Invention (Patent Application Publication): Taylor S. Prosthetic joint with annular contact bearing surface. US20050261776A1 (2005).
US20050261776A1 US
Inventor: Scott Taylor
Current Assignee: Howmedica Osteonics Corp
Worldwide applications 2004 US 2005 CA EP AU
Application US10/849,343 events:
2004-05-19 Application filed by Howmedica Osteonics Corp
2004-05-19 Priority to US10/849,343
2004-06-10 Assigned to HOWMEDICA OSTEONICS CORP.
2005-05-18 Priority to EP05010779A
2005-05-18 Priority to CA002507770A
2005-05-19 Priority to AU2005202173A
2005-11-24 Publication of US20050261776A1
Status: Abandoned
Prosthetic joint with annular contact bearing surface
Scott Taylor
Abstract
A prosthetic joint has
a head member with a load-bearing surface, and a bearing member with a concave
bearing surface oriented and configured such that during articulation of the
prosthetic joint the load-bearing surface engages the concave bearing surface
along an annular intermediate surface portion located between first and second
ends of the bearing member and spaced from each of the first and second ends.
The configuration of the bearing surface provides clearance between the head
member and the bearing surface along portions of the bearing surface lying
between the annular intermediate surface portion and each end of the bearing member
to assure engagement of the load-bearing surface at the annular intermediate
surface portion. An opening passes through the bearing member at the first end
of the bearing member and communicates with the concave bearing surface.
Description
[0001]
The present invention relates generally to prosthetic
implants and pertains, more specifically, to bearing members used in connection
with head members in prosthetic joints, such as hip joints, in which a
spherical head is engaged for articulation within a generally complementary
bearing member.
[0002]
The successful
replacement of diseased or injured body joints, such as hip joints and shoulder
joints, wherein a spherical head member is articulated within a bearing member,
has led to the development of a very wide variety of prosthetic joints and
surgical procedures which facilitate the replacement of such joints. More
recently, it has been proposed that these prosthetic joints be constructed of
materials which provide higher levels of performance, including improved
articulation for greater comfort and increased range of motion, and improved
resistance to wear for greater longevity.
[0003]
The present
invention provides a prosthetic joint construction having a unique geometry at
the articular surfaces of the joint for realizing increased levels of
performance. As such the present invention attains several objects and
advantages, some of which are summarized as follows: Promotes minimally
invasive surgical procedures by providing a prosthetic joint with a profile
configuration of reduced dimensions for enabling implant procedures utilizing
smaller openings requiring incisions of minimal length and lower profile
surgical instruments; enables the use of an annular bearing member having an
apical opening which allows access to bone at an implant site subsequent to the
implant of the bearing member at the site; deters dislocation of a head member
from the bearing member of a prosthetic joint during service; allows an increased
range of motion during articulation of a prosthetic joint, without deleterious
impingement of a stem component on a cup component of the prosthetic joint;
facilitates removal of the bearing member of a prosthetic joint, should such
removal become necessary for replacement or revision; reduces any tendency
toward pressure-induced osteolysis behind an implanted cup component of a
prosthetic joint; assists in the natural lubrication of an implanted prosthetic
joint; enables preservation of the round ligament (ligamentum capitus femoris
or ligamentum teres) in a hip joint replacement; reduces cost and complexity in
prosthetic joints; requires less bone removal, with a concomitant preservation
of healthy bone, during joint replacement procedures; allows successful
replacement of a natural joint at sites heretofore not amenable to the implant
of conventional prosthetic joints; enables a wider choice of materials for the
construction of prosthetic joints having increased levels of performance and
longevity.
[0004]
The above objects
and advantages are attained by the present invention which may be described
briefly as providing, in a prosthetic joint in which a head member is engaged
with a bearing member for articulation within the prosthetic joint, the head
member having a load-bearing surface for engaging the bearing member during
articulation of the prosthetic joint, an improvement wherein the bearing member
extends axially between a first end and a second end and includes a concave
bearing surface having an orientation and a surface configuration arranged such
that during articulation of the prosthetic joint, the load-bearing surface of
the head member is engaged with the concave bearing surface along an annular
intermediate surface portion located between the first and second ends of the
bearing member, with the surface configuration of the concave bearing surface
providing a first clearance between the head member and the concave bearing
surface and extending in a first direction from the intermediate surface portion
toward the first end of the bearing member, and a second clearance between the
head member and the concave bearing surface and extending in a second direction
from the intermediate surface portion toward the second end of the bearing
member.
[0005]
Further, the present
invention provides, in a prosthetic joint in which a head member is engaged
with a bearing member for articulation within the prosthetic joint, the head
member having a longitudinal axis, circular surface contour configurations in
planes transverse to the longitudinal axis, and a load-bearing surface with a
predetermined radius extending from a given origin on the longitudinal axis for
engaging the bearing member during articulation of the prosthetic joint, an
improvement wherein: the bearing member extends axially between a first end and
a second end, the bearing member including a concave surface extending axially
between the first end and the second end and having an annular contact surface
portion and a central axis for passing through the given origin when the head
member is engaged with the bearing member; the concave surface having a surface
contour configuration including circular profiles in radial planes transverse
to the central axis, the circular profiles including a contact circular profile
lying in a contact plane passing through the contact surface portion of the
concave surface during articulation of the prosthetic joint, first circular
profiles lying in respective first radial planes spaced axially from the
contact plane and located between the contact plane and the first end of the
bearing member, second circular profiles lying in respective second radial
planes spaced axially from the contact plane and located between the contact
plane and the second end of the bearing member, the contact circular profile
having a prescribed contact radius, the first circular profiles each having a
radius less than the prescribed contact radius and greater than a corresponding
radius of a corresponding circular surface contour configuration of the head
member, and the second circular profiles each having a radius greater than the
prescribed contact radius and greater than a corresponding radius of a
corresponding circular surface contour configuration of the head member; such
that during articulation of the prosthetic joint, the load-bearing surface of
the head member is engaged with the concave surface along the contact circular
profile, intermediate the first and second ends of the bearing member, with the
first circular profiles providing a first clearance between the head member and
the surface contour configuration of the concave surface, and with the second
circular profiles providing a second clearance between the head member and the
surface contour configuration of the concave surface.
[0006]
The invention will
be understood more fully, while further objects and advantages will become
apparent, in the following detailed description of preferred embodiments of the
invention illustrated in the accompanying drawing, in which:
[0007]
FIG. 1 is a
partially diagrammatic longitudinal cross-sectional view of an acetabular
component and a femoral component engaged therewith for articulation in a
conventional prosthetic hip joint;
[0008]
FIG. 2 is a
partially diagrammatic longitudinal cross-sectional view of an acetabular
component constructed in accordance with the present invention and a femoral
component engaged therewith for articulation in a prosthetic hip joint;
[0009]
FIG. 3 is a
fragmentary diagrammatic depiction of the prosthetic hip joint of FIG. 2;
and
[0010]
FIG. 4 is an
elevational cross-sectional view showing an implanted prosthetic hip joint
constructed in accordance with the present invention.
[0011]
Referring now to the
drawing, and especially to FIG. 1 thereof, a conventional prosthetic
joint is shown in the form of prosthetic hip joint 10 and is
seen to comprise an acetabular component 12 and a femoral
component 14. Femoral component 14 includes a femoral
head 16 having a spherical surface 18 which engages a
generally complementary bearing surface 20 of a bearing
member 22 secured within acetabular cup 24 of acetabular
component 12 for articulation of the prosthetic hip joint 10,
in a manner now well-known in the construction and operation of prosthetic
joints.
[0012]
Ideally, spherical
surface 18 and bearing surface 20 would be made congruent
for effective articulation of prosthetic hip joint 10; however, in
order to avoid equatorial loading during articulation, as well as to meet the
necessity for providing a range of sizes to accommodate various recipients of a
prosthetic joint, as well as to compensate for manufacturing tolerances,
the radius 30 of spherical surface 18 usually is
made somewhat smaller than the radius 32 of the bearing
surface 20. As a result, at least initial contact between the femoral
head 16 and the bearing member 22 nominally is at
a point 34 lying along a line 36 of load
application. Deviations in the contour of bearing surface 20 in the
vicinity of point 34 have been proposed in order to better
distribute the load and reduce stresses at the load-bearing area of the bearing
surface 20. Nevertheless, the load-bearing areas of the bearing
surface 20 and of the spherical surface 18 remain
juxtaposed with point 34.
[0013]
Turning now
to FIG. 2, a prosthetic joint constructed in accordance with the present
invention is shown in the form of prosthetic hip joint 50 comprised
of an acetabular component 52 and a femoral component 54.
As before, femoral component 54 includes a head member in the
form of a femoral head 56 having a spherical surface 58.
A bearing member in the form of bearing 60 is affixed within
an acetabular cup 62 and extends axially between a first,
or upper end 64 and a second, or lower end 66, along
a central axis 68. A bearing surface 70 within bearing 60 is
oriented and configured such that during articulation of the prosthetic
hip joint 50, a load-bearing surface 72 of femoral
head 56 engages bearing surface 70 along an
annular intermediate surface portion 74 of the bearing
surface 70, the intermediate surface portion 74 being
spaced from each of the upper and lower ends 64 and 66. Bearing
surface 70 is concave and includes a surface profile configuration
which provides a first, or upper clearance in the form of a proximal
gap 80 between femoral head 56 and
bearing surface 70 and a second, or lower clearance in the form
of a distal gap 82 between femoral head 56 and
bearing surface 70, the upper clearance extending in a first, or
upward direction from intermediate surface portion 74 toward upper
end 64 and the lower clearance extending in a second, or downward
direction from intermediate surface portion 74 toward lower
end 66. Thus, the surface profile configuration of bearing
surface 70 assures that contact between spherical surface 58 of femoral
head 56 and bearing surface 70 of bearing 60 lies
along an annular seat 84 having an annular contact area 86 and
that contact stresses are distributed over annular contact area 86 of
annular seat 84.
[0014]
The aspherical
articulating geometry described above enables the distribution of contact
stresses over annular contact area 86 of annular seat 84,
resulting in a reduction of unit stress applied to the material
of bearing 60. Further, by assuring that contact between femoral
head 56 and bearing 60 is along an annular contact
area 86 located between the ends 64 and 66 of
the bearing 60, both the bearing 60 and
the acetabular component 52 may be truncated, as compared to the
configuration of conventional acetabular components. Thus, as illustrated in
phantom in FIG. 2, apical portion 90 of a conventional
acetabular component no longer need be present and acetabular
component 52 is rendered more compact, with a
reduced height 92 providing a lower profile configuration as
compared to a conventional acetabular component. The lower profile
configuration enables acetabular component 52 to be implanted
with a surgical procedure which requires a smaller, minimal incision and lower
profile surgical instruments, with a concomitant reduction in surgical trauma
and convalescence. Further, less bone removal is required, enabling
preservation of healthy bone at an implant site.
[0015]
In addition,
deletion of apical portion 90 provides an opening 94 at
the upper end 64 of bearing 60, and
a corresponding aperture 96 at the top of the acetabular
component 52, enabling access to outer surfaces 98 of
the acetabular cup 62, and to the acetabulum itself, subsequent to
implant of the acetabular component 52 and insertion of
the bearing 60 into the acetabular cup 62, without the
necessity for interrupting the connection between the bearing 60 and
the acetabular cup 62, and the possibility of compromising any
locking mechanism which secures the bearing 60 in place in
the acetabular cup 62. In this manner, a surgeon is able to make
adjustments and corrections without disturbing the placement of
the acetabular cup 62 at the acetabulum or the placement of the
bearing 60 within the acetabular cup 62. Should it become
necessary to remove the bearing 60 from the acetabular
cup 62, removal is facilitated by the ability to grasp
the bearing 60 at the opening 94, and such removal is
accomplished readily without damage to either bearing 60 or acetabular
cup 62.
[0016]
Opening 94 and corresponding
aperture 96 provide additional advantages in that the effective area
for the transfer of fluid between the interior of the acetabular
component 52 and the surrounding bone is increased, with a
concomitant reduction in fluid pressures transferred to the acetabulum during
service. The reduction of such fluid pressures avoids the creation of
pressure-induced osteolysis behind the implanted acetabular
component 52. In addition, fluid distribution to the articular surfaces is
facilitated, thereby avoiding fluid starvation conditions during articulation,
and promoting enhanced wear characteristics.
[0017]
The aspherical
articulating geometry of prosthetic hip joint 50 is illustrated
diagrammatically in FIG. 3. Head 56 of femoral
component 54 is engaged with bearing 60 of acetabular
component 52 and includes a longitudinal axis 100 shown
coincident with central axis 68 of bearing 60. Spherical
surface 58 of head 56 has a predetermined
radius 102 extending from a center 104 located in
an equatorial plane 106 and placed on longitudinal
axis 100, coincident with central axis 68, and is seated
against bearing surface 70 at load-bearing surface 72. Spherical
surface 58 includes circular surface contour configurations in planes
transverse to longitudinal axis 100, one such plane being illustrated
in the form of contact plane 112, within which contact
plane 112 load-bearing surface 72 has a
circular surface contour configuration 114 with a
prescribed radius 116 extending from a given origin 118 on longitudinal
axis 100 to the bearing surface 70.
[0018]
As described above,
load-bearing surface 72 contacts bearing surface 70 along
a surface portion 74 spaced from each end 64 and 66 of bearing 60. Bearing
surface 70 is concave and has a surface contour configuration which
includes circular profiles 120 in radial planes transverse
to central axis 68, one such circular profile being illustrated in
the form of a contact circular profile 122 lying
within contact plane 112, coincident with circular surface
contour configuration 114 of spherical surface 58. Contact
between load-bearing surface 72 and bearing surface 70 during
articulation is along the annular intermediate surface portion 74,
nominally along contact circular profile 122, within contact
plane 112 spaced upwardly, in a proximal direction,
from equatorial plane 106. The upward spacing between
the equatorial plane 106 and the contact plane 112 is
determined by an acute contact angle A between the equatorial plane 106 and
the radius 102 of the spherical surface 58 which
intercepts the contact plane 112 at the circular contact
profile 122. The annular contact between head 56 and bearing 60 is
spaced laterally from central axis 68 throughout articulation of
the prosthetic joint 10 such that resultant load forces direct
the femoral head 56 toward the acetabular component 52,
thereby militating against dislocation of the head 56 from
the bearing 60. Forces imposed by the load are distributed over the
annular area of intermediate surface portion 74, rather than being
concentrated in the vicinity of central axis 68, as would be the case
with conventional prosthetic hip joint 10, thereby reducing unit
stress along the bearing surface 70. Angle A is selected so as to
optimize the attributes gained from the employment of an annular contact
at intermediate surface portion 74. Thus, angle A may be within the
range of about five to eighty-five degrees, with the preferred range being
twenty to fifty degrees and a most-preferred nominal angle A being about thirty
degrees.
[0019]
Clearances provided
by the proximal gap 80 and the distal gap 82 assure
that the contact plane 112, and consequently contact
between head 56 and bearing surface 70, occurs
intermediate the ends 64 and 66 of bearing 60,
thereby precluding excessive stresses at either end of the bearing
surface 70 and the possibility of unwanted bearing failure or
dislocation of the head 56 from the bearing 60. Gaps 80 and 82 are
created by the relationship between spherical surface 58 and the
surface contour configuration of bearing surface 70. More
specifically, each gap 80 and 82 is established by a
deviation between the contour of spherical surface 58 and the
contour of bearing surface 70 at locations axially above and
axially below the contact plane 112.
[0020]
Looking first at
the proximal gap 80, clearance between the spherical
surface 58 and the bearing surface 70 is accomplished
by a difference between the radius 130 of each circular
profile 132 of the bearing surface 70 lying in each
corresponding radial plane 134 spaced axially from
the contact plane 112 and located between the contact
plane 112 and the proximal end 64, and
the radius 136 of a corresponding circular surface contour
configuration 138 of the head 56. Contact plane 112 is
located above equatorial plane 106 and the circular
profiles 132 of the bearing surface 70 each have
a radius 130 less than the prescribed contact radius 116.
Looking next at the distal gap 82, clearance between
the spherical surface 58 and the bearing surface 70 is
accomplished by a difference between the radius 140 of
each circular profile 142 of the bearing surface 70 lying
in each corresponding radial plane 144 spaced axially from
the contact plane 112 and located between the contact
plane 112 and the distal end 66, and the radius 146 of
a corresponding circular surface contour configuration 148 of
the head 56. Contact plane 112 is located
above equatorial plane 106 and the circular profiles 142 of
the bearing surface 70 each have a radius 140 greater
than the prescribed contact radius 116.
[0021]
The magnitude of
each gap 80 and 82 is selected to accommodate
different conditions encountered at the site of the implant, as well as to
enable a reduction in the dimensions of the bearing 60. Gaps 80 and 82 accommodate
different fluid conditions at the implant site and allow for the egress of any
particles which may be generated by wear. The clearance provided
by gaps 80 an 82, as measured radially between
the spherical surface 58 and the bearing surface 70,
may be in the range of ten to two-thousand microns, with the preferred range
being twenty to two-hundred microns and the most-preferred clearance nominally
being forty microns.
[0022]
While the spherical
bearings employed in conventional prosthetic joints require a relatively broad
hemispherical area in order to accommodate a contact point which moves during
articulation, the location of the annular contact provided by the aspherical
geometry described above remains essentially unchanged during articulation.
Thus, the amount of material needed to support the load applied during articulation
is a function only of the strength of the material and lower profiles are
attained in prosthetic hip joint 50 by deleting excess material
at the distal end of the bearing 60. Both the contact angle A and the
radial clearance provided at gaps 80 and 82 are
selected for a reduction in the profile dimensions of the bearing 60.
The aspherical geometry is produced readily by conventional machining
techniques and can be molded of various bearing materials. Hard materials are
better choices, with ceramics being preferred over metals and composite
materials. Both monolithic and modular prosthetic joints can incorporate the
aspherical geometry described herein.
[0023]
Referring now
to FIG. 4, a truncated, annular acetabular component 200 constructed
in accordance with the present invention is shown implanted within
the natural acetabulum 210 of a hip joint 212. The
natural femoral head 220 of femur 222 has been
restored with a spherical surface replacement component 224.
The acetabular component 200 is provided with
an opening 230, as described above in connection with acetabular
component 52, and a corresponding aperture 232 is provided
in the replacement component 224. In this manner, the round
ligament 240 (ligamentum capitus femoris, or ligamentum teres) is
preserved, thereby avoiding sacrifice of the round ligament 240. The
conduit for the supply of blood to the femoral head 220 is
preserved. Access to ligament 240 for detachment and subsequent
reconstruction and re-attachment is shown at 242. In addition, preservation
or even reconstruction of the round ligament 240 assists in
resisting femoral head dislocation under certain hip movements, thereby
reducing the incidence of dislocation. Further, the construction of
the truncated acetabular component 200 allows for the use of a
synthetic ligament.
[0024]
It will be seen that
the present invention attains all of the objects and advantages summarized
above, namely: Promotes minimally invasive surgical procedures by providing a
prosthetic joint with a profile configuration of reduced dimensions for
enabling implant procedures utilizing smaller openings requiring incisions of
minimal length and lower profile surgical instruments; enables the use of an
annular bearing member having an apical opening which allows access to bone at
an implant site subsequent to the implant of the bearing member at the site;
deters dislocation of a head member from the bearing member of a prosthetic
joint during service; allows an increased range of motion during articulation
of a prosthetic joint, without deleterious impingement of a stem component on a
cup component of the prosthetic joint; facilitates removal of the bearing
member of a prosthetic joint, should such removal become necessary for
replacement or revision; reduces any tendency toward pressure-induced
osteolysis behind an implanted cup component of a prosthetic joint; assists in
the natural lubrication of an implanted prosthetic joint; enables preservation
of the round ligament (ligamentum capitus femoris or ligamentum teres) in a hip
joint replacement; reduces cost and complexity in prosthetic joints; requires
less bone removal, with a concomitant preservation of healthy bone, during
joint replacement procedures; allows successful replacement of a natural joint
at sites heretofore not amenable to the implant of conventional prosthetic
joints; enables a wider choice of materials for the construction of prosthetic
joints having increased levels of performance and longevity.
[0025]
It is to be understood that the above detailed description of preferred embodiments of the invention is provided by way of example only. Various details of design, construction and procedure may be modified without departing from the true spirit and scope of the present invention, as set forth in the appended claims.
Claims:
1. In a prosthetic joint in which a head member is
engaged with a bearing member for articulation within the prosthetic joint, the
head member having a longitudinal axis, circular surface contour configurations
in planes transverse to the longitudinal axis, and a load-bearing surface with
a predetermined radius extending from a given origin on the longitudinal axis
for engaging the bearing member during articulation of the prosthetic joint, an
improvement wherein:
the bearing member extends axially between a first end
and a second end, the bearing member including a concave surface extending
axially between the first end and the second end and having an annular contact
surface portion and a central axis for passing through the given origin when
the head member is engaged with the bearing member;
the concave surface having a surface contour
configuration including circular profiles in radial planes transverse to the
central axis, the circular profiles including
a contact circular profile lying in a contact plane
passing through the contact surface portion of the concave surface during
articulation of the prosthetic joint,
first circular profiles lying in respective first
radial planes spaced axially from the contact plane and located between the
contact plane and the first end of the bearing member,
second circular profiles lying in respective second
radial planes spaced axially from the contact plane and located between the
contact plane and the second end of the bearing member,
the contact circular profile having a prescribed
contact radius,
the first circular profiles each having a radius less
than the prescribed contact radius and greater than a corresponding radius of a
corresponding circular surface contour configuration of the head member, and
the second circular profiles each having a radius
greater than the prescribed contact radius and greater than a corresponding
radius of a corresponding circular surface contour configuration of the head
member;
such that during articulation of the prosthetic joint,
the load-bearing surface of the head member is engaged with the concave surface
along the contact circular profile, intermediate the first and second ends of
the bearing member, with the first circular profiles providing a first
clearance between the head member and the surface contour configuration of the
concave surface, and with the second circular profiles providing a second
clearance between the head member and the surface contour configuration of the
concave surface.
2. The improvement of claim 1 wherein the
bearing member includes an opening at the first end, the opening extending
axially and communicating with the concave surface.
3. The improvement of claim 1 wherein the
head member includes a spherical surface and the circular surface contour
configurations are located on the spherical surface.
4. The improvement of claim 3 wherein the
prosthetic joint comprises a prosthetic hip joint, the bearing member comprises
an acetabular bearing, the first end comprises a proximal end of the bearing
member and the second end comprises a distal end of the bearing member.
5. The improvement of claim 4 wherein the
bearing member includes an opening at the proximal end, the opening extending
axially through the bearing member and communicating with the concave surface.
6. The improvement of claim 3 wherein the
spherical surface has a predetermined radius extending between a center and the
contact circular profile, the center being placed in an equatorial plane of the
head member and located on the central axis of the concave surface when the
head member is engaged with the bearing member, the predetermined radius making
an acute angle with the equatorial plane such that the contact plane is located
between the equatorial plane and the first end of the bearing member.
7. The improvement of claim 6 wherein the
acute angle is in a range of about twenty to fifty degrees.
8. The improvement of claim 6 wherein the
acute angle is about thirty degrees.
9. The improvement of claim 1 wherein the
first clearance is in a range of about twenty to two-hundred microns.
10. The improvement of claim 1 wherein the
first clearance is about forty microns.
11. The improvement of claim 1 wherein the
second clearance is in a range of about twenty to two-hundred microns.
12. The improvement of claim 1 wherein the
second clearance is about forty microns.
13. In a prosthetic joint in which a head member is
engaged with a bearing member for articulation within the prosthetic joint, the
head member having a load-bearing surface for engaging the bearing member
during articulation of the prosthetic joint, an improvement wherein the bearing
member extends axially between a first end and a second end and includes a
concave bearing surface having an orientation and a surface configuration
arranged such that during articulation of the prosthetic joint, the
load-bearing surface of the head member is engaged with the concave bearing
surface along an annular intermediate surface portion located between the first
and second ends of the bearing member, with the surface configuration of the
concave bearing surface providing a first clearance between the head member and
the concave bearing surface and extending in a first direction from the
intermediate surface portion toward the first end of the bearing member, and a
second clearance between the head member and the concave bearing surface and
extending in a second direction from the intermediate surface portion toward
the second end of the bearing member.
14. The improvement of claim 13 wherein the
bearing member includes an opening at the first end, the opening extending
axially through the bearing member and communicating with the concave bearing
surface.
15. The improvement of claim 13 wherein the
head member includes a spherical surface and the load-bearing surface is
located on the spherical surface.
16. The improvement of claim 15 wherein the
prosthetic joint comprises a prosthetic hip joint, the bearing member comprises
an acetabular bearing, the first end comprises a proximal end of the bearing
member and the second end comprises a distal end of the bearing member.
17. The improvement of claim 16 wherein the
bearing member includes an opening at the proximal end, the opening extending
axially through the bearing member and communicating with the concave bearing
surface.
18. The improvement of claim 15 wherein the
spherical surface has a predetermined radius extending between a center and the
intermediate surface portion, the center being placed in an equatorial plane of
the head member and located on a central axis of the concave bearing surface
when the head member is engaged with the bearing member, the predetermined
radius making an acute angle with the equatorial plane such that the
intermediate surface portion is located between the equatorial plane and the
first end of the bearing member.
19. The improvement of claim 18 wherein the
acute angle is in a range of about twenty to fifty degrees.
20. The improvement of claim 18 wherein the
acute angle is about thirty degrees.
21. The improvement of claim 13 wherein the
first clearance is in a range of about twenty to two-hundred microns.
22. The improvement of claim 13 wherein the
first clearance is about forty microns.
23. The improvement of claim 13 wherein the
second clearance is in a range of about twenty to two-hundred microns.
24. The improvement of claim 13 wherein the
second clearance is about forty microns.
External links
Taylor S. Prosthetic joint with annular contact bearing
surface. US20050261776A1, May 19, 2004.
2005. patents.google
Publications
of invention
AU2005202173 (А1)
CA2507770 (А1)
EP1598033 (А1)
US20050261776 (A1)
2005TaylorS
Authors & Affiliations
Scott Taylor – Ridgewood, NJ (US)
Keywords
ligamentum capitis femoris, ligamentum teres, ligament
of head of femur, endoprosthesis, prosthesis,
invention, unipolar, subtotal
NB! Fair practice / use: copied for the purposes of criticism, review, comment, research and private study in accordance with Copyright Laws of the US: 17 U.S.C. §107; Copyright Law of the EU: Dir. 2001/29/EC, art.5/3a,d; Copyright Law of the RU: ГК РФ ст.1274/1.1-2,7
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