Inaccuracy of the migration percentage and center-edge angle in predicting femoral head displacement in cerebral palsy

Six patients (seven hips) with total-body-involvement cerebral palsy were assessed for a hip reconstruction, Four patients (five hips) underwent three-dimensional computerized tomographic (3D CT) scans, and in two patients, faux profile views were obtained. The femoral head was subluxed or dislocated anteriorly in all seven hips. The migration percentage (MP) and center-edge angle (CEA) underestimated the pathology. We conclude that the MP and CEA do not exclude an anterior displacement of the femoral head and calls into question the accuracy of methods relying on two-dimensional imaging in assessing hip containment in this group of patients. The faux profile view is sufficient to show an anterior hip displacement but a 3D CT gives superior detail to help in planning a surgical reconstruction.