Pivot-Flex Foot: Torsionally Adaptive Prosthesis for Individuals With Lower Limb Amputation
Trial Snapshot
- Phase
- Not Applicable
- Status
- Completed
- Enrollment
- 14
- Locations
- 1
- Primary Endpoint
- Peak Transverse-plane Prosthetic Socket Torque Normalized to Body Mass
Study Overview
Brief Summary
When prescribing a prosthetic foot, clinicians face a dizzying array of choices as more than 200 different prosthetic feet are available. While these conventional prosthetic feet primarily function in the sagittal plane, the intact foot and ankle comprise a complex set of joints that allow rotation in multiple planes of motion. Some of these motions are coupled, meaning rotation in one plane induces motion in another. One such coupling is between the sagittal and transverse planes. For every step, plantar- and dorsi-flexion motion in the sagittal plane is coupled with external and internal rotation of the shank relative to the foot in the transverse plane. There is no prosthetic foot available for prescription that mimics this natural coupling.
To investigate the need for this coupling, the investigators have built a torsionally adaptive prosthesis where the coupling ratio between the transverse- and sagittal-planes can be independently controlled with a motor.
This research has one specific aim: to identify the optimal coupling ratio between transverse- and sagittal-plane motions using a novel, torsionally adaptive prosthesis for individuals with lower limb amputation. The investigators will conduct a human subject experiment wearing the motor-driven and computer controlled torsionally adaptive prosthesis. Individuals with lower limb amputation will be asked to walk in a straight line and in both directions around a circle while the coupling ratio between transverse- and sagittal-plane motions is varied between trials. Participants will be blinded to the coupling ratio.
The investigators hypothesize that: (1) a coupling ratio exists that minimizes undesirable transverse-plane socket torque and (2) there will be a coupling ratio that individuals with lower limb amputation prefer.
Detailed Description
The human ankle is a complex mechanism that does not behave like a simple hinge. Instead, rotations in all three axes are allowed and some are coupled together. In particular, the axis of rotation of the talo-crural joint during ankle flexion is inclined downwards and laterally relative to horizontal, and the rotation ranges from 10 to 26 degrees among individuals. This rotation couples plantar- and dorsi-flexion motion with external and internal rotation of the shank relative to the foot, respectively. This feature of the natural limb has not been replicated in prosthetic feet and ankles.
Lower limb amputees take thousands of steps on their prosthesis each day and none feature coupled motion between the transverse- and sagittal-planes. The absence of this natural coupling may be related to the high incidence of residual limb soft tissue injuries, the need for compensatory gait, and overall dissatisfaction with their prostheses.
Transverse rotation adapters, consisting of simple torsional springs, are available for prescription. These devices can increase transverse-plane rotations and decrease transverse-plane torques, but their use is not widespread and if excessively compliant, may reduce gait stability. Cost, weight, prosthesis build height, and the inability for the user to adjust the stiffness may all play a role in their lack of adoption, but it may also be that the transverse-plane rotation is not coupled with the sagittal-plane. With these devices, motion only occurs in the transverse-plane when a transverse-plane torque is applied.
This research has one specific aim: to identify the optimal coupling ratio between transverse- and sagittal-plane motions using a novel, torsionally adaptive prosthesis for individuals with lower limb amputation. The investigators will fit a sample population of unilateral transtibial amputees with the motor-driven and computer controlled torsionally adaptive prosthesis.
Participants perform three activities: walking in a straight line (study visit 1) and in both directions around a circle (study visit 2). During each of these three activities, the torsionally adaptive prosthesis will be set to five different coupling ratios in random order. Participants will be blinded to the coupling ratio.
Study Design
- Study Type
- Interventional
- Allocation
- Randomized
- Intervention Model
- Factorial
- Primary Purpose
- Treatment
- Masking
- None
Eligibility Criteria
- Ages
- 18 Years to 70 Years (Adult, Older Adult)
- Sex
- All
- Accepts Healthy Volunteers
- No
Inclusion Criteria
- •Unilateral transtibial amputation
- •Been fit with a prosthesis and used it for at least six months
- •Wear the prosthesis for four or more hours on an average day
- •Prescribed prosthesis can accommodate fitment of the study prosthetic components to be tested (determined at initial visit)
Exclusion Criteria
- •Improper fit and suspension with current prosthesis and one cannot be achieved with clinical resources (determined at initial visit)
- •Current skin irritation or injury on residual limb
- •Osteoarthritis, injury, or pain that interferes with walking ability
- •Currently incarcerated
- •Pregnant (determined via self-report)
- •Inadequate cognitive function or language proficiency to consent to participate
Arms & Interventions
Straight line walking
All participants will walk in a straight line while wearing the study prosthesis.
Intervention: Torsionally adaptive prosthesis with 0:1 coupling ratio (Device)
Straight line walking
All participants will walk in a straight line while wearing the study prosthesis.
Intervention: Torsionally adaptive prosthesis with 1:6 coupling ratio (Device)
Straight line walking
All participants will walk in a straight line while wearing the study prosthesis.
Intervention: Torsionally adaptive prosthesis with 1:4 coupling ratio (Device)
Straight line walking
All participants will walk in a straight line while wearing the study prosthesis.
Intervention: Torsionally adaptive prosthesis with 1:3 coupling ratio (Device)
Circle walking with prosthesis outside
All participants will walk around a 1-meter radius circle with their prosthesis on the outside of the circle.
Intervention: Torsionally adaptive prosthesis with 1:3 coupling ratio (Device)
Straight line walking
All participants will walk in a straight line while wearing the study prosthesis.
Intervention: Torsionally adaptive prosthesis with 1:2 coupling ratio (Device)
Circle walking with prosthesis inside
All participants will walk around a 1-meter radius circle with their prosthesis on the inside of the circle.
Intervention: Torsionally adaptive prosthesis with 0:1 coupling ratio (Device)
Circle walking with prosthesis inside
All participants will walk around a 1-meter radius circle with their prosthesis on the inside of the circle.
Intervention: Torsionally adaptive prosthesis with 1:6 coupling ratio (Device)
Circle walking with prosthesis inside
All participants will walk around a 1-meter radius circle with their prosthesis on the inside of the circle.
Intervention: Torsionally adaptive prosthesis with 1:4 coupling ratio (Device)
Circle walking with prosthesis inside
All participants will walk around a 1-meter radius circle with their prosthesis on the inside of the circle.
Intervention: Torsionally adaptive prosthesis with 1:3 coupling ratio (Device)
Circle walking with prosthesis inside
All participants will walk around a 1-meter radius circle with their prosthesis on the inside of the circle.
Intervention: Torsionally adaptive prosthesis with 1:2 coupling ratio (Device)
Circle walking with prosthesis outside
All participants will walk around a 1-meter radius circle with their prosthesis on the outside of the circle.
Intervention: Torsionally adaptive prosthesis with 0:1 coupling ratio (Device)
Circle walking with prosthesis outside
All participants will walk around a 1-meter radius circle with their prosthesis on the outside of the circle.
Intervention: Torsionally adaptive prosthesis with 1:6 coupling ratio (Device)
Circle walking with prosthesis outside
All participants will walk around a 1-meter radius circle with their prosthesis on the outside of the circle.
Intervention: Torsionally adaptive prosthesis with 1:4 coupling ratio (Device)
Circle walking with prosthesis outside
All participants will walk around a 1-meter radius circle with their prosthesis on the outside of the circle.
Intervention: Torsionally adaptive prosthesis with 1:2 coupling ratio (Device)
Outcomes
Primary Outcomes
Peak Transverse-plane Prosthetic Socket Torque Normalized to Body Mass
Time Frame: During walking trials for each coupling ratio
Peak transverse-plane prosthetic socket torque measured while walking normalized to body mass
Secondary Outcomes
- Satisfaction With the Prosthesis(Immediately following walking trials for each coupling ratio)