Congenital Hip Dislocation (also called developmental dysplasia of the hip)

 

Condition Description

Congenital hip dislocation, now most often called developmental dysplasia of the hip, is the name of a variable problem involving abnormal formation of the hip joint during fetal life and infancy. Instability of the hip socket results, which is a condition that is sometimes detectable at birth. However, in some infants, the dysplasia is not detectable until a bit later in infancy. The hip joint is rarely dislocated at birth but laxity in the joint and a shallow, undeveloped hip socket causes a potential for dislocation as the baby grows. This is an ongoing process of hip development that has many subtle variations. It is an inherited condition and is also thought to be influenced by the baby's maternal hormones. In some cases, the position of the baby in the womb is the cause (i.e. breech-birth babies are more prone to hip problems).

Most babies simply have looseness of the ligaments (fibrous bands that connect bones to joints) and the hip is thus able to slip out of position. Hormones from the mother are thought to further loosen the ligaments.

All babies' hips must be examined for hip dysplasia after birth and at their early check-ups using 2 maneuvers (the Barlow test and the Ortolani test) where the examiner will push on the baby's bended legs to determine how mobile the joint is and to see if it will "clunk" out of place.

Prevalence

Looseness of the ligaments of the hip joint occurs in 1 of 100 live births (a "hip click"), but only 1 of 800 babies has hips that truly dislocate (a "hip clunk"). Females are affected 9 times more often than males, and 20% of hip problems will occur in babies born in the breech position (hips first instead of head-first in the birth canal). It is somewhat more common in first-born children.

Common Associated Conditions

Associated conditions include congenital torticollis ("wry neck"), metatarsus adductus (toes bent inward) or talipes equinovarus (clubbed feet).

Short-Term Treatment and Outcomes

If there is a "click" on the Barlow or Ortolani maneuvers, an x-ray will be needed to examine the shape of the hip joint (the acetabulum). After 2 months of age these tests are no longer helpful, so the leg lengths will be checked and the thigh creases examined for symmetry. X-rays done early can also be hard to read because cartilage (not visible on x-rays) gradually converts to bone (that is visible on x-ray). X-rays will have to be repeated to follow the ossification (bone formation) process. A hip ultrasound will be most helpful after 4 months of age.

Treatment aims to keep the head of the thigh bone (femur) tightly positioned in the hip joint (acetabulum) for about 2 months so that the hip joint will form a normal cup-shape and the head of the femur will be a round, smooth ball that fits nicely in that socket. Most commonly used is a device called a "Pavlik Harness" that keeps the baby's legs bent and brought up towards the baby's body. The baby will quickly adjust to being in that somewhat awkward position, and parents will learn how to diaper, bathe and hold the baby while maintaining this position. The harness will be used until x-rays or ultrasounds are normal, perhaps a couple of months. This treatment is very successful in most children.

Long-Term Treatment and Outcomes

In some babies, hip problems are hard to detect in the early days and weeks, and sometimes the Pavlik harness is not sufficient to cause the proper development of the joint. Those babies will require surgical repair of the hip joint (osteotomy). Surgery later in life may also be necessary if the hip joint does not develop into a smoothly functioning joint. Plaster casts will be used for weeks or months following surgical repair (called hip spica cast). While uncomfortable, children can adapt to these casts and find ways to be mobile.

A hip replacement is sometimes needed in late middle-age. Arthritis, a painful limp, and leg shortening can later occur. Periodic follow-up with an orthopedic specialist might be necessary if the hip causes discomfort or gait problems. However, most hip problems are corrected in infancy with excellent outcomes.

Common Complications

Complications include malformation of the hip socket despite treatment. If not treated, dislocation will occur when the child starts to walk, causing twisting of the thigh bone (called femoral anteversion) and shortening of the hip muscle (contractures). Walking with a dislocated hip will lead to a waddling gait with in-toeing, pain, arthritis, unequal leg length and decreased mobility. Lordosis ("sway back") can also result from uncorrected hip dislocation.

Implications for Children's Development

Screening babies at their early examinations detects most hip problems, and the correction usually occurs very early in life before a baby is aware of the problem. They quickly become used to the harness, and using the harness does not generally affect the timing of the child's learning to walk. If the hip is very difficult to correct and multiple surgeries are required, and if other conditions affect the neck or feet, the baby may have some delays in gross motor development (walking, running, coordination of large muscles). Special orthotic devices in the shoes might be needed later in life to assist with a comfortable gait.

Reliable sources of information and support for parents are available online.