title: Material properties of individual menisci and their attachments obtained through inverse FE-analysis.
abstract: Meniscal properties for computational methods have already been proposed. However, it is well known that there is high intra subject variability in the material properties of soft tissues and that disruption of the fiber network alters the biomechanics of the meniscus. Therefore, the objective of this study was to establish a non invasive method to determine the material properties of the individual menisci and their attachments using inverse FE-analyses. In a previous study, the 3D displacements of the meniscus and its attachments under axial joint loads were determined for intact porcine knees. To simulate the experimental response in individual FE-analyses (n=5), an anisotropic, hyperelastic meniscus matrix was embedded in a poroelastic model. During a particle swarm optimization, the difference between the force applied to the meniscus during the experiment and the femoral surface reaction force of the FE model at equilibrium was minimized by varying four material parameters. Afterwards, a prediction error was determined to describe how well the material parameter fit to each of the three displacement directions. Additionally, the stresses occurring in the meniscus were evaluated. The error of the material parameter optimization was on average 6.5±4.4%. The best fitting material parameter combination revealed an error of 1.2%. The highest stresses occurred in the region between the pars intermedia and posterior horn of the meniscus. The individual material properties of the meniscus were successfully obtained with a combination of previously reported, noninvasively measured 3D displacements and inverse FE-analyses. The methodology presented in this study is a promising contribution to the detection of degeneration within the meniscus.
authors.affiliation: Institute of Orthopaedic Research and Biomechanics, Centre of Musculoskeletal Research Ulm, University of Ulm, Ulm, Germany. Electronic address: maren.freutel@uni-ulm.de.
authors.forename: Maren
authors.initials: M
authors.lastname: Freutel
authors.affiliation: Laboratory of Biological Structures Mechanics, IRCCS Galeazzi Orthopedic Institute, Milan, Italy.
authors.forename: Fabio
authors.initials: F
authors.lastname: Galbusera
authors.affiliation: Institute of Orthopaedic Research and Biomechanics, Centre of Musculoskeletal Research Ulm, University of Ulm, Ulm, Germany.
authors.forename: Anita
authors.initials: A
authors.lastname: Ignatius
authors.affiliation: Institute of Orthopaedic Research and Biomechanics, Centre of Musculoskeletal Research Ulm, University of Ulm, Ulm, Germany.
authors.forename: Lutz
authors.initials: L
authors.lastname: Dürselen
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D020342:Finite Element Analysis; D008592:Menisci, Tibial / Q000033:anatomy & histology / Q000502:physiology*; D008954:Models, Biological; D013552:Swine
keywords: Finite element analysis; Material properties; Meniscus; Optimization