Estimated effect of secondary screening for hip dislocation

Abstract

ObjectivesTo quantify the effect of secondary screening for hip dislocations.DesignRetrospective analysis of hospital files from participants in a prospectively collected nationwide registry.SettingChild healthcare centres and orthopaedic departments in Sweden.ParticipantsOf 126 children with hip dislocation diagnosed later than 14 days age in the 2000–2009 birth cohort, 101 had complete data and were included in the study.InterventionsThe entire birth cohort was subject to clinical screening for hip instability at 6–8 weeks, 6 months and 10–12 months age. Children diagnosed through this screening were compared with children presenting due to symptoms, which was used as a surrogate variable representing a situation without secondary screening.Main outcome measuresAge at diagnosis and disease severity of late presenting hip dislocations.ResultsChildren diagnosed through secondary screening were 11 months younger (median: 47 weeks) compared with those presenting with symptoms (p<0.001). Children diagnosed through secondary screening had 11% risk of having a high (severe) dislocation, compared with 38% for those diagnosed due to symptoms; absolute risk reduction 27% (95% CI: 9.7% to 45%), relative risk 0.28 (95% CI: 0.11 to 0.70). Children presenting due to symptoms had OR 5.1 (95% CI: 1.7 to 15) of having a high dislocation, and OR 11 (95% CI: 4.1 to 31) of presenting at age 1 year or older, compared with the secondary screening group. The secondary screening was able to identify half of the children (55%, 95% CI: 45% to 66%) not diagnosed through primary screening.ConclusionsSecondary screening at child healthcare centres may have substantially lowered the age at diagnosis in half of all children with late presenting hip dislocation not diagnosed through primary screening, with the risk of having a high dislocation decreased almost to one-quarter in such cases.