Surgical suture abstract
A synthetic nonabsorbable surgical suture compound of segmented
polyether - ester block copolymers is disclosed.
Surgical suture claims
We claim:
1. An annealed non-absorbable monofilament sterile surgical suture
or ligature comprising a polymeric block (A) consisting of a polyalkylene
ether of the formula ##STR11## having a number average molecular
weight of from about 500-3000 wherein R is a straight chain alkyl
group of about 4 carbon atoms and R.sub.2 is 14-phenylene and n
is the number of repeating units; and a polymeric block (B) which
is the reaction product of an aromatic dicarboxylic acid and a short
chain aliphatic diol, having the formula ##STR12## wherein R.sub.1
is a straight chain alkyl group of about 4 carbon atoms and R.sub.2
is 14-phenylene, said block (B) comprising about 82% of the copolymer,
and said copolymer having a number average molecular weight of from
about 25000 to 30000 such that said suture has good flexibility,
good fatigue life and high tensile strength.
2. The surgical suture or ligature of claim 1 having an attached
needle.
3. A surgical suture package comprising a sterile enclosure and
therein a non-absorbable monofilament sterile surgical suture or
ligature of claim 1 or 2.
4. The surgical suture or ligature of claim 2 or 3 wherein said
suture or ligature is heated at constant length.
Surgical suture description
BACKGROUND OF THE INVENTION
This invention relates to a surgical suture composed of block polyether-esters
which contain (1) a polymeric block of polyalkene esters and (2)
a polymeric block of aromatic dicarboxylic acids or cycloaliphatic
acids with short chain aliphatic or cycloaliphatic diols. This surgical
suture can be a monofilament, or a twisted or braided multifilament
article.
The medical profession is continuously seeking more satisfactory
sutures to be used in closing wounds, whether such wounds are incisions
from operations, or tears, cuts or abrasions from accidental or
other causes. Many materials have been suggested for use as sutures.
Sutures are divided into two broad classes, the absorbable sutures,
such as catgut or polyglycolic acid sutures, which are absorbed
by the body tissues, and nonabsorbable sutures which either remain
in the tissues in substantially their original form for prolonged
periods or are removed from the skin surfaces after the underlying
tissues have been healed. For nonabsorbable sutures many materials
have been suggested which range from cotton and silk through various
synthetic filaments such as polypropylene to stainless steel or
nickel or other metallic filaments.
Other things being equal, the medical profession usually prefers
the suture which is strongest. In spite of many disadvantages stainless
steel has met with considerable acceptance because of its extremely
high tensile strength. Such plastic materials as polypropylene are
meeting currently with considerable commercial acceptance because
of comparatively high tensile strength and because of other advantages
over stainless steel.
Additionally, the suture material needs good handling characteristics.
The handling characteristics of a suture, as a general statement,
are difficult to define but should include a high degree of flexibility.
Handling characteristics include knot strength and knot security.
That is, the suture must have such characteristics that a knot can
be tied in the suture. Some materials are so brittle that if a suture
made from them is knotted, the strength of the suture is markedly
reduced. For some materials an overhand knot in a strand can reduce
the strength of the strand by a factor of two or more. In addition
to knot strength, the suture should have such characteristics that
the knot when tied remains in position. Also, the suture should
be "throwable" so that when the free end is placed in
position by the surgeon it will remain in that position until moved.
Similarly, the suture should have such characteristics that it can
be thrown or moved from side to side and yet retain the position
into which it is thrown.
A surgical suture comprising a high degree of tensile strength
with a high degree of flexibility is therefore needed in the medical
profession.
A polypropylene monofilament suture is one attempt at solving this
need. The tensile strength of this suture is good when compared
to stainless steel; and the flexibility of the suture, though better
than stainless steel, is still considered to be stiff and springy.
See, e.g., U.S. Pat. No. 3630205 which is incorporated herein
by reference.
A polyurethane suture is another attempt. The primary advantage
of this suture is its very high degree of flexibility. However,
this has low tensile strength and extremely high elongations at
break which make it unsatisfactory for general wound closure methods.
See, e.g., U.S. Pat. No. 3454011 which is incorporated herein
by reference.
Other attempts include the braiding of materials with a high tensile
strength but a low degree of flexibility. Dacron.RTM. is an example
of a suture with a satisfactory tensile strength after braiding
and an increased degree of flexibility. A monofilament suture is
generally preferred in most surgical procedures to a braided suture
because of the reduced tissue drag of the monofilament. Also, in
skin suturing a monofilament suture is generally preferred because
it is usually less susceptible to capillary action than a braided
suture.
This invention has advantages over these prior art attempts. The
suture of this invention shows excellent strength and flexibility
as a monofilament. Specifically, the surgical suture of this invention
combines the tensile strength of a suture such as a polypropylene
monofilament suture, with the flexibility of a braided or polyurethane
suture.
SUMMARY OF THE INVENTION
The discovery has now been made that a non-absorbable monofilament
sterile surgical suture or ligature is comprised of a polymeric
block (A) consisting of a polyalkylene ether of the formula ##STR1##
having a number average molecular weight of from about 500-3000
wherein R is a straight or branched chain alkyl group of from about
2 to 10 carbon atoms and R.sub.2 is 14-phenylene or cyclohexylene
and n is the number of repeating units; and a polymeric block (B)
which is the reaction product of an aromatic dicarboxylic acid or
a cycloaliphatic acid, and a short chain aliphatic or cycloaliphatic
diol, having the formula ##STR2## wherein R.sub.1 is a straight
or branched chain alkyl group of from about 2 to 10 carbon atoms
or a cyclic group having the formula ##STR3## and R.sub.2 is 14-phenylene
or cyclohexylene; and the block (B) comprising from about 30% to
95% of the copolymer. The copolymer has a number average molecular
weight of from about 25000 to 30000. This suture has good flexibility,
good fatigue life and high tensile strength.
The surgical suture or ligature wherein the polymeric block (B)
comprises from about 55% to 80% of the copolymer is most preferred.
The surgical suture or ligature described above wherein R is selected
from the group consisting of ethylene, propylene or butylene is
also preferred, and where R is butylene is most preferred.
Within the scope of this invention is the surgical suture or ligature
described above having an attached needle.
The non-absorbable monofilament sterile surgical suture or ligature
described above has approximately the following characteristics:
______________________________________ Straight Pull, pounds per
square inch At least about 50000 Knot Pull, pounds per square inch
At least about 35000 Flexual Modulus, pounds per square inch Less
than about 3.5 .times. 10.sup.5 Flexual Fatigue, cycles to failure
At least about 1000 Elongation at break, percent Less than about
100% Draw ratio Between about 5.times. and 10.times. ______________________________________
The surgical suture wherein the Elongation at break percent is
between about 25 and 55 is preferred.
Within the scope of this invention is a surgical suture package
comprising a sterile enclosure and therein a non-absorbable monofilament
sterile surgical suture or ligature described above comprising a
polymeric block (A) consisting of a polyalkylene ether of the formula
##STR4## having a number average molecular weight of from about
500-3000 wherein R is a straight or branched chain alkyl group of
from about 2 to 10 carbon atoms and R.sub.2 is 14-phenylene or
cyclohexylene; and a polymeric block (B) which is the reaction product
of an aromatic dicarboxylic acid or a cycloaliphatic acid, and a
short chain aliphatic or cycloaliphatic diol, having the formula
##STR5## wherein R.sub.1 is a straight or branched chain alkyl group
of from about 2 to 10 carbon atoms or a cyclic group having the
formula ##STR6## and R.sub.2 is 14-phenylene or cyclohexylene,
and the block (B) comprising from about 30% to 95% of the copolymer.
The copolymer has a number average molecular weight of from about
25000 to 35000. The suture or ligature has good flexibility, good
fatigue life and a high tensile strength. The surgical suture package
wherein R in the copolymer is butylene is preferred.
DESCRIPTION OF THE INVENTION
These sutures combine the advantages of a braided suture material
(i.e., flexibility and knot security) and those of a monofilament
suture material (i.e., smooth surface, low tissue drag, inertness,
and ease of knot run down). Specifically, these dutures are non-absorbable
monofilament sutures which combine flexibility fatigue life, and
high tensile strength.
The structures of the block copolymers of this invention may be
represented by the following general formula: ##STR7## wherein R
and R.sub.1 are the same or different straight or branched chain
alkyl groups of 2 to 10 carbon atoms; R.sub.2 is selected from the
group comprising phenylene and cyclohexylene; and n is the number
of repeating units.
In the polymeric block A, for example, polyethylene oxide or polybutylene
oxide may constitute the soft segment of the block copolymer.
In the polymeric block B, for example, polyethylene terephthalate
or polybutylene terephthalate may constitute the hard segment of
the block copolymer.
In order to have the desired qualities of flexibility and high
tensile strength, the sutures of this invention must be formed from
a copolymeric mixture of blocks A and B, wherein the hard segment
B constitutes 30-95% of the mixture. Preferably, the B component
should constitute 50-85% of the mixture.
Generally, the soft segment A is derived from a (tetramethylene
ether)glycol having a number average molecular weight in the range
of about 500-3000 may be used. The total number average molecular
weight of the block polyether-esters is about 25-30000.
The hard segment B can be derived from (1) a diacid, for example,
______________________________________ (a) terephthalic acid, or,
##STR8## (b) 14-cyclohexane dicarboxylic acid, or ##STR9## (c)
from the dimethyl esters of these acids; and, (2) a short chain
glycol, for ex- ample, (a) a linear or branched chain glycol of
2 to 10 carbon atoms; and preferably of 4 carbon atoms, or, (b)
14-cyclohexanedimethanol, or, ##STR10## or, (c) 14-bis(hydroxymethyl)benzene
______________________________________
The reaction product of (1) and (2) forms the hard segment B.
The methods for preparing these block copolymers are known in the
art. See, e.g., Great Britain Pat. No. 1458341 published Dec.
15 1976; U.S. Pat. No. 3763109 issued Oct. 2 1973; and U.S.
Pat. No. 3766146 issued Oct. 16 1973 which are incorporated herein
by reference.
Sutures formed from the block copolymers described in this application,
when extruded and drawn from 5X to 10X (where X is the original
length of the undrawn strand), preferably from 6X to 8X, have the
desired qualities of flexibility, fatigue life, tensile strength,
knot security, smooth surface, low tissue drag, inertness and ease
of knot run down.
The sutures formed from the block copolymers in accordance with
this invention can be sterilized by a variety of methods recognized
in the art including exposure to a gaseous sterilizing agent such
as ethylene oxide, and exposure to radiation of gamma rays. Generally,
the sutures of this invention cannot be sterilized by exposure to
heat because the flexible properties of the sutures may be effected.
The sutures of this invention can be colored by mechanically blending
with a pigment. Pigments such as titanium dioxide, iron oxide or
carbon black give identifiable colors. Other colored pigments which
do not cause deleterious tissue reactions may also be used to impart
color to the strands. Other colored pigments which may also be used
are disclosed in U.S. Pat. Nos. 3636956; 3297033 and 2909177
and British Pat. No. 1375008. These patents are incorporated herein
by reference.
The sutures formed from the block copolymers of this invention
were tested for toxicity by placing two 4 cm. segments on each of
three plates of HEp-2 cell culture. The cultures were incubated
for 24 hours at 36.degree. C., stained with crystal violet and checked
for degeneration of the cell monolayer in the area of the suture
segment. None of the suture segments showed any evidence of cytotoxicity.
The sutures were also tested in mice by the Systemic Injection
Test according to the U.S.P. Biological Test for Plastic Containers
No. 19. The sutures were subjected to an extraction procedure and
the extractant was injected into mice. No adverse reactions were
observed in any of the test animals.
For use as sutures, any size may be used, depending upon the preference
of the surgeon. In the United States the more common standard sizes
are the United States Pharmacopeia, which is abbreviated U.S.P.,
sizes (United States Pharmacopeia Convention, Inc., Mack Publishing
Co., Easton, Pa.).
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