The natural history of hip development in cerebral palsy

AIM: The purpose of this study was to evaluate a population-based radiographic hip surveillance programme for children with cerebral palsy (CP) and to assess the natural history of hip displacement. METHOD: The study comprised 335 children (188 males, 147 females), born during 2002 to 2006 in the 10 south-eastern counties in Norway. Their mean age at the first radiograph was 3 years (range 6mo-7y 11mo) and the mean age at the most recent follow-up was 5 years 5 months. Distribution according to CP type was spastic hemiplegia in 38%, diplegia in 27%, quadriplegia in 21%, dyskinesia in 10%, and ataxia in 3%; Gross Motor Function Classification System (GMFCS) levels I to V were, 44%, 14%, 8%, 11%, and 23% respectively. Migration percentage (MP), acetabular index, and pelvic obliquity were measured on the radiographs. RESULTS: Hip displacement (MP>33%) occurred in 26% of all children (subluxation in 22% and dislocation in 4%) and in 63% of those in GMFCS levels IV or V. Dislocation occurred in 14 children at a mean age of 4 years 5 months (range 1y 10mo-9y 7mo). The mean migration percentage was 20.4% at the initial radiographs and 34.0% at the last follow-up. Mean progression in migration percentage increased markedly with decreasing functional level, from 0.2% per year at GMFCS level I to 9.5% at level V. INTERPRETATION: There is a pronounced trend towards hip displacement in nonambulant children. Close surveillance from age 1 to 2 years is needed to find the appropriate time for preventive surgery. Since 12% of the nonambulant children developed dislocation, our routines for hip surveillance need improvement.