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A Detailed Nonlinear Finite Element Model of the L4-L5 Motion Segment to Predcit Spinal Loads during in Vivo Activities

Azari, Fahime | 2016

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 48732 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Arjmand, Navid; Parnianpour, Mohammad
  7. Abstract:
  8. Several geometrically-detailed passive finite element (FE) models of the lumbar spine have been developed and validated under in vitro loading conditions. As these models are devoid of muscles, they are either not used to simulate in vivo activities or muscle forces are modeled by a hypothetical compressive follower load (FL). A number of symmetric and asymmetric static tasks were first simulated using a validated musculoskeletal model of the thoracolumbar spine to predict trunk muscle forces. The predicted muscle forces along with the gravity loading were then applied to a passive FE model of the L4-L5 motion segment (developed and validated here) to estimate load sharing among the disc, ligaments, and facets for each task. When derived by muscle forces, the passive FE model predicted intradiscal pressures that closely matched measured in vivo values (R2 = 0.98 and RMSE = 0.18 MPa). However, when the in vivo tasks were simulated using a constant FL of either 500 or 1175 N, the predicted L4-L5 IDPs deviated, both qualitatively and quantitatively, from the in vivo data (R2 = 0.85 and RMSE = 0.58 MPa for FL = 500 N and R2 = 0.84 and RMSE = 0.32 MPa for FL = 1175 N). In clinical applications and design of implants, considering a constant FL, rather than muscle forces, on the passive FE models does not represent the in vivo loading conditions. Realistic in vivo loading conditions under muscle forces reported in this study should be used
  9. Keywords:
  10. Spine ; Ligaments ; Lumbar Muscule Force ; L4-L5 Motion Segment ; Finite Element Modeling ; Intradiscal Pressure

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