Instability of the hip in neonates. An ethnic and geographical study in 24,101 newborn infants in Malmö

In a prospective study conducted between 1990 and 1997, 24 101 newborn infants were examined for neonatal instability of the hip and classified by the ethnic origin of their parents. In 63% their mother and father were of Swedish extraction and in 24% they were born in a foreign country. Those of foreign extraction were split into ethnic and geographical subgroups. Although the incidence of treated (dislocatable-unstable) hips was greater in Swedes (7.6/thousand), than in other geographical groups (5.8/thousand) it was not significantly different (p = 0.065). A total of 12.7/thousand were referred from the neonatal ward to the orthopaedic clinic with suspected dislocatable or unstable hips; 6.8/thousand were treated (5.4/thousand dislocatable, 1.4/thousand unstable), but 5.9/thousand were not treated since their ultrasound examination was normal. Two hips were diagnosed late and one case of mild avascular necrosis was found. Examination by dynamic ultrasound decreased the number of treated cases by 5.9/thousand but was not an absolute guarantee of diagnosis.