Motorized knee and ankle prostheses for people with above-knee amputations

Lightweight Motorized Prostheses for Lower-limb Amputees

We will test whether a lightweight powered knee combined with different ankle setups and controllers can reduce effort and improve walking and stair mobility for people with a single above-knee amputation.

Quick facts

• Phase: EARLY_PHASE1
• Study type: Interventional
• Enrollment: 40 (estimated)
• Ages: 18 Years to 80 Years
• Sex: All
• Sponsor: University of Utah (other)
• Locations: 1 site (Salt Lake City, Utah)
• Trial ID: NCT07486063 on ClinicalTrials.gov

What this trial studies

Participants with unilateral above-knee amputation will complete repeated laboratory sessions using their usual passive prosthesis and a lightweight powered knee paired with powered, semi-active, and passive ankle configurations under different volitional controllers. Testing includes level and inclined treadmill walking at self-selected speeds to measure residual limb hip torque, contralateral effort, gait symmetry, and balance, as well as instrumented stair ascent and descent to measure prosthesis and residual limb work and upper-body effort. Each tested condition includes familiarization and a training session, and participants will rate intuitiveness, safety, and physical and mental demand with a 5-point questionnaire. Data will compare biomechanics and functional mobility across device and controller combinations to identify configurations that reduce effort or improve performance.

Who should consider this trial

Good fit: Adults (18+) with a unilateral above-knee amputation who are at least one year post-amputation, K2–K4 ambulators, and currently using a mechanically passive or microprocessor-controlled prosthesis are ideal candidates.

Not a fit: People who weigh over 350 lbs, are pregnant, have major cardiac, neurologic, or other comorbidities that limit participation, have cognitive impairment, or rely on a wheelchair for outdoor mobility may not receive benefit or be ineligible.

Why it matters

Potential benefit: If successful, the powered knee and ankle combinations could reduce walking and stair-climbing effort and improve mobility and comfort for above-knee amputees.

How similar studies have performed: Prior small laboratory studies of powered lower-limb prostheses have reported improved gait symmetry, reduced metabolic cost, and better stair negotiation in some participants, but large-scale clinical evidence is still limited.

Eligibility criteria

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

Where this trial is running

Salt Lake City, Utah

• University of Utah — Salt Lake City, Utah, United States (RECRUITING)

Study contacts

• Principal investigator: Tommaso Lenzi, PhD — University of Utah
• Study coordinator: Tommaso Lenzi, PhD

Conditions: Lower-Limb Amputation