A normal screening ultrasound does not provide complete reassurance in infants at risk of hip dysplasia; further follow-up is required.

BACKGROUND Screening for developmental hip dysplasia (DDH) continues to evolve with the use of ultrasound (US) in either selective or universal screening methods. The possibility of delayed evidence of DDH, and thus the need for radiographic follow-up at a later stage of development have been suggested by some authors. AIMS The aim of this review was to evaluate the number of patients in our hospital network with a normal screening US at 6 weeks with evidence of DDH at the time of radiographic review at 6 months. Secondary aim; to determine the outcomes for these patients. METHODS A retrospective review was done to infants undergoing DDH ultrasound screening between January and December 2015. Initial US and radiographs at 6 months were reviewed. Patients with normal screening US who had subsequent radiographs were included for analysis. RESULTS In total, there were 829 patients included for analysis. Sixty-three patients (8%) had evidence of DDH at 6 months, representing 34% of all DDH diagnoses for the study period. Five of the 63 patients were lost to follow-up. The remaining 58 babies were treated in Boston bracing. Four patients with evidence of persistent DDH were referred for tertiary review. The osteotomy rate in the radiograph diagnosed group was 2%, versus 6% and 3% in the unstable and US diagnosed groups, respectively. CONCLUSION Eight percent of patients with a normal screening US had evidence of DDH at time of radiograph at 6 months, reflecting 34% of all our DDH cases for the year. Based on these findings, patients in our hospital network undergo radiographic evaluation at 6 months even if the initial screening US is normal.