The hip joint is a ball-and-socket joint in which the ball (femoral head) articulates with a socket (acetabulum). Normally, the socket is deep and cup-shaped.
Developmental Dysplasia of the Hip’ (DDH) is a condition in which the socket fails to develop normally and is shallow like a saucer. It occurs with a frequency of 1 in 1000 live births.
This leads to instability of the hip joint. This instability may be of varying severity:
• Dysplasia: The socket is shallow, but the ball is still within the socket.
• Subluxated: The ball is partially outside the socket.
• Dislocated – The ball is completely outside the socket.
Risk factors for DDH:
Factors that increase the risk of a child having DDH include:
• Breech position: When the baby is delivered legs first instead of head first
• Family history: When either one of the baby’s parents had suffered from DDH during childhood, their baby is 12 times more likely have DDH.
• Intra-uterine overcrowding: This can occur in cases of twin pregnancy, oligohydramnios and uterine malformations.
• Unsafe swaddling practices: Cultures where babies are swaddled after forcible holding the hips in extension have higher incidence of DDH.
• DDH is much more common is girls, eight out of every ten cases of DDH are seen in baby girls. Six out of every ten cases are seen in first born children.
DDH is painless. Hence it very often goes undiagnosed in infancy unless a child is specifically examined for it. In infancy, parents may note tightness and difficulty in spreading the hips during diaper change. Asymmetric thigh skin folds may also be noted in unilateral DDH.
Suspicion of an abnormality is usually raised only when the child starts to walk. The child walks with a limp. One of his/her legs appears to be shorter than the other, and the child may walk on the toes on the shorter side to compensate. When both the hip joints are dislocated, the only sign may be that the child walks like with a limp i.e. leaning over from side to side while walking.
An orthopaedic surgeon can usually make a diagnosis of DDH after examining the child’s hip joints. On clinical examination, asymmetric thigh skin folds, hip adductor tightness, +ve telescopy sign, +ve Ortolani and Barlow signs (in reducible DDH), limb length discrepancy and Trendelenberg gait during walking are noted.
Diagnosis of DDH is confirmed in children smaller than 4 months by performing an Ultrasonography. In older children, an x-ray is sufficient to confirm the diagnosis.
DDH is painless during childhood. However, if it remains untreated, as the child grows older, the abnormal walking puts a strain on other parts of the body. Eventually, they develop pain in the back and knees.
Treatment for DDH is simpler the earlier it is done. Older children require more complicated surgeries and have poorer results.
Treatment of DDH depends on the age at which it is diagnosed.
Up to 6 months:
In infants this small, treatment consists of a brace known as a Pavlik harness. This is a soft brace made of fabric, that is fastened into position with Velcro straps. It acts by gently keeping your baby’s legs in a position that allows the hip to get back into the joint. The brace is very easy to apply. And quite comfortable, as your baby is free to kick and move around in it. You can also change your baby’s diaper and clean him while the brace is in place.
For treatment with the Pavlik harness to be successful, it is very important that you keep it applied all the time. Repetitively removing and re-applying the brace is an important cause for failure.
During the initial few weeks, the brace must be worn 24*7. Your doctor will get repeat sonographies of the hip done, with the baby in the harness, usually once in one or two weeks, until the hip joint is back in position and stable. After this, he/she will advise you to reduce the number of hours in the brace gradually over a few weeks until it is discontinued completely.
If treatment with the Pavlik harness is unsuccessful, your baby may need to be treated as for slightly older children (see below)
6 months to 1 year:
Children seen at this stage are usually treated by something called ‘arthrogram and closed reduction’. This is done under anaesthesia in the operation theatre. Once your baby is asleep, the surgeon gently attempts to restore the dislocated hip back into the joint. He/she checks the stability of the reduced joint by moving it in different directions. He/she will also inject a dye into the hip joint and take X-rays to confirm that the hip is in a good position. If this is successful, a body cast known as ‘hip spica’ is applied. This is a plaster that extends from the waist down, including the entire leg on the affected side, and up to the knee on the normal side. This cast will remain for two months, changed once in between. After the first spica has been applied, a CT scan or MRI may be obtained to confirm the position of the hip joint.
Closed reduction means that the joint has been reduced without actually opening it. This is not always possible however, especially in older children. When closed reduction fails, or if your doctor feels it is unlikely to be successful, he/she will advise ‘open reduction’ (see below).
Older than 1 years:
In children older than 1 years, open reduction is usually necessary. In this, with your child under anaesthesia, your surgeon will make an incision in the groin and open up the hip joint. He/she will then see what is stopping the hip from getting reduced, usually fat and fibrous tissues and tight muscles. These obstructions are removed and the joint is reduced. Often the joint reduces but does not remain stable, because the shape of the femur or acetabulum or both are abnormal. In such cases, the surgeon will cut the femur and change its direction and/or cut the acetabulum and make it deeper. Sometimes, a small piece of bone must be removed from the femur to shorten it and make the reduction more stable.
After this surgery also, a hip spica cast is applied, usually for two months.
The above is only an outline to the approach to treatment of a child with DDH. Actual treatment depends on many factors and not just the age of the child.