Biomechanical Study of the Effect of Different Lumbar Fusion Cage on Adjacent Segments

In this paper we simulated the cage insertions on the level L3-L4 of lumbar with three types of lumbar cage used in different lumbar fusion.Biomechanics of the adjacent level with each type of cage stands alone were analyzed.A finite element model of lumbar spine on L2-L5 was generated from computer tomography scans and validated.Diskectomy,partial laminectomy or facetectomy and kinds of cage insertion were simulated onto the model,with the pre-load of 400 N and pure movements of ± 7.5 Nm applied on the top of vertebrae of L2,the changes of range of movement(ROM)in flexion,extension,lateral bending,axial rotation in the adjacent levels,and the max von mises in the adjacent disks were analyzed and compared between intact and fusion models of anterior lumbar interbody fusion(ALIF) cage or transforaminal lumbar interbody fusion(TLIF) cage or posterior lumbar interbody fusion(PLIF) cage.The ALIF cage provides higher adjacent segment stability than the other two cages,but the differences between TLIF cages are minor,and the PLIF cage significantly increases the ROM of adjacent levels and max von mises in the adjacent disks.