Biomechanical Comparison of Two New Stand-alone Anterior Lumbar Interbody Fusion Cages with Established Fixation Techniques-A Three-dimensional Finite Element Analysis

兩種新型前位椎間融合器與傳統融合固定法之生物力學特徵比較－有限元素模擬分析

陳世豪(Shih-Hao Chen) ； 趙時恆(Shih-Heng Chao) ； 鍾政成(Zheng-Cheng Zhong) ； 洪景華(Ching-Hua Hung)

《Journal of Orthopaedic Surgery Taiwan》 26卷4期 (2009/12) Pp. 170-179

並列摘要

Purpose: Anterior lumbar interbody fusion (ALIF) device avoids posterior fixation by enhancing stability via the locking screws or threaded cylinder into the vertebral bodies. Two new stand-alone cages were compared with established fixation methods based on a finite element (FE) analysis to investigate the stabilization effect among all cage designs.
Methods: A validated FE model of the L1-L5 was used to implant three types of ALIF cages (SynCage-Open, SynFix, and Stabilis) at the L3-4 level; the SynCage-Open model was supplemented with pedicle screw implant, as established fixation. The ends of the L5 vertebral bodies of each model were fixed and a 400N follower load plus a 10N-m moment were applied to the top of the L1 vertebra to produce flexion-extension, lateral bending, and axial rotation, respectively. The FE software (ANSYS 9.0) was used to calculate parameters, including range of motion (ROM), facet contact force, and stresses of the annulus and implants, for comparison with those of the intact (INT) model.
Results: At the surgical level, the SynCage-open model supplemented with pedicle screw fixation decreased ROM (＞77.7%) and annulus stress (＞74.4%) mostly; while the SynFix model decreased ROM over 53.4% and annulus stress over 58.8% in all motions, as compared with the IN T model. However, the Stabilis model decreased ROM slightly in extension (15.5%), lateral bending (24.9%), and axial rotation (36.2%). It also decreased annulus stress in lateral bending (35.8%) and axial rotation (39.5%). At the adjacent levels, there were no obvious differences of ROM and annulus stress among the implanted models. In addition, the Stabilis model had twice higher facet contact force than the SynFix model in extension and axial rotation.
Conclusions: ALIF implanted with the SynFix cage has an acceptable stability for clinical use without the requirement of additional posterior spinal fixation; while the Stabilis cage is not favored because of insufficient stabilization in extension and lateral bending.

並列關鍵字

anterior lumbar interbody fusion ； stand-alone cage ； finite element analysis