Auto Control of Volume Management for Limb Loss
Phase: NA
Conditions: Lower Limb Amputation Below Knee (Injury)
Sponsor: University of Washington

Auto Control of Volume Management for Limb Loss 
NCT03550118 
Date: 4/27/2023 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

Study Protocol 
The objective of this research is to develop and test an automatically-adjusting prosthetic socket system 
for prosthesis users. The system integrates with a range of adjustable socket technologies, including those 
that are commercially available. The system we will develop allows small size adjustments for both 
tightening and loosening the socket. Adjustable panels may be attached to the prosthetic liner using a 
mechanical method such as Velcro, adhesive, or a thin strap or clasp to allow the liner to be pulled out 
with the panels when the socket is loosened. The user does not need to remove the prosthesis or bend 
down to make adjustments. The system will later be enhanced to automatically change the fit of an 
adjustable socket without distracting the user. It helps to maintain consistent limb fluid volume when the 
service member or Veteran is actively using the prosthesis. It does this using information from sensors 
within the socket and small motors that control adjustable panels in the socket wall.  
The developed technology will apply two concepts learned from our recent researched funded by the 
DOD. One concept is to slowly enlarge the socket the right amount during dynamic activity. The other 
concept is to loosen the socket during resting to allow healthy fluid return to the limb.  
A multi-aim, longitudinal study will be carried out to test this new prosthetic technology. All aims of the 
study will involve similar procedures meant to investigate the use of our adjustable socket (the interface 
between the prosthesis and residual limb), with iterative improvements made in each aim.  
SPECIFIC AIMS: 
Aim 2: Assess the performance of an adjustable socket in our laboratory. 
Aim 3: Assess how prosthetic users use a wireless, adjustable socket to manage change in limb volume. 
Aim 4: Assess the performance of an automatic, adjustable socket in our laboratory. 
Aim 6A: Assess the performance of an adjustable socket in our laboratory that is able to quickly enlarge 
and quickly return to normal size to enable full or partial doffing while seated. 
Aim 6B: Assess how prosthetic users respond to an adjustable socket that is able to quickly enlarge and 
quickly return to normal size automatically to enable full or partial doffing while seated. 
Aim 8: Assess how prosthetic users respond to an adjustable socket, which is attached to their liner, that is 
able to enlarge while seated and return to normal size before ambulation. 
Aim 9: Assess how prosthetic users respond to an adjustable socket, which is attached to their liner, that is 
able to quickly enlarge and quickly return to normal size automatically during ambulation. 
Aim 10: Involves in-field testing of the adjustable prosthetic system developed in the prior aims. Subjects 
will use the test socket in 3 different configurations throughout the course of this study: (A) automatic 
control mode, (B) manual control mode, and (C) adjustment disabled mode. (A) In the automatic control 
mode, sensors that are built into the socket will be used to monitor the movement and position of the limb 
within the socket and use this information to automatically adjust the socket panels in an effort to improve 
the fit. Adjustments may occur while they are sitting, standing, and walking. The system will be 
integrated into an app on a smartphone. We will provide the phone. (B) In the manual control mode 
subjects will be able to make adjustments to the panels using the smartphone app. Changes will not be 
made automatically. (C) In the disabled mode, the ability to adjust panels will be turned off. 

A description of the study procedures that will be used is given here; the attached table outlines what 
specific procedures will be done at the study visits for each aim: 
 
 
Aim 2, Aim 8, 
Aim 9 
Aim 3 
Aim 4 
Aim 6A 
Aim 6B 
Visit 1—may 
not be needed 
if the 
participant has 
already had a 
socket made 
and has 
answered 
health 
questions 
3 hours 
-Walk on 
treadmill 
-Questions 
related to 
prosthesis and 
limb health 
-Scan socket to 
make an 
adjustable test 
socket 
-vascular tests 
3 hours 
-Walk on 
treadmill 
-Questions 
related to 
prosthesis and 
limb health 
-Scan socket to 
make an 
adjustable test 
socket 
-vascular tests 
3 hours 
-Walk on 
treadmill 
-Questions 
related to 
prosthesis and 
limb health 
-Scan socket to 
make an 
adjustable test 
socket 
-vascular tests 
2 hours 
-Questions 
related to 
prosthesis and 
limb health 
-Scan socket to 
make an 
adjustable test 
socket 
-vascular tests 
 
2 hours 
-Questions 
related to 
prosthesis and 
limb health 
-Scan socket to 
make an 
adjustable test 
socket 
-vascular tests 
Visit 2—
approximately 
4 weeks after 
visit 1, when 
their adjustable 
test socket is 
ready 
3 hours 
-May place 
electrodes on 
skin of residual 
limb 
-Test socket fit 
-May place 
sensors onto 
socket and/or 
liner to measure 
activity and limb 
movements in 
the socket.  
-Stand then walk 
on treadmill at 
varying speeds 
while adjustable 
socket is 
controlled by 
researchers to 
reduce limb 
movement 
within the socket 
5 hours 
-May place 
electrodes on 
skin of residual 
limb 
-Test socket fit 
-May place 
sensors onto 
socket and/or 
liner to measure 
activity and 
limb 
movements in 
the socket 
-May wear 
heart rate 
monitoring 
watch 
-Teach 
participant how 
to use the 
controller to 
adjust the 
socket, practice 
in the lab and 
then around the 
building; once 
comfortable 
leave the lab for 
up to 4 hours 
wearing the 
socket and 
conduct normal 
activities or 
follow a more 
structured 
protocol. 
3 hours 
-May place 
electrodes on 
skin of residual 
limb 
-Test socket fit 
-May place 
sensors onto 
socket and/or 
liner to measure 
activity and 
limb 
movements in 
the socket.  
-May wear 
heart rate 
monitoring 
watch 
-Stand then 
walk on 
treadmill at 
varying speeds 
while adjustable 
socket is 
controlled 
automatically to 
reduce limb 
movement 
within the 
socket 
4 hours 
-May place 
electrodes on 
skin of residual 
limb 
-Test socket fit 
-May place 
sensors onto 
socket and/or 
liner to measure 
activity and limb 
movements in 
the socket.  
-Perform series 
of sit-to-stand 
and stand-to-sit 
transitions, with 
periods of 
walking or 
resting in 
between. 
Researchers will 
make the socket 
release to 
become larger 
when seated and 
recover back to 
normal size 
when preparing 
to stand 
7 hours 
-May place 
electrodes on 
skin of residual 
limb 
-Test socket fit 
-May place 
sensors onto 
socket and/or 
liner to measure 
activity and limb 
movements in 
the socket.  
-Teach 
participant how 
to use the 
adjustable socket 
with release 
mechanism; they 
will practice in 
the lab and 
around the 
building while 
being monitored 
by a staff 
member. Once 
comfortable they 
will leave the lab 
for 3-4 hours 
wearing the 
socket and 
conduct normal 
activities 

 
Aim 10 
Lab Visit 1—may not be needed if the participant has 
already had a socket made and has answered health 
questions  
Up to 2 hours  
-Walk on treadmill  
-Questions related to prosthesis and limb health  
-Scan socket to make an adjustable test socket  
-vascular tests  
Lab Visit 2—up to 3 weeks after visit 1, when their 
adjustable test socket is ready  
3 hours  
-Test socket fit  
-May place sensors onto socket and/or liner to measure 
activity and limb movements in the socket  
-Teach participant how to use the adjustable socket in 
the 3 different modes that will be tested. Once they are 
comfortable, they will leave the lab for 4-7 days with 
socket in the first mode to be tested.  
Research engineer visits (2) –at the end of each of the 
first two socket test modes  
1-2 hours each.  
-Questionnaire and dialog regarding socket test mode 
that was just completed  
-Socket will be changed over to next test mode  
-Refresh participant training on how to use the new test 
mode  
-Once comfortable in new test mode, subject will 
continue using the mode for next 4-7 days.  
Lab Visit 3—at the end of the 3rd socket test mode  
1-3 hours  
-Questionnaire and dialog regarding socket test mode 
that was just completed AND all socket modes tested 
in the study  
-Original socket will be returned to initial state and all 
study instruments will be retained by the lab  
 
Primary quantitative data will be collected via custom study instruments, such as a bioimpedance 
measurement system to assess limb volume changes and inductive sensors built into the test socket wall 
to measure limb movement/distance. Qualitative data will be collected from participants directly through 
self-report of their health history, during study procedures. All data for this research will be collected 
prospectively. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

Statistical Analysis Plan:  
Aim 2, Aim 6A, Aim 6B, and Aim 8  
The primary outcome measure of change in limb volume was taken at times of socket enlargement and 
socket reduction. A Shapiro-Wilk test will be used to determine normalcy. Normally distributed data will 
be compared using paired t-tests. If data is not normally distributed, a Wilcoxon Signed Rank Test will be 
used to make comparisons. A significance level of 0.05 will be used to determine whether measured 
differences in limb volume were statistically significant between interventions.  
 
Aim 3  
The primary outcome measure of change in limb movement was taken at times of socket enlargement and 
socket reduction. A Shapiro-Wilk test will be used to determine normalcy. Normally distributed data will 
be compared using paired t-tests. If data is not normally distributed, a Wilcoxon Signed Rank Test will be 
used to make comparisons. A significance level of 0.05 will be used to determine whether measured 
differences in limb movement were statistically significant between socket enlargement and socket 
reduction.  
 
Aim 4  
The primary outcome, integral of absolute error, was measured as participants walked with the adjustable 
socket’s controller maintaining a set socket volume (set point). A Shapiro-Wilk test will be used to 
determine normalcy. Normally distributed data will be compared using paired t-tests. If data is not 
normally distributed, a Wilcoxon Signed Rank Test will be used to make comparisons. A significance 
level of 0.05 will be used to determine whether differences were statistically significant between 
interventions.  
 
Aim 9  
The primary outcome measure of participants who experienced increase in limb fluid volume was 
assessed after a structured protocol involving socket enlargements and socket reductions. A Shapiro-Wilk 
test will be used to determine normalcy. Normally distributed data will be compared using paired t-tests. 
If data is not normally distributed, a Wilcoxon Signed Rank Test will be used to make comparisons. A 
significance level of 0.05 will be used to determine whether differences were statistically significant 
between interventions.  
 
Aim 10  
The secondary outcome measure of adjustable socket mode preference was taken after testing the socket 
in all test modes. A Shapiro-Wilk test will be used to determine normalcy. Normally distributed will be 
compared using paired t-tests. If data is not normally distributed, a Wilcoxon Signed Rank test will be 
used to make comparisons. A significance level of 0.05 will be used to determine whether socket 
preference was statistically significant following testing the socket in all modes.