DDH (Developmental Dysplasia of the Hip)

DDH (Developmental Dysplasia of the Hip) is a condition in which there is an abnormal development of the hip giving rise to abnormalities.

The newborn’s hip is relatively unstable as muscles are underdeveloped, cartilaginous surfaces are soft and deformable, and ligaments are lax. An exaggerated position while in the uterus may occur (particularly in the breech type of presentation), stretching the posterior hip capsule and rendering the joint unstable.

There are several risk factors such as family history, aforementioned breech presentation, ligamentous laxity, large fetal size, Oligohydramnios(less volume of amniotic fluid), female gender and being 1st born.

There are also a number of conditions associated with it such as torticollis, CTEV (club foot), knee hyperextension, Calcaneovalgus and metatarsus adductus. These are known as packaging disorders.

The femoral head has to be stable within the hip joint to develop normally. As this is not going to be the case in the subluxated or dislocated hip, it goes into a vicious cycle perpetuating dysplasia instead.

Dislocated hips may lead to a false acetabulum (hip joint)being created, which is then beset with arthritis.

Dislocated hips without a false acetabulum, can lead to back pain from hyperlordosis of the spine with consequent degenerative changes.

The single dislocated hip can lead to Limb-Length Discrepancy (LLD), knee deformity and degenerative changes, gait disturbance as well as scoliosis (curve in the spine).

The Subluxated hip succumbs to arthritis by 30-40 years as the asymmetrical pressure over its surfaces lead to flattening and deformity.

Therefore it is important to diagnose early and correct the deformity where possible in order to obviate these scenarios.

In Singapore, babies are routinely screened at birth, so the presentation is early and treatment can be instituted early.

The neonatologist observes for asymmetric skin folds, and looks for shortening (Galeazzi sign), and assesses the range of movement of the baby’s hips.

A DDH would limit the amount of abduction of the hip joint in question. The specific tests of Klisic; Barlow’s/ Ortolani’s are performed as well.

The child who presents later in life upon the commencement of walking will demonstrate a limp. The abnormal gait, due to change in biomechanics from length discrepancy, as well as wasting of the muscles subsequently, is known as a trendelenberg or waddling gait. The child would also arch the back to compensate for the hip contractures.

The diagnosis is made clinically in the child younger than 3-4 months of age. Ultrasound Imaging is performed in order to ensure the treatment instituted is working and that the hip is developing normally. Ultrasounds are not done routinely for screening purposes.

The Pavlik Harness is used to hold the hip in flexion and abduction in order to encourage the correct development of the hip. This can be done in the child 0-6 months of age. This is worn until clinical and ultrasound/ radiographical findings corroborate the development of a normal hip.

The clinician checks to ensure that the harness is worn properly as improper positioning can lead to complications known such as avascular necrosis of the femoral head.

Xrays can be performed in the child 4-6 months of age as the femoral head can be visualised then. There are parameters the clinician looks out for on X-rays.

In the child 6 months to 2 years of age who has failed the treatment with Pavlik harness, an attempt can be made for reduction with a hip spica cast.

If this fails, an open reduction of surgery is required.

Surgery aims to reduce the hip joint by removing anatomical blocks which may have developed over time, as well as to release antagonistic muscles. This is followed with the application of the hip spica cast.

Children older than 2 years may require bone cuts to be made to the femur bone, in addition to the above. More rarely, bone cuts may need to be done on the pelvic bone to accommodate the hip that is refractory to the above. This is performed more regularly in the older child >4 years of age.