Between 1956 1999, 132 601 living children were born in and Malmö, and screened for neonatal instability of the hip. All late diagnosed patients have been followed and re-examined clinically and radiologically. During the first years of screening, less than five per 1000 living newborn infants were treated. This figure increased to 35 per 1000 in 1980, but later diminished again to about six per 1000 annually after 1990. The number of referred cases decreased from 45 per 1000 in 1980 to between 10 to 15 per 1000 from 1990. During the period of high rates of referral and treatment a larger number of paediatricians were involved in the screening procedure than during the periods with low rates of referral and treatment. Altogether 21 patients (0.16 per 1000) with developmental dislocation of the hip were diagnosed late, after one week. At follow-up, 18 were free from symptoms and 15 considered to be radiologically normal.

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‰), than in other geographical groups (5.8‰) it was not significantly different (p = 0.065). A total of 12.7‰ were referred from the neonatal ward to the orthopaedic clinic with suspected dislocatable or unstable hips; 6.8‰ were treated (5.4‰ dislocatable, 1.4‰ unstable), but 5.9‰ 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‰ but was not an absolute guarantee of diagnosis.