Congenital Hip Dysplasia
This condition is also known as hip dysplasia or developmental dysplasia of the hip (DDH).
The definition of DDH is not universally agreed upon. Typically, the term DDH is used in referring to patients who are born with dislocation or instability of the hip, which may then result in hip dysplasia. More broadly, DDH may be defined simply as abnormal growth of the hip. Abnormal development of the hip includes the osseous structures, such as the acetabulum and the proximal femur, as well as the labrum, capsule, and other soft tissues. This condition may occur at any time, from conception to skeletal maturity.
The cause of DDH is not clear. However, there are factors that are known to contribute to the chance of a baby being born with DDH. Only 1 in 75 babies with a risk factor have a dislocated hip.
Risk factors include:
Family history. If there is a parent, brother or sister with DDH then this makes it five times more likely than normal for a child to have DDH.
Gender. About 8 in 10 cases of DDH are female. This may be due to oestrogen (the female hormone) that is made by the female fetus (the unborn baby). This makes the ligaments stretchier and means that the bones are more likely to move out of position.
Pregnancy conditions. If there is only a small amount of fluid in the womb (uterus) this is called oligohydramnios. This can increase the risk of developing DDH because the baby is not able to move about within the uterus as much.
Breech position. If an unborn baby is in the breech position (feet down position in the uterus), this can put the legs in a position which increases the risk of DDH. Most breech babies are born by Caesarean section. These babies have a risk of DDH seven times higher than normal. (The risk of DDH for a breech baby delivered vaginally is 17 times higher than normal.)
Firstborn baby. About 6 in 10 cases of DDH occur in firstborn children. This may be because the uterus is tighter and less elastic than in future pregnancies so that the baby has less room to move.
Other abnormalities. If the baby has cerebral palsy, spinal cord problems or other nerve and muscle disorders, this increases the risk of developing DDH. DDH is also more common in premature babies or babies born weighing more than 5 kg.
Race. The risk of a child having DDH is much greater in certain races. For example, DDH is much more common in Native American children and much less common in Chinese and African American children. This may be due partly to the position that Native American babies are swaddled in.
More specific terms are often used to describe the condition more precisely; these are defined as follows:
- Subluxation – Incomplete contact between the articular surfaces of the femoral head and acetabulum
- Dislocation – Complete loss of contact between the articular surface of the femoral head and acetabulum
- Instability – Ability to subluxate or dislocate the hip with passive manipulation
- Teratologic dislocation – Antenatal dislocation of the hip
Early diagnosis is the most crucial aspect of the treatment of children with DDH. The use of ultrasonography and other diagnostic imaging modalities and the implementation of improved educational programs will most likely decrease the number of children with DDH who are diagnosed late. Newer, less invasive surgical techniques (eg, endoscopic techniques and image-guided surgery) are being developed in an effort to decrease the morbidity of surgery and to ease recovery.
Treatments available for DDH
Treatment is needed because if the head of the femur is left in an abnormal position then the hip joint develops abnormally. The earlier treatment is started after birth, the greater the likely success of treatment and the lower rate of long-term complications.
The goal of treatment is to relocate the head of the femur into the acetabulum. This then allows the structures of the rapidly developing hip joint (femur, acetabulum, supporting ligaments, etc) to become established normally. The treatment goal can be achieved through a variety of methods, depending on the age of your child. The success rate of simple non-surgical treatments reduces significantly after 7 weeks of age.
Commonly used treatments are as follows:
This is a device that is used to hold the hips in the correct position. It is often the first treatment used in children under 6 months old. It usually needs to be worn for at least six weeks full-time and six weeks part-time in young babies. Older babies may need to wear it for longer. During this time, ultrasound scans are usually done to check that the hip is in the correct position. This harness keeps the legs bent and turned outwards, but allows certain movements. It does not allow your child to straighten their legs or turn them inwards. The harness is adjusted as the child grows and as the hip stabilises.
For mild DDH (subluxation) this harness works in more than 9 in 10 children if used at this young age. In severe DDH (dislocation) the harness is effective in about 8 in 10 children. The main possible complication of the harness is called avascular necrosis. This is uncommon (about 2 in 100 babies treated with the harness) but sometimes occurs if the hip is not held in the correct position. (Avascular necrosis means that the bone tissue at the head of the femur dies due to undue pressure on the blood supply to the bone.)
Closed reduction and hip spica
This method is used in children over 6 months of age, or if the Pavlik harness is not effective. This involves your child being given an anaesthetic. While they are anaesthetised, the doctor positions the hip the correct way and then applies a special cast or plaster to keep the hip in the right position. The position of the hip is confirmed as correct by an MRI or CT scan done after the procedure. This cast is kept on for at least 12 weeks.
If the above options fail or your child is much older when DDH is diagnosed, then an operation is needed. The operation involves loosening the tendons around the hip and removing anything that is stopping the hip from moving freely. Once the bones are in a good position, the joint is strengthened.
Other types of surgery
If DDH has not resolved by 18 months, more complicated surgery is required. This involves removing some parts of the bone and joint so that the hip can be kept in the right position.
What if developmental dysplasia of the hip is not treated?
If your child’s DDH is not diagnosed and treated early, they may develop early arthritis of the hip joint. This causes pain and reduced movement. The treatment of DDH gets more complex and with less chance of success once your child’s bones have fully developed. Even at this stage though, treatment can still provide a long-term outcome which is better than the alternative of no treatment.
What is the outlook (prognosis)?
Most children who are diagnosed early and treated before the age of 6 months have an excellent outcome. However, they will usually need to be reviewed with X-ray pictures taken throughout childhood until their bones have fully developed. The outlook is less good if the diagnosis or treatment is delayed, especially if the child has begun to walk before DDH is diagnosed. About 3 in 10 hip replacement operations done in people under the age of 60 years are because of DDH (either untreated, unsuccessfully treated, or delayed in treatment).
Making a claim for misdiagnosis of DDH
DDH claims involve the failure to timely diagnose and treat hip dysplasia and are typically brought against hospital paediatricians or general practitioners who negligently fail to detect the condition at an early stage so that appropriate treatment can be commenced. Diagnosis at birth in hospital or at 8 weeks by the GP is best because if it is detected early it can usually be dealt with with simple, non-invasive treatment. Checks are also carried out by health visitors at 8-9 months and 2yrs. A delay in the diagnosis of hip dysplasia may result in unnecessary surgery and disability over the lifetime of the child.