Developmental dysplasia of the hip in infants referred for a combined pediatric orthopedic and radiologic examination. A prospective cohort study

Introduction: The study aimed to determine the proportions of infants with developmental dysplasia of the hip (DDH) and hip dislocation in infants referred for combined pediatric orthopedic and radiologic assessment, and to describe the association between DDH and different reasons of referral. Methods: A prospective study of all infants aged 0-6 months referred for a combined examination of the hips 2013-2019. The proportion of DDH and unstable hip(s) stratified by different reasons of referral were calculated. Acetabular index > 30° in radiography or Graf Type 2b or worse in ultrasonography was considered diagnostic of DDH. Results: Of the 1,989 infants included, 17% had stable dysplastic hip(s), and 4.7% had unstable dysplastic hip(s). The proportions of infants with DDH among infants with a single reason of referral were 36% for breech position, 25% for familial disposition, 14% for hip click, 8% for asymmetry, and 3% for twins. The proportions of infants with unstable hip(s) were 14% for familial disposition, 12% for breech position, 3% for hip click, 3% for twins, and 1% for asymmetry. Conclusion: The study demonstrates that a considerable proportion of infants referred for the combined examination have radiological signs of DDH and that DDH were regularly diagnosed in infants referred due to hip click or asymmetry.