Congenital Dislocation of the Hip

Definition/diagnostic criteria Congenital dislocation of the hip (CDH), also known as developmental dysplasia of the hip (DDH), refers to a spectrum of conditions where the neonatal hip is unstable, dislocated or at risk of dislocation. DDH encompasses a range of abnormalities, from a shallow acetabulum (hip socket) to complete dislocation of the femoral head from the acetabulum. The condition can be present at birth or develop during the first year of life.

Epidemiology DDH occurs in approximately 1-2 per 1,000 live births in the UK. There is a higher prevalence in females and in first-born children. Other risk factors include breech presentation, family history of DDH and oligohydramnios. Ethnicity plays a role, with a lower incidence reported in black African and Chinese populations.

Diagnosis
Clinical features: The diagnosis of DDH in infants relies on careful clinical examination. Key features include:

• Asymmetry of the gluteal and thigh folds (though in isolation these are less important as they are commonly found in normal babies).
• Limitation of hip abduction.
• Apparent shortening of the femur (Galeazzi sign).

The Ortolani and Barlow tests are essential clinical manoeuvres for detecting hip instability in newborns. However, it’s important to note that a significant proportion of cases may not demonstrate any clinical signs, especially after the neonatal period.

Investigations: Ultrasound imaging is the investigation of choice for infants less than 4-6 months of age. It allows for dynamic assessment of the hip and can detect both structural abnormalities and hip instability.

In older infants and children, where ossification of the femoral head has occurred, plain radiography is preferred. Typical radiographic findings include delayed ossification of the femoral head, shallow acetabulum and lateral displacement of the femoral head.

Treatment The goal of treatment is to achieve and maintain a stable, concentric reduction of the hip. In infants, treatment usually involves the use of a Pavlik harness, which holds the hips in a position of flexion and abduction. This treatment is most effective when started early, ideally before the age of 6 months. The success rate of Pavlik harness treatment is high, with failure rates reported to be around 10%. In cases where the Pavlik harness is unsuccessful, or in older children, alternative treatments include closed or open reduction followed by spica cast immobilisation. Surgical intervention may be required for severe cases or those diagnosed late.

Prognosis The prognosis for DDH is generally good, especially when diagnosed and treated early. Untreated DDH can lead to problems in later life, such as early-onset osteoarthritis and gait abnormalities.