Intuitive Control of a Hybrid Prosthetic Leg During Ambulation

Study Overview
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Brief Summary
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The objective of this research is to determine the clinical benefits of an innovative and lightweight powered leg controlled using our intent recognition framework in laboratory and community environments.

Detailed Description
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The hypothesis of this study is that using the Hybrid Leg with seamless, automatic transitions will result in participants choosing to become more active and improve their community participation compared to when using their own passive prosthetic leg. The Hybrid Leg is an an innovative and lightweight powered leg that has 2 operating modes: active and passive. When in active mode, the Hybrid Leg is capable of supplying 120 NM of knee torque and actively repositioning the ankle during non-weight bearing phases of gait. When in passive mode, the motor and transmission are decoupled from the knee, which then behaves like an Ottobock 3R95 passive prosthetic knee, and the non-backdriveable mechanism of the ankle allows it to behave as an energy return foot. Allowing the device to behave passively if the battery becomes depleted or the actuators become damaged is an important enabling safety factor that will allow us to complete our study. Phase 1: We will enroll 20 subjects a clinical trial of the leg and control system who will be fit with the Hybrid Leg and receive in-lab therapy to learn how to ambulate with the device. Phase 2: Subjects will be randomized into a clinical trial of the leg and control system with an AB-BA design; condition A - subjects own device; condition B - Hybrid Leg. Subjects will complete an extensive ambulation and community mobility training to learn optimal use of their own passive device or the Hybrid Leg. After training the subjects will complete a full biomechanical analysis for each device as they complete ambulation circuits that include standing, level-ground walking, walking on slopes and on stairs, sit-stand transitions and transitions between these activities. Phase 3: After completing phase 2 subjects will complete 4-week trials using their assigned prosthesis (Condition A or B) at home and within their community. During the trials subjects will be monitored using mobile phone based sensors and socket mounted activity monitor to determine how often the user performs the ambulation activities.

Official Title
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Intuitive Control of a Hybrid Prosthetic Leg During Ambulation

Conditions
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Amputation

Intervention / Treatment
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* Device: Hybrid Leg
* Device: Prescribed Passive Prosthesis


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: A unilateral or bilateral lower limb amputation K2/K3/K4 ambulator with a prosthesis English speaking Exclusion Criteria: Significant new injury that would prevent use of a prosthesis: The ability to consistently wear a prosthesis and perform activities of daily living and specific performance tasks is necessary to evaluate the relative benefits of the interventions. Cognitive impairment sufficient to adversely affect understanding of or compliance with study requirements, ability to communicate experiences, or ability to give informed consent: The ability to understand and comply with requirements of the study is essential in order for the study to generate useable, reliable data. The ability to obtain relevant user feedback through questionnaires and informal discussion adds significant value to this study. Significant other comorbidity: Any other medical issues or injuries that would preclude completion of the study, use of the prostheses, or that would otherwise prevent acquisition of useable data by researchers.

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 95 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Basic Science
Allocation: Randomized
Intervention Model: Crossover Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Condition A: Hybrid Leg<br>Subject will be trained on use of the experimental device, the Hybrid Leg. | Device: Hybrid Leg<br>* The Hybrid Knee uses an actively variable transmission in combination of a passive spring/damper system. This allows the motor torque output to be adapted to the requirements of active dynamic tasks - changing the effective transmission ration from zero (fully passive) for level ground walking to a maximum value (fully active) for sit-to-stand transfers. This provides physiological knee torque and speed with a small motor and primary transmission system while also maximizing electrical efficiency, which minimized battery weight. The knee prototype weights 1.7kg. The Semi-active ankle can actively reposition during non-weight bearing phases of gait and uses a non back driveable transmission to maintain its set point during weight bearing activities.<br>|
| Other: Condition B: Passive Leg<br>Subject will use their currently prescribed home passive prosthesis | Device: Prescribed Passive Prosthesis<br>* Participants will participate in training sessions of community skills and advanced ambulation training for their home, prescribed passive prosthesis.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Average daily number of steps | This outcome will be assessed using an accelerometery data measured using a mobile phone during the entire 4-week home trial of each device (Hybrid Leg and prescribed home device), resulting in a pair of outcomes for each subject. Statistical analysis will be done , first using a paired t-test (which assumes no carry-over and no device sequence effects), followed by the analysis using a linear mixed model with device and sequence group as fixed effects, and subject as the random effect. We expect that sequence will not be a statistically significant predictor, but that average daily steps will be significantly different between devices, with subjects taking significantly more steps when using the Hybrid Leg. | 4 weeks - data collected during 4 week home trial of each device, analyzed upon completion of 4 week home trial | 
| Average daily number of times subject switches between activities | This outcome will be assessed using an accelerometery data measured using a mobile phone during the entire 4-week home trial of each device (Hybrid Leg and prescribed home device), resulting in a pair of outcomes for each subject. Statistical analysis will be done , first using a paired t-test (which assumes no carry-over and no device sequence effects), followed by the analysis using a linear mixed model with device and sequence group as fixed effects, and subject as the random effect. We expect that sequence will not be a statistically significant predictor, but that average transitions will be significantly different between devices, with subjects taking significantly more transitioning between activities more when using the Hybrid Leg. | 4 weeks - data collected during 4 week home trial of each device, analyzed upon completion of 4 week home trial | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| 10 Meter Walk Test | The 10mWT is used to assess walking speed in meters/second (m/s) over a short distance. | Lab visit prior to start of home trial and lab visit upon completion of 4 week trial with each device | 
| GPS tracking analysis | Subject-specific map of movement within the community will be generated and investigated for individual changes in community mobility and cross-referenced with their survey results. These data could provide insight into how well patient-reported measures reflect actual community participation, although this possibility is acknowledged to be exploratory | End of each 4 week home trial | 
| Six-Minute Walk Test | The 6MWT is a sub-maximal exercise test used to assess walking endurance and aerobic capacity. Participants will walk around the perimeter of a set circuit for a total of six minutes. | Lab visit prior to start of home trial and lab visit upon completion of 4 week trial with each device | 
| Hill Assessment Index | The Hill Assessment Index (HAI) is a 12 level ordinal scale developed to address different characteristics of hill ascent and descent in preparation comparing different prosthetic knee units. The HAI assesses gait patterns on hills combined with assistive device usage reflecting the quality of independence. | Lab visit prior to start of home trial and lab visit upon completion of 4 week trial with each device | 
| Stair Assessment Index | The Stair Assessment Index is a 14 level ordinal scale that assesses the functional ability of transfemoral amputees for stair ascent and descent. It is being used as a physical measurement tool to document different gait styles on the stairs. | Lab visit prior to start of home trial and lab visit upon completion of 4 week trial with each device | 
| Berg Balance Scale | The Berg Balance Scale is a 14 item objective measure that assesses static balance and fall risk in adults. | Lab visit prior to start of home trial and lab visit upon completion of 4 week trial with each device | 
| Functional Gait Assessment | The FGA is used to assess postural stability during walking and assesses an individual's ability to perform multiple motor tasks while walking. The tool is a modification of the 8-item Dynamic Gait Index, developed to improve reliability and reduce ceiling effect. | Lab visit prior to start of home trial and lab visit upon completion of 4 week trial with each device | 
| 5 Times Sit to Stand | The Five Times Sit to Stand Test measures one aspect of transfer skill. The test provides a method of quantify functional lower extremity strength and /or identify movement strategies a patient used to complete transitional movements. | Lab visit prior to start of home trial and lab visit upon completion of 4 week trial with each device | 
| 4 -Square Step Test | Test of dynamic balance that clinically assesses the person's ability to step over objects forward, sideways, and backwards. | Lab visit prior to start of home trial and lab visit upon completion of 4 week trial with each device | 
| Amputee Mobility Predictor | This instrument measures the ambulatory potential of lower limb amputees with and without the use of a prosthesis. It assesses the mobility of people with lower limb amputation prior to prosthetic fitting and predicts function following prosthetic prescription. | Lab visit prior to start of home trial and lab visit upon completion of 4 week trial with each device | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Transfemoral Amputation