• N. Farahpour
  • P. Allard
  • M. Duhaime


The coupling mechanism of the spine motion is reported in 3-D kinematic assessment of the spine, Panjabi et al. (1989). Pearcy et al. (1984) and trunk, Farahpour et al. (1994). It was reported that the primary movement of bending was accompanied by secondary motions in two other planes. This coupling phenomena is essential to understand spine kinematics and for detection of some injuries. In this paper a novel technique is used to document the effects of velocity on the coupling mechanism of the spine in a normal population. A Vshaped triad including 3 nonlinear markers was attached over the spinous process landmark of TI, T3, T6, T8, T10, T11, T12, L1, L3, L5 and another spherical marker was used to identify the pelvis. Slow and fast movements of lateral bending of four normal subjects were collected by the Motion Analysis System and the 3-D coordinates of each marker were reconstructed by DLT technique. The relative angles between any two vertebra were estimated by Euler angle equation with the following sequences: bending, rotation, and flexion. Primary results are given for the thoracic region of a subject. In normal speed (A) for 25 degree right bending, there is about a 7 degree right rotation without any considerable pattern of flex./exten. while in fast bending (B) for almost 12 degrees of right bending there is a 10 degree right rotation and a 5 degree flexion. It seems that more twisting is happening during fast lateral bending movement. In some sport events where fast bending is combined with loading of the spine, the larger ratio of (rotation bending) may exist and this may lead to a higher risk for back.