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Effects of Spinal Fusion Surgery on the Kinetics of Adjacent Segments, Using Medical Imaging and Finite Element Modeling; Comparison with Musculoskeletal Model

Abbasi Ghiri, Alireza | 2021

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 54908 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Arjmand, Navid
  7. Abstract:
  8. Passive finite element (FE) models of the spine are commonly used to simulate intact and various pre- and postoperative pathological conditions. Being devoid of muscles, these traditional passive FE models are driven by simplistic loading scenarios, e.g., a constant moment and compressive follower load (FL) that do not properly mimic the complex in vivo loading condition of the spine under muscle exertions. The present works therefore aims to develop novel passive FE models that are driven by more realistic yet simple loading scenarios, i.e., in vivo measured vertebral rotations and pathological-condition dependent FLs (estimated based on detailed musculoskeletal finite element (MS-FE) spine models). In these novel force-displacement control passive FE models, unlike the traditional passive FE models, FLs vary not only at different spine segments (T12-S1) but between intact, pre- and post-operative conditions. Three intact, preoperative degenerated, and postoperative fused conditions at the L4-L5 segment for five static in vivo activities in upright and flexed postures were simulated by the traditional passive FE, novel force-displacement control passive FE, and gold-standard detailed MS-FE spine models. Our findings indicate that, when compared to the MS-FE models, the force-displacement control passive FE models driven by in vivo vertebral kinematics and condition-dependent FLs could accurately predict the magnitude of disc compression force, intradiscal pressure, annulus maximal von Mises stress, and vector sum of all ligament forces at adjacent segments (L3-L4 and L5-S1) but failed to predict disc shear force and facet joint forces. In this regard, the force-displacement control passive FE models were much more accurate than the traditional passive FE models. Clinical recommendations made based on traditional passive FE models should, therefore, be interpreted with caution. Moreover, only detailed MS-FE models should be used when shear disc and facet joint forces are of concern in simulating intact and/or pathological conditions.
  9. Keywords:
  10. Spine ; Kinetic Model ; Load ; Adjacent Segment Disease (ASD) ; Finite Element Modeling ; Musculoskeletal Modeling ; Musculoskeletal Injuries ; Fusion Surgery

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