U.S. patent application number 11/692070 was filed with the patent office on 2007-12-13 for milling system for resecting a joint articulation surface.
This patent application is currently assigned to MedicineLodge, Inc.. Invention is credited to Carlyle J. Creger, E. Marlowe Goble, Robert A. Hodorek, Daniel F. Justin.
Application Number | 20070288029 11/692070 |
Document ID | / |
Family ID | 37532757 |
Filed Date | 2007-12-13 |
United States Patent
Application |
20070288029 |
Kind Code |
A1 |
Justin; Daniel F. ; et
al. |
December 13, 2007 |
MILLING SYSTEM FOR RESECTING A JOINT ARTICULATION SURFACE
Abstract
A milling system for use in resecting at least a portion of a
joint articulation surface of a bone includes an alignment guide
having a top surface and an opposing bottom surface with an opening
extending therebetween. Fasteners are used to secure the alignment
guide to the bone so that the alignment guide is suspended above
the bone. A template is removably mounted to the alignment guide so
that a plurality of guide paths extending through template are
aligned with the opening in the alignment guide. A mill extends
down through the guide path and has a burr on the end thereof for
resecting the bone.
Inventors: |
Justin; Daniel F.; (Logan,
UT) ; Hodorek; Robert A.; (Warsaw, IN) ;
Goble; E. Marlowe; (Logan, UT) ; Creger; Carlyle
J.; (Logan, UT) |
Correspondence
Address: |
WORKMAN NYDEGGER
60 EAST SOUTH TEMPLE
1000 EAGLE GATE TOWER
SALT LAKE CITY
UT
84111
US
|
Assignee: |
MedicineLodge, Inc.
180 South 600 West
Logan
UT
84321
Zimmer Technology, Inc.
150 North Wacker Drive, Suite 1200
Chicago
IL
60606
|
Family ID: |
37532757 |
Appl. No.: |
11/692070 |
Filed: |
March 27, 2007 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
11149912 |
Jun 10, 2005 |
|
|
|
11692070 |
Mar 27, 2007 |
|
|
|
Current U.S.
Class: |
606/87 |
Current CPC
Class: |
A61B 17/1764 20130101;
A61B 2017/1602 20130101; A61B 17/1675 20130101; A61B 17/1615
20130101; A61B 2090/034 20160201 |
Class at
Publication: |
606/087 |
International
Class: |
A61B 17/56 20060101
A61B017/56 |
Claims
1. A milling system for use in resecting at least a portion of a
joint articulation surface of a bone, the system comprising: an
alignment guide having a top surface and an opposing bottom surface
with an opening extending therebetween; means for removably
mounting the alignment guide to a bone; a template having a top
surface and an opposing bottom surface with a plurality of guide
paths extending therebetween, the plurality of guide paths being
elongated and extending along both the top surface and the opposing
bottom surface; and means for removably securing the template to
the alignment guide so that the plurality of guide paths are
aligned with the opening of the alignment guide.
2. The milling system as recited in claim 1, wherein at least a
portion of the plurality of guide paths are interconnected.
3. The milling system as recited in claim 1, wherein the top
surface of the template has a convex curvature.
4. The milling system as recited in claim 3, wherein the plurality
of guide paths intersect with the top surface of the template at an
orientation substantially normal to the top surface of the
template.
5. The milling system as recited in claim 3, wherein at least a
portion of the plurality of guide paths intersect with the top
surface of the template at an orientation substantially normal to
the top surface of the template.
6. The milling system as recited in claim 1, wherein at least a
portion of the plurality of guide paths are curved along the length
thereof.
7. The milling system as recited in claim 1, wherein the template
comprises: a body that at least partially bounds an opening
extending through the body; and a plurality of partition walls
disposed within the opening of the body and connected to the body,
the plurality of partition walls bounding the plurality of guide
paths.
8. The milling system as recited in claim 1, further comprising: a
mill comprising an elongated shaft having a burr mounted on an end
thereof, the burr radially outwardly projecting beyond at least a
portion of the shaft; and the plurality of guide paths of the
template having a first portion sized so that the burr can pass
therethrough and a second portion sized so that the shaft can pass
therethrough but the burr cannot pass therethrough.
9. The milling system as recited in claim 8, further comprising a
bearing housing mounted on the shaft of the mill and at least one
bearing disposed within the bearing housing.
10. The milling system as recited in claim 8, wherein each of the
plurality of guide paths has a portion sized so that the shaft of
the mill can pass therethrough but the burr cannot pass
therethrough.
11. The milling system as recited in claim 8, further comprising:
the burr having an effective radius radially outwardly extending
from the exterior surface of the shaft to a maximum outer radius of
the burr; and a template comprising: a body at least partially
bounding an opening; and a partition wall disposed within the
opening of the body and connected to the body, the partition wall
having opposing side surfaces with a thickness extending
therebetween, the thickness being not more than twice the effective
radius of the burr.
12. The milling system as recited in claim 8, further comprising a
tubular bearing housing encircling the shaft of the mill such that
the mill can freely rotate within the bearing housing, the bearing
housing having a lower stem portion received within a select one of
the plurality of guide paths of the template and an annular
shoulder resting on a top surface of the template.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional of U.S. patent application
Ser. No. 11/149,912, filed Jun. 10, 2005, which is incorporated
herewith by reference.
BACKGROUND OF THE INVENTION
[0002] 1. The Field of the Invention
[0003] The present invention relates to milling systems and related
guides and mills for resecting at least a portion of a joint
articulation surface of a bone and mounting an implant thereat.
[0004] 2. The Relevant Technology
[0005] The human body has a variety of movable orthopedic joints
such as the knee joint, hip joint, shoulder joint, and the like.
These joints are formed by the intersection of two bones. The
intersecting end of each bone has a smooth articular surface that
is comprised of articular cartilage. As a result of injury, wear,
arthritis, disease or other causes, it is occasionally necessary to
replace all or part of an orthopedic joint with an artificial
implant. This procedure is referred to as a joint replacement or
arthroplasty. For example, a total knee arthroplasty comprises
cutting off or resecting the articular surfaces at both the distal
end of the femur and the proximal end of the tibia. Complementary
artificial implants are then mounted on the distal end of the femur
and the proximal end of the tibia. Where only a portion of a joint
is damaged, a partial joint arthroplasty can be performed. In this
procedure, one or more artificial implants replace only a portion
of a joint.
[0006] Although joint replacement is now a common procedure that
has met with popular success, conventional implants and related
mounting techniques have significant shortcomings. One significant
drawback of many joint replacements is the extended and painful
patient recovery. For example, a traditional knee replacement
requires an open procedure wherein a relatively large incision is
made which severs a portion of the muscle bounding the femur. The
large incision is made so as to fully expose the respective ends of
the femur and tibia.
[0007] This exposure is necessary when using conventional
techniques to resect the femur and tibia and to mount the implants.
For example, resecting the femur and tibia is typically
accomplished by a reciprocating saw which requires substantially
full exposure of the respective ends of the femur and tibia.
Furthermore, some conventional tibial implants are screwed directly
into the resected end face of the tibia. Mounting such screws again
requires substantially full exposure of the resected end face. In
yet other embodiments, the implants are formed with posts
projecting therefrom. The posts are received within sockets formed
on the resected end face of the tibia and femur. Forming of the
sockets and inserting the posts into the sockets requires
substantially full exposure of the resected end face of the tibia
and femur.
[0008] Substantially the same procedures are often used when
resurfacing only a portion of a joint articulation surface. That
is, the joint is exposed and a reciprocating saw is used to resect
half or a portion of the articular cartilage. The implant is then
mounted by using screws or posts. Thus, even in procedures where
only a portion of the joint articulation surface is being
resurfaced, conventional procedures make an invasive retraction of
the soft tissue and remove a large portion of the bone.
[0009] In general, the more invasive the surgery, the more painful,
difficult, and time consuming the patient recovery. Furthermore,
extensive resection of bone not only increases bone trauma but can
also make subsequent replacement operations more difficult.
[0010] Accordingly, what is needed are systems and methods for
preparing a joint articulation surface to receive an implant which
are easy to use while minimizing the impact on soft tissue and the
amount of bone resection. What is also needed are implants which
can be used with such systems that can be mounted with minimum
trauma.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] Various embodiments of the present invention will now be
discussed with reference to the appended drawings. It is
appreciated that these drawings depict only typical embodiments of
the invention and are therefore not to be considered limiting of
its scope.
[0012] FIG. 1 is a perspective view of the distal end of a
femur;
[0013] FIG. 2 is a perspective view of the femur shown in FIG. 1
having a guide assembly mounted on a condyle thereof;
[0014] FIG. 3 is an exploded view of the guide assembly shown in
FIG. 2;
[0015] FIG. 4 is a bottom perspective view of the assembled guide
assembly shown in FIG. 2;
[0016] FIG. 5 is a perspective view of an alternative embodiment of
the positioning guide shown in FIG. 3;
[0017] FIG. 6 is a perspective view of the alignment guide shown in
FIG. 3 mounted on the femur;
[0018] FIG. 7 is a perspective view of the alignment guide shown in
FIG. 6 having a template mounted thereon and a mill assembly
interacting therewith;
[0019] FIG. 8A is a top plan view of the template shown in FIG.
7;
[0020] FIG. 8B is an elevated side view of the template shown in
FIG. 8A;
[0021] FIG. 8C is an elevated end view of the template shown in
FIG. 8A;
[0022] FIG. 9 is a perspective view of the mill assembly shown in
FIG. 7;
[0023] FIG. 10 is an exploded view of the mill assembly shown in
FIG. 9;
[0024] FIG. 11 is an elevated side view of the template shown in
FIG. 7 having the mill assembly extending therethrough;
[0025] FIG. 12 is a perspective view of the femur shown in FIG. 7
having a recessed pocket formed thereon;
[0026] FIG. 13A is a top plan view of an alternative embodiment of
the template shown in FIG. 7A;
[0027] FIG. 13B is an elevated end view of the template shown in
FIG. 13A;
[0028] FIG. 14 is a top perspective view of a condylar implant;
[0029] FIG. 15 is a bottom perspective view of the condylar implant
shown in FIG. 14;
[0030] FIG. 16 is a perspective view of the femur shown in FIG. 12
having the implant shown in FIGS. 14 and 15 mounted within the
recessed pocket thereof; and of an alternative embodiment of
the
[0031] FIG. 17 is a perspective view of an alternative embodiment
of the alignment guide shown in FIG. 3.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0032] The present invention relates to milling systems and related
guides, templates, and mills for use in resecting an articulation
surface of an orthopedic joint so that an implant can be mounted on
the resected surface. As used in the specification and appended
claims, the term "articulation surface" is broadly intended to
include all surfaces of natural articular cartilage forming a
portion of an orthopedic joint and all articulation wear surfaces
of a bone forming a portion of orthopedic joint that, as a result
of wear, trauma, disease or other causes, have all or a portion of
the natural articular cartilage removed.
[0033] In the below illustrated embodiment of the present
invention, milling systems and related guides, templates, and mills
are shown which are specifically designed for mounting a condylar
implant at the distal end of a femur. It is appreciated, however,
that the illustrated embodiments are simply examples of the present
invention and that the same technology can also be used for
resecting a portion of the articulation surface at a different
location on the same articulation surface or on a variety of other
joint surfaces to receive a variety of other different types of
implants. By way of example and not by limitation, the present
invention can be used for resecting all or a portion of a condyle
and then mounting a unicondylar or partial condylar implant.
[0034] The present invention can also be used for resecting all or
a portion of the trochlear groove of a femur and then mounting an
implant thereat. In still other embodiments, the present invention
can be used for resurfacing any articulation surface of a knee
joint, ankle joint, hip joint, shoulder joint, elbow joint, wrist
joint, interfrangial joint, or other joints. As such, the milling
systems of the present invention can be used for preparing the
articulation surface at the proximal or distal end of the femur,
tibia, humors, radius, and ulna and on other articulation surfaces
of the scapula, pelvis, bones within the foot and hand, and other
bone articulation surfaces.
[0035] Depicted in FIG. 1 is a distal end 10 of a femur 12. Distal
end 10 has a medial side 14 and a lateral side 16 that each extend
between an anterior side 18 and a posterior side 20. Distal end 10
of femur 12 terminates at a medial condyle 22 and a lateral condyle
24 with a trochlear groove 26 disposed therebetween. Articular
cartilage 28 defines an articulation surface for distal end 10 of
femur 12. Articular cartilage 28 terminates at a margin 30.
[0036] On occasion, due to arthritis, disease, trauma, or the like,
it is necessary to replace all or a portion of medial condyle 22 or
lateral condyle 24. In the depicted embodiment of the present
invention, the illustrated milling system and related guides,
templates, and mills are designed to form a recessed pocket on
medial condyle 22 so that an implant can be mounted within the
recessed pocket.
[0037] Depicted in FIG. 2 is a guide assembly 34 incorporating
features of the present invention and forming a portion of a
milling system. Guide assembly 34 comprises an alignment guide 36,
a positioning guide 38, and a handle 40 that removably couples
positioning guide 38 on alignment guide 36. As depicted in FIG. 3,
alignment guide 36 has a top surface 44 and an opposing bottom
surface 46 that each extend between a first end 48 and an opposing
second end 50. Surfaces 44 and 46 also extend between a first side
52 and an opposing second side 54.
[0038] In the present embodiment alignment guide 36 has a
substantially continuous arch extending from first end 48 to
opposing second end 50. That is, bottom surface 46 has a
substantially constant concave curvature while top surface 44 has a
substantially constant convex curvature. This configuration helps
to minimize the size of alignment guide 36 to facilitate the
greatest ease of insertion during use. In alternative embodiments,
however, one or both of top surface 44 and bottom surface 46 can be
flat or have any other desired configuration.
[0039] To further facilitate complementary positioning of alignment
guide 36 over medial condyle 22 while minimizing size, alignment
guide 36 can also have an arched curvature extending between
opposing sides 52 and 54. That is, bottom surface 46 can have a
substantially constant concave curvature extending between opposing
sides 52 and 54 while the top surface 44 can have a substantially
constant convex curvature. As previously discussed, these surfaces
can also be flat or have other configurations. It is appreciated
that the configuration of alignment guide 36 can vary depending on
the articulation surface being resected. For example, where
trochlear groove 26 (FIG. 1) is being resected, alignment guide 36
can have a substantially V-shaped configuration such that alignment
guide 36 can sit within trochlear groove 26. Although not required,
alignment guide 36 is typically designed so as to have a contour
complementary to the contour of the portion of the bone over which
alignment guide 36 sits during use.
[0040] Alignment guide 36 also has an interior surface 56 that
bounds an opening 58 extending through alignment guide 36 between
top surface 44 and bottom surface 46. As will be discussed below in
greater detail, opening 58 generally corresponds to the size of the
pocket that will be formed on the bone. It is appreciated that
opening 58 can have a variety of different sizes and shapes
depending on the size and location of the area to be resurfaced. In
the embodiment depicted, alignment guide 36 completely encircles
opening 58 having substantially linear sides and semi-circular
ends. In other embodiments, alignment guide 36 can bound only a
portion of opening 58. For example, alignment guide can have a
substantially C-shaped configuration. In other embodiments, opening
58 can have a substantially circular, elliptical, polygonal,
irregular, or other configuration.
[0041] Alignment guide 36 can also be defined as having a body
portion 60 that bounds opening 58 and has the surfaces as discussed
above, a first bracket 62 that projects from side 52 of body
portion 60, and a second bracket 64 that projects from side 54 of
body portion 60. Both of brackets 62 and 64 project away from body
portion 60.
[0042] Extending through first bracket 62 are a pair of spaced
apart mounting holes 68A and 68B. A mounting hole 68C also extends
through second bracket 64. Although not required, in the
embodiments depicted each mounting hole 68A-C has an annular
shoulder 70 that radially, inwardly projects into the corresponding
mounting hole at a location between the opposing ends thereof. As
will be discussed below in greater detail, fasteners are designed
to pass through mounting holes 68A-C and engage femur 12 so as to
secure alignment guide 36 to femur 12. A pair of spaced apart,
threaded coupling holes 72 can also be formed on first bracket 62.
Coupling holes 72 are used in the attachment of positioning guide
38 to alignment guide 36.
[0043] Positioning guide 38 comprises a support 78 having an arm 80
projecting therefrom. Support 78 has a top surface 82 and an
opposing bottom surface 84 with an exterior side surface 86
extending therebetween. Exterior side surface 86 has a
configuration complementary to interior surface 56 of alignment
guide 36 such that support 78 can be received within opening 58 of
alignment guide 36. Although not required, support 78 also has an
interior surface 88 bounding an opening 90 extending between top
surface 82 and opposing bottom surface 84.
[0044] Arm 80 projects from top surface 82 and has a pair of spaced
apart coupling holes 92 extending therethrough. Coupling holes 92
are configured so that when support 78 of positioning guide 38 is
received within opening 58 of alignment guide 36, coupling holes 92
are aligned with coupling holes 72. A threaded tip 94 of handle 40
can then be passed down through one of coupling holes 92 and
engaged with a corresponding coupling hole 72. As tip is threaded
into coupling hole 72, a shoulder 96 on handle 40 biases against
arm 80 so that handle 40 facilitates a releasable, secure
engagement between alignment guide 36 and positioning guide 38 as
depicted in FIG. 2. Due to the elongated nature of handle 40,
handle 40 can be easily held and operated by the surgeon to
facilitate proper positioning and removal of guides 36 and 38. It
is appreciated that any number of different types of fasteners can
be used to removably secure guides 36 and 38 together. For
examples, clamps, expansion bolts, or other forms of threaded
connection can be used. Furthermore, handle 40 is not required and
can be replaced with bolts, screws, or other fasteners that extend
through one or both sets of coupling holes 72 and 92.
[0045] As depicted in FIG. 4, positioning guide 38 is configured
such that when positioning guide 38 is mated with alignment guide
36, support 78 of positioning guide 38 projects a distance below
bottom surface 46 of alignment guide 36. As a result, positioning
guide 38 can be used to mount alignment guide 36 on femur 12 so
that alignment guide 36 is suspended above femur 12. Specifically,
during use, alignment guide 36 is coupled with positioning guide 38
using handle 40 as discussed above. As depicted in FIG. 2, through
the use of handle 40, the coupled guides 36 and 38 are then
positioned on medial condyle 22 so that opening 58 of alignment
guide 36 is positioned over the portion of articular cartilage 28
that is desired to be resurfaced by an implant.
[0046] Here it is again noted that during the positioning, support
78 of positioning guide 38 rests directly against articular
cartilage 28 while alignment guide 36 is suspended above or spaced
apart from articular cartilage 28 so that it does not directly
contact articular cartilage 28. As a result of forming opening 90
on support 78 only a narrow ring portion of support 78 rests on
articular cartilage 28. This configuration enables greater
stability of positioning guide 38 on articular cartilage 28. In yet
other embodiments, support 78 can be formed with a plurality of
legs projecting therefrom that rest against the articular cartilage
28. For example, support 78 can be formed with three or more spaced
apart legs. The use of three spaced apart legs enables support 78
to be easily stabilized on an uneven surface of articular cartilage
28.
[0047] It is appreciated that support 78 need not have a circular
configuration but can have any desired configuration that can be
received within opening 58 of alignment guide 36 so as to project
below bottom surface 46 and that can be seated in a stable fashion
on articular cartilage 28. For example, depicted in FIG. 5 is an
alternative embodiment of a positioning guide 38A having a support
118 extending from arm 80. Support 118 comprises three, spaced
apart, downwardly projecting legs 120A-C with legs 120B and C being
mounted on elongated braces 122 and 123, respectively. During use,
legs 120A-C rest directly against articular cartilage 28. The
configuration of positioning guide 38 can vary depending on the
configuration of the articulation cartilage 28 to be removed.
[0048] Once positioning guide 38 is seated on articulation
cartilage 28, fasteners are then used to removably secure alignment
guide 36 to femur 12. Specifically, as depicted in FIG. 3, in one
embodiment of the present invention means are provided for securing
alignment guide 36 to femur 12. By way of example and not by
limitation, fasteners are designed to pass through mounting holes
68A-C and engage femur 12 so as to removably secure alignment guide
36 to femur 12. In the depicted embodiment, the fasteners comprise
threaded screws 93A-C. Each screw 93 comprises an elongated shaft
95 having a first end 97 and an opposing second end 98. Threads 100
are formed along shaft 95 while an enlarged head 102 is formed at
first end 97. In the embodiment depicted, enlarged head 102
comprises a flange 104 that encircles and radially outwardly
projects from first end 97. An engagement head 106 extends above
flange 104 and has a polygonal or non-circular cross section so
that a driver can be connected to engagement head 106 for selective
rotation of screws 93.
[0049] It is appreciated that enlarged head 102 can be formed with
a socket, slot(s), or other engaging surfaces to engage with other
types of drivers. Each screw 93A-C is configured so that second end
98 can be received within and slid through a corresponding mounting
hole 68A-C of alignment guide 36. Enlarged head 102 is larger than
mounting holes 68A-C and thus functions as a stop. In alternative
embodiments, screws 93A-C can be replaced with other conventional
forms of fasteners such as bone anchors, expansion bolts, barbed
shafts, and the like.
[0050] Once guides 36 and 38 are appropriately positioned, screws
93A-C are passed through correspondence mounting holes 68A-C on
alignment guide 36 so as to rigidly fix alignment guide 36 at the
desired orientation and position. As depicted in FIG. 6, it is
appreciated that brackets 62 and 64 and mounting holes 68A-C are
positioned so that screws 93A-C screw into femur 12 at margin 30 of
articular cartilage 28 or spaced apart from articular cartilage 28.
This prevents any unwanted damage to articular cartilage 28.
[0051] In one embodiment, screws 93A-C can be used in association
with guide sleeves. By way of example, guide sleeves 136A-C are
depicted in FIG. 3. Each guide sleeve 136 comprises a tubular stem
138 having a first end 139 and an opposing second end 141. A
passageway 140 centrally extends through stem 138 between opposing
ends 139 and 141. A flange 142 encircles and radially outwardly
projects from first end 139 of stem 138. Each guide sleeve 136A-C
is configured so that second end 141 can be received within and
slid through a corresponding mounting hole 68A-C. In the depicted
embodiment, each mounting hole 68A-C is counter bored so as to form
internal constricting shoulder 70 as previously discussed. Flange
142 is sized to rest on shoulder 70 so as to prevent guide sleeves
136A-C from passing completely through corresponding mounting holes
68A-C.
[0052] In part, guide sleeves 136A-C function as guides for screws
93A-C. That is, as a result of positioning guide 38 projecting
below alignment guide 36, bottom surface 46 of alignment guide 36,
and thus the bottom of mounting holes 68A-C, are spaced above femur
12. However, as a result of this gap or space between the bottom of
mounting holes 68A-C and femur 12, there is a potential for screws
93A-C to become misaligned from the central longitudinal axis of
each corresponding mounting hole 68A-C as screws 93A-C are passed
from mounting holes 68A-C to femur 12. This misalignment can cause
binding of screws 93A-C against alignment guide 36 which in turn
can cause unwanted displacement or improper securing of alignment
guide 36. By using guide sleeves 136A-C which extend from mounting
holes 68A-C to or adjacent to femur 12, guide sleeves 136A-C help
maintain proper orientation and alignment of each screw 93A-C.
[0053] Specifically, once guides 36 and 38 are appropriately
positioned, each guide sleeve 136A-C is advanced through a
corresponding mounting hole 68A-C so that second end 141 of each
guide sleeve 136 is disposed adjacent to or butts against
articulation surface 28. FIG. 4 shows guide sleeves 136C projecting
below bottom surface 46 of alignment guide 36. Screws 93A-C are
then passed through guide sleeves 136A-C and screwed into femur 12.
Screws 93A-C are advanced until flange 104 biases against the first
end of a corresponding guide sleeve 136A-C, thereby securely fixing
each guide sleeve 136A-C to femur 12. It is noted that flange 142
of guide sleeves 136A-C need not bias directly against alignment
guide 36. Flange 142 primarily functions to prevent guide sleeves
136A-C from falling through mounting holes 68A-C during placement
of alignment guide 36. In alternative embodiments, flange 142 can
be eliminated.
[0054] Here it is noted that each mounting hole 68A-C has a central
longitudinal axis 110A-C (FIG. 4), respectively, along which each
screw 93A-C is intended to extend. Mounting holes 68A-C are
oriented at different angles relative to each other so that merely
screwing screws 93A-C into femur 12 through guide sleeves 136A-C
positioned within mounting holes 68A-C cause alignment guide 36 to
be locked in place. That is, it is not necessary for screws 93A-C
to downwardly bias directly against alignment guide 36 to secure
alignment guide 36 relative to femur 12. Due to the offset angles
of screws 93A-C and thus the offset angles of the guide sleeves
136A-C, it is sufficient if the screws 93A-C merely secure guide
sleeves 136 in place to lock alignment guide 36 in place.
[0055] Once each screw 93A-C is secured in place so that alignment
guide 36 is secured in place, positioning guide 38 is removed from
alignment guide 36. This is accomplished by simply unscrewing
handle 40 and then lifting off positioning guide 38. As depicted in
FIG. 6, alignment guide 36 is then securely fixed to and suspended
above femur 12 at the appropriate location. Suspending alignment
guide 36 above femur 12 ensures that alignment guide 36 does
unintentionally damage articular cartilage 28 during mounting of
alignment guide 36 and/or resecting. Although positioning guide 38
directly sits upon articular cartilage 28, that portion of
articular cartilage 28 is ultimately resected and thus any damage
caused by positioning guide 38 is irrelevant. In general, the area
of articular cartilage 28 bounded by alignment guide 36, i.e., the
area within opening 58, is the portion of articular cartilage 28
that will be resected and is referred to herein as cutting surface
66.
[0056] Turning to FIG. 7, once positioning guide 38 is removed from
alignment guide 36, a template is mounted on alignment guide 36.
Depicted in FIGS. 7 and 8A-8C is one embodiment of a template 150
incorporating features of the present invention which can be used
with the inventive milling systems. With reference to FIG. 8A,
template 150 comprises a base 152 having an arm 154 projecting
therefrom. Base 152 has a top surface 156 and an opposing bottom
surface 158 each extending between a first end 160 and an opposing
second end 162. Base also has a first side 164 and an opposing
second side 168.
[0057] Base 152 can be further defined as having an outer body 163
having an interior surface 170 that bounds an opening 172 extending
through body 163 from top surface 156 to bottom surface 158. In the
embodiment depicted, body 163 has substantially the same
configuration as body portion 60 of alignment guide 36 and is
designed to rest on top surface 44 thereof. For example, body 163
can have parallel sides that terminate at semi-circular ends. Other
shapes such as elliptical, circular, polygonal, irregular, or the
like, can also be used. Opening 172 of body 163 can have
substantially the same size and configuration as opening 58 of
alignment guide 36.
[0058] Projecting from interior surface 170 of body 163 into
opening 172 are a plurality of interconnected partition walls 174.
In general, each partition wall 174 has opposing side faces 176 and
178. Partition walls 174 divide opening 172 into a plurality of
guide paths 180, some of which are interconnected. Specifically,
guide paths 180 are bounded between opposing side faces of adjacent
partition walls 174 and are formed between interior surface 170 of
body 163 and a side face on an adjacent partition wall 174. As will
be discussed below in greater detail, guide paths 180 function as
guides for a mill used in resecting cutting surface 66.
[0059] In the depicted embodiment, interior surface 170 and the
side surfaces of partition walls 175 are disposed in parallel
alignment. That is, in contrast to having surfaces that slope
relative to each other so that projections of such surfaces diverge
and intersect, projections of the interior and side surfaces of
base 152 can all intersect a common plane at right angles. As will
be discussed below in greater detail, other designs can also be
used.
[0060] Turning to FIG. 8B, base 152 has a substantially constant
curvature extending between first end 160 and opposing second end
162. Specifically, top surface 156 has a convex curvature while
bottom surface 158 has a concave curvature extending between
opposing ends. Similarly, as depicted in FIG. 8C, top surface 156
has a substantially convex curvature extending between opposing
sides 164 and 168 while bottom surface 158 can have a complementary
concave curvature. In this regard, top surface 156 and bottom
surface 158 have a substantially dome-shaped configuration. As will
be discussed below in greater detail, the configuration of top
surface 156 in part dictates the configuration of the floor of the
recessed pocket. Bottom surface 158 of base 152 is typically
configured complimentary to top surface 44 of alignment guide 36
but can be other desired shapes.
[0061] Returning to FIG. 8A, a pair of spaced apart coupling holes
182 extend through arm 154. Arm 154 and coupling holes 182 are
configured such that when base 152 is mounted on alignment guide
36, coupling holes 182 of template 150 are aligned with coupling
holes 72 of alignment guide 36. As a result, handle 40 can be used
to secure template 150 to alignment guide 36 through alignment
holes 72 and 182 in substantially the same manner that position
guide 38 was removable attached alignment guide 36, as previously
discussed. Again, other removable mounting techniques can be used.
It is appreciated that alignment holes 72 and 182 can each comprise
one hole or three or more holes. The formation of more than one
alignment hole can be used for additional fasteners or for
selective placement of handle 40.
[0062] As shown in FIG. 7, once template 150 is secured to
alignment guide 36, a mill assembly 200 is used in conjunction with
template 150 to resect cutting surface 66. Depicted in FIGS. 9 and
10 is one embodiment of mill assembly 200 incorporating features of
the present invention. Mill assembly 200 comprises a mill 202
having an elongated shaft 204 extending between a first end 206 and
an opposing second end 208. Shaft 204 has an annular shoulder 210
encircling and radially outwardly projecting at second end 208. An
annular locking groove 212 is centrally formed on shaft 204. Mill
202 further comprises a burr 214 mounted on second end 208 of shaft
204 so that burr 214 radially outwardly projects from shaft 202.
Burr 214 is comprised of a plurality of cutting teeth 216 that
enables burr 214 to cut from the side and the bottom. As used in
the specification and appended claims, the term "burr" is broadly
intended to include any arrangement of cutting teeth or cutting
surfaces that when mounted on shaft 204 can be used to cut bone
when shaft 204 is rotated. For example, in contrast to having one
or more defined cutting teeth, burr 214 can also comprise a rough
surface that can grind or cut away bone.
[0063] Mill assembly 200 further comprises a bearing housing 220.
Bearing housing 220 has an interior surface 226 that bounds a
passageway 228 extending between a first end 222 and a second end
224. Bearing housing 220 can be further defined as comprising a
tubular first sleeve 230 formed at first end 222 that bounds a
compartment 234 and a tubular second sleeve 232 formed at second
end 224. First sleeve 230 has an outer diameter larger than second
sleeve 232 with a rounded tapered shoulder 236 extending between
sleeves 230 and 232.
[0064] During assembly, second end 223 of bearing housing 220 is
advanced over first end 206 of shaft 204 until second end 232 of
bearing housing 220 comes to rest on support shoulder 210 of mill
202. A pair of bearing 238 and 240 are also advanced over shaft 204
so as to be received within compartment 234 of first sleeve 230. A
clip 242 is then received within locking groove 212 so as to secure
bearing housing 220 and bearings 238 and 240 on mill 202. Bearings
238 and 240 can be ball bearings, roller bearings, or other forms
of bearings. In one alternative, one or three or more bearings can
be used.
[0065] Depicted in FIG. 7, during use, burr 214 is passed through
template 150 so that shaft 204 is disposed within a guide path 180.
In one embodiment, guide paths 180 have a minimum diameter D
extending between adjacent partition walls 174 or between the
partition walls 174 and interior surface 170 of base 152 that is
smaller than the maximum diameter of burr 214. As such, burr 214 is
prevented from traveling through or out of guide paths 180.
However, guide paths 180 are formed so that an area of intersecting
guide paths 180 forms an access area 250 having an area sized so
that burr can pass therethrough. Either before or after passing
mill 202 through template 150, a drill or other form of driver is
coupled with first end 206 of shaft 206 so as to enable rapid
rotation shaft 204 about the longitudinal axis thereof.
[0066] As shaft 204 is rotated, burr 214 cuts away at articular
cartridge 28 of cutting surface 66. Burr 214 cuts down through
articular cartridge 28 until shoulder 236 of bearing housing 220
comes to rest on top surface 156 of template 150 as shown in FIG.
11. Shoulder 236 thus defines the depth at which burr 214 cuts.
During the procedure, the surgeon slowly advances mill assembly 200
along each of guide paths 180 so as to resect cutting surface 66
and thereby form the recessed pocket. Because the cutting depth of
burr 214 is regulated by the interaction between shoulder 236 and
top surface 156 of template 150, movement of milling assembly 200
about the curved top surface 156 of template 150 produces a
recessed pocket having a floor with a contour similar to the
contour of top surface 156.
[0067] Furthermore, burr 214 has an effective radius that extends
from shaft 204 to the maximum outer radius of burr 214. The
effective radius is equal to or greater than at least half the
thickness of each partition wall 174. As a result, as mill 202 is
advanced down a guide path 180 on adjacent sides of a partition
wall 174, burr 216 undercuts the partition wall 174 so as to remove
all of the articular cartridge directly below the partition wall
174. Burr 176 also undercuts interior surface 170 of template
150.
[0068] During the milling process, as shoulder 236 of bearing
housing 220 rides along template 150, first sleeve 232 of bearing
housing 220 is disposed within the corresponding guide path 180. In
one embodiment, each guide path has a diameter substantially equal
to but slightly larger then the outer diameter of first sleeve 232
of bearing housing 220. This configuration enables free movement of
bearing housing 220 along guide paths 180 but prevents unwanted
lateral tipping of mill 202. As a result, the recessed pocket can
be formed with greater precision and tolerance. In one embodiment,
the minimum diameter of a guide path is typically less than 15%
greater than the maximum diameter first sleeve 232 and is typically
less than 10% or 5% greater than the maximum diameter first sleeve
232. In alternative embodiments, the minimum diameter of a guide
path 180 can be greater than the maximum diameter of burr 214.
[0069] Once mill 202 has been advanced down each of guide paths 180
so as to complete the resection of cutting surface 66, mill
assembly 200 is removed. Template 150 and alignment guide 36 can
then also be removed, thereby exposing resected pocket 310 as
depicted on FIG. 12. Pocket 310 is bounded by a floor 312 having an
encircling side wall 314 upstanding around the perimeter thereof.
Pocket 310 has opposing sides 316 and 318 that extend between a
proximal end 317 and an opposing distal end 318. Due to the
controlled movement of mill 202, floor 312 has a convex curvature
that extends between opposing ends 317 and 318 and a convex
curvature that extends between opposing sides 315 and 316. As will
be discussed below in greater detail, the configuration of recessed
pocket 310 enables the use of a low profile implant having
substantially uniform thickness. Furthermore, the formation of
pocket 310 produces a stable platform for the implant having a
complementary configuration.
[0070] It is appreciated that template 150 used in forming pocket
310 can come in a variety of different sizes, shapes, and
configurations depending on the location, size, and contour of
articular cartilage to be removed. Depicted in FIG. 13A is one
alternative embodiment of a template 254 that can replace template
150. Template 254 comprises a base 256 having arm 154 projecting
therefrom. Base 256 has a top surface 257 having an arched contour
substantially the same as top surface 156 of template 150. Base 256
includes an outer body 258 having an interior surface 259 that
bounds an opening 260. Projecting from interior surface 259 are a
plurality of partition walls 262 that bound a plurality of guide
paths 264. By comparing templates 150 and 254, it is appreciated
that the partition walls and guide paths, can have any desired
configuration, contour and/or layout as long as they enable mill
202 to properly remove articular cartilage 28. In this regard, the
partition walls and guide paths can be interconnected, separated,
or combinations thereof. The partition walls and guide paths can
also be linear, curved, or have other desired orientations.
[0071] Furthermore, in contrast to template 150 wherein the side
faces are in parallel alignment as discussed above, in template 254
select side faces of the partition walls 262 are sloped at
different angles relative to each other. Specifically, as depicted
in FIG. 13B, the various side faces of partition walls 262 and
interior surface 259 of body 258 intersect at substantially right
angles with top surface 257 of base 256. Expressed in other terms,
guide paths 264 projecting from top surface 257 of base 256, as
depicted by dashed lines 266, project normal to top surface 257.
This is in contrast to template 150, as depicted in FIG. 8C, where
many of the guide paths 180 project from top surface 156 at
orientations that are not normal to top surface 156. One of the
benefits of template 254 is that during use, mill 202 is oriented
normal to the final floor 312 of recessed pocket 310. As a result,
the use of template 254 results in floor 312 of recessed pocket 310
having a more uniformly smooth, arched surface in comparison to
floor 312 resulting from the use of template 150.
[0072] Returning to FIG. 12, once recessed pocket 310 is finished,
a tunnel 330 can be formed extending from pocket 310 to a location
spaced apart from the articular cartilage 28, such as medial side
14 or lateral side 16 of femur 12. Tunnel 330 can be formed by
simply using a drill to manually form the tunnel. That is, tunnel
330 can be drilled by starting at recessed pocket 310 and extending
to the lateral or medial side of the femur 12. Other techniques,
guides and instruments for forming tunnel 330 are disclosed in U.S.
patent application Ser. No. 10/901,941, filed Jul. 28, 2004 which
is incorporated herein by specific reference.
[0073] Once tunnel 330 is formed, an implant is then secured within
the recessed pocket 310. Depicted in FIGS. 14 and 15 is one
embodiment of a condylar implant 320 incorporating features of the
present invention. Condylar implant 320 comprises an elongated body
322 having a first side 324 and an opposing second side 326 that
each extend between opposing ends 328 and 330. Body 322 also has a
curved articular surface 322 and an opposing bottom surface 334. In
one embodiment, articular surface 332 can have a continuous convex
curvature that extends between opposing sides 324 and 326 and a
continuous convex curvature that extends between opposing ends 328
and 330.
[0074] A pair of pockets 344A and B are formed on bottom surface
334 and are separated by a bridge 346. Disposed within each pocket
344A and B is an inlay 348A and B of porous bone ingrowth material.
Bridge 346 and inlays 348A and B substantially comprise a bone
apposition surface 350. Bone apposition surface 350 can have a
configuration complementary to the formation of recessed pocket
310. Bone apposition surface 350 can also have a configuration
complementary to articular surface 332. In one embodiment, bone
apposition surface 350 can have a continuous concave curvature
which extends between opposing sides 324 and 326 and a continuous
concave curvature which extends between opposing ends 328 and 330.
As a result, condylar implant can have a substantially uniform
thickness along its length. In other embodiments, implant 340 may
be slightly tapered along a perimeter edge 352 thereof Thus, at all
locations at least 2 mm in from the perimeter edge 352, body 322
can have a thickness extending between the bone apposition surface
350 and the articular surface 322 that does not vary by more than
30%, 20%, or more commonly 15%. Other percentages can also be used.
The actual thickness depends on the desired implant and is
typically in a range between about 3 mm to about 10 mm.
[0075] Connected to bridge 346 is a flexible line 360. As used in
the specification and append claims, the term "line" is broadly
intended to include wire, cable, cord, suture, braded line,
combinations thereof or any other type of flexible filament. The
line can be made of metal, alloys, synthetics, composites, or any
other desired material. In one embodiment of the present invention
the line comprises braded filaments of a cobalt chrome alloy having
a diameter in a range between about 0.25 mm to about 5 mm with
about 0.5 mm to about 3 mm being more common and about 0.5 mm to
about 2 mm being most common. Other dimensions can also be used.
The line can be of any desired length.
[0076] In one embodiment, the line can also be defined in that for
an unsupported length of line of 4 cm, the line has substantially
no compressive strength. In yet other embodiments, for an
unsupported length of line of 4 cm, the line fails under buckling
when an axial compressive load of 0.25 Newtons (N), 1 N, 2 N, 5 N,
20 N, or 50 N is applied. That is, different lines can be used that
fail under different loads. Stiffer lines can also be used.
[0077] It is also appreciated that the line can be static or
resiliently stretchable. In one embodiment where the line is
resiliently stretchable, the line can be comprised of a material
having shape memory of pseudo elastic properties. One example of
such a material is a nickel titanium alloy sold under the name
Nitinol. In yet other embodiment, it is appreciated that sections
of the line could be replaced with a spring member such as a coiled
spring or rubber or bungee type member. It is appreciated that line
360 can be permanently or removably attached to implant 320.
Examples of methods for attaching line 360 to implant 320 are
disclosed in U.S. patent application Ser. No. 10/901,941 which was
previously incorporated by reference.
[0078] It is appreciated that implant 320 as discussed above and
depicted herein is only one example of an implant that can be used
in association with the present invention. In alternative
embodiments, implant 320 can have a variety of different sizes,
shapes, configurations, components, and other modifications. For
example, spikes or other forms of projections can be formed
projecting from bone apposition surface 350. Furthermore,
conventional implants using conventional mounting techniques can be
secured within recessed pocket 310. Examples of alternative
implants that can be used with the present invention are disclosed
in U.S. patent application Ser. No. 10/901,941 which was previously
incorporated by reference.
[0079] Finally, turning to FIG. 16, condylar implant 320 is secured
within recessed pocket 310 of femur 12. In the depicted embodiment,
this is accomplished by passing line 360 (FIG. 15) within tunnel
300 (FIG. 12) and then using a tensioner and anchor assembly to
secure line 360 within tunnel 300. Examples of bone anchors and
tensioners that can be used in association with the present
invention are disclosed in U.S. patent application Ser. No.
10/901,941. Again, other conventional techniques can be used to
secure implant within pocket 310. In such other techniques, line
360 can be eliminated.
[0080] The above disclosure discusses a number of different guides,
mills, templates, and other related instruments, implants and
methods. It is appreciated that the individual components and
sub-combination of components are novel and can be used
independently or mixed and matched with other conventional systems.
For example, in one alternative embodiment the function of
positioning guide 38 can be integrally incorporated into alignment
guide 36. Depicted in FIG. 17 is an alignment guide 126 wherein
like elements between alignment guides 36 and 126 are identified by
like reference characters.
[0081] Alignment guide 126 includes body portion 60 bounding
opening 58. Bracket 62 projects from body portion 60 and has
coupling holes 72 formed thereon. However, bracket 64 and mounting
holes 68A-C have been eliminated. Alignment guide 126 further
includes hubs 128A-C projecting from interior surface 56 of body
portion 60 into opening 58. Support legs 130A-C downwardly project
from hubs 128A-C, respectively, so that support legs 130A-C project
below the bottom surface of body portion 60. Extending down through
each hub 128A-C and support leg 130A-C is a corresponding mounting
hole 132A-C.
[0082] During use, alignment guide 126 is positioned on articular
cartilage 28 so that support legs 130A-C directly rest against
articular cartilage 28 and body portion 60 is suspended above
articular cartilage 28. Fasteners, such as screws 93 (FIG. 3), are
then passed down through mounting holes 132A-C so as to secure
alignment guide 126 to femur 12. Template 150 is then mounted on
alignment guide 126 and cutting surface 66 is resected in
substantially the same matter as discussed above. After removal of
alignment guide 126, the portion of articular cartilage 28 disposed
below support legs 130A-C is manually removed, such as with a hand
held mill, so as to complete the formation of recessed pocket 310.
Because the portion of articular cartilage 28 on which support legs
130A-C rests is ultimately resected, any damage to articular
cartilage 28 by support legs 130A-C resting thereagainst or screws
penetrating therein, is irrelevant. Further disclosure with regard
to this method for mounting a guide is disclosed in U.S. patent
application Ser. No. 11/138,016, filed May 26, 2005, entitled
Milling System and Method for Resecting a Joint Articulation
Surface in the name of Carlyle J. Creger et al., which is
incorporated herein by specific reference.
[0083] Different features of the present invention provide a number
of benefits over conventional systems and methods. For example, in
contrast to many conventional processes which require the removal
of an entire articulation surface for the mounting of an implant,
the present invention enables the resurfacing of an isolated
location on the articulation surface. As a result, the procedure is
less invasive and recovery time is increased. The milling systems
of the present invention enable the formation of the pocket while
minimizing retraction of soft tissue, minimizing the amount of bone
removal, and minimizing the time required to remove the bone and
mount the implant. Using a high speed burr, as opposed to a saw
blade or rasp, also has advantages in that the burr requires less
effort to cut and can more precisely remove sections of bone.
Furthermore, unlike saw blades and rasps which during use often
cover a portion of the bone that is desired to be removed, burrs
allow for greater visibility of the bone during removal, thereby
improving accuracy of bone removal.
[0084] The milling system is also unique in that the milling system
is either suspended above the articulation surface or is mounted
only over the area of the articulation surface that is to be
resurfaced. As a result, the potential for unintentional damage to
the portion of the surrounding articular surface that is not to be
resurfaced is minimized. Another advantage of the present invention
is that it provides a system that is easy to mount and use on
uneven or irregular surfaces, is easy to operate, and is easy to
remove. The present invention also provides other advantages which
will be apparent to those skilled in the art.
[0085] The present invention may be embodied in other specific
forms without departing from its spirit or essential
characteristics. The described embodiments are to be considered in
all respects only as illustrative and not restrictive. The scope of
the invention is, therefore, indicated by the appended claims
rather than by the foregoing description. All changes which come
within the meaning and range of equivalency of the claims are to be
embraced within their scope.
* * * * *