A simulation-based analysis of the effects of variable prosthesis stiffness on interface dynamics between the prosthetic socket and residual limb

Introduction: Loading of a residual limb within a prosthetic socket can cause tissue damage such as ulceration. Computational simulations may be useful tools for estimating tissue loading within the socket, and thus provide insights into how prosthesis designs affect residual limb-socket interface dynamics. The purpose of this study was to model and simulate residual limb-socket interface dynamics and evaluate the effects of varied prosthesis stiffness on interface dynamics during gait.

Methods: A spatial contact model of a residual limb-socket interface was developed and integrated into a gait model with a below-knee amputation. Gait trials were simulated for four subjects walking with low, medium, and high prosthesis stiffness settings. The effects of prosthesis stiffness on interface kinematics, normal pressure, and shear stresses were evaluated.

Results: Model-predicted values were similar to those reported previously in sensor-based experiments; increased stiffness resulted in greater average normal pressure and shear stress (p < 0.05).

Conclusions: These methods may be useful to aid experimental studies by providing insights into the effects of varied prosthesis design parameters or gait conditions on residual limb-socket interface dynamics. The current results suggest that these effects may be subject-specific.

Design Optimization in Lower Limb Prostheses: A Review

This paper aims to develop a knowledge base and identify the promising research pathways toward designing lower limb prostheses for optimal biomechanical and clinical outcomes. It is based on the literature search representing the state of the art in the lower limb prosthesis joint design and biomechanical analysis. Current design solutions are organized in terms of fulfilling four key functional roles: body support, propulsion, task flexibility, and loading relief. Biomechanical analyses of these designs reveal that the hypothesized outcomes are not consistently observed. We suggest that these outcomes may be improved by incorporating tools that can predict user performance metrics to optimize the device during the initial design process. We also note that the scope of the solution space of most current designs is limited by focusing on the anthropomorphic design approaches that do not account for the person's altered anatomy post-amputation. The effects of the prosthetic joint behavior on whole-body gait biomechanics and user experience are likewise under-explored. Two research paths to support the goal of better predicting the user outcomes are proposed: experimental parameterization of designs and model-based simulations. However, while work in these areas has introduced promising new possibilities, connecting both to improve real-world performance remains a challenge.