Shoulder Dislocation in Emergency Medicine Workup

Updated: Nov 12, 2017
  • Author: Sharon R Wilson, MD; Chief Editor: Trevor John Mills, MD, MPH  more...
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Workup

Imaging Studies

Radiographs

Anterior dislocation is characterized by subcoracoid position of the humeral head in the anteroposterior (AP) view. Management of anterior shoulder dislocation starts with an analysis of the causative mechanism and a physical exam to establish the diagnosis, and the case can be classified as simple or accompanied by complications (most notably vascular or nerve injuries). Two radiographs perpendicular to each other can confirm the diagnosis and should then be repeated after reduction. Additional imaging studies may be necessary to assess bony lesions (eg, impaction lesions or fractures). [20, 21]

The dislocation is often more obvious in a scapular view, where the humeral head lies anterior to the "Y." In an axillary view, the "golf ball" (ie, humeral head) is said to have fallen anterior to the "tee" (ie, glenoid). In posterior dislocation, the AP view may show a normal walking stick contour of the humeral head, or it may resemble a light bulb or ice cream cone, depending upon the degree of rotation. The scapular "Y" view reveals the humeral head behind the glenoid (the center of the "Y"). In an axillary view, the "golf ball" falls posteriorly off the "tee." [14, 22, 23]  In inferior dislocation (luxatio erecta), the AP view may show the arm raised over the head with the radial head inferior to the glenoid.

Prereduction films are commonly performed to document the nature of the dislocation and to establish the existence of any associated pathology, such as a Hill-Sachs lesion or other humeral fractures. In cases where patients have experienced repeated anterior dislocations, prereduction films may not be necessary prior to attempts at reduction. [24]

Postreduction films confirm relocation of the humerus and may reveal new or previously obscured pathology. Postreduction immobilization is imperative. A prospective observational study examined whether postreduction radiographs add clinically important information to what is seen on prereduction radiographs in patients with anterior shoulder dislocations who are seen in the ED. The authors found that, although most fractures (62.5%) were seen on prereduction radiographs, more than one third (37.5%) were only visible on postreduction films. None of the missed fractures changed ED management, and no persistent dislocations were found on postreduction films. [25]

Other imaging

Arteriography, angiography, and Doppler flow studies may be used to evaluate suspected vascular injury. Electromyography (EMG) may be used later to evaluate nerve injuries. [7]

In a study of computed tomography for the detection of Hill-Sachs lesions, 142 shoulders were evaluated preoperatively by CT (30 with primary instability and 112 with recurrent instability) before arthroscopic Bankart repair. Hill-Sachs lesions were detected in 90 shoulders by initial CT evaluation and were found in 118 shoulders at arthroscopy. In patients with primary subluxation, the prevalence of Hill-Sachs lesions was 26.7%; primary dislocation, 73.3%; and all shoulders, 56.3%. In patients with recurrent episodes of complete dislocation, the prevalence of Hill-Sachs lesions was increased, and the lesions were larger. [15]

Horst et al used magnetic resonance imaging to identify the correlation between Bankart and Hill-Sachs lesions in 105 patients with anterior shoulder dislocation. They found that the co-occurrence of injuries was high [odds ratio (OR) = 11.47; 95% confidence interval (CI) = 3.60-36.52; P < 0.001] and that Bankart lesions co-occurred more often with large Hill-Sachs lesions (O  = 1.24; 95% CI = 1.02-1.52; P = 0.033). In addition, patients older than 29 years more often presented with a bilateral injury (OR = 16.29; 95% CI = 2.71-97.73; p = 0.002). If either lesion was diagnosed, the patient was 11 times more likely to have suffered the associated injury. [16]

Magnetic resonance angiography has been shown to have a high sensitivity when used to identify associated injuries in shoulder dislocation. [26]

In a study of point-of-care ultrasonography for shoulder dislocation in emergency departments, sensitivity and specificity for identifying dislocation were both 100%. For excluding shoulder fracture, point-of-care ultrasound had a sensitivity of 100% and a specificity of 84.2%. [27]