Mechanical effects of continuous passive motion on the lumbar spine in seating

The aim of this study was to develop a model which describes the mechanical spinal response to small alternating pelvic stimulation induced by an acti ve rotational movement of a normal chair. The rotary continuous passive mot ion (RCPM) of the seat about a vertical axis of only 0.6 degrees resulted i n an increased in spinal length as opposed to the: normal daily shrinkage, and back patients experienced pain relief. Passive and active exercies have been broadly applied for treating and healing spinal disorders. A rigid bo dy package (ADAMS Android) was used to translate the stimulation of the isc hial tubersoity in caudo-cranial handing-over visualisation. The parameters of the model were set so that the values of the global stiffness and geome try of the intervertebral discs could be changed. In vivo validation of the model was based on force and moment measurements using an internal AO fixa tor. The predicitons of the model concerning natural frequency (4.5 Hz) in vertical direction and the axial torsion response on small pelvic torsion a re comparable with experimental data. (C) 2000 Elsevier Science Ltd. All ri ghts reserved.