# Pivot-Flex Foot

> **NIH VA I01** · VA PUGET SOUND HEALTHCARE SYSTEM · 2021 · —

## Abstract

Project Summary (Public Abstract)
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 is coupled with
external and internal rotation of the shank relative to the foot, respectively. There is no prosthetic foot available
for prescription that mimics this natural coupling.
The purpose of the proposed research is to develop a passive prosthesis (Pivot-Flex Foot) that mimics the natural
coupling of the intact limb and determine if this coupling can reduce transverse-plane socket torque and
compensatory gait biomechanics when compared to a standard-of-care prosthesis. We anticipate the long-term
outcomes from wearing a Pivot-Flex Foot are a lower incidence of soft tissue and compensatory gait injuries.
To investigate the need for this coupling, we have already built a torsionally adaptive prosthesis (TAP) where the
coupling ratio between the transverse- and sagittal-planes can be independently controlled with a motor. The
TAP can be used to discover the optimal coupling ratio, but is a bit unwieldy for long-term, everyday use. A more
robust solution for daily wear is the Pivot-Flex Foot, a passive prosthesis we have built using industry standards.
We plan to use the TAP to identify the optimal coupling ratio and then build a selection of Pivot-Flex Feet for
testing by individuals with lower limb amputation.
Our proposed research has two specific aims:
(1) To identify the optimal coupling ratio between transverse- and sagittal-plane motions using a
novel, torsionally adaptive prosthesis. We propose to conduct a human subject experiment (n=15) with
below-knee amputees wearing the motor-driven and computer controlled TAP. Participants will walk in a
straight line and in both directions around a circle while we vary the coupling ratio between transverse- and
sagittal-plane motions. Participants will be blinded to the coupling ratio. We hypothesize that: (1) a coupling ratio
exists that minimizes undesirable transverse-plane socket torque and (2) there will be a coupling ratio that
amputees prefer. The results from this test will be used to specify the coupling ratio of the more practical Pivot-
Flex Feet we plan to test in specific aim 2.
(2) To determine if a passive prosthesis with an optimal coupling ratio (Pivot-Flex Foot) can
reduce transverse-plane socket torque and compensatory gait biomechanics when compared to
a standard-of-care prosthesis. We propose to design and build Pivot-Flex Feet of various sizes and
stiffnesses that can be worn by a majority of below-knee amputee...

## Key facts

- **NIH application ID:** 10424359
- **Project number:** 5I01RX002456-04
- **Recipient organization:** VA PUGET SOUND HEALTHCARE SYSTEM
- **Principal Investigator:** Glenn Klute
- **Activity code:** I01 (R01, R21, SBIR, etc.)
- **Funding institute:** VA
- **Fiscal year:** 2021
- **Award amount:** —
- **Award type:** 5
- **Project period:** 2018-01-01 → 2022-09-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10424359

## Citation

> US National Institutes of Health, RePORTER application 10424359, Pivot-Flex Foot (5I01RX002456-04). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/10424359. Licensed CC0.

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