Pivot-Flex Foot: Optimal Coupling Ratio Between Transverse and Sagittal-plane Motions Using a Torsionally Adaptive Prosthesis for Individuals With Lower Limb Amputation
| Status: | Recruiting |
|---|---|
| Healthy: | No |
| Age Range: | 18 - 70 |
| Updated: | 11/14/2018 |
| Start Date: | April 18, 2018 |
| End Date: | September 30, 2021 |
| Contact: | Glenn K Klute, PhD |
| Email: | Glenn.Klute@va.gov |
| Phone: | (206) 764-2991 |
Pivot-Flex Foot: Torsionally Adaptive Prosthesis for Individuals With Lower Limb Amputation
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.
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.
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 will walk in a straight line and in both directions around a circle with the
torsionally adaptive prosthesis set at different coupling ratios (blinded and random order).
The general hypotheses for this study are: (H1) a coupling ratio exists between 0 (no
coupling) to 1:2 (one degree of transverse-plane motion for every two degrees of
sagittal-plane motion) that minimizes transverse-plane socket torque and (H2) an amputee
preferred coupling ratio will exist within this range.
This research will discover how best to couple transverse- and sagittal-plane motion in the
prostheses of lower limb amputees.
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 will walk in a straight line and in both directions around a circle with the
torsionally adaptive prosthesis set at different coupling ratios (blinded and random order).
The general hypotheses for this study are: (H1) a coupling ratio exists between 0 (no
coupling) to 1:2 (one degree of transverse-plane motion for every two degrees of
sagittal-plane motion) that minimizes transverse-plane socket torque and (H2) an amputee
preferred coupling ratio will exist within this range.
This research will discover how best to couple transverse- and sagittal-plane motion in the
prostheses of lower limb amputees.
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
We found this trial at
1
site
Seattle, Washington 98108
Principal Investigator: Glenn K Klute, PhD
Phone: 206-764-2991
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