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 6mo7y 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 10mo9y 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.