Why is congenital dislocation of the hip still missed? Analysis of 96,891 infants screened in Malmö 1956-1987.

During 1956 through 1987, 96,891 children have been screened for neonatal hip instability according to the tests of Ortolani and Barlow. In 1956 through 1972 only 4/58, 759 (0.07 permille) were missed, whereas during 1980 through 1987, 12/19, 398 (0.6 permille) were missed. This increase is not caused by any formal alteration of the screening programme. The screening has prevented a late diagnosis in all children born in breech presentation and in all boys except one. General factors such as female sex and joint laxity imply an increased risk for being missed in the screening, whereas mechanical factors such as breech presentation and the primogeniture effect likely facilitate an early diagnosis in the screening. The time between birth and the first examination is also of some importance.