Abstract
Finite element modelling has long been proposed to support prosthetic socket design. However, there is minimal detail in the literature to inform practice in developing and interpreting these complex, highly nonlinear models. To identify best practice recommendations for finite element modelling of lower limb prosthetics, considering key modelling approaches and inputs. Computational modelling. This study developed a parametric finite element model using magnetic resonance imaging data from a person with transtibial amputation. Comparative analyses were performed considering socket loading methods, socket-residuum interface parameters and soft tissue material models from the literature, to quantify their effect on the residuum's biomechanical response to a range of parameterised socket designs. These variables had a marked impact on the finite element model's predictions for limb-socket interface pressure and soft tissue shear distribution. All modelling decisions should be justified biomechanically and clinically. In order to represent the prosthetic loading scenario in silico, researchers should (1) consider the effects of donning and interface friction to capture the generated soft tissue shear stresses, (2) use representative stiffness hyperelastic material models for soft tissues when using strain to predict injury and (3) interrogate models comparatively, against a clinically-used control.
Highlights
The residual limb for a person with limb loss represents a constantly evolving interface for mechanical loading from a prosthesis, most commonly through a personalised socket
Inclusion of socket donning increased proximal interface shear (22 kPa in donning vs. 4 kPa in overclosure), whereas the residuum tip pressure was predicted to decrease (0 kPa in donning vs. 41 kPa in overclosure). This effect of increased longitudinal shear on the residuum tip pressure was observed with an increase in the socket–liner coefficient of friction (COF) for the same baseline model (Figure 3(b))
This comparative analysis tested a range of inputs, in addition to different socket designs and loading scenarios
Summary
The residual limb (or ‘residuum’) for a person with limb loss represents a constantly evolving interface for mechanical loading from a prosthesis, most commonly through a personalised socket. Very particular requirements arise in the robustness of finite element (FE) models when used to inform clinical practice and in extracting relevant data, due to the complexity of the biomechanical processes being modelled, patient variability across the population and appropriate parameter selection.[5,6]. Comparative analyses were performed considering socket loading methods, socket–residuum interface parameters and soft tissue material models from the literature, to quantify their effect on the residuum’s biomechanical response to a range of parameterised socket designs. In order to represent the prosthetic loading scenario in silico, researchers should (1) consider the effects of donning and interface friction to capture the generated soft tissue shear stresses, (2) use representative stiffness hyperelastic material models for soft tissues when using strain to predict injury and (3) interrogate models comparatively, against a clinically-used control
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