Developmental Dysplasia of the Hip

What Is It?

In a normal hip joint, the rounded top of the thigh bone (femur) fits into a cup-shaped socket in the pelvis called the acetabulum. This type of joint is called a ball-and-socket joint. In developmental dysplasia (dis-PLAY-shah) of the hip, the hip joint is unstable, and the top of the femur moves in and out of the socket either partially or completely. In some cases, the top of the femur is dislocated — displaced completely from its normal position in the socket.

This condition is present at birth and can be related to birth.

Developmental dysplasia of the hip probably is caused by a combination of inborn factors and birth-related stress. For example, many babies with this condition are born with unusually loose or lax hip ligaments, the fibrous tissues that strap the femur into its socket. These loose ligaments allow the femur to move too much within the hip joint, making the hip unstable and prone to dislocation. This risk of dislocation seems to be highest during birth, when the squeezing pressure of a vaginal delivery stresses a baby's hips. Children who are delivered in the breech position (buttocks first) are particularly vulnerable, especially if their hips are sharply flexed during passage through the birth canal.

In the United States, this type of hip problem causes hip dislocations in about one out of every 1,000 newborns. The condition is much more common in girls than in boys, between 80 percent to 90 percent. The risk of developmental dysplasia of the hip is higher in firstborns, and about 40 percent of babies with the condition were delivered in the breech position.

Developmental dysplasia of the hip is a serious condition that must be diagnosed and treated early. Unless the baby's hip is replaced in its socket and its supporting ligaments are strengthened appropriately, the child can develop a variety of long-term orthopedic problems, including chronic hip pain, arthritis at a young age, a shortened leg on the affected side, and difficulty walking.

Symptoms

In an infant, developmental dysplasia of the hip can cause the following symptoms:

• One leg is shorter than the other.
• The right and left kneecaps are at different levels when the legs are compared side to side.
• One thigh has a different number of skin folds than the other or a different pattern of skin folds.
• One leg moves less than the other or seems to be less flexible.

Diagnosis

Doctors routinely check for symptoms of developmental dysplasia of the hip during the first physical exam of a newborn (within a day or two of birth) and also at follow-up well-baby visits. As part of the normal screening for this condition, your doctor will want to know whether your child was delivered in the breech position, is a firstborn, or has a parent or sibling who had the problem.