Biomechanical study of oblique lumbar interbody fusion (OLIF) augmented by different instrumentations: a finite element analysis

Abstract

Background: To explore the biomechanical differences in oblique lumbar interbody fusion (OLIF) augmented by different types of instrumentation.Methods: A three-dimensional nonlinear finite element (FE) model of an intact L3-S1 lumbar spine was built and validated. The intact model was modified to develop five OLIF surgery models (stand-alone OLIF; OLIF with lateral plate fixation [OLIF+LPF]; OLIF with unilateral pedicle screws fixation [OLIF+UPSF]; OLIF with bilateral pedicle screw fixation [OLIF+BPSF]; OLIF with translaminar facet joint fixation + unilateral pedicle screw fixation [OLIF+TFJF+UPSF]) in which the surgical segment was L4-L5. Under a follower load of 500 N, a 7.5-Nm moment was applied to all lumbar spine models to calculate the range of motion (ROM), equivalent stress peak of fixation instruments (ESPFI), equivalent stress peak of cage (ESPC), equivalent stress peak of cortical endplate (ESPCE), and equivalent stress average value of cancellous bone (ESAVCB).Results: Compared with the intact model, the ROM of the L4-L5 segment in each OLIF surgery model decreased by > 80%. The ROM values of adjacent segments were not significantly different. The ESPFI, ESPC, and ESPCE values of the OLIF+BPSF model were smaller than those of the other OLIF surgery models. The ESAVCB value of the normal lumbar model was less than the ESAVCB values of all OLIF surgical models. In most postures, the ESPFI, ESPCE, and ESAVCB values of the OLIF+LPF model were the largest. The ESPC was higher in the stand-alone OLIF model than in the other OLIF models. The stresses of several important components of the OLIF+UPSF and OLIF+TFJF+UPSF models were between those of the OLIF+LPF and OLIF+BPSF models.Conclusions: Our biomechanical FE analysis indicated the greater ability of OLIF+BPSF to retain lumbar stability, resist cage subsidence, and maintain disc height. Therefore, in the augmentation of OLIF, bilateral pedicle screw fixation may be the best approach.

Biomechanical characteristics of 2 different posterior fixation methods of bilateral pedicle screws: A finite element analysis

“…Therefore, this is consistent with broken nails caused by stress fatigue in some patients after long-term activity. [37][38][39] This experiment verified that the pedicle screw internal fixation system has an obvious effect on the lumbar spine and that role in maintaining stability can reduce the probability of spinal instability. In this experiment, both models produced stress concentration at the root of the screw and the connection of the screw rod, which is consistent with the position of internal fixation failure and fracture commonly observed in the clinic.…”

“…Therefore, this is consistent with broken nails caused by stress fatigue in some patients after long-term activity. [37–39]…”