title: Comparison of cage application modality in posterior lumbar interbody fusion with posterior instrumentation--a finite element study.
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.
authors.affiliation: Taipei City Hospital, Taipei, Taiwan.
authors.forename: Yang-Hwei
authors.initials: YH
authors.lastname: Tsuang
authors.forename: Yueh-Feng
authors.initials: YF
authors.lastname: Chiang
authors.forename: Chih-Yi
authors.initials: CY
authors.lastname: Hung
authors.forename: Hung-Wen
authors.initials: HW
authors.lastname: Wei
authors.forename: Chang-Hung
authors.initials: CH
authors.lastname: Huang
authors.forename: Cheng-Kung
authors.initials: CK
authors.lastname: Cheng
mesh_terms: D000328:Adult; D005260:Female; D020342:Finite Element Analysis; D006801:Humans; D016268:Internal Fixators; D008159:Lumbar Vertebrae / Q000502:physiology / Q000601:surgery*; D008953:Models, Anatomic; D008954:Models, Biological; D013123:Spinal Fusion / Q000295:instrumentation*; D013314:Stress, Mechanical