Biomechanical Assessment of Gait in Lower-Extremity-Amputees

Study Overview
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Brief Summary
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This study is investigating the influence of several simulated real life conditions on the symmetry of gait with trans-tibial prostheses Hypotheses: It is hypothesized that the observable differences in gait pattern between amputees can be detected by a combination of forces and moments that are measured internally in the prosthesis, and electromyography data. It is further hypothesized that changing conditions such as uneven walking surface, prosthetic misalignment or user fatigue are characterized by typical values in the measured data or combinations thereof.

Detailed Description
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In amputee walking, an optimal static alignment of the artificial leg is important in order to achieve the best possible performance. Comfort, energy expenditure, mobility and walking speed should ideally be similar to those of able bodied persons. Of course, amputation level, overall health status and other factors often pose certain individual limitations that may prevent an amputee from reaching this goal. Irrespective of that, the artificial leg must be aligned properly to eliminate unnecessary inhibitions. Apart from manufacturing a well fitting socket, and selecting the appropriate functional components of the prosthesis, the prosthetist has to routinely optimize the static alignment during the fitting process. Hereby, objective measures and guidelines are scarce. Despite various more or less useful tools that are available, the alignment optimization in praxis is often based on subjective gait assessment and rules of thumb. Commonly accepted is the notion, that the gait pattern should be most symmetrically, that is step lengths, stance times, knee angles etc. should be identical between sound and prosthetic leg. There are different questions that our study wants to address: Is gait symmetry indeed a valid measure of prosthetic performance (e.i. is it the most energy efficient way to walk)? How does the gait pattern change when the prosthesis user walks on different surfaces, becomes tired or tries to compensate for a less-than-optimal prosthesis fit? How can gait symmetry be objectively assessed without using an expensive motion analysis laboratory? We hope that our findings will provide practically useful information that can help improve prosthetic fittings in the field. The study will be based on data from up to 15 trans-tibial prosthesis users. Participants will walk with their standard prosthesis, which will be equipped with a small sensor unit for the measurement of forces and moments during walking. The muscle activity of the thigh muscles will be measured using surface EMG sensors. All of the data collection will take place at the USR facilities (115 E Reindl Way, Milwaukee), where a multi camera motion analysis system is set up. Trials will require an overall time commitment of 5 hours at most, and will include normal walking, walking on carpet and gravel, walking up and down stairs, walking with fatigued thigh muscles.

Official Title
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Biomechanical Assessment of Gait in Lower-Extremity-Amputees

Conditions
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Prosthesis User

Intervention / Treatment
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* Device: Alignment perturbations


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Trans tibial amputation Able to walk 30 minutes comfortably Modular prosthesis Exclusion Criteria: Prosthesis does not provide enough space between socket and foot module to fit the mobile measuring unit Physically or mentally unable to perform the required tasks

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 80 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Intervention Model: Single Group Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Alignment perturbations<br>The following modifications will be applied to the prostheses: increased foot plantar flexion, increased foot dorsal flexion, increased foot supination, increased foot pronation (always 2 degrees from the neutral position) | Device: Alignment perturbations<br>* Increased foot plantar flexion, increased foot dorsal flexion, increased foot supination, increased foot pronation (always 2 degrees from the neutral position)<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Overall Asymmetry Index | Gait data was continuously recorded and was post processed to determine symmetry between left and right legs. Symmetry was computed by dividing the difference between legs by the average of both legs. 0 marks perfect symmetry and greater values higher asymmetry. There is no maximum limit. The overall asymmetry index was calculated as the mean of the following: max knee flex, dorsi flexion, plantar flexion (1st and 2nd peak), knee moment, dorsi-flexion moment, plantar-flexion moment, times of max in % of the gait cycle, Stance phase % of gait cycle and step length. The kinematics asymmetry index was calculated as the mean of the following: maximal knee flex, dorsi flexion, plantar flexion (1st and 2nd peak), the times of max in % of the gait cycle, Stance phase % of gait cycle and step length. The kinetics asymmetry index was calculated as the mean of the following variables: knee moment, dorsi-flexion moment, plantar-flexion moment, the times of max in % of the gait cycle. | 1 hour | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Heart Rate Change | Subjects were wearing a wireless heart rate monitor. The respective readings were noted and assessed during and immediately following the trials to estimate individual exertion rates. Changes in heart rate between resting and exertion across the sample were investigated to be able to interpret the primary outcome measures and to discuss limitations of the protocol. Unequal exertion rates within the sample would cause uneven trends biomechanical changes that are related to exertion. | 1 hour |