Technical Note: A Device to Assist in
the Alignment and Finishing of the
Syme's Prosthesis
James B. Brant, B.Sc. (H.K.),C.O.(c)
Introduction
One of the more difficult set of alignment
alterations to be performed in prosthetics
are those involving the Syme's prosthesis.
This is due to the limited space available
between the end of the stump and the prosthetic foot. A reasonable cosmetic appearance of a finished prosthesis is also desirable.
After reading the article by Robert Gilley,
C.P. (1) which dealt with the cosmetic shaping of the Syme's prosthesis, this author took
Gilley's technique a step further to provide
an alignment aid for this amputation site.
The present method for alignment of a
Syme's prosthesis requires that the attachment nut is attached inside the socket. This
method must be extremely precise to enable
the bolt to be attached without undue stress.
If the socket requires tilting during the dynamic alignment, excess stress will be created in the bolt increasing the possibility of
breakage. It is virtually impossible to shift
the socket relative to the foot without removing the plate or reconstructing the socket. The following discussion describes a technique used for bench and dynamic alignment, which allows for more versatility when
tilting and shifting the socket while at the
same time creating less stress in the ankle
bolt.
Discussion
Similar to Gilley's (1) method, the proximal portion of a Kingsley Syme's foot (catalogue #K07) is removed and sanded flush
with the wooden keel (Figure 1)
. This provides a flat surface for attachment of the nut
and wood block.
A piece of wood, 18mm thick, is cut large
enough to cover the cut surface of the Syme's
foot. The grain of the wood should run anterior-posterior to provide greater strength. A
Syme's nut is then set into the wood creating
as much surface contact between the nut and
the wood as possible (Figure 2a)
. Care
should be taken that the proximal and distal
surfaces of the attachment block are maintained flat. The nut is then secured in place
using Otto Bock's Ziegelharz` sealing resin
(Figure 2b)
. A T-nut may be used, but there
is a greater possibility of it pulling through
the wood. The larger surface area of the
Syme's nut will reduce this risk.
Once the nut has been secured to the
wood, the entire block is attached to the foot
using the bolt provided. The excess bolt is
cut flush with the proximal surface of the
block, and the wood is trimmed to allow
donning of the shoe (Figure 3)
.
The socket is fabricated in the usual manner, with the exception of not laminating the
nut within the socket. This maintains a
smooth distal surface inside the socket. The
socket is removed from the positive mold,
and the distal end is sanded flat with the
desired amount of flexion and adduction incorporated.
A second piece of 18mm-thick wood is cut,
once again ensuring the grain is running anterior-posterior. The socket is embedded in
the wood, similar to the procedure used for
the Syme's nut (Figure 4a
and Figure 4b
), and secured to the wood with sealing resin. As can
be seen in Figure 4b
, the distal end of the
socket is flush with the distal surface of the
wood. This results in the nut being virtually
attached directly to the socket with no extra
space between the socket and the nut.
Again, care should be taken to provide flat
surfaces on the distal end of the socket and
the proximal surface of the attachment plate.
The socket is placed on the foot in standard bench alignment, and secured using
two #12 wood screws 1 1/2 inches in length,
placed anterior and posterior. The prosthesis is now ready for dynamic alignment. Any
alignment changes that may be required are
performed by removing the two wood
screws, shifting or tilting the socket and then
replacing the screws.
Excessive anterior and medial shift of the
socket was performed in Figure 5a
and Figure 5b
, to
illustrate the versatility and ease of this
method. During linear shifts, the attachment
block remains stationary and the socket is
moved. If tilting is required, the socket is
removed and sanded to the desired angle,
then replaced. During dynamic alignment
changes, the bolt remains perpendicular to
the nut, thus not creating undue stress in the
bolt or nut. Any length adjustment is
achieved by grinding the proximal portion to
decrease length or by adding a piece between
the sections to increase length.
Once dynamic alignment is completed,
the two blocks are marked and the wood
screws removed. The two blocks are laminated together using Zieglharz sealing resin.
Following completion of this, the wood is
shaped to the foot and socket as with any
exoskeletal ankle block. The space around
the distal socket and wood block is filled with
foam and cosmetically shaped. Additional
foam may be used proximally about the
socket and shaped to provide a more aesthetic appearance. The prosthesis is then laminated and finished in the usual manner (Figure 6a
and Figure 6b
).
If an energy storing foot is used, the perpendicular relationship of the bolt to the
plate is of even greater importance. This reduces as much as possible the stress in the
bolt and nut and, in doing so, decreases the
chance of breakage. Figure 7
illustrates the
modification performed for the use of the
Carbon Copy II foot. The remainder of the
process is completed in the same manner as
described above. The finished product in
Figures 8a and 8b is a Syme's prosthesis using
a Silastic inner wall and a Carbon Copy II
foot.
Conclusion
The method described may require more
time during bench alignment, but the benefits attained during dynamic alignment and
with the finished product compensate for it.
This technique provides a number of advantages over the previous method of laminating the Syme's attachment nut directly into
the socket:
- An alignment aid for dynamic alignment
of a Syme's prosthesis;
- Alterations during dynamic alignment do
not create undue stress in the bolt and attachment nut;
- A smooth distal surface inside the socket;
- Bench alignment may be performed by a
technician unsupervised by a prosthetist;
and
- Improved cosmetic appearance of the finished product.
Any questions or comments may be directed to
him at Northeastern Amputee and Orthopedic
Supply Centre, 1060 Lorne Street, Sudbury, Ontario, Canada P3C 4R9, where he is currently
employed.
Acknowledgements
Many thanks to Don McLeod and Charles
Teresbessy, C.P.O.(c) for their assistance in editing this article.
James E. Brant B.Sc. (H.K.) C.0.(c) received
his honors degree in Human Kinetics from the
University of Guelph, Guelph, Ontario, Canada.
He also received a diploma in Clinical Prosthetics
and Orthotics from George Brown College, Toronto, Ontario, Canada. He obtained certification in orthotics in 1989 and is currently doing his
internship in prosthetics.
References:
- Gilley, R. Fabrication of the symes prosthesis. Clinical Prosthetics and Orthotics Winter
1987/88;12:2:41-43.
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