Note: Descriptions are shown in the official language in which they were submitted.
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IMPLANTABLE STRUCTURE
One of the reasons for deafness is the failure of the
bony chain, i.e., the hammer, the anvil and the stirrup to
transmit the vibrations of the ear drum to the inner ear.
Efforts have been made to repair the elements of the bony chain
and to substitute components therefor. With the substitution
of components, one difficulty encountered is the securing of
such components in the desired organic position. One example
of a suitable implant structure is described in our German
Offenlegungsschrift 2,458,932 which provides an implant
structure having a biocompatible columella and a biocompatible
porous pad secured to at least one of the ends of the columella.
The present invention is an improvement over such structure
in that the biocompaptible porous material can be used to form
the columella as well as each of its ends. The tissue ingrowth
at the ends as well as along the columella can ensure the
securing of the implant in the desired position. The structure
of the present invention offers an improved structure, for
example, for the transmission of sound vibrations in the ear
because it can be made from a continuous, single block of
material throughout which tissue may grow.
Also, during recent years, many efforts have been made
to provide a simple, reversible, birth control method devoid
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of side effects. The use of the pill for birth control has
such undesirable side effects. A positive method of sterili~
zation for women involves closing the fallopian tubes. This
method is not reversible. The improved structure of the pre-
sent invention, however, is especially adapted for implanta-
tion in the end of the fallopian tubes opening into the
uterus. Accordingly, a birth control method using the im-
plant structure of this invention provides for reversibility
when desired.
Also, certain physiological processes, such as fracture
healing, heartbeat pacing, pain modulation, etc., can be con-
trollably modified by passing electric current into a
selected tissue of a living organism. A common means o~
passing electric current is to insert a noble metal electrode
into the organism. Using such metal electrodes, it was found
that the current density distribution to the selected tissue
cannot be easily controlled.
A~cording to the present invention, there is provided
a structure for in vivo implantation, the str~cture being an
integral elongated body made of a resilient and distensible
material an end of which body is enlarged whereby the remainder
of the body forms a stem extending ~rom said enlarged end, said
enlarged end and said stem being biocompatible, and at least a
substantial portion of the material of which said enlarged end
is made and at least a portion of the material of which said stem
is made being a porous material which promotes living tissue to
~row into the pores of the material when implanted to secure the -
structure in the implanted position.
The enlarged end and the stem are bicompatible and
promote the ingrowth of living tissue. For most applications,
the stem can have transverse dimensions between 0.25 and 3
millimeters, and the pad's largest dimension can be between
0.5 and 8 millimeters.
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The improved structure is adapted to be implanted in place
of at least a portion of the bony chain of the middle ear. The
stem is made sufficiently long to approximate the dimensions
of the bony chain which it replaces, and, preferably, the
surface pores of the center portion of the stem are closed.
Also, it is preferred that the surface pores of nearly
the entire stem be closed when the structure is used as a plug
for the fallopian tubes opening into the uterus. The pad has
a dimension to allow sufficient tissue ingrowth to secure the
structure in its implanted position. Added securing by ridges
along the stem can be provided to resist movement of the
structure from its implanted position.
A fluoroethylene propylene tube can be heat shrunk onto
the stem for closing its surface pores. The end of the stem
which extends beyond the tube can have one or more leaves, or
the end can be enlarged in one dimension to form a flat, bulbous
end portion with sufficient flexibility to bend at a substantially
right angle to the longitudinal axis of the stem. A wire can
be connected to an end of the stem. Also, a disc of porous
ingrowth-promoting material can be bonded to one end of the stem.
In general, the pad will be frusto-conical in shape with
its larger end facing outwardly. When the pad defines a shallow
recess for receiving a portion of the bony chain
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therein, the improved structure can serve as a stapes replacement.
The porous material of the element forming the structure
can have the property of conducting electric current. Therefore,
such structure can serve as an improved in-vivo electrode, which
is totally biocompatible. By virtue of having a substantial
tissue ingrowth within its pores, such electrode offers a
relatively-large contact area for current distribution between
the electrode and the ingrown and thereto contiguous tissue.
In this manner, better control of electric current distribution
between the electrode and the contiguous tissue can be achieved. -~
The objects and advantages of the invention will become
better understood from the following description when taken
in conjunction with the accompanying drawings, in which:
Fig. 1 is a side elevational view of one shape of the
improved structure of the present invention;
Pig. 2 is a sectional view taken along line 2-2 in Fig. l;
Fig. 3 is a side elevational view partly in section of the
improved structure used for replacement of the stapes of the
ear;
Fig. 3a is an end view taken along line 3a-3a on Fig. 3;
Fig. 4 is an elevational view, partly in section, of
another form of implantable structure of the present invention;
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Fig. 5 is a sectional view taken along line 5-5 on
Fig. 4;
Fi8. 6 is a side elevational view of another form of
improved structure of the present invention;
Fig. 7 is an end view taken along line 7-7 in Fig. 6;
Fig. 8 is a side elevational view of another form of
improved structure for use as a bony chain replacement in the
ear;
Fig. 9 is a side elevational view of another form of
implantable structure of the present invention;
Fig. 10 is side elevational view, partly in section,
of another form of implantable structure of the present
invention; and
Fig. 11 is a side elevational view of still another
modified form of implantable structure of the present invention.
In Fig. 1 is shown an implantable structure, generally
designated as 10, which may be used either as a tube plug or as
a bony chain substitute. Structure 10 includes an enlarged
end 12, the preferred form of which is generally frusto-conlcal.
A stem 14 is integral with and extends from the central portion
13 of enlarged end 12. For most applications, the enlarged
end's largest dimension is between 0.5 and 8 millimeters. Stem
14 has transverse dimensiQn6 between 0.25 and 3 millimeters.
At least a substantial por-
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ion of the surface of enlarged end 12 and the end of stem
14 away from enlarged end 12 are porous and of a material which
promotes the ingrowth of tissue when the structure is used as a
bony chain substitute. Only the surface of enlarged end 12 need
be porous when the structure is used as a tube plug.
In applications in which structure 10 is to be used as
a substitute for at least a portion of the bony chain of the
ear, it is preferred that the outer surface of the center part
of stem 14 be either compressed or otherwise treated to have
limited porosity to avoid the ingrowth of tissue in and around
its surface. When so compressed, the structure will have a
non-uniform density distribution along its longitudinal axis.
Theimproved structure of the present invention is made
of a body of material at least a portion of which is porous and
which readily promotes the growth of living tissues into the
pores and voids within the material. Our British Patent
1,390,445 describes a porous material of carbon fibers bonded
by polytetrafluorethylene which can be used as the growth-
promoting material. Other suitable growth-promoting materials
are also disclosed in said British patent. The present
invention also has application to other biocompatible growth-
promoting materials which may be implanted and cause living
tissues to ingrow.
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The structure 16 illustrated in Fig. 3 is suitable as a
stapes replacement for implantation in the ear. Such structure
includes a frusto-conical enlarged end 18 and a stem 20. The
structure 16 is similar to structure 10 except that the outer
end 21 of enlarged end 18 now defines a concave recess 22 shaped
to receive a portion of the bony chain therein when implanted.
The center portion 15 of the stem 20 has its surface pores at
least partially closed as indicated by the shaded area 24.
Structure 10 can be cut out from a block of the ingrowth-
promoting material and is completely porous, as shown. On
theother hand, structure 16 can be developed from a cylindrical
bloc~ of such material and the stem 20, except for its outer
end 25, can be compressed to the shape illustrated in Fig. 3
to obtain the surface 24 with the pores closed or sufficiently
restricted to prevent growth of tissue in and through such
external surface 24. The end 25 of stem 20 may be trimmed to
size, if desired. Preferably, the end 25 should not exceed the
diameter of the recess of the vestibule to the inner ear but
form a close fit therein. An unexpected advantage of structure ~ -
16 formed by compression along the central portion 15 of the
stem 20 is that such portion exhibits substantially no mechanical
hysteresis. This mechanical characteristic can be advantageous
in allowing the surgeon to more precisely shape the geometry of
structure 16 relative to the middle ear architecture. -
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The closing of the pores, as represented by the shaded
area 24 in Fig. 3, can be accomplished by pressure, pressure
and heat, or any other suitable process, mechanical or chemical
to ensure that the surface porosity is reduced sufficiently
so that tissue growth cannot take place in and through the surface.
In addition to surface treatments, mechanical means such as
shrink sleeves or pore-occluding coatings of medical grade
materials, such as silicone rubber, polymeric dispersions, etc.,
can also be used as the pore~closing means, as hereinafter
described.
In structure 26 shown in Figs. 4 and 5, the enlarged end
28 is frusto-conical in shape and has the stem 30 integral there-
with and extending therefrom. The stem 30 is surrounded by a
mechanical pore-closing means for closing the pores around its ~ -
exterior, such as a tubular sleeve 32 which surrounds the
exterior of stem 30 except for the outer end 33 thereof.
Tubular sleeve 32 is a biocompatible plastic tube which has
been shrunk into its position surrounding stem 30, as shown.
Sleeve 32 and all materials used for in-vivo implants are to
be completely biocompatible so that they do not cause any
adverse reaction by the local tissues in and around the
implantation site. An example of a suitable material for sleeve
32 is a fluorinated ethylene propylene tube which may be shrunk
onto stem 30 at temperatures between 400F to 450F without
damaging the porous material of structure 26. These sleeves
are characterized as being good electrical insulators. -
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The structure 34 shown in Figs. 6 and 7 is similar to the
structure 26 of Fig. 4, but has an enlarged flat end 36 into
which a wire 38 is fixed. A sleeve 40 is shrunk about the
central portion 41 of stem 42. The opposite ends 36 and 44 of
the stem extend outwardly of sleeve 40. Structure 34 can be
used either as a stapes replacement or as an electrode, as will
be hereinafter set forth.
The structure 46 shown in Fig. 8 is substantially similar
to structure 34, except that structure 46 is longer and is
designed to be a replacement for the entire bony chain of the
ear. Structure 46 includes an elongated flat end 48 integral
with stem 50 about which a sleeve 52 is shrunk, leaving
opposite ends 48 and 54 extending therefrom. End 48 is
sufficiently thin to be flexible. End 48 can be easily bent so
that it may be positioned at a substantially right angle to
stem 50 and rest flat on the ear drum. With such geometric
configuration, a large area of the porous material is exposed
to the ear drum to ensure positive fixation by the growth
of tissues in and through the pores of the material from which
structure 46 is made.
The shrink fitting of the sleeves is done by any process
well known in the art. For example, the shrink fitting can
be accomplished by passing heated air over an expanded tubular
sleeve 52 which has been placed in surrounding relation to the
central part 51 of stem 50 for a relatively short period
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f time, for example, a few seconds. In such case, sufficient
heat should be provided to exceed the setting temperature of
the sleeve and the material of the sleeve remembers its
original size and returns thereto, squeezing the central portion
51 of stem 50 as shown. The shrink sleeves are of a material
which prevents living tissue from growing and attaching thereto.
The material also should be selected so that it does not cause
appreciable dampening of the vibration transmission from the
ear drum to the oval window of the inner ear.
A modified structure 56 is shown in Fig. 9. Stem 57 is
provided with a shrink fit sleeve 58. One end of the stem 57 -~
projecting outwardly from sleeve 58 has been separated into a
plurality of leaves 60. The leaves make an improved connection
to the ear drum as compared to a single ended stem. The other
projecting end 62 is as described in relation to end 44 of
structure 34.
Another modified structure 63 is shown in Fig. 10. The
stem 64 is surrounded by a shrink fit sleeve 66 over the central
portion thereof. Only one end 68 of the stem projects outwardly
of one end of the sleeve. The other end of the sleeve is
flush with the stem and is covered by a disc 70 of a biocompatible
porous material that promotes the ingrowth of tissue. A film
72, such as fluorinated ethylene propylene, bonds disc 70 to
the end of sleeve 66 and to stem 64. Structure 63 can be made,
if desired, without an end 68 projecting outwardly of sleeve 66.
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A modified structure 74 is shown in Fig. 11 designed to
be used as a Fallopian tube closure plug. It includes an enlarged
end 76 and a stem 78 provided with external ridges 80 facing
toward enlarged end 76. Ridges 80 are preferably formed in such
a manner that their external surfaces have their pores closed,
as represented by the shaded area 84, so as to prevent the
ingrowth of tissue. Such ridges 80 can be formed by compressing
or molding of stem 78 so long as the external pores on the
ridges 80 are sufficiently closed to prevent tissue ingrowth.
When structure 74 is used as a plug for a tube, ridges 80 will
provide sufficient resistance to the traveling contractions of
the tube so that the plug will not be displaced from its desired
position before the ingrowth of tissue has progressed
sufficiently within the enlarged end 76 to secure the structure
in place. Hence, ridges 80 serve to impede the displacement
of the plug within the tube.
Thus, the structures of the present invention for implant-
ation in the ear are characterized as having an elongate porous
element with pore-closing means over a central part of the
element with one or both ends of the element extending beyond
the pore-closing means.
The porous material as described in said British patent
No. 1,390,445 is a fairly good electric conductor and, therefore,
electric current density would be distributed over the entire
structure of this invention and would flow into the ingrown
tissue. Therefore, each of the structures shown in
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Figs, l-ll can also serve as an implant current-carrying
electrode. In its simplest form shown in Fig. 6, wire 38
would carry an electric current to the tissues in the pores
of structure 34, while sleeve 40 would serve to insulate the
tissues adjoining the sleeve, thereby providing selective current
density distribution.
In a modified form, a wire 37 can be attached to end 33
of stem 30 (Fig. 4) with the aid of a thin biocompatible layer
or film 35 of a noble metal such as gold or platinum. Wire 37
can also be mechanically secured to end 33. Similarly, each
of the shown embodiments of the implant structure can be adapted -~
to serve as an implant electrode.
From the foregoing it will be appreciated that the present
invention provides an improved structure for in-vivo implantation,
such as a Fallopian tube plug, or in place of all or part of the
bony chain between the ear drum and the inner ear, or as an
implant electrode with selective current density distribution;
the structure is relatively simple to make and involves the use
of a porous biocompatible material and relatively simple
~ 20 manufacturing proceclures.
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