U.S. patent application number 09/840324 was filed with the patent office on 2001-08-16 for ligament fixation device and method.
This patent application is currently assigned to Mark E. Steiner. Invention is credited to Burke, Dennis W., Prudden, John JR., Steiner, Mark E..
Application Number | 20010014825 09/840324 |
Document ID | / |
Family ID | 22433864 |
Filed Date | 2001-08-16 |
United States Patent
Application |
20010014825 |
Kind Code |
A1 |
Burke, Dennis W. ; et
al. |
August 16, 2001 |
Ligament fixation device and method
Abstract
The invention relates to a device for attaching a ligament graft
to the inside of a bone passage from a proximal location, the
device including (1) a non-expansible ring having an interior
passage through which the ligament graft may extend, the ring sized
to fit within the bone passage; (2) a radially expansible gripping
member sized to enter the ring and to press the ligament outwardly
against the interior surface of the ring; and (3) an expander
coupled to the expansible gripping member, constructed to expand
the expansible gripping member to grip the ligament against the
ring.
Inventors: |
Burke, Dennis W.; (Milton,
MA) ; Prudden, John JR.; (Essex, MA) ;
Steiner, Mark E.; (Wellesley, MA) |
Correspondence
Address: |
PETER J. DEVLIN
Fish & Richardson P.C.
225 Franklin Street
Boston
MA
02110-2804
US
|
Assignee: |
Mark E. Steiner
Wellesley
MA
|
Family ID: |
22433864 |
Appl. No.: |
09/840324 |
Filed: |
April 23, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09840324 |
Apr 23, 2001 |
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09128145 |
Aug 3, 1998 |
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6221107 |
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Current U.S.
Class: |
623/13.14 ;
623/13.17 |
Current CPC
Class: |
A61F 2002/0835 20130101;
A61F 2/0811 20130101; A61F 2002/0864 20130101; A61F 2002/0882
20130101; A61F 2/0805 20130101 |
Class at
Publication: |
623/13.14 ;
623/13.17 |
International
Class: |
A61F 002/08 |
Claims
What is claimed is:
1. A device for attaching a ligament graft to the inside of a
predetermined bone tunnel from its proximal aspect, the device
comprising: a non-expansible ring having an interior passage
through which the ligament graft may extend, the ring sized and
adapted to fit within and be secured in the bone tunnel; a radially
expansible gripping member sized to enter the ring and to press the
ligament outwardly against the interior surface of the ring; and an
expander coupled to the expansible gripping member, constructed to
expand the expansible gripping member to grip the ligament against
the ring.
2. The device of claim 1 in which the ring is sized smaller than
the tunnel and including a securing device located proximally of
the ring.
3. The device of claim 1 including a strut which extends proximally
to a securing member attached to its proximal end, the securing
member constructed and arranged to engage an exterior surface of
the bone and to secure the ring in the cortical region of the bone
passage.
4. The device of claim 1 wherein the ring is rigid.
5. The device of claim 1 in which the gripping member, when in
position within the ring, has a distal portion extending beyond the
ring that positions a corresponding portion of the ligament graft
against or near the surface of the bone tunnel, in the path of
in-growing bone.
6. The device of claim 1 wherein the ring includes at least one
aperture disposed to permit in-growth of bone about the ligament
graft.
7. The device of claim 1, further comprising: at least one strut
extending distally from the ring; and a distal member disposed at
the distal end of the strut in position to limit distal movement of
the gripping member.
8. The device of claim 7 in which there are at least two spaced
apart struts that extend distally, in supporting relationship with
said distal member.
9. The device of claim 7 in which the distal member is a base from
which a rod extends proximally through the ring passage, upon which
a member acts to expand the gripping member.
10. The device of claim 9 in which the rod is threaded and the
gripping member is associated with a threaded expander engaged upon
the threaded rod for expanding the expansible member.
11. The device of claim 10 in which the threaded expander is of
wedge form, arranged to radially wedge apart portions of the
expansible gripping member.
12. The device of claim 9, wherein a strut extends proximally from
the ring to a securing member attached to its proximal end, the
securing member constructed and arranged to engage an exterior
surface of the bone and to secure the ring in the cortical region
of the bone passage.
13. The device of claim 1 in which the expansible gripping member
comprises a set of circumferentially arranged proximally extending
leg portions constructed and arranged to be splayed apart by
wedging action of a centrally introduced member.
14. The device of claim 13 in which the exterior surface of the leg
portions have ligament gripping projections.
15. The device of claim 14 in which the gripping projections
comprise portions of at least one circumferential ledge, barb or
tooth.
16. The device of claim 14 in which the gripping projections
comprise screw threads.
17. The device of claim 14 in which the ring supports a threaded
rod that extends through the gripping member, in combination with a
threaded expander wedge constructed and arranged to be threaded on
the threaded rod into the expansible gripping member in a wedging
relationship.
18. The device of claim 14 in which the expansible gripping member
supports a threaded rod extending proximally from the gripping
member in combination with a threaded expander wedge constructed
and arranged to be threaded on the threaded rod into the expansible
gripping member in a wedging relationship.
19. The device of claim 14 in which the expansible gripping member
has a distally extending formation arranged to deflect to lock the
gripping member in position relative to the ring.
20. The device of claim 14 in which the expansible gripping member
has screw threads on its exterior that are disposed to engage and
thread into ligament graft lying between the ring and the gripping
member during advance of the gripping member.
21. The device of claim 1 in which the expansible member supports a
threaded rod extending proximally from the gripping member in
combination with a threaded wedge element constructed and arranged
to be threaded on the threaded rod into the expansible gripping
member in a wedging relationship.
22. A device for attaching a ligament graft to the inside of a bone
tunnel from a proximal aspect, the device comprising: a
non-expansible ledge structure providing an interior passage
through which the ligament graft may extend, the structure sized
and adapted to fit within and be secured in the bone tunnel; a
gripping member sized to be opposed to the ledge structure and to
grip the ligament against a portion of the ledge structure; and at
least one strut extending distally from the portion of the ledge
structure against which the ligament is gripped, a distal member
disposed at the distal end of the strut in position to limit distal
movement of the gripping member.
23. The device of claim 22 in which the gripping member is
expansible radially to grip the ligament against the ledge
structure and position the ligament for incorporation by in-growth
of bone from the wall of the tunnel.
24. The device of claim 22 in which the ledge structure is carried
on a continuous ring.
25. A device for attaching a ligament graft to the inside of a bone
tunnel from an extra-articular location, the device comprising: a
rigid ring having an interior passage through which the ligament
graft may extend, the ring sized to fit within the bone tunnel; a
gripping member constructed and arranged to grip a ligament graft
against the interior surface of the rigid ring; and at least one
strut extending proximally from the ring, a securing member
attached to the proximal end of the strut, the securing member
sized to engage an exterior surface of the bone to secure the ring
in the cortical region of the bone tunnel.
26. The device of claim 25 in which the peripheral outer surface of
the ring is cylindrical.
27. The device of claim 25 in which a bone-penetrating formation is
carried by the securing member.
28. The device of claim 25 in which the securing member is a
flange.
29. The device of claim 28 in which the flange has bone-penetrating
formations.
30. The device of claim 25 in which the securing member is a flange
having a hole sized to receive an awl-like tool to hold the member
in position against rotation while a portion of the device is
turned during the procedure.
31. The device of claim 25 in which the gripping member is
expansible to grip the ligament against the ring; and an expander
is coupled to the expandable gripping member, constructed to expand
the gripping member to grip the ligament against the ring.
32. The device of claim 31 in which the gripping member, when in
position within the ring, has a distal portion extending beyond the
ring that positions a corresponding portion of the ligament near or
against the surface of the bone passage in the path of in-growing
bone.
33. A device for attaching a ligament graft to the inside of a bone
tunnel from a proximal aspect, the device comprising: a
non-expansible ring having an interior passage through which the
ligament graft may extend, the ring sized and adapted to fit within
and be secured in the bone passage; strut portions extending
proximally and distally from the ring; a securing member attached
to the end of the proximally-extending strut portion, the securing
member sized to engage an exterior surface of the bone to secure
the ring in the cortical region of the bone tunnel; a base member
attached to the distal end of the distally extending strut portion;
a threaded rod extending proximally from the base member through
the ring; and a gripping member disposed between the rod and the
ring, the gripping member constructed to grip the ligament against
the ring.
34. The device of claim 25 in which the gripping member is
expansible to grip the ligament against the ring.
35. A method of attaching a ligament graft to the inside of a bone
tunnel from a proximal location, the method comprising: providing a
device comprising providing a structure comprising a non-expansible
ring, a rigid rings, or a ledge structure that provides an interior
passage through which the ligament graft may extend, the structure
sized to fit within the bone tunnel; a gripping member sized to
press the ligament outwardly against the interior surface of the
structure; and providing a cylindrical bone tunnel within a bone;
inserting the non-expansible ring into the bone tunnel; passing the
ligament graft through the interior passage of the ring; inserting
the gripping member through the interior passage of the ring;
expanding or otherwise urging the gripping member into a position
that the gripping member grips the ligament against the structure,
thereby securing the ligament graft to the inside of the bone
tunnel.
36. The method of claim 35, wherein an expander is screwed into a
gripping member to expand it to grip the ligament graft.
37. The method of claim 35, wherein a radially expansible gripping
member is screwed into the interior passage of the ring.
38. The method of claim 35 employed in cruciate ligament grafts in
which the graft is secured to the femur.
39. The method of claim 38 in which multiple strands of graft
extend through the tunnel and are affixed in spaced apart
positions.
Description
BACKGROUND OF THE INVENTION
[0001] This invention relates to fixation of ligament grafts.
[0002] When a ligament ruptures, it is usually replaced by a
ligament graft or a prosthetic ligament. In many cases, a ligament
graft is preferable because prosthetic ligaments can wear out.
[0003] For example, the anterior cruciate ligament (ACL) when
ruptured, often requires replacement and a graft is preferred.
[0004] In such ACL reconstruction procedures, a bone tunnel is
created through the tibia and one through the femur. The ligament
graft is then affixed to each bone tunnel by a variety of means,
with the goal that the graft will securely heal to the bone in the
tunnel.
[0005] Presently available techniques are not satisfactory in all
respects.
SUMMARY OF THE INVENTION
[0006] According to one aspect of the invention a device is
provided for attaching a ligament graft to the inside of a bone
tunnel from its proximal aspect (extra-articular point of access).
The device comprises: a non-expansible ring having an interior
passage through which the ligament graft may extend, the ring sized
and adapted to fit within and be secured in the bone tunnel; a
radially expansible gripping member sized to enter the ring and to
press the ligament outwardly against the interior surface of the
ring; and an expander coupled to the expansible gripping member,
constructed to expand the expansible gripping member to grip and
secure the ligament against the ring.
[0007] Preferred embodiments of this aspect of the invention have
one or more of the following features.
[0008] The gripping member, when in position within the ring, has a
distal portion extending beyond the ring that positions a
corresponding portion of the ligament near or against the surface
of the bone tunnel, in the path of in-growing bone.
[0009] The ring is rigid.
[0010] The ring includes at least one aperture disposed to permit
in-growth of bone through the side of the ring and about the
ligament graft.
[0011] The device further comprises at least one strut extending
distally from the ring and a distal member is disposed at the
distal end of the strut in position to limit distal movement of the
gripping member. Preferably there are one strut or two spaced apart
struts that extend distally, in supporting relationship with said
distal member. Preferably the distal member is a base from which a
threaded rod extends proximally through the ring passage, the
gripping member being expanded by a threaded expander engaged upon
the threaded rod, preferably the threaded expander being of wedge
form, arranged to radially wedge apart portions of the expansible
gripping member.
[0012] Preferably, in the foregoing case or generally, a strut
extends proximally from the ring to a securing member attached to
its proximal end, the securing member being constructed and
arranged to engage an exterior surface of the bone to secure the
ring in the cortical region of the bone passage.
[0013] The expansible gripping member comprises a set of
circumferentially arranged proximally extending leg portions
constructed and arranged to be splayed apart by the wedging action
of a centrally introduced expander member, preferably the exterior
surface of the gripping member leg portions have ligament gripping
projections. In certain preferred embodiments the gripping
projections comprise portions of at least one barb or ledge and
preferably an axially spaced set of, circumferential ledge or barb
and in other preferred embodiments the gripping projection comprise
screw threads, including lands, preferably of helical form.
[0014] The ring supports a threaded rod that extends through the
gripping member, in combination with a threaded expander wedge
member constructed and arranged to be threaded on the threaded rod
into the expansible gripping member in a wedging relationship.
[0015] The expansible gripping member supports a threaded rod
extending proximally from the gripping member in combination with a
threaded expander wedge constructed and arranged to be threaded on
the threaded rod into the expansible gripping member in a wedging
relationship.
[0016] An expansible gripping member has a distally extending
formation arranged to deflect to lock the gripping member in
position relative to the ring, preferably this formation comprising
a set of circumferentially arranged, resilient fingers that are
preferably integral with the main body of the gripping member.
[0017] An expansible gripping member has screw threads on its
exterior that are disposed to engage and thread into ligament graft
lying between the ring and the gripping member during advance of
the gripping member.
[0018] The expansible gripping member supports a threaded rod
extending proximally from the gripping member in combination with a
threaded expander wedge threaded into the gripping member for a
wedging relationship.
[0019] According to another aspect of the invention a device is
provided for attaching a ligament graft to the inside of a bone
tunnel from its proximal aspect (extra-articular point of access),
the device comprising: a non-expansible structure ledge providing
an interior passage through which the ligament graft may extend,
the structure sized and adapted to fit within and be secured in the
bone tunnel; a gripping member sized to be opposed to the ledge
structure and to grip the ligament against a portion of the
structure; and at least one strut extending distally from the
portion of the ledge structure against which the ligament is
gripped, a distal member disposed at the distal end of the strut in
position to limit distal movement of the gripping member.
[0020] In preferred embodiments of this aspect of the invention the
gripping member is expansible radially to grip the ligament against
the ledge structure and position the ligament for incorporation by
in-growth of bone from the wall of the tunnel. Preferably the ledge
structure is carried on a continuous ring.
[0021] According to another aspect of the invention a device is
provided for attaching a ligament graft to the inside of a bone
tunnel from an extra-articular location, the device comprising: a
rigid ring having an interior passage through which the ligament
graft may extend, the ring sized and adapted to fit within and be
secured in the bone tunnel; a gripping member constructed and
arranged to grip a ligament graft against the interior surface of
the rigid ring; and at least one strut extending proximally from
the ring, a securing member attached to the proximal end of the
strut, the securing member sized to engage an exterior surface of
the bone to secure the ring in the cortical region of the bone
tunnel.
[0022] Preferably the peripheral outer surface of the ring is
cylindrical.
[0023] Preferred embodiments of this aspect of the invention have a
bone-penetrating formation carried by the securing member.
[0024] Preferably the securing member is a flange extending
laterally from the axis of the passage; preferably the flange has
bone-penetrating formation, preferably projecting distally toward
the bone.
[0025] In other embodiments the securing member is a flange having
a hole sized to receive an awl-like tool to hold the member in
position against rotation while a portion of the device is turned
during the procedure.
[0026] Preferably, the gripping member is expansible to grip the
ligament against the ring, and an expander is coupled to the
expansible gripping member, constructed to expand the gripping
member to grip the ligament against the ring.
[0027] Preferably the gripping member, when in position within the
ring, has a distal portion extending beyond the ring that positions
a corresponding portion of the ligament near or against the surface
of the bone passage in the path of in-growing bone.
[0028] According to another aspect of the invention, a device is
provided for attaching a ligament graft to the inside of a bone
tunnel from its proximal aspect, the device comprising: a
non-expansible ring having an interior passage through which the
ligament graft may extend, the ring sized and adapted to fit within
and be secured in the bone passage; strut portions extending
proximally and distally from the ring; a securing member attached
to the end of the proximally-extending strut portion, the securing
member sized to engage an exterior surface of the bone to secure
the ring in the cortical region of the bone tunnel; a base member
attached to the distal end of the distally extending strut portion;
a rod extending proximally from the base member through the ring;
and a gripping member disposed between the rod and the ring, the
gripping member constructed to grip the ligament against the
ring.
[0029] Preferably the gripping member is expansible to grip the
ligament against the ring.
[0030] According to another aspect of the invention a method is
provided for attaching a ligament graft to the inside of a bone
tunnel from a proximal location, the method comprising: providing a
device according to any of the aspects of the invention, that have
been described; providing a bone tunnel within a bone; introducing
a non-expansible ring, or a rigid ring, with a ledge structure into
the bone passage; passing the ligament graft through the interior
passage of the introduced element; inserting a gripping member and
expanding or otherwise urging the gripping member into a position
that the gripping member grips the ligament against the introduced
element, thereby securing the ligament graft to the inside of the
bone tunnel. In preferred embodiments an expander is screwed into
the gripping member or the radially expansible gripping member is
screwed into the interior passage of the ring.
[0031] In the case of cruciate ligament graft, in which the graft
is secured to the femur, the device is preferably introduced at an
extra-articular location. Preferably multiple, e.g. 4, strands of
graft, e.g. tendon, extend through the tunnel, preferably each of
the grafts or at least pairs of grafts, being separated from the
others in position for individual incorporation into in-growing
bone.
BRIEF DESCRIPTION OF DRAWINGS OF PREFERRED EMBODIMENTS
[0032] FIG. 1 is a side view of components that comprise a
preferred ligament fixation set according to the invention.
[0033] FIG. 1A is a distal end view and FIG. 1B a proximal end view
of an expandable gripping element component of the set taken
respectively on lines 1A-1A and 1B-1B of FIG. 1.
[0034] FIG. 1C is a cross-sectional view taken on-line 1C-1C of
FIG. 1, showing features of the fixed ring member.
[0035] FIG. 1D is a cross-section profile of the ring element of
the fixed ring member taken on lines 1D-1D of FIG. 1C.
[0036] FIG. 2 is a view similar to FIG. 1 of another preferred
fixed ring member while FIG. 2A is a partial side view of another
preferred construction.
[0037] FIG. 3 is an assembly view, with ligament graft in place,
showing the expandable gripping element seated in the fixed ring
member by the driving component of the fixation set of FIG. 1.
[0038] FIG. 3A is a cut away view of part of the assembly of FIG. 3
showing details of the seating of the distal end of the gripping
element.
[0039] FIG. 4 shows the expandable assembly of FIG. 3 with the
gripping element now expanded by action of a conical wedge member
of the set of FIG. 1.
[0040] FIG. 4A is a diagrammatic view on an enlarged scale of the
gripping action of the expanded gripping member against a preferred
ledge formation of a fixed ring member.
[0041] FIG. 5 is a diagrammatic view of the ligament fixation
device of FIG. 1 in place in a tibia tunnel, securing replacement
ligaments in the knee.
[0042] FIGS. 6 through 6E are views of the tibia of FIG. 5
illustrating the sequence of steps for placing the device in the
tibia.
[0043] FIGS. 7A through 7C are views of another embodiment of the
invention illustrating the sequence of steps for placing the device
in the tibia.
[0044] FIG. 7D is an enlarged view showing a fixed ligament using
the device shown in FIG. 7C.
[0045] FIG. 8 is a view similar to parts of FIG. 7A of another
embodiment of the invention.
DESCRIPTION OF PREFERRED EMBODIMENTS
[0046] FIG. 1 shows five parts that comprise a ligament fixation
set. A fixed ring member 10 has ring element 11 that has on its
inner periphery a fixed ledge 12 (See FIGS. 1C, 1D). The ring
element 11, here in the form of a rigid cylindrical wall, has a
series of in-growth apertures 13 formed in the wall. A pair of
opposed distally extending struts 16 are integral with ring 11.
Both extend distally to base 18. One of the struts has a proximally
extending portion 16A which extends proximally to a retaining
flange 14. The flange of Strut 16a serves as a buttress against the
tibial cortex at the beginning of a tunnel in the tibia, the
remainder of the device being sized to extend into the tunnel. Base
18 of ring member 10 supports a shaft that defines a threaded rod
20 that extends axially, parallel to struts 16 and proximally
beyond ring element 11 to a joint 24 aligned with flange 14. A
threaded rod extension 22 lying on the same axis is connected to
threaded rod 20 by snap joint 24. At the proximal tip of the
threaded rod extension is a reduced diameter pilot portion 23.
[0047] An expander formation 26 is formed as part of the shaft
close to, but spaced proximally from base 18. The space between the
expander and the base provides a relief region 28 defined by a
reduced diameter portion at the root of the shaft.
[0048] The expandable gripping element 30 defines distal expansion
sliding fingers 31 that are designed to resiliently spread and
slide over the expander formation 26, and contract into the relief
region 28, see FIG. 3A. The expandable gripping element 30 has
angular gripping teeth 32 or ridges arranged to apply pressure to
the ligament graft. The expandable gripping element 30 has proximal
expansion slots 34 that allow expansion of distally extending,
resilient portions of the expandable gripping element 30 by the
conical wedge 42.
[0049] Also provided in the fixation set is driving nut 36 which
has internal threads 37, matched to the external threads of the
threaded rod 20, 22. The driving nut 36 has a driving head 38 for
engagement by a hand powered driver 40 which is included in the
fixation set. Only a portion of the driver is shown in FIG. 1. The
remaining portion comprises a hollow shaft and handle such as that
of a screw driver.
[0050] Also included in the set is conical wedge member 42. It has
internal threads 43 also matched to the rod and a driving head 44
for engagement by driver 40.
[0051] An alternative construction of the ligament fixation device
is shown in FIG. 2. In this case one of the struts 16 of the ring
member has been eliminated. In the further embodiment of FIG. 2A,
similar to that of FIG. 2, bone penetrating formations 46 depend
from flange 14, for penetrating the tibia and locking the ring
member from rotation.
[0052] In another embodiment a hole is provided in a flange for use
of a awl-type instrument to securely hold the fixed ring member
opposed to the tibia-during the fixation procedure.
[0053] Use of the Ligament Fixation Device
[0054] Arthroscopic assisted ligament reconstruction of the knee
requires rigid fixation of ligament grafts to bone. This enables
accelerated rehabilitation and achievement of a stable knee. The
present device enables secure fixation of soft tissue grafts, such
as harvested tendons, to the endosteal surface of bone, that avoids
reliance upon compression of the grafts against cancellous bone,
and thus the strength of the fixation does not depend upon the
underlying strength of the cancellous bone, and therefore promotes
early rehabilitation even in the case of relatively soft cancellous
bone.
[0055] In conjunction with the use of the ligament fixation device
described, the grafts are secured on the femoral side of the knee
using any of several methods. A common technique is to loop the
tendons around a fixed post that is either attached to a button on
the outer cortex of the femur or is placed directly across the
femoral tunnel. Typically four strands of tendon are disposed
across the knee joint for reconstructing the new ligament, which
exit the joint through a tibial tunnel, to the outer cortex of the
tibia.
[0056] Referring to FIG. 5, a ligament reconstruction technique is
illustrated, that employs the device of the invention. Four
ligament graft strands 48 extend from loops about a secure ring 52
which is attached to a button device 50 that is placed across the
femoral tunnel 51. The four ligament grafts 48 traverse the tibial
tunnel 54 and exit on the outer cortex of the tibia, 56.
[0057] FIG. 6 shows the four graft strands traversing the tibial
tunnel 60 before the fixation device is in place. FIG. 6A
illustrates introduction of the fixed ring member 10 in a fashion
whereby two of the ligament grafts 48 pass on one side of the base
18 and two of the ligament grafts 48 pass on the other side. The
ring member is inserted into the tibia tunnel 54 from the proximal
aspect to the point where the retaining flange 14 is securely
lodged upon the tibial cortex 15 as shown in FIG. 6A. If bone
penetrating formations 46 as shown in FIG. 2a are employed, these
penetrate the cortex and add to the action of the retainer flange
14 in securing the device to the tibial cortex. As shown in 6B, the
expandable gripping element 30 is introduced into the ligament
fixation ring member by sliding it over the pilot portion 23 of the
threaded rod extension 22. The driving nut 36 is then also placed
on the threaded rod extension 22, being introduced over pilot
portion 23 of the rod. The driver 40 is then placed upon the
driving head 38, and rotated clockwise to introduce the expandable
gripping element into the fixation device to the point where the
fingers defined by distal expansion slots 31 resiliently lock over
the expander ledge 26, as shown in FIG. 3A. The driving nut 36
provides axial force to thus implant the expandable gripping
element 30 in the device.
[0058] The driving nut 36 is then removed from the fixation device
by rotating the driver 40 counterclockwise. As suggested in FIG.
6D, the conical wedge member 42 is then threaded on the threaded
rod extension 22 over the pilot portion 23. The conical wedge is
rotated past the snap joint 24 to the threaded rod region 20. It is
driven into the expandable gripping element 30 by further rotation
of the driver 40 until it is seated as is shown in FIG. 6E. As it
is seated, the conical wedge surface 42 expands the proximal leg
portions of the expandable gripping element 30, a motion permitted
by the proximal expansion slots 34 formed in the member. The
expanded condition obtained is shown in FIG. 4. Suitably high
compression is developed between the expandable gripping element 30
and the interior surface of ring 11. The ligament grafts 48 which
are separately disposed between ring 11 and expandable gripping
element 30 are thus gripped securely by the expansion of expandable
gripping element 30 toward the inner surface of ring 11. Where, as
in the embodiment of FIG. 4A, an internal stress concentrating
ledge 12 is provided on the ring, the maximum compression and
securing action on the ligaments occurs in the vicinity of this
ledge.
[0059] After suitable compression upon the ligament grafts has been
achieved, the driver 40 is disengaged from the conical wedge and
the threaded rod extension 22 is disengaged from the threaded rod
20 by bending applied to snap joint 24, that joint having been
preselected to produce fracture under pressures that are not
disruptive of the now-in place fixation device.
[0060] Recapping FIGS. 6-6C, FIG. 6 shows the four discrete
ligament grafts traversing the tibial tunnel 60, FIG. 6a shows the
introduction of the fixed ring member 10 with one pair of the
ligament grafts 48 on one side and another pair of ligament grafts
48 on the other side of base 18, with the grafts exiting the tibial
tunnel 54 through the fixed ring member 10. As shown in FIG. 6B,
the expandable gripping element 30 is introduced by use of driving
nut 36, the expandable gripping element 30 being driven into the
fixed ring member 10 until the resilient elements forming its
distal tip (enabled by distal expansion slots 31) have snapped over
the expander ledge 26 as shown in FIG. 3A. The conical wedge 42 is
introduced, FIG. 6D, to the point where the expandable gripping
element 30 is compressed greatly against the inner aspect of the
ring element 11, see FIGS. 4 and 4A.
[0061] As shown in FIG. 6E, the threaded rod extension 22 has been
removed from the threaded rod 20 leaving the final fixation device
configuration, i.e. the fixed ring member 10, securely implanted in
the tibia with the expandable gripping element 30 compressed by the
in-place conical wedge member 42. FIG. 4 shows the conical wedge
member 42 expanding the expandable gripping element 30 within the
fixed ring member 10. The ligament grafts 48 are cut off at the end
of the procedure, shown as dotted line "C" in FIG. 6E.
[0062] Referring to the magnified view of FIG. 4A the ligament
grafts 48 are shown wedged outwardly by the expandable gripping
element 30. In the inner aspect of this embodiment of the ring
element 11 there is a relatively narrow fixation ledge 12, at which
the ligament grafts are tightly gripped with suitable non-damaging
distortion of the grafts. The ligament grafts are transected at the
end of the procedure just beyond the ring element 11. FIGS. 5 and
6E show by dotted line where the ligament grafts 48 are transected
at the end of the procedure. The expandable portion of the distal
aspect of the expandable gripping element provides an indication
that the gripping element has been securely placed down to the
base, which limits its motion and hence limits the available
wedging movement to an appropriate amount. A mark on the driver or
a mark on the flange may provide a visual verification that the
gripping element has fully seated.
[0063] Operative Technique for Ligament Fixation Device
[0064] The arthroscopic assisted ACL reconstruction is performed
with the leg either bent over the end of an operating room table or
with the knee bent but with the patient supine on an operating
table. Using hamstring tendons as the ligament graft requires the
use of an incision on the proximal medial tibia of about 3 finger
breadths length, placed just medial to the tibial tunnel. Through
this incision the gracilis and semitendinosus tendons can be
obtained as free grafts to reconstruct the anterior cruciate
ligament.
[0065] A tunnel is drilled through this incision into the knee
under arthroscopic visualization (all portions of the procedure
that are to be performed intra-articularly are done under
visualization by way of the arthroscope).
[0066] The tunnel which begins on the anteromedial tibia enters the
intra-articular portion of the tibia at the insertion point of the
anterior cruciate ligament on the tibia. Through this tibial tunnel
a second tunnel is drilled into the femur. The second tunnel is
placed at the second attachment site of the anterior cruciate
ligament.
[0067] At this point there are two tunnels in the knee, one from
the exterior portion of the tibia to the intra-articular region,
and a second one in the femur, both tunnels as depicted in FIG.
5.
[0068] These tunnels are placed such that their openings are at the
normal anterior cruciate origin and insertion sites.
[0069] At this point the grafts are placed across the knee, usually
by use of sutures that are drilled through the lateral cortex of
the femur and brought out to the lateral aspect of the thigh. The
looped ends of the grafts are brought up into the femoral tunnel
where they are secured by looping them around either a fixed post
or the secure loop extending from a metal button as shown in FIG.
5. The grafts then lie across the knee joint in the anatomic
configuration of the anterior cruciate ligament. They exit through
the tibial tunnel and are splayed out through the incision on the
proximal medial tibia.
[0070] These tendon grafts need to be securely fixed on the tibial
side.
[0071] Many previous operative techniques have relied upon staples
or screws and washers to secure tendon grafts to the tibial
cortical surface. These fixation techniques leave painful,
prominent hardware directly beneath the skin, their fixation
strength is not always reliable, and a certain portion of tendon
beneath these compressive devices is devascularized, that can be
injurious.
[0072] The ligament fixation device here-described rigidly secures
the ligament grafts within the tibial tunnel and leaves no
prominent hardware. The construction enables in-growth of
cancellous bone directly to the ligament grafts through apertures
in ring element 11 and in the region just distal of ring element 11
where the tendons have been splayed out against or close to
cancellous bone tissue.
[0073] The ligament fixation device thus provides temporary
fixation until the body's normal healing process incorporates the
ligament grafts into the bone. It is known from animal studies and
clinical experience that by eight weeks, ligament grafts have
incorporated into bone such that the weakest link of the new
ligament construct is no longer the fixation point, but rather the
intra-articular portion of the ligament. The presently preferred
ligament fixation device provided herein has a relatively narrow
ring element that minimizes the compression of the soft ligament
tissue, the device providing a large open region distal to the ring
element where the expandable gripping element pushes the ligament
grafts into intimate contact with the cancellous bone to facilitate
early healing of the grafts to the cancellous bone.
[0074] The rigid fixation of the hamstring grafts, thus achieved,
can facilitate an accelerated rehabilitation, whereby a full range
of motion and weight bearing, as tolerated, are begun based on
patient comfort and not on any concern for protection of the
fixation region.
[0075] An advantage of the ligament fixation device is that all of
the ligament grafts are securely opposed to bone, allowing healing
of each graft to bone so as to obtain the full strength potential
of the composite.
[0076] Other Embodiments
[0077] In another embodiment, as shown in FIG. 7A, a fixed ring
member 111 is implanted into a tibial tunnel 154, fixed ring member
111 being internally open, not having a threaded rod. A pair of
opposed struts 116 are integral with ring 111 and support base 118
in position to limit distal advance of gripping element 130.
Referring to FIG. 7A, the gripping element 130 has screw thread
formations 132 on its conical exterior, constructed to be screwed
into portions of graft 148 within ring member 111. Referring to
FIG. 7B, the gripping element 130 is introduced to ring member 111
by rotation until its proximal end is roughly flush with ring
member 111, at which point thread formations 132 interact with
graft 148 to provide the reaction force that enables gripping
element 130 to be driven into the tibial tunnel and into the inner
portion of ring member 111. In so doing, the thread formations 132
of gripping element 130 deform the tendon (see FIG. 7D) and thereby
define its path into ring member 111.
[0078] In a preferred modification shown in FIG. 8, a screw-form
gripping member 230 has a hollowed bore 231 in its proximal portion
and is expandable much in the nature of the expandable gripping
element of FIG. 1. When seated, screw 230 is expanded securely
toward ring member 111 by a second conical member 242 that is
turned into bore 231 of the embodiment of FIG. 8 either by a
threaded rod 222 incorporated into the plastic screw 230, extending
proximally for receiving an expander 242 which may be identical to
wedge member 42 of FIG. 1, or by the action of screw threads on the
conical surface, that interact with the interior surface of the
gripping element.
[0079] In a further alternative, the support base section may be
omitted.
[0080] In preferred embodiments the ring member including its
struts, base and flange are formed integrally of biologically
acceptable, strong metal. The expansible gripping member
advantageously is of one piece construction of engineering plastic
that has suitable resiliency.
[0081] Numerous other embodiments employ other details to achieve
secure fixation following the principles at various levels of
generality, that have been presented here.
* * * * *