What is Developmental Dysplasia of the Hip (DDH)?

Developmental Dysplasia of the Hip (DDH) is a term used to describe hip joints which are loose or unstable in babies or children due to abnormalities with the development of the hip joint.
This condition was previously known as Congenital Dislocation of the Hip (CDH). DDH is now used to describe this condition as it not only occurs at birth but can develop as the child grows.

The normal hip joint

The normal hip joint consists of the head of the femur bone which is held in place by the acetabulum (a cup-like structure on the pelvis). This forms a ball and socket joint which is normally held tightly in place by surrounding ligaments and joint capsule (refer to diagram)

What happens in DDH?

In DDH, the head of the femur and the acetabulum are not in the usual close contact with each other. This is due to abnormalities in the head of femur or the acetabular surface or the surrounding structures. As a result, the hip joint becomes unstable. There are varying degrees of instability depending on the extent of the abnormalities of the hip joint structures. The abnormalities can cause mild subluxation to even complete dislocation of the hip (refer diagram)

Who gets it?

DDH occurs in about 1 in 1000 babies. This condition is more common in girls and is usually present at birth but may occur later on. The left hip is more commonly affected though both hips can be affected at the same time.

What causes DDH?

The exact causes are not known though this condition is understood to be a developmental or formation problem with the hips.
Several factors however are associated with a higher risk of developing DDH:

• Family history of DDH
• Gender (Female)
• First born
• Pregnancy conditions in the mother such as Oligohydramnios (insufficient amniotic fluid in the uterus)
• Breech position in the uterus
• Other medical conditions such as cerebral palsy, nerve or muscle problems in the baby

What are the symptoms of DDH?

Babies who are born with DDH will not be in pain or appear distressed. This condition is often detected by the doctor who examines the hips of a newborn baby soon after birth.
Other signs which indicate a hip problem in babies are:

• A shorter leg on the side of the affected hip
• An abnormal position of the affected leg with the leg turned outward
• Uneven skin folds over the thighs or buttocks

In older children, signs may include:

• A difference in leg length
• Walking with a limp

How is it diagnosed?

If a baby is suspected to have instability of the hips from a clinical examination, an ultrasound of the hip will be ordered to assess the hip joints better. In older children, hip x-rays are more helpful to help diagnose the condition.

What is the treatment for DDH?

Treatment of this condition ranges from simple observation (watchful waiting) to bracing/harnessing or surgery.
The goal of treatment is to relocate the head of femur back into the correct position thereby allowing normal development of the hip joint. The earlier treatment is initiated, the higher the chance of success and the lesser the likelihood of long term complications.
 If your child is suspected to have an unstable hip, please consult your doctor as soon as possible.

What is the prognosis?

If DDH is not treated or if there is delay in diagnosis/treatment, this may lead to early arthritis of the hip joint which causes significant pain and restriction in hip movements. In addition, delay in treatment will also make subsequent treatment more complex and lessen the chances of success.
Most babies who are diagnosed early and treated before 6 months will generally have a good outcome. The outlook is less good for children who are diagnosed only after they start walking.