Developmental dysplasia of the hip: prevalence based on ultrasound diagnosis.

The prevalence of sonographically normal, immature and dysplastic hips, the association between hip morphology and gender, and known risk factors for developmental dysplasia of the hip (DDH) were determined for 3613 randomly selected, healthy newborns. Hip morphology was determined according to a modified Graf's method, and stability was evaluated using a Barlow equivalent maneuver. A higher proportion of girls than boys had immature hips [16.9 % vs 9.3 %; relative risk (RR) = 2.0, 95 % confidence interval (CI) = 1.6-2.4], minor dysplasia (4.5 % vs 1.0 %; RR = 4.8, 95 % CI = 2.9-8.1), and major dysplasia (1.2 % vs 0.2 %; RR = 5.5, 95 % CI = 1.9-16.2). An increased risk was associated with having a sibling or parent with DDH (RR = 2.2, 95 % CI = 1.0-4.6 and RR = 3.6, 95 % CI = 1.1-12.5 for girls and boys, respectively), but not with DDH in more distant relatives. Breech delivery represented a significant risk factor only for the girls (RR = 2.2, 95 % CI = 1.1-4.4). There was a strong association between hip morphology and sonographic stability (gamma = 0.98).