Comparison of cage application modality in posterior lumbar interbody fusion with posterior instrumentation—A finite element study

Tsuang, Yang-Hwei; Chiang, Yueh-Feng; Hung, Chih-Yi; Wei, Hung-Wen; Huang, Chang-Hung; Cheng, Cheng-Kung

doi:10.1016/j.medengphy.2008.11.012

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Volume 31, Issue 5 , Pages 565-570, June 2009

Comparison of cage application modality in posterior lumbar interbody fusion with posterior instrumentation—A finite element study

Yang-Hwei Tsuang
- Taipei City Hospital, Taipei, Taiwan
Yueh-Feng Chiang
- Taipei City Hospital, Taipei, Taiwan
- Orthopaedic Biomechanics Laboratory, Institute of Biomedical Engineering, National Yang Ming University, Taipei, Taiwan
Chih-Yi Hung
- Industrial Technology Research Institute, Hsing Chu, Taiwan
Hung-Wen Wei
- Joint Prosthesis Technology Research Center, National Yang Ming University, Taipei, Taiwan
Chang-Hung Huang
- Biomechanics Research Laboratory, Department of Biomedical Research, Mackay Memorial Hospital, Taipei, Taiwan
Cheng-Kung Cheng
- Orthopaedic Biomechanics Laboratory, Institute of Biomedical Engineering, National Yang Ming University, Taipei, Taiwan
- Corresponding author at: Orthopaedic Biomechanics Laboratory, Institute of Biomedical Engineering, National Yang Ming University, No. 155, Sec. 2, Li-Nung St., Shih-Pai, Taipei 11221, Taiwan.

Received 12 May 2008; received in revised form 30 October 2008; accepted 17 November 2008. published online 05 January 2009.

Abstract

Background

Posterior lumbar interbody fusion (PLIF) cages have achieved satisfactory fusion results, but cases of cage migration or mechanical failure were repeatedly reported. Therefore, we conducted a finite element study to determine the impact of cage applications including number, positioning, and adding posterior instrumentation (PI).

Methods

A finite element model of the lumbar spine was generated from Computer Tomography scans and was validated. Partial laminectomy, diskectomy with partial facetectomy, and single or double-cage insertion were simulated onto the model, with or without posterior pedicle screws instrumentation. The maximal von Mises stresses between different loading conditions were compared between modalities to evaluate the risks of migration or mechanical failure.

Results

Posterior instrumentation decreases at least half the distortion stress of cage–endplate interface and facet joints, and diminishes the differences between the stresses of inserting one or two cages. Based on one cage insertion, adding posterior instrumentation provides more efficient stability than an additional cage. Furthermore, an obliquely inserted cage with posterior instrumentation produced lower stress than a cage inserted on one side due to better structural symmetry. Conclusively, one oblique anterior cage and bilateral posterior pedicle screws reconstructed the tripod system as the intact disc and facet joints, and provided similar stability as two cages did.

Keywords: Posterior lumbar interbody fusion (PLIF), Cage position, Finite element analysis (FEA)