Preprocedural Evaluation
Anterior dislocation
In patients with anterior shoulder dislocations, the x-ray panel, when indicated, should include anteroposterior (AP), lateral (Y), and axillary views of the shoulder. Radiographs are generally recommended for first-time dislocations or those caused by direct trauma. Empiric reductions should be limited to those patients with clinically apparent anterior shoulder dislocation if they are neurovascularly intact and if reduction can be performed easily and rapidly.
Clinical factors that have been associated with clinically significant fractures include first episode, patient age exceeding 40 years, or involvement in selected mechanisms of injury (ie, fall from more than one flight of stairs, fight or assault, and motor vehicle collision). [17] Some argue that prereduction films are necessary only in patients who have one or more of these risk factors, especially those patients aged 40 years and older. [18]
When in doubt, bedside ultrasonography (US) can also be used to diagnose a shoulder dislocation. [19, 20, 21, 22] Images of the glenohumeral joint can be obtained by using either a high-frequency linear array or a low-frequency curvilinear transducer. In an anterior dislocation, anterior displacement of the humeral head in relation to the glenoid is observed when the joint is viewed via the posterior approach (see the images below). [23]
Ultrasound probe placement for viewing glenohumeral joint via posterior approach.
Ultrasound image of normal (right) and anteriorly dislocated shoulder (left). Arrow points to humeral head. Image courtesy of Michael A Secko, MD, RDMS.
Posterior dislocation
Posterior shoulder dislocations are often missed or diagnosed only after a significant delay; thus, prompt identification of these relatively rare dislocations is the critical element of the preprocedural evaluation. Radiography beyond AP views is important when clinical suspicion of an occult posterior dislocation is high. Because posterior dislocations may be missed on AP views alone, complete radiographs (Y view or axillary view) are essential for diagnosis.
To avoid a missed diagnosis, a thorough examination should be performed, and radiographs should be obtained that definitively show the orientation of the glenoid with respect to the humeral head. On an AP view of the shoulder, a posterior dislocation is very subtle. Several findings on AP views have been described, including the so-called trough sign, which is caused by a reverse Hill-Sachs defect, or loss of overlap of the humeral head and glenoid fossa (see the images below). However, these subtle findings frequently are missed.
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.
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.
Radiographic projections such as an axillary view or a transscapular Y view are much more reliable and should be ordered routinely when a posterior dislocation is suspected. On both of these views, the humeral head can be seen posterior to the glenoid fossa. [9]
A patient with a posterior dislocation presents with the affected arm held in adduction and internal rotation. Efforts by the examiner to abduct or externally rotate the extremity result in pain and very little movement. Additionally, a prominent acromion and coracoid are typically noted, with the humeral head palpable posteriorly. These findings may be obscured if swelling is massive swelling or if the patient is particularly large.
Inferior dislocation
Before any attempted reduction of an inferior shoulder dislocation, a focused neurovascular examination should be performed to screen for the presence of nerve or vascular injury, and the examination should be repeated after reduction to document any change.
Injuries to the brachial plexus are common in the setting of inferior glenohumeral dislocations. The sensory function of the axillary nerve can be tested by assessing pinprick sensation over the “regimental badge” area of the affected arm (see the image below). Radial nerve motor function of the affected arm can be assessed by examining the strength of wrist extension. Distal pulses and capillary refill should also be examined before and after reduction.
"Regimental badge" area. Examine pinprick sensation to this area to assess axillary nerve sensory function.
To gain a multiplanar view of the glenohumeral joint, AP and transscapular lateral or Y views of the shoulder should be obtained. These radiographs should be taken both before and after reduction. In inferior humeral head dislocations, the humeral shaft is parallel to the spine of the scapula, with the humeral head lying inferior to the glenoid (without making contact with the glenoid). [24]
Equipment
The equipment required depends on the technique used (see Technique), as follows:
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The Stimson technique requires 5- to 10-lb (2.25- to 4.5-kg) weights, weight straps, and sheets or extra straps
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The traction-countertraction technique requires several sheets or wide straps
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The axial (inline) traction technique requires a lengthwise-folded or rolled-up bed sheet
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Scapular manipulation, external rotation, the Milch technique, the Spaso technique, and two-step reduction require no equipment
Patient Preparation
Anesthesia
Pain control and muscle relaxation may be necessary for reduction of a dislocated shoulder. An experienced provider may be able to perform reduction without anesthesia while causing remarkably little discomfort, but only in select cooperative patients. Various methods may be employed, depending on the patient and the nature of the dislocation.
Anterior dislocation
Pain control options for a patient with an anterior shoulder dislocation include the following:
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Intravenous (IV) procedural sedation and/or analgesia - Commonly used agents include propofol, etomidate, ketamine, fentanyl, and midazolam
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Intra-articular anesthetic (e.g. 1% lidocaine) injection
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US-guided nerve block
Procedural sedation may be necessary in patients who are anxious or uncooperative, those with a high degree of muscle spasm, or those who have undergone unsuccessful attempts at reduction without premedication. [7]
Intra-articular anesthetic injection is performed via the lateral (most common), or posterior injection techniques. The lateral technique is as follows. Under sterile conditions, insert a 35-mm needle (18-20 gauge) or spinal needle 2 cm inferior to the lateral edge of the acromion into the glenohumeral joint. After aspirating any blood present, inject 10-20 mL of 1% lidocaine, with or without epinephrine, over 30 seconds. Then, wait 15-20 minutes before performing the procedure. [7] The injection can also be performed under US guidance.
Potential advantages of intra-articular anesthetic injection include the following [25, 26, 27] :
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Reduced time to relocation and patient relief of symptoms.
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Reduction of the risks of respiratory depression and cardiac compromise
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Drainage of hemarthrosis
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Elimination of the need for IV access
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Shorter emergency department (ED) stay
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Reduced cost
A systematic review (based on five small studies) evaluating intra-articular lidocaine against IV analgesia with or without sedation using benzodiazepines and opiates reported that intra-articular lidocaine may provide comparable rates of successful anterior shoulder reduction with a lower rate of adverse events. [28]
The main potential disadvantage is the risk of infecting the joint space. However, a retrospective review of six randomized controlled trials comparing intra-articular lidocaine injection with procedural sedation found no reported cases of joint infection with the former. [29]
Anesthesiologists routinely perform brachial plexus nerve blocks for shoulder surgery with the aid of nerve stimulators or US guidance. [30, 31] The literature suggests that a US-guided interscalene nerve block of the brachial plexus can be used to provide adequate anesthesia for the reduction of shoulder dislocations. [32, 33]
A prospective randomized study by Blaivas et al found that a US-guided interscalene block not only is feasible in the ED but also can yield a significantly shorter ED stay than procedural sedation. [33] A linear-array probe was used to identify the brachial plexus in the neck between the anterior and middle scalene muscles on the same side as the dislocated shoulder. [32, 33] The brachial plexus appeared as three anechoic circles when viewed in the short axis. A 20- or 21-gauge 1.5-cm noncutting spinal needle was used to inject 20-30 mL of 1% lidocaine with or without epinephrine or 0.25% bupivacaine. Full loss of sensory and motor function of the arm was achieved in most patients after 15-30 minutes.
Potential advantages of nerve blocks over procedural sedation in this setting include the following:
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Reduced length of ED stay
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No need for hemodynamic monitoring
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Absence of airway or cardiovascular compromise
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Reduced amount of one-on-one health care provider time needed
Potential disadvantages include the following:
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Vascular puncture (though US guidance decreases this risk substantially as a result of direct nerve and needle visualization)
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Hoarseness or diaphragmatic symptoms due to possible involvement of the recurrent laryngeal nerve or the phrenic nerve
Posterior dislocation
Procedural sedation and analgesia are required if there is significant pain or muscle spasm. An experienced practitioner may be able to perform reduction without analgesia or sedation in a cooperative, calm patient when there is minimal muscle spasm.
Inferior dislocation
Adequate analgesia and amelioration of muscle spasm are the keys to successful reduction of an inferior shoulder dislocation. Intra-articular anesthetic injection, which is useful for most humeral head dislocations, can be difficult, if not impossible, in the setting of inferior dislocation, where hyperabduction of the arm alters the position of landmarks used to target needle placement. The use of systemic analgesics, muscle relaxants, or procedural sedation is often necessary to facilitate reduction of inferior dislocations.
The degree of anesthesia should be determined on a case-by-case basis, with the following patient-related factors taken into account:
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Age
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level of anxiety and cooperation
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Time since injury
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History of previous shoulder dislocations
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History of adverse reactions to systemic analgesics, muscle relaxants, or sedatives
In general, younger and more anxious patients, those with no previous history of shoulder dislocations, and those whose injury occurred a significant amount of time before presentation are more likely to require higher levels of analgesia, muscle relaxation, or procedural sedation.
The following non-patient-related factors should also be taken into consideration in the choice of an anesthesia method:
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Operator comfort and experience with the reduction technique
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Resource availability
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Time
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Ancillary support
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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.
