Volume 48 Number 5, 2011
Pages 587 — 596
Abstract — One main question in spinal kinematics is the determination of the spine's apparent axial center of rotation. Previous research on this topic has yielded contradictory results. The objective of this study was to determine the apparent axial center of rotation for seven lumbar and six thoracic spinal segments by developing and validating a new method. A custom six-degree-of-freedom device, allowing full range of motion, was used with motion recording and analysis software. This system tracked a grid of markers on a specimen when rotational torque was applied in both clockwise and counterclockwise directions at 3.53 Nm, 7.05 Nm, 10.58 Nm, and 14.10 Nm. The area encompassing the apparent axial center of rotation was determined by identifying the five markers with the least amount of motion. The marker angular displacement was calculated as the angle between a virtual line drawn between two points in the initial and final torque conditions. Rotation in both directions was averaged. The lumbar and thoracic spinal segments averaged an apparent axial center of rotation at the posterior border of the vertebral endplates and the anterior border of the spinal canal, with average clockwise to counterclockwise angular displacement ratios of 0.87 and 0.97, respectively.
Key words: axial, biomechanics, center of rotation, lumbar spine, new method, rehabilitation, rotational torque, spinal injuries, spinal kinematics, thoracic spine.
Last Reviewed or Updated Thursday, May 26, 2011 10:38 AM