Shoulder dislocation

Shoulder dislocation is the most common joint dislocation, occurring mostly in younger males. It is often associated with other injuries, like fractures, tears of the rotator cuff, and injuries to the axillary artery or nerve. Most dislocations are anterior. Anterior dislocation occurs due to fall on extended, externally rotated arm, while posterior dislocation occurs during electrocution or seizure. Shoulder dislocations are often recurrent. A Bankart or Hill-Sachs lesion may be present on x-ray. Dislocations should be reduced under anaesthesia.

Shoulder dislocations are often recurrent as the joint capsule becomes lax after the first dislocation. This is called recurrent shoulder dislocation.

Etiology

Anterior shoulder dislocation occurs due to fall on an extended, externally rotated arm, or due to direct trauma. Posterior dislocations occur due to overpulling of the subscapularis or latissimus dorsi muscles, due to electrocution or seizure.

Classification

Shoulder dislocations are classified according to the direction of the dislocation. Anterior dislocations are the most common (95%). Posterior and inferior dislocations are rare. Inferior dislocation is called luxatio erecta, due to the presentation.

Bankart lesion refers to rupture of the anterior glenoid labrum and may be seen after reduction. Hill-Sachs lesion refers to a cortical depression on the posterior/lateral humeral head.

Clinical features

Patients with shoulder dislocations present with severe shoulder pain, and usually use the unaffected arm to stabilise the affected arm to reduce movements. In case of anterior dislocation, the arm is in an adducted position. A gap below the acromion may be palpated, as well as the head of the humerus below the clavicle. In case of posterior dislocation, the arm is internally rotated and abducted. In case of luxatio erecta, the patient’s shoulder is locked in an overhead and abducted position.

Diagnosis and evaluation

Shoulder dislocations require x-ray before and after reduction. In case of posterior dislocation, the “lightbulb sign” and “vacant glenoid sign” may be seen. Associated injuries should be ruled out.

Treatment

Shoulder dislocations should be reduced under anaesthesia (usually general) or local analgesia (like intraarticular lidocaine). There are multiple techniques for reduction (Hippocrates, Stimson, Snowbird). In case of failed closed reduction, Bankart lesion, or rotator cuff tear, surgery is indicated.

Reduction and operation should be followed by immobilisation and physiotherapy to prevent recurrence and frozen shoulder.