Radiographic threshold values for hip screening in cerebral palsy

<jats:sec><jats:title>Purpose</jats:title><jats:p> To analyse the consequences of using different radiographic measurements and different threshold values for hip screening in children with cerebral palsy (CP). </jats:p></jats:sec><jats:sec><jats:title>Methods</jats:title><jats:p> In a total sample of children with CP a standardised radiological follow-up of the hips was carried out as a part of a hip prevention programme. Acetabular index (AI) and migration percentage (MP) were measured on all radiographs. In this study, 1,067 radiographs of 272 children born 1992–1998 were analysed. </jats:p></jats:sec><jats:sec><jats:title>Results</jats:title><jats:p> Lateral displacement of the femoral head was common without acetabular dysplasia, and acetabular dysplasia occurred at a later stage than femoral head lateralisation. Hip dysplasia without lateral displacement of the femoral head was rare. In 16 of the 56 hips (29%) with AI ≥ 27° and in 23 of the 71 (32%) hips with MP ≥ 33% the values decreased below the threshold value without operative treatment. In hips with AI ≥ 30° only 2 of 31 hips (6%) and in hips with MP ≥ 40% only 5 of 44 hips (11%) decreased below the threshold values without operative treatment. </jats:p></jats:sec><jats:sec><jats:title>Conclusions</jats:title><jats:p> Radiographic follow-up with only measurement of the MP seems sufficient in screening for dislocation in children with CP. MP ≥ 33% is recommended as threshold for reaction or intensified observation. In children with MP ≥ 40%, the lateral displacement increased over time in most hips, thus indicating the need for operative intervention. In children with MP 33–40%, treatment should be based on other clinical signs and the progression of MP over time. </jats:p></jats:sec>