Developmental Dysplasia of the Hip

Developmental dysplasia of the hip, or DDH, occurs when the joint that connects the body with the leg forms abnormally. The hip is a ball-and-socket joint, where the ball is the head of the femur (thigh bone) and the socket is the acetabulum, which is part of the pelvis.

There are two main types of DDH:

  • Unstable or Dislocated — The ball is dislocated from, or falls out of, the socket.
  • Stable or Subluxated — There's no dislocation, but the socket is too small or too shallow to adequately cover or contain the ball. As a result the ball shifts around inside the socket but doesn't completely fall out.
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Think of the head of the femur as an egg and the acetabulum as a spoon. In the first type of DDH, the egg falls out of the spoon. In the second type, the spoon is too shallow or too small for the egg, causing it to roll from side to side inside the spoon.

Although the cause of DDH is unknown, we do know that it's more likely in children who have relatives with DDH as well as those born via breech delivery. It's also slightly more common among firstborns, girls and Caucasians.

DDH can strike at any time during childhood, even after it has been treated successfully. This means that a child diagnosed with DDH needs to be seen by an orthopedic surgeon until maturity. After successful treatment of DDH, your child can live a full and productive life, including full participation in sports.

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DDH is associated with the following symptoms:

  • Weakness of the hip muscles and limping
  • Stiffness and loss of hip movement
  • Painful arthritis

Stiffness and painful arthritis are long-term problems that may take years or even decades to set in. A child with untreated or undetected DDH generally doesn't complain, which is why some people refer to DDH as a silent condition — and why it's important for pediatricians to screen children for it.

During physical examination, hip instability, where the ball comes out of the socket, produces a "clunk" that can be felt as the hips move. With a dislocated hip, range of motion is reduced and the affected lower limb appears shorter than the other, non-affected side.

If DDH is suspected, the next step for a child less than 6 months of age is an ultrasound. This painless and non-invasive test, which takes about 15 minutes, is done in the doctor's office. Ultrasound provides a picture of the ball and socket, from which the severity of the DDH can be determined.

For a child older than 6 months, the best test is an X-ray. This test is also painless and non-invasive, and the radiation exposure is less than the routine background radiation present in the environment.

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Treatment of DDH depends on the age of the child and is divided into three phases.

First Phase: Under 6 Months

The infant with DDH is placed in a Pavlik harness full-time, except for half an hour in the morning and half an hour in the evening for bathing. The Pavlik harness directs the ball into the center of the socket. Force transmitted by the ball into the center of the socket causes the socket to become deeper and wider.

After the child has worn the harness for one week, an ultrasound test is done to make sure that the ball is sitting in the socket. Once this is confirmed, the harness is worn for six more weeks.

At that point, a second ultrasound test checks if the angles and ratios of the ball and socket are normal. If so, the child continues to wear the harness, but only at night, for another six weeks. If the ball fails to sit properly in the socket after three weeks using the Pavlik harness, use of the harness is discontinued and the child moves to the second phase of treatment.

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Reviewed by health care specialists at UCSF Benioff Children's Hospital.

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