Controlling Locomotion Over Continuously Varying Activities for Agile Powered Prosthetic Legs
- Conditions
- Amputation
- Interventions
- Device: Powered prosthesis
- Registration Number
- NCT06138977
- Lead Sponsor
- University of Michigan
- Brief Summary
The overall goal of this project is to model human joint biomechanics over continuously-varying locomotion to enable adaptive control of powered above-knee prostheses. The central hypothesis of this project is that variable joint impedance can be parameterized by a continuous model based on measurable quantities called phase and task variables. This project will use machine learning to identify variable impedance functions from able-bodied data including joint perturbation responses across the phase/task space to bias the solution toward biological values.
- Detailed Description
The overall goal of this project is to model human joint biomechanics over continuously-varying locomotion to enable adaptive control of powered above-knee prostheses. Above-knee amputees often struggle to perform the varying activities of daily life with conventional prostheses due to the lack of positive mechanical work and active control. Emerging powered prostheses have motors that can perform these missing functions, but the biomechanics experienced by the user depend on the control of these motors. The way the prosthesis interacts with both the user and environment can be controlled through joint impedance--the relationship between joint motion and torque. Prosthetic joint impedance is typically defined via a stiffness, viscosity, and equilibrium angle for discrete phases of gait within a limited set of discrete activities, but this framework does not allow continuous variations of steady-state activities (e.g., walking at different speeds/inclines) or continuous transitions between activities (e.g., walk to stair ascent). The central hypothesis of this project is that variable joint impedance can be parameterized by a continuous model based on measurable quantities called phase and task variables. This project will use machine learning to identify variable impedance functions from able-bodied data including joint perturbation responses across the phase/task space to bias the solution toward biological values. The resulting impedance model will be used with real-time estimates of phase and task variables to control a custom powered knee-ankle prosthesis and the Ossur PowerKnee across activities. The clinical trial will comprise the following human subject experiments.
Aim 1.3: N=5 able-bodied subjects will be recruited for initial testing of the walking and stair controllers. Once the powered knee-ankle prosthesis achieves satisfactory performance, we will enroll N=5 amputee subjects to validate these controllers.
Aim 2.3: N=5 able-bodied subjects will be recruited for initial testing of the sit-to-stand and walk-stair transition controllers. Once the powered knee-ankle prosthesis achieves satisfactory performance, we will enroll N=5 amputee subjects to validate these controllers.
Aim 3.1: N=5 amputee subjects will be enrolled to validate the clinical interface for the powered prosthesis controllers.
Aim 3.2: N=5 amputee subjects will be enrolled to validate the transfer of the controllers to the PowerKnee.
Aim 3.3: N=10 amputee subjects will be enrolled in a study of endurance and symmetry outcomes with the PowerKnee compared to their take-home prosthesis.
Recruitment & Eligibility
- Status
- RECRUITING
- Sex
- All
- Target Recruitment
- 40
Not provided
Not provided
Study & Design
- Study Type
- INTERVENTIONAL
- Study Design
- SINGLE_GROUP
- Arm && Interventions
Group Intervention Description Prosthesis Powered prosthesis Participants in this arm of the study will perform various tasks while wearing the powered prosthesis
- Primary Outcome Measures
Name Time Method Endurance test time 1 day The time to complete multiple cycles through an ambulation circuit will be recorded with above-knee amputee participants' take-home prosthesis and a powered prosthesis. The ambulation circuit comprises, sit-to-stand, walking, stair ascent/descent, ramp descent/ascent, and stand-to-sit.
Joint work 1 day Mechanical work at the prosthetic knee and ankle will be assessed for participants using the powered prosthesis in A1.3 and A2.3, with comparisons to able-bodied averages. Joint work will be calculated by multiplying the joint's commanded torque by its measured velocity, resulting in units of Joules.
Tuning time 1 day The time for a prosthetist to configure the powered prosthesis for above-knee amputee participants will be assessed in A3.1 and A3.3.
- Secondary Outcome Measures
Name Time Method Inter-leg symmetry 1 day Kinematic and kinetic symmetry will be assessed between the sound side and prosthetic side of participants using the powered prosthesis in A1.3 and A2.3, with comparisons to able-bodied averages. The units will be % difference between legs, where 0% indicates perfect symmetry.
Step length symmetry 1 day Step length symmetry (between sound and prosthetic side) of above-knee amputee participants will compared using their take-home prosthesis and a powered prosthesis in A3.3. The units will be % difference between legs, where 0% indicates perfect symmetry.
Step width symmetry 1 day Step width symmetry (between sound and prosthetic side) of above-knee amputee participants will compared using their take-home prosthesis and a powered prosthesis in A3.3. The units will be % difference between legs, where 0% indicates perfect symmetry.
Step time symmetry 1 day Step time symmetry (between sound and prosthetic side) of above-knee amputee participants will compared using their take-home prosthesis and a powered prosthesis in A3.3. The units will be % difference between legs, where 0% indicates perfect symmetry.
Prosthesis Evaluation Questionnaire-Mobility 1 day Amputee participant responses to the Prosthesis Evaluation Questionnaire-Mobility Subscale will be compared between the take-home leg and powered leg in A3.3. Questions will be answered on a scale from 0 (extremely dissatisfied) to 5 (extremely satisfied).
Stance-swing time ratio 1 day The stance-swing time ratio will be assessed for participants using the powered prosthesis in A1.3 and A2.3, with comparisons to able-bodied averages. The stance-swing time ratio for above-knee amputee participants will compared between their take-home prosthesis and a powered prosthesis in A3.3.
Trial Locations
- Locations (1)
Rehab Lab, University of Michigan
🇺🇸Ann Arbor, Michigan, United States