An anatomically based patient-specific finite element model of patella articulation: towards a diagnostic tool

Abstract

A 3D anatomically based patient-specific finite element (FE) model of patello-femoral (PF) articulation is presented to analyse the main features of patella biomechanics, namely, patella tracking (kinematics), quadriceps extensor forces, surface contact and internal patella stresses. The generic geometries are a subset from the model database of the International Union of Physiological Sciences (IUPS) (http://www.physiome.org.nz) Physiome Project with soft tissue derived from the widely used visible human dataset, and the bones digitised from an anatomically accurate physical model with muscle attachment information. The models are customised to patient magnetic resonance images using a variant of free-form deformation, called 'host-mesh' fitting. The continuum was solved using the governing equation of finite elasticity, with the multibody problem coupled through contact mechanics. Additional constraints such as tissue incompressibility are also imposed. Passive material properties are taken from the literature and implemented for deformable tissue with a non-linear micro-structurally based constitutive law. Bone and cartilage are implemented using a 'St-Venant Kirchoff' model suitable for rigid body rotations. The surface fibre directions have been estimated from anatomy images of cadaver muscle dissections and active muscle contraction was based on a steady-state calcium-tension relation. The 3D continuum model of muscle, tendon and bone is compared with experimental results from the literature, and surgical simulations performed to illustrate its clinical assessment capabilities (a Maquet procedure for reducing patella stresses and a vastus lateralis release for a bipartite patella). Finally, the model limitations, issues and future improvements are discussed.

Experimental measurement and quantification of frictional contact between biological surfaces experiencing large deformation and slip

“…This distance is obtained by taking the dot product of g M1 and the unit normal to the master surface, defined by the cross product of the two tangent vectors. (15) (16) (17) Contact is typically defined as a gap distance of zero (Fernandez and Hunter, 2005), (Pietrzak and Curnier, 1999), and negative magnitudes, representing overlapping surfaces, are prohibited. However, for experimental data where the outermost tracked points lie slightly below the surface, it is practical to define contact as a gap distance below a prescribed threshold, D contact ; negative gap distances would still be impossible, and distances lower than the contact threshold would be possible and represent compression of the surface-most tissue layers.…”

“…In recent years, advancements in the field of contact mechanics have been driven by the formulation of robust finite element approaches and increased computing power. Models have been developed for a variety of physiological (Herzog and Federico, 2006), and even patient-specific (Fernandez and Hunter, 2005), geometries, and more detailed macro-scale boundary conditions have been prescribed by realtime tracking of movement in human subjects (Fernandez and Hunter, 2005). In biological tissues, the complex nature of the materials (e.g.…”

In silico clinical trials: how computer simulation will transform the biomedical industry

“…[3][4][5][6][7][8][9][10] In the early 2000s, the computational ecology community started to debate the virtues of individual-based models for population ecology. 11 Soon after, in silico medicine research also began to use the first patient-specific models [12][13][14][15][16][17] and some analysts started to suggest that such approaches could be useful in the development of new medical products. 18 In 2007, a group of experts published "seeding the EuroPhysiome: a roadmap to the virtual physiological human".…”

Evaluation of a geometry-based knee joint compared to a planar knee joint

“…There are also smaller forces acting inside the joint such as soft tissue constraints, contact forces and forces created by internal friction. Due to this complexity the knee joint has mostly been modeled and simulated using finite element method (FEM), which has been used in great success to analyze joint kinematics and a variety of problems relating to the knee joint [24,11,12]. In these models the knee includes structures as ligaments and sophisticated materials [31,23] which implement properties as transverse isotopy, nonlinear stress-strain curve and to a certain degree viscoelastic behavior.…”