U.S. patent application number 14/471519 was filed with the patent office on 2015-04-23 for dynamic bioabsorbable fastener for use in wound closure.
The applicant listed for this patent is Incisive Surgical, Inc.. Invention is credited to Joseph M. Gryskiewicz, David B. Herridge, James A. Peterson, Delmer L. Smith, Christopher J. Sperry.
Application Number | 20150112369 14/471519 |
Document ID | / |
Family ID | 46303579 |
Filed Date | 2015-04-23 |
United States Patent
Application |
20150112369 |
Kind Code |
A1 |
Peterson; James A. ; et
al. |
April 23, 2015 |
DYNAMIC BIOABSORBABLE FASTENER FOR USE IN WOUND CLOSURE
Abstract
A fastener for insertion into pierced openings of a tissue wound
has a body formed of a generally bioabsorbable polymer defining an
initial capture area. The body includes a pair of arms, each with
an inwardly projecting cleat operably joined at an elbow portion
defining an internal elbow angle. The arms are operably joined to a
backspan at a shoulder portion defining an internal shoulder angle.
A durable tissue retention zone is defined between the cleat and
the arm. The elbow portion and the internal elbow angle define an
insertion width greater than a width of the pierced openings
resulting in the pierced openings stretching over the cleat and
being elastically retained within the durable tissue retention
zone. The fastener captures wound tissue in the initial capture
area and then dynamically reforms in response to lateral stresses
without a fracture failure of the fastener until a minimum
degradation period.
Inventors: |
Peterson; James A.; (Edina,
MN) ; Sperry; Christopher J.; (Plymouth, MN) ;
Gryskiewicz; Joseph M.; (Edina, MN) ; Smith; Delmer
L.; (Edina, MN) ; Herridge; David B.; (Mendota
Heights, MN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Incisive Surgical, Inc. |
Plymouth |
MN |
US |
|
|
Family ID: |
46303579 |
Appl. No.: |
14/471519 |
Filed: |
August 28, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13796798 |
Mar 12, 2013 |
8821517 |
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14471519 |
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13314978 |
Dec 8, 2011 |
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13796798 |
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11022319 |
Dec 23, 2004 |
8074857 |
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13314978 |
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10448838 |
May 30, 2003 |
7686200 |
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11022319 |
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10179628 |
Jun 25, 2002 |
6726705 |
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10448838 |
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10607497 |
Jun 25, 2003 |
7950559 |
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11022319 |
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10603397 |
Jun 25, 2003 |
7112214 |
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10607497 |
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Current U.S.
Class: |
606/151 |
Current CPC
Class: |
A61B 17/10 20130101;
A61B 17/0682 20130101; A61B 2017/00004 20130101; A61B 2017/081
20130101; A61B 17/068 20130101; A61B 17/08 20130101; A61B 17/30
20130101; A61B 17/064 20130101; A61B 2017/00407 20130101; A61B
17/0644 20130101; A61B 17/282 20130101 |
Class at
Publication: |
606/151 |
International
Class: |
A61B 17/08 20060101
A61B017/08 |
Claims
1-9. (canceled)
9. A bioabsorbable fastener, comprising: a fastener body having a
pre-deployment orientation, the fastener body includes a backspan
having a first arm and a second arm attached to as to define first
and second shoulder portions respectively, the first arm and second
arm each having an internally projecting cleat so as to define
first and second elbow portions respectively, the first arm and the
second arm extending generally transversely from the backspan when
in the pre-deployment orientation, and wherein the fastener body
has a post-deployment orientation in which the fastener body
remains intact, wherein the first arm and the second arm are spread
apart in the post-deployment orientation so as to define first and
second shoulder angles at the first and second shoulder portions
that exceed 90.degree. and wherein a first and second elbow angles
defined at the first and second elbow portions are less than
90.degree. in the post-deployment orientation so as to continue
retaining captured tissue in the post-deployment orientation.
10. A bioabsorbable fastener, comprising: a fastener body having a
pre-deployment orientation, the fastener body includes a backspan
having a first arm and a second arm, the first arm and the second
arm extending generally transversely from the backspan when in the
pre-deployment orientation, and wherein the fastener body had has
post-deployment orientation in which the fastener body remains
intact, wherien the first arm and the second arm are spread apart
so as to define first and second shoulder angles between the first
arm and second arm relative to the backpan that exceed
90.degree..
11. A method for retaining wound closure with a bioabsorbable
fastener, the method comprising: placing a fastener having a first
disposition across a wound such that a first fastener arm is
inserted into a first tissue surface and a second fastener arm is
inserted into a second tissue surface such that a fastener backspan
resides across the wound and the first tissue surface and second
tissue surface are approximated, the first disposition having the
first fastener arm and the second fastener arm arranged generally
transversely to a backspan axis defined by the backspan;
maintaining approximation of the first tissue surface and the
second tissue surface as the fastener transitions to an open
disposition at a time subsequent to initial placement of the
fastener across the wound in response to lateral forces applied by
the first tissue surface and the second tissue surface, the open
disposition having the first fastener arm and the second fastener
arm arranged generally parallel to the backspan axis.
Description
PRIORITY CLAIM AND RELATED APPLICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 13/796,798, filed Mar. 12, 2013, which in turn
is a continuation of U.S. patent application Ser. No. 13/314,978,
filed Dec. 8, 2011 (now abandoned), which in turn is a continuation
of U.S. patent application Ser. No. 11/022,319, filed Dec. 23, 2004
(now U.S. Pat. No. 8,074,857 issued Dec. 13, 2011), which in turn
is a continuation-in-part of U.S. patent application Ser. No.
10/448,838, filed May 30, 2003 (now U.S. Pat. No. 7,686,200 issued
Mar. 30, 2010), which is a divisional of U.S. patent application
Ser. No. 10/179,628, filed Jun. 25, 2002 (now U.S. Pat. No.
6,726,705 issued Apr. 27, 2004), and U.S. patent application Ser.
No. 11/022,319 is also a continuation-in-part of U.S. patent
application Ser. No. 10/607,497, filed Jun. 25, 2003 (now U.S. Pat.
No. 7,950,559 issued May 31, 2011), and U.S. patent application
Ser. No. 11/022,319 is also a continuation-in-part of U.S. patent
application Ser. No. 10/603,397, filed June 25, 2003 (now U.S. Pat.
No. 7,112,214 issued Sep. 26, 2006), all of which are herein
incorporated by reference in their entirety.
FIELD OF THE INVENTION
[0002] The present invention relates generally to the field of
surgical fasteners for use in wound closure. More particularly, the
present invention relates to a design for a dynamic, bioabsorbable
fastener designed for through-and-through insertion across a wound
having a capacity to reform when exposed to wound stresses greater
than the initial static strength of the fastener while continuously
retaining and approximating opposing sides of a wound during the
healing process.
BACKGROUND OF THE INVENTION
[0003] When an opening in tissue is created either through an
intentional incision or an accidental wound or laceration,
biological healing of the opening commences through the proximity
of the opposed living tissue surfaces. If the opening is very large
or if its location subjects the wound to continual movement, a
physician will seek to forcibly hold the sides of the opening
together so as to promote the healing process.
[0004] In the case of skin tissue, for example, healing occurs best
when the opposing dermal layers of the skin tissue are held in
tight, primary proximity with each other. Human skin tissue is
comprised of three distinct layers of tissue. The epidermal layer,
also known as the epidermis, is the outermost layer and includes
non-living tissue cells. The dermal layer, or dermis, is the middle
layer directly below the epidermal layer and comprises the living
tissue of the skin that is the strongest of the three layers. The
subcutaneous, or hypodermis layer, is the bottom layer of skin
tissue and includes less connective tissue, making this the weakest
layer of skin tissue.
[0005] The most prevalent method for forcibly closing a tissue
opening is through the use of a suture or "stitches." As early as
the second century, the Greeks were using sutures to physically
close skin openings. In its simplest form, a suture is simply a
length of material that is attached to a tissue-piercing device,
such as a needle, and looped through the opposing sides of a tissue
opening. The suture is then pulled tight and the loop closes,
causing the opposing sides of the tissue opening to come into close
physical contact. The suture loop is held tight by the tying of a
knot, or knots, or some other locking mechanism. The first sutures
were made of animal gut. Eventually other natural suture materials
including leather, horsehair, flax, cotton and silk came into use.
As the sciences of medical and materials technology have advanced
over the course of the past century, new bioabsorbable materials
have been developed to further improve upon the basic suturing
concept.
[0006] While traditional suturing remains a popular method of
effectuating closure of skin openings, the use of fasteners, for
example staples and staplers, as a skin closure technique has
become increasingly popular, especially in surgical settings where
the opening is created through a purposeful incision. In these
settings, the incision tends to make a clean, straight cut with the
opposing sides of the incision having consistent and non-jagged
surfaces. Typically, stapling of a skin opening, for example, is
accomplished by manually approximating the opposing sides of the
skin opening and then positioning the stapler so that a staple will
span the opening. The stapler is then manipulated such that the
staple is driven into the skin with one leg being driven into each
side of the skin opening and the cross-member of the staple
traversing the skin opening. Generally, the staple is made of a
deformable material such as surgical stainless steel and the legs
of the staple are driven into an anvil causing the staple to deform
so as to retain the skin tissue in a compressed manner within the
staple. This process can be repeated along the length of the
opening such that the entire incision is held closed during the
healing process.
[0007] The earliest medical staple designs were manufactured of
metal and designed to deform around the captured tissue. Examples
of these staples include U.S. Pat. Nos. 2,684,070, 3,273,562 and
4,485,816. Although effective, metal staples suffer from the
drawback of requiring post-operative removal. As the science of
medical polymers developed, staple designs incorporating
bioabsorbable materials became available. The use of these
bioabsorbable materials eliminated the need for post-operative
removal of the staples. Examples of these staples include U.S. Pat.
Nos. 3,757,629, 4,317,451, 4,741,337, 4,839,130 and 4,950,258. Due
to the nature of bioabsorbable polymers; however, bioabsorbable
staples could not be inserted with the same deformation approach
used by metal staples. In fact, bioabsorbable staples were
purposefully designed to avoid any deformation requirement, as
deformation was seen as a potential failure mechanism. An example
of such a design is illustrated by the inwardly biased skin
fastener of U.S. Pat. No. 5,089,009. Thus, as the physical and
chemical properties of bioabsorbable surgical staples evolved, the
development of designs and insertion methods associated with
bioabsorbable staples have focused on avoiding deformation of the
bioabsorbable fastener.
[0008] One potential use for bioabsorbable fasteners is in the
subcuticular application of such fasteners for use in closing skin
wounds as shown, for example in a series of patents to Green et al.
in U.S. Pat. Nos. 5,292,326, 5,389,102, 5,423,856, 5,489,287 and
5,573,541. These patents disclose the use of a bioabsorbable,
rod-like fastener inserted in a subcuticular manner to assist the
healing process. Another bioabsorbable fastener design contemplated
for subcuticular wound closure is U.S. Pat. No. 5,618,311 to
Gryskiewicz, in which a more traditional staple design is
promoted.
[0009] If they could effectively retain tissue, the bioabsorbable
staples of these designs would have many advantages over
conventional metal staples, such as no visible scarring and no need
for subsequent removal by a physician. Unfortunately, none of the
designs for bioabsorbable staples to date has been incorporated
into a medically or commercially efficacious fastener. It would be
desirable to provide a bioabsorbable fastener for use in wound
closure that could achieve the advantages of a bioabsorbable
material and still provide for an efficacious wound closure.
SUMMARY OF THE INVENTION
[0010] The present invention is a bioabsorbable fastener for
insertion into pierced openings on opposed sides of a tissue wound.
A fastener body is formed of a generally bioabsorbable polymer
material and defines an initial tissue capture zone internal to the
fastener body. The fastener body includes a pair of fastener arms,
a cleat operably joined to each fastener arm at an elbow portion
and a backspan operably joined to each fastener arm at a shoulder
portion. Each fastener arm is insertable into one of the pierced
openings. Each cleat projects backward into the initial tissue
capture zone with an internal elbow angle defined between the cleat
and the fastener arm. A durable tissue retention zone of each
fastener arm is defined between the cleat and the fastener arm.
Each fastener arm has a maximum insertion width defined between
outermost surfaces of the cleat and the fastener arm. Corresponding
internal shoulder angles are defined between the backspan and each
fastener arm and an internal midspan angle is defined between a
midpoint of the backspan and the apex of each durable tissue
retention zone.
[0011] The elbow portion and the internal elbow angle of each
fastener arm are constructed with the maximum insertion width being
greater than a width of the corresponding pierced opening such that
at least a portion of the tissue surrounding the pierced opening is
stretched over the cleat and elastically retained in the durable
tissue retention zone for longer than a minimum degradation period
of the bioabsorbable polymer material. The shoulder portions and
the internal shoulder angles are constructed so as to capture wound
tissue within the initial tissue capture zone during deployment of
the fastener and then dynamically reform in response to lateral
stresses applied by the wound tissue after deployment such that a
sum of the internal elbow angles and the internal midspan angle
remains less than 360 degrees without a fracture failure of the
bioabsorbable polymer material until the minimum degradation period
of the bioabsorbable polymer material.
[0012] While the use of bioabsorbable materials for a tissue
fastener offers many advantages, the present invention is the first
to recognize that the effective use of bioabsorbable materials in
the design of a surgical fastener must both understand and overcome
a number of issues related to the nature of bioabsorbable materials
and human tissue, as well as the dynamic process of tissue
healing.
[0013] First, the thermoplastic polymers used in typical
bioabsorbable staples possess a viscoelastic quality or polymer
creep when subjected to continuous stress loading due to the nature
of their molecular level bonding and entanglements. Traditionally,
bioabsorbable fastener designs have compensated for this creep by
either thickening the backspans or staple legs to prevent or reduce
the deformation of the staple, or adding retaining clips or latches
to preclude such deformation. Instead of trying to counteract the
viscoelastic qualities of the polymer, the present invention takes
advantage of these properties to provide for a dynamic response to
lateral tissue forces that can deform the fastener, but not so far
that the cleats of the fastener would release the tissue in the
durable tissue retention zone.
[0014] Second, if tissue is being retained as opposed to skewered,
large amounts of subcuticular tissue must be retained by the
fastener because subcuticular tissue tends to be elastic. Grabbing
smaller volumes of tissue with a fastener might not ensure that the
tissue will be approximated to achieve an efficacious closure. The
fastener of the present invention accommodates this requirement
without the need for an excessively large or excessively strong
fastener. The fastener of the present invention utilizes two
different types of tissue capture zones, a first larger initial
tissue capture zone that can capture a sufficient amount of tissue
when the fastener is deployed to counteract the initial elasticity
of the tissue and still obtain an efficacious fastening. A second
set of much smaller durable tissue retention zones within the
cleats are then used to provide long term holding force while the
main body of the fastener can dynamically reform in response to the
lateral forces exerted by the tissue during the healing
process.
[0015] Finally, when fastening opposing sides of a wound, the
opposing sides must be physically approximated during placement of
the fastener. Once the opposing sides have been retainably
fastened, the opposing sides tend to return to a more relaxed
disposition during the healing process, thereby increasing lateral
pressure on the bioabsorbable fastener. In conventional practice,
the bioabsorbable fastener ends up being over-designed in order to
assist in the initial approximation of the tissue that can result
in a design that is more susceptible to failure as a result of the
longer term lateral pressures applied during the wound healing
process. In contrast, the bioabsorbable fastener of the present
invention is designed for use with an insertion apparatus that
mechanically approximates the opposing sides of wound tissue to
insure the creation of consistent and repeatable pierced openings
into which the fastener is positioned in a through-and-through
manner to take advantage of elastically securing the tissue within
the durable tissue retention zones created by the cleats of the
fastener.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 is a top view of a fastener of the present
invention;
[0017] FIG. 2 is a side view of the fastener of FIG. 1;
[0018] FIG. 3 is a perspective view of the fastener of FIG. 1;
[0019] FIG. 4 is a top view of a fastener arm of the fastener of
FIG. 1;
[0020] FIG. 5 is a top view of the fastener of FIG. 1;
[0021] FIG. 6 is a perspective view of a skin wound;
[0022] FIG. 7 is a sectional view of the skin wound of FIG. 6;
[0023] FIG. 8 is a top view of a delivery device used in closing
the skin wound of FIG. 6;
[0024] FIG. 9 is a top view of a delivery device including the
fastener of FIG. 1;
[0025] FIG. 10 is a perspective view of a piercing member;
[0026] FIG. 11 is a perspective view of an embodiment of a delivery
device;
[0027] FIG. 12 is a sectional view of the skin wound of FIG. 6 in
an everted disposition;
[0028] FIG. 13 is a perspective view of an applicator head
including the fastener of FIG. 1;
[0029] FIG. 14 is a perspective view of a fastener tip and
cleat;
[0030] FIG. 15 is a section view of the everted skin wound of FIG.
12 including the fastener of FIG. 1 positioned within a pair of
target tissue zones;
[0031] FIG. 16 is a section of the everted skin wound of FIG. 12
including a plurality of the fasteners of FIG. 1;
[0032] FIG. 17 is a top view of the fastener of FIG. 1 positioned
within the skin wound of FIG. 6;
[0033] FIG. 18 is a top view of lateral forces presented along a
fastener arm and cleat;
[0034] FIG. 19 is a top view of the fastener of FIG. 1 in a
semi-open disposition;
[0035] FIG. 20 is a top view of the fastener of FIG. 1 in a
generally open disposition;
[0036] FIG. 21 is a top view of the fastener of FIG. 20 within the
skin wound of FIG. 6;
[0037] FIG. 22 is a perspective view of a plurality of the
fasteners of FIG. 20 within the skin wound of FIG. 6;
[0038] FIG. 23 is a top view of an embodiment of a fastener;
[0039] FIG. 24 is a top view of an embodiment of a fastener;
[0040] FIG. 25 is a top view of an embodiment of a fastener;
[0041] FIG. 26 is a perspective view of an embodiment of a
fastener;
[0042] FIG. 27 is a perspective view of an embodiment of a fastener
being extruded;
[0043] FIG. 28 is a perspective view of an embodiment of a fastener
being stamped;
[0044] FIG. 29 is a perspective view of an embodiment of a
fastener;
[0045] FIG. 30 is a perspective view of an embodiment of a
fastener;
[0046] FIG. 31 is a top view of the fastener of FIG. 30; and
[0047] FIG. 32 is a top view of the fastener of FIG. 30.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0048] Depicted in FIGS. 1-3 is a preferred embodiment of a
dynamic, bioabsorbable fastener 100 of the present invention.
Generally, fastener 100 comprises a pair of arms 102, 104 being
operably connected with a common backspan 106 at shoulder portions
103 and 105, also depicted in FIG. 5, respectively. Arms 102, 104
each preferably include a rounded tip 108, 110. Fastener 100 is
further defined by an arcuate exterior, perimeter surface 112 and
an arcuate interior surface 114. The arcuate shape of interior
surface 114 functions to even out and focus staple loading forces
and reduces potential rocking of fastener 100 when in place within
tissue. Most typically, fastener 100 has a generally circular
cross-section taken through backspan 106 that gradually tapers to a
more rectangular cross-section. In order to facilitate mold
removal, fastener 100 can include a plurality of distinct segments
and surfaces as shown for example in FIGS. 3 and 29.
[0049] Depending from each of tips 108, 110 at an elbow region 115,
117 is a rounded cleat 116, 118. As is more clearly depicted in
FIG. 4, cleats 116, 118 are defined by an outwardly facing cleat
surface 122, an inwardly facing cleat surface 124 and a rounded
cleat tip 126. Inwardly facing cleat surface 124 connects to
interior surface 114 at a cleat base 128 defining a durable tissue
retention zone 129. In combination, interior surface 114 along arms
102, 104 and backspan 106 along with the inwardly facing cleat
surfaces 124 define an initial tissue capture zone 130.
[0050] Design elements of fastener 100 are further depicted in FIG.
5. These design elements include an effective arm center line 132,
an effective backspan center line 134, and an effective cleat
center line 136. With regard to effective arm center line 132,
effective backspan center line 134 and effective cleat center line
136, the center lines generally refer to a line relatively
equidistant between perimeter surface 112 and interior surface 114
or a line relatively equidistant between outwardly facing cleat
surface 122 and inwardly facing cleat surface 124. Due to the
arcuate nature of fastener 100, such center lines are only an
approximation. The intersection of effective arm center line 132
and effective backspan center line 134 creates an internal shoulder
angle 138 relative to fastener 100. Shoulder regions 103, 105 are
defined as the areas proximate shoulder angles 138. The
intersection of effective arm center line 132 and effective cleat
center line 136 creates an internal elbow angle 142 relative to
fastener 100. Elbow regions 115, 117 are defined as the area
proximate the elbow angles 142. Other design elements include a
backspan width 146, an arm width 147, an arm length 148, a cleat
length 150, a cleat tip length 152, a cleat tip 126 to cleat tip
126 distance 154 and a tip-to-tip distance 156.
[0051] For purposes of a description of the present invention,
fastener 100 is comprised of a generally bioabsorbable polymer
selected to maintain effective retention strength for a period of
at least 5 to 21 days within the body, and optimally at least 14
days before eventually being fully absorbed within the human body.
Most preferably, bioabsorbable polymer comprises a blended
bioabsorbable copolymer comprised of 63% polylactide and 37%
polygycolide, commonly referred to as PLGA. While the PLGA
copolymer is used in a preferred embodiment, other bioabsorbable
polymers such as polylactide, polyglycolide and polycaprolactone,
either individually, in blends or as copolymers, sharing similar
traits including absorption traits, injection molding traits and
polymer creep traits could be used as well. Similar to other
polymers, the PLGA copolymer used in the preferred embodiment
exhibits viscoelastic properties in which the entangled molecules
under stress tend to slide past one another, creating a
viscoelastic creep.
[0052] Due to the expense of bioresorbable polymer resins, it is
preferable to avoid unnecessary waste during the molding process.
In order to reduce waste, fastener 100 is preferably formed using a
micromolding injection molding process. Micromolding injection
molding is typically used when the molding shot size is less than 1
gram. Using an appropriate micromolding injection system, for
example a Battenfeld Microsystem M50, resin waste can be
significantly reduced during production of a fastener 100 in
accordance with the present invention. In addition, a micromolding
injection system has other processing advantages such as allowing
high injection speeds to promote dimensional stability, low
residence times at elevated temperatures and integrated part
handling capabilities.
[0053] For purposes of maintaining wound closure during the healing
process, fastener 100 is designed to supply a minimum dry initial
closure strength of greater than 1.2 lb.sub.f per centimeter of
wound length. In a preferred embodiment used in subcuticular wound
closure, the dry initial closure strength correlates to a minimum
fastener strength of 1.2 lb.sub.f per fastener 100 measured
laterally between the durable tissue retention zones 129. One way
to achieve a dry initial closure strength of 1.2 lb.sub.f per
centimeter of wound length is to increase the amount of
bioabsorbable polymer present in fastener 100 as opposed to current
fastener designs. In an embodiment of fastener 100, the additional
polymer is added proportionally to both the arms 102, 104 and
backspan 106 to optimize the strength of fastener 100. In this
embodiment, proportionally adding polymer eliminates weaknesses in
fastener 100, for instance along the backspan 106, in the shoulder
regions 140, in arms 102, 104 or in elbow regions 144. Such
weaknesses may ultimately lead to fastener 100 failure. In this
embodiment of fastener 100, the combination of the arcuate
perimeter surface 112 and the arcuate interior surface 114,
distribute lateral forces supplied by the tissue along the shoulder
regions 103, 105. By proportionally increasing backspan width 146
and arm width 147, fastener 100 can accommodate the concentration
of lateral forces without suffering a failure. Such a design
optimizes the use of the expensive, bioabsorbable polymer thus
eliminating unnecessary waste and expense in meeting the dry
initial strength goals.
[0054] A preferred use of fastener 100 is in the subcuticular
bilateral fastening of dermal tissue to close a skin wound 158,
depicted in FIGS. 6 and 7, as well as in U.S. patent application
Ser. No. 10/179,628 entitled, "Mechanical Method And Apparatus For
Bilateral Tissue Fastening," and U.S. patent application Ser. No.
10/448,838, which is a divisional application also entitled
"Mechanical Method And Apparatus For Bilateral Tissue Fastening,"
both of which are commonly assigned to the assignee of the present
invention and are hereby incorporated by reference in their
entirety. Skin wound 158 generally comprises a pair of opposing
skin surfaces 160, 162 separated by a gap 164. Gap 164 can be
created through either purposeful means, such as a surgical
incision, or accidental means such as an accidental cut. Opposing
skin surfaces 160, 162 each comprise three distinct layers: an
epidermal layer, or epidermis 166; a dermal layer, or dermis 168;
and a subcuticular layer 170. The epidermis 166 comprises dead skin
tissue that may hinder but does not assist in the biological
healing process. The subcuticular layer 170 comprises a layer of
fatty tissue typically lacking the strength necessary to anchor and
hold skin closure fasteners throughout the biological healing
process. Generally, a physician closes skin wound 158 by forcibly
approximating the dermis 168 of opposing skin surfaces 160, 162. As
the dermis 168 comprises living tissue, biological healing of skin
wound 158 commences immediately upon approximation and limited
healing occurs within the first 24 hours of approximation. In
addition, the dermis 168 possesses enough strength and elasticity
to anchor, hold and retain fastener 100.
[0055] Generally as depicted in FIGS. 8, 9, 10 and 11, a delivery
device 172 incorporating a pair of piercing members 174, 176 is
used to introduce fastener 100 into wound 158. Most typically,
delivery device 172 includes a handle 177 and trigger assembly 178
attached to an applicator head 180 for advancing and retracting the
piercing members 174, 176. Piercing members 174, 176 include a
sharp tip 182 for piercing tissue as well as a semi-circular
cross-section 184 defining a retaining space 186 that interfaces
with and transports fastener 100 into wound 158. Cross-section 184
defines a maximum piercing width 188. Piercing members 174, 176 are
connected with a backspan member 190. Applicator head 180 can also
include a guide member 192, a pair of capture zones 194, 196, a
pair of compression members 198, 200 and a pair of bores 202,
204.
[0056] In a preferred use of fastener 100, subcuticular bilateral
fastening of dermal tissue present in wound 158 is accomplished
using a through-and-through bilateral tissue fastening technique
described in U.S. patent application Ser. No. 10/607497, filed Jun.
25, 2003, entitled "Mechanical Method And Apparatus For Bilateral
Tissue Fastening," which is commonly assigned to the assignee of
the present invention, the disclosure of which is hereby
incorporated by reference in its entirety. In this bilateral tissue
fastening technique as shown, for example, in FIG. 8, fastener 100
is loaded between piercing members 174, 176 and backspan member
190. Cross-section 184 is designed to snugly accommodate exterior
surface 112 such that only cleats 116, 118 protrude inwardly from
cross-section 184. Once fastener 100 has been loaded, guide member
192 is positioned within skin wound 158. Compression members 198,
200 are used to approximate opposing skin surfaces 160, 162 and
force them within capture zones 194, 196. Compression members 198,
200 force skin wound 158 into an everted disposition 206 shown in
FIG. 12. As will be apparent, delivery device 172 is capable of a
variety of alternative embodiments including varying orientations
of guide member 192, the incorporation of compression members 198,
200 into delivery device 172 and designs in which delivery device
172 includes storage and loading means allowing for a multi-shot
design.
[0057] Through precise dimensioning of capture zones 194, 196, a
pair of target tissue zones 208, 210 defined in the dermis 168 of
opposing skin surfaces 160, 162 are presented to tips 182 of
piercing members 174, 176 as depicted in FIG. 15. Using trigger
assembly 178, piercing members 174, 176 are advanced forward into
capture zones 194, 196 and correspondingly through the target
tissue zones 208, 210 resulting in openings being pierced in dermal
layer 168. Tips 182 continue to advance out of the target tissue
zones 208, 210 and into the bores 202, 204 present in guide member
192 as shown in FIG. 13. As piercing members 174, 176 advance,
fastener 100 is simultaneously advanced into target tissue zones
208, 210. As shown in FIG. 14, the outwardly facing cleat surface
122 of cleat 116, and similarly cleat 118, define a maximum
insertion width 212 that is purposely designed and manufactured to
be greater than the maximum piercing width 188 of piercing members
174, 176. Consequently, the openings pierced in the dermis 168 by
tips 182 of piercing members 174, 176 must stretch to accommodate
maximum insertion width 212. As cleats 116, 118 are advanced into
bores 202, 204, dermis 168 is forced to elastically stretch past
the tips 126 of cleats 116, 118. Dermis 168 then rebounds and
elastically snaps into position around cleat bases 128 and into
durable tissue retention zone 129.
[0058] Using trigger assembly 178, piercing members 174, 176 are
sequentially withdrawn from bores 202, 204, target tissue zones
208, 210 and capture zones 194, 196. However, fastener 100 remains
within target tissue zones 208, 210 as cleats 116, 118, durable
tissue retention zone 129 and especially cleat bases 128 cooperate
to retain the captured dermis 168, preventing fastener 100 from
being withdrawn. Backspan 106 traverses gap 164, such that opposing
skin surfaces 160, 162, and especially dermis 168, are forcibly
approximated to promote the biological healing process. The
through-and-through insertion method is typically repeated along
the length of skin wound 158 such that a plurality of fasteners 100
cooperate to forcibly close skin wound 158 as depicted in FIG. 16.
Through the use of multiple fasteners 100, the minimum dry initial
closure strength can be increased beyond the typical 1.2 lb.sub.f
per centimeter of wound length by reducing the distance between
fasteners 100 along skin wound 158. Correspondingly, the use of
multiple fasteners 100 allows fastener 100 to be sized and designed
for other wound closure applications or on differing locations of
the body. In the preferred embodiment, fastener 100 is placed
within skin wound 158 such that it resides generally parallel to
the skin surface.
[0059] As depicted in FIG. 17, fastener 100 is shown following
insertion into wound 158 via the through-and-through method. Prior
to and immediately following wound closure, fastener 100 is present
in a first disposition 212 having initial tissue capture zone 130.
When in first disposition 212, shoulder angle 138 is slightly
greater than 90.degree., while elbow angle 142 is substantially
less than 90.degree., most preferably about 25.degree.. First
disposition 212 is representative of fastener 100 at time of
insertion, herein referred to as T1. In a preferred embodiment,
fastener 100 is symmetrical around a center axis 214 depicted in
FIGS. 5 and 17. However, alternative embodiments can include
asymmetrical designs, for example, varying arm lengths 148, cleat
lengths 150, backspan widths 146, differing shoulder angles 138 and
elbow angles 142. Preferably, fastener 100 is positioned such that
equal amounts of first opposing side 160 and second opposing side
162 are retained within tissue capture zone 130. Following
through-and-through insertion of fastener 100 within wound 158,
fastener 100 is exposed to a series of lateral forces 216 as shown
in FIG. 18. Lateral forces 216 act along interior surface 114 from
cleat base 128 to shoulder regions 103, 105 during a period of time
after initial deployment of fastener 100.
[0060] To prevent fastener 100 from failing when exposed to lateral
forces 216, fastener 100 is manufactured of a bioabsorbable polymer
specifically selected to have polymeric creep during the healing
period. If the sum of lateral forces 216 exceed the minimum dry
initial closure strength of fastener 100, fastener 100 will
immediately begin to reform. Once fastener 100 is placed within
wound 158, the closure strength of fastener 100 begins to decrease
as the combination of body temperature and body moisture begins to
soften, then degrade the bioabsorbable polymer used in fastener
100. Even if the sum of lateral forces 216 do not initially exceed
the maximum dry initial closure strength of fastener 100,
degradation of bioabsorbable polymer will typically cause fastener
100 to reform at some time T2 subsequent to wound closure.
[0061] Depicted in FIG. 19 is fastener 100 in a semi-open
disposition 218 following exposure to lateral forces 216 greater
than the fastener closure strength. Preferably, fastener 100 does
not reform to semi-open disposition 218 until a period of time T2
of at least 24 hours from insertion, though depending upon
placement and wound location, reformation may occur immediately
upon insertion. As depicted, lateral forces 216 exceeding fastener
closure strength induce polymer creep primarily in both shoulder
regions 103, 105 and to a lesser degree in elbow regions 115, 117.
However, fastener 100 continues to retain and approximate the
captured tissue due to the continuous retention of the elastic
dermis around cleat bases 128 and within durable tissue retention
zones 129.
[0062] Depicted in FIGS. 20 and 21, is fastener 100 in a generally
open disposition 220 following exposure to lateral forces 216
exceeding those required to reform to semi-open disposition 218.
Preferably, fastener 100 does not reform to generally open
disposition 220 until a period of time T2 of at least 1 to 14 days
and optimally at least 7 days from insertion, though depending upon
placement and wound location, reformation may occur immediately
upon insertion. Fastener 100 is again reformed through polymer
creep in shoulder regions 103, 105 and elbow regions 115, 117. It
should be noted that the closure strength of fastener 100 decreases
over time due to the breakdown of the bioabsorbable polymer by the
human body. As such, lateral forces 216 which may not initially be
enough to induce reforming of fastener 100, will likely induce at
least some degree of fastener reforming at a time subsequent to
placement of fastener 100 in wound 158. In generally open
disposition 220, captured tissue remains approximated during the
healing process as the elastic dermis continues to be retained
within cleat bases 128. In general, cleat bases 128 will continue
to retain the elastic dermis until the bioabsorbable polymer is
absorbed to a point where failure, such as a fracture of arms 102,
104 or backspan 106 occurs or polymeric creep in elbow regions 115,
177 results in elbow angle 142 opening beyond 90.degree. such that
the elastic dermis 168 slides off of cleats 128. In generally open
disposition 220, shoulder angles 138 are increasingly difficult to
distinguish and instead, an internal midspan angle 221 defined by a
midpoint of the backspan 106 and the apex of each durable tissue
retention zone 129, is created. In the preferred embodiment of
subcuticular bilateral fastening of dermal tissue as depicted in
FIG. 22, a pair of fasteners 100 that have reformed to generally
open disposition 220 subsequent to insertion continue to
approximate wound 158. Due to the continuing capture of the dermis
168 within cleat bases 128, wound 158 remains closed throughout the
healing period, typically up to twenty-one (21) days. Throughout
the reformation process, the sum of elbow angles 142 and the
midspan angle remains less than 360.degree. allowing fastener 100
to continually retain captured tissue beyond the minimum
degradation period. Following minimum degradation period referred
to as T3, fastener 100 is increasingly likely to suffer a fracture
failure of the arms 102, 104, cleats 116, 118 or backspan 106.
[0063] While a preferred embodiment of fastener 100 and its method
of use has been described, a variety of other staple configurations
featuring the same dynamic reforming traits as well as
through-and-through insertion method can be utilized. For example,
FIGS. 23, 24 and 25 depict alternative fastener designs
incorporating additional retaining elements to further assist in
wound closure. Depicted in FIG. 23, a fastener 222 comprises a
backspan 224 and arms 226, 228. Arms 226, 228 include tips 230, 232
having a hammerhead orientation 234 including an internal cleat 236
and an external recess 238. Internal cleat 236 includes a cleat
base 240 to similarly capture elastic tissue using the
through-and-through insertion method. Depicted in FIG. 24, a
fastener 242 comprises a backspan 244 and arms 246, 248. Arms 246,
248 include tips 250, 252 include an internal cleat 254 to
similarly capture elastic tissue using the through-and-through
method. In addition, arms 246, 248 include a series of internal
projections 256 to further assist in retaining captured tissue as
fastener 242 reforms in response to lateral forces supplied by
captured tissue. Depicted in FIG. 25, a fastener 258 comprises a
backspan 260 and arms 262, 264. Arms 262, 264 include tips 266, 268
having an internal cleat 270 to similarly capture elastic tissue
using the through-and-through method. In addition, backspan 260
includes a pair of opposed projections 272, 274 to further assist
in retaining captured tissue as fastener 258 reforms in response to
lateral forces supplied by captured tissue. Although the fasteners
of the present invention have been described with respect to an
initial tissue capture zone that is defined by just two arms and
within a single plane, it will be seen that a multiplicity of arms
could be provided and that multiple planes could be accommodated
for the tissue capture zone by, for example, making an angle in the
backspan at the midpoint.
[0064] Depicted in FIG. 26 is another embodiment of a fastener of
the present invention. A fastener 276 can comprise any of the
alternative fastener configurations but in a design using at least
two distinct bioabsorbable layers. As depicted, fastener 276
includes a first bioabsorbable layer 278, a second bioabsorbable
layer 280 and a third bioabsorbable layer 282. While this
embodiment depicts a planar arrangement of different bioabsorbable
materials, it will be recognized that multiple injection points
along a mold could also be used to accomplish a similar
construction with different polymer materials being present at the
shoulder and elbow regions, for example. In practice, fastener 276
can be formed by adhesive, thermal or molding processes where the
layers are bonded after being separately manufactured using the
previously described micromolding process or alternatively, through
an extrusion process 284 as shown in FIG. 27. In yet another
alternative manufacturing process, fastener 276 can be stamped or
cut from a sheet 286 comprising a plurality of bioabsorbable layers
288 as shown in FIG. 28. Fastener 276 having multiple bioabsorbable
layers 288 has a number of design advantages including the ability
to mix and match faster degrading bioabsorbable polymers with
slower degrading bioabsorbable polymers. In addition, fastener 276
could be used as a delivery instrument by incorporating drugs or
medicants, such as antibiotics, clotting agents, or even gene
therapy between layers or zones to provide a time release as the
layers are broken down within the body, or even onto the exterior
surfaces of the fastener to facilitate the healing process.
[0065] Depicted in FIG. 29 is another alternative embodiment of a
fastener 290. Fastener 290 comprises a backspan 292 and arms 294,
296. Fastener 290 included a thickness 297 that is generally
consistent through backspan 292 and arms 294, 296. Arms 294, 296
further include tips 298, 300, each tip 298, 300 having an internal
cleat 302 having a cleat base 304. Arms 294, 296 in combination
with internal cleat 302 and cleat base 304 define a durable tissue
retention zone 306 to capture elastic tissue using the
through-and-through insertion method as previously described.
[0066] In FIGS. 30 and 31, there is shown an earlier embodiment of
a fastener 400 of the present invention. Fastener 400 has body
portion 402, which comprises a cross-member 408 connecting a pair
of fork members or legs 406. The outer margins 410 of each leg 406
are dimensioned and shaped accommodatingly to the retaining space
186 of piercing members 174, 176, allowing fastener 400 to fit and
slide between the piercing members 174, 176. Shoulders 414
preferably are provided to engage the solid cylindrical
cross-section of the backspan member 190, thus allowing fastener
400 to be advanced distally with motion of the piercing members
174, 176. The distal end 412 of each leg 406 is incurvately shaped
to allow easier passage through an opening in skin, referred to as
a skive, that is created by piercing members 174, 176. Inwardly
directed barbs 404 preferably are provided on each leg 406 to
resist withdrawal of the fastener once emplaced.
[0067] Although an overall U-shape for the fastener 400, as shown
in FIGS. 30 and 31 is preferred, other shapes having a capability
for bilateral tissue engagement are also possible and within the
scope of the invention. Such other shapes include for example, but
are not limited to, a square shape similar to an ordinary staple, a
semi-circular or C-shape or a V-shape or W-shape, in which the
cross-member 408 has bends or other features. While the shape of
fastener 400 is generally determined in a planar configuration, it
will be recognized that other non-planar shapes and configurations
can be used, such as a fastener having multiple projections for
each leg 406, with each projection oriented in a different plane,
or a fastener having cross-member 408 arranged in a V-shape
projecting out of the normal plane of the fastener 400. Two leg
members 406 are preferred, but it will be understood that
additional leg members 406 could be added in the same or a
different plane of the fastener 400 such that the leg members of
each side of the fastener form a dident or trident configuration,
for example.
[0068] As shown in FIG. 32, an inner cross-sectional area 409 is
defined by the fastener 400 for capturing the compressed dermal
tissue. In a preferred embodiment, inner cross-sectional area 409
ranges from 1.5 sq. mm to 50 sq. mm and most preferably about 5 sq.
mm to 10 sq. mm. This area is generally defined by an inner
diameter length of between 1.5 mm and 9 mm and most preferably
about 3.8 mm and an inner diameter width of between 1 mm and 5 mm
and most preferably about 2 mm. It will be apparent that numerous
shapes and configurations can be used for the shape and arrangement
of cross-sectional area 409. Preferably, inner cross-sectional area
409 is generally arrowhead shaped as a result of the positioning of
the barbs 412. As will be described, the barbs 412 or similar
anti-reversing projections resist against the withdrawal of
fastener 400. While the barbs 412 are preferably oriented into the
inner cross-sectional area 409, it will be appreciated that barbs
412 may be omitted or may be oriented outwardly.
[0069] Although it is possible for fastener 400 to be deformed
during delivery and application, preferably the majority of dermal
tissue retained within cross-sectional area 409 is captured in a
compressed state by a fastener 400 that is sufficiently rigid so as
to retain the dimensional integrity of cross-sectional area 409
within +/-30% of its designed area for a period of preferably at
least 10 days. Most preferably, structural integrity of fastener
400 is maintained for at least 21 days. In this way, the dermal
tissue captured in fastener 400 is retained in a compressed state
for a period sufficient to allow the biological healing process to
occur without the dermal tissue being under tension during the
healing process. Preferably, the dimensions of the fastener 400 and
the operation of the applicator assembly 100 coordinate to create a
compression ratio of dermal tissue within the inner cross-sectional
area 409 that is greater than one. The compression ratio is defined
either as a ratio of area or a ratio of width. In the case of
width, the compression ratio is the ratio of the dimension defined
by the position of the skive relative to the vertical interface 51
when the dermal tissue is at rest divided by the position of the
skive relative to the vertical interface as held by the fastener
400. In the case of area, the compression ratio is the ratio of the
area of dermal tissue that will be retained by the fastener 400
when that dermal tissue is at rest divided by the actual
cross-sectional area 409.
[0070] Alternatively, it is possible to take advantage of the
bilateral tissue fastening in the tissue target zone as taught by
the present invention with a deformable fastener where the
deforming of a bioresorbable or bioabsorbable fastener serves to
provide at least some of the compression of the dermal tissue such
that the need for a mechanical tissue manipulator is reduced or
potentially eliminated. In this embodiment, a bioresorbable or
bioabsorbable fastener would be deformed by the applicator
apparatus in order to appropriately compress the dermal tissue.
Deformation of a bioresorbable or bioabsorbable fastener could be
accomplished in a number of ways, including prestressing the
fastener into an open configuration such that it returns to a
closed configuration, with or without mechanical assistance from
the applicator, application of ultrasound, heat or light energy to
alter the shape of, or reduce or relax stresses in, the fastener in
situ, designing a polymer material with appropriate shapes and
compositions that the material is deformable upon deployment
without fracturing, or any combination of these techniques.
[0071] Fastener 400 is preferably formed from any suitable
biodegradable material. The currently most preferred biodegradable
material is a lactide/glycolide copolymer where the ratio is never
less than at least 10% of one element and preferably in a range of
60%-70% lactide. Examples of other suitable materials include
poly(dl-lactide), poly(l-lactide), polyglycolide, poly(dioxanone),
poly(glycolide-co-trimethylene carbonate),
poly(l-lactide-co-glycolide), poly(dl-lactide-co-glycolide),
poly(l-lactide-co-dl-lactide) and poly(glycolide-co-trimethylene
carbonate-co-dioxanone). In addition, other suitable materials
could include compositions with naturally occurring biopolymers
such as collagen and elastin, or stainless steel, metal, nylon or
any other biocompatible materials in the case of a non-absorbable
fastener, or even various combinations of such materials depending
upon the desired application and performance of the fastener.
[0072] While a preferred embodiment of a dynamic, bioabsorbable
fastener of the present invention has been described, it will be
apparent to one skilled in the art that a fastener in accordance
with the present invention is capable of numerous other embodiments
without departing from the scope and spirit of the present
invention.
* * * * *