Verification of the Robin and Graham classification system of hip disease in cerebral palsy using three‐dimensional computed tomography

Aim We evaluated the validity of the Robin and Graham classification system of hip disease in cerebral palsy (CP) using three‐dimensional computed tomography in young people with CP. Method A total of 91 hips in 91 consecutive children with bilateral spastic CP (57 males, 34 females; nine classified at Gross Motor Function Classification System level II, 42 at level III, 32 at level IV, and eight at level V; mean age 5y 2mo, SD 11mo; range 2–6y) were investigated retrospectively using anteroposterior plain radiographs and three‐dimensional computed tomography (3D‐CT) of the hip. The migration percentage was calculated on plain radiographs and all participants were classified into four groups according to migration percentage: grade II, migration percentage ≥10% but ≤ 15%, (four hips), grade III, migration percentage >15% but ≤30%, (20 hips); grade IV, migration percentage >30% but