U.S. patent application number 17/161056 was filed with the patent office on 2021-05-20 for acetabular cup assembly for multiple bearing materials.
The applicant listed for this patent is Smith & Nephew, Inc.. Invention is credited to Charles Wayne Allen, Roger William Frank Ashton, Jason A. Capriotti, Michael A. Croxton, Terry W. McLean, Jeffrey J. Shea, Sureshkumar Srinivasan, William L. Waltersdorff, Justin M. Waugh.
Application Number | 20210145604 17/161056 |
Document ID | / |
Family ID | 1000005370743 |
Filed Date | 2021-05-20 |
View All Diagrams
United States Patent
Application |
20210145604 |
Kind Code |
A1 |
Allen; Charles Wayne ; et
al. |
May 20, 2021 |
ACETABULAR CUP ASSEMBLY FOR MULTIPLE BEARING MATERIALS
Abstract
A modular acetabular cup assembly for use with multiple bearing
liners is disclosed. The acetabular cup assembly includes a shell
having a tapered inner wall and two circumferential grooves. The
shell may be used with polyethylene, ceramic, metal, and other
types of liners.
Inventors: |
Allen; Charles Wayne;
(Southaven, MS) ; Capriotti; Jason A.; (Senatobia,
MS) ; Croxton; Michael A.; (The Woodlands, TX)
; Ashton; Roger William Frank; (Warwick, GB) ;
Waugh; Justin M.; (Memphis, TN) ; Shea; Jeffrey
J.; (Memphis, TN) ; Srinivasan; Sureshkumar;
(Coimbatore, IN) ; Waltersdorff; William L.;
(Hernando, MS) ; McLean; Terry W.; (Eads,
TN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Smith & Nephew, Inc. |
Memphis |
TN |
US |
|
|
Family ID: |
1000005370743 |
Appl. No.: |
17/161056 |
Filed: |
January 28, 2021 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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16460753 |
Jul 2, 2019 |
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17161056 |
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15288568 |
Oct 7, 2016 |
10383745 |
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16460753 |
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14171828 |
Feb 4, 2014 |
9463094 |
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15288568 |
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12293705 |
Sep 29, 2010 |
8679187 |
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PCT/US2006/060044 |
Oct 18, 2006 |
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14171828 |
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60783937 |
Mar 20, 2006 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61F 2002/4629 20130101;
A61F 2002/30331 20130101; A61F 2002/30827 20130101; A61F 2002/3403
20130101; A61F 2002/3611 20130101; A61F 2310/00239 20130101; A61F
2002/305 20130101; A61F 2250/0062 20130101; A61B 17/86 20130101;
A61F 2/4609 20130101; A61F 2002/30822 20130101; A61F 2002/30604
20130101; A61F 2310/00203 20130101; A61F 2002/30578 20130101; A61F
2002/4681 20130101; A61F 2002/30474 20130101; A61F 2/30767
20130101; A61F 2002/30403 20130101; A61F 2002/30593 20130101; A61F
2002/30092 20130101; A61F 2002/3241 20130101; A61F 2310/00167
20130101; A61B 17/68 20130101; A61F 2002/30378 20130101; A61F
2002/3401 20130101; A61F 2002/3052 20130101; A61F 2002/30367
20130101; A61F 2/4684 20130101; A61F 2002/30332 20130101; A61F
2310/00179 20130101; A61F 2310/00395 20130101; A61F 2/30744
20130101; A61F 2002/30787 20130101; A61F 2002/4641 20130101; A61F
2250/0025 20130101; A61F 2002/30906 20130101; A61F 2002/30925
20130101; A61F 2/34 20130101; A61F 2210/0014 20130101; A61F
2002/3093 20130101; A61F 2/32 20130101; A61F 2002/30487 20130101;
A61F 2002/4666 20130101; A61F 2002/4688 20130101; A61F 2002/3054
20130101; A61F 2310/00023 20130101; A61F 2002/30495 20130101; A61F
2220/0033 20130101; A61F 2002/4632 20130101; A61F 2002/30321
20130101; A61F 2002/3216 20130101; A61F 2/4637 20130101; A61F
2002/30607 20130101; A61F 2002/30616 20130101; A61F 2002/30968
20130101; A61F 2310/00017 20130101; A61F 2220/0025 20130101; A61F
2310/00029 20130101 |
International
Class: |
A61F 2/46 20060101
A61F002/46; A61F 2/30 20060101 A61F002/30; A61F 2/32 20060101
A61F002/32; A61F 2/34 20060101 A61F002/34 |
Claims
1. An acetabular cup system, comprising: a shell having a generally
concave inner surface, an outer surface, an end face formed at an
upper end of the shell, an apex formed at a lower end of the shell,
and a central axis extending through the apex, wherein the inner
surface comprises an inwardly-facing scallop positioned adjacent
the end face, an upper wall defining a taper with respect to the
central axis and extending below the scallop, a lower wall located
below the upper wall, a protrusion located below the lower wall,
and a lower groove located below the protrusion, wherein the lower
groove is partially defined by the protrusion; a polymer liner
comprising a plurality of tabs sized and shaped to be received in
the scallops, and a lower bump sized and shaped to be received in
the lower groove; a metal liner comprising a tapered outer surface;
a locking mechanism including the lower groove of the shell and the
lower bump of the polymer liner, wherein the locking mechanism has
a locking state in which the lower bump is engaged with the lower
groove, an interference fit is formed between the polymer liner and
the shell, and the locking mechanism couples the polymer liner with
the shell, and wherein the interference fit includes engagement of
the bump with the groove; and an engagement mechanism including the
upper wall of the shell and the tapered outer surface of the metal
liner, wherein the engagement mechanism has an engaged state in
which the upper wall is engaged with the tapered outer surface and
the engagement mechanism couples the metal liner with the
shell.
2. The system of claim 1, wherein, the inner surface of the shell
has a polished finish, and the tapered outer surface of the metal
liner has a roughened finish.
3. The system of claim 2, wherein a surface roughness of the inner
surface is less than 16 microinches.
4. The system of claim 1, wherein the lower wall is parallel to the
central axis.
5. The system of claim 1, wherein the shell further comprises an
upper groove located above the protrusion, wherein the upper groove
is partially defined by the protrusion, wherein the polymer liner
further includes an upper bump located above the lower bump,
wherein the locking mechanism further includes the upper groove and
the upper bump, and wherein with the locking mechanism in the
locking state, the upper bump is engaged with the upper groove.
6. The system of claim 5, wherein with the locking mechanism in the
locking state, a dimension of the locking mechanism in a direction
parallel to the central axis is less than 20 millimeters.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is a divisional of pending U.S. application
Ser. No. 16/460,753, filed Jul. 2, 2019, which is a divisional of
pending U.S. application Ser. No. 15/288,568, filed Oct. 7, 2016
and now issued as U.S. Pat. No. 10,383,745, which application is a
continuation of U.S. application Ser. No. 14/171,828, filed Feb. 4,
2014 and now issued as U.S. Pat. No. 9,463,094, which is a
continuation of U.S. application Ser. No. 12/293,705, filed Sep.
29, 2010 and now issued as U.S. Pat. No. 8,679,187, which is a U.S.
National Phase filing of International Application No.
PCT/US2006/060044, filed Oct. 18, 2006, which claims the benefit of
U.S. Provisional Application No. 60/783,937, filed Mar. 20, 2006.
The disclosure of each of these applications is hereby incorporated
by reference in its entirety.
BACKGROUND OF THE INVENTION
Field of the Invention
[0002] The present invention relates to acetabular cups and, more
particularly, to acetabular cup assemblies for use with multiple
bearings.
Related Art
[0003] In hip arthroplasty, various bearing materials are available
for the acetabular cup portion of an implant. The selection of the
bearing material is typically determined by the surgeon prior to
performance of the procedure. At times, however, final selection of
the bearing material is not completed until the implant site is
prepared and conditions at the site are evaluated. Thus, it is
sometimes advantageous to utilize an acetabular shell that accepts
multiple bearing liners so that the surgeon can revise the initial
assessment if required.
[0004] Acetabular shells that accept multiple bearings have been
used in Europe since the early 1980s. Typically, the outer shell
featured a tapered inside geometry in which a tapered hard or soft
bearing could be inserted. In these cases, soft bearing thickness,
lock integrity and wear performance were compromised in an effort
to accommodate both bearings.
[0005] More recently, Stryker Corp. of Kalamazoo, Mich., U.S.A.,
has developed an acetabular cup that accepts a fully
metal-encapsulated ceramic insert, which is held via a taper lock
connection. The shell also accepts a polyethylene insert that is
locked via one circumferential bead located mid-point along the
inner taper and is rotationally stabilized by four conforming
features between the shell and the liner.
[0006] An acetabular cup assembly for use with multiple bearings is
desirable from a manufacturing standpoint because it is only
necessary to produce one shell for use in many applications. This
increases the volume of shells produced, which decreases overall
production costs. Further, production of a single shell reduces
distribution costs.
[0007] An acetabular cup assembly for use with multiple bearings is
desirable from a revision standpoint because it gives the surgeon
greater flexibility and reduces the overall time of the operation.
First, the assembly gives the surgeon greater flexibility because
the surgeon can easily make adjustments to the hip prosthesis. For
example, if the original prosthesis had a polyethylene liner, the
surgeon can easily substitute a ceramic or metal liner without
changing the shell. Second, the assembly reduces the overall
operation time because it is not necessary to remove the shell.
Typically, the installed shell is surrounded by ingrown bone, which
is very difficult and time consuming to remove. Further, removal of
the installed shell may result in significant bone loss. By
eliminating the step of removing the shell, the surgeon can
complete the revision in less time with less effort and the result
is less traumatic to the patient.
[0008] Micromotion between a polyethylene liner and an acetabular
shell is undesirable as the motion creates polyethylene debris,
which eventually causes bone osteolysis. Prior polyethylene bearing
lock mechanism were designed to exhibit minimal micromotion between
the liner and the shell. However, these mechanisms also required an
excessive interoperative insertion force for insertion of the
liner. A high insertion force is undesirable as it requires greater
effort on behalf of the surgeon to install the liner.
[0009] Traditionally, ceramic liner manufacturers have advised
against reinsertion of ceramic liners due to the stress sensitive
nature of the material. The material may fracture at break if
stressed inappropriately. However, for various reasons, it may be
desirable to remove and reinstall a liner. As an example, a surgeon
may want to remove the ceramic liner during installation change the
shell position, and reinstall the liner. As ceramic manufactures
presently advise against this, a surgeon takes on great risk when
making these types of adjustments during ceramic liner
installation.
[0010] There remains a need in the art for an acetabular cup
assembly for use with multiple bearings.
SUMMARY OF THE INVENTION
[0011] The invention is briefly, an acetabular cup assembly. The
assembly includes a shell and a liner. The shell has an inner
surface and an outer surface. The inner surface has a first groove,
a second groove, and a tapered inner wall. The liner is adapted to
fit within the inner surface of the shell. The liner is selected
from the group consisting of a polymer liner, a ceramic liner, and
a metal liner, and the polymer liner has an inner portion and an
outer portion, the outer portion includes a first bump and a second
bump, the ceramic liner includes a band, and the metal liner
includes a tapered outer portion.
[0012] In one embodiment of the invention, the polymer liner is
selected from the group consisting of cross-linked polyethylene and
conventional polyethylene.
[0013] In another embodiment of the invention, the liner includes
anti-rotation tabs and the shell includes at least one scallop. The
scallops are dimensioned to receive the anti-rotation tabs.
[0014] In yet another embodiment of the invention, the shell
includes an insertion tool hole.
[0015] The insertion tool hole may be used in conjunction with a
tool to install the shell.
[0016] In still another embodiment of the invention, the inner
surface of the shell is highly polished. The inner surface may have
a surface roughness of about one to about sixteen microinches, and
rather about one to about eight microinches. The highly polished
surface reduces polymer liner debris if micromotion happens to
occur between the shell and the liner.
[0017] In another embodiment of the invention, the shell is made
from a material selected from the group consisting of titanium,
cobalt chromium, and stainless steel.
[0018] In yet another embodiment of the invention, the shell
further comprises at least one fixation hole. The fixation hole is
adapted to receive one or more fixation devices to attach the shell
to bone.
[0019] In still another embodiment of the invention, the shell
further comprises a porous coaling on the outer surface. The porous
touting allows for bone in growth.
[0020] In another embodiment of the invention, the band has a
taper. The band may be tapered from about two degrees to about
thirty-six degrees, and rather the band has a taper of about
eighteen degrees.
[0021] In yet another embodiment of the invention, the tapered
inner wall, the band or the tapered outer portion includes a
surface enhancement. The surface enhancement may be selected from
the group consisting of an acme-type stair-step, a reverse
stair-step, or a predetermined surface roughness. The surface
enhancement augments the locking of the liner.
[0022] In still another embodiment of the invention, the acetabular
cup assembly may have a constrained bearing liner. The liner may
utilize a locking feature, such is a metal locking ring or an
annular flange.
[0023] The acetabular cup assembly may have a two-piece liner that
includes a bearing surface component and a capture mechanism. The
capture mechanism is locked into the shell after hip reduction.
[0024] In another embodiment of the invention, the liner is
selected from the group consisting of a constrained liner, a
neutral liner, an anteverted liner, a lipped bearing liner, and a
lateralized bearing liner.
[0025] In yet another embodiment of the invention, the acetabular
cup assembly further comprising an installation tool attached to
the liner. The installation tool is comprised of metal or
plastic.
[0026] In one particular embodiment of the invention, the invention
is a modular acetabular cup assembly for use with multiple bearing
liners. The acetabular cup assembly includes a shell having an
inner wall, two annular grooves, and a plurality of anti-rotation
tabs. The shell may be used with polyethylene, ceramic, metal, and
other types of liners. In the case of a ceramic liner, a band is
attached to the liner. The band is adapted to mate with the inner
wall. The band on the ceramic liner enables the shell to be used
with an off-the-shelf liner without the need for more expensive,
custom made liners.
[0027] In yet another embodiment of the invention, the shell has a
face and an apex, a central axis extends through the apex, a line
extends from where the inner surface meets the lower groove to
where the central axis meets a planar surface defined by a plane
extending through the face of the shell, the central axis and the
line defining an angle, and wherein the angle ranges from about ten
degrees to about eighty degrees. In other embodiments, the angle
ranges from about forty to about seventy degrees.
[0028] In another embodiment of the invention, the first groove and
the second groove are separated by a first distance, and the first
distance ranges from about one millimeter to about twenty
millimeters. In other embodiments, the first distance ranges from
about two millimeters to about four millimeters.
[0029] In yet another embodiment of the invention, the band has an
inner surface and an outer surface spaced apart from the inner
surface by a second distance, and the second distance varies from
about one-half millimeter to about 30 millimeters. In other
embodiments, the distance ranges from about one-half millimeter to
about ten millimeters.
[0030] The invention offers the advantage of two annular grooves or
cavities that receive annular bumps or ribs of the liner. The
grooves may or may not fully extend about an interior of the shell.
The use of two ribs and grooves is significant as the effective
push-in and push-out of the liner can be controlled and optimized
by adjusting the tolerances and dimensions of these four items and
the interference between the shell and the liner. Thus, the
acetabular cup assembly may be designed such that a surgeon may
easily be able to push in the liner by hand but the liner will not
disassemble front the shell without the use of a tool.
[0031] The band also allows the ceramic liner to be reinserted
should this become necessary intraoperatively. Furthermore, the
band improves the force distribution around the liner and
significantly reduces the potential for liner fracture,
particularly in the event of a misalignment.
[0032] Further areas of applicability of the present invention will
become apparent from the detailed description provided hereinafter.
It should be understood that the detailed description and specific
examples, while indicating the preferred embodiment of the
invention, are intended for purposes of illustration only and are
not intended to limit the scope of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0033] The present invention will become more fully understood from
the detailed description and the accompanying drawings,
wherein:
[0034] FIG. 1 is a sectional side view of an acetabular cup
assembly in a first embodiment;
[0035] FIG. 2 is a front perspective view of the acetabular cup
assembly shown in FIG. 1;
[0036] FIG. 3 is a front perspective view of a shell;
[0037] FIG. 4A is a partial sectional side view of the acetabular
cup assembly;
[0038] FIG. 4B is a sectional view of an exemplary shell having
intermittently spaced grooves;
[0039] FIG. 4C is a partial sectional view of an exemplary shell
having bumps that are separate components coupled to an outer body
of the shell and engaged with an adjacent groove;
[0040] FIG. 5 is a sectional side view of the shell;
[0041] FIG. 6 is a sectional side view of an acetabular cup
assembly in a second embodiment;
[0042] FIG. 7 is a partial from perspective view of Ute acetabular
cup assembly shown in FIG. 6;
[0043] FIG. 8 is a sectional side view of an acetabular cup
assembly in a third embodiment;
[0044] FIG. 9 is a partial front perspective view of the acetabular
cup assembly shown in
[0045] FIG. 8;
[0046] FIG. 10 is a first embodiment of a surface enhancement;
[0047] FIG. 11 is a second embodiment of a surface enhancement;
[0048] FIG. 12 is a third embodiment of a surface enhancement;
[0049] FIG. 13 is an exploded side view of an acetabular cup
assembly in a fourth embodiment;
[0050] FIG. 14 is an exploded side view of in acetabular cup
assembly in a fifth embodiment;
[0051] FIG. 15 is an exploded front perspective view of a modular
acetabular trialing system;
[0052] FIG. 16 is a front perspective view of the modular
acetabular trialing system shown in
[0053] FIG. 15;
[0054] FIG. 17 is a sectional side view of an installation tool in
a first embodiment in use on a liner;
[0055] FIG. 18 is a front perspective exploded sectional view of
the shell, the installation tool applied to the liner, and an
impactor head;
[0056] FIG. 19 is a front perspective view of the shell,
installation tool, and liner;
[0057] FIG. 20 is a sectional side view of the shell, the
installation tool applied to the liner, and the impactor head;
[0058] FIG. 21 is a top view of the installation tool in a second
embodiment;
[0059] FIG. 22 is a sectional front view of the embodiment shown in
FIG. 21;
[0060] FIG. 23 is a sectional front view of a fixture for mounting
a band to a liner in a first embodiment; and
[0061] FIG. 24 is a sectional front view of a fixture for mounting
a band to a liner in a second embodiment.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0062] The following description of the preferred embodiment(s) is
merely exemplary in nature and is in no way intended to limit the
invention, its application, or uses.
[0063] FIGS. 1 and 2 illustrate, an acetabular cup assembly 10. The
acetabular cop assembly 10 includes a shell 12. The shell 12 is
adapted ferule with multiple bearing linen, such us a first liner
32. The first liner 32 may be any number of liners but is a polymer
liner in the embodiment depicted in FIGS. 1 and 2. For example, the
first liner 32 may be a cross-linked polyethylene liner or a
conventional polyethylene liner. The first liner 32 includes
anti-rotation tabs 33. The shell 12 includes an insertion tool hole
38, which is used to receive a tool (not shown) for installation of
the shell. In the depicted embodiment, the insertion tool hole 38
is threaded.
[0064] As best seen in FIG. 3, the shell 12 includes un inner
surface 14. In the embodiment illustrated in FIG. 3, the inner
surface 14 has a concave shape but other shapes may be used. In
some embodiments, the inner surface 14 is highly polished such that
it appears mirror-like. For example, the inner surface may have a
roughness from about one microinch to about sixteen microinches. In
the depicted embodiment, the inner surface has a roughness from
about eight microinches to about sixteen microinches. In some
embodiments, the inner surface has a roughness of about 1 microinch
to about eight microinches. A highly polished inner surface 14
significantly reduces or prevents polymer liner debris
generation.
[0065] In the embodiment depicted in FIG. 3, the shell 12 is made
of metal but those skilled in the art would understand that other
materials could equally be used. As examples, the shell 12 may be
made of titanium, cobalt chromium, stainless steel, or other
biocompatible material.
[0066] The shell 12 includes a face 54 and scallops 16 which
receive anti-rotation tabs 33. In the embodiment depicted in FIG.
3, the shell 12 includes twelve scallops 16 and the first liner 33
has twelve corresponding anti-rotation tabs 33 to achieve greater
microstability. Each scallop 16 forms a lip or lodge 18 on an inner
wall 28 of the shell 12. The shell 12 further includes an annular
groove 20 that extends peripherally or circumferentially about the
inner wall 28. The shell 12 also includes a notch 22. The notch 22
allows a pry tool access to the liner portion of the assembly.
[0067] In some embodiments, the shell 12 may include one or more
fixation holes 40. A screw, modular peg, or other fixation device
(not shown) may be inserted through the fixation hole 40 to attach
the shell 12 to bone. Further, in some embodiments the shell may
have a porous coating on its exterior. As examples, the exterior of
the shell 12 may have a sintered metal coating, a vapor deposited
metal coating, a thermal spray metal coaling, or be chemically
etched. The porous coating may allow for bone in-growth into the
shell 12.
[0068] The shell 12 includes a first groove 24 and a second groove
26. Alternatively, the grooves 24, 26 may be termed indentations or
cavities. The grooves 24, 26 may or may not fully extend about an
interior 30 of the shell 12. Thus, as seen in FIG. 4B, the groove
24, 26 may form annular rings, have a "C" shape, be intermittently
spaced about the circumference, have a hemispherical shape, or have
some other shape. As best seen in FIG. 4, the first groove 24 and
the second groove 26 respectively receive a first bump 34 and it
second bump 36 of the first liner 32. The first bump 34
alternatively may be referred to as a first insertion member or
first rib and the second hump 36 alternatively may be referred to
as a second insertion member or second rib. As seen in FIG. 4C, in
the case of a metal or ceramic liner, the bumps 34, 36 may be a
separate component, such as a split ring or spring, or molded to
the exterior, or outer body 35, of the liner.
[0069] The use of two protrusions and grooves is significant as the
effective push-in and push-out of the liner 32 can be controlled by
adjusting the tolerances and dimensions of these four items. For
example, it is possible to have the liner 32 installed with a small
push-in force but also have a significant push-out force. Thus, a
surgeon may easily be able to push-in the liner by hand but the
liner will not disassemble from the shell without the use of a
tool. In another example, the liner 32 may be installed with a high
push-in force and have an even greater push-out force. A protrusion
25 is formed in between the grooves 24, 26, and can inwardly extend
from an adjacent inner portion of a segment of the inner surface
14. By controlling the interference between she protrusion 25 and
the second bump 36 and the other dimensions, one can adjust the
push-in and push-out force. If the second bump 36 greatly
interferes with the protrusion 25, then the liner 32 will have both
a high push-in and push-out. In this case, it may be necessary to
significantly cool the liner 32 prior to installation to
temporarily reduce its size. However, if the second bump 36 only
slightly interferes with the protrusion 25, then the liner 32 may
be inserted utilizing a low push-in force and removed utilizing a
high push-out force. This is because once the bumps 34, 36 engage
the grooves 24, 26, both bumps will contribute to the push out
force required. However, in the case of push-in, the force required
is only enough for the second bump 36 to clear the protrusion 25
and for the first bump 34 to engage the first groove 24.
[0070] The first groove 24 and the second groove 26 are located
below the inner wall 28. This is significant because the location
of the grooves 24,26 shelters the locking mechanism of the first
liner 32 from soft tissue interference. In other words, because the
bumps 34, 36 engage the grooves 24, 26 on a lower portion of the
shell 12, the likelihood of soft tissue interference with the
locking of the first liner 32 to the shell is significantly
reduced.
[0071] FIG. 5 illustrates a view of the shell 12. The shell 12 has
a central axis 50 that extends through the apex of the shell. The
grooves 24, 26 are located on the inner surface 14 of the shell 12.
A line L extends from where the inner surface 14 meets the lower
groove 26 to where the central axis 50 meets a planar surface 52.
The planar surface 52 is defined by a plane extending through the
face 54 of the shell 12. An angle A is defined by the central axis
and the line L. The angle A is about 10 degrees to about 80
degrees. In the embodiment depicted in FIG. 5, the angle A is about
-40 degrees to about 70 degrees. FIG. 5 also illustrates a first
distance or dimension D1. The dimension D1 is the distance between
the upper groove 24 and the lower groove 26. The dimension D1 is
about 1 to about 20 millimeters. In the embodiment depicted in FIG.
5, the dimension D1 is about 2 to about 4 millimeters.
[0072] FIGS. 6 and 7 illustrate a second embodiment of the
acetabular cup assembly generally indicated by reference numeral
100. The acetabular cup assembly 100 includes a second liner 110, a
band or ring 112, and the shell 12. As an example, the second liner
110 may be a ceramic liner, such as an alumina ceramic liner.
Further examples include a diamond liner, a liner made of a
polycrystalline diamond composite material, a liner made from
oxidized zirconium, or a liner made from polyethylene, including
cross linked polyethylene. The band 112 may be made of metal. For
example, the band 112 may be made of stainless steel, titanium,
cobalt chromium, or a shape memory alloy, such as nitinol. The band
112 is affixed to an outer portion 114 of the liner 110. The band
112 is adapted to mate with the inner wall 28 of the shell 12. The
band 112 and the inner wall 28 may be tapered. For example, the
inner wall 28 may be tapered from about two degrees to about
thirty-six degrees. In the embodiment depicted in FIG. 6, the inner
wall 28 has about an eighteen degree taper. The band 112 allows a
ceramic liner to be removed and reinserted. This is significant, as
previously removal and reinstallation of a ceramic liner was
inadvisable. Further, the band 112 improves the force distribution
around the second liner 110 and eliminates, or at least
significantly reduces, the potential for cracking of a ceramic
liner upon insertion, especially if there is any misalignment. The
liner 110 has a face 130. The band 112 may extend above the face
130, below the face 130, or substantially flush with the face 130.
If the band 112 extends above the face 130, the band 112 may
prevent impingement in some circumstances. In the embodiment
depicted in FIGS. 6 and 7, the band is substantially flush with the
lace 130.
[0073] The band 112 has an inner surface 140 and an outer surface
142 spaced apart from the inner surface 140. The inner surface 140
is sized and shaped to compliment the outer portion 114 of the
liner 110, and the outer surface 142 is sized and shaped to
compliment the inner wall 28. The outer surface 142 is spaced apart
from the inner surface 140 by a second distance or second dimension
D2. The distance D2 may vary from about one-half millimeter to
about 30 millimeters, and rather from about one-half millimeter to
about ten millimeters. In the embodiment depicted in FIG. 6, the
distance D2 is about three-fourths of a millimeter.
[0074] In some embodiments, the shell 12 way accept differently
sized liners. The acetabular cup assembly 100 may include a
plurality of liners, each having a band with a differently sized
inner surface but each having the same size outer surface. Thus,
the plurality of liners all fit the same shell because the outer
surface is the same size. However, the inner surface is differently
sized allowing for differently sized liners, the difference in size
is adjusted by adjusting the distance D2 of the band 112. As an
example only, the single shell 12 may accept 26, 28, and 32
millimeter inner diameter liners. This is significant as the
modularity reduces manufacturing costs and provides surgeons with a
greater number of interoperative choices.
[0075] In other embodiments, the liner 110 may fit within
differently sized shells. The acetabular cup assembly 100 may
include a plurality of liners, each having a band with a
differently sized outer surface hut each having the same size inner
surface. Thus, the plurality of liners each have the same inner
diameter size but has differently sized outer surface that
compliments a particular size of shell. The difference in size is
adjusted by adjusting the distance D2 of the band 112. As an
example only, the single liner 110 may fit within 46, 48, and 50
millimeter inner diameter shells. This is significant as the
modularity within manufacturing costs and provides surgeons with a
greater number of intraoperative choices.
[0076] FIGS. 8 and 9 illustrate a third embodiment of the
acetabular cup assembly, generally indicated by reference numeral
200. The acetabular cup assembly 200 includes a third liner 212 and
the shell 12. As an example, the third liner 212 may be a metal
liner, such as cobalt chromium. Alternatively, the third liner 212
may be a ceramic, plastic, or composite. The liner 212 includes an
outer portion 216. The outer portion 216 is adapted to mate with
the inner wall 28 of the shell 12. The outer portion 216 and the
inner wall 28 may be tapered. For example, the inner wall 28 may be
tapered from about two degrees to about thirty-six degrees. In the
embodiment depicted in FIG. 8, The inner wall 28 has about an
eighteen degree taper. In some embodiments, the assembly 200 may
further include plug 214. The plug 214 may be used to cover
fixation devices or used to fill unused holes. In FIG. 9, the plug
214 has been removed for clarity.
[0077] FIGS. 10, 11, and 12 illustrate various surface enhancements
that may be applied to the band 112 or the outer portion 214 for
lock enhancement of the liner. In FIG. 10, an Acme-type
"stair-step" 220 may be machined into the band 112 or the outer
portion 216. Similarly, in FIG. 11 a "reverse stair-step" 222 may
be machined into the band 112 or the outer portion 216. The
stair-step surface configuration 220 or are reverse stair-step
configuration may be lined to maintain lock integrity even after
multiple reinsertions. In FIG. 12, the band 112 or the outer
portion 216 may have predetermined surface roughness 224. The
surface roughness 224 may be achieved by coarse media blasting,
such as by grit blast, glass bead blast etc. Alternatively, the
surface enhancements 220, 222, 224 could be applied to the inner
wall 28. Moreover, numerous types of coatings may be applied to the
band 112, the outer portion 214, or the inner wall 28. As examples,
these surfaces may have a metal, plastic, diamond, or composite
coating.
[0078] FIG. 13 illustrates a fourth embodiment of the acetabular
cup assembly, generally indicated by reference numeral 300. The
acetabular cup assembly 300 includes the shell 12 and a constrained
bearing liner 310. In a constrained bearing liner, a femoral head
312 is captured within the liner. Constrained bearing liners often
utilize a third locking feature as they typically require a higher
disassociation force. In FIG. 13, a metal locking ring 314
interfaces with the first groove 24. Alternatively, an annular
flange may be attached to the liner and the annular flange engages
the first groove 24. The locking ring 314 may be used with either a
one-piece or two-piece constrained liner construct.
[0079] FIG. 14 illustrates a fourth embodiment of the acetabular
cup assembly, generally indicated by reference numeral 350. The
acetabular cup assembly is a two-piece construct that includes the
shell 12, a bearing surface component 354, and a capture mechanism
358. For the two-piece construct, the bearing surface component 354
is inserted into the shell, the femoral head 356 is placed in the
liner, and the capture mechanism 358 is placed over the femoral
component 356 prior to head assembly. Once the hip is reduced, the
capture mechanism 358 is inserted and locked into the shell thereby
securing the full assembly construct. As an example, the capture
mechanism may engage the annular groove 20 (best teen in FIG.
3).
[0080] The liners 32, 110, 212, 310, 354 may be neutral liners,
anteverted bearing liners, lipped bearing liners, or lateralized
bearing liners. Thus, the depicted embodiments are merely
exemplary. Further, an interior or an exterior of the linen 32,
110, 212, 310, 354 may be coated with various types of coatings.
For example, these surfaces may have a metal, plastic, diamond, or
composite coating.
[0081] FIGS. 15 and 16 illustrate a modular acetabular trialing
system 400. The acetabular trialing system 400 includes a trial
liner 410, a trial spacer 412, and a trial shell 414. Modularity
greatly reduces the number of trialing components necessary to
cover the full range of sizes offered in the acetabular cup system,
which further simplifies the amount of instrumentation required for
surgery. The trial liner 410 and the trial spacer 412 may be used
with the trial shell 414 or the implantable shell 12.
[0082] FIGS. 17, 18, 19 and 20 illustrate a method and apparatus
for installing the liner 32, 110, 212, 310, 354. A first embodiment
of an installation tool 500 is attached to the liner 32, 110, 212,
310, 354. The installation tool 500 is substantially circular. In
some embodiments, the installation tool 500 has a cutout 502. The
installation tool 500 has a first shoulder 504 and a second
shoulder 506. Alternatively, these features may be termed as a
first capture, recess 504 and a second capture recess 506. In some
embodiments, the first shoulder is identical to the second shoulder
such that either side of the installation tool may be used. In
outer embodiments, the first shoulder 504 is larger or smaller than
the second shoulder 506 such that the installation tool 500 may
accommodate various sizes of liners 32, 110, 212, 310, 354. The
first shoulder 504 and the second shoulder 506 may be square or
tapered. In the tapered embodiments, the first and second shoulders
504, 506 may taper outwardly for manufacturing purposes or taper
inwardly to provide line contact with the liner.
[0083] In the method, the installation tool 500 is slightly spread
open and attached to the liner 32, 110, 212, 310, 354 until either
the first shoulder 504 or the second shoulder 506 contact the
liner. The installation tool 500 is resilient and biased to spring
back into its original position. Thus, the installation tool 500 is
attached to the liner 32, 110, 212, 310, 354 through the use of a
spring force.
[0084] Once the installation tool 500 is assembled to the liner 32,
110, 212, 310, 354, the installation tool 500 and the liner 32,
110, 212, 310, 354 are placed over the shell 12. Thereafter, an
impactor head 510 may be used to press on the liner 32, 110, 212,
310, 354 to remove the liner from the installation tool 500 and
install the liner in the shell 12. The use of the installation tool
500 allows for automatic centering and alignment of the liner 32,
110, 212, 310, 354 within the shell 12. The use of the installation
tool 500 significantly reduces the possibility that the liner may
become askew relative to the shell upon installation. Further, the
installation tool 500 may serve as a soft tissue retractor during
installation. The outer portion of the installation tool 500 may be
used to push soft tissue aside as the liner is inserted into the
shell.
[0085] The installation tool 500 may be re-usable or disposable.
For example, the installation tool 500 may be made of metal, such
as stainless steel, and the installation tool may be sterilized and
re-used after installation of the liner. Alternatively, the
installation tool 500 may be made from a polymer or plastic and
disposed of after liner insertion. In the case of a plastic
material, the installation tool may be color coded to indicate a
particular size or to indicate a particular brand.
[0086] FIGS. 21 and 22 illustrate a second embodiment of the
installation tool, generally indicated by numeral reference 600.
The installation tool 600 includes a notch 610. The notch 610
allows an inner portion 620 of the installation tool 600 to flex.
Thus, the bending of the inner portion 620 provides a spring force
that can be applied in the liner 32, 110, 212, 310, 354. Similar to
the first embodiment, the installation tool 600 is assembled to the
liner 32, 110, 212, 310, 354, the installation tool 600 and the
liner are placed over the shell 12. Thereafter, an impactor head
510 may be used to press on the liner to remove the liner from the
installation tool 600 and install the liner in the shell 12. The
use of the installation tool 600 allows for automatic centering and
alignment of the liner within the shell 12.
[0087] FIG. 23 illustrates a first embodiment of a fixture 700 for
use in installing the band 112 on the liner 110. The fixture 700
includes a fixture face 704 and a well 706. To install the band 112
on the liner 110, the band 112 and the liner 110 are placed on the
fixture 700 and a press (not shown) with a press platen 702 is used
to press the band 112 on the liner 110. First, the fixture 700 is
mounted to the press, which may be a computer numerically
controlled press. Second, the press is set with a displacement
rate, a minimum force, and a maximum force. The displacement rate
may be from about 0.01 inch per minute to about 2.00 inches per
minute maximum. In the depicted embodiment, the displacement rate
is about 0.80 inches per minute to about 1.10 inches per minute
maximum. The minimum force ranges from about 5000 pounds to 11000
pounds. In the depicted embodiment, the minimum force is about 8000
pounds. The maximum force ranges from about 8000 pounds to about
15000 pounds. In the depicted embodiment, the maximum force is
about 10000 pounds. Third, the band 112 is placed on the liner 110
by hand. Fourth, the band 112 and the liner 110 are placed on the
fixture 700 with the liner 110 protruding into the well 706 and the
hand 112 resting on the fixture face 704. Fifth, the press platen
702 is advanced until it makes contact with me face 130 of the
liner 110. The initial preload force on the liner 110 may be from
about zero pounds to about ten pounds. Sixth, the press platen 702
applies a force F on the liner 110 until a displacement D3 is
achieved between the band 112 and the liner 110. The displacement
D3 is zero with a tolerance of one millimeter in either direction.
Optimally, the displacement D3 is zero with a tolerance of about
one-quarter of a millimeter in either direction. Thereafter, the
assembled hand 112 and the liner 110 are inspected for material
transfer blemishes. A microscope may be used to inspect the
assembly.
[0088] FIG. 24 illustrates a second embodiment of a fixture 800 for
use in installing the band 112 on the liner 110. The fixture 800
includes a counter bore 803, a fixture face 804 and a well 806. To
install the band 112 on the liner 110, the band 112 and the liner
110 are placed on the fixture 800 and a press (not shown) with a
press platen 802 is used to press the band 112 on the liner 110.
First, the fixture 800 is mounted to the press, which may be a
computer numerically controlled press. Second, the press is set
with a displacement rate, a minimum force, and a maximum force. The
displacement rate may be from about 0.01 inch per minute to about
2.00 inches per minute maximum. In the depicted embodiment, the
displacement rate is about 0.80 inches per minute to about 1.10
inches per minute maximum. Thu minimum force ranges from about 5000
pounds to 11000 pounds. In the depicted embodiment, the minimum
force is about 8000 pounds. The maximum force ranges from about
8000 pounds to about 15000 pounds. In the depicted embodiment, the
maximum force is about 10000 pounds. Third, the band 112 is placed
on the liner 110 by hand. Fourth, the band 112 and the liner 110
are placed on the fixture 800 with the liner 110 protruding into
the well 806 and the band 112 resting in the counter bore 803 and
on the fixture face 804. The counter bore 803 provide the advantage
of self-centering the assembly over the well 806. Fifth, the preys
platen 802 is advanced until it makes contact with the face 130 of
the liner 110. The initial preload force on the liner 110 may be
from about zero pounds to about ten pounds. Sixth, the press platen
802 applies a force F on the liner 110 until a displacement D3 is
achieved between the hand 112 mid the liner 110. The displacement
D3 is zero with a tolerance of one millimeter in either direction.
Optimally, the displacement D3 is zero with a tolerance of about
one-quarter of a millimeter in either direction. Thereafter, the
assembled hand 112 and the liner 110 are inspected for material
transfer blemishes. A microscope may be used to inspect the
assembly.
[0089] In view of the foregoing, it will be seen that the several
advantages of the invention are achieved and attained.
[0090] The embodiments were chosen and described in order to best
explain the principles of the invention and its practical
application to thereby enable others skilled in the art to best
utilize the invention in various embodiments and with various
modifications as are suited to the particular use contemplated.
[0091] As various modifications could be made in the constructions
and methods herein described and illustrated without departing from
the scope of the invention, it is intended that all matter
contained in the foregoing description or shown in the accompanying
drawings shall be interpreted as illustrative rather than limiting.
For example, while the first groove and the second groove have been
depicted as annular, those of ordinary skill in the art would
understand that the grooves may be intermittently spaced about the
inner surface of the shell and still achieve the same function.
Thus, the breadth and scope of the present invention should not be
limited by any of the above-described exemplary embodiments, but
should be defined only in accordance with the following claims
appended hereto and their equivalents.
* * * * *