Influence prediction of tissue injury on frequency variations of the lumbar spine under vibration.

A three-dimensional finite element model of the spine T12-S1 segment was developed and used to investigate biodynamics characteristics of the human lumbar spine. The T12-S1 model was carefully built including spinal vertebrae, intervertebral discs, and ligaments so as to approach the real human spine. Finite element modal analysis was carried out to obtain vibration modes and resonant frequencies of the spine. The analytical results indicate that the vertical resonant frequency of the spinal T12-S1 segment with a mass of 40 kg on the top vertebra is 7.68 Hz. The vertical resonant frequencies of spine motion segments decrease with the number of spine motion segments increasing. The tissue injury, such as disc denucleation and removal both of facet articulations and their capsular ligaments may decrease the resonant frequencies of spine in different extent. The denucleation makes larger influence on vertical resonant frequencies than facetectomy does. The denucleation is more harmful to the facet articulations under whole body vibration. The dynamic characteristics of the T12-S1 model accords with the actual human spine, and it is useful for the relative studies of the human spine, such as biomechanical characteristics, vibration-related injury mechanism of the human spine, and development of vibration-related mechanical products.