Developmental Dysplasia of the Hip

Question

Answer

DDH is multifactorial. Many factors may contribute to DDH. These factors include:

• Malpositioning or mechanical factors in utero.
• Hormone-induced ligamentous laxity. This is one of the reasons we see DDH more in females because they're more responsive to hormonal levels (e.g., relaxin, estrogen) in their mother. There may be some degree of ligament hyperlaxity related to those hormones that result in instability of the hip.
• Genetics. If someone in your family had hip dysplasia, you're more likely to have hip dysplasia.
• Cultural or environmental factors. There are some cultures in which women carry children in flexion external rotation and abduction, which helps position the femoral head directly in contact with the acetabulum. However, in some cultures, children are swaddled with their hips and knees in extension and limited abduction. At that point, you're putting that hip at risk because it's not in good contact with the acetabulum. If you keep doing that on a regular basis, that predisposes a child to develop hip dysplasia.
• Concurrent pathology 

DDH in infancy is the most common abnormality in the neonate. One out of 20 full-term babies has some degree of instability. Two to three out of 1000 babies will need therapy. There are several risk factors associated with DDH in otherwise healthy children, including:

• Sex (female; related to hormonal response)
• Genetics (parents or siblings)
• Race and ethnicity (non-black)
• Intrauterine position (breech; higher birth weight)
• Maternal age (older than 35 years)
• Oligohydramnios
• Clicking hips on clinical exam
• Postural deformities (torticollis; lower extremity deformities)

Of the above factors, the most critical risk factors are: being female, positive family history, race/ethnicity, and intrauterine position.