Developmental dislocation of the hip (DDH): The abnormal formation of the hip joint in which the ball at the top of the thighbone (the femoral head) is not stable within the socket (the acetabulum). The ligaments of the hip joint may also be loose and stretched.
The degree of instability or looseness varies. A baby born with this condition may have the ball of the hip loosely in the socket (subluxed) or the ball of the hip may be completely dislocated at birth.
Untreated, the condition may cause legs of different lengths and a "duck-like" walk and lead to pain on walking and early osteoarthritis. There is a familial tendency. It usually affects the left hip and is more common in girls than boys, in first-born children and in babies born in the breech position. It is more common in Native Americans than in whites and is rarely seen in African-American children.
One of the early signs that a baby has been born with a dislocated hip may be a clicking sound when the baby's legs are moved apart. With a full dislocation, the leg "rides up" so it is shorter than its mate. The buttocks folds also may not be symmetrical with more creases on the dislocated side. When the child begins to walk, he or (more often) she may favor one side or limp, if the hip problem has not been diagnosed early and treated effectively.
The earlier the diagnosis is made, the better. The usual treatment is a device called the Pavlik harness, which has straps that allow the baby to move about freely while holding the hip in place and preventing movements that would make the condition worse. In most up to 97% of cases, the Pavlik harness is effective. If it is not, the hip may be positioned into place under anesthesia (closed reduction) and maintained with a body cast (a spica).