Sviluppo di metodi per la valutazione a banco delle performance di componenti protesiche per velocisti paralimpici

Sports prosthetic feet (RPF) are a fundamental element of sports prosthetic systems (RPS) for athletes who run and jump with trans-tibial (TT) and trans-femoral (TF) amputations. Numerous studies have demonstrated the influence of stiffness on the biomechanics of running and jumping. However, the lack of a uniquely defined test method and the absence of a reference standard influence the evaluation and reference values based on the chosen model. Furthermore, RPF manufacturers do not provide a numerical value expressed with engineering quantities by declaring a test method, but a numerical reference associated with the athlete's mass. This leads to uncertainty in interpreting the values proposed in catalogs, understanding their meaning, and a lack of homogeneity between different manufacturers. The PhD OLYMPIA project focused on the definition of materials, methods, and models for the execution of RPF tests based on data acquired in vivo using force platforms and a Motion capture system in test sessions with athletes with TT and TF amputations of the Italian Paralympic national team. To support the biomechanical analysis, a protocol of marker sets and reference systems for the body and the prosthetic system was defined that allowed the calculation of the kinetic and kinematic parameters to describe the biomechanics of running but also specific load parameters for the RPF such as the ρCL defined as the force ratio between the X and Y components of the decomposed GRF in the clamp reference system. For the execution of the in vivo tests, a triaxial bench called Colossus1.0 was enhanced, designed to apply load ratios in the reference system of clamps expressed by ρCL based on what was acquired in vivo and which has the possibility of tilting the contact plate with the RPF sole modifying the contact angle ϑG. The results of the tests, performed on 18 commercial RPFs and prototypes, allowed for approximating load-deflection curves with polynomial functions, to calculate the stiffness with a local approach based on the first derivatives, to define an equivalent stiffness Keq through an energy equivalence approach with the energy stored in a linear spring and to define sensitivity models to the load ratios. To standardize the test system, a foot bench alignment protocol was defined considering the prosthetic alignment, a protocol linked to the loading procedures that define the maximum force values based on the nominal stiffness category and the test angle, and a test protocol that defines the function and hierarchy of each phase. The comparison of RPFs of different stiffness categories, shapes, and manufacturers has allowed us to verify the validity of the test method highlighting notable differences in the behavior between different RPFs and demonstrating how the defined quantities can be used for comparison based on significant engineering quantities. For a generalized stiffness assessment, from the results of the test combinations of the independent variables ρCL and ϑG, predictive models based on polynomial maps of the coefficients of the stiffness curves were defined for the prediction of local and equivalent Keq stiffness. Models were evaluated for values coming from the in vivo acquisitions to calculate the stiffness, showing coherence between them and demonstrating how they can be used to globally describe the RPF behavior creating an association between predicted values and the sensations perceived by the athletes during the race. The Colossus 1.0 test bench has been improved and enhanced developing a new Colossus 2.0 bench that, thanks to the introduction of a third electric actuator, dynamically simulates the step from FC to FO. Materials, methods, and models will be the basis for the proposed international regulatory standardization.