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Description  |
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BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to anchors for attaching soft tissue to bone. More
particularly, the invention relates to apparatus and methods related to
inserting suture anchors in bone in order to attach soft tissue thereto.
2. Description of the Prior Art
In the course of certain surgical procedures, soft tissue is secured to a
selected bone surface either directly, via some type of implant, or
indirectly via an implant (i.e. an anchor) to which suture is attached,
the suture then being tied to the soft tissue to hold it in place. Anchors
may be used to attach soft tissue such as ligaments, tendons, muscles,
etc. to a surface from which the soft tissue has become detached and may
also be used to secure soft tissue to supplementary attachment sites for
reinforcement. For example, in urological applications anchors may be used
in bladder neck suspensions to attach a portion of the bladder to an
adjacent bone surface. Such soft tissue attachment may be done during
either open or closed surgical procedures, the latter being generally
referred to as arthroscopic or endoscopic surgery. The terms
"arthroscopic" and "endoscopic" may be used interchangeably herein and are
intended to encompass arthroscopic, endoscopic, laparoscopic,
hysteroscopic or any other similar surgical procedures performed with
elongated instruments inserted through small openings in the body.
In procedures requiring suturing of soft tissue to bone, the suture may
either be first anchored by so-called suture anchors to the bone before
passing the suture through the soft tissue, or the tissue may first be
sutured and the anchor may then be slid down one leg of the suture and
then implanted into bone. The prior art includes numerous types of suture
anchors adapted to be secured in the bone, sometimes directly in one step
and sometimes in pre-drilled holes or tunnels. The term "suture anchor" is
used broadly and will be understood to refer to devices having a similar
structure even if material other than suture is connected to the device.
Some prior art suture anchors are elongated and have annular ribs or
radially extending barbs and are required to be pushed or hammered
directly into bone or into a pre-formed bone tunnel (exemplified by U.S.
Pat. Nos. 5,102,421 (Anspach, Jr.); 5,141,520 (Goble et al.); 5,100,417
(Cerier et al.); 5,224,946 (Hayhurst et al.) and 5,261,914 (Warren)).
Pushing an anchor into place has the disadvantage of potential trauma and
damage to surrounding bone tissue, and has limited applicability where the
location of the bone tunnel or pre-drilled hole is not axially aligned
with an arthroscopic portal to permit transmission of the impacting force
through an impactor to the anchor. An impacted suture anchor is not easily
removable without damaging the bone into which it has been placed.
Consequently, threaded suture anchors are often used as exemplified by
U.S. Pat. Nos. 5,156,616 (Meadows et al.) and 4,632,100 (Somers et al.).
Depending upon the type of threaded anchor, the insertion procedure may
enable direct threading of the anchor into the bone or it may sometimes
require that a pilot hole first be drilled into the bone, the hole then
either enabling an anchor to be screwed in or enabling threads to be
tapped to receive the anchor.
Devices used to insert suture anchors into bone surfaces provide an
interface between the actual implant and the surgeon performing the
procedure. While this interface is most important in endoscopic surgical
procedures because of the limited accessibility of the surgical site,
prior art endoscopic procedures generally utilize devices and methods
designed for open surgical procedures. All known procedures used to insert
suture anchors endoscopically rely on elongated extensions which pass
through the portals or cannulas used in the procedures. Similar elongated
extensions are also used in open procedures. With respect to non-threaded
or non-turnable suture anchors, these extensions merely are required to
transmit longitudinal forces from the proximal end to the distal end where
the suture anchor is situated. With respect to turnable or threaded suture
anchors, the inserting device must be elongated as well as strong enough
to transmit sufficient torque from the proximal end to the distal tip to
turn the anchor.
Threaded suture anchors are preferably inserted into the bone surface so
that the proximal end of the anchor lies at or beneath the bone surface in
order not to injure the soft tissue which is intended to be approximated
to the bone surface. Consequently, the inserting device must be able to
countersink the anchor a sufficient degree. Furthermore, known suture
anchors are inserted with the suture already joined to the anchor so the
anchor driver must, therefore, accommodate suture while it is turning.
A known threaded anchor inserting device is used to drive a threaded anchor
of the type shown in aforementioned U.S. Pat. No. 4,632,100 (Somers et
al.), incorporated herein by reference. The anchor is known as the
STATAK.TM. soft tissue attachment device, available from the assignee
hereof, and is premounted with suture in a disposable driver which fits
any standard cannulated drill. The driver is an elongated hollow tube
having a drive recess at its distal end for engaging a corresponding drive
surface on the anchor (FIG. 1). The driver has an annular shoulder near
its distal end, proximal to the drive recess in order to abut the bone
surface at the site of implantation of the anchor. When the driver is
turned, the threaded anchor advances into the bone (FIGS. 2 and 3) and,
after the shoulder abuts the bone, the driver continues to turn to advance
the anchor further to assure that its proximal end becomes countersunk
(FIG. 4). The driver includes an automatic release feature to disengage
from the anchor when it is properly positioned. This feature causes the
anchor to automatically stop advancing and turning when it reaches a
predetermined depth below the bone surface, that depth being defined at
the point where its driver portion advances beyond the distal tip of the
driver. Removal of the driver deploys the suture which was arrayed inside.
While in open procedures the anchor and driver assembly may be directly
used as described above, in endoscopic procedures the anchor and driver
assembly must first be inserted through a portal or cannula to position
the anchor at the implantation site. Preferably, a cannula is used to
avoid injuring tissue with the anchor. The internal diameter of the
cannula must be large enough to pass the driver. The shoulder at the
distal end of the driver necessitates the use of a large diameter cannula.
Furthermore, in order to minimize trauma to the patient and facilitate the
use of suture anchors at certain sites, a cannulated drill guide is
necessary to hold the driver in place as it is turned. Using such a drill
guide in addition to the known driver necessitates the use of a still
larger cannula in order to enable the suture anchor to be properly used
endoscopically. Because of the limited visibility available in endoscopic
procedures, it is always desirable to minimize the size of the
instrumentation as much as possible. This decrease in size improves
visualization and enables the use of endoscopic instruments in small
confined spaces. It would be desirable to produce a smaller diameter
driver than presently known so that smaller cannulae could be used to
minimize the size of the required portal and also to facilitate anchor use
in certain small, confined locations (shoulder, etc.).
Additionally, insertion of threaded suture anchors in some situations may
be improved if the anchor could be inserted to varying depths. It would be
desirable, therefore, to produce a driver capable of inserting an anchor
to different depths.
Prior art anchor drivers of the type having a distal shoulder are only
suitable for driving the threaded anchor into place. Once the anchor
advances beyond the tip of the drive shaft, the anchor is no longer
reachable with the driver and, if one desires to remove the anchor, a
separate instrument must be used. It may in some instances be desirable to
remove the anchor and having a driver which could serve as a remover could
be helpful in certain situations.
It is accordingly an object of this invention to produce a system for
inserting threaded suture anchors.
It is also an object of this invention to produce a driving system capable
of countersinking a threaded suture anchor while minimizing the diameter
of the driver.
It is another object of this invention to produce a driving system capable
of countersinking a threaded suture anchor to varying depths.
It is an additional object of this invention to produce a driving system
for inserting threaded suture anchors which is smaller than known systems
in order to improve visualization and provide greater access to confined
spaces.
It is also an object of this invention to produce a driver which can also
be used for removal of a threaded suture anchor while also enabling
countersinking of the suture anchor upon insertion.
SUMMARY OF THE INVENTION
These and other objects of this invention are achieved by the preferred
embodiment disclosed herein which comprises a driver system for inserting
a threaded bone anchor having a cylindrical body provided with a threaded
external surface, a driver-receiving portion for engaging a driver and a
suture-receiving portion for engaging a suture. The driver system
comprises a tubular drill guide provided with a cylindrical axial bore
having a predetermined diameter and a predetermined length and a tubular
drive shaft having a distal end and a proximal end. The distal end of the
drive shaft has an automatically releasable drive means for engaging the
driver-receiving portion of the anchor and releasing the anchor when it
reaches a predetermined depth. The tubular drive shaft has an outer
diameter smaller than that of the drill guide interior to enable the drive
shaft to pass through the drill guide. A stop means is affixed to the
drive shaft at a predetermined distance from its distal end, this distance
being greater than the length of the drill guide. The stop means enables
the drive shaft to rotate relative to the drill guide while preventing the
drive shaft from moving longitudinally relative to the drill guide beyond
a predetermined point.
The invention also comprises a method of inserting a threaded bone anchor.
The method comprises the steps of providing a tubular drill guide provided
with a cylindrical axial bore having a predetermined diameter and a
predetermined length, and providing a tubular drive shaft having a distal
end and a proximal end. The distal end of the drive shaft has an
automatically releasable drive means for engaging the threaded anchor and
the body of the drive shaft has an outer diameter smaller than the
predetermined diameter to enable the drive shaft to pass through the drill
guide. The method further comprises the steps of assembling the anchor
onto the distal end of the drive shaft; placing the distal end of the
drill guide at a selected site targeted to receive the anchor and
inserting the drive shaft and anchor assembly into the proximal end of the
drill guide. The method also comprises the steps of providing a stop means
at the proximal end of the drive shaft and turning the drive shaft to
advance the anchor into the selected site to abut the stop means against
the proximal end of the drill guide.
In another aspect of the invention, the method includes the threading of
suture through the anchor after its implantation and additionally
comprises the steps of threading through the anchor eyelet a "threading
suture" which is sufficiently small in diameter to enable both ends of the
suture to extend from one side of the eyelet while the central or bight
portion of the suture extends from the other side of the eyelet to create
a loop. The "holding suture" actually used to hold tissue to the anchor is
then passed through the tissue and one leg of this suture is passed
through the "threading suture" loop. Pulling the ends of the "threading
suture" causes one leg of the "holding suture" to pass through the anchor
eyelet. The legs of the "holding suture" may then be tied in a
conventional manner.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows a side elevation view of a prior art threaded suture anchor
assembled with a driver.
FIG. 2 is a diagrammatic view of the distal end of a driver/anchor assembly
of FIG. 1 shown inserted into a drill chuck and situated above an
implantation site on a bone surface.
FIG. 3 is a view of FIG. 2 showing the threaded anchor partially advanced
into the bone.
FIG. 4 is a view of FIG. 3 showing the anchor further advanced into the
bone and the driver and drill moving a direction away from the
implantation site.
FIG. 5 is a side elevation view in perspective showing a threaded anchor
driver constructed in accordance with the principles of this invention.
FIG. 6 is a side elevation view in perspective showing a drill guide for
use with the threaded anchor driver of FIG. 5.
FIG. 7 is a side elevation view of a driver anchor system comprising the
assembly of the components of FIGS. 5 and 6 and showing the distal end of
the driver system adjacent a bone surface.
FIG. 8 is a side elevation view of another alternative embodiment of a
threaded anchor driver having a movable stop member.
FIGS. 9 and 10 are exploded views of a portion of FIG. 8 showing alternate
arrangements of parts.
FIG. 11 is a top plan view of an alternate stop member for use with the
driver of FIG. 8.
FIGS. 12a, 12b and 12c are sequential diagrammatic views showing some steps
of a method of passing suture through the eyelet of a threaded anchor
after the anchor has been embedded in bone.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The present invention will be better understood by reference to a prior art
device used to insert threaded suture anchors. As mentioned above, FIGS. 1
through 4 show a prior art STATAK.TM. driver and some of the steps in
using the driver to insert the STATAK.TM. threaded suture anchor at a site
of implantation.
The STATAK.TM. driver 10 is a hollow tube having a distal end 12 and a
proximal end 14. Distal end 12 is provided with a drive recess portion 16
into which the proximal end of a STATAK.TM. suture anchor 18 is inserted.
As will be best seen in FIG. 4, anchor 18 has at its proximal end a drive
portion 20 and an eyelet 22 for receiving a suture 24. The drive recess
has a non-circular bore adapted to engage a similarly shaped drive portion
of anchor 18. Alternatively, the drive recess can engage the eyelet
portion of the implant and turn the implant by using the eyelet portion as
a non-circular drive portion. Suture 24 is placed within the interior of
driver 10 and may extend proximally from the proximal end 14 as shown in
FIG. 1. The suture is tied to or threaded through the eyelet 22 so that
two ends of suture 24 may extend from the proximal end of driver 10. In
actuality, the two lengths of the suture may be folded on themselves near
the proximal end of tube 10 so the suture remains totally within the tube.
The proximal end of the tube may be closed with a plug (not shown). The
distal end 12 of driver 10 has a shoulder 30 which, although not shown as
such, will be understood by reference to FIGS. 2 through 4 to abut the
bone surface around the hole formed at the site of implantation.
Referring now to FIGS. 2 and 3, anchor 18 is shown in position above a site
of implantation 40 during an open surgical procedure. Driver 10 is rotated
and pushed distally in order to embed anchor 18 into the site of
implantation. As the anchor continues advancing distally, the drive recess
portion 16 follows the anchor into the drilled hole formed by the anchor,
and abutment shoulder 30, being larger in diameter than drive recess 16
abuts the annular surface of the bone immediately adjacent the drilled
hole. The shoulder may be radiused into the outer surface of portion 16
(not shown). Further turning of the driver causes anchor 18 to advance to
the depth shown in FIG. 4 at which point drive recess 16 no longer engages
drive portion 20 because shoulder 30 prevents drive recess 16 from
entering further into the hole. At this point, anchor 18 is properly
countersunk and the driver 10 may be removed thereby pulling suture 24
from its interior.
While FIGS. 2 through 4 show the use of the prior art driver during an open
procedure, a similar procedure could be used endoscopically. However, it
is preferable in endoscopic procedures to insert the driver and anchor
through a separate cannula which passes through a portal at the surgical
site. Such a cannula (best seen in FIG. 7) is helpful to decrease the
likelihood of trauma to the tissue created by the sharp edges of the
threaded implant. Moreover, some tubular guide is also generally required
in endoscopic procedures to assure that the implant and driver are able to
be held during implantation. Thus, in endoscopic procedures using a
cannula, the internal diameter of the cannula must be large enough to
accommodate the outer diameter of any drive shaft used to drive the anchor
as well as the guide within which the driver fits. If a driver designed
for use in open surgical procedures were to be used in endoscopic
procedures, unacceptable part dimensions would result. For example, while
the outer diameter of drive shaft 10 varies as a function of the size of
the implant, the general range of such diameters is 0.208 inches to 0.250
inches (approximately 5.3-6.4 mm). In order to accommodate these drivers
alone, without any tubular guide, the external diameters of the associated
cannula, given the necessity for a predetermined amount of cannula wall
thickness, must be on the order of 8-10 mm. Adding a tubular guide, even
one having a fairly thin wall thickness would add at least 2 mm or more to
such a cannula. Such cannula sizes are not normally produced and, even if
they were, they would preclude the use of such drivers in certain
endoscopic procedures. Common cannula (outer) diameters are on the order
of 8 mm to 10 mm having internal diameters of 6 mm to 8.5 mm,
respectively. The preferred embodiment of the invention may be made to fit
in these cannulae without the need to produce larger sizes which would
limit visualization and restrict access to implantation sites.
A threaded anchor driver constructed in accordance with the principles of
the invention is shown in FIG. 5 comprising an elongated tubular drive
shaft 100 having a distal end 102 and a proximal end 104. Distal end 102
is provided with a drive recess 106 having a cross-section complementary
to the drive portion of threaded anchor 108 (identical to previously
described threaded anchor 18). Distal end 102 is sized to that it may
follow anchor 108 into the hole made by the anchor. That is, there is no
stop surface at end 102 since the function of limiting the depth of
penetration of the anchor is accomplished differently in the preferred
embodiment. In the preferred embodiment, anchor 108 is pre-threaded with
suture 110 and inserted in drive recess 106 so that suture 110 either
extends from the proximal end 104 as shown or is otherwise coiled, folded
or retained in the interior of drive shaft 100 (similar to the manner in
which the prior art driver is loaded). For purposes to be described below,
drive shaft 100 is provided with a movable annular shoulder stop 120
intermediate ends 102 and 104. The shoulder stop is adjustable along shaft
100 and is fixed thereof by set screw 121.
Drive shaft 100 is used in conjunction with a tubular guide 130 shown in
FIG. 6. Both drive shaft 100 and guide 130 are sufficiently elongated to
enable their use during endoscopic surgical procedures. Guide 130 has a
distal end 132, a proximal end 134 and an internal axial bore 136 having
an inside diameter slightly larger than the outside diameter of driver
shaft 100. The diameter of driver shaft 100 may be less than or equal to
the major diameter of the thread of the anchor. A handle 138 may be
provided to manipulate guide 130 as desired.
The drive shaft and guide are assembled as shown in FIG. 7 and operate as a
drive system 140 to insert anchor 108 into bone 142 at an implantation
site 144. The system is inserted through a cannula 146 inserted in a
portal 148. A drill or handle (not shown) is attached to proximal end 104
in order to turn anchor 108. As the anchor advances into the bone,
shoulder stop 120 approaches the proximal end 134 of guide 130. The
lengths of drive shaft 100 and guide 130 are such that when the distal end
132 of guide 130 abuts the implantation site, the distally facing surface
120a of shoulder stop 120, abuts end 134 when the anchor 108 is properly
countersunk to a desired depth. To minimize any resistance between the
turning of shoulder stop and the stationary guide, a bearing or coating
150 may be provided at proximal end 134 (or on stop surface 120a).
Additionally, shoulder stop 120 may be continuously adjustable along the
length of drive shaft 100 by tightening set screw 121 as desired to vary
the position of stop surface 120a and, therefore, the depth to which
anchor 108 can be inserted. Indicia 152 may be provided to facilitate
proper placement of the stop on the shaft. In another drive shaft
embodiment 200 as shown in FIGS. 8 and 11, discrete depth adjustments are
made possible by providing the surface of the drive shaft with
longitudinally spaced detent grooves 202 to receive a snap collet 204 or
snap ring 206. An additional benefit of snap collet 204 is that it may be
reversed so that a stop surface 204a may face distally as shown in FIG. 9
or the other side 204b of collet 204 may be faced distally as shown in
FIG. 10. In the configuration of FIG. 9, the distance D1 from distal tip
208 to surface 204a is, therefore, greater than the distance D2 of the
configuration shown in FIG. 10. Thus, the mere positioning of collet 204
enables one drive shaft to provide a greater number of choices of depth
penetration.
Normally, the outer diameter of drive shaft 100 (or 200) is defined by the
diameter of the distal annular edge which abuts the bone. The internal
diameter is defined by this outer diameter less a certain necessary wall
thickness. In certain embodiments in which suture extending from an anchor
is kept totally within the hollow driver, the minimum size of the internal
diameter of the drive shaft is constrained by the size of the suture which
may be threaded through the anchor and which may be doubled up on itself
or otherwise arrayed within the driver. In some embodiments as described
above, the suture threaded through the anchor extends into the driver
towards its proximal end and then both legs of the suture are doubled back
towards the distal end of the driver so that in effect there are four
strands of suture within the interior of the driver. This creates a
convenient situation for driving the anchor by turning the drive shaft
without having any suture extending outside the periphery of the drive
shaft. In the preferred embodiment, since a large diameter drive shaft is
no longer necessary to limit the depth of implantation of the anchor, the
size of the drive shaft may be minimized but for the internal space that
must be maintained to accommodate storing the suture in the drive shaft.
However, for certain suture sizes the necessity for providing a large
internal diameter of the drive shaft to accommodate four suture strands
may require such drivers to be undesirably large, especially for
endoscopic applications. Additionally, certain types or sizes of suture
may be difficult to use in known methods of inserting anchors.
The invention disclosed herein includes an improvement in this method of
inserting a threaded anchor by minimizing the size of the driver required
for any given suture size. As shown in FIGS. 12a, 12b and 12c, threaded
anchor 300 is inserted at an implantation site 302 with a doubled up
length of temporary "threading" suture 304 already in place in the eyelet
306 of the anchor. Threading suture 304 is folded about its center point
or bight 308 to produce a loop 309 and legs 310 and 312. Suture | | |
