Developmental dislocation of the hip (DDH) is a condition primarily affecting newborns and children. It 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). Also, the ligaments of the hip joint may be loose and stretched. The degree of instability or looseness varies. A baby born with DDH may have the ball of his or her hip loosely in the socket. The looseness may worsen as the child grows and becomes more active, or the ball may be completely dislocated at birth. Left untreated, DDH leads to pain and osteoarthritis by early adulthood. It may cause legs of different lengths or a "duck-like" walk and decreased agility.

Causes
The exact cause of developmental dysplasia of the hip is not known. However, there are a number of risk factors that increase a child's chances of having DDH. The condition tends to run in families. It usually affects the left hip and is predominant in girls, first born children, and babies born in the breech position (especially with feet up by the shoulders). The American Academy of Pediatrics now recommends ultrasound screening of all female, breech newborns.

Symptoms
Although some dislocated hips show no signs, contact your pediatrician if your baby has legs of different lengths, uneven thigh skin folds, or less mobility or flexibility on one side. In children who have begun to walk, limping, toe walking and a waddling "duck-like" gait are also signs of DDH.

Treatment
Treatment depends on the child's age.

Newborn: An unstable hip recognized at birth is treated with a soft, simple positioning device (Pavlik harness) for 1-2 months to keep the hip bone in its socket. This may help tighten ligaments and stimulate normal hip socket formation.

1-6 months: Treatment to reposition the hip ball in the socket uses a harness or similar device. The method is usually successful; if it is not, the joint may be positioned into place under anesthesia (closed reduction) and maintained with a body cast (spica).

6 months-2 years: Manipulation of the socket under anesthesia (closed reduction) is the major method of treatment. Open surgery may be necessary. Both require a body cast (spica).

After 2 years: Deformities may have become severe, making major open surgical intervention necessary to realign the hip. This is followed by a body cast (spica).
The child will need a body cast and/or brace to keep his or her hip bone in the joint while healing after operations. Periodic X-rays and other regular monitoring follow-ups are needed after DDH treatment until the child's growth is complete. Complications may include a small delay in the development of walking abilities if the child uses a cast. Positioning devices may cause skin irritation, and a difference in leg lengths may remain. Growth disturbance of the upper thigh rarely occurs.

If dysplasia is treated successfully - and the earlier the better -- children end up with normal hip joint function, have no further problems and go on to lead active lives.