Biomechanical Comparison of Transforaminal and Posterior Lumbar Interbody Fusion Devices after Decompressive Surgery: A Finite Element Analysis

Purpose: To investigate the biomechanical differences in transforaminal lumbar interbody fusion (TLIF) and posterior lumbar interbody fusion (PLIF) performed with bilateral or unilateral posterior fixation. Methods: A validated finite element model of L1-L5 was established to implant four types of cages (PLIF with two parallel cages and TLIF with a single anterior, middle, or diagonal cage) at the L3-4 level after decompressive surgery. Each model was applied with a 400N compressive load plus a 10N-m moment in all motions. The effect of unilateral or bilateral pedicle screw fixation in each TLIF model was compared. Several parameters were analyzed numerically, including range of motion (ROM) and adjacent disc and screw stress in each construct, and were compared with those of the intact model. Results: The difference in ROM between the PLIF and TLIF models with bilateral pedicle screw fixation was less than 10%, except in flexion. All TLIF cages positioned with bilateral screw fixation showed similar ROM at surgical and adjacent levels. On the other hand, changes that occurred in the TLIF cage models with unilateral (left) screw fixation were as follows: 15-20% higher extension, 27-57% higher right lateral bending, and 26-29% higher right torsion at the surgical level. However, there were fewer changes at the adjacent levels. In TLIF with a diagonal cage and unilateral screw fixation, the greatest variability of motion and annulus stress occurred during contralateral torsion and lateral bending. Conclusions: TLIF surgery is not favored for implanting a diagonal cage and unilateral pedicle screw fixation, because asymmetrical positioning of cage-andscrews in the TLIF constructs cannot provide sufficient stabilization.

並列關鍵字

transforaminal lumbar fusion ； pedicle screw fixation ； finite element analysis ； spine biomechanics

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