Developmental Dysplasia of the Hip (DDH)
The hip is a "ball-and-socket" joint. In a normal hip, the ball at the upper end of the thighbone (femur) fits firmly into the socket, which is part of the large pelvis bone. In babies and children with developmental dysplasia (dislocation) of the hip (DDH), the hip joint has not formed normally. The ball is loose in the socket and may be easily dislocate.
Although DDH is most often present at birth, it may also develop during a child's first year of life. Recent research shows that babies whose legs are swaddled tightly with the hips and knees straight are at a notably higher risk for developing DDH after birth. As swaddling becomes increasingly popular, it is important for parents to learn how to swaddle their infants safely, and to understand that when done improperly, swaddling may lead to problems like DDH.
In all cases of DDH, the socket (acetabulum) is shallow, meaning that the ball of the thighbone (femur) cannot firmly fit into the socket. Sometimes, the ligaments that help to hold the joint in place are stretched. The degree of hip looseness, or instability, varies among children with DDH.
- Dislocated. In the most severe cases of DDH, the head of the femur is completely out of the socket.
- Dislocatable. In these cases, the head of the femur lies within the acetabulum, but can easily be pushed out of the socket during a physical examination.
- Subluxatable. In mild cases of DDH, the head of the femur is simply loose in the socket. During a physical examination, the bone can be moved within the socket, but it will not dislocate.
In the United States, approximately 1 to 2 babies per 1,000 are born with DDH. Pediatricians screen for DDH at a newborn's first examination and at every well-baby checkup.
What causes Developmental Dysplasia of the Hip (DDH)?
DDH tends to run in families. It can be present in either hip and in any individual. It usually affects the left hip and is predominant in:
- Firstborn children
- Babies born in the breech position (especially with feet up by the shoulders). The American Academy of Pediatrics now recommends ultrasound DDH screening of all female breech babies.
- Family history of DDH (parents or siblings)
- Oligohydramnios (low levels of amniotic fluid)
What are the symptoms of Developmental Dysplasia of the Hip (DDH)?
Some babies born with a dislocated hip will show no outward signs. Contact your pediatrician if your baby has:
- Legs of different lengths
- Uneven skin folds on the thigh
- Less mobility or flexibility on one side
- Limping, toe walking, or a waddling gait