Acetabular development in the infant's dislocated hips.

The course of development of acetabulae after the reduction of congenitally dislocated hips was investigated to identify factors that might predict the need for acetabuloplasty. One hundred five congenitally dislocated hips in 83 children were followed roentgenographically for an average of eight years after reduction. While the percentage of children requiring later acetabuloplasty increased somewhat with advancing age at the time of reduction, numerous acetabulae in the older groups developed satisfactorily without later surgery. The prereduction acetabular index proved a much more reliable predictor of the need for later acetabuloplasty. Sixty percent of those with an acetabular index greater than 37 degrees required later pelvic surgery, compared with 17% of those with a prereduction index less than 30 degrees. The major acetabular response occurred in the first year after reduction in children whose hips were reduced before the age of three years, whereas the maximal response in children whose hips were reduced after three years of age occurred in the second through fourth years. A further drop can be expected in all reduced hips of children between the ages of eight and 11 years.