U.S. patent application number 15/077055 was filed with the patent office on 2016-09-15 for instruments for knee placement.
The applicant listed for this patent is Smith & Nephew, Inc.. Invention is credited to Ryan L. Landon.
Application Number | 20160262899 15/077055 |
Document ID | / |
Family ID | 45568208 |
Filed Date | 2016-09-15 |
United States Patent
Application |
20160262899 |
Kind Code |
A1 |
Landon; Ryan L. |
September 15, 2016 |
INSTRUMENTS FOR KNEE PLACEMENT
Abstract
There are provided various embodiments of medical instruments to
perform knee surgery. In one embodiment a finned platform for
mounting a cutting block is provided. The finned platform can be
used on either a femur or tibia to allow for the proper cuts when
performing a knee surgery. In another embodiment, a tibial trial is
shown having a fin. The fin is useful to reinforce the bone to
reduce the risk of fracture during bone preparation. In another
embodiment, a reamer is provided having a plurality of cutting
flutes. It may be desirable to utilize a guide with the reamer to
allow the reamer to cut a non-circular portion of the tibial bone.
In yet another embodiment, a plurality of fixation pegs are
provided on the tibial implant to allow for easy removal of such
implant if a revision surgery becomes necessary.
Inventors: |
Landon; Ryan L.; (Southaven,
MS) |
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Applicant: |
Name |
City |
State |
Country |
Type |
Smith & Nephew, Inc. |
Memphis |
TN |
US |
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|
Family ID: |
45568208 |
Appl. No.: |
15/077055 |
Filed: |
March 22, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13816844 |
Mar 12, 2013 |
9301846 |
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PCT/US11/47542 |
Aug 12, 2011 |
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15077055 |
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61373709 |
Aug 13, 2010 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61B 2017/922 20130101;
A61B 17/1764 20130101; A61F 2002/30884 20130101; A61F 2002/30354
20130101; A61B 17/92 20130101; A61F 2210/0004 20130101; A61F
2002/30405 20130101; A61B 17/157 20130101; A61B 17/1659 20130101;
A61F 2002/30332 20130101; A61B 17/155 20130101; A61B 2017/90
20130101; A61B 17/154 20130101; A61F 2/389 20130101; B33Y 80/00
20141201; A61F 2002/30604 20130101; A61B 17/1675 20130101; A61F
2310/00011 20130101; A61F 2/3859 20130101; A61F 2/3877
20130101 |
International
Class: |
A61F 2/38 20060101
A61F002/38; A61B 17/92 20060101 A61B017/92; A61B 17/15 20060101
A61B017/15 |
Claims
1. A platform that supports a medical device, comprising: a head
having a substantially planar upper support surface; a shaft
depending from the head; and a fin laterally extending from the
shaft for gripping a bone segment such that upon insertion of the
shaft and fin into the bone segment, the substantially planar upper
support surface of the head is contiguous with a corresponding
surface of the medical device to thereby support the medical device
on the platform.
2. The platform according to claim 1, wherein the fin is in the
form of a continuous thread extending about the shaft.
3. The platform according to claim 1, wherein the fin is in the
form of a plurality of ribs extending about the shaft.
4. The platform according to claim 1, wherein the fin is in the
form of a plurality of longitudinally extending ribs extending
along the shaft.
5. The platform according to claim 1, wherein the bone segment is
the distal portion of the femur adjacent the knee joint.
6. The platform according to claim 1, wherein the bone segment is
the proximal portion of the tibia adjacent the knee joint.
7. The platform according to claim 1, wherein the medical device is
a bone cutting block.
8. The platform according to claim 1, wherein the medical device is
an orthopedic knee implant.
9. The platform according to claim 1, wherein the head defines a
depression or opening that receives a spike or projection depending
from the medical device to thereby engage the medical device with
the head.
10. The platform according to claim 1, wherein the fins has a
greater lateral surface relative to a thickness of the fin to
adequately engage the relatively soft, spongy bone segment.
11. The platform according to claim 1, wherein the platform is made
of a metal material.
12. The platform according to claim 1, wherein the platform is made
of a polymer material.
13. The platform according to claim 1, wherein the platform is made
of a resorbable material.
14. The platform according to claim 7, wherein the platform is
removable from the bone segment alter use with the bone cutting
block.
15. The platform according to claim 8, wherein the platform is
permanently maintained in the bone segment to support the
orthopedic knee implant.
16. A platform that supports a medical device, comprising: a
platform including a head having a substantially planar upper
support surface, a shaft projecting axially from the head, and at
least one fin extending laterally from the shaft and configured for
gripping a bone segment; and wherein the medical device is
supported by the platform with the upper support surface of the
head contiguously engaged with a corresponding surface of the
medical device.
17. The platform according to claim 16, wherein the fin comprises a
thread extending about the shaft.
18. The platform according to claim 16, wherein the fin comprises
at least one rib extending longitudinally along a length of the
shaft.
19. The platform according to claim 16, wherein the head defines a
depression or opening that receives a tip portion of the medical de
vice to thereby engage the medical device with the head.
20. The platform according to claim 16, wherein the shaft comprises
a peg projecting axially from the head, the peg having a solid
inner core portion and a porous outer portion positioned about the
solid inner core portion.
21. The platform according to claim 20, wherein the porous outer
portion comprises a porous cap positioned over the solid inner core
portion.
22. The platform according to claim 20, wherein the solid inner
core portion has a non-circular shape that defines a plurality of
thin portions to facilitate cutting of the inner core portion.
23. The platform according to claim 16, wherein the medical device
comprises a cutting guide engaged with the head of the
platform.
24. The platform according to claim 16, wherein the medical device
comprises an orthopedic knee implant engaged with the head of the
platform.
25. The platform according to claim 16, wherein the medical device
comprises a cutting instrument engaged with the head of the
platform and configured to cut bone.
26. The platform according to claim 25, wherein the cutting
instrument comprises a reamer having one or more cutting
flutes.
27. A platform that supports a medical device, comprising: a
platform having a substantially planar upper support surface and an
opposite lower bone engagement surface, the lower bone engagement
surface including a plurality of teeth extending therefrom and
configured for embedment in underlying bone; and wherein the
medical device is supported by the platform with the upper support
surface of the platform contiguously engaged with a corresponding
surface of the medical device.
28. The platform according to claim 27, wherein the rasp platform
includes a central platform portion movably positioned between a
pair of outer platform portions; and wherein an impaction force
imparted to the central platform portion forces the outer platform
portions in an outward direction away from the central platform
portion to cut and smooth the underlying bone with the plurality of
teeth extending from the lower bone engagement surface.
29. The platform according to claim 28, wherein the central
platform portion is movably interconnected with the pair of outer
platform portions.
30. The platform according to claim 27, further comprising an
impactor engaged with the substantially planar upper support
surface and structured to impart an impaction force on the platform
to embed the plurality of teeth in the bone.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present application is a divisional of U.S. patent
application Ser. No. 13/816,844 filed on Mar. 12, 2013, which is a
U.S. National Phase of International PCT Application No.
PCT/US2011/047542 filed on Aug. 12, 2011, which claims the benefit
of U.S. Provisional Patent Application Ser. No. 61/373,709 filed on
Aug. 13, 2010. The contents of each application are incorporated by
reference in their entirety.
RELATED FIELDS
[0002] Orthopaedic implants and methods involving the same, such
as, but not limited to, orthopaedic implants and methods for the
proximal tibia, such as tibial trays that may include one or more
of a keel and/or a stem and methods for revising the same.
BACKGROUND
[0003] There are several factors that are potentially relevant to
the design and performance of orthopaedic implants. In the example
of a tibial tray, a non-exhaustive list of such factors includes
the implant's flexibility (or the flexibility of certain portions
of the implant or its flexibility about certain axes or other
constructs), which may indicate the degree to which the tray will
conform to the potentially uneven resected surfaces of a proximal
tibia; the implant's rigidity (or the rigidity of certain portions
of the implant or its rigidity about certain axes or other
constructs), which may indicate the degree to which stresses or
other forces imposed by the bony and other anatomy associated with
the knee joint will be transmitted to the peripheral hard cortical
shell of the proximal tibia; the implant's resistance to rotation;
the amount of bone preserved; and/or other potentially relevant
factors. In some instances, accommodation of these or other factors
may require trade-offs to balance competing factors. In some
instances, one or more of these factors will not be considered or
given a high level of importance to the design of an orthopaedic
implant.
[0004] Some known tibial trays include a fin or a keel that may
increase the strength of the implant while also helping to prevent
rotation relative to the bone. In some instances, such fins or
keels may present certain drawbacks. For instance, in some cases,
the fin or keel may impede the visualization of the implant and
surrounding anatomy using x-ray or other imaging technologies. For
instance, it may be desirable in some cases to visualize the
implant and its surrounding anatomy, including the surrounding bony
anatomy, by taking one or more x-rays in planes such as coronal and
sagittal planes or in other planes to assess whether the implant
may be loosening over time. Such loosening might be indicated by
lucent lines appearing in the x-ray image around portions of the
implant or other indications that the bone has receded from the
implant or otherwise has become loose. In some instances, a fin or
keel of the implant may obstruct the ability to view such lucent
lines or may otherwise hinder the evaluation of the image. Other
orthopaedic components might feature these or other structures
similarly impairing visualization of the implant in the bone and
other anatomy.
[0005] Some known tibial trays are difficult to remove or revise.
For some revision procedures, it is necessary to cut around the
existing implant or otherwise position instrumentation about the
implant to loosen it from the surrounding bone and/or other anatomy
before removal. In some instances, particularly, for instance, some
instances where the implant is a tibial tray having a keel, it may
be difficult to cut around certain portions of the keel or
otherwise access certain areas of the bone-implant interface to
loosen the implant. It may be particularly difficult, for instance,
to access certain areas of the bone-implant interface depending on
the surgical approach taken. For instance, if an anterior-medial
incision is used to access the knee joint, the keel structure may
impede a surgeon's access to posterior-lateral portions of the
bone-implant interface. In such instances, removal of the implant
may undesirably require excessive or unintended bone removal as
well.
[0006] In some instances, stability or fixation of the implant,
such as a tibial tray or other implant, in the bone may be of some
significance. For instance, the distribution of "hard" versus
"soft" bone is not always uniform or predictable, and, in some
instances, during bone preparation a punch, drill or other
instrument may penetrate the bone at an undesired angle or position
since it may tend to follow the path of least resistance into
softer bone. Moreover, in some instances, such as some tibial
cases, distal metaphyseal bone may tend to be spongier and softer
than proximal metaphyseal bone. In some implant cases, it may be
difficult to achieve adequate fixation or other stability in the
distal metaphyseal bone. Moreover, with some implants, including
some tibial implants, there may be a tendency over time for the
implant to subside or migrate.
SUMMARY
[0007] There are provided various embodiments of medical
instruments to perform knee surgery. In one embodiment a finned
platform for mounting a cutting block is provided. The finned
platform can be used on either a femur or tibia to allow for the
proper cuts when performing a knee surgery. In another embodiment,
a tibial trial is shown having a fin. The fin is useful to
reinforce the bone to reduce the risk of fracture during bone
preparation. In another embodiment, a reamer is provided having a
plurality of cutting flutes. It may be desirable to utilize a guide
with the reamer to allow the reamer to cut a non-circular portion
of the tibial bone. In yet another embodiment, a plurality of
fixation pegs are provided on the tibial implant to allow for easy
removal of such implant if a revision surgery becomes necessary. In
yet another embodiment, various rasp type instruments are shown to
properly prepare the tibia for a tibial implant. In some
embodiments, the tibial trial is provided with a rasp feature to
allow the trial to be used to properly prepare the tibia for the
tibial implant.
[0008] Some of the non-limiting embodiments of tibial trays
described herein include one or more fins or keels that include or
define holes, openings, recesses, areas formed or filled with
different materials, or other structures or features. Some of the
non-limiting embodiments of tibial trays described herein may
additionally or alternatively include a monolithic, modular or
otherwise connected fluted stem. The present application is not
limited to tibial trays; however, and one of skill in the art will
recognize that at least some of the concepts presented herein could
be applied to other orthopaedic implants.
BRIEF DESCRIPTION OF DRAWINGS
[0009] FIG. 1 is a top plan view of one non-limiting example of a
tibial tray.
[0010] FIG. 2 is a rear elevation view of the tibial tray of FIG.
1.
[0011] FIG. 3 is a side elevation view of the tibial tray of FIG.
1.
[0012] FIG. 4 illustrates a modular stem that may optionally be
used with the tibial tray of FIG. 1.
[0013] FIG. 5 is a distal view of the modular stem of FIG. 4.
[0014] FIG. 6 is a cross-section of the stem of FIG. 4 taken along
line 6-6 shown in FIG. 5.
[0015] FIG. 7 is a cross-section of the stem of FIG. 4 taken along
line 7-7 shown in FIG. 5.
[0016] FIG. 8 illustrates a distal view of an alternative
embodiment of fluting useable with a modular stem such as the
modular stem of FIG. 4.
[0017] FIGS. 9-14 illustrate schematically an alternative
embodiment of a tibial tray with a modular stem.
[0018] FIGS. 15-18 illustrate a finned platform for mounting a
cutting block.
[0019] FIGS. 19-22 illustrate tibial trays having a fin.
[0020] FIGS. 23-26 illustrate a rotatable reamer.
[0021] FIGS. 26-29 illustrate fixation pegs.
[0022] FIGS. 30-34 illustrate instruments for tibial surface
preparation.
[0023] FIGS. 35-39 illustrate a tibial trial for tibial surface
preparation.
DETAILED DESCRIPTION
[0024] FIGS. 1 through 3 illustrate a non-limiting example of a
tibial component 100. As shown in FIGS. 2 and 3, the tibial
component 100 includes support member 110 defining a pair of
openings 112. In some, although not necessarily all, embodiments,
these openings may be sized, positioned, oriented and otherwise
constructed to: (1) reduce by a certain degree the stiffness of the
implant while maintaining a certain degree of strength; (2)
facilitate the visualization (such as through x-ray imaging or
other techniques) of lucent lines or other signs that the implant
is loosening; (3) facilitate the loosening of the tray from the
bony anatomy in the event resection is necessary, such as by
facilitating the movement of cutting or other types of
instrumentation through and to the far side of the keel/stem
portion that would not otherwise be accessible to the cutter or
other instrumentation; and/or (4) facilitate bony-ingrowth or
otherwise enhance the stability of the implant in the bone. In some
embodiments, the openings may not feature all of these benefits or
may provide other beneficial features.
[0025] The support member 110 shown in FIGS. 2 and 3 includes a
stem portion 114 and two arms 116 extending therefrom. In this
particular example, the support member 110 is attached to an
underside of a tibial tray 118 at three points forming a
tripod-like construct. The stem portion 114 shown includes a lower
cylindrical portion 120 and an upper portion 122 that is blended to
the arms 116. In the depicted embodiment, the stem portion 114
slants at an angle a and in an anterior-posterior direction as it
extends away from an inferior surface 124 of the tray 118; however,
in other embodiments, the stem portion 114 may have other
geometries. The stem portion 114 of this particular tibial
component 100 is located anteriorly on the tray 118, although other
locations are also possible. The arms 116 shown in FIGS. 2 and 3
extend posteriorly and outwardly from a mid-point of the stem 114
and curve to connect to the underside of the tibial tray 118. In
other embodiments, other numbers of arms and/or stems in other
configurations and geometries can be employed.
[0026] The arms 116 and stem portion 114 of the support member 110
shown in FIGS. 2 and 3 define two openings 112 abutting the
inferior surface 124 of the tibial tray 118. In other embodiments,
different numbers, configurations, shapes, orientations, and
positionings of the openings may be possible. As discussed below,
in some embodiments, the openings 112 of the support member 110 may
not be "openings" at all in the traditional sense, but may be areas
where other materials or components are located, or in which the
material forming the tibial component 100 has different properties
or characteristics.
[0027] In some embodiments, the openings 112 formed in the support
member 110 increase certain flexibility characteristics of the
tibial component 100 while not overly impinging on a desired
strength characteristic of the component. In some embodiments, the
openings 112 can be sized and shaped so that the remaining solid
material is relatively uniform in shape. In some embodiments, the
remaining solid material is uniform in shape in the regions of
highest stress at the most peripheral edges of the arms 116. In
some embodiments, the opening size can be configured to be short
enough to allow a sawblade to easily clear material away from the
sides while being tall enough to allow a thin and narrow osteotome
to pass through in order to facilitate revision surgery. In other
embodiments, the openings 112 may be configured to only permit a
sawblade or an osteotome, but not both. In some embodiments, such
as, for example, where revisability is not a primary goal, taller
and deeper openings may be used to facilitate maximal ingrowth
through and around the openings.
[0028] In some embodiments, the openings 112 formed in the support
member 110 provide for better visualization of the tibial component
100, the bone surrounding the tibial component, and the interface
or interfaces between the bone and the tibial component 100. The
openings 112, in some embodiments, may act as "windows"
facilitating the visualization of lucent lines or other visual
indications on the imaging data, which may suggest or indicate that
the tibial component is loosening or provide other information for
evaluating other issues or concerns. In some embodiments, the size,
shape, placement and/or orientation of the openings 112 can be
optimized to facilitate visualization of bone-implant interfaces
and other areas of interest for future visualization of the implant
after installation. For instance, as shown in the Figures, the
openings 112 are primarily oriented in a coronal plane, although,
in other embodiments, they could be primarily oriented in a
sagittal plane or other orientations. In some embodiments, a wider
attachment region with a less abrupt thickness change may be used
to provide for lower stress in the region. In some embodiments, a
more narrow attachment region may be used to increase visibility by
lessening the amount of material that could block a user's
view.
[0029] In some embodiments, the openings 112 are not physical
openings extending through the support member 110 or other portion
of the tibial component, but may instead be components or areas
that do not completely or partially impair visualization such as by
x-ray technologies or other visualization technologies. For
instance, in some embodiments, the "openings" may be filled or may
be comprised of materials of lower density (such as materials for
facilitating bony in-growth or other materials) or that are
otherwise semi or completely radio-lucent.
[0030] In some embodiments, the openings 112 allow a cutting device
or other instrument to physically pass through one or more of the
openings 112 to facilitate cutting or otherwise loosening the
tibial component from the bone in the event a revision procedure is
necessary. In the embodiment shown in FIGS. 2 and 3, the openings
112 are oriented such that posterior-lateral portions of the
bone-implant interface can be accessed by a surgical cutter or
other instrument if an anterior-medial approach to accessing the
joint space is used. The openings 112 shown in FIGS. 2 and 3 also
may allow this and other portions of the bone-implant interface to
be accessed from other approaches or directions. In other
embodiments, the position, orientation, size, shape and number of
openings 112 could be altered to facilitate access to remote
portions of the bone-implant interface depending on the particular
implant involved, the expected surgical approach or approaches that
may be utilized, and/or other factors (e.g. the size and shape of
the instrument(s) that might need to pass through the opening). In
some embodiments, the "openings" are not necessarily physical
openings through the support member 110 but are areas that are
frangible or otherwise capable of being relatively-easily
penetrated by a surgical instrument to access the remote portions
of the bone-implant interface if necessary. In some embodiments,
the opening(s) could be designed to function as guides for the
instrumentation passing through them, which, in some uses, might
control depth and/or direction of insertion of the instrument (e.g.
to lessen chance of damaging surrounding anatomy, such as
postero-lateral nerves or arteries) or other aspects of the
procedure. In some embodiments, openings 112 can be configured for
improved visibility and an ability to approach from anterior to
posterior. In some embodiments, the opening(s) 112 could be
designed to accommodate surgical cutting instruments such as
reciprocating or oscillating planar saw blades having cutting edges
on either or both of a distal end or one or both sides, milling
bits and other types of rotating cutting devices, chisels, other
osteotomes, prying devices, or any other type of surgical
instrument that might be used for a revision procedure.
[0031] As mentioned above, in some embodiments, the openings 112
could be filled with a porous structure or material or otherwise
define in-growth surfaces. In some embodiments, the porous
structure or material could be formed from the same material as the
rest of the support member 110 but having a different porosity,
density or other characteristics than other portions of the support
member 110. In some embodiments, the porous structure is not
necessarily confined to the opening 112 and could occupy geometric
volumes outside of and around other portions of the support member
110. Indeed, in some embodiments, the support member 110 could
function as an internal scaffolding for a volume of bone in-growth
material(s) that completely or at least in portions encompass the
support member 110. In other embodiments, other materials or
structures may fill the openings 112 and a porous structure or
treatment is not necessary. In some embodiments, the filling
material or structure may be intended to facilitate anti-rotation
aspects of the implant.
[0032] FIG. 1 shows a superior surface 126 of the tibial tray 118,
which includes attachment feature 128 for receiving and/or securing
one or more articular inserts (not shown) to the tibial tray 118,
such inserts designed to contact and articulate with a femoral
orthopaedic implant (not shown) in use. In the depicted embodiment,
the attachment feature 128 is a shaped channel to receive and
lock-in the articular insert. In other embodiments, the tibial tray
118 itself may include articular surfaces and does not require
separate articular inserts. The tibial tray 118 shown in FIGS. 1
through 3 includes a posterior notch 130, which may be designed to
allow preservation of the attachment site of a posterior cruciate
ligament, although, in other embodiments, the tibial tray 118 may
or may not include this or other notches or gaps for preserving one
or both of the cruciate ligaments. In other words, the tibial tray,
in some embodiments, may be for use in a cruciate sacrificing
procedure, a posterior cruciate preserving procedure, or a
bi-cruciate preserving procedure. In some embodiments, the tibial
tray 118 may be used for a mobile bearing knee joint or a fixed
bearing knee joint. It will be appreciated that a variety of upper
surface and peripheral shapes are possible according to various
embodiments and that such shapes can be influenced, at least in
part, by strength requirements for the tray. For example, in some
embodiments, a cruciate notch or dovetail mechanism may be used,
but may also act as a stress-riser.
[0033] The tibial component 100 shown in FIGS. 1 through 3 may be
part of a set of tibial trays of various standard sizes, or may be
a patient-matched tibial tray with certain geometries and/or other
aspects of the tray customized for a particular patient's anatomy.
The tibial component 100 shown in FIGS. 1 through 3 may be formed
from bio-compatible materials typically used to manufacture
orthopaedic implants or may be formed from other materials. The
tibial component 100 shown in FIGS. 1 through 3 may be formed using
any desired or appropriate methodologies or technologies.
[0034] In some embodiments, the tibial component 100 may be
manufactured using Selective Laser Sintered technologies ("SLS") or
other free-form fabrication technologies, such as one or more of
the EOS Laser-Sintering systems available from EOS GmbH of Munich,
Germany. For instance, in some embodiments, the entire tibial
component 100 may be formed as a monolithic implant (including any
porous or other in-growth promoting surfaces or materials). In
other embodiments, portions of the tibial component 100 may be
formed using SLS technology and then additional in-growth
materials, surfaces, and/or treatments could be added or applied to
the implant. In other embodiments, electron beam melting methods or
methods that use lasers to subtract or remove select portions of
material from an initially solid fin may be used. In other
embodiments, portions or all of the tibial component can be formed
using casting or other technologies or methods. In some
embodiments, a non-porous implant such as a tibial component may be
formed using SLS technologies and subsequently that implant may be
subjected to acid etching, grit blasting, plasma spraying (e.g. of
titanium oxide or another metal to promote in-growth) or other
treatments.
[0035] FIGS. 4 through 8 illustrate a modular stem 200 that may be
used with the tibial component 100 of FIGS. 1 through 3 in some,
although not necessarily all, embodiments. Indeed, in some
embodiments, the tibial component of FIGS. 1 through 3 will be used
without any modular stem or otherwise incorporating any of the
features or constructs of the modular stem shown in FIGS. 4 through
8. The modular stem 200 may connect to the stem portion 114 of the
support member 110 of the tibial component of FIGS. 1 through 3 via
a taper fit mechanism (which may be further secured by a screw or
other fastener in some embodiments). In other embodiments, other
mechanical attachment mechanisms may be employed, or, in still
other embodiments, the stem is not modular but an integral part of
the tibial component.
[0036] The embodiment of the modular stem 200 shown in FIGS. 4
through 8 includes an inner core 210 from which a plurality of
flutes 212 extend. In some embodiments, the inner core 210 has a
tapered, conical or press fit geometry positioned and oriented for
where it is most likely (at least in some cases) to encounter
"harder" bone, and the flutes 212 are positioned where they are
most likely to encounter "softer" bone. In some embodiments the
general shape of the modular stem 200 facilitates implantation in a
relatively close orientation and position to a pre-defined
orientation and position.
[0037] As shown in FIG. 6, the inner core 210, in some embodiments,
may be slightly tapered and/or define a somewhat conical shape.
Conical features such as this one (whose axes, at least in some
embodiments, may be directed generally parallel to the direction of
load application) may be beneficial because, in some uses, they may
convert what otherwise would be a purely compressive load into a
compressive load that also has a transverse component (i.e. a
direction of which could be characterized, at least in some
embodiments, as orthogonal to the direction of the compressive
load). In some embodiments, this may be beneficial in preventing
bone immediately adjacent to the implant from being shielded from
loading, at least for some of the time. In some cases, bone that is
shielded from loading could remodel, resorb or otherwise degrade,
resulting in a poor quality bone-implant interface. The tapered or
conical shape of the modular stem 200 may also facilitate the
prevention of subsidence or migration. The tapered or conical
nature of the inner core 210 may also facilitate a press-fit type
interface between the implant and bone. In the embodiment shown, a
distal tip 214 of the inner core is rounded.
[0038] As shown in FIGS. 4, 5, and 7, several flutes 212 extend
radially from the inner core 210 of the modular stem 200. In the
particular embodiment shown, the flutes 212 extend in a radially
symmetric pattern such that the apexes of the flutes 212 are
parallel to a central axis CA of the inner core 210. In other
words, although the inner core tapers, the apexes of the flutes
extend along a virtual cylinder. In other embodiments, the apexes
of the flutes may also taper as they extend towards the distal tip
of the stem; although, in at least some of these embodiments, the
flutes do not taper as much as the inner core. Because, at least in
some embodiments, the inner core tapers to a greater degree than
the apex of the flutes, the flutes will "protrude" from the stem to
a greater extent at distal portions of the stem than at proximal
portions of the stem. Accordingly, in some embodiments, such a
design may pose less of a risk of fracturing the hard bone that is
located proximate the proximal portions of the stem while still
achieving fixation (rotational and/or translational) in the soft
bone located proximate the distal portions of the stem.
Additionally, in some embodiments, there may be less of a risk of
deflection or mal-orientation or mal-position due to lack of or
lessening of press-fit between the flutes and the hard bone.
[0039] As shown best in FIG. 8, in addition to the flutes 212
described in the previous paragraph, the inner core of the modular
stem may also include secondary/smaller fluting 212' extending
therefrom. In some embodiments, the secondary fluting 212' may be
rounded or sharp, and may further facilitate a tight fit with the
surrounding bone, while, because they are smaller, lessening the
chance of tibial pain. In some embodiments, the fluting is radially
symmetric and facilitates insertion of the stem 200 to follow a
pilot hole. FIG. 8 shows fluting useable in some embodiments of
modular stems in which the stem 200 has fluting (or at least
primary fluting) that is spaced 120 degrees apart.
[0040] In some embodiments, the fluting is not radially
symmetrical, but instead exhibits planar symmetry. Planar symmetry
may allow, in some embodiments, matching of the fluting to the
support member geometry of a tibial component. In some embodiments,
the fluting is not radically symmetrical and is instead "handed"
and specific for left or right tibias to accommodate particular or
expected locations of hard and soft bone. In some embodiments,
patient matched technologies could be employed to customize the
fluting to the hard vs. soft bone distribution of the specific
patient.
[0041] In some embodiments, the fluting may be tapered. In some
embodiments, the "soft bone flutes" may be designed in such a way
that over small sections, they may be lower than the "hard" bone
flutes. In some embodiments, the "soft" bone flutes could be
parallel to the "hard" bone flutes but become tangentially wider to
increase their effectiveness in soft bone. In some embodiments, the
flutes could be discontinuous. In some embodiments, the flutes
could be made of a material different than that of the rest of the
stem. In some embodiments, portions of the stem could be porous
coated or have surface finishes applied.
[0042] FIGS. 9-11 illustrate alternative possible support member
shapes. For example, in FIGS. 9 and 10, there are two branches 310
(or arms or wings) of the support member 300. In FIG. 9, the
branches 310 are angled relative to one another, but in FIG. 10 the
branches 310 are substantially aligned with one another. In FIGS.
11 and 12, the support member 300 has three branches or arms 312.
Fewer or greater numbers of branches are possible.
[0043] As illustrated in FIGS. 12, 13 and 14, the tibial tray 410
and support member 420 may be modular and may have a male/female
arrangement. Although in the FIGS. the stem portion 420 is shown to
have a female portion and the tibial tray 410 is shown to have a
male portion, these could be reversed. In the embodiment depicted
in FIG. 13, the tibial tray 410' has a shoulder 430 that engages a
ledge 440 of the stem portion 420'. The shoulder/ledge arrangement
allows force to be transferred from the tibial tray 410' to the
stem portion 420'. The shoulder 430 also may provide a porous
surface area for bone in-growth. As best seen in FIG. 13, the stem
portion 420' may engage in a taper lock with a portion of the
tibial tray 410'.
[0044] FIGS. 15-18 illustrate a finned platform 500 for mounting a
cutting block 502. FIG. 15 illustrates a state of the art cutting
block 502 having a spike 504 that is used to hold the block
temporarily in place. The spike has certain drawbacks. For example,
the cutting block may shift with an applied load as a surgeon tries
to keep even contact between a sawblade 506 and the cutting surface
508. This may result in uneven or mal-rotated, poorly positioned
cuts.
[0045] FIG. 16 illustrates a finned platform 500. The finned
platform 500 has a head 510, a shaft 512, and fins 514 on the shaft
512. The head 510 has a planar surface at its uppermost portion or
may have an enlarged planar surface 526 at its uppermost portion.
The finned platform 500 may be cannulated as shown at 516 to
receive a spike 518 of a bone cutting block 520 as shown in FIG.
18. The fins may be in the form of a thread 514' (finned platform
500' in FIG. 16b) or a plurality of ribs. The fins 514 may have a
large surface to adequately engage soft, spongy bone. The fins
and/or head may resist movement. The finned platform 500 may be
made of metal or a polymer. In some embodiments, the finned
platform 500 is removed after cutting the bone. In some
embodiments, the finned platform 500 is left in after surgery to
assist in mounting an implant to the bone. In some embodiments, the
finned platform 500 is made from a resorbable material. In some
embodiments, the finned platform 500 is made from a shape memory
material. In use, the finned platform 500 is placed into bone 522.
Optionally, a pilot hole 524 may be drilled prior to placement of
the finned platform 500. A cutting block 520 with a spike 518 is
engaged with the finned platform 500. In some embodiments, the
spike may extend beyond the finned platform or vice versa.
Thereafter, the cutting block 520 is used as guide by a sawblade
506, cutting tool, or other instrument. The finned platform 500 may
stabilize the cutting block for more reproducible cuts. The finned
platform 500 of the present invention may be used on either the
femoral bone component or the tibial bone component to properly
prepare the respective bone portion for receiving either a femoral
knee implant or a tibial tray implant. FIG. 16a shows an
alternative embodiment of the finned platform 530. The finned
platform 530 is shown having a head 532, a shaft 534 and a
plurality of fins 536 extending longitudinally along the shaft 534.
There may be any number of fins 536, however, FIG. 16a shows the
finned platform 530 having four equally spaced fins 536. The finned
platform 530 may also be cannulated as shown at 538 to receive the
spike 518 of a bone cutting block 520 (shown in FIG. 18). The
benefit of the fins 514 and 536 of platforms 500 and 530 are to
resist lateral movement of the cutting block as shown by arrows in
FIG. 15 depicting the prior art.
[0046] FIGS. 19-22 illustrate a tibial trial 550 having a fin 552.
The fin 552 may be in the form of a raised portion 554 on the
underside of the tibial trial 550. The top side of the tibial trial
or implant is often called a tray 556. The tibial trial 550 with
the fin 552 may be used to reinforce bone to reduce the risk of
fracture during bone preparation. The tibial trial 550 with the fin
552 may aid in securing the tray 556 during trialing. During
trialing, a number of trial inserts (not shown) may be positioned
on the tray 556 to determine the correct spacing of the tibial
implant with respect to the femoral implant portion of the overall
knee implant. The tibial trial 550 with the fin 552 may aid in
securing the tray 556 during bone preparation. The tibial trial 550
with the fin 552 may provide a foundation for other instruments,
such as punches, reamers, and drills (not shown). As best seen in
FIG. 20, the fin 552 may be in the form of two arms 558 and 560.
And, as best seen in FIG. 21, the fin 552 may be in the form of two
arms 562 and 564 with a center portion 566. As examples, the center
portion 566 may be in the form of a circle, cylinder, square,
rectangle, or triangle. As best seen in FIG. 22, the fin 552 may be
in the form of a series of protrusions 568. For example, the fin
552 may be in the form of a series of cylinders. In use, the tibial
trial 550 is placed upon bone and impacted to force the fin 552
into the bone. It would also be possible that the tibial trial has
a plurality of holes placed where the protrusions 568 are shown to
allow the user to drill a plurality of holes through the trial 550
and into the bone underneath the trial. It would then be easier to
place the tibial tray implant into the bone without fracturing the
bone site.
[0047] FIGS. 23-25 illustrate a reamer 600. FIG. 23 illustrates a
reamer 600 in a first embodiment. The reamer 600 has a shaft 602, a
depth stop 604 and one or more cutting flutes 606 mounted to the
shaft 602. The shaft can be rotated and pivoted to engage the
cutting flutes 606 with bone. The shaft 602 may have different
shapes. In one embodiment, the shaft 602 may be circular, however
the shaft 602 may also be oval (as shown in FIG. 23) or otherwise
have any other more complex shape. The benefit of such a reamer is
the ability to cut or carve out a non-circular portion of the bone.
FIG. 24 illustrates a reamer 620 in a second embodiment. The reamer
610 has a shaft 612 and one or more cutting flutes 614 mounted to
the shaft 612. The reamer 610 can be used in conjunction with an
anchor 616. The anchor 616 would be inserted within a tibia, for
example, to allow for the user to cut or carve out a portion of the
bone. The anchor 616 may have a depression 618 to receive a tip 620
of the shaft 612 of the reamer 610. The tip 620 may be rounded. The
anchor 616 may be temporary or permanently positioned within the
tibia. The shaft can be rotated and pivoted to engage the cutting
flutes 614 with bone. FIGS. 24 and 25 illustrate a guide 630 that
can be used with the second embodiment of the reamer 610. The guide
630 has a stator 632 with a cam opening 634. The shaft 612 is moved
along the cam opening 634 to restrict and or limit movement of the
reamer within the bone. The shape of the cam opening 634 would
determine the shape of the bone cutout in the tibia.
[0048] FIGS. 26-29 illustrate fixation pegs 640. The fixation pegs
640 are placed on both the tibial and femoral implant components to
prevent such components from twisting once placed over the bone
portion. FIG. 26 illustrates a fixation peg 640 with a solid center
642 and a porous outer portion 644. The shape of the solid center
portion 642 provides a fixation peg 640 having portions that are
thin enough such that a saw can cut through them but are still
thick enough to withstand loading. This is significant as prior
fixation pegs were such that a saw could not cut through without
significant difficulty. Thus, the pegs shown in FIG. 26 may be
beneficial if the implant must be replaced or revised. FIG. 27
illustrates a cap 650 (porous or solid) that can be placed over an
existing solid fixation peg. FIG. 28 illustrates a peg 660 with a
cylindrical solid core 662 and a porous exterior portion 664. The
solid core 662 can be molded together with the porous exterior
portion 664 or the porous exterior portion 664 can be slid over the
solid core 662 during use. FIG. 29 illustrates a modular trial 680
and punch 682. The punch 682 can be attached to the trial 680 with
a quick connect feature. The punch 682 may include a portion 684 to
prepare for the lugs and a portion 686 to prepare for one or more
arms (or fins). The portion 684 of the punch 682 may be in the form
of spikes 688 which would pass through the trial 680 and into the
bone underneath the trial. The pegs (like those shown in FIG. 26)
of a tibial tray implant would then be inserted into the prepared
holes in the bone.
[0049] FIGS. 30-34 illustrate instruments for tibial surface
preparation. FIG. 30 illustrates the current state of the art
wherein there remains an uneven surface after the bone surface is
cut. As shown therein a trial 700 could sit unevenly on top of an
improperly cut tibial bone. FIGS. 31-33 illustrate a rasp 702 that
is impacted on top of the tibial bone will produce a surface that
is more planar. The rasp 702 may be struck by an impactor 704 one
time or repeatedly until the rasp 702 is embedded onto the tibial
bone to create an even uniform bone surface as shown in FIG. 33. In
some cases, the bone will flow onto the teeth 706 of the rasp 702
to assist in creating an even bone surface. In some embodiments,
the rasp may form a portion of or replace the trial. FIG. 34
illustrates a multi-part rasp 710. The rasp 720 has a center
portion 712 that is struck by an impactor in the direction of the
arrow. Impacting the center portion 712 forces the outer rasp
portions 714 and 716 apart to cut and smooth the bone.
[0050] FIGS. 35-39 illustrate a tibial trial 800 for tibial surface
preparation. FIGS. 35 and 36 illustrate the state of the art. The
tibial trial 800 is placed upon the prepared surface after cutting
of the tibial bone. However, the prepared surface is shown uneven
such that the trial 800 does not sit well upon the prepared surface
802. FIGS. 37-39 illustrate a trial 810 with a build-in rasp 812.
In use, the bone 814 is cut and the surface is prepared. The
combination trial 810 and rasp 812 is placed upon the bone surface
and moved in the directions of the arrows shown in FIG. 37 to
engage the rasp 812 with bone. For example, the combination trial
810 and rasp 812 may be rotated or moved in an A-P or M-L direction
to engage the rasp 812 with bone 814 to cut and smooth the surface.
Thereafter, normal trialing may be carried out and an implant can
be properly mounted to the bone.
[0051] One of skill in the art will recognize that changes,
deletions, alterations, additions and other modifications could be
made to the non-limiting embodiments described above without
departing from the scope or spirit of the inventions described
herein.
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