There are four types of anterior dislocations. In subcoracoid dislocation, the commonest type, the humeral head is displaced anterior to the glenoid and inferior to the coracoid. In a subglenoid dislocation, the humeral head lies inferior and anterior to the glenoid fossa. In a subclavicular dislocation, the head of the humerus is displaced medial to the coracoid below the clavicle. In the very rare intrathoracic dislocation, the head of the humerus lies between the ribs and thoracic cavity.
The mechanism of injury may be direct force, but an indirect force is commoner. The combination of abduction, extension, and external rotation with sufficient force will cause an anterior dislocation.
The patient is usually in severe pain. The arm is in slight abduction and external rotation. The shoulder is "squared off," lacking the normal rounded contour. The patient resists abduction and internal rotation. The humeral head can often be palpated anteriorly. Because neurovascular injuries occur, a careful examination must be performed. The axillary nerve is most commonly injured. This nerve may be tested by pinprick sensation over the skin of the deltoid muscle.
Anteroposterior and scapular lateral or Y radiographs should be obtained before reduction is attempted. Although the anteroposterior radiograph will reveal the dislocation, the scapular Y radiograph will indicate the direction of dislocation: anterior or posterior. Bony injuries reported in the literature include fractures of the anterior glenoid lip, greater tuberosity, coracoid, and acromion, and compression fractures of the humeral head (Hill-Sachs lesion).
Many reduction techniques have been described. The three main categories are traction, leverage, and scapular manipulation. Success rates are between 70 and 90 percent regardless of technique. The use of conscious sedation is recommended, but any reduction technique may be attempted without medication when performed slowly and atraumatically. It is important for the physician to be comfortable with two or three techniques in case of a failed first attempt. Considerations in selection of a technique include ease of performance, effectiveness, as little trauma and pain as possible, requirement for medication, number of assistants, and time for procedure.
HIPPOCRATIC (MODIFIED) A modification of the Hippocratic method uses traction-countertraction ( Fig 2.6.3.-6). The patient is supine with the arm abducted and elbow flexed at 90°. A sheet is tied and placed across the thorax of the patient and then around the waist of the assistant. Another sheet is tied and placed around the forearm of the patient at the elbow and the waist of the physician. The physician gradually applies traction as the assistant provides countertraction. Gentle internal and external rotation or outward pressure on the proximal humerus may aid reduction.
STIMSON The patient is placed prone on a gurney with the dislocated extremity hanging over the side and a 10-pound weight attached to the wrist. Complete muscle relaxation is required. Twenty to 30 min is required to allow reduction to occur.
Although safe, effective, and easy to learn, the time involved and constant monitoring by a nurse are drawbacks to this technique.
MILCH The patient is supine. The physician slowly abducts and externally rotates the arm to the overhead position ( Fig. 263-7). With the elbow fully extended, traction is applied. With the other hand, pressure may be placed on the humeral head to manipulate it over the lip of the glenoid.
This technique is well tolerated by the patient, effective, and atraumatic. It is the technique of choice for many physicians
SCAPULAR MANIPULATION The patient is positioned with weights in the same manner as the Stimson technique (Fig.,263-8). After adequate sedation, the physician pushes the tip of the scapula medially using the thumbs, while stabilizing the superior aspect with the cephalad hand.
FIG. 263-8. Scapular manipulation technique.
Several reports have recently been published. Physicians have found this technique relatively painless, fast, and in one study 90 percent successful.
EXTERNAL ROTATION The patient is supine with the arm adducted to the patient's side. With the elbow at 90° of flexion, the arm is slowly externally rotated. No longitudinal traction is applied. It is important to perform the movement slowly to allow time for spasm and pain to resolve. Reduction is usually complete prior to reaching the coronal plane and is often not noted either by the patient or physician.
This method has been reported to be 78 percent successful, relatively atraumatic, safe, and easily learned.
COMPLICATIONS Complications are frequently encountered in patients with anterior glenohumeral dislocations. The most common complication is recurrent dislocation, which is age dependent. Those patients less than 20 years of age have a greater than 90 percent recurrence; those older than 40 years have a 14 percent recurrence. Other complications include fractures and injuries to nerves and the rotator cuff. Vascular injuries are rare but when they occur tend to involve the axillary artery in elderly patients. Clinical findings of vascular injury include absent radial pulse, axillary hematoma, bruising of the lateral chest wall, and an axillary bruit.
Bony injuries are common and include fractures of the humeral head (Hill-Sachs lesion), anterior glenoid lip, and greater tuberosity. Neural injuries occur in 10 to 25 percent of acute dislocations. Of these injuries, which are the result of traction neuropraxia, most occur in the axillary nerve. This injury is temporary and resolves spontaneously. The common test of sensation over the skin of the deltoid muscle may not be reliable, with only an electromyogram providing an accurate evaluation. Other nerves injured are the radial, ulnar, median, musculocutaneous, and brachial plexus.
A frequent but often missed injury is a tear of the rotator cuff. This injury, which increases with age, has a greater than 80 percent occurrence in patients older than 60 years. Treatment is surgical.
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