Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
1998-11-23
2001-08-21
Buttner, David J. (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S413000, C525S415000, C528S354000, C606S230000
Reexamination Certificate
active
06277927
ABSTRACT:
TECHNICAL FIELD
Absorbable block copolymers having one of the blocks made from randomly polymerized glycolide and lactide and another block made substantially entirely from lactide are described. Processes for making the copolymers and surgical articles made totally or in part from such copolymers, including sutures, are also described.
BACKGROUND
Bioabsorbable surgical devices made from copolymers derived from glycolide and lactide are known in the art. Such bioabsorbable surgical devices include surgical sutures.
A desirable characteristic of a bioabsorbable suture is its ability to exhibit and maintain desired tensile properties for a predetermined time period followed by rapid absorption of the suture mass (hereinafter “mass loss”.)
Absorbable multifilament sutures such as DEXON sutures (made from glycolide homopolymer and commercially available from Davis & Geck, Danbury, Conn.), VICRYL sutures (made from a copolymer of glycolide and lactide and commercially available from Ethicon, Inc., Sommerville, N.J.), and POLYSORB sutures (also made from a copolymer of glycolide and lactide and commercially available from United States Surgical Corporation, Norwalk, Conn.) are known in the industry as short term absorbable sutures. The classification short term absorbable sutures generally refers to surgical sutures which retain at least about 20 percent of their original strength at three weeks after implantation, with the suture mass being essentially absorbed in the body within about 60 to 90 days post implantation.
Early attempts to increase in vivo strength retention have resulted in monofilament sutures, which are generally classified as long term absorbable sutures capable of retaining at least about 20 percent of their original strength for six or. more weeks after implantation, with the suture mass being essentially absorbed in the body within about 180 days post implantation. For example, PDS II sutures (commercially available from Ethicon, Inc., Sommerville, N.J.), are synthetic absorbable monofilament sutures that reportedly retain at least about 20 to 30 percent of its original strength six weeks after implantation. However, PDS II reportedly exhibits minimal mass loss until 90 days after implantation with the suture mass being essentially absorbed in the body about 180 days after implantation. MAXON suture (commercially available from Davis & Geck, Danbury, Conn.) is another absorbable synthetic monofilament that reportedly generally fits this absorption profile.
Later attempts to provide an acceptable absorbable monofilament sutures resulted in MONOCRYL sutures, a suture available from Ethicon, Inc.
Most recently, United States Surgical Corporation has introduced BIOSYN monofilament sutures which exhibit good flexibility, handling characteristics, knot strength and absorption characteristics similar to those of presently available short term absorbable multifilament sutures.
It would be advantageous to provide a bioabsorbable synthetic multifilament surgical suture which exhibits and maintains tensile properties and handling characteristics comparable to commercially available long term absorbable monofilament sutures, without substantially increasing the time at which the suture mass is absorbed in the body.
SUMMARY
It has now surprisingly been found that absorbable surgical articles formed from a block copolymer having one of the blocks made from a random copolymer of glycolide and lactide and another block made from a predominant amount of lactide combined with glycolide exhibit increased in vivo strength retention without exhibiting any substantial decrease in the rate of bioabsorption as measured by mass loss. Preferably, the block copolymers used in forming surgical articles include one block having between about 20 and about 80 mole percent of lactic acid ester units and between about 80 and 20 mole percent of glycolic acid ester units, and lactic acid ester units constitute from about 40 to about 90 mole percent of the overall block copolymers.
The copolymers are prepared by first copolymerizing glycolide and lactide to form a random prepolymer. Lactide is then added to the reaction vessel and combines with the random prepolymer and any residual unreacted monomer to produce a block copolymer.
In particularly useful embodiments, the block copolymers can be spun into fibers. The fibers can be advantageously fabricated into braided multifilament sutures.
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Jiang Ying
Roby Mark S.
Buttner David J.
United States Surgical Corporation
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