CHAPTER 196 Shoulder Dislocations

Dislocations of the shoulder are quite common. Approximately 50% of shoulder injuries in the emergency department are dislocations. Anterior dislocations are far more common than posterior dislocations. The four types of anterior dislocations account for 96% of all shoulder dislocations.

Of the four types of anterior dislocations, subcoracoid dislocations occur three times more frequently than all the others (subglenoid, subclavicular, and thoracic) combined. This chapter deals only with care of subcoracoid, anterior dislocations. All others should be treated with the assistance of an orthopedic surgeon.

The shoulder is the most flexible joint in the human body; consequently, it is the most unstable and most commonly dislocated joint. It is designed to enable a wide range of motion of the upper extremity, in all directions. To accomplish this feat, the actual bony articulation occupies only a very small part of the overall functional area of the joint. The glenohumeral joint surface and capsule are small sliding structures without significant fixed, ligamentous limitations. The tendons around the joint, making up the rotator cuff (Fig. 196-1), are the structures primarily responsible for the integrity of the joint and its complex function.

Figure 196-1 Anatomy of the shoulder joint and how the tendons of the muscles (supraspinatus, infraspinatus, subscapularis, and teres minor) form the rotator cuff. Also see Chapter 185, Musculoskeletal Ultrasonography, and Chapter 192, Joint and Soft Tissue Aspiration and Injection (Arthrocentesis).

When the normal joint capsule and rotator cuff restraints are exceeded, the shoulder moves out of joint. Most frequently the clinician encounters a dislocation in which the humeral head has been pulled out of joint and is then held anteriorly and medially by spasm of the anterior chest wall muscles. This is the subcoracoid, anterior shoulder dislocation, usually occurring when an abducted, extended, and externally rotated upper extremity takes a major jolt. The resulting lever forces the proximal humerus anteriorly out of the glenoid socket. After the humeral head comes to rest under the coracoid process, the patient usually presents to the clinician in extreme pain with a nonfunctional arm. Dislocations may also occur during a seizure.

The patient will have a loss of the normal shoulder contour, with a step-off where the deltoid muscle used to be prominent. Instead, the acromion becomes very prominent. The contour of the humeral head may be noted in the anterior chest wall region. Clinically, a hollow can be appreciated beneath the acromion process, due to the missing humeral head. The arm will frequently be held in a slightly abducted, externally rotated posture. A neurologic deficit, most frequently involving the axillary nerve (provides innervation for shoulder abduction and sensation over the deltoid), may be noted on careful examination. Additional neurovascular compromise may be evident, but it is uncommon with subcoracoid, anterior dislocations.

Radiographs should be obtained; it is important to determine the presence (24% of anterior dislocations) or absence of a fracture before attempting to reduce the shoulder. Obtain standard radiographs of the shoulder. A single anteroposterior (AP) view of the shoulder will usually demonstrate the abnormal location of the humeral head. Another view at roughly 90 degrees will not only confirm the direction of humeral head movement, but help exclude a fracture or posterior dislocation. A lateral transcapular or a “Y”-type view will provide this information; an axillary view (Fig. 196-2) is preferred by some clinicians but it is often difficult to get the patient to move his or her arm into the necessary position. Alternatively, in some obese individuals, a computed tomography (CT) scan may be necessary to determine the direction of the shoulder dislocation and the presence of concomitant fractures.

Figure 196-2 Radiographs should include a view at 90 degrees from the anteroposterior view, such as this axillary view. Such a projection helps document the direction (anterior vs. posterior) of the shoulder dislocation.

Equipment and Supplies

• Stretcher

• Washcloth or small towel

• Soft restraints such as sheets or blankets

• Cloth tape, gauze or elastic bandage, padded wrist restraint or commercially available device for hanging weights from wrist

• Weights (5 to 15 lbs) or bucket ( to 1 gallon size and adequate tap water or intravenous [IV] fluid)

• Intra-articular anesthetic (10 to 20 mL of 50 : 50 mixture 1% or 2% lidocaine with sterile saline), antiseptic solution (e.g., chlorhexidine, povidone–iodine), 10- to 20-mL syringe, 25-gauge, -inch needle

• Procedural sedation forms, consent, equipment (see Chapter 2, Procedural Sedation and Analgesia) and medications (e.g., analgesia, muscle relaxant, narcotics, benzodiazepines, reversal agents)

• Shoulder immobilizer or sling and swath

Technique

There are a number of available techniques, all designed to apply gentle and persistent tension on the spasmodic chest wall muscles, to elongate them, and to reestablish the mobility of the humeral head. Once this is done, the humeral head will usually track or be gently manipulated back into the glenoid fossa. The patient is probably best served by the simplest technique, the one that minimizes both operator and patient stress. Typically, this is the Stimson technique, wherein weight loading and time can be used to gently stretch the muscles and reduce the joint. Certainly, this is the least traumatic technique for the shoulder and should help minimize the chances of a fracture developing related to the reduction process.

Other techniques may also be successful. Although many have been described in the literature, all of the listed techniques have been tested and are effective in a situation where the clinician is willing to take his or her time with the reduction. Experience suggests that the clinician should not attempt more than two reduction procedures. If the second attempt is unsuccessful, the resultant muscle spasm will likely prevent closed reduction in a safe manner. Call the orthopedic surgeon if the second attempt is unsuccessful.

Intra-articular Anesthetic

Some experts recommend the injection of intra-articular anesthetic with every shoulder reduction (see also Chapter 192, Joint and Soft Tissue Aspiration and Injection [Arthrocentesis]). It can also be used if procedural sedation is contraindicated.

1 Identify the hollow area where the humeral head used to be located, 2 cm (two fingerbreadths) directly inferior to the lateral border of the now prominent acromion process. Apply antiseptic solution to the skin over this area and allow to dry.

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