Developmental dysplasia (or dislocation) of the hip (DDH) is an abnormal development of the hip joint leading to a joint that is dislocated or prone to dislocation. The condition is found in babies or young children and affects 1-3% of newborns.
A dislocation is where the two bones that make up the joint are not lined up properly. The hip joint is made up of a ball at the top of the thighbone (called the femoral head) which sits inside the socket (called the acetabulum) of the pelvis. In DDH the femoral head slips and does not properly join the hip socket or acetabulum.
In hips affected by DDH, the ball is not stable within the socket because the socket is abnormally shallow. The ligaments around the hip joint that normally help hold the hip joint in place, are also abnormal, allowing the ball to slip out of the socket.
DDH can vary from mild forms where there is slightly less stability in the joint to severe where the joint easily dislocates. It may be present on one side only or it may affect both hips.
Symptoms
Because this a condition affecting newborns and young infants, the diagnosis of developmental dysplasia of the hip (DDH) is highly dependent on screening tests and clinical observations. However the following signs and symptoms may indicate that DDH may be present:
New born
- Asymmetry of the legs: this may be noticed by an asymmetry of thigh or buttock creases, a shortened leg on the affected side
- Clicking: this is an unreliable indicator of DDH. Many normal hips will click when moved but this can occur in DDH as well.
3 Months – 1 year
- Restricted leg movements: Moving the leg to the side is the movement that is usually limited in DDH. This may cause difficulty when putting on nappies or difficulty in sitting astride an adults knee.
- Difficulty in crawling: rather than crawling evenly, one leg may be dragging to the side when crawling
Early childhood
- Limping: usually a limp caused by DDH will not be painful.
- The child may walk on their toes on the affected side
- Despite these problems, walking is not usually delayed
Late childhood and adulthood
If DDH is not picked up in early stages of life, the hip will become worn out and cause symptoms similar to osteoarthritis of the hip. These can include:
- Walking with a limp which may become painful
- Restriction of leg movements to the side (abduction of the hip)
- Pain in the groin or buttock area on hip movements
Causes
The precise cause of developmental hip dysplasia (DDH) is unknown, but genetic and environmental factors may both play a role.
There is an increased risk of developing DDH if someone in the family has previously had this condition. This suggests that DDH may be caused partly by genetic factors. Currently there is not a clear understanding of how this occurs.
As well as genetic factors that may play a role, there are ‘environmental’ factors that may affect the hip such as the position of the hip within the womb or in the first few months of life. How the baby is born may also impact on the hip, particularly if the baby is delivered in the breech position (feet first). It is thought that pressure on the infants hips either in the womb or whilst being born, may stretch the ligaments of the hips and lead to the joint becoming unstable. Once the baby is born, certain swaddling techniques may place the hip in a position that stretches the ligaments and leads to instability.
Risk Factors
The risk factors for developing developmental hip dysplasia (DDH) are as follows:
- Family history: If other family members have been diagnosed with DDH then this is risk factor for developing the condition
- Breech position at birth: This means the baby is born feet first. If the baby is in the breech position and a Caesarian section is performed, there is still a slightly increased risk of DDH but not as high as if the birth is a vaginal delivery.
- High birth weight (>5kg): A large baby will have less room to move in the womb. It is thought that due to the size of the baby there is more pressure on the hips which stretches the ligaments and makes them more susceptible to DDH
- Prematurity: If a baby is born before 38 weeks of the pregnancy, this holds a slightly increased risk of DDH
- Low amount of fluid in the womb: The medical term for this condition is oligohydramnios. This may cause DDH in the same way that a high birth weight affects the hips (see above).
- Positioning or swaddling: Overly tight swaddling may lead to pressure on the hips and lead to instability
- Female gender: girls suffer DDH more commonly than boys
It is important to note that infants and children with DDH may have none of these risk factors and all babies should be screened for this condition at birth. Of note is the fact that the left hip is more commonly affected than the right.
Investigations
When a dislocated hip joint is put back in place, the DDH often normalises within the first months of life. If the hip remains dislocated, muscles will shorten, locking the hip in the wrong place and surgery is likely to be required. For this reason early diagnosis is very important
Newborn investigations
All babies should be examined for congenital hip dislocation within 24 hours of birth before leaving the hospital; at 6 weeks; between 6-9 months; and at walking age.
These examinations are called screening tests as all infants receive them. If the initial examination reveals a suspicion of an unstable or loose hip, further examination may be required.
Clinical examination
All infants are assessed in the hospital by a doctor when they are born in order to test the stability of their hip joints. The doctor will perform two maneuvers that test whether the hip is sitting in the socket or if the hip moves more than it should. These maneuvers are called Ortolani and Barlow tests named after the doctors that developed them. If these test indicate that the hip is dislocated or unstable, further investigation is required.
Observation of additional signs, such as a discrepancy in leg length or asymmetrical thigh and buttock skin folds, may also be present and re-enforce the need for further investigations
Further Investigation – ultrasound
Ultrasound scans of the hip are the best investigation from birth until the age of 4-5 months, while the hips are mainly cartilage instead of bone. The ultrasound will be able to show the shape of the hip socket and also whether the ball of the hip is sitting in the socket.
Infant and child investigations
Clinical examination
Ortolani and Barlow tests may still be used in infants under 1 year of age but increasingly these tests become less valuable as the child ages. The most reliable indicator of DDH in a young child is the inability to move the hip away from the midline (to abduct the hip). If the child is crawling with one leg swinging to the side, walking with a limp or has an observable leg length discrepancy, then this may also indicate DDH. If following a clinical examination, the doctor suspects that DDH may be present, then further investigations are required to confirm this.
Further investigations – X-ray
Ultrasound imaging is only effective in diagnosing DDH in infants under 4 months of age. As the infant ages, the hip joint progresses from being largely made of cartilage to being made of bone. X-rays are the most effective tool of imaging a hip joint that has made the progression to bone. In children over 4 months of age, an X-ray is used to diagnose DDH.
Complications
Early diagnosis and treatment for DDH is essential to avoid progression of hip problems relating to this condition. If the hip is unstable or dislocated due to DDH, the muscles of the hip will shorten as the infant grows leading to the hip being stuck in the dislocated position. This will lead to the socket of the hip joint not forming properly. If the socket is more shallow than it should be then the ball (femoral head) may change shape, becoming more flattened. This process is termed ‘dysplasia’ of the hip and means abnormal development. If dysplasia of the hip is left untreated, the following complications can occur:
- a persistent limp on the affected side
- premature osteoarthritis of the hip which may eventually require a total hip replacement
- lower back or hip pain
If DDH is treated early, the problem usually resolves with no further complications. If however, the condition is treated late, when some degree of dysplasia or abnormal development has occurred, then there are complications associated with this treatment. These include:
- Recurrent dislocations: If a hip is dislocated due to DDH and is put back into place late in early childhood then it may be prone to future dislocations due to a shallow hip socket.
- Avascular necrosis: This means that the blood supply to the hip joint is disrupted and the bone dies. This can occur when the hip is put back in place after it has been sitting out of the socket for a prolonged period of time. To learn more about this condition follow the link to osteonecrosis of the hip.
Treatment
Early treatment – birth to 6 months
The primary aim of treatment is to achieve a stable hip that does not dislocate and moves freely. If diagnosed and treated early, the outcomes for DDH are very good.
The early treatment consists of the use of a soft brace that is called the Pavlik Harness. This brace is a device that allows the baby to move their legs in all directions that do not cause dislocation of the hips. It restricts movements that the baby may perform which can lead to dislocation.
The harness may need to be worn for several months and it is important that the full course recommended by your doctor is completed. Whilst the child is wearing the harness they will have regular check ups to readjust the fitting of the harness and also to assess how the hips are responding. Over a period of weeks to months the ligaments and muscles around the hips will tighten and strengthen leading to a stable hip joint.
Following completion of this period, most children require no further treatment.
Later treatment – after 6 months of age
If DHH is not diagnosed early, more invasive treatment may be required. If a splint has been tried but the hips remain unstable or if the diagnosis is made after 6 months of age, relocation of the hip under anesthesia or surgery is often required.
The first step is to relocate the hip whilst the child is either sedated or under anesthetic. If this is unsuccesful, an operation may be required. The operation involves surgically putting the hip back into the socket and often also involves releasing tight muscles that are holding the hip out of place.
For children aged 18-24 months, the operation may include reshaping either the pelvic bone or the thigh bone to create a stable hip joint. This type of operation is called a femoral or pelvic osteotomy. Generally, the older the child at the time of diagnosis, the more invasive the surgery becomes in order to correct the problem. This is why early diagnosis is so important in DDH. These operations are followed by a period where a more rigid cast must be worn to ensure the hips stay in the right place.
Adult treatment
If DDH is left untreated in childhood, the hip will become abnormally developed (dysplastic). This can lead to premature osteoarthritis. Treatment in this situation is often to perform a total hip replacement.
Seeking Advice
DDH is screened for in all infants at the time of birth and during check ups in their first 6 months of life. If you are concerned about your child’s hips, your family GP is the best place to start. They will be able to make an assessment and decide if a specialist referral is necessary.
Prevention
The best prevention of DDH is early diagnosis and treatment. If the problem is identified early then the abnormal formation of the hip can be effectively avoided. Aside from early treatment, avoiding placing a babies hips in a position that may lead to increased stress on the hip joint and subsequent dislocation is important.
Certain swaddling practices such as the use of cradle boards (common to American Indian populations) or tight swaddling (common in Japan) should be avoided as this is thought to be a risk factor for DDH.
F.A.Q. | Frequently Asked Questions
How common is hip dysplasia?
Hip dysplasia is the most common developmental hip deformity in children. The condition affects one or two out of 1,000 babies.
How is developmental dysplasia of the hip diagnosed?
All babies in Australia are examined in the first few days of life and then at various intervals in the first year of life for any hip abnormalities. If a doctor is concerned that DDH may be present, they will refer you for an ultrasound. Hip dysplasia can almost always be diagnosed with ultrasound screening of an infant.
Will my child be OK?
The vast majority of children treated for DDH have treatment that enable their bones to grow normally—so they can walk, play, grow and live active lives. Diagnosing and treating your child’s DDH in infancy greatly increases the likelihood of a successful outcome.