Incidence of the boundary condition between bone and soft tissue in a finite element model of a transfemoral amputee

Abstract

Background: Many finite element investigations have been made in the field of lower limb prosthetics; however, friction between bone and soft tissues as a boundary condition has not been considered. Objectives: To establish whether the change in the contact boundary condition between bone and soft tissues in a transfemoral amputee affects the stress-strain state on the residual limb. Study Design: Finite element analysis comparison. Methods: Finite element models of four transfemoral amputees were developed. In these models the socket, soft tissues and femur were included and two simulations were made for each model, in one of them the interaction between bone and soft tissues was defined as tied (there is no relative displacement between surfaces) and in the other it was defined as a friction boundary condition. Results: The von Mises stress and strain peaks are higher when the friction definition is used than for tied contact definition. The distribution pattern of stresses and strains also change when the contact definition varies from tied to friction. Conclusions: It was concluded that the friction between bone and soft tissues have a significant impact on the results of finite element models of lower limb prosthetic systems, and therefore in its predictive capabilities. Clinical relevanceUnderstanding the bone-soft tissue interaction can lead to more realistic and accurate finite element models used to predict the stress-strain state in the residual limb of prosthetic users and therefore predict the occurrence of deep tissue injuries.

Combining Freehand Ultrasound-Based Indentation and Inverse Finite Element Modeling for the Identification of Hyperelastic Material Properties of Thigh Soft Tissues

“…The current study presents a method to combine inverse FEM and freehand ultrasound-based indentation for the identification of the passive material properties of the soft tissues of the thigh. Factually, most of the studies dealing with FEM of the thigh do not personalise the material properties of soft tissues, and would rather turn to values from literature [1,[6][7][8]10]. Indeed, very few studies developed the necessary process to estimate the personalised mechanical behaviour of soft tissues, especially when large soft tissues thicknesses are involved, like in the thigh area.…”

“…Amongst these, the application of subject-specific tissue material parameters is an important issue. As a matter of fact, most of the studies in the literature used nonpersonalised values from animal specimens and human cadavers [7][8][9][10][11][12][13], even though it has been established that variations in material properties can have a significant impact on the interface loads predicted by the model [14].…”

Analysis of Pressure Distribution in Transfemoral Prosthetic Socket for Prefabrication Evaluation via the Finite Element Method

“…The second contact definition applied corresponded to a tied contact between the bone and muscle, which is a simple way of permanently bonding surfaces and preventing slave nodes from separating or sliding relative to the master surface. This method of contact was obtained from a previous study [20]. The definition of contact was based on the hypothesis applied to the connection between the skin and fat and the fat and muscle, in which relative motion was neglected.…”

Preliminary results on the effects of orthopedic implant stiffness fixed to the cut end of the femur on the stress at the stump-prosthetic interface

“…The stresses at the stump-prosthetic interface are primarily responsible for these problems. Several studies have discussed the stresses at the residual limb interface using the finite element method (FFM) [6][7][8][9][10][11][12][13][14][15][16][17][18]. The models developed in these studies can be divided into three types.…”