A method for reducing prosthetic loading failure including the steps of providinga prosthesis for a vertebral column comprising at least an upper part for attachmentto an upper vertebrae and a lower part for attachment to a lower vertebrae, theupper part having a lower curved surface and the lower part having an upper curvedsurface, wherein the upper and lower curved surfaces have a centre of radius ofcurvature offset rearwardly with respect to a central vertical axis throughthe upper and lower vertebrae, and positioning the centroid of at least one ofthe upper and lower parts substantially on the same vertical axis of the centreof radius of curvature.
