U.S. patent number RE42,526 [Application Number 10/365,628] was granted by the patent office on 2011-07-05 for bicortical tibial fixation of acl grafts.
This patent grant is currently assigned to Arthrex, Inc.. Invention is credited to Bernard Reiser, Reinhold Schmieding.
United States Patent |
RE42,526 |
Reiser , et al. |
July 5, 2011 |
Bicortical tibial fixation of ACL grafts
Abstract
A method of securing a graft in a bone tunnel, in which graft is
secured within the tunnel at both the entrance and the exit ends of
the tunnel to provide bicortical fixation of the graft in the bone.
Interference screws or other fixation devices are used to secure
the graft within the tunnel. For tibial tunnel fixation using an
interference screw, the back end of the distal screw is angled so
that it closely approximates the angle of the outer tibial tunnel
rim. The distal screw is non-cannulated to prevent hematomas from
being formed by blood flowing from the tibial tunnel into the
surrounding soft tissue. The proximal screw has a restricted
cannula to minimize the flow of synovial fluid entering the tibial
tunnel. Advantageously, the space between the two screws fills with
blood to promote faster healing and incorporation of the graft in
the tibial tunnel.
Inventors: |
Reiser; Bernard (Pfinztal,
DE), Schmieding; Reinhold (Naples, FL) |
Assignee: |
Arthrex, Inc. (Naples,
FL)
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Family
ID: |
26760485 |
Appl.
No.: |
10/365,628 |
Filed: |
June 12, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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09243995 |
Feb 4, 1999 |
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60078391 |
Mar 18, 1998 |
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Reissue of: |
09259302 |
Mar 1, 1999 |
6387129 |
May 14, 2002 |
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Current U.S.
Class: |
623/13.14 |
Current CPC
Class: |
A61B
17/888 (20130101); A61B 17/8645 (20130101); A61F
2/0805 (20130101); A61F 2/0811 (20130101); A61B
17/8615 (20130101); A61B 17/864 (20130101); A61F
2002/0882 (20130101); Y10S 606/908 (20130101); A61F
2002/0841 (20130101); Y10S 606/916 (20130101); A61F
2002/0858 (20130101) |
Current International
Class: |
A61F
2/08 (20060101) |
Field of
Search: |
;623/13.12,13.14,13.11-13.2 ;606/99,326,308,321,310,305 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
"Orthopedic Screw Machined in One Step", Tooling and Production,
Apr. 1994. cited by other .
Mark H. Gonzalez, M.D. and Robert F. Hall, Jr. "Intramedullary
Fixation of Metacarpal and Proximal Phalangeal Fractures of the
Hand", pp. 47-54, Clinical Orthopaedics and Related Research, No.
327, 1996. cited by other .
Thomas A. Russell, et al. "Mechanical Characterization of Femoral
Interlocking Intramedullary Nailing Systems", pp. 332-340, Journal
of Orthopaedic Trauma, Vol. 5, No. 3, 1991. cited by other.
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Primary Examiner: Stewart; Alvin J.
Attorney, Agent or Firm: Dickstein Shapiro LLP
Parent Case Text
This application claims the benefit of U.S. Provisional Application
Ser. No. 60/078,391, filed Mar. 18, 1998, and is a
continuation-in-part of U.S. patent application Ser. No.
09/243,995, filed Feb. 4, 1999, now abandoned, the disclosures of
which are incorporated herein by reference.
Claims
What is claimed is:
1. A method of securing a graft in a .Iadd.single .Iaddend.bone,
the method comprising the steps of: .Iadd.(a) .Iaddend.forming a
tunnel through the .Iadd.single .Iaddend.bone, the tunnel having an
entrance and an exit at opposing ends of the tunnel; .Iadd.(b)
subsequently to step (a), .Iaddend.extending a portion of the graft
within the tunnel between the entrance and the exit; and .Iadd.(c)
subsequently to step (b), .Iaddend.securing the graft within the
tunnel to cortical bone .Iadd.by inserting and rotating
interference screws .Iaddend.at both the entrance and the exit of
the tunnel to provide bicortical fixation of the portion of the
graft in the tunnel.
.[.2. The method of claim 1, wherein the step of securing the graft
comprises installing an interference fixation device at each of the
opposing ends of the tunnel..].
3. The method of claim 1, further comprising the steps of extending
the graft between the bone and another bone, and securing the graft
to the other bone.
.[.4. The method of claim 1, wherein the step of securing the graft
is performed using interference screws..].
5. The method of claim 1, wherein the step of securing the graft is
performed using an adhesive.
6. The method of claim 1, wherein the bone is a tibia.
7. The method of claim 1, wherein the graft replaces an anterior
cruciate ligament.
8. A set .[.of fixation devices.]. for securing .[.a graft.].
.Iadd.an autograft or allograft .Iaddend.in a tunnel formed through
a single bone, the tunnel having a proximal end and a distal end
located at opposing ends of the tunnel, the set of fixation devices
comprising: .Iadd.an autograft or allograft;.Iaddend. a proximal
.[.fixation device.]. .Iadd.interference screw .Iaddend.configured
to secure the .[.graft.]. .Iadd.autograft or allograft .Iaddend.to
cortical bone at the proximal end of the tunnel; and a distal
.[.fixation device.]. .Iadd.interference screw .Iaddend.configured
to secure the .[.graft.]. .Iadd.autograft or allograft .Iaddend.to
cortical bone at the distal end of the tunnel.Iadd., wherein the
distal interference screw is partially cannulated and has a back
end with a surface disposed at an angle relative to a central axis
of the interference screw.Iaddend..
9. The set .[.of fixation devices.]. of claim 8, wherein the
proximal device has a tip with a rounded profile.
10. The set .[.of fixation devices.]. of claim 8, wherein the
proximal device is fully-threaded.
.[.11. The set of fixation devices of claim 8, wherein the distal
device is partially cannulated and has a back end with a surface
disposed at an angle relative to a perpendicular to a central axis
of the fixation device..].
.[.12. The set of fixation devices of claim 8, wherein at least one
of the distal device and the proximal device is an interference
screw..].
13. The set of .[.fixation devices according to.]. claim 8, wherein
the proximal and distal .[.fixation devices.]. .Iadd.interference
screws .Iaddend.are configured to substantially occlude the
respective opposing ends of the tunnel.
.[.14. An interference screw for graft fixation, the screw having a
fully-threaded outer surface, and at least one of a back end with a
surface disposed at an angle relative to a perpendicular to a
central axis of the interference screw and a front end having a
rounded profile..].
.Iadd.15. A method of securing a graft in a tibia during ligament
reconstruction surgery, comprising the steps of: forming a tunnel
through the tibia, the tunnel having an entrance at a tibial
plateau and an exit at an anterior surface of the tibia; extending
a portion of the graft within the tunnel between the entrance and
the exit; and securing the graft within the tunnel by inserting,
into the exit of the tunnel at the anterior surface of the tibia,
an interference screw having a fully-threaded outer surface and a
back end with an angled profile and a face disposed
non-orthogonally relative to a central axis of the interference
screw, the interference screw being turned during insertion so that
the angled face of the back end of the screw is substantially flush
with the anterior surface of the tibia, to wedge the graft directly
against the tibia by the interference screw..Iaddend.
.Iadd.16. The method of claim 15, wherein the graft extends between
the tibia and a femur, and replaces an anterior cruciate
ligament..Iaddend.
.Iadd.17. The method of claim 15, wherein the interference screw is
formed of a bioabsorbable material..Iaddend.
.Iadd.18. The method of claim 17, wherein bioabsorbable material
comprises poly-(L-lactic acid)..Iaddend.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to endosteal fixation of a ligament
by device insertion and, more specifically, to methods and devices
for bicortical tibial fixation of anterior cruciate ligament
grafts.
2. Description of the Related Art
When a ligament becomes detached from a bone, surgery usually is
required to reconstruct the ligament. Often, a substitute ligament
or graft is secured into bone tunnels to facilitate incorporation
and permanent attachment.
Various methods of graft attachment are known, including the use of
interference screws to secure the graft against the walls of a
tunnel drilled through the tibia and a socket formed in the femur.
A strong graft attachment is obtained by using a metal interference
screw to wedge a graft bone block to the wall of a graft tunnel
formed through the bone, as disclosed in U.S. Pat. No. 5,211,647 to
Schmieding. If a bioabsorbable interference screw is used, the
graft can be wedged directly against the bone by the screw, without
a bone component.
In either case, the graft usually is secured as close as possible
to the normal ligament origin and insertion site, which are at the
top of the tibial tunnel (the tibial plateau) and the entrance to
the femoral socket in ACL reconstructions. The portion of the graft
extending out the bottom of the tibia is ordinarily secured to the
outside of the bone with a staple or using screw/washer
fixation.
The above-described secondary fixation of the graft to the exterior
surface of the tibia is disadvantageous in that it is subject to
abrasion from external elements, and is generally less secure than
internal fixation. Accordingly, a graft fixation technique is
needed which provides increased fixation strength of the graft in
the tibial tunnel, and improved healing of the tibial tunnel and
associated tissue.
SUMMARY OF THE INVENTION
The present invention overcomes the disadvantages of the prior art
and achieves the foregoing objectives by providing apparatus and
methods for bicortical fixation of ligament grafts, whereby the
graft is fixed at two cortical locations ("bicortical") within the
tibial tunnel using a pair of fixation devices. The invention
advantageously improves fixation strength, and also minimizes the
likelihood of damage to the graft and the bone tunnel during and
after fixation, such as by preventing widening of the bone tunnel
by graft motion. In addition, as described below, bicortical
fixation improves the healing environment of the ligament
graft.
The fixation strength of the graft is advantageously increased by
engaging the graft against the denser, cortical bone at the ends of
the tunnel. The fixation method and devices of the present
invention preferably are designed to match the anatomy of the
tibial tunnel, and to provide fixation at the original insertion
point of the ligament. The fixation devices also are designed to
minimize graft abrasion, while maximizing fixation strength.
Further, the preferred fixation methods and devices advantageously
restrict blood loss from the fixation site to improve healing and
graft incorporation. The preferred fixation modes advantageously
plug both ends of the bone tunnel, and leave the internal bone
tunnel cavity unobstructed between the plugged ends. Accordingly,
the bone tunnel cavity, through which the graft passes, is allowed
to fill with serous fluids to promote faster healing and enhance
graft incorporation within the tunnel.
Various modes of fixation can be used in the present invention,
including, for example, interference screws, wedges, expanding
devices, and adhesives. Preferred alterative devices are those that
securely engage the cortical wall of the tunnel, and preferably
include threads, ridges, and/or other enhancements to maximize bone
fixation.
Preferred methods and devices disclosed herein utilize interference
screw fixation, although any other type of fixation device capable
of being secured bicortically also could be used. Further,
identical modes of fixation need not be used at both ends of the
tunnel. Preferably, the mode of fixation also will at least
substantially occlude both ends of the bone tunnel, resulting in
the further advantage of an improved healing environment within the
tunnel, as described further below.
According to a preferred embodiment using interference screw
fixation, the interference screws used in the present invention
preferably have a hex socket for receiving a hex-head screwdriver.
The hex socket extends substantially the length of the screw to
optimize the distribution of insertion torque along the length of
the screws. In order to maintain wall thickness, the hex socket is
tapered in correspondence with the tapered outer profile of the
device. The taper also permits easy insertion of the hex driver
(also tapered) into the fixation screw. A cannulated hex-head
screwdriver is used for guide pin insertion methods.
The interference screws preferably are fully-threaded to maximize
fixation strength within the tunnel. Preferably, the proximal screw
(i.e., the screw closest to the joint) has a smooth, rounded tip
profile so as to minimize abrasion with the graft. The distal screw
(i.e., the screw farthest from the joint) has an angled back end so
that it can be oriented substantially flush with the outer surface
of the bone (e.g., the tibia) into which the screw has been
installed. These and other features for minimizing graft abrasion
and maximizing graft fixation also apply to the other modes of
bicortical fixation envisioned by the present invention.
The fixation devices of the present invention, preferably
interference screws, optimally are formed of a bioabsorbable
material. Bioabsorbable materials known to those of skill in the
art include poly-(L-lactic acid) (PLA), poly-(D,L-lactide), and
poly glycolic acid (PGA), for example. Other bioabsorbable,
non-metallic materials, especially those tailored for hardness,
tensile strength, and compressive strength may be utilized. Other
known biocompatible materials which could be used include plastics,
titanium, titanium alloys, allograft bone, and inert bone
substitute materials.
In the preferred method of ACL reconstruction of the present
invention, the graft (preferably a hamstring tendon autograft or
allograft) is secured femorally preferably by interference screw
fixation in a socket formed through the tibial tunnel, as
described, for example, in U.S. Pat. No. 5,320,626, the disclosure
of which is incorporated herein by reference. The preferred femoral
interference screw is inserted into the femoral socket, and has a
rounded back end to prevent tissue damage after insertion. Other
forms of femoral fixation also could be used.
Bicortical tibial fixation is provided by delivering the proximal
fixation device to the inner opening of the tibial tunnel and
installing the device to secure the ligament graft at the
anatomical position on the tibial plateau. The distal device is
delivered and installed to secure the graft within the tibial
tunnel at the outer end of the tunnel. Prior to device insertion,
the tunnel may be pre-tapped and/or dilated to enhance interference
fixation.
A guide pin preferably is employed as necessary to guide the
femoral interference screw and the proximal tibial interference
screw during delivery and installation. For this reason, these two
devices preferably are fully cannulated. The distal tibial screw,
on the other hand, preferably is non-cannulated, to prevent blood
from flowing from the tibial tunnel and into the surrounding
tissue.
Femoral graft insertion and fixation can be achieved by various
methods and devices known in the art, including the transverse,
intraosseous pin and technique disclosed in allowed U.S. patent
application Ser. No. 09/015,618, filed Jan. 29, 1998, or in U.S.
Pat. No. 5,601,562, the disclosures of which are incorporated
herein by reference.
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
FIG. 1 is a cut-away plan view of a proximal tibial interference
screw according to the present invention.
FIG. 2 is a perspective view of the proximal tibial interference
screw of FIG. 1.
FIG. 3 is a cut-away plan view of a distal tibial interference
screw according to the present invention taken along the line
III--III in FIG. 4.
FIG. 4 is a back end view of the distal tibial interference screw
of FIG. 3.
FIG. 5 is a plan view of a femoral interference screw according to
the present invention.
FIG. 6 is a back end view of the femoral interference screw of FIG.
5.
FIG. 7 shows schematically the completed steps in a preferred
method of securing a graft in a graft tunnel according to the
present invention.
FIG. 8 is an elevation of a driver for a bioabsorbable interference
screw according to the present invention.
FIG. 9 is a back end view of the driver shown in FIG. 7.
FIG. 10 is a front end view of the driver shown in FIG. 7.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring to FIGS. 1 and 2, a proximal interference screw 2 for
fixation of an ACL graft according to the present invention is
shown. The screw fixates the graft in the tibial tunnel, and is
installed at the normal ligament anatomical insertion at the tibial
plateau according to a preferred method described more fully below.
Proximal screw 2 includes a body 4 around which a continuous thread
6 is formed. Thread 6 extends to the back end 8 of the screw 2. The
front end 10 of screw 2 has a rounded profile. Thread 6 terminates
somewhat away from the front end 10.
Screw 2 has a hexagonal socket 12 which tapers inwardly and extends
from the back end substantially to the front end of the screw. At
front end 10, a small, circular cannula 14 is formed for receiving
a guide wire or pin. The smaller opening minimizes the amount of
synovial fluid which can flow through the screw from the joint
space into the interbone space of the tibial tunnel; synovial fluid
can retard sharpie fiber growth into the graft within the bone
tunnel.
Referring to FIGS. 3 and 4, a distal tibial interference screw 20
having an angled back end is shown. Distal tibial interference
screw 20 includes a body 22 around which a substantially continuous
thread 24 is formed. The back end 26 of the screw is formed with an
angled profile which, upon insertion, is aligned by rotation with
the adjacent tibial bone surface to prevent damage to nearby tissue
while maximizing fixation in the angled tibial tunnel. The front
end 28 of screw 20 is tapered.
Distal interference screw 20 has a hexagonal socket 28 which tapers
inwardly and extends from the back end substantially to the front
end of the screw. Front end 30 is not cannulated. Accordingly, the
screw advantageously plugs the distal end of the tibial tunnel to
prevent blood from flowing into the surrounding soft tissue.
Referring to FIGS. 5 and 6, a femoral interference screw 40 having
a rounded back end or head is shown. Femoral interference screw 40
includes a body 42 around which a continuous thread 44 is formed.
Thread 44 terminates before reaching the back end 46 of the screw
40, the back end being formed with a hemispherical, smooth rounded
profile.
Screw 40 has a tapered front end 48 terminating in a flat profile.
Thread 44 extends substantially to the tip of the screw. Screw 40
is fully cannulated with a hexagonal socket 50 which tapers
inwardly from the back end to the front end of the screw. At front
end 48, the socket is formed to provide a substantially circular
edge 52.
Referring to FIG. 7, a graft 60 is shown having been inserted into
a knee 62 inside of a femoral socket 64 and a tibial tunnel 66.
In the method of the present invention, once the graft has been
accurately sized, a tunnel is created with a combination of
drilling and/or cancellous bone dilation. The tibial tunnel angles
proximally from the anterior portion of the tibia to the tibial
plateau at an angle of approximately 50.degree.. The tunnel
preferably is about 50 mm in length. The tunnel preferably is
drilled initially 1 or 2 mm smaller than the final diameter
depending on the density of the bone. Subsequent dilation of the
tunnel increases the level of fixation and insertion torque
especially in the tibia where the cancellous bone is less dense.
Preferably, the socket is formed by first drilling the tibial
tunnel and then inserting a drill through the tibial tunnel and
boring into the femur using a guide such as the guide disclosed in
U.S. Pat. No. 5,320,626, the disclosure of which is incorporated
herein by reference.
In the method of the present invention, graft 60 is first inserted
into femoral socket 64. Before securing the graft into the femur,
sutures on the graft preferably are tensioned on both ends while
keeping the graft in position high in the femur. This dual
tensioning helps prevent the graft from rotating during screw
insertion. Transverse femoral pin 67 is then inserted through an
arthroscopy portal to secure the graft in the femoral socket in
accordance with the teachings of allowed application Ser. No.
09/015,618, previously incorporated by reference. Alternative
methods include interference fixation using femoral interference
screw 40 (FIGS. 5 and 6).
When employing femoral interference fixation, a femoral
interference screw 40 is chosen with a diameter that ultimately
matches or is larger than the graft/tunnel size (e.g., 8 mm
graft/tunnel, 8 mm or 1 mm larger in diameter screw). The femoral
screw preferably is 8 or 9 mm in diameter, and about 23 mm in
length. For interference screw fixation within the tibia, screws
are chosen which are 1 mm larger than the size used in the femur.
The proximal tibial screw is preferably between about 10-25 mm in
length, while the distal tibial screw is about 10-20 mm long
overall. Prior to passing the graft, a tunnel notcher (Arthrex Part
No. AR-1844) preferably is used to create an anterior-superior
starting point for the implant.
Graft 60 is secured in the tibial tunnel 66 bicortically using
interference screws 2 and 20, as follows: After the femoral
interference screw 40 is installed, proximal tibial screw 2 is
guided through tibial tunnel 66 over a guide pin (not shown) and
turned or otherwise positioned at the tibial plateau using a
cannulated inserter, such as the driver shown in FIGS. 8-10 and
described more fully below. The guide pin then is withdrawn, and
the distal tibial interference screw 20 is installed to secure the
graft at the distal exit 68 of tibial tunnel 66. A distal tibial
screw having 1 mm larger diameter than the proximal screw can be
used to accommodate any further dilation of the tunnel which may
have occurred during prior screw installation. Screw 20 is turned
so that the angled face on the back end 26 of the screw implant is
substantially flush with the anterior surface of the tibia.
A preferred driver 70 for a bioabsorbable interference screw will
be described with reference to FIGS. 8-10. Driver 70 includes a
cannulated handle 72 attached to a cannulated shaft 74. Shaft 74
has a larger diameter cannulated opening 76 in the section closer
to handle 72, and a narrower cannulation 78 toward and through
drive tip 80. Tip 80 is hexagonal, and has a tapered shape which
corresponds to the sockets of bioabsorbable interference screws 2
and 20. Advantageously, the tapered hexagonal drive tip allows for
secure engagement of the screws, as described above. Laser depth
lines 82 on shaft 74 are provided.
Advantageously, the present invention provides bicortical fixation
within the tibial tunnel. The two device method maximizes tibial
fixation by securing the soft tissue graft at the cortical bone
layers at both the entrance and the exit of the tibial tunnel. The
back end of the distal device is angled so that it closely
approximates the angle of the distal tibial tunnel rim. The distal
device is non-cannulated to prevent hematomas from being formed by
blood flowing from the tibial tunnel into the surrounding soft
tissue.
The proximal device can be a known device that is positioned up to
the tibial plateau to maximize fixation in cortical bone.
Preferably, the proximal device has a restricted cannula to
minimize the flow of synovial fluid entering the tibial tunnel. The
proximal device prevents the graft from moving side to side during
cyclic loading, which enhances biological fixation and prevents
tunnel widening. Cortical fixation at both ends of the tibial
tunnel also advantageously results in the retention of blood
between the devices, creating an advantageous environment for
healing and incorporation of the graft.
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.
* * * * *