Portable Bioimpedance Monitoring: Testing a New Diagnostic Interface
Phase: NA
Conditions: Transtibial Amputee
Sponsor: University of Washington

Bioimpedance as a Diagnostic Tool for Assessing the Need for Socket Modification in Transtibial Amputees 
NCT #: NCT03164356 
Date: 4/27/2023 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

Study Protocol 
The purpose of the proposed study is to conduct a study on individuals with lower limb amputation evaluating if residual limb fluid volume data 
collected using a novel non-invasive device is beneficial towards prosthetic prescription, fit, and comfort as determined by amputee test subjects 
and practitioners (prosthetists). Residual limb volume/mass changes typically affect prosthetic limb fit of people with limb amputation, and 
changes in limb volume/mass can put the limb at risk of injury and preclude use of the prosthesis. 
Participants’ residual limb fluid volume will be monitored through segmental bioimpedance analysis both before and after a practitioner-issued 
modification to the prosthesis as an observational cohort study and a blinded randomized clinical trial in which the data may or may not be shared 
with the practitioner before the modification is made to the prosthesis. 
The Specific Aims are to:  
Aim 1. Characterize residual limb volume accommodation strategies and associated clinical outcomes experienced by prosthetic users with 
different activity/volume profiles. Changes in users' limb volume, prosthetic fit, performance, and satisfaction will be used to determine which 
strategies are most predictive of positive clinical outcomes. This aim will be accomplished using an Observational Cohort Study. 
Aim 2. Compare the effectiveness of bioimpedance-enhanced and traditional prosthetic evaluation, design, and fitting practices for lower limb 
participants who require adjustment or replacement of their volume management system. Differences in participants’ limb volume, prosthetic fit, 
performance, and satisfaction will be used to assess if bioimpedance-enhanced fitting produces superior outcomes compared to traditional, 
experience-based fitting methods. This aim will be accomplished by using a Randomized Controlled Trial (RCT). 
Primary quantitative data will be collected via custom study instruments, such as a bioimpedance measurement system to assess limb volume 
changes. 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. 
A more detailed timeline of the study procedures is given on the following pages. 
 
 
 
 
 
 

 
 
 
 
Pre-Mod 
Session
Post-Mod 
Session
Follow-up 
Session
AG Monitoring
Locals Only
4-12 weeks
6 months
2 wks
2 wks
2 wks
1
2
3
4
AG Researcher
Dead Battery
~8 weeks
Attach ankle and 
thigh AG, provide 
sock log
Transfer ankle AG
Switch to post-mod liner + AG
(if receiving new liner)
Remove ankle AG and study liner
Mail/Bring devices to UW
1
2
3
Document socket shape (if changed)
Attach ankle/thigh AG (study liner)
Bioimpedance protocol
Provide sock log
Document socket shape
Attach ankle/thigh AG
Bioimpedance protocol
Send post-mod liner + AG
Provide sock log
UW Researcher
Document socket shape
Charge ankle/thigh AG
Bioimpedance protocol
Retrieve pre-mod liner + AG
Send AG shipping materials
Provide sock log
1
Informed consent,
activity monitor 
attachment
Remove ankle AG and study liner
Mail/Bring devices to UW
Patient Subject
2
4
6
Background information, 
limb volume 
measurement, surveys, 
activity monitor, 
complete sock log
5
Modification
7
Aim 1
Subject
Researcher
3
Activity 
monitor 
transfer
Limb volume 
measurement, surveys, 
activity monitor, 
complete sock log
Update background 
information, limb 
volume measurement, 
surveys, activity 
monitor
Activity monitor 
removal, complete 
sock log
Activity monitor 
removal, complete 
sock log

 
 
 
 
 
 

 
Statistical Analysis Plan 
Aim 1 
Aim 1 is an exploratory study with the objective of generating potential volume management strategies based on the measurement of limb fluid 
volume fluctuations via bioimpedance. As such, it does not involve statistical hypothesis testing per se, and therefore, no power analysis is 
involved. The primary outcome measure of socket comfort score (SCS), pre and post socket modification will be analyzed. 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 2 
Data collected at each assessment (i.e., pre-implementation, 1-month follow-up, and 6-month follow-up) in Aim 2 will be visually analyzed using 
histograms and boxplots. Next, we will test data for normality using a Shapiro-Wilk test. If the data is found to be normally distributed, our 
hypothesis will be evaluated using clinical outcome measure scores (e.g., SCS) in a repeated-measures analysis of variance (rmANOVA) to assess 
differences in outcomes achieved by participants assigned to the treatment (i.e., bioimpedance-enhanced fitting) group vs. control (i.e., traditional 
fitting) group over time. In the event that data are not normally distributed, we will use a nonparametric Friedman test to assess differences in 
outcomes between bioimpedance-enhance and traditional fitting. Significance for statistical tests will be set at  < 0.05. Our hypothesis will be 
evaluated using outcome variables of number of visits and total visit time. We will compare the total number of visits and total time over the 6-
month period between the treatment and control groups using a t-test for independent samples.