eMedicine Specialties > Emergency Medicine > Trauma & Orthopedics

Dislocation, Shoulder: Differential Diagnoses & Workup

Author: Sharon R Wilson, MD, Assistant Professor of Emergency Medicine, Department of Emergency Medicine, University of California at Davis Medical Center
Coauthor(s): Daniel D Price, MD, Director of Ultrasound Fellowship, Department of Emergency Medicine, Highland General Hospital, Alameda County Medical Center
Contributor Information and Disclosures

Updated: Feb 27, 2008

Differential Diagnoses

Acromioclavicular Injury
Fracture, Clavicle
Fractures, Humerus

Other Problems to Be Considered

Associated fractures occur in approximately 30% of dislocations. The most common fractures include the Hill Sachs lesion, which is a compression fracture that results in the formation of a groove in the posterolateral aspect of the humeral head. This lesion is seen in 54-76% of dislocations. The Bankart lesion is a fracture of the anterior rim of the glenoid fossa. This lesion results from impaction of the humeral head against the anteroinferior glenoid labrum. It is associated with rupture of the joint capsule and inferior glenohumeral ligament injury. Avulsion fractures of the greater tuberosity are seen in 10-16% of cases. Humeral shaft and coracoid process fractures are rare. (See Complications.)

The rotator cuff is injured in 35-86% of dislocations and is more commonly seen in elderly patients. Glenohumeral ligament injury occurs in approximately 55% of cases and is most common in young patients. The axillary nerve is injured in 3% of anteroinferior dislocations. It is the most frequently injured, but brachial plexus, radial, and other nerve injury can occur. (See Complications.)

If a brachial plexus injury is diagnosed, axillary artery injury, though rare, should be considered. Patients with axillary artery rupture present with axillary hematoma, a cool limb, and absent pulses. However, patients with collateral blood flow may have distal pulses. Luxatio erecta has the highest incidence (3.3%) of vascular compromise. Evaluation of vascular injury should include Doppler blood flow studies, angiography, and arteriography. (See Complications.)

Workup

Laboratory Studies

• No lab studies are specifically indicated for evaluation of shoulder dislocation.

Imaging Studies

• Shoulder trauma series - Anteroposterior (AP) and axillary or scapular "Y" views  
  • Anterior dislocation is characterized by subcoracoid position of the humeral head in the AP view. The dislocation is often more obvious in a scapular "Y" 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."
  • In inferior dislocation (luxatio erecta), the AP view may show the arm raised over the head with the radial head inferior to the glenoid.
• Pre-reduction 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, pre-reduction films may not be necessary prior to attempts at reduction.
• Post-reduction films confirm relocation of the humerus and may reveal new or previously obscured pathology. Post-reduction immobilization is imperative. A recent prospective observational study examined whether post-reduction radiographs add clinically important information to what is seen on pre-reduction radiographs in patients with anterior shoulder dislocations who are seen in the ED. The authors found that, even though the majority (62.5%) of fractures were seen on pre-reduction radiographs, more than one third (37.5%) were only visible on post-reduction films. None of the missed fractures changed ED management, and no persistent dislocations were found on post-reduction films.⁴

Other Tests

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

Procedures

• The key to a successful reduction is slow and steady application of a maneuver with adequate analgesia and relaxation.
• Procedural sedation and analgesia (PSA) protocols in the ED assist in relaxing the musculature of the shoulder and make reduction a more comfortable and easier procedure. (For further information, see Procedural Sedation.)
• Other adjuncts to facilitate reduction for patients who are high risk or may not be candidates for PSA include intra-articular lidocaine and ultrasound-guided interscalene (lidocaine) block of the brachial plexus.  
  • Successful reduction is evidenced by marked reduction in pain and increased range of motion. A palpable or audible relocation ("clunk") may also be noted.
  • The patient may be asked to touch the uninjured shoulder to safely demonstrate a successful reduction.
• Some authors recommend an orthopedic consultation prior to reduction of posterior and inferior dislocations.
• After the completion of all reductions, apply a shoulder immobilizer with a sling and swathe. A careful neurovascular examination must be performed pre- and post-reduction.
• Post-reduction radiography is still recommended, especially if the procedure was difficult.
• Reduction of an anterior dislocation (For further information, see Joint Reduction, Shoulder Dislocation, Anterior.)
  • Inappropriate traction and poor technique can result in complications with otherwise safe methods of reduction. The Kocher method has been discouraged because of the increased incidence of complications. When performed correctly, it does not involve traction and has been demonstrated to be a safe technique.
  • Kocher's original method: Bend the arm at the elbow, press it against the body, rotate outwards until resistance is felt. Lift the externally rotated upper part of the arm in the sagittal plane as far as possible forwards and finally turn inwards slowly.
  • Stimson technique: The patient lies prone on the bed with the dislocated arm hanging over the side. Traction is provided by up to 10 kg of weight attached to the wrist or above the elbow. Apply gentle internal/external humeral rotation. Reduction may take 20-30 minutes.
  • External rotation method: While the patient lies supine, adduct the arm and flex it to 90° at the elbow. Slowly rotate the arm externally, pausing for pain. Reduce the shoulder before reaching the coronal plane. Often successful, this procedure requires only one physician and little force (see Special Concerns).
  • Traction-countertraction: While the patient lies supine, apply axial traction to the arm with a sheet wrapped around the forearm and the elbow bent at 90°. An assistant should apply countertraction using a sheet wrapped under the arm and across the chest while the shoulder is gently rotated internally and externally to disengage the humeral head from the glenoid.
  • Scapular rotation: This less traumatic technique has success rates of more than 90% in experienced hands, often without sedation. With the patient lying prone, apply manual traction or 5-15 lb of hanging weight to the wrist. After relaxation, rotate the inferior tip of the scapula medially and the superior aspect laterally. Alternatively, the patient can be seated while an assistant provides traction-countertraction by pulling on the wrist with one hand and bracing the upper chest with the other. The same scapular rotation is then performed.
• Reduction of a posterior dislocation: Apply gentle, prolonged axial traction on the humerus. Then, add gentle anterior pressure while coaxing the humeral head over the glenoid rim. Slow external rotation may be needed.
• Reduction of an inferior dislocation: Maintain gentle axial traction on the humerus while gentle abduction is applied. Apply countertraction across the ipsilateral shoulder. Following reduction, slowly adduct the arm. Buttonholing of the humeral head through the capsule usually requires open reduction.

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