Role of Additional Screws and Rod Fixation in Cage Loading During Oblique Lateral Interbody Fusion: A Finite Element Analysis.

Abstract

<b>Background/Objectives</b>: Additional lateral fixation is a method with the potential to redistribute cage loading during oblique lumbar interbody fusion (OLIF). However, its biomechanical effects remain poorly understood. This study aimed to compare the mechanical responses of the lumbar spine following OLIF, both with and without additional lateral fixation, using a finite element (FE) analysis. <b>Methods</b>: An FE lumbar model with an OLIF cage at the L4-L5 levels was developed. A lateral fixation system comprising screws and a rod was incorporated to redistribute the cage loading and enhance spinal stability. Two OLIF cage positions-centered and at an oblique angle-were compared. <b>Results</b>: The additional lateral fixation reduced cage loading by 70% (409 to 123 N) and 72% (411 to 114 N) for the centered and oblique cage positions, respectively. Without lateral fixation, the peak equivalent stress on the cage during extension increased threefold (66 to 198 MPa) for the oblique position compared with that for the centered position. <b>Conclusions</b>: An additional lateral screw-rod fixation system is suggested as a complementary approach to the OLIF technique to mitigate endplate loading and pressure.