Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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METHOD AND APPARATUS FOR PERFORMING AN
OPEN WEDGE, HIGH TIBIAL OSTEOTOMY
Reference To Pending Prior Patent Applications
This patent application:
(i) is a continuation-in-part of pending prior
U.S. Patent Application Serial No. 11/047,159, filed
01/31/05 by Vincent P. Novak for OPEN WEDGE OSTEOTOMY
SYSTEM AND SURGICAL,METHOD (Attorney's Docket No.
NOVAK-0102031);
(ii) is a continuation-in-part of pending prior
U.S. Patent Application Serial No. 11/047,551, filed
01/31/05 by Vincent P. Novak for OPEN WEDGE OSTEOTOMY
SYSTEM AND SURGICAL METHOD (Attorney's Docket No.
NOVAK-010203SM);
(iii) is a continuation-in-part of pending prior
U.S. Patent Application Serial No. 11/352,103, filed
02/09/06 by Vincent P. Novak et al. for MULTI-PART
IMPLANT FOR OPEN WEDGE KNEE OSTEOTOMIES (Attorney's
Docket No. NOVAK-4);
(iv) is a continuation-in-part of pending prior
U.S. Patent Application Serial No. 11/350,333, filed
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02/08/06 by Vincent P. Novak et al. for METHOD AND
APPARATUS FOR FORMING A WEDGE-LIKE OPENING IN A BONE
FOR AN OPEN WEDGE OSTEOTOMY (Attorney's Docket No.
NOVAK-5);
(v) is a continuation-in-part of pending prior
U.S. Patent Application Serial No. 11/396,490, filed
04/03/06 by Kelly Ammann et al. for METHOD AND
APPARATUS FOR PERFORMING AN OPEN WEDGE, HIGH TIBIAL
OSTEOTOMY (Attorney's Docket No. NOVAK-060708);
(vi) claims benefit of pending prior U.S.
Provisional Patent Application Serial No. 60/741,313,
filed 12/01/05 by Kelly Ammann et al. for METHOD AND
SYSTEM OF FIXATION FOR PERFORMING AN OPENING WEDGE
OSTEOTOMY (Attorney's Docket No. NOVAK-9 PROV);
(vii) claims benefit of pending prior U.S.
Provisional Patent Application Serial No. 60/742,772,
filed 12/06/05 by Kelly G. Ammann et al. for METHOD AND
SYSTEM OF FIXATION FOR PERFORMING AN OPENING WEDGE
OSTEOTOMY (Attorney's Docket No. NOVAK-10 PROV);
(viii) claims benefit of pending prior U.S.
Provisional Patent Application Serial No. 60/753,366,
filed 12/22/05 by Kelly G. Ammann et al. for METHOD AND
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SYSTEM OF FIXATION FOR PERFORMING AN OPENING WEDGE
OSTEOTOMY (Attorney's Docket No. NOVAK-11 PROV);
(ix) claims benefit of pending prior U.S.
Provisional Patent Application Serial No. 60/835,172,
filed 08/02/06 by Kelly G. Ammann et al. for METHOD AND
SYSTEM OF FIXATION FOR PERFORMING AN OPENING WEDGE
OSTEOTOMY (Attorney's Docket No. NOVAK-13 PROV);
(x) claims benefit of pending prior U.S.
Provisional Patent Application Serial No. 60/835,269,
filed 08/03/06 by Kelly G. Ammann et al. for METHOD AND
SYSTEM OF FIXATION FOR PERFORMING AN OPENING WEDGE
OSTEOTOMY (Attorney's Docket No. NOVAK-14 PROV);
(xi) claims benefit of pending prior U.S.
Provisional Patent Application Serial No. 60/835,292,
filed 08/03/06 by Robert E. Schneider et al. for BONE
ANCHOR FOR FIXATION TO A DISTAL CORTICAL WALL THROUGH
CANCELLOUS BONE (Attorney's Docket No. NOVAK-15 PROV);
(xii) claims benefit of pending prior U.S.
Provisional Patent Application Serial No. 60/835,268,
filed 08/03/06 by Kelly G. Ammann et al. for OPEN WEDGE
OSTEOTOMY SYSTEM (Attorney's Docket No. NOVAK-16 PROV);
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(xiii) claims benefit of pending prior U.S.
Provisional Patent Application Serial No. 60/847,527,
filed 09/27/06 by Vincent P. Novak et al. for KEYHOLE
OSTEOTOMY SYSTEM (Attorney's Docket No. NOVAK-17 PROV);
and
(xiv) claims benefit of pending prior U.S.
Provisional Patent Application Serial No. 60/860,595,
filed 11/22/06 by Kelly Ammann et al. for METHOD AND
APPARATUS FOR PERFORMING AN OPEN WEDGE, HIGH TIBIAL
OSTEOTOMY (Attorney's Docket No. NOVAK-19 PROV).
The fourteen (14) above-identified patent
applications are hereby incorporated herein by
reference.
Field Of The Invention
This invention relates to surgical methods and
apparatus in general, and more particularly to surgical
methods and apparatus for performing open wedge, high
tibial osteotomies of the knee.
Background Of The Invention
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Osteotomies of the knee are an important technique
for treating knee osteoarthritis. In essence, knee
osteotomies adjust the geometry of the knee joint so as
to transfer weight bearing load from arthritic portions
of the joint to relatively unaffected portions of the
joint.
Knee osteotomies are also an important technique
for addressing abnormal knee geometries, e.g., due to
birth defect, injury, etc.
Most knee osteotomies are designed to modify the
geometry of the tibia, so as to adjust the manner in
which the load is transferred across the knee joint.
There are essentially two ways in which to adjust
the orientation of the tibia: (i) the closed wedge
technique; and (ii) the open wedge technique.
With the closed wedge technique, a wedge of bone
is removed from the upper portion of the tibia, and
then the tibia is manipulated so as to close the
resulting gap, whereby to reorient the lower portion of
the tibia relative to the tibial plateau and hence
adjust the manner in which load is transferred from the
femur to the tibia.
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With the open wedge technique, a cut is made into
the upper portion of the tibia, the tibia is
manipulated so as to open a wedge-like opening in the
bone, and-then the bone is secured in this position
(e.g., by screwing metal plates to the bone or by
inserting a wedge-shaped implant into the opening in
the bone), whereby to reorient the lower portion of the
tibia relative to the tibial plateau and hence adjust
the manner in which load is transferred from the femur
to the tibia.
While both closed wedge osteotomies and open wedge
osteotomies provide substantial benefits to the
patient, they are procedurally challenging for the
surgeon. Among other things, with respect to open
wedge osteotomies, it can be difficult to create the
wedge-like opening in the bone with the necessary
precision and with a minimum of trauma to the
surrounding tissue (e.g., the neurological and vascular
structures at the back of the knee). Furthermore, with
open wedge bsteotomies, it can=be difficult to
stabilize the upper and lower portions of the tibia
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relative to one another and to maintain them in this
position while healing occurs.
The present invention is directed to open wedge,
high tibial osteotomies of the knee, and is intended to
provide increased precision and reduced trauma when
creating the wedge-shaped opening in the bone, and to
provide increased stability to the upper and lower
portions of the tibia while healing occurs.
Summary Of The Invention
The present invention comprises a novel method and
apparatus for performing an open wedge, high tibial
osteotomy. More particularly, the present invention
comprises the provision and use of a novel method and
apparatus for forming an appropriate osteotomy cut into
the upper portion of the tibia, manipulating the tibia
so as to open an appropriate wedge-like opening in the
tibia, and then inserting an appropriate wedge-shaped
implant into the wedge-like opening in the tibia, so as
to stabilize the tibia with the desired orientation,
whereby to reorient the lower portion of the tibia
relative to the tibial plateau and hence adjust the
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manner in which load is transferred from the femur to
the tibia.
In one preferred form of the present invention,
there is provided apparatus for performing an open
wedge, high tibial osteotomy, the apparatus comprising:
a wedge-shaped implant for disposition in a
wedge-shaped opening created in the tibia, wherein the
wedge-shaped implant comprises at least two keys,
laterally offset from one another, for disposition in
corresponding keyholes formed in the tibia adjacent to
the wedge-shaped opening created in the tibia.
In another form of the present invention, there is
provided a method for performing an open wedge, high
tibial osteotomy, the method comprising:
cutting the bone along a cutting plane, with the
cut terminating at a boundary line, and forming at
least two keyholes in the tibia adjacent to the cut,
wherein the two keyholes are laterally offset from one
another;
moving the bone on either side of the cut apart so
as to form a wedge-like opening in the bone; and
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positioning a wedge-shaped implant in the wedge-
shaped opening created in the tibia, wherein the wedge-
shaped implant comprises at least two keys, laterally
offset from one another, and further wherein the at
least two keys are disposed in the at least two
keyholes formed in the tibia.
In another form of the present invention, there is
provided apparatus for performing an open wedge, high
tibial osteotomy, the apparatus comprising:
a wedge-shaped implant for disposition in a
wedge-shaped opening created in the tibia, wherein the
wedge-shaped implant comprises at least two keys,
vertically offset from one another, for disposition in
corresponding keyholes formed in the tibia adjacent to
the wedge-shaped opening created in the tibia, and a
shear rib, laterally offset from the at least two keys,
for disposition in a corresponding shear rib keyhole
formed in the tibia adjacent to the wedge-shaped
opening created in the tibia.
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In another form of the present invention, there is
provided a method for performing an open wedge, high
tibial osteotomy, the method comprising:
cutting the bone along a cutting plane, with the
cut terminating at a boundary line, and forming at
least two keyholes in the tibia adjacent to the cut,
wherein the two keyholes are vertically offset from one
another, and forming a shear rib keyhole in the tibia
adjacent to the cut, wherein the shear rib keyhole is
laterally offset from the at least two keyholes;
moving the bone on either side of the cut apart so
as to form a wedge-like opening in the bone; and
positioning a wedge-shaped implant in the wedge-
shaped opening created in the tibia, wherein the wedge-
shaped implant comprises at least two keys, vertically
offset from one another, and a shear rib, laterally
offset from the at least two keys, and further wherein
the at least two keys are disposed in the at least two
keyholes formed in the tibia, and the shear rib is
disposed in the shear rib keyhole formed in the tibia.
In another form of the present invention, there is
provided a shear rib end mill comprising:
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a shaft having a distal end and a proximal end,
and a relief area formed on the shaft proximal to the
distal end;
a cutting edge formed on the shaft distal to
relief area, and a flute communicating with the cutting
edge and extending into relief area; and
a stop formed on the shaft, proximal to the relief
area.
Brief Description Of The Drawings
These and other objects and features of the
present invention will be more fully disclosed or
rendered obvious by the following detailed description
of the preferred embodiments of the invention, which is
to be considered together with the accompanying
drawings wherein like numbers refer to like parts, and
further wherein:
Figs. 1-3 are schematic views showing the
formation of a wedge-like opening in the tibia for an
open wedge, high tibial osteotomy, and positioning of a
wedge-shaped implant into the wedge-like opening in the
tibia;
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Fig. 3A is a schematic view showing selected
anatomical planes;
Figs. 4-9 show the relevant planar surfaces in an
open wedge, high tibial osteotomy conducted in
accordance with the present invention;
Figs. 10-30 are schematic views showing a
preferred method and apparatus for forming an
appropriate osteotomy cut into the upper portion of the
tibia, manipulating the tibia so as to open an
appropriate wedge-like opening in the tibia, and then
inserting an appropriate wedge-shaped implant into the
wedge-like opening in the tibia;
Figs. 31-33 are schematic views showing an
alternative wedge-shaped implant also formed in
accordance with the present invention;
Fig. 34 is a schematic view showing a keyhole
drill guide which may be used in conjunction with the
wedge-shaped implant shown in Figs. 31-33;
Fig. 35 is a schematic view showing another
wedge-shaped implant formed in accordance with the
present invention;
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Figs. 36-38 are schematic views showing still
another wedge-shaped implant formed in accordance with
the present invention;
Figs. 39-41 are schematic views show a keyhole
drill guide and an end mill which may be used in
conjunction with the wedge-shaped implant shown in
Figs. 36-38; and
Figs. 42-48 are schematic views showing
alternative apparatus which may be used to form a cut
in the tibia.
Detailed Description Of The Preferred Embodiments
Overview Of An Open Wedge, High Tibial Osteotomy
Looking first at Figs. 1-3, there is shown a knee
joint 5 upon which an open wedge osteotomy is to be
performed. Knee joint 5 generally comprises a tibia 10
and a femur 15. In accordance with the present
invention, the open wedge osteotomy is effected by
first making a cut 20 (Fig. 1) into the upper tibia,
and then manipulating the lower portion of the tibia so
as to open a wedge-like opening 25 (Fig. 2) in the
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bone, with the wedge-like opening 25 being configured
so as to adjust the manner in which load is transferred
from the femur to the tibia. In this respect, it
should be appreciated that a variety of methods are
well known in the art for determining the degree of
correction necessary to correctly re-align the
weight-bearing axis of the knee. Furthermore, cut 20
and wedge-like opening 25 may be formed in a variety of
ways well known in the art.
Among other things, the present invention provides
a new and improved method and apparatus for forming cut
and wedge-like opening 25, as will be discussed in
detail below.
Once the desired wedge-like opening 25 has been
15 formed in tibia 10 so as to reconfigure tibia 10 to the
desired geometry, the bone may be secured in position
in a variety of ways.well known in the art (e.g., by
screwing metal plates to the bone or by inserting a
wedge-shaped implant into the opening in the bone),
20 whereby to adjust the manner in which the load is
transferred from the femur to the tibia. By way of
example, Fig. 3 shows a wedge-shaped implant 27
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inserted into the wedge-like opening 25 formed in the
tibia, whereby to stabilize the tibia in its
reconfigured geometry.
Among other things, the present invention also
provides a new and improved wedge-shaped implant, and
an associated method and apparatus for depl.oying the
same into the wedge-shaped opening in the tibia, as
will be discussed in detail below.
Discussion Of The Relevant Planar Surfaces In The Open
Wedge, High Tibial Osteotomy Of The Present Invention
In order to appreciate certain aspects of the
present invention, it is helpful to have a thorough
understanding of the planar surfaces of the tibia that
are relevant in performing the open wedge, high tibial
osteotomy of the present invention. Thus, the
following discussion presents a geometric description
of the planar surfaces that are relevant to the open
wedge, high tibial osteotomy of the present invention.
For the purposes of the present discussion, it.. can
sometimes be helpful to make reference to selected
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anatomical planes, e.g., the coronal plane, the
sagittal plane and the transverse plane (Fig. 3A).
Looking now at Figs. 1-4, for the purposes of the
present invention, the tibial plateau 30 may be
described as a horizontal (or transverse) plane that
extends along the top surface of tibia 10. For
reference, the sagittal plane 32 is also shown in Fig.
4. As seen in Fig. 5, tibial plateau 30 is also
perpendicular to the frontal (or coronal) plane 40.
The anterior-posterior (A-P) slope is defined by an
anterior-posterior (A-P) slope plane 45 that extends
along the sloping top surface of the tibia, from
anterior-to-posterior. Published research has
demonstrated that the anterior-posterior (A-P) slope
typically extends at an angle of approximately 7 to
110 to the tibial plateau 30; however, the specific
angle may vary from individual to individual.
Looking next at Fig. 6, for the open wedge, high
tibial osteotomy of the present invention, it is
generally desirable to stay about 2 cm inferior to the
A-P slope plane 45. This offset can be referred to as
the A-P offset plane 50.
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As seen in Fig. 7, the lateral aspect and cut
depth of the cut 20 may be defined by a lateral aspect
plane 55 and a cut depth plane 60, with the cut depth
being about 1 cm medial to the lateral aspect of the
tibia.
Looking next at Fig. 8, the osteotomy cut plane 65
(when seen from the direct frontal view of Fig. 8) is
formed by a plane that is rotated away from the A-P
offset plane 50 through an axis which is formed by the
intersection of the cut depth plane 60 and the A-P
offset plane 50. The degree of rotation is selected so
as to be sufficient to place the entry of the osteotomy
cut plane 65 at the medial neck 66 (Fig. 8) of the
tibia. It should be noted that the A-P offset plane 50
and the osteotomy cut plane 65 are "tilted" slightly
from anterior to posterior (but not seen in the direct
frontal view of Fig. 8), since the A-P offset plane 50
and the osteotomy cut plane 65 follow the tilt of the
A-P slope plane 45 (Fig. 6). The intersection of the
A-P offset plane 50 and the cut depth plane 60 forms an
axis 70 which, in accordance with the present
invention, defines the lateral limit of the osteotomy
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cut 20. In other words, axis 70 defines a line through
the tibia which is (i) parallel to A-P slope plane 45,
and (ii) contained within.osteotomy cut plane 65.
Furthermore, in accordance with the present invention,
axis 70 is used to define the lateral limit of the
osteotomy cut 20 which is to be made into the tibia.
As seen in Fig. 9, the direct view of the
osteotomy plane is a direct view in line with the
osteotomy. This view is tilted downward (e.g., at an
angle of approximately 7 ) from the direct frontal
view. Again, the angle of tilt downward is equal to
the A-P slope. In other words, with the present
invention, the osteotomy cut plane 65.extends parallel
to the A-P slope plane 45 (in the anterior-to-posterior
direction, although not in the medial-to-lateral
direction), and typically slopes downward (e.g., at an
angle of approximately 7-11 ) when viewed in the
anterior-to-posterior direction. Furthermore, with the
present invention, the axis 70 (which defines the
lateral limit to the osteotomy cut 20) is contained
within the osteotomy cut plane 65.
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Novel Method And Apparatus For Performing The Open
Wedge, High Tibial Osteotomy Of The Present Invention
In one preferred embodiment of the present
invention, there is provided a novel osteotomy system
which comprises instrumentation for use in making
precise and repeatable osteotomy cuts for use in open
wedge, high tibial osteotomies, preferably using an
antero-medial approach. The novel osteotomy system
generally comprises a positioning guide 100 (Fig. 16),
a slope guide 200 (Fig. 11), an apex pin 300 (Fig. 16),
a keyhole drill guide 400 (Fig. 18), a posterior
protector 500 (Fig. 20), and a cutting guide 600 (Fig.
20), as will hereinafter be discussed in further
detail.
The novel osteotomy system preferably also
comprises a novel opening jack 700 (Fig. 22) for
opening the cut 20 in the tibia so as to form the
wedge-like opening 25 in the tibia, as will also
hereinafter be discussed in further detail.
And the novel osteotomy system preferably also
includes a novel implant 800 (Fig. 24) for positioning
in the wedge-like opening in the tibia so as to
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stabilize the tibia in its corrected configuration, as
will also hereinafter be discussed in further detail.
Furthermore, in some instances, it may be advantageous
to use an implant trial base 830 (Figs. 27 and 28) in
the course of preparing the tibia to receive implant
800, and in order to confirm proper fit of implant 800
in its seat, as will also hereinafter be discussed in
further detail.
Thus, with the present invention, the surgeon
first determines (using methods well known in the art)
the degree of correction necessary to correctly
re-align the weight-bearing axis of the knee; then the
surgeon uses the system to make the appropriate cut 20
into the tibia; then the surgeon opens the bone cut to
the extent required so as to form the desired
wedge-like opening 25 in the tibia; and then the
surgeon stabilizes the tibia in its corrected
configuration (e.g., with the novel implant 800) while
healing occurs.
In a preferred form of the invention, the novel
osteotomy system is configured so that:
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(i) the axis 70 formed at the lateral limit of
the osteotomy cut 20 (which forms the lateral limit of
the remaining bony hinge when the osteotomy cut 20 is
thereafter opened) is parallel to the A-P tibial slope;
(ii) the axis of the lateral limit of the bony
hinge created by the osteotomy cut lies in a plane that
is perpendicular to the frontal (i.e., coronal) plane;
and
(iii) when the osteotomy cut 20 is completed and
the wedge is opened, the distal (i.e., lower) tibia is
rotated about the bony hinge so as to substantially
maintain, in anatomical alignment, the A-P slope and
the frontal plane.
In a preferred form of the invention, the novel
osteotomy system is also configured so that:
(iv) the osteotomy can be performed less
invasively; and
(v) the osteotomy can be performed with minimum
incising of soft tissue such as the medial collateral
ligament, the lateral collateral ligament, and the
hamstrings.
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In a preferred form of the invention, the novel
osteotomy system is also configured so that the
delicate neurological and vascular tissues at the back
of the knee are fully protected during the osteotomy
procedure.
In one preferred form of the present invention,
the novel osteotomy system is constructed and used as
follows.
1. A vertical incision is first made on the
antero-medial portion of the knee, approximately 1 cm
from the medial edge of the patellar tendon, with the
incision beginning approximately 2.5-3 cm superior to
the anterior tibial tubercle, and extending
approximately 6-10 cm in length.
2. The soft tissue between the patellar tendon
and the proximal surface of the tibia is then dissected
in order to make a small tunnel-like opening beneath
the patellar tendon, just above the patellar tendon's
insertion to the proximal tibia.
3. Looking now at Fig. 10, an assembly
comprising positioning guide 100 (Figs. 10 and 16),
slope guide 200 (Figs. 10 and 11) and an introducer 105
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(Figs. 10 and 11) is advanced to the surgical site.
Preferably the assembly of positioning guide 100, slope
guide 200 and introducer 105 is pre-assembled prior to
opening the skin. This assembly is assembled by first
mounting slope guide 200 to positioning guide 100, and
then mounting introducer 105 to both slope guide 200
and positioning guide 100 by using a screw 115 (Fig.
10) which passes through slope guide 200 and is
received in a threaded bore 120 (Fig. 16) formed in
positioning guide 100.
In one preferred form of the invention, slope
guide 200 may comprise two separate elements which'are
secured together, e.g., a base 210 and a guide element
215 which are connected together by pins 205, with base
210 being formed out of a radio-translucent material
(e.g., plastic) and guide element 215 being formed out
of a radio-opaque material (e.g., stainless steel),
whereby guide element 215 will be visible under
fluoroscopy and base 210 will be effectively invisible
under fluoroscopy, as will hereinafter be discussed.
In one preferred form of the invention, introducer 105
may comprise an arm 125 and a handle 130. Arm 125 and
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handlb 130 may be formed as two separate elements
secured together, or arm 125 and handle 130 may be
formed as a singular construction.
4. Next, the foregoing assembly is maneuvered so
that a tibial tubercle locating tab 135 (Figs. 10 and
16) of positioning guide 100 is inserted between the
patellar tendon (not shown) and the tibia, and so that
tibial tubercle locating tab 135 is set against the
superior margin of the tibial tubercle. In this way,
the tibial tubercle provides a rough alignment guide
for aligning positioning guide 100 with the tibia. If
desired, the underside of tibial tubercle locating tab
135 may include serrations, ridges, ribs, etc. (Fig.
11E) so as to facilitate stabilization of tibial
tubercle locating tab 135 (and hence the
instrumentation) against the tibia.
5. Using a lateral fluoroscope view, taken from
the medial side at the level of the tibial plateau, the
assembly is then aligned so that the underside surface
220 (Fig. 11) of guide element 215 of slope guide 200
is aligned with the top of the medial condyle 75 of the
tibia. Alternatively, if the surgeon prefers to shift
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the osteotomy slightly distally on the tibia, the top
edge 225 of guide element 215 of slope guide 200 can be
aligned with medial condyle 75, thereby offsetting the
osteotomy by a fixed distance distally (e.g., 3 mm).
By forming the guide element 215 of slope guide
200 out of a radio-opaque material and by forming the
base 210 of slope guide 200 out of a radio-translucent
material, base 210 will be effectively invisible under
fluoroscopy-and guide element 215 will stand out in
clear relief against the bone.
It should be noted that guide element 215 of slope
guide 200 is preferably formed with a"Z shape" (Figs.
10 and 11A) so as to provide additional functionality.
More particularly, by forming guide element 215 with a
"Z shape", several significant advantages are obtained.
First, this construction permits guide element 215 to
wrap around the perimeter of the tibia. Second, the "Z
shape" of guide element 215 also operates to indicate
if the slope guide is not vertically aligned with the
level of the fluoroscope. More particularly, if slope
guide 200 is not vertically aligned with the level of
the fluoroscope, the "Z shape" of guide element 215
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will appear as a jagged or zig-zag shape on the
fluoroscope (Fig. 11B). However, if guide element 215
is vertically aligned with the level of the
fluoroscope, then the guide element will appear as a
straight line on the fluoroscope (Figs. 11 and 11C).
This vertical alignment is important, since it enables
alignment of slope guide 200 (and hence positioning
guide 100) with the medial condyle, i.e., with the A-P
slope plane.
If desired, and looking now at Figs. 11D, 11E and
11F, it is also possible to provide guide element 215
of slope guide 200 with an "L shape" configuration,
rather than the "Z shape" configuration discussed
above. Again, this construction provides several
benefits. First, the "L shape" configuration permits
guide element 215 to wrap around the perimeter of the
tibia. Second, the "L shape" of guide element 215 also
operates to indicate if the slope guide is not
vertically aligned with the level of the fluoroscope.
More particularly, if slope guide 200 is not vertically
aligned with the level of the fluoroscope, the "L
shape" of guide element 215 will appear as an "L shape"
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on the fluoroscope. However, if guide element 215 is
vertically aligned with the level of the fluoroscope,
then the guide element will appear as a straight line
on the fluoroscope. Again, this vertical alignment is
important, since it enables alignment of slope guide
200 (and hence positioning guide 100) with the medial
condyle, i.e., with the A-P slope plane.
7. The assembly is then maneuvered so that the
medial locating pin 140 (Figs. 10, 11 and 16),
preferably formed as a pin although it could also be
formed as a tab, fin, etc., is located against the
medial aspect 80 (Fig. 16) of the tibia. As further
adjustments in position are made, medial locating pin
140 is held in contact with the medial aspect of the
tibia, thereby ensuring proper alignment of the
instrumentation. Medial locating pin 140 references
the medial aspect of the tibia, thus setting the
distance from the medial aspect of the tibia to the
apex pin 300 (Fig. 10), as will hereinafter be
discussed. This reference distance is used in
conjunction with the sizing of the osteotomy implant 27
(Fig. 3) so as to ensure a proper tibial
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reconstruction, e.g., the distance from the medial
aspect of the tibia to the center of apex pin 300 may
correspond to the distance from the medial aspect of
the implant to the vertex of the wedge angle of the
implant.
In another form of the invention, the reference
distance may be the distance from the medial aspect of
the tibia to a neutral axis of rotation in the bony
hinge, which could be estimated by calculation. In
this case, the distance from the medial aspect of the
tibia to the neutral axis of the bony hinge may
correspond to the distance from the medial aspect of
the implant to the vertex of the wedge angle of the
implant.
8. The assembly is then rotated around the
primary tibial anatomical axis, by sliding introducer
handle 130 in a side-to-side motion, such that the
instrumentation is aligned perpendicular to the frontal
(coronal) plane, i.e., so that introducer 105 and apex
pin 300 (see below) will extend parallel to the
sagittal plane of the patient. To this end, slope
guide 200 is provided with a ball 230 and a groove 235
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(Fig. 10). With the fluoroscope arranged so that it is
set in the lateral mode, with the image being taken
from the medial side at the level of the tibial plateau
(see Fig. 11), the assembly is maneuvered until ball
230 is centered in groove 235 (Fig. 11). When this
occurs, the system is aligned with the sagittal plane
(i.e., positioning guide 100 is disposed so that apex
pin 300 will extend perpendicular to the frontal plane,
as will hereinafter be discussed).
9. Thus, when slope guide 200 is aligned with
the medial condyle 75, and when ball 230 is aligned
with groove 235, the system is aligned with (i) the A-P
slope, and (ii) the sagittal plane. In other words,
when slope guide 200 is aligned with medial condyle 75,
and when ball 230 is aligned with groove 235, the
instrumentation is positioned so that apex pin 300 (see
below) is aligned with both the A-P slope and the
sagittal plane, as will hereinafter be discussed.
10. With all of the previous adjustments
established, the positions of (i) tibial tubercle
locating tab 135, (ii) slope guide 200, (iii) medial
locating pin 140, and (iv) the ball and groove sights
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230, 235 are verified. With all positions confirmed,
the frontal pin 145 (Fig. 16) and the antero-medial (A-
M) pin 150 (Fig. 16) are inserted through positioning
gqide 100 and into the tibia. This secures positioning
guide 100 to the tibia with the desired alignment.
11. Next, apex pin 300 is inserted through
positioning guide 100 and into the tibia. An apex
aimer 155 (Figs. 14 and 16) serves to guide apex pin
300 into the tibia with the proper orientation, i.e.,
so that apex pin 300 is positioned along the axis 70
which is located at the lateral limit of the intended
osteotomy cut, with apex pin 300 extending parallel to
the A-P slope and perpendicular to the coronal plane,
and being coplanar with cutting plane 65. As a result,
apex pin 300 can serve as the lateral stop for the
osteotomy saw, whereby to clearly define the perimeter
of the bony hinge, as will hereinafter be discussed.
Apex pin 300 may be tapped or drilled into virgin bone,
or it may be received in a pre-drilled hole (e.g.,
formed using apex aimer 155 and a standard surgical
drill). A thumbscrew 160 (Fig. 16) may be used to
secure apex pin 300 to positioning guide 100.
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Apex pin 300 may be generally cylindrical in shape
and, if desired, apex pin 300 may be provided with a
rounded, or "bullet-shaped", nose 303, or other tapered
end configuration, so as to facilitate deployment into
the tibia (Fig. 11G).
Furthermore, if desired, apex pin 300 may have a
flat 305 (Figs. 12 and 13) formed thereon to promote a
complete cut-through of the osteotomy. Where apex pin
300 is provided with a distinct flat 305, it is
preferably provided with a counterpart flat 310 (Figs.
12 and 13), such that when apex pin 300 is positioned
within the tibia and thumbscrew 160 is tightened
against flat 310, the aforementioned flat 305 will be
aligned with the osteotomy cut, whereby to ensure that
the osteotomy blade cuts completely through the bone to
reach the apex pin. See Figure 13.
In another version of this construction (not
shown), the flats 305, 310 may be diametrically opposed
to one another, with thumbscrew 160 also being aligned
with the osteotomy cut, whereby to make insertion of
apex pin 300 less prone to error.
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And in another embodiment of the present
invention, apex pin 300 may be necked down to a smaller
diameter in the area of the osteotomy. As a result of
this construction, a slight relief area exists to
accommodate the saw blade so as to help promote a
complete cut-through, but does not require any specific
orientation of the apex pin with respect to the
osteotomy plane, as is the case where the apex pin is
formed with distinct flats.
And in another version of the present invention,
apex aimer 155 may be used with a guide sleeve 161
(Fig. 14) and a small-diameter guide pin 165 in order
to first check the position of the small-diameter guide
pin 165 relative to the desired axis for the apex pin,
before thereafter deploying the larger-diameter apex
pin 300. In this respect, it will be appreciated that
repositioning a misdirected small-diameter guide pin
165 is easier and less traumatic to the host bone than
repositioning a misdirected larger-diameter apex pin
300.
As seen in Fig. 15, tibial tubercle locating tab
135 is preferably sized so that it also functions as an
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anterior protector, by providing a protective shield
between the oscillating saw blade (to be used later in
the procedure to form the osteotomy cut 20) and the
anterior soft tissue structures, e.g., the patellar
tendon. Thus,-tibial tubercle locating tab 135 also
functions as a patellar tendon protector.
12. By virtue of the foregoing, it will be seen
that apex pin 300 is positioned in the patient's tibia
so that the apex pin extends (i) parallel to the A-P
slope of the tibia, and (ii) parallel to the sagittal
plane of the patient. As a result, when the osteotomy
cut 20 is subsequently formed in the bone (see below)
by cutting along the osteotomy cut plane until the apex
pin is engaged by the bone saw, so that the perimeter
of the bony hinge is defined by the location of the
apex pin, the bony hinge will extend (i) parallel to
the A-P slope of the tibia, and (ii) parallel to the
sagittal plane of the patient. By ensuring that apex
pin 300 is set in the aforementioned fashion, and hence
ensuring that the bony hinge is so created, the final
configuration of the tibia can be properly regulated
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when the bone cut is thereafter opened so as to form
the open wedge osteotomy.
13. Once apex pin 300 has been properly
positioned in the bone, slope guide 200 and introducer
105 are removed, leaving positioning guide 100 properly
aligned on, and secured to, the tibia, with apex pin
300 extending parallel to the A-P slope and parallel to
the sagittal plane of the patient. See Figure 16.
The size of positioning guide 100 and the
associated instrumentation are used to prepare the
osteotomy to fit a particular implant sizing of small,
medium or large. More particularly, the medial
locating pin 140, the size of positioning guide 100,
and apex pin 300 all combine to implement an implant
sizing scheme of small, medium or large. As seen in
Fig. 17, medial locating pin 140, positioning guide 100
and apex pin 300 combine to provide a known, fixed
distance from the medial aspect of the tibia to the
apex pin. The size of the planned osteotomy is then
set, allowing a specifically-sized implant (e.g.,
small, medium or large) to nominally fit between the
medial aspect of the tibia and the apex pin.
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In the embodiment shown in Fig. 17, there is a
known lateral offset between medial locating pin 140
and the.entry point of the osteotomy. The implant size
is reduced slightly to factor in this offset distance
so as to yield a proper fit.
In a more preferred construction, and looking now
at Fig. 17A, medial locating pin 140 is substantially
aligned with the entry point of the planned osteotomy.
14. Looking next at Fig. 18, keyhole drill guide
400 is then attached to positioning guide 100 by
passing keyhole drill guide 400 over frontal pin 145
and apex aimer 155. Keyhole drill guide 400 is then
secured in this position with thumbscrew 405. At this
point, a distal pin 410 is inserted through keyhole
drill guide 400 and into the tibia. Distal pin 410
further secures the instrumentation to the tibia.
Next, a surface locator pin 415 is inserted through
keyhole drill guide 400. Surface locator pin 415
slides through keyhole drill guide 400 until the distal
tip of surface locator pin 415 contacts the surface of
the tibia. For the purposes of the present invention,
this surface may be referred to as the "antero-medial
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surface" or the "A-M surface", which is the anatomical
surface of the tibia corresponding to the antero-medial
approach of the osteotomy. When surface locator pin
415 contacts the A-M surface, the surface locator pin
can act as an indicator as to the location of the A-M
surface. This information can then be used to set the
depth of the keyholes which are to be formed in the
tibia (see below) for an improved implant fit.
Next, an end mill 420 is inserted into the distal
hole 425 (i.e., the bottom hole 425) of keyhole drill
guide 400 and drilled until a stop flange 430 on end
mill 420 contacts the proximal end of surface locator
pin 415, whereby to form the distal keyhole 85 (Fig.
21) in the tibia. The drilling procedure is then
repeated for the proximal hole 435 (i.e., the top hole
435), whereby to form the proximal keyhole 90 (Fig. 21)
in the tibia. Thus, keyholes 85 and 90 are formed so
that one keyhole (i.e., proximal keyhole 90) sits above
the other keyhole (i.e., distal keyhole 85). While it
is possible to drill the proximal keyhole before the
distal keyhole, it is generally preferable to drill the
distal keyhole first. This is because drilling the
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distal keyliole before the proximal keyhole reduces the
possibility that the sloping nature of the bone will
cause a later-drilled keyhole to slip into an
earlier-drilled keyhole. It should be appreciated that
keyhole drill guide 400 is configured so that distal
hole 425 and proximal hole 435 will overlap the
osteotomy cutting plane 65 to some extent (Fig. 21), so
that when osteotomy cut 20 is thereafter formed and the
tibia subsequently.opened so as to create the wedge-
like opening 25, distal keyhole 85 and proximal keyhole
90 will overlap, and communicate with, the wedge-like
opening 25 (Fig. 29).
15. Once the two implant keyholes have been
drilled into the tibia, end mill 420 is removed,
thumbscrew 405 is loosened, and then keyhole drill
guide 400 is removed.
16. Next, and looking now at Fig. 19, posterior
protector 500 is attached to an introducer 505 with a
thumbscrew 510. Posterior protector 500 preferably
comprises a far tip 515 and a curved portion 520. Far
tip 515 is preferably formed out of a flexible material
so as to facilitate passage of the posterior protector
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along the surface of the posterior cortex and beneath
overlying soft tissue. Curved portion 520 comprises a
relatively stiff material which provides support for
far tip 515. Far tip 515 of posterior protector 500 is
inserted into the incision and worked along the
posterior cortex of the tibia until far tip 515 of
posterior protector 500 substantially crosses the axis
of, and in some cases actually engages, apex pin 300
(Fig. 21). Once posterior protector 500 has been
properly deployed, the thumbscrew 510 is unscrewed, and
introducer handle 505 is removed, leaving posterior
protector 500 extending along the posterior cortex of
the tibia, interposed between the tibia and the
delicate neurological and vascular structures located
at the back of the knee.
17. Looking next at Fig. 20, cutting guide 600 is
then attached to positioning guide 100 and secured in
place using cutting guide thumbscrew 605. Cutting
guide 600 comprises alignment rods 610 (Fig. 21) that
extend from the cutting guide into the pre-drilled
keyholes 85, 90 (Fig. 21) to assist with cutting
alignment. More particularly, alignment rods 610
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ensure proper alignment between cutting guide 600, its
cutting slot 615 (Figs. 20 and 21) and the pre-drilled
keyholes 85, 90 previously formed in the tibia with end
mill 420 and, ultimately, ensure the desired fit
between the implant and the tibia.
Then, posterior protector 500 is attached to
cutting guide 600 using thumbscrew 620 (Fig. 20).
At this point, the instrumentation is ready to
form the osteotomy cut, with cutting slot 615 of
cutting guide 600 properly aligned with the osteotomy
cut plane, apex pin 300 properly positioned at the far
(lateral) limit of the osteotomy cut, tibial tubercle
locating tab 135 forming a protective shield for the
patellar tendon, and with posterior protector 500
forming a protective shield for the vascular and
neurological structures at the back of the knee. In
this respect it should be appreciated that cutting
guide 600 is sized and shaped, and cutting slot 615 is
positioned, so that, in addition to being aligned with
the apex pin 300, the entry point of the cutting plane
into the tibia is located at an appropriate location on
the tibia's medial neck 66.
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18. Next, a saw blade 625 (attached to an
oscillating saw, not shown) is inserted into cutting
slot 615 of cutting guide 600. The osteotomy cut is
then made by plunging the oscillating saw blade through
cutting slot 615 and into the bone (Fig. 20). The saw
blade is used to cut completely through the medial and
posterior cortices. The saw is operated until saw
blade 625 contacts posterior protector 500 and apex pin
300. As the saw blade cuts through the tibia, it is
constrained by cutting slot 615, apex pin 300 and
posterior protector 500, so that the saw blade may only
cut bone along the osteotomy plane, up to (but not
beyond) the desired location of the bony hinge, and
does not cut soft tissue. During cutting, tibial
tubercle locating tab 135 also ensures that the saw
blade will not inadvertently cut the patellar tendon.
After saw blade 625 forms the desired osteotomy
cut 20 along the cutting plane, the saw blade is
removed, and a hand osteotome (not shown) of the sort
well know in the art is inserted through cutting slot
615 and into the osteotomy cut 20, and then the cut is
completed through the posterior cortical bone near apex
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pin 300 and posterior protector 500. Then the hand
osteotome is removed.
At this point the osteotomy cut 20 has been
completed, with the osteotomy cut terminating on the
lateral side at apex pin 300, so that the bony hinge is
properly positioned at the desired location, i.e.,
parallel to the A-P slope and perpendicular to the
coronal plane.
Next, thumbscrew 620 is loosened and posterior
protector 500 removed. Then thumbscrew 605 is loosened
and cutting guide 600 is removed.
At this point, the desired osteotomy cut 20 has
been formed in the tibia, with keyholes 85 and 90
formed below and above, respectively, the osteotomy
cut.
In order to complete the procedure, the bone must
now be opened so as to reconfigure the tibia to the
desired geometry, and then the tibia stabilized with
the desired configuration, e.g., by inserting a
wedge-shaped implant 27 into wedge-like opening 25.
19. Looking next at Fig. 22, opening jack 700 is
assembled onto the instrumentation by receiving frontal
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pin 145 in a hole 705 formed in jack arm 710, by
receiving apex aimer 155 in another hole 715 formed in
jack arm 710 and jack arm 725, and by receiving distal
pin 410 in a slot 720 formed in jack arm 725. Opening
jack 700 is secured to positioning guide 100 with a
thumbscrew 730.
Once opening jack 700 is in place, the jack is
opened by rotating jack screw 735. This causes jack
arm 725 to pivot about apex aimer 155 so as to open the
jack and thereby open the desired wedge-like opening 25
in the tibia. See Fig. 23. Preferably the patient's
lower leg is manipulated as jack screw 735 is turned so
as to assist in opening of the bone. As the wedge-like
opening 25 is created in the bone, the tibia will be
reoriented in a highly controlled manner, due to the
fact that the bony hinge will be precisely positioned
at axis 70 through the use of apex pin 300, i.e., the
bony hinge will extend parallel to the A-P slope and
parallel to the sagittal plane. Furthermore, as the
wedge-like opening 25 is created in the bone, the risk
of bone cracking will be minimized, due to the fact
that apex pin 300 forms an oversized hole 95 (Figs. 23A
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and 27) at the lateral end of the bone cut, i.e.,
"oversized" relative to the thickness of the osteotomy
cut, whereby to reduce the occurrence of stress risers
and the like as the bone is opened.
The surgeon uses opening jack 700 to open the bone
to the extent necessary to correctly re-align the
weight-bearing axis of the knee.
20. Then, with opening jack 700 still in place,
an implant is positioned in the wedge-like opening 25.
If desired, the implant may be a "generic" implant
such as the implant 27 shown in Fig. 3.
More preferably, however, and looking now at Fig.
24, there is shown a wedge-shaped implant 800 formed in
accordance with the present invention. Wedge-shaped
implant 800 is characterized by a wedge-like side
profile configured to match the geometry of the wedge-
like opening 25 (i.e., to match the prescribed
correction angle of the open wedge, high tibial
osteotomy). Preferably, wedge-shaped implant 800 is
also formed so as to have a U-shaped top profile, such
that it can form a barrier about the perimeter of the
wedge-like opening 25, whereby to contain graft
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material (e.g., bone paste, bone cement, etc.) which
may be positioned within the interior of the wedge-like
opening 25. In one preferred form of the present
invention, wedge-shaped implant 800 is formed so as to
have an asymmetric configuration when viewed in a top
view, so as to mate with the geometry of the tibia when
the implant is positioned using an antero-medial
approach. Wedge-shaped implant 800 is sized so as to
match the known distance from the medial aspect of the
tibia to the axis of the bony hinge, which is set by
the position of apex pin 300. Wedge-shaped implant 800
may be formed out of absorbable material or non-
absorbable material, as desired.
In one preferred form of the invention, and
looking now at Figs. 25 and 26, implant 800 preferably
comprises a three-part assembly, comprising posterior
graft containment arm (GCA) 805, a base 810 and an
anterior graft containment arm (GCA) 815. The
individual components of implant 800 may each be formed
out of absorbable material and/or non-absorbable
material, as desired. Furthermore, where one or more-
of the implant components is formed out of an
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absorbable material, the absorption characteristics of
the material may vary as desired. By way of example
but not limitation, base 810 may be formed out of a
relatively slowly-absorbing material, while posterior
graft containment arm (GCA) 805 and anterior graft
containment arm (GCA) 815 may be formed out of a
relatively faster-absorbing material. Base 810
preferably comprises a pair of keys 820, 825.
In one preferred form of the invention, implant
800 is formed so that posterior graft containment arm
(GCA) 805 has a generally wedge-shaped profile
including an engagement seat 826 comprising an
alignment post 827, and an introducer hole 828 opening
on the antero-medial side of the component for
engagement with introducer 845 (see below). A
strengthening rib 829 is preferably provided as shown.
Additionally, raised points or dimples 831 may be
provided to help fix posterior graft containment arm
(GCA) 805 to the bone. An alignment tab 832 is
provided for extension into upper keyhole 90 (Fig. 29)
when posterior graft containment arm (GCA) 805 is
positioned in the wedge-shaped opening 25.
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And in one preferred form of the invention, base
805 is formed so that its keys 820, 825 each includes a
bore 833, 834, respectively, with the keys being
slotted longitudinally so as to permit expansion of the
keys when screws 865 are thereafter deployed in the
bores, whereby to help lock the implant against the
hard cortical bone of the tibia. External ribs 836 may
be provided on the outer surfaces of keys 820, 825 so
as to help fix keys 820, 825 in keyholes 85, 90,
respectively, when keys 820, 825 are expanded, as will
hereafter be discussed in further detail. External
ribs 836 may extend longitudinally or
circumferentially. Keys 820, 825 protrude from the
upper and lower surfaces of base implant 810, and
accommodate shear loads which may be imposed across the
implant. Furthermore, expansion of keys 820, 825
creates an interference fit with the cortical bone of
the tibia, and can help support tensile loads which may
be imposed across the implant. An alignment mechanism
(not shown) is provided for mating with alignment post
827 of posterior graft containment arm (GCA) 805.
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The bores 833, 834 may be axially aligned with the
longitudinal axes of keys 820, 825, respectively.
Alternatively, the bores 833, 834 may be arranged so
that they diverge from one another, downwardly and
upwardly, respectively, so as to direct screws 865
deeper into the adjacent portions of the tibia.
Anterior graft containment arm (GCA) 815 also
comprises a generally wedge-shaped profile, and an
alignment tab 837 is provided for extension into lower
keyhole 85 when GCA 815 is positioned in the
wedge-shaped opening 25.
Implant 800 is preferably assembled in situ.
In some instances, it may be advantageous to use
an implant trial base 830 (Figs. 27 and 28) in the
course of preparing the tibia to receive implant 800,
and in order to confirm proper fit of implant 800 in
its seat.
More particularly, a pre-assembled assembly
comprising posterior graft containment arm (GCA) 805,
an implant trial base 830 and two guide sleeves 835,
840 are first inserted into wedge-like opening 25 in
the bone using an introducer 845. See Figs. 27 and 28.
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Next, a drill sleeve 850 and a drill 855 are
inserted into guide sleeve 840 (Fig. 27). An upper
hole is drilled into the tibia with the drill. The
drilling procedure is then repeated for guide sleeve
835 so as to create a lower hole. Then drill sleeve
850 and drill 855 are removed from the surgical site.
Next, a tap 860 is inserted into guide sleeve 840 and
the upper hole is tapped. See Fig. 28. Then the tap
is inserted into guide sleeve 835 and the lower hole is
tapped. Then tap 860 is removed from the surgical
site.
21. Next, posterior graft containment arm (GCA)
805 is released from introducer 845, and then
introducer 845 and implant trial base 830 are removed.
Posterior graft containment arm (GCA) 805 remains in
wedge-like opening 25.
22. Then, if desired, graft material is packed
into the osteotomy opening.
23. Next, anterior graft containment arm (GCA)
815 is placed into the osteotomy opening and aligned
with the prepared implant holes. See Fig. 29. If
necessary, jack screw 735 is rotated as needed so as to
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facilitate insertion of anterior GCA 815. At this
point in the procedure, posterior graft containment arm
(GCA) 805 and anterior graft containment arm (GCA) 815
are positioned in wedge-like opening 25.
24. Then implant base 810 is inserted into the
prepared osteotomy, with keys 820 and 825 seated in
tibial holes 85 and 90, respectively, and with base 810
capturing posterior graft containment arm (GCA) 805 and
anterior graft containment arm (GCA) 815 against the
bony hinge. Keys 820 and 825, seating in keyholes 85
and 90, help ensure a precise fit of the implant to the
bone. As this is done, jack screw 735 is adjusted as
necessary so as to facilitate insertion of the base
into the osteotomy. Then jack screw 735 is tightened
slightly so as to ensure that the implant components
are fully seated into the osteotomy wedge, with at
least implant base 810, and preferably also posterior
graft containment arm (GCA) 805 and anterior graft
containment arm (GCA) 815, providing load bearing
support to the tibia. Next, fixation screws 865 are
inserted through keys 820 and 825 in base 810 and into
the tapped holes in the tibia, and then tightened into
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place. As this occurs, fixation screws 865 expand keys
820, 825 so as to lock keys 820, 825 to the adjacent
cortical bone, and fixation screws 865 extend into the
tibia, so as to further lock the implant in position.
See Fig. 30. Finally, opening jack 700, positioning
guide 100, apex pin 300, distal pin 410, frontal pin
145 and A-M pin 150 are removed from the surgical site,
and the incision closed.
Providing implant 800 with two graft containment
arms, e.g., posterior graft containment arm (GCA) 805
and anterior graft containment arm (GCA) 815, is
frequently preferred. However, in some circumstances',
it may be desirable to omit one or both of posterior
graft containment arm (GCA) 805 and anterior graft
containment arm (GCA) 815. Thus, in one preferred form
of the invention, implant 800 comprises only base 810
and omits both posterior graft containment arm (GCA)
805 and anterior graft containment arm (GCA) 815.
Providing implant 800 with a pair of keys 820, 825
is generally preferred. However, in some
circumstances, it may be desirable to omit one or the
other of keys 820, 825. Furthermore, in other
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circumstances, it may be desirable to provide more than
two keys, e.g., to provide three keys.
Furthermore, each of the keys 820, 825 may include
more than one bore 833, 834. Thus, for example, a key
may include two bores, one angled leftwardly so as to
direct a fixation screw leftwardly into the tibia to
the left of the key, andlor one angled rightwardly so
as to direct a fixation screw rightwardly into the
tibia to the right of the key.
The use of apex pin 300 is significant for a
number of reasons:
(1) the oversized, circular diameter hole 95
formed in the tibia by apex pin 300, which forms the
limit of bone cut 20, effectively displaces the stress
forces created at the edge of the bony hinge when the
cut is opened to form the wedge-like opening 25,
thereby adding significantly to the effective strength
of the bony hinge;
(2) by using apex pin 300 to control the length
of bone cut 20 (as measured from the medial aspect of
the tibia to the apex pin), the seat for the implant is
always of known size, thereby simplifying proper
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fitting of the implant to its seat in the bone, and
also reducing the inventory of different-sized implants
which must be on hand during the surgery;
(3) with apex pin 300 in place, bone resecting
tools can be used with increased confidence, without
fear of inadvertently cutting into, or even through,
the bony hinge; and
(4) since apex pin 300 controls the depth of bone
cut 20, the implant can be reliably manufactured to
appropriately address the required degree of correction
needed to effect knee realignment (e.g., a 4 degree
implant slope will always provide a 4 degree angle of
correction).
Furthermore, the provision of (i) apex pin 300,
posterior protector 500 and tibial tubercle locating
tab 135 creates a "protection zone", and (ii) cutting
guide 600 creates a closely constrained cutting path
for saw blade 625, thereby together ensuring that only
the desired portion of the bone is cut. Among other
things, the provision of posterior protector 500
ensures that the delicate neurological and vascular
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tissues at the back of the knee are protected during
cutting of the tibia.
The provision of keyholes 85, 90 in the tibia, and
the provision of keys 820, 825 in the implant, is
significant inasmuch as they provide improved
stabilization of the implant, particularly against
rotational and shearing forces. This is particularly
true inasmuch as keyholes 85, 90 extend through the
hard cortical bone at the periphery of the tibia.
Additional Constructions
Looking next at Figs. 31-33, there is shown an
implant 800A also formed in accordance with the present
invention. Implant 800A is generally similar to the
implant 800 disclosed above, except that implant 800A
has its keys disposed in a"side-by-side" disposition,
rather than the "over-under" disposition of implant
800, as will hereinafter be discussed in further
detail. Furthermore, implant 800A also provides an
alternative approach for joining the posterior graft
containment arm (GCA) to the base, and an alternative
approach for joining the anterior graft containment arm
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(GCA) to the base, as will hereinafter also be
discussed in further detail.
More particularly, and still looking now at Figs.
31-33, implant 800A comprises a posterior graft
containment arm (GCA) 805A, a base 810A and an anterior
graft containment arm (GCA) 815A. Base 810A preferably
comprises a pair of keys 820A, 825A. Keys 820A, 825A
are laterally displaced along the width of base 810A,
in a "side-by-side" configuration. This is in contrast
to the construction of implant 800, which uses an
"over-under" configuration for its keys 820, 825 (Fig.
24). Among other things, it has been found that the
"side-by-side" configuration provides, at the base of
the implant, excellent load-bearing characteristics and
substantial resistance to rotational and shear forces.
Posterior graft containment arm (GCA) 805A
includes a tab 870A, and base 810A includes a groove
873A, whereby posterior graft containment arm (GCA)
805A can mate with base 810A. A screw 875A is used to
secure tab 870A in groove 873A, and hence posterior
graft containment arm (GCA) 805 to base 810. Anterior
graft containment arm (GCA) 815A includes a flange
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878A, and implant base 810A includes a recess 881A,
whereby anterior graft containment arm (GCA) 815A can
mate with base 810A. Another screw 875A is used to
secure flange 878A in recess 881A, and hence anterior
graft containment arm (GCA) 815 to base 810.
Posterior graft containment arm (GCA) 805A, and/or
anterior graft containment arm (GCA) 815A, may include
raised points or dimples 831A.
Keys 820A, 825A each include a bore 833A, 834A,
respectively. Bores 833A, 834A receive fixation screws
865A for fixing implant 800A to the tibia. Bores 833A,
834A preferably diverge from the longitudinal axes of
keys 820A, 825A, respectively, so as to direct fixation
screws 865A downwardly or upwardly into the adjacent
portions of the tibia. Keys 820A, 825A may also
include external ribs 836A. External ribs 836A may
extend longitudinally or circumferentially. Keys 820A,
825A may also be slotted (i.e., in a manner analogous
to the slots provided in keys 820, 825 of implant 800),
whereby to permit keys 820A, 825A to expand when
fixation screws 865A are received in bores 833A, 834A.
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In order to provide appropriate keyholes 85A, 90A
(Fig. 31) for receiving keys 820A, 825A, a keyhole
drill guide 400A (also sometimes referred to as a
"keystone drill template") may be used (Fig. 34).
Keyhole drill guide 400A is generally similar to the
keyhole drill guide 400 disclosed above, except that
keyhole drill. guide 400A'has its two guide holes 425A,
435A disposed in a "side-by-side" disposition, rather
than the "over-under" disposition of the two guide
holes 425, 435 of drill guide 400.
Implant 800A (and drill guide 400A) may be used in
an open wedge, high tibial osteotomy in a manner which
is generally similar to that previously described with
respect to implant 800 (and drill guide 400).
Providing implant 800A with two graft containment
arms, e.g., posterior graft containment arm (GCA) 805A
and anterior graft containment arm (GCA) 815A, is
frequently preferred. However, in some circumstances,
it may be desirable to omit one or both of posterior
graft containment arm (GCA) 805A and anterior graft
containment arm (GCA) 815A. Thus, in one-preferred
form of the invention, implant 800A comprises only base
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810A and omits both posterior graft containment arm
(GCA) 805A and anterior graft containment arm (GCA)
815A.
Providing implant 800A with a pair of keys 820A,
825A is generally preferred. However, in some
circumstances, it may be desirable to omit one or the
other of keys 820A, 825A. Furthermore, in other
circumstances, it may be desirable to provide more than
two keys, e.g., to provide three keys.
Furthermore, each of the keys 820A, 825A may
include more than one bore 833A, 834A. Thus, for
example, a key may include two bores, one angled
upwardly so as to direct a fixation screw upwardly'into
the tibia above the key, and/or one angled downwardly
so as to direct a fixation screw downwardly into the
tibia below the key.
Looking next at Fig. 35, there is shown another
implant 800B also formed in accordance with the present
invention. Implant 800B is generally similar to the
implant 800A disclosed above, except that implant 800B
provides an alternative approach for joining the
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anterior graft containment arm (GCA) to the implant
base, among other things.
More particularly, and still looking now at Fig.
35, implant 800B comprises a posterior graft
containment arm (GCA) 805B, a base 810B and an anterior
graft containment arm (GCA) 815B. Base 810B preferably
comprises a pair of keys 820B, 825B. Keys 820B, 825B
are laterally displaced along the width of base 810B,
in a"side-by-side" configuration. Again, this is in
contrast to the construction of implant 800, which uses
an "over-under" configuration for its keys 820, 825
(Fig. 24).
Posterior graft containment arm (GCA) 805B
includes a tab 870B, and base 810B includes a.groove
873B, whereby posterior graft containment arm (GCA)
805B can mate with base 810B. Anterior graft
containment arm (GCA) 815A includes a slide face 883B,
and implant base 810B includes an opposing slide face
885B, whereby anterior graft containment arm (GCA) 815B
can mate with base 810B. A bridge-type fastener 888B
is used to secure anterior graft containment arm (GCA)
815B in position, with arm slide face 883B engaging
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base slide face 885B, after the implant is positioned
within positioned within the wedge-like opening 25.
Posterior graft containment arm (GCA) 805B, and/or
anterior graft containment arm (GCA) 815B, may include
raised points or dimples 831B.
Keys 820B, 825B each include a bore 833B, 834B,
respectively. Bores 833B, 834B receive fixation screws
865B for fixing implant 800B to the tibia. Bores 833B,
834B preferably diverge from the longitudinal axes of
keys 820B, 825B, respectively, so as to direct fixation
screws 865B downwardly or upwardly into the adjacent
portions of'the tibia. Keys 820B, 825B may also
include external ribs 836B. External ribs 836B may
extend longitudinally or circumferentially. Keys 820B,
825B may also be slotted (i.e., in a manner analogous
to the slots provided in keys 820, 825 of implant 800),
whereby to permit keys 820B, 825B to expand when
fixation screws 865B are received in bores 833B, 834B.
Implant 8'OOB may be used in an open wedge, high
tibial osteotomy in a manner which is generally similar
to that previously described with respect to implant
800.
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Providing implant 800B with two graft containment
arms, e.g., posterior graft containment arm (GCA) 805B
and anterior graft containment arm (GCA) 815B, is
frequently preferred. However, in some circumstances,
it may be desirable to omit one or both of posterior
graft containment arm (GCA) 805B and anterior graft
containment arm (GCA) 815B. Thus, in one preferred
form of the invention, implant 800B comprises only base
810B and omits both posterior graft containment arm
(GCA) 805B and anterior graft containment arm (GCA)
815B.
Providing implant 800B with a pair of keys 820B,
825B is generally preferred. However, in some
circumstances, it may be desirable to omit one or the
other of keys 820B, 825B. Furthermore, in other
circumstances, it may be desirable to provide more than
two keys, e.g., to provide three keys.
Furthermore, each of the keys 820B, 825B may
include more than one bore 833B, 834B. Thus, for
example, a key may include two bores, one angled
upwardly so as to direct a fixation screw upwardly into
the tibia above the key, and/or one angled downwardly
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so as to direct a fixation screw downwardly into the
tibia below the key.
Looking next at Figs. 36-38, there is shown an
implant 800C also formed in accordance with the present
invention. Implant 800C is generally similar to the
implant 800 disclosed above, except that implant 800C
has a shear rib 890C on its base, laterally displaced
from the two keys, as will hereinafter be discussed in
further detail. Furthermore, implant 800C also
provides an alternative approach for joining the
posterior graft containment arm (GCA) to the base, and
an alternative approach for joining the anterior graft
containment arm (GCA) to the base, as will hereinafter
also be discussed in further detail. Furthermore,
implant 800C also provides a means for joining the
distal end of posterior graft containment arm (GCA)
805C to the distal end of anterior graft containment
arm (GCA) 815C, as will hereinafter also be discussed
in further detail.
More particularly, and still looking now at Figs.
36-38, implant 800C comprises a posterior graft
containment arm (GCA) 805C, a base 810C and an anterior
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graft containment arm (GCA) 815C. Preferably a bridge
892C connects the distal end of posterior graft
containment arm (GCA) 805C with the distal end of
anterior graft containment arm (GCA) 815C.
A shear rib 890C is formed in base 810C, laterally
displaced from the two keys 820C, 825C.
Posterior graft containment arm (GCA) 805C
includes a recess 893C, and base 810C includes a
shoulder 894C, whereby posterior graft containment arm
(GCA) 805C can mate with base 810C. Anterior graft
containment arm (GCA) 815C includes a recess 895C, and
implant base 810C includes a shoulder 896C, whereby
anterior graft containment arm (GCA) 815C can mate with
base 810C.
Posterior graft containment arm (GCA) 805C, and/or
anterior graft containment arm (GCA) 815C, may include
raised points or dimples 831C.
Keys 820C, 825C each include a bore 833C, 834C,
respectively. Bores 833C, 834C receive fixation screws
865C for fixing implant 800C to the tibia. The bores
833C, 834C may be axially aligned with the longitudinal
axes of keys 820C, 825C, respectively. Alternatively,
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the bores 833C, 834C may be arranged so that they
diverge from one another, downwardly and upwardly,
respectively, so as to direct screws 865C deeper into
the adjacent portions of the tibia. Keys 820C, 825C
may also include external ribs 836C. External ribs
836C may extend longitudinally or circumferentially.
Keys 820C, 825C may also be slotted (i.e., in a manner
analogous to the slots provided in keys 820, 825 of
implant 800), whereby to permit keys 820C, 825C to
expand when fixation screws 865C are received in bores
833C, 834C.
Shear rib 890C is laterally offset from keys 820C,
825C. Shear rib 890C projects above and below the top
and bottom surfaces of base 810C. Among other things,
it has been found that the provision of shear rib 890C
provides, at the base of the implant, excellent
load-bearing characteristics and substantial resistance
to rotational and shear forces.
In order to provide appropriate keyholes 85C, 90C
(Fig. 36) for receiving keys 820C, 825C, and also for
providing a shear rib keyhole 897C for receiving shear
rib 890C, a keyhole drill guide 400C (also sometimes
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referred to as a "keystone guide") may be used (Figs.
39 and 40). Keyhole drill guide 400C is generally
similar to the keyhole drill guide 400 disclosed above,
except that keyhole drill guide 400C has, in addition
to its two guide holes 425C, 435C, a shear rib
guidehole 440C for forming shear rib keyhole 897C.
Implant 800C (and drill guide 400C) may be used in
an open wedge, high tibial osteotomy in a manner which
is generally similar to that previously described with
respect to implant 800 (and drill guide 400), except
that the bridged graft containment unit, i.e.,
posterior graft containment arm (GCA) 805C, bridge 892C
and anterior graft containment arm (GCA) 815C, is
installed as a single construction. Furthermore, when
drill guide 400C is used to form keyholes 85C and 90C,
it is also used to form shear rib keyhole 897C.
Providing implant 800C with two graft containment
arms, e.g., posterior graft containment arm (GCA) 805C
and anterior graft containment arm (GCA) 815C, is
frequently preferred. However, in some circumstances,
it may be desirable to omit one or both of posterior
graft containment arm (GCA) 805C and anterior graft
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containment arm (GCA) 815C. Thus, in one preferred
form of the invention, implant 800C comprises only base
810C and omits both posterior graft containment arm
(GCA) 805C and anterior graft containment arm (GCA)
815C.
Providing implant 800C with a pair of keys 820C,
825C is generally preferred. However, in some
circumstances, it may be desirable to omit one or the
other of keys 820C, 825C. Furthermore, in other
circumstances, it may be desirable to provide more than
two keys, e.g., to provide three keys.
Furthermore, each of the keys 820C, 825C may
include more than one bore 833C, 834C. Thus, for
example, a key may include two bores, one angled
leftwardly so as to direct a fixation screw leftwardly
into the tibia to the left of the key, and/or one
angled rightwardly so as to direct a fixation screw
rightwardly into the tibia to the right of the key.
If desired, shear rib keyhole 897C can be formed
using a conventional drill. More preferably, however,
and looking now at Figs. 40 and 41, shear rib keyhole
897C is formed using a shear rib end mill 445C. Shear
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rib end mill 445C generally comprises a shaft 450C
having cutting edges 455C, a corner radius 460C and
flutes 465C. A relief area 470C is formed just
proximal to corner radius 460C. An end stop 475C
liinits, through engagement with drill guide 400C, the
depth of shear rib keyhole 897C.
It is also possible to use a modified form of
posterior protector 500, and a modified form of
positioning guide 100, when practicing the present
invention:
More particularly, and looking now at Figs. 42 and
43, there is shown a posterior protector 500A which is
intended to be used in conjunction with an introducer
505A having a clamping collar 525A and a plunger 530A.
Posterior protector 500A includes a flexible far tip
515A and stiff curved portion 520A. A bore 540A
extends through curved portion 520A. A base 545A is
formed at the end of the curved portion 520A. Base
545A includes a bore 550A. Posterior protector 500A
may be releasably secured to clamping collar 525A by
positioning base 545A in clamping.collar 525A and
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advancing plunger 530A against the proximal end of
posterior protector 500A.
Posterior protector 500A may be used in
=conjunction with the positioning guide 100A shown in
Figs. 44 and 45. Positioning guide 100A includes, in
addition to its normal elements, an introducer
alignment pin 170A. Introducer alignment pin 170A
preferably extends at a right angle to medial locating
pin 140A. In use, and looking now at Figs. 46-48,
introducer 505A is used to position posterior protector
500A so that far tip 515A and curved portion 520A are
properly positioned relative to the patient's anatomy,
and so that medial locator pin 140A extends through
bore 540A and introducer alignment pin 170A extends
through bore 550A. Then introducer 505A is disengaged
from posterior protector 500A (Fig. 46), leaving
posterior protector 500A extending across the posterior
cortex of the tibia, interposed between the tibia and
the delicate neurological and vascular structures
located at the back of the knee. Thereafter a cutting
guide 600A may be secured to positioning guide 100A
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(Fig. 47), and saw blade 625A is used to form osteotomy
cut 20.
Anterio-Lateral Osteotomies
In the foregoing description, the present
invention is discussed in the context of performing an
open wedge osteotomy using an antero-medial approach so
as to effect a medial opening wedge osteotomy. Of
course, it should be appreciated that the present
invention may also be used in antero-lateral approaches
so as to effect a lateral opening wedge osteotomy, or
in other approaches which will be well known to those
skilled in the art.
Modifications
It will be understood that many changes in the
details, materials, steps and arrangements of parts,
which have been herein described and illustrated in
order to explain the nature of the invention, may be
made by those skilled in the art without departing from
the principles and scope of the present invention.
