NCT03532100

Pivot-Flex Foot: Optimal Coupling Ratio Between Transverse and Sagittal-plane Motions Using a Torsionally Adaptive Prosthesis for Individuals With Lower Limb Amputation

Completed NA Results posted Last updated 19 November 2025

What this trial tests

NA trial testing Torsionally adaptive prosthesis with 0:1 coupling ratio in Lower Extremity Amputation in 14 participants. Completed in 18 November 2024.

Timeline

18 April 2018

Primary endpoint
1 October 2024

18 November 2024

Quick facts

Lead sponsor	VA Office of Research and Development
Phase	NA
Status	Completed
Study type	INTERVENTIONAL
Allocation	randomized
Design	factorial
Masking	none
Primary purpose	treatment
Enrollment	14
Start date	18 April 2018
Primary completion	1 October 2024
Estimated completion	18 November 2024
Sites	1 location across United States

Drugs / interventions tested

• Torsionally adaptive prosthesis with 0:1 coupling ratio
• Torsionally adaptive prosthesis with 1:6 coupling ratio
• Torsionally adaptive prosthesis with 1:4 coupling ratio
• Torsionally adaptive prosthesis with 1:3 coupling ratio
• Torsionally adaptive prosthesis with 1:2 coupling ratio

Conditions studied

• Lower Extremity Amputation — all drugs for Lower Extremity Amputation →

Sponsor

VA Office of Research and Development — full company profile →

Who can join

Adults 18 to 70, any sex, with Lower Extremity Amputation. Patients with the condition only — healthy volunteers not accepted.

Results — posted to ClinicalTrials.gov

Per-arm endpoint measurements with 95% confidence intervals where reported. Source: trial results section.

Peak Transverse-plane Prosthetic Socket Torque Normalized to Body Mass Primary · During walking trials for each coupling ratio

Peak transverse-plane prosthetic socket torque measured while walking normalized to body mass

Sagittal:transverse coupling ratio 1:0

Group	Value	95% CI
Straight Line Walking	0.299	± 0.025
Circle Walking With Prosthesis Inside	0.340	± 0.026
Circle Walking With Prosthesis Outside	0.306	± 0.026

Sagittal:transverse coupling ratio 6:1

Group	Value	95% CI
Straight Line Walking	0.292	± 0.013
Circle Walking With Prosthesis Inside	0.324	± 0.023
Circle Walking With Prosthesis Outside	0.306	± 0.026

Sagittal:transverse coupling ratio 4:1

Group	Value	95% CI
Straight Line Walking	0.312	± 0.011
Circle Walking With Prosthesis Inside	0.331	± 0.023
Circle Walking With Prosthesis Outside	0.322	± 0.025

Sagittal:transverse coupling ratio 3:1

Group	Value	95% CI
Straight Line Walking	0.323	± 0.012
Circle Walking With Prosthesis Inside	0.343	± 0.019
Circle Walking With Prosthesis Outside	0.336	± 0.021

Sagittal:transverse coupling ratio 2:1

Group	Value	95% CI
Straight Line Walking	0.350	± 0.019
Circle Walking With Prosthesis Inside	0.349	± 0.021
Circle Walking With Prosthesis Outside	0.358	± 0.021

Satisfaction With the Prosthesis Secondary · Immediately following walking trials for each coupling ratio

An 11-point Likert scale will be used to record the subject's perception of satisfaction with the prosthesis after completing the trials for each coupling ratio. Participants will be asked to rate their satisfaction with the prosthesis on a 0 - 10 scale. Zero represented the most uncomfortable socket fit the subject could imagine, and ten represented the most comfortable socket fit.

Sagittal:transverse coupling ratio 1:0

Group	Value	95% CI
Straight Line Walking	8.0	± 1.3
Circle Walking With Prosthesis Inside	7.5	± 1.3
Circle Walking With Prosthesis Outside	7.7	± 1.7

Sagittal:transverse coupling ratio 6:1

Group	Value	95% CI
Straight Line Walking	8.2	± 1.3
Circle Walking With Prosthesis Inside	7.9	± 1.1
Circle Walking With Prosthesis Outside	7.9	± 1.2

Sagittal:transverse coupling ratio 4:1

Group	Value	95% CI
Straight Line Walking	8.0	± 1.0
Circle Walking With Prosthesis Inside	7.1	± 1.7
Circle Walking With Prosthesis Outside	7.4	± 1.3

Sagittal:transverse coupling ratio 3:1

Group	Value	95% CI
Straight Line Walking	7.7	± 1.2
Circle Walking With Prosthesis Inside	7.5	± 0.7
Circle Walking With Prosthesis Outside	7.8	± 1.1

Sagittal:transverse coupling ratio 2:1

Group	Value	95% CI
Straight Line Walking	8.5	± 1.0
Circle Walking With Prosthesis Inside	8.1	± 1.3
Circle Walking With Prosthesis Outside	7.7	± 1.5

Sponsor's own description

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.

Publications & conference data

No peer-reviewed publications indexed yet for this trial. Completed trials usually publish results within 12-18 months.