Method

The radiographs of GMFCS Level III – V children from a surveillance programme database were analysed and migration percentage (MP) and HSA measured. The first radiograph of each patient was taken to remove the effect of the surveillance programme. The most displaced hip in each child, by MP, was used for analysis and the corresponding HSA measured. Hip displacement was defined as MP > 40% and logistic regression was used to adjust for HSA, GMFCS, age and sex.