U.S. patent application number 10/327070 was filed with the patent office on 2003-05-29 for prosthesis and method therefor.
This patent application is currently assigned to Rothschild's Orthopedics, Inc.. Invention is credited to Fox, John R., Rothschild, Kelly A., Rothschild, Russell J., Rothschild, Vernon R..
Application Number | 20030097746 10/327070 |
Document ID | / |
Family ID | 24819974 |
Filed Date | 2003-05-29 |
United States Patent
Application |
20030097746 |
Kind Code |
A1 |
Rothschild, Vernon R. ; et
al. |
May 29, 2003 |
Prosthesis and method therefor
Abstract
Improved prosthetic components and a method for assembly
therefor are described wherein the prosthesis comprises
prefabricated modular components including a socket adapter, shank
or pylon, a keel, and a foot. The method for preparation of the
improved prosthesis reduces the time required for prosthesis
preparation over that of the prior art, and includes the steps of
making a cast of the remaining leg stump and forming a socket
therefor; placing the socket in an alignment jig; assembling
modular pieces including a prefabricated keel, pylon, and socket
adapter; attaching the socket adapter to the socket; draping a
final coating of copolymer on the prosthesis; and removing the
pylon and socket adapter from the interior of the prosthesis.
Inventors: |
Rothschild, Vernon R.;
(Berlin, MD) ; Fox, John R.; (Trappe, MD) ;
Rothschild, Russell J.; (Chester, MD) ; Rothschild,
Kelly A.; (Berlin, MD) |
Correspondence
Address: |
NIXON PEABODY, LLP
8180 GREENSBORO DRIVE
SUITE 800
MCLEAN
VA
22102
US
|
Assignee: |
Rothschild's Orthopedics,
Inc.
Salisbury
MD
|
Family ID: |
24819974 |
Appl. No.: |
10/327070 |
Filed: |
December 24, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10327070 |
Dec 24, 2002 |
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09702131 |
Oct 31, 2000 |
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6497028 |
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Current U.S.
Class: |
29/460 |
Current CPC
Class: |
Y10T 29/49796 20150115;
A61F 2002/5001 20130101; A61F 2/60 20130101; A61F 2/5046 20130101;
Y10T 29/4981 20150115; Y10T 29/49888 20150115; A61F 2002/5053
20130101 |
Class at
Publication: |
29/460 |
International
Class: |
B23P 019/04 |
Claims
What is claimed is:
1. A method for constructing a prosthesis for placement on a
remaining stump of a human limb, comprising the steps of: making a
cast of the remaining stump and forming a socket therefor;
selecting appropriate prefabricated modular components including at
least a keel, a pylon, and a socket adapter; assembling said
prefabricated components; adjusting a relative angle between said
socket and said keel; attaching said socket adapter to said socket;
draping a coating of copolymer over said assembled keel, pylon,
socket adapter, and socket; and removing substantially all of said
pylon and socket adapter from an interior of said coating of
copolymer.
Description
FIELD OF THE INVENTION
[0001] This invention is directed to artificial prosthetic
components and assembly methods therefor for use in a human lower
limb prosthesis. More particularly, this invention is directed to
improved human prostheses and methods therefor wherein the
prosthesis comprises modular prefabricated components.
DESCRIPTION OF RELATED ART
[0002] The most common artificial leg for below knee amputees is of
a rigid nature. A solid shank connects the socket, which mounts the
artificial leg to the residual limb of the amputee, and the
artificial foot. The shank is often made out of a rigid alloy, such
as one containing titanium, or from shaped wood or plastic. It can
be solid for strength, or it can be hollow for lightness.
[0003] In a typical conventional prosthesis fabrication technique,
a significant amount of time and effort is wasted in duplicating
fabrication steps. Generally, conventional fabrication includes
taking a cast of the patient's stump and making a socket
incorporating the necessary fittings, including (a) an alignment
fitting for angular adjustments; (b) a tubular fitting for length
and rotational adjustment; (c) a fitting for linear adjustments;
and (d) an ankle fitting for angular adjustments and to allow
attachment of a foot. The prosthesis is assembled for bench
alignment and the patient is scheduled for dynamic alignment. When
the patient and prosthesis are satisfied with both the fit of the
socket and the alignment of the prosthesis, the prosthesis is
duplicated in an alignment device that captures the prosthetic
alignment and allows removal of the metal components and replacing
them with polyurethane. The area between the top of the keel and
the bottom of the socket is foamed in place, and when the foam
hardens, the shank is hand shaped to the desired configuration
between the keel and the socket. The prosthesis is prepared for the
final draping of copolymer plastic. If the finished prosthesis is
not satisfactory and can not be adjusted, the process is repeated
using the same components. The approximate fabrication time for
this procedure is 5 to 8 hours.
[0004] As an example, U.S. Pat. No. 4,314,398 discloses a method of
making a lower leg prosthesis comprising the steps of (a) forming a
temporary prosthesis socket having an inner shape corresponding to
the remaining lower leg stump of the amputee to which the
prosthesis is to be attached; (b) forming a test prosthesis by
fixing an adjustable position testing device to the temporary
socket and connecting the testing device to the prosthesis foot
through a temporary connecting member; (c) testing the test
prosthesis on the patient and adjusting the testing device so as to
obtain a proper alignment of the temporary socket in relation to
the prosthesis foot; (d) providing a positive prosthesis socket in
the temporary socket of the test prosthesis and reproducibly fixing
the assembly comprised of the positive socket, the temporary
socket, the testing device and at least the temporary connecting
member in a support device; (e) removing the test prosthesis parts
from the support device; (f) placing the connecting member adjacent
the positive socket in the support device in the aligned relative
position reproducibly set in the support device in step (d); and
(g) forming the prosthesis socket on the positive socket while
simultaneously securing the connecting member to the prosthesis
socket in the aligned relationship thereby obtaining an
individually aligned lower leg prosthesis. However, the method
associated with this reference requires duplicating assembly steps;
i.e., fixing the adjustable position testing device to a temporary
socket and temporarily connecting this device to the prosthesis
foot, followed by removing the test prosthesis and replacing it
with a permanent member in the position formerly occupied by the
testing device.
[0005] U.S. Pat. No. 5,152,800 discloses a below the knee
prosthesis and method for making the same. The prosthesis includes
a socket for receiving the stump of the below-the-knee amputee, a
keel having a peripheral groove formed about the periphery of a
bottom portion of the keel, a tubular shin member extending from
the socket and surrounding lateral and medial portions of the keel
and filling the peripheral grooves formed about the bottom portion
of the keel leaving a substantial portion of the bottom of the keel
exposed. A resilient foot member is then secured to the exposed
portion of the keel with the material of the tubular shin member
being formed into the grooves of the keel and maintaining such keel
within the shin member. The method thereof includes the steps of
forming a socket for receiving a stump of the below-the-knee
amputee; constructing a shin support about the socket including an
ankle block and keel about the socket in accordance with the size
and stature of the amputee; forming a retaining means in a bottom
surface of the keel for retaining the keel in a predetermined
position with respect to the socket; molding a sheet of copolymer
material about the shin support, into the retaining means and over
the bottom surface of the keel to form a shin member; removing the
copolymer material from the bottom surface of the keel; removing a
substantial portion of material used to construct the shin support
from within the shin member; and securing a foot member to the
keel. The method for assembly of this device does not take
advantage of a prefabricated socket adapter/pylon/keel assembly,
instead requiring several distinct steps for assembling the
prosthesis including assembling a shin support between the socket
adapter and the keel, foaming the support, draping a copolymer
exterior on the assembly, and drilling out the foam shin
support.
[0006] The prior art also includes continuous one-piece prostheses,
such as that shown in U.S. Pat. No. 5,219,364. That prosthesis
offers the advantages of light weight and improved energy storage
and release characteristics. Because of its design, however, this
prosthesis can require multiple patient trips to the prosthetist
for fitting. In certain cases the patient may have to be fitted
with another prosthesis which will be adjusted for various
parameters, including height, pylon length, inversion, and
eversion. Once the prosthesis is adjusted, the measurements from
the adjusted prosthesis are then used to form the one-piece
prosthesis, following a time consuming process. Further, once the
prosthesis is manufactured, adjustments may require reheating and
reforming the prosthesis.
[0007] U.S. Pat. No. 5,993,487 discloses a prosthetic component for
use in a human lower limb prosthesis. The component consists of an
preformed integrated pylon-keel or foot component. In practice, the
prosthetist would perform a stump measurement on the amputee to
determine the overall height of the prosthesis from which the pylon
length could be determined, then cut a preformed integrated pylon
keel prosthesis to fit the pylon to an adjustable tube clamp,
whereby the clamp itself is secured to the socket. Then the
prosthetist adjusts the tube clamp for inversion eversion, foot
position, and rotation, then the integrated pylon/keel is attached
to the tube clamp and the apparatus is covered with plastic.
However, this is not a complete prosthesis, but merely the
pylon/keel assembly. Further, the invention requires the use of an
adjustable tube clamp attached to the socket. This additional
component adds complexity and weight to the structure. Moreover,
because the keel and pylon are an integrated unit, an inventory
that could allow for the naturally occurring variety of needed keel
sizes and pylon lengths would require an extremely large assortment
of integrated keel/pylon units.
[0008] It would be advantageous to provide an improved method and
prosthesis therefor that avoids the problems associated with the
prior art. It would further be advantageous to provide a
lightweight modular prosthesis and a method of assembly therefor
that can be assembled in a single sequence of steps, maximizing
simplicity and minimizing the time expended by the wearer in
achieving an acceptable fit.
SUMMARY OF THE INVENTION
[0009] The difficulties associated with the prior art are overcome
by providing an improved prosthetic component and method for
assembly wherein the prosthesis comprises prefabricated modular
components including a socket adapter, shank or pylon, a keel, and
a foot. The method for preparation of the improved prosthesis
reduces the time required for prosthesis preparation over that of
the prior art, and includes the steps of making a cast of the
remaining leg stump and forming a socket therefor; placing the
socket in an alignment jig; selecting and assembling a
prefabricated keel, pylon, and socket adapter; shaping the socket
adapter to a desired configuration; attaching the socket adapter to
the socket; draping a final coating of copolymer on the interior
pieces, and removing the pylon and socket adapter. There is a
single method of adjustment of the prosthesis, which is
accomplished by presetting the position of the foot prior to
attaching the socket adapter/pylon/keel to the socket. The
connecting face of the socket adapter is shaped to incorporate the
proper alignment between the socket and the keel, and the length of
the pylon is selected to provide the proper length of the
prosthesis. The approximate fabrication time for this method is
less than one hour, which is a substantial time savings per unit.
Because of the reduced preparation time, should the prosthesis
prove unsatisfactory, which is common in prosthesis manufacturing,
making another prosthesis results in much less wasted man
hours.
[0010] A solid cast of the residual stump is made in a standard
method. When making this cast, a hollow tube or pipe is put in the
cast, which provides a basis for vacuum forming a polymer socket
over the cast. The socket is allowed to cool and harden, and the
plaster is removed. After this, another pipe is held in a correct
position in the socket, and a new cast is poured using the socket
as a mold.
[0011] The socket is supported by the pipe and set up in a support
jig until proper orientation is achieved. This can be achieved by
aligning and bending the metal pipe to a proper orientation. After
this, the appropriate keel, pylon, and socket adapter are selected
and assembled under the properly oriented socket. The components
are glued to each other, and the assembled keel/pylon/socket
adapter is then placed in the correct orientation to the socket and
bonded to the socket using rigid foam.
[0012] The unit is then removed from the alignment jig, and a
majority of the socket is cut away from the cast. The cast then
receives any desired modifications. The final coating of copolymer
is then applied to the unit, shaped, and allowed to cool and
harden. After this step, the pylon, socket adapter, and socket are
removed from the shell, and the socket is then returned to the
shell and secured. The foot is then glued to the keel.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] The detailed description is best understood by reference to
the following figures, in which:
[0014] FIG. 1 is a side elevational view of a typical lower leg
prosthesis;
[0015] FIG. 2 is a side elevational view of a semi-completed
prosthesis, including intermediate components used in an embodiment
of a method of the present invention;
[0016] FIG. 3 is side view of a pylon according to an embodiment of
the present invention;
[0017] FIG. 4 is a side elevational view of a semi-completed
prosthesis, including intermediate components used in an embodiment
of a method of the present invention;
[0018] FIG. 5 is side elevational view of a nearly completed
prosthesis, including intermediate components used in an embodiment
of a method of the present invention;
DETAILED DESCRIPTION OF THE INVENTION
[0019] Referring first to FIG. 1, a prosthetic device 100 is
illustrated. The preferred prosthetic device is designed to
replicate certain functional aspects of the human leg, especially
for lower limb amputees. The prosthetic device 100 is configured to
fit over a residual stump 105 of a limb. The preferred adaptation
is with a socket 110, which is made to ultimately conform to the
shape of the stump 105. At the lower end, the keel 115 replicates
the structure of the foot, and generally has a foot prosthesis 120
of suitable shape attached to further imitate the appearance and
functional characteristics of a human foot. The shank 125 of the
prosthesis is a generally vertical component functioning to
transmit forces between the residual limb, or stump, of the amputee
and the keel 105.
[0020] During the fabrication of a prosthetic device, intermediate
components are needed prior to the final draping, or drop, of the
exterior of a prosthesis. FIG. 2 is a side elevational view of
intermediate components used in an embodiment of a method of the
present invention. In this view, the keel 115 and foot 120 portions
are already assembled together. Projecting from the keel 115 is a
pylon 205, which longitudinally fixes the keel from the socket 110.
Topping the pylon 205 is a socket adapter 210, which adapts the
pylon 205 to the socket 110. The socket 110 is made to conform to
the residual stump 105 of the patient. This socket 110 is also
referred to as a cup, which becomes more apparent toward the end of
the assembly procedure when it is trimmed to height of only a few
inches. This socket 110 will be removed from the interior of the
prosthesis 100 at the same time as the pylon 205 and socket adapter
210, but it will be replaced and secured in the prosthesis 100
following removal of the pylon 205 and socket adapter 210.
[0021] The pylon 205 is shown with a square cross section, but any
cross section that provides suitable strength may be used.
Additionally, the pylon 205 can be hollow or solid. However, since
one of the benefits of this invention is to enhance ease and speed
of assembly, the shape should be that which enables simple
fabrication and handling of the pylon 205.
[0022] In FIG. 3, the pylon is shown in isolation. It is shown with
a square cross section, which facilitates production. The diameter
of the pylon is sized to fit inside the shank of the prosthesis,
preferably on the order of approximately one inch. One end 305 of
the pylon 205 is smaller than the general diameter of the pylon,
approximately 7/8 inch, so that it can fit into a similarly sized
female hole in the keel 115. The opposite end 310 is not so sized,
and therefore may fit into an approximate one inch female hole in
the socket adapter 210, and may be cut down in length without
affecting its fit. FIG. 4 shows the reduced end 305 and the
opposite end 310 of the pylon in an assembled position between the
socket adapter 210 and the keel 115.
[0023] A complete method according to an embodiment of the present
invention for production of a prosthesis is hereinafter
described.
[0024] Cast Preparation for Initial Drop
[0025] An exterior negative cast of the stump is made in any
standard manner. This can be accomplished by surrounding the stump
with plaster of Paris, allowing the mold to dry, and carefully
removing the negative mold from the stump. This negative mold is
then filled with plaster to create a mold of the stump. A hollow
metal pipe, which will be the primary conduit for applying vacuum
for the initial drop, is placed in the plaster extending outward.
After drying, the exterior negative mold is removed, leaving a
positive cast of the stump with the hollow pipe extending
therefrom.
[0026] Two small holes are drilled in the pipe within 1.5 inches
from top of the cast. The holes are then covered with screen to
allow air evacuation, and to prevent the later-applied plastic from
sealing off the holes. The top of the cast is covered with Dacron
felt adhered with spray adhesive. The cast is placed in a vise and
a vacuum hose is connected to the pipe. At this point, the
popliteal should be faced down towards the floor.
[0027] Preferably, 1/8-inch thick copolymer plastic is used to
fabricate the socket 110, which is shown in FIG. 2. Copolymer of
natural or any flesh tone color can be used for this socket as long
as is consistent with between 90/10 and 93/7 ratio of polypropylene
and polyethylene.
[0028] A plastic sheet is cut to a width six inches greater than
the circumference of stump, and a length of six inches longer than
the length of the socket. The plastic is cleaned and deburred, and
aligning marks made on the center of bottom and top of plastic with
a marker, which will aid in centering the plastic over the cast
when molding.
[0029] The plastic is then placed in an oven at an appropriate
temperature to render it pliable. This will vary depending on the
particular plastic composition, but is generally around 400.degree.
F. The required heating time will vary according to thickness of
the plastic, but will generally be between 8-24 minutes.
Immediately prior to removal of the plastic from the oven, nylon
knee high panty hose material is saturated with silicone oil and
pulled over the cast with the seam placed laterally to medially on
the distal end. The nylon stocking functions to maintain air
passages along the surface of the cast. These air passages reduce
the chances of bubbles forming in the socket by pockets of air
trapped between the copolymer sheet and the mandrel assembly and
hence allow a more definite conformance of the copolymer sheet to
the cast. Further, the nylon stocking aids in removing the socket
from the cast. The plastic is removed from the oven when
appropriate and is aligned over the center of the cast using the
previously made marks. The plastic is carefully draped while
avoiding any stretching or drooping, and is manually sealed around
the cast and pipe to ensure tightness of the vacuum, which should
be pulling between 10 and 20 pounds of pressure. The seam of the
plastic is trimmed 1/4-inch and the distal end of the seam is
rolled with a 1-inch dowel rod for a smoother distal end cap.
[0030] The plastic is allowed to cool for approximately 15 minutes
and is then removed from the cast using the following method. The
plastic is cut with a cast saw around the entire superior edge of
the socket. The socket is then removed from the cast by either
blowing it off or by the conventional method of breaking out the
cast. Socket removal by air pressure is preferred for casts conical
in shape and without prominent undercuts. For this method, a small
hole is drilled through the distal end of the socket and liner. The
positive model is secured in a vise, and a nozzle of an air pistol
is placed against the hole. When pressure is applied, the socket
should pop off the cast. Tapping of the superior rim of the socket
with a hammer against a block of wood may be used in stubborn
cases.
[0031] The proximal edge of the socket is trimmed flat, and the
distal end of socket is then prepared for foaming by using a router
to roughen the area that will be contacting the socket adapter.
[0032] Pouring the Socket
[0033] The inside of the socket, which will now function as a mold
for another plaster cast, is lightly powdered. Marks are made mid
line on the lateral side of the socket and mid line on the
posterior aspect of socket.
[0034] A hollow metal pipe is positioned to extend to at least 16
inches from the top of the socket. The socket is positioned to be
filled vertically on a level surface in 1 degree of flexion (the
crest of the tibia is the guideline for this). The pipe is centered
in the socket and aligned to the center lateral and posterior lines
previously marked on the socket. The pipe should also be positioned
in the center of the socket as well as being perpendicular to the
flat surface that the socket is on. A small level may be used to
achieve this. The new plaster cast is slowly poured, maintaining
the pipe position, and allowed to set up.
[0035] Aligning Socket in Vertical Jig
[0036] A collar is temporarily placed on the pipe approximately
three inches from the top. The socket is placed in a vertical jig
and checked for alignment so that the socket's popliteal area is
parallel to the line of progression. At this point, if the
abduction or adduction is not correct the pipe is bent until
corrected, then the unit is remounted in the jig. It is important
to make adjustments one at a time until the correct alignment is
achieved.
[0037] The center of the patella tendon is marked on the socket so
that the patella tendon line is the same height to the base of the
vertical jig as the anatomical height of the patella tendon
recorded from the patient's sound extremity. The distance from the
bottom of the socket to the base of the vertical jig is measured,
and this number minus one inch is recorded.
[0038] Assembling the Components
[0039] The foot is placed on a 1/2-inch heel wedge directly under
the socket, which is being held in the jig. The keel is inserted
into the foot so that the alignment square on foot is in the square
hole in keel. The pylon is then inserted into the keel, and the
socket adapter placed over the other end of the pylon.
[0040] When the components are assembled but not yet glued, the
length of the prosthesis from the bottom of the foot as it stands
on the bench to the top of the socket adapter is measured. The
previously recorded measurement taken from bottom of the socket to
the base of vertical jig is subtracted from the prosthesis length.
The remainder is cut off the length of the top of the pylon after
removing the socket adapter. The components are reassembled and
placed under the socket on the vertical jig base with the 1/2-inch
heel wedge in place. At this point, there should be approximately
1/4 inch between the bottom of the socket and the inside of the
socket adapter.
[0041] The components are disassembled and both ends of the pylon
are lightly sanded where they fit into the keel and socket adapter.
The inside of the well on the socket adapter is roughed up with a
cone on the router, which will ensure good bonding between the
distal end of the socket and the inside of the socket adapter. A
small amount of 10-minute epoxy is used to bond keel and socket
adapter to the pylon.
[0042] Aligning and Attaching Assembled Components to the
Socket
[0043] The assembled components are placed under the socket with
the 1/2-inch heel wedge in place. The foot is then turned to
achieve correct toe out. The mid center lateral line is aligned so
it is in alignment to the point where the lateral corner of the
keel and pylon meet. A ruler or plumb line are helpful in this
regard. The posterior mid line previously marked on the socket is
aligned so that the point where the pylon inserts into the keel is
1/2 inch medially to the socket. This should be done while still
maintaining the correct toe out.
[0044] Bonding the Components to the Socket
[0045] After alignment is achieved, the foot is secured and a small
amount of rigid foam is slowly poured into the well of the socket
pylon adapter. The foot should not be released until the foam
starts to solidify. The foam should be allowed to harden before
moving the unit.
[0046] Preparing for Final Drop
[0047] The prosthesis is removed from the vertical alignment jig.
The area where the plastic socket begins an inward flair on the
distal end is located; some foam might have to be removed to find
this point. On each of the medial and lateral sides a dowel hole is
drilled at a 45-degree angle through the plastic into the cast
approximately one to two inches in depth.
[0048] The socket is then split medially using the cast saw to
remove the socket from the cast. Sometimes a lateral split is
needed as well. The socket should not be cut within one inch of the
dowel holes.
[0049] At this time the semi-completed prosthesis can be checked on
a level surface, with the heel wedge in place or in the shoe. If
changes are needed, the pylon is heated and manipulated as
necessary. If linear changes are required the pylon can be cut
(usually at the thickest part of the socket adapter), moved as
necessary and rebonded with 10-minute epoxy.
[0050] Preparing Distal End and Finalizing
[0051] A cast saw is used to cut through entire socket, at the
distal end approximately 1/4 inch above the dowel holes. The part
of the socket that remains is referred to as a cap. The outer edge
of the cap is then sanded to a thickness of {fraction (1/32)} inch
at its proximal edge. Two 5-inch dowels ({fraction (3/16)}-inch
diameter) are cut and one end of each is sharpened to a point in,
for example, a pencil sharpener. With the cap replaced on the cast,
the holes are aligned and the dowels can be gently tapped through
the cap into the cast until they bottom out. The dowels are cut
flush and the ends mushroomed to hold the prosthesis on the
cast.
[0052] At this time the cast above the distal end cap may be
modified as needed, for example, for fibula head relief or distal
tibia.
[0053] FIG. 4 shows a semi-completed prosthesis that has been
prepared for the final drop. The plaster cast 405 is clearly
visible in the cap or socket 110, which has been cut down according
to the above steps.
[0054] The cast is placed in a horizontal position and plaster is
used to smooth any irregularities and transitions in the foam. The
plaster should be allowed to dry before lightly sanding.
[0055] Preparation for vacuum forming includes drilling two small
holes in the pipe as close to the top of the cast as possible.
These holes are covered with two layers of sanding screen and taped
in place. For the final drop, {fraction (3/16)}-inch plastic is cut
to the following measurements: top width=circumference+6 inches;
bottom width=15 inches; length=prosthesis length+6 inches.
[0056] The plastic is cleaned and deburred and the center of the
top and bottom are marked to assist in centering plastic during the
drop.
[0057] To assist the eventual removal of the inner foam core, the
following procedure is used. Using clean dry panty hose, the toe is
tied in a knot and the excess is cut away. The panty hose is placed
over a model with the knot kept in the center portion of the
proximal keel. Once in place a piece of aluminum foil large enough
to encircle the pylon from just below the top of the cap to within
1 inch of the base of the keel is pressed around the pylon and the
excess removed. Over this is placed another nylon in the same
manner as above. A plastic bag is pulled over the entire model and
vacuum applied. This assists in removal of wrinkles from the foil.
The bag is then removed.
[0058] A small indentation in the center lower portion of the base
of the keel is created using an awl. Secondary vacuum is connected
by pushing a metal vacuum rod tip into the indentation. A thin
strip of Dacron felt interlaced with screen is attached to the rod
to prevent the air vacuum from being sealed off.
[0059] A reinforcement strut of 1/4-inch.times.{fraction
(3/16)}-inch copolymer can be added to the prosthesis for
additional strength, if needed. It is put in place at the same time
as the initial drop, and runs the anterior length of the prosthesis
from one inch above the distal tibia to center of the dorsum of the
keel.
[0060] Once the plastic has heated to temperature, the vacuum is
turned on. The heated plastic is removed from the oven and
positioned over the prosthesis from near the top of the cast to the
keel, aligning center marks on the center of the prosthesis. The
plastic is allowed to conform to the contours. Once the vacuum has
sealed the plastic, the posterior seam is cut within 1 inch of the
prosthesis. A cut is then made perpendicular to and through the
seam on the underside of the primary pipe, and the secondary pipe
is tied off with nylon cord.
[0061] FIG. 5 is side elevational view of a nearly completed
prosthesis, including intermediate components used in an embodiment
of a method of the present invention,. and shows the final polymer
coating 505 over the supporting structure, which includes the cast
405, the socket 110, socket adapter 210, pylon 205, and keel 115.
The foot 120 is show for reference purposes; it gets permanently
attached during the next step.
[0062] Preparing the Prosthesis for Bonding of the Foot
[0063] Once the plastic has cooled for at least 20 minutes, it is
disconnected from the primary and secondary vacuums. A cast saw is
used to cut around the perimeter of the socket above the trim lines
exposing the plaster, which is then chiseled out. A belt sander can
be used to reduce the posterior seam to the appropriate size
considering patient weight and activity level. The posterior seam
should generally be rounded and reduced to {fraction (1/32)} inch
at the top of the popliteal area. On heavier or more active
patients the seam is preferably at least 1/4 inch.
[0064] The plastic on the bottom of the keel is removed using the
belt sander to expose the two raised segments of foam. The
periphery and the apex of the keel are then roughened with a
36-grit cone on low speed.
[0065] A rounded edged 7/8-inch spade bit is used to drill through
the keel at the dimple on the bottom until the space in the keel
where the pylon inserts into the keel is reached. Epoxy on the base
of the pylon should be visible at this point. A 1/2-inch solid pipe
can be used in this hole to drive the foam pylon, socket adapter
and cap from the prosthesis through the inside of the socket. The
foam in the base of the keel is then hollowed out using a small
acorn bit. It is important to that the diameter of the hole created
by the spade bit is kept as small as possible. A screwdriver may
assist in removal of the foam. The excess foam is removed from the
cap and the cap replaced in the prosthesis and is wet-glued in
place using a barge cement.
[0066] The "skin" is removed from the bottom of keel and a cross
pattern of cuts no deeper than {fraction (3/32)} inch is made on
all exposed surfaces on the keel bottom.
[0067] Bonding the Foot
[0068] With the foot on prosthesis and the assembly on a 1/2-inch
heel wedge the foot and prosthesis are held firmly in place. The
area around the rubber flange encircling the keel is marked and the
foot removed. Methyl ethyl ketone is used to wipe the foot clean,
particularly in the well area, and the foot is allowed to dry.
[0069] Epoxy is applied between the foot and the prosthesis, and
the assembly is placed in a bag and vacuum attached. With the toe
flat on the work surface, the epoxy is allowed to cure.
[0070] The above method may also be adapted for transferring a
fitting prosthesis. In this option, a piece of natural copolymer is
attached to the base platform of the vertical alignment jig. The
prosthesis that is to be transferred is centered on the platform
with a 1/2-inch heel wedge under the heel, and the socket is poured
using a pipe with a collar attached and inserted in the jig. After
the plaster has hardened the outline of the foot is traced on the
plastic platform. The height of the collar as it is attached to the
main strut of the vertical alignment jig is noted, the prosthesis
is removed from the jig, and the socket is removed from the cast.
The socket is dropped in 1/8-inch copolymer and then the complete
method above is employed. The alignment must be lengthened 1/2 inch
from the height at which it was poured.
[0071] While the above detailed description describes the preferred
embodiments of the present invention, it will be understood that
the present invention is susceptible to modification, variation and
alteration without deviating from the scope of the fair meaning of
the subjoined claims.
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