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

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.

Conditions

• Lower Extremity Amputation

Interventions

DEVICE

Torsionally adaptive prosthesis with 0:1 coupling ratio

The torsionally adaptive prosthesis can be programmed to couple the motion between the transverse- and sagittal-planes. A coupling ratio (transverse:sagittal) of 0:1 means there will be no coupling between the transverse- and sagittal-plane motion. That is, regardless of any motion in the sagittal plane, there will be zero motion in the transverse plane.

DEVICE

Torsionally adaptive prosthesis with 1:6 coupling ratio

The torsionally adaptive prosthesis can be programmed to couple the motion between the transverse- and sagittal-planes. A coupling ratio (transverse:sagittal) of 1:6 means there will be one degree of motion in the transverse plane for every six degrees of motion in the sagittal plane.

DEVICE

Torsionally adaptive prosthesis with 1:4 coupling ratio

The torsionally adaptive prosthesis can be programmed to couple the motion between the transverse- and sagittal-planes. A coupling ratio (transverse:sagittal) of 1:4 means there will be one degree of motion in the transverse plane for every four degrees of motion in the sagittal plane.

DEVICE

Torsionally adaptive prosthesis with 1:3 coupling ratio

The torsionally adaptive prosthesis can be programmed to couple the motion between the transverse- and sagittal-planes. A coupling ratio (transverse:sagittal) of 1:3 means there will be one degree of motion in the transverse plane for every three degrees of motion in the sagittal plane.

DEVICE

Torsionally adaptive prosthesis with 1:2 coupling ratio

The torsionally adaptive prosthesis can be programmed to couple the motion between the transverse- and sagittal-planes. A coupling ratio (transverse:sagittal) of 1:2 means there will be one degree of motion in the transverse plane for every two degrees of motion in the sagittal plane.

Sponsors & Collaborators

• VA Office of Research and Development

  lead FED

Principal Investigators

• Glenn K Klute, PhD · VA Puget Sound Health Care System Seattle Division, Seattle, WA

Study Design

Allocation

RANDOMIZED

Purpose

TREATMENT

Masking

NONE

Model

FACTORIAL

Eligibility

Min Age

18 Years

Max Age

70 Years

Sex

ALL

Healthy Volunteers

No

Timeline & Regulatory

Start

2018-04-18

Primary Completion

2024-10-01

Completion

2024-11-18

Countries

• United States

Study Locations