Motorized Prostheses for Lower-limb Amputees

Lightweight Motorized Prostheses for Lower-limb Amputees

The investigators will assess biomechanical and functional mobility outcomes in individuals with unilateral, above-knee amputations using different knee/ankle configurations of a lightweight powered prosthesis and different volitional controllers in individuals with unilateral, above-knee amputations.

Study Overview

• Status: Recruiting
• Conditions: Lower-Limb Amputation
• Intervention / Treatment: Device: Powered and passive lower limb prosthesis and control

Detailed Description

AIM1:

For all studies, participants will repeat the same experimental protocol with their passive prostheses and our lightweight powered knee combined with powered, semi-active, and passive ankle. The investigators will also administer a questionnaire based on a 5-point Likert scale to rate intuitiveness, safety, physical demand, and mental demand for each tested condition. Participants will have time to familiarize themselves with the protocol and the prosthesis in a separate training session.

Part 1: Level and Inclined Walking Effort. The study will assess walking effort as participants walk on an instrumented treadmill at their self-selected comfortable speed. The primary outcome of the first study will be residual limb effort measured through peak hip flexion torque on the prosthesis side. Secondary outcomes will include contralateral leg effort, gait symmetry, and balance. The experimental protocol will be repeated for different inclines (e.g., 0%, +/-10%) during separate experimental sessions.

Part 2: Ambulation on Stairs. The study will analyze speed and effort during stair ascent and descent. Participants will ambulate on an instrumented staircase that includes seven steps (four instrumented). The primary outcome for stair ascent will be the ratio between prosthesis work and residual limb work, whereas, for stair descent, the investigators will use sound knee and ankle work. Residual limb, contralateral leg, and upper body effort (handrail force) will be the secondary outcomes, together with subjective preference.

Part 3: Sit-to-Stand Transitions. This study will assess biomechanics as the participant transitions between sitting and standing. Participants will perform sit-to-stand and stand-to-sit transitions from a chair with no armrests at their self-selected pace. The investigators will assess full-body biomechanics similar to our previous sit-to-stand and stand-to-sit studies. The primary outcome of this study will be the degree of asymmetry.

AIM2:

Participants will repeat the experimental protocols with their prescribed prostheses and our lightweight powered prosthesis using direct electromyographic control and indirect volitional control. The experiments will be conducted in a motion capture lab to assess full-body kinematics and kinetics. The investigators will also administer a questionnaire based on a 5-point Likert scale to rate intuitiveness, safety, physical demand, and mental demand for each tested condition. Participants will have time to familiarize themselves with the protocol and the prosthesis controllers in dedicated training sessions.

Part 1: Inclined Walking at different speeds and loading conditions. This study will assess the ability to walk at various speeds on inclines/declines while carrying objects. To this end, participants will walk on an instrumented treadmill both at their self-selected speed and 130% of their self-selected speed with and without holding a 20-lb load in both hands. The difference between hip peak torque on the sound and prosthesis sides will be used as a primary outcome. Secondary outcomes will include gait symmetry, balance, and subjective preference. During separate sessions, the experimental protocol will be repeated at 10% incline and 10% decline.

Part 2: Stair Climbing at different speeds and loading conditions. This study will assess the ability to ascend and descend stairs under different speeds and loading conditions. Participants will ascend an instrumented staircase at comfortable and fast self-selected speeds. Participants will climb stairs at both speeds with and without a 20-lb object carried in their hands or a backpack. The difference between knee peak torque on the sound and prosthesis sides will be used as a primary outcome. Secondary outcomes will include contralateral leg effort, gait symmetry, and balance.

Part 3: Stand up, Squat, Lunge, and Kneel. This study will assess the ability to stand up, squat, and lunge under different loading conditions. Participants will perform five repetitions of sit-to-stand transfers. Then, they will squat, lunge, and kneel five times. The primary outcome will be prosthesis weight-bearing. Secondary outcomes will include time to completion, joint effort, and subjective preference.

AIM3:

Participants will repeat the experimental protocols with their prescribed prostheses and our lightweight powered prosthesis. During dedicated training sessions, they will have time to familiarize themselves with the protocol.

Part 1 Ambulation Circuit. Participants will perform ten trials of the ambulation circuit. Starting in a chair, standing up, walking to a 4-step staircase, climbing up the stairs to an elevated platform, continuing to walk on the platform, turning, descending an intermediate platform using a two-step staircase, descending a ramp, walking to the chair, and ending by sitting down. Next, ten trials of the reverse circuit will be completed, starting with sitting in the chair and ending with the ramp ascent. The primary outcome will be the average time to complete the circuit. Secondary outcomes will be joint kinematics during transitions and subjective preference.

Part 2: Self-Selected Walking Speed. Participants will perform the timed 10-meter walking test on a self-paced instrumented treadmill. Walking speed will be the primary outcome. Secondary outcomes will include spatiotemporal gait symmetry and subjective preference.

Part 3: Amputee Mobility Predictor. This study aims to assess clinical outcome measures using the Amputee Mobility Predictor, a reliable performance measure validated for those with lower-limb loss, to identify limitations in prosthetic mobility and measure several functional mobility tasks needed during daily living activities.

Part 4: Real-World Mobility. This study will provide a quantitative assessment of mobility in complex home and community environments. To this end, the investigators will measure performance and satisfaction while participants perform common activities of daily living, which will include household chores (mopping floors, making beds, cooking, grocery shopping) and leisure activities (walking the dog, strolling in a park, gardening). Subjective preference will be the primary outcome and will be assessed by administering a questionnaire with separate ratings for intuitiveness, safety, physical demand, and mental demand. The secondary outcome will be kinematics, which the investigators will assess using an IMU-based motion capture system.

• Study Type: Interventional
• Enrollment (Estimated): 40
• Phase: Early Phase 1

Contacts and Locations

• Study Contact: Name: Tommaso Lenzi, PhD; Phone Number: 3126190442; Email: t.lenzi@utah.edu
• Study Contact Backup: Name: Rosie Murray, PhD; Phone Number: 8012133637; Email: rosemarie.murray@utah.edu

Study Locations

• United States
  • Utah
    • Salt Lake City, Utah, United States, 84112
      • Recruiting
      • University of Utah
      • Contact: Tommaso Lenzi, PhD; Phone Number: 3126190442; Email: t.lenzi@utah.edu
      • Contact: Rosie Murray, PhD; Phone Number: 8012133637; Email: rosemarie.murray@utah.edu
      • Principal Investigator: Tommaso Lenzi, PhD

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: Yes

Description

Our inclusion criteria will be

• Above-knee amputation
• K2/K3/K4 ambulators
• At least 18 years old
• At least one year since amputation
• At least six months since the definitive prosthesis fitting
• Currently prescribed and using a mechanically passive or microprocessor-controlled prosthesis

Our exclusion criteria will be

• Over 350 lbs. body weight, the weight limit for our safety suspension systems
• Cognitive deficits or visual impairment that could impair their ability to give informed consent or to follow simple instructions during the experiments
• Pregnant women due to elevated safety concerns for this population
• Co-morbidity that limits their ability to participate in the study protocol (e.g., stroke, pacemaker placement that would interfere with the powered prosthesis, severe ischemia, cardiac disease, etc.)
• Adults who are unable to consent
• Individuals who are not yet adults (infants, children, teenagers)
• Individuals who use a wheelchair for mobility both outdoors and indoors because they may not be able to perform the necessary activities with their passive prosthesis or the powered prosthesis
• Prisoners, due to concerns with informed consent

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Basic Science
• Allocation: N/A
• Interventional Model: Single Group Assignment
• Masking: None (Open Label)

Number of Arms

1

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Main Arm; Powered and passive lower limb prosthesis and control	Device: Powered and passive lower limb prosthesis and control; Effect of prosthesis function on mobility and ambulation

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Amputee Mobility Predictor with Prosthesis (AMPPRO)	The AMPPRO is used to assess functional mobility through a standardized sequence of mobility tests while using a prosthesis. Individual tasks are scored and combined, resulting in a total assessment. The minimum score is zero, and the maximum score on this scale is 47. Higher scores indicate better mobility	Baseline and Day 1
Ten-meter walking test	The 10-meter walking test assesses walking speed in meters per second over a short duration.	Baseline and Day 1
Ambulation circuit	Average time to complete an ambulation circuit that requires subjects to standup from a chair, walk to a 4-step staircase, climb up the staircase to an elevated platform, continue to walk on the platform, turn, descend an intermediate platform using a two-step staircase, descending a ramp, walking to the chair, and ending by sitting down.	Baseline and Day 1
Usability questionnaire	A custom questionnaire based on a 5-point Likert scale to rate intuitiveness, safety, physical demand, and mental demand for each tested condition	Baseline and Day 1
Prosthesis weight-bearing	Vertical ground reaction force generated by the user on the prosthesis side when standing up and sitting down from a chair.	Baseline and Day 1
Knee torque symmetry	Difference between the knee peak torque on the sound side and on the prosthesis side when the subject climb stairs at different speeds and loading conditions.	Baseline and Day 1
Hip torque symmetry	Difference between the hip peak torque on the sound side and on the prosthesis side when the subject walks on inclines at different speeds and loading conditions.	Baseline and Day 1
Weight bearing asymmetry	Difference between the vertical ground reaction force on the prosthesis side and the sound side when the subject stands up and sits down from a chair.	Baseline and Day 1
Prosthesis to residual-limb work ratio	Ratio between the mechanical work generated by the prosthesis and the residual limb when ascending and descending stairs.	Baseline and Day 1
Residual limb effort	Peak hip flexion torque on the prosthesis side when subjects walk at different speeds and inclines.	Baseline and Day 1

Collaborators and Investigators

• Sponsor: University of Utah
• Collaborators: Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD)
• Investigators: Principal Investigator: Tommaso Lenzi, PhD, University of Utah

Study record dates

Study Major Dates

• Study Start (Actual): July 1, 2025
• Primary Completion (Estimated): May 1, 2031
• Study Completion (Estimated): June 1, 2032

Study Registration Dates

• First Submitted: March 12, 2026
• First Submitted That Met QC Criteria: March 17, 2026
• First Posted (Actual): March 20, 2026

Study Record Updates

• Last Update Posted (Actual): March 20, 2026
• Last Update Submitted That Met QC Criteria: March 17, 2026
• Last Verified: March 1, 2026

More Information

Terms related to this study

• Other Study ID Numbers: IRB_00103197; R01HD098154 (U.S. NIH Grant/Contract)

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: YES
• IPD Plan Description: All IPD that underlie results in a publication
• IPD Sharing Time Frame: At the time of publication of results.
• IPD Sharing Access Criteria: Anybody will be able to access the IPD and supporting information, all published data will be accessible, and they will be able to download the data from the publisher's website together with the paper
• IPD Sharing Supporting Information Type: STUDY_PROTOCOL; SAP

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No