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Oxford University Hospitals NHS Foundation Trust
Paediatric Orthopaedics

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Developmental Dysplasia of the Hip in older children

What is Developmental Dysplasia of the Hip (DDH)?

DDH is a condition where the ball and socket hip joint fails to develop normally. It can occur before birth or in the first months of life. The socket of the hip joint (acetabulum) is usually shallow and the ball (femoral head - top of the thigh bone) can be loose or completely dislocated instead of fitting snugly into the socket (the severity of the condition varies).

Although screening programmes allow us to detect most babies with unstable or abnormal hips, some children have an abnormality which simply cannot be detected with clinical examination and the hip may fail to develop normally.

Typically when the hip displaces a little or completely, the baby's leg lies with thigh creases which do not line up perfectly and with the affected leg looking slightly shorter and rolled out sideways. Examination of the hip may show that the hip will not bend out as fully sideways or move as freely as the other hip. Sometimes both hips can be involved.

Management

When a General Practitioner, Health Visitor or Paediatrician recognises these problems in an older child (after the age of 10-12 months) it is important to take an X-ray so that the degree of displacement can be seen and judged.

Treatment

It is sometimes possible in a child of four or five months for the hip to reduce - i.e. for the ball to go back into the socket - without any other additional treatment being necessary. Under these circumstances it is entirely reasonable to see whether a period in a Pavlic harness (a harness that keeps the baby's hips and knees bent upwards and outwards) allows the hip to stabilise more safely in the joint and allows the socket to grow more satisfactorily around the ball of the hip joint.

If the hip will not reduce, or if the Pavlic harness does not allow the hip to grow properly, other treatment is necessary. For children under the age of two years most surgeons arrange for admission into hospital for a period of preliminary traction. This means gently pulling on the leg to relax the muscles etc.

After a period of such traction it is usual to examine the baby's hips under a general anaesthetic. Often in association with this anaesthetic an arthrogram is performed. In this test a small amount of dye that shows up on X-ray is injected into the hip joint while the baby is asleep, and X-rays are taken to see if it is possible to put the ball back into the socket safely and completely. If, after traction, it is possible to put the hip back in joint in this way, the baby is placed in a plaster hip spica cast which extends from the waist down to the knees or feet. Plasters such as this always need to be changed after six weeks or sometimes earlier, under a general anaesthetic. Great care needs to be taken in looking after them!

The duration that children need to be in plaster varies. It is likely to be at least three months and may be significantly longer if it takes a long time for the hip to grow properly. Often when the plaster is removed a period of more flexible splintage may be used to keep the hip in a safe position. The great majority of babies tolerate these plasters or splints well, and immobilisation does not upset them.

Sometimes the child is walking or older still when the problem is recognised. A delay in diagnosis is likely to be greater if both hips are affected because any limp is less striking when both hips are displaced. Once children start to walk the likelihood of a successful closed reduction (i.e. putting the hip into the joint without an operation) becomes less. For children after walking age there is a significant likelihood that a surgical operation is necessary to put the ball properly back into the socket. Often there are small obstructions inside the socket which prevent the ball from falling into place properly. An open reduction will remove these obstacles to reduction and often lengthen some of the tendons that feel tight about the hip joint. Once again a period in a plaster cast after operation is necessary and once again it is likely that at least three months in plaster are required.

It sometimes happens that children are noticed with a hip problem for the first time when they are over 2-3 years old. Sometimes in older children preliminary traction does not seem to be so effective and it is often necessary when an open reduction of the hip is performed to shorten and untwist the thigh bone a little to make reduction safer and more straightforward. Once again a period in a plaster cast after the operation is likely to be necessary.

Follow-up

Whenever children are treated for a hip problem it is essential that they be kept under long-term outpatient review. Initial treatment (plaster or surgery) aims at relocating the femoral head in the socket of the hip joint. The ball and socket are not always entirely normal in shape, however, and further development of the hip relies on the capacity of the body to remodel (reshape) the hip joint after it has been relocated. Most children, particularly the younger ones respond well to this challenge. Some do not, and may need additional operations to reshape the socket or the top of the thigh bone. Secondary procedures are therefore sometimes necessary if the hip fails to develop as well as one would wish. X-rays are usually necessary for following-up hip development. We arrange to take X-rays which deliver a much smaller dose of irradiation than a normal one. This is much safer.

In general, the older the child when the diagnosis of developmental dysplasia of the hip is made, the more difficult treatment is, and the more unpredictable the results of treatment. In other words it is best if the problem is recognised in infancy and worst if it is recognised in a child over three years old. In older children the ball of the hip joint is no longer properly spherical, and the socket is no longer round, and although when the hip is put in the right place improvement can be expected with time, matching of the two slightly uneven shapes may not be perfect and may lead to early wear and tear in adult life.