Quantitative analysis of hip dysplasia in cerebral palsy: a study of radiographs and 3-D reformatted images.

Cerebral palsy patients (31 hips) were evaluated using radiographic and three-dimensional (3-D) images to quantify hip anatomy. The 3-D images overcome distortions caused by joint contractures. Changes were more pronounced in the non-ambulators and characterized by shallow sockets with increased neck-shaft angles. These hips tended to subluxate in a posterior-superior direction and most had defects in the femoral heads. Ambulators had increased femoral anterversion but other hip parameters tended to improve with age. The 3-D measures of roof steepness and socket depth were found to correlate strongly with radiographic parameters of subluxation.