Spine kinematics: a digital videofluoroscopic technique.

It is notoriously difficult to quantify the kinematic behaviour of vertebral segments in the assessment and localization of mechanical disorders of the spine. This paper describes the use of an image processor and an X-ray machine with image intensifier for the measurement of lumbar spine angular rotation and instantaneous centres of rotation in the coronal plane. The system was calibrated against a model under realistic conditions employing multiplanar motion and X-ray scatter.