Anterior dislocations account for more than 90% of dislocations. They are frequently caused by falling with the arm externally rotated and abducted, causing patients to present with the affected extremity held in adduction and internal rotation due to pain. The acromion becomes prominent with loss of the rounded contour of the deltoid. Neurovascular exam of the upper extremity should be performed to rule out associated injury, most commonly of the axillary nerve (sensation over the deltoid) and musculocutaneous nerve (anterolateral forearm). Vascular injuries are rare. Standard radiographs to evaluate for fracture should include AP and either axillary lateral or scapular Y views.
Anterior Shoulder Dislocation. This right anterior shoulder dislocation occurred when the patient fell while playing basketball. There is an obvious contour deformity as well as prominence of the acromion. (Photo contributor: Kevin J. Knoop, MD, MS.)
Posterior shoulder dislocations are commonly missed because of subtle radiographic findings. The arm is held internally rotated and slightly abducted. Patients are unable to externally rotate their shoulder. On exam, a posterior prominence exists. Posterior dislocations can occur with a posterior-directed force as seen during grand mal seizures or electric shock.
Management and Disposition
Closed reduction is the treatment and should be completed as soon as possible to avoid humeral head avascular necrosis. Due to shoulder girdle spasm, conscious sedation is often required. There are many methods to reduce anterior shoulder dislocations, including Stimson, Rockwood traction and countertraction, and Milch. The basic premise is to apply axial traction, externally rotate, and abduct. Neurovascular and radiographic examination should occur before and after reduction. The patient should be placed in a sling after reduction, and follow-up with a musculoskeletal specialist is recommended.
Occult, nondisplaced greater tuberosity fracture can be identified on postreduction radiographs. These usually occur during the traumatic event, not as a result of the reduction, and are usually only identified when there is no radiographic bony overlap.
Luxatio erecta is inferior glenohumeral dislocation and is rare. The humeral head is forced below the inferior aspect of the glenoid fossa due to arm hyperabduction. These patients present with the arm locked fully abducted and externally rotated. Axillary nerve injury is reported to occur in 60% of cases. Vascular injury occurs most frequently with this type of dislocation. Reduction is accomplished with overhead traction.
Posterior shoulder dislocations can be bilateral and are often missed due to preserved symmetry on standard chest x-rays.
Hill-Sachs lesions (an impaction fracture of the posterolateral humeral head) can occur in up to 50% of anterior shoulder dislocations. Reverse Hill-Sachs lesions, also called Mclaughlin lesions (impaction fracture of anteromedial aspect of humeral head), can occur in posterior shoulder dislocations.
Anterior Shoulder Dislocation. Radiographic evaluation demonstrates in both the AP (A...