Biomechanical effect of vibration on the fused lumbar spine with different stabilizers

This study aimed to compare effect of whole-body vibration on biomechanics of fused lumbar spine with different posterior stabilizers, including interspinous process spacer (IPS) and bilateral pedicle screw system (BPSS). Finite element model of lumbar interbody fusion with IPS or BPSS at L4–L5 level was constructed based on a healthy human whole lumbar spine. Transient dynamic and static analyses were employed to compute dynamic responses of deformation and stress for the models to a sinusoidal axial vibration load of ±40 N and its corresponding static axal loads (−40 N and 40 N), respectively. The results showed that for both the IPS and BPSS models, vibration amplitudes of the responses were significantly higher than corresponding changing amplitudes under static loads. The increasing effect of vibration load in endplate stress at L4–L5 reached 128.3% and 146.0% for IPS and BPSS models. By contrast, the increasing effects of vibration load in disc bulge and annulus stress at adjacent L3–L4 were nearly the same for these two models. It indicates that vibration sensitivity of fused level is lower when using IPS compared with BPSS, but there is no obvious difference in vibration sensitivity of adjacent level when using these two stabilizers.