P0835 - Late Hip Dysplasia After Normal Ultrasound in Breech Babies: Implications on Surveillance Recommendations

Introduction: There is significant controversy in the literature over rates of late developing dysplasia following normal screening ultrasound in breech babies, with reported rates varying from 7-29%. The purpose of this study is to investigate the rate of radiographic dysplasia in breech babies after a normal ultrasound with a minimum of 1 year of radiographic follow up.

Methods: This study was an IRB-approved prospective study of all patients referred to a tertiary pediatric orthopaedic center by their pediatrician for concern for developmental dysplasia of the hip (DDH) between 2008-2013. We identified all subjects with breech presentation and excluded those with an abnormal initial exam/ultrasound or with less than 12 months of radiographic follow up. Anterior-posterior pelvis films were obtained after >12 months and acetabular indices (AI) measured and compared to contemporary normative data. Dysplasia was diagnosed as >2SD above the mean for AI.

Results: 812 patients were referred with a history of breech presentation, and 306 (37.7%) were found to have clinical instability or sonographic evidence of dysplasia on initial presentation and were subsequently observed with serial imaging or treated. Of the remaining, 506 subjects with normal clinical exam and screening ultrasound were asked to return at 1 year, and 135 (26.7%) patients (74.8% females, 25.2% males) were followed until at least 12 months of age (mean final follow up 20.7±6.7 months). 3/135 (2.2%) patients had a dysplastic hip with an acetabular index greater than 2 standard deviations above the mean (Figure). Only 27/135 (20.0%) had acetabular indices of at least one hip greater than 1 standard deviation above the mean (reflecting the 68th-95th percentiles). No patients underwent treatment other than observation during the study period.

Discussion: Our study’s findings suggest that late dysplasia following normal screening ultrasound in breech babies may be less common than previously reported. This discrepancy with existing literature may be due to our prolonged follow up period and suggests that standard surveillance follow up visits before 12 months of age may offer little benefit.