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Developmental Dysplasia of the Hip

In the newborn nursery the pediatrician examined the hips of baby Phoebe. The hips were appropriately aligned, however, the pediatrician knew that Phoebe was at risk for abnormal hip development because of her breech birth. The family understood that close follow up would help to answer the questions about treatment and outcome. When Phoebe was a month old they visited the Rocky Mountain Hospital for Children pediatric orthopedic office. At that visit, her ultrasound demonstrated a mild case of hip dysplasia and treatment was started.

What is hip dysplasia?

The hip is a ball-and-socket joint. In a normal hip, the ball fits well in the deep socket. In Developmental Dysplasia of the Hip (DDH) the ball or socket may be abnormally shaped or unstable. DDH can be diagnosed early after birth (congenital), or it can develop as the child grows.

In mild cases of DDH, the femoral head moves back and forth within the socket, causing a child to have an unstable hip. In more serious cases, the head slips completely out of the socket becoming dislocated. The hip socket may be too shallow and the ligaments too loose to allow for normal development of the hip joint. This abnormal development causes the femoral head to put too much pressure on the rim of the hip socket. During childhood this is usually painless but, with the passage of time, the cartilage within the hip will be damaged, resulting in degenerative osteoarthritis and disability.

Is hip dysplasia common?

Hip dislocations are relatively uncommon, affecting 1-2 out of 1,000 babies. Most commonly it involves only a single side, but bilateral cases have been diagnosed. The left side is more often affected than the right because of intra uterine positioning that limits the motion in the left hip.

What causes hip dysplasia?

The causes of DDH aren't completely understood, but experts think that many factors are involved.

Higher risk of Hip Dysplasia occurs in infants with any situation that stretches hip ligaments. Positioning of the infant in utero can also play a role in influencing the ball to slip out of the socket. The most common risk factors that raise concern are:

  • Breech positioning strains ligaments in the hip
  • Females tend to have more lax ligaments
  • Firstborn children are constrained by a tight uterine wall
  • Family history may indicate a genetic coding for increased laxity of the ligaments

What are the symptoms of hip dysplasia?

Most babies with DDH experience no pain. The gentle physical exam performed by your child’s doctor is the most sensitive test and best indication that a problem exists with the hip. Infants often don't show signs that they have DDH, and there may be no signs at all. Still, doctors look for these indicators:

  • The leg on the side of the dislocated hip may appear shorter
  • The leg on the side of the dislocated hip may turn outward
  • The fat folds in the skin of the thigh may be uneven
  • In a frog position of the legs there is asymmetry
  • “Clicks” or “clunks” may be felt during exam

How is hip dysplasia diagnosed?

The doctor’s exam is the most reliable means of detecting a hip dislocation. With gentle hip manipulations that include pushing and pulling on the child's thighbones, the physician can assess range of motion and stability to determine whether the hips are loose in their sockets. Pain is not a reliable indicator of hip dysplasia in infancy because it is a pain-free condition. Because developmental hip dysplasia can be present even as the child grows, the hip exam continues to be an important component of a well child check-up.

Sometimes a doctor will recommend an x-ray or ultrasound to get a better view of a hip at risk. X-rays are helpful for babies who are least 6 months of age or older, but ultrasounds are preferred for babies under 6 months of age. Ultrasounds can be more helpful in these younger patients because their hip structures are cartilage which does not show up on x-rays.

Howis hip dysplasia treated?

Treatment for DDH depends on the age of the child and the severity of the condition. Mild cases may correct themselves in the first few weeks of life, but close monitoring is necessary to assure that the hip is growing and improving normally.

The good news for parents is that the vast majority of hips with dysplasia will respond beautifully to treatment. The goal of these treatment methods is to align the ball and socket so that they begin to influence each other to create a normal hip. Treatment options can include:

  • Pavlik harness…this flexible, soft harness uses straps to maintain a leg position that encourages the hip to develop a deeper socket, thus providing better coverage and stability for the femoral head. This is the least risky form of treatment for hip dysplasia with success rates approaching 95% in children with a single hip involved.
  • Rigid brace…if the pavlik harness is not effective, a rigid hip orthosis will provide additional support to maintain the desired position that we know is necessary to treat hip dysplasia
  • Casting…is the next step in treatment for dysplastic and unstable hips that do not respond to the pavlik or the rigid orthosis. Usually, the cast application is combined with an exam and arthrogram under anesthesia.

The spica cast covers both legs and extends up onto the baby’s trunk to provide firm support maintaining the desired relationship between the femoral head and the socket.

Arthrograms are x-ray studies that involve injecting “dye” into the hip to visualize the cartilage structures of the ball and socket that otherwise do not show up on x-rays.

  • Surgery…for infants surgery is used for the hip that remains persistently dislocated. The procedure balances the tight and loose tissues about the hip to keep the ball centered within the existing shallow socket. The baby is then protected with a hip spica cast so that the dysplastic hip structures can grow into a more normal shape.

Children older than one year of age, who are diagnosed with hip dislocations, will usually require surgery as the first line of treatment.

For nearly all the options the length of treatment is on average 12 weeks. The goal is a great hip. For some hips this happens faster than it does for others. The length of treatment is personalized so that each child has the best possible outcome.

What is the long-term outlook for my child?

Q: What’s the long-term outlook for a child who has DDH?

A: Treating your child’s DDH in infancy greatly increases the likelihood of a successful outcome. The vast majority of children treated for DDH at Children’s have treatments that enable their bones to grow normally—so they can walk, play, grow and live active lives.

Q: What are the causes and risk factors for DDH?

A: In hip dysplasia, the socket is too shallow and/or the ligaments too loose—allowing the ball of the thigh bone slip in and out of the socket, partially or completely. Researchers are looking for a definitive cause, but it’s thought that genetics plays a role.

The risk for hip dysplasia and hip instability increases with any situation that stretches the baby’s hip ligaments or causes her legs and hips to be positioned so that the ball of the thigh bone slips out of the hip socket, as can happen with:

  • children in families where there’s a genetic predisposition for the condition
  • females, who have looser ligaments than males
  • first-born babies, whose fit in the uterus is tighter than in later babies
  • breech babies, whose constrained position tends to strain the joint’s ligaments