U.S. patent application number 10/780378 was filed with the patent office on 2004-08-19 for tibial augments for use with knee joint prostheses, method of implanting the tibial augment, and associated tools.
This patent application is currently assigned to Zimmer Technology, Inc.. Invention is credited to Blaylock, Jeff, Cook, Michael, Donkers, Ron, Dykema, Scott, Hanssen, Arlen D., Jones, David, Lewallen, David G., Meyers, John, Vankoski, Stephen.
Application Number | 20040162619 10/780378 |
Document ID | / |
Family ID | 36648366 |
Filed Date | 2004-08-19 |
United States Patent
Application |
20040162619 |
Kind Code |
A1 |
Blaylock, Jeff ; et
al. |
August 19, 2004 |
Tibial augments for use with knee joint prostheses, method of
implanting the tibial augment, and associated tools
Abstract
A tibial augment for use with a knee joint prosthesis, composed
of annular members of different stock sizes, each size being
configured to fit within a cavity formed in a human tibia. The
augment may include a stepped distal surface. A provisional
(temporary) tibial augment used to ensure a proper fit for the
permanent augment is also provided. The provisional may include
grooves configured to cooperate with a set of ribs on a tong-like
holder used for removing the provisional from the cavity. A pusher
for use implanting the tibial augment is also provided. In
addition, a system for creating a cavity in a human tibia is also
described. The system preferably includes a guide with a slot
therein and a set of osteotomes that are inserted within different
portions of the slot. Methods for using the tools and/or implanting
the prosthetic devices discussed above are also described.
Inventors: |
Blaylock, Jeff; (Fort Wayne,
IN) ; Cook, Michael; (Claypool, IN) ; Donkers,
Ron; (Warsaw, IN) ; Dykema, Scott; (Warsaw,
IN) ; Jones, David; (Elkhart, IN) ; Meyers,
John; (Columbia City, IN) ; Vankoski, Stephen;
(Fort Wayne, IN) ; Hanssen, Arlen D.; (Rochester,
MN) ; Lewallen, David G.; (Rochester, MN) |
Correspondence
Address: |
GREER, BURNS & CRAIN
300 S WACKER DR
25TH FLOOR
CHICAGO
IL
60606
US
|
Assignee: |
Zimmer Technology, Inc.
Mayo Foundation for Medical Education and Research
|
Family ID: |
36648366 |
Appl. No.: |
10/780378 |
Filed: |
February 17, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10780378 |
Feb 17, 2004 |
|
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10225774 |
Aug 22, 2002 |
|
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60315148 |
Aug 27, 2001 |
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Current U.S.
Class: |
623/20.16 ;
606/84; 606/88; 623/20.32 |
Current CPC
Class: |
A61F 2002/30217
20130101; A61F 2/30734 20130101; A61F 2230/0067 20130101; A61F
2/389 20130101; A61F 2002/30736 20130101; A61F 2002/4628 20130101;
A61F 2310/00131 20130101; A61F 2002/30209 20130101; A61F 2/4684
20130101; A61F 2250/0036 20130101; A61F 2/30942 20130101; A61F
2250/0084 20130101; A61B 2090/034 20160201; A61B 17/1764 20130101;
A61F 2002/30326 20130101; A61F 2002/30616 20130101; A61B 17/1604
20130101; A61F 2/461 20130101; A61B 17/1675 20130101; A61F
2002/30708 20130101; A61B 17/1735 20130101; A61F 2002/30324
20130101; A61F 2250/0037 20130101 |
Class at
Publication: |
623/020.16 ;
623/020.32; 606/088; 606/084 |
International
Class: |
A61F 002/38; A61F
002/46; A61B 017/88 |
Claims
What is claimed is:
1. A tibial augment for use with a knee joint prosthesis,
comprising: an annular member with a proximal surface, a distal
surface, an outer anterior surface, an inner anterior surface, an
outer posterior surface, an inner posterior surface, an inner
lateral surface, an outer lateral surface, an inner medial surface
and an outer medial surface; said outer lateral surface being
curved to define a continuous surface connecting said outer
posterior surface and said outer anterior surface; said outer
medial surface being curved to define a continuous surface
connecting said outer posterior surface and said outer anterior
surface; said outer anterior surface being a slightly curved
surface; and said outer posterior surface being a generally planer
surface.
2. The tibial augment defined in claim 1, wherein said annular
member is sized to fit, at least partially, within a cavity formed
in a proximal portion of a human tibia.
3. The tibial augment defined uniform thickness, whereby each outer
surface of said substantially uniform in claim 1, wherein at least
a majority portion of said annular member is of a substantially
thickness majority portion is spaced a substantially constant
distance from each associated inner surface.
4. The tibial augment defined in claim 3, wherein said inner
anterior surface includes a distal/proximal extending channel
therein, thereby defining a reduced thickness portion.
5. The tibial augment defined in claim 4, wherein said majority
portion of a substantially uniform thickness is approximately 5 mm
thick and said reduced thickness portion is approximately 3 mm
thick at the narrowest point thereof.
6. The tibial augment defined in claim 1, wherein said inner
anterior surface includes a distal/proximal extending channel
therein, thereby defining a reduced thickness portion.
7. The tibial augment defined in claim 1, wherein said annular
member is composed of a tantalum based porous metal.
8. The tibial augment defined in claim 1, wherein said outer
posterior surface has a distal taper of less than approximately
17.degree..
9. The tibial augment defined in claim 1, wherein said outer medial
surface and said outer lateral surface each have a distal taper of
between approximately 8.degree. and approximately 30.degree..
10. The tibial augment defined in claim 1, wherein said outer
anterior surface has essentially no distal taper.
11. The tibial augment defined in claim 1, further comprising a
stepped distal surface, thereby defining a first distal surface and
a second distal surface with a transition surface therebetween,
wherein said first distal surface is located at a greater distance
from said proximal surface than said second distal surface.
12. The tibial augment defined in claim 11, wherein said transition
surface is located midway between said outer lateral surface and
said outer medial surface.
13. The tibial augment defined in claim 11, wherein said transition
surface is located closer to said outer lateral surface than to
said outer medial surface.
14. The tibial augment defined in claim 11, wherein said transition
surface is located closer to said outer medial surface than to said
outer lateral surface.
15. The tibial augment defined in claim 1, wherein said annular
member is composed of a material that is substantially transparent
to provide an indication of bony contact when said annular member
is used as a provisional.
16. The tibial augment defined in claim 1, wherein said annular
member is made of a photo-elastic material that provides an
indication of bony contact when said annular member is used as a
provisional.
17. The tibial augment defined in claim 1, further comprising at
least one set of generally lateral/medial extending grooves formed
on at least two opposing inner surfaces of said annular member to
facilitate insertion and removal of the tibial augment when used as
a provisional.
18. The tibial augment defined in claim 17, wherein said at least
one set of generally lateral/medial extending grooves are formed on
said inner lateral surface and said inner medial surface; and
further wherein said annular member is composed of a material that
is substantially transparent.
19. An implant system for use with a knee joint prosthesis, said
implant system comprising: a plurality of differently-sized tibial
augments, wherein each said tibial augment is an annular member
that is substantially shaped as a truncated cone with a generally
oblongated oval cross-section that is symmetric about its minor
axis, each of said annular members being sized to fit within a
cavity of a corresponding size formed in a proximal portion of a
human tibia of an appropriate size.
20. The implant system as defined in claim 19, further comprising:
a plurality of differently-sized tibial augment pushers, with at
least one pusher configured for use with each size of tibial
augment, said pushers being configured and arranged for implanting
each of said differently-sized tibial augments within a human
tibia
21. The implant system as defined in claim 20, wherein at least one
pusher of said plurality of pushers is configured for use with more
than one size of said differently sized tibial augments.
22. The implant system as defined in claim 20, wherein each of said
pushers includes: a handle portion; and an augment seating portion,
connected to one end of said handle portion, wherein said augment
seating portion is configured and arranged to seat a tibial augment
of at least one particular size.
23. The implant system as defined in claim 19, further comprising:
a plurality of differently-sized guides, with one guide being
configured for use with each size of tibial augment; and a
plurality of osteotomes configured and arranged to cooperate with
each of said guides, said osteotomes and said guides being
configured and arranged to create an appropriately sized cavity
within a proximal portion of a human tibia for implanting an
appropriately sized tibial augment therein.
24. The implant system as defined in claim 19, further comprising:
a plurality of differently-sized provisional tibial augments, with
one of said provisional tibial augments corresponding in size and
shape to each of said tibial augments, and each of said provisional
tibial augments being composed of a material that is substantially
transparent.
25. The implant system as defined in claim 24, wherein: each of
said provisional tibial augments includes a plurality of grooves on
a plurality of inner surfaces thereof; a plurality of
differently-sized holders, configured for use with said provisional
tibial augments, each of said holders including a plurality of
ribs, with each of said ribs being configured and arranged to
correspond to one of said grooves on said provisional tibial
augment, such that an appropriately sized one of said holders is
capable of holding one of said provisional tibial augments during
removal of said provisional tibial augment from a cavity formed
within a proximal portion of a human tibia.
26. A method of correcting for tibial defects during knee
replacement surgery: preparing an existing cavity, or creating a
cavity in a proximal portion of a human tibia; inserting a tibial
augment within said cavity; and attaching a tibial portion of a
knee joint prosthesis to said tibial augment.
27. The method of correcting for tibial defects, as defined in
claim 26, further comprising the step of: selecting an
appropriately sized tibial augment from a group of differently
sized tibial augments.
28. The method of correcting for tibial defects, as defined in
claim 26, wherein: during said step of preparing or creating said
cavity, a guide and a set of osteotomes are utilized to form said
cavity, said guide including a slot with different portions thereof
configured for accepting different osteotomes of said set of
osteotomes.
29. The method of correcting for tibial defects, as defined in
claim 26, further comprising the step of inserting a second tibial
augment within said cavity, wherein said second tibial augment is
stacked upon said tibial augment originally inserted within said
cavity.
30. The method for correcting for tibial defects, as defined in
claim 26, wherein prior to said step of inserting a tibial augment
within said cavity, a provisional tibial augment is temporarily
inserted into said cavity.
31. The method for correcting for tibial defects, as defined in
claim 30, further comprising the step of using said provisional
tibial augment as a tamp to tamp a bone graft into position.
32. A pusher for use with a tibial augment, said pusher comprising:
a handle portion; and an augment seating portion, connected to one
end of said handle portion, wherein said augment seating portion is
configured and arranged to seat at least one particularly sized
tibial augment.
33. The pusher as defined in claim 32, wherein: said augment
seating portion includes a head portion and a platform portion,
which are attached together, and wherein said platform portion is
attached to said handle portion of said pusher; said platform
portion including a generally planar surface at an interface
between said platform portion and said head portion; and said head
portion including a plurality of tapered surfaces, such that a
cross-section of said head portion decreases with increasing
distance from said generally planar surface of said head
portion.
34. An osteotome used for creating a cavity in a bone, said
osteotome comprising: a handle portion; and a cutting portion
attached to said handle portion, wherein said cutting portion
includes: a tapered edge at a distal end thereof; at least one stop
for hindering penetration of said cutting portion into said bone
past a predetermined distance.
35. The osteotome as defined in claim 34, wherein said at least one
stop includes two stops, with one of said stops being configured
for hindering penetration of said cutting portion into said bone
past a first predetermined distance and with the other one of said
stops being configured for hindering penetration of said cutting
portion into said bone past a second predetermined distance.
36. The osteotome as defined in claim 35, wherein: one of said
stops is configured to cooperate with a guide of a first size and
the other of said stops is configured to cooperate with a guide of
a second size, where said second size is different from said first
size.
37. The osteotome as defined in claim 34, wherein said cutting
portion is curved into an arc shape.
38. The osteotome as defined in claim 35, wherein: said cutting
portion is generally planar, with said plane defined by said
generally planar cutting portion being situated at an oblique angle
with respect to a longitudinal axis of said handle portion.
39. The osteotome as defined in claim 35, wherein said osteotome is
configured and sized to create a cavity in a proximal portion of a
human tibia.
40. A guide for use with at least one osteotome when creating a
cavity in a bone, said guide comprising: an upper surface; a
generally planar lower surface; a generally C-shaped slot extending
from said upper surface to said generally planar lower surface; and
a securing arrangement to secure said guide to the bone within
which the cavity is being created, said securing arrangement
securing said guide such that said generally planar lower surface
faces the bone within which a cavity is being created.
41. The guide as defined in claim 40, wherein said securing
arrangement includes: an aperture with a central axis extending in
a direction generally perpendicular to said generally planar lower
surface, wherein said aperture is configured to accept an
intramedullary rod.
42. The guide as defined in claim 41, wherein said securing
arrangement further includes: a threaded hole extending in a
direction generally transverse to said plane of said generally
planar lower surface; and a setscrew configured to extend through
said threaded hole and to contact the intramedullary rod such that
said guide is retained in position with respect to the
intramedullary rod within said aperture.
43. The guide as defined in claim 41, wherein said aperture is
generally triangular-shaped, and said aperture extends completely
through said guide from said generally planar lower surface to said
upper surface.
44. The guide as defined in claim 40, wherein portions of said
generally C-shaped slot are tapered inwardly toward said generally
planar lower surface.
45. A system used for creating a cavity in a proximal portion of a
human tibia for use prior to implanting a knee joint prosthesis,
said system comprising: a guide that includes: an upper surface; a
lower surface; a generally C-shaped slot extending from said upper
surface to said lower surface; and a securing arrangement to secure
said guide to the bone within which the cavity is being created,
said securing arrangement securing said guide such that said lower
surface faces the bone within which the cavity is being created;
and a set of osteotomes configured and arranged to be inserted
within said generally C-shaped slot of said guide.
46. The system according to claim 45, wherein each of said
osteotomes within said set includes at least one stop for hindering
penetration of a cutting portion of said osteotome into said bone
past a predetermined distance by contacting a surface of said upper
surface of said guide adjacent to said C-chapped slot.
47. The system as defined in claim 46 wherein said at least one
stop on each of said osteotomes within said set includes two stops,
with one of said stops being configured for hindering penetration
of said cutting portion into said bone past a first predetermined
distance and with the other one of said stops being configured for
hindering penetration of said cutting portion into said bone past a
second predetermined distance.
48. A holder for inserting and/or removing a provisional augment
to/from a cavity in a bone, said holder comprising: a body portion
defining a longitudinal axis; a pair of legs extending from said
body portion; a finger connected to each of said legs; and a rib
extending outwardly from each of said fingers, each of said ribs
extending in a direction generally perpendicular to said
longitudinal axis of said body portion, wherein said ribs are
configured and arranged to correspond to grooves on an inner
surface of a provisional augment.
49. The holder as defined in claim 48, further comprising a pair of
stops configured and arranged to be seated upon a proximal surface
of the provisional augment, whereby said stops serve as locators
for properly locating said ribs of said holder with respect to the
grooves of the provisional augment.
50. The holder as defined in claim 48, wherein said pair of legs
comprises a pair of flexible legs, such that application of a force
upon outer surfaces of said legs allows for said ribs to be
disengaged from the grooves on the inner surface of the provisional
augment without significantly altering the location of the
provision augment.
51. The holder as defined in claim 48, wherein: each of said legs
is a relatively rigid member; and each of said fingers is attached
to one of said legs such that said fingers are movable with respect
to said legs, whereby movement of said fingers with respect to said
legs allows for said ribs to be disengaged from the grooves on the
inner surface of the provisional augment without significantly
altering the location of the provision augment.
52. The holder as defined in claim 51, wherein a distance between
said fingers is adjustable to permit said holder to be used with
provisional augments of different sizes.
53. The holder as defined in claim 51, wherein said fingers are
attached to said legs via a threaded shaft that is threaded in one
direction where one of said fingers is connected thereto and in an
opposite direction where the other of said fingers is connected
thereto, whereby when said threaded shaft is rotated in a first
direction with respect to said legs, said fingers are moved towards
each other and when said threaded shaft is rotated in an opposite
direction with respect to said legs, said fingers are moved away
from each other.
54. The holder as defined in claim 51, further comprising: a
threaded shaft that extends from one of said legs to the other of
said legs and is rotatable with respect to said legs and connects
said fingers to said legs, said threaded shaft being threaded in
one direction where one of said fingers is connected thereto and in
an opposite direction where the other of said fingers is connected
thereto; and a secondary shaft that extends from one of said legs
to the other of said legs, with said fingers being movably attached
thereto.
55. The holder as defined in claim 54, wherein said secondary shaft
includes a slight taper from a center thereof outwardly towards
each of said legs.
Description
[0001] This application is a continuation-in-part of prior
application Ser. No. 10/225,774, filed Aug. 22, 2002, which claims
the benefit of Provisional Application No. 60/315,148, filed Aug.
27, 2001, both of which are hereby incorporated by reference.
[0002] The present invention relates generally to a bone augmenting
member used to reinforce damaged bone, and more particularly to an
augment for the proximal portion of a human tibia, where the
augment is intended to be implanted in the proximal portion of the
tibia, just slightly below the tibial portion of a knee joint
prosthesis. The present invention also relates to the tool used for
implanting the tibial augment, and the tools used for making the
cavity in the bone to receive the augment. In addition, the
invention also relates to a provisional augment used temporarily to
ensure that the permanent augment will be seated within the bone
correctly, as well as to a holder used for holding, inserting and
removing the provisional augment.
BACKGROUND OF THE INVENTION
[0003] Knee replacement surgery methods and knee joint prostheses
are known in the art. A typical knee joint prosthesis includes a
rounded femoral component that is attached to the distal portion of
the femur, and a tibial component, which may be formed of a single
piece or from two separate pieces that are joined together, that is
attached to the proximal portion of the tibia. The femoral
component rides on the exposed surface of the tibial component,
replicating natural knee movement as closely as possible. When such
knee replacement surgery is performed, an incision is made to
expose the knee joint in order to enable removal of both the
proximal portion of the tibia and the distal portion of the femur,
which creates surfaces upon which the tibial and femoral components
of the knee prosthesis can be attached.
[0004] In certain situations, additional portions of the tibia,
other than the relatively narrow proximal portion being removed
during knee replacement surgery, it may also be damaged by
arthritis or other problems. In such situations, a relatively thick
proximal portion of the tibia is often removed, and it is replaced
with an augment block shaped like the bone that has been removed.
However, such previously known methods often result in the removal
of an unnecessary amount of healthy bone, along with the damaged
bone. Thus, for example, even in cases where the peripheral bone
was healthy, and only the internal bone was damaged, prior art
methods often removed both the healthy peripheral bone and the
damaged internal bone
BRIEF SUMMARY OF THE INVENTION
[0005] The present invention is intended for situations in which
the proximal portion of the tibia is defective, and it provides a
method and devices that allow for preservation of healthy
peripheral bone, while still providing the necessary augmentation
to the proximal portion of the tibia. Preservation of the healthy
peripheral bone provides for early onset of bony ingrowth into the
tibial augment and allows the bone to infiltrate the augment,
restoring the bony platform upon which other implants can
reside.
[0006] More specifically, the present invention provides a tibial
augment for use with a knee joint prosthesis that is made of an
annular member with a proximal surface, a distal surface, an outer
anterior surface, an inner anterior surface, an outer posterior
surface, an inner posterior surface, an inner lateral surface, an
outer lateral surface, an inner medial surface and an outer medial
surface. Preferably, the outer lateral surface is curved to define
a continuous surface connecting the outer posterior surface and the
outer anterior surface; and the outer medial surface is also curved
to define a continuous surface connecting the outer posterior
surface and the outer anterior surface. In addition, the outer
anterior surface is slightly curved and the outer posterior surface
is a generally planar surface. The annular member can be made in a
variety of different stock sizes, with each size being configured
to fit within a cavity formed in a proximal portion of a different
sized human tibia.
[0007] In certain embodiments, the tibial augment of the present
invention can include a stepped distal surface, thereby defining a
first distal surface and a second distal surface with a transition
surface therebetween, where the first distal surface is located at
a greater distance from the proximal surface than the second distal
surface. The transition surface can be located at different
portions of the augment, such as: (1) midway between the outer
lateral surface and the outer medial surface; (2) closer to the
outer lateral surface than to the outer medial surface; or (3)
closer to the outer medial surface than to the outer lateral
surface.
[0008] The present invention also includes a provisional or
temporary tibial augment that is used to ensure a proper fit for
the permanent augment. The provisional augment is preferably
composed of a material that is substantially transparent to allow
visualization of the bony contact surfaces that will likely contact
the augment. In addition, in the preferred embodiment, the
provisional augment preferably includes at least one set of
generally lateral/medial extending grooves to facilitate removal of
the provisional from the cavity formed in the tibia. The grooves
are configured to cooperate with a set of ribs on a tong-like
holder used for inserting and removing the provisional from the
cavity.
[0009] The present invention also relates to a pusher for use in
implanting the tibial augment, where the pusher includes a handle
portion and an augment seating portion. The augment seating portion
is connected to one end of the handle portion, and is configured
and arranged to seat a particularly sized tibial augment.
[0010] In addition, the present invention also relates to a system
used for creating a cavity in a proximal portion of a human tibia
for use prior to implanting a knee joint prosthesis. The system
preferably includes a guide with a slot therein and a set of
osteotomes that are configured and arranged to be inserted within
different portions of the slot on the guide.
[0011] Additionally, the present invention also relates to a holder
for inserting and/or removing a provisional augment to/from a
cavity in a bone. The holder preferably includes a body portion, a
pair of legs extending from the body portion, a finger connected to
each of the legs, and a rib extending outwardly from each of the
fingers. Each of the ribs preferably extends in a direction that is
generally perpendicular to the longitudinal axis of the body
portion, and the ribs are configured and arranged to correspond to
grooves on an inner surface of a provisional augment. In a first
preferred embodiment of the holder, the pair of legs comprises a
pair of flexible legs, such that application of a force upon outer
surfaces of the legs allows for the ribs to be disengaged from the
grooves on the inner surface of the provisional augment without
significantly altering the location of the provision augment. In
the second preferred embodiment of the holder, each of the legs is
a relatively rigid member, and each of the fingers is attached to
one of the legs such that the fingers are movable with respect to
the legs, whereby movement of the fingers with respect to the legs
allows for the ribs to be disengaged from the grooves on the inner
surface of the provisional augment without significantly altering
the location of the provision augment. The second embodiment of the
holder is also preferably adjustable to permit a single holder to
be used with provisional augments of different sizes.
[0012] The present invention also relates to the methods of using
the tools and/or implanting the prosthetic devices discussed
above.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] Preferred embodiments of the present invention are described
herein with reference to the drawings wherein:
[0014] FIG. 1 is a perspective view of a preferred embodiment of a
tibial augment of the present invention;
[0015] FIG. 2 is a top view of the tibial augment of FIG. 1;
[0016] FIG. 3 is an anterior view of the tibial augment of FIG. 1,
with the posterior view being identical due to symmetry along the
major axis;
[0017] FIG. 4 is a lateral view of the augment of FIG. 1, with the
medial view being a mirror image thereof;
[0018] FIG. 5 is a perspective view of a tibial augment of a
different height than that shown in the FIG. 1 embodiment;
[0019] FIGS. 6A-6C are anterior views of three different stepped
versions of the tibial augment of the present invention;
[0020] FIG. 7 is a view of a tibia, shown with the damaged proximal
bone surface removed and also including a cavity within which a
tibial augment of the present invention will be implanted;
[0021] FIG. 8 is a view of a tibial augment of the present
invention, shown implanted in place below a knee joint
prosthesis;
[0022] FIG. 9 is a perspective view of a provisional tibial augment
of the present invention;
[0023] FIG. 10 is a top view of a holder of the present invention,
where the holder is intended for use with the provisional of FIG.
9;
[0024] FIG. 11 is a side view of the holder of FIG. 10;
[0025] FIG. 12 is a perspective view of a second embodiment of a
holder of the present invention;
[0026] FIG. 13 is a front view of the holder of FIG. 12;
[0027] FIG. 14 is a perspective view of a pusher of the present
invention, which pusher is intended to be used to implant the
tibial augment;
[0028] FIG. 15 is a bottom view of the pusher of FIG. 14;
[0029] FIG. 16 is a side view of the pusher of FIG. 14;
[0030] FIG. 17 is a front view of the pusher of FIG. 14, and an
enlarged view of the augment seating portion upon which a tibial
augment has been seated;
[0031] FIG. 18 is a perspective view of a guide and a curved
osteotome of the present invention, which are used for making a
cavity for the augment;
[0032] FIG. 19 is a bottom view of the guide of FIG. 18;
[0033] FIG. 20 is a side view of the guide of FIG. 18;
[0034] FIG. 21 is a side view of the osteotome of FIG. 18;
[0035] FIG. 22 is a rear view of the osteotome of FIG. 18;
[0036] FIG. 23 is a bottom view of the osteotome of FIG. 18;
[0037] FIG. 24 is a bottom view of the osteotome of FIG. 25;
[0038] FIG. 25 is a perspective view of the guide of FIG. 18, shown
with a second osteotome of the present invention;
[0039] FIG. 26 is a perspective view of the guide of FIG. 18, shown
with a third osteotome of the present invention;
[0040] FIG. 27 is a side view of the osteotome of FIG. 26; and
[0041] FIG. 28 is a rear view of the osteotome of FIG. 26.
DETAILED DESCRIPTION OF THE INVENTION
[0042] Referring to FIGS. 1 through 4, a first embodiment of the
tibial augment of the present invention is shown. The tibial
augment is preferably an annular member 10, and it is preferably
made from a tantalum based porous material, such as Trabecular
Metal.TM.. Trabecular Metal.TM. is desirable because it resembles
bone and approximates the physical and mechanical properties of
bone better than other materials. Use of such a metal enables
increased bonding with the adjacent bone by allowing the bone to
grow into its highly porous surface. The tibial augment may also be
made of other materials, and it is preferably made of a material
that facilitates bony ingrowth.
[0043] The tibial augment 10 is anatomically sized and shaped to
fill an existing cavitary defect within the proximal human tibia or
a cavity prepared in the proximal portion of a human tibia. In the
preferred embodiment, a system of different stock sizes of augments
would be available, as discussed more fully below, with different
sizes being used for different sized tibias. Further, if desired
two augments of different sizes may be stacked upon each other if
such stacking is necessary to fill the cavity.
[0044] As shown in FIGS. 1 through 4, the tibial augment 10
includes a proximal surface 12, a distal surface 14, an outer
anterior surface 16, an inner anterior surface 18, an outer
posterior surface 20, an inner posterior surface 22, an inner
lateral surface 24, an outer lateral surface 26, an inner medial
surface 28 and an outer medial surface 30. Of course, depending on
which tibia (right or left) the augment is being implanted into,
the surfaces designated as the medial and lateral surfaces will be
reversed. However, since the augment is symmetric with respect to
its lateral and medial sides, such distinctions are irrelevant, and
the terms lateral and medial are being used for convenience of
description only.
[0045] To mimic the portion of the tibia bone that the tibial
augment is being implanted into, the outer lateral surface 26 is
curved to define a continuous surface that connects the outer
posterior surface 20 and the outer anterior surface 16. Likewise,
the outer medial surface 30 is curved to define a continuous
surface that connects the outer posterior surface 20 and the outer
anterior surface 16. The outer anterior surface 16 is slightly
curved and the outer posterior surface 20 is a generally planar
surface.
[0046] As best shown in FIGS. 2 through 4, a majority of the
annular member 10 is of a substantially uniform thickness, as most
readily depicted by the hidden lines of FIGS. 3 and 4. The major
exception to the uniform thickness is a channel 32, shown in FIGS.
1 and 2, which defines a reduced thickness portion. In the
preferred embodiment, the thickness of the majority of the augment
is preferably approximately 5 mm thick, and the thickness of the
reduced thickness portion is preferably approximately 3 mm at its
narrowest point. However, other dimensions are also contemplated as
being within the scope of the invention. Although the preferred
embodiment includes walls of a substantially uniform thickness,
with a reduced thickness portion near channel 32, it is also
contemplated that the walls could be tapered, in either direction,
between the proximal and distal surfaces.
[0047] The reduced thickness portion is preferably included to
provide a space for the stem of a stemmed tibial base plate of a
knee joint prosthesis. One example of such a stemmed tibial base
plate is shown in FIG. 8, which shows a knee joint prosthesis 100
that includes stemmed tibial base plate 102 with a stem 104
extending through the tibial augment 10. FIG. 8 also shows a tibial
articulating surface 106 and a femoral component 108, which are
also parts of the knee joint prosthesis 100. Although the present
augment 10 is shown and described for use with a stemmed tibial
base plate and includes a channel for accommodating the base
plate's stem, it is contemplated that the present invention could
also be used with other forms of base plates without stems, and
therefore the channel could be omitted. Further, it is also
contemplated that the inner surfaces of the tibial augment of the
present invention could be modified to accommodate other designs of
tibial base plates, such as pegged base plate designs.
[0048] As shown in FIG. 3, both the outer medial surface 30 and the
outer lateral surface 26 have a distal taper (i.e. downward slope)
of between approximately 8 degrees and approximately 30 degrees,
with a taper of approximately 19 degrees being preferred. Such
tapers replicate the tapers commonly found in corresponding areas
of the proximal portions of human tibias. Since the thickness of
the annular member 10 is generally uniform from its proximal side
to its distal side, the inner medial surface 28 and the inner
lateral surface 24 will also have the same taper as the outer
lateral and medial surfaces.
[0049] Referring now to FIG. 4, the outer posterior surface 20 has
a distal taper of less than approximately 17 degrees, with a taper
of approximately 12 degrees being preferred. The outer anterior
surface 16 is an essentially normal surface relative to the
proximal surface 12. Like the tapers of the lateral and medial
surfaces, those of the anterior and posterior surfaces were also
chosen to mimic the tapers of the appropriate portions of a human
tibia. Once again, due to the relatively uniform thickness, the
tapers of the inner posterior and anterior surfaces (22 and 18,
respectively) will be the same as those of the corresponding outer
posterior and anterior surfaces (20 and 16, respectively).
[0050] The present invention also comprises a system of a plurality
of differently sized augments that can be held on hand in order to
accommodate tibias of different sizes. It is contemplated that
three or four different sizes in the
anterior/posterior-medial/lateral direction should suffice for most
applications. For example, the lateral/medial dimension could range
from about 40 mm to about 80 mm, when measured from its widest
point (which is at the proximal surface). Thus, if four sizes were
to be used, the lateral/medial dimension of the smallest tibial
augment (at its widest point) would be 48 mm for an extra small
augment, 52 mm for a small augment, 59 mm for a medium augment and
67 mm for a large augment. Additionally, the anterior/posterior
dimension could range from about 30 mm to about 40 mm, when
measured from the widest point in the anterior/posterior direction
(which is at the proximal surface). Thus, the approximate minimum
dimensions for extra small, small, medium, and large augments would
be 33 mm, 34 mm, 36 m and 38 mm, respectively.
[0051] Further two different heights of augments should be
available, where the height is measured from the proximal surface
12 to the distal surface 14. In cases where the decay has only
extended a small distance into the tibia, a shorter augment can be
used than that needed where the decay has extended to a greater
depth of the bone. As a general rule, as much healthy bone should
be preserved as possible. However, if the decay is relatively deep,
two augments of different sizes may be stacked upon each other. For
example, a small augment may be stacked upon an extra small
augment; a medium augment may be stacked upon a small augment; or a
large augment may be stacked upon a medium augment. Due to the
shapes of the outer peripheries of the augments, stacking
essentially creates extensions of the outer lateral, medial,
posterior and anterior surfaces.
[0052] It is believed that two different heights should be
sufficient to remedy most tibial bone decay situations that are
suitable for correction by implantation of a tibial augment. For
example, augments could be available in 15 mm and 30 mm heights.
However, more than two heights may also be produced, if desired.
The tibial augment 10 shown in FIGS. 1 through 3 is one example of
an augment of the 30 mm height, and the tibial augment 40 shown in
FIG. 5 is one example of an augment of the 15 mm height. The
augment 40 of FIG. 5 is essentially the same as the augment 10 of
FIGS. 1 through 4, except for the height thereof. Accordingly, the
same index numbers have been used in FIG. 5 as those used in FIGS.
1 through 4.
[0053] In order to accommodate the requirements of most situations,
multiple sizes and shapes of augments may be desired. In the
preferred embodiment of a set of augments, six different sizes of
augment are believed to be sufficient--extra small, small, medium
and large in a short height (such as 15 mm) and medium and large in
a tall height (such as 30 mm). Thus, in a system including these
basic sizes, there is no tall height (such as 30 mm) augments in
the extra small size or the small size. It is believed that
defective bone portions corresponding to these two sizes are better
suited to be corrected by other methods.
[0054] Of course, all of the dimensions discussed above (and below)
are being provided by way of example only, and other dimensions are
also contemplated as being within the scope of the invention.
However, the dimensions provided, as divided into four different
increments, are believed to be able to accommodate the needs of the
majority of patients. Accordingly, only a limited stock of
differently sized augments would need to be kept on hand. Thus, for
example, a kit of augments would only need to contain four
different sizes of augments of the 15 mm height, and two different
sizes of augments of the 30 mm height.
[0055] Turning now to FIGS. 6A through 6C, three different stepped
versions of a tibial augment are shown. More specifically, FIG. 6A
shows stepped augment 50, FIG. 6B shows stepped augment 60 and FIG.
6C shows stepped augment 70. Since only the distal surface of the
stepped augments is different from the augment of FIGS. 1 through
4, only that portion needs to be discussed. In addition, the same
index numbers as those used in FIGS. 1 through 4 will be used for
similar features found in FIGS. 6A through 6C.
[0056] FIG. 6A shows tibial augment 50, which includes a stepped
distal surface 14a/14b with a transition surface 52 therebetween.
As shown in the figure, distal surface 14a is located at a greater
distance from the proximal surface 12 than distal surface 14b. In
this embodiment, the transition surface 52 is located approximately
midway between the outer medial surface 30 and the outer lateral
surface 26.
[0057] A second embodiment of a stepped tibial augment is shown in
FIG. 6B, as represented by tibial augment 60. In this embodiment,
as in the FIG. 6A embodiment, distal surface 14a is located at a
greater distance from the proximal surface 12 than distal surface
14b. The main difference between this embodiment and the FIG. 6A
embodiment is the location of the transition surface 52. In this
embodiment, the transition surface 52 is located closer to the
outer lateral surface 26 than to the outer medial surface 30.
[0058] FIG. 6C shows a third embodiment of a stepped tibial augment
70. In this embodiment, as in the embodiments of FIG. 6A and 6B,
distal surface 14a is located at a greater distance from the
proximal surface 12 than distal surface 14b. The main difference
between this embodiment and the other two embodiments is the
location of the transition surface 52. In this embodiment, the
transition surface 52 is located closer to the outer medial surface
30 than to the outer lateral surface 26.
[0059] The embodiments of FIGS. 6A through 6C are especially useful
where there has been uneven tibial decay, i.e., where there is more
decay on either the lateral side or the medial side than on the
other side. By using one of the stepped tibial augments shown in
FIGS. 6A through 6C, more healthy bone, if it exists on one side or
the other, can be preserved, and mostly only defective bone will
end up being removed when forming a stepped cavity to implant the
tibial augment. In other words, the base of the cavity into which
the stepped tibial augment will be implanted will be stepped to
correspond to the stepped distal surface of the augment. Such a
stepped-base cavity provides for preservation of more healthy bone
on the shallower side, as compared with a flat-based cavity where
bone has been removed to a depth equal to the depth of the lowest
damaged area of bone.
[0060] Suggested heights for the stepped tibial augments of FIGS.
6A through 6C are 15 mm and 30 mm (as measured from the proximal
surface 12 to the distal surfaces 14b and 14a, respectively). Of
course, other heights are also contemplated as being within the
scope of the invention.
[0061] FIG. 7 shows an example of a human tibia 80 into which a
cavity 82 has been prepared or formed in a proximal portion
thereof. The cavity 82 of this example has a flat base 84, so it is
suitable for tibial augments with flat distal surfaces, such as
those depicted in FIGS. 1 through 5. However, those of ordinary
skill in the art should be able to adapt the flat base 84 into a
stepped base using the cavity forming techniques described
hereinbelow.
[0062] The tibia 80 of FIG. 7 is shown in a state prior to
implantation of a tibial augment and a knee joint prosthesis. More
specifically, the extreme proximal portion of the tibia 80 has been
removed. Normally, most, if not all, of the removed proximal
portion will be damaged tibial bone. However, a small amount of
healthy bone may also need to be removed at the same time in order
to provide a relatively flat surface upon which the flat-bottomed
tibial base plate 102 (FIG. 8) can be seated.
[0063] Either prior to removing the extreme proximal portion 86, or
immediately after removing it (depending upon which surgical
techniques are used), an intramedullary rod 88 may be inserted and
used to define the relationship between the knee prosthesis stem
and the tibial augment.
[0064] An example of a tibial augment 10 that has been implanted
into a human tibia is shown in FIG. 8. This figure shows how the
tibial augment 10 that is seated within a cavity, such as cavity 82
of FIG. 7, is positioned directly distal of the stemmed tibial base
plate 102. Preferably, the tibial base plate 102 is cemented to the
tibial augment 10. The remainder of the components of the knee
joint prosthesis 100 (the articulating surface 106, the femoral
component 108, etc.) are all implanted in the customary manner. It
should be noted that although only one form of knee joint
prosthesis has been shown and described, the tibial augments of the
present invention can be used with other types of knee joint
prostheses.
[0065] FIG. 9 shows an example of a provisional tibial augment 90,
which is a temporary augment used as a test to ensure that the
permanent augment will fit properly within the cavity. Although
only one size provisional is shown and described, provisional
augments should be made to correspond to every size of tibial
augment, including the stepped augments. There are two main
differences between the provisional augment 90 and the permanent
augments of FIGS. 1 through 6C.
[0066] First, the provisional augment 90 may be made of a material
which indicates the bony areas of the provisional so that the
surgeon can visualize how the augment fits within the cavity. For
example, the provisional may be made of a transparent or
photo-elastic material. One example of a suggested material for the
provisional is polyphenylsulfone, although other materials are also
contemplated.
[0067] Second, provisional augments preferably include a set of
grooves 92/94 on the inner medial surface 28 and the inner lateral
surface 24. These grooves 92 and 94 extend in the generally
lateral/medial direction, and are configured to cooperate with ribs
96 on holder 110 shown in FIG. 10. The holder 110 is designed to
facilitate insertion and removal of the provisional augment 90
to/from the cavity 82 (FIG. 7) in order to determine that there is
a proper fit between the cavity and the provisional augment (and
therefore there is necessarily a proper fit with the permanent
augment also, since both the provisional and the permanent augment
are the same size and shape).
[0068] The holder 110 includes two flexible legs 112 that extend in
one direction (to the left, as shown in FIGS. 10 and 11) to a body
portion 114 that is topped with a crown portion 116. As shown
towards the right-hand sides of FIGS. 10 and 11, each leg 112
connects with a shoulder portion 118. Each shoulder portion 118 in
turn extends into a finger portion 120, upon which the ribs 96 are
situated. The lowermost surfaces of the shoulders 118 each include
a stop surface 122, which is used to align the holder 110 with the
proximal surface 12 of the provisional 90 (FIG. 9) to facilitate
the mating of the ribs 96 of the holder 110 with the grooves 92 and
94 of the provisional 90.
[0069] The holder 110 is preferably made of stainless steel, but it
is contemplated that it may also be fabricated from plastic. A key
consideration when selecting material is that the legs 112 must be
flexible enough to be able to be biased inwardly towards each other
with light force applied from the surgeon's thumb and forefinger,
but they must also be resilient enough to return to their original
positions when the force is removed.
[0070] In use, the legs 112 of the holder 110 are flexed inwardly
by the surgeon, and the fingers 120 are inserted into the interior
of the provisional 90 (which is an annular member). Once the stops
122 contact the proximal surface 12 of the provisional, the ribs 96
of the holder should be face to face with the grooves 92 and 94 of
the provisional 90. Pressure on the legs 112 can now be released,
and the legs 112 will flex outwardly until the ribs 96 mate with
the grooves 92 and 94. At this point, the holder 110 can be moved
(such as by holding the crown portion 116 and/or by the body
portion 114), and the provisional 90 will remain attached to the
holder 110, for inserting/removing the provisional 90 to/from the
cavity 82 (FIG. 7).
[0071] One important feature of the holder 110 is that it can be
disengaged from the provisional without affecting the position of
the provisional. Thus, once the provisional is seated in the
desired position, the legs 112 can be squeezed together, and the
holder 110 can be removed without disrupting the position of the
provisional.
[0072] Only one size holder 110 has been shown, but it should be
understood that since the ribs of the holder are specifically
configured to make contact with the grooves on the inner surfaces
of a provisional tibial augment, a different sized holder is
necessary for each different sized provisional. However, since the
grooves are near the proximal surface of the each provisional, no
additional holder needs to be fabricated for a provisional that has
the same sized proximal surface as another provisional. In the
preferred set of augments and provisionals, there are six basic
sizes--(1) extra small with 15 mm height; (2) small with 15 mm
height; (3) medium with 15 mm height; (4) medium with 30 mm height;
and (5) large with 15 mm height and (6) large with 30 mm height.
However, in the preferred embodiment, the 30 mm height medium-sized
provisional (or augment) is essentially a 15 mm height medium-sized
provisional (augment) stacked upon a 15 mm height small-sized
provisional (augment). Similarly, in the preferred embodiment, the
30 mm height large-sized provisional (or augment) is essentially a
15 mm large-sized provisional (augment) stacked upon a 15 mm
medium-sized provisional (augment). Thus, the 30 mm height
medium-sized provisional can employ the same holder as the 15 mm
medium-sized provisional (since they have the same proximal
dimensions), and the 30 mm large-sized provisional can employ the
same holder as the 15 mm large-sized provisional. Accordingly, in
the preferred set of six differently sized provisionals, only four
holders are utilized because one holder does double duty for both
the 30 mm medium provisional and the 15 mm medium provisional, and
another holder does double duty for both the 30 mm large
provisional and the 15 mm large provisional.
[0073] Further, if extra small, small, medium and large stepped
provisionals are also included, the number of holders does not need
to be increased because the rib spacing on a stepped provisional is
the same as that of a similarly sized flat-bottomed provisional.
Thus, the extra small holder can be used with the extra small
stepped provisional, the small holder with the small stepped
provisional, the medium holder with the medium stepped provisional,
and the large holder with the large stepped provisional.
[0074] Turning now to FIGS. 12 and 13, a second embodiment of the
holder will be shown and described. The second embodiment of the
holder, which will be designated as holder 111, is adjustable so
that it can be used with provisionals of a variety of different
sizes, as well as with provisionals other than tibial augment
provisionals, such as femoral provisionals. Holder 111 includes a
body portion 113 that serves as a handle and may optionally include
a ribbed surface 115 that allows for a more secure grip. The body
portion 113, which defines a longitudinal axis (a vertical axis as
shown in FIGS. 12 and 13), is connected to a pair of legs 117.
These legs 117 are each preferably L-shaped, and are preferably
attached to the lower portion of the body portion 113 by welding
(although other attaching means, such as screws, may be used
instead). On the other hand, if desired, the legs 117 and the body
portion 113 may be formed as a single unit, such as by casting,
which will eliminate the need for any attaching means for
connecting the legs with the body portion. When viewed together,
the body portion 113 and the legs 117 define a generally
fork-shaped component, as shown in FIG. 13.
[0075] Each of the legs 117 includes a finger 119 connected
thereto. The fingers 119 are preferably connected to the legs 117
via an externally threaded shaft 121. The threaded shaft 121 is
divided in half such that one half is threaded in one direction and
the other half is threaded in the opposite direction. Each of the
fingers includes an internally threaded aperture 123 that is
configured to mate with the associated portion of the threaded
shaft 121. Thus, when knob 125 is turned in one direction, the
threaded shaft 121 will rotate within threaded apertures 123, which
will cause the fingers 119 to separate from each other, and when
the knob is turned in the other direction, the fingers 119 will
move towards each other. For example, the threaded shaft 121 could
be configured such that clockwise rotation of the knob 125 will
cause the fingers 119 to move closer together and counterclockwise
rotation will cause the fingers to move farther apart (or, if
desired, it could be configured in the opposite manner, where
clockwise rotation causes greater separation and counterclockwise
rotation reduces the separation distance). As shown in FIG. 13,
each of the fingers 119 preferably includes a thickened portion
129, which serves to increase the contact area between the threaded
aperture 123 and the threaded shaft 121. Thickened portions 129
also provide stops that prevent the fingers 119 from coming too
close together.
[0076] For the purpose of connecting the threaded shaft 121 to the
legs 117, each of the legs preferably includes an open-ended slot
127 for receiving the ends of the shaft, which are preferably not
threaded. After one end of the threaded shaft 121 has been inserted
into each slot 127, a small metal block is welded to each slot to
close its open-end, which serves to maintain the threaded shaft in
position, while still allowing rotation of the threaded shaft with
respect to the legs. Of course, other methods of attaching the
threaded shaft 121 to the legs 117 are also contemplated as being
within the scope of the invention.
[0077] A secondary shaft 131 is also provided in parallel with the
threaded shaft 121. The secondary shaft 131 is preferably not
threaded, and is provided in order to prevent the fingers 119 from
rotating with respect to the legs 117 when the threaded shaft 121
is rotated. The fingers 119 are connected to the secondary shaft
131 via a pair of apertures 133 (where one aperture extends through
each finger), which allows the fingers to slide along, as well as
rotate with respect to, the secondary shaft 131. Optionally, in
order to alleviate possible binding as the fingers 119 travel along
the secondary shaft 131, the secondary shaft may be slightly
tapered from the center thereof. For example, the center portion
135 may be made of full diameter, and extending outwardly therefrom
towards the legs 117, the secondary shaft 131 may include a one
degree taper (although tapers of different degrees may also be
provided), with the ends seated within apertures 133 preferably
being of the same diameter as the center portion 135. Preferably,
the secondary shaft 131 is welded in place at the apertures 133,
although other ways of attaching the secondary shaft to the legs
may also be used. Additionally, other means of preventing the
fingers 119 from rotating with respect to the threaded shaft are
also contemplated as being within the scope of the invention. For
example, the legs and/or the body portion may include some form of
protrusion extending therefrom for preventing rotation of the
fingers 119 with respect to the legs 117, but which still permits
the fingers to move sideways (i.e., towards and away from each
other) with respect to the legs. As another example, the upper
portions of the fingers 119 may be configured to include forks that
extend upwardly to straddle the legs 117 and/or the lower portion
of the body portion 113.
[0078] Each of the fingers 119 also includes a rib 137, and they
also each preferably include a stop surface 139. As with holder 110
of FIGS. 10 and 11, the ribs 137 of holder 111 are configured to
mate with the grooves 92 and 94 of the provisional 90 (FIG. 9) for
inserting and removing the provisional to/from the cavity, and the
stop surfaces 139 are used to align the holder 111 with the
proximal surface 12 of the provisional 90 to facilitate mating the
ribs of the holder with the grooves of the provisional.
[0079] The holder 111 is preferably made of stainless steel or of
another metal, but other materials may be used for all or for only
some of the components. For example, plastic may be used for
certain parts such as the body portion 113, the knob 125 and the
secondary shaft 131, while a metal or other different material may
be used for the remaining components.
[0080] In order to accommodate many different sizes of tibial
augment provisionals, as well other types of provisionals (such as
femoral provisionals), the spacing of the fingers 119 should be
able to be adjusted so that the fingers are far enough apart to
enable the ribs 137 to engage with the grooves of the largest
provisional, as well as to be adjusted to be close enough together
for use with the smallest provisional. For example, a distance of
approximately two inches between the outer surfaces of the fingers
119 when separated at the maximum distance and a distance of
approximately three quarters of an inch when separated at the
minimum distance should be sufficient for most uses. Of course,
these dimensions are only provided as a suggestion, and other
dimensions may also be used.
[0081] In use, the knob 125 is rotated to separate the fingers 119
by a distance that is less than the distance that separates the
grooves of the provisional being acted upon (such as grooves 92 and
94 of provisional 90 in FIG. 9). The stop surface 139 is positioned
upon the proximal surface of the provisional, and the ribs 137 of
the holder are aligned with the grooves 92 and 94 of the
provisional 90 (FIG. 9). The knob 125 is again rotated to make the
ribs 137 engage the grooves 92 and 92, and the provisional 90 is
inserted into the cavity 82 (FIG. 7). The holder 111 can be
disengaged from the provisional 90 by rotating the knob 125 to
bring the fingers 119 closer together, separating the ribs 137 from
the grooves 92 and 94. One important feature of the holder 111 is
that is allows the ribs to be disengaged from the grooves without
significantly altering the location of the provisional within the
cavity. When the provisional 90 is to be removed from the cavity
82, the holder 111 is again used in the manner described above.
[0082] The preferred embodiments of the provisional and holder
combination have been shown and described with grooves on the inner
lateral and medial surfaces. However, it is also contemplated that
the grooves could be placed on the inner anterior and posterior
surfaces, and that the spacing of the fingers on the holder could
be adjusted accordingly. Further, detents could be substituted for
the grooves, and a spring loaded holder for mating with the detents
could also be used.
[0083] It is also contemplated that other means for inserting the
provisional may also be used. For example, the provisional may
include a threaded circular holder into which a threaded handle
member can be inserted and removed.
[0084] Turning now to FIGS. 14 through 17, these figures show an
example of a tibial augment pusher 130, which is used to seat a
tibial augment within the cavity of the proximal portion of the
tibia. The pusher 130 (or one of the holders) may also be used in
conjunction with the provisional tibial augment as a tamp. In
situations where a bone graft is necessary to fill a void within
the tibia in preparation for receiving the provisional tibial
augment within the cavity, the void could be filled with morselized
bone and the provisional tibial augment (in combination with a
holder or pusher) could be used to tamp the morselized bone into
place.
[0085] The pusher 130 includes a handle portion 132 and an augment
seating portion 134. The augment seating portion 134 is further
divided into a head portion 136 and a platform portion 138. The
head portion 136 is preferably shaped to mimic the interior
surfaces of the tibial augment 10 (FIG. 1), except the head portion
136 is slightly smaller than the corresponding surfaces of the
tibial augment 10 associated therewith, which permits the head
portion 136 to be easily seated within (and easily withdrawn from)
the tibial augment 10. More specifically, there is preferably
approximately 0.030 inches (0.762 mm) clearance between the outer
surface of the head portion 136 and the inner surfaces of the
tibial augment 10, as represented by distance "X" in FIG. 17, which
includes (in the main view) a front view of pusher 130 and a
magnified view of part of the head portion 136 of the same pusher,
but with a tibial augment 10 seated thereon. That is, the magnified
view of FIG. 17 shows the head portion 136 in hidden lines to
represent that the head portion is hidden behind the augment 10,
with the inner surface of the augment (also in hidden lines) spaced
from the outer surface of the head portion 136 by distance "X."
[0086] As also shown in the magnified portion of FIG. 17, the
proximal surface 12 of the augment 10 contacts the planar surface
140 of the platform portion 138, which provides a surface from
which the surgeon can apply light pressure to the augment 10 to
align, locate, and to seat it within the cavity 82 (FIG. 7). As can
be seen in FIGS. 16 and 17, the planar surface 140 is provided upon
the platform portion 138 at the interface between the platform
portion 138 and the head portion 136.
[0087] Since the shape of the head portion 136 mimics the shape of
the interior surfaces of the augment 10, it follows that the head
portion 136 should have a taper of approximately 19 degrees (+/-3
degrees) at the surface that corresponds to the inner medial and
lateral surfaces (as shown in FIG. 17), and that it should have a
taper of approximately 12 degrees (+/-3 degrees) at the surface
that corresponds to the inner posterior surface (as shown in FIG.
16). Further, as also shown in FIG. 16, the surface of the head
portion 136 that corresponds to the inner anterior surface is not
tapered, but is instead substantially perpendicular to the platform
portion 138.
[0088] In order to properly orient a tibial augment 10 within a
cavity, the pusher 130 must have a head portion 136 that is
appropriately shaped, as discussed above, and the head portion must
also be appropriately sized. Thus, as with the provisional holders
110 discussed earlier, a number of pushers may be provided for the
set of augments. For example, if there are four sizes of augments
(extra small, small, medium and large), with two heights available
(15 mm and 30 mm) for the medium and the large sizes only, then
there is a total of six differently sized augments. Accordingly, as
with the provisional holders 110, there should also be four
differently sized pushers--one pusher for the 15 mm extra small
augment; one for the 15 mm small augment; one for the 15 mm medium
augment, the 30 mm medium augment, and the medium stepped augments;
and one for the 15 large augment, the 30 mm large augment, and the
large stepped augments.
[0089] In its preferred form, each pusher 130 is preferably made
with an aluminum handle portion 132 and an acetyl seating portion
134. However, other materials can also be used. For example, the
seating portion could be made from various polymers or metals and
the handle portion could be made of a different metal or from
plastic.
[0090] Turning now to FIGS. 18 through 28, a guide and several
associated osteotomes that are all used to create a cavity in the
tibia are shown and will be described next. One important aspect of
the present invention is that the cavity formed in the tibia (such
as cavity 82 of FIG. 7) must be carefully created so that the
tibial augment fits as precisely as possible. Among the advantages
of a precise fit is that the more precise the fit, the greater the
stability of the implant. Accordingly, the present invention
includes tools and a method of creating a cavity of the proper size
and shape. Although only one method of creating the cavity will be
shown and described, other methods may also be used as a supplement
to or in place of the method described. For example, a rasp
technique may be used to either create the cavity or to make fine
adjustments to a cavity created by another method. With such a
technique, a rasp shaped like a tibial augment (with a rasp-like
outer surface and a handle) is used to remove the bone and form the
cavity (or to make fine adjustments to the shape of the
cavity).
[0091] FIG. 18 shows a preferred embodiment of a guide 142 with a
first curved osteotome 144 inserted into a portion of a slot 146
formed within the guide 142. FIG. 25 shows a second curved
osteotome 148 (inserted into the guide 142), and FIG. 26 shows a
straight osteotome 150 (also inserted into the guide 142). As the
following description will show, all three different osteotomes
(144, 148 and 150) are required to form the cavity 82 (FIG. 7)
because of the configuration of the slot 146, which is specifically
configured to properly orient the osteotomes to create a cavity
that corresponds to the tibial augment being implanted therein. The
osteotomes 144, 148 and 150 are preferably made of stainless steel,
although other materials are also contemplated.
[0092] As with several of the other components, the osteotomes and
guides are preferably configured in a variety of different sizes.
In the preferred embodiment, there are four sets of osteotomes
(extra small, small, medium and large) and four guides (extra
small, small, medium, and large). As described more fully below,
these four sets of osteotomes and four guides can be used to create
a cavity in the tibia for any of the 15 mm, 30 mm or stepped
augments of the preferred embodiment.
[0093] Turning first to FIGS. 18, 21 and 22, the first curved
osteotome 144 includes a handle 152 with a crown 154 at the top end
thereof. The curved osteotome 144 also includes a cutting portion
156 attached to the handle 152, and the cutting portion includes a
tapered edge 158 at its far end and a plurality of first (or
distal) stops 160 for hindering the cutting portion from extending
into the slot 146 of the guide 142 past a predetermined distance.
The cutting portion 156 of the osteotome 144 also includes at least
one second (or proximal) stop 162. As described more fully below,
the slot 146 in the guide 142 preferably includes a plurality of
cutouts 147 (FIG. 19), which allow the distal stops 160 to pass
through in order to use the proximal stop 162.
[0094] The proximal stop 162 is placed at a greater distance from
the tapered edge 158 than the distal stops 160, as can be seen in
FIGS. 21 and 22. The use of such staggered stops allows a single
osteotome to be used to make two different cavities of two
different depths, depending upon which stop is used and also
depending upon which size guide is used. Thus, for example,
assuming that tibial augments are provided in two different heights
(such as 15 mm and 30 mm), accommodations must be made to provide
cavities of two different depths (15 mm and 30 mm) so that the
depth of the cavity coincides with the height of the tibial augment
being placed therein. When a shallow cavity is needed, the set of
osteotomes is inserted into the same sized guide (e.g., the set of
small osteotomes is used with the small guide, etc.) whereby the
exterior stops 160 contact a planar top surface 143 of the guide,
hindering the cutting portion 156 from extending further into the
guide, and accordingly hindering further extension into the bone.
By inserting the set of osteotomes into the same sized guide,
distal stops 160 do not mate with cutouts 147, and therefore stops
160 do not pass through cutouts 147. On the other hand, if a deep
cavity is needed, the same set of osteotomes are inserted into the
incrementally larger guide (e.g. the small osteotomes are used with
the medium guide), whereby the distal stops 160 pass through
cutouts 147 and the proximal stop 162 contacts the planar top
surface 143 of the guide, hindering the cutting portion 156 from
extending further into the guide, and accordingly hindering further
extension into the bone. The distal and proximal stops of the other
osteotomes function in a similar manner. Although in the examples
provided the distal and proximal stops have been shown and
described as being on the radially exterior sides of the
osteotomes, some or all of the stops may be provided on the
radially interior sides of the osteotomes. Of course, if all stops
are provided on the radially interior sides of the osteotomes, then
the cutouts 147 on the guide 142 would have to be changed to be on
the radially interior side of the slot 146. Additionally, if the
distal stops are provided on the radially exterior side of the
osteotome and the proximal stops are provided on the radially
interior side (or vice versa), then the cutouts 17 could be
omitted, if desired, as long as the slot was made wide enough to
accept the cutting portion 156 including the stops.
[0095] As mentioned above, FIG. 25 shows an example of a second
curved osteotome 148. The second curved osteotome 148 is very
similar to the first curved osteotome 144 in that it also includes
a handle 164, a crown 166, and a cutting portion 168 with a tapered
edge 170 and a plurality of distal stops 172, as well as at least
one proximal stop 174.
[0096] Although it appears as though the first curved osteotome 144
and the second curved osteotome 148 are identical to each other,
but are just shown in different orientations, in actuality, they
are mirror images of each other. More specifically, the front
cutting area 176 of the first curved osteotome 144 and the front
cutting area 178 of the second curved osteotome 148 each have no
inclination, which corresponds to the outer anterior surface 16 of
the tibial augment 10 (FIG. 4) that also has no incline. Similarly,
since the outer posterior surface 20 preferably has an incline of
approximately 12 degrees (although inclines within the range of
between about 0 to about 17 degrees may also be used), as shown in
FIG. 4, the posterior cutting area 184 of the first curved
osteotome 144 and the posterior cutting area 186 of the second
curved osteotome 148 is also provided with an incline of 12 degrees
(or a corresponding incline within the range of about 0 to about 17
degrees, depending upon the exact degree of incline provided to the
anterior surface of the tibial augment). Likewise, the outer medial
surface 30 and the outer lateral surface 26 of the tibial augment
10 are preferably inclined at 19 degrees (or within the range of
between about 8 to about 30 degrees), as shown in FIG. 3, the side
cutting area 180 of first curved osteotome 144 and the side cutting
area 182 of second curved osteotome 148 are also inclined at 19
degrees (or at whatever selected angle between 8 and 30 degrees
that the outer lateral and outer medial surfaces of the augment are
provided at). FIGS. 23 and 24 also show how cutting portion 156 is
a mirror image of cutting portion 168. Accordingly, the second
curved osteotome 148 is not interchangeable with the first curved
osteotome 144.
[0097] FIGS. 26 through 28 show straight osteotome 150. Like the
other osteotomes, the straight osteotome includes a handle 188, a
crown 190, and a cutting portion 192 with a tapered edge 194,
distal stops 196, and at least one proximal stop 198. As shown in
FIG. 27, the cutting portion 192 is preferably inclined with
respect to the handle. This degree of incline corresponds to the
degree of incline of the outer posterior surface 20 of the tibial
augment 10 (FIG. 4). Thus, in the preferred embodiment, there is an
incline of approximately 12 degrees. However, inclines of between
approximately 0 degrees and approximately 17 degrees are also
contemplated as being within the scope of the invention, as well as
other degrees of incline. The orientation of the cutting portion
192 with respect to the handle 188 of this osteotome, as well as
the other osteotomes, is intended to allow for the proper cutting
angle when the handle is held perpendicular to the tibial surface
within which the cavity 82 (FIG. 7) has been formed.
[0098] Moreover, as shown in FIGS. 18 through 20, 25 and 26, the
guide 142 is also provided so that the proper cutting orientation
of the osteotomes is maintained, which thereby aids in making a
cavity with sidewalls of inclines that correspond to the inclines
on the outer surfaces of the tibial augment. As mentioned earlier,
the guide 142 includes a slot 146 for guiding the cutting portions
(156, 168, 192) of the osteotomes (144, 148, 150). Each portion of
the slot 146 is made with a particular incline that matches the
incline of the corresponding outer surface of the tibial augment
associated therewith. Thus, for example, as shown in hidden lines
in FIG. 18, the slot's lateral portion 200 and the slot's medial
portion 202 are inclined, respectively, to match the slopes of the
outer lateral surface 26 and the outer medial surface 30 of the
tibial augment 10, which in the preferred embodiment is a 19 degree
incline. Likewise, the slot's posterior portion 204 and its
anterior portion 206 are also configured to correspond of the
incline of, respectively, the outer posterior surface 20 and the
outer anterior surface 16 of the tibial augment 10. Thus, in the
preferred embodiment, the slot's posterior portion 204 will be
inclined at approximately 12 degrees and the slot's anterior
portion 206 will have no incline.
[0099] The guide 142 also includes a securing arrangement that is
used to secure the guide to the bone within which the cavity is
being formed. The securing arrangement includes an aperture 208
that is configured to receive the intramedullary rod 88 (FIG. 7),
which serves as both a reference point for the guide and as the
stable member that the guide is secured upon. The securing
arrangement also includes a threaded hole 210 (FIG. 18) that is
configured to receive a setscrew 212 (FIG. 19), which is comprised
of a head 214 and a threaded shaft 216. Alternately, the setscrew
could also be replaced with a thumbscrew or the head could be
replaced with a lever or small handle to facilitate tightening
without the need for a screwdriver. The threaded hole 210 is
preferably made within a collar 218, which allows for additional
length of the setscrew 212, and also allows for also easier access
to the head of the setscrew, which may be necessary, especially if
a thumbscrew of other similar component is used in place of the
setscrew.
[0100] The slot 146 of the guide 142 is not annular, but instead
includes a gap near its anterior portion 206, as best shown in FIG.
19. This gap is where the threaded shaft 216 of the setscrew
extends through the guide. If this gap in the slot 146 were not
present, there is a chance that the threaded shaft 216 of the
setscrew could accidentally be damaged if an osteotome were
inserted into the slot at this area. Damaging the setscrew could
result in misalignment of the guide with respect to the bone, or it
could make it difficult to remove the guide from the intramedullary
rod 88.
[0101] With regard to sizing, there should be one guide and one set
of three osteotomes (two curved and one straight osteotome) for
each 15 mm sized tibial augment. Further, additional guides and
osteotomes need not be provided for the 30 mm sized or for the
stepped augments. Thus, if four sizes of augments (extra small,
small, medium and large) are provided, there should be four
different sizes of guides and four sets of osteotomes, with three
osteotomes in each set, for a total of twelve different osteotomes.
To make cavities for any of the 15 mm augments, the same sized set
of osteotomes and guide are used. For example, to make a cavity for
a 15 mm extra small augment, the extra small set of osteotomes and
the extra small guide is used. However, to make a cavity for one of
the 30 mm augments, the same sized guide is used, but the set of
osteotomes for the next smaller size is used. For example, to make
a cavity for a 30 mm medium augment, the medium guide is used along
with the small set of osteotomes. In other words, no matter what
depth cavity is being created (15 mm or 30 mm), the guide that is
the same size as the augment being inserted (extra small, small,
medium or large) will always be used. However, when 30 mm depth
cavities are being created, the set of osteotomes of one size
smaller than the augment are used, otherwise (for 15 mm depth
cavities), the set of osteotomes of the same size as the augment
are used.
[0102] To further clarify this point, the following specific
examples are provided. Assume that one intends to prepare a cavity
suitable for the medium sized augment (of either 15 mm height or 30
mm height). First, for either case (15 mm or 30 mm), the medium
sized guide 142 is affixed to the intramedullary rod 88. For
creating a 15 mm depth cavity for the medium augment, medium
osteotome 144 is inserted into the correspondingly sized medium
guide, whereby the distal stop 160 contacts the planar top surface
143 of the guide, hindering the cutting portion 156 from extending
further into the guide, past the desired 15 mm depth. The other
medium osteotomes are also used in the same manner, with the stops
operating in a similar manner to create a 15 mm depth cavity for
the 15 mm medium augment.
[0103] To create a 30 mm depth cavity for the 30 mm medium augment,
the set of small osteotomes (i.e., the osteotomes of one
incremental size smaller than the augment) would be inserted into
the appropriate position of the slot 146, instead of using the
medium osteotomes discussed above. When small osteotome 144 is
appropriately inserted into the incrementally larger medium guide,
the distal stop 160 passes through the medium guide cutout 147,
allowing the cutting portion 156 of the osteotome to extend further
into the bone until the proximal stop 162 contacts the planar top
surface 143 of the guide. The contact of the proximal stop 162 with
the top planar surface hinders the cutting portion from extending
further into the guide than the desired 30 mm, and accordingly
hinders further extension into the bone. (On the other hand, if
small osteotome 144 is inserted into the correspondingly sized
small guide, the distal stop 160 contacts the planar top surface
143 of the guide, hindering the cutting portion of the 156 from
extending further into the guide so that a 15 mm deep cavity can be
created). The distal and proximal stops of the other small
osteotomes function in a similar manner, and a 30 mm depth cavity
for the medium augment is created by using all three small
osteotomes with the medium guide.
[0104] To form a cavity in the proximal portion of the tibia, an
appropriately sized guide 142 and an appropriately sized set of
osteotomes are selected. After the intramedullary rod 88 (FIG. 7)
has been implanted within the tibia 80, the aperture 208 of the
guide 142 is slid over the intramedullary rod 88, and the guide 142
is secured in place by tightening the setscrew 212. It should be
noted that the aperture 208 is preferably triangular, as best shown
in FIG. 19, which allows for the intramedullary rod 88 to have an
increasingly secure fit as the setscrew is tightened because of the
way the rod is seated at the apex of the triangle.
[0105] Once the guide 142 is securely attached to intramedullary
rod 88, one of the appropriately sized osteotomes, such as the
first curved osteotome 144, is inserted into the appropriate
position of the slot 146. More specifically, the first curved
osteotome 144 is inserted into portion 200 of the slot 146. It
should be noted that the osteotomes may be used in any desired
order.
[0106] As discussed above, the desired depth of cavity is formed by
using the appropriate combination of a particularly sized set of
osteotomes with an appropriately sized guide, whereby either
proximal stops 198 or distal stops 196 are utilized to result in a
cut of an appropriate depth. Also, if one of the stepped tibial
augments shown in FIGS. 6A through 6C is intended to be implanted,
cuts of one depth may be made at one area of the cavity and cuts of
another depth may be made at another area in order to form an
appropriate cavity with a stepped bottom to accommodate the stepped
distal surface 14a/14b of FIGS. 6A through 6C.
[0107] Next, one of the other osteotomes, such as the straight
osteotome 150 (FIGS. 26-28), is inserted into the appropriate
portion of the slot. As shown in FIG. 26, the straight osteotome
150 is inserted into the slot's posterior portion 204 (best seen in
FIG. 19). As described above, the appropriate stop, or stops,
(either proximal stop 198 or distal stops 196) is/are utilized to
result in a cut of the appropriate depth.
[0108] Finally, the remaining osteotome, which in this case is the
second curved osteotome 148 (FIG. 25), is inserted into the
appropriate portion of the slot 146, which in this case is the
medial portion 202 (FIG. 19). As with the other osteotomes, the
appropriate stop, or stops, (either proximal stop 174 or distal
stops 172) is/are utilized to result in a cut of the appropriate
depth. After all three osteotomes have been used, the guide 142 may
be removed from the intramedullary rod 80 by loosening the setscrew
218 and sliding the guide upwardly and off of the intramedullary
rod. At this point, the bone to be removed should be cut to the
desired depth, and it merely needs to be taken from the site to
form the cavity 82 (FIG. 7). If necessary, an additional cut may
need to be made with the straight osteotome 150, or one of the
other osteotomes, at the area below the gap in the slot 146,
between the two edges of the anterior portion 206 (FIG. 19).
However, the decayed bone at that area may is simply fall from the
peripheral bone without requiring an additional cut. Once the bone
is completely removed from within the cut area formed by the
osteotomes, a cavity that corresponds to the tibial augment being
inserted therein should result.
[0109] After forming the cavity, which alternatively could be
formed using the rasp technique mentioned earlier, as well as by
other known techniques, the provisional augment 90 (FIG. 9) may be
temporarily implanted to determine whether the cavity is properly
sized, or if additional bone needs to be removed. The provisional
may be inserted either with the aid of one of the holders 110 or
111 (FIGS. 10 and 12) or by using one of the pushers 130 (FIG. 14),
or with a combination of both a holder and a pusher. At this point,
the provisional 90 may also be used to trial the locations of the
tibial base plate provisionals (or the provisionals of the tibial
tray and stem). After the fit is adequately tested with the
provisional 90, it can be removed by using the provisional holder
110 or 111 in the manner previously described. Then, the permanent
tibial augment, such as augment 10 of FIG. 1, is inserted using the
pusher 130 (FIG. 12). After properly seating the augment within the
cavity, cement is applied to the proximal surface 12 of the
augment, and the stemmed tibial base plate 102 (FIG. 8) is attached
to the augment and to the peripheral bone remaining around the
cavity. Then, the remainder of the knee joint prosthesis 100 is
attached using any desired method, and the surgical procedure
continues in the customary manner.
[0110] While various embodiments of the present invention have been
shown and described, it should be understood that other
modifications, substitutions and alternatives may be apparent to
one of ordinary skill in the art. Such modifications, substitutions
and alternatives can be made without departing from the spirit and
scope of the invention, which should be determined from the
appended claims.
[0111] Various features of the invention are set forth in the
appended claims.
* * * * *