Lower Extremity Amputation
Conditions
Keywords
lower limb prosthesis, transtibial amputation, below knee amputation, biomechanics, gait
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. 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.
Interventions
DEVICETorsionally 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.
DEVICETorsionally 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.
DEVICETorsionally 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.
DEVICETorsionally 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.
DEVICETorsionally 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
VA Office of Research and Development
Study design
Allocation
RANDOMIZED
Intervention model
FACTORIAL
Primary purpose
TREATMENT
Masking
NONE
Intervention model description
This within-subject, cross-over, factorial design study (3 arms x 5 intervention settings) aims to identify the optimal coupling ratio between transverse- and sagittal-plane motions using a torsionally adaptive prosthesis. The 3 arms including walking in a straight line (study visit 1) and walking in a circle with their lower limb prosthesis on the inside and outside of the circle (study visit 2). The order in which the participants walk around a circle with their prosthesis on the inside or the outside will be randomized. The study intervention, a torsionally adaptive prosthesis, can be set to 5 different settings (i.e., coupling ratios) including 0:0, 1:6, 1:4, 1:3, and 1:2 (transverse:sagittal). Within each arm, each participant will walk with the torsionally adaptive prosthesis set to the 5 different settings in random order. Participants will not be blinded to the arm but will be blinded to the intervention setting (coupling ratio).
Eligibility
Sex/Gender
ALL
Age
18 Years to 70 Years
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
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Peak Transverse-plane Prosthetic Socket Torque Normalized to Body Mass | During walking trials for each coupling ratio | Peak transverse-plane prosthetic socket torque measured while walking normalized to body mass |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| Satisfaction With the Prosthesis | 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. |
Countries
United States
Participant flow
Pre-assignment details
Two enrolled participants decided they were no longer interested in participating before beginning the study protocol. One enrolled participant had a long residual limb and could not accommodate the build height of the study intervention.
Participants by arm
| Arm | Count |
|---|---|
| Individuals With a Lower Limb Amputation All participants were block randomized to the order in which they walked in a straight line, walked around a 2m diameter circle with their prosthesis on the inside of the circle, and walked around a 2m diameter circle with their prosthesis on the outside of the circle. Additionally, the order of the sagittal:transverse coupling ratio of 1:0, 6:1, 4:1, 3:1, and 2:1 were also block randomized and blinded to the participant. | 11 |
| Total | 11 |
Withdrawals & dropouts
| Period | Reason | FG000 |
|---|---|---|
| Overall Study | Intervention malfunction | 1 |
Baseline characteristics
| Characteristic | Individuals With a Lower Limb Amputation |
|---|---|
| Age, Continuous | 53 years STANDARD_DEVIATION 15 |
| Ethnicity (NIH/OMB) Hispanic or Latino | 0 Participants |
| Ethnicity (NIH/OMB) Not Hispanic or Latino | 11 Participants |
| Ethnicity (NIH/OMB) Unknown or Not Reported | 0 Participants |
| Race (NIH/OMB) American Indian or Alaska Native | 0 Participants |
| Race (NIH/OMB) Asian | 0 Participants |
| Race (NIH/OMB) Black or African American | 0 Participants |
| Race (NIH/OMB) More than one race | 1 Participants |
| Race (NIH/OMB) Native Hawaiian or Other Pacific Islander | 0 Participants |
| Race (NIH/OMB) Unknown or Not Reported | 0 Participants |
| Race (NIH/OMB) White | 10 Participants |
| Sex: Female, Male Female | 0 Participants |
| Sex: Female, Male Male | 11 Participants |
Adverse events
| Event type | EG000 affected / at risk |
|---|---|
| deaths Total, all-cause mortality | 0 / 11 |
| other Total, other adverse events | 0 / 11 |
| serious Total, serious adverse events | 0 / 11 |
Outcome results
Primary
Peak Transverse-plane Prosthetic Socket Torque Normalized to Body Mass
Peak transverse-plane prosthetic socket torque measured while walking normalized to body mass
Time frame: During walking trials for each coupling ratio
| Arm | Measure | Group | Value (MEAN) | Dispersion |
|---|---|---|---|---|
| Straight Line Walking | Peak Transverse-plane Prosthetic Socket Torque Normalized to Body Mass | Sagittal:transverse coupling ratio 3:1 | 0.323 Nm/kg | Standard Error 0.012 |
| Straight Line Walking | Peak Transverse-plane Prosthetic Socket Torque Normalized to Body Mass | Sagittal:transverse coupling ratio 4:1 | 0.312 Nm/kg | Standard Error 0.011 |
| Straight Line Walking | Peak Transverse-plane Prosthetic Socket Torque Normalized to Body Mass | Sagittal:transverse coupling ratio 1:0 | 0.299 Nm/kg | Standard Error 0.025 |
| Straight Line Walking | Peak Transverse-plane Prosthetic Socket Torque Normalized to Body Mass | Sagittal:transverse coupling ratio 6:1 | 0.292 Nm/kg | Standard Error 0.013 |
| Straight Line Walking | Peak Transverse-plane Prosthetic Socket Torque Normalized to Body Mass | Sagittal:transverse coupling ratio 2:1 | 0.350 Nm/kg | Standard Error 0.019 |
| Circle Walking With Prosthesis Inside | Peak Transverse-plane Prosthetic Socket Torque Normalized to Body Mass | Sagittal:transverse coupling ratio 4:1 | 0.331 Nm/kg | Standard Error 0.023 |
| Circle Walking With Prosthesis Inside | Peak Transverse-plane Prosthetic Socket Torque Normalized to Body Mass | Sagittal:transverse coupling ratio 1:0 | 0.340 Nm/kg | Standard Error 0.026 |
| Circle Walking With Prosthesis Inside | Peak Transverse-plane Prosthetic Socket Torque Normalized to Body Mass | Sagittal:transverse coupling ratio 6:1 | 0.324 Nm/kg | Standard Error 0.023 |
| Circle Walking With Prosthesis Inside | Peak Transverse-plane Prosthetic Socket Torque Normalized to Body Mass | Sagittal:transverse coupling ratio 3:1 | 0.343 Nm/kg | Standard Error 0.019 |
| Circle Walking With Prosthesis Inside | Peak Transverse-plane Prosthetic Socket Torque Normalized to Body Mass | Sagittal:transverse coupling ratio 2:1 | 0.349 Nm/kg | Standard Error 0.021 |
| Circle Walking With Prosthesis Outside | Peak Transverse-plane Prosthetic Socket Torque Normalized to Body Mass | Sagittal:transverse coupling ratio 2:1 | 0.358 Nm/kg | Standard Error 0.021 |
| Circle Walking With Prosthesis Outside | Peak Transverse-plane Prosthetic Socket Torque Normalized to Body Mass | Sagittal:transverse coupling ratio 3:1 | 0.336 Nm/kg | Standard Error 0.021 |
| Circle Walking With Prosthesis Outside | Peak Transverse-plane Prosthetic Socket Torque Normalized to Body Mass | Sagittal:transverse coupling ratio 1:0 | 0.306 Nm/kg | Standard Error 0.026 |
| Circle Walking With Prosthesis Outside | Peak Transverse-plane Prosthetic Socket Torque Normalized to Body Mass | Sagittal:transverse coupling ratio 4:1 | 0.322 Nm/kg | Standard Error 0.025 |
| Circle Walking With Prosthesis Outside | Peak Transverse-plane Prosthetic Socket Torque Normalized to Body Mass | Sagittal:transverse coupling ratio 6:1 | 0.306 Nm/kg | Standard Error 0.026 |
Comparison: Hypothesis testing for the association between outcome and coupling ratio was carried out using conditional F-tests with degrees of freedom estimated using the Kenward-Roger method.p-value: 0.029Regression, Linear
Comparison: 6:1 versus 3:1p-value: 0.047Regression, Linear
Comparison: 6:1 versus 2:1p-value: 0.016Regression, Linear
Comparison: Hypothesis testing for the association between outcome and coupling ratio was carried out using conditional F-tests with degrees of freedom estimated using the Kenward-Roger method.p-value: 0.34Regression, Linear
Comparison: Hypothesis testing for the association between outcome and coupling ratio was carried out using conditional F-tests with degrees of freedom estimated using the Kenward-Roger method.p-value: 0.04Regression, Linear
Comparison: 6:1 versus 3:1p-value: 0.036Regression, Linear
Comparison: 6:1 versus 2:1p-value: 0.028Regression, Linear
Secondary
Satisfaction With the Prosthesis
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.
Time frame: Immediately following walking trials for each coupling ratio
| Arm | Measure | Group | Value (MEAN) | Dispersion |
|---|---|---|---|---|
| Straight Line Walking | Satisfaction With the Prosthesis | Sagittal:transverse coupling ratio 3:1 | 7.7 score on a scale | Standard Deviation 1.2 |
| Straight Line Walking | Satisfaction With the Prosthesis | Sagittal:transverse coupling ratio 4:1 | 8.0 score on a scale | Standard Deviation 1 |
| Straight Line Walking | Satisfaction With the Prosthesis | Sagittal:transverse coupling ratio 1:0 | 8.0 score on a scale | Standard Deviation 1.3 |
| Straight Line Walking | Satisfaction With the Prosthesis | Sagittal:transverse coupling ratio 6:1 | 8.2 score on a scale | Standard Deviation 1.3 |
| Straight Line Walking | Satisfaction With the Prosthesis | Sagittal:transverse coupling ratio 2:1 | 8.5 score on a scale | Standard Deviation 1 |
| Circle Walking With Prosthesis Inside | Satisfaction With the Prosthesis | Sagittal:transverse coupling ratio 4:1 | 7.1 score on a scale | Standard Deviation 1.7 |
| Circle Walking With Prosthesis Inside | Satisfaction With the Prosthesis | Sagittal:transverse coupling ratio 1:0 | 7.5 score on a scale | Standard Deviation 1.3 |
| Circle Walking With Prosthesis Inside | Satisfaction With the Prosthesis | Sagittal:transverse coupling ratio 6:1 | 7.9 score on a scale | Standard Deviation 1.1 |
| Circle Walking With Prosthesis Inside | Satisfaction With the Prosthesis | Sagittal:transverse coupling ratio 3:1 | 7.5 score on a scale | Standard Deviation 0.7 |
| Circle Walking With Prosthesis Inside | Satisfaction With the Prosthesis | Sagittal:transverse coupling ratio 2:1 | 8.1 score on a scale | Standard Deviation 1.3 |
| Circle Walking With Prosthesis Outside | Satisfaction With the Prosthesis | Sagittal:transverse coupling ratio 2:1 | 7.7 score on a scale | Standard Deviation 1.5 |
| Circle Walking With Prosthesis Outside | Satisfaction With the Prosthesis | Sagittal:transverse coupling ratio 3:1 | 7.8 score on a scale | Standard Deviation 1.1 |
| Circle Walking With Prosthesis Outside | Satisfaction With the Prosthesis | Sagittal:transverse coupling ratio 1:0 | 7.7 score on a scale | Standard Deviation 1.7 |
| Circle Walking With Prosthesis Outside | Satisfaction With the Prosthesis | Sagittal:transverse coupling ratio 4:1 | 7.4 score on a scale | Standard Deviation 1.3 |
| Circle Walking With Prosthesis Outside | Satisfaction With the Prosthesis | Sagittal:transverse coupling ratio 6:1 | 7.9 score on a scale | Standard Deviation 1.2 |