Coated surgical staple

Sterile surgical staples for use with a stapling instrument with the surface of the staple coated with a low molecular weight fluorocarbon polymer.

The invention relates to the use of a low molecular weight fluorocarbon 
polymer as a coating for a metallic surgical staple, to the use of the 
coated staple in a stapler, and to the use of such coated staple in a 
procedure for closing wounds. 
DESCRIPTION OF THE PRIOR ART 
Surgical stapling instruments which are actuated in a repetitive manner to 
discharge and form a series of surgical staples are well known. Such 
stapling instruments have found considerable acceptance in the closing of 
wounds to the skins of humans and animals. The staples themselves are 
metal staples and are made from stainless steel, tantalum, or other 
biologically acceptable metal. In prior commercial practice, the staples 
have often been coated with a soap composition or with a high molecular 
weight polytetrafluoroethylene ("TEFLON") coating, to assist in both the 
placement of the staple and/or the function of the stapling instrument. 
There is, however, room for improvement in the performance of both 
materials. Soap, being bioabsorbable, tends to be absorbed from the 
implanted staple so that some tissue adhesion to the staple can begin to 
occur after wound healing begins; this tends to make staple removal more 
traumatic and painful. TEFLON tends to collect at the anvil, and in a 
multiple fire stapler, jamming can occur. In the commercialized version, 
the TEFLON coating is sprayed on the array of staples after the staples 
have been loaded into the stapler. The coating is present as discrete 
particles on only one side of the staple. It serves only as a mechanical 
lubricant and has little or no effect on the staple performance in the 
wound. 
Noiles, in U.S. Pat. No. 4,275,813, discloses a coherent stack of surgical 
staples bonded together in parallel contiguous relationship by a plastic 
adhesive that can be, inter alia, "halogenated polyalkylenes such as 
polytetrafluoroethylene . . ." 
Bogaty et at., in U.S. Pat. No. 4,012,551, discloses razor blades having 
the cutting edges thereof coated with a mixture of two fluorocarbon 
polymers, one of which can be a low molecular weight fluorinated 
hydrocarbon polymer (referred to in the patent as a "fluorocarbon 
telomer"). 
Homsy et al., in an article entitled "REDUCTION OF TISSUE AND BONE ADHESION 
TO COBALT ALLOY FIXATION APPLIANCES", J. Biomed. Mater. Res. 6, 451-464 
(1972), disclose the use of high molecular weight polytetrafluoroethylene 
as a coating on internal fixation appliances to reduce tissue adhesion to 
such appliances. 
Zambelli et al., in U.S. Pat. No. 3,977,081, disclose the use of a layer of 
polytetrafluoroethylene on a dental implant for the purpose of enabling an 
optimum epithelial adhesion to be generated between the implant and the 
surrounding mucosa and fibromucosa. 
Everett, in U.S. Pat. No. 2,814,296, discloses polytetrafluoroethylene 
coated surgical needles. 
The commercial manufacturer of low molecular weight polytetrafluoroethylene 
(referred to by the manufacturer as a "fluorotelomer") recommends that it 
be used in a number of industrial lubricating and release applications, 
including a heavy duty release agent for application to industrial 
equipment such as presses and rolls, especially in the manufacture and 
processing of hardboard, plywood, laminated wood products, and related 
materials. It is also recommended for use as a thickener for synthetic 
oils and other types of liquid lubricants to produce greases. 
BRIEF SUMMARY OF THE INVENTION 
The invention provides a surgical metallic staple coated with a thin layer 
of a low molecular weight fluorocarbon polymer, an array of such coated 
staples, a surgical stapler containing such coated staples, and a method 
of closing a wound utilizing such a coated staple, especially in those 
wound closure cases wherein the staple will be removed after a 
predetermined degree of healing has occurred. 
Among the advantages that are obtained from using the invention are that 
the surgical stapler containing the subject coated staples is less apt to 
jam after extended operation than is the case with surgical staples coated 
with materials such as silicone and high molecular weight 
polytetrafluoroethylene, (even though the low molecular weight 
polytetrafluoroethylene may collect at the anvil, this does not interfere 
with the operation of the instrument) the staples of the invention 
penetrate tissue quite readily and therefore minimize trauma associated 
with their use, the staples of the invention have little or no tendency to 
adhere to tissue while implanted in the body, and they can be withdrawn 
with relatively little effort. Also, the low molecular weight 
polytetrafluoroethylene is much more readily coated on individual staples, 
forms a more adherent coating thereon, and can be used with less add-on, 
than TEFLON.

DETAILED DESCRIPTION OF THE INVENTION 
In FIG. 1 there is shown one configuration of a sterile surgical staple 10 
of the invention. The staple comprises a pair of legs 11 and 12 connected 
at one end by a crown 13. In this embodiment, the crown is substantially 
perpendicular to the legs. Substantially all of the surface of the legs 
and crown is coated with a low molecular weight fluorocarbon polymer 14. 
In FIG. 2, the staple 15 comprises a pair of legs 16 and 17 joined at one 
end by a crown; however, in this configuration the crown comprises two 
sections 19 and 20 which extend angularly from the legs and are connected 
at the apex 21. Again, substantially the entire surface of the legs and 
crown is coated with a low molecular weight fluorocarbon polymer 22. 
The low molecular weight fluorocarbon-coated staple is produced by 
initially forming the staple in its desired configuration by procedures 
known to the art. The staple is then cleaned, as by ultra-sonic cleaning, 
and is then coated with the fluorocarbon. The coating may be accomplished 
by coating the staple with a dispersion of the low molecular weight 
fluorocarbon polymer in a suitable liquid vehicle, such as 
trifluorotrichloroethane or similar halogenated liquid material, 
evaporating the liquid vehicle, and then, preferably, heating the coated 
staple to fuse the fluorocarbon polymer. The coating can be applied by 
immersing the staple in the dispersion, by spraying, or any other 
convenient method. After draining and air drying to remove most of the 
vehicle, the coated staple is then preferably heated to a temperature of 
from about 570.degree. to 600.degree. F. (299.degree. to 316.degree. C.) 
for 5 to 10 minutes to melt the polymer. This smooths out the coating, 
significantly improves the adhesion of the coating to the staple, and 
removes the remainder of the liquid vehicle for the polymer. Usually, the 
dispersion of polymer in the liquid vehicle will have a polymer solids 
content of from about 5 to 15 weight per cent (based on weight of the 
total disper although the exact proportion has not been found to be 
narrowly critical. An add-on of about 0.05 to about 0.2 weight per cent of 
the staple is usual. After coating, the staple may be sterilized by the 
usual procedures, such as ethylene oxide sterilization or exposure to 
gamma radiation from a radioactive source such as cobalt-60. 
The low molecular weight fluorocarbon polymers are known in the art. They 
are sold commercially, usually in a dispersion of a halogenated liquid 
such as described above. They usually have molecular weights in the range 
of from about 2000 to about 50,000. The polymers contemplated are 
predominantly polymers of tetrafluoroethylene. 
In FIG. 3 there is shown a stack 25 of staples. Each staple 26 comprises a 
pair of legs 27 and 28 connected at one end by a suitable crown 29 with 
the surface of the legs and crown coated with a low molecular weight 
fluorocarbon polymer coating 30. The staples are stacked or butted side to 
side in a suitable array. 
In FIG. 4 there is shown an automatic disposable skin stapling instrument. 
The instrument is loaded with low molecular weight fluorocarbon polymer 
coated sterile surgical staples of the invention. In FIG. 4 only the 
primary components of the surgical stapling instrument are shown. The 
stapling instrument 31 generally comprise a body 32 having a rear portion 
33 which serves as the handle and a forward portion 34. The forward 
portion 34 of the instrument includes a surgical staple magazine indicated 
at 35. The instrument is actuated by the trigger mechanism 36. The 
magazine 35 is affixed to the lower edge of the forward portion of the 
body. The magazine comprises a lower member 37 and an upper member 38 with 
an anvil plate 39 located between these members. The anvil plate 39 
terminates at its forward end in a coextensive anvil surface 40. Slidably 
mounted on the plate is a row of low molecular weight fluorocarbon polymer 
coated staples 41 of the invention. Also slidably mounted on the anvil 
plate 39 is a feeder shoe 42 which is constantly urged towards the anvil 
surface 40 by the double coil spring 43. The forward end of the magazine 
35 provides a channel 44 for a staple driver 45 mounted within the forward 
portion of the instrument body. The staple driver 45 is affixed to a 
staple driver actuator 47. The trigger is operatively connected to the 
staple driver actuator to shift it and the staple driver 45. A return 
spring 48 is located within the forward portion of the instrument body. 
The upper end of the return spring is in contact with the staple driver 
actuator 47 and the lower end of the return spring is mounted on a return 
spring seat 49. The return spring is intended to bias the staple driver to 
its retracted position and at the same time to bias the trigger 36 to its 
normal position. The forward portion 50 of the trigger joins and is 
integral with a pivot pin 51. A portion of the pivot pin is adapted to be 
received in the side walls of the instrument body. The central portion of 
the pivot pin is of a reduced diameter as at 52. It provides clearance for 
the feeder shoe. Hence, the trigger 36 is pivotally fixed to the 
instrument body 32 and is operatively connected to the staple driver 
actuator 47 and the staple driver 45. Instruments of this type, are more 
fully described in U.S. Pat. Nos. 4,109,844 and 4,179,057 assigned to 
Senco Products Inc. and incorporated herein by reference. In operation of 
the stapling instrument, the trigger 36 is pressed and a staple 41 is 
formed about the anvil end 40 and inserted in the skin to close a wound. 
Once the staple is formed about the anvil 40 the trigger 36 is released 
and the instrument may be removed from the staple leaving the staple 
closing the wound. 
In FIG. 5 there is a perspective view of a skin wound closure utilizing the 
staples of the invention. The incised section of the wound (60) is 
approximately in an everted orientation and the staples 61 formed along 
the length of the wound to close the wound. 
FIG. 6 shows a staple 70 joining two sections of skin tissue 71 together. 
The staple is in its formed position. The staple has been bent at points 
along the crown 72 spaced from the legs 73 and 74 to form perpendicular 
areas 75 and 76 to allow the legs to be inserted into the skin. Once the 
wound is healed it is a relatively simple matter to remove the staple with 
an appropriate instrument. Such removal is schematically depicted in cross 
section FIG. 7. The extractor comprises a pair of parallel stationary 
prongs 81 and 82. These prongs are adapted so they will fit beneath the 
crown 72 of the staple at its bent points. The extractor also includes a 
movable central lever 83 which may be pushed between the stationary 
prongs. The prongs are placed beneath the crown and the central lever 
urged between the prongs or the prongs moved upwardly about the center 
lever. The staple shwon in FIG. 7 has been extracted from the wound. 
In the example below, the low molecular weight fluorocarbon polymer 
employed was VYDAX Fluorotelomer 550, a 5 weight per cent dispersion in 
trichlorotrifluoroethane of a polytetrafluoroethylene having an average 
molecular weight of about 3700. The polymer per se has a density at 
77.degree. F. (25.degree. C.) of 2.16 grams per cubic centimeter, a 
softening point (by ASTM E-28-58T) of 510.degree. F. (265.degree. C.), and 
a crystalline melting point of 572.degree. F. (300.degree. C.) 
EXAMPLE 1 and CONTROL EXAMPLE 1 
In this Example, steel surgical skin staples were compared with a 
commercial product, i.e., the same staples coated with soap. The staples 
of the invention were coated by dipping the staples, held on a strainer, 
into VYDAX 550 Fluorotelomer dispersion. The strainer holding the staples 
was removed from the VYDAX dispersion, drained, air dried for 16 hours, 
and then heated in an oven for 10 minutes at 305.degree. C. 
The staples were then loaded into a commercial surgical skin stapler, 
sterilized by exposure to gamma radiation, and then used in the following 
experiment: 
Three healthy mature female Beagle dogs were anesthetized and prepared for 
aseptic surgery. Eight dorsal and five ventral midline full thickness skin 
incisions approximately 3.0cm in length were made in each dog. The cut 
edges of each incision were brought into apposition with subcuticular 
suture of 4-0 VICRYL. The dorsal skin incisions were closed with wide size 
soaped and Vydax coated staples and the ventral incisions were closed with 
regular size soaped and Vydax coated staples. 
Four and seven days following surgery the dogs were anesthetized and the 
staples extracted. Photographs of the extractions were taken at the four 
day time period. 
RESULTS 
Visual and tactile differences in extraction characteristics between the 
soaped and Vydax coated skin staples were more pronounced at seven than 
four days postoperatively. The wide staples in the thicker dorsal skin 
provided extractions that were more demonstrably different than did the 
regular staples in the thinner ventral skin. Variances in wound healing 
also affected extraction differences. Wounds with greater amounts of escar 
formation masked differences in the staple extractions. 
It was concluded that at seven days postoperatively Vydax coated (wide 
size) skin staples appeared to require less force for extraction than did 
soaped (wide size) skin staples, based in differences in visual and 
tactile observations. This distinction could not be made at four days. 
After healing and scar tissue formation, the low molecular weight 
fluorocarbon polymer coated staples of the invention had apparently 
developed less adhesion to the healing tissue than the commercial 
soap-coated staples. 
It has been noted in other experiments that the coated staples of this 
invention have little or no tendency to jam the stapler after repeated 
use. This is an improvement over high molecular weight silicone-coated 
surgical staples, which have not been commercialized for this reason. 
EXAMPLE 2 and CONTROLS 2 and 3 
Straight, pointed surgical staple wire blanks coated with VYDAX 
Fluorotelomer 550 by the procedure described above in Example 1, were 
compared to uncoated controls and TEFLON-coated controls (the TEFLON was 
sprayed on, to duplicate as closely as possible the commerical product), 
in the following experimert: 
The force to insert and extract the staples in dog skin and in moleskin 
(adhesive-backed cotton flannel) was measured. The results are shown below 
in the table 
TABLE I 
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Dog Skin Moleskin 
Insertion 
Extraction 
Extraction 
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Uncoated, Control 2 
Average 236 gms. 7.9 gms 83 gms 
Range 190-350 2-24 36-43 
Number Tested 12 92 15 
TEFLON Coated, Control 3 
Average -- -- 41 gms. 
Range -- -- 18-64 
Number Tested -- -- 12 
VYDAX Coated, Example 2 
Average 167 3.3 12 
Range 100-205 0.1-10 1-38 
Number Tested 12 112 15 
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