Objective:

To evaluate the effects of three lumbar interbody fusion techniques on the occurrence of complications in an osteoporotic spine under whole-body vibration.

Methods:

A previously developed and validated nonlinear finite element model of L1-S1was modified to develop ALIF, PLIF and TLIF models with osteoporosis. In each model, the lower surface of sacrum was absolutely fixed, a follower load of 400N was applied through the axis of the lumbar spine, and an axial sinusoidal vertical load of ± 40N (5 Hz) was imposed on the superior surface of L1, to perform a transient dynamic analysis. The maximal values of intradiscal pressure, shear stress on anulus substance, disc bulge, facet joint stress, and screw and rod stress, along with their dynamic response curves, were collected.

Results:

Among these three models, the TLIF model generated the greatest screw and rod stress, and PLIF model generated the greatest cage-bone interface stress. At L3-L4 level, compared with the other two models, the maximal values and dynamic response curves of intradiscal pressure, shear stress of annulus ground substance and disc bulge were all lower in the ALIF model. However, the facet contact stress at adjacent segment in the ALIF model was higher than that in the other two models.

Conclusion:

In an osteoporotic spine under whole-body vibration, TLIF has the highest risk of screw and rod breakage, PLIF has the highest risk of cage subsidence, and ALIF has the lowest risk of upper adjacent disc degeneration, but the highest risk of adjacent facet joint degeneration.