U.S. patent application number 12/550961 was filed with the patent office on 2010-01-21 for tissue repair device and apparatus and method for fabricating same.
Invention is credited to Steven Howansky, Daniel R. Lee, Wayne C. Person, Thomas W. Sander.
Application Number | 20100016966 12/550961 |
Document ID | / |
Family ID | 22508655 |
Filed Date | 2010-01-21 |
United States Patent
Application |
20100016966 |
Kind Code |
A1 |
Sander; Thomas W. ; et
al. |
January 21, 2010 |
Tissue Repair Device And Apparatus And Method For Fabricating
Same
Abstract
A method for fabricating a device for repairing torn tissue or
muscle such as the meniscus of the knee. The device includes a pair
of anchoring members having a plurality of barb-like projections
extending outwardly therefrom. The anchoring members are joined by
a flexible linking member which connects the ends of the anchoring
members opposite one another. Such a device can be fabricated by
insert molding of the appropriate members together.
Inventors: |
Sander; Thomas W.; (Winona
Lake, IN) ; Lee; Daniel R.; (Madison, CT) ;
Person; Wayne C.; (Newtown, CT) ; Howansky;
Steven; (Wilton, CT) |
Correspondence
Address: |
Tyco Healthcare Group LP
60 MIDDLETOWN AVENUE
NORTH HAVEN
CT
06473
US
|
Family ID: |
22508655 |
Appl. No.: |
12/550961 |
Filed: |
August 31, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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08369858 |
Jan 6, 1995 |
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12550961 |
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08144453 |
Oct 27, 1993 |
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08369858 |
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07699991 |
May 13, 1991 |
5269783 |
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08144453 |
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Current U.S.
Class: |
623/13.14 |
Current CPC
Class: |
A61B 17/06166 20130101;
B29K 2995/0082 20130101; A61B 2017/00526 20130101; A61B 2017/00004
20130101; B29L 2031/753 20130101; B29K 2105/20 20130101; A61B
2017/06057 20130101; A61B 2017/0647 20130101; A61B 17/06 20130101;
A61B 17/06066 20130101; A61B 2017/06176 20130101; B29C 45/14778
20130101; B29C 70/76 20130101; A61B 2017/0619 20130101; B29C
45/14336 20130101 |
Class at
Publication: |
623/13.14 |
International
Class: |
A61F 2/08 20060101
A61F002/08 |
Claims
1-9. (canceled)
10. A repair device for repairing a torn meniscus in a knee joint,
comprising: a pair of needles a pair of anchoring members, each of
the pair of anchoring member being secured to one of the pair of
needles; a flexible material interconnecting the pair of anchoring
members; a retaining flange on each of the pair of anchoring
members.
11. The repair device according to claim 10, wherein the needles
are secured to the anchoring members by a detachable joint.
12. The repair device according to claim 10, wherein each of the
pair of anchoring members has a plurality of barbs.
13. The repair device according to claim 12, wherein the barbs are
oriented to allow the anchoring members to pass through tissue in a
first forward direction, but grip tissue in a second reverse
direction.
14. The repair device according to claim 10, wherein each of the
pair of needles are curved.
15. The repair device according to claim 10, wherein the flexible
material includes filaments.
16. The repair device according to claim 10, wherein the flexible
material includes a polymeric material.
17. The repair device according to claim 16, wherein the flexible
material includes a bio-absorbable polymer.
18. The repair device according to claim 10, wherein the needles
are formed from a metallic material.
19. The repair device according to claim 10, wherein the needles
and anchoring members are fused to one another.
20. The repair device according to claim 10, wherein the retaining
flanges are separate members that are slipped over the needles onto
the anchoring members.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application is a continuation of U.S. patent
application Ser. No. 08/369,858 filed on Jan. 6, 1995, which is a
continuation of U.S. patent application Ser. No. 08/144,453 filed
on Oct. 27, 1993, now abandoned, which is a continuation-in-part of
U.S. patent application Ser. No. 07/699,991 filed May 13, 1991, now
U.S. Pat. No. 5,269,783 all of which are incorporated herein in its
entirety by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a device for repairing torn
tissue and muscle in the body, and more particularly to a device
for repairing a torn meniscus in the human knee. A method of
repairing torn meniscal tissue is also disclosed. The present
invention is also directed to apparatus and method for fabricating
the invention device.
[0004] 2. Discussion of the Prior Art
[0005] The surgical repair of torn tissue and muscles in the body
has typically been performed through incisions in the body to
expose the area under repair and the actual procedure includes the
provision of sutures, staples or fasteners. The advent of
arthroscopic techniques and endoscopic equipment have reduced the
size and depth of the incision required to perform the repair
procedure. However, the use of conventional devices in many cases
requires a highly skilled surgeon to perform the repair, and
usually requires complete immobilization of the surgical area
following the repair procedure.
[0006] Surgical repair of cartilage and muscle in joints such as
the knee often requires extraordinary skill on the part of the
surgeon to reduce damage to adjacent nerves, blood vessels, muscles
and tendons in the knee joint. In particular, surgical repair of
the fibrocartilage disks within the knee known as the menisci,
which are attached peripherally to the joint capsule, requires
precision to avoid such damage.
[0007] In the past, meniscal surgery has included procedures for
partial to complete removal of a torn meniscus, as well as attempts
to surgically suture, staple or tack the tear in the meniscus to
allow for healing. Other techniques have included removal of
portions of the meniscus to arrest the spread of the tear.
[0008] A technique has been developed using arthroscopic
instruments which provides for meniscal repair through the use of a
pair of surgical needles which are inserted through cannuli into
the knee on opposite sides of the tear in the meniscus to be
repaired. The needles are linked by a single suture which is pushed
down through the cannuli and across the tear. An incision is made
in the skin at the point where the needles exit the knee joint so
that the leading end of each needle may be grasped and pulled
through the joint. The ends of the sutures are then grasped after
the needles are removed from the suture ends and the suture is then
tied outside the skin so that a horizontal suture is created in the
meniscus. This procedure is repeated for placement of as many
sutures as necessary to repair the meniscus tear. This process is
very time consuming, and the strength of the repair is dependent
upon the tension created by the knot tied in the suture.
[0009] The need exists for a device for repairing torn tissue, such
as the meniscus of the knee, which obviates the disadvantages
encountered in the prior art and provides an efficient, suture-type
device which expedites the surgical procedure and reduces the
amount of precision necessary on the part of the surgeon during the
procedure. Additionally, there is a need for providing smooth,
reliable fabrication of a suture-type device for repairing torn
tissue such as the knee meniscus, especially for fabricating such a
device out of material having dissimilar flexibilities.
[0010] In this regard, two general processing techniques have been
previously utilized for attaching a fiber or filamentous structure
such as a braid to a solid object. The first such general process
involved the mechanical crimping or tying of the braid to a solid
piece. The second technique involved welding the braid to the solid
piece by using energy such as heat, ultrasound, etc. or chemicals
such as solvent, glue or adhesive, etc. However, these prior
techniques are either extremely cumbersome or fail to form
reliable, secure attachment between materials of dissimilar
flexibilities. Accordingly, the need exists for smooth, reliable
fabrication of such tissue repair devices, notably surgical
implants prepared from resorbable materials such as surgical clips
or staples.
SUMMARY OF THE INVENTION
[0011] The present invention provides a novel device for repairing
torn tissue and muscle such as the menisci in the knee joint which
expedites the surgical process and facilitates complete healing of
the tear. The device of the present invention reduces the precision
required on the part of the surgeon to accurately place and secure
the suture at the tear site, and expedites the surgical process by
eliminating the requirement of securing the ends of the sutures
together to stitch the tear. The device of the present invention
allows a surgeon to reduce the trauma to the surrounding tissue and
facilitates healing of the torn muscle tissue by providing a
completely resorbable suture-like device which may remain in place
until the tear is completely healed.
[0012] The device for repairing torn tissue and muscles of the
present invention comprises a pair of surgical needles each secured
at one end to a pair of surgical needles each secured at one end to
a pair of anchoring members which essentially comprise absorbable
rods having outwardly projecting barbs. Each anchoring member is
secured at a second end to an absorbable flexible material such as
a suture which extends between the two anchoring members. The means
of securement between the needles and anchoring members, and
between the anchoring members and the suture may include adhesives,
swaging, crimping or a quick-release connection such as
heat-shrinkable tubing. Preferably, the suture and the anchoring
members are constructed of a bioresorbable material.
[0013] The barbs of the anchoring member have a tapered
configuration towards the needles so that as the needles are pushed
through the tissue, the barbs easily pass through the tissue with
the needle. The configuration of the barbs is such that the
anchoring members pass easily through the tissue in the forward
direction, but are prevented from moving in the reverse direction.
The barbs are provided to anchor the device in the tissue.
[0014] The needles of the present invention may be straight
needles, preferably constructed of stainless steel or other
surgical grade metal alloy. Although preferably straight, it is
contemplated that the needles may be curved, similar to suture-type
needles.
[0015] In use, the damaged or torn meniscus in the knee is
arthroscopically approached from the front of the knee by inserting
the needles across the tear and then advancing the needles through
the meniscus across the tear, drawing the absorbable anchoring
means through the meniscus and then through the joint capsule to
exit through a previously made incision. The suture is then pulled
substantially flush with the meniscus across the tear, whereby the
surgeon may the pull the needles through the incision, which had
been made to expose the outer surface of the joint capsule. The
needles are then cut, or may be detached by a sharp pull when the
suture contacts the meniscus across the tear. The barbed anchoring
means are then cut substantially flush with the joint capsule on
the side opposite the suture, the incision is closed; and the
anchoring means holds the suture in place. The barbs on the
anchoring means serve to maintain the position of the device within
the meniscus, and the suture and anchoring means serve to maintain
the tear at close approximation to enhance healing. The material
compositions of the suture and the anchoring means are selected to
provide the desired resorption rate to allow sufficient time for
healing.
[0016] In the event that the tissue being repaired is not
sufficiently strong to retain the barb members in place, a
retaining flange may be utilized which is slipped over the barbs
after it is drawn through the tissue to apply counter pressure
against the surface of the joint capsule to pull the suture tight
across the tear.
[0017] The present invention is also directed to apparatus and
method for fabricating the repair device supra which are effective
for joining elements formed of materials having dissimilar
flexibilities to provide a device that will effectively function
when used to repair torn tissue. In particular, the invention
apparatus and method can be used to fabricate a series of tissue
repair devices at one time.
[0018] In the fabrication of a composite device of materials having
dissimilar flexibilities in accordance with the invention, one of
the pieces of material, e.g., the material of greater flexibility,
is first placed in a mold such as a compression or injection mold.
The material of different flexibility, e.g., polymeric material of
less flexibility, is then injection or compression molded about the
material previously placed in the mold cavity. When forming a
meniscal staple, a segment of braided suture material which can be
resorbable is placed within a channel or groove of the mold that
interconnects cavities for molding the substantially rigid tips.
Into each rigid tip cavity, a portion of the length of braided
suture material is centrally located within the respective
cavities. The mold halves are then closed and the molding polymer
is introduced into the cavities, e.g., by injection. The molten or
flowable polymer then surrounds and encapsulates the braided suture
material extending into the rigid tip cavities. Upon cooling of the
molten material, a composite meniscal staple device is formed from
materials having dissimilar flexibilities where the braided suture
is firmly attached to the molded rigid tips of the staple.
[0019] The present invention provides for facilitated attaching of
a flexible member, e.g., a braided suture, to a rigid part, notably
where both flexible and rigid members are fabricated from
resorbable material as in the case of forming surgical implants. A
composite member which can be used as a tissue repair device is
thereby fabricated and possesses secure attachment between
materials of dissimilar flexibilities, e.g., a uniquely shaped,
rigid, hard solid component reliably coupled to a flexible yet
tensilely strong fibrous or filamentous structure.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] The foregoing features of the present invention will become
more readily apparent and may be understood by referring to the
following detailed description of illustrative embodiments of the
device for repairing torn tissue and muscle and apparatus and
method for fabricating the same taken in conjunction with the
accompanying drawings, in which:
[0021] FIG. 1 illustrates a perspective view of the device of the
present invention;
[0022] FIG. 2 illustrates a perspective view of an alternate
embodiment of the device of the present invention;
[0023] FIG. 3 illustrates a perspective posterior view of the
muscular structure of the knee;
[0024] FIG. 4 illustrates a cut-away perspective view of the knee
of FIG. 3 along line 4-4 showing the device of the present
invention in position during the meniscal repair procedure;
[0025] FIG. 5 illustrates a perspective anterior view of the knee
of FIG. 3 with the device of the present invention in position
during the meniscal repair procedure;
[0026] FIG. 6 illustrates a perspective view of an alternate
embodiment of the device of FIG. 1;
[0027] FIG. 7 illustrates a perspective view of a further alternate
embodiment of the device of FIG. 1;
[0028] FIG. 8 is a top plan view of a portion of apparatus for
fabricating the device of the present invention;
[0029] FIGS. 9 and 10 are a schematic perspective views of the
apparatus portion shown in FIG. 8 illustrating steps in the
fabrication of the invention device;
[0030] FIG. 11 is a side view of the device fabricated with the
apparatus of FIGS. 8-10;
[0031] FIG. 12 is a broken top view of an alternative embodiment of
apparatus used to fabricate the invention device;
[0032] FIG. 13 is a broken side view of the invention device
fabricated with the apparatus illustrated in FIG. 12;
[0033] FIG. 14 is a top plan view of an alternative embodiment of a
tissue repair device fabricated in accordance with the present
invention.
[0034] FIG. 15 is a top view of an alternative embodiment of
apparatus used to fabricate the invention device; and
[0035] FIG. 16 is a side view of a portion of the apparatus of FIG.
16 and its countermold in the direction of arrows A-A in FIG.
15.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0036] Referring now in specific detail to the drawings, in which
like reference numerals identify similar or identical elements
throughout the several views, FIG. 1 shows the repair device 10 of
the present invention. Repair device 10 generally comprises a pair
of metal needles 12, preferably constructed of stainless steel or
other surgical metal alloy, having a sharp tip 13 at one end to
facilitate penetration through tissue, and a blunt end at the other
end. In a preferred embodiment, the length of each needle is
between 6 inches and 10 inches. However, this is not intended to be
limiting as clearly needles of various lengths may be utilized.
[0037] Secured to needles 12 are a pair of anchoring members 14
which are constructed of a bioresorbable material, such as
homopolymers and copolymers of lactide, glycolide, polydioxanone,
trimethylene carbonate, polyethylene oxide or other bioabsorbable
materials or blends of these copolymers. Preferably, the anchoring
members 14 are formed of a copolymer of lactide and glycolide.
Anchoring members 14 are linked by a flexible material 16 such as a
suture, also constructed of a bioresorbable material, such as a
lactide/glycolide copolymer. Flexible material 16 allows for
movement of anchoring members 14 with respect to one another.
Anchoring members 14 preferably have a length of between about
0.040 inch and 2 inches, more preferably between about 0.050 inch
and one inch.
[0038] Needles 12 are secured to anchoring members 14 as indicated
at joint 20, and the anchor members 14 are secured to suture 16 as
at joint 22. The anchoring members 14 of device 10 may be secured
to the needles 12 by means of adhesives, crimping, swaging or the
like, and joint 20 may be formed by heat-shrinkable tubing. It is
preferred that joint 20 is a detachable connection, such that
needle 12 may be removed from anchoring member 14 by a sharp tug or
pull or by cutting as described below. Anchoring members 14 are
secured to suture 16 preferably by insert molding.
[0039] Anchoring members 14 are provided with a plurality of
barb-like projections 18 which serve to anchor device 10 in the
tissue to be repaired. Barbs 18 have a tapered shape to allow the
anchoring members 14 to be pushed through tissue or muscle, such as
the menisci of the knee, in a first forward direction and to
prevent the anchor members from traveling in a reverse direction.
Although as shown in FIG. 1 five barbs 18 are provided, any number
may be provided, so long as the barbs penetrate the tissue to
anchor the device 10.
[0040] FIG. 2 illustrates an alternate embodiment of the device of
the FIG. 1. Device 30 is similar in construction to device 10
except that curved needles 32 are provided. Needles 32 are secured
to anchoring members 14 as described above, which are provided with
a plurality of barbs 18 which taper in the direction of needles 32
to facilitate insertion of the device into tissue. Anchoring
members 14 are connected through suture 16 as described above. The
remaining elements of device 30 are identical to those of device 10
as illustrated in FIG. 1.
[0041] FIG. 3 illustrates the muscular and ligament structure of
the knee 34, including the pertinent components of the knee to
which the present invention is directed. As is well known, the
femur 35 is joined to tibia 36 and fibula 37 by muscles, tendons
and ligaments, and these bones are separated and cushioned by the
medial meniscus 44 and lateral meniscus 45. Condyles 38 of femur 35
rest on the menisci, and the bones are joined and supported by
anterior cruciate ligament 39, ligament of Wrisberg 40, posterior
cruciate ligament 41, and transverse ligament 46 (see FIG. 5). The
joint capsule is formed by tibial collateral ligament 42 and
fibular collateral ligament 43.
[0042] FIG. 4 illustrates the device 10 of the present invention in
use, showing knee 34 along lines 4-4 of FIG. 3. The lateral
meniscus 45 of a knee 34 having a tear 52 is repaired with the
present invention by forcing needles 12 through the meniscus on one
side of the tear, through the torn region, and out the meniscus
tissue on the opposite side of the tear on the outside of the knee.
The device is fully inserted so that flexible member 16 becomes
substantially flush with meniscus 45 and is pulled taut. Barbs 18
of anchoring members 14 anchor the device in the meniscus 45 and
prevent the device from backing off, so that tear 52 is maintained
in an abutting relationship across itself to facilitate healing.
Needles 12 may then be removed from anchoring members 14 by means
of a sharp yank or tug, or are cut as they are accessed from the
opposite side of the knee by a suitable incision. Anchoring members
14 are then trimmed so as to be flush with the surface of meniscus
45 or the joint capsule. The material of which anchoring members 14
and suture 16 are constructed are preferably bio-resorbable
materials which resorb at a rate which is slow enough to facilitate
healing of the tear in the tissue.
[0043] During arthroscopic surgery, as best seen in FIG. 5, the
surgeon will approach the torn meniscus from in front of the knee
and insert the two needles 12 into the meniscus 44 or 45. As the
needles 12 are pushed through the meniscus 45 to draw the edges of
the tear together, the surgeon will make an incision on the
opposite side of the knee adjacent the needles to avoid pushing the
needles through the skin. As the needles are withdrawn, the suture
16 is pulled tight to hold the edges of the tear together while the
barbs 18 prevent the backing off of the device 10 through the
tissue. The needles are then removed and the anchor members are
trimmed to the surface level of the joint capsule and the incisions
are stitched.
[0044] Turning now to FIG. 6, there is shown a further embodiment
of the device of the present invention. Device 60 is identical to
device 10 except for the provision of retaining flanges 62 which
slip over needles 12 and anchoring members 14 to apply counter
pressure against the surface of the joint capsule to pull the
suture 16 tight across the tear in the meniscus. Flanges 62 are
utilized when the strength of the tissue through which the device
passes is insufficient to hold barbs 18 in place.
[0045] FIG. 7 illustrates a further embodiment of the device of the
present invention. Device 70 is identical to device 10 except that
barbs 18 are aligned with each other, rather than staggered as in
accordance with FIG. 1. Clearly, device 70 may include curved
needles as shown in FIG. 2 or retaining flanges 62 as shown in FIG.
6.
[0046] As noted supra, anchoring members 14 are preferably secured
to suture 16 by insert molding. The techniques of compression and
injection molding are per se well-known. For example, injection
molding is described, e.g., by Paul N. Richardson, "Plastics
Processing", Encyclopedia of Chemical Technology, Volume 18 (Third
Edition), John Wiley & Sons, pp. 195-199; Irvin N. Rubin,
"Injection Molding", Encyclopedia of Polymer Science and
Engineering, Volume 8 (Second Edition) John Wiley & Sons, pp.
102-138; and A. B. Glanvill, "Injection Moulding", Thermoplastics:
Effects of Processing, London Iliffe Books Ltd., 1969, pp. 110-182.
More specifically, the injection molding process involves heating
thermoplastic material so that such material is rendered in
flowable condition. After the thermoplastic material has been
rendered sufficiently molten, the material is then injected into
the mold cavity defined between the mold and counter mold portions,
e.g., by a piston head or extruder screw. Compression molding is
described, e.g., by Herbert Rees, "Mold", Encyclopedia of Polymer
Science and Engineering, Supplemental Volume (Second Edition), John
Wiley & Sons, pp. 507-509, which also describes injection
molding and a combination of injection-compression molding.
[0047] Using the technique of compression molding, the material
retaining its initial form, e.g., a flexible braided suture, is
first placed in an open mold, followed by introduction of an excess
of molten thermoplastic material. The mold is then closed with the
mold halves compressed together to shape the molten material as it
hardens and forms rigid members attached to, e.g., the flexible
braid. In this respect, using an excess of thermoplastic material
together with proper application of heat and pressure in a
compression mold allows the material to flow within the mold cavity
and then solidify to form rigid members of proper dimensions. A
heating/cooling pipe and/or other heating/cooling sources can be
provided within the mold portions to control heat application and
prevent damage or changes to the braid structure.
[0048] In this regard, compression or injection molding apparatus
is provided as part of the present invention for joining the suture
16 and anchoring members 14. An embodiment of such apparatus is
illustrated in FIGS. 8-10. More particularly, FIG. 8 illustrates a
mold portion 80 forming part of the injection molding apparatus,
this mold portion 80 comprises various tracks or recesses 81-85 and
projecting pegs 86 and 87. A countermold portion 80' (FIG. 10) is
formed as an exact mirror image to mold portion 80, the only
difference being that recesses 86', 87' are provided in the
countermold portion 80' at the location corresponding to projecting
pegs 86 and 87 in mold portion 80. Projecting pegs 86 and 87 are in
the countermold portion 80 when the mold portion 80 and countermold
portion 80' are secured together, thereby defining internal
channels or cavities along recesses 81-85 which are entirely
enclosed except for the open end 88 of recess 81. Additional pegs
and corresponding recesses can be provided upon mold portion 80 and
the countermold portion 80' for securing these portions 80, 80'
together to form an endorsed cavity. The recesses 81-85 of the mold
portion 80 and recesses in the countermold portion 80' can be
substantially symmetrical, however they need not necessarily be
symmetrical as long as the properly shaped internal cavity is
defined for injection molding the tissue repair device when the
mold 80 and countermold 80' portions are brought together.
[0049] Tracks or recesses 84 and 85 in mold portion 80 (and the
corresponding tracks or recesses in countermold portion 80' are
each shaped to define anchoring members 14 with barbs 18 thereon.
In this regard, recess 89 interconnecting recesses 84 and 85 is
positioned in mold portion 80 as shown in FIG. 8 to receive
flexible material 16 for linking anchoring members 14 together.
Flexible material 16 is retained in place in mold portion 80
between projecting pegs 86 and 87 and shown in FIG. 9. Tracks or
recesses 81, 82 and 83 serve as inlet channels for injection of
fluid material under pressure into recesses 84 and 85 when the mold
portion 80 and countermold portion 80' are closed.
[0050] The insert molding process of the present invention can be
utilized to prepare the tissue repair devices illustrated in FIGS.
1-3, 4 and 7 of the present application and also the surgical clip
device of U.S. Pat. No. 5,002,562 issued Mar. 26, 1991, the
contents of which are incorporated by reference herein. In this
regard, anchoring members 14 are formed of moldable material that
can be subjected to injection molding, i.e., thermoplastic material
which is rendered flowable upon requisite application of heat
and/or pressure so that such material will flow into and fill the
mold cavity taking the shape thereof, and then solidify upon
cooling. Any of the suitable bioresorbable materials enumerated
supra are capable to being injection molded into the requisite
anchoring members 14. However, there is no requirement that the
material used to form anchoring members 14 must be bioresorbable as
long as such material is biocompatible and capable of being
molded.
[0051] The bioabsorbable polymers which can be compression and/or
injection molded include those derived from polyglycolic acid,
glycolide, lactic acid, lactide, dioxanone, e-caprolactone,
trimethylene carbonate, polyethylene oxide, etc., and various
combinations of these and related monomers. Polymers of this type
are known in the art, principally as materials for the fabrication
of such surgical devices as sutures, wound clips, and the like, as
disclosed, e.g., in U.S. Pat. Nos. 2,668,162; 2,703,316; 2,758,987;
3,225,766; 3,297,033; 3,422,181; 3,531,561; 3,565,077; 3,565,869;
3,620,218; 3,626,948; 3,636,956; 3,736,646; 3,772,420; 3,773,919;
3,792,010; 3,797,499; 3,839,297; 3,867,190; 3,878,284; 3,982,543;
4,047,533; 4,060,089; 4,137,921; 4,157,437; 4,234,775; 4,237,920;
4,300,565; and 4,523,591; U.K. Patent No. 779,291; D. K. Gliding et
al., "Biodegradable polymers for use in
surgery--polyglycolic/poly(lactic acid) homo- and co-polymers: 1",
Polymer, Volume 20, pages 1459-1464 (1979), and D. F. Williams
(ed.), Biocompatibility of Clinical Implant Materials, Vol. II, ch.
9: "Biodegradable Polymers" (1981). Copolymers of glycolide and
lactide with or without additional monomers are preferred and of
these glycolide-lactide copolymers are most preferred, for example
a mixture of 80% by weight a 25/75 mole ratio Glycolide/Lactide
copolymer blended with 20% by weight glycolide.
[0052] Material forming linking member 16 coupling the anchoring
members 14 has flexibility greater than the material forming
anchoring members 14. In this regard, the linking member 16 can be
fabricated from the same bioresorbable materials supra and/or
nonresorbable materials infra for fabricating the anchoring members
14. Flexibility is imparted to linking member 16 by providing the
linking member 16 in fiber or filamentous form such as a suture. As
used herein the term "fiber" or "filamentous" refers to materials
which may be characterized as having a denier (see, e.g., Plastics
Terms Glossary, Fourth Edition, Phillips Chemical Company,
Bartlesville, Okla.).
[0053] Fiber-forming materials which are relatively inelastic are
suitable for providing the linking member 16 provided such
materials are more flexible than the anchoring members 14 and
fairly rapidly bioabsorbed by the body, e.g., exhibiting a loss of
tensile strength in from about 2 to about 26 weeks and total
absorption within from about two to about fifty two weeks. It is to
be understood, however, that the expression "relatively inelastic"
does not preclude the presence of some minor degree of
elasticity.
[0054] The linking member 16 can be composed of fibers or filaments
of bioresorbable or nonresorbable material or from a blend of
filaments possessing different bioabsorbabilities and elasticities
to create a member 16 that is semi-absorbable. For example, linking
member 16 can be fabricated from the composite yarn described in
U.S. Pat. No. 4,990,158 issued Feb. 5, 1991 and the connective
tissue prosthesis described in U.S. Pat. No. 5,147,400 issued Sep.
15, 1992, the contents of these United States patents being
incorporated by reference herein.
[0055] The present invention may also be practiced with
non-bioabsorbable absorbable polymeric materials having
thermoplastic properties such as nylon, polyester, polypropylene,
polytetrafluoroethylene (PTFE), polyethylene terephthalate
(Dacron), etc. Non-absorbable materials which are especially
suitable for fabricating the anchoring member or linking member of
the invention device include silk, polyamides, polyesters such as
polyethylene terephthalate, polyacrylonitrile, polyethylene,
polypropylene, silk, cotton, linen, etc. Carbon fibers, steel
fibers and other biologically acceptable inorganic fibroid
materials can also be employed.
[0056] The term "non-bioabsorbable" as used herein applies to
materials which permanently remain within the body or at least
remain in the body for a relatively long period of time, e.g., at
least about two years. It is preferred to employ a material which
is also elastic, i.e., a polymeric material which in filamentous
form exhibits a relatively high degree of reversible extensibility,
e.g., an elongation at break of a least about 30 percent,
preferably at least about 40 percent and more preferably at least
about 50 percent. Fiber-forming polymers which are both
non-bioabsorbable and elastic, and as such preferred for use
herein, include fiber-forming polyolefins such as polyethylene
homopolymers, polypropylene homopolymers, ethylene propylene
copolymers, ethylene propylene terpolymers, etc., fluorinated
hydrocarbons, fluorosilicones, isobutylenes, isoprenes,
polyacrylates, polybutadienes, polyurethanes, polyether-polyester
copolymers, and the like. Hytrel (DuPont), a family of copolyester
elastomers based on (soft) polyether segments and (hard) polyester
segments, and spandex, an elastomeric segmented polyurethane,
provide especially good results.
[0057] Hytrel is manufactured in various commercial grades by
DuPont, such as Hytrel 4056, 5526, and 7246. Hyrel 5556 is
especially suitable when used to form a vascular graft, while
Hytrel 7246 is well-suited when used to form a ligament prosthesis
or tendon augmentation device.
[0058] Several properties of the various Hytrel grades are
presented in the table below:
TABLE-US-00001 Hytrel Grade No. (Injection Molded at 23.degree. C.
for Testing) Hardness in durometer points (ASTM Test No. D2240 4056
5526 5556 7246 Flexural Modulus (ASTM Test No. D790) at -40.degree.
C. in MPa 155 930 930 2,410 at -40.degree. F. in psi 22,500 135,000
135,000 350,000 at 23.degree. C. in MPa 55 207 207 518 at
73.degree. F. in psi 8,000 30,000 30,000 75,000 at 100.degree. C.
in MPa 27 110 110 207 at 212.degree. F. in psi 3,900 16,000 16,000
30,000 AST Test No. D638 .sup.(i)Tensile Strength at Break, MPa
28.0 40.0 40.0 45.8 psi 4050 5800 5800 6650 .sup.(i)Elongation at
550 500 500 350 Break, % .sup.(ii)Tensile Stress at 5% Strain, MPa
2.4 6.9 6.9 14.0 psi 350 1,000 1,000 2,025 .sup.(ii)Tensile Stress
at 10% Strain, MPa 3.6 10.3 10.3 20.0 psi 525 1,500 1,500 2,900
Izod Impact (Notched) (ASTM Test No. D256, Method A) at -40.degree.
C. in J/cm No Break No Break No Break 0.4 at -40.degree. F. in
ft-lbf/in No Break No Break No Break 0.8 at 23.degree. C. in J/cm
No Break No Break No Break 2.1 At 73.degree. F. in ft-lbf/in.
Resistance to Flex Cut Growth, Ross (Pierced), in Cycles to 100%
cut growth (ASTM. Test No. D1052) .sup.(iii)Initial Tear >1
.times. 10.sup.6 >5 .times. 10.sup.5 >5 .times. 10.sup.5 --
Resistance, Die C (ASTM Test No. D1004), in kN/m 101 158 158 200 in
lbf/in. 580 900 900 1,146 Melt Flow Rate in g/10 min. 5.3 18 7.0
12.5 (ASTM Test No. D1238) Test conditions: Temperature, .degree.
C./Load, 190/2.16 220/2.16 220/2.16 240/2.16 Kg .sup.(iv)Melting
Point (ASM Test No. D3418) in .degree. C. 148 202 202 219 in
.degree. F. 298 396 396 426 Vicat Softening Point (ASTM Test No.
D1525) in .degree. C. 108 180 180 207 in .degree. F. 226 356 356
405 Specific Gravity (ASTM 1.16 1.20 1.20 1.25 Test No. D792) Water
Absorption, 24 hr. 0.6 0.5 0.5 0.3 in % (ASTM Test No. D570)
.sup.(i)head speed 50 mm/min. or 2 in./min. .sup.(ii)head speed 25
mm/min. or 1 in/min. .sup.(iii)specimens 1.9 mm or 0.075 in. thick.
.sup.(iv)differential scanning calorimeter (DSC), peak of
endotherm
Corresponding properties of other goods of Hytrel are available
from DuPont.
[0059] The fibers or filaments forming the linking member can be
woven, braided or knitted in whole or in part and will ordinarily
possess a relatively high tensile strength, e.g., a straight
tensile strength of at least about 30,000 p.s.i., preferably at
least about 60,000 p.s.i. and more preferably at least about 90,000
p.s.i.
[0060] Bioabsorbable polymers of high lactide or glycolide content,
e.g., those in which at least about 75 percent of the monomeric
units are derived from either glycolide or lactide, are preferred
for the construction of the linking member 16 of tissue repair
device. Typical polymers are disclosed in U.S. Pat. Nos. 4,523,591
and 4,744,365 which are incorporated by reference. Polymers of high
glycolide content tend to be absorbed more quickly than those
possessing a high lactide content. Accordingly, the glycolide-based
polymers may be preferred, e.g., for both the anchoring members 14
and even the linking member 16. An especially preferred
lactide-glycolide copolymer for forming the linking member 16
contains from about 70 to about 90 percent, and preferably from
about 75 to about 85 mole percent lactide monomer with the balance
being provided by the glycolide monomer. Thus, for example, fibers
or filaments formed from a lactide-glycolide copolymer based on 80
mole percent lactide-20 mole percent glycolide is especially
advantageous for constructing the linking member 16, and
ultimately, the tissue repair device of the present invention. When
a composite yarn is used to form the linking member 16, then the
sheath yarn component, which is preferably braided around the core
yarn component, may comprise a plurality of bioabsorbable fibers in
turn comprising at least two different chemical compositions. This
copolymer is also suitable for injection molding anchoring members
14 about linking member 16.
[0061] As pointed out supra, the various fibers or filaments can be
woven, braided or knitted together to form linking member 16. In
this regard, the term "braid" or "braided" refers to an arrangement
of discrete units or bundles, denominated "sheath yarns," made up
of individual filaments with individual sheath yarns interlocking
or interlacing each other in a regular criss-cross pattern. For
example, a suitable braided suture which can be utilized as the
linking member 16 is disclosed in U.S. Pat. Nos. 5,019,093 issued
May 28, 1991 and 5,226,912 issued Jul. 13, 1993, the contents of
which are incorporated by reference herein. Such braided yarn
encompasses core and sheath designs as well as braid over braid
designs. The core is optional and can be twisted, ply or cable.
[0062] In another embodiment, the fibers or filaments forming the
linking member 16 are woven into a spiroid braid construction. The
expression "spiroid braid" and "spiroid braided" refer to various
types of a solid arrangement of discrete units or bundles,
denominated "yarns", made up of individual filaments or fibers. The
yarns are arranged substantially parallel to the longitudinal axis
of the suture or linking member 16 and internally engaging each
other in a repetitive spiral pattern. The term "solid" is intended
to designate a suture or linking member 16 in which the filamentous
material of its construction occupies substantially the entire
cross-sectional areas of the suture or linking member 16 with at
most a minor percentage of such area (not exceeding about 25% in
the larger suture sizes) constituting void spaces or interstices
between adjacent yarns and fibers. Such construction contrasts with
that of e.g., a standard suture which, in the absence of a core
component, possesses a lumen representing a significant percentage
of the cross-sectional area of the suture.
[0063] Spiroid braided suture component or linking member 16 can
also be fabricated from a wide variety of natural and synthetic
fibrous materials such as any of those heretofore disclosed for the
construction of sutures. Such materials include non-absorbable as
well as partially and fully bio-absorbable (i.e., resorbable)
natural and synthetic fiber-forming polymers. Examples of spiroid
braid constructions which can be utilized as the linking member 16
in the tissue repair device of the present invention are found in
U.S. Pat. Nos. 5,133,738 issued Jul. 28, 1992 and 5,181,923 issued
Jan. 26, 1993, the contents of which are incorporated by reference
herein.
[0064] The present invention is especially suited for preparing the
tissue repair device by injection molding which will be described
infra with respect to FIGS. 8-10.
[0065] Initially, the mold is opened and the fiber or filament-like
material forming the linking member 16 is positioned between
projecting pegs 86 and 87 as schematically illustrated in FIG. 9.
The mold is then closed by fitting mold portion 80 and countermold
portion 80' together in the direction of arrows A and B as shown in
FIG. 10. After mold portion 80 and countermold portion 80' are
secured together, the thermoplastic material forming the anchoring
members 14 is heated to a temperature at which this material
becomes flowable. In this regard, the thermoplastic material is
preferably heated to a temperature from about 120 to about
240.degree. C., more preferably from about 140 to about 200.degree.
C. The thermoplastic material is heated in a plunger machine (not
illustrated) remote from the mold portions, an example of which is
shown in the Encyclopedia of Polymer Sciences and Engineering
citation noted supra.
[0066] The mold portion 80 is provided with proximal ends 180,
sidewalls 182 and pointed distal ends 184. Likewise the countermold
80' is provided with such structure. Next, the molten thermoplastic
material is injected, under pressure, into the mold cavity defined
by recesses or channels 81-85 of mold portion 80 and corresponding
recesses or channels 81'-85' of countermold portion 80'. The molten
material is injected into the mold cavity through opening 88-88'
defined by mold 80 and countermold 80' portions. Injection is
carried out from the (non-illustrated) plunger apparatus which is
preferably an extruder screw having a nozzle or an end thereof
extending into opening 88-88' during injection. In this regard, the
molten thermoplastic material is preferably injected at a pressure
of about 400 to about 4,000 psi, more preferably about 500 to about
2,000 psi.
[0067] During the injection, the mold/countermold portions are
preferably at about room temperature (about 20.degree. C.) so that
the injected thermoplastic material will ultimately cool to form
the hardened anchoring members 14 about the linking member 16. In
this regard, the mold/countermold portions 80 and 80' can be
desirably heated to enhance smooth flowing of the thermoplastic
material along tracks or recesses 81-85 and 81'-85'. The mold
portion can be preferably heated to a temperature up to about
50.degree. C., more preferably up to about 40.degree. C. However,
the mold portions 80 and 80' will ultimately have cool to room
temperature in order to ensure hardening of the thermoplastic
material into anchoring member 14. The channels are formed in mold
80 and countermold 80' portions such that thermoplastic material
will not flow into the cavity defined by recesses 89 and 89', i.e.
the channel defining the linking member 16. Accordingly, when the
molten thermoplastic material is injected into the mold portions 80
and 80', the material will be unable to flow into channels 89 and
89' and will not cover the filamentous or fiber material forming
linking member 16 at this point. As a result, flexibility of
linking member 16 will be maintained even after anchoring members
14 have hardened upon cooling of the thermoplastic material forming
the same.
[0068] Injection is carried out until the cavity defined by
channels 81-85 and 81'-85' is completely filled with thermoplastic
material, i.e. the thermoplastic material can no longer flow into
the mold cavity through opening 88-88'. After injection is
completed, the thermoplastic material is allowed to cool and set
within the mold cavity to form anchoring members 14. Preferably,
the thermoplastic material is allowed to cool and set after
injection is completed for about 0 to about 1 minute, more
preferably from about 1 to about 8 seconds.
[0069] After the injected thermoplastic material has sufficiently
cooled and solidified, then the mold and countermold portions 80
and 80' are opened and the molded part contained therein removed
from mold portion 80. The gates formed on anchoring members 14
(where channels 84 and 85 respectively meet channels 82 and 83 in
mold portion 80) are cut, preferably by means of a manual or
powered cutting tool, so that anchoring members 14 are separated
from the thermoplastic material that has solidified along channels
81-83. The resulting product 90 is shown in FIG. 11 and comprises
anchoring members 91, 91' secured to flexible material 92 forming
the linking member. The tips 93, 93' of respective anchoring
members 91, 91' can then be secured to appropriate needles, e.g.,
by adhesives, crimping, swaging, etc.
[0070] The mold and countermold portions 80 and 80' along with the
molding cavity formed therebetween can have any suitable dimensions
required for molding a suture repair device. For example, the
length of the entire product shown in FIG. 11 (from tip 91 to tip
91') is preferably about 0.120 to about 6 inches with the
corresponding length of each anchoring member 91, 91' about 0.040
to about 2 inches, leaving an exposed area of filament-like
flexible material 92 of about 0.040 to about 2 inches in length.
Dimensions of the molding cavity formed by tracks or recesses
81-85, 89 and 81'-85', 89' can be accordingly prepared to mold the
product 90 possessing these dimensions. The length of material 92
cut and positioned within tracks or recesses 84, 85 and 89 as shown
in FIGS. 9 and 10 will naturally vary depending upon the
appropriate dimensions of these tracks.
[0071] As noted supra, the structure of flexible material 16 which
is preferably filamentous or fiber-like, can be woven, braided or
knitted, e.g., take the form of a tubular or solid spiroid braid.
The material forming the linking member 92 can be different from,
or even the same as the material used to form anchoring members 91,
91' shown in FIG. 11. In other words, linking member 92 and
anchoring members 91, 91' can be formed from the same material
which possesses greater flexibility in a filament or fiber-like
condition (linking member 92) than when present as a solidified
mass of previously molten thermoplastic material (anchoring members
91, 91').
[0072] However, preferably the linking member 92 (FIG. 11) is
constructed out of material such that the portion of the braid that
contacts the molten thermoplastic material will itself undergo a
partial melting. The braid will then fuse to the molten material as
the material cools and hardens, forming a strong secure bond
between flexible linking member 92 and substantially rigid
anchoring members 91, 91' which will not prematurely fail prior to
and during insertion into tissue. Typically the length "L" of
linking member 92 extending from anchoring member 91 to anchoring
member 91' is in the range of about 1 mm to about 50 mm. Typically,
length "L" is sufficient for anchoring members 91, 91' to be
arranged parallel after solidification.
[0073] It is possible to mold a series of tissue repair devices
formed along single, extending strands or ligature of flexible
material which can then be severed at appropriate locations to form
multiple tissue repair devices. The molding procedure to form a
series of these devices is the same as the molding procedure
described supra, the only difference being that mold and
countermold portions define a cavity for retaining a length of
flexible material with appropriate recesses positioned therealong
to mold several anchoring members along the length of the flexible
material. An example of such a mold portion 110 is shown in FIG. 12
which is a partial view of the same. The mold portion 110 is
provided with proximal ends 280, sidewalls 282 and sharp pointed
distal ends 284. As can be seen in this view, the tracks or
recesses 94-97 defining the flow of molten thermoplastic material
are substantially identical to tracks or recesses 82-85 in the mold
portion 80 shown in FIGS. 8-10. Additionally, tracks or recesses
100, 101 and 102 are provided for retaining a length of flexible
material 16 between the respective tracks or recesses 96, 97, etc.
for molding anchoring members. Tracks 101 and 102 are offset from
respective recesses 120/97 and 96/121 as illustrated in FIG. 12.
Respective projecting pegs 122/123 and 124/125 are also provided on
either side of tracks 101 and 102. The countermold portion for this
mold apparatus also comprises tracks and recesses forming the exact
mirror image of tracks 94-97, 100-102, 120-121, etc. of mold
portion 110 with the exception of recesses being provided to
receive projecting pegs 98, 99, 122, 123, 124 and 125 when the mold
and countermold portions are secured to one another.
[0074] An example of the product prepared with the mold of FIG. 12
is shown in FIG. 13 (after removal of the gates therefrom) where a
series of tissue repair devices 103, 104, 105 (in part) are
illustrated with respective anchoring members 106, 106', 107, 107',
108, 108' (not illustrated) molded about the flexible material
having exposed sections 111, 112, 113, 114, 115. The mold tracks
101 and 102 have been positioned in the mold portion of FIG. 12
such that the exposed sections of flexible material 115, 112, 114
positioned therein are offset from the tips 130-134 of the
respective anchoring members. It is particularly preferred not to
have the flexible material pass through the points of tips 130-134.
This preserves the sharpness of the points of the respective
anchoring members. After injection molding has been completed and
the resulting repair device series removed from the mold with the
gates being severed, then the flexible material is cut at the
appropriate locations, i.e., at exposed sections 109, 112, 114 to
form the individual tissue repair devices 103, 104 and 105.
Anchoring members 106, 106', 107, 107', 105, 105' can then be
attached to appropriate needles by the methods described supra or
left alone.
[0075] The tracks or recesses formed within the mold cavity can
take any convenient size or shape to ultimately form a tissue
repair device having any suitable dimensions or shapes. for
example, the mold cavity can be configured to mold a tissue repair
device 140 illustrated in FIG. 14 where unlike the devices
illustrated in FIGS. 11 and 13, the anchoring members 141, 141' do
not possess barbs (reference numeral 142 denotes the linking
member).
[0076] FIG. 15 shows additional details of a mold 210 employed with
the present invention. A length of flexible material 200A enters
the mold at entry port 210, passes along a track 202, past a peg
244 and into a recess 296. Recesses 296 and 297 communicate with
tracks 294, 295 to provide a path for molten polymer. Flexible
material 200A passes from the recess 296 along a channel 200
between pegs 222 and 233 and into and out of recess 297 as
illustrated in FIG. 15. Then, the material 200A passes along a
channel 201 past a peg 255 and exits the mold 210 at exit port 300.
Leaf springs 302, 304 are respectively located at the entry port
210 and exit port 300 and are attached to the mold 210 by
respective bolts 306 and 308. FIG. 16 illustrates an enlarged view
of a portion of the mold 210 in the direction of arrows A-A in FIG.
15 in addition to a portion of countermold 210A mating with mold
210.
[0077] The following examples are illustrative of the fabrication
of a tissue repair device in accordance with the present
invention.
Example 1
[0078] A length of about 0.25 inches of spiroid braided flexible
material formed of a copolymer of glycolide and lactide of
approximately 18 mol % glycolide and 82 mol % lactide is cut and
placed in mold portion 80 as shown in FIG. 9 in the channel 89
between projecting pegs 86 and 87. The mold 80 and countermold 80'
portions (FIG. 10) are then secured together. Then, material of the
same composition is separately heated to a temperature of about
150.degree. C. so that the material melts and is in flowable
condition. Next, this molten flowable material is injected into the
mold cavity under a pressure of about 2,000 psi., until the mold
cavity is completely filled with the molten, thermoplastic
material, i.e., the material can no longer flow into the mold
cavity. The mold cavity itself, i.e. mold parts 80 and 80', are at
a temperature of 15.degree. C.
[0079] After filling of the mold cavity with the thermoplastic
material is completed, the mold portions 80 and 80' are allowed to
cool to room temperature over a period of about 2 seconds, at which
time the thermoplastic material has solidified into fairly rigid
members 91, 91'. The mold cavity is opened and the gates attaching
members 91, 91' to the solidified material in tracks 82 and 83 are
cut, resulting in the tissue repair device illustrated in FIG. 11
and which is then attached to needles at points 93, 93'
thereof.
[0080] The above procedure is also carried out with tubular braided
material of the same composition to form linking member 92.
Example 2
[0081] The procedure of Example 1 supra is repeated in its entirely
but with about 4-6 inches of a U.S.P. size 2-0 braided suture
material composed of about 92.5 mol % glycolide and about 7.5 mol %
lactide as the flexible material 92 and a copolymer of about 92.5
mol % glycolide and about 7.5 mol % lactide as the molten
thermoplastic material hardening to form rigid members 91, 91'.
[0082] While the invention has been particularly shown and
described with reference to the preferred embodiments, it will be
understood by those skilled in the art that various modifications
and changes in form and detail may be made therein without
departing from the scope and spirit of the invention. Accordingly,
modifications such as those suggested above, but not limited
thereto, are to be considered within the scope of the
invention.
* * * * *