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VOLUME 3, ISSUE 2
2020
RESEARCH ARTICLE
Marable W.R, Smith C, Sigurjónsson B.Þ, Atlason I.F, Johannesson G.A. Transfemoral socket fabrication method using direct casting: outcomes regarding
patient satisfaction with device and services. Canadian Prosthetics & Orthotics Journal. 2020;Volume 3, Issue 2, No.6. https://doi.org/10.33137/cpoj.v3i2.34672
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https://doi.org/10.33137/cpoj.v3i2.34672
1
Marable W.R, Smith C, Sigurjónsson B.Þ, Atlason I.F, Johannesson G.A. Transfemoral socket fabrication method using direct casting: outcomes regarding
patient satisfaction with device and services. Canadian Prosthetics & Orthotics Journal. 2020;Volume 3, Issue 2, No.6. https://doi.org/10.33137/cpoj.v3i2.34672
RESEARCH ARTICLE
TRANSFEMORAL SOCKET FABRICATION METHOD USING DIRECT CASTING: OUTCOMES
REGARDING PATIENT SATISFACTION WITH DEVICE AND SERVICES
Marable W.R1, Smith C1, Sigurjónsson B.Þ2, Atlason I.F3, Johannesson G.A2,4*
1 Össur Americas, Foothill Ranch, California, USA.
2
Össur HF, Reykjavik, Iceland.
3
Quick Lookup, Reykjavik, Iceland.
4
TeamOlmed, Stockholm, Sweden.
INTRODUCTION
Transfemoral (TF) amputation(s) is a devastating procedure
for any person and expensive in terms of acute healthcare
cost1 and rehabilitation cost.2,3 TF amputation highly
restricts the amputee’s overall mobility4 and requires a good
functional prosthesis, especially the interface (i.e. the
socket, the liner and its suspension) to enable the amputee
to regain as much of their previous mobility as possible.5,6
TF amputation is also associated with longer amputee
rehabilitation time compared with transtibial (TT)
amputation and more need of assistance, especially in
elderly patients.7 TF amputees report their general health
related quality of life to be lower than that of non-amputees
or TT amputees. Furthermore, specific problems have been
related to the use of TF prostheses, including limited hip
joint range of motion that restricts users comfort or ability to
perform daily activities such as sitting, walking, picking
OPEN ACCESS Volume 3, Issue 2, Article No.6. 2020
Journal Homepage: https://jps.library.utoronto.ca/index.php/cpoj/index
ABSTRACT
BACKGROUND: Direct Socket for transfemoral (DS-TF) prosthetic user is a novel method of fabricating
a laminated interface on to the residual limb but requires different training, production method and service
model than what most prosthetists are familiar with. This method and model may improve patient
satisfaction by enabling interface fabrication and delivery in one visit.
OBJECTIVES: Document patient satisfaction regarding DS-TF interface versus the prosthetic users’
previous socket in terms of interface function and the clinic service model.
METHODOLOGY: In this longitudinal study (from July 2018 to April 2020), the DS-TF was implemented
in six prosthetic clinics across the United States. Certified prosthetists (CP) and assistants were trained
using a standard protocol. 47 prosthetic users participated, both those in need of a new socket and those
without need. Two modules from the Orthotics and Prosthetics Users’ Survey (OPUS), involving
questions related to satisfaction with the Device and Services, was used to evaluate each DS-TF user
outcome vs. baseline. The only part of the prosthesis that was replaced was the interface, except in 2
cases.
FINDINGS: Each DS-TF interface was fabricated, fit and delivered in a single clinic visit. At 6-months
follow-up, 38 users reported an average of 29.8% increase in satisfaction with their new interface
compared with original, and a 14.8% increase in satisfaction with the services they received from the
clinic in providing of the new prosthesis vs. their original prosthesis. The main outcome increases were
between baseline (initial fitting) and 6-week follow-up and remained consistent after 6 months. This
improvement was consistent irrespective if the user needed a new socket for clinical reasons or not.
CONCLUSION: This study shows that after a standardized training and implementation, the DS-TF
fabrication process including a new interface, improves the user’s satisfaction with their prosthetic device
and services.
ARTICLE INFO
Received: August 3, 2020
Accepted: November 16, 2020
Published: November 23, 2020
CITATION
Marable W.R, Smith C,
Sigurjónsson B.Þ, Atlason I.F,
Johannesson G.A. Transfemoral
socket fabrication method using
direct casting: outcomes
regarding patient satisfaction
with device and services.
Canadian Prosthetics &
Orthotics Journal. 2020;Volume
3, Issue 2, No.6.
https://doi.org/10.33137/cpoj.v3i
2.34672
KEYWORDS
Transfemoral amputation,
Amputee, Prosthesis, Socket,
Interface, Outcome measure,
Satisfaction, Direct casting
* CORRESPONDING AUTHOR:
G. Anton Johannesson, PhD
TeamOlmed, Kistagången 12, 164 40 Kista, Stockholm, Sweden.
E-mail: ajohannesson@teamolmed.se
ORCID: https://orcid.org/0000-0001-8729-458X
https://doi.org/10.33137/cpoj.v3i2.34672
https://jps.library.utoronto.ca/index.php/cpoj/index
https://doi.org/10.33137/cpoj.v3i2.34672
https://doi.org/10.33137/cpoj.v3i2.34672
mailto:ajohannesson@teamolmed.se
https://orcid.org/0000-0001-8729-458X
2
Marable W.R, Smith C, Sigurjónsson B.Þ, Atlason I.F, Johannesson G.A. Transfemoral socket fabrication method using direct casting: outcomes regarding
patient satisfaction with device and services. Canadian Prosthetics & Orthotics Journal. 2020;Volume 3, Issue 2, No.6. https://doi.org/10.33137/cpoj.v3i2.34672
ISSN: 2561-987X TRANSFEMORAL SOCKET FABRICATION METHOD USING DIRECT CASTING
Marable et al. 2020
CPOJ
objects up from the floor, and tying their shoes.8,9 Despite
new materials and technology, the most frequently reported
problem with the usage of TF prosthesis is still sores/skin
irritation from the interface.10,11
Prosthetic fitting of TF amputees has always been a
challenging and time-consuming procedure that requires
the user (and often family member or care giver) to make
on average 4 visits to a prosthetic clinic.12 Between 6 and
16 weeks pass from amputation to delivery of a TT or TF
prostheses in high-income countries.13–15 Fabricating a
definitive TF interface has been reported to take at least 14
days using a traditional laminated interface process of
casting, check socket(s) and laminated definitive
interface.16 Reducing the number of days in rehabilitation
can reduce amputee rehabilitation costs by up to 25%.2 It
has also been demonstrated that in patients amputated due
to vascular reasons, functional mobility level declines as the
number of days between amputation and start of
rehabilitation increases. In the same study shorter time to
prosthetic fitting was demonstrated to lead to improved
functional outcomes six months after amputation.17
Although many interesting new socket designs have been
introduced to the market in the last 50 years, few studies
have documented long term outcomes and/or quantitative
data of a specific socket design.11 Most published studies
focus on TF amputee gait, socket design, suspension
and/or function of the components including less than 15
amputees.8,18–20 Kahle et al found that different socket
designs may have an effect on gait speed and risk of
falling.8 Fatone et al., have described a new interface and
the fabrication methods used to produce a TF socket,
including outcomes from two cases.21,22 Kahle et al.,
investigated the trimline level and compared outcomes
between socket designs in 15 cases, although only in a
clinical setting.18
The socket designs in these studies are mainly grounded
on the prosthetist’s experience, with few measurable
design parameters or description of how the design is
intended to affect and interact with the user’s residual limb
during the gait cycle.11 Various terms have been proposed
to describe the way forces are transferred between the
residuum and the socket, the biomechanical principles upon
which these terms are based are ill-defined.23 Most
recognized are terms used to describe the axial and
transversal stabilization, e.g. Ischial Containment or Inter
Ramus Containment sockets.11 Contact between this part of
the hip bone (ischium and ramus inferior) and the socket
can only be obtained during stance phase, which is
approximately 0.6 sec of a full 1.07 sec gait cycle.24 During
the rest of the gait cycle the ramus is moving in and out of
the socket with little or no socket interaction. The position
and effect of the “ischial-ramus containment” has not been
revealed in studies except in theory.25 When this support or
function is presumed to be lacking the term ”sub-ischial
socket” has been used.26
The problem with this “definition” is that a transtibial or toe
prosthesis could also be referred to as sub-ischial socket.
This lack of detail and consistency in definitions prevents
objective comparison.27 In an effort to provide detail and
resolve the inconsistency, ISO standard 13405-2:2015
contains recommendations on how to systematically
describe an interface and provides a base for comparison
between different interface design and function.23
A method of fabricating a finished laminated TT interface
directly on the patient’s residual limb has been on the
market since 1996. First introduced as ICEX by Össur HF
of Iceland, ICEX was based on the inventor’s philosophy of
pressure casting28 and was included in a variety of studies
related to user satisfaction, cost and function.29–32 Since
then ICEX was improved to Modular Socket System (MSS)
in 2005,31 and finally to Direct Socket in 2018.33 This system
enables a prosthetist to fabricate a custom-made interface
directly on the TT residual limb in a single visit. The lesson
learned from the use of DS-TT in Scandinavia for over two
decades and the finding related to the process, e.g. shorter
rehabilitation time, demanded a solution for TF level.13
A TF version of Direct Socket (DS-TF) began testing in
2016 in select Scandinavian clinics.30,31 The proximal
portion of a DS-TF interface design differs significantly from
the proximal portion of sockets typically called Ischial
Containment or Inter Ramus Containment sockets, as the
proximal part of the DS-TF includes a size-specific silicone
brim. The method of fabricating directly on the residual limb
requires a different approach to prosthetist training and
fabrication compared to the socket fabrication process most
prosthetists apply today.33
The primary aim of this study was to collect data on
prosthetic users satisfaction regarding DS-TF interface in
terms of both interface function and the clinic service model
(i.e. one patient visit to the clinic for fabrication of custom TF
interface, prosthesis assembly, alignment, gait analysis,
and delivery).
LIST OF ABBREVIATIONS
• CP: Certified Prosthetist
• CSD: Client Satisfaction with Device
• CSS: Client Satisfaction with Services
• DS-TF: Direct Socket for transfemoral
• DS-TT: Direct Socket for transtibial
• ISO: International Organization for Standardization
• ISO/TC: 168 Prosthetic and Orthotics working group within ISO
• ISPO: International Society for Prosthetics and Orthotics
• OPUS: Orthotics and Prosthetics User’s Survey
• O&P: Orthotics and Prosthetic
• TF: transfemoral
• TT: transtibial
• 6WFU: six-weeks follow-up
• 6MFU: six-month follow-up
https://doi.org/10.33137/cpoj.v3i2.34672
3
Marable W.R, Smith C, Sigurjónsson B.Þ, Atlason I.F, Johannesson G.A. Transfemoral socket fabrication method using direct casting: outcomes regarding
patient satisfaction with device and services. Canadian Prosthetics & Orthotics Journal. 2020;Volume 3, Issue 2, No.6. https://doi.org/10.33137/cpoj.v3i2.34672
ISSN: 2561-987X TRANSFEMORAL SOCKET FABRICATION METHOD USING DIRECT CASTING
Marable et al. 2020
CPOJ
METHODOLOGY
In this study, a new direct casting procedure for TF
amputees called Direct Socket TF (DS-TF),34 was
implemented in six different prosthetic clinics across the
United States. The product includes all materials and tools
to make a definitive socket. In the DS-TF fabrication
process, a special 2.5mm casting liner is rolled onto the
residual limb followed by a protective silicone sheath over
the casting liner to prevent the resin from contacting the
residual limb. Next, a size-specific silicone brim is placed at
the proximal part of the limb. A glass or basalt fabric with
pre-attached distal adapter is then rolled on the length of the
limb. A second protective sheath is applied on the outside
of the fabric and a two-part resin is injected through the
distal adapter (Figure 1, Figure 2) to approximately ½ to ¾ of
the fabric length. The resin is absorbed through the fiber and
kept isolated from the amputee by the two silicone sheaths
on each side of the fabric. Over the next 10-15 minutes the
resin undergoes an exothermic reaction as it hardens,
during which the CP can mold and shape the socket wall
around the residual limb muscles that are relaxed or
contracted as directed by the CP. The amputee can feel the
warming socket, but socket temperature does not exceed
37.5 degree Celsius, a typical adult body temperature.
DS-TF interface description
According to ISO 13405-2:2015 section 5, (5.1.2.1
General) the force-transmission properties of DS-TF can
be described, as follows:
• (5.1.2.2) AXIAL STABILIZATION: the direct socket
shape conforms to the shape of the femur, and soft
tissues about the femur, causing even compression of
the soft tissue, which creates axial stabilization (see also
5.1.3).
• (5.1.2.3) TRANSVERSE STABILIZATION: even
tissue compression created during the direct lamination
process increases soft tissue density, creating
anteroposterior, mediolateral, and rotational stabiliz-
ation (see also 5.1.3).
• (5.1.2.4) SUSPENSION: to minimize the axial
movement, several suspension methods may be used;
preferably a Seal-In liner which creates partial distal
vacuum, a locking liner with lanyard or pin can also be
used.
• (5.1.3) STIFFNESS: The socket is laminated with a
distal 4-hole adapter and a proximal brim made of
flexible silicone. This makes the socket flexible
proximally while most of the socket is rigid. The flexible
circumference silicone brim encompasses and
compresses the proximal thigh muscles when
contracted, thereby stabilizing the hip at initial contact,
loading response, mid-stance, and terminal-stance, and
creating axial and transverse stabilization. During the
rest of the gait (pre-, initial-, mid-, and late swing) the
brim is only following the hip movement.
The selection criteria for study principle investigators
included a Certified Prosthetist (CP) with more than 5-years
clinical experience in serving TF amputees with interest in
improving patient outcomes and satisfaction, willingness to
follow a defined novel fabrication protocol, and commitment
to document outcome measures at defined time intervals.
The inclusion criteria (rationale) is listed in Table 1.
Figure 1: Direct Socket
Table 1: Amputee inclusion criteria (rationale)
Amputee inclusion criteria (rationale)
• 50Kg< body weight < 160Kg (the ISO validated weight limit of the
DS-TF)
• Cognitive ability to understand all instructions and questionnaires
in the study
• Patients who have undergone a TF amputation > 1-year post
amputation (this was to avoid postoperative problems and/or
adjustments related the initial prosthetic fitting of a new amputee)
• Older than 18 years
• Willing and able to participate in the study and follow the protocol
• Circular dimension of 40-65 cm at the crotch (limited to available
silicone brim sizes)
• Residual limb length at least 20 cm from ischium to distal end
(fabrication limitation of the DS-TF)
• Currently using a prosthetic liner (this was to avoid potential
confounding influence from transitioning an amputee from a skin
fitting interface (i.e. without a liner), to an interface with a liner)
• Willing to use a silicone prosthetic liner as called for in Direct
Socket Instructions For Use.
34
Silicone brim
Socket
Valve
https://doi.org/10.33137/cpoj.v3i2.34672
4
Marable W.R, Smith C, Sigurjónsson B.Þ, Atlason I.F, Johannesson G.A. Transfemoral socket fabrication method using direct casting: outcomes regarding
patient satisfaction with device and services. Canadian Prosthetics & Orthotics Journal. 2020;Volume 3, Issue 2, No.6. https://doi.org/10.33137/cpoj.v3i2.34672
ISSN: 2561-987X TRANSFEMORAL SOCKET FABRICATION METHOD USING DIRECT CASTING
Marable et al. 2020
CPOJ
Training protocol
Direct Socket fabrication was performed by a two-person
team consisting of a lead and an assistant (Figure 2). The
lead was typically a CP while the assistant was commonly
a prosthetic tech or certified prosthetic assistant. CP’s and
assistants were trained in each CP’s clinic by certified
Clinical Specialists using a standard protocol. Prior to
starting training and fabrication, demographic/clinical
information and measurements were documented to ensure
subjects were within the clinical limitations of the study.
Also, all necessary materials (sized for the scheduled
amputees) were on hand, including Direct Socket Toolkit,
Direct Socket Material Kits, Direct Socket casting liners and
Direct Socket Fabrication Manual. All training and
fabrication were completed following the step-by-step
process of the Direct Socket Fabrication Manual.34
Amputees selected for clinician training were relatively
uncomplicated without invaginations, unusual limb shapes
or extreme alignments. After training, the Clinical training
Figure 2: DS-TF process A) application of material, B) resin injection, C) moulding of resin, D) first fit and alignment
check.
A B
C D
https://doi.org/10.33137/cpoj.v3i2.34672
5
Marable W.R, Smith C, Sigurjónsson B.Þ, Atlason I.F, Johannesson G.A. Transfemoral socket fabrication method using direct casting: outcomes regarding
patient satisfaction with device and services. Canadian Prosthetics & Orthotics Journal. 2020;Volume 3, Issue 2, No.6. https://doi.org/10.33137/cpoj.v3i2.34672
ISSN: 2561-987X TRANSFEMORAL SOCKET FABRICATION METHOD USING DIRECT CASTING
Marable et al. 2020
CPOJ
Specialist remained available to remotely consult with
trainee CP’s as needed.
Follow Up and Data Collection
Including the baseline, three time periods were used to
assess outcomes (Figure 3). After 6 weeks subjects
returned to the clinic and completed the same standardized
surveys regarding their new prosthesis (6WFU). Subjects
returned to the clinic again and completed the same surveys
after 6 months as well (6MFU).
Prior to the fitting each amputee subject was asked to fill out
a standardized survey regarding their existing prosthesis
and the experience of the service that they previously
received. After baseline the CP and assistant fabricated and
delivered a new DS-TF interface and liners.
For the evaluations the Orthotics and Prosthetics User’s
Survey (OPUS) was used. The OPUS is a set of self-
reported outcome measures to be used within O&P clinics
for the assessment of functional status, quality of life, and
client satisfaction.35 The OPUS was originally developed in
English and has been translated into multiple languages,
including Spanish, Swedish and Slovenian. The OPUS has
displayed good internal consistency and has been validated
in US and Swedish populations.36 The OPUS instrument
consists of five independent modules, two of which were
used in this study: Client Satisfaction with Device (CSD) and
Client Satisfaction with Services (CSS). The CSD and CSS
include a total of 21 questions, scored on a 1 - 6, discrete
scale:
Strongly Agree, Agree, Neither agree nor disagree,
Disagree, Strongly disagree and Don´t Know/Not
Applicable.
The OPUS can be used on prosthesis and/or orthosis users.
However, since this study was exclusively on prosthesis
users, to prevent confusion the words “orthosis” and
“orthotist” used in the original survey text were not included
in this study’s user surveys.
The CSD Score is the sum of scores for items 1-11 (11 – 55
points) and relates to the function of the device and the
user’s cost to acquire the device. Meanwhile the CSS Score
is the sum of the scores for items 12-21 (10 – 50 points) and
relates to the service the amputee received. A higher score
indicates a better outcome. These raw scores were then
converted to Rasch Measure (0 – 100 scale) and measure
of variability is reported with the mean.36
The “Device” that is referred to in the questionnaire includes
the complete prosthesis, of which questions 1, 3, 4, 8 and 9
only pertain to the interface. The DS-TF was delivered
without any additional finishing components at baseline.
This study uses the K-scale system established in 1995,
also called Medicare Functional Classification Levels
(MFCL). The K levels divide lower limb amputees into five
categories ranging from K level 0 (least mobile) to K level 4
(most mobile) intended to indicate a person’s rehabilitation
potential.37
Sample size calculation and statistical methods
A pretrial power analysis for the estimated required sample
size was conducted using GPower38 version 3.1.9.6 and
effect size was estimated based on published articles9,39,40
for the primary endpoint assuming a normally distributed
amputee population. It was therefore expected that 38
subjects were required to complete the protocol with a
power of 0,95 and α at 0,05. Drop-out rate was estimated at
proximally 20% and therefore 47 subjects were recruited.
We used R version 4.03 (R-Studio Version 1.2.5033) and
lme441 to perform a linear mixed effects analysis of the
relationship between the OPUS outcomes and clinical need.
As fixed effects, we entered age, gender, and evaluation
point (tested for interaction with “clinical need”) into the
model. As random effects, we had intercepts for subjects
and investigators, as well as by-subject and by-item random
slopes for the effect of clinical need. P-values were obtained
by likelihood ratio tests of the full model with the effect in
question against the model without the effect in question.
For comparison of individual OPUS items, the Benjamini &
Hochberg method was used to control for Type I error due
to multiple comparisons.42
RESULTS
Between July 2018 and October 2019, 47 TF prosthetic
users that fulfilled the eligibility criteria and agreed to
participate in the study were enrolled. Ethical approval was
obtained from Advarra® IRB (CR00128417) and the
investigation was registered at Clinical trials.gov
NCT04312724. Signed informed consent was obtained
from all participants.
Study subjects, included for data collection and analysis,
consisted of prosthetic users fitted during the training of
each CP on DS-TF fabrication, as well as users fitted by
CP’s post training. The study group consisted of both users
who needed a replacement prosthetic interface, according
to new referral, due to wear and tear or volume changes
(n=28; 26 analyzed; “clinical need”), and those with no
clinical need of replacement (n=10) (Table 2). Study
investigators indicate their criteria to determine if a new
interface was clinically justified included: volume reduction
requiring 5-7 sock ply or more (>7% volume reduction),43
socket discomfort, socket instability or significant skin
irritation. The Mean age of subjects was 59 years (36-79
years) and represented wide range of activity levels. Study
subjects exhibited baseline activity levels from K-level 1 to
K-level 4, (K-level 1, n=4; K-level 2, n=11; K-level 3, n=21;
and finally K-level 4, n=11).
https://doi.org/10.33137/cpoj.v3i2.34672
6
Marable W.R, Smith C, Sigurjónsson B.Þ, Atlason I.F, Johannesson G.A. Transfemoral socket fabrication method using direct casting: outcomes regarding
patient satisfaction with device and services. Canadian Prosthetics & Orthotics Journal. 2020;Volume 3, Issue 2, No.6. https://doi.org/10.33137/cpoj.v3i2.34672
ISSN: 2561-987X TRANSFEMORAL SOCKET FABRICATION METHOD USING DIRECT CASTING
Marable et al. 2020
CPOJ
Data was collected and analysed for 47 subjects at
baseline. At 6WFU the results from 40 subjects were
included and 6MFU included results from 38 subjects
(Figure 3), providing a power of 95.3% and 95.2% for the
follow-ups, respectively. Two subjects, from the group “with
clinical need for new interface” did not complete the OPUS
instrument at all three measurement time periods and are
therefore not included in the data analysis for 6MFU.
All prosthetic users included in the study used a liner with
their interface. Thirty-three of them used Seal-In liners, 5
used locking liners, 5 used lanyard and the rest used
various types of liners and suspensions. The most frequent
liner size was 35cm (range 25-50cm). While 36 of the
users used microprocessor-controlled prosthetic knees
from 2 different manufacturers, 11 knees were non-
microprocessor-controlled prosthetic knees from 3 different
manufacturers. Subjects’ prosthetic feet included extensive
functional variation depending on user K-level, from a
SACH foot to high activity feet, made by 4 different
manufacturers. All subjects retained their existing knee
and/or foot, except for two subjects that received a new
knee and foot with the new interface.
Nine of the subjects dropped out of the study, 7 of them
before 6WFU (including one deceased) and 2 of them
before 6MFU (Figure 3). One subject who had advanced
vascular disease and a very small limb decided to withdraw
from the study after one week. Three subjects withdrew
from study, preferring their previous socket.
One subject had shoulder surgery and was non-ambulatory
for a significant part of the study for reasons not having to
do with the prosthesis. Since the subject did not fulfil all
steps of the study, he was considered a drop-out, however,
the subject was still using the new interface when the study
ended. Three subjects did not respond to follow-up. At least
two of them continue to use the new DS-TF interface.
Figure 3: Flow chart of the investigation
Drop out before six-weeks:
• 1 subject died
• 4 subject went back to their previous interface
• 1 due to sever vascular problems (not device related)
• 3 due to poor M-L stability (compared with existing interface)
• 2 lost to follow-up (one still using the new interface)
At six-months follow-up (6MFU)
(N =38)
(N = 38; 36 analysed as 2 subjects were missing full OPUS data sets)
Evaluations measurement used:
• OPUS (21 items)
At six-weeks follow-up (6WFU)
(N = 40)
Evaluations measurement used:
• OPUS (21 items)
All subject that was enrolled into the study at 6 different prosthetic clinics (Baseline)
(N = 47)
Evaluations measurement used:
• OPUS (21 items)
Drop out at six-month:
• 1 subject went for additional surgery on the contralateral side (still uses the
new interface)
• 1 lost from follow-up (still using the new interface)
https://doi.org/10.33137/cpoj.v3i2.34672
7
Marable W.R, Smith C, Sigurjónsson B.Þ, Atlason I.F, Johannesson G.A. Transfemoral socket fabrication method using direct casting: outcomes regarding
patient satisfaction with device and services. Canadian Prosthetics & Orthotics Journal. 2020;Volume 3, Issue 2, No.6. https://doi.org/10.33137/cpoj.v3i2.34672
ISSN: 2561-987X TRANSFEMORAL SOCKET FABRICATION METHOD USING DIRECT CASTING
Marable et al. 2020
CPOJ
Table 2: Characteristics of the study population stratified into follow-up periods according to those prosthetic users in need or not in need of
a new interface.
Baseline 6WFU 6MFU
N 47 40 38
Men/Women 33/14 29/11 28/10
Age (SD) in years 58.9 (11.8) 58.3 (11.7) 58.0 (12.0)
Subjects in need of new interface 34 29 28 (-2)**
Age (SD) in years) 59.0 (11.8) 58.2 (11.8) 58.1 (12.2)
Average K-level* 2.7 (0.9) 3.0 (0.8) 3.0 (0.9)
Subjects not in need of new interface 13 11 10
Age (SD) in years 58.8 (12.3) 58.5 (11.9) 57.9 (12.5)
Average K-level* 3.0 (0.8) 3.3 (01.0) 3.3 (0.8)
Age is referred to as means + SD
* K-level 1, K-level 2, K-level 3, K-level 4
** Two subject did not complete all measurement at all three time periods
Table 3: A: OPUS Client Satisfaction Device (CSD) (questions 1-11). B: OPUS Client Satisfaction with Services (CSS) (questions 12-21)
A
Baseline 6WFU 6MFU
All subjects (n=47) (n=41) (n=36) P
1. My prosthesis fits well… 3.0 (1.2)* 4.3 (1.0) 4.6 (0.9) <.001
2. The weight of my prosthesis is manageable… 3.8 (1.1) 4.5 (0.8) 4.5 (0.8) <.001
3. My prosthesis is comfortable throughout the day… 3.0 (1.3) 4.0 (1.2) 4.4 (0.9) <.001
4. It is easy to put on my prosthesis... 3.7 (1.1) 4.4 (0.9) 4.6 (0.6) <.001
5. My prosthesis looks good… 3.8 (1.1) 4.2 (0.9) 4.7 (0.6) <.001
6. My prosthesis is durable… 4.0 (1.1) 4.4 (0.9) 4.7 (0.5) <.001
7. My clothes are free of wear and tear from my prosthesis... 3.3 (1.4) 4.1 (1.0) 4.1 (1.1) <.001
8. My skin is free of abrasions and irritations… 3.1 (1.4) 4.0 (1.1) 4.0 (1.1) <.001
9. My prosthesis is pain free to wear… 2.8 (1.3) 3.7 (1.0) 4.1 (1.2) <.001
10. I can afford the out-of-pocket expenses to purchase and maintain my prosthesis 2.6 (1.4) 3.3 (1.5 2.7 (1.5) 0.91
11. I can afford to repair or replace my prosthesis as soon as needed 2.5 (1.5) 3.1 (1.6) 2.6 (1.5) 0.91
B
12. I received an appointment with a prosthetist within a reasonable amount of time… 4.6 (0.7) 4.8 (0.4) 4.9 (0.4) 0.03
I was shown the proper level of courtesy and respect by the staff… 4.8 (0.4) 4.9 (0.5) 5.0 (0.2) 0.25
14. I waited a reasonable amount of time to be seen… 4.6 (0.9) 4.9 (0.4) 4.9 (0.3) 0.03
15. Clinic staff fully informed me about equipment choices… 4.6 (0.7) 4.9 (0.3) 4.9 (0.2) 0.03
16. The prosthetist gave me the opportunity to express my concerns regarding my
equipment…
4.8 (0.5) 4.9 (0.3) 4.9 (0.3) 0.15
17. The prosthetist was responsive to my concerns and questions.... 4.8 (0.4) 5.0 (0.2) 4.9 (0.3) 0.25
18. I am satisfied with the training I received in the use and maintenance of my
prosthesis…
4.7 (0.5) 5.0 (0.2) 4.7 (0.9) 0.95
19. The prosthetist discussed problems I might encounter with my equipment… 4.7 (0.5) 5.0 (0.0) 4.9 (0.4) 0.13
20. The staff coordinated their services with my therapists and doctors… 4.5 (0.8) 4.4 (1.3) 4.9 (0.3) 0.15
21. I was a partner in decision-making with clinic staff regarding my care and
equipment…
4.7 (0.5) 4.9 (0.3) 4.9 (0.3) 0.08
*All data are presented as mean (SD)
https://doi.org/10.33137/cpoj.v3i2.34672
8
Marable W.R, Smith C, Sigurjónsson B.Þ, Atlason I.F, Johannesson G.A. Transfemoral socket fabrication method using direct casting: outcomes regarding
patient satisfaction with device and services. Canadian Prosthetics & Orthotics Journal. 2020;Volume 3, Issue 2, No.6. https://doi.org/10.33137/cpoj.v3i2.34672
ISSN: 2561-987X TRANSFEMORAL SOCKET FABRICATION METHOD USING DIRECT CASTING
Marable et al. 2020
CPOJ
Each DS-TF interface was fabricated, fit and delivered in a
single clinic visit. 36% of subjects surveyed at 6WFU had
required minor adjustments by the study CP to the DS-TF
between initial fitting and the 6WFU.
Satisfaction assessment of all participants (Table 3 A,B)
Average CSD scores (the sum of questions 1-11 on a 100-
point Rasch Measure scale) for participants that completed
the 6MFU (n=36) were:
• 46.9 (SD=9.8) at baseline (i.e. existing interface/prosth-
esis)
• 60.6 (SD=14.5) at 6WFU, an increase of 29.8 (SD=3.3)%
compared to baseline with P<.001
• 61.0 (SD=14.0) at 6MFU, an increase of 29.8 (SD=3.3)%,
compared to baseline, with P<.001
Each question directly related to the use of the new interface
(items 1-9), showed significant improvement in outcome,
with the main difference between baseline and 6WFU.
Improvement was sustained in all 9 questions between
6WFU and 6MFU (Table 3 A for individual scores; F statistic
= 29.1 degrees of freedom = 5). No study subject responded
to any survey question with the selection "Don´t Know / Not
Applicable".
Mixed effect model analysis showed that “clinical need” did
not affect the CSD measure (Chi squared = 0.27, P = 0.60).
Average CSS scores (the sum of questions 12-21 on a 100
point Rasch Measure scale) for participants that completed
the 6MFU (n=36) were:
• 81.3 (SD=19.9) at baseline
• 90.6 (Sd=14.1) at 6WFU, an increase of 12.3 (SD=2.2)%
compared to baseline with P=0.009
• 93.1 (SD=13.8) at 6MFU, an increase of 14.8 (SD=2.2)%
compared to baseline with P=0.001
See Table 3B for individual scores; F statistic = 8.2; degrees
of freedom = 5). Mixed effect model analysis showed that
“clinical need” did not affect the CSS measure (Chi squared
= 0.04, P=0.85).
Satisfaction assessment of participants with the
clinical need for new interface (Table 4 A,B)
For participants that completed the 6MFU (n=26)
Average CSD scores were:
• 45.5 (SD=9.1) at baseline
• 60.5 (SD=14.0) at 6WFU, an increase of 33.3 (SD=3.9) %
with P<.001
• 61.9 (SD=14.1) at 6MFU, an increase of 37.8 (SD=4.0) %,
compared to baseline with P<.001
Average CSS scores were:
• 80.8 (SD=20.2) at baseline
• 91.0 (SD=15.2) at 6WFU, an increase of 12.3 (SD=3.4) %
with P=0.055
• 93.3 (SD=13.4) at 6MFU, an increase of 14.8 (SD=3.4)%
compared to baseline with P<.005.
Satisfaction assessment of participants without the
clinical need for new interface (Table 5 A,B)
For participants that completed the 6MFU (n=10)
Average CSD scores were:
• 50.7 (SD=11.1) at baseline
• 61 (SD=16.4) at 6WFU, an increase of 19.6 (SD=4.5)%
with P=0.018
• 58.7 (SD=14.0) at 6MFU, an increase of 15.6 (SD=4.9) %
compared to baseline with P=0.047
Average CSS scores were:
• 82.8 (SD=20.0) at baseline
• 89.5 (SD=11.6) at 6WFU, an increase of 8.8 (SD=7.5)%
compared to baseline with P=0.195
• 92.6 (SD=15.5), at 6MFU, an increase of 12.0 (SD=7.9)%
compared to baseline with P= 0.103.
DISCUSSION
OPUS CSD questions related to the function of the interface
for all subjects indicate a significant improvement in user
satisfaction with their DS-TF interface over their previous
interface in terms of weight, comfort, donning, appearance,
durability, and reduced clothing wear and tear. Results also
showed significantly improved satisfaction regarding skin
abrasions and irritation, as well “pain free to wear”. All
improvements were consistent between the 6-week and 6-
month study periods. At 6MFU the average CSS score was
93, or 14.8% higher, a significant improvement compared
with baseline.
One might think that amputees who need a new socket for
clinical reasons may be more dissatisfied with their existing
socket than amputees who do not need a new socket for
clinical reasons, and might therefore be more inclined to
show greater satisfaction improvement with a new
prosthesis than the subjects who did not need a new
interface. To identify this potential influence, all completed
subject data was analyzed together, as well as broken into
two separate cohorts- “with clinical need of new interface”
and “without clinical need of new interface”. Analysis
indicates that “clinical need” did not significantly affect the
CSD and CSS measures.
https://doi.org/10.33137/cpoj.v3i2.34672
9
Marable W.R, Smith C, Sigurjónsson B.Þ, Atlason I.F, Johannesson G.A. Transfemoral socket fabrication method using direct casting: outcomes regarding
patient satisfaction with device and services. Canadian Prosthetics & Orthotics Journal. 2020;Volume 3, Issue 2, No.6. https://doi.org/10.33137/cpoj.v3i2.34672
ISSN: 2561-987X TRANSFEMORAL SOCKET FABRICATION METHOD USING DIRECT CASTING
Marable et al. 2020
CPOJ
Table 4: A: OPUS Client Satisfaction Device (CSD) (questions 1-11); B: OPUS Client Satisfaction with Services (CSS) (questions 12-21).
A Baseline 6WFU 6MFU
Subject with clinical need (n=26) (n=26) (n=26)
1. My prosthesis fits well… 2.8 (1.2) 4.3 (0.8) 4.6 (1.0)
2. The weight of my prosthesis is manageable… 3.6 (1.2) 4.4 (0.9) 4.5 (0.9)
3. My prosthesis is comfortable throughout the day… 2.8 (1.4) 4.0 (1.1) 4.3 (1.0)
4. It is easy to put on my prosthesis... 3.6 (1.2) 4.4 (0.9) 4.7 (0.6)
5. My prosthesis looks good… 3.7 (1.1) 4.2 (1.1) 4.7 (0.5)
6. My prosthesis is durable… 3.8 (1.4) 4.3 (1.0) 4.7 (0.5)
7. My clothes are free of wear and tear from my prosthesis... 3.2 (1.4) 4.2 (1.0) 4.3 (0.9)
8. My skin is free of abrasions and irritations… 3.3 (1.4) 4.2 (0.8) 4.2 (1.0)
9. My prosthesis is pain free to wear… 2.6 (1.2) 3.8 (1.0) 4.2 (1.1)
10. I can afford the out-of-pocket expenses to purchase and maintain my prosthesis… 2.5 (1.4) 3.5 (1.5) 2.7 (1.5)
11. I can afford to repair or replace my prosthesis as soon as needed 2.5 (1.5) 3.3 (1.6) 2.5 (1.4)
B
12. I received an appointment with a prosthetist within a reasonable amount of time… 4.7 (0.5) 4.8 (0.4) 4.9 (0.4)
13. I was shown the proper level of courtesy and respect by the staff… 4.8 (0.4) 4.8 (0.6) 5.0 (0.2)
14. I waited a reasonable amount of time to be seen… 4.6 (0.9) 4.8 (0.5) 4.9 (0.3)
15. Clinic staff fully informed me about equipment choices… 4.6 (0.8) 4.9 (0.3) 4.9 (0.3)
16. The prosthetist gave me the opportunity to express my concerns regarding my equipment… 4.7 (0.5) 4.8 (0.4) 4.9 (0.3)
17. The prosthetist was responsive to my concerns and questions.... 4.8 (0.4) 5.0 (0.2) 4.9 (0.3)
18. I am satisfied with the training I received in the use and maintenance of my prosthesis… 4.7 (0.5) 5.0 (0.2) 4.9 (0.3)
19. The prosthetist discussed problems I might encounter with my equipment… 4.7 (0.5) 5.0 (0.0) 4.8 (0.5)
20. The staff coordinated their services with my therapists and doctors… 4.5 (0.9) 4.5 (1.4) 4.9 (0.3)
21. I was a partner in decision-making with clinic staff regarding my care and equipment… 4.6 (0.5) 4.9 (0.3) 4.9 (0.3)
Table 5: A: OPUS Client Satisfaction Device (CSD) (questions 1-11); B: OPUS Client Satisfaction with Services (CSS) (questions 12-21).
A Baseline 6WFU 6MFU
Subject with no clinical need (n=10) (n=10) (n=10)
1. My prosthesis fits well… 3.6 (0.8) 4.7 (0.7) 4.5 (0.5)
2. The weight of my prosthesis is manageable… 4.5 (0.5) 4.9 (0.3) 4.6 (0.5)
3. My prosthesis is comfortable throughout the day… 3.5 (1.0) 4.5 (0.7) 4.4 (0.7)
4. It is easy to put on my prosthesis... 3.9 (0.7) 4.8 (0.4) 4.6 (0.7)
5. My prosthesis looks good… 4.0 (0.7) 4.5 (0.7) 4.6 (0.7)
6. My prosthesis is durable… 4.3 (0.7) 4.7 (0.7) 4.6 (0.7)
7. My clothes are free of wear and tear from my prosthesis... 3.5 (1.4) 4.3 (1.1) 3.7 (1.3)
8. My skin is free of abrasions and irritations… 3.0 (1.2) 3.6 (1.4) 3.6 (1.2)
9. My prosthesis is pain free to wear… 3.4 (1.3) 3.6 (1.1) 3.7 (1.3)
10. I can afford the out-of-pocket expenses to purchase and maintain my prosthesis… 2.7 (1.4) 2.6 (1.5) 2.8 (1.6)
11. I can afford to repair or replace my prosthesis as soon as needed 2.4 (1.4) 2.6 (1.6) 2.9 (1.7)
B
12. I received an appointment with a prosthetist within a reasonable amount of time… 4.4 (1.0) 4.7 (0.5) 5.0 (0.0)
13. I was shown the proper level of courtesy and respect by the staff… 4.8 (0.4) 5.0 (0.0) 5.0 (0.0)
14. I waited a reasonable amount of time to be seen… 4.5 (1.0) 5.0 (0.0) 5.0 (0.0)
15. Clinic staff fully informed me about equipment choices… 4.8 (0.4) 4.9 (0.3) 5.0 (0.0)
16. The prosthetist gave me the opportunity to express my concerns regarding my equipment… 4.8 (0.4) 5.0 (0.0) 5.0 (0.0)
17. The prosthetist was responsive to my concerns and questions.... 4.8 (0.4) 5.0 (0.0) 4.9 (0.3)
18. I am satisfied with the training I received in the use and maintenance of my prosthesis… 4.7 (0.5) 5.0 (0.0) 4.3 (1.7)
19. The prosthetist discussed problems I might encounter with my equipment… 4.7 (0.5) 5.0 (0.0) 5.0 (0.0)
20. The staff coordinated their services with my therapists and doctors… 4.6 (0.5) 4.4 (1.1) 5.0 (0.0)
21. I was a partner in decision-making with clinic staff regarding my care and equipment… 4.8 (0.4) 4.9 (0.3) 4.9 (0.3)
All data are presented as mean (SD)
https://doi.org/10.33137/cpoj.v3i2.34672
10
Marable W.R, Smith C, Sigurjónsson B.Þ, Atlason I.F, Johannesson G.A. Transfemoral socket fabrication method using direct casting: outcomes regarding
patient satisfaction with device and services. Canadian Prosthetics & Orthotics Journal. 2020;Volume 3, Issue 2, No.6. https://doi.org/10.33137/cpoj.v3i2.34672
ISSN: 2561-987X TRANSFEMORAL SOCKET FABRICATION METHOD USING DIRECT CASTING
Marable et al. 2020
CPOJ
Across both user groups average CSD OPUS scores were
significantly improved after fitting subjects with DS-TF
interfaces. In all cases, the CP was able to fabricate, align,
fit, adjust, and deliver the new interface in the same visit,
with only 36% of subjects returning to the clinic for a post-
delivery socket adjustment.
To our knowledge this study is one of largest and longest
prosthetic user satisfaction outcome studies published to
date with focus on a new interface design. In this study we
followed 38 TF amputees, comprised of household
ambulators up to high active users (K1 to K4) for 6-months.
Our observed 19% drop-out rate (9 out of 47) can be
expected in such a group over multiple data collection
intervals and 6-months’ time.40
We believe the improved user satisfaction with service is
from two factors that DS-TF enables: 1) single-visit
fabrication and delivery, and 2) that subjects feel more
“involved” in their socket fabrication. While it is possible that
baseline OPUS scores may include subject recall bias since
patients received their existing prosthesis and interfaces
months or years in the past, we believe a comparison is
informative.
As the DS-TF fabrication and delivery can usually be
completed in a single (but longer) clinic visit, DS-TF
eliminates or reduces the hassle of multiple trips to the clinic
by the amputee and family or care givers. During the current
Covid-19 pandemic, TF amputees may especially value
fewer clinic visits in order to reduce their risk of infection.
CP’s fabricate DS-TF sockets directly on the residual limb;
anecdotal subject reports indicate users enjoyed the
opportunity to be more involved in the entire process, to see
each step, to communicate with their CP and be a part of
design decisions (e.g. the position of the brim, how to
manage sensitive areas, placement of the valve, etc.).
In liquid form the two-part resin used in DS-TF fabrication
can cause injury to amputee and clinicians if handled
improperly. It is therefore critical to follow safe DS-TF
fabrication procedures using protective equipment for
clinicians and amputee which means process training and
practice of DS-TF fabrication should never be underrated.34
The current standard of care for TF interface design focuses
on the proximal aspect of the socket to achieve a stable
stance-phase connection between socket and amputee.
The proximal socket brim extends above the femur and is
intended to contain the ischial ramus, thereby preventing a
lateral shift of the socket and enhancing user stability.26 To
deliver a finished laminated TF interface of this type most
CP´s use a complicated multi-step fabrication process
including: hand casting, one or more test sockets, one or
more laminated sockets, and usually at least one post-fitting
adjustment where patient comes back to the clinic.
However, this socket design has never been described
using the ISO standard 13405-2:2015. This method is also
dependent on many years of CP experience and rarely
based on evidence and/or outcome studies.
The direct casting method used in this study is a different
concept and process, unlike most CP’s traditional
processes. The DS-TF socket is a true transfemoral socket
as no rigid part of the DS-TF socket bears load from the
ischium bone. DS-TF instead focuses on a unique way of
supporting the hip joint through the hip muscles; i.e. when
the hip muscles contract and expand during stance phase,
the DS-TF brim supports the hip muscles. The support that
the DS-TF brim provides, activates and stimulates important
hip muscle function44 to enable axial and transverse stability
during normal walking.23 These different interfaces (their
function and design) should follow standardized method
when they are described, this to enhance baseline
comparison.23
It should be noted that the cost of prosthetic provision has
been shown to be less than 10% of the total cost of an
amputation,45 with delayed rehabilitation adding consider-
able expense to the total cost.2 It has also been
demonstrated that less time between amputation and
weight bearing or ambulation therapy can both contribute to
faster restoration of the walking ability after a lower limb
amputation46 and reduce the cost of rehabilitation of these
patients.2 Using DS-TF a prosthetist can potentially reduce
the time between amputation and start of weight bearing
and physical therapy down to 6 weeks as shown in study
when using the DS-TT.13 DS-TF can be an important tool to
improve lower limb amputee outcomes and potentially
reducing the overall health care costs to society of treating
transfemoral amputees.
Limitations
Study subjects received their existing interfaces months or
years in the past. Therefore, having users complete the
OPUS on their existing socket introduces the possibility of
recall bias. Primary study limitation is not having the
amputees randomized into DS-TF (intervention) and control
(traditional interface) groups. Dividing the cohort into groups
based on “clinical need” for a new interface versus no
clinical need for a new interface was a partial mitigation of
this limitation. However, the aim of this study was to
evaluate the implementation of direct fabrication on the
amputee’s limb and to gather subject outcomes over an
extended and clinically meaningful time.
New amputees often take an extended time to adjust to the
interface, therefore we suggest that future studies would
follow new users over one year, randomized into two groups
of traditional interfaces versus DS-TF interfaces. Several
study subjects provided anecdotal reports of significantly
reduced phantom pain, therefore another potential area of
further research would be to investigate the impact of DS-
TF on phantom pain.
https://doi.org/10.33137/cpoj.v3i2.34672
11
Marable W.R, Smith C, Sigurjónsson B.Þ, Atlason I.F, Johannesson G.A. Transfemoral socket fabrication method using direct casting: outcomes regarding
patient satisfaction with device and services. Canadian Prosthetics & Orthotics Journal. 2020;Volume 3, Issue 2, No.6. https://doi.org/10.33137/cpoj.v3i2.34672
ISSN: 2561-987X TRANSFEMORAL SOCKET FABRICATION METHOD USING DIRECT CASTING
Marable et al. 2020
CPOJ
CONCLUSION
This study shows that following a standardized training and
implementation plan, the DS-TF process can be
successfully applied in caring for TF prosthetic users. The
unique DS-TF interface design yields greater user
satisfaction regarding interface function and comfort
compared to a traditional TF interface design. The novel
DS-TF interface fabrication method also yields increased
user satisfaction with the CPs’ fabrication and delivery of the
interface and prosthesis compared to the service users
received along with their previous interface.
ACKNOWLEDGEMENTS
We would like to acknowledge the CP´s who participated in the
study; J. Walker, R. Camper, J. Arnold, K. Keeling, B. Sampson, E.
Thompson, S. Parkinson, C. Smith, B. Clark and all of the
technicians involved.
DECLARATION OF CONFLICTING
INTERESTS
All authors are employees of Össur HF except I. F. Atlason. Study
Principle Investigators received no compensation from Össur HF.
AUTHOR CONTRIBUTION
• W. Russ Marable: Conceptualization; Study oversight; Data
collection; Writing original; Review and editing
• Christian Smith: Conceptualization; Data collection; Writing
original; Review and editing
• Benedikt Þorri Sigurjonsson: Conceptualization; Obtained
funding; Study oversight; Data analysis; Review and editing
• Ingi Freyr Atlason: Data analysis
• G. Anton Johannesson: Conceptualization; Study oversight;
Data analysis; Writing original; Review and editing
SOURCES OF SUPPORT
This study was financially supported by Össur HF.
ETHICAL APPROVAL
Ethical approval was obtained from Advarra® IRB (CR00128417)
and the investigation was registered at Clinical trials.gov
NCT04312724. Signed informed consent was obtained from all
participants.
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