Shoulder Dislocation in Emergency Medicine

Updated: Sep 24, 2018
  • Author: Sharon R Wilson, MD; Chief Editor: Trevor John Mills, MD, MPH  more...
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Overview

Practice Essentials

The shoulder is the most frequently dislocated joint. It moves almost without restriction but pays the price of stability. The shoulder's integrity is maintained by the glenohumeral joint capsule, the cartilaginous glenoid labrum (which extends the shallow glenoid fossa), and muscles of the rotator cuff. Most dislocations are anterior, but less frequently, posterior, inferior (luxatio erecta), superior, and intrathoracic dislocations are also possible. Arthroscopic stabilization is performed in nearly 90% of shoulder stabilization surgeries in the United States. [1]  Patients with shoulder dislocation generally complain of severe shoulder pain and an associated decreased range of motion of the affected extremity. [2]

Shoulder dislocations constitute up to 50% of all major joint dislocations. Anterior dislocations occur in as many as 97% of cases. [3] Anterior displacement of the humeral head is the most common dislocation seen by emergency physicians and is depicted in the image below.

Y-view radiograph of the right shoulder shows ante Y-view radiograph of the right shoulder shows anterior dislocation of the humeral head relative to the glenoid fossa.

Posterior displacement is the next most frequently occurring dislocation (2-4%). Inferior (luxatio erecta), superior, and intrathoracic dislocations are rare (< 1%)and are usually associated with complications. [3, 4, 5, 6]

Anterior dislocation is characterized by subcoracoid position of the humeral head in the anteroposterior (AP) view. 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 on the degree of rotation. The scapular "Y" view reveals the humeral head behind the glenoid (the center of the "Y"). 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]

Procedural sedation and analgesia (PSA) protocols, intra-articular lidocaine, and ultrasound-guided brachial plexus nerve block assist in making reduction an easier and more comfortable procedure.

For excellent patient education resources, visit eMedicineHealth's First Aid and Injuries Center. Also, see eMedicineHealth's patient education article Shoulder Dislocation.

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Epidemiology

In the United States, the incidence of shoulder dislocations is 23.9 per 100,000 person years, and approximately 85-98% of shoulder dislocations are anterior dislocations. Dislocated shoulders tend to occur more often in males than in females. In males, the peak age of incidence is 20-30 years (with a male-to-female ratio of 9:1),  and in females it is 61-80 years (with a female-to-male ratio of 3:1). The incidence of proximal humerus fractures increases with age, with a population-adjusted incidence of 101 per 100,000 person years in those older than 65 years. [8]

Shoulder dislocation occurs more frequently in adolescents than in younger children because the weaker epiphyseal growth plates in children tend to fracture before dislocation occurs. In older adults, collagen fibers have fewer cross-links, making the joint capsule and supporting tendons and ligaments weaker and dislocation more likely. Anterior dislocation is most commonly seen in those aged 18-25 years due to sporting injury. The second most common age group to sustain anterior dislocation is in elderly persons because of their susceptibility to falls. [8]

A Danish study estimated the incidence of shoulder dislocation at 17 cases per 100,000. [9]  In a random sample of people in Sweden, 1.7% reported a history of shoulder dislocation. [10]  A Greek study examined the demographic data and recurrence rates of shoulder dislocations of 308 patients (170 men and 138 women) and found that the most frequent mechanism of injury was falling, and 92% of reductions were in the ED. The overall recurrence rate in all ages was 50% but rose to almost 89% in the 14-20 year age group. [1]

 

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Prognosis

Age is a major factor in the likelihood of sustaining a recurrent shoulder dislocation. [11]  Approximately 80-94% of patients younger than 20 years at the time of the initial dislocation have a recurrence. The major pathology in this age group is thought to be a Bankart lesion with associated inferior glenohumeral ligament injury.

Of patients younger than 40 years, 26-48% develop recurrent dislocation. The major pathology for this age group is thought to be disruption of the labral attachment of the glenohumeral ligaments. Dislocation recurs in only 0-10% of patients older than 40 years. Rotator cuff tear is the major pathology.

Minor trauma that results in a dislocation is associated with an 86% recurrence rate. Many orthopedic surgeons believe that more than one complete anterior dislocation justifies considering surgical repair.

There is general agreement that before being allowed to return to sports after anterior shoulder dislocation, athletes should be pain free and should demonstrate symmetric shoulder and bilateral scapular strength with functional range of motion. Usually, returning to play can occur 2-3 weeks after  dislocation; however, athletes with in-season shoulder injury who return to play during the season have demonstrated recurrence rates of 37-90%. [12]

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