64 - congenital dislocation of hip ( CDH )

Synonyms: CDH, Developmental dysplasia of the hip, DDH, dysplasia of the hip

Developmental dysplasia of the hip (DDH) was formerly referred to as congenital dislocation of hip. DDH is now the preferred term to reflect that DDH is an ongoing developmental process, which is variable in presentation and not always detectable at birth. Developmental dysplasia of the hip refers to a range of developmental hip disorders, from a hip that is mildly dysplastic, concentrically located, and stable, to one that is severely dysplastic and dislocated.1

There is a suggestion that the national screening programme in the UK, that has operated since 1969, has not resulted in any less operations for late disease.2 Even the use of ultrasound has failed to improve the situation.3 It may be that the use of more experienced clinicians in the screening programme, rather than very junior doctors, produces better results.4
Epidemiology

* The prevalence of developmental dysplasia of the hip varies with age and method of assessment. In unscreened populations the median prevalence of persistent and clinically diagnosed hip dysplasia is estimated to be 1·3 per 1,000 births.1
* The prevalence of neonatal clinical hip instability detected through the Ortolani and Barlow manoeuvres is higher, ranging from 1·6 to 28·5 per 1,000.1
* The left hip is dislocated more often than the right. This is thought to be due to the common position of the baby's left hip against the mother's sacrum, restricting movement.
* It is more common in cultures that use swaddling of babies, forcing the hips into extension and adduction.5

Risk factors

* There are racial differences. In the USA it is found that native Americans and Laplanders have a high incidence whilst Chinese and African Americans have a low incidence.
* Positive family history of the condition increases the risk in a manner suggestive of multifactorial inheritance.6
* About 80 to 85% are female.
* About 60% of cases are first-born, compared with about 40% of all babies.
* Breech presentation increases the risk of DDH. The extended breech position in which knees are extended is a higher risk than with knees flexed. Elective caesarean section reduces the risk compared with vaginal breech delivery7 but it remains higher than after a cephalic presentation.
* Restriction of movement as with oligohydramnios increases the risk.
* It is commoner with neuromuscular disorders, such as cerebral palsy, meningomyelocele and arthrogryposis.

Examination

* The Ortolani and Barlow tests are the most common clinical tests for newborn babies.
* In the Ortolani test, the examiner applies forward pressure to each femoral head in turn, in an attempt to move a posteriorly dislocated femoral head forwards into the acetabulum. Palpable movement suggests that the hip is dislocated or subluxed, but reducible.
* In the Barlow test, backward pressure is applied to the head of each femur in turn, and a subluxable hip is suspected on the basis of palpable partial or complete displacement.8
* A clunk feels like turning a light switch on or off. A click is much lighter and probably of no significance.
* Some units insist that the neonatal test should be performed only by an experienced person, usually an orthopaedic surgeon or a paediatrician, and not repeated by others less skilled for fear that numerous tests, perhaps with a little more force than necessary, may encourage instability of the joints.
* An early sign is limitation of hip abduction.

Children between 1 and 2 months

* True dislocation has occurred and the Ortolani test is used.
* The thigh is flexed and abducted and the femoral head is lifted anteriorly into the acetabulum. Reduction will be felt as a clunk rather than heard as a click. This procedure is impossible after 2 months because soft tissue contractures develop.

3 to 6 months

* The physical signs are rather different and so are the requirements of examination.
* If the hip is dislocated it is in a fixed position.
* The Galeazzi sign:
o The child is examined lying supine with the hips and knees flexed.
o A positive sign is that one leg appears shorter than the other.
o This is usually due to dislocation of the hip but any discrepancy of limb length will produce a positive sign.
* Other physical signs for late dislocation include asymmetry of the gluteal thigh or labral skin folds, decreased abduction on the affected side, standing or walking with external rotation of the affected leg, and leg length inequality.

Bilateral dislocation of the hip

* Can be quite difficult to diagnose, especially after the neonatal period.
* There is often a waddling gait with hyperlordosis.
* The Galeazzi sign for hip shortening is often absent as are asymmetrical thigh and skin folds, or asymmetrically decreased abduction.
* Careful examination is needed with a high level of suspicion.

Investigations

* Dynamic ultrasound is used to assess hip stability and acetabular development in infants.
* It is the technique of choice and has even been suggested as a universal screening procedure.9
* In older children, x-rays of the pelvis are required.
* Arthrography, CT and MRI may also be needed.

Management

* Bracing is first-line treatment in children younger than six months. Surgery is an option for children in whom nonoperative treatment has failed and in children diagnosed after six months of age.10
* It is important to diagnose developmental dysplasia of the hip early to improve treatment results and to decrease the risk of complications.10
* However early detection and treatment does not entirely avoid the need for subsequent surgery, and surgery is needed by up to 5% of infants treated with abduction splinting.1
* The indications for the various procedures and the most effective management interventions remain controversial.

At birth

* It is usually sufficient to maintain the unstable hip in a position of flexion and abduction for one or two months.
* This keeps the femoral head in the correct position and allows time for the ligamentous structures to tighten as well as bones to grow normally.
* The Pavlik harness, Frejka splint and other orthoses are kept in place until the hip is clinically stable with normal ultrasound or X-ray measurements. Controversially, double or triple nappies are often used in newborns for 2 or 3 weeks until splints and harnesses will fit properly.

Between 1 and 6 months

* A true dislocation may have occurred, so the aim of treatment is to reduce the femoral head into the acetabulum.
* The Pavlik harness is used to put the hip in the normal position by flexing it at least 90° and preferably 100 to 110°, with relatively full but gentle abduction of 50 to 70°.
* Spontaneous reduction of the femoral head usually occurs within 3 or 4 weeks and the harness is continued until X-ray measurements are normal. This is usually 3 months for dislocation and 2 months for subluxation.11
* If this does not occur, closed surgical reduction is attempted with 1 to 3 weeks of preliminary skin traction to place the femoral head opposite the acetabulum, percutaneous adductor tenotomy, closed reduction and a hip spica cast.

Between 6 months and 2 years

* Surgical closed reduction may work but, if there is significant instability, an open reduction may be necessary.
* Open reduction is required for children above 2 years of age. A hip spica cast is worn for 6 weeks with a gradual return to full activities.
* Pelvic osteotomies and femoral shortening may be required.

Complications

* Surgery can result in a number of complications including re-dislocation, stiffness, blood loss and avascular necrosis of the capital femoral epiphysis (which occurs in 5 to 15% cases).
* Avascular necrosis of the capital femoral epiphysis is caused by compression of cartilage when reducing the femoral head under pressure, which may result in occlusion of intra-articular and extraosseous epiphyseal blood vessels causing infarction.
* Although it revascularises, there may be abnormal growth and development.
* Extreme abduction, especially combined with extension and internal rotation, results in a higher rate of avascular necrosis.