A classification system for hip disease in cerebral palsy

In population-based studies, hip displacement affects approximately one-third of children with cerebral palsy (CP). Given the extreme range of clinical phenotypes in the CP spectrum, it is unsurprising that hip development varies from normality, to dislocation and degenerative arthritis. Numerous radiological indices are available to measure hip displacement in children with CP; however, there is no grading system for assessing hip status in broad categorical terms. This makes it difficult to audit the incidence of hip displacement, determine the relationship between hip displacement and CP subtypes, assess the outcome of intervention studies, and to communicate hip status between health care professionals. We developed a categorical, radiographic classification of hip morphology based on qualitative indices and measurement of the key continuous variable, the migration percentage of Reimers. One hundred and thirty-four radiographs were reviewed of 52 female and 82 male adolescents with CP who were at, or close to, skeletal maturity (mean age 16y 1mo [SD 1y 4mo] range 14y to 19y 1mo). Twenty-nine were classified at Gross Motor Function Classification System level I, 25 at level II, 27 at level III, 24 at level IV, and 29 at level V. A classification system was developed to encapsulate the full spectrum of hip morphology in CP, with and without intervention.