Biomechanical and Displacement-Related Considerations in the Design of a 3D-Printed Composite Energy-Storage-and-Return Prosthetic Foot

In this work, the effects of different design features on the mechanical and biomechanical properties of Continuous Fiber-Reinforced (CFR) 3D printed prosthetic feet are investigated. It is discussed how this novel technology can offer opportunities to obtain tuneable characteristics of the prosthesis through the use of modular elements. The fiber-reinforced loops (FRL) are introduced as a design feature to locally reinforce the core of the prosthesis and affect its mechanical response. Eight prosthetic concepts, exploring different possible design solutions, are described and modelled using Finite Element simulations to evaluate their stiffness and Roll-over Shape (ROS). The results are compared with a reference commercial prosthesis (Proflex XC, & Ouml;ssur). The final concept is then 3D printed and characterized experimentally using standard mechanical testing according to PD ISO/TS 16955, with the addition of optoelectronic measurements to better evaluate local displacements of the prosthesis. The results show a decrease in the average stresses at toe-off from 40 +/- 0.59 MPa to 13.5 +/- 037 MPa for the outer shells of the structure, and in the core from 5.5 +/- 0.07 MPa to 4.4 +/- 0.08 MPa. The total vertical displacement of the foot is, respectively 35 mm and 33 mm. It is thus concluded that, by exploiting FRL, it is possible to improve stress distribution, and achieve, with CFR prostheses, a mechanical and biomechanical response similar to that of commercial prostheses.