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Effect of Translational Degrees of Freedom of Intervertebral Joints on Prediction of Spinal Load and Muscle Forces in AnyBody Modeling System

Nikpour, Hassan | 2014

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 46522 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Arjmand, Navid; Parnianpour, Mohammad
  7. Abstract:
  8. Biomechanical models are indispensable tools in predictions of muscle forces and joint loads towards design of prevention and treatment programs. In most of these models intervertebral joints are modeled as hinge joints thus neglecting the existing translational degrees of freedom (DOFs). This simplification can alter the results of the model as changes in model kinematics affect the prediction of the joint and muscle forces. The current study aims to evaluate the likely effect of this simplification on the predictions of the musculoskeletal model of AnyBody Modeling System (AMS) for muscle forces and spinal loads. Clinical application of this study is in assessing the limitation of artificial disc replacements which similarly allow only postoperative rotational DOFs. Lumbar spine model of AMS is modified to incorporate both rotational and translational stiffness of intervertebral joints. A number of physical activities in upright and flexed postures are simulated using two distinct modes; Hard Joint (having only rotational degrees of freedom) and Stiff Joint (having joints with all six degrees of freedom). Results indicate that in activities involving large flexion angles and hand loads (approximately 80¬o flexion with 25 kg hand load), the effect of neglecting translational stiffness on model predictions is considerable. For most of the simulated activities in this study, however, neglecting translational DOFs plays a negligible to moderate role. Considering the computational costs to include translational DOFs, simplification of intervertebral joints as ball-and-socket joints can hence be acceptable. The algorithm used to introduce translational DOFs to AMS can be used to simulate other human body joints
  9. Keywords:
  10. Spine ; Lumbar ; Musculoskeletal Modeling ; Anybody Software ; Intervertebral Joint

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