title: Biomechanical comparisons of different posterior instrumentation constructs after two-level ALIF: a finite element study.
abstract: Anterior lumbar interbody fusion (ALIF) with cylindrical cages and supplemental posterior fixation has been widely used for internal disc derangement. However, most researchers have focused on single-level ALIF. Therefore, the biomechanical performance of various fixation constructs after two-level ALIF is not well characterized. This research used three-dimensional finite element models (FEM) with a nonlinear contact analysis to evaluate the initial biomechanical behavior of five types of fixation devices after two-level ALIF (L3/L4, L4/L5) under six loading conditions. These fixation constructs included a three-level pedicle screw and rod, a two-level translaminar facet screw, a two-level transfacet pedicle screw, a bisegmental pedicle screw and rod, and a bisegmental pedicle screw and rod with cross-linking. The FEM's developed in this study demonstrate that, compared to the other four types of posterior fixation constructs analyzed, the three-level pedicle screw and rod provide the best biomechanical stability. Both two-level facet screw fixation constructs showed unfavorable loading in lateral bending. For the construct of the three-level pedicle screw and rod, the middle-segment pedicle screw should not be omitted even though a cross-link is used. The two-level ALIF models with cages and posterior fixation constructs that we developed can be used to evaluate the initial biomechanical performance of a wide variety of posterior fixation devices prior to surgery.
authors.affiliation: Department of Mechanical Engineering, National Taiwan University of Science and Technology, Taipei, Taiwan.
authors.forename: Chang-Yuan
authors.initials: CY
authors.lastname: Fan
authors.forename: Ching-Chi
authors.initials: CC
authors.lastname: Hsu
authors.forename: Ching-Kong
authors.initials: CK
authors.lastname: Chao
authors.forename: Shang-Chih
authors.initials: SC
authors.lastname: Lin
authors.forename: Kuo-Hua
authors.initials: KH
authors.lastname: Chao
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena; D020342:Finite Element Analysis; D006801:Humans; D016268:Internal Fixators; D008159:Lumbar Vertebrae / Q000033:anatomy & histology / Q000502:physiology / Q000601:surgery*; D008297:Male; D008953:Models, Anatomic; D013123:Spinal Fusion; D013314:Stress, Mechanical