U.S. patent application number 09/259302 was filed with the patent office on 2001-11-15 for bicortical tibial fixation of acl grafts.
This patent application is currently assigned to Peter F.McGee. Invention is credited to RIESER, BERNHARD, SCHMIEDING, REINHOLD.
Application Number | 20010041937 09/259302 |
Document ID | / |
Family ID | 26760485 |
Filed Date | 2001-11-15 |
United States Patent
Application |
20010041937 |
Kind Code |
A1 |
RIESER, BERNHARD ; et
al. |
November 15, 2001 |
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: |
RIESER, BERNHARD; (PFINZTAL,
DE) ; SCHMIEDING, REINHOLD; (NAPLES, FL) |
Correspondence
Address: |
OSTROLENK, FABER, GERB & SOFFEN, LLP
1725 K STREET, N.W.
WASHINGTON
DC
20006
US
|
Assignee: |
Peter F.McGee
|
Family ID: |
26760485 |
Appl. No.: |
09/259302 |
Filed: |
March 1, 1999 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
09259302 |
Mar 1, 1999 |
|
|
|
09243995 |
Feb 4, 1999 |
|
|
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60078391 |
Mar 18, 1998 |
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Current U.S.
Class: |
623/13.11 ;
623/13.12 |
Current CPC
Class: |
A61B 17/8645 20130101;
A61B 17/8615 20130101; Y10S 606/916 20130101; Y10S 606/908
20130101; A61F 2/0805 20130101; A61B 17/888 20130101; A61F 2/0811
20130101; A61F 2002/0882 20130101; A61F 2002/0841 20130101; A61B
17/864 20130101; A61F 2002/0858 20130101 |
Class at
Publication: |
623/13.11 ;
623/13.12; 606/72 |
International
Class: |
A61F 002/30; A61B
017/56; A61B 017/58 |
Claims
What is claimed is:
1. A method of securing a graft in bone, the method comprising the
steps of: forming a tunnel through the bone, the tunnel having an
entrance and an exit at opposing ends of the tunnel; extending a
graft within the tunnel between the entrance and the exit; and
securing the graft within the tunnel at both the entrance and the
exit of the tunnel to provide bicortical fixation of the graft in
the bone.
2. The method of claim 1, wherein the step of securing the graft by
interference fixation comprises installing two fixation devices at
the opposite 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. A set of fixation devices for securing a graft in a bone tunnel,
the tunnel having a proximal end and a distal end located at
opposing ends of the tunnel, the set of fixation devices
comprising: a proximal device for securing the graft at the
proximal end of the tunnel; and a distal device for securing the
graft at the distal end of the tunnel.
7. The set of fixation devices of claim 6, wherein the proximal
device has a rounded tip.
8. The set of fixation devices of claim 6, wherein the proximal
device is fully-threaded.
9. The set of fixation devices of claim 6, wherein the distal
device is non-fully cannulated and has a back end with an angled
surface.
10. The set of fixation devices of claim 6, wherein at least one of
the distal device and the proximal device is an interference
screw.
11. An interference screw for graft fixation, the screw having at
least one of a fully-threaded outer surface, a back end with an
angled surface, and a rounded front end.
Description
[0001] 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, the disclosures of which are
incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] 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.
[0004] 2. Description of the Related Art
[0005] 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.
[0006] 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.
[0007] 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.
[0008] 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
[0009] 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.
[0010] 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.
[0011] 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.
[0012] 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.
[0013] 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.
[0014] 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.
[0015] 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.
[0016] 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.
[0017] 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.
[0018] 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.
[0019] 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.
[0020] 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.
[0021] 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
[0022] FIG. 1 is a cut-away plan view of a proximal tibial
interference screw according to the present invention.
[0023] FIG. 2 is a perspective view of the proximal tibial
interference screw of FIG. 1.
[0024] 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.
[0025] FIG. 4 is a back end view of the distal tibial interference
screw of FIG. 3.
[0026] FIG. 5 is a plan view of a femoral interference screw
according to the present invention.
[0027] FIG. 6 is a back end view of the femoral interference screw
of FIG. 5.
[0028] FIG. 7 shows schematically the completed steps in a
preferred method of securing a graft in a graft tunnel according to
the present invention.
[0029] FIG. 8 is an elevation of a driver for a bioabsorbable
interference screw according to the present invention.
[0030] FIG. 9 is a back end view of the driver shown in FIG. 7.
[0031] FIG. 10 is a front end view of the driver shown in FIG.
7.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0032] 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.
[0033] 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 inter-bone space of the tibial tunnel;
synovial fluid can retard sharpie fiber growth into the graft
within the bone tunnel.
[0034] 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.
[0035] 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.
[0036] 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.
[0037] 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.
[0038] 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.
[0039] 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.
[0040] 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).
[0041] 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.
[0042] 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.
[0043] 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, an 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.
[0044] 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.
[0045] 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.
[0046] 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.
* * * * *