U.S. patent application number 11/707067 was filed with the patent office on 2007-06-21 for corkscrew suture anchor.
Invention is credited to Mark Brunsvold, R. Donald Grafton, Reinhold Schmieding.
Application Number | 20070142836 11/707067 |
Document ID | / |
Family ID | 37047006 |
Filed Date | 2007-06-21 |
United States Patent
Application |
20070142836 |
Kind Code |
A1 |
Schmieding; Reinhold ; et
al. |
June 21, 2007 |
Corkscrew suture anchor
Abstract
A suture anchor has a continuous thread spiraling around a
tapering central core. At the distal end, the suture anchor
terminates in a rounded point. At the proximal end of the suture
anchor is an eye for receiving suture. The suture anchor has a
large thread surface per turn of thread. Anti-backout ridges can be
formed on the front and/or back faces of the threads. A driver for
the suture anchor is provided, the driver including a shaft having
a central axis, a length, a distal end, and a proximal end. The
shaft is provided at its distal end with an opening aligned with
the central axis of the shaft, for receiving the hexagonal proximal
end of the suture anchor. One or more sutures threaded through the
suture eye are threaded through the hollow tubular shaft. The
suture is pulled into and captured by V-shaped notches on the
proximal end of the handle to hold the suture anchor in place on
the distal end of the driver under the tension of the captured
sutures.
Inventors: |
Schmieding; Reinhold;
(Naples, FL) ; Grafton; R. Donald; (Naples,
FL) ; Brunsvold; Mark; (Naples, FL) |
Correspondence
Address: |
DICKSTEIN SHAPIRO LLP
1825 EYE STREET NW
Washington
DC
20006-5403
US
|
Family ID: |
37047006 |
Appl. No.: |
11/707067 |
Filed: |
February 16, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11177365 |
Jul 11, 2005 |
7195634 |
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|
11707067 |
Feb 16, 2007 |
|
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|
10285553 |
Nov 1, 2002 |
6916333 |
|
|
11177365 |
Jul 11, 2005 |
|
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|
09823988 |
Apr 3, 2001 |
6511499 |
|
|
10285553 |
Nov 1, 2002 |
|
|
|
09588065 |
Jun 5, 2000 |
6214031 |
|
|
09823988 |
Apr 3, 2001 |
|
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|
08954206 |
Oct 20, 1997 |
6117162 |
|
|
09588065 |
Jun 5, 2000 |
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08905393 |
Aug 4, 1997 |
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08954206 |
Oct 20, 1997 |
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60023011 |
Aug 5, 1996 |
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Current U.S.
Class: |
606/232 |
Current CPC
Class: |
A61B 2017/0409 20130101;
A61B 17/0401 20130101; A61B 2017/0414 20130101; A61B 2017/00004
20130101; A61B 2017/044 20130101; Y10S 606/916 20130101 |
Class at
Publication: |
606/072 |
International
Class: |
A61B 17/58 20060101
A61B017/58 |
Claims
1. A method of anchoring suture in bone, comprising inserting an
anchor into bone, the anchor comprising: a central body having a
central axis, a distal end and a proximal end; a drive head
disposed on the proximal end of the central body; and a continuous
thread disposed in a spiral around the central body and having an
inner diameter, an outer diameter, and a thickness, the thickness
of the thread at the outer edge of the thread increasing proximally
along a portion of the thread, the outer diameter of the thread
being at least twice the inner diameter of the thread along a
portion of the thread.
2. The method of claim 1, wherein the bone is in the shoulder.
3. The method of claim 2, wherein the anchor is used for rotator
cuff repair.
4. The method of claim 1, wherein the bone is soft or cancellous
bone.
5. The method of claim 1, wherein the anchor is installed
arthroscopically.
6. The method of claim 1, wherein the thread has a distal and a
proximal face, the proximal face forming a radial angle of about 5
to about 10 degrees from a perpendicular to a central axis of the
anchor.
7. The method of claim 6, wherein the distal face forms a radial
angle of about 15 to about 20 degrees from the perpendicular to the
central axis of the anchor.
8. The method of claim 1, wherein the ratio of the outer diameter
to the inner diameter of the thread is between about 2.25 and about
2.75 along a portion of the thread.
9. The method of claim 1, wherein the thread has a pitch between
about 6 and about 9 flights per inch.
10. The method of claim 1, wherein the central body tapers from the
proximal end to the distal end.
11. The method of claim 1 further comprising channels for suture on
the drive head.
12. The method of claim 1, further comprising two lengths of suture
attached to the anchor by threading the suture through an eyelet in
the anchor.
13. The method of claim 1, wherein the drive head is hexagonal.
14. The method of claim 1, wherein the anchor is inserted into the
bone using a driver formed of a cannulated tube secured to a
cannulated handle.
15. The method of claim 14, wherein the driver includes a hexagonal
socket on the distal end of the cannulated tube which is inserted
over and holds the anchor for rotation and installation into
bone.
16. The method of claim 14, wherein the cannulated tube of the
driver has an outer diameter which is equal to or less than the
outer diameter of the proximal end of the anchor body.
Description
[0001] This application is a continuation of U.S. application Ser.
No. 11/177,365, filed Jul. 11, 2005, which is a continuation of
U.S. application Ser. No. 10/285,553, filed Nov. 1, 2002, now U.S.
Pat. No. 6,916,333, which is a continuation of U.S. application
Ser. No. 09/823,988, filed Apr. 3, 2001, now U.S. Pat. No.
6,511,499, which is a continuation of U.S. application Ser. No.
09/588,065, filed Jun. 5, 2000, now U.S. Pat. No. 6,214,031, which
is a continuation of U.S. application Ser. No. 08/954,206, filed
Oct. 20, 1997, now U.S. Pat. No. 6,117,162, which is a continuation
of U.S. application Ser. No. 08/905,393, filed Aug. 4, 1997, now
abandoned. This application also claims the benefit of U.S.
Provisional Application Ser. No. 60/023,011, filed Aug. 5,
1996.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to an apparatus and method for
anchoring surgical suture to bone. More specifically, the present
invention relates to arthroscopic apparatus and methods for
anchoring suture to cancellous bone using a suture anchor having an
auger-like configuration.
[0004] 2. Description of the Related Art
[0005] When soft tissue tears away from bone, reattachment becomes
necessary. Various devices, including sutures alone, screws,
staples, wedges, and plugs have been used to secure soft tissue to
bone. Recently, various types of threaded suture anchors have been
developed for this purpose.
[0006] Suture anchors have been developed that are designed to be
inserted into a pre-drilled hole. Other suture anchors are
self-tapping. Self-tapping screws are shown, for example, in U.S.
Pat. No. 4,632,100, which discloses a cylindrical suture anchor.
The suture anchor of the '100 patent includes a drill bit at a
leading end for boring a hole in a bone, followed by a flight of
threads spaced from the drill bit for securing the anchor into the
hole created by the drill bit. U.S. Pat. No. 5,370,662 discloses a
self-tapping suture anchor having a flight of threads around a
solid body. U.S. Pat. No. 5,156,616 discloses a similar suture
anchor having an axial opening for holding a knotted piece of
suture.
[0007] All of the above-noted suture anchors rely on a flight of
threads disposed on the outer surface of a shank to secure the
anchor to the bone. They all provide a relatively easy method of
suture fixation in hard, cortical bone.
[0008] Recent studies indicate, however, that the above-noted
suture anchors may have problems related to inadequate "pull-out"
strength. This is true especially in softer bone sites, such as
cancellous bone, or in bone tissue that has become compromised,
such as in osteoporotic bone sites. The structure of cancellous, or
cancellated, bone is lattice-like, or spongy. Osteoporotic bone is
the result of a condition that reduces the quantity of bone or
atrophies skeletal tissue, causing a porous condition of the bones.
These bone types may present a limited range of specific fixation
points that are available to the surgeon.
[0009] Also, certain known suture anchors also have a tendency to
"back out" of the implantation site. Moreover, substantial bone
loss is incurred simply upon installation of the above-described
prior art suture anchors. This problem is acute particularly during
procedures that require removal or relocation of suture
anchors.
[0010] Accordingly, a need exists for a suture anchor that can be
secured easily and effectively, especially in softer types of bone.
A need also exists for a suture anchor that displaces a minimum
amount of bone upon insertion. In addition, a need exists for a
suture anchor having exceptional pull-out strength, especially in
soft bone. A need also exists for a suture anchor that is averse to
"backing out" of the insertion site.\
SUMMARY OF THE INVENTION
[0011] The suture anchor of the present invention overcomes
disadvantages of the prior art, such as those noted above, and
achieves the foregoing objectives by providing a corkscrew suture
anchor having preferably a single thread spiralling helically
around a central body.
[0012] The corkscrew suture anchor has a central body, a distal
end, and a proximal end. The central body preferably tapers from
the proximal end to terminate in a point at the distal end. The
distal point preferably is rounded to avoid possible breakage
sometimes encountered when using a sharp point. The point is
approached by a concave cone having a taper more pronounced than
that of the central body.
[0013] The proximal end of the corkscrew suture anchor body has a
hex drive head incorporating a slotted suture eye for receiving one
or more pieces of suture. At the junction between the hex drive
head and the central body, the circumference of the central body
advantageously is larger than the outer circumferential dimension
of the hex drive head. Accordingly, the enlarged body adjacent the
hex drive head forms a hole sufficient to accommodate a hex driver
disposed over the hex drive head. The hex driver is described more
fully below. This allows the suture anchor to be at least partially
countersunk below the surface of the bone upon installation by
preventing impingement of the distal end of the hex driver on the
bone surface.
[0014] Advantageously, the threads of the suture anchor of the
present invention provide an increased percentage of thread surface
area for each turn of the screw, as compared with known suture
anchors, thus providing increased pull-out strength, and a
decreased tendency for back-out. The increase in the surface area
of the thread is achieved in part by increasing the ratio of the
outer diameter of the threads to the inner diameter of the threads.
Preferably, the ratio is between 2.25 and 2.75. Most preferably,
the ratio of the outer diameter to the inner diameter is 2.5.
[0015] In addition, the suture anchor has a higher thread pitch
than prior art screws, thus increasing the area of thread for each
turn of the screw, which also leads to greater pull-out strength.
Significantly, due to the increased pitch, fewer turns of the
corkscrew screw thread are required to advance the suture anchor
into position. Accordingly, the suture anchor is easy to install,
and displaces less tissue material upon insertion than known suture
anchors.
[0016] The pull-out strength and minimal tissue damage are enhanced
by the relatively compressed cross-sectional aspect of the thread,
particularly in relation to the broad axial faces of the threads.
The distal and proximal faces of the threads preferably form a
square or rounded break edge at the outer diameter of the thread.
In addition, the thickness of the thread increases proximally, such
that at least the most proximal flight is thicker than each of the
more distal flights.
[0017] Increased back-out resistance is enhanced by surface
features, such as radial ridges, on the top and/or bottom faces of
the screw threads. The surface features augment the engagement
between the thread surfaces and the surrounding tissue once the
suture anchor is installed.
[0018] The present invention also provides a suture anchor and
driver assembly for driving the corkscrew suture anchor into bone.
The driver is formed of a cannulated tube secured to a cannulated
handle. A hexagonal socket formed on the distal end of the tube
holds the suture anchor for rotation and installation into the
bone. The outer diameter of the tube is equal to or less than the
outer diameter of the proximal end of the suture anchor's central
body.
[0019] The driver is provided with a cleat on the side of the
handle. Consequently, suture threaded through the cannulated driver
can be wrapped around the cleat and fixed for shipping in a slot in
the cleat using adhesive foam. One or more sutures, threaded
through the suture anchor eye and up through the cannulated driver,
can be pulled and secured around the cleat, whereby the suture is
pinched under tension. Advantageously, the tensioned suture helps
to hold the suture anchor in place at the distal tip of the driver.
The suture anchor and driver assembly can be shipped, pre-loaded
with suture, as a sterile, surgery-ready unit.
[0020] The present invention also provides a method of anchoring
suture in bone using the suture anchor of the present invention.
The method includes threading suture through the suture eye on the
proximal end of the suture anchor. The driver is then turned to
advance the suture anchor into the bone.
[0021] The anchors of the present invention can be used for
arthroscopic procedures. Advantageously, the suture anchor can be
installed using a hollow, cannulated grasper as described in U.S.
Pat. No. 5,466,243 to Schmieding, the disclosure of which is
incorporated herein by reference. The anchors also are advantageous
for open and mini-open surgical procedures, such as open rotator
cuff repair, as described in U.S. Pat. No. 5,575,801 to Habermeyer
et al.
[0022] Other features and advantages of the present invention will
become apparent from the following description of the invention,
which refers to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] FIG. 1 is a side view of a corkscrew suture anchor according
to the present invention.
[0024] FIG. 2 is a proximal end view of the corkscrew suture anchor
of FIG. 1.
[0025] FIG. 3 is a distal end view of the suture anchor of FIG.
1.
[0026] FIG. 4 is a side view of a suture anchor assembly including
a suture anchor, threaded with suture, and a driver according to
the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0027] Referring to FIG. 1, the suture anchor 2 of the present
invention includes a body 4 provided in the shape of a tapered
cylinder. A continuous thread 6 wraps around body 4 in a clockwise
direction, as shown.
[0028] Suture anchor 2 is provided at a proximal end 8 of body 4
with hexagonal drive head 10 having a suture eye 12. The suture eye
12 preferably is in the form of an oval aperture in the drive head
for holding at least one, and preferably two or more pieces of
braided suture. Channels 14, also shown in FIG. 2, are formed along
either side of the drive head 10 to accommodate the suture, such as
when the suture anchor is held in a suture anchor driver, set forth
more fully below.
[0029] A tip 18 is provided. Tip 18 terminates in a rounded point
20, which is approached by a concave, conically tapered surface 22.
Conical taper 22 begins at the distal end of the screw thread, and
features an angle of taper deeper than the taper of body 4.
[0030] The body preferably is formed of a biocompatible material
such as stainless steel or titanium alloy. The central core
preferably is circular in cross-section, and tapers from a maximum
diameter near proximal end 8 to a minimum diameter toward distal
end 14.
[0031] Corkscrew thread 6 has a proximal face 24, a distal face 26
and a break edge 28. Referring to FIG. 2, suture anchor 2 is shown
from the proximal end. Radial ridge lines 30 are shown on proximal
face 24 of corkscrew thread 6.
[0032] The major, outside diameter of the suture anchor thread of
the present invention preferably is about 2.5 times the minor,
inner diameter of the thread, or the minor diameter of the body
toward distal end 16. Accordingly, on a 5 mm. diameter suture
anchor, for example, where central core 4 is approximately 2 mm. in
diameter, the outer diameter of the thread is 5 mm.
[0033] Preferably, between two and three flights or turns of thread
6 are provided along body 4, between proximal end 8 and distal end
16. The thickness of the thread increases proximally, such that at
least the outer edge of the most proximal flight is thicker than
the edge of each of the more distal flights, as shown in FIG. 1.
Adjacent sections of each flight are separated by a gap that is
determined by the number of turns per inch of the suture anchor
thread. For example, a 5 mm. suture anchor preferably has about 6
turns per inch, while a 3.5 mm. suture anchor preferably has about
9. Accordingly, on a 5 mm or 6.5 mm suture anchor, the pitch
distance A from flight to flight is 0.167 inches. On a 3.5 mm
suture anchor, pitch distance A typically is 0.118 inches.
[0034] Referring again to FIG. 1, proximal thread surface 24 forms
a 10 .degree. angle alpha. with an axial perpendicular to the
central axis of the body 4, in the case of a 3.5 or 5.0 mm suture
anchor, and a 5 .degree. angle alpha. in a 6.5 mm suture anchor.
Distal thread surface 26 preferably forms a 20.degree. angle .beta.
with an axial perpendicular to the central axis of the body 4, in
the case of a 3.5 or 5.0 mm suture anchor, and a 15.degree. angle
.beta. in a 6.5 mm suture anchor, as shown in Table I, as follows:
TABLE-US-00001 TABLE I Suture Anchor Dimensions and Features Size
3.5 5.0 6.5 Thread No. 2.5 2 2 Flights Pitch 3.0 4.24 4.24 (A) (mm)
Diameter Major 3.5 5.0 6.5 (mm) Minor 1.22 1.40 1.40 Thread 10 10 5
Angle. .beta. 20 20 15 (.degree.)
[0035] FIG. 4 shows suture anchor 2 threaded with two pieces of
suture 32 and held on a cannulated suture anchor driver 34. The
suture is wrapped around cleat 36. Tension on the suture aids in
retaining the suture anchor in the distal end of the driver. The
suture is held in place in slot 38 using a foam adhesive, for
example, during shipping. The assembly is provided as a sterile
unit ready for surgical application.
[0036] I show the results of various pullout tests performed with
suture anchors according to the present invention, as follows:
TABLE-US-00002 TABLE II Pull-out strength of corkscrew suture
anchors 5.0 mm anchor 6.5 mm anchor 20 lb. bone 30 lb. bone 20 lb
bone Test No. block block block 1 N/A 112.2 (wire 98.4 (wire break)
break) 2 116.1 106.9 (wire 119.2 (wire (pulled out) break) break) 3
95.4 (pulled 111.5 (wire 125.1 (wire out) break) break) 4 104.9
(pulled 99.6 (wire 99.7 (slot out) break) break) 5 125.1 84.7 (wire
125.2 (wire (pulled out) break) break) Avg. 110.375 103.0 113.52
St. dev. 13.0 11.4 13.4
[0037] Although the present invention has been described in
relation to particular embodiments thereof, many other variations
and modifications and other uses will become apparent to those
skilled in the art. Therefore, the present invention is to be
limited not by the specific disclosure herein, but only by the
appended claims.
* * * * *