U.S. patent number RE42,805 [Application Number 11/801,429] was granted by the patent office on 2011-10-04 for elbow prosthesis.
This patent grant is currently assigned to Tornier. Invention is credited to Graham King, Shawn O'Driscoll, Yves Alain Ratron, Bruno Scialom, Alain Tornier, Ken Yamaguchi.
United States Patent |
RE42,805 |
Tornier , et al. |
October 4, 2011 |
**Please see images for:
( Certificate of Correction ) ** |
Elbow prosthesis
Abstract
A humeral component, forming a first articulating surface, and
an ulnar component forming a second articulating surface adapted to
be disposed around a part of the first articulating surface and to
pivot about its longitudinal axis. This ulnar component is provided
with structure for mounting a locking element which forms a third
articulating surface extending the second and adapted likewise to
be disposed around a part of the first surface. These mounting
structure comprise guiding structures adapted to cooperate with
complementary structure provided on the locking element in order to
guide this element in translation with respect to the ulnar
component, up to a position where blocking structure provided
respectively on the locking element and on the ulnar component may
be employed to immobilize this element on this component, these
blocking structure being able to be employed only in this
position.
Inventors: |
Tornier; Alain (Saint Ismier,
FR), O'Driscoll; Shawn (Rochester, MN), King;
Graham (London, CA), Yamaguchi; Ken (Saint Louis,
MO), Ratron; Yves Alain (Grenoble, FR), Scialom;
Bruno (Gieres, FR) |
Assignee: |
Tornier (Saint-Ismier,
FR)
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Family
ID: |
33104505 |
Appl.
No.: |
11/801,429 |
Filed: |
May 9, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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60473446 |
May 28, 2003 |
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Reissue of: |
10849899 |
May 21, 2004 |
6890357 |
May 10, 2005 |
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Foreign Application Priority Data
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May 28, 2003 [FR] |
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03 06519 |
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Current U.S.
Class: |
623/20.12;
623/20.11; 623/20.13 |
Current CPC
Class: |
A61F
2/3804 (20130101) |
Current International
Class: |
A61F
2/38 (20060101) |
Field of
Search: |
;623/20.11-20.13 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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19512854 |
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Aug 1996 |
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DE |
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0006314 |
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Jan 1980 |
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EP |
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0098466 |
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Jan 1984 |
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EP |
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0913133 |
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May 1999 |
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EP |
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1051954 |
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Nov 2000 |
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EP |
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2663838 |
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Jan 1992 |
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FR |
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1537479 |
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Dec 1978 |
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GB |
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Other References
US. Appl. No. 11/401,415, filed Apr. 11, 2006. cited by other .
U.S. Appl. No. 11/735,027, filed Apr. 13, 2007. cited by other
.
U.S. Appl. No. 11/770,285, filed Jun. 28, 2007. cited by
other.
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Primary Examiner: Willse; David H
Assistant Examiner: Blanco; Javier
Attorney, Agent or Firm: Faegre & Benson LLP
Parent Case Text
This application claims the benefit of U.S. provisional application
No. 60/473,446 filed May 28, 2003.
Claims
What is claimed is:
1. Elbow prosthesis comprising a humeral component, forming a first
articulating surface, and an ulnar component forming a second
articulating surface adapted to be disposed around a part of
.[.said.]. .Iadd.the .Iaddend.first articulating surface and to
pivot about a longitudinal axis of .[.said.]. .Iadd.the
.Iaddend.first articulating surface, .[.said.]. .Iadd.the
.Iaddend.ulnar component being provided with means for mounting a
locking element which forms a third articulating surface extending
.[.said.]. .Iadd.the .Iaddend.second articulating surface and
adapted likewise to be disposed around a part of .[.said.].
.Iadd.the .Iaddend.first articulating surface, wherein .[.said.].
.Iadd.the .Iaddend.mounting means comprise guiding means adapted to
cooperate with complementary means provided on .[.said.]. .Iadd.the
.Iaddend.locking element in order to guide .[.said.]. .Iadd.the
locking .Iaddend.element in translation with respect to .[.said.].
.Iadd.the .Iaddend.ulnar component, up to a position where blocking
means provided respectively on .[.said.]. .Iadd.the
.Iaddend.locking element and on .[.said.]. .Iadd.the .Iaddend.ulnar
component may be employed to immobilize .[.said.]. .Iadd.the
.Iaddend.locking element on .[.said.]. .Iadd.the .Iaddend.ulnar
component, .[.said.]. .Iadd.the .Iaddend.blocking means being able
to be employed only in this position.
2. The prosthesis of claim 1, wherein .[.said.]. .Iadd.the
.Iaddend.blocking means .[.comprise.]. .Iadd.comprises .Iaddend.a
screw and a complementary tapping provided respectively on
.[.said.]. .Iadd.the .Iaddend.locking element and on .[.said.].
.Iadd.the .Iaddend.ulnar component, or vice versa, the direction of
relative translation between .[.said.]. .Iadd.the locking
.Iaddend.element and .[.said.]. .Iadd.the ulnar .Iaddend.component
as imposed by .[.said.]. .Iadd.the .Iaddend.guiding means being
non-parallel to the longitudinal axis of .[.said.]. .Iadd.the
.Iaddend.tapping and/or of .[.said.]. .Iadd.the .Iaddend.screw.
3. The prosthesis of claim 1, wherein .[.said.]. .Iadd.the
.Iaddend.guiding means .[.comprise.]. .Iadd.comprises .Iaddend.at
least one element in relief projecting with respect to a principal
part of .[.said.]. .Iadd.the .Iaddend.ulnar component, while the
complementary means provided on .[.said.]. .Iadd.the
.Iaddend.locking element are adapted to interact with .[.said.].
.Iadd.the locking .Iaddend.element in relief by cooperation of
shapes.
4. The prosthesis of claim 3, wherein .[.said.]. .Iadd.the locking
.Iaddend.element in relief is a nose, while .[.said.]. .Iadd.the
.Iaddend.complementary means .[.comprise.]. .Iadd.comprises
.Iaddend.a fork of which two branches define therebetween a volume
for receiving and for .[.slide of said.]. .Iadd.sliding the
.Iaddend.nose.
5. The prosthesis of claim 1, wherein .[.said.]. .Iadd.the
.Iaddend.guiding means and .[.said.]. .Iadd.the .Iaddend.blocking
means are arranged in the vicinity of two opposite edges of
.[.said.]. .Iadd.the .Iaddend.second articulating surface, while
.[.said.]. .Iadd.the .Iaddend.complementary means and the blocking
means provided on .[.said.]. .Iadd.the .Iaddend.locking element are
arranged on two opposite edges of .[.said.]. .Iadd.the
.Iaddend.locking element.
6. The prosthesis of claim 1, wherein .[.said.]. .Iadd.the
.Iaddend.blocking means .[.comprise.]. .Iadd.comprises .Iaddend.a
screw and a tapping.[.,.]. which are complementary and respectively
provided on .[.said.]. .Iadd.the .Iaddend.locking element and on
.[.said.]. .Iadd.the .Iaddend.ulnar component, or vice versa, and
means are provided for blocking .[.said.]. .Iadd.the .Iaddend.screw
in rotation.
.[.7. The prosthesis of claim 6, wherein the piece against which
the head of said screw bears, is provided with a tab foldable into
configuration of blocking of said head..].
.[.8. The prosthesis of claim 7, wherein the head of said screw is
of polygonal profile, with faces whose width is greater than the
width of said foldable tab..].
.[.9. The prosthesis of claim 6, wherein the head of said screw is
of non-circular section, while the piece against which said head
bears, forms a space for receiving said head, with contact between
the surface of said piece and the outer surface of said
head..].
.[.10. The prosthesis of claim 9, wherein said head is provided
with catch elements adapted to penetrate superficially in the
surface of said piece..].
.Iadd.11. The prosthesis of claim 6, wherein when a head of the
screw bears against the ulnar component, the ulnar component is
provided with a tab foldable into a configuration capable of
blocking the head, and wherein when the head of the screw bears
against the locking element, the locking element component is
provided with a tab foldable into a configuration capable of
blocking the head..Iaddend.
.Iadd.12. The prosthesis of claim 11, wherein a head of the screw
has a polygonal profile having faces with widths greater than a
width of the tab..Iaddend.
.Iadd.13. The prosthesis of claim 6, wherein a head of the screw is
of non-circular section, wherein when the head of the screw bears
against the ulnar component, the ulnar component forms a space for
receiving the head with contact between a surface of the ulnar
component and an outer surface of the head and wherein when the
head of the screw bears against the locking element, the locking
element forms a space for receiving the head with contact between a
surface of the locking element and an outer surface of the
head..Iaddend.
.Iadd.14. The prosthesis of claim 6, wherein a head of the screw is
provided with catch elements adapted to penetrate superficially in
the surface of either the ulnar component or the locking element,
whichever the head bears against..Iaddend.
.Iadd.15. An elbow prosthesis comprising: a humeral component
comprising a first articulating surface having a curved and concave
generatrix and a first longitudinal axis; an ulnar component
comprising a first guide portion and a second articulating surface
adapted to be disposed around a portion of the first articulating
surface and to pivot about the first longitudinal axis; a locking
element comprising a second guide portion and a third articulating
surface that extends an arc length of the second articulating
surface and is adapted to extend around a portion of the first
articulating surface, the first and second guide portions of the
ulnar component and the locking element, respectively, forming a
complementary guide structure including an extension adapted to be
slidingly received within a projecting element in a complementary
fit such that the complementary guide structure imposes sliding
translation of the locking element relative to the ulnar component
along a direction of slide; and a fastening structure adapted to
immobilize the locking element with respect to the ulnar component
when the locking element and the ulnar component are
engaged..Iaddend.
.Iadd.16. The elbow prosthesis of claim 15 wherein the first
articulating surface comprises a component attached to a humeral
stem..Iaddend.
.Iadd.17. The elbow prosthesis of claim 15 wherein the humeral
component comprises: a stem adapted to be inserted in a medullary
canal of a humerus; and a member adapted to abut against an
external surface of the humerus..Iaddend.
.Iadd.18. The elbow prosthesis of claim 15 wherein the second and
third articulating surfaces comprise similar cross-sectional
profiles..Iaddend.
.Iadd.19. The elbow prosthesis of claim 15 wherein the second and
third articulating surfaces comprise low-friction
linings..Iaddend.
.Iadd.20. The elbow prosthesis of claim 15 wherein the second and
third articulating surfaces comprise a material adapted to engage a
first articulating surface, wherein the first articulating surface
is formed of metal..Iaddend.
.Iadd.21. The elbow prosthesis of claim 15 wherein the second and
third articulating surfaces combine to surround the first
articulating surface..Iaddend.
.Iadd.22. The elbow prosthesis of claim 15 wherein the guide
structure translates the locking element relative to the ulnar
component..Iaddend.
.Iadd.23. The elbow prosthesis of claim 15 wherein the guide
structure comprises a direction of assembly that is non-parallel to
a longitudinal axis of the fastening structure..Iaddend.
.Iadd.24. The elbow prosthesis of claim 15 wherein the locking
element and the ulnar component are engaged when the second
articulating surface abuts with the third articulating
surface..Iaddend.
.Iadd.25. The elbow prosthesis of claim 15 wherein the first guide
portion of the ulnar component is located at a first edge of the
second articulating surface and at least a portion of the fastening
structure is located at a second edge of the second articulating
surface..Iaddend.
.Iadd.26. The elbow prosthesis of claim 15 wherein the fastening
structure comprises a first hole in the locking member that is
aligned with a second hole in the ulnar component only when the
locking member is in the engaged position..Iaddend.
.Iadd.27. The elbow prosthesis of claim 11 comprising a member
adapted to prevent rotation of a fastener in the fastening
structure once the locking element is in the engaged
position..Iaddend.
.Iadd.28. An elbow prosthesis comprising: a humeral component
comprising a first articulating surface having a curved and concave
generatrix and a first longitudinal axis; an ulnar component
comprising a guide element and a second articulating surface
adapted to be disposed around a part of the first articulating
surface and to pivot about the longitudinal axis; a locking element
comprising a nose and a third articulating surface that extends an
arc length of the second articulating surface and is adapted to
extend around a portion of the first articulating surface, the nose
being complementary to the guide element such that the guide
element is adapted to slidingly receive the nose within the guide
element and impose sliding translation of the locking element along
a direction of slide relative to the ulnar component; and a
fastening structure adapted to immobilize the locking element with
respect to the ulnar component..Iaddend.
.Iadd.29. An elbow prosthesis comprising: a humeral component
comprising a first concave articulating surface with a first
longitudinal axis; an ulnar component comprising a second
articulating surface adapted to be disposed around a part of the
first concave articulating surface and to pivot about the
longitudinal axis, the ulnar component comprising at least one hole
adapted to receive a fastener; a locking element comprising a third
articulating surface that extends an arc length of the second
articulating surface and is adapted to extend around a portion of
the first articulating surface, the locking element comprising at
least one hole adapted to receive a fastener; and a guide structure
comprising a projecting element and an extension adapted to be
received within the projecting element in a complementary fit to
impose a direction of slide of the locking element relative to the
ulnar component, wherein the projecting element is located on one
of the ulnar component and the locking element and the extension is
located on the other of the ulnar component and the locking
element, and further wherein the hole in the locking member is
substantially aligned with a hole in the ulnar component only when
the locking member is fully engaged with the ulnar
component..Iaddend.
.Iadd.30. An elbow prosthesis comprising: a humeral component
comprising a first curved articulating surface including a first
longitudinal axis; an ulnar component comprising a second
articulating surface adapted to be disposed around a portion of the
first curved articulating surface and to pivot about the
longitudinal axis; a locking element comprising a third
articulating surface that extends an arc length of the second
articulating surface and is adapted to extend around a portion of
the first articulating surface; a guide structure comprising a nose
and a fork adapted to receive the nose within the fork to impose a
direction of slide between the ulnar component and the locking
element, wherein one of the nose and the fork is located on the
ulnar component and the other of the nose and the fork is located
on the locking element; and a fastening structure adapted to
immobilize the locking element with respect to the ulnar component,
wherein the guide structure comprises a direction of assembly that
is non-parallel to a longitudinal axis of the fastening
structure..Iaddend.
Description
FIELD OF THE INVENTION
The present invention relates to an elbow prosthesis comprising at
least one humeral component and one ulnar component.
It concerns more particularly an elbow prosthesis of which the
ulnar component is adapted to receive a locking element which forms
an articulating surface extending that of the ulnar component, the
articulating surfaces of the locking element and of the ulnar
component being adapted to be arranged together around at least a
part of another articulating surface belonging to a humeral
component. A prosthesis of this type is known from EP-A-1 051
954.
BACKGROUND OF THE INVENTION
In such a prosthesis, the locking element is maintained in position
on the ulnar component thanks to a screw introduced in a through
housing in this element and tightened in a tapping provided on the
ulnar component. It has proved in practice that the positioning of
the locking element on the ulnar component is not always optimum
when such a screw is tightened, which may lead to a skewed
positioning of the screw with respect to the tapping, to such a
point that the thread of the screw or the tapping may be distorted,
thus preventing the locking element from being mounted. In
addition, the afore-mentioned screw serves both to bring the
locking element into correct position with respect to the ulnar
component and to ensure blocking of these two elements with respect
to each other. As a result, such an ulnar component must most often
be fitted while the articulation of the elbow is in maximum
flexion, which renders the surgeon's work more complex. It even
happens that such fitting in maximum flexion is not possible,
particularly in the case of marked obesity of the patient.
It is a more particular object of the invention to overcome these
drawbacks by proposing an elbow prosthesis whose fit is
facilitated, when it comprises a locking element as mentioned
hereinabove.
SUMMARY OF THE INVENTION
To that end, the present invention relates to an elbow prosthesis
comprising a humeral component, forming a first articulating
surface, and an ulnar component forming a second articulating face
adapted to be disposed around a part of the first articulating
surface and to pivot about a longitudinal axis of this surface, the
ulnar component being provided with means for mounting a locking
element which forms a third articulating surface extending the
second articulating surface and adapted likewise to be disposed
around a part of the first articulating surface. This prosthesis is
characterized in that the afore-mentioned mounting means comprise
guiding means adapted to cooperate with complementary means
provided on the locking element in order to guide this element in
translation with respect to the ulnar component, up to a position
where blocking means provided respectively on the locking element
and on the ulnar component may be employed to immobilize the
locking element on the ulnar component, these blocking means being
able to be employed only in this position.
Thanks to the invention, the guiding means ensure an adequate
positioning of the locking element with respect to the ulnar
component before the blocking means are employed to effect an
efficient immobilization of the locking element with respect to the
ulnar component. In other words, the blocking means do not serve to
bring the locking element in a configuration allowing its blocking,
this function being performed by the guiding means which may be
positioned and configured to ensure this function best.
In addition, an elbow prosthesis may incorporate one or more of the
following characteristics, taken in any technically admissible
combination:
The blocking means comprise a screw and a complementary tapping
provided respectively on the locking element and on the ulnar
component, or vice versa, the direction of relative translation
between the locking element and the ulnar component as imposed by
the guiding means being non-parallel to the longitudinal axis of
the tapping and/or of the afore-mentioned screw.
The guiding means comprise at least one element in relief
projecting with respect to a principal part of the ulnar component,
while the complementary means provided on the locking element are
adapted to interact with this element in relief by cooperation of
shapes. In that case, the aforementioned element in relief may be a
nose, while the complementary means comprise a fork of which two
branches define therebetween a volume for receiving and for slide
of this nose.
The guiding means and the blocking means are arranged in the
vicinity of two opposite edges of the second articulating surface
of the ulnar component, while the complementary means and the
blocking means provided on the locking element are arranged on two
opposite edges of that element.
The blocking means comprise a screw and a tapping, which are
complementary and respectively provided on the locking element and
on the ulnar component, or vice versa, while means are provided for
blocking this screw in rotation. The head of the screw may thus be
of non-circular section, while the piece against which this head
bears forms a space for receiving this head, with contact between
the surface of this piece and the outer surface of the head. More
particularly, the head of the screw may be provided with catch
elements adapted to penetrate superficially in the surface of the
afore-mentioned piece. In a variant, the piece against which the
head of the screw bears may be provided with a tab foldable into
configuration of blockage of this head. In that case, the head of
the screw may be of polygonal profile, with faces whose width is
greater than the width of the foldable tab.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will be more readily understood and other advantages
thereof will appear more clearly in the light of the following
description of a form of embodiment of a prosthesis in accordance
with its principle, given solely by way of example and made with
reference to the accompanying drawings, in which:
FIG. 1 is an exploded view in perspective of an elbow prosthesis
according to the invention.
FIG. 2 is a longitudinal section of the ulnar component and of the
locking element in the course of assembly.
FIG. 3 is a section similar to FIG. 2 while the locking element is
mounted on the ulnar component.
FIG. 4 is a view in perspective of the metal part of the ulnar
component.
FIG. 5 is a section along line V-V of FIG. 3 and
FIG. 6 is a view in perspective of the ulnar component and of the
locking element of the prosthesis, on a larger scale.
DESCRIPTION OF PREFERRED EMBODIMENT
Referring now to the drawings, the prosthesis visible in FIGS. 1 to
3 comprises a humeral component 10 comprising a stem 11 intended to
be driven in the medullary canal of a humerus H and extending in
two branches 12 and 13, each pierced with an orifice 12a, 13a for
passage of a hollow screw 14 forming pin. The hollow nature of the
screw 14 allows the passage of suture yarns. The orifice 12a is
tapped, allowing the screw 14 to be screwed. The stem 11 also
extends in a third branch 15 intended to come into abutment against
the cortex of the humerus.
An elongated piece 16 is provided with a central bore 16a whose
dimensions are such as to receive the screw 14, this making it
possible to mount the piece 16 between the branches 12 and 13. The
piece 16 is provided with two end surfaces 16b and 16c provided to
come respectively into contact with the opposite surfaces of the
branches 12 and 13.
Between the surfaces 16b and 16c, the piece 16 is substantially
cylindrical, with circular base, and forms a surface of
articulation S.sub.1 which is also substantially cylindrical, whose
generatrix G.sub.1 is curved and concave, in that the diameter of
the surface S.sub.1 is minimum in the central part of the piece 16
included between the surfaces 16b and 16c. X.sub.1 denotes the axis
of symmetry of the surface S.sub.1.
The piece 16 extends in an extension 16d whose outer surface
S.sub.4 is convex and which covers the branch 12 when the piece 16
is mounted between the branches 12 and 13.
The whole of the humeral component 10 is made of metal.
The ulnar component 20 comprises a metal stem 21 intended to be
inserted in the medullary canal of the ulna C and which is in one
piece with a branch 22 likewise made of metal, of concave shape and
whose inner surface is covered with a lining 23 made of a material
adapted to the friction with the metal piece 16, for example
polyethylene. The lining 23 is mounted on the branch 22 by
cooperation of shapes. A pin 27 makes it possible to immobilize
elements 22 and 23 with respect to each other.
The inner surface of the lining 23 forms a surface of articulation
S.sub.2 whose shape is complementary to that of surface S.sub.1.
X.sub.2 denotes the central axis of elements 22 and 23.
The respective diameters of surfaces S.sub.1 and S.sub.2, which
diameters are variable along axes X.sub.1 and X.sub.2, are chosen
so that the surface S.sub.2 may be disposed around the surface
S.sub.1, with a slight clearance, this allowing a rotation of the
components 10 and 20 with respect to each other about axes X.sub.1
and X.sub.2 which, in that case, merge.
Moreover, the profiles of the generatrices of surfaces S.sub.1 and
S.sub.2 are chosen so as to allow a degree of mobility of the
surface S.sub.1 in surface S.sub.2, in the sense of varus-valgus,
i.e. about an axis perpendicular to X.sub.1 and X.sub.2.
A locking element 30 is intended to be mounted on the component 20
and comprises a metal casing 32 and a lining 33 immobilized with
respect to each other by clipping. The lining 33 is advantageously
made of the same material as the lining 23 and forms a concave
articulating surface S.sub.3 intended to extend the surface S.sub.2
and, with it, surround the surface S.sub.1.
In order to facilitate assembly of the element 30 on the component
20, this component is provided, in extension of the outer surface
24 of the branch 22, with an element in relief 25 in the form of a
nose or beak which projects beyond the part 22a of the branch 22
covered by the lining 23.
Furthermore, the casing 32 of the element 30 extends beyond its
part 32a covered by the lining 33, in an extension in the form of a
fork 35 of which the two branches 35a and 35b together define a
volume 35c for slide and reception of the nose 25 when the element
30 is mounted on the component 20.
The nose 25 is disposed in a space 23c defined by the lining 23
which extends beyond the part 22a of the branch 22 that it covers.
In its part 23d which extends in overhang with respect to the part
22a, the lining has a substantially U-shaped cross-section. The
space 23c is defined at the centre of this U.
The nose 25 has a width decreasing in the direction of the bottom
of the U formed by the part 23d. In this way, the sides 25a and 25b
of the nose 25 diverge, moving away from this bottom and
approaching the branches of the U formed by the part 23d. The nose
25 has a section substantially in the form of a dove-tail.
In addition, grooves 25c and 25d are formed on either side of the
nose 25. These grooves have profiles allowing them to receive
convex parts 35d and 35e of the branches 35a and 35b.
The branches 35a and 35b thus have a geometry compatible with their
introduction in the space 23c, on either side of the nose 25. Their
surfaces intended to face towards the nose 25 deviate from each
other towards the outside of the element 30, with the result that
these surfaces are substantially parallel to sides 25a and 25b.
In this way, the direction of assembly of the element 30 on the
component 20 is necessarily that indicated by arrow F.sub.1 in FIG.
2, this direction being imposed by the cooperation of shapes
between the nose 25 and the fork 35. In effect, as indicated
hereinabove, the transverse sections of the nose 25 on the one hand
and of the inner parts of the branches 35 are chosen to impose this
direction of slide.
Furthermore, the component 20 is provided with a tapping 26 for
receiving a screw 36 which traverses a through housing 37 provided
to that end in the element 30.
The tapping 26 and the housing 37 are configured so that they are
aligned, in a direction Y.sub.1 perpendicular to axis X.sub.2, at
the end of the slide of the element 30 with respect to the
component 20. Such slide takes place until the linings 23 and 33
come into abutment against each other in the vicinity of the
members 25 and 35, as shown in FIG. 3. It is then possible to screw
the screw 36 in the tapping 26, in the direction of arrow F.sub.2
in FIGS. 2 and 3. In the configuration of FIG. 3, the central axes
of the screw 36 and of the tapping 26 merge and are parallel to
direction Y.sub.1.
The direction Y.sub.1 is not parallel to the direction of
displacement of the element 30 with respect to the component 20
during its assembly, i.e. to arrow F.sub.1, with the result that
the screw 36 can be introduced in the tapping 26 only at the end of
slide of the clement 30 on the component 20 in the direction of
arrow F.sub.1.
In this way, the screw 36 serves solely for blocking the element 30
in position on the component 20 and can be tightened only once a
correct position of the element 30 on the component 20 has been
attained. The risks of the screw 36 being tightened askew in the
tapping 26 are thus avoided.
In addition, the mechanical strength of the assembly formed by the
elements 20 and 30 in the configuration of FIG. 3 is much greater
than that able to be obtained with the prosthesis known from EP-A-1
051 954 as, once the screw 36 is tightened, the element 30 is
immobilized with respect to the component 20 on its two sides.
In effect, the nose 25 is provided in the vicinity of a first edge
20a of the component 20 and of the surface S.sub.2, while the
tapping 26 is provided near the opposite edge 20b of this
component. In the same way, elements 35 and 37 are respectively
provided in the vicinity of the two opposite edges 30a and 30b of
the element 30 and of the surface S.sub.3.
In other words, the function of guiding of the element 30 with
respect to the component 20 is obtained in the vicinity of the
edges 20a and 30a of these members, while the function of blocking
is obtained in the vicinity of the edges 20b and 30b.
The housing 37 is formed by a circular orifice 37a made in the
metal casing 32 for the passage of the shank of the screw 36, as
well as by a concave zone 37b made in an end part of the lining 33,
in the vicinity of the edge 30b.
The head 36a of the screw 36 presents a non-circular external
section as it is equipped with peripheral catching elements or
teeth 36b provided to engage superficially in the inner radial
surface 37c of the concave zone 37b, this contributing to the
immobilization of the screw 36 in rotation and thus ensures an
efficient blocking of the element 30 on the component 20.
In addition, a tab 38 extends the casing 32 in the vicinity of the
housing 37, this tab being able to be folded into abutment against
the head 36a of the screw 36 when the latter is tightened, in the
direction of arrow F.sub.3 in FIG. 3, so that it performs a
function of non-return for this screw, this also contributing to
the efficient blocking of the element 30 on the component 20.
According to a variant embodiment of the invention (not shown), the
head 36a may present a polygonal profile, for example hexagonal or
octagonal, with planar faces. In that case, the width of the tab 38
is chosen to be less than the width of the lateral faces of this
head, this allowing the screw 36 to be blocked in rotation by
surface abutment of one of these faces against this tab.
When the element 30 is mounted on the component 20, the assembly
thus produced may pivot about axis X.sub.1 and the joining of
surfaces S.sub.2 and S.sub.3 surrounds the surface S.sub.1 over
360.degree..
A radial component adapted to be mounted on the radius R is
advantageously provided in the prosthesis according to the
invention, this component 40 defining a surface intended to
cooperate with the surface S.sub.4. However, this is not
compulsory.
The invention is not limited to the sole form of embodiment
represented. In particular, it may concern a prosthesis in which
the projecting element, such as the nose 25, is provided on the
element 30, while a structure of fork type is provided on the ulnar
component. Similarly, the tapping for receiving the blocking screw
may be provided on the locking element, the ulnar component in that
case defining a housing for receiving the locking screw.
Any mechanical means for blocking the locking element on the ulnar
component may be envisaged within the framework of the present
invention.
* * * * *