Axiomatic design of a foot-ankle mechanism of a transtibial prosthesis in the Colombian context

The rehabilitation of people with motor disabilities derived from transtibial amputation is a complex task that requires the use of different technical aids, such as prostheses, for effective performance. According to the background analysis consulted, the different solutions present limited information on the design procedure followed to ensure proper behavior in a given environment. In this sense, this work proposes the axiomatic design of a foot-ankle mechanism to emulate natural gait in the Colombian context. Where, focusing on the user, a progressive refinement of the functional requirements was carried out that allowed to clearly define the specification sequence of the design parameters, favoring the analysis and synthesis of the solution in different aspects related to aesthetics and function.La rehabilitación de personas con discapacidad motora, derivada de la amputación transtibial, es una tarea compleja que requiere del uso de diferentes ayudas técnicas, como prótesis, para una efectiva realización. Según el análisis de los antecedentes consultados, las diferentes soluciones presentan una limitada información sobre el procedimiento de diseño seguido para asegurar un adecuado comportamiento en un determinado entorno. En este sentido, considerando el contexto colombiano, este trabajo propone el diseño axiomático para la especificación de un mecanismo pie-tobillo de una prótesis transtibial, que permita emular la marcha natural. Por lo que, centrándose en el usuario, se realizó un refinamiento progresivo de los requisitos funcionales que permitió definir claramente la secuencia de especificación de acuerdo con los parámetros de diseño, favoreciendo el análisis y síntesis de la solución en diferentes aspectos relacionados con la estética y función

Sci Robot

Robotic leg prostheses promise to improve the mobility and quality of life of millions of individuals with lower-limb amputations by imitating the biomechanics of the missing biological leg. Unfortunately, existing powered prostheses are much heavier and bigger and have shorter battery life than conventional passive prostheses, severely limiting their clinical viability and utility in the daily life of amputees. Here, we present a robotic leg prosthesis that replicates the key biomechanical functions of the biological knee, ankle, and toe in the sagittal plane while matching the weight, size, and battery life of conventional microprocessor-controlled prostheses. The powered knee joint uses a unique torque-sensitive mechanism combining the benefits of elastic actuators with that of variable transmissions. A single actuator powers the ankle and toe joints through a compliant, underactuated mechanism. Because the biological toe dissipates energy while the biological ankle injects energy into the gait cycle, this underactuated system regenerates substantial mechanical energy and replicates the key biomechanical functions of the ankle/foot complex during walking. A compact prosthesis frame encloses all mechanical and electrical components for increased robustness and efficiency. Preclinical tests with three individuals with above-knee amputation show that the proposed robotic leg prosthesis allows for common ambulation activities with close to normative kinematics and kinetics. Using an optional passive mode, users can walk on level ground indefinitely without charging the battery, which has not been shown with any other powered or microprocessor-controlled prostheses. A prosthesis with these characteristics has the potential to improve real-world mobility in individuals with above-knee amputation.R01 HD098154/HD/NICHD NIH HHSUnited States/T42 OH008414/OH/NIOSH CDC HHSUnited States

A Generalized Method for Predictive Simulation-Based Lower Limb Prosthesis Design

Lower limb prostheses are designed to replace the functions and form of the missing biological anatomy. These functions are hypothesized to improve user outcome measures which are negatively affected by receiving an amputation – such as metabolic cost of transport, preferred walking speed, and perceived discomfort during walking. However, the effect of these design functions on the targeted outcome measures is highly variable, suggesting that these relationships are not fully understood. Biomechanics simulation and modeling tools are increasingly capable of analyzing the effects of a design on the resulting user gait. In this work, prothesis-aided gait is optimized in simulation to reduce both muscle effort and peak loads on the residual limb using a generalized prosthesis model. Compared to a traditional revolute powered ankle joint model, a two degree-of freedom generalized model reduced muscle activations by 50% and peak loads by 15%. Simulated prosthesis behaviors corresponding to the optimal gait patterns were translated into a two degree-of-freedom ankle-foot prosthesis design with powered bidirectional linear translation and plantarflexion. The prototype is capable of delivering up to 171 N-m of plantarflexion torque and 499 N of translation force, with 15° dorsi-/35° plantarflexion and 10 cm translation range of motion. The mass and height of the ankle-foot are 2.29 kg and 19.5 cm, respectively. The mass of the entire system including the wearable offboard system is 8.58 kg. This platform is designed to emulate the behavior of the simulated prosthesis, as well as be configurable to emulate alternate behaviors obtained from simulations with different optimization objectives. The prototype is controlled to replicate simulated walking patterns using a high level finite state controller, mid-level stiffness controller, and low level load controller. Closed loop load control has bandwidth of 15 Hz in translation and 7.2 Hz in flexion. Load tracking during walking with a single able-bodied human subject ranges from 93 to 159 N in translation and 4.6 to 21.3 N-m in flexion. The contribution of this work is to provide a framework for predictive simulation-based prosthesis design, evidence of its practical implementation, and the experimental tools to validate future predictive simulation studies