Surgery – Instruments – Suture or ligature
Reexamination Certificate
2001-04-26
2003-09-09
Hale, Gloria M. (Department: 3765)
Surgery
Instruments
Suture or ligature
C606S230000
Reexamination Certificate
active
06616687
ABSTRACT:
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 &egr;-caprolacton homopolymer or a copolymer of &egr;-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 &egr;-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 &egr;-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 &egr;-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 &egr;-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 &egr;-caprolacton and lactide.
10. The suture as defined in Item 9 in which a percentage composition of a copolymer of &egr;-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 &egr;-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 &egr;-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 &egr;-caprolacton in which lactide:&egr;-caprolacton is 70-85:30-15 mole % and the average number of continuous &egr;-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 &egr;-caprolacton, which may be a homopolymer of &egr;-caprolacton or a copolymer of &egr;-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 &egr;-caprolacton and lactic acid, such as lactide as a repeating unit. The copolymer having a repeating unit of &egr;-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 &egr;-caprolacton monomer alone or a copolymer which consists of lactic acid and &egr;-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 &egr;-caprolacton monomer alone or a copolymer alone which consists of lactic acid and &egr;-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 &egr;-caprolacton and lactic acid employed in the copolymer is expressed as mole % of &egr;-caprolacton and lactide, that is a dimer of lactic acid, preferable ratios of &egr;-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
Sasaki Ikuo
Suzuki Masakazu
Tomihata Kenji
Gunze Limited
Hale Gloria M.
Knobbe Martens Olson & Bear LLP
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