U.S. patent number 3,818,894 [Application Number 05/215,126] was granted by the patent office on 1974-06-25 for laryngeal implant.
This patent grant is currently assigned to Ceskoslovenska akademie ved. Invention is credited to Zdenek Kresa, Otto Wichterle.
United States Patent |
3,818,894 |
Wichterle , et al. |
June 25, 1974 |
LARYNGEAL IMPLANT
Abstract
This invention relates to an implant for surgical purposes and
which is especially useful for the operative treatment of afflicted
vocal cords, as well as to the method for its production. The
implant is made from water-swellable and physiologically inert
material, such as a synthetic cross-linked hydrophilic gel, and has
in a dry state, when it is ready for use in an operation, the shape
of a straight or bent stick provided with a sharp, pointed tip. The
implant body except the tip may contain physiologically inert
plasticizers.
Inventors: |
Wichterle; Otto (Praha,
CS), Kresa; Zdenek (Plzen, CS) |
Assignee: |
Ceskoslovenska akademie ved
(Praha, CS)
|
Family
ID: |
5336824 |
Appl.
No.: |
05/215,126 |
Filed: |
January 3, 1972 |
Foreign Application Priority Data
Current U.S.
Class: |
128/899;
623/9 |
Current CPC
Class: |
A61L
27/16 (20130101); A61F 2/20 (20130101); A61L
27/16 (20130101); C08L 33/14 (20130101) |
Current International
Class: |
A61F
2/20 (20060101); A61L 27/00 (20060101); A61L
27/16 (20060101); A61b 019/00 () |
Field of
Search: |
;128/334R,335,335.5,348,214R,1R ;3/1 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Truluck; Dalton L.
Attorney, Agent or Firm: Schaffer; Murray
Claims
We claim:
1. A larynreal implant for surgical purposes, for use in the
surgical treatment of vocal cords comprising a body of hydrophilic
polymeric crosslinked gel material having the form of a rod-like
needle with a sharp, pointed tip in the dry state in which it is
applied, said implant being swellable after implantation in the
vocal cord to help improve closure of glottis.
2. An implant in accordance with claim 1 wherein the hydrophilic
polymeric crosslinked material is an insoluble, hydrophilic gel
having a linear swelling capacity in the region from 10 to 45
percent.
3. The implant according to claim 1 wherein said tip is glassy
hard.
4. The implant according to claim 1 wherein the hydrophilic
material is a copolymer selected from the group of glycol
methecrylate and acrylate containing up to 2 weight percent of a
material selected from the group consisting of glycol
dimethacrylate and diacrylate and up to 3 weight percent of
material selected from the group consisting of methacrylic acid or
acrylic acid.
5. The implant according to claim 1 wherein a physiologically inert
plasticizer is added to said material along the length of the body
except at its tip to provide said rod with a lower modulus of
elasticity.
6. The implant according to claim 1 wherein said material contains
an additive selected from the group consisting of dyes, pigments
and contrast substances.
7. The implant according to claim 1 which has approximately the
same length in a dry state as after equilibrium swelling in water.
Description
BACKGROUND OF THE INVENTION
Vocal cords afficted with atropy or with a unilateral disorder of
motion such as paralysis of the recurrent nerve cannot be used to
any normal extent when treated by known methods. To improve the
voice and reduce the subjective difficulties, such as hoarseness,
injections of paraffin, polytetrafluorethylene or silicone polymer
particles emulsified in glycerol, or of the cartilage of the nasal
septum, which was surgically removed, crushed and emulsified in the
physiologic saline, have been employed. All these method have a
distinct disadvantage that is it is impossible to determine by the
injection precisely in which direction the injected material shall
penetrate the vocal cords. The aforementioned materials, such as
paraffin and the others move inside the vocal cords over a period
of time and eventually escape into the space below the glottis. The
crushed cartilage, on the other hand, is absorbed in the course of
time, so that the success of all the aforesaid operations is only
temporary and the shape of the vocal cords after the operation
cannot be determined in advance.
In the treatment of paralysis of the recurrent nerve bleeding is
sometimes used as an operative procedure, necessitating an incision
and subsequent scar on the throat. The larynx is opened from
outside in this operation, as a rule by a cut between the thyroid
cartilages, and a part of the cartilage of the nasal septum or of a
plastic, respectively, is implanted in the paralysed cord.
The operations performed up until now have been of necessity
carried out by indirect laryngoscopy and by one hand only.
SUMMARY OF THE INVENTION
The implant according to the invention overcomes all above
mentioned disadvantages comprises a physiologically inert material
which swells in water and has in the dry state, as prepared for the
operation, the shape of a straight or bent elongated body, such as
a stick provided with a sharp, pointed tip.
Hydrophilic material with a linear swelling capacity from 10 to 45
percent may be used as an inert material swelling in water. The
copolymers of glycol methacrylate (or acrylate, respectively) which
contain up to 2 weight percent of glycol dimethacrylate (or
diacrylate, respectively) and up to 3 weight percent of methacrylic
acid (or acrylic acid, respectively) are preferably used. This
material can be substituted by other hydrophilic materials of
similar properties which are based, for example, on acrylamide,
N-substituted or N,N-disubstituted acrylamides and their
copolymers. The implant may contain dyestuffs, pigments or contrast
substances. The implant according to the invention has preferably
the same length in a dry state as after equilibrium swelling in
water. Its modulus of elasticity may be decreased, except with
respect to the tip, by adding water or another physiologically
inert plasticizer. Glycol as employed in the expression "glycol
methacrylate" (or "glycol acrylate", respectively) to include not
only simple ethyleneglycol, but also diethyleneglycol,
triethyleneglycol, propyleneglycol, butyleneglycol and the like,
that is, an arbitrary hydrophilic aliphatic diol. Glycerol
monomethacrylate or acrylate may be also used.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
To prepare the implant according to this invention, the elongated
body such as a stick is prepared in the dry state from the
physiologically inert material swelling in water, preferably from a
synthetic cross-linked hydrophilic gel, and this stick is provided
with a sharp, pointed tip before or after drying. The stick is
advantageously made from a material which contains a
physiologically inert plasticizer or is impregnated with the
plasticizer, and wherein the tip or the part used for making the
tip is freed from the plasticizer by extraction. The stick can be
also swollen in water, the clamped in such a way to be unable to
shrink lengthwise, dried and provided with the tip, or the dried
stick can be heated above the glass transition temperature,
stretched in this state, cooled and provided with the tip.
The implant according to the invention may be prepared also in any
manner such that the body has an uneven or combined shape made from
a physiologically inert polymer swelling in water, which is dried
and then shaped at a temperature above the glass transition point
into a straight or bent rod, which is provided with a pointed tip.
In this case the implant returns into the original uneven or
combined shape after being swollen, due to its shape memory.
The characteristic glassy hard state of hydrophilic polymers in
their dry condition is necessary only in the region of the stabbing
tip for introduction of the implant into tissue. The remaining part
of the implant need not to be in the glassy hard state. However,
the body of the implant has to be sufficiently rigid to enable its
introduction into tissue by overcoming the resistance of the
opening tissue. The modulus of elasticity of the implant body is
generally sufficiently high when above about 100 kg/cm.sup.2.
However, a modulus about 1,000 kg/cm.sup.2 is especially
advantageous. In general the hydrophilic materials show
considerable decrease of brittleness when their modulus of
elasticity in the dry state is reduced from the usual value of
20,000 - 50,000 kg/cm.sup.2 to 5,000 kg/cm.sup.2. The required
reduction of modulus and thus also the high toughness of the
implant body can be achieved by introduction of a small amount of a
convenient plasticizer into the three-dimensional network of the
hydrophillic polymer. This can even be water, in the simpliest
case, which may be absorbed for instance from aqueous solutions of
sodium chloride. The amount of water in the gel decreases with the
increase of the concentration of the salt in water, since it is in
equilibrium with this solution. For instance, sparingly
cross-linked glycol methacrylate gel softens by long soaking in a
15 percent solution of salt in such a way that its elasticity
modulus is then about 500 kg/cm.sup.2. Under these circumstances
the tip is also softened. Therefore, it is necessary to dry the
sharp end of the implant before application and to preserve the
absorbed water in the residual material of the implant, for
instance, by wrapping the implant in an aluminium foil and drying
of the uncovered tip only.
If a non-volatile and physiologically inert plasticizer is used
instead of water, the implant can be made so that it has a
different hardness in its individual parts so that it has
relatively long-term stability. For example, larger or smaller
amounts of glycerol may be absorbed by the gel along with water
from dilute solutions of glycerol at elevated temperature, and will
remain in the gel permanently after drying. Subsequently, all of
the glycerol may be extracted from the tip by dipping the tip into
water so that it leashes out from the tip leaving the presence of
glycerol limited to the remaining parts of the implant. The
required effect is obtained at low concentrations of glycerol, such
as at 0.2 - 2%. The glycerol remains localized in the implant, in
the slightly swollen state, for a long time and its migration into
the non-plasticized tip does not take place. The implant can be
prepared in this condition in a sterilized package, ready for
instant use without any special preparation before use by the
consumer. Besides glycerol, several other substances may be used as
plasticizers which are absorbed by the gel and are physiologically
unobjectionable in small amounts, such as diacetin,
triethyleneglycol, butanediol-1,3,urethane acetoin, diethyl
tartrate, N,N'-dilactyl urea, lactamide and the like. These
compounds may be introduced into the gel either from aqueous
solutions or from solutions in other volatile solvents which
heavily swell the gel and thus open the gel structure for the rapid
diffusion of plasticizers. The same solvents are convenient for the
reverse washing of plasticizers from the tip of the implant.
However, the procedure can be also employed, where the tip is
protected from the softening action of the solutions by coating,
e.g. with paraffin, or where only other parts of the implant are
dipped into the solutions.
The operation, employing the implant according to the invention,
comprises insertion of the implant into the predetermined place of
the vocal cord by direct laryngoscopy methods using a multiple
magnifying surgical microscope, preferably after a very small
incision in the mucous membrane at the upper surface of vocal cord
is made. The implant is used in a dry state and is of almost glassy
hardness. The implant swells in the tissue for several minutes,
increases its volume as it has been predeterminedly designed to do
and thus increases the mass of the atrophied vocal cord, shifting
its edge more to the center and thereby contracting, or liquidating
the slot between cords occuring hitherto at voice formation. This
improves the voice in the objectively evident way and removes
hoarseness and subjective difficulties, mainly the voice
tiredness.
The implant can be employed in similar way for the treatment of
paralysis of the recurrent nerve, when the afficted vocal cord is
slack and excavated and the opposite vocal cord is unable to
compensate for the disturbance formed by drawing across middle
line. In this case the purpose of the implant is similar as in the
case of atrophy of the vocal cords and it has to level the
excavation by taking up the slack vocal cord, to improve the
closure of glottis and to improve the voice and subjective
difficulties of the patient. The application of the implant
according to the invention has the distinct advantage in that the
patient can speak within several minutes at the operation, while
with other methods total vocal inactivity is required usually for
from 3 to 7 days.
Analogously as with atrophied vocal cords, the implant can be used
for surgical treatment in other regions which are afflicted with
atrophy, such as with atrophy of nasal mucous membrane and the
like.
The following examples will further illustrate the invention. It is
to be understood that the examples are illustrative only and not
limitative. In the example all parts and percentages are by weight
unless otherwise stated.
EXAMPLE 1
A mixture consisting of 70 parts of hydroxyethyl methacrylate
containing 0.2 % of ethylene dimethacrylate, 15 parts of 0.25 %
aqueous solution of ammonium persulfate and 15 parts of 0.25 %
aqueous solution of sodium disulfite is charged by a pipette into a
plurality of thin-walled 30 cm long glass capillary tubes having a
inner diameter 0.8 to 2.5 mm which are placed horizontally.
Polymeriz mixture is sucked into the whole length of the tubes by
capillarity. The polymerization takes place at ambient temperature
and is completed within 8 hours. The several gel sticks are then
isolated either by breaking the capillary tubes and careful
separation of the crushed glass, or, in more convenient way, by
dissolving the glass in cold 20 % hydrofluoric acid. The sticks are
thoroughly washed in water and then the ends cut off to remove any
portions not perfectly polymerized due to diffusing oxygen.
Thereafter, one end of each stick, preferably in semi-dry state, is
cut with a sharp knife in a fairly oblique angle to form a shape
similar to the tip of an injection needle. As a rule, the stick
deforms in the course of further drying but the original shape was
recovered and release of internal stress obtained by heating the
stick above the softening point, i.e., to 120.degree. - 140.degree.
C. The sticks were thereafter either laid loose on stretched
knitted fabric made from terylene monofilament or suspended in
boiling xylene. Fine files and abrasive paper are used for forming
the finish and sterilization is carried out in an ethylene oxide
atmosphere.
In like manner other water-swelling gels can be prepared from other
neutral monomers, such as from N-methyl methacrylamide, acrylamide
or vinylpyrrolidone in the presence of suitable cross-linking
agents, such as methylene-bis-acrylamide. Also monomers containing
ionizable groups in their molecule can be employed (such as
methacrylic acid) which, present in slightly cross-linked gels,
when employed in the amount of up to several percent substantial
increase of swelling capacity in neutral aqueous solutions. With
gels based on glycol methacrylate a substantial increase of
swelling may also be achieved by esterification of hydroxy groups
with sulfuric acid.
EXAMPLE 2
The monomer mixture as described in Example 1 is charged into a 3 m
long thin-walled silicone rubber tube having an inner diameter of
1.2 mm. The opposite end of the tube is sealed and 1ml more mixture
is pressed into the tube by a syringe so that the tube expands and
is able to compensate precisely for the polymerization contraction.
Then the other end is sealed, the tube is inserted into a wider
glass tube, which is freed from all oxygen by a stream of nitrogen
and sealed. After polymerization is completed, the silicone tube is
split by two lengthwise cuts and the casted rod is released. It is
quite regular, intact and free of contraction bubbles. The rod may
be, after cutting to pieces and washing in water, impregnated with
plasticizers, such as by heating in a 3 % aqueous solution of
glycerol. If a rod is dried in the lengthwise fixed position, it is
obtained in stretched state and by swelling under physiological
condition only gets wider but not longer. To finish the implant,
the tip is formed, freed from the plasticizer by dipping in water,
and, after final drying, is sharpened with fine emery.
EXAMPLE 3
A mixture consisting of 30 parts of acrylonitrile, 70 parts of
nitric acid (density 1.5) and 0.1 parts of ammonium persulfate was
charged into similar capillary tubes, as those which are described
in Example 1. The capillary tubes were inerted into a pressure
vessel, air was replaced by nitrogen and the pressure of nitrogen
was increased to 3 atm. After five days the capillary tubes were
removed from the pressure vessel and heated for 10 hours to
45.degree. C. Further working was analogous to Example 1. The
volume swelling capacity was about 60 %.
The foregoing fully reveals the gist of the present invention that
others can by applying current knowledge readily adapt it for
various applications without omitting features that, from the
standpoint of the prior art, fairly constitute esential
characteristics of the generic and specific aspects of this
invention and, therefore, such adaptations should and are intended
to be comprehended within the meaning and range of equivalence of
the following claims.
* * * * *