Developmental Dysplasia of the Hip (DDH) is the medical term for a spectrum of disorders of hip instability. It is associated with a number of risk factors including female gender, first born baby, breech presentation and a first degree relative (parent or sibling) with DDH, but can also occur in the absence of these. DDH has a wide range of severity and the investigation and management will depend on any risk factors and the findings when your paediatrician examines your baby’s hips. Early detection of DDH is vital as management with bracing allows the hip joint to develop normally in most cases. If it is left untreated the hip joint can develop abnormally and surgery may eventually be required.
The hip is a “ball and socket” joint that is held together by ligaments. The ball is called the femoral head and the socket is called the acetabulum. The femoral head fits into the acetabulum and the joint is held in place by the surrounding ligaments and capsule. Hip instability occurs when the femoral head is able to move outside the acetabulum (dislocation) or to move abnormally within the acetabulum (subluxation).
A “click” refers to a click or pop that occurs when the baby’s hips are being examined. There are many ligaments inside the joint that can cause a click when the hip is moved but a click can also be a sign of hip subluxation. Having a click does not necessarily mean that the baby has DDH, but may lead to further investigation depending on the rest of the clinical picture.
A “clunk” refers to the feeling of the hip joint dislocating when it is examined.
Asymmetrical buttock creases can sometimes suggest DDH but asymmetrical thigh creases are rarely a sign of DDH if the buttock creases are normal. Careful clinical examination of the hip remains the most important way to detect DDH.
When your paediatrician examines your baby, they will look for any obvious instability of the hip as well as “clicks”, “clunks” and asymmetrical creases. If these are present, or if there are risk factors in a baby with normal hips, your paediatrician may either organise a hip ultrasound after you leave hospital and/or refer your baby to a paediatric orthopaedic specialist (an expert in managing DDH). Sometimes, several ultrasounds will be needed to make sure the hip is developing normally over time.
Since DDH can develop after the immediate newborn period, all babies with normal initial examinations should have their hips regularly examined by their family doctor and Maternal and Child Health Nurse during the first year of life.