There’s no one cause of developmental dysplasia of the hip (DDH).
It’s more likely to happen if your child was born breech (the position in the womb where the baby’s head is up instead of being down) or if you have a family history of DDH. DDH is also more common in girls than in boys by a ratio of 4 to 1, and in first-born children.
The structures that support the hip might be loose and the socket of the hip joint might be shallow. These problems might cause the hip to become unstable and even come out of the joint (‘dislocated hip’).
Signs and symptoms
DDH can vary from mild to severe, and one or both hips can be affected. It isn’t painful in babies and young children.
The signs of DDH in your newborn won’t always be obvious to you, but a skilled and experienced doctor, midwife or maternal and child health nurse will be able to pick them up. These professionals will do a series of careful checks and tests, described below.
If DDH isn’t picked up when your child is a newborn, you might later notice that the skin creases in the backs of your baby’s thighs are uneven. Or when you’re changing your child’s nappy, you might notice that one thigh doesn’t seem to move as far or as easily as the other.
Later still, the leg on the affected side might seem to be in an abnormal position, or the leg might even be shorter than the other. Your child might walk with a limp or with the pelvis tilted to one side.
Dislocated hip occurs in about 1 in 1000 births. Mild abnormalities that need treatment occur in up to 1 in 100 births. Usually, only one hip is affected, but both hips are involved in 25% of cases.
When to see your doctor
See your doctor if you notice any of the features described above. If there’s any doubt, an ultrasound can confirm the diagnosis. Your GP might refer you to a paediatric orthopaedic surgeon for a specialist opinion.
A very careful physical examination of both hips in all newborn babies should be done in the first few days of life. This is repeated at six weeks of age, and then by your maternal and child health nurse at every appointment in the first 12 months of your baby’s life.
The doctor or maternal and child health nurse will do several tests and check both your baby’s hips very carefully for any signs of DDH or an unstable hip. The doctor or nurse might feel a faint ‘clunk’ in your baby’s hip or hips. This might be caused by stretched ligaments and just need monitoring. If an abnormal movement of the hip comes with the clunk, a diagnosis of DDH is likely.
In experienced hands, these tests should pick up most cases of DDH, although they’re not reliable after eight weeks of age. It’s common for your baby to be sent for an ultrasound if your baby’s in a high-risk group or has an abnormal result from the physical examination.
If DDH is picked up when your child’s a newborn or young baby, treatment is usually simple and straightforward, and will usually fix the problem completely. But the later DDH is diagnosed and treatment started, the more difficult it is to fix, and the more uncertain the final result.
If the doctor suspects your newborn baby has a dislocated hip, your baby might be placed immediately in a special harness or splint, which holds the hip in the socket of the hip joint by keeping the thighs apart. Your baby wears this for around three months.
If treatment starts after your child turns one, traction and often surgery are needed, followed by 6-9 months in a plaster cast. The cast is changed every few weeks to allow for growth.
DDH needs to be monitored throughout the first year of your baby’s life. Your baby’s hip should be thoroughly examined immediately after birth, again at six weeks and then at every maternal and child health nurse appointment in the first 12 months of your baby’s life.
If you have a family history of DDH or your baby was breech, special care needs to be taken with the examination.
Although DDH can’t be prevented, early detection and immediate treatment are very important.