The acetabulum is the cup-shaped part of the pelvis, where the head of the femur meets the pelvis, forming the hip joint. Hip dysplasia is a condition wherein the acetabulum is inadequately developed, and remains shallow and dish shaped, instead of the usual cup-shaped. Congenital hip dysplasia (CDH) is a condition that exists at the time of birth of the baby, whereas developmental dysplasia of the hip (DDH) is seen in children that are born with apparently normal hips, but develop the problem within the first year of their life.
The first noticeable symptom of hip dysplasia is a clicking in the joint during movement. Additional symptoms include pain in the joint during activity, a noticeable limp, difference in the length of the legs. X-ray of the hip bones in suspected individuals can clearly diagnose the condition. If diagnosed before the age of 6-months, the main aim of treatment would be to fix the hip in a correct position, usually using a device called a Pavlik Harness. Children diagnosed later than 6-months, need a more prolonged form of treatment, but can still expect to have a good prognosis. Children diagnosed and treated later than 1-year of age may require surgical correction, and prognosis may not be as good as in those diagnosed earlier. The factors that play a role in the development of DDH include race, female sex, being the first born child, and breech delivery.
An underlying genetic disposition has been noticed in DDH. A 10-fold increase in the frequency of hip dysplasia has been seen to occur in children whose parents also had DDH. Recent research has shown a linkage to chromosome 13q22 for familial hip dysplasia, although it is not yet clear what genes are involved.