U.S. patent application number 11/104974 was filed with the patent office on 2006-10-12 for method for making a metal-backed acetabular implant.
This patent application is currently assigned to Zimmer Technology, Inc.. Invention is credited to Kirt L. Case.
Application Number | 20060226570 11/104974 |
Document ID | / |
Family ID | 37082443 |
Filed Date | 2006-10-12 |
United States Patent
Application |
20060226570 |
Kind Code |
A1 |
Case; Kirt L. |
October 12, 2006 |
Method for making a metal-backed acetabular implant
Abstract
A method of making a metal-backed acetabular implant includes
roughening a surface of a metallic integument and compression
molding a bearing to the surface after the roughening step.
Inventors: |
Case; Kirt L.; (Warsaw,
IN) |
Correspondence
Address: |
ZIMMER TECHNOLOGY - ROBERTS
P.O. BOX 1268
ALEDO
TX
76008
US
|
Assignee: |
Zimmer Technology, Inc.
|
Family ID: |
37082443 |
Appl. No.: |
11/104974 |
Filed: |
April 12, 2005 |
Current U.S.
Class: |
264/162 ;
264/265; 264/274 |
Current CPC
Class: |
A61F 2002/30487
20130101; A61F 2002/3611 20130101; A61F 2/34 20130101; A61F
2002/30957 20130101; A61F 2002/30604 20130101; A61F 2/30771
20130101; A61F 2002/3448 20130101; A61F 2002/30906 20130101; A61F
2002/3054 20130101; Y10T 29/49826 20150115; A61F 2002/30378
20130101; B29L 2031/7532 20130101; A61F 2/32 20130101; A61F
2220/0025 20130101; A61F 2/36 20130101; A61F 2002/30345 20130101;
A61F 2310/00029 20130101; A61F 2/30767 20130101; A61F 2/3662
20130101; A61F 2220/0033 20130101; A61F 2/3094 20130101; A61F
2002/3437 20130101; A61F 2310/00023 20130101; A61F 2002/305
20130101; A61F 2002/4653 20130101; B29C 43/003 20130101; A61F
2/4637 20130101 |
Class at
Publication: |
264/162 ;
264/274; 264/265 |
International
Class: |
B29C 45/14 20060101
B29C045/14 |
Claims
1. A method of making a metal-backed acetabular implant, comprising
the steps of: roughening a surface of a metallic integument; and
compression molding a bearing to the surface after the roughening
step.
2. The method of claim 1, wherein the bearing is substantially
plastic.
3. The method of claim 2, wherein the plastic is substantially
ultra high molecular weight polyethylene.
4. The method of claim 1, wherein the roughening step includes dry
blasting the surface.
5. The method of claim 4, wherein the dry blasting step includes
dry blasting the surface with a 60 grit material.
6. The method of claim 5, wherein the 60 grit material includes
alumina.
7. The method of claim 6, wherein the bearing is substantially
plastic.
8. The method of claim 7, wherein the plastic is substantially
ultra high molecular weight polyethylene.
9. The method of claim 8, further comprising the step of taper
coupling the integument into a metallic acetabular shell.
Description
FIELD OF THE INVENTION
[0001] The present invention relates generally to the field of
orthopaedics, and, more particularly, to a method of making a
metal-backed acetabular implant for a hip prosthesis.
BACKGROUND
[0002] A conventional hip prosthesis is primarily composed of an
acetabular implant and a femoral implant. The acetabular implant
typically includes a generally hemispherical dome-like or cup-like
metallic shell secured within the acetabulum and a dome-like or
cup-like plastic or ceramic bearing secured within the shell.
Accordingly, the shell typically includes an exterior configured to
be anchored into the acetabulum and further typically includes an
interior configured to align and retain the bearing, while the
bearing typically includes an exterior configured to cooperate with
the interior of the shell to align and secure the bearing within
the shell and further typically includes an interior defining an
artificial hip socket (which may or may not be off-centered from
the exterior of the bearing, depending on the particular design).
The femoral implant typically includes an elongated metallic spike
or post at one end and a metallic ball at the other. The post is
typically configured to be anchored into the distal femoral
medullary canal and the ball is typically configured to insert into
the artificial socket. Pivotal freedom of the ball within the
socket allows articulation of the prosthetic joint.
[0003] A substantial dislocation and/or rotation of the bearing
relative to the shell can potentially degrade the biomechanics
and/or wear characteristics of the conventional hip prosthesis.
Historically, balancing the needs for effective bearing retention
with competing desires for design simplicity and versatility has
been challenging.
SUMMARY OF THE INVENTION
[0004] The present invention provides a method of making a
metal-backed acetabular implant. The method includes roughening a
surface of a metallic integument and compression molding a bearing
to the surface after the roughening step.
[0005] The above-noted features and advantages of the present
invention, as well as additional features and advantages, will be
readily apparent to those skilled in the art upon reference to the
following detailed description and the accompanying drawings, which
include a disclosure of the best mode of making and using the
invention presently contemplated.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] FIG. 1 shows an exemplary hip prosthesis including an
exemplary femoral implant and further including an exemplary
acetabular implant according to the present invention;
[0007] FIG. 2 shows a perspective view of the exemplary acetabular
implant of FIG. 1;
[0008] FIG. 3 shows an exploded axial cross-sectional view of the
exemplary acetabular implant of FIG. 1;
[0009] FIG. 4 shows an axial cross-sectional view the shell of the
exemplary acetabular implant of FIG. 1;
[0010] FIG. 5 shows an axial cross-sectional view the bearing of
the exemplary acetabular implant of FIG. 1;
[0011] FIG. 6 shows an axial cross-sectional view of the integument
of the exemplary acetabular implant of FIG. 1;
[0012] FIG. 7 shows an exploded axial cross-sectional view of an
exemplary alternative acetabular implant according to the present
invention; and
[0013] FIG. 8 shows an exploded axial cross-sectional view of
another exemplary alternative acetabular implant according to the
present invention.
DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENT(S)
[0014] Like reference numerals refer to like parts throughout the
following description and the accompanying drawings. As used
herein, the terms "medial," "medially," and the like mean
pertaining to the middle, in or toward the middle, and/or nearer to
the middle of the body when standing upright. Conversely, the terms
"lateral," "laterally," and the like are used herein as opposed to
medial. For example, the medial side of the knee is the side
closest to the other knee and the closest sides of the knees are
medially facing, whereas the lateral side of the knee is the
outside of the knee and is laterally facing. Further, as used
herein the term "superior" means closer to the top of the head
and/or farther from the bottom of the feet when standing upright.
Conversely, the term "inferior" is used herein as opposed to
superior. For example, the heart is superior to the stomach and the
superior surface of the tongue rests against the palate, whereas
the stomach is inferior to the heart and the palate faces
inferiorly toward the tongue. Also, as used herein the terms
"anterior," "anteriorly," and the like mean nearer the front or
facing away from the front of the body when standing upright, as
opposed to "posterior," "posteriorly," and the like, which mean
nearer the back or facing away from the back of the body.
Additionally, as used herein the term "generally hemispherical" is
intended its broadest sense to encompass all concave and convex
geometries suitable for applicable components of prosthetic
ball-and-socket type joints such as acetabular and glenoid shells,
integuments, bearings, and the like, and, accordingly, includes
hemispherical geometries, includes partially spherical geometries
that are more than hemispherical, includes partially spherical
geometries that are less than hemispherical, and includes all
suitable curved polygonal and geodesic geometries as well. Further,
as used herein the terminology "taper couple" and inflections
thereof mean to fasten together via a taper joint. In general, a
taper joint or taper coupling is formed by pressing together
("press-fitting") a male part ("male taper") and a female part
("female taper") having impinging angled or flared surfaces. Taper
couplings are generally known in the art. For example, the
disclosure of U.S. Pat. No. 6,610,097 to Serbousek et al, which is
expressly incorporated herein by reference, discusses manners of
making and using various taper couplings that may be suitable for
incorporation into applicable embodiments of the present
invention.
[0015] FIG. 1 shows an exemplary hip prosthesis 100 including an
exemplary femoral implant 120 and further including an exemplary
acetabular implant 140 according to the present invention. Among
other things, implant 120 is configured as known to replace natural
hip components (not shown) of a distal femur 160. In the exemplary
embodiment, implant 120 is metallic and preferably made from
titanium. In alternative embodiments, implant 120 may be made from
a cobalt chrome alloy or any other suitable biocompatible
material(s). Implant 120 includes a post 180. Among other things,
post 180 is configured as known to anchor into a medullary canal
200 of distal femur 160. Implant 120 also includes a substantially
spherical ball 220. Among other things, implant 140 is configured
to replace natural hip components (not shown) of an acetabulum 240.
Accordingly, implant 140 defines a generally hemispherical
artificial hip socket 260 (see FIG. 2 and FIG. 5) that receives
ball 220 as known such that ball 220 has suitable pivotal freedom
within socket 260. Implant 140 is discussed further below.
[0016] FIG. 2 shows a perspective view of exemplary implant 140.
Implant 140 includes a dome-like or cup-like acetabular shell 300,
and a dome-like or cup-like metal-backed bearing sub-assembly 320
(see also FIG. 3). Among other things, shell 300 is configured to
be anchored into acetabulum 240 (see FIG. 1) in a known manner, and
is configured to taper couple to sub-assembly 320 in accordance
with the exemplary embodiment. In the exemplary embodiment, shell
300 is metallic and preferably made from titanium. In alternative
embodiments, shell 300 may be made from a cobalt chrome alloy or
any other suitable biocompatible material(s). Further, shell 300 is
symmetrical about an axis 340 and includes a generally concave
inner surface 360 (see FIG. 4) defining a generally concave cavity
or socket 380 (see FIG. 4) that is symmetrical about axis 340.
Further, shell 300 includes a generally hemispherical outer surface
400 facing generally outwardly away from socket 380. In the
exemplary embodiment, surface 400 is suitably textured as known to
facilitate fixation in acetabulum 240. Additionally, it is noted
that surface 400 may be suitably covered with a porous material
(not shown) as known to enhance acetabular fixation of shell 300
through bone in growth.
[0017] FIG. 3 shows an exploded axial cross-sectional view of
implant 140. As at least partially discernable in FIG. 3,
sub-assembly 320 includes a dome-like or cup like bearing 406 and a
dome-like or cup-like backing or integument 412. Shell 300 and axis
340, among other things, are also at least partially discernable in
FIG. 3. Bearing 406 and integument 412 are discussed further
below.
[0018] FIG. 4 shows an axial cross-sectional view of shell 300. As
at least partially discernable in FIG. 4, surface 360 of shell 300
includes an annular rim 420 centered about axis 340 with a radius
440. Surface 360 also includes a circular flat 460 centered about
axis 340 with a radius 480. Flat 460 is disposed from rim 420 by an
axial dimension 500. Socket 380 opens at rim 420, while flat 460
bounds socket 380 axially inwardly from rim 420. Further, surface
360 defines an annular female taper 520 extending from flat 460
generally towards rim 420 at a taper angle 540 relative to axis
340. Axially, taper 520 extends from flat 460 by a dimension 560.
Surface 360 also defines an annular female taper 580 extending from
taper 520 generally towards rim 420 at a taper angle 600 relative
to axis 340. Axially, taper 580 extends from taper 520 by a
dimension 620. Surface 360 also defines an annular female taper 640
extending from taper 580 generally towards rim 420 at a taper angle
660 relative to axis 340. Axially, taper 640 extends from taper 580
by a dimension 680. In the exemplary embodiment, radius 480 is less
than radius 440, angle 600 is less than angle 540, and angle 660 is
less than angle 600, while dimension 620 is greater than dimension
560, and dimension 680 is greater than dimension 620.
[0019] FIG. 5 shows an axial cross-sectional view of bearing 406.
Among other things, bearing 406 is configured as known to receive
ball 220 (see FIG. 1) in socket 260 and is configured to couple
into integument 412 according to the exemplary embodiment of the
present invention. In the exemplary embodiment, bearing 406 is made
from a plastic, preferably ultra high molecular weight polyethylene
("UHMWPE"). In alternative embodiments, bearing 406 may be made
from any other suitable biocompatible material(s). As at least
partially discernable in FIG. 5, bearing 406 includes a generally
hemispherical and generally concave inner surface 740 that is
suitably machined as known to define socket 260. Bearing 406 also
includes a generally convex outer surface 760 that faces generally
outwardly away from socket 260. Surface 760 includes an annular rim
820 centered about axis 340 with a radius 840. Surface 760 also
includes a circular flat 860 centered about axis 340 with a radius
880. Flat 860 is disposed from rim 820 by an axial dimension 900.
Further, surface 760 defines an annular male taper 920 extending
from flat 860 generally towards rim 820 at a taper angle 940
relative to axis 340. Axially, taper 920 extends from flat 860 by a
dimension 960. Surface 760 also defines an annular male taper 980
extending from taper 920 generally towards rim 820 at a taper angle
1000 relative to axis 340. Axially, taper 980 extends from taper
920 by a dimension 1020. Surface 760 also defines an annular male
taper 1040 extending from taper 980 generally towards rim 820 at a
taper angle 1060 relative to axis 340. Axially, taper 1040 extends
from taper 980 by a dimension 1080. In the exemplary embodiment,
radius 880 is less than radius 840, angle 1000 is less than angle
940, and angle 1060 is less than angle 1000, while dimension 1020
is greater than dimension 960, and dimension 1080 is greater than
dimension 1020.
[0020] FIG. 6 shows an axial cross-sectional view of integument
412. Among other things, integument 412 is configured to couple
around bearing 406 and to couple into shell 300 according to the
exemplary embodiment of the present invention. In the exemplary
embodiment, integument 412 is metallic and preferably made from
titanium. In alternative embodiments, integument 412 may be made
from a cobalt chrome alloy or any other suitable biocompatible
material(s). As at least partially discernable in FIG. 6,
integument 412 includes a generally concave inner surface 1160 that
defines a generally concave socket 1170. Surface 1160 includes an
annular rim 1220 centered about axis 340 with a radius 1240.
Surface 1160 also includes a circular flat 1260 centered about axis
340 with a radius 1280. Flat 1260 is disposed from rim 1220 by an
axial dimension 1300. Further, surface 1160 defines an annular
female taper 1320 extending from flat 1260 generally towards rim
1220 at a taper angle 1340 relative to axis 340. Axially, taper
1320 extends from flat 1260 by a dimension 1360. Radius 1280, angle
1340 and dimension 1360 are sized such that taper 1320 securely
taper couples to taper 920 (of bearing 406; see FIG. 5) upon
assembly of sub-assembly 320 (see FIG. 3). Surface 1160 also
defines an annular female taper 1380 extending from taper 1320
generally towards rim 1220 at a taper angle 1400 relative to axis
340. Axially, taper 1380 extends from taper 1320 by a dimension
1420. Angle 1400 and dimension 1420 are sized such that taper 1380
securely taper couples to taper 980 (of bearing 406; see FIG. 5)
upon assembly of sub-assembly 320 (see FIG. 3). Surface 1160 also
defines an annular female taper 1440 extending from taper 1380
generally towards rim 1220 at a taper angle 1460 relative to axis
340. Axially, taper 1440 extends from taper 1380 by a dimension
1480. Angle 1460 and dimension 1480 are sized such that taper 1440
securely taper couples to taper 1040 (of bearing 406; see FIG. 5)
upon assembly of sub-assembly 320 (see FIG. 3). In the exemplary
embodiment, dimension 1300 is about equal to dimension 900 (of
bearing 406; see FIG. 5), radius 1280 is less than radius 1240,
angle 1400 is less than angle 1340, and angle 1460 is less than
angle 1400, while dimension 1420 is greater than dimension 1360,
and dimension 1480 is greater than dimension 1420.
[0021] Integument 412 also includes a generally convex outer
surface 1560 that faces generally outwardly away from socket 1170.
Surface 1560 includes an annular rim 1620 centered about axis 340
with a radius 1640. Surface 1560 also includes a circular flat 1660
centered about axis 340 with a radius 1680. Flat 1660 is disposed
from rim 1620 by an axial dimension 1700. Further, surface 1560
defines an annular male taper 1720 extending from flat 1660
generally towards rim 1620 at a taper angle 1740 relative to axis
340. Axially, taper 1720 extends from flat 1660 by a dimension
1760. Radius 1680, angle 1740 and dimension 1760 are sized such
that taper 1720 and flat 1660 have clearance with flat 460 and
taper 520 upon assembly of implant 140. Surface 1560 also defines
an annular male taper 1780 extending from taper 1720 generally
towards rim 1620 at a taper angle 1800 relative to axis 340.
Axially, taper 1780 extends from taper 1720 by a dimension 1820.
Angle 1800 and dimension 1820 are sized such that taper 1780 has
clearance with taper 580 upon assembly of implant 140. Surface 1560
also defines an annular male taper 1840 extending from taper 1780
generally towards rim 1620 at a taper angle 1860 relative to axis
340. Axially, taper 1840 extends from taper 1780 by a dimension
1880. Angle 1860 and dimension 1880 are sized such that taper 1840
securely taper couples to taper 640 (of shell 300; see FIG. 4) upon
assembly of implant 140 (see FIG. 3). In the exemplary embodiment,
dimension 1700 is less than dimension 500 (of shell 300; see FIG.
4), radius 1680 is less than radius 1640, angle 1800 is less than
angle 1740, and angle 1860 is less than angle 1800, while dimension
1820 is greater than dimension 1760, and dimension 1880 is greater
than dimension 1820.
[0022] To begin assembly of implant 140, bearing 406 is
press-fitted axially into socket 1170 (of integument 412) to
assemble or unite sub-assembly 320. Here, it is noted that although
implant 140 is fully exploded in FIG. 3 for clarity of exposition,
bearing 406 is preferably pre-operatively press-fitted into socket
1170 by a manufacturer to unite sub-assembly 320 separately from
shell 300. Such pre-operative unification of sub-assembly 320 may
include temporarily cooling bearing 406 (by immersing it in liquid
nitrogen or by any other suitable refrigeration method(s))
immediately prior to press-fitting it into socket 1170, followed by
allowing bearing 406 to warm or reheat to a normal temperature (and
thus un-shrink or re-expand) within socket 1170 so as to
additionally tighten bearing 406 within socket 1170. Upon
unification of sub-assembly 320, taper 1040 taper couples to taper
1440, which taper couples surface 760 to surface 1160, and, thus,
taper couples bearing 406 to integument 412. It is noted that the
strength of the taper coupling reduces or eliminates needs for
additional undesirably complex and/or costly structures that might
otherwise be required to prevent dislocation and/or rotation of
bearing 406 within integument 412.
[0023] Assembly of implant 140 is completed by suitably
rotationally aligning sub-assembly 320 relative to shell 300 about
axis 340 and then press-fitting sub-assembly 320 axially into
socket 380 (of shell 300). Here, it is noted that the annular
designs of taper 1720, taper 520, taper 1780, taper 580, taper
1840, and taper 640 allow for infinite rotational orientation or
alignment of sub-assembly 320 (including bearing 406 and, thus,
socket 260 as well) prior to press-fitting sub-assembly 320 into
socket 380. Such infinite rotational resolution may be especially
advantageous for alternative embodiments of the present invention
in which socket 260 is off-centered from axis 340. Upon
press-fitting sub-assembly 320 into socket 380, taper 1840 taper
couples to taper 640, which taper couples surface 1560 to surface
360, and, thus, taper couples integument 412 (and thus,
sub-assembly 320) to shell 300. It is noted that the strength of
the taper coupling reduces or eliminates needs for additional
undesirably complex and/or costly structures that might otherwise
be required to prevent dislocation and/or rotation of sub-assembly
320 within shell 300.
[0024] To assemble prosthesis 100, distal femur 160 and acetabulum
240 are suitably resected, post 180 is suitably anchored into
medullary canal 200, and shell 300 is suitably anchored into
acetabulum 240. Sub-assembly 320 is rotationally aligned relative
to shell 300 and then press-fitted into socket 380. Lastly, ball
220 is inserted into socket 260.
[0025] In operation of prosthesis 100, bearing 406 stays taper
coupled to integument 412 within socket 1170; sub-assembly 320
(including bearing 406 and integument 412) stays taper coupled to
shell 300 within socket 380; and pivotal freedom of ball 220 within
socket 260 allows articulation of implant 120 relative to implant
140.
[0026] FIG. 7 shows an exploded axial cross-sectional view of an
exemplary alternative acetabular implant 2000 according to the
present invention. Implant 2000 is made and used in a like manner
to implant 140 (discussed above) except that sub-assembly 320 is
replaced with an alternative dome-like or cup-like metal-backed
bearing sub-assembly 2020. Sub-assembly 2020 includes an
alternative dome-like or cup like bearing 2100 and an alternative
dome-like or cup-like backing or integument 2120. Bearing 2100 is
made and used in a like manner to bearing 406 except that rim 820
is replaced with a radially inwardly extending annular ledge 2200.
Integument 2120 is made and used in a similar manner to integument
412 except that rim 1220 is replaced with a radially inwardly
extending annular flange 2300. When sub-assembly 2020 is united,
flange 2300 abuts ledge 2200 to additionally inhibit dislocation
and/or rotation of bearing 2100 within integument 2120.
[0027] FIG. 8 shows an exploded axial cross-sectional view of
another exemplary alternative acetabular implant 3000 according to
the present invention. Implant 3000 is made and used in a like
manner to implant 140 (discussed above) except that sub-assembly
320 is replaced with an alternative dome-like or cup-like
metal-backed bearing sub-assembly 3020. Sub-assembly 3020 includes
an alternative dome-like or cup like bearing 3100 and an
alternative dome-like or cup-like backing or integument 3120.
Bearing 3100 and integument 3120 are made and used in similar
manners to bearing 406 and integument 412, respectively, except
that bearing 3100 and integument 3120 are not taper coupled to each
other; instead, surface 1160 is replaced with a generally
hemispherical generally concave surface 3160, and bearing 3100 is
compression molded directly onto surface 3160. Further, prior to
compression molding bearing 3100 onto surface 3160, surface 3160 is
preferably roughened to produce a more adherent substrate. The
roughening is preferably accomplished by dry blasting surface 3160
with 60 grit alumina, or, in alternative embodiments, via any other
suitable method.
[0028] The foregoing description of the invention is illustrative
only, and is not intended to limit the scope of the invention to
the precise terms set forth. Further, although the invention has
been described in detail with reference to certain illustrative
embodiments, variations and modifications exist within the scope
and spirit of the invention as described and defined in the
following claims.
* * * * *