Developmental Dysplasia of The Hip

Developmental dysplasia of the hip (DDH) is the most common disorder affecting the hip joints of children under age 3. DDH occurs when structures in the hip joint articulate abnormally. The condition may be unilateral or bilateral. It occurs in three forms of varying severity:

• unstable hip dysplasia, in which the hip is positioned normally but the ligaments around the hip are loose, predisposing it to dislocation, especially by manipulation
• subluxation or incomplete dislocation, in which the head of the femur is partially displaced and rides on the edge of the acetabulum
• complete dislocation, in which the head of the femur lies completely outside the acetabulum.

About 60% to 70% of affected infants are female. Dislocation is 10 times more common after breech delivery than after normal cephalic delivery. It also may be more common among large neonates and twins. With prompt treatment, the prognosis is good.

Causes

Experts are uncertain about the cause of DDH. Some theorize that the hormones that relax maternal ligaments in preparation for labor may also relax the ligaments around the infant's hip joint.

Signs and Symptoms

• Reduced movement in the affected side
• The leg may seem shorter on the affected side
• The folds on the thigh fat may seem uneven
• After 3 months of age, the affected leg may turn outward or be shorter than the other leg
• The leg positions may be different

Diagnostic tests

X-rays reveal the location of the femur head and a shallow acetabulum and allow monitoring of the progress of the disorder or treatment. X-rays are difficult to interpret because the femoral head isn't evident until ossification begins at age 3 to 4 months.

Ultrasonography can define the relationship between the head of the femur and the acetabulum without the use of ionizing radiation.

Treatment

The earlier an infant receives treatment, the better the chances of normal development. Treatment for an older child depends on the patient's age.

Infants younger than age 3 months receive gentle manipulation to reduce the dislocation, followed by placement of a splintlike brace or harness (such as the Frejka pillow or the Pavlik harness) to maintain the hips in a flexed and abducted position. The infant must wear the appliance continuously for 2 to 3 months and then wear a night splint for another month so the joint capsule can tighten and stabilize in correct alignment.

If treatment doesn't begin until after age 3 months, it may include bilateral skin traction (Bryant's traction). Skeletal traction may be necessary if the child has started walking. Both treatments are used to reduce the dislocarion by gradually abducting the hips.

If traction fails, gentle closed reduction under general anesthesia can further abduct the hips; the infant then wears a spica cast for 4 to 6 months. If closed reduction fails, the doctor may perform open reduction and apply a spica cast for about 6 months, or he may perform an osteotomy.

Treatment for children ages 2 to 5 is difficult; it includes skeletal traction and subcutaneous adductor tenotomy. Treatment started after age 5 usually fails to restore satisfactory hip function.

Prevention

Prevention is probably not possible, but early detection and treatment before complications occur is of paramount importance.