Design and Development of a Quasi-Passive Transtibial Biarticular Prosthesis to Replicate Gastrocnemius Function in Walking

Abstract

Lower-limb amputees experience many gait impairments and limitations. Some of these impairments can be attributed to the lack of a functioning biarticular gastrocnemius (GAS) muscle. We propose a transtibial prosthesis that implements a quasi-passive spring mechanism to replicate GAS function. A prototype biarticular prosthesis (BP) was designed, built, and tested on one subject with a transtibial amputation. They walked on an instrumented treadmill with motion capture under three different biarticular spring stiffness conditions. A custom-developed OpenSim musculoskeletal model, which included the BP, was used to calculate the work performed and torque applied by the BP spring on the knee and ankle joints. The BP functioned as expected, generating forces with similar timing to GAS. Work transfer occurred from the ankle to the knee, with stiffer springs transferring more energy. Driven mostly by kinematics, the quasi-passive design of the BP consumed very low power (5.15 W average) and could lend itself well to future lightweight, low-power designs.

A Robotic Emulator for the Systematic Exploration of Transtibial Biarticular Prosthesis Designs

“…Our prior work has shown that the COBRA ankle-foot prosthesis can deliver ankle push-off power similar to other powered prostheses [28], indicating that the BP emulator is capable of emulating devices in all quadrants of the design matrix in Figure 1. For example, future work may emulate quasi-passive BP devices [18,21] using our device's joint encoder signals within an impedance controller and virtual clutch that changes its behavior based on gait events. Overall, using a BP emulator allows for a cost-and timeeffective and efficient way to develop and test biarticular prostheses.…”

A Computational Gait Model With a Below-Knee Amputation and a Semi-Active Variable-Stiffness Foot Prosthesis

“…Previous work in gait simulations with biomechatronic devices has often relied on abstract representations of components such as motors, electronics, and control systems [16,37,38]. In contrast, Simscape Multibody and Simulink offer a large library of these components, which can be readily integrated into the model for more realistic representations of biomechatronic systems.…”

“…However, the models used in these studies are not suitable for simulating gait among individuals with LLA, due to the altered lower limb mass, inertial properties and mechanical properties associated with a prosthetic foot and socket. LaPré et al (2018) [15] and Willson et al (2020) [16] developed limb loss-specific models in OpenSim [12], a popular musculoskeletal modeling and simulation platform. These studies used simulations to investigate the effects of prosthesis alignment and a biarticular clutched spring mechanism on gait mechanics, respectively.…”

A Robotic Emulator for the Systematic Exploration of Transtibial Biarticular Prosthesis Designs

“…Recent research has begun to investigate the potential of assistive devices that integrate ankle prostheses with knee-assistance mechanisms, herein referred to as biarticular prostheses (BPs). A range of designs has emerged, encompassing both passive and powered ankle prostheses as well as quasi-passive and powered knee exoskeletons or exosuits [17][18][19][20][21][22], While some preliminary studies report encouraging outcomes, such as enhanced metabolic walking economy and reduced hip compensations [18,19,23], BPs are not currently available for clinical use. In summary, BPs represent an emerging area of research, and additional studies are needed to explore basic questions about their design, control, and potential to improve walking outcomes in PwTA.…”