Biomechanical Comparison of the Influence of Osteoporosis on the Lumbar Spine After Lumbar Interbody Fusion Surgery or Non-fusion Dynamic Stabilization Surgery Under Whole Body Vibration

Objective

The objective of this study was to determine and compare the influence of osteoporosis on biomechanics of the spine after lumbar interbody fusion (LIF) surgery or non-fusion dynamic stabilization (NFDS) surgery under whole body vibration (WBV) which is typically present in moving vehicles.

Methods

Based on a previously validated finite element (FE) model of normal human lumbosacral spine, four surgical models including LIF, LIF with osteoporosis (LIF-OST), NFDS, and NFDS with osteoporosis (NFDS-OST) were constructed. Biomechanical responses of the surgical models to an axial cyclic load were calculated using transient dynamic analysis. Response parameters include vibration amplitudes of the endplate stress and screw stress at surgical L4–L5 level, vibration amplitudes of the disc bulge and intradiscal pressure at adjacent L3–L4 level.

Results

Osteoporosis increased vibration amplitudes of all these investigated response parameters. Further, we found that vibration amplitudes of the endplate stress and screw stress for the LIF-OST model were significantly higher than those for the NFDS-OST model, but there was very small difference in vibration amplitudes of the disc bulge and intradiscal pressure between the LIF-OST and NFDS-OST models.

Conclusions

For both the LIF and NFDS surgeries, osteoporosis might increase the risk for implant failure and accelerate adjacent segment degeneration (ASD) under WBV. When osteoporosis occurs, LIF might be associated with a higher likelihood of implant failure at the surgical level compared with NFDS, and the surgical approach (LIF or NFDS) might have little influence on biomechanics of the adjacent level.