Ability of the finite element models to predict response of the human spine to sinusoidal vertical vibration.

STUDY DESIGN

The study examined the efficacy of the finite element models of various spinal segments in predicting the vibration response of the human spine.

OBJECTIVE

To determine the optimal spinal segment finite element model to understand the effects of vibration on its biomechanics.

SUMMARY OF BACKGROUND DATA

Several finite element models (one and two motion segments) have been proposed to look into the effects of vibration on the lumbar spine. However, they cannot be used to predict biomechanical parameters in the lumbar spine in response to whole body vibration.

METHODS

A finite element model of the upper body from the head to the sacrum (H-S1) was generated. The H-=S1 model was altered to generate models of one motion segment (L3-L4), two motion segments (L3-L5), and the entire thoracolumbar spine and rib cage (T1-S1). The resonant frequencies of these models and effects of the trunk muscles and gravity were studied.

RESULTS

The resonant frequencies decreased with the increase in the number of motion segments. However, the decrease plateaued beyond the T1-S1 segment model. The first resonant frequency in the vertical direction for the H-S1 model was 8.32 Hz. Inclusion of the trunk muscles and the preload of self-weight changed it to 8.91 and 6.82 Hz, respectively.

CONCLUSIONS

Both the T1-S1 and H-S1 finite element models were able to predict vibration response of the human spine that closely matched in vivo experimental data reported in the literature.