Developmental Dysplasia of the Hip (DDH)

What is developmental dysplasia of the hip (DDH)?

Developmental dysplasia of the hip is a congenital (present at birth) condition of the hip joint. It occurs once in every 1,000 live births. The hip joint is created as a ball and socket joint. In DDH, the hip socket may be shallow, letting the "ball" of the long leg bone, also known as the femoral head, slip in and out of the socket. The "ball" may move partially or completely out of the hip socket.

The greatest incidence of DDH occurs in first-born females with a history of a close relative with the condition.

What causes developmental dysplasia of the hip (DDH)?

Hip dysplasia is considered a "multifactorial trait." Multifactorial inheritance means that many factors are involved in causing a birth defect. The factors are usually both genetic and environmental.

Often, one gender (either male or female) is affected more frequently than the other in multifactorial traits. There appears to be a different "threshold of expression," which means that one gender is more likely to show the problem than the other gender. For example, hip dysplasia is more common in females than males.

One of the environmental influences thought to contribute to hip dysplasia is the baby's response to the mother's hormones during pregnancy. A tight uterus that prevents fetal movement or a breech delivery may also cause hip dysplasia. The left hip is involved more frequently than the right due to intrauterine positioning.

What are the risk factors for developmental dysplasia of the hip (DDH)?

First-born babies are at higher risk since the uterus is small and there is limited room for the baby to move; therefore affecting the development of the hip. Other risk factors may include the following:

• family history of developmental dysplasia of the hip, or very flexible ligaments
• position of the baby in the uterus, especially with breech presentations
• associations with other orthopaedic problems that include metatarsus adductus, clubfoot deformity, congenital conditions, and other syndromes

What are the symptoms of developmental dysplasia of the hip (DDH)?

The following are the most common symptoms of DDH. However, each baby may experience symptoms differently. Symptoms may include:

• the leg may appear shorter on the side of the dislocated hip
• the leg on the side of the dislocated hip may turn outward
• the folds in the skin of the thigh or buttocks may appear uneven
• the space between the legs may look wider than normal

A baby with developmental dysplasia of the hip may have a hip that is partially or completely dislocated, meaning the ball of the femur slips partially or completely out of the hip socket. The symptoms of DDH may resemble other medical conditions of the hip. Always consult your baby's physician for a diagnosis.

How is developmental dysplasia of the hip (DDH) diagnosed?

Developmental dysplasia of the hip is sometimes noted at birth. The pediatrician or newborn specialist screens newborn babies in the hospital for this hip problem before they go home. However, DDH may not be discovered until later evaluations. Your baby's physician makes the diagnosis of developmental dysplasia of the hip with a clinical examination. During the examination, the physician obtains a complete prenatal and birth history of the baby and asks if other family members are known to have DDH.

Diagnostic procedures may include:

• x-ray - a diagnostic test which uses invisible electromagnetic energy beams to produce images of internal tissues, bones, and organs onto film.
• ultrasound (Also called sonography.) - a diagnostic imaging technique which uses high-frequency sound waves and a computer to create images of blood vessels, tissues, and organs. Ultrasounds are used to view internal organs as they function, and to assess blood flow through various vessels.
• computed tomography scan (Also called a CT or CAT scan.) - a diagnostic imaging procedure that uses a combination of x-rays and computer technology to produce cross-sectional images (often called slices), both horizontally and vertically, of the body. A CT scan shows detailed images of any part of the body, including the bones, muscles, fat, and organs. CT scans are more detailed than general x-rays.
• magnetic resonance imaging (MRI) - a diagnostic procedure that uses a combination of large magnets, radiofrequencies, and a computer to produce detailed images of organs and structures within the body.

Treatment for developmental dysplasia of the hip (DDH):

Specific treatment for DDH will be determined by your baby's physician based on:

• your baby's gestational age, overall health, and medical history
• the extent of the condition
• your baby's tolerance for specific medications, procedures, or therapies
• expectations for the course of the condition
• your opinion or preference

The goal of treatment is to put the femoral head back into the socket of the hip so that the hip can develop normally.

Treatment options vary for babies and may include:

• Non-surgical positioning device or placement of a Pavlik harness
  The Pavlik harness is used on babies up to 6 months of age to hold the hip in place, while allowing the legs to move a little. The harness is put on by your baby's physician and is usually worn full time for at least six to eight weeks, then part-time (12 hours per day) for six weeks. Your baby is seen frequently during this time so that the harness may be checked for proper fit and to examine the hip. At the end of this treatment, x-rays (or an ultrasound) are used to check hip placement. The hip may be successfully treated with the Pavlik harness, but sometimes, it may continue to be partially or completely dislocated.

• casting
  If the hip continues to be partially or completely dislocated, casting or surgery may be required. 

• surgery
  If the other methods are not successful, or if DDH is diagnosed at age 6 months to 2 years, surgery may be required to put the hip back into place manually, also known as a "closed reduction." Children older than 2 years may require an "open surgery" to realign the hip, followed by spica cast. If successful, a special cast (called a spica cast) is put on the baby to hold the hip in place. The spica cast is worn for approximately three to six months. The cast is changed from time to time to accommodate the baby's growth and to ensure the cast's rigidity, as it may soften with daily wear. The cast remains on the hip until the hip returns to normal placement. Following casting, a special brace and/or physical therapy exercises may be necessary to make the muscles around the hip and in the legs stronger.
  
  

What is a short leg hip spica cast?

A short leg hip spica cast is applied from the chest to the thighs or knees. This type of cast is used to hold the hip in place after surgery to allow healing.

Cast care instructions:

• Keep the cast clean and dry.
• Check for cracks or breaks in the cast.
• Rough edges can be padded to protect the skin from scratches.
• Do not scratch the skin under the cast by inserting objects inside the cast.
• Use a hairdryer placed on a cool setting to blow air under the cast and cool down the hot, itchy skin. Never blow warm or hot air into the cast.
• Do not put powders or lotion inside the cast.
• Cover the cast during feedings to prevent spills from entering the cast.
• Prevent small toys or objects from being put inside the cast.
• Elevate the cast above the level of the heart to decrease swelling.
• Do not use the abduction bar on the cast to lift or carry the baby.

When to call your baby's physician:

Contact your baby's physician or healthcare provider if your baby develops one or more of the following symptoms:

• fever
• increased pain
• increased swelling above or below the cast
• drainage or foul odor from the cast
• cool or cold toes

Long-term outlook for a baby with developmental dysplasia of the hip (DDH):

While newborn screening for DDH allows for early detection of this hip condition, starting treatment immediately after birth may be successful. Many babies respond to the Pavlik harness, and/or casting. Additional surgeries may be necessary since the hip dislocation can reoccur as the child grows and develops. If left untreated, differences in leg length or a duck-like gait, and a decrease in agility may occur. In children 2 years or older with DDH, deformity of the hip and osteoarthritis may develop later in life. DDH can also lead to pain and osteoarthritis by early adulthood.

Source: Lucile Packard Children’s Hospital