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Biomechanical Analysis of the Effects of L4-L5 Fusion Surgery on Adjacent Segments Using Musculoskeletal and Finite Element Modeling

Ebrahimkhani, Mahdi | 2023

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 55882 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Arjmand, Navid; Shirazi Adl, Aboulfazl
  7. Abstract:
  8. Background: Degeneration of intervertebral joints due to kinetical alterations after fusion surgery is a prevalent back disorder. While in-vivo studies are limited to medical imaging techniques, in-vitro and in-silico (passive FE modeling) investigations lack the crucial role of muscle forces. Available musculoskeletal modeling studies, not only suffer oversimplification of intervertebral joints, but have some shortcomings in incorporation of the contributing factors (that may alter postoperative kinetics). On the other hand, one of the main shortcomings in the available musculoskeletal models is their inability to account for dynamic effects and modeling transient events. Purpose: 1- Investigation on postoperative spinal kinetical alterations after fusion surgery using biomechanical models, 2- Development of a dynamic coupled musculoskeletal-finite element model. Method: First, a musculoskeletal model (MS) was exploited to analyze the effects of various biomechanical changes (i.e., changes in movement kinematics, changes in optimal standing posture and iatrogenic muscle injuries) on kinetical alterations of adjacent segments. Second, by combination of the MS model and a passive finite element model of intervertebral joints, a coupled MS-FE model was developed and used to evaluate the alterations in postoperative spinal kinetics. Finally, the developed coupled static model was modified to a coupled dynamic model by addition of inertia, dynamic properties and change in integration procedure. The model was used to investigate the effects of movement pace on internal spinal loads. Results: Results indicated that changes in the kinetics of adjacent segments (e.g., by up to 115% and 73% in shear loads and passive moments, respectively) depended on the preoperative L4–L5 disc condition, postoperative lumbopelvic kinematics and, to a lesser extent, postoperative changes in the L4–L5 segmental lordosis and muscle injuries. Results of simulations with dynamic model depicted changes in muscle activation pattern and internal spinal loads (up to 30% and 93% increase in compression and shear forces, respectively, in the last phase of flexion) in fast-paced movements in comparison to slow-paced ones
  9. Keywords:
  10. Fusion Surgery ; Kinematics ; L4-L5 Motion Segment ; Spine ; Finite Element Method ; Musculoskeletal Injuries ; Adjacent Segment Disease (ASD) ; Biomechanical Models ; Coupled Musculoskeletal Finite Element Modeling ; Muscles Force

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