Surgical suture abstract
The present invention relates to a coating material for surgical
sutures which comprises as essential ingredients a copolymer having
repeating units of lactic acid and .epsilon.-caprolacton and calcium
stearate; and a surgical suture comprising a lactic acid/.epsilon.-caprolacton
copoymer in which a lactide/.epsilon.-caprolacton ratio is (70-85
mol %)/(30-15 mol %) and the number of .epsilon.-caprolacton repeating
unit is 2.5 or greater on the average.
Surgical suture claims
What is claimed is:
1. A coating material adapted to be applied onto a surface of a
suture, comprising a copolymer of .epsilon.-caprolacton and lactide,
and calcium stearate, wherein a percentage composition of said copolymer
of .epsilon.-caprolacton and lactide is 88-97:12-3% in molar ratio
and a blending ratio of said calcium stearate is 0.01 to 1.5 wt.
%.
2. A coating material adapted to be applied onto a surface of a
suture, comprising a copolymer of .epsilon.-caprolacton and lactide,
and calcium stearate, wherein a percentage composition of said copolymer
of .epsilon.-caprolacton and lactide is 70-80:30-20% in molar ratio
and a blending ratio of said calcium stearate is 0.1 to 2.5 wt.
%.
3. A coating material adapted to be applied onto a surface of a
suture, comprising a copolymer of .epsilon.-caprolacton and lactide,
and calcium stearate, wherein a percentage composition of said copolymer
of .epsilon.-caprolacton and lactide is 45-55:55-45% in molar ratio
and a blending ratio of said calcium stearate is 1.0-3.0 wt. %.
4. A coating material adapted to be applied onto a surface of a
suture, comprising a homopolymer of .epsilon.-caprolacton and calcium
stearate, wherein a blending ratio of said calcium stearate is 0.01
to 1.0 wt. %.
5. An absorbable suture coated with the coating material as defined
in any of claims 1-4.
6. The suture as defined in claim 5 in which the absorbable suture
is a monofilament suture.
7. The suture as defined in claim 6 which is a copolymer of .epsilon.-caprolacton
and lactide.
8. The suture as defined in claim 7 in which a percentage composition
of a copolymer of .epsilon.-caprolacton and lactide in the absorbable
suture is 15-30:85-70% in molar ratio.
9. The suture as defined in claim 8 in which the average number
of continuous .epsilon.-caprolacton repeating unit is 2.5 or more.
10. The suture as defined in claim 8 in which a percentage composition
of a copolymer of .epsilon.-caprolacton and lactide in the absorbable
suture is 20-30:80-70% in molar ratio.
11. The suture as defined in claim 5 in which a knot pull strength
has been improved by 10 to 50% by coating.
12. A surgical suture comprising a copolymer of lactic acid and
.epsilon.-caprolacton in which lactide: .epsilon.-caprolacton is
70-85:30-15 mole % and the average number of continuous .epsilon.-caprolacton
repeating unit is 2.5 or more.
13. The surgical suture as defined in claim 12 in which the suture
is a monofilament.
Surgical suture description
TECHNICAL FIELD
The present invention relates to surgical sutures and, more specifically,
to coating materials for surgical sutures and to absorbable sutures
having a coating.
BACKGROUND ART
The surgical suture is one of the medical devices used for a long
time. In recent years, absorbable sutures which obviate the need
of the removal of the suture after surgery have been increasingly
produced by using absorbable materials. Although sutures comprising
mainly polyglycolic acid were developed, the threads were so rigid
that the suture was produced in the form of a multifilament consisting
of a number of filaments.
However, a multifilament had problems of, for example, requiring
a complicated production process, having poor slip properties due
to its surface roughness during manipulation, occasionally causing
tissue injuries during suturing procedures, and entailing a risk
of infection due to capillary properties.
In order to solve those problems, various methods have been proposed
to apply a coating onto the surface of multifilament sutures, as
disclosed in Japanese Unexamined Patent Publication No. 229111/1996.
On the other hand, a monofilament provides advantages that the
production process can be simplified, that the suture does not cause
tissue injuries during suturing procedures due to its smooth surface,
and that the risk of infection may be considerably reduced due to
no capillary properties.
Products of absorbable monofilament surgical sutures have been
commercially available so far, using as raw materials a copolymer
of glycolic acid and caprolacton, a copolymer of glycolic acid and
trimethylene carbonate or polydioxanone.
However, monofilament sutures have shortcomings of poor handling
characteristics due to rigidity and difficulty in suture and knot.
Additionally, monofilament sutures have the shortcoming of requiring
formation of knots many times, since a tied knot is likely to loosen.
In order to overcome those shortcomings, a absorbable monofilament
suture composed of a lactic acid/caprolacton copolymer was designed,
as disclosed in Japanese Unexamined Patent Publication No.317968/1996.
This material had moderate softness, flexibility and formability
to allow formation of smaller knots and further made it possible
to reduce the number of tying knots owing to good knot security.
Although a sufficient handling characteristics was achieved as
set forth above, the absorbable monofilament surgical suture made
of a lactic acid/caprolacton copolymer had difficulty in enhancing
tenacity of the strand due to the nature of the material.
In order to overcome those shortcomings of monofilament sutures,
the method for coating the suture with, for example, silicone oil
has been commonly performed to impart lubricity on the surface of
suture.
However, in case the material of the suture is degradable and absorbable
in the living body, it is not preferable to apply coating of materials
which are not degradable, absorbable or excretory in the living
body.
It is an object of the present invention to improve tenacity of
the suture composed of a lactic acid/caprolacton copolymer while
retaining flexibility of the suture.
It is another object of the present invention to provide a coating
composition which exhibits a good affinity for the suture body and
synergistically improves knot strength, and to provide a suture
which has such a coating.
DISCLOSURE OF THE INVENTION
The present invention relates to a method for applying coating
onto surgical sutures.
1. A coating material to be applied onto the surface of a suture,
comprising a .epsilon.-caprolacton homopolymer or a copolymer of
.epsilon.-caprolacton and another absorbable monomer, and calcium
stearate.
2. The coating material as defined in Item 1 in which said another
absorbable monomer is lactide.
3. The coating material as defined in Item 1 in which a percentage
composition of a copolymer of .epsilon.-caprolacton and lactide
is 88-97:12-3% in molar ratio and a blending ratio of calcium stearate
is 0.01 to 1.5 wt. %.
4. The coating material as defined in Item 1 in which a percentage
composition of a copolymer of .epsilon.-caprolacton and lactide
is 70-80:30-20% in molar ratio and a blending ratio of calcium stearate
is 0.1 to 2.5 wt. %.
5. The coating material as defined in Item 1 in which a percentage
composition of a copolymer of .epsilon.-caprolacton and lactide
is 45-55:55-45% in molar ratio and a blending ratio of calcium stearate
is 1.0-3.0 wt. %.
6. The coating material as defined in Item 1 comprising a homopolymer
of .epsilon.-caprolacton and calcium stearate whose blending ratio
is 0.01 to 1.0 wt. %.
7. An absorbable suture coated with the coating material as defined
in any of Items 1-6.
8. The suture as defined in Item 7 in which the absorbable suture
is a monofilament suture.
9. The suture as defined in Item 8 which is a copolymer of .epsilon.-caprolacton
and lactide.
10. The suture as defined in Item 9 in which a percentage composition
of a copolymer of .epsilon.-caprolacton and lactide in the absorbable
suture is 15-30:85-70% in molar ratio.
11. The suture as defined in Item 10 in which the average number
of continuous .epsilon.-caprolacton repeating unit is 2.5 or more.
12. The suture as defined in Item 10 in which a percentage composition
of a copolymer of .epsilon.-caprolacton and lactide in the absorbable
suture is 20-30 80-70% in molar ratio.
13. The suture as defined in Item 7 in which a knot pull strength
has been improved by 10 to 50% by coating.
14. A surgical suture comprising a copolymer of lactic acid and
.epsilon.-caprolacton in which lactide:.epsilon.-caprolacton is
70-85:30-15 mole % and the average number of continuous .epsilon.-caprolacton
repeating unit is 2.5 or more.
15. The surgical suture as defined in Item 14 in which the suture
is a monofilament.
(1) Sutures having a coating
The coating material to be applied onto the absorbable monofilament
surgical suture according to the present invention comprises as
an essential ingredient .epsilon.-caprolacton, which may be a homopolymer
of .epsilon.-caprolacton or a copolymer of .epsilon.-caprolacton
and another absorbable monomer or monomers. Examples of another
absorbable monomer include lactide, glycolide, trimethylene carbonate,
dioxanone and the like, among which lactide is specifically mentioned.
A preferred copolymer is a copolymer of .epsilon.-caprolacton and
lactic acid, such as lactide as a repeating unit. The copolymer
having a repeating unit of .epsilon.-caprolacton and lactic acid
such as lactide may further comprise an additional biodegradable
and bioabsorbable repeating unit in an amount not causing considerable
adverse effects. As such an additional repeating unit, for example,
glycolic acid, trimethylene carbonate, dioxanone are exemplified.
It is preferable that the coating material to be applied onto the
absorbable monofilament surgical suture according to the present
invention comprises an .epsilon.-caprolacton monomer alone or a
copolymer which consists of lactic acid and .epsilon.-caprolacton
as a repeating unit. However, the coating composition according
to the present invention may comprise an additional biodegradable
and absorbable polymer in an amount not causing adverse effects
to the physical properties as the coating material. Examples of
such polymers include polyglycolic acid, trimethylene carbonate
and polydioxanone.
The coating material to be applied onto the absorbable monofilament
surgical suture according to the present invention can serve as
a coating material even when the material comprises an .epsilon.-caprolacton
monomer alone or a copolymer alone which consists of lactic acid
and .epsilon.-caprolacton as the repeating unit. However, if it
is desired to further improve handling properties during manipulation,
calcium stearate, that is a commonly used additive, is preferably
used in combination.
When a proportion of .epsilon.-caprolacton and lactic acid employed
in the copolymer is expressed as mole % of .epsilon.-caprolacton
and lactide, that is a dimer of lactic acid, preferable ratios of
.epsilon.-caprolacton:lactide is 88-97:12-3 mole %, or 70-80:30-20
mole %, or 45-55:55-45 mole %.
Lactic acids may be any of L-lactic acid, D-lactic acid and D,L-lactic
acid (racemate), but L-lactic acid is preferably used.
The absorbable monofilament surgical suture which is coated with
the coating material of the invention may be made of any material
such as, for example, a copolymer of .epsilon.-caprolacton and glycolic
acid, polydioxanone, a glycolic acid/trimethylene carbonate/lactic
acid copolymer, a glycolic acid/trimethylene carbonate/dioxanone
copolymer, and the like. In view of compatibility with the coating
material, a lactic acid/.epsilon.-caprolacton copolymer is preferable.
More preferably, lactide:.epsilon.-caprolacton=70-85:30-15 mol %,
and particularly preferably lactide:.epsilon.-caprolacton=70-80:
30-20 mol %. The applicable size of the suture can range from USP
2 to 10-0.
It is possible to coat the absorbable monofilament surgical suture
with an .epsilon.-caprolacton unit alone or a copolymer alone which
consists of lactic acid and .epsilon.-caprolacton as a repeating
unit. However, if improved handling properties during a surgical
procedure as well as enhanced breaking strength represented by knot
tenacity which is measured according to the USP Codex are desired,
it is necessary to simultaneously use a higher fatty acid salt such
as calcium stearate. The optimum amounts of calcium stearate used
may vary depending on the polymers employed.
The optimum amounts of calcium stearate added are defined as follows.
When the biodegradable and bioabsorbable polymer employed in the
coating material is a homopolymer of .epsilon.-caprolacton, the
optimum amount of calcium stearate is 0.01-1.0 wt. %. In the case
of .epsilon.-caprolacton:lactide=88-97:12-3 mol %, the optimum amount
of calcium stearate is 0.01-1.5 wt. %, in the case of .epsilon.-caprolacton:lactide=70-80:30-20
mol %, the optimum amount is 0.1-2.5 wt. %, and in the case of .epsilon.-caprolacton:
lactide=45-55:55-45 molt, the optimum amount is 1.0-3.0 wt. %. The
optimum amounts may vary in relation to the concentration of the
polymers employed in the coating material.
Specifically, the coating method begins with thorough dissolution
of the polymer in a solvent. The solvent employed may be any commonly
used organic solvent. Preferably, acetone is used since aceton does
not considerably dissolve the suture body. Through this dissolution,
the coating material becomes more adhesive to the suture body and
the incidence of peeling of coatings decreases.
In case a higher fatty acid salt such as calcium stearate is simultaneously
used, this salt is added in a predetermined amount to the solution
described above which contains the polymer. The higher fatty acid
salt is slightly soluble in solvents of various kinds, and therefore,
the higher fatty acid salt is used in the form of a dispersion.
For the purpose of uniform coating, it is preferred to maintain
stirring of the coating solution continuously throughout coating
procedures.
Knot-pull strength improvement introduced by applying coating is
preferably 10 to 50%, more preferably at least 20%.
(2) Surgical sutures
The surgical suture according to the present invention is a copolymer
consisting of lactic acid and .epsilon.-caprolacton as a repeating
unit. When the proportion is expressed by the molar ratio of lactide,
that is a dimer of lactic acid, to .epsilon.-caprolacton, lactide:.epsilon.-caprolacton=70-85:30-15
mol %, preferable 72.5-77.5:27.5-22.5. In case the proportion of
.epsilon.-caprolacton is too high, the resultant copolymer has a
problem in stability such as causing shrinkage at the time of thermosetting
and sterilization treatment. In the case of lactide:.epsilon.-caprolacton=50:50
mol %, the resultant copolymer, although rapidly degradable and
satisfactorily flexible, does not meet the requirements of the suture
owing to its rubber-like nature. From the foregoing, the above-stated
ratios are adopted for polymerization.
Lactic acids (lactides) may be any of L-lactic acid (L-lactide),
D-lactic acid (D-lactide), DL-lactic acid (racemic modification)
(DL-lactide). L-lactic acid (L-lactide) is preferably used.
The surgical suture according to the present invention can achieve
enhanced tenacity when the length of one repeating unit of the two
components becomes longer. In more detail, the average number of
continuous .epsilon.-caprolacton determined by 1H-NMR is preferably
2.5 or greater, more preferably 2.7 or greater, most preferably
about 2.8-4.
Too small average number of the continuous repeating unit results
in lower tenacity of the suture, while too large average number
of continuous repeating unit results in too rigid sutures. The upper
limit of the average number of continuous chain unit is not limited
insofar as the portion like a block copolymer, in which .epsilon.-caprolacton
alone has been polymerized, is not contained in the polymer. However,
the limit is preferably about 10 or less, more preferably about
6 or less, most preferably about 4 or less.
The weight average molecular weight of the copolymer according
to the present invention preferably ranges from 100000 to 1000000.
The suture produced by using a copolymer in which the average number
of continuous .epsilon.-caprolacton is 2.5 or greater can not only
achieve enhanced strength over the suture obtained using a copolymer
with a shorter repeating unit, but also provide inproved knot breaking
strength enough to meet the requirements of the suture as measured
according to the USP.
The sutures according to the present invention may be a monofilament
strand or a multifilament strand, preferably a monofilament strand.
In order to elongate the length of the specific repeating unit
of the copolymer according to the present invention, a bulk polymerization
method is preferably carried out, as typically disclosed in Japanese
Unexamined Patent Publication No.501045/1994. The publication sets
forth that there is a tendency that the average number of continuous
repeating unit of each constitutional component generally becomes
longer when polymerization is conducted at a lower temperature for
a longer period of time. The copolymers having a longer average
length of the continuous constituent, suitable enough for use as
the raw material according to the present invention, can be produced
if polymerization is carried out at a lower temperature and for
a longer period of time. Thus, it is possible for the copolymer,
even within a common category of a random copolymer, not only to
satisfy the physical properties required as fibers, specifically
as medical sutures, such as tenacity (in pulling and knotting),
but also to exhibit flexibility needed for use as the suture when
the average length of the continuous component is lengthened. Polymerization
temperature is usually at about 70.degree. C. to 160.degree. C.,
preferably at about 110.degree. C. to 150.degree. C.
Although Japanese Unexamined Patent Publication No.59356/1997 discloses
an A-B or A-B-A block copolymer produced by polymerizing caprolacton
followed by polymerizing another constituent (lactide), the block
copolymer is not preferable for use as a suture since the block
copolymer achieves high pulling tenacity but provides rather low
flexibility.
BEST MODE FOR CARRYING OUT THE INVENTION
The present invention will now be illustrated by the following
Examples, but it is to be understood that the invention is not limited
to the Examples.
EXAMPLE 1A
Using a copolymer of L-lactic acid and .epsilon.-caprolacton (lactide/.epsilon.-caprolacton=25/75
mol %) together with calcium stearate (CaSt.), a coating material
was applied to the copolymer. (1) Solvent acetone (2) Concentration
of copolymer (polymer) 2 W/V % (3) Concentration of calcium stearate
0.2 and 2 W/V %
The above three ingredients were mixed and a strand was passed
through the mixture to apply coating thereto at the rate of about
10 m/min, with continuously stirring the mixture. The strand used
was a monofilament having a lactide/.epsilon.-caprolacton ratio
of 75/25 mol % and corresponding to the USP size 0.
Knot-pull strength of the coated strand was measured according
to the USP established to assess Knot-pull strength of the suture.
Knot breaking extension was the value of extension measured at break.
Knot-pull strength of the strand prior to applying coating was measured
for reference. The results are shown in Table 1 below.
TABLE 1 Knot Breaking Knot-pull Knot-pull Elongation strength strength
(g) (%) Improvement (%) Before 4025 29.4 Coating 2% polymer, 5067
40.6 25.9 0.2% CaSt. 2% polymer, 4676 40.5 16.1 2% CaSt.
Knot-pull strength improvement was calculated by dividing the value
of improved strength by the value of the strength measured prior
to applying coating, followed by multiplied by 100.
EXAMPLE 2A
Using a copolymer of L-lactic acid and .epsilon.-caprolacton (lactide/.epsilon.-caprolacton=50/50
mol %) together with calcium stearate, a coating material was applied
to the copolymer. (1) Solvent acetone (2) Concentration of copolymer
2 W/V % (3) Concentration of calcium stearate 0.2 and 2 W/V %
The above three ingredients were mixed and the strand, which was
the same one as used in Example 1 was passed through the mixture
at the rate of about 10 m/min *to apply coating thereto, with continuously
stirring the mixture. The suture used was a monofilament having
a lactide/.epsilon.-caprolacton ratio of 75/25 mol % and corresponding
to the USP size 0.
Knot-pull strength of the coated strand was measured according
to the USP established to assess strength of the suture. Knot-pull
strength of the strand prior to applying coating was measured for
reference. The results are shown in Table 2 below.
TABLE 2 Knot Breaking Knot-pull Knot-pull Elongation strength strength
(g) (%) Improvement (%) Before 4025 29.4 Coating 2% polymer, 4086
32.7 1.5 0.2% CaSt. 2% polymer, 5023 42.3 24.8 2% CaSt.
EXAMPLE 3A
Using a copolymer of L-lactic acid and .epsilon.-caprolacton (lactide/.epsilon.-caprolacton=8/92
mol %) together with calcium stearate, a coating material was applied
to the copolymer. (1) Solvent acetone (2) Concentration of copolymer
2 W/V % (3) Concentration of calcium stearate 0 0.1 0.2 0.5
1 and 2 W/V %
The above three ingredients were mixed and the strand, which was
the same one as used in Example 1 was passed through the mixture
at the rate of about 10 m/min to apply coating thereto, with continuously
stirring the mixture. The strand used was a monofilament having
a lactide/.epsilon.-caprolacton ratio of 75/25 mol % and corresponding
to the USP size 2-0.
Knot-pull strength of the coated suture was measured according
to the USP which is established to assess strength of the suture.
Knot-pull strength of the strand prior to applying coating was measured
for reference. The results are shown in Table 3 below.
TABLE 3 Knot Breaking Knot-pull Knot-pull Elongation strength strength(g)
(%) Improvement (%) Before 2219 30.6 Coating 2% polymer, 2432 33.7
9.6 0% CaSt. 2% polymer, 2937 39.4 32.4 0.1% CaSt. 2% polymer, 2640
39.6 20.0 0.2% CaSt. 2% polymer, 2597 41.1 17.0 0.5% CaSt. 2% polymer,
2625 41.3 18.3 1% CaSt. 2% polymer, 2372 35.0 6.9 2% CaSt.
EXAMPLE 4A
Using an .epsilon.-caprolacton polymer together with calcium stearate,
a coating material was applied thereto. (1) Solvent acetone (2)
Concentration of an .epsilon.-caprolacton polymer 0.1 0.5 1.0
W/V % (3) Concentration of calcium stearate 0.1 W/V %
The above three ingredients were mixed and the strand, which was
the same one as used in Example 1 was passed through the mixture
at the rate of about 10 m/min to apply coating thereto, with continuously
stirring the mixture. The strand used was a monofilament having
a lactide/.epsilon.-caprolacton ratio of 75/25 mol % and corresponding
to the USP size 0.
Knot-pull strength of the coated strand was measured according
to the USP established to assess strength of the suture. Knot-pull
strength of the strand prior to applying coating was measured for
reference. The results are shown in Table 4 below.
TABLE 4 Knot-pull Knot Breaking Knot-pull strength Elongation strength
(g) (%) Improvement (%) Before 3799 28.2 Coating 0.1% polymer, 3815
24.9 0.4 0.1% polymer, 4855 34.9 27.8 0.1% CaSt. 0.5% polymer, 5284
40.3 39.1 0.1% CaSt. 1.0% polymer, 5000 39.6 31.6 0.1% CaSt.
EXAMPLE 1B
Monofilament strands were produced according to the method disclosed
in Japanese Unexamined Patent Publication No.317968/1996 using
a copolymer of lactic acid and .epsilon.-caprolacton having a variety
of the average number of continuous .epsilon.-caprolacton repeating
unit (hereinafter referred to simply as Lc), analyzed by the method
of Gebriele Perego et al (Biomaterials, Vol.15 189 (1994)) and
the method of Hans R. Kricheldorf et al (J. Macromol. Sci. -Chem.,
Vol.A24 1345 (1987)) using .sup.1 H-NMR spectra. The resultant
monofilament strands were subjected to tests.
Two kinds of polymers, No.1 (Lc=2.95) and No.2 (Lc=2.23), were
employed and strands having an average diameter of 0.5 mm were prepared.
Those strands were evaluated for tensile strength at a chuck distance
of 100 mm and a pulling rate of 100 mm/min. The results are shown
in Table 5 below.
TABLE 5 Strength (g) Strength (g/d) Lc No. 1 8746 4.00 2.95 No.
2 7059 3.23 2.23
EXAMPLE 2B
Monofilament strands were produced according to the method disclosed
in Japanese Unexamined Patent Publication No.317968/1996 using
a copolymer of lactic acid and .epsilon.-caprolacton having a variety
of the average number of continuous .epsilon.-caprolacton repeating
unit (hereinafter referred to simply as Lc), analyzed by the method
of Gebriele Perego et al (Biomaterials, Vol.15 189 (1994)) and
the method of Hans R. Kricheldorf et al (J. Macromol. Sci. -Chem.,
Vol.A24 1345 (1987)) using .sup.1 H-NMR spectra. The resultant
monofilament strands were subjected to tests.
Two kinds of polymers, No.1 (Lc=3.36) and No.2 (Lc=1.93), were
employed and the strands having an average diameter of 0.315 mm
were obtained. Those strands were evaluated for tensile strength
at a chuck distance of 100 mm and a pulling rate of 100 mm/min.
The results are shown in Table 6 below.
TABLE 6 Strength (g) Strength (g/d) Lc No. 3 3240 3.75 3.36 No.
4 2838 3.36 1.93
Specific conditions (which are the same as in Examples 1 and 2)
to produce the monofilament strands were illustrated as follows.
Step 1. melt spinning and primary drawing: drawing nine-fold in
a water-bath at a spinning temperature and a water-bath temperature
shown in Table 3; Step 2. secondary drawing (re-drawing): 120 to
130.degree. C., drawing 1.67-fold; Step 3. heat treatment (thermosetting):
120.degree. C., 60 min while the copolymer was wound around a bobbin
with moderate tension; and Step 4. shrinkage treatment: 60.degree.
C., 15 hours.
Monofilament strands Nos.1 to 4 produced under the conditions
described above, are characterized by the following lactide(LA)/.epsilon.-caprolacton(CL)
ratios (mol %), Lc, spinning temperature and water-bath temperature
shown in Table 7.
TABLE 7 LA:CL Spinning Water-Bath No (mol %) Lc Temperature (.degree.
C.) Temperature (.degree. C.) 1 75.5:24.5 2.95 235 86 2 76.9:23.1
2.23 224 80 3 75.3:24.7 3.36 243 82 4 74.6:25.4 1.93 217 76
According to the method of the present invention to apply coating,
absorbable monofilament surgical sutures achieve improvement in
slip properties on their surface and handling properties during
use. These improvements may prevent break of strands caused by excess
force applied during manipulation due to poor slip properties in
spite of sufficient tenacity. Furthermore, in comparison with uncoated
sutures, the coated sutures achieve improvement in knot-pull strength
by 10 to 50% as measured according to the USP Codex.
According to the present invention, absorbable surgical sutures
can be provided which are flexible, easy to tie knots and unlikely
to render the tied knots loosen, and furthermore have high knot-pull
strength. |