Prosthetics and Orthotics International, 1981, 5,129-134
The TC double socket above-knee prosthesis
K. KOIKE, Y. ISHIKURA*, S. KAKURAI and T. IMAMURA
Tokyo Metropolitan Rehabilitation Center for the Physically and Mentally Handicapped, Japan
*lshikura Prosthesis Manufacturing Co. Ltd, Tokyo, Japan.
The conventional total contact suction AK
prosthesis presents several disadvantages, such
as difficulty in wearing the socket in a sitting
position, difficulty in obtaining a favourable
disposition of the stump soft tissues in the socket
and difficulty in avoiding stump perspiration
problems. In an attempt
disadvantages, a new AK prosthesis with a
thermoplastic double socket was developed at
the Tokyo Metropolitan Rehabilitation Center
for the Physically and Mentally Handicapped.
The double socket is composed of an external
socket attached to the lower parts and a
detachable internal socket, and appears to solve
all the disadvantages
prosthesis. This prosthesis is called the TC
prosthesis, an abbreviation for the
Metropolitan Rehabilitation Center. The first
model of this prosthesis, (TC-1) has a metal
valve. A new rubber sheet valve was developed
to solve several disadvantages of the metal valve
in the TC-2 prosthesis. Since November 1978 the
TC-1 has been fitted to 295 AK amputees,
including 9 bilateral AK amputees, and since
March 1980, 145 AK amputees have received the
TC-2, including 6
Satisfactory results have been obtained with
to solve these
of the conventional
Since the suction socket AK prosthesis was
first patented by Dubois Parmelee of New York
in 1863, improvements have resulted from the
contributions by specialists in various countries.
A practical suction socket was developed in
Germany at the beginning of World War II,
however, use of this prosthesis was limited to
Germany until the end of the war. Since 1945 use
of the suction socket has spread throughout the
world (Thorndike, 1949). Although the suction
socket AK prosthesis did not need additional
suspension aids, it led to stump oedema caused
by the negative pressure in the interspace
between the stump and the socket. To solve this
problem, the total contact suction socket was
developed by Kuhn in 1962.
The value of the modern total contact suction
socket is well-known throughout the world.
However, the total contact suction socket still
has the following disadvantages:
1. difficulty in wearing the socket in a sitting
2. difficulty in obtaining
disposition of the stump soft tissues in the
3. difficulty in avoiding stump perspiration
4. difficulty in modifying the socket shape
according to the changes of the stump
5. difficulty in obtaining a comfortable fit
Many improvements have been made to
overcome these disadvantages. For instance,
Sinclair (1969) devised a new double socket
suction prosthesis which was composed of a rigid
polyester socket with various cut-outs and a
detachable flexible silicon liner socket. It was
hoped that geriatric amputees with heart disease
could wear this prosthesis in a sitting position,
but it did not work as well as had been hoped. A
bathing is produced by the Otto Bock Company.
The double socket cannot be separated and has
no substantial changes from
A transparent polycarbonate socket
introduced by Mooney (1972) and a lightweight
adjustable socket was developed by Irons
(1977). However, an improved prosthesis which
socket prosthesis for
All correspondence to be addressed to Katsuaki
Koike, Tokyo Metropolitan Rehabilitation Center for
the Physically and Mentally Handicapped, 3-17-2
Toyama, Shinjuku-ku, Tokyo 162, Japan.
K. Koike, Y. Ishikura, S. Kakurai and T. lmamura
solves all the disadvantages described above has
yet to appear.
The TC-1 prosthesis
Since the disadvantages listed above are
caused mainly by the properties of the socket
itself, a new AK prosthesis was devised with a
double socket. This new type of AK prosthesis is
called the TC-1 (Fig. 1 left), an abbreviation for
the Tokyo Metropolitan Rehabilitation Center
Type-1 (Koike, 1979).
The double socket is composed of both an
internal and an external socket. The external
socket is attached directly to the metal plate on
top of the lower part of the prosthesis by four
bolts without using a wooden block as is
normally used in the conventional total contact
suction prosthesis (Fig. 1 right). The external
socket is constructed to have enough area to
maintain sufficient contact with the internal
socket and also to have enough space to hold the
perspiration coming down through the valve of
the internal socket.
The metal screw valve is attached at the
bottom central portion of the internal socket
(Fig. 2, top).
The two sockets (Fig. 2, bottom) can be
attached and detached quite easily by means of a
Velcro strap at the outer lateral wall of the
external socket pulled through a " D " ring at the
lateral upper edge of the internal socket. A low
density polyethylene sheet is used for the
internal socket and a low density polypropylene
sheet is used for the external socket. To
materials and manufacturing
manufacture the internal socket a polyethylene
sheet, 500 mm square and 10 mm thick, is
softened in an oven and then draped over a
prepared positive model. It is moulded over the
cast by means of vacuum-forming
1974). To make the
polypropylene sheet, 500 mm square 3 mm thick,
is softened by heat and then placed cylindrically
around the internal socket after an appropriate
amount of plaster has been placed over its
bottom part. It is welded at both
(Donaldson, 1977). The thickness of the
polypropylene sheet can be changed according
to the amputee's weight. A middle density
polyethylene sheet can also be used to simplify
the welding process.
socket external a
1. Because of the reduced weight and ease in
handling the internal socket, donning is
easy in a standing or sitting position (Fig. 3,
left). The wearer can easily insert his stump
into the internal socket and then into the
external socket in one pushing motion (Fig.
3, right). Donning the TC-1 is completed
by attaching both sockets together with the
Velcro strap. Wearers of the conventional
of the TC-1 prosthesis:
Fig. 1. Left, the TC-1 prosthesis. Right, section
through the double socket.
Fig. 2. Top, position of the valve. Bottom, internal
socket with D ring and external socket with Velcro
The TC double socket
total contact AK prosthesis
experience the socket slipping off the
stump while in a sitting position because
the suction cannot
However, with the TC-1, flexibility of the
internal socket allows the stump to
maintain close contact with the socket at all
times. The external socket can be shifted
while sitting for long periods, hence sitting
tolerance is markedly
internal socket is also used as a stump
shrinker while the wearer is sleeping.
2. Distortion of the remaining muscles and
other soft tissues, which could be the cause
of abnormal gait patterns, is prevented in
the TC-1 because the valve is set at the
bottom central portion of the internal
socket. This provides
disposition of all the soft tissues along the
socket axis and ease in pulling out the cloth
from the stump.
3. Slipping off during the swing phase, sweat
stains on clothing, and problems hindering
the proper functioning of the knee joint
mechanism due to perspiration are solved
to a great degree by the double socket
system and the position of the valve with
4. Changes in contour and circumference of
the stump are easily accommodated as the
shapes of both sockets can be modified
easily with heat application even in a
training room. The same prosthesis can be
used therefore, from the first day until the
last day of the training programme.
5. Wearing the TC-1 is comfortable because
pressure between the stump and the well-
contoured and flexible sockets of the TC-1
is equally distributed.
6. Adequate contact area of the stump to the
internal socket and adequate contact area
between the two sockets can be observed
through the semi-transparent
of the sockets without an X-ray exam
7. The cost of the prosthesis is reasonable
because the manufacturing procedures are
not complicated and mass production of
the sockets is possible.
The TC-2 prosthesis
The metal valves of the TC-1 are not without
some problems. Sometimes injury to the stump
skin occurs while screwing the valve into the
socket. At other times there is difficulty in
maintaining total contact
protrusion exists on the end of the stump. The
valve's thickness can also create problems at
times. In an attempt to solve these problems a
new rubber sheet valve was developed. The
thermoplastic base containing the valve hole is
welded to the bottom central portion of the
internal socket (Fig. 4, top). The valve hole is
then covered by a thin sheet of rubber which is
held in place by a screw on the posterior side and
when a bony
Fig. 3. Left, donning the internal socket in a sitting
position. Right, the internal socket in position prior to
donning the complete prosthesis.
Fig. 4. Top thermoplastic base with valve hole of the
TC-2 prosthesis. Bottom, the rubber sheet valve.
K. Koike, Y. Ishikura, S. Kakurai and T. Imamura
a hook on the anterior side (Fig. 4, bottom). The
prosthesis using this new rubber sheet valve is
known as the TC-2.
1. As the rubber sheet valve does not have a
metal base, the dimensions of the valve
hole can be made larger than those of the
metal valve (Fig. 5, top). Consequently,
pulling out the cloth from the stump and
allowing the perspiration to leave the
internal socket become much easier.
2. The thickness of the rubber sheet valve is
less than 1/3 of that of the metal valve (Fig.
5, bottom) so lowering the knee joint can
be minimized in
3. The shape of the valve hole can be changed
according to the condition of each stump
(Fig. 6, top).
4. Since this valve does not cause pain, total
contact between the stump and the socket
can be maintained even in cases with bony
protrusions (Fig. 6, bottom).
5. The rubber sheet valve does not injure the
stump skin and can be easily attached.
6. The TC-2 is much more comfortable to
wear (Fig. 7).
of the TC-2 prosthesis
the case of knee
7. The cost of the rubber sheet valve is far less
than the metal valve.
Various disadvantages of the conventional
total contact suction prosthesis are caused
mainly by the hard single socket made of
thermosetting plastics or wood. Great efforts
have been continuously made to solve the
disadvantages by many
A new total contact suction socket was devised
by Sinclair (1969). This prosthesis was composed
of a rigid socket with variously located cutouts
and a detachable flexible liner socket. The liner
socket was made of RTV silicon and the valve
was located at the same position as the ordinary
socket. Although this prosthesis was aimed at
making it possible for geriatric AK amputees
with heart disease to wear the suction socket in a
sitting position, it resulted in failure. This failure
might have been caused by the excessive
flexibility of the detachable liner socket and the
position of the valve.
A double socket AK prosthesis made of
polymethylmethacrylate is produced for bathing
by the Otto Bock Company. All components
in the medical
Fig. 5. Top, the TC-2 valve hole can be made larger
than that for the metal valve. Bottom, the rubber sheet
valve is 1/3 the thickness of the metal valve.
Fig. 6. Top. the shape of the valve hole may be altered
to accommodate the stump condition. Bottom, TC-2
internal socket shown on amputee.
The TC double socket
except the foot of this prosthesis, including the
knee joint, are fabricated
methacrylate. The internal socket cannot be
removed from the prosthesis and is rigid. While
the wearer of this prosthesis can stand in a pool
or shower room, the prosthesis cannot withstand
the heavy duty required for daily living. The
socket can be modified partially with heat
application but cannot be modified over the
entire socket surface to accommodate a greatly
changed circumference of the stump.
The TC prosthesis can be donned in a sitting
position because the
detachable from the prosthesis and the valve is
attached to the bottom central portion of the
The internal socket of the TC prosthesis is not
affected in any way while pulling out the cloth
from the stump because the strength and
flexibility of polyethylene socket are adequate.
This is very convenient, especially for bilateral
amputees and geriatric amputees.
A lightweight adjustable AK prosthesis made
of polypropylene was developed for geriatric
amputees by Irons (1977). This prosthesis cannot
be used for heavy duty and its production is
internal socket is
rather complex and requires considerable time.
On the other hand, the TC prosthesis is simple to
produce, requires little time and is very light.
The lightest TC prosthesis is 2 1 kg and is
being worn with ease by a seventy-four year old
man with a mid thigh amputation.
The transparent polycarbonate socket was
introduced by Mooney (1972). Although the
transparent polycarbonate socket is useful in
checking socket fitting, it takes a long time to
produce and is difficult to modify. The socket
fitting of the polyethylene socket of the TC
prosthesis can be observed through the semi-
transparent material of the internal socket.
The TC prosthesis
thermoplastic sockets in themselves are lighter
than the polyester socket and can be attached
directly without a wooden block. Due to the
reduced weight of the thigh part of the TC
prosthesis and a favourable disposition of all the
stump soft tissues in the socket because of the
valve position at the bottom central portion, a
functional pendulum motion of the shank is
achieved and favourable gait patterns have been
observed in many TC wearers from the first day
The overcoming of the stump perspiration
problems should be a boon to people living in
The concept of socket fitting which requires
exactness of the socket shape and dimensions to
the stump should change by the development
and use of the flexible socket.
The strength and durability of the
prosthesis have been demonstrated by the fact
that some of the younger amputees using it are
able to play baseball and to ski.
is lighter than the
Since November 1978, 295 AK amputees,
including 9 bilateral AK amputees, have been
fitted with TC-1 prostheses.
advantages of the TC prostheses have been
demonstrated as described above. The durability
of the TC-1 prosthesis has been proved by the
fact that none of the 295 TC-l's have been
broken in use. Since March 1980, the TC-2
prosthesis has been applied to 145 amputees,
including 6 bilateral amputees, and satisfactory
results have been obtained.
Fig. 7. The prosthesis in use.