MATERIAL and METHODS: A normal finite element model, an anterior lumbar interbody fusion model and a transforaminal lumbar interbody fusion model of L3-5 were developed. 800 N compressive loading plus 10 Nm moments simulating flexion, extension, lateral bending and axial rotation were imposed on L3 superior endplate. The intradiscal pressure, intersegmental rotation and tresca stress in L3-4 were investigated.

RESULTS: Under all loading directions, the values of three parameters in transforaminal lumbar interbody fusion model were the highest and those in normal model were the lowest, and the values in the ALIF model were higher than the normal model while lower than the TLIF model. In the ALIF and normal models, the values of the three parameters on left lateral bending and axial rotation were equal to those on right lateral bending and axial rotation. However, in the TILF model, the values on right lateral bending and axial rotation were larger than those on left lateral bending and axial rotation.

CONCLUSION: Transforaminal lumbar interbody fusion aggravates adjacent segmental degeneration more adversely than anterior lumbar interbody fusion. Keywords : Anterior lumbar interbody fusion (ALIF), Transforaminal lumbar interbody fusion (TLIF), Adjacent segmental degeneration (ASD)