title: Nonlinear viscoelastic material property estimation of lower extremity residual limb tissues.
abstract: Axisymmetric nonlinear finite-element analysis was used to simulate force-relaxation and creep data obtained during in vivo indentation of the residual limb soft tissues of six individuals with trans-tibial amputation [1]. The finite-element models facilitated estimation of an appropriate set of nonlinear viscoelastic material coefficients of extended James-Green-Simpson material formulation for bulk soft tissue at discrete, clinically relevant test locations. The results indicate that over 90% of the experimental data can be simulated using the two-term viscoelastic Prony series extension of James-Green-Simpson material formulation. This phenomenological material formulation could not, however, predict the creep response from relaxation experiments, nor the relaxation response from creep experiments [2-5]. The estimated material coefficients varied with test location and subject indicating that these coefficients cannot be readily extrapolated to other sites or individuals.
authors.affiliation: Middle East Technical University, Department of Mechanical Engineering, TR-06531 Ankara-Turkey. tonuk@metu.edu.tr
authors.forename: Ergin
authors.initials: E
authors.lastname: Tönük
authors.forename: M Barbara
authors.initials: MB
authors.lastname: Silver-Thorn
mesh_terms: D000671:Amputation, Surgical; D000672:Amputation Stumps / Q000503:physiopathology*; D003198:Computer Simulation; D003238:Connective Tissue / Q000503:physiopathology* / Q000601:surgery*; D004548:Elasticity; D006244:Hardness; D006245:Hardness Tests / Q000379:methods; D006801:Humans; D007719:Knee Joint / Q000503:physiopathology* / Q000601:surgery*; D035002:Lower Extremity / Q000503:physiopathology / Q000601:surgery; D008954:Models, Biological; D017711:Nonlinear Dynamics; D013314:Stress, Mechanical; D014783:Viscosity