Developmental dysplasia of the hip
hip; dislocation; dysplasia; pelvis; joint; ball; congenital; baby; click; clicky; DDH; CDH ;
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Developmental Dysplasia of the Hip (DDH) is the name used to describe a range of ways a baby’s hip might not develop normally. In the past the name Congenital Dislocation of the Hip (CDH) was often used, but not all hip joints that are growing abnormally are dislocated. Dysplasia means growing abnormally.
Development of the hip
Normal hip For the hip joint to grow normally the ball shaped head of the thigh bone (femur) needs to be inside the cup shaped socket on the side of the pelvis (called the acetabulum).
The head of the femur is held in place by ligaments, muscles and a joint capsule. |
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Abnormal development If the head of the femur is not held tightly in place, the socket may be flatter than usual (acetabular dysplasia), making the joint less stable and the head of the femur may be able to move in and out of the socket (subluxation).
If the head of the femur loses contact with the socket and stays out of the joint, this is called dislocation. |
Causes of dysplasia
The causes of a hip joint not developing normally are not fully known, but include:
- genetic factors (the problem is more common in families where another person in the family has also had a developmental problem with a hip)
- factors during the baby’s development before birth, for example if the baby is in the breech position.
Around the time of delivery, hormones in the mother cause ligaments around her birth passage (pelvis) to relax a bit, to make it easier for the baby to pass through her pelvis during birth. These hormones may pass through the placenta to the baby and cause the ligaments around the baby’s joints to also relax, making the baby’s hip joint less stable. As the level of hormones in the baby decreases, the ligaments around the hip tighten again.
Risk factors
Risk factors are things that make it more or less likely that a problem will happen.
Research done in South Australia showed that:
- a baby in the breech position before birth is 10 times more likely to have DDH than other babies
- a female baby is 4 times more likely to have DDH than a male baby
- a baby who has little fluid around it before birth (oligohydramnios) has 4 times the risk
- a big baby (over 4.5 kg) has 2 times the risk
- a first born baby has 2 times the risk
- babies born into families where another baby had DDH and babies who had other birth defects such as foot abnormalities also have an increased risk.
However most babies with some of these risk factors will not have DDH, and many babies with DDH will not have any of these risk factors.
How often does DDH occur?
In research about DDH, the numbers of children with DDH are reported to vary due to how early after birth the baby’s hips are checked. This is because the ligaments around the baby’s hips tighten as the mother’s hormones are washed out of the baby.
Australian research has reported that 1% of babies have DDH.
Checking hips of babies and infants
All babies, including those who do not have any risk factors, should have their hips checked several times in the first year of their life, and all children should have the way that they walk checked soon after they start to walk. Young children who have a dislocated hip that has not been discovered before they start to walk have an unusual 'waddling' way of walking (gait).
A doctor, midwife or community child health nurse should check a baby’s hips:
- soon after birth
- on discharge from hospital (or about a week after birth)
- around 6 weeks
- around 3 months.
The Barlow and Ortolani tests
These tests are done by moving the baby’s legs in ways that will show whether the hip is stable or whether the head of the femur moves more than usual (including into or out of the hip joint). This needs to be done when the baby is calm, and should not hurt the baby.
- If the baby has an unstable hip, the Barlow test will move the head of the femur out of the hip socket causing a ‘clunk’ feeling.
- If the hip is dislocated, the Ortolani Test will move the head of the femur back into the hip socket, again causing a ‘clunk’ feeling.
- Sometimes a ‘click’ will be felt or heard even though the hip has developed normally. This is usually a normal hip noise. Most babies with ‘clicky hips’ have normal hips.
Ultrasound
An ultrasound examination of the hips is able to pick up small abnormalities of the shape of the acetabulum and head of the femur, or more movement of the head of the femur within the joint than usual. These are not always felt when the hips are tested by hand. Most of the minor abnormalities do not cause any problems with hip development (they are called ‘false positives’, which means that the test has suggested a problem which does not exist).
Asymmetrical creases
Babies who have a dislocated hip may have asymmetrical creases of their buttocks. This is not a reliable sign.
Checking the lengths of the baby’s thighs
If the baby has a dislocated hip, the length of the baby’s thighs will appear to be different. But if both hips are dislocated, there will not be a leg length difference.
Checks done after the baby is 6 months old.
By the age of 6 months the baby’s ligaments around the hip will be strong and it may no longer be possible to move the head of the femur into the hip joint if the head is dislocated.
Instead the baby’s hips are examined by laying the baby on her back and moving the knees apart as though you were putting a nappy on. If the hip joint is dislocated the knee on that side will not be able to move as far down to the bed. |
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Having an unstable or dislocated hip will cause problems in later life if it is not treated.
- It is important to recheck a baby’s hips several times during the first 12 months of life.
- The first tests may not have shown the problem, and there have been times when the hip has dislocated after birth.
What is done next?
Note: The information on this site should not be used as an alternative to professional care. It is important to see your doctor or health professional for information specific to a health concern you may have about your child.
If it seems possible that a baby might have an unstable hip, the baby is usually referred to an orthopaedic surgeon as soon as possible, and then the baby is put into a splint.
- The splint will hold the hip in the best position for normal hip development.
- When this treatment is started as soon as possible after birth, most hips develop normally, and further treatment is not needed.
- Ultrasound examination of the hip (which can be done while the baby is in the splint) will show if the joint is in place.
- X-ray examination is not as useful under 3 months of age because the bones being examined do not show on x-ray yet.
Treatment
If a young baby has an unstable hip, holding the baby’s head of the femur in the right position inside the socket on the pelvis will make the socket grow into the shape needed for the hip to be stable.
- Several splints have been developed for this, including the ‘Denis Browne Splint’ and the ‘Pavlik harness’. At the Women's and Children's Hospital in South Australia the Denis Browne hip splint is preferred. The splint is used for 10 weeks.
- Wearing a splint does not alter the baby’s normal development, and, in fact, the baby usually gets a stronger neck and back earlier than normal due to the way that the pelvis is held stable.
- Ultrasound is used to make sure that the baby’s hip is in the right position while the splint is on, and after the splint has been taken off. This will show whether the acetabulum (the socket) is developing normally.
- Surgery may be needed if the hip does not stay in place in the splint, or if the child is older (eg over 6 months) when the dislocated hip is found.
Taking care of the splint
The splint will be put on by a physiotherapist, who will explain how to look after the baby and the splint.
- The splint has to stay in the right position all of the time. It is not to be taken off even for bathing. The physiotherapist or nurse will show you how to bathe the baby.
- Straps are tied to the bar on the back of the splint, to hold the legs in place.
- Disposable nappies are used under the splint, and most clothing will fit over the splint.
- The splint is adjusted about every two weeks.
- Most babies will fit into a car seat used for 0 to 2 year old children.
References
Women's and Children's Hospital pamphlet 'Developmental Dysplasia of the Hip (DDH)',
www.wch.sa.gov.au
Women’s and Children’s Hospital, Adelaide ‘Neonatal Hip Instability Care Pathway’.
Chan A, McCaul KA, Cundy PJ, Haan EA, Byron-Scott R, ‘Perinatal risk factors for developmental dysplasia of the hip’ Archives of Diseases in Childhood, March 1997, Vol 76, No 2, pF94-F100.
Chan A, Cundy PJ, Foster BK, Keane RJ, Byron-Scott R, ‘Late diagnosis of congenital dislocation of the hip and presence of a screening programme: South Australian population-based study’, The Lancet, Vol 354, October 30 1999.
Garfunfel et al ‘Mosby’s Pediatric Clinical Advisor’ p279 (Developmental dysplasia of the hip) Mosby, Harcourt Health Science Company 2002
Little D, ‘Developmental Dislocation of the Hips’ The New Children’s Hospital, Westmead (NSW) www.medicineau.net.au/clinical/paediatrics/DDH.html
The information on this site should not be used as an alternative to professional care. If you have a particular problem, see a doctor, or ring the Parent Helpline on 1300 364 100 (local call cost from anywhere in South Australia).
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