Developmental Dysplasia of the Hip
Developmental Dysplasia of the Hip (DDH), replaces the term Congenital Dislocation of the Hip, reflecting a spectrum of pathology which can develop over time, as well as a range of presentations.
DDH refers to a spectrum of problems between the acetabulum and the femoral head. There may be acetabular dysplasia, with slight flattening of the acetabulum, to severe dysplasia with abnormal shape of the acetabulum and femoral head. The hip may be stable or unstable, with the potential to sublux and dislocate. DDH affects around 1-3% of all newborns, is more common in girls and 20% are bilateral. Risk factors for DDH include vaginal breech delivery, caesarian breech delivery, oligohydramnios, multiple pregnancy, prematurity, and neuromuscular disorders (e.g. cerebral palsy).
DDH may be detectable at birth, and hence is screened for as part of the newborn check, as well as at the 6 week check at the GP surgery. This is done by performing Barlow’s and Ortolani’s tests, which look for the ability to dislocate and relocate a femoral head respectively. Limited abduction when the hip is flexed is an important sign - most infants should be able to fully abduct a flexed hip so that the lateral knee touches the examination couch. It is important to assess for asymmetry, but some cases can be bilateral and limited abduction may be present equally on both sides.
When DDH is suspected on screening, diagnosis is confirmed by ultrasound. Babies at high risk are those with a family history of hip problems in early life, breech presentations and should be referred for ultrasound scan of the hips regardless.
DDH may not be detectable or may be missed at birth and some children therefore present later with limp. After 2-3 months of age, Barlow’s and Ortolani’s tests become more difficult to perform, due to development of muscle tone, and are therefore unsuitable.
The photograph shows DDH left hip
After 3 months of age, DDH may be suggested by asymmetrical skin folds, leg length discrepancies, buttock flattening, and walking with the affected leg in external rotation. Older children may present with a gradual onset of a painless limp, tip-toe walking on the affected side, as well as leg length discrepancies. Delay in walking is not commonly seen.
Early diagnosis is important, as it leads to improved outcomes. The majority of unstable hips in neonates resolve spontaneously with 2-6 weeks, and this can be monitored through ultrasound. Wearing an oversized nappy helps to keep the hips abducted and femoral head in the acetabulum. If they do not resolve, prompt treatment is required. In children <6 months of age, first line treatment consists of bracing - a harness or splint which must be worn continuously for around 6-8 weeks, being adjusted as the infant grows. The aim is to maintain hip reduction. In children >6 months, splinting and reduction may not be suitable and surgery may be required.
Paediatric Orthopaedic surgeons should be involved in the management of DDH.