A Comparative Assessment of Conventional and Adjustable Transfemoral Prosthetic Sockets
Phase: NA
Conditions: Amputation, Amputation; Traumatic, Leg, Lower
Sponsor: University of Michigan

 
A Comparative Assessment of Transfemoral Prosthetic Sockets 
 
Identifiers: 
NCT04038580    
Unique Protocol ID: HUM00140733 
Document Date: 10/7/2021 
 

HUM00140733 
Title: A comparative assessment of conventional and adjustable transfemoral prosthetic sockets 
Principal Investigator: Deanna Gates, Ph.D. 
 
BACKGROUND:  
Within the next three decades, well over one million Americans are expected to be living with an 
amputation of the lower limb (Ziegler-Graham et al. 2008) yet many will not wear them due to 
discomfort. Nearly 40% of individuals with lower limb amputation report that their biggest 
concern when receiving a prosthesis is comfort and fit (Seaman 2010), and, in a study of 78 
traumatic-amputees, 57% reported dissatisfaction with prosthetic comfort (Dillingham et al. 2001). 
Discomfort is one of the leading factors limiting prosthetic use and the amount of time spent in 
weight-bearing activity (Ali et al., 2012), in turn limiting physical activity. Inactivity resulting 
from prosthetic disuse may potentially contribute to reductions in residual limb muscle mass and 
strength (Sherk et al. 2010) and, inactivity is a well-recognized pathway to increased morbidity 
and mortality. Thus, for individuals with lower limb amputation, prosthetic comfort is vital to the 
maintenance of a healthy life style. The primary cause of this discomfort is the prosthetic socket - 
the portion of the prosthesis that fits snugly over the residual limb. Indeed, a 2001 clinical review 
on current and future developments in the field stated that: “The single most critical aspect of any 
prosthesis is the quality of the interface between the limb …and… prosthesis. The …socket 
determines the amputee's comfort and ability to control the artificial limb” (Marks and Michael 
2001). 
Even in a well-suspended, well-fitting socket, diurnal fluctuations in the volume of the residual 
limb can limit the extent to which prosthesis users are able to maintain fit throughout the day. 
During an average work day, the residual limb may lose between 6-7% of its volume (Board et al. 
2001) due to fluid imbalance during loading and unloading.  To accommodate for changes in limb 
volume throughout the day, prosthesis users are instructed to add or remove prosthetic socks for a 
traditional socket (Fig 1D) or to adjust the size of the socket using an adjustable socket system.  
There are several adjustable socket systems that have recently come on the market, including the 
The Quatro Socket (Quorum Prosthetics, Windsor, CO, USA), Infinite Socket (LIM Innovations, 
San Francisco, CA, USA), and CJ Socket (CJ Sockets Technologies, Beverly, MA, USA).   
The patented Quatro Socket design (Joseph Johnson, Quorum Prosthetics, Windsor, CO) has 4 
opposing zones of compression based on the patented HiFi interface (Randall Alley, biodesigns, 
inc., Westlake Village, CA). The original design has three independently adjustable zones (2 
longitudinal compression, 1 circumferential brim) which allow for macro and micro adjustments 
throughout the users day. These adjustments can improve the ease and time to don and doff the 
prosthesis, account for volume fluctuations from -5% to 11%, and change the amount of 
compression that the user feels most comfortable in. The wearer can quickly loosen, tighten and 
modify the compression by simply adjusting one of the three Boa dials located on the socket. 
  
The LIM Infinite socket (Fig. 1B) consists of a heat moldable textile brim, carbon fiber struts, 
flexible plastic inner cup, a lanyard suspension unit, and anodised alignment base plate.   The CJ 
socket system (Fig 1C) consists of a rigid J-shaped frame, a non-elastic garment referred to as the 
‘sail’ and an adjustable closure.  While implemented differently, each allow the user to adjust the 

fit of the socket manually while it is donned.  Each socket system claims to improve socket comfort 
and fit and some also claim to improve mobility and walking endurance.  However, as they are so 
new to the market, there is no objective outcomes research to support these claims.  
 
 
Figure 1. New prosthetic socket options. A) Quorum Prosthetics ’ “The Quatro” (opquorum.com/) B) LiM’s 
“Infinite Socket” (liminnovations.com), C) CJ Socket Technologies’ “CJ Socket” (image from 
www.pvopinc.com/products_services/). 
D) 
Conventional, 
laminated 
socket 
(image 
from 
www.blatchford.co.uk/endolite/one-shot-socket/) 
A search of company websites and scientific databases (e.g. Pubmed and GoogleScholar) revealed 
only patents for device design and two published case studies on the LIM Infinite Socket.  Mitton 
et al. (2017) found that an LiM Infinite socket enabled a 38-year old female with transfemoral 
amputation and large residual limb volume fluctuations to wear a prosthesis for at least 8 hours a 
day.  Previously, she had only been able to wear the prosthesis for up to an hour and was otherwise 
wheelchair bound.  The patient’s socket comfort score improved from a 4 in a conventional 
laminated socket to an 8 (of 10) and her Special Interest Group in Amputee Medicine (SIGAM) 
mobility score (Ryall et al. 2003) rose from grade C to E with the new dynamic socket fit (Mitton 
et al. 2017).  In a second case study, a 24-year old male with transfemoral amputation wore an 
Infinite Socket and an ischial ramus containment (IRC) laminated socket with his standard 
prosthetic componentry. The patient had a 37% improvement in socket comfort score with the 
adjustable socket.  He also improved on timed tests of functional mobility (L-Test improved 21%, 
Four Square Step Test improved 19%) but his 2 minute walk test did not differ between conditions 
(Kahle et al. 2016). Additionally, the researchers simulated volume loss by removing his five-ply 
sock from the residual limb, resulting in a 2-cm circumferential volume reduction. Under this 
condition, his socket comfort score improved 93%, the L-test improved 22%, the four-square step 
test improved 25% and the 2 minute walk test improved 25% with the Infinite socket compared to 
conventional (Kahle et al. 2016).   
While the results of these case studies are promising, there is a critical need to better understand 
patient outcomes with adjustable prosthetic sockets through larger clinical trials.  In fact, there is 
an overall scarcity of literature regarding the impact of the different interfaces on movement in 
people with lower limb amputation. A recent literature review found only four clinical trials and 
two systematic reviews on prosthetic interface and suspension systems (Highsmith et al. 2016).  
Collectively, they found that the use of gel liners compared with specific weight-bearing sockets 
improved load distribution (Baars and Geertzen 2005, Klute et al. 2010), comfort (Baars and 
Geertzen 2005, Klute et al. 2010), and ambulatory independence (Baars and Geertzen). 

Additionally, use of a vacuum-assisted suspension system (VASS) relative to total surface bearing 
suspension reduced pistoning (Klute et al. 2011) and time to prosthetic fitting (Traballesi et al. 
2012), but also reduced step activity (Klute et al. 2011).    
 
 
OBJECTIVE AND SPECIFIC AIMS: 
The objective of the proposed work is to enhance understanding of the potential benefits of 
adjustable sockets and inform clinical decision making.  We will explore a range of outcomes that 
have been found to be important for prostheses users and specifically assess the claims made by 
device manufacturers. Thirty adults with a transfemoral amputation will participate in four test 
sessions; one with their clinically prescribed socket, and three with different test sockets. 
Participants with prescribed laminated sockets will be fitted for three different adjustable sockets. 
Participants with a prescribed adjustable socket will be fitted with two different adjustable sockets 
and one laminated socket. We will test the following aims: 
Aim 1: Compare socket comfort and prosthetic satisfaction between prosthetic sockets. 
Participants will complete three self-report surveys to assess comfort and condition-specific 
quality of life with each socket tested. Additionally, participants will complete several activities in 
the lab including sitting, standing, and walking. After each task, we will ask the user to rate their 
socket comfort and pain in their residual limb. Based on published case studies, we hypothesize: 
H1: Participants will report greater satisfaction and comfort when using adjustable sockets 
compared to conventional, laminated sockets.   
Aim 2: Determine the impact of prosthetic socket on patient mobility and confidence. 
Mobility will be assessed using several tests that are easy to perform in a clinic: 10-m walk test, 
timed-up-and-go (TUG), the L-Test, narrow beam-walking, and five times sit-to-stand (FTSTS) 
(described in Research Strategy).  We will also ask participants about their confidence performing 
different activities in the home using the Activities specific balance confidence (ABC) scale, and 
their self-reported mobility using the Plus-M and mobility sub-section of the Prosthetic Evaluation 
Questionnaire (PEQ).  Based on published case studies, we propose the following hypotheses: 
H2a: Mobility, as measured by the 10-m walk test, TUG, L-Test and FTSTS, will be improved 
when wearing adjustable sockets compared to conventional, laminated sockets. 
H2b: Participants will self-report greater mobility on the PLUS-M and mobility subscale of the 
PEQ and greater confidence when wearing adjustable sockets compared to laminated sockets. 
Aim 3: Determine if prosthetic socket design influences prosthetic use in the home.  Each 
adjustable sockets should enable the user to tighten manually to maintain fit while donned. In 
contrast, with a conventional, non-adjustable socket, users would need to remove the prosthesis to 
add or remove socks.  Here we will monitor how many times the participants don and doff the 
prosthesis during the day while using each socket using a sensor in the socket. We will also 
measure how long it takes to don and doff the prosthesis (in the lab) to quantify the time devoted 
to this process.  Finally, we will monitor the participants’ step activities during the last week of 
accommodation to determine it the socket design influences what they actually do in daily life.  
We will test the hypothesis: 

H1a: The number of times donned and doffed will be fewer and overall wear time will increase 
for all adjustable sockets compared to conventional, laminated sockets.  
H1b: The time to don and doff the prosthesis will be less for adjustable sockets versus conventional 
per device manufacturer claims.  
H1c: Participants will be more active in daily life when wearing an adjustable socket.  
Aim 4: Determine individual characteristics that are associated with benefits of specific 
socket designs.  If adjustable sockets are successful in improving comfort and performance, our 
secondary goal will be to identify which patients are the best candidate for which specific socket 
system. Therefore, we will also collect basic demographic information including residual limb 
length, age, BMI, K-level, time since amputation, and prosthesis type.  We will determine if any 
of these demographic characteristics or personal factors (taken from the PEQ) are associated with 
whether the participant benefited from a specific device (over standard-of-care).   
RESEARCH STRATEGY: 
Thirty (30) adults with transfemoral amputation will be recruited over two sites. Participants will 
be recruited from personal interaction with the clinical collaborators involved in this study, 
including Tony Gutierrez, C.P.O. (Bionic Prosthetics and Orthotics) and Bharathi Swaminathan, 
M.D. (Captain James A. Lovell Federal Health Care Center) in Chicago, Illinois and Jeffrey 
Wensman, C.P.O. (UM Orthotics and Prosthetics Center), Brian Kelly, D.O. (Dept. of Physical 
Medicine and Rehabilitation, Michigan Medicine), and Lisa DiPonio, M.D. (Ann Arbor VA 
Medical Center) in Ann Arbor, Michigan.  
 
Potential participants will be screened to ensure that they meet the following inclusion criteria: 
• Unilateral lower-limb amputation 
• Two months of independent ambulation with a prosthesis 
• Minimum functional level of K2 on the Medicare Functional Classification Level 
(MFCL): corresponding to “the ability or potential for ambulation with the ability to 
traverse low-level environmental barriers such as curbs, stairs, or uneven surfaces. 
Typical of the limited community ambulator”  
 
Potential participants will be excluded if they meet any of the following exclusion criteria:  
• Pathology or injury of the intact limb that significantly affects walking 
• Medication that affects their ability to walk 
• Neurologic disease that affects ability to walk  
• Significant and/or recent cardiovascular history 
• Significant vision problems     
• Suffer from an impaired mental capacity that negatively impacts verbal communication 
with the clinicians and research team, or requires a Legally Authorized Representative to 
facilitate communication 
 
Potential participants will be screened via phone call prior to enrollment using an IRB approved 
health history questionnaire developed at the University of Michigan and used in several on-going 
studies.  
 

STUDY DESIGN:   
We propose a randomized crossover study of four prosthetic sockets.  Patients will come 
to the lab for four separate testing visits (Fig. 5), one in each of four sockets.  First they will come 
to the clinic where they will be consented and screened to ensure eligibility in the study.  At this 
interview, participants will be enrolled if the prosthetist and/or physician can medically justify the 
prescription of at least two of the types of sockets used in the study.  The three adjustable sockets 
to be tested are the The Quatro™, Infinite Socket™, and CJ SocketTM.  Participants will complete 
all testing first in their currently prescribed socket and then in each of the three adjustable sockets 
(or two adjustable sockets and one laminated socket depending on participant’s currently 
prescribed socket).  The order of testing will be randomized by a computer and a staff member not 
involved in this study will place the order in sealed envelopes with the subject number on the 
outside of the envelope. This envelope will be opened by the prosthetist once the participant 
enrolls.   
 
 
Figure 5. Example flow diagram illustrating the study design. Participants will complete the same 
clinical tests (Outcomes) in each of four prosthetic sockets (prescribed + 3 experimental). 
 
Participants’ level of amputation, cause of amputation, prosthetic history and functional 
level (i.e., Medicare Functional Classification Level (MFCL) or K-Level) will be obtained from 

medical records. Sociodemographic characteristics (e.g. sex, race, ethnicity, veteran status), will 
be obtained via a self-report.  The presence of comorbidities will be assessed using the Charlson 
Comorbity Index (Charlson et al. 1994).  Additionally, while we will not control for it, prosthetists 
will document participants’ prosthetic ankle and knee types and all components used.  We will 
also document whether the individual is in physical therapy.  Individuals may also utilize different 
types of suspension.  Based on a review of medical records, we expect that this will be 
predominantly elevated vacuum suspension in Illinois and predominantly lanyard suspension at 
the University of Michigan.  We chose not to standardize prosthetic componentry as it takes time 
to accommodate to each change made to the prosthetic system.  Therefore, the only variable that 
will change within each participant will be their socket and the results therefore, indicate this effect 
of this change alone.  This choice also enables us to determine if any specific componentry is 
related with patient outcomes (Aim 4). 
Participants will be fitted with an adjustable socket by Jeffrey Wensman, C.P.O. 
(Michigan) or Tony Gutierrez, C.P. (Illinois), who are certified by the American Board for 
Certification in Orthotics, Prosthetics and Pedorthics, and will be trained in each fitting process by 
the socket manufacturer. Manufacturers’ representatives will be consulted as needed to ensure that 
each patient fitting meets the design specifications for each design.  Representatives will not be 
allowed to meet independently with any subjects or allowed to question them about their socket 
design, except as needed to aid in the fitting of the socket. 
The participant will be given one week to accommodate and make adjustments and then 
four weeks of accommodation once the patient and prosthetist agree that the patient is comfortable 
and stable.  If stable, comfortable gait is not achieved after 3 weeks, the socket will be removed 
and the patient will be excluded from that condition.  This adverse event will be reported in all 
publications arising from this work.   
Surveys will be given in the third week of accommodation to reduce potential bias for the 
end of conditions when participants anticipate a change to a different socket (Coleman et al. 2004).  
At that time, participants will be given a device to measure how many times the socket is donned 
and doffed (see description below) and an activity monitor (ActiGraph Link, Pensacola, FL) to 
monitor activity during the last week of wear.  This session will be conducted by the Clinical 
Coordinator, who will be blind to the condition the participant is assigned to. Participants will then 
come to the clinic (Chicago or Ann Arbor) where they will perform a series of clinical assessments 
(described below).  After each new socket, the participant will return to their initial socket for a 
one-week ‘wash-out’ before trying the subsequent socket.  At the end of testing, participants will 
be able to keep whatever socket they choose, and this choice will be documented. 
 
 
OUTCOME MEASURES:  
Comfort:  Participants will report their comfort with each socket using The Socket Fit Comfort 
Score (SCS).  This is a single question in which subjects are asked: “On a scale from 0-10, if 0 
represents the most uncomfortable socket fit you can imagine and 10 represents the most 
comfortable socket fit, how would you score the comfort of the socket fit of your artificial limb at 
the moment?” (Hanspal et al. 2003).   This question will be asked in the third week of 
accommodation.  Additionally, during the lab visit, participants will be asked their SCS after brief 

periods (2 minutes) of standing, sitting, and walking. Participants will also report comfort using 
the Comprehensive Lower Limb Amputee Socket Survey (CLASS) in which subjects are asked 
questions utilizing a likert scale. The questionnaire is divided into 4 sections including Stability, 
Suspension, Comfort, and Appearance (Gailey, et al., 2019). 
Satisfaction & Quality of Life: Surveys will be administered after each thee week home use period 
when the participants return the monitoring devices. Condition-specific quality of life will be 
measured with the Prosthetic Evaluation Questionnaire (PEQ) (Legro et al. 1998).  The PEQ 
consists of 82 questions that describe the function of a lower-limb prosthesis and assess prosthesis-
related quality of life. The questionnaire is divided into ten functional scales, addressing four major 
domains: prosthetic function, mobility, psychosocial experience, and well-being. Finally, 
participants will complete Prosthetic Socket Preference Questionnaire after each socket which asks 
which device they prefer on a 100 mm visual analog scale from their prescribed laminated socket 
to the test socket (Ferris et al. 2012). A score of 0 would be 100% preference for their prescribed 
socket while 100 mm represents 100% preference for the socket tested in that condition. 
Confidence: Confidence performing different activities in the home will be assessed using the 
Activities specific balance confidence (ABC) scale (Powell and Myers 1995).  The ABC scale is 
a 16-item self-reported measure scored on a rating scale from 0 to 100, with higher scores indicate 
greater balance confidence.  An average score is calculated by adding all item scores and dividing 
by the total number of items.  The ABC scale has demonstrate high internal consistency, good test-
retest validity, and good construct validity in people with lower limb amputation (Miller et al. 
2003).  It can be administered in 10 to 20 min.    
  
  
Figure 6. Top) Illustration of the L-Test from (Kim et al. 2015), Bottom) Illustration of the LEGSys 
system for assessing gait 
Mobility: Participants will complete several standard clinical tests designed to measure mobility.  
The 10-m walk test measures elapsed time over 10 m from a standing start (Datta et al. 1996).  
This measure uses customary walking speed as a measure of walking ability/capacity and has 
shown content and metric reliability and validity (Deathe et al. 2009). The timed-up-and-go (TUG) 
assesses several aspects of mobility including getting out of a chair, walking 3 m, turning, and 
sitting down (Schoppen et al. 1999).  The outcome is the time from buttocks off the chair to 
buttocks down.  The L-test (Deathe and Miller 2005) is a modified version of the TUG which 
incorporates two transfers and four turns of which at least one would be to the opposite side (Fig 
6). We will complete both tasks as the TUG has ceiling effects in fit individuals and the L-Test 
can be too difficult for some amputees (Deathe and Miller 2005). For the narrow-beam walking 
test, the participant will attempt to walk the length of a narrowing beam five times. The beam is 
7.32 m in length and 1.5 inches in height with four segments of varying widths (wide = 18.6 cm, 
intermediate = 8.6 cm, narrow = 4.0 cm, and very narrow = 2.0 cm). The mean distance walked 
across each trial, relative to overall beam length, is recorded for the outcome (Sawers and Hafner, 
2018).Finally, participants will complete a five-times-sit-to-stand (FTSTS) test, which is measure 
of functional mobility, lower limb strength, and dynamic balance (Whitney et al. 2005, Goldberg 
et al. 2012).  During each of these tasks, participant will wear a portable device consisting of five 

sensors that analyzes gait (LEGSys+, Biosensics, Watertown, MA). This system measures 
temporal-spatial parameters such as stride length, time, cadence, and velocity.  It also measures 
knee and hip angles and motion of the pelvis (Fig. 3).  This system is already available in the 
amputee clinics in both Michigan and Illinois.   
We will also ask participants about their self-reported mobility using the mobility sub-scale of the 
PEQ (described above) and the Prosthetic Limb Users Survey of Mobility (PLUMS-M) (Hafner 
et al. 2017).   The full PLUS-M survey has 44 items and there are two short-forms (12 and 7 items 
each).  Here we will use the 12-item short form as it has shown excellent agreement with the 44-
item score and good construct validity (Hafner et al. 2017). Additionally, normative data for 1019 
people with lower limb amputation is available at (http://www.plus-m.org) to aid in interpretation 
of the findings.    
Activity in Daily Life: Our study will employ accelerometers to objectively measure physical 
activity levels and step count, as has been done previously in subjects with prostheses (Chou et al. 
2009, Albert et al. 2013).  Specifically, an ActiGraph Link accelerometer (ActiGraph, Pensacola, 
FL, USA) will be secured to the participant’s prosthesis during the last week of accommodation. 
The ActiGraph Link is a waterproof device that measures 3.5 x 3.5 x 1 cm and weighs 14 grams. 
The sampling frequency will be set to 80 Hz, which will allow for 10 days of raw data collection 
without need to charge the batter (See Preliminary Study 3). The average acceleration per day and 
the average acceleration during the participant’s most active 5 hours per day will be calculated in 
R using the GGIR package, an open source R-package for analysis of raw accelerometer data 
(http://cran.r-project.org/web/packages/GGIR/GGIR.pdf). The GGIR program 1) detects and 
corrects for: calibration error using local gravity as a reference (van Hees et al. 2014); unusually 
high sustained values (an indication of device malfunction); and non-wear and 2) calculates 
activity-related acceleration using all three axes (i.e., √(x^2+ y^2+ z^2  )-1g). Step counts will be 
determined using the ActiLife Software package, ActiGraph’s data analysis and management 
software program.  
 
Ease and number of times donned and doffed: Based on a prior case report (Mitton et al. 2017), 
we expect that total wear time will increase for adjustable sockets. To test this, we will monitor 
how many times the participants don and doff the prosthesis during the day using a TCRT5000 
Reflective Optical Sensor in the base of the socket. This device will be connected to a small data 
logger (Arduino Nano: 7.62x1.27x3.05cm) which will be attached to the socket.  The Nano will 
record the time when it detects a sharp change in proximity corresponding with the donning or 
doffing of the prosthetic.  On a 10,000 mAh battery we expect this system to maintain functionality 
for 233 hours.  This data will be collected continuously during the last week of the accommodation 
period.   
 
STATISTICAL PLAN AND DATA ANALYSIS: 
We will recruit 30 people with unilateral transfemoral amputation (TFA). Half of the participants 
will be recruited at University of Michigan and the other half will be recruited at Rosalind Franklin 
University.  We anticipate about a third of our participants will not complete all aspects of the 

study based on a prior literature review (Highsmith et al. 2016).  Sample size estimates are 
described by Aim. All power calculations were performed in G*Power Version 3.0 (Universitat 
Keil, Germany).  With the given sample we should be sufficiently powered to detect differences 
across all four Aims.  In some cases, this means we are overpowered for a particular comparison, 
but all participants need to complete earlier aims to be included in Aim 4, requiring the largest 
sample size.   
Aim 1: Compare socket comfort and prosthetic satisfaction between prosthetic sockets. To test the 
hypothesis that  
H1: Participants will report greater satisfaction and comfort when using adjustable sockets 
compared to conventional, laminated sockets.   
We will compare PEQ scores, socket comfort scores, patient preference, and quality of life 
measues between conventional and adjustable prosthetic sockets using a linear mixed model with 
subjects as a random variable, and socket type (conventional, CJ Socket, Infinite Socket, Quatro) 
as repeated, fixed factor.  Significant effects of socket type will be explored using post-hoc testing 
with LSD corrections. The minimal detectable change (MDC) will be used to assess the clinical 
significance of this difference. The MDC for subscales of the PEQ range between 0.8 and 1.7 
(Resnik and Borgia 2011) while the MDC of the socket comfort score is 2.73 (Hafner et al. 2016).   
Power Analysis: Power calculations were done using a repeated-measures ANOVA, as G*Power 
cannot calculate power for linear mixed models.  These analyses are similar, except that in the 
multivariate approach, if a subject is missing data for one socket, they will be dropped from the 
entire analysis. In the mixed approach, only that one socket will be dropped and the remaining data 
will be retained.  With 30 participants, we have 72% power to detect a small effect (f =0.2), and 
100% power to detect a medium effect (f = 0.5, α = 0.05).  With 20 participants (full model, 33% 
attrition), we have 51% power to detect a small effect (f =0.2), and 99% power to detect a medium 
effect. 
Aim 2: Determine the impact of prosthetic socket on patient mobility and confidence.  The primary 
dependent measures for mobility are time in seconds for the 10-m walk test, timed-up-and-go 
(TUG), L-Test and five times sit-to-stand (FTSTS) (described in Research Strategy).  To test the 
hypothesis: 
H2a: Mobility, as measured by the 10-m walk, TUG, L-Test and FTSTS, will improve when 
wearing adjustable sockets compared to conventional, laminated sockets. 
We will use a linear mixed model with subjects as a random variable, and socket type as a repeated, 
fixed factor.  Significant effects of socket type will be explored using post-hoc testing with LSD 
corrections.  Results will also be compared to published measurement errors, where they exist, to 
establish their clinical relevance.  The standard error of the measure (SEM) for the L-test is 3 s 
(Deathe and Miller 2005) The MDC for the TUG in people with lower limb amputation is 3.6 s 
(SEM = 1.6 s) (Resnik and Borgia 2011).    
Participants confidence performing different activities in the home will be assessed using the 
Activities specific balance confidence (ABC) scale (scored 1-100) (Powell and Myers 1995) and 
self-reported mobility using the Plus-M (Hafner et al. 2017) .  The PLUS-M 12-Item Short Form 
provides T-scores that range from 21.8 to 71.4 where higher scores indicate better mobility.  

Survey scores will be compared using a linear mixed model with subjects as a random variable, 
and socket type (conventional, CJ Socket, Infinite Socket, Limitless Socket) as repeated, fixed 
factor to test the hypothesis:  
H2b: Participants will self-report equal or greater mobility on the PLUS-M and mobility subscale 
of the PEQ and equal or greater confidence when wearing adjustable sockets compared to 
laminated sockets. 
Significant effects of socket type will be explored using post-hoc testing with LSD corrections.   If 
mobility changes between sockets, we will perform secondary analyses to understand why this 
change occurred. For example, if we see improved 10-m walk test times, we will compare joint 
kinematics and temporal-spatial measures from the LegSys+ system.  Here, we might expect that 
the altered trimlines of some of the adjustable sockets enable individuals to increase their hip 
flexion/extension, enabling a longer step length.   
Power Analysis: Although there is not sufficient data in the adjustable sockets tested to estimate 
standard deviations, we can draw from existing literature assessing a different type of socket, the 
High-Fidelity Interface™ (HiFi, biodesigns, inc., Westlake Village, CA, USA), which is unique 
in that it has areas of tissue compression and release.  In an experimental study of people with a 
transfemoral amputation (n = 11), the HiFi improved ABC score from 77.2±16.8 with a standard-
of-care ischial ramus containment socket to 90.7±5.7 (Kahle et al. 2016). This indicates that the 
socket has a strong effect (effect size = 0.92) on balance confidence.  Thus with 30, we are 100% 
powered to detect a difference in ABC scores.  
Aim 3: Determine if prosthetic socket design influences prosthetic use in the home.  We will 
monitor the participant in their daily life for a one-week period. We calculate the average number 
of times the prosthesis is taken on and off during the day for a seven-day period.  Wear time will 
be determined as the total time from donning to doffing for a 24-hr period.  This will then be 
averaged over the seven-day monitoring period.  Finally, we will time how long it takes the 
participant to don and doff their prosthesis at a comfortable pace.  We will first determine whether 
the resulting data is normally distributed by visual inspection of the sample frequency distribution 
and the Kolmogorov-Smirnov test. We will appropriately transform the data if is not normally 
distributed (Myles et al. 1999).  Data will then be compared using a linear mixed model (as 
described above) to test the hypothesis: 
H1a: The number of times donned and doffed will be fewer and overall wear time will increase 
for all adjustable sockets compared to conventional, laminated sockets.  
H1b: The time to don and doff the prosthesis will be less for adjustable sockets versus conventional 
per device manufacturer claims.  
Physical activity measures (i.e., average acceleration, step counts, number of bouts, steps per bout) 
will be calculated for each day within the one-week period.  Since we are attaching the 
accelerometer to the prosthetic device, we do not need to specify a minimum threshold of wear 
time for a valid day (i.e., we do not need to require a specific number of hours and a minimum 
number of days of accelerometer wear time for a day to be considered valid). Daily activity levels 
will be averaged across all days in the one-week period for an average activity level per day.  

Comparisons between prosthetic sockets will be made using a linear mixed model with sockets as 
fixed effect and subjects as a random effect.  We will use these results to test the hypothesis: 
H1c: Participants will be more active in daily life when wearing an adjustable socket.  
Aim 4: Determine individual characteristics that are associated with benefits of specific socket 
designs.  If adjustable sockets are successful in improving comfort and performance, our secondary 
goal will be to identify which patients are the best candidate for which specific socket system.  We 
will determine if any of these demographic characteristics or personal factors (taken from the PEQ, 
SF-36) are associated with whether the participant benefited from a specific socket (over standard-
of-care non-adjustable sockets).  To do this, we will first determine which outcome measure 
demonstrates the strongest effect of socket design.  We will then perform correlation analysis to 
determine which participant characteristics correlate with this outcome measure (as describe in 
Preliminary Study 2).  As this is the first large study on adjustable sockets, this analysis will be 
exploratory.  However, based on two case studies, we expect the strongest effect will be in socket 
comfort score (SCS).  We also believe that BMI, residual limb length, and K-Level will be strong 
predictors of SCS.  We need 29 participants to detect a large-effect size (r≥0.50, α = 0.05, β = 0.8).  
The results of this exploratory analysis can be used in the design of future studies to assess 
outcomes in the patients most likely to benefit from adjustable socket technologies.      
 
Confidentiality and Security 
 All data will be stored in a locked file cabinet or password protected computer. Only members 
of the study team will have access to this data. These data will have no identifiable information, 
only participant ID numbers. All identifiable information will be destroyed once the study is 
complete.  
 
 
 
 
 
 
 
 
 
 

 
 
 
 
 
 
 
Albert, M. V., C. McCarthy, J. Valentin, M. Herrmann, K. Kording and A. Jayaraman (2013). "Monitoring 
functional capability of individuals with lower limb amputations using mobile phones." PLoS One 8(6): 
e65340. 
Baars, E. C. and J. H. Geertzen (2005). "Literature review of the possible advantages of silicon liner 
socket use in trans-tibial prostheses." Prosthet Orthot Int 29(1): 27-37. 
Berke, G. M., J. H. L-CPO and V. Nguyen (2010). "Comparison of satisfaction with current prosthetic care 
in veterans and servicemembers from Vietnam and OIF/OEF conflicts with major traumatic limb loss." 
Journal of rehabilitation research and development 47(4): 361. 
Board, W. J., G. M. Street and C. Caspers (2001). "A comparison of trans-tibial amputee suction and 
vacuum socket conditions." Prosthetics and Orthotics International 25(3): 202-209. 
Charlson, M., T. P. Szatrowski, J. Peterson and J. Gold (1994). "Validation of a combined comorbidity 
index." Journal of Clinical Epidemiology 47(11): 1245-1251. 
Chou, T. G. R., J. B. Webster, M. Shahrebani, T. L. Roberts and R. D. Bloebaum (2009). "Characterization 
of Step Count Accuracy of Actigraph Activity Monitor in Persons With Lower Limb Amputation." JPO: 
Journal of Prosthetics and Orthotics 21(4): 208-214 210.1097/JPO.1090b1013e3181b1084a1066. 
Coleman, K. L., D. A. Boone, L. S. Laing, D. E. Mathews and D. G. Smith (2004). "Quantification of 
prosthetic outcomes: Elastomeric gel liner with locking pin suspension versus polyethylene foam liner 
with neoprene sleeve suspension." Journal of Rehabilitation Research and Development 41(4): 591-602. 
Couture, M., C. D. Caron and J. Desrosiers (2010). "Leisure activities following a lower limb amputation." 
Disability and Rehabilitation 32(1): 57-64. 
Datta, D., R. Ariyaratnam and S. Hilton (1996). "Timed walking test—an all-embracing outcome measure 
for lower-limb amputees?" Clinical rehabilitation 10(3): 227-232. 
Deathe, A. B. and W. C. Miller (2005). "The L test of functional mobility: measurement properties of a 
modified version of the timed "up & go" test designed for people with lower-limb amputations." Phys 
Ther 85(7): 626-635. 
Deathe, A. B., D. L. Wolfe, M. Devlin, J. S. Hebert, W. C. Miller and L. Pallaveshi (2009). "Selection of 
outcome measures in lower extremity amputation rehabilitation: ICF activities." Disabil Rehabil 31(18): 
1455-1473. 
Dillingham, T. R., L. E. Pezzin, E. J. MacKenzie and A. R. Burgess (2001). "Use and satisfaction with 
prosthetic devices among persons with trauma-related amputations: a long-term outcome study." 
American Journal of Physical Medicine & Rehabilitation 80(8): 563-571. 
Ferris, A. E., J. M. Aldridge, C. A. Rabago and J. M. Wilken (2012). "Evaluation of a powered ankle-foot 
prosthetic system during walking." Arch Phys Med Rehabil 93(11): 1911-1918. 

Fischer, H. and I. Ave (2013). " U. S. Military Casualty Statistics : Operation New Dawn , Operation Iraqi 
Freedom, and Operation Enduring Freedom.". 
Gallagher, P., M. A. O'Donovan, A. Doyle and D. Desmond (2011). "Environmental barriers, activity 
limitations and participation restrictions experienced by people with major limb amputation." 
Prosthetics and Orthotics International 35(3): 278-284. 
Gailey, R., Kristal, A., Lucarevic, J., Harris, S., Applegate, B., & Gaunaurd, I. (2019). The development and 
internal consistency of the comprehensive lower limb amputee socket survey in active lower limb 
amputees. Prosthetics and Orthotics International, 43(1), 80–
87. https://doi.org/10.1177/0309364618791620Gardinier, E. S., B. M. Kelly, J. Wensman and D. H. Gates 
(2017). "A controlled clinical trial of a clinically-tuned powered ankle prosthesis in people with transtibial 
amputation." Clin Rehabil: 269215517723054. 
Goldberg, A., M. Chavis, J. Watkins and T. Wilson (2012). "The five-times-sit-to-stand test: validity, 
reliability and detectable change in older females." Aging clinical and experimental research 24(4): 339-
344. 
Hafner, B. J., I. A. Gaunaurd, S. J. Morgan, D. Amtmann, R. Salem and R. S. Gailey (2017). "Construct 
Validity of the Prosthetic Limb Users Survey of Mobility (PLUS-M) in Adults With Lower Limb 
Amputation." Archives of Physical Medicine and Rehabilitation 98(2): 277-285. 
Hafner, B. J., S. J. Morgan, R. L. Askew and R. Salem (2016). "Psychometric evaluation of self-report 
outcome measures for prosthetic applications." Journal of rehabilitation research and development 
53(6): 797-812. 
Hanspal, R. S., K. Fisher and R. Nieveen (2003). "Prosthetic socket fit comfort score." Disabil Rehabil 
25(22): 1278-1280. 
Highsmith, M. J., J. T. Kahle, R. M. Miro, M. S. Orendurff, A. L. Lewandowski, J. J. Orriola, B. Sutton and J. 
P. Ertl (2016). "Prosthetic interventions for people with transtibial amputation: Systematic review and 
meta-analysis of high-quality prospective literature and systematic reviews." J Rehabil Res Dev 53(2): 
157-184. 
Kahle, J. T., T. D. Klenow and M. J. Highsmith (2016). "Comparative Effectiveness of an Adjustable 
Transfemoral Prosthetic Interface Accommodating Volume Fluctuation: Case Study." Technol Innov 
18(2-3): 175-183. 
Kahle, J. T., T. D. Klenow, W. J. Sampson and M. J. Highsmith (2016). "The Effect of Transfemoral 
Interface Design on Gait Speed and Risk of Falls." Technol Innov 18(2-3): 167-173. 
Kim, J., A. Davidson and D. H. Gates (2017). Characterizing ambulatory tendencies for lower limb 
amputees. . 41th Annual Meeting of the American Society of Biomechanics, Boulder, CO. 
Kim, J. S., D. Y. Chu and H. S. Jeon (2015). "Reliability and validity of the L test in participants with chronic 
stroke." Physiotherapy 101(2): 161-165. 
Klute, G. K., J. S. Berge, W. Biggs, S. Pongnumkul, Z. Popovic and B. Curless (2011). "Vacuum-Assisted 
Socket Suspension Compared With Pin Suspension for Lower Extremity Amputees: Effect on Fit, Activity, 
and Limb Volume." Archives of Physical Medicine and Rehabilitation 92(10): 1570-1575. 
Klute, G. K., B. C. Glaister and J. S. Berge (2010). "Prosthetic Liners for Lower Limb Amputees: A Review 
of the Literature." Prosthetics and Orthotics International 34(2): 146-153. 
Legro, M. W., G. D. Reiber, D. G. Smith, M. del Aguila, J. Larsen and D. Boone (1998). "Prosthesis 
evaluation questionnaire for persons with lower limb amputations: assessing prosthesis-related quality 
of life." Arch Phys Med Rehabil 79(8): 931-938. 
Marks, L. J. and J. W. Michael (2001). "Science, medicine, and the future - Artificial limbs." British 
Medical Journal 323(7315): 732-735. 

Miller, W. C., A. B. Deathe and M. Speechley (2003). "Psychometric properties of the Activities-specific 
Balance Confidence Scale among individuals with a lower-limb amputation." Arch Phys Med Rehabil 
84(5): 656-661. 
Mitton, K., J. Kulkarni, K. W. Dunn and A. H. Ung (2017). "Fluctuating residual limb volume 
accommodated with an adjustable, modular socket design: A novel case report." Prosthet Orthot Int 
41(5): 527-531. 
PDAC. (2016). "Medicare Pricing, Data Analysis and Coding."   Retrieved 12/29/17, from 
https://www.dmepdac.com/resources/articles/2016/06_16_16b.html. 
Powell, L. E. and A. M. Myers (1995). "The activities-specific balance confidence (ABC) scale." The 
Journals of Gerontology Series A: Biological Sciences and Medical Sciences 50(1): M28-M34. 
Reiber, G. E., L. V. McFarland, S. Hubbard, C. Maynard, D. K. Blough, J. M. Gambel and D. G. Smith 
(2010). "Servicemembers and veterans with major traumatic limb loss from Vietnam war and OIF/OEF 
conflicts: survey methods, participants, and summary findings." J Rehabil Res Dev 47(4): 275-297. 
Resnik, L. and M. Borgia (2011). "Reliability of outcome measures for people with lower-limb 
amputations: distinguishing true change from statistical error." Phys Ther 91(4): 555-565. 
Rosenblatt, N. J., T. Ehrhardt, R. Fergus, A. Bauer and R. Caldwell (2017). "Effects of Vacuum-Assisted 
Socket Suspension on Energetic Costs of Walking, Functional Mobility, and Prosthesis-Related Quality of 
Life." JPO: Journal of Prosthetics and Orthotics 29(2): 65-72. 
Ryall, N., S. Eyres, V. Neumann, B. Bhakta and A. Tennant (2003). "The SIGAM mobility grades: a new 
population-specific measure for lower limb amputees." Disability and rehabilitation 25(15): 833-844. 
Sawers, A., & Hafner, B. J. (2018)." Narrowing beam-walking is a clinically feasible approach for assessing 
balance ability in lower-limb prosthesis users." Journal of Rehabilitation Medicine, 50(5), 457–464. 
https://doi.org/10.2340/16501977-2329 
Schoppen, T., A. Boonstra, J. W. Groothoff, J. de Vries, L. N. Göeken and W. H. Eisma (1999). "The Timed 
“up and go” test: reliability and validity in persons with unilateral lower limb amputation." Archives of 
physical medicine and rehabilitation 80(7): 825-828. 
Seaman, J. P. (2010). "Survey of Individuals Wearing Lower Limb Prostheses." JPO: Journal of Prosthetics 
and Orthotics 22(4): 257-265. 
Sherk, V. D., M. G. Bemben and D. A. Bemben (2010). "Inter limb Muscle and Fat Comparisons in Persons 
With Lower-Limb Amputation." Archives of Physical Medicine and Rehabilitation 91(7): 1077-1081. 
Traballesi, M., A. S. Delussu, A. Fusco, M. Iosa, T. Averna, R. Pellegrini and S. Brunelli (2012). "Residual 
limb wounds or ulcers heal in transtibial amputees using an active suction socket system. A randomized 
controlled study." Eur J Phys Rehabil Med 48(4): 613-623. 
VA/DoD (2017). VA/DoD Clinical Practice Guideline for the Rehabilitation of Individuals with Lower Limb 
Amputation. V. A. D. o. Defense. 
van Hees, V. T., Z. Fang, J. Langford, F. Assah, A. Mohammad, I. C. da Silva, M. I. Trenell, T. White, N. J. 
Wareham and S. Brage (2014). "Autocalibration of accelerometer data for free-living physical activity 
assessment using local gravity and temperature: an evaluation on four continents." J Appl Physiol (1985) 
117(7): 738-744. 
Whitney, S. L., D. M. Wrisley, G. F. Marchetti, M. A. Gee, M. S. Redfern and J. M. Furman (2005). "Clinical 
measurement of sit-to-stand performance in people with balance disorders: validity of data for the Five-
Times-Sit-to-Stand Test." Physical therapy 85(10): 1034-1045. 
Ziegler-Graham, K., E. J. MacKenzie, P. L. Ephraim, T. G. Travison and R. Brookmeyer (2008). "Estimating 
the prevalence of limb loss in the United States: 2005 to 2050." Arch Phys Med Rehabil 89(3): 422-429.