The shoulder is the most mobile joint in the body, and by design, it is inherently unstable. (Clin Sports Med 2004;23:335.) Because of this, it can dislocate anteriorly, posteriorly, or inferiorly.
The glenohumeral joint (the articulation between the humerus and distal scapula border, known as the glenoid) is a “ball-and-socket” design stabilized by a fibrocartilaginous ring (labrum), ligaments (superior, middle, and inferior glenohumeral and coracohumeral), and muscular components. In acute anterior dislocations, the humeral head is forced out of the glenoid anteriorly and becomes positioned beneath the coracoid process (75%), clavicle, or glenoid. A dislocation is disassociation of the humeral head from the glenoid fossa, which often requires manual reduction. A subluxation, on the other hand, occurs when the humeral head shifts to the glenoid edge, beyond normal physiologic limits, followed by self-reduction. (Phys Med Rehabil Clin N Am 2004;15:575.)
Dislocation of the glenohumeral joint is the most common major joint dislocation evaluated in the ED (Emergency Medicine Concepts: A Comprehensive Study Guide.  St. Louis, MO: McGraw-Hill; pp .1236-44), and is estimated to occur in 0.5 percent to 1.7 percent of individuals. (Clin Sports Med 2005;24:47.) Anterior dislocations account for approximately 95 percent of all shoulder injuries (Emerg Med 2001;33:20) and 95 percent of all shoulder dislocations (Clin Sports Med 2004;23:335), with approximately 76 percent of anterior dislocations occurring during athletic activity. (Am J Sports Med 1990;18:25.)
Glenohumeral joint instability can be the result of acute major trauma, chronic repetitive microtrauma, congenital abnormalities (Orthop Clin North Am 2001;32:463), or connective tissue disorders. Repeat dislocations or subluxation can result in a chronically unstable joint that is prone to dislocation after minimal trauma. Anterior instability is most frequently the result of a tear in the anterior-inferior glenohumeral joint capsule or detachment of the anterior-inferior labrum from the glenoid rim. (Am J Sports Med 2000;28:910.)
The emergency physician should obtain a history that includes patient handedness, vocation, recent trauma, and previous dislocations or subluxations, and determine whether manual reduction was necessary. Patients with baseline glenohumeral joint instability may complain of shoulder pain, popping, catching, locking, a “loose” sensation, stiffness, and swelling. (Clin Sports Med 2000;19:331.)
Humeral dislocation may or may not be clinically obvious. On inspection, patients may demonstrate anterior shoulder fullness and loss of the normal round lateral deltoid contour with a palpable dimple in the skin beneath the acromion. Typically, the patient supports the injured arm by holding it close to the body, abducted and slightly externally rotated, with range of motion limited by pain. The patient classically cannot adduct or internally rotate the shoulder.
Evaluation for secondary injuries should be performed, including associated fractures, ligament rupture, and injuries to the adjacent neurovascular structures. Nerve injury after an anterior dislocation is fairly common, occurring in nine percent to 18 percent of cases, but is more common in older patients. (Clin Sports Med 2004;23:xv.) It is important that the EP document the neurovascular examination prior to manual reduction or manipulation to distinguish between pre-existing injury and possibly unavoidable iatrogenic injury. The nerve most often injured is the axillary (42%), followed by the radial nerve (7%), with the probability of nerve injury doubled when associated with a concomitant fracture. (Euro J EM 2006;13:233.) Associated fractures are detected in 15 percent to 35 percent of anterior shoulder dislocations; the most common are greater tuberosity fractures.
Other common injuries are the Bankart lesion; detachment of the labrum from the glenoid rim (complete detachment is seen in 62% to 97% of anterior dislocations [Clin Sports Med 2004;23(3):xv] and Hill-Sachs lesion; and compression fracture of the posterolateral aspect of the humeral head (evident in approximately 80% of anterior dislocations. (Clin Orthop 1985;194:153.) Rotator cuff injuries can occur with anterior dislocations and appear to be age-related. Tears are uncommon in young patients, but the incidence climbs to approximately 30 percent in patients over 40 and to nearly 80 percent by age 60. (Clin Sports Med 2004;23:xv.) Vascular injuries are rare, but can occur in patients with severe atherosclerotic disease.
Closed reduction should be performed as quickly as possible in all patients with an acute dislocation that does not spontaneously reduce. A pre-reduction x-ray should be obtained to identify any fracture fragments that may impede manual reduction. The initial radiographs should include anteroposterior, axillary lateral view, and scapular “Y” views.
There are many techniques described to reduce an anteriorly dislocated shoulder, with little data to support the optimal method. (Sports Med Arthroscopy Review 2006;14:192.) The decision about which technique to use depends on a number of factors including the availability of an assistant, patient discomfort, ability to position the patient on the bed (e.g., prone), and operator preference.
Reduction techniques that have been successful are scapular manipulation, external rotation method, Stimson technique (patient placed prone with 10 to 15 pounds of weight attached to wrist of affected arm), Milch technique (reaching up to pull an apple from a tree), traction-countertraction, and Spaso technique (patient lays supine, and his arm is lifted with gentle traction to 90 degrees of flexion at the shoulder, and then the shoulder is externally rotated). (Clinical Procedures in Emergency Medicine.  Philadelphia: Saunders.)
Shoulder dislocation reductions are typically painful procedures requiring analgesia and sedation for successful reduction and patient comfort. Because procedural sedation may have undesired consequences such as a prolonged ED stay (need for pre-procedure oral abstinence four to six hours [Acad Emerg Med 2002;9:35] and recovery time), are staff intensive, and have sedation-associated risks, many have described techniques not requiring intravenous sedation. One study reported 100 percent success, no complications, and no narcotics or sedation required to reduce nine anterior dislocations using the Oza maneuver (direct humeral head manipulation). (Ann Emerg Med 2004;44:282.)
The Kochar method (a combination of external rotation at the elbow with an over-the-head grasping technique) has been modified over time to include traction. One report describes successful painless reduction of 12 anterior shoulder dislocations with no sedation or analgesia using the traditional (not traction) Kochar method. (Injury 2005;36:1182.) Many have described techniques using local anesthetic to decrease the need for intravenous sedation. One review concluded that premedication with 20 mL of 1% lidocaine intra-articular resulted in fewer complications, shorter ED procedure time, and no detectable differences in reduction success rates versus intravenous sedation. (Sports Med Arthroscopy Review 2006;14:192.) Regional anesthesia using an ultrasound-guided intrascalene block technique also has been described to reduce the need for procedural sedation and decrease ED length of stay. (Am J Emerg Med 2006;24:293.)
Post-reduction x-rays should be performed in two planes to confirm relocation and exclude associated fracture. (Am J Sports Med 2000;28:414.) Neurovascular reassessment also should be performed.
A review of the literature reveals no consensus on whether immobilization is helpful or what the optimal duration of immobilization may be after an initial dislocation. (Clin Sports Med 2004;23:xv.) Some recent studies suggest that immobilization in external rotation may be of some benefit. (J Shoulder Elbow Study 2003;12:413.) Immobilization has not been shown to decrease the rate of recurrence and is done only for comfort. (Phys Med Rehabil Clin N Am 2004;15:575.) Ice and analgesics should be prescribed for initial pain control.
Patients who reduce spontaneously or with manual manipulation may be discharged home after appropriate post-sedation parameters are met, and should be referred to an orthopedist for follow-up. Immediate orthopedic consultation is required if reduction is not achieved in the ED or for any dislocation associated with a fracture. (Primary Care: Clinics in Office Practice 2006;33:751.) After an initial dislocation, the shoulder is less stable and more susceptible to dislocation again, with a recurrence rate between 10 percent and 90 percent. (Clin Sports Med 2005;24:47.) At this time, orthopedists have not yet agreed on what the definitive therapy is for first-time dislocators (open or arthroscopic operative versus non-operative) (J Bone Joint Surg 2007;89:244), particularly in young athletes.