Hip Dysplasia

Developmental dysplasia of the hip is an abnormal formation of the hip joint in which the ball at the top of the thighbone (femoral head) is not stable in the socket (acetabulum). The hip is a ball and socket joint, and dysplasia can refer to a hip that is subluxatable (unstable if stressed), dislocatable (can come out of socket under stress), or currently dislocated. The severity of instability or looseness varies in each patient. Newborns and infants with DDH may have the ball of his or her hip loosely in the socket, or the hip may be completely dislocated at birth. Developmental dysplasia of the hip (DDH) may occur during fetal development, at delivery, or after birth.

What Causes Hip Dysplasia/DDH?

The exact cause of DDH is unknown, but research has discovered several theories and risk factors for hip dysplasia.

The four F's of DDH:

• First born
• Female
• Foot First (breech)
• Family history

In the United States, the overall incidence of DDH is approximately 3-4 per 1,000 live births. There is often a genetic component, or familial tendency. Anything that causes cramping or crowding of the fetus inside the uterus (large birth weight, oligohydramnios, decreased amniotic fluid) is thought to cause an increased incidence of DDH. More significant risk factors for DDH include female gender, first born babies, and babies born in the breech position. Hip dysplasia is approximately 5-9 times more common in females than males. In addition, DDH affects the left hip more often than the right hip (approximately 60% affect only left hip, 20% only right hip, and 20% are bilateral.) Finally, it is thought that there is a slightly higher incidence of DDH when other orthopaedic (torticollis, metatarsus adductus, clubfoot) or connective tissue disorders (Larsen syndrome) are present.

What Are the Signs and Symptoms of DDH?

Neonatal Examination: Every newborn will be screened for signs of hip instability. Most commonly, DDH is diagnosed by physical examination in young infants. To test for hip instability, the provider will move the hip around to feel and palpate for a "clunk" as the femoral head slides out of the acetabulum (pelvis). In early infancy, instability is the most reliable sign for DDH. If DDH is suspected based on the physical examination, or if there are several risk factors (female, first born, breech position) a screening hip ultrasound can be performed. It is usually preferred to wait until 4-6 weeks of age to perform screening ultrasounds to decrease the incidence of false positives.

The signs of DDH change will change as the infant grows. There will sometimes be asymmetrical thigh and buttock skin folds or creases. In addition, the legs may appear to be different lengths. The hip may also have a decreased amount of motion, and the toddler or child may walk with an abnormal gait or limp.

What is a hip ultrasound?

Hip ultrasounds are used to detect DDH in newborns and young infants. The ultrasound can accurately determine the stability of the hip joint, and can be useful in the diagnoses and management of DDH. By using high frequency sound waves, there is no risk of radiation exposure to the baby. Because many of the bones making up the hip joint are made of soft cartilage, not hard bone, plain x-rays are generally not helpful until the baby is 5-6 months old. Ultrasound enables direct imaging of the cartilaginous portions (bones that are not yet ossified) of the hip that cannot be seen on plain radiographs.

Treatment

Once the diagnosis if DDH has been made, the treatment will depend on the age of the child and the degree of instability.

What is a Pavlik harness and when is it used in DDH?

If the ultrasound shows that the hip is subluxating, dislocated, or that the acetabulum is shallow (decreased femoral head coverage), the initial treatment may consist of a Pavlik harness. The Pavlik harness is often used as the initial treatment of hip dysplasia in infants. It is a soft dynamic brace that maintains the hip in flexion (knee up towards the head) and abduction (knee away from the centerline). This position maintains the proper position of the femoral head and allows for "tightening up" of the ligamentous structures as well as for stimulation of normal formation and deepening of the hip socket.

The Pavlik harness is successful in approximately 90-95% of infants with hip dysplasia. The Pavlik harness is usually needed for approximately 6-12 weeks, as long as there is continued improvement seen on serial hip ultrasounds. If there is no improvement seen, the Pavlik harness will be discontinued, and it will be necessary to proceed with closed reduction and spica body casting (done in the operating room). Pavlik harnesses are ordinarily the first line of treatment for DDH in newborns and infants under six months of age.

How do I care for the Pavlik harness?

The Pavlik harness will initially be adjusted at frequent intervals. The harness will be marked with a pen on the leg straps and both shoulder straps, and you should not make any adjustments. The Pavlik is designed so that you can change the baby's diaper without having to remove the harness. The harness can be removed for bathing, and can be washed and dried if necessary. Washing of the harness should be done by hand with a gentle detergent, and then allowed to drip dry. For faster drying, the harness can be put in the dryer on ‘air fluff – no heat.’

What if the Pavlik harness does not correct the hip dysplasia?

If there is no improvement in the hip dysplasia with the Pavlik harness, the baby will most likely require a closed reduction and spica casting in the operating room. Once the hips are placed in the correct position, a hard fiberglass body cast is applied. The spica cast will remain on for approximately total of three months. At approximately six weeks, we will remove the spica cast, a new ultrasound will be done to confirm improvement, and a new spica cast will be applied.

What are other treatments for DDH?

If the hip dysplasia cannot be corrected with the Pavlik harness or closed reduction and casting, it may be necessary to proceed with open reduction and spica casting. It may also be necessary to perform a pelvic or femoral osteotomy (cut of the bone) to correct the DDH. The open reduction requires an incision to correct the hip dysplasia. Structures that are obstructing the hip from being reduced are removed or corrected, and a full spica body cast is applied post-operatively for six-twelve weeks. The older the infant or child is at the time of diagnosis, the more likely he/she will require operative intervention to correct the dysplasia.

How long will my child be followed for developmental hip dysplasia?

Generally follow-up appointments occur at 6 months, 12 months, 2 years and 4-5 years. While the frequency of follow-up will depend on the specific treatment, we will often follow your child through the end of growth (skeletal maturity). Clinical examination and follow-up radiographs (x-rays) will be taken to assess the development and growth of the hips over time.