Note: Descriptions are shown in the official language in which they were submitted.
3 ~
BACKGROUND OF THE INVENTION
This invention relates to a braided suture of
improved construction.
Sutures intended for the repair of body tissues
must meet certain requirements: they must be substantially
non-toxic, capable of being readily sterilized, they must
have good tensile strength and have acceptable knot-tying
and knot-holding characteristics and if the sutures are of
the absorbable or biodegradable variety, the absorption or
biodegradation of the suture must be closely controlled.
Sutures have been constructed from a wide variety
of materials including surgical gut, silk, cotton, a
polyolefin such as polypropylene, polyamide, polyglycolic
acid, polyesters such as polyethylene terephthalate and ~ -
glycolide-lactide copolymer, etc. Although the optimum
structure of a suture is that of a monofilament, since
certain materials of construction would provide a stiff
monofilament suture lacking acceptable knot-tying and knot-
holding properties, sutures manufactured from such
materials are preferably provided as braided structures.
Thus, for example, sutures manufactured from silk,
polyamide, polyester and bio-absorbable glycolide-lactide
copolymer are usually provided as multifilament braids.
Commercial examples of such sutures include DEXON* (Davis
& Geck, Inc.,~ and VICRYL* (Ethicon, Inc.).
*Trade-marks
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~ 1 Currently available braided suture products are
i acceptable in terms of their knot-tying and knot-holding
properties. However, as removed from the package, they tend
to be stiff and wiry and retain a "set" or "memory" such
that at the time of use, it is usually necessary for the
surgeon or assistant personnel to flex and stretch the
suture to make it more readily handible. Furthermore, the
surfaces of known sutures are perceptibly rough. Thus, if
one passes one's hand or fingers along the braid, surface
irregularities will be readily detected. The result of this
rough surface is that the suture will exhibit drag or
chatter as it is drawn through tissue, characteristics which
militate against smooth, neat, accurately placed wound
approximation so necessary to excellence in surgical
practice.
In the case of one braided suture now on the
market, due to the necessity of having to meet fiber
strength requirements while at the same time retaining ,i -
acceptable knot-tying and knot-holding properties, the ~l
20 suture is constructed from a greater amount of fiber and ; -
consequently is of larger diameter than the accepted industry
standard.
It is an object of this invention to provide a
braided suture of improved characteristics, specifically one : ; -
exhibiting greater flexibility, better hand and less chatter
and drag, than braided sutures of known construction. ~-
It is a particular object of the invention to 'i-~
provide a braided suture possessing a greater number of
sheath yarns, a finer denier for the individual filaments ~---
30 comprising an individual sheath yarn and a greater pick ~ ~ -
count for a suture of any given overall denier (crossovers
per linear inch).
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1 It is still another object of the invention to
provide a braided absorbable suture possessing the aforesaid
improved characteristics.
SUMNARY OF THE INVENTION
By way of satisfying the foregoing objects as well
as other objects of the invention, there is provided in
accordance with this invention a braided suture of improved
construction possessing a significantly greater number of
sheath yarns for a given overall denier, said sheath yarns
being fabricated from individual filaments of finer denier
than filaments which are typical of known types of braided
suture, said improved suture exhibiting perceptibly improved
flexibility and hand and reduced chatter and drag compared
with braided sutures of known construction.
More particularly, in accordance with this
invention, a braided suture of improved construction is ! -:
provided wherein for a given range of overall suture denier, i.. --
the range of pick count, number of.sheath yarns and denier
of individual.filaments comprising a sheath yarn are related
to each other as follows:
Overall Number of Denier of
Suture Pick Sheath Individual
Denier Count Yarns Filaments
~-:......... .
from about 50 from about 50 from about 4 from about 0.2
to about 125 to about 100 to about 16to about 1.8 . .
greater than from about 50 from about 4 from about 0.2
about 125 to to about 100 to about 16 to about 1.8
about 200 .
:
greater than from about 50 from about 4 from about 0.2 . - -
about 200 to to about 100 to about 16to about 1.8 ~.
about 300
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l Overall Number of Denier o'
Suture Pick Sheath Individual
Denier Count Yarns Filaments
~-,
greater than from about 50 from about 10 from about 0.2
about 300 to to about 100 to about 20 to about 1.8
about 500
greater than from about 50 from about 14 from about 0.2
about 500 to to about 100 to about 20 to about 1.8 ~ -
about 800 -
greater than from about 50 from about 16 from about 0.2 ~ I
about 800 to to about 100 to about 32 to about 1.8
about 1200 t~
greater than from about 50 from about 20 from about 0.2
about 1200 to to about 100 to about 36 to about 1.8 ; - -
about 2000 ;
greater than from about 50 from about 20 from about 0.2 - :
about 2000 to to about 200 to about 36 to about 1.8
about 4000
As a result of its possessing a greater number of i-
sheath yarns for a suture of given overall denier and in ! ~
20 some cases, pick count, and together with the finer denier ~ -
o~ the filaments making up a sheath yarn, the braided suture
of the present invention exhibits far fewer surface --
discontinuities thereby providing a suture which is
considerably smoother than braided sutures of known
construction.
The term "suture" is intended to embrace both the
non-absorbable as well as the bio-absorbable varieties.
The term "braid" or "braided" as applied to the
suture of this invention refers to an arrangement of
I discrete units, or bundles, denominated "sheath yarns", made ~-
up cf individual filaments with individual sheath yarns
interlocking or interlacing each other in a regular
criss-cross pattern.
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The term "pick count" refers to the number of
crossovers of sheath yarns per linear inch of suture and,
together with the overall denier of the suture, the denier
of the individual filaments constituting a sheath yarn and
the number of sheath yarns employed, defines the principal
construction characteristics of the braided suture herein.
The braided suture of this invention can
optionally possess, in addition to the braided structure
itself, a core component around which the braid is
constructed. In the case of this embodiment, it is
preferred that the core constitute a larger proportion of
overall suture denier than the core component of a known
braided suture.
The invention will now be described with reference
to the accompanying drawings in which:
FIG. 1 is a photomicrograph (200x) of a cross-
sectional view of a comparison suture outside the scope of
~ 20 the present invention:
; FIG. 2 is a photomicrograph (50x) of a linear view
of the suture of FIG. l;
F~G. 3 is a photomicrograph S200x) of a cross- -~
sectional view of a suture within the scope of the present
invention; and
` FIG. 4 is a photomicrograph (50x) of a linear view
of the suture of FIG. 3.
DESCRIPTION OF THE PREFERRED EMBODIMENTS -~
In a preferred embodiment, the braided suture of
the present invention is fabricated from a bio-absorbable
or biodegradable resin such as one derived from
polyglycolic acid, glycolide, lactic acid, lactide,
dioxanone, trimethylene carbonate, etc., and various
combinations of these and related monomers. Sutures
35 prepared from resins of this type are known in the art, ~ i -
e.g., as disclosed in U.S. Patent Nos. 2,668,162; -~
2,703,316; 2,758,987; 3,225,766; 3,297,033; 3,422,181;
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3,531,561; 3,565,077; 3,565,869; 3,620,218; 3,626,948;
3,636,956; 3,736,646; 3,772,420; 3,773,919; 3,792,010;
3,797,499; 3,839,297; 3,867,190; 3,878,284; 3,982,543;
4,047,533; 4,060,089; 4,137,921; 4,157,437; 4,234,775;
4,237,920; 4,300,565; and, 4,523,591; U.K. Patent No.
779,291; D.K. Gilding et al., "Biodegradable polymers for
use in surgery -- polyglycolic/poly(lactic acid) homo- and
co-polymers: 1, Polvmer, Volume 20, pages 1459-1464
(1979), and D.F. Williams (ed.), Biocompatibility of
Clinical Imlant Materials, Vol. II, ch.9: "Biodegradable
Polymers" (1981).
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1 The defining characteristics of the braided suture
of this invention, apart from the material of its
construction, are:
(1) overall suture denier;
(2) the pattern of the interlocking yarns
expressed as the pick count, which is to say,
the number of crossovers of individual sheath
yarns per linear inch of suture;
(3) the number of sheath yarns comprising the -
braid;
(4) the denier of the ;ndividual filaments
comprising each sheath yarn; and,
(5) the denier of the core, where present.
(1) Overall Denier of the Suture
The overall denier of the braided suture can vary
from about 50 to about 4000. Within this range, the ranges
of overall denier for particular sutures are: from about 50
to about 125 denier; from above about 125 to about 200 ¦ -
denier; from above about 200 to about 300 denier; from above
about 300 to about 500 denier; from above about 500 to about ;-~
800 denier; from above about 800 to about 1500 denier; from
above about 1500 to about 2000 denier; and, from above about `
~ 2000 to about 3600 denier.
`~ (2) Pattern of the Interlockin~ Sheath Yarns rPick Count)
`~ 25 For a suture of any range of overall denier, pick
count can vary from about 50 to about 100 crossovers/inch with
about 55-80 crossovers/inch being preferred. For sutures - ~
constructed within any range of overall denier, as larger -- - -
~` numbers of sheath yarns are employed, the pick-count for
r 30 acceptable sutures will also increase within the above ranges.
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1 For a suture of a particular range of denier and
number of sheath yarns, pick count is advantageously
established to achieve a balance in the properties desired. In
general, with increasing pick count, surface roughness of the
5 suture tends to increase and with decreasing pick count, the -
ability of the external braided sheath to contain the core (if
present) tends to decrease even reaching the point where the
braid may become so loose as to result in the core protruding
therethrough.
For sutures of any specific denier range and number
of sheath yarns, it is preferable to have as low a pick count
as possible in order to achieve optimum surface smoothness,
consistent, of course, with the need to provide a compact braid
which prevents the core (if present) from protruding through -
the exterior sheath yarn structure.
(3) The Number of Sheath Yarns
The number of sheath yarns bears some relation to :- -
overall suture denier, the number generally increasing with -
the weight of the suture. Thus, across the range of suture
weight (denier) indicated above,the braided suture of this
invention can be constructed with from about 4 up to as many as
about 36 individual sheath yarns constructed from individual
filaments having the deniers discussed below. ` ~ -
Table I below sets forth broad and preferred
25 ranges for the numbers of sheath yarns which are suitable !- -
for the construction of braided sutures of various ranges of
overall denier.~ The pick counts of the sutures vary from -~
about 50 to about 100 and deniers of individual filaments i`
vary from about 0.2 to about 1.8 for the broad range of ,-;
number of sheath yarns and the pick counts vary from about
55 to about 80 and the deniers of individual filaments vary -
from about 0.8 to about 1.4 for the preferred range of
number of sheath yarns.
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1 Table I: Sheath Yarns Related to Suture Denier
Number of Number of
Overall Suture Suture Sheath Yarns Sheath Yarns
Denier Size (Broad Range) (Preferred Range)
50 to about 125 7/0,8/0 4-16 6-14
greater than about
125 to about 200 6/0 4-16 6-14 -~-
greater than about - .
200 to about 300 .5/0 4-16 6-14
greater than about . -
300 to about 500 4/0 10-20 12-14 ~ :
greater than about .
500 to about 800 3/0 14-20 14-18 -
greater than about
800 to about 1200 2/0 18-32 20-30
greater than about i
~ 1200 to about 2000 0 20-36 24-34
- grsater than about -~ . - -~.. -.
`~ 2000 to about 4000 1,2 20-36 24-34 !...... .~.. : :.
~:~ While the ~heath yarns need not be twisted, it is i. ;
generally preferred that they be provided with a twist so as
:~ to minimize snagging during braid construction. i~
(4) Individual Filament Denier
The individual filaments comprising each sheath ! -
yarn can vary in weight from about 0.2 to about 1.8 denier .
and preferably from about 0.8 to about 1.4 denier. The
number of such filaments present in a particular sheath yarn '
will depend on the overall denier of the suture as well as ;~
~ 30 the nur~er of sheath yarns utlli~ed in tho construction of `
_ 35
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1 the suture. Table II sets forth some typical numbers ~f
filaments per sheath yarn f~r both the broad and preferred
ranges of filament weight:
¦ 5 Table II: Number of Filaments ~er Sheath Yarn
! approximate approximate Filament
I minimum maximum Denier
,
j 45 450 0.2
150 0.5
1.5
3 40 1.8
(5) Core (O~tional~
For all but the lowest range of overall denier,
the braided suture herein can optionally be constructed
around a filamentous c~re which itself can be braided or
which can be provided in some other configuration such as a
twist, ply, cable, etc. The filament(s) comprising the core
20 need not be as fine as those comprising the sheath yarns. ~
It is particularly advantageous for sutures of heavier - : -
denier to possess a core. Where a core is provided, it is
generally preferred that it possess a weight which is
significantly greater than that of a core of a known suture
of equivalent overall denier.
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1 Table III below provides some typical core deniers
for sutures of various deniers.
Table III: co~e Denier Related to Suture Denier
Denier of Denier of . .- ~ :
Overall Suture Suture Optional Core optional Core ::
Denier Size (Broad Range) tPreferred Range)
.
from about 50 to
about 125 8/0,7/o none none
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greater-than about . .
125 to about 200 6/9 20-8Q 25-50
greater than about -
200 to about 300 5/0 30-100 50-80
greater than about -
300 to about 500 4/0 80-50 80-12
greater than about
500 to about 800 3/0 150-300 180-280
. greater than about
800 to about 1200 2/0 250-700 350-650
greater than about `.
1200 to about 2000 0 400-1200 500-1000
greater than about --~
2000 to about 40001,2 800-2400 1000-2200
It can be advantageous to apply one or more :~
~ coating compositions to the braided suture of this invention
;; to improve such properties as surface lubricity and knot .`-~
tie-down behavior.- A variety of suture coating compositions
;~ proposed for either or both purposes is known in the art,
30 e.g., those disclosed in U.S. Patent No. 4,047,S33
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l It is also within the scope of this invention to
impregnate the suture with, or otherwise apply thereto, one
or more medico-surgically useful substances, e.g., those
which accelerate or beneficially modify the healing process -
when the suture is applied to a wound or surgical site. SG,
for example, the braided suture herein can be provided with
a therapeutic agent which will be deposited at the sutured
site. The therapeutic agent can be chosen for its
antimicrobial properties, capability for promoting wound
repair and/or tissue growth or for specific indications such
as thrombosis. Antimicrobial agents such as broad spectrum
antibiotics (gentamycin sulphate, erythromycin or
derivatized glycopeptides) which are slowly released into
the tissue can be applied in this manner to aid in combating
clinical and sub-clinical infections in a surgical or trauma
wound site. To promote wound repair and/or tissue growth,
one or several growth promoting factors can be introduced
into the suture, e.g., fibroblast growth factor, bone growth
~- factor, epidermal growth factor, platelet derived growth
factor, macrophage derived grown factor, alveolar deri~ed
growth factor, monocyte derived growth factor, magainin, and
so forth. Some therapeutic indications are: glycerol with
tissue or kidney plasminogen activator to cause thrombosis,
superoxide dismutase to scavenge tissue damaging free -
` 25 radicals, tumor necrosis factor for cancer therapy or colony
stimulating factor and interferon, interleukin-2 or other
lymphokine to enhance the immune system. ~-
In the examples which follow, Comparison Examples
l to ll are illustrative of known type sutures while
Examples l to 12 are illustrative of sutures constructed n ; - ~ -
accordance with this invention. ~ ~
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1 ComPariSOn Exam~les 1-7 - -
The following braided suture configurations are
disclosed in U.S. Patent No. 3,565,077:
Overall Denier of . -- -~;
Comparison Suture Pick Number of Individual Denier
Example Denier Count Sheath Yarns Filaments of Core
'~' ,. ~:
1 175 40 6 6 25 ~ ;;:
2 300 46 8 6 100
3 500 40 8. 6 100
4 800 50 12 6 200 :
5 1200 50 16 6 400 .
6 1500 50 12 6 600 -
7 2000 40 16 6 800
.~ - Sutures possessing approximately these ,~
20 configu,rations are relatively inflexible, rough-surfaced and !~
`~ exhibit a relatively high level of chatter and drag.
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1 Comparison ExamPles 8~
The following braided suture configurations are -
those of four commercially available sutures:
Number
Overall of Denier of Denier
Comparison Suture Suture Pick Sheath Individual of
Example Denier Size Count Yarns Filaments Core
8 259 5/0 47 8 2.1 29
9 698 3~0 52 12 2.1 55
1566 0 50 16 2.1 252
11 2122 1 44 16 2.2 330
'
Micrographs obtained by scanning electron
microscopy (SEM) of the suture of Comparison Example 10
(Figures 1 and 2: cross-sectional view at 200x and linear
view at 50x, respectively) clearly show the structural ~
details of the suture. The suture braid is made up of j
- relatively few sheath yarns and the circumferential ,~~ 20 indentations, plainly evident in Figure 1, cause the braid
surface to be relatively rough.
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1 Exam~les 1-8
These examples illustrate various size braided
sutures constructed in accordance with the present
invention.
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Number . - -.-.--
Overall of Denier of D~nier .
Suture Su'_ure Pick Sheath Individual of . ~.
Example Denier Size Count Yarns Filaments Core
- ~:~'
1 96 7/o 828 1.2 --~
2 173 6/0 75'12 1.2 29 :~ .
3 240 5/O 658 1.2 48 : . -
4 389 4/o 7512 1.2 101
5 600 3/O 6516 1.2 216 - .
61080 2/0 7224 1.2 504
71378 0 6528 1.2 706
82028 1 6532 1.21260
l; ~ .'.s
Comparing the details of construction of the !~
~:~ 20 foregoing braided sutures with those of the known braided .
: sutures as set forth in Comparison Examples 1-11, it will be
noted that for sutures of comparable overall denier, the .. ... :.--
suture of this invention possesses a significantly greater
.~ pick count and number of sheath yarns and a significantly !` .
.~ 25 finer denier for.the individual filaments ma~ing up a sheath
yarn than the equivalent characteristics of the known
suture. ....
,~ As a result of their unique construction .. ~
; characteristics, the sutures of this.invention exhibit :." ,,., . .. .:
. .3o perceptibly improved flexibility and hand and reduced
chatter and drag compared with the known sutures of . .
.`:: Comparison Examples 1~
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-15- 13391 8~
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1 Exam~les 9 - 12
The following braided sutures were fabricated in
accordance with the present invention:
Number
Overall of Denier of Denier
suture Suture Pick Sheath Individual of
Example Denier Size Count Yarns Filaments Core -
. -.
9 240 5/0 688 1.240
0 10 600 3/0 71 16 1.2 180
1374 0 67 ' 281.2 702
2 2230 1 5732 1.2 ' 975
In contxast to the suture of Comparison Example
10, su~ra, SEM micrographs of the suture of Example 11
(Figures 3 and 4: cross-6ectional view at 200X and linear
view at 50x, respectively) show a smooth circumferential
, surface as the result of the increased number of sheath j .
:~ yarns and smaller diameter of individual filaments.
Figure 1 as compared to Figure 3 sh~ws the .
; relatively larger core present in the suture of Example 11
as compared to that of Comparison Example 10.
Comparison between Figures 2 and 4 shows the
increased number of picks (crossovers/inch) of the suture of ~ :
: ;25 Example 11 as compared to that of Comparison Example 10. ,:
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