Surgical suture abstract
The invention relates to a surgical suture comprising a copolymer
as an essential component, the copolymer consisting of lactic acid
(lactide) and .epsilon.-caprolacton as repeating unit, wherein shrinkage
ratio of said surgical suture is 5% or less after heat treatment
at 60.degree. C. for 20 hours and method for production thereof.
Surgical suture claims
We claim:
1. A surgical suture comprising a copolymer of lactic acid or lactide
and .epsilon.-caprolacton in an amount sufficient to reduce the
shrinkage ratio of said surgical suture to 5% or less when treated
at 60.degree. C. for 20 hours.
2. The surgical suture according to claim 1 wherein molecular weight
of said suture determined by GPC ranges from about 100000 to 250000.
3. The surgical suture according to claim 1 wherein a mole percentage
of said lactic acid or lactide is about 99.9-50 mole % and the mole
percentage of said .epsilon.-caprolacton is about 0.1-50 mole %,
based on the total moles of said lactic acid or lactide and said
.epsilon.-caprolacton.
4. The surgical suture according to claim 1 wherein tensile strength
of said suture is at least 2.5 g/d.
5. The surgical suture according to claim 1 wherein knot-pull strength
of said suture is at least 2.0 g/d.
6. The surgical suture according to claim 1 wherein elongation
at break of said suture is 50.+-.10%.
7. The surgical suture according to claim 1 wherein knot-pull elongation
at break of said suture is 45.+-.10%.
8. The surgical suture according to claim 1 wherein said suture
is in the form of a monofilament.
9. The surgical suture according to claim 1 wherein said suture
is in the form of a multifilament.
10. A method for producing a surgical suture, comprising the steps
of:
(i) melt-spinning a copolymer of lactic acid or lactide and .epsilon.-caprolacton;
and
(ii) drawing the melt-spun copolymer of step (i) in hot water.
11. The method for producing surgical suture according to claim
10 further comprising the step of:
(iii) redrawing the copolymer drawn in step (ii).
12. The method for producing a surgical suture according to claim
11 wherein said redrawing step (iii) is carried out at 90.degree.-140.degree.
C. under draw ratio of 1.2-2.5.
13. The method for producing a surgical suture according to claim
11 further comprising the step of:
(iv) heating the redrawn copolymer of step (iii).
14. The method for producing a surgical suture according to claim
13 wherein said heat treatment step (iv) is carried out at 90.degree.-130.degree.
C. for 0.2-24 hours.
15. The method for producing a surgical suture according to claim
13 comprising the step of:
(v) relaxing the resulting copolymer of step (iv).
16. The method for producing a surgical suture according to claim
15 wherein said relaxation treatment step (v) is carried out at
60.degree.-110.degree. C. for 0.2-20 hours.
17. The method for producing a surgical suture according to claim
10 wherein said drawing step (ii) in hot water is carried out at
60.degree.-90.degree. C. at a draw ratio of 8-12.
18. A method for suturing an open wound of a patient, comprising
the steps of suturing said open wound using a surgical suture comprising
a copolymer of lactic acid or lactide and .epsilon.-caprolacton
in an amount sufficient to reduce the shrinkage ratio of said surgical
suture to 5% or less when treated at 60.degree. C. for 20 hours;
and knotting said suture.
Surgical suture description
FIELD OF THE INVENTION
The present invention relates to a surgical suture and a method
for preparing the suture.
BACKGROUND OF THE INVENTION
A polymer of lactic acid (lactide), and a copolymer of lactic acid
(lactide) and the other biodegradable monomer are hydrolyzed in
vivo and absorbed. These polymers are applied to biomaterials as
follows. For example, biodegradable polymers are utilized as microsphere
for DDS; anti-adhesive material in the form of film; a guide tube
for regeneration of peripheral nerve; and a surgical suture. In
particular, several bioabsorbable surgical sutures made of glycolic
acid homopolymer or copolymer chiefly consisting of glycolic acid
are on the market. Because of stiffness of polylactic acid (polylactide),
polyglycolic acid and like bioabsorbable materials, however, said
bioabsorbable materials are difficult to use as a monofilament.
Therefore, the bioabsorbable materials are used as braided multifilament
to impart flexibility to the material.
However, a suture prepared by braiding a number of multifilament
has disadvantages of complicated manufacturing process, higher risk
of microorganism infection, etc.
Production of suture consisting of monofilament has been tried
in a variety of ways so as to solve said problems and cut costs.
Such sutures consisting of monofilament are inferior in workability
such as flexibility and ease of knot formation, as well as strength
required as suture.
Because melt spinning is not suitable for copolymer of lactic acid
(lactide), wet spinning of copolymer of lactic acid (lactide) is
tried after dissolving copolymer of lactic acid (lactide) in an
organic solvent (Japanese Unexamined Patent Publication 64-56055).
However, complete removal of solvent from monofilament suture produced
by wet spinning is very difficult. The suture is inferior in uniformity
due to existence of solvent within the suture. Specifically, such
suture is likely to be infected by bacteria due to ease of concave
and convex formation. Such suture is also likely to be broken due
to slip-resistant characteristics during knot formation. In addition,
the suture has low breaking strength and requires a large amount
of agent for coagulating bath.
It is an object of the invention to provide a monofilament suture
for medical use with improved economy and performance.
It is another object of the invention to provide a multifilament
suture with improved productivity.
It is another object of the invention to provide a method for producing
monofilament suture made of copolymer containing lactic acid (lactide)
with outstanding flexibility and smooth handling as well as required
strength. |