Note: Descriptions are shown in the official language in which they were submitted.
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ARTICULAR SURFACE IMPLANT'
FIELD
The present disclosure is directed at a system and method for accessing an
articular joint surface. The present disclosure is further directed at a
method and system
for replacing at least a portion of an articular surface.
BACKGROUND
Articular cartilage, found at the ends of articulating bone in the body, is
typically
composed of'hyaline cartilage, which has many unique properties that allow it
to
function effectively as a smooth and lubricious load bearing surface. Hyaline
cartilage .,
problems, particularly in knee, hip joints, and should joints, are generally
caused by
disease such as occurs with rheumatoid arthritis or wear and tear
(osteoarthritis), or
secondary to an injury, either acute (sudden), or recurrent and chronic
(ongoing). Such
cartilage disease or deterioration can compromise the articular surface
causing pain and
eventually, loss of joint movement. As a result, various methods have been
developed
to treat and repair damaged or destroyed articular cartilage. -
For smaller defects, traditional options for this type of problem include
leaving
the lesions or injury alone and living with it, or performing a procedure
called abrasion
arthroplasty or abrasion chondralplasty. The principle behind this procedure
is to
attempt to stimulate natural healing. The bone surface is drilled using a high
speed
rotary burr or shaving device and the surgeon removes,about 1mm of bone from
the
surface of the lesion. This creates an exposed subchoindral bone bed that will
bleed and
will initiate a fibrocartilage healing response. One problem with this
procedure is that
the exposed bone is not as smooth as it originally was following the drilling
and burring
which tends to leave a series of ridges and valleys, affecting the durability
of the
fibrocartilage response. Further, although this procedurecan provide good
short term
results, (1-3 years), fibrocartilage is seldom able to support long-term
weight bearing and
is prone to wear, soften and deteriorate.
Another procedure, called Microfracttire incorporates some of the principles
of
drilling, abrasion and chondralplasty. During the procedure, the calcified
cartilage layer
of the chondral defect is renioved. Several pathways or "microfractures" are
created to
the subchondral bleeding bone bed by impacting a metal pick or surgical awl at
a
minimum number of locations within the lesion. By establishing bleeding in the
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and by creating a pathway to the subchondral bone, a fibrocartilage healing
response is
initiated, forming a replacement surface. Results for this technique may be
expected to
be similar to abrasion chondralplasty.
Another means used to treat damaged articular cartilage is a cartilage
transplant.
Essentially, this procedure involves moving cartilage from an outside source
or other
knee or from within the same knee into the defect. Typically, this is done by
transferring
a peg of cartilage with underlying bone and fixing it in place with a screw or
pin or by a
press fit. Although useful for smaller defects, large defects present a
problem, as this
procedure requires donor pegs proportionate to the recipient bed. Large
dianieter lesions
may exceed the capacity to borrow from within the same, knee joint and fule
out
borrowing from another source.
Larger defects, however, generally require a more aggressive intervention.
Typically treatment requires replacing the articular surface with an implant
or prosthetic
having an outer layer that that is polished or composed of a material that
provides a
lubricious load bearing surface in approximation of an undamaged'cartilage
surface.
Replacement of the articular surface requires first cutting, boring, or
reaming the
damaged area to remove the damaged cartilage. A recess to receive an implant
or
prosthetic is formed at the damaged site. The implant or prosthetic is then
secured to the
bone in an appropriate position in the recess.
BRIEF DESCRIPTION OF THE DRAWINGS
The subject matter of the present disclosure is set forth by description of
embodiments consistent therewith, which description should be considered in
combination with the accompanying drawings, wherein:
FIG. 1 is an exploded perspective view of an embodiment of an implant system
including an implant consistent with the present disclosure and a fixation
element that
niay be used in conjunction with the implant;
FIG. 2 is a perspective view of the embodiment of an implant system shown in
FIG. 1 showing the implant assembled to the fixation element;
FIG. 3 is a perspective view of another embodiment of an implant system
consistent with the present disclosure including an implant and a fixation
element;
FIG. 4 illustrates the implant system shown in FIG. 3 from another
perspective;
FIG. 5 shows an ankle including a talus implant consistent with the present
disclosure;
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FIG. 6 shows an ankle including a talus implant consistent with the present
disclosure;
FIG. 7 shows an ankle including a talus implant consistent with the present
disclosure;
FIG. 8 is a perspective view of another implant consistent with the present
disclosure;
FIG. 9 shows the implant of FIG. 8 from another perspective;
FIG. 10 is a perspective view of yet another implant consistent with the
present
disclosure;
FIG. 11 shows the implant of FIG. 10 from another perspective; and
FIG. 12 shows of a trochlear implant consistent with the present disclosure.
DESCRIPTION
By way of overview, the present disclosure may provide an implant for
replacing
at least,a portion of an articular surface. Furthermore, the present
disclosure is also
directed at a general design methodology for developing and producing a
surface contour
of an implant for replacing at least a portion of an articular surface. An
implant
consistent with the present disclosure may be provided having a load-bearing
surface that
is adapted to interact with a cooperating articulating feature. The
cooperating.,
articulating feature may include, for example, a cooperating articular
surface, a
cooperating surface of an implant replacing at least a portion of a
cooperating articular
surface, etc. In one embodiment, a portion of an articular surface to be
replaced by an
articular surface implant herein may be identified and replaced using a
minimally
invasive surgical procedure, for example, using diagnostic and/or surgical
arthroscopy
procedures. Generally, an implant according to the present disclosure may have
a load '
bearing surface that may be based on an original geometry of an articular
surface to be
replaced by the implant.
Referring to FIGS. 1 through 4, an embodiment of an implant system 100 is
schematically depicted in various views. The implant system 100 may be
employed to
replace at least a portion of an articular surface, e.g., at least a portion
of an articular
surface of a joint. As shown, the implant system 100'may generally include an
articular
surface implant 102 and a fixation element 104. The fixation element 104 may
be
capable of coupling the implant 102 to bone and/or other tissue in the region
of the
portion of the articular surface to be replaced by the implant 102. As shown
in the
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illustrated embodiment of FIG. 1, the fixation element 104 may be provided as
a separate
component from the implant 102. In such an embodiment, the fixation element
104 may
be capable of being coupled to the implant 102 and may be capable of being
coupled to
bone and/or tissue in the general region of the portion of the articular
surface to be
replaced by the implant system 100.
The articular surface implant 102 may generally include an implant body 106.
The implaiit body 106 may have a load bearing surface 108 and a bone
contacting region
110. The load bearing surface 108 may generally be configured to interact with
a
cooperating articulating feature; such as a cooperating articular surface, a
cooperating
articular surface implant, etc. In one embodiment, the implant body 106 may be
at least
partially received in an implant site provided by excising at least a portion
of the articular
surface and underlying bone. In such an embodiment, the load bearing surface
108 'may
be disposed generally replacing at least a-portion of the excised articular
surface. In an. '
embodiment herein, the bone contacting region 110 may engage and/or contact
subchondral within and/or forming at least a portion of a bottom of the
implant site.
As mentioned previously, and consistent with the illustrated embodiment, the
fixation element 104 maybe provided as a separate component from the iniplant
102.
Providing the fixation element 104 as a separate component froni the implant
102 may,
facilitate installation of the implant system 100. The fixation element 104
may' first be '
coupled to bone and/or other tissue in and/or around the implant site. The
implant 102
may then be positioned relative to the surrounding articular surface and the
implant 102
may be coupled to the fixation element 104. In such a manner, the iniplant
102'may be
secured in position relative to the articular surface.
In the illustrated embodiment, the fixation element 104 is depicted as a screw-
type feature. Consistent with this illustrated embodiment, the fixation
element 104 may
be threadably engaged with bone and/or other tissue in and/or around the
implant site. In
addition to engaging bone and/or other tissue, a screw-type fixation element
104 may
also facilitate depth positioning of the fixation element 104, and thereby
depth
positioning of the implant 102, relative to the articular surface. Suitable
screw-type 30 fixation elements are known in the'art, for example, from U.S.
Patent No. 6;520,964,
issued on February 18, 2003. Consistent with various alternative embodiments,
the
fixation element may be configured having a barbed member or other similar
features
capable of engaging bone and/or other tissue in and/or around the implant
site. In still
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other embodimeiits, the fixation element may include features that may be
adhesively
coupled to bone and/or other tissue in and/or around the implant site.
As illustrated, in an embodiment consistent with the present disclosure, the
implant 102 and the fixation element 104 may be provided as separate
components. The
implant 102 may be coupled to the fixation element 104 to, at least in part,
secure the
implant 102 in position in the implant site. The implant 102 and the fixation
element 104
may, accordingly, include interacting features wherein the implant 102 and
fixation
element 104 are capable of being coupled to one another. An embodiment of an
implant
102 may be provided including a post 112 extending from the implant body 106.
The
fixation element 104 may include an opening 114 capable of receiving at least
a portion
of the post 112. In one such embodiment, the post 112 and,the opening 114 may
be'
provided having complimentary precision tapers. The implant 102 and the
fixation
element 104 may be coupled to one .another by inserting the post 112 into the
opening
114 and pressing the features together, e.g., as by applying an impact force.
The '
precision taper of the post 112 and the opening 114 may achieve a secure
frictional
interaction between the implant 102 and the fixation element 104.
Various additional and/or alternative features and/or arrangements may be -
utilized for coupling the implant and the fixation element within the context
of the
present disclosure. Furthermore, in various embodiments in which the implant
and the
fixation element are provided as separate components, the implant and the
fixation
element may be assembled to one another prior to installation into an implant
site.
Consistent with some such embodiments, the fixation element may be configured
to
engage and/or to be coupled to bone and/or tissue in and/or around the implant
site
during installation. In one such einbodiment, the fixation element may include
a barbed
post or similar feature. According to still fitrther embodiments, the implant
and the
fixation element may be provided as a unitary structure.
The illustrated implant system 100 depicted in FIGS. 1 through 7 shows an
implant 102 configured to replace a portion of the articular surface of the
talus.
Particularly, the illustrated implant system 100 shown in FIGS. 1 through 7 is
configured
to replace at least a portion of the lateral ridge of the trochlear surface of
the talus, which
articulates with the tibia. Damage to the lateral ridge of the trochlear
surface of the talus
may include fracture or shearing off of a portion of the ridge resulting from
trauma.
From a general perspective, the load bearing surface 108 may have a contour
and/or
geornetry that may be capable of cooperating with an'interacting articulating
feature,
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including a cooperating articular surface, at least a portion of an iinplant
replacing at
least a portion of a cooperating articular surface, etc. In the context of the
illustrated
embodiment, the load bearing surface 108 may have a contour and/or geometry
that may
be capable of cooperating with an interacting articular surface of a tibia.
According to a=
related embodiment in the context of the illustrated embodiment, the load
bearing surface
108 of the implant 102 may include a geometry and/or contour that may be
capable of
cooperating with an interacting surface of an iinplant replacing at least a
portion of an
articular surface of a tibia.
Consistent with the foregoing, an implant may include a load bearing surface
having a contour and/orgeometry that may be capable of cooperating with an
interacting
articulating surface. In one embodiment, the load bearing surface may have a
oontour
and/or geometry that may generally approximate and/or be based on a contour
and/or
geometry of the portion of the articular surface being replaced by the
implant. In an
embodiment, the portion of the articular surface being replaced may be mapped
using
various know techniques to quantitatively and/or qualitatively assess the
contour and/or
geometry of the portion of the articular surface that may be replaced by the
implant. An
implant may be constructed and/or selected from a set of implants having
various
contours and/or geometries. Consistent with such an embodiment, the load
bearing
surface of the implant may be based on the contour and/or geometry of the
portion of the
articular surface to be replaced by the implant. In an alternative embodiment,
an implant
may be fabricated or selected from a set of standard size and/or shape
implants to
provide a general approximation of the articular surface being replaced.
Selection and/or
fabrication of an implant may rely on various degrees of quantitative
reference to the
articular surface being replaced, including no quantitative reference to the
articular
surface.
Referring to FIGS. 1 through 4, according to one aspect, a contour and/or
geometry of the load bearing surface 108 of an implant 102 may genexally be
defined by
a first curve string 116 and a second curve string 118. As used in any
embodiment
herein, a curve string may include a single curve and/or a plurality of curves
joined
together curves in =a plane. The first curve string 116 and the second curve
string 118
generally defining the contour and/or geometry of the load bearing surface 108
may be
disposed in intersecting planes. In the illustrated.embodiment, the plane of
the first
curve string 116 and.the plane of the second curve strirrg 118 may generally
be mutually
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perpendicular. Various other angular relationships of the planes including the
first curve
string 116 and the second curve string 118 may also suitably be employed
herein.
A design methodology capable of achieving a load bearing surface of an implant
herein may include providing a curve string defining a coiitour and/or
geometry of the
load bearing surface and sweeping the curve string along another curve string.
defining an
intersecting contour and/or geometry of the load bearing surface. As alluded
to above,
curve strings defining the contour and/or geometry of the load bearing surface
may be
derived based on mapped curves and/or approximations of curves of a portion of
an
articular surface to be replace, a portion of a cooperating articulating
feature, etc. In one
such embodiment, measurements of the contour and/or geometry of the portiori
of the
articular surface to be replaced may be taken. Measurement of the contour
and/or
geometry of the portion of the articular surface to be replaced by the implant
may be
achieved using direct contact contour mapping of the articular surface, e.g.,
measuring
relative heights,of various regions of the articular surface, and/or using
various imaging
techniques, such as radiological imaging techniques.
According to one embodiment, the load bearing surface 108 may have a contour
and/or geometry corresponding to the second curve string 118 lofted over the
first curve
string 116. In one such embodiment, the contour and/or geometry of the load
bearing
surface 108 may be achieved by sweeping the second curve string 118 along the
first
curve 116 while maintaining the second curve 118 normal to,the first curve
116. Jn such
an embodiment, the first curve 116 may be provided in a first plane, e.g. a
plane defined
by the X and Z axis. The second curve 118 may be provided in a perpendicular
plane.
The angular pitch of the perpendicular plane relative to the first plane niay
vary along the.
first curve 116 to maintain the second curve 118 normal to the first curve 116
along the
sweep of the first curve 116. According to another embodiment, the second
curve 118
may be swept along the first curve 116 with the first curve 116 and the second
curve. 118
in orthogonal planes. For example, the first curve 116 may be provided in a
first plane,
e.g., a plane defined by the Y and Z.axis and the second curve may be provided
in an
orthogonal plane, 'e.g., a plane defined by the X and Z axis. As shown in
FIGS. 3 and 4,
an embodiment of an implant provided consistent with the preceding design
methodology may be generally symmetrical in each of the planes including the
first,
curve string and the second curve string.
In another embodiment the load bearing surface 108 may have a contour and/or
geometry resulting from a faired transition between the first curve string 116
and the
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second curve string 118. That is, the contour and/or geometry of the load
bearing surface
108 may be. provided by a smooth transition between the first curve string 116
and the
second curve string 118 at each quadrant between the first curve string 116
and the
second curve string 118. In similar embodiments, providing a faired transition
between
the first curve string and the second curve string may be achieved using
various
averaging techniques known for surface generation. Various such averaging
techniques
are commonly employed in commercial surfacing design and solid modeling
computer
assisted drafting software packages.
The implant 102 may include a relieved edge 120 around the perimeter of the
load bearing surface 108. The relieved edge 120 may include a rounded over,
e.g.,
radiused, edge, a chamfer edge, etc. According to one aspect, when the implant
102 is
installed in an articular surface and replacing at least a portion of the
articular surface,
the relieved edge 120 around the load bearing surface 108 may reduce the
presence of a
hard edge at a transition between the implant and surrounding articular
surface.' A
reduction and/or elimination of a hard edge at. the transition between the
load bearing
surface of the implant and the surrounding articular surface may reduce and/or
eliminate
scraping of an interacting articular surface during articulation of the joint.
Additionally,
the relieved edge 120 may accommodate manufacturing and/or installation
tolerances.
The relieved edge 120 may, permit smooth operation of the joint in a situation
in which
the implant 102 sits slightly proud above and/or slightly recessed below the
surrounding
articular surface.
With particular reference to FIGS. 5 through 7, the load bearing surface 108
of
the implant is depicted. As mentioned previously the illustrated implant
system 100 may
replace a portion of the lateral trochlear ridge of the talus. In one
enibodiment, ain
implant site may be prepared using a rotating excision tool, e.g., an excision
blade
rotating about an axis. Accordingly, the implant site may include a circii.lar
excision
projected along the axis of rotation of the excision blade. In such an
embodiment, the
cross-sectional geometry of the implant may generally correspond to the
intersection of a
projected circular excision with the articular surface of the talus. Various
additional
and/or alternative excision site preparation tools and techniques are also be
contemplated
by the present disclosure, along with the attendant changes to the implant
configuratio,n:
The location of the fixation element and the orientation, of the load bearing
surface to the fixation element may be selected to provide secure and stable
anchoring of
the implant relative to the articular surface. In an embodiment, the implant
system may
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have a configuration wherein the fixation element may extend into the talus at
an angle
to, and/or spaced from, the lateral ridge. Such a configuration may provide
secure
anchoring of the implant and/or may reduce the occurrence of tear-out and/or
crumbling
of the talus resulting from weakening of the talus caused by extension of the
fixation
element along the lateral face adjacent the trochlear surface. Various
additional and/or
alternative configurations may also be employed.
Turning to FIGS. 8 and 9, another embodiment of an implant 200 is shown. The
illustrated implant 200 is generally configured to replace at least a portion
of an articular
surface of a patella. Similar to the previously described embodiment, the
implant 200
may generally include an implaiit body 202 having a load bearing surface 204.
The load
bearing surface 204 of the illustrated implant 200 may have a contour and/or
geometry
that may siiitably replace at least a portion of an articular surface of a
patella. The
implant 200 may also include a post 206 capable of coupling with a fixation
element (not
shown) for anchoring the implant 200 to an articular surface and/or underlying
bone.
Various other features in addition to, or as an alternative to, a post may be
employed for
coupling the implant 200 to a fixation element. Furthermore, an embodiment of
an
implant herein may be provided including an integral fixation element. 'In
such an
embodiment, the feature for coupling to a fixation element may optionally be
excluded.
Similar to the preceding embodiment, the load bearing surface 204 of the
implant
200 may be defined by a first curve string 208 and a second curve string 210.
The
contour and/or geometry of the load bearing surface 204 may be provided as the
first
curve string 208 lofted over the second curve string 210, and/or vice-versa.
As
previously described,. the lofted load.bearing surface 204 may be achievedby
sweeping
the first curve string 208 along the second curve string 210. In another
embodiinent, the
load bearing surface of the implant may be provided using averaging algorithms
to
provide a faired surface in between the first curve string and the second
curve string.
Yet another embodiment of an implant 300 is depicted with refer.ence to FIGS.
10
and 11. The illustrated implant 300 may be capable of replacing at least a
portion of a
trochlear articular surface, for example a trochlear articular surface of a
humerus, etc. As
with the previously described embodiments, the implant-300 may generally
include an
implant body 302 having a load bearing surface 304. The load bearing surface
304 may
be defined by a first curve string 306 and a second curve string 308. The load
bearing
surface 304 may be provided by sweeping the second curve string 308 along the
first
curve string 306 consistent with the previously described design methodology:
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Furthermore, the load bearing surface may also be provided as a faired surface
defined
by a first and second intersecting curve string.
Referring to FIG. 12, a model articular surface is shown including an implant
capable of replacing at least a portion of a trochlear surface is shown. The
implant
depicted in FIG. 12 may be generally consistent with the embodiment described
with
reference to FIGS. 10 and 11. The load bearing surface of the implant, visible
in the
photograph of the model, may generally have a contour and/or geometry that may
generally correspond to the portion of the articular surface being replaced by
the implant.
In such an embodiment, the implant may provide smooth interaction with a
cooperating
articular surface, such as depicted in FIG. 12. As previously described, in
one
embodiinent an implant site may be created in an articular surface using a
rotating
excision tool. A rotating excision tool may provide a circular cutting path
that may, be
projected into the articular surface and/or the underlying subchondral bone.
The shape of
the implant may, in such an embodiment, generally correspond to the
intersection of the
circular cutting path and the articular surface.
In summary, according to one aspect, an implant may be provided for replacing
a
portion of an articular surface. The implant may include a load bearing
surface. having a
contour defined by a first curve string based on a contour of the articular
surface in a first
plane and by a second curve string based on a contour of the articular surface
in a second
plane. The first and second planes may be planes which intersect one anotller.
The
implant may further include a bone contacting surface.
According to another aspect, the present disclosure may provide an implant
system for replacing a portion of an articular surface. The implant system may
include
an implant having a load bearing surface,which is defined by a. first and a
second curve
string. The first curve string may be based on a contour of the articular
surface in a first
plane and the second curve string may be based on a contour of the articular
surface in a
second plane. The first and second planes may intersect one another. The
implant
system may also include a fixation element capable of engagxng bone and
capable of ,.:
being coupled to the implant.
According to yet another aspect, the present disclosure may provide a method
of
forming an implant. The method may include measuring a contour of an articular
surface in a first plane and measuring a contour of the articular surface in a
second plane,
in which the first and second planes are intersecting planes. The method may
further
include providing an implant body having a load bearing surface. The load
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surface of the implant body may have a contour defined by the contour 'of the
articular
surface in the first plane and the contour of the articular surface in the
second plane.
While the embodiments of the implant system illustrated and described above
are
provided in the context of*an implant configured to replace at least a portion
of the talus,
patella, and humerus trochlea, an implant consistent with the
present.disclosure may be"
sized and shaped for replacing at least a portion of various other articular
surfaces of the
body. Accordingly, consistent with the present disclosure, an implant system
may be
provided to replace at least a portion of various articular surfaces in
addition to a portion
of an articular surface of a talus. For example, an implant herein may
suitably be
employed to replace a portion of an articular surface of a knee joint, a hip
joint, a
shoulder joint, etc. Accordingly, the foregoing example should not be
construed as
limiting on the application of an implant consistent with the present
disclosure.
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