Congenital dislocation of the hip in Southland.

A study of incidence of congenital dislocation of the hip in Southland was undertaken. Covering as it does a 20-year period during which the common age of diagnosis was reduced from 20 months to three months, this series shows a rising recorded incidence of CDH in a period associated with the arrival of a resident orthopaedic surgeon and introduction of the test of limited abduction with x-ray confirmation. The incidence in the succeeding 10 years rising to 2.9 per thousand live births was between the old average for late diagnosis and that obtained with neonatal examination. A higher incidence among winter births, being twice that of summer, agrees with previously published series. An area of higher incidence on the South coast appears to be explained by two families which include seven of the 25 children born in that zone and 12 of the total 103 in the series. In these two families, the affected children are related by being cousins or second cousins.