Wireless Non-Invasive Advanced Control of Microprocessor Prostheses and Orthoses II
Phase: NA
Conditions: Prostheses, Upper Limb Amputation Below Elbow
Sponsor: Liberating Technologies, Inc.

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Wireless Prosthetic Control Effectiveness Study 
 
Investigators 
Edward (Ted) A. Clancy, PhD 
Worcester Polytechnic Institute (WPI) 
100 Institute Road 
Worcester, MA 01609 
(508) 831-5778, 
 
Todd Farrell, PhD 
Liberating Technologies, Inc.  
325 Hopping Brook Road, Suite A 
Holliston, MA 01746 
(508) 893-6363 
 
Funding Source 
Department of Defense  
IRB Protocol # 
IRB-23-0722 
NCT# 
NCT06821412 
Version 
V04 
IRB Approval Date 
October 26, 2023 
 
 

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Protocol: Wireless Non-Invasive Advanced Control of Microprocessor 
Prostheses and Orthoses II 
 
Note 1: Figure and citation numbers refer to those in the original grant application that funds this 
work. Referenced figures are shown herein but are not numbered starting from “1” and 
numbering does not advance sequentially. Any new figures (that did not appear in the original 
grant application) are referenced by letter (i.e., “A”, …). 
Note 2: We believe that our use of this prototype re-chargeable, wearable electrode is exempt from 
requirement of an Investigational Device Exemption (IDE) prior to initiation of the experimental 
work because its use does not involve significant risk (https://www.fda.gov/medical-
devices/investigational-device-exemption-ide/ide-application).  The wireless electrode is non-
invasive.  It does not by design or intention introduce energy into a subject. It monitors muscle 
electrical activity (electromyogram, or EMG) non-invasively. The device is battery powered and 
the battery is only charged when the device is not in operation on the subject (i.e., the battery is 
charged while sitting on a desktop).  (See Figure A below for a mock-up view of the wireless 
electrode.) 
 
HUMAN SUBJECT TESTING LABORATORY AND TAKE-HOME STUDY 
There are multiple advantages to wearing a 
prosthetic liner (i.e., a sleeve most commonly made 
from silicone or thermoplastic elastomer material and 
covered in fabric) [Figure 5] that have made them 
very popular with lower limb prosthesis wearers. 
These advantages 
include improved comfort, 
improved suspension, and potentially less aggressive 
socket trimlines. However, upper limb prosthesis 
users with myoelectric control cannot wear a liner as the electromyogram (EMG) electrode must touch the 
skin to transduce the myoelectric signal. Therefore, upper limb users miss out on the comfort and suspension 
benefits of the liner, while also not being able to use prosthetic socks for limb volume management. 
Therefore, upper limb myoelectric users would benefit from the ability to wear prosthetic liners. 
The proposed ASTERISK system would allow for liners to be worn with upper limb myoelectric 
systems. By creating wireless sensors that can be worn under a liner, the sensors can be placed on the skin 
to collect the myoelectric signal, the liner then rolled over the top of the sensors when donning, and the 
sensors can transmit the EMG signal wirelessly to the prosthesis. 
 
Figure 5 | Photograph of prosthetic liner 

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Our overall hypothesis is that allowing users to wear a liner with their myoelectrically-controlled 
prosthesis will allow them to realize the benefits of liners and therefore increase their overall satisfaction 
with the prosthetic device while not sacrificing functional performance. Stated more explicitly, our primary 
hypothesis is that myoelectric 
prosthesis users will show an 
improvement 
in 
device 
satisfaction, as measured by 
the Orthotics and Prosthetics 
User 
Survey 
(OPUS)—
Satisfaction with Device (SD) 
survey, when using a prosthetic 
liner with our “ASTERISK” 
wireless 
EMG 
electrodes 
(Figure A) as compared to their 
standard 
myoelectric 
prosthesis. The OPUS-SD was 
selected because it is a self-
report measure that focuses on prosthesis fit, comfort, skin health, etc., is likely to be sensitive to the 
proposed intervention, and has established validity and reliability in prosthesis users [15,16]. Figure B 
shows a diagram of a complete hand prosthesis using our wireless electrode system. As shown, two separate 
electrode nodes are independently secured to the forearm, one over flexion muscles and the other over 
                
 
                      (A)                                                                (B) 
Figure A | Front view (A) and cut-away cross-section view (B) of a mock-up of our 
proposed wireless, re-chargeable electrode. Overall dimensions are 30 mm length x 
20 mm width x 10 mm height. Both views show the two recording electrode contacts 
with a reference electrode contact between them. The electrode contacts are held in 
electrical contact with the skin over the muscle(s) of interest during use. 
 
Figure B | Top shows a diagram of our hand prosthesis system. Each “Wireless Sensor Node” is a battery-powered 
electromyogram (EMG) electrode-amplifier in its own separate, independent case. [Figure A (above) shows how such 
electrode nodes might look.] One electrode node would typically be applied over remnant flexion muscles in the forearm 
and the other over remnant extension muscles in the forearm. The electrode nodes are held in place by an armband. These 
nodes transmit wirelessly to a receiver-controller that is integrated into the hand prosthesis near its wrist (labelled “Coapt 
Gen 2.5” in the diagram). The receiver-controller receives the EMG signals and generates hand control commands that are 
issued (via electrical wires) to the adjacent hand. The photo in the lower right, shows a Coapt Gen 2.5 integrated into the 
wrist section of a hand prosthesis. 

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extension muscles. The receiver is then integrated into the hand prosthesis. The received electromyogram 
signals are used to control the prosthetic hand, which is electrically wired to the receiver-controller. 
 
In addition to our primary hypothesis, we will also evaluate multiple secondary hypotheses such as the 
reported Socket Comfort Score (SCS), all or portions of the Prosthesis Evaluation Questionnaire (PEQ), 
elbow range of motion (due to the ability to use less aggressive socket trimlines), and wear time of the 
prosthesis (i.e., greater comfort/satisfaction should lead to longer wear). The Socket Comfort Score was 
developed to assess socket fit and has evidence of validity and sensitivity to changes in socket fit [17]. We 
plan to utilize the recently released expanded SCS version, that has shown superior psychometric 
performance to the original [18]. The Prosthesis Evaluation Questionnaire is comprised of nine scales, each 
of which can be administered independently. These scales measure ambulation, appearance, frustration, 
perceived response, residual limb health, social burden, sounds, utility, and well being. To monitor upper 
limb prosthesis usage, we will deploy the methods used in prior studies to monitor linear acceleration, 
rotation and orientation (with respect to gravity) of the prosthetic limb [19] (e.g., ActiGraph GT9X activity 
monitors). 
Finally, to demonstrate that the improved comfort does not come at the expense of decreased function, 
we will also collect functional outcomes measures in the laboratory, including the Activities Measure for 
Upper Limb Amputees (AMULA) [20]. A secondary hypothesis is that we will demonstrate equivalency 
between the two test conditions (i.e., standard socket configuration vs. liner with ASTERISK wireless 
electrodes socket configuration). The AMULA is attractive because it 1) evaluates the use of the prosthesis 
in a relatively large distribution of “zones” (i.e., over the head, below the waist, etc.) that have the potential 
to create control challenges due to electrode liftoff, 2) requires the use of a large percentage of bi-manual 
tasks (to ensure that tasks cannot simply be completed with the unaffected limb), and 3) has had its 
psychometric attributes established on our proposed study population (to ensure its reliability and validity) 
[21]. 
 
STUDY DESIGN 
The study evaluates the ASTERISK system to determine if ASTERISK will increase a user’s self-
reported satisfaction with their prosthesis as measured by the Orthotic and Prosthetic User Survey—
Satisfaction with Device (OPUS-SD) when compared to their current prosthesis. While the technology has 
the 
potential 
to 
benefit 
other 
patient 
populations, we will focus this initial pilot 
study on individuals with trans-radial limb 
absence to reduce potential confounding 
variables associated with including other 
amputation levels. 
We plan to conduct a randomized 2x2 
crossover study to evaluate benefits provided 
by prostheses utilizing liners with the 
ASTERISK 
electrodes 
over 
standard 
prostheses. The study design is shown in 
Figure 25 with the two crossover test 
 
Figure 25 | ASTERISK study design – a randomized crossover 
study. 

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conditions shown as “Experimental” (myoelectric control with the liner and ASTERISK system) and 
“Control” (standard prosthetic device configuration). For the control condition, the subject will be using 
their everyday prosthesis. For the experimental condition, we will fabricate and provide a new socket to 
allow for the additional socket volume necessary for liners worn with the ASTERISK electrodes. Each 
subject will participate in both conditions of the study. The condition that each subject completes first will 
be chosen by a random number generator that also ensures block randomization with an equal number of 
participants assigned to each condition first in the test sequence using a custom program that was created 
under a prior research project. 
Subjects will participate in four research visits and will take part in two, one-month long take-home 
periods. Some researchers have suggested that persons with transradial amputation require, on average, 3–
5 weeks of training [22], while others have suggested that 5 hours of training is sufficient [23]. Therefore, 
we expect a one-month take-home period to be sufficient to allow users to become comfortable with each 
socket configuration while optimizing the take-home duration to maximize study efficiency. 
Twelve subjects will be recruited for this study to allow for a 25% dropout rate and still ensure that we 
meet our goal of at least 9 subjects to achieve our desired statistical power level (described in the Statistical 
Plan below). Each subject will use their current prosthetic terminal device (e.g., prosthetic hand) with the 
experimental socket. If the subject normally uses a wrist rotator prosthesis, then LTI will provide one to be 
installed in their experimental socket. As described above, the OPUS-SD (survey) will serve as our primary 
outcome measure for this study, but we will also collect secondary outcome measures, including the Socket 
Comfort Score (survey), Prosthesis Evaluation Questionnaire (survey), AMULA, prosthetic wear 
time/usage, and elbow range of motion. 
Participant Eligibility: All subjects must be current wearers of trans-radial myoelectric prostheses or 
orthoses, have used their prostheses/orthoses for at least six months, be between the ages of 18 and 89 years, 
understand spoken and written English (for the purpose of consenting), and not have any neurological or 
physical conditions which would prevent them from performing the experimental tasks. The risks to 
pregnant people and fetuses are unknown and therefore those who are pregnant should not participate in the 
study and will be screened by self-disclosure. Subjects in this study will not be discriminated against due 
to sex/gender or race/ethnicity. Potential subjects will be screened via telephone for eligibility for the study. 
 
STUDY PROTOCOL 
Visit 1: During the first visit, the subject will be consented and enrolled in the study. Measurements and 
casts will be taken so an experimental socket can be fabricated. Subjects will then be asked to complete the 
in-lab validated outcomes measures (OPUS-SD, PEQ, AMULA, elbow range of motion, SCS, etc.) as 
described above to provide a baseline measure of function and satisfaction with their usual prosthesis. If 
there is leftover time and the subject is not fatigued, this battery of tests may be repeated to help to reduce 
the learning effects associated with performing a new task. By having the subject practice these tests, 
learning effects will be reduced as they enter into the 2x2 crossover portion of the study. The 2x2 crossover 
design was specifically chosen to help mitigate the impact of learning effects related to the administration 
of outcome measures that are new to the test subjects by randomizing the order of conditions. Over the next 
few weeks following Visit 1, a study prosthetist will create the experimental socket with our ASTERISK 
system integrated into it. Once the experimental socket is fabricated, the subject will return for Visit 2. 

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Visit 2: Two to four weeks after Visit 1, subjects will return for Visit 2. During this visit, the subjects 
will first repeat the battery of outcomes administered in Visit 1 to both serve as the baseline of the 2x2 
crossover portion of the study as well as identify test-retest variability in their results. The subjects will then 
be randomly assigned to a group to determine the order of test condition for that subject. If the subject is 
randomized into the experimental condition, they will be fit with the experimental socket with the installed 
ASTERISK technology. All subjects, regardless of test condition, will then receive training on controlling 
their prosthesis in their current test condition by the site occupational therapist (OT). The training will start 
with basic skills, including opening and closing the device, and grasping various shapes such as cone/cups, 
regular/irregular block shapes, and various size and weight balls. Then they will advance to splinter skills, 
involving partial completion of ADL tasks, for example, positioning the device on the handle of a large 
mug and gripping the handle. And finally, they will practice full task skills, i.e., grasping the handle of a 
large mug and bringing the mug up to the subject’s mouth to drink from it, putting the mug back down, and 
releasing the grip. All subjects will also receive instructions on how to fill out the daily log (for the ensuing 
at-home portion of the study). For those starting with the experimental condition, instructions will be given 
on how to don, connect, and charge the ASTERISK sensors. Once they are comfortable using the device, 
they will be sent home with the experimental prosthesis. 
One-Month At-Home (Condition A): Subjects will be asked to wear their experimental prosthesis and 
perform their daily activities either using their everyday socket (control condition) or socket with liner and 
ASTERISK sensors (experimental condition). An ActiGraph activity monitor (worn like a wristwatch; 
provided by the experimenters for use by the subjects) will be worn on the prosthesis to monitor prosthesis 
usage throughout the day. The ActiGraph contains an inertial measurement unit that records prosthetic lime 
acceleration, rotation and orientation.  It does not record a subject’s location.  All subjects will be asked to 
keep a daily log to track any issues they have with their prosthesis and help identify and document any 
issues with real-world use of the device. Researchers will periodically check-in with the subject (by phone, 
text, email, etc.) to maximize adherence to the daily log, debug any technical issues, etc. 
Visit 3: After one month, subjects will return for Visit 3. At this time the data will be downloaded from 
the ActiGraph monitor and the daily log collected. Subjects will perform the same in-lab testing as in Visits 
1 & 2, with subjects performing the functional outcomes measures using the prosthetic control modality 
used in the prior month and providing feedback on the system via a custom survey developed as part of this 
effort. The test conditions will then be switched (those using the control condition in the first month will 
now use the experimental condition and vice versa) and subjects will receive training on the second test 
condition. For those switching to the experimental condition, instructions will be given on the use of the 
ASTERISK sensors. All subjects will be instructed and trained on their newly assigned prosthesis control 
condition by a study OT as described in Visit 2. Once trained, subjects will again be sent home to use the 
device in a real-world environment. 
One-Month At-Home (Condition B): This is the same as the first one-month take-home session, except 
subjects have swapped conditions. All subjects will once again be asked to keep a daily log to track any 
technical issues. Researchers will periodically check-in with the subject to maximize adherence to the daily 
log, debug any technical difficulties, etc. 
Visit 4: After one month, the subjects will return for Visit 4. This visit is the same as Visit 3. At this 
time the data will be downloaded from the ActiGraph monitor and the daily log collected. Subjects will 
perform the same in-lab testing as in Visits 1–3, with subjects performing the functional outcomes measures 
using the prosthesis control modality used the prior month and providing feedback on the system via the 

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custom survey that will include questions related to overall preference (control vs. experimental) as well as 
other pertinent feedback. Upon conclusion of the in-lab testing, the experimental socket will then be 
returned, and the subject set back up on their usual socket by a study prosthetist. At the end of this visit, the 
subject’s participation in the study is complete. 
Extra Visit(s): In certain cases, subjects may become too fatigued (physically or mentally) to complete 
the entire planned activity during the scheduled visit. Additionally, in some cases, equipment failures may 
delay completion of the activity planned for a visit.  In such a case, subjects may be invited to return to 
complete the visit activity at the next mutually agreed date. If the return visit is due to equipment failures, 
subjects will be offered the standard travel stipend for the secondary visit. 
 
STATISTICAL PLAN AND DATA ANALYSIS 
Pilot Validation Study: A pilot study is defined by Moore, et al. [24] as a timely and cost-effective 
preparatory investigation intended to inform the successful design of future, often larger, clinical studies by 
testing study designs, measures, procedures, recruitment criteria, etc. The proposed pilot study is intended 
to mimic a future clinical trial and will be used to confirm our processes, including an assessment of the 
feasibility of our test protocols, recruitment and retention rates, etc. However, even more importantly, the 
pilot study is intended to provide outcomes data related to interparticipant and intraparticipant variance 
parameters from the target patient population for our primary and secondary outcomes. These data can be 
used in a robust power analysis that will determine the required sample size for a larger, follow-on clinical 
trial. In addition, this trial will allow us to confirm that our processes are sufficient for our planned data 
analyses or identify gaps that can be addressed before the initiation of the follow-on clinical trial. 
While larger sample sizes can yield more precise estimates of confidence intervals and variance 
estimates, there are diminishing returns with larger samples sizes. These diminishing benefits often become 
outweighed by practicalities such as time and funding. Therefore, we will follow the recommendation of 
Moore et al. [24], as well as the power analysis described below, and include 12 participants to estimate 
average values and variances of our specific outcome measures in the target population. We recognize that 
this pilot study may not demonstrate definitive evidence for a treatment effect of the ASTERISK 
intervention. However, it provides a method that optimizes value and practicality to prepare for a definitive 
clinical trial to demonstrate the potential effectiveness of the ASTERISK system on prosthesis satisfaction 
and other secondary measures. 
Power Analysis: We also performed a power analysis to evaluate the insights and conclusions that may 
result from the proposed take-home portion of the study. While many tests may be carried out in a particular 
study, Baguley [25] states that the power analysis should be conducted on the “principal hypothesis” to 
determine the sample size. Our principal hypothesis is that ASTERISK will increase prosthesis satisfaction 
when compared to standard socket configurations as measured by the Orthotics and Prosthetics User Survey 
(OPUS) – Satisfaction with Device (SD) measure. Two primary parameters are required to perform the 
power analysis associated with the proposed study design: the size of the difference in our primary outcome 
measure that we are trying to detect (δ) and standard deviation (SD) of the difference between two values 
for the same subject (σ). We aim to be able to detect a change that provides a minimum detectable change 
(MDC) on the OPUS-SD. Jarl et al., [16] reported that the minimum detectable change of the OPUS-SD 
was 15 points (δ). Other studies are currently using the OPUS to test the efficacy of an intervention on upper 
limb prosthesis performance. Dr. Matt Wernke at WillowWood is currently using the measure to examine 
the change in scores on the OPUS using the aforementioned MyoLiner. He was kind enough to share yet 

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unpublished data [26] in which he had observed a standard deviation (SD) of the difference between two 
values for the same subject on the OPUS-SD (σ) to be 12.2 points on 14 patients, when one outlier (as 
confirmed by Z-scores) subject’s data were excluded. 
A power analysis was conducted using the MGH sample size calculator software for cross-over studies 
[27] to determine the study population needed to reject the null hypothesis that the ASTERISK does not 
change prosthesis satisfaction as measured by the OPUS-SD. This calculation was performed with the 
assumptions that we are planning a study of a normally distributed, continuous response variable from a 
2x2 cross-over of study subjects. Data described above indicated that the difference in the response of 
matched pairs is normally distributed with a standard deviation of 12.2. If the true difference in the mean 
response of the matched pairs is 15 points on the OPUS-SD, the calculation concluded that we would need 
to study 9 subjects to achieve the standard target of 80% statistical power. From the MGH calculator, with 
9 subjects, the probability is 89 percent that the study will detect a treatment difference at a two-sided 0.05 
significance level. 
Subject Recruitment, Test Sites, and Sub-Populations: To account for potential subject attrition, we 
will recruit 12 subjects that are current wearers of trans-radial myoelectric prostheses to allow for a 25% 
dropout rate to ensure that we will reach our goal of 9 subjects completing the study. The 12-subject estimate 
from this analysis directly aligns with the 12-subject recommendation for pilot studies from Moore et al. 
[24] described above, and therefore we are confident that our proposed pilot study will allow us to generate 
valuable information to guide the design of future clinical trials. 
Recruitment of more than a modest number of upper limb prosthetics subjects can be difficult. 
Therefore, planned subject recruitment has been distributed across three test sites: LTI (2 subjects), WPI (6 
subjects) and Handspring Clinical Services (4 subjects), and can be redistributed as necessary. While the 
ASTERISK could have great benefit to users of other amputation levels, this pilot study will focus on trans-
radial users to keep the population as homogeneous and focused as possible. 
In addition to the three experimental sites visited by subjects, three other entities will participate in the 
project team. Debra Latour (Occupational Therapist; Assistant Professor, Western New England 
University) will provide occupational therapy on-site to subjects at all experimental sites.  Elizabeth Newton 
(Newton Statistical Consulting) will provide data analysis and statistical consulting for the overall project. 
Lastly, faculty and staff from Nursing and Health Professions at University of Hartford will also provide 
prosthesis fabrication for the experimental work occurring at all three sites. 
Secondary Measures: As described above, we performed the power analysis based on our principal 
hypothesis. However, we plan to do much more in depth and rigorous analysis of our 2x2 randomized 
crossover study data upon completion of data collection. We will also examine several other outcome 
measures such as elbow range of motion, AMULA scores, SCS scores, PEQ scores, and prosthesis wear 
time. Again, we recognize that this pilot study may not demonstrate definitive evidence for a treatment 
effect of the intervention. However, it will allow us to explore models that can be used in future clinical 
studies. In addition, we hope that the proposed experiments will generate variance data across the battery 
of additional outcomes measures that can be published to help future researchers plan their clinical studies. 
Statistical Model: The primary statistical analysis will be led by Dr. Newton and will consist of the 
development of a generalized liner mixed model (GLMM) for crossover designs. In this 2x2 crossover 
study, 2 treatments will be administered in 2 periods and 2 sequences, as described above. We will employ 
a linear mixed model for this design as discussed in multiple references [28,29]. The model will contain 

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fixed effects for treatment, sequence, and period as well as random effects for subject and test site. Models 
with and without treatment carryover effects will be examined. 
With 6 subjects in each treatment sequence group, the model, without covariates, is as follows: 𝑦𝑖𝑗𝑘=
𝜇+ 𝛼𝑖+ 𝛽𝑘+ 𝜏𝑑+ 𝜆𝑐+ 𝑑𝑖𝑗+ 𝑒𝑖𝑗𝑘, where: i, k, d, c =1, 2; j=1, 2, …, 6; 𝑦𝑖𝑗𝑘 is the response of the jth subject 
in the ith sequence and the kth period; 𝜇 is the general mean; 𝛼𝑖 is the sequence effect; 𝛽𝑘 is the period effect; 
𝜏𝑑 is the direct treatment effect; 𝜆𝑐 is the carryover effect (0 for period 1); 𝑑𝑖𝑗 is the random effect associated 
with the jth subject in the ith treatment sequence; and 𝑒𝑖𝑗𝑘 is random error associated with the jth subject in 
sequence i at period k. Additional terms in the model will include a random effect for test site (as testing 
will occur at LTI, WPI, U. Hartford and Handspring Clinical Services) to increase precision of the estimates. 
In a 2x2 crossover design, carryover effects are confounded with the other effects. We will examine models 
omitting each of the effects in turn to assess their contribution and we will consider the inclusion of a 
washout period between test conditions to better characterize these effects when finalizing the study design. 
Statistical Analysis: Prior to fitting models, exploratory data analysis, including numerical and 
graphical summaries, will be conducted to examine distributions and check for outliers. In addition, plots 
will allow visual assessment of relationships between predictors and outcome. The fitted models also will 
be assessed by graphical and numerical means. Residuals will be examined for conformance to model 
assumptions. It is possible that transformation of some of the response variables may be necessary. 
Additionally, we will provide appropriate corrections for any sets of multiple comparisons during post-hoc 
analyses (e.g., Bonferroni-Holm) as required. We will work with our statistician, Dr. Elizabeth Newton, to 
design the study to get as much useful data out of a relatively small number of subjects as possible. 
 
REFERENCES (Those used in this “protocol” and as numbered from the original grant application.) 
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[23] Atkins D. Prosthetic training. In: Smith DG, Michael JW, editors. Atlas of amputations and limb 
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