Developmental dysplasia of the hip (DDH or hip dysplasia) is a relatively common condition in the developing hip joint, affecting around one in one hundred babies. Around one in 1,000 babies have DDF that requires treatment.
Developmental dysplasia of the hip (DDH) is an abnormality in the development of the hip. It can happen before birth, during the birth process or it can happen later.
Dr Eissa Al Hemrani, Consultant Paediatric Orthopaedic Surgeon, Dubai Hospital, DHA, says that, generally, there are two types of DDH.
“The typical type of DDH is when there is no known cause to find in the child. The second type of DDH, is related to disease in the child (neuromuscular or syndrome-related),” he says.
“The second type of DDH usually develops before birth and is more difficult to treat. It is usually related to an abnormality in the nerves, muscles or bones and it can lead to a more complex form of hip dysplasia.
The majority of DDH cases are female, accounting for 80 per cent of the cases and 60 per cent of cases are in firstborn kids. Dr Al Hemrani says that mothers usually have small uteruses and tighter abdominal muscles during their first pregnancy, causing conditions that are more crowded for the baby in utero. This leads to a possible increase in the risk of DDH that may be associated with feet and neck deformities related to the “packaging effect”. He also says that girls are more susceptible because they tend to be more lax than boys are. “The theory is that towards the end of pregnancy, some hormonal changes happen in the mother’s body and girls tend to respond more.
If the hip isn’t treated well, the patient could be at risk of osteoarthritis later on but with proper treatment, the hip will survive for many years to come.
“The Relaxin hormone tends to relax all of the muscles, tendons and ligaments so that the mother is prepared for the delivery process. However, some of these hormones will affect the female babies more and make them lax, making them more prone to hip dislocation as there is no restraining effect from the muscles and ligaments to hold the hip in place.”
The left hip is more commonly affected than the right simply because the 60 per cent of babies lie with their left hip against the sacrum [at the bottom of the spine] in the uterus, putting it under pressure and increasing the risk of dislocation.
Around 20 per cent of cases are infants who have both hips dislocated, which can be more difficult to diagnose. “As both hips are dislocated, there is no asymmetry to show that there is a problem. Even if the child can crawl or walk, there will be no obvious signs except subtle swayback, a duck-like gait or limited hip movement - so a lot of these cases are discovered at a later stage unfortunately,” says Dr Al Hemrani.
There are also genetic factors that can increase a child’s likelihood of suffering from the condition. “Having a sibling with DDH means that there is a 6 per cent chance that the baby will have DDH and having a mother with DDH means there is a 12 per cent chance that the newborn will have DDH,” says Dr Al Hemrani. “Having both a mother and sibling who have suffered from DDH means there is a 36 per cent risk that the child will have DDH.”
Infants in the breech position (feet first) are also at risk for hip dysplasia. Swaddling is also one of the major practices that leads to DDH in some of the cultures, where the child is wrapped tightly around the hips.
Parents and general physicians should suspect DDH before the walking age if there are abnormal clunk sounds in the hips, asymmetry of the buttock, thigh creases, or limited hip range of motion. However, after the walking age; any limp should lead to examination of the hips to rule out DDH.
Diagnosis and treatment
Dr Al Hemrani says that at DHA, all newborn babies are clinically assessed for DDH. For those with risk factors or for those that are difficult to assess, an ultrasound scan will be carried out. DHA is also moving towards scanning almost all newborns to reduce the chances of missed cases.
“Once DDH has been diagnosed, then we like to start the treatment as soon as possible as it takes a few months for the hip to stay stable within the socket.
“If we detect hip dysplasia in newborns up to six months, then we use braces and harnesses to treat them as outpatients. The babies are braced for three to four months and we like them to be used almost full time as much as possible, so that the hip can be kept in position.”
Once the bracing period is complete with stable hips guided by frequent radiographic imaging studies, the babies are gradually weaned off the braces and harnesses, such as wearing them only at night.
For babies aged between six months to a year old or for children whose treatment with braces was unsuccessful, a closed reduction of the hip will be carried out, which is done under general anaesthesia.
“The hip is examined and gradually placed back into the socket guided by real-time radiographic studies.
“Sometimes we may need to release specific tendons so that the hip can dock into the socket properly. The child will then be placed in a hip spica cast [to immobilise the hip and facilitate healing] for around three months.
“For children over the age of one or one-and-a-half or for cases where other treatments have failed, an open reduction of the hip will be carried out. It is an open surgery where the hip is reduced back into place. The procedure may also require bony surgery to adjust the position of the bones and tighten the capsule of the hip.”
Following treatment, the infants need to be checked regularly to ensure that the hip is in position and maturing properly. The patients also need to be checked for avascular necrosis of the hips [compromised blood supply to the hip].
With timely treatment though, Dr Al Hemrani says that the child should be able live normally, with no physical impairment. “If the hip isn’t treated well, the patient could be at risk of osteoarthritis later on but with proper treatment, the hip will survive for many years to come.”