A method to calculate relative spinal motion without digitization

In conclusion, an alternative data reduction method in both Euler and projection angles to calculate range of motion for in vitro spine biomechanical studies was presented. The method was validated on a human cadaveric lumbar motion segment under axial torsion, lateral bending, and flexion extension. Because the relative spinal motion does not depend on how local coordinate systems are oriented, the digitization process can be eliminated in most multidirectional flexibility tests. Compared with previous methods, this new method provides more consistent kinematical results and significantly simplifies experimental procedures.