title: Long-term effects of placing one or two cages in instrumented posterior lumbar interbody fusion.
abstract: Posterior lumbar interbody fusion (PLIF) is an established surgical procedure for spine stabilization after the removal of an intervertebral disc. Researches have shown that inserting a single oblique cage has a similar immediate effect to coupled cages, and it has been proposed that single-cage PLIF is a useful alternative to traditional two-cage PLIF. However, it is not clear whether placing one or two cages represents the best choice for long-term fusion. The aim of this study is to examine how cage placement affects bone remodeling after PLIF surgery, and how this consequently impacts the long-term fusion process.
  
  
  
  A finite element model of a L3-L4 lumbar spine with PLIF was developed. The spinal segment was modeled with a partial laminectomy and a discectomy with partial facetectomy, and implanted with posterior pedicle screws. Two models were analyzed, one with coupled parallel cages and one with a single oblique cage. Adaptive bone remodeling was simulated according to Huiskes' criterion.
  
  
  
  The results showed that in the initial state prior to any bone remodeling, cage stress, cage subsidence and cage dislodgement in the single cage model were all greater than in the coupled cage model. In the final state after significant bone remodeling had taken place, these parameters had decreased in both models and the differences between the two models were reduced. Also, the single cage model demonstrated superior bone development in the bone graft when placed under a constant 400 N axial compressive load.
  
  
  
  Based on the long-term results, instrumented PLIF with a single cage could also be encouraged in clinical practice.
authors.affiliation: Key Laboratory for Biomechanics and Mechanobiology of Ministry of Education, School of Biological Science and Medical Engineering, Beihang University, Beijing, 100191, Peoples Republic of China.
authors.forename: Mingzheng
authors.initials: M
authors.lastname: Zhang
authors.affiliation: Key Laboratory for Biomechanics and Mechanobiology of Ministry of Education, School of Biological Science and Medical Engineering, Beihang University, Beijing, 100191, Peoples Republic of China.|State Key Laboratory of Virtual Reality Technology and Systems, Beihang University, No. 37 Xueyuan Road, Haidian District, Beijing, 100191, Peoples Republic of China.
authors.forename: Fang
authors.initials: F
authors.lastname: Pu
authors.affiliation: Key Laboratory for Biomechanics and Mechanobiology of Ministry of Education, School of Biological Science and Medical Engineering, Beihang University, Beijing, 100191, Peoples Republic of China.
authors.forename: Liqiang
authors.initials: L
authors.lastname: Xu
authors.affiliation: Key Laboratory for Biomechanics and Mechanobiology of Ministry of Education, School of Biological Science and Medical Engineering, Beihang University, Beijing, 100191, Peoples Republic of China.
authors.forename: Linlin
authors.initials: L
authors.lastname: Zhang
authors.affiliation: Key Laboratory for Biomechanics and Mechanobiology of Ministry of Education, School of Biological Science and Medical Engineering, Beihang University, Beijing, 100191, Peoples Republic of China.
authors.forename: Jie
authors.initials: J
authors.lastname: Yao
authors.affiliation: Key Laboratory for Biomechanics and Mechanobiology of Ministry of Education, School of Biological Science and Medical Engineering, Beihang University, Beijing, 100191, Peoples Republic of China.
authors.forename: Deyu
authors.initials: D
authors.lastname: Li
authors.affiliation: Key Laboratory for Biomechanics and Mechanobiology of Ministry of Education, School of Biological Science and Medical Engineering, Beihang University, Beijing, 100191, Peoples Republic of China. wangyu@buaa.edu.cn.
authors.forename: Yu
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Key Laboratory for Biomechanics and Mechanobiology of Ministry of Education, School of Biological Science and Medical Engineering, Beihang University, Beijing, 100191, Peoples Republic of China. yubofan@buaa.edu.cn.|State Key Laboratory of Virtual Reality Technology and Systems, Beihang University, No. 37 Xueyuan Road, Haidian District, Beijing, 100191, Peoples Republic of China. yubofan@buaa.edu.cn.
authors.forename: Yubo
authors.initials: Y
authors.lastname: Fan
mesh_terms: D016723:Bone Remodeling; D020342:Finite Element Analysis; D006801:Humans; D007403:Intervertebral Disc / Q000601:surgery; D008159:Lumbar Vertebrae / Q000601:surgery*; D008161:Lumbosacral Region; D065289:Pedicle Screws / Q000009:adverse effects*; D013123:Spinal Fusion / Q000379:methods*; D016896:Treatment Outcome
keywords: Bone remodeling; Finite element analysis (FEA); Lumbar spine model; Posterior lumbar interbody fusion (PLIF); Spinal cage