DEAR DOCTOR K: My baby has developmental dysplasia of the hip. How will it be treated?
DEAR READER: Because I'm not a pediatrician, I haven't seen a baby with developmental dysplasia of the hip since I was in medical school. But I talked with pediatrician colleagues here at Harvard Medical School and refreshed my memory.
Our hips are designed to support our full weight while allowing movement in all directions. To accomplish this, the rounded top of the thigh bone (femur) fits into a cup-shaped socket in the pelvis called the acetabulum. The “ball” of the femur sits inside the socket. (I've put an illustration of the hip joint on my website, AskDoctorK.com.)
In developmental dysplasia of the hip, the ball at the top of the femur moves in and out of the socket either partway or all the way. That's not supposed to happen: It makes the hip unreliable in supporting the baby's weight.
The ball of the femur slips in and out of the socket because the ligaments that hold the two bones together are very loose or because the cup-shaped socket is not deep enough. This condition usually is present at birth, but it can develop after birth, during infancy or childhood. In about 20 percent of children, it affects both hips.
The condition is more common in babies who were breech deliveries. It also seems to run in families. It happens more often in little girls than in little boys, and more often in firstborn infants. We don't know why.
Doctors routinely check for developmental dysplasia of the hip in newborns and at follow-up well-baby visits. If the doctor feels unusual movement of the hip, he or she will use ultrasound or X-rays to confirm the diagnosis.