CA1274742A

CA1274742A - Surgical staple

Info

Publication number: CA1274742A
Application number: CA000556882A
Authority: CA
Inventors: Thomas H. Barrows; Harold E. Froehlich
Original assignee: Minnesota Mining and Manufacturing Co
Current assignee: 3M Co
Priority date: 1987-02-17
Filing date: 1988-01-20
Publication date: 1990-10-02
Anticipated expiration: 2007-10-02
Also published as: EP0283127B1; DE3879990T2; EP0283127A1; DE3879990D1; JP2587851B2; JPS63203149A; US4719917A

Abstract

ABSTRACT OF THE DISCLOSURE

A surgical staple comprises a central portion of a strong ductile material, lower legs of bioabsorbable material, and a means of attaching the central portion to the lower legs to provide a simple, safe method for stapling mammalian tissue.

Description

~2~

SURGICAL STAPLE
FIELD OF THE INVENTION
_ The present invention relates to a surgical skin staple comprising bioabsorbable and nonabsorbable parts.
In another aspect, a method of stapllng skin using the stapla of the invention is disclosed.

BACKGROUND OF THE INVENTION
The use of surgical stapling as a method for suturing has increased dramatically in recent years. Staples have been used both internally and in the skin. The first staples used were metallic staples, and they are still widely used; see, for example, U.S. Patent No. 4,321,002.
For internal use metallic staples are frequently permanently implanted, while metallic staples in the skin are removed as soon as healing permits. For some purposes two piece staples are used wherein a fastening member and receiving member are used. Although these two piece staples were initially metallic, several polymeric fasteners have now been described, or example in U.S.
Pat~nt Nos. 4,532,926; 4,534,352; and 4,534,350. A
multi-part surgical fastener for inserting multiple staples in soft body tissue (but not skin) includes "absorbable plastic" parts and is described in U.S. Patent Nos. 4,060,0B9 and 4,513,746.
Polymeric surglcal staple6 deslgned for use in one piece are limited, but a one piece devlce using a hinge and cam principle is describecl in U.S. Patent No.
4,~28,376. U.S. Patent No. ~,317,451 discloses plastic surgical ~taples which can be made of totally absorbable or totally nonabsorbable materials.
The type of staple commonly used for stapling skin is different from most other staples. Skin staples, to be closed, are acted upon by forces only Erom one sicle of the ~7~

stapled medium, whereas other types oE staples are acted upon by forces above ancl below the stapled mediu~. Sucll skin staples may be supplied singly or in array for use ln a cartridge or stapling instrument. An example of an array of metallic staples bonded together by a biodegradable absorbable plastic is found in U.S. Patent No. 4,275,~13.

SUMMARY OF THE INVENTION
__ Briefly, the present invention provides a novel staple for use in mammalian tissue comprising a conventional central portion of strong, ductile material physically or chemically coupled to bioabsorbahle legs, the staple being used in a process for stapling tissue which does not require a special tool for removal.
The staple of the present invention has certain advantages compared with skin staples known in the art.
It requires no significant modification of either insertion hardware or user procedures for insertion; the load-bearing strength and ductility of the preferahly metallic central portion is maintained; staple removal is required only for the central portion; the pain of removal is minimized since the bioahsorbable legs remain embedded;
and the cost of staple removal can be eliminated since it can be carried out by the patient rather than by medical personnel.

In this application:
'7bloabsorbable" means that a substantial portion (preferably greater than 50~) is gradually degraded by mammalian tissue to the point that it is no longer present at the implant site and is ~etabolized by and/or excreted from the body;
"nonabsorbable" means resistant to degradation by hydrolysis and/or enzymatic attack in mammalian tissue;
"degraded" means broken down chemically so as to provide species with lower molecular weight and/or different chemical structure;

~2~

"coupled" means a joining by physical (e.g., mechanical~ means, as by use of a socket, rivet, pin, crimp, screw, tongue and groove, locking taper, or chemical means, as }~y use of adhesive ~cyanoacrylate, hot melt, pressure-sensitive, priming, and the like);
"mammalian tiSSlJe" means living tissue, mucous membranes, skin, gingival tissue, and the like of a mammal;
"lower leg portions" means the bioabsorbable portion of a staple that can be curved (e.g. arcuate), or bent, and having tapered and pointed ends;
"upper leg portions" means the parts of the central portion provided by subjecting the central portion to bending;
"central portion" means a wire-like or hollow metal member of a staple out of which a crown and upper leg portions are formed; it can be initially straight, curved, or combinations thereof;
"crown" means the portion of the staple external to the skin when the staple is implanted;
"closed shape" means that when the staple is bent into its fully implanted configuration, it has a circular, elliptical, rectangular, square, D-shape, or variation or modification thereof, with the tips essentially directly apposed (touching or not touching) or overlapping; and "approximating" means touching, not touching but aligned with a gap, or overlapping.

BRIEF DESCRIPTIOM OF' THE DRAWING
_____ _ . __ _ __. _ _ _ FlG. 1 shows an elevational view of one embodiment of a skin staple of the present invention in open configuration;
FIG. 2 shows the skin staple of FIG. 1 in a partially closed confi~uration;
FIG. 3 shows the skin staple of FIG. 1 in a fully closed configuration;

~2741~%
_g_ FIG. ~I shows the skin staple of FIG. 1 wherein the central portion is separated from implanted lower ley portions;
FIG. 5 shows a portion of a second embodiment of a staple of the invention having tongue and groove coupling means;
FIG. 6 shows a portion of a staple of a third embodiment having a tongue and groove coupling means which includes a pin for joining the central portion of the staple to the lower leg portion;
FIG. 7, a fourth embodiment, shows a stapls having a curved central portion which is generally "u", "v" or "m"
6haped and having arcuate lower leg portions;
FIG. 8 shows the skin staple of FIG. 7 in closed position which ~orms a D-shaped configuration;
FIG. 9, a fifth embodiment, shows a staple having a curved central portion which is generally "u", "v", or "m"
shaped and having bent lower leg portions;
FIG. 10 shows the staple of FIG. 9 in a closed position; and FIG. 11 shows a portion of a staple of a sixth embodiment in which coupling is achieved by adherance.

DETAILED DESCRIPTIOM_ F T~IE INVENTION
The present invention provides a surgical staple for use in closing an opening in mammalian tls6ue, the staple, when open, comprising a central portion of strong, ductile, non~absorbable material, and lower leg ~ortions at opposite ends of the central portion, the lower leg portions comprising bioabsorbable material and flanking the central portion and having points at their ends and being ~oined by coupling means to the central portion, which staple when closed is bent in the central portion to form the crown portion and upper leg portlons which with the bioabsorbable lower leg portions form generally into a closed shape with the lower leg portions in a position approximating one another so that each of the lower leg portions of the staple can extend through the tlssue on one side of the closed tissue opening 60 as to ho]d the tissue firmly in closed position.
The mechanical coupling means between the central portion of the staple and the bioabsorbable lower leq can be a socket that frictionally or telescopically receives the lower leg, as illustrated in the Drawinq in FIGS. 1,

2, 3, and 4, or it can be a tongue and groove frictional coupling means as in FIGS. 5, 6, 7, 8, 9 and 10, or comblnations of any of these coupling means. For example, the central portion of the staple as shown in FIG. ~ can be a hollow tube or it can be a solid wire. In the embodiment of FIG. 6, the coupling means can be a mechanical fastener (i.e., tongue and groove) with, for example, a bioabsorbable pin or rivet. In still another embodiment as shown in Fig. 11, a bioabsorhable lower leg is caused to adhere to the metal central portion of the staple during an insert injection molding process.
The present invention also relates to a method of suturing wherein the upper portion of a two-component (one of the two components represents two parts which are the same, i.e. two legs) one-piece staple is removed from a stapled site after the bioabsorbable legs have heen partially degraded.
The upper portion of the staple o~ the present invention maintains its integrity and i6 generally metallic, but could be any material which meets the needs of strength and ductility and is tissue-compatible. For example the upper portion i~ a nondegradabla material which preferably is any conventional metal, including alloys, which is suitable as a metalllc staple component, e.g., stainless steel, such as 316L stainless st~el, titanium, steel alloys, titanium alloys, nickel chromium alloy (NichromeTM), nickel/cobalt/chrome, or comhinations therèof.

~27~7~2 The lower leg portion of the skin staple of the invention can be any bioabsorbable material6 whether natural or synthetic. Synthetic bioabsorbable polymers are preferred. Copolymers or combination6 of suita~le bioabsorbable polymers are also included within the scope of suitable materials. That is, the lower staple legs of the invention can consist of a mixture or combination of two or more bioabsorbable polymers. Natural polymers are preferably used in admixture with synthetic polymers.
Representative bioabsorbable natural and synthetic polymers include:

Natural Polymers 1) Partially oxidized cellulose surgical hemostats (see U.S. Patent No. 3,364,200) such as Oxycel (fibrous surgical hemostatic material, Parke~Davis) and Surgic~lrM
(woven fabric hemostatic material, Surgikos).
2) Chitin and/or chitin derivatives (e.g. U.S.
Patent No. 4,074,366).

3) Collagen, regenerated collagen or catgut suture materialO

Synthetic Polymers 1) Polyamino acids, polyamino acid copolymers and derivatives such as partially esterified poly-L-glutamic acid (U.S. Patent No. 3,371,069), amino acid-hydroxy acid copolymer (U.S. Patent No. 3,773,737), and nylon 2/nylon 6 copolymer (W.J. Bailey, et. al., "Biodegradable Polyamides", Pr_ _edinq~_of 3rd International Biode~radation _ y~e~ium, Sharpley and Kaplan eds., Applied Science Publishers Ltd., London, 1976, E~.
765-773).
2) Polyesters Eormed from diols and succinic and/or oxalic acid such as those described in U.S. Patent Nos.

4,032,993 and 3,883,901, isomorphic copolyoxalates (U.S.

~2'7~2 Patent No. 4,141,0~7), and poly(alkylene oxalate6) (U.S.
Patent No. 4,140,678).
3) Polymalic acid (U.S. Patent No. 4,265,247).
4) Polydioxanone (U.S. Patent No. 4,052,9~8).

5) Poly-beta-hydroxy acids such as polyhydroxybutyrate (U.S. Patent No. 3,225,766).

6) Poly-alpha-hydroxy acids such as polyglycolic acid, polylactic acid, (V.S. Patent No. 3,636,956), copolymers of lactic and glycolic acids, (U.S. Patent No.
4,137,921), and said polymers copolymerized with other polyesters (U.S. Patent No. 4,118,470).

7) Polymers made from unsymmetrically-substituted 1,4-dioxane-2,5-diones (U.S. Patent No. 3,960,152).

8) Polyesteramides such as those described in U.S.
Patent Nos. 4,209,607 and 4,343,931.

9) Copolymers of glycolide and trimethylene carbonate such as described in U.S. Patent No. 4,429,080.

10) Polycaprolactone and copolymers of lactide with epsilon caprolactone such as described in U.S. Patent No.
4,057,537.
Preferred biodegradable polymers and copolymers for use in the invention are polylactic acid (IJ.S.
Patent No. 3,636,956), polyglycolic acid (U.S. Patent No. 3,297,033), polydioxanone (U.S. PateIlt No. 9,052,988), copolymers of glycolide and trimethylene carbonate (U.S.
Patent No. 4,429,080), poly(lactide-co-glycolide) (U.S.
Patent No. 4,137,921) and poly(esteramides) such as poly(oxysucclnoyloxydodecane~1,12-di~amidocarbonylmethylene)~co~10 percent~
oxysuccinoyloxy-4,9-dioxadodecane-1,12~
di(amidocarbonylmethylene)~ and poly[oxy~uccinoyloxyhexarle-1,6~t1i~amidocarbonylmethylene)]
(U.S. Patent No. 4,3~3,931), and mixtures thereof. ~rhese polymers and copolymers are preferred because they are known to be well tolerated hy the body upon implantation in ~2~7~

addition to being bioabsorbable. Mixtures of polymers allow for variation of properties of the staple legs.
The bioabsorbable lower legs of the skin staple of the invention are selected to provide sharp, penetrating tips which release from the central portion of the staple at a specific time post-implantation thereby permitting painless removal or sloughing of the staple crown and upper legs.
The release time can be varied, for example, by choice o~
bioabsorbable lower leg material, the coupling means and its conEiguration, and the configuration between the interface of metal and polymer.
The bioabsorbable polymer lower legs (which inclu~e tips) can readily be insert injection molded onto the ends of the upper leg portions of the central ~ortion of the staple. The bond between the lower and upper leg portions can be an adhesive one that results from the cooling of the polymer in contact with metal. Part of the adhesion results from shrinkage of the polymer upon cooling when it is in a configuration so as to surround the metal upper leg portion as is shown in FIG 11. Other conventional methods such as casting from a solvent or melt pressing can also be used. Alternatively, polymer tips can be inserted into hollow metal tubes at the ends of the upper leg portions.
In such a case, a bioabsorbable adhesive can be useEul. In such metal tubes various mechanical or friction means for locking in the polymer lower legs can be used, see, for example, FIGS. 5 and 6. Other locking mechanisms include a locking taper, a screw, a rivet, etc. Lower leg portions can be reinforced using polymer in combination with inorganic compounds such as tricalcium phosphate, potassium meta-phosphate, or hydroxylapatite, or resorbable ylasses and ceramics such as those described by Orthopedlcs, 8:7, ~07-915 (July 1985).
Referring now to the Drawing, FIG. 1 shows one embodiment of a staple 10 oE the inventicn in open position. Central wire portion 2 is frictionally attached to bioabsorbable lower legs ~ having tips 5.

7D~2 _9_ In FIGS. 2, 3, and 4 varlous confi~urations of a surgical staple of the invention are shown. Staple 10 is shown in FIG. 2 (par~ially closed) and in FIG. 3 (clo.sed position). The crown 6 ancl upper leg portions 8 are rnetallic of solid or hollow stock and the lower legs ~ are made of a bioabsorbable material. '~he staple can be dispensed from a conventional mechanical device and can be inserted by means of sharp, needle-like t~ps 5 into the skin 3 to close a break 7 in the skin 3 such as a wound as shown in FIGS. 2 and 3. FIG. 4 shows the wound 3 to 7 days post implantation where sufficient healing has taken place to permit staple removal. The crown ~ and upper ley portions a of staple 10 have been separated from the bioabsorbable lower leg portions 4 and explanted from the tissue by application of gentle traction on the exposed crown 6. This can be accomplished, ~or example, by the patient plucking out the metal using fingernails, or by the action of a wash cloth used during bathing. An alternative method for rapid staple removal is to place a strip of adhesive tape on top of a row of staples in the skin and then to quickly strip off the tape which will pull out all the staple crowns.
The absorbable lower legs ~ and tips 5, which are not necessarily completely absorbed at this time, remain buried ~5 under the skin and are slowly absorbe~ by the body. ~rimes for absorption can range from about 2 months to about 2 years depending on the composition oE the lower leg portions and their shapes. Polymer thus implanted should have no effect on the rapicl healing of the holes 9 (shown in FIG. 4) made by the staple 10 once the crown 6 is removed.
Various curved and angled staples and staple tips using various arcurate aspect ratios can be used ancl are contemplated as part of the invenkion.
FIGS. 5 and 6 show enlarged fragmentary portions of a staple of the invention. Upper leg portion 18 is ~Z7D~

mechanically coupled, by a means having tongue 16 and groove 12, to bioabsorbahle lower leg portion 14 having tip 15. In ~IG. 6, it can be seen that pin 11, which is bioabsorbable, secures the tongue 13 and groove 17 coupling means.
FIG. 7 shows staple 20 in open position having curved crown 26, upper leg portions 28, and arcuate lower leg portions 25 with sharp tips 27~ The coupling means has tongue 22 and groove 24. FIG. 8 shows staple 20 in closed position so as to form a D-shaped configuration with tips 27 closely approximating (in this case, slightly overlapping) each other.
FIG. 9 shows staple 30 in open position having curved crown 36, upper leg portions 38, and bent lower legs 32 with sharp tips 34. The coupling means has tongue 33 and groove 35. FIG. 10 shows staple 30 in closed position so as to form a rectangular-shaped configuration with lower leg tips 34 in close approximation and slightly overlapping.
FIG. 11 shows an enlarged fragmentary portion of a staple, another embodiment, o~ the invention. Upper leg portion' 46 is adhesively coupled to lower leg portion 48 as a result of an lnjection molding process in which end part 42 of upper leg portion ~6 is pressed into end part 4g of lower leg pprtion ~8 when lower leg portion ~8 is in a molten sta~e. It is also within the scope of the present invention to utili%e a bioabsorbable adhesive to adhere upper leg'portion ~6 and lower leg portion ~8 together.
In addition to the characteristics of materials being employed, other factors influence a satisfactory and cosmetically appealing skin closure. Skin thickness varies from patient to patient and also'with the particular body ~urface being stapled. This in turn, necessitates'the use of differing implantation techniques and in some cases a staple of different design. Skin thickness, applicati'on tt~chnique, and staple design all impact staple performance.

, .

7~:

Staples have been known to fall out of the sl<in, fall to puncture the skln, let the wound gap open, gather excessive amounts of tissue, invert the skin eclges, produce a stepped closure at the incision line, rotate in the wound, and fall to close properly.
~ satisfactory staple design must eliminate, or at least minimize these performance deficiencies. Asi~e from the material properties, there are certain geometric design parameters which alter staple performance. From an analytical standpoint, eleven staple performance characteristics have been defined and are measureable.
These are: linear gather, compression ratio, staple rotation, gathering angle, penetration angle, tissue scarring, penetration force, removal characteristics, staple formation forces, actuator staple interactions, and anvil restraint requirements.
In analysing staple performance, the single most important aspect is the path various points on the staple tip follow as the staple is closed. Particular designs perform better in certain situations. FIG. 1 shows an example of a staple which gathers a lot o~ tissue. FIG. 7 shows example of a staple that punctures a wide range oE
skin thicknesses very well. FIG. 9 shows an example of a staple which maintains an everted skin edge.
Objects and advantages of this invention are further illustrated by the following examples, but the particular materials and amounts thereof recited in these examples, as well as other conditions and details, should not be construed to unduly limit this invention.
Example 1 In order to discover whether or not an absorbable polymer component will in fact separate from a wire component at a useful time post-implantation, an l_ vitro evaluation using pH 7.4 Krebs-Ringer phosphate solution at 37C to simulate physiological conditions was performed.

~2~742 The samples were made from melt pressed films of poly[N,N'-dodecamethylenebls(amidome~hylene)-succinate-co-10%-N,N'-~,9-dioxadodecamethylenebis-(amidomethylene)succinate] prepared according to the procedure of Example ll in U.S. Patent No. 4,529,792 and Nichrome wire (2~ guage). Films of two diEferent thicknesses (29 samples of 0.28 mm thickness and 27 samples of 0.3~ mm) were each cut into pieces measuriny 5xlOmm.
Wire was cut into 10cm lengths and a loop was formed at one end of each piece. The straight end was then heated in a flame and carefully pressed into the center of a polymer sample resting on a block of polytetra~luoroethylene (TeflonTM, Dupont) to provide a coupliny means similar to that of FIG. 1.
~ The polymer-wire samples were placed in the Krebs-Ringer solution at 37Ç and tested periodically by supporting the polymer and hanging a 150 g weight on the wire loop. Under these conditions the wire either pulled out of the polymer and was noted as a release or remained embedded and was returned to the 37C solution for further soaking.
The 150g dead load release limit was selected after determining that twice this value is approximately the maximum weight that can he supported on the volar surface of the index fingernail without causing discomfort.
As shown in TABLE I, the average time re~uired for release o the wire from the polymer in vitro was 1.1 days for a 0.28 mm deep embedding and 1.8 days for a 0.38 mm deep embedding. These values demonstrate that the polymer in this Example was useful for the present staple application.

Poly~L-lactide-co-30%-glycolide) was synthesized according to a published procedure (D. K. Gilding and A. M.
R~ed, Biodegradable Polymers for Use in i Surgery-Polyglycolic/Polylactic acld) Homo- and Copolymers, Polymer, 20, 1459-1~64, lg79). ~he polymer was melt pressed into 0.33 mm and 0.56 mm thick sheets and Cllt into 5xlO mm test samples. Nichrome wires were embedded in the samples and tested as described in Example 1. As shown in TA~LE I, release of wire from the poly(lactide-glycolide) sample was dependent on the thickness of the film (i.e.
depth of wire embedding). The 0.33 mm thick polymer released from the wire after an average of 1.5 days, whereas the 0.56 mm sample released after an average of 3.2 days. Since staple removal is normally permissible after 3 to 7 days, these data indicate that an ideal value for release performance can be achieved with this type of polymer.
Example 3 A 0.33 mm thick sheet of polydioxanone was obtained by melt pressing commercially available size 2-0 polydioxanone (PDS~M) violet monofilament absorbable s~tures (Ethicon, Inc., Some~ville, NJ 0~876). Polydioxanone reprocessed in this manner gave a soft, somewhat rubbery material. In the actual manufacture of staples, the molten polydioxanone could be solidified under controlled conditions which develop higher crystallinity and thus greater stiffness.
Samples of wire embedded in polydioxanone and tested as described in the previous examples released after an average of 1.2 days ln vitro (T~sLE I). The data show that the polydioxanone-metal bond is also susceptible to moisture induced loosening and can be utilized in the manuacture of staples o the present invention.

~ tF~
U~

oo Ll~
a) o a ~ ~ ~ V~ ~1r l ~, /a ~t) Q) ~
.rl~ ~rl a) i¢ ~ ~_ O I II ' r-l CO
I I I
tJ~ U) 1--a) I I I
O U~ ~D
I I ' I ~ I
~1 a1 ~1~') r~l 11~ Ir lr l ~7 1_1 Ir-l (~) ~ ¦
1 ~
a) 4~ a) ~ r-- o~ o ~r ~10 ~ ~1 ~I r l a ,_ O ~
r-l U~ ~Z; O O O O O O
~ .
r-l ~ O
~ a , r-l n r H
O ~

:qR ~?
E-~ a) r l .rl ~ Ei :z; (n ~ ' ~
a U~ , ~
' Eio~) ~
~r o ~
r-l Ll ~ U~ ~000 ~)~D (~
IJ O
a O O O O O
~rl a '' o ~r~
."
o ~I
Ll O
U~ , ~) ~ _ .
'' ~ a Z~
.,~
er ~4 o o 0 U~ U
~ o ^-- :~ ~ ' ~,1: Wa) r-l r-~
~1- .rl ~rl I I 11) al 0 0 ra ~ o .1 rl ~rl o c a.) ~ JJ ~ 0 "~ X
I u~ 0 U~ I (L) ~ )r-lr~l .rl _ ~
a)~ ~ ~ ~ ~ ~ ~ , . ;.
r 1 ~1) rl r l~.1r-l r-l r~l .
(L)~I O OOOOO

Various modifications and alterations of thi.s invention will become apparent to those sk.illed in the art Witllout departing from the scope and spirit of this invention, and it should be understood that this invention is not to be unduly limited to the illustrative embodiments set forth herein.

.

,

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A surgical staple for use in closing an opening in mammalian tissue, said staple, when open, comprising a central portion of strong, ductile, non-absorbable material, and lower leg portions at opposite ends of the central portion, said lower leg portions comprising bioabsorbable material and flanking said central portion, said lower leg portions having points at their ends and being joined by coupling means to said central portion, which staple when closed is bent in the central portion to form a crown portion and upper leg portions which with said lower leg portions form generally into a closed shape with said lower leg portions in a position approximating one another so that each of said lower leg portions of the staple can extend through the tissue on one side of the closed opening so as to hold said tissue firmly in closed position.

2. The staple according to claim 1 wherein said coupling means is a socket that frictionally receives said lower leg portions of said staple.

3. The staple according to claim 1 wherein said coupling means is a tongue and groove frictional coupling means.

4. The staple according to claim 1 wherein said coupling means is a mechanical fastener.

5. The staple according to claim 1 wherein said coupling means is an adhesive bond.

6. The staple according to claim 5 wherein said adhesive bond is formed by insert injection molding.

7. The staple according to claim 4 wherein said mechanical fastener comprises a rivet or pin.

8. The staple according to claim 1 wherein said bioabsorbable material is a natural or synthetic polymer or a combination thereof.

9. The staple according to claim 8 wherein said bioabsorbable material is a synthetic polymer selected from the group consisting of polyglycolic acid, polylactic acid, polycaprolactone, poly(esteramides), polydioxanone, and copolymers and mixtures thereof.

10. The staple according to claim 8 wherein said bioabsorbable material is a poly(esteramide).

11. The staple according to claim 1 wherein said central portion comprises at least one surgical metal or alloy.