Hip dislocations are true orthopedic emergencies that the Emergency Physician must be capable of reducing. Neurovascular damage to the hip and leg is a known consequence of hip dislocations. Avascular necrosis (AVN) may occur in up to 20% of patients with a hip dislocation, with some studies showing that AVN following a hip dislocation occurs in a time-dependent fashion. In other words, the longer a hip is dislocated, the higher the incidence of AVN.1 Dislocation for more than 6 hours almost universally results in AVN.2-4 A hip dislocation can be diagnosed clinically with the help of radiologic studies.5 The advantages of plain films and computed tomography (CT) scans, over the use of ultrasonography, are to identify associated fractures.
The most common causes of hip dislocations are traumatic dislocations of a normal hip, mechanical dislocations of a prosthetic hip, spontaneous dislocations, and pathologic dislocations. Dislocations may occur with minor mechanisms at the extremes of age. Examples include falling from a standing height for elderly patients or during athletic activities in children.6,7
Many techniques have been described to reduce dislocated hips.3,8-15 The Emergency Physician must be familiar with each of these techniques and how to apply them appropriately to optimize patient management and outcome. Dislocations of both normal and prosthetic hips are seen in the Emergency Department, with prosthetic hip dislocations now occurring more commonly than normal hip dislocations.16-18 Although these are not associated with AVN, the pressure from the dislocated prosthetic head may still result in other neurovascular complications.
ANATOMY AND PATHOPHYSIOLOGY
Ball-and-socket joints are inherently stable. The strong muscles, ligaments, and fibrous joint capsule of the hip further reinforce this innate stability. Consequently, in the average adult, a great deal of force must be transmitted to dislocate the hip. This is significant, as the patient with a hip dislocation may have other life-threatening injuries that take precedence over the management of the hip dislocation. The increased mortality rate associated with a hip dislocation typically results from associated injuries of the head, thorax, or pelvis.
Hip dislocations are classified into anterior, posterior, inferior, and central based on the relationship of the dislocated femoral head to the acetabulum.2,7 Anterior hip dislocations account for 5% to 10% of hip dislocations and occur with the leg in a neutral or abducted position. The femoral head is pushed anterior to the coronal plane of the acetabulum. These patients present in extreme pain with the hip and knee flexed to 90° and the leg held in external rotation. A slight shortening of the leg may also be noted, but this is difficult to detect with the knee in flexion. There are three subtypes of an anterior hip dislocation: anterior obturator, anterior iliac, and anterior pubic. In anterior obturator dislocations, the femoral head displaces medially and lies in the obturator ...