INTERNATIONAL FORUM--Silicone Suction Socket (3S)
Versus Supracondylar PTB
Prosthesis with Pelite Liner:
Transtibial Amputees'
Preferences
A.M. Boonstra, MD, PHD
W. van Duin
W Eisma
ABSTRACT
The purpose of this article is to evaluate the preference of
transtibial amputees for the Silicone Suction Socket (3S) versus the supracondylar PTB prosthesis with pelite liner and to
explore the reasons for their preferences.
Eight patients with residual-limb problems were asked to
wear each type of prosthesis for a minimum of 10 weeks (except if no definitive 3S was made due to problems with the
trial socket) and subsequently were asked to complete questionnaires to discuss comfort, ambulation and activities of
daily life, working conditions, and sports activities with the
prostheses. Two patients did not receive a definitive 3S because they could not walk comfortably on the trial socket.
Two of the six amputees who used both socket designs
preferred the 3S, two preferred the supracondylar PTB with
pelite liner, and two were satisfied with both prostheses.
Introduction
Socket inserts commonly are made of silicone, the benefits
of which have been documented for both transfemoral (1)
and transtibial amputees (2-5). The silicone liner creates a
negative atmospheric pressure and an adhesive bond to the
skin so it moves with the tissue. While documented studies
of force measurements are lacking, friction and shear forces
are said to be lower with the silicone liner than with a gel
or leather liner (1). The silicone liner also is reported to reduce perspiration of the residual limb.
The Silicone Suction Socket (3S) for transtibial prostheses originally was introduced by Fillauer et al. (4) in the
1980s and was introduced in the Netherlands in 1990. The
3S contains an individually casted silicone liner and a laminated socket connected with a shuttle-lock mechanism. An
elaborate description of the production of the socket is given by Fillauer et al. (4).
The present study is a qualitative comparison of the 3S
and the supracondylar patellar tendon-bearing (PTB) prosthesis with pelite liner (made from a polyethylene closed-cell foam)a. The study was conducted to answer the following questions. Which of the two sockets do most transtibial
amputees prefer, and what are the main reasons for their
preference?
MethodsSubjects
Eight patients were included in the study. A ninth patient
was excluded after withdrawing during the course of the
study due to medical problems not related to the study. All
of the patients gave informed consent.
The patients were transtibial amputees living in the
northern area of the Netherlands. The authors anticipated
the liner would be most beneficial to patients with skin
problems; therefore, only patients with sores or folliculitis
were included in the study. The severity of each individual's
skin problem was indefinable because objective criteria
were lacking. However, it was mandated that the skin problems had to be present for at least two months. Five patients
complained about extreme perspiration of the skin of the
residual limb. The amputees had no other major diseases of
the lower extremities.
The mean age of the subjects was 41 years (range 24-62
years). Six participants were male, and two were female.
The mean residual-limb length, measured from the lateral
proximal end of the tibia to the distal end of the tibia, was
12.5 cm (range 11-15 cm). The maximum walking distance
before becoming involved in the study was approximately
50-500 m for three patients, approximately 0.5-2 km for
four patients and approximately 2-5 km for one patient.
Causes for amputation included trauma (five patients),
malignant tumor removal (two patients), and amputation
secondary to congenital deformity (one patient). The mean
time since amputation was 16 years (range 2-50 years). All
but one patient had been using a supracondylar PTB prosthesis with a pelite or leather socket before being included
in the study. One patient had a PTB prosthesis with pelite
socket. None had previously used silicone liners.
Prostheses
Four patients were randomly selected to walk first with the
3S, and the remaining four patients walked first with the
supracondylar PTB socket with pelite liner. About eight
weeks after the fitting of the first socket, a new mold was
made for the second prosthesis. After using the first prosthesis for at least 10 weeks, the amputees were switched to the
second prosthesis.
The authors deviated from Fillauer et al. (4)'s description
of the 3S socket by making the laminated socket of the 3S
as a supracondylar PTB socket. The PTB prosthesis with
pelite liner was made as a supracondylar, full-contact socket. The thickness of the pelite liner was 5 mm. If the patient
was unable to walk comfortably with the 3S test socket in
the lab, no definitive 3S socket was made.
Both the 3S prosthesis and the supracondylar PTB with
pelite liner were made with endoskeletal constructions. The
patients continued to wear the type of foot with which they
were familiar.
Data Collection
After having used both prostheses, each amputee was asked
which device he or she preferred. During the same assessment, each participant completed a self-administered questionnaire comprised of 34 questions comparing the two
prostheses. (Some of the questions are given in Table A
.)
The subjects were asked about comparative ambulation
(11 questions); comfort of the residual limb during walking
and standing (eight questions); standing (one question); cycling (one question); bending the knee (one question); walking on stairs, hills, grass, etc. (five questions); donning and
doffing (one question); perspiration (one question); noise
(one question); sports and leisure (two questions); housekeeping (one question); and work (one question). Each amputee also was asked the reason for his or her preference in
an open-ended question after the final assessment.
Data Analysis
Because of the small number of patients included in the
study, no statistical tests were conducted. A descriptive
analysis of the data was performed.
Results
Two patients did not receive a definitive 3S socket since
they were unable to walk comfortably on the test socket.
The traction on the residual limb resulting from the shuttlelock mechanism seemed to be the main reason for the failure of this design in these two patients. One of the two patients was not satisfied with the supracondylar PTB prosthesis with pelite liner either. After the study, she was given
a prosthesis of a different design (financed by health insurance). The other patient was satisfied with the supracondylar PTB with pelite liner.
Six patients used each of the two prostheses for at least
10 weeks. Two preferred the 3S socket. Two preferred the
supracondylar PTB with pelite liner. The remaining two reported being satisfied with both prostheses, but when asked
to choose, they showed a slight preference for the supracondylar PTB with pelite liner.
The four patients who preferred the supracondylar PTB
with pelite liner seemed to favor the device because of the
traction it provided during the swing phase. The four participants also disliked the different pressure distribution of
the 3S. Two of the patients preferring the supracondylar
PTB said they liked the ease with which this type of prosthesis is donned and doffed.
The two amputees who preferred the 3S said they preferred the close contact the device provided between the
residual limb and the socket and the feeling that the residual limb and socket were more unified.
From the questionnaires, the authors concluded the following:
- The silicone liner causes less perspiration than the
pelite liner.
- The 3S seems to feel less comfortable to the skin.
- Donning and doffing the 3S takes more time than donning and doffing the supracondylar PTB with pelite liner.
Other differences between the two types of prostheses
mentioned in the questionnaire were indicated by two amputees. In particular, differences in the prostheses' effects
on work and sports activities were not clear.
Responses to the questions mentioned in Table A are
given in Table B
.
There was not a clear correlation between the differences mentioned in the questionnaire and the patients'
preferences for one or the other socket design.
Discussion
The authors compared the silicone suction socket (3S) to
the supracondylar full-contact PTB prosthesis with pelite
liner in eight patients. The comparisons did not find one design to be superior to the other with regard to comfort and
ambulation. Some amputees cited a preference for the 3S
because of the close connection between liner and socket
resulting from the mechanisms' shuttle-lock construction
and the different pressure distribution of the 3S compared
with the PTB socket with pelite liner. But for others, these
were reasons to reject the 3S socket. The residual limb
seemed to perspire less with the silicone liner. This reduced
perspiration, however, was not cited as a reason to prefer
the 3S by any of the amputees-maybe due to the mild climate in the Netherlands. Differences in the mechanisms' effects on work and sports activities were not clear because of
the short duration of the study.
In other studies (2,5), the patients seemed to be more
satisfied with the silicone liner than the patients in this
study. This may be due to the fact that this study was a randomized clinical study in which two good fitted sockets
were compared. Another reason may be that in the studies
of Cluitmans et al. (5) and Kristinsson (2) the ICEROSS silicone liner was investigated and not the 3S as in this study.
The authors studied only the 3S silicone liner compared
with the pelite liner, and only a small number of patients
was included. Further studies of other silicone liners involving more amputees would be necessary to fully explore
the benefit of different types of liners.
Acknowledgements
This study was financially supported by "De Heyne Stichting."
A.M. BOONSTRA, MD, PHD, works in the department for rehabilitation medicine at the University Hospital Groningen, P0. Box
30.001, 9700 RB Groningen, The Netherlands.
W VAN DUIN is a prosthetists at The Orthopaedic Workshop "Noord-Nederland," The Netherlands.
W EISMA is a prosthetists at The Orthopaedic Workshop "Noord-Nederland," The Netherlands.
References:
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- Kristinsson 0. The Iceross concept: a discussion of a philosophy. Pros Orth Int 1993; 17:1:49-55.
- Wall M. Silicone BK sockets. Indication and acceptance. Proceedings of the 7th World Congress of ISPO II, June 28-July 3,
1992, Chicago; 42.
- Fillauer CE, Pritham CH, Fillauer KD. Evolution and development of the silicone suction socket (3S) for below-knee prostheses. JPO 1989; 1:2:92-103.
- Cluitmans J, Geboers M, Deckers J, Rings F Experiences
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