Note: Descriptions are shown in the official language in which they were submitted.
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SURGICAL IMPLANTATION OF CARTILAGE REPAIR UNIT
BACKGROUND OF THE INVENTION
This invention relates to a bio-absorbable
cartilage repair system for regenerating articular
~ 5 cartilage and, more particularly, a system which allows
for vascular invasion and cellular migration between the
system and the adjacent healthy area of articular
cartilage and c:ancellous bone, thereby resulting in
regeneration of the damaged articular cartilage. More
specif~cally, the present invention relates to a method
of surgically implanting such a bio-absorbable cartilage
repair system andL to apparatus useful therein.
Articular cartilage on the surface of bones in
joints, most particularly the knee and hip joints, is
susceptible to deterioration caused by injury or
disease. This deterioration of cartilage leads to pain
and eventually loss of joint movement
and severe pain. As a result, various methods have been
developed to treat and repair damaged or destroyed
articular cartilage.
Prosthetic devices are often used to replace
damaged or destroyed articular cartilage. For example,
U.S. Patent No. 4,627,853 discloses prosthesis which are
used for articular cartilage replacement. The
prosthesis are prepared by demineralization of a bone
segment, the demineralized bone segment serving as a
replacement for articular cartilage.
U.S. Patent No. 4,880,429 discloses a
prosthetic meniscus which is implanted in the knee. The
prosthetic meniscus acts as a scaffold for regrowth of
native meniscal tissue, and comprises collagen fibers
interspersed with glycoaminoglycan molecules.
U.S. Patent No. 5,176,710 discloses a
prosthesis for replacing bone material on the
articulating surface of a joint. The prosthesis has a
specific modulus of elasticity so as to confer stiffness
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to the prosthesis, and contains concave shapes which are
suitable for biologic ingrowth.
U.S. Patent No. 4,502,161 discloses a
prosthetic meniscus which replaces the natural meniscus
between the articular surfaces of the bones and the
joints, and comprises an insert and extension for
attachment to the bone and a reinforcing fabric or mesh
embedded therein.
U.S. Patent No. 3,745,590 discloses a
prosthesis for the repair or replacement of joints,
which prosthesis comprises a body portion, including a
stem and ligamentous elements, and allows for tissue
ingrowth.
U.S. Patent No. 5,123,927 discloses a knee
prosthesis comprising bone cement containing an
antibiotic.
Although there are several prosthetic devices
which can
be used in the replacement of damaged or destroyed
articular cartilage, prosthetic devices have several
disadvantages. For example, cements which are used to
attach prosthetic devices to bones may loosen and
eventually fail. In addition, fragmented cement can
move into the joints and associated lymph tissue and
cause inflammation and further damage. Further, cements
result in the formation of fibrous tissue between the
bone and the prosthesis. Another major disadvantage
associated with the use of prosthesis is that the
prosthetic device may be larger than the damaged
cartilage that needs to be replaced, thereby requiring
removal of portions of healthy bone and/or cartilage in
order to accommodate the prosthetic device. Hence, the
need remains for a system for repairing and regenerating
articular cartilage which avoids the problems associated
with prosthetic devices.
Another means used to treat damaged articular
cartilage is the placement of repair pieces onto the
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bone, which repair pieces substitute for cut-out pieces
of cartilage. For e~ample, U.S. Patent No. 5,067,964
discloses an articular cartilage repair piece which
comprises a layer of non-woven, felted fibrous material
which is limp antl readily conformable to flat and curved
surfaces. The articular cartilage repair piece is
attached to the bone, for example, by bio-absorbable
screws or pins or like temporary fixation techniques.
Fibrous tissue ingrowth eventually surrounds the repair
piece, thereby causing the repair piece to be
permanently attac:hed to the bone. Although U.S. Patent
No. 5,067,964 discloses an alternative method for
repairing damaged articular cartilage, it does not
disclose any means or method of regenerating damaged or
destroyed articular cartilage.
Quite recently, a system for regenerating
damaged or destroyed articular cartilage, wherein the
regenerated articular cartilage is functionally similar
to non damaged articular cartilage, has been developed.
Unfortunately, t~le method of surgically implanting the
system assembly using the conventional tools available
to the surgeon is both time consuming and laborious. In
addition, where the damaged articular cartilage is of
sufficient size to require the surgical implantation of
2S a plurality of the system assemblies rather than just
one, t.he several assemblies should be placed in
appropriate juxta]position relative to one another and to
the periphery of the undamaged articular cartilage
surrounding the injury. It can be difficult, especially
for the inexperienced surgeon, to rapidly and accurately
place the several assemblies in appropriate relative
locations.
Accordins~ly, an object of the present invention
i5 to provide a method of surgically implanting a system
for regenerating articular cartilage.
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Another object is to provide such a method
which is relatively fast and easy to perform, even for a
surgeon with limited experience in this method.
A further object is to provide in one
embodiment such a method involving the placement of a
plurality of repair assemblies which utilizes apparatus
for determining the placement of one repaired assembly
relative to another.
It is another object of the present invention
to provide such a method which facilitates a three
dimensional approximation of the original surface of the
articular cartilage.
SUMMARY OF THE INVENTION
It has now been found that the above and
related objects of the present invention are obtained by
a method of surgically implanting into a site with
cancellous bone a bio-absorbable cartilage repair system
including an assembly. The method comprises the steps
of partially preparing the site to receive the assembly
by removing at least a portion of the damaged or
destroyed articular cartilage. Then the forward tip of
a guide wire is removably fixed in the cancellous bone
under the removed articular cartilage. Utilizing the
guide wire, the site is further prepared to receive the
assembly by drilling and countersinking the subchondral
cancellous bone. Again utilizing the guide wire, the
assembly is seated into the drilled and countersunk
subchondral cancellous bone until the assembly is flush
with the surrounding articular surface. Finally, the
guide wire is removed.
In a preferred embodiment, the assembly is
adapted to regenerate damaged or destroyed articular
cartilage on the surface of a bone by establishing a
chondrogenic growth- supporting matrix between an area
of damaged or destroyed articular cartilage that has
been removed and an adjacent healthy area of articular
cartilage and cancellous bone. The assembly includes a
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bio-absorbable polygonal delivery unit configured and
dimensioned to be mounted in both the removed area and
the adjacent healthy area of bone, and a porous
bio-absorbable insert supported by and in the delivery
5 unit and establishing communication between the removed
area and the acljacent healthy area for a chondrogenic
growth-supportinl3 matri~.
In the preferred embodiment, the site is
partially prepared using a cannulated punch, preferably
a polygonal one. The guide wire is inserted through the
cannula of the punch after removal of a portion of the
damaged or destroyed articular cartilage. A cannulated
drill/countersin]~ is passed over the guide wire prior to
drilling and countersinking, and the assembly is passed
lS over t]~e guide wLre prior to seating.
Preferably the method includes the preliminary
step of inserting an arthroscope adjacent the area of
damaged or destroyed articular cartilage to enable
viewing of the area.
The punch is impacted with a mallet until the punch
reaches a depth of about 3-4 mm into the articular
cartilage and subchondral cancellous bone. The guide
wire has a seli-tapping threaded forward tip and is
rotated by a power drill. A cannulated inserter and
then a cannulated impactor are passed over the guide
wire after the assembly and then the impactor is used to
drive the inserter by itself along the guide wire and
against the assembly to seat the assembly in the drilled
and countersùnk subchondral cancellous bone, followed by
removing the inserter and impactor from the guide wire.
The present invention further encompasses a
method of surg:ically implanting into a site with
cancellous bone a bio-absorbable cartilage repair system
including at least first and second assemblies. The
me~hod comprises the steps of proving a spacer for use
in SpE~Cing apart two guide wires during surgical
implantation of ~he second guide wire a fixed distance
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from the implanted first guide wire. The site is
partially prepared to receive the first assembly by
removing at least a portion of the damaged or destroyed
articular cartilage. The forward tip of a first guide
wire is removably fixed in the cancellous bone under the
removed articular cartilage. The spacer and the first
guide wire are utilized to removably fix the forward tip
of the second wire guide in the cancellous bone a fixed
distance from the first guide wire. The second guide
wire is then utilized to partially prepare the site to
receive the second assembly by removing another portion
of the damaged or destroyed articular cartilage. The
first and second guide wires are utilized to further
prepare the site to receive the assembly by drilling and
countersinking the subchondral cancellous bone. The
first and second guide wires are then utilized to seat
the first and second assemblies, respectively, into the
drilled and countersunk subchondral cancellous bone
until the assemblies are flush with the surrounding
articular surface. Finally, the guide wires are removed.
In a preferred embodiment, the spacer includes
a first cannulated polygonal member having an axis X, N
sides, a ma~imllm width W and a length L, and a second
cannulated polygonal member having an axis x, n sides, a
m~imllm width w, and a length 1, where N and W are at
least equal to (or exceed) n and w, L exceeds 1, and
axes X and x are substantially parallel. One side of
the first cannulated member and one side of the second
cannulated member are rigidly joined. One end of the
first cannulated member and one end of the second
cannulated member are disposed in the same plane, and
the opposite end of the first cannulated member and the
opposite end of the second cannulated member are
disposed in spaced apart parallel planes. The method
~5 including the steps of passing the first cannulated
member of the spacer over the first guide wire with the
second cannulated member of the spacer disposed over
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another portion of the damaged or destroyed articular
cartilage area, inserting a second guide wire through
the cannula of the second cannulated member of the
spacer and then removably fixing the forward tip thereof
~ 5 in the cancellous bone, and removing the spacer from
both guide wires.
The present invention further encompasses the
spacer for use i.n spacing apart two guide wires during
surgical implantation of the second guide wire a fixed
distance from the implanted first guide wire, as
described above.
BRIEF DESCRIPTION OF THE DRAWING
The above brief description, as well as further
objects, featur~-s and advantages of the present
inventi.on, will ~le more fully understood by reference to
the following detailed description of the presently
preferred, albei.t illustrative, embodiments of the
present invention when taken in conjunction with the
accompanying drawings wherein:
FIG. 1 is a fragmentary schematic view of a
knee having therein a pair of assemblies of the
cartilage repair system surgically implanted by the
method of the pre'sent invention;
FIG. 2 is an exploded isometric view of one
assembly of the cartilage repair system;
FIG. 3 i:~ a top plan view thereof;
FIG. 4 is a si,de elevational view thereof;
FIG. 5 is a sectional view thereof taken along
line 5-5 of FIG. 3 and fragmentarily shows the cartilage
repair system inserted into a bone;
FIG. 6 is a sectional view thereof taken along
line 6-6 of FIG. 5, with potential adjacent assemblies
being fragmentari].y illustrated in phantom line;
FIG. 7 .is a fragmentary schematic view of a
knee having damaged or destroyed articular cartilage,
with a arthroscope being disposed adjacent thereto
according to the method of the present invention;
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FIG. 8 is a view similar to FIG. 7, but showing
a mallet pounding a cannulated punch into the damaged or
destroyed articular cartilage to remove the same;
FIG. 9 is a view similar to FIG. 8, but with a
guide wire being inserted through the punch;
FIG. 9A is a sectional view taken along the
line 9A-9A of FIG. 9;
FIG 9B is a sectional view taken along the line
9B-98 of FIG. 9A;
FIG. 10 is a view similar to FIG. 9 but after
removal of the punch, leaving there behind the guide
wire;
FIG. 11 is a view similar to FIG. 10, but with
a cannulated drill/countersink on the guide wire;
FIG. llA is a sectional view thereof taken
along the line llA-llA of FIG. 11;
FIG. llB is a sectional view thereof taken
along the line llB-llB of FIG. llA;
FIG. llC is an isometric view of the
drill/countersink shown in FIG. 11, to a greatly
enlarged scale;
FIG. 12 is a view similar to FIG. 11, but with
the assembly passing over the guide wire;
FIG. 12A is a sectional view thereof taken
along the line 12A-12A of FIG. 12;
FIG. 12B is a sectional view thereof taken
along the line 12B-12B of FIG. 12A;
FIG. 13 is a view similar to FIG. 12, but
showing the assembly being seated, with a cannulated
inserter and a cannulated impactor being shown on the
guide wire;
FIG. 14 is a view similar to FIG. 13 wherein,
after removal of the inserter and impactor, the
procedure has been repeated to implant another assembly
adjacent to the first assembly;
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_g_
FIG. 15 is a view similar to FIG. 9 but showing
the seating of a second guide wire using a spacer
according to the present invention;
FIGS. ].5A a~d 15B are isometric views of the
~ 5 spacer from the distal and proximal ends, respectively,
and
FIG. lfi is a view similar to FIG. 15, but
showing the drilling and countersinking of the first
assembly after the second guide wire is in place and the
spacer removed.
DEI'AILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring now to the drawing, and in particular
to FIG. 1 thereof, therein illustrated is a cartilage
repair system
useful in the method of the present invention, generally
designated by the reference numeral 10. More
particularly, the cartilage repair system 10 illustrated
in FIG. 1 is comprised of a plurality of assemblies
generally design,ated 12 (two being illustrated, but it
being understood that the requisite number is determined
by the e~tent of the damaged area). Each assembly 12 is
in turn comprised of a bio-absorbable delivery unit 14
and a porous bio-absorbable insert 16. The delivery
unit 1~ is configured and dimensioned to be mounted in
both the area from which damaged or destroyed articular
cartilage has b,een removed and the adjacent healthy
cancellous bone area of the bone. The porous insert 16
is supported by and in the delivery unit 14 and
establishes communication between the removed area (that
is, the area from which the damaged or destroyed
articular cartilage has been removed) and the adjacent
healthy area for a chondrogenic growth-supporting
matris, thereby promoting vascular invasion and cellular
migration to achileve articular cartilage regeneration.
While the system 10 is illustrated in FIG. 1 as
being used to regenerate damaged or destroyed articular
cartilage on the femoral knee joint surface K, those
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--10--
skilled in the medical arts will readily appreciate that
the system 10 is equally useful in other articular
joints such as the shoulder, hip, and the like. The
extent of the damaged or destroyed articular cartilage
on the surface of the bone will determine whether the
system 10 employs a single assembly 12 or a plurality of
assemblies 12. The illustrated assemblies 12 (and in
particular the delivery units 14 thereof) are polygonal
in plan and interfitting -- that is, disposed such that
they preferably can be mounted in contiguous abutting
contact in a side-to-side relationship. The polygonal
nature of the periphery of the assemblies permits
interfitting of the assemblies 12 (as generally
illustrated in FIG. 6) and is thus preferred where a
plurality of the assemblies 12 are to be used to
completely cover a designated area of the bone.
However, where only a single assembly 12 will be used,
other configurations, such as a circular configuration,
may be preferred.
While theoretically it might be possible to
create in a single manufacturing operation a unitary,
one-piece, integral assembly 12 which performs the
functions of both the delivery unit 14 and the insert
16, two separate and independently formed components are
preferably utilized -- namely, the delivery unit 14 and
the insert 16. As will be discussed below in detail,
the insert 16 can be made of a relatively wide variety
of different materials and may even include a repair
factor (such as a growth factor or an attachment factor)
releasably disposed therein to assist in establishing
the chondrogenic growth-supporting matrix. Accordingly,
the two-component nature of the assembly 12 enables the
insert 16 to be selected from a supply o~ different
inserts 16 at the time of surgery so as to meet the
particular needs of the patient at the time with regard
to both the basic composition of the insert 16 and any
repair factor composition therein. Again, because of
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the differing natures of the insert 16 (and any repair
factors therein) and its delivery unit 14, it may be
~ necessary for particular types of inserts 16 to be
stored before use in different environments from the
delivery units 14 -- for example, in order to provide
appropriate preservation of the repair factor. Finally,
the delivery unit 14 and insert 16 of an assembly 12
must have different functional characteristics which
would be difficult to achieve through known
manufacturing techniques in an integral, one-piece,
unitary element. Thus, as will be discussed below, the
delivery unit 14 must have sufficient strength and
integrity to enable it to be tamped into the bone
without significant bending
or deforming, while the insert 16 is preferably a
flexible and resilient porous material in the form of a
matrix to enable it to be interconnected with the
delivery unit 14 and thereby provide a chondrogenic
growth-supporting matrix positioned by the delivery unit
14.
Referring specifically to FIGS. 2 and 5,
delivery unit 1~ is comprised of an upper cup-like
support frame 22 and a lower T-like elongate member 23.
The support frame 22 has an upper rim 24 defining an
open top, side walls 26 and a bottom portion 30. The
elongate member 23 (which is preferably cylindrical)
extends downwardly from the bottom portion 30 (which is
preferably concavle) and has radially extending ribs 38,
a blunt bevelled bottom 40 and a bore 42 (preferably
about 1.5 mm in diameter) extending axially there
through. The disc or waferlike insert 16 has a top
surface 52, side walls 54, a bottom surface 56 and a
bore 58 (preferably about 1.5 mm in diameter) extending
axially there through and after insertion into delivery
unit 14 coaxial with bore 42 thereof.
The support frame 22 of the delivery unit 14
receives the insert 16 therein, with the side walls 26
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of the support frame 22 receiving there within the side
walls 54 of the insert 50. The bottom surface 56 of the
insert 16 and the bottom portion 30 of the support frame
22 are correspondingly shaped, preferably with the
bottom surface of the insert 16 defining a protrusion
and the upper surface of the bottom portion 30 de fining
a protrusion-receiving cavity, so that the two bores 42,
58 are automatically and accurately coaxially disposed
after the insertion process. In other words, when the
insert 16 is secured in the supporting frame 22, the
bore 42 through the elongate member 23 and the bore 58
through the insert 16 are in vertically aligned
contiguous relationship.
As will readily be appreciated by those skilled
in the implant arts, if vascular invasion and cellular
migration is to be effected between the healthy
cancellous bone area and the area of removed damaged
cartilage via the insert 16, means must be provided to
preclude relative rotation of the delivery unit 14 and
20 the insert 16. This may be accomplished in a number of
different ways.
First, as best seen in FIGS. 2-3 and 6, the
external periphery of the insert 16 and the internal
periphery of the support frame 22 may be polygonal or
irregular (that is, non- circular) and sized to abut one
another so that they are locked together for rotation
only as a unit. For example, as illustrated, the
hexagonal outer periphery of insert 16 snugly fits
within hexagonal inner periphery of support frame 22 to
preclude relative rotation.
Second, the upper surface of the concave bottom
portion 30 of the support frame 22 may define upwardly
extending bosses 60 adjacent the side walls 26, while
the lower surface of the insert 16 may define upwardly
35 extending recesses 62 configured and dimensioned to
receive the bosses 60, as best seen in FIGS. 3 and 6.
When a boss/recess system is employed, the number of
-
-
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bosses 60 and recesses 62, as well as the shape, size
and placement thereof, are selected so that, when the
~ insert 16 is wit:hin the delivery unit 14, the bosses 60
axe snugly received in the recesses 62, such that the
insert 16 and delivery unit 14 are precluded from
relative rotatio:n as long as the insert 16 is within the
support ~rame 22.
Third, the side walls 54 of the insert 16 may
define radially outwardly extending flanges 64 therein
or there- through, and the side walls 26 of the support
frame 22 may define windows 66 there through configured
and dimensioned to snugly receive the flanges 64 therein
or there through. The number of flanges 64 and windows
66, as well as the size, shape and spacing thereof, are
selected so that, when the insert 16 is within the
support: frame 22,, relative rotation of the insert 16 and
the delivery unit: 14 is precluded as long as the flanges
64 snugly extend into (and possibly through) the windows
66. In order to enable the insert 16 with its flanges
64 to be easily inserted into the supporting frame 22
with its windows 66, the insert 16, or at least the
flanges 64 thereof, are preferably resiliently
flexible. The flanges 64 or windows 66 may also have
bevelled edges to facilitate snapping the flanges 64
into the windows 66 during the insertion process.
In the last two alternatives, the height of the
bosses 60 and t:he depth of the recesses 62 or the
relative heights of the flanges 64 and windows 66 are
selected so that the bottom surface 56 of the insert 16
will rest on the upper surface of the bottom portion 30
of the delivery unit 14. It will be appreciated by
those skilled in the mechanical arts that a wide variety
of different keying mechanisms well known in the
mechanical arts may be used in order to preclude
relative rotation of the insert 16 and the delivery unit
14. Howe~er, it must be kept in mind that, over time,
the bio-absorbabl.e elements -- that is, the delivery
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--14--
unit 14 and the insert 16 -- will be disappearing as the
human body hydrolyzes the material from which they are
made. Accordingly, the selection of an appropriate
keying mechanism to preclude relative rotation of the
insert 16 and the delivery unit 14 must be made with
this consideration in mind. It will be appreciated that
while, for the purposes of exposition, a variety of
different keying mechanisms have been illustrated in a
single embodiment, in fact a single keying mechanism may
suffice for a particular embodiment, although a
plurality of such mechanisms may also be used.
In order to enable the insert 16 to function as
a chondrogenic growth-supporting matrix, it must have
access to vascular invasion and cellular migration to
regenerate the articular cartilage defect. Such access
is provided on the internal periphery of the insert 16
by the bore 58. On the external periphery of the insert
16, the windows 66 on the supporting frame 22 provide
direct contact to the adjacent healthy articular
cartilage or to the adjacent repair assemblies. These
windows 66 allow cellular migration to occur to the
insert. The entire top surface 52 of the insert 16 is
exposed to the articular environment of the affected
joint, and a substantial portion of the bottom surface
56 of the insert 16 is exposed to the cancellous bone
through channels 68, which extend axially through the
bottom 30 of support frame 22. Providing communication
between the area of removed damaged articular cartilage
and the healthy cancellous or trabecular bone, the
30 number of the channels 68, as well as the size, shape
and placement thereof, is selected to provide a
desirable level of communication without unduly
deleteriously affecting the strength of the delivery
unit 14. The axially disposed channels
3S 68 are, of course, disposed radially outwardly of the
elongate member 23 so that the channels 68 do not have
to extend axially there through.
-
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The delivery unit 14 is hard and preferably
does not bend or deform under expected pressures. It is
preferably integrally molded. It is critical that the
delivery unit 1~l be made of a bio-absor~able material
such as those well known in the implant art. For
e~ample, it is preferably made of polyglycolic acid,
polylactic acid or combinations thereof (e.g.,
co-polymers and mixtures thereof).
Several delivery units 14 can be placed
contiguously in an area of removed damaged articular
cartilage such that a large portion of the removed area
will be fi-lled with the assemblies 12. In this case,
the delivery units 14 are preferably regular polygons
and interfitting in an abutting and contiguous
relation. A circular delivery unit may be used where
only one delivery unit is employed or where only partial
coveraqe of the removed area is desired.
The insert 16 is made substantially of porous
material in the form of a matrix or sponge, preferably
defining at least 95% voids by volume, so that it can
serve as a biological scaffold for an invasion of cells
to regenerate the articular cartilage. It typically has
the felt-like feel of a non-woven fabric. The insert 16
may be manually bendable or flexible when it is
necessary to push, press or snap the same into the
delivery unit 14. It is critical that the insert 16
consists substantially (typically at least 99% by
weight) of a bio- absorbable material selected from the
group consisting of hyaluronic acid (e.g. as a fiber
matrix), polyglycolic acid (e.g., as fiber matrix),
collagen, including type I collagen (e.g., as a sponge
matris), polylactic acid (e.g. as a fiber matrix),
fihrin clot (which can be filled and molded into the
delivery unit), collagen gel (which can be overlayed
into a polyglycolic acid matrix), isolated periosteal
cells, polydioxane, polyester, alginate or combinations
thereof. The polylactic acid, and to a lesser degree
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the hyaluronic acid, polyglycolic acid, and alginate,
contribute to the hardness and longevity (i.e., life in
after implantation) of the insert 16. The insert
may be annealed (i.e., heat-treated or cooked) to modify
its crystallinity and thus its hardness and longevity.
The isolated periosteal cells may be cultured in the
insert material or overlaid at the time of surgery into
the insert material. Other cell types, such as
mesenchymal stem cells or chondrocytes, may also be
added to the insert material.
In addition, preferably the insert 16 contains
within the matrix "repair factors" such as growth
factors and/or attachment factors well known in the
medical arts. For example, the insert 16 can contain,
as growth factors, fibroblast growth factor (acidic or
basic), transforming growth factor-beta (1, 2, 3 or one
of the members of the supergene family of TGF-beta, such
as bone morphogenic protein; BMP), insulin, insulin-like
growth factor 1 & 2, platelet-derived growth factor or
combinations thereof. The attachment factors which can
be used in the insert include fibronectin, RGD
polypeptide and combinations thereof. Typically, the
repair factors total less than 1% by weight of the
insert, but can range up to 10~ depending on the
factors' specific activities and release kinetics. The
repair factors may be chemically combined with the basic
implant composition (e.g., during polymerization
thereof) or may be added to an already formed basic
implant composition. In the former case, additional
repair factor will typically become available as the
basic implant composition biodegrades.
Referring now to FIG. 5, after surgical removal
of the damaged or destroyed articular cartilage, the
elongate member 23 (extending downwardly from the
concave bottom portion 30 of the support frame 22) is
placed into the cancellous bone 74 through the
subchondral bone plate 72 which is below the damaged
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-17-
articular carti]age area. The support frame 22 is
supported by the subchondral bone plate 72. The
elongate member 23 has a blunt bevelled bottom 40 so
that the elongate member 23 can be placed easily into
- 5 the cancellous bone 74, which is a soft region of the
bone, while still creating frictional retention of the
elongate member. The bottom 40 of the elongate
cylindrical member 23 is blunt so that the bottom 40
does not break when the elongate cylindrical member 23
is placed inside the cancellous bone 74. When the
elongate member 23 is placed into the soft cancellous
bone 7~, the cancellous bone 74 is displaced by, and
reforms around, the radially extending ribs 38 of the
elongate member 23. In this manner, the elongate member
23~ and thereby the entire cartilage repair system 10,
is held in place.
When the delivery unit 20 is placed in the
bone, the upper rim 24 of the support frame 22 is flush
with undamaged articular cartilage 76. The windows 66
and the upper rim 24 of the support frame 22 are not
placed inside the bone, but rather remain exposed to the
surrounding articular cartilage. The top surface 52 of
the polymer insert 50 is exposed to the joint space
environrnent. The top portion of the exterior surface of
2S the side walls 26 of the support frame 22 laterally
abuts either the top portion of the exterior surface of
the side walls 26 of adjacent support frames 22 (see
FIG. 6), or undamaged peripheral articular cartilage 76
when placed adjac:ent to an area of removed cartilage.
The bottom portion of the e~terior surface of the side
walls 26 of the support frame 22 (i.e., the portions
below windows 66) rests on and laterally abuts the
subchondral bone plate 72.
When the cartilage repair system is placed in
an area of removed damaged articular cartilage, through
the subchondral bone plate 72 into the cancellous bone
74, the channels 68 in the bottom portion 30 of the
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support frame 22 allow for communication between the
healthy cancellous bone 74 and the damaged articular
cartilage area via a chondrogenic growth-supporting
matrix. This permits vascular invasion and cellular
migration, which results in regeneration of the
articular cartilage. The regenerated articular
cartilage is functionally similar to undamaged articular
cartilage. The cartilage repair system of the invention
is bio-absorbed over time and therefore need not be
surgically removed during or after carti~age
regeneration. The absorption rate is formula controlled
and can range from 6-12 weeks to one year depending on
its site-specific application.
As the basic bio-absorbable composition of the
insert 16 degrades or hydrolyzes over time, any repair
factors contained therein are progressively released
into the site, thus further promoting cellular
regeneration. Cellular regeneration occurs throughout
the insert.
The term "bio-absorbable" is used in the
specification and claims hereof to indicate a material
which will be degraded or absorbed by the body such that
regenerated articular cartilage thereabout is
functionally similar to non-damaged articular cartilage.
Referring now to FIGS. 7-13 in sequence,
therein illustrated is the method of surgically
implanting into a site with cancellous bone a
bio-absorbable cartilage repair system 10 including an
assembly 12, according to the present invention.
Referring now to FIG. 7 in particular, a
conventional arthroscope 100 is disposed adjacent the
femoral condyle to provide the surgeon with a relatively
unobstructed view of the injury site 102 (herein
illustrated as part of the knee K).
Referring now to FIG. 8 in particular, the site
of the injury is partially prepared to receive the
assembly 12 by removing at least a portion of the
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damaged or destroyed articular cartilage. To this end,
a cannulated punch 104 (as best illustrated in FIGS. 9A
and 9B) is provided. The punch, generally designated
104, defines a cannula 106 of sufficient diameter to
accommodate a guide wire passing therethrough and an
outer or lateral configuration which preferably matches
that of the assembly 10. The distal end 108 of the
punch 104 is configured and dimensioned to remove all of
the damaged or clestroyed articular cartilage where only
a single assembly 12 will be deployed, and to remove at
least a portion of the damaged or destroyed articular
cartilage when a plurality of assemblies 12, 12' will be
deployed (as best seen in FIG.6). The width of the
punch distal end 108 is preferably selected to abut
agains~ the healthy articular cartilage about the injury
site (unless the assembly 12 to be inserted will
subsequently be surrounded by other assemblies 12').
Except for the cannula 106 extending therethrough, the
distal or cutting end of the punch 104 is of
-20 conven~ional design. The distal punch end 108, when
tapped home, removes at least a portion of the aligned
damaged or destroyed articular cartilage 102 and the
subchondral bone plate 72 intermediate the damaged
articular cartillage 102 and the cancellous bone 74 (as
2S best seen in FIG. 9). FIG. 8 shows a conventional
surgeon's mallet 110 being used by a surgeon to impact
the proximal or near end 112 of punch 104, thereby to
drive the punch distal end 108 into the damaged or
destroyed articular cartilage 102 and the subchondral
bone 72. Prefecably the punch 104 is inserted to a
depth of about 3-4 millimeters into the articular
cartilage and subchondral cancellous bone plate 72 (as
measured from the cartilage outer surface).
~ eferring now to FIGS. 9-9B in particular, A
conventional surgeon's power drill 118 or like
instru~ent is used to rotate and drive a guide wire 120
through the punch cannula 106 (through the punched-out
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segment of damaged or destroyed articular cartilage and
the subchondral bone plate 72, yet to be removed) and
into the cancellous bone 74. To this end the distal end
of the guide wire 120 is preferably threaded and
self-tapping. The guide wire 120 is preferably 1.25
millimeter in diameter, and formed of stainless steel,
titanium, or another material which, at least over the
short period of the implantation operation, is
biocompatiable and generally rigid (at least when
disposing in a channel such as punch cannula 106).
Referring now to FIG. 10 in particular, as the
power drill 118, and then the punch 104 are withdrawn
from the guide wire 120, the punch distal end 108 takes
therewith the removed portion of the damaged or
destroyed articular cartilage 102 and the underlying
portion of the subchondral bone plate 72, thereby
exposing to view the cancellous bone 74 therebelow. Due
to limitations on the size of the cutting recess of the
punched distal end 108, it may not be possible to remove
in a single step all of the damaged or destroyed
articular cartilage 102 and the underlying portion of
the subchondral bone plate 72 aligned with the punch
104. In this instance, after the detritus has been
removed from the punch distal end 108, the punch 104 may
be passed over the guide wire 120 (which enters the
cannula 106) and driven home again by the mallet 110,
and detritus removed with standard arthroscopic
instruments.
Where appropriate the cannulated punch 104 may
be configured as a cannulated chisel or like tool for
performing the same function.
Referring now to FIGS. ll-llB in particular, a
cannulated drill/countersink, generally designated 130,
mounted on a power drill 131 (which may be the same or a
different power drill then the power drill 118) is then
slid over the pro~imal end of guide wire 120 and
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advanced in the direction of arrow 134 to drill and
countersink the subchondral bone plate 72.
Referring now to FIG. llC in particular,
therein illustraled is a drill/countersink 130 according
to the present invention. Comparing FIG. llC and FIG.
4, it will be appreciated that the distal end 132 of the
drill/countersink 130 is similar to the elongate member
23. A central portion 134 of the drill/counter sink 130
has ribs 136 at an angle similar to the bottom 30 of the
support frame ~'2 (see FIG. 2). Thus, the forward
drill/countersink portion 132 provides an opening in the
cancellous bone for the elongate number 23 while the
central drill/countersink portion 134 provides a
countersink opening for bottom 30 partially in the
cancellous bone 74 and partially in the subchondral bone
plate '72 .
Referring now to FIGS. 12-12B in particular,
after removal of the power drill 131 and the
drill/countersink 130 from the guide wire 120, the
assem~:ly 12 is mounted over the proximal end of the
guide wire 120 and advanced forwardly in the direction
of arrow 140 into the drilled and countersunk
subchondral cancellous bone until the assembly 12 is
flush with the surrounding articular surface. Surgeons
25 of substantial experience with implantation of the
assembly 12 should choose to use a conventional
cannulated mallet (not shown) disposed over the guide
wire 120 for seating the assembly 12 in the cancellous
bone 74. However, care must be taken to ensure that the
mallet does not cause the assembly 12 to impact upon the
subchondral bone plate 72 and cancellous bone 74 with
suffic:ient force to damage either the bone or the
assembly~
Referring now to FIG. 13 in particular, in
35 order to avoid the possibility of damage from the
assembly seating procedure, in a preferred embodiment of
the present invention after the assembly 12 is mounted
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on the guide wire 120 a cannulated assembly inserter 141
and a cannulated impactor or mallet 142 are disposed on
the guide wire 120. (The cannulated punch 104 should
not be used as the cannulated inserter 141.) The
cannulated impactor 142 is a device of known weight
selected so that, when the surgeon manually moves it
rapidly along the guide wire 120 until it impacts the
inserter 141, it imparts a predictable momentum to the
inserter 141 such that the assembly 12 is seated in the
drilled and countersunk subchondral cancellous bone
without damage either to the bone or the assembly.
Thereafter the impactor 142 and the inserter 141 are in
turn removed from the guide wire 120. Accordingly, even
an inexperienced surgeon can rapidly and safely seek the
assembly 12 into its previously prepared site.
Finally, the guide wire 120 is removed either
manually or with a power drill. FIG. 12A shows the
guide wire 120 being withdrawn in the direction of arrow
160 from the implanted assembly 12.
Where necessary, as illustrated in FIG. 14,
additional portions of the destroyed or damaged
articular cartilage 102 may be removed and replaced with
a second assembly 12', following the procedures outlined
above, until substantially all of the damaged or
destroyed articular cartilage 102 has been removed and
replaced by assemblies 12, 12'. At that point, the
arthroscope 100 may be removed. It will be appreciated,
however, that great care must be taken in this instance
in order to assure that the first implanted assembly 12
and subsequent implanted assemblies 12' are properly
disposed relative to each other and to the surrounding
articular cartilage and that one side of assembly 12 and
one side of an abutting and parallel assembly 12' will
serve as a common wall between the two implanted
assemblies 12, 12'.
Where two or more assemblies 12, 12' are to be
implanted, it is strongly preferred that all of the
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punching steps ~e performed prior to the seating of any
assembly. This prevents damage to a seated assembly
from a punchinsl operation performed adjacent to the
already seated assembly
- 5 Where the area of damaged or destroyed
cartilage is so extensive that the bio-absorbable
cartilage repair system must include a plurality of the
assemblies 12, 12' a rapid and accurate placement of the
several assemblies in the appropriate relative locations
may be achieved using a jig or spacer 150 according to
the present invention. Referring now to FIGS. 15A-15B,
the spacer 150 is comprised of a first cannulated
(preferably po:Lygonal where the assemblies are
polygonal) member 152 having an axis X, N sides, a
maximum width (or diameter) W and a length L and a
second cannulated (preferably polygonal where the
assemblies are polygonal) member 154 having an axis x, n
sides, a maximum width (or diameter) w, and a length 1.
The axes X and x of the first and second cannulated
members 152, ].54, respectively, are substantially
parallel. The number of sides N and the maximum width W
of the first cannulated member 152 are at least equal
to, and generally exceed, the number of sides n and the
maximum width w, respectively, of the second cannulated
member 154.
It will be appreciated that one side of the
first cannulated member 152 and one side of the second
cannulated member 154 are rigidly joined and in effect
define a common wall e~tending at least a portion of the
length of the spacer 150. This ensures that the guide
wires 120, 120 to be disposed through the cannulae of
the spacer 150 will be appropriately positioned in the
cancellous bone ~4 and that eventually one side of the
first assembly 12 will be parallel and contiguous to the
adjacent side of the second assembly 12. Typically the
first and second cannulated members 152, 154 of the
spacer 150 are of integral, one piece, unitary
,
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-24 -
construction formed in a single operation. Where the
assembly 12 is polygonal in design, typically the ~irst
and second cannulated members 152, 154 will also be
polygonal in design.
As best seen in FIG. 15-15B, one end of the
first cannulated member and one end of the second
cannulated member (the proximal ends as seen in FIG.
15B) are disposed in the same plane, while the opposite
end of the first cannulated member 152 and the opposite
end of the second cannulated member 154 ~the distal ends
as seen in FIG. 15A) are disposed in spaced apart
parallel planes. More particularly, the distal end of
the first cannulated member 152 extends forwardly
further than the distal end of the second cannulated
member 154, as seen in FIG. lS. This permits the distal
end of the first cannulated member 152 to occupy the
removed area of destroyed or damaged articulate
cartilage 102, while the distal end of the second
cannulated member 15~ is resting on another portion of
damaged or destroyed articulated cartilage 102 (a
portion which has not yet been removed and will only be
removed after the second guide wire 120 is in place), as
illustrated in FIG. 15.
The spacer 150 is used for spacing apart two
guide wires 120, 120' during surgical implantation of
the second guide wire 120' so that the second guide wire
120' is a fi~ed distance from the already implanted
first guide wire 120. Thus the spacer is used for only
a brief portion of the total time of the surgical
implantation procedure. More particularly, the first
cannulated member 152 of the spacer is passed over the
first guide wire 120, with the second cannulated member
154 of the spacer being disposed over another portion of
the damaged or destroyed articular cartilage. Once a
second guide wire 120' is inserted through the cannula
of the second cannulated member 154 of the spacer and
the forward tip thereof removeably fixed in cancellous
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--25--
bone 74 (e.g., by power drill 118, as shown in FIG. 15),
the spacer 150 is removed from both guide wires 120,
120'. Where the guide wires 120, 120' are resilient,
the removal of the spacer 150 may result in the guide
wires angling slightly apart at the proximal ends as
they attempt to conform with the femoral condyle or
other rounded su:rfaces.
After removal of the spacer 150 from the guide
wires 120, 120', a punch 104 is mounted on the second
guide wire 120' to remove another portion of the damaged
or destroyed articular cartilage 102 and the underlying
portion of the subchondral bone plate 72, thereby
exposing to view the cancellous bone 74 therebelow.
Then all of the procedures described above with regard
to first guide wire 120 may be completed prior to any
utilization of the second guide wire 120'. Only then
are the drill~countersink and seating procedures
repeated using the second guide wire 120' (as
illustrated in FIG. 16).
Alternatively, work may proceed apace,
performing each procedure with each of the guide wires
120, 120' in tur;n. Thus, in the alternative procedure,
after removal of the spacer 150 from guide wires 120,
120', a cannulated punch 104 is passed over the second
guide wire 120' and tapped into place. Then cannulated
punch 104 is then removed from the second guide wire
120'. Thereafter, cannulated drill/countersinks 130 are
in turn placed on each of the guide wires 120, 120',
used in the drill/countersink procedures) and then
replaced by assemblies 12, 12' for the assembly seating
procedures (with impacters 142 and inserters 141 being
used if desired to assist in seating the assemblies 12,
12' in turn in their prepared sites prior to removal of
the guide wires 120, 120').
Assuming that spacers and assemblies of
appropriate configurations and dimensions have been
used, t:he implanted assemblies are not only in the
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-26-
appropriate position relative to one other, but also
relative to the periphery of the undamaged articular
cartilage surrounding the injury. It is contemplated
that the surgeon will have available to him at the time
of the operation a plurality of different spacers where
the cannulated members vary in configuration and/or
dimensions so that the surgeon may select the spacer(s)
most appropriate for the particular injury.
To summarize, the present invention provides a
method of surgically implanting a system for
regenerating articular cartilage, the method being
relatively fast and easy to perform even for a surgeon
with little experience in this method. The method in
one embodiment involving the placement of a plurality of
repair assemblies and utilizes apparatus (i.e., a
spacer) for determining the appropriate placement of one
repair assembly relative to another and facilitates a
three dimensional approximation of the original surface
of the articular cartilage. The present invention
further provides such a spacer.
Now that the preferred embodiments of the
present invention have been shown and described in
detail, various modifications and improvements thereon
will become readily apparent to those skilled in the
art. Accordingly, the spirit and scope of the present
invention is to be construed broadly and limited only by
the appended claims, and not by the foregoing
specification.
