A custom-designed multi-axis spine machine was used to test cadaveric three-vertebra two-disc motion segments until failure, 13 in combined flexion-anterior shear and six in flexion only loading. The average shear force was 1.99±0.64 kN with a shear displacement of 15.61±5.03 mm; flexion moment of 174.27±58.21 N-m and flexion angle of 14.10±2.3 degrees at failure for the 13 specimens loaded in combined anterior shear-flexion. For the six specimens loaded in flexion, failure moment was 140.43±18.4 N-m at a flexion angle of 12.7±2.29 degrees. This difference was not statistically significant. Also, there were no significant differences in the failure flexion moment and compressive force between those in combined and standalone condition. The average compressive forces at failure were lower than the values needed to fracture a vertebra as reported in the literature review.
Keywords: spine; force; biomechanics; automobiles; accidents