What is hip dysplasia?
Hip dysplasia is the name given to a variety of related developmental hip problems that can affect babies and children from birth onwards. The exact definition used by your doctor is associated with how the condition presents itself. You may have heard your doctor using one of the following terms:
- Congenital hip dislocation – meaning the hip is completely dislocated at birth
- Congenital dislocatable hip – where the hip is not dislocated at birth, but becomes completely dislocated when stressed
- Congenital subluxatable hip – where the hip is not dislocated at birth but becomes partially dislocated when stressed
- Acetabular dysplasia – where the hip socket is not deep enough to keep the hip joint stable
- Developmental dysplasia (or dislocation) of the hip – where a baby is born with apparently normal hips but develops problems by one year of age
Signs and symptoms of hip dysplasia in children
Hip dysplasia is usually spotted by your child’s doctor during the first examination after birth. The doctor will move your child’s legs at the hips or knees to feel for a “hip click” or a “hip clunk”. An Ortolani test (where the thighs of your child are spread apart) or the Barlow test (where the knees are brought together) assists your doctor in identifying a “hip click” from a “hip clunk”. A clunk is indicative of instability in the hip.
If your child is an older infant, the following signs may lead your doctor to believe hip dysplasia is present:
- Tightness in the hips which makes it difficult to spread your child’s thighs
- Differences (asymmetry) in the skin creases in the groin or buttocks
- A difference in leg lengths
By the time your child reaches the age of one, they may have developed a limp. As the condition is not linked to pain, the problem can be overlooked and go undiagnosed. However, in adulthood, problems such as arthritis and pain in the hips can develop.
Common causes of hip dysplasia
In general about four children in every 1,000 live births are born with hip dysplasia. It is known to be more common in Laplanders and American Indians. It also tends to run in families and affects girls and first born children more commonly. This indicates that genetics may play a part.
Despite this, doctors are still not completely certain about the exact cause of hip dysplasia, but the following factors are thought to play a part:
- The presence of a hip click
- Being born in the breech position
- A family history of hip dysplasia
- Sternomastoid torticollis (wry-neck)
- Foot deformities
- A lack of fluid in the uterus during pregnancy
There are also certain environmental factors that may increase the risk of your child developing hip dysplasia:
- Swaddling your baby
- The use of a cradleboard
When a baby is swaddled or put on a cradleboard, it causes the hips and legs to be in an extended position for long periods. It has been shown that there is a higher incidence of hip dysplasia in cultures that take part in these practices, compared to cultures which have a low incidence and wear their babies on their backs. These findings indicate that it is beneficial to keep a child’s legs and hips spread apart versus keeping them extended.
The hormone, oestrogen, which is present in high levels in your baby after birth, can cause the ligaments to relax. Babies who are particularly sensitive to oestrogen may develop an unstable hip due to this slackness of the ligaments.
Diagnosing hip dysplasia
There is a screening test available now that uses an ultrasound machine to check for hip dysplasia in newborns. This is preferable to performing an x-ray which involves radiation exposure and is also known for being inaccurate for diagnosing hip dysplasia.
The ultrasound scan helps to look at the following:
- The location of the ball part of the leg bone (the femur) that sits within the socket of the hip
- The depth of the socket
- The stability of the hip whilst under stress
This type of test is considered safe as there is no risk of radiation to the baby. It is usually recommended for infants deemed at risk of hip dysplasia, and is usually performed at 4 to 6 weeks of age.
Treating hip dysplasia
When treating hip dysplasia, the main goal is to get the hip into a good position. The hips are then fixed in that position for a period of time.
From the age of 4 months up to 6 months, a device called a Pavlik harness is usually fitted. There are some less commonly used harnesses called the Frejka pillow and the Ilfeld splint but in general, the Pavlik harness has become the standard approach for treating hip dysplasia in babies.
The harness is fitted at your child’s shoulders, with straps that attach to stirrups for the feet. When your child’s feet are in the stirrups, their hips are kept in an ideal, open position that allows a degree of movement within a safe range. This restriction allows the ball at the end of the thigh bone to move within a limit inside the hip socket, and this helps to shape and deepen the socket as your child grows.
Sometimes the harness may be fitted at birth, and in this case it is worn full time for 6 weeks until the hip is stabilized. It remains in place for a further 6 weeks during weaning. The length of the time the harness must be worn for can vary depending on when treatment is started. Your doctor will advise you on what is appropriate for your child.
In some cases, if a child is older than 6 months, the Pavlik harness may not be fully successful and surgery may be required. Surgery involves the child going under general anaesthetic so that the doctor can manipulate the ball at the end of the thigh bone back into the hip socket. This technique is called a closed reduction.
If a child is older than one year, a closed reduction may not be possible and an open reduction may be required. This involves making an incision so that the doctor can access the hip directly to reinforce the socket. There is a chance that after surgery, the hip could dislocate again. If this happens, further and more drastic surgery may be required to correct the abnormalities. This surgery may be a pelvic or femoral osteotomy (or both).
After surgery, your child may need to be in traction for a period. They will also be placed in a cast called a hip spica cast for around 3 months after surgery. After this, your child is provided with a removable hip abduction brace which should be worn for a further 3 months. Your doctor will advise you on the exact timescales depending on your child and the surgery they have had.