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Transition of Mechanical Environment What is an Optimal Fixation Size? How do Cells Respond to Stress Gradients? Few Studies on Cellular Responses to Gradients of Solid Mechanical Stresses. Stretch. 5%. 10%. 15%. 20%. 25%. R i = r i = 1.0 R o = 2.0.
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Transition of Mechanical Environment • What is an Optimal Fixation Size? • How do Cells Respond to Stress Gradients? • Few Studies on Cellular Responses toGradients of Solid Mechanical Stresses Stretch 5% 10% 15% 20% 25% Ri = ri = 1.0 Ro = 2.0 Skin Biopsy Arthroscopy Stent Deployment Circumferentially Stiffer Case Isotropic Case Radially Stiffer Case Procedural Failure Wound Healing Suture Success? Prolonged Hospital Stays Finite DeformationModeling PredictableStress Distributions In VitroExperiments Fixation (Zero-displacement)Sutures, Wound Healing,Apposition of Stent Failure? Ri, ri 0.001 0.5 1.0 1.5 Defect Fixation Ro = 2.0 Stretch: 10% Defect (Traction-free) Circumferentially Stiffer Case Isotropic Case Radially Stiffer Case • Theoretical Framework (David & Humphrey 2004) • Cauchy Stress • Fung-type Exponential Pseudostrain-energy Function • Equilibrium Equation • Boundary Conditions • Outer Boundar t0: Uniform Radial Stress • Inner Boundary (Zero-displacement) lI: Principal Stretch ratio Reference EII: Green Strain Ri Ro David, G., Humphrey, J. D., 2004. Redistribution of stress due to a circular hole in a nonlinear anisotropic membrane. Journal of Biomechanics 37, 1197-1203 c, ci: Material Parameters Rectangular MembraneStretch Apparatus Circular Membrane Stretch Apparatus (R, Q) (r, q) ri ro Ro: Outer Radius Ri: Inner Radius ro: Outer Radius ri: Inner Radius Reference Configuration Deformed Configuration Elastic Response of Thin Circular Membrane tqq trr Stress gradients in circular membranous tissues with central fixationsDaisuke Mori, Guido David, Jay D Humphrey, and James E Moore Jr.Texas A&M University, Department of Biomedical Engineering Introduction Results Discussion • Medical Interventions Including Minimally Invasive Techniques • Effect of Stretch Ratio Induce Changes in Mechanical Environment Risk of: • How do Cells Respond to the Complex Stress EnvironmentsFollowing Interventional Procedures? • Stress Patterns Depend on a Defect or Fixation • Effect of Size of Fixation Future Direction Methods • Experiments of Cellular Reactions to StressGradients Following Interventional Procedures • Rigid Fixations Play an Important Role in the Distribution of Stress and Strain in a Manner Different From Tissue Defects. • Stress and its Gradients due to Interventional Treatments may Depend on the Size of Fixation, as well as the Material Behavior of the Tissue. • Material Parameters
