though the incidence of neurovascular injuries is lower with posterior dislocations than with anterior dislocations. [3] Posterior shoulder dislocations are commonly associated with posterior glenoid rim fractures and anterior compression fractures of the humeral head.
Inferior dislocation
Patients with inferior glenohumeral dislocations present with the affected arm “locked” in abduction of varying degrees. [10] Classically, the affected arm is hyperabducted, with the elbow flexed and the forearm resting on top of or behind the head (see the image below). Often, the dislocated humeral head is palpable along the lateral border of the chest wall. The patient is generally in a substantial amount of pain, particularly when attempts are made to move the injured extremity.
Classic presentation of inferior shoulder dislocation. Affected arm is hyperabducted, with elbow flexed and forearm resting on top of head.
Outcomes
Anterior dislocation
In some cases of anterior shoulder dislocation, standard reduction efforts will fail. If multiple attempts at closed reduction fail or signs of neurovascular injury develop, an orthopedic surgeon should be consulted to evaluate for closed or open reduction in the OR with general anesthesia.
Injuries may occur as a consequence of reduction. These may be minimized by applying the smallest effective amount of force during reduction with traction and leverage techniques so as to avoid the formation or exacerbation of existing fractures or vascular (eg, hemarthrosis) or nerve injuries (eg, neurapraxia). New fractures rarely appear on postreduction films.
Recurrence is the most common complication adverse outcome after reduction, especially in young active patients. Age at the time of dislocation is inversely related to the rate of recurrence. [11] Common fractures (eg, Hill-Sachs deformity or Bankart fracture) require prompt orthopedic follow-up because they are associated with increased joint instability and a higher risk of redislocation. After evaluation of the shoulder’s postreduction ROM, immediate immobilization with a sling and swathe or shoulder immobilizer is crucial to prevent recurrence.
Posterior dislocation
The most common complication of attempted closed reduction of a posterior shoulder dislocation is a humeral fracture, especially in older patients. Acute redislocation may also occur. Complications of the dislocation itself include the following:
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Posttraumatic osteoarthritis
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Joint stiffness and functional incapacity
Inferior dislocation
An estimated 50-60% of patients with luxatio erecta have associated brachial plexus injury. [12] Assessment and documentation of the presence of neurologic deficits should be carried out both before and after reduction. [13] Injury to the axillary artery, including arterial thrombosis, has also been reported. [14]
Rotator cuff tears occur very often with inferior dislocations. [15, 16] Ligamentous and connective tissue injuries include disruption of the glenohumeral ligament, the inferior glenoid capsule, or both.
Associated bony injuries include fractures of the glenoid rim, greater tuberosity, acromion, clavicle, and coracoid process. [1] These injuries can be induced or exacerbated by attempted reduction; however, they more often occur as a result of the dislocation itself.
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Ultrasound probe placement for viewing glenohumeral joint via posterior approach.
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Ultrasound image of normal (right) and anteriorly dislocated shoulder (left). Arrow points to humeral head. Image courtesy of Michael A Secko, MD, RDMS.
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Reduction of shoulder dislocation: Stimson maneuver.
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Reduction of shoulder dislocation: Stimson maneuver.
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Reduction of shoulder dislocation: scapular manipulation. Hand placement.
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Reduction of shoulder dislocation: scapular manipulation. Sitting position.
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Reduction of shoulder dislocation: external rotation.
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Reduction of shoulder dislocation: Milch technique.
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Reduction of shoulder dislocation: Spaso technique.
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Reduction of shoulder dislocation: traction and countertraction.
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Reduction of shoulder dislocation: traction and countertraction.
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Classic presentation of inferior shoulder dislocation. Affected arm is hyperabducted, with elbow flexed and forearm resting on top of head.
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"Regimental badge" area. Examine pinprick sensation to this area to assess axillary nerve sensory function.
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Reduction of shoulder dislocation: axial traction and countertraction. Axial traction is applied to arm, and parallel countertraction is applied with sheet wrapped over shoulder. Increasing degree of abduction (if possible) and applying cephalad pressure to displaced humeral head (star) can aid in reduction.
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Reduction of shoulder dislocation: axial traction and countertraction. After inferior dislocation is reduced, arm is adducted, supinated, and immobilized for postreduction radiography.
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Reduction of shoulder dislocation: two-step reduction. Step 1, part 1. Push anteroinferiorly on midhumerus with hand A while pulling posteriorly on medial condyle with hand B.
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Reduction of shoulder dislocation: two-step reduction. Step 1, part 2. After conversion of inferior dislocation to anterior dislocation, adduct arm and grasp patient's wrist.
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Reduction of shoulder dislocation: two-step reduction. Step 2. Hand A holds patient's arm in adduction while hand B externally rotates arm to reduce now anteriorly dislocated humeral head.
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Anteroposterior radiograph of left shoulder shows posterior glenohumeral dislocation. Impaction of humeral head on posterior glenoid results in reverse Hill-Sachs defect (trough sign) on anterior aspect of humeral head. Image courtesy of Dr M A Png, Singapore General Hospital.
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Axial spin-echo T1-weighted magnetic resonance arthrogram of right shoulder shows tear of posterior glenoid labrum (arrow) and reverse Hill-Sachs defect (arrowhead). Patient had previous posterior dislocation.
