Hip Dislocations

Hip dislocations can be classified as anterior, posterior, and central. Acetabular fracture with central hip dislocation has been discussed under acetabular fractures.

ANTERIOR DISLOCATIONS About 10 percent of hip dislocations are anterior (Fjg^SS^O/i and Fjg^BS^Oe), and the majority are secondary to automobile accidents, but they may also result from a fall, or a blow to the back while squatting. In anterior dislocations, the femoral head rests anterior to the coronal plane of the acetabulum. Anterior dislocations can be superior or inferior (obturator, thyroid, perineal) depending on the degree of hip flexion present at the time of injury. If the hip is abducted, externally rotated, and flexed at the time of injury, inferior dislocation occurs. If the hip is abducted, externally rotated, and extended, superior dislocation occurs. The mechanism of injury is forced abduction that causes the femoral head to be levered out through an anterior capsular tear. The affected extremity is in abduction and external rotation. However, the clinical appearance of superior versus inferior dislocations is dramatically different ( Fig 265:20.C and Fig 265:20.C). Neurovascular compromise is an unusual, but possible complication.

FIG. 265-20. A. Anterior superior dislocation of the hip. B. Inferior dislocations (obturator, thyroid, or perineal). C. Clinical appearance of a superior-type anterior dislocation of the hip. D. Clinical appearance of an inferior-type dislocation of the hip. (From Rockwood CA Jr, Green DP, Bucholz RW (eds). Fractures in Adults, 3rd ed, vol. 2. Philadelphia: JB Lippincott, 1991, pp 1576, 1578, 1587, 1588. Used with permission).

An AP film of the pelvis easily demonstrates the femoral head to be anterior to the acetabulum. A lateral view illustrates the anterior dislocation more clearly, although it may be difficult to obtain because of the patient's pain.

Treatment for the dislocation is early closed reduction, usually under conscious sedation. Strong, in-line traction is done with simultaneous flexion and internal rotation. Finally, the hip is abducted once the head clears the rim of the acetabulum. The dislocation should be reduced quickly, within a few hours, because the longer the delay in reduction, the higher the incidence of avascular necrosis. Postreduction radiographs should be specifically examined for acetabular or femoral head fractures and the possibility of small fragments in the joint not appreciated on the initial films.

POSTERIOR DISLOCATIONS Posterior dislocations (Fig 265-21 A) constitute 80 to 90 percent of hip dislocations. They are caused by force applied to a flexed knee, directed posteriorly. Acetabular fractures may result as well. On examination, the extremity is found to be shortened, internally rotated, and adducted ( Fig. 265-2.1.B). Concomitant life-threatening injuries must be ruled out.

FIG. 265-21. A. Posterior dislocation of the hip. B. The clinical appearance of a posterior dislocation of the right hip. (From Rockwood CA Jr, Green DP, Bucholz RW (eds). Fractures in Adults, 3rd ed, vol. 2. Philadelphia: JB Lippincott, 1991, pp 1580, 1591. Used with permission.)

Anteroposterior and lateral x-ray films of the pelvis and hip will reveal the dislocation, but further assessment of the acetabulum and femur must be done to rule out fractures. The oblique views of Judet and colleagues will reveal an acetabular fracture. Also, inferior femoral head fracture will be seen on the AP or oblique view. Hip dislocations are difficult to recognize if there is an associated femoral shaft fracture, so roentgenograms of the pelvis and hips should be routinely obtained in such cases.

The treatment of posterior dislocation without fracture is closed reduction under conscious sedation or general anesthesia, as quickly as possible and always within six hours. In-line traction, gentle flexion to 90°, and then gentle internal-to-external rotation is done (Allis maneuver, Fjg.265:22.). The Stimson maneuver (Fig, 2.6.5:2.3)

may prove useful in certain situations.

Allis Maneuver
FIG. 265-23. Stimson maneuver.

Complications include sciatic nerve injury in about 10 percent of the patients and avascular necrosis that increases in direct proportion to the delay in adequate reduction.

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