Note: Descriptions are shown in the official language in which they were submitted.
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PLASTIC SURGICAL S~APLE
BACKGROUND
In recent years, surgical staples have come into wide use
as an alternative to sutures in closing incisions of skin,
fascia, and internal organs. Staples have an advantage
over sutures in some applications due to the speed and
ease with which staples may be placed. In addition,
special stapling instruments have been designed which
place an entire row or ring of staples in a single
operation to further simplify and speed up the surgical
procedure.
Surgical staples currently in use are fabricated of
tantalum or stainless steel wire having sufficient tensile
strength and bending modulus to assure that the staple
will remain closed after it has been set in place.
Although it has long been recognized that staples made of
plastic or polymeric materials would be desirable for use
in surgical applications, the development of such staples
has been difficult due to inherent resiliency of such
materials. Staples of known plastic compositions and of
the same configuration as a metallic staple do not have
sufficient strength and bending modulus to stay closed
after being set in place. One approach to utilizing
plastic materials in surgical stapling procedures has been
to provide cooperating mechanical means to secure the
staple in its set configuration. U.S. Patent No.
2,881,762 proposed a circular, open ring-type staple
wherein the ends were designed to pierce the tissue,
overlap and lock to form a closed ring through the tissue
similar to a knotted suture. More recently, a two-piece
staple was suggested in U.S. Patent No. 4~060/089 wherein
a pronged fastener strip pierced the tissue and a
cooperating retainer strip gripped the prongs on the
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opposite side of the tissue. This device is limited in
its application to situations where access to both sides
of the tissue is available, and a special tool is required
to apply the device.
It is an object of the present invention to provide a
plastic staple which functions in a manner analagous to
that of a metallic staple, i.e., a one-piece device which
is applied from one side of the tissue. It is a further
object of the present invention to provide a plastic
staple which can be set with a tool of conventional
design. It is yet a further object of the present
invention to provide plastic staples fabricated of
biologically absorbable polymers as well as of
conventional nonabsorbable polymers. These and other
objects of the present invention will be apparent from the
ensuing description and claims.
SUM~ARY
A one-piece, self-locking, molded plastic staple is
provided which comprises a central beam having outward and
downward L-shaped staple legs secured to each end thereof
by integral hinge means. The central beam has expanding
side wall cam surfaces at each end thereof, and each leg
has a resilient arm extending over the cam surface of the
central beam and terminating in an inward facing cam
follower.
As the staple is closed by rotating the staple legs about
the hinge means, the resilient arms rotate and are de-
flected as the cam followers traverse the cam surface
until the cam follower overrides the end of the central
beam, whereupon the arms close and engage the ends of the
beam to lock the staple legs in their rotated position.
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The staple is emplaced in the tissue with a conventional
stapling mechanism comprising an anvil and forming die.
The anvil supports the ce~tral beam of the stapel while
the forming die acts upon each leg member, causing the
legs to rotate about the hinge means. As the staple
closes, the legs pierce the tissue and form a box-like
configuration enclosing a segment of tissue with the ends
of the staple leg approaching one another within the tissue.
The staple may be machined or molded of any suitable
polymeric material including both biologically absorbable
and nonabsorbable compositions. Preferred absorbable
materials include polymers of lactide and glycolide.
Preferred nonabsorbable materials include nylon and
polypropylene.
~ccording to a further broad aspect of the present inven-
tion there is provided a self-locking surgical staple.
The staple comprises a center beam having opposing side
walls and two staple legs, one extending from each end
of the center beam. The staple legs are joined to the
center beam by hinge means adapted to permit the staple
legs to rotate relative to the center beam. The staple
legs terminate in tissue piercing segments w~lich assume
substantially end-to-end alignment when the staple legs
are rotated relative to the center beam. Cam means is
cooperatively disposed on the side walls and the staple
legs and adapted to lock the staple legs in position with
the tissue piercing segments in substantially end-to-end
alignment when the staple legs are rotated.
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DESCRIPTION OF DR~WINGS
FIGURE 1 is a view in perspective of a surgical staple
according to the present invention.
FIGURE 2 is a plan top view of the staple of Figure 1.
FIGURE 3 ls a side elevational view in partial section
of the staple of Figure 1.
FIGURE 4 is a sectional view through line 4-4 of Figure 2.
FIGURE 5 is a sectional view through line 5-5 of Figure 2.
FIGURE 6 is a view showing the staple of Figure 1 in i.ts
relation to the forming anvil, the forming die and the
wound which is to be closed.
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FIGURE 7 is a view similar to FIGURE 6 showing the staple
in the process of being formed.
FIGURE 8 is a similar view showing the staple completely
formed and closing the wound.
FIGURE 9 is a view similar to FIGURE 5 showing the wound
after the forming tool has been removed.
FIGURE 10 is a view in perspective showing the staple of
FIGURE l in its fully closed and locked position.
FIGURE 11 is a perspective view of a wound properly closed
by a plurality of staples according to the invention.
FIGURE 12 is a view in perspective showing a plurality of
the staples of FIGURE 1 on a stringer for use in a repeat-
ing stapler unit.
DESCRIPTION
With reference to FIGURES 1~3, there is illustrated staple
10 of the present invention comprising center beam 11 and
staple legs 12 which are joined at their base through
hinges 14. Center beam ll has expanding side walls
forming cam surfaces 13 and dwell surfaces 15 at each end
thereof. Extending from the hinge end of each staple leg
are arms 16 which overlie cam surfaces 13 and terminate in
inward facing cam followers 17. The distal ends of staple
legs 12 are sharpened to form tissue piercing points l9.
The base of beam ll is optionally channeled at 20 as
illustrated to form an anvil guide as further described
below.
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Cam followers 17 are beveled at 18 as illustrated in
Figure 4 to provide a cam face angled for engagement with
the cam surfaces of the center beam. FIGURE 4 is a view
of Figure 2 in cross secticn through line 4-4.
FIGURE 5 is a view in cross section through line 5-5 of
FIGURE 2 and illustrates the relative dimensions of
central beam 11 and arms 16. Beam 11 preferably has a
height to width ratio of at least about 1.5 to provide the
desired structural rigidity.
The emplacement of staple 10 to approximate the tissue of
a skin wound is illustrated progressively in FIGURES 6
through 9. The staple is closed by use of a conventional
staple-forming tool which includes anvil 21 and a bridging
die 22 as illustrated in part in FIGURES 6-8.
Referring now to FIGURE 6, staple 10 is positioned in the
forming tool by suitable means with center beam 11
supported by anvil 21 and the extremities of die 22
abutting staple legs 12. Anvil 21 includes a central
stepped section to engage channel 20 of beam 11 and assure
that the staple is centered on the anvil prior to closure.
The forming tool and staple are placed directly over wound
24 in tissue 25. Since the staple legs extend below the
level of the anvil, the legs are caused to make initial
contact with and may penetrate the tissue slightly as the
forming tool is moved into position.
The staple is closed and the wound secured by lowering die
22 beyond anvil 21 as illustrated in FIGURES 7 and 8. In
FIGURE 7, as the staple begins to close, legs 12 penetrate
the skin in a tissue gathering arc and arms 16 rotate
upward with cam followers 17 riding against cam surfaces
13 of beam 11. Beveled face 18 of the cam follower
conforms to the angle of the cam surface and permits
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easier passage of the arms during this motion. As arms 16
rotate upward, opposing arms extending from each leg are
forced apart by the camming action. As the degree of
rotation exceeds about 90 degrees, the cam followers
traverse dwell surface 15 and override the end of beam 11,
whereupon the arms snap back to their original spaced
relation~hip and the cam followers engage the end surface
of beam 11 as best illustrated in FIGURE 10. The staple
is thereupon securely locked in its closed position. Once
the staple is so locked, die 22 is raised and the forming
tool removed leaving the staple securely fastened in the
tissue across the wound with the edges o the wound pro-
perly everted as illustrated in FIGURE 9. FIGURE 11
illustrates a complete incision properly closed with a
series of staples in accordance with the present
invention.
Dwell surfaces 15 are optional but preferably included to
provide mass and strength to the edges of the end walls of
beam 11, and to eliminate the possibility of the end wall
failing under stress once the arms of staple legs are
engaged in the locked position. For similar considera-
tions, bevel 18 of the cam followers does not extend to
the base of arm 16 in order to assure the structural
integrity of the cam follower.
As illustrated and described above, the external parts of
the staple may generally be of a rectangular configuration
while the tissue piercing segments of the staple legs are
preferably of circular cross section for ease of
penetration and to minimize tissue trauma.
The staples of the present invention may be molded as a
series of staples joined by stringer as illustrated in
FIGURE 12. Stringer 26 permits a plurality of staples to
be loaded into a repeating staple setting instrument
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which, in addition to the setting die and anvil previously
described, also includes knife means for severing individ-
ual staples from the stringer as the staples are moved to
the setting position in the instrument. The instrument
preferably also provides means for collecting the severed
stringer pieces to prevent their accidental loss into the
wound site.
In FIGURE 12, the staples are widely spaced on the
stringer for clarity of illustration while in actual
practice, the staples would be in close proximity. Other
methods for providing a plurality of joined staples may
also be used as, for example, molding a plurality of
staples with adjacent arms tacked together at one or two
spots. Individual staples may be severed from such a
molding without concern for collecting severed stringer
pieces.
While the staple of the present invention has been
described and illustrated in a skin closure application,
the staple may be used for closing fascia or internal
organs as well. Since the staple is adapted for use with
staple emplacement tools of a conventional design, the use
of individual staples in cartridge ed, repeating stapling
instruments or in instruments which set a plurality of
staples in a straight line or in a circle with a single
firing is also included within the scope of this inven-
tion. It is understood that some modification of existing
stapling instruments may be required to physically accom-
modate the staples of the present invention, but suchmodification is well within the present skill of surgical
instrument manufacturers.
The staples of the present invention may be constructed in
sizes corresponding to the size of conventional metallic
staples. In an average size staple, the central beam may
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be from about 0.25 to 0.6 cm in length, while the L-shaped
staple leg members and arm extensions are sized propor-
tionately as illustrated, for example, in FIGURE 1.
The staples may be fabricated by any suitable plastic
forming technique including extrusion and injection
molding depending upon staple design and composition of
material which may be any of polymeric compositions known
to be biocompatible in surgical applications. Nylon,
polypropylene, polyester and polysulfone are illustrative
of materials which may be used to form nonabsorbable
staples. Homopolymers and copolymers of lactide,
glycolide and p-dioxanone are illustrative of materials
which may be used to fabricate absorbable staples for
internal application. Other suitable polymeric composi-
tions are known to those familiar with the art and may
also be used in accordance with the present invention.
Nonabsorbable staples of, for example, polypropylene or
nylon may be used in internal applications where absorp-
tion is not an important factor. Where such staples are
used externally, they are easily removed after the wound
has sufficiently healed by inserting an appropriate tool
under the center beam and forcing the staple legs back to
their original position as illustrated in FIGURE 1.
During such removal, the resilient arms of the staple legs
twist until the cam followers are forced past the end of
the center beam, allowing the staple legs to pivot about
the hinge point and return to their original position.
The preceding description and the Figures of the illus-
tration have been directed to a particularly preferred
embodiment of the present invention, and many variations
thereof which will be apparent to those skilled in the
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art are included within the total scope of the present
invention. For example, in addition to permissible
variations mentioned above, it will be apparent that the
details of the staple leg cam and locking means may be
varied consiberably. Each staple leg may, for example,
employ only a single arm extension and cam follower, or
the other suitable staple leg cam and locking means may be
employed. In yet other variations, the center beam and
staple legs may be molded as individual pieces and joined
together by means of hinge pins extending through the arms
of the staple leg and into the sidewall near the end of
the center beam. These and other structural variations
are contemplated by and included within the scope of the
present invention.
