U.S. patent application number 09/342857 was filed with the patent office on 2001-12-13 for prosthetic implant and surgical tool.
This patent application is currently assigned to Kurt F. James. Invention is credited to TUKE, MICHAEL ANTHONY, WOZENCROFT, ROBERT MICHAEL.
Application Number | 20010051830 09/342857 |
Document ID | / |
Family ID | 33458906 |
Filed Date | 2001-12-13 |
United States Patent
Application |
20010051830 |
Kind Code |
A1 |
TUKE, MICHAEL ANTHONY ; et
al. |
December 13, 2001 |
PROSTHETIC IMPLANT AND SURGICAL TOOL
Abstract
The invention relates to a prosthetic implant comprising a main
body portion having a first surface for presentation to a receptive
bone surface or into a bone cavity and a second surface for receipt
of an articulating joint, and means on the implant adapted for
attachment of a filamentary member, such as a cable. The invention
also relates to a surgical tool for gripping the implant,
comprising an elongate body having a first end surface for bearing
on the prosthetic implant and means for attachment of the tool to
the implant, directly or indirectly by means of the cable.
Inventors: |
TUKE, MICHAEL ANTHONY;
(GUILFORD, GB) ; WOZENCROFT, ROBERT MICHAEL;
(SURBITON, GB) |
Correspondence
Address: |
SENNIGER POWERS LEAVITT & ROEDEL
ONE METROPOLITAN SQUARE
16TH FLOOR
ST LOUIS
MO
63102
|
Assignee: |
Kurt F. James
|
Family ID: |
33458906 |
Appl. No.: |
09/342857 |
Filed: |
June 29, 1999 |
Current U.S.
Class: |
623/22.12 ;
623/22.21 |
Current CPC
Class: |
A61F 2/4609 20130101;
A61F 2002/30462 20130101; A61F 2220/0075 20130101; A61F 2002/30718
20130101; A61F 2002/3417 20130101; A61F 2002/4681 20130101; A61F
2230/0069 20130101; A61F 2002/305 20130101; A61F 2/4603 20130101;
A61F 2002/30225 20130101; A61F 2002/343 20130101; A61F 2310/00796
20130101; A61F 2310/00029 20130101; A61F 2/0095 20130101; A61F 2/34
20130101; A61F 2/30767 20130101 |
Class at
Publication: |
623/22.12 ;
623/22.21 |
International
Class: |
A61F 002/34 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 17, 1997 |
GB |
2323036 |
Claims
What is claimed is:
1. A prosthetic implant comprising a main body portion, having a
first surface for presentation to a receptive bone surface and a
second surface for receipt of an articulating joint, and
filamentary member attachment means adapted for attachment of a
filamentary member to the implant.
2. A prosthetic implant according to claim 1, wherein the
filamentary member attachment means comprises a lug on the main
body portion around which a filamentary member can be looped.
3. A prosthetic implant according to claim 1, wherein the
filamentary member attachment means comprises a bore in the main
body portion through which a filamentary member can be
threaded.
4. A prosthetic implant according to claim 1, wherein the
attachment means comprises a plurality of bores in the main body
portion through which a filamentary member can be threaded.
5. A prosthetic implant according to claim 1, further comprising a
cable attached to the main body portion of the implant by the
filamentary member attachment means.
6. A prosthetic implant according to claim 1, wherein the
filamentary member attachment means comprises a plurality of bores
in the main body portion and wherein a filamentary member is
threaded through each of the plurality of bores in turn, the free
ends of the filamentary member being secured one to another so as
to form a closed loop of filamentary member.
7. A prosthetic implant according to claim 6, wherein the free ends
of the filamentary member are secured to one another by means of a
sleeve having first and second ends, the sleeve snugly receiving a
first looped portion of filamentary member located near a first end
portion of the filamentary member and inserted from the first end
of the sleeve so as to project as a first loop from the second end
of the sleeve with the first end portion being passed through the
first loop, and the sleeve further snugly receiving a second looped
portion of filamentary member located near a second end portion of
the filamentary member and inserted from the second end of the
sleeve so as to project as a second loop from the first end of the
sleeve with the second end portion being passed through the second
loop, whereby upon tension being applied to the closed loop of
filamentary member the first and second end portions of the
filamentary member are firmly gripped by the first and second loops
respectively.
8. A prosthetic implant according to claim 6, wherein the
filamentary member is a poly-filament cable.
9. A prosthetic implant comprising a main body portion, having a
first surface for presentation to a surgically prepared bone cavity
of a patient and a second surface for receipt of an articulating
joint, and filamentary member attachment means adapted for
attachment of a filamentary member to the implant.
10. A prosthetic implant according to claim 9, wherein the
filamentary member attachment means comprises a lug on the main
body portion around which a filamentary member can be looped.
11. A prosthetic implant according to claim 9, wherein the
filamentary member attachment means comprises a bore in the main
body portion through which a filamentary member can be
threaded.
12. A prosthetic implant according to claim 9, wherein the
filamentary member attachment means comprises a plurality of bores
in the main body portion through which a filamentary member can be
threaded.
13. A prosthetic implant according to claim 9, further comprising a
cable attached to the main body portion of the implant by the
filamentary member attachment means.
14. A prosthetic implant according to claim 9, wherein the
attachment means comprises a plurality of bores in the main body
portion and wherein a filamentary member is threaded through each
of the plurality of bores in turn, the free ends of the filamentary
member being secured one to another so as to form a closed loop of
filamentary member.
15. A prosthetic implant according to claim 14, wherein the free
ends of the filamentary member are secured to one another by means
of a sleeve having first and second ends, the sleeve snugly
receiving a first looped portion of filamentary member located near
a first end portion of the filamentary member and inserted from the
first end of the sleeve so as to project as a first loop from the
second end of the sleeve with the first end portion being passed
through the first loop, and the sleeve further snugly receiving a
second looped portion of filamentary member located near a second
end portion of the filamentary member and inserted from the second
end of the sleeve so as to project as a second loop from the first
end of the sleeve with the second end portion being passed through
the second loop, whereby upon tension being applied to the closed
loop of filamentary member the first and second loops are tightened
and the first and second end portions of the filamentary member are
firmly gripped by the first and second loops respectively.
16. A prosthetic implant according to claim 14, wherein the
filamentary member is a poly-filament cable.
17. An acetabular hip prosthesis for implantation in a surgically
prepared socket in a hip of a patient comprising: a generally
cup-shaped body having: an outer generally convex surface for
contact with bone of a surgically prepared socket in a hip of a
patient; an inner generally concave surface; a peripheral bridge
portion whose surface extends between the outer generally convex
surface and the inner generally concave surface; and at least one
bore which extends from a first opening in the surface of the
bridge portion through an interior portion of the substantially
cup-shaped body to a second opening in the surface of the bridge
portion, the bore being adapted for receipt of a filamentary member
therethrough for holding the prosthesis on the end of an insertion
tool to facilitate insertion of the prosthesis into the prepared
socket.
18. An acetabular hip prosthesis according to claim 17, wherein a
filamentary member is threaded through said at least one hole, the
free ends of the filamentary member being secured one to another so
as to form a closed loop of filamentary member by means of a sleeve
having first and second ends, the sleeve snugly receiving a first
looped portion of filamentary member located near a first end
portion of the filamentary member and inserted from the first end
of the sleeve so as to project as a first loop from the second end
of the sleeve with the first end portion being passed through the
first loop, and the sleeve further snugly receiving a second looped
portion of filamentary member located near a second end portion of
the filamentary member and inserted from the second end of the
sleeve so as to project as a second loop from the first end of the
sleeve with the second end portion being passed through the second
loop, whereby upon tension being applied to the closed loop of
filamentary member the first and second loops are tightened and the
first and second end portions of the filamentary member are firmly
gripped by the first and second loops respectively.
19. An acetabular hip prosthesis for implantation in a surgically
prepared socket in a hip of a patient comprising: a generally
cup-shaped body having: an outer generally convex surface for
contact with bone of a surgically prepared socket in a hip of a
patient; an inner generally concave surface; a peripheral bridge
portion whose surface extends between the outer generally convex
surface and the inner generally concave surface; and a plurality of
bores each of which extends from a first opening in the surface of
the bridge portion through an interior portion of the substantially
cup-shaped body to a second opening in the surface of the bridge
portion, the bore being adapted for receipt of a filamentary member
therethrough for holding the prosthesis on the end of an insertion
tool to facilitate insertion of the prosthesis into the prepared
socket.
20. An acetabular hip prosthesis according to claim 19, wherein the
outer generally convex surface of the cup-shaped body is provided
with a coating of hydroxyapatite.
21. An acetabular hip prosthesis according to claim 19, wherein the
outer generally convex surface of the cup-shaped body is texturised
to facilitate ingrowth of bone after implantation into a surgically
prepared hip socket of a patient.
22. An acetabular hip prosthesis according to claim 19, wherein a
filamentary member is threaded through said plurality of holes, the
free ends of the filamentary member being secured one to another so
as to form a closed loop of filamentary member.
23. An acetabular hip prosthesis according to claim 22, wherein the
free ends of the filamentary member are secured to one another by
means of a sleeve having first and second ends, the sleeve snugly
receiving a first looped portion of filamentary member located near
a first end portion of the filamentary member and inserted from the
first end of the sleeve so as to project as a first loop from the
second end of the sleeve with the first end portion being passed
through the first loop, and the sleeve further snugly receiving a
second looped portion of filamentary member located near a second
end portion of the filamentary member and inserted from the second
end of the sleeve so as to project as a second loop from the first
end of the sleeve with the second end portion being passed through
the second loop, whereby upon tension being applied to the closed
loop of filamentary member the first and second loops are tightened
and the first and second end portions of the filamentary member are
firmly gripped by the first and second loops respectively.
24. A protected prosthetic implant comprising a main body portion,
having a first surface for presentation to a receptive bone surface
and a second surface for receipt of an articulating joint,
filamentary member attachment means adapted for attachment of a
filamentary member to the implant, and a protective cap for
covering at least part of the second surface of the main body
portion of the implant.
25. A protected prosthetic implant according to claim 24, wherein
the protective cap is attached to the main body portion of the
implant by means of a cable.
26. A protected prosthetic implant according to claim 25, wherein
the cable is tensioned so that the protective cap is tightly
attached to the main body portion of the implant.
27. A protected prosthetic implant according to claim 24, wherein
the protective cap is of a rigid material.
28. A protected prosthetic implant according to claim 24, wherein
the protective cap is provided with a number of holes, through
which the filamentary member is threaded for attachment of the
protective cap to the prosthetic implant.
29. A protected prosthetic implant according to claim 24, wherein
the protective cap is a disposable protective cap.
30. A protected prosthetic implant according to claim 24, wherein
the protective cap is reusable after appropriate sterilisation.
31. A protected acetabular hip prosthesis for implantation in a
surgically prepared socket in a hip of a patient comprising: (i) a
generally cup-shaped metal body having: an outer generally convex
surface for contact with bone of a surgically prepared socket in a
hip of a patient; an inner substantially part spherical cavity in
the metal body, the cavity having a generally concave polished
surface for receipt of a ball head on a femoral prosthesis and a
periphery surrounding the cavity and defining a mouth; a peripheral
bridge portion whose surface extends between the periphery of the
cavity and the outer generally convex surface; and at least one
bore which extends from a first opening in the surface of the
peripheral bridge portion through an interior portion of the
substantially part spherical body to a second opening in the
surface of the bridge portion, the at least one bore being adapted
for receipt of a filamentary member therethrough for holding the
prosthesis on the end of an insertion tool to facilitate insertion
of the prosthesis into the surgically prepared socket; (ii) a cover
member adapted to bridge the cavity, the cover having apertures
therethrough which correspond to the first and second openings in
the metal body and are adapted for passage of the filamentary
member ; and (iii) a filamentary member threaded through the at
least one hole in the metal body and through the apertures in the
cover member, the free ends of the filamentary member being secured
one to another to form a closed loop of filamentary member which
secures the cover to the metal body.
32. A protected acetabular hip prosthesis according to claim 31,
wherein the free ends of the filamentary member are secured to one
another by means of a sleeve having first and second ends, the
sleeve snugly receiving a first looped portion of filamentary
member located near a first end portion of the filamentary member
and inserted from the first end of the sleeve so as to project as a
first loop from the second end of the sleeve with the first end
portion being passed through the first loop, and the sleeve further
snugly receiving a second looped portion of filamentary member
located near a second end portion of the filamentary member and
inserted from the second end of the sleeve so as to project as a
second loop from the first end of the sleeve with the second end
portion being passed through the second loop, whereby upon tension
being applied to the closed loop of filamentary member the first
and second end portions of the filamentary member are firmly
gripped by the first and second loops respectively.
33. A protected acetabular hip prosthesis for implantation in a
surgically prepared socket in a hip of a patient comprising: (i) a
generally cup-shaped metal body having: an outer generally convex
surface for contact with bone of a surgically prepared socket in a
hip of a patient; an inner substantially part spherical cavity in
the metal body, the cavity having a generally concave polished
surface for receipt of a ball head on a femoral prosthesis and a
periphery surrounding the cavity and defining a mouth; a peripheral
bridge portion whose surface extends between the periphery of the
cavity and the outer generally convex surface; and a plurality of
bores each of which extends from a first opening in the surface of
the peripheral bridge portion through an interior portion of the
substantially part spherical body to a second opening in the
surface of the bridge portion, the bores being adapted for receipt
of a filamentary member therethrough for holding the prosthesis on
the end of an insertion tool to facilitate insertion of the
prosthesis into the surgically prepared socket; (ii) a cover member
adapted to bridge the cavity, the cover having apertures
therethrough which correspond to the first and second openings in
the metal body and are adapted for passage of the filamentary
member; and (iii) a filamentary member threaded through each of the
plurality of holes in the metal body and through the apertures in
the cover member, the free ends of the filamentary member being
secured one to another to form a closed loop of filamentary member
which secures the cover to the metal body.
34. A protected acetabular hip prosthesis according to claim 33,
wherein the outer generally convex surface of the cup-shaped metal
body is provided with a coating of hydroxyapatite.
35. A protected acetabular hip prosthesis according to claim 33,
wherein the outer generally convex surface of the cup-shaped metal
body is texturised to facilitate ingrowth of bone after
implantation into a surgically prepared hip socket of a
patient.
36. A protected acetabular hip prosthesis according to claim 33,
wherein the free ends of the filamentary member are secured to one
another by means of a sleeve having first and second ends, the
sleeve snugly receiving a first looped portion of filamentary
member located near a first end portion of the filamentary member
and inserted from the first end of the sleeve so as to project as a
first loop from the second end of the sleeve with the first end
portion being passed through the first loop, and the sleeve further
snugly receiving a second looped portion of filamentary member
located near a second end portion of the filamentary member and
inserted from the second end of the sleeve so as to project as a
second loop from the first end of the sleeve with the second end
portion being passed through the second loop, whereby upon tension
being applied to the closed loop of filamentary member the first
and second loops are tightened and the first and second end
portions of the filamentary member are firmly gripped by the first
and second loops respectively.
37. A protected acetabular hip prosthesis for implantation in a
surgically prepared socket in a hip of a patient comprising: (i) a
generally cup-shaped metal body having: an outer generally convex
surface for contact with bone of a surgically prepared socket in a
hip of a patient; a cavity in the metal body for receipt of a liner
of plastics material, the cavity having a periphery surrounding the
cavity and defining a mouth; a peripheral bridge portion whose
surface extends between the periphery of the cavity and the outer
generally convex surface; and a plurality of bores each of which
extends from a first opening in the surface of the peripheral
bridge portion through an interior portion of the substantially
part spherical body to a second opening in the surface of the
bridge portion, the bores being adapted for receipt of a
filamentary member therethrough for holding the prosthesis on the
end of an insertion tool to facilitate insertion of the prosthesis
into the surgically prepared socket; (ii) a liner of plastics
material secured in the cavity of the cup shaped metal body, the
liner having an outer surface adapted to conform to the inner
surface of the cavity in the cup-shaped metal body and a
substantially part spherical inner surface for receipt of a ball
head on a femoral hip prosthesis; (iii) a cover member having a
first face adapted to bridge the cavity, the cover member having
apertures therethrough which correspond to the first and second
openings in the metal body and are adapted for passage of the
filamentary member; and (iv) a filamentary member threaded through
each of the plurality of holes in the metal body and through the
apertures in the cover member, the free ends of the filamentary
member being secured one to another to form a closed loop of
filamentary member which secures the cover to the metal body.
38. A protected acetabular hip prosthesis according to claim 37,
wherein the outer generally convex surface of the cup-shaped metal
body is provided with a coating of hydroxyapatite.
39. A protected acetabular hip prosthesis according to claim 37,
wherein the outer generally convex surface of the cup-shaped metal
body is texturised to facilitate ingrowth of bone after
implantation into a surgically prepared hip socket of a
patient.
40. A protected acetabular hip prosthesis according to claim 37,
wherein the free ends of the filamentary member are secured to one
another by means of a sleeve having first and second ends, the
sleeve snugly receiving a first looped portion of filamentary
member located near a first end portion of the filamentary member
and inserted from the first end of the sleeve so as to project as a
first loop from the second end of the sleeve with the first end
portion being passed through the first loop, and the sleeve further
snugly receiving a second looped portion of filamentary member
located near a second end portion of the filamentary member and
inserted from the second end of the sleeve so as to project as a
second loop from the first end of the sleeve with the second end
portion being passed through the second loop, whereby upon tension
being applied to the closed loop of filamentary member the first
and second loops are tightened and the first and second end
portions of the filamentary member are firmly gripped by the first
and second loops respectively.
41. A protected acetabular hip prosthesis according to claim 37,
wherein the cavity in the cup-shaped metal body is provided with an
inwardly projecting lip surrounding the mouth of the cavity and in
which the liner is provided with a peripheral ledge which is
adapted to snap fit under the inwardly projecting lip of the
cup-shaped metal body.
42. A protected acetabular hip prosthesis according to claim 41,
wherein the cavity in the cup-shaped metal body is provided with a
circumferential internal ridge below and adjacent the inwardly
projecting lip and wherein the liner is provided with a
corresponding circumferential groove on its outer surface which is
adapted to receive the circumferential ridge.
43. A protected acetabular hip prosthesis according to claim 37,
wherein the liner is made from high density polyethylene.
44. A protected acetabular hip prosthesis according to claim 37,
wherein the cover member is provided on a second face opposite its
first face with an axial blind bore for location of a corresponding
axial locating peg on an insertion tool.
45. A protected acetabular hip prosthesis according to claim 44,
wherein the cover member is provided on its second face with an
auxiliary bore whose axis is parallel to and offset from the axis
of the axial blind bore, the auxiliary bore being adapted to
receive a corresponding offset peg on an insertion tool to prevent
relative rotation of the acetabular hip prosthesis and cover member
about the axis of the axial locating peg of the insertion tool.
46. A surgical tool for gripping a protected acetabular hip
prosthesis for implantation in a surgically prepared socket in a
hip of a patient, the protected acetabular hip prosthesis
comprising a generally cup-shaped metal body which has an outer
generally convex surface and a cavity defining a mouth, a
protective cap over the mouth of the cavity, and a closed loop of
filamentary member secured to the acetabular hip prosthesis, the
tool comprising an elongate body having a first end for engagement
with the protective cap and adjustable filamentary member
engagement means for engagement with and tightening of the closed
loop of filamentary member so as to locate the protective cap
against the first end of the tool and to draw the acetabular hip
prosthesis towards the first end surface thereby to hold the
prosthetic implant securely on the first end of the tool during
surgical implantation of the acetabular hip prosthesis, the tool
and protective cap being removable after such surgical implantation
by loosening the tension in the closed loop of filamentary member
and then severing the closed loop of filamentary member to allow it
to be disengaged from the implanted acetabular hip prosthesis.
Description
1. FIELD OF THE INVENTION
[0001] The present invention relates to a prosthetic implant and to
a surgical tool for gripping the prosthetic implant during a
surgical procedure.
2. BACKGROUND OF THE INVENTION
[0002] The replacement of all or a part of the bone surface of an
articulation with a prosthetic implant has become a common surgical
procedure. The procedure requires the surgeon to exercise both
precision and delicacy in the placement of the prosthetic implant.
However, it is frequently necessary for the surgeon also to
exercise a degree of force, sometimes a vigorous force, in order to
situate the prosthetic implant in a desired location on the bone
surface.
[0003] For example, in an operation to insert a prosthetic
acetabulum in a patient's pelvis the surgeon first uses a reamer to
grind a cavity of appropriate size in the patient's pelvis. The
surgeon then inserts an acetabular cup into the cavity. By
"appropriate size" is meant a size which is selected by the surgeon
as being the most appropriate for that particular patient.
Normally, it is desirable to retain as much of the original healthy
bone surface as possible.
[0004] Commercially available acetabular cups are sold in a range
of sizes to suit the needs of individual patients. Generally,
acetabular cups are available in sizes of from 42 mm to 62 mm
diameter, with 2 mm increments between neighbouring sizes.
[0005] Prosthetic acetabular cups generally require the use of an
insertion tool to achieve correct positioning of the prosthesis in
the patient's pelvic cavity. A typical insertion tool is described
in U.S. Pat. No. 4,305,394 (Bertuck).
[0006] There are a number of different types of prosthetic
acetabular cups. Firstly, cups made from polyethylene are
available. Polyethylene cups are cemented into the acetabulum and
require only light pressure to seat them in the cement. Secondly,
there are cups which comprise a metal shell for insertion into the
pelvic cavity and a polyethylene liner for articulation with the
femur. Some polyethylene cups with metal shells are implanted
without cement and rely on a jam fit between the metal shell and
the patient's acetabulum. Often these metal shells have surfaces or
coatings which encourage bone to grow into them over time. A
typical coating material is hydroxyapatite. With this type of
prosthesis, the polyethylene liner is snapped or screwed into the
metal shell after the metal shell has been seated in the acetabulum
to form the socket part of the patient's joint.
[0007] Cups which rely on a jam fit require a greater force to be
applied via the insertion tool than is the case with cemented
polyethylene cups. This force is usually applied as a direct impact
into the acetabulum, for example by use of a mallet on the free end
of the insertion tool. However, it may also be necessary to adjust
the angular position of the cup in the bone or to take it out if
positioned incorrectly. Therefore the insertion tool must
positively grip the cup by some mechanical feature. This feature
cannot impinge upon the outside of the metal shell because the
insertion tool may then become trapped between the shell and the
bone. Also there is little room around the rim of the shell because
the wall thickness of the shell is generally kept to a minimum.
Therefore the insertion tool usually grips on a mechanical feature
on the inner hemisphere of the metal shell. An insertion tool of
this type is described in International Patent Publication No. WO
94/21199 (Howmedica Limited). The mechanical feature is usually
designed so as to cause minimum compromise to the function of the
prosthetic hip joint. As a result it is often not strong enough for
the impaction forces applied. This often results in damage to the
insertion tool, or metal shell or both.
[0008] A third category of prosthetic hip joint exists which is
manufactured entirely from metal so that the prosthetic
articulation comprises a metal on metal joint. These are nearly
always implanted without cement, relying on a jam fit in the
acetabulum. With this type of cup the inner hemisphere is not a
convenient place to locate a mechanical feature for the insertion
tool to grip on. First, it would reduce the surface area of the
prosthetic articulation. Secondly, it could cause damage to the
highly polished concave metal against which the ball of the
patient's femur or the ball head of a femoral prosthesis is to
bear.
[0009] Therefore, the provision of means for attaching an insertion
tool to a prosthetic implant so that the attachment is sufficiently
robust to withstand the impaction and other forces to which it may
be subject during insertion of the prosthesis and yet which does
not compromise the structural strength or the articulating
properties of the prosthesis itself remains a problem in the
art.
[0010] Another disadvantage of conventional tools is that they must
be manufactured in a range of different sizes to receive acetabular
cups or sheaths of the different sizes referred to above.
[0011] The difficulty of gripping and positioning prosthetic
implants applies not only to acetabular implants but more generally
to implants such as the tibial and femoral components of a
prosthetic knee.
[0012] U.S. Pat. No. 5,376,126 (Lin) discloses use of cords to
assist in fastening a femoral implant to the upper end of a
resected femur.
3. SUMMARY OF THE INVENTION
[0013] It is an object of the present invention to provide a
prosthetic implant which does not suffer from one or more of the
disadvantages of the prior art devices. It is further an object of
the present invention to provide a surgical tool for use with such
an implant.
[0014] Accordingly, the present invention provides a prosthetic
implant comprising a main body portion, having a first surface for
presentation to a receptive bone surface or to a surgically
prepared bone cavity and a second surface for receipt of an
articulating joint, and filamentary member attachment means adapted
for attachment of a filamentary member to the implant.
[0015] The filamentary member can be a monofilamentary member, such
as a Kevlar.TM. monofilament, or a multifilament member such as a
Kevlar.TM. polyfilamentary thread or a metallic cable made, for
example, from stainless steel. Such a cable may be, for example,
from about 0.5 mm thick to about 2 mm thick. If desired, the cable
can be coated with an inert material, such as polypropylene.
Preferably the filamentary member is formed into a closed loop.
[0016] In one form of prosthetic implant according to the invention
the filamentary member attachment means comprises a lug on the main
body portion around which a filamentary member can be looped.
Alternatively the filamentary member attachment means can comprise
a bore in the main body portion through which a filamentary member
can be threaded. In such a case it will normally be preferred to
provide plurality of such bores, for example, three such bores.
[0017] The invention further provides such a prosthetic implant
further comprising a cable attached to the main body portion of the
implant by the filamentary member attachment means. Thus in a
preferred embodiment of the invention the filamentary member
attachment means comprises a plurality of bores in the main body
portion and a filamentary member is threaded through each of the
plurality of bores in turn, the free ends of the filamentary member
being secured one to another so as to form a closed loop of
filamentary member. The free ends of the filamentary member can be
secured to one another by means of a sleeve having first and second
ends, the sleeve snugly receiving a first looped portion of
filamentary member located near a first end portion of the
filamentary member and inserted from the first end of the sleeve so
as to project as a first loop from the second end of the sleeve
with the first end portion being passed through the first loop, and
the sleeve further snugly receiving a second looped portion of
filamentary member located near a second end portion of the
filamentary member and inserted from the second end of the sleeve
so as to project as a second loop from the first end of the sleeve
with the second end portion being passed through the second loop,
whereby upon tension being applied to the closed loop of
filamentary member the first and second end portions of the
filamentary member are firmly gripped by the first and second loops
respectively.
[0018] The invention also provides an acetabular hip prosthesis for
implantation in a surgically prepared socket in a hip of a patient
comprising:
[0019] a generally cup-shaped body having:
[0020] an outer generally convex surface for contact with bone of a
surgically prepared socket in a hip of a patient;
[0021] an inner generally concave surface;
[0022] a peripheral bridge portion whose surface extends between
the outer generally convex surface and the inner generally concave
surface; and
[0023] at least one bore which extends from a first opening in the
surface of the bridge portion through an interior portion of the
substantially cup-shaped body to a second opening in the surface of
the bridge portion, the bore being adapted for receipt of a
filamentary member therethrough for holding the prosthesis on the
end of an insertion tool to facilitate insertion of the prosthesis
into the prepared socket.
[0024] In such an acetabular hip prosthesis there is preferably
provided a plurality of bores each of which extends from a first
opening in the surface of the bridge portion through an interior
portion of the substantially cup-shaped body to a second opening in
the surface of the bridge portion, the bore being adapted for
receipt of a filamentary member therethrough for holding the
prosthesis on the end of an insertion tool to facilitate insertion
of the prosthesis into the prepared socket.
[0025] Preferably the outer generally convex surface of the
cup-shaped body is provided with a coating of hydroxyapatite and
also is texturised to facilitate ingrowth of bone after
implantation into a surgically prepared hip socket of a
patient.
[0026] In another aspect of the invention there is provided a
protected prosthetic implant comprising a main body portion, having
a first surface for presentation to a receptive bone surface and a
second surface for receipt of an articulating joint, filamentary
member attachment means adapted for attachment of a filamentary
member to the implant, and a protective cap for covering at least
part of the second surface of the main body portion of the implant.
The protective cap can be attached to the main body portion of the
implant by means of a cable. In this case the cable can be is
tensioned so that the protective cap is tightly attached to the
main body portion of the implant.
[0027] The protective cap is preferably made of a rigid material.
It can be provided with a number of holes, through which the
filamentary member is threaded for attachment of the protective cap
to the prosthetic implant.
[0028] It will often be preferred for the protective cap to be a
disposable protective cap. Alternatively it can be reusable after
appropriate sterilisation.
[0029] The invention further provides a protected acetabular hip
prosthesis for implantation in a surgically prepared socket in a
hip of a patient comprising:
[0030] (i) a generally cup-shaped metal body having:
[0031] an outer generally convex surface for contact with bone of a
surgically prepared socket in a hip of a patient;
[0032] an inner substantially part spherical cavity in the metal
body, the cavity having a generally concave polished surface for
receipt of a ball head on a femoral prosthesis and a periphery
surrounding the cavity and defining a mouth;
[0033] a peripheral bridge portion whose surface extends between
the periphery of the cavity and the outer generally convex surface;
and
[0034] at least one bore which extends from a first opening in the
surface of the peripheral bridge portion through an interior
portion of the substantially part spherical body to a second
opening in the surface of the bridge portion, the at least one bore
being adapted for receipt of a filamentary member therethrough for
holding the prosthesis on the end of an insertion tool to
facilitate insertion of the prosthesis into the surgically prepared
socket;
[0035] (ii) a cover member adapted to bridge the cavity, the cover
having apertures therethrough which correspond to the first and
second openings in the metal body and are adapted for passage of
the filamentary member; and
[0036] (iii) a filamentary member threaded through the at least one
hole in the metal body and through the apertures in the cover
member, the free ends of the filamentary member being secured one
to another to form a closed loop of filamentary member which
secures the cover to the metal body.
[0037] Yet again the invention provides a protected acetabular hip
prosthesis for implantation in a surgically prepared socket in a
hip of a patient comprising:
[0038] (i) a generally cup-shaped metal body having:
[0039] an outer generally convex surface for contact with bone of a
surgically prepared socket in a hip of a patient;
[0040] an inner substantially part spherical cavity in the metal
body, the cavity having a generally concave polished surface for
receipt of a ball head on a femoral prosthesis and a periphery
surrounding the cavity and defining a mouth;
[0041] a peripheral bridge portion whose surface extends between
the periphery of the cavity and the outer generally convex surface;
and
[0042] a plurality of bores each of which extends from a first
opening in the surface of the peripheral bridge portion through an
interior portion of the substantially part spherical body to a
second opening in the surface of the bridge portion, the bores
being adapted for receipt of a filamentary member therethrough for
holding the prosthesis on the end of an insertion tool to
facilitate insertion of the prosthesis into the surgically prepared
socket;
[0043] (ii) a cover member adapted to bridge the cavity, the cover
having apertures therethrough which correspond to the first and
second openings in the metal body and are adapted for passage of
the filamentary member ; and
[0044] (iii) a filamentary member threaded through each of the
plurality of holes in the metal body and through the apertures in
the cover member, the free ends of the filamentary member being
secured one to another to form a closed loop of filamentary member
which secures the cover to the metal body.
[0045] In addition, the invention provides a protected acetabular
hip prosthesis for implantation in a surgically prepared socket in
a hip of a patient comprising:
[0046] (i) a generally cup-shaped metal body having:
[0047] an outer generally convex surface for contact with bone of a
surgically prepared socket in a hip of a patient;
[0048] a cavity in the metal body for receipt of a liner of
plastics material, the cavity having a periphery surrounding the
cavity and defining a mouth;
[0049] a peripheral bridge portion whose surface extends between
the periphery of the cavity and the outer generally convex surface;
and
[0050] a plurality of bores each of which extends from a first
opening in the surface of the peripheral bridge portion through an
interior portion of the substantially part spherical body to a
second opening in the surface of the bridge portion, the bores
being adapted for receipt of a filamentary member therethrough for
holding the prosthesis on the end of an insertion tool to
facilitate insertion of the prosthesis into the surgically prepared
socket;
[0051] (ii) a liner of plastics material secured in the cavity of
the cup shaped metal body, the liner having an outer surface
adapted to conform to the inner surface of the cavity in the
cup-shaped metal body and a substantially part spherical inner
surface for receipt of a ball head on a femoral hip prosthesis;
[0052] (iii) a cover member having a first face adapted to bridge
the cavity, the cover member having apertures therethrough which
correspond to the first and second openings in the metal body and
are adapted for passage of the filamentary member ; and
[0053] (iv) a filamentary member threaded through each of the
plurality of holes in the metal body and through the apertures in
the cover member, the free ends of the filamentary member being
secured one to another to form a closed loop of filamentary member
which secures the cover to the metal body.
[0054] Preferably the cavity in the cup-shaped metal body is
provided with an inwardly projecting lip surrounding the mouth of
the cavity and the liner is provided with a peripheral ledge which
is adapted to snap fit under the inwardly projecting lip of the
cup-shaped metal body. It will also often be preferred that the
cavity in the cup-shaped metal body is provided with a
circumferential internal ridge below and adjacent the inwardly
projecting lip and wherein the liner is provided with a
corresponding circumferential groove on its outer surface which is
adapted to receive the circumferential ridge. It will further often
be desirable for the liner to be is made from high density
polyethylene. In one particularly preferred form of the invention
the cover member is provided on a second face opposite its first
face with an axial blind bore for location of a corresponding axial
locating peg on an insertion tool. In addition the cover member can
be provided on its second face with an auxiliary bore whose axis is
parallel to and offset from the axis of the axial blind bore, the
auxiliary bore being adapted to receive a corresponding offset peg
on an insertion tool to prevent relative rotation of the acetabular
hip prosthesis and cover member about the axis of the axial
locating peg of the insertion tool.
[0055] In another aspect of the invention there is provided a
surgical tool for gripping a protected acetabular hip prosthesis
for implantation in a surgically prepared socket in a hip of a
patient, the protected acetabular hip prosthesis comprising a
generally cup-shaped metal body which has an outer generally convex
surface and a cavity defining a mouth, a protective cap over the
mouth of the cavity, and a closed loop of filamentary member
secured to the acetabular hip prosthesis, the tool comprising an
elongate body having a first end for engagement with the protective
cap and adjustable filamentary member engagement means for
engagement with and tightening of the closed loop of filamentary
member so as to locate the protective cap against the first end of
the tool and to draw the acetabular hip prosthesis towards the
first end surface thereby to hold the prosthetic implant securely
on the first end of the tool during surgical implantation of the
acetabular hip prosthesis, the tool and protective cap being
removable after such surgical implantation by loosening the tension
in the closed loop of filamentary member and then severing the
closed loop of filamentary member to allow it to be disengaged from
the implanted acetabular hip prosthesis, a prosthetic implant
comprising a main body portion, having a first convex surface for
presentation to a receptive bone surface or into a bone cavity, a
second concave surface for receipt of an articulating joint, and
means adapted for attachment of a cable to the implant.
[0056] Also provided in accordance with the invention is a surgical
tool for gripping the prosthetic implant of the invention,
comprising an elongate body having a first end surface for bearing
on the implant and means on the tool adapted for attachment thereto
of a cable from the implant.
[0057] The attachment of the tool to the prosthetic implant is
achieved by means of a filamentary member, such as a cable. The
attachment may be a direct attachment, in which case a cable is
passed between the implant and the tool and secured to each by the
respective attachment means. The attachment may be an indirect
attachment, by which is meant that the cable may be used to attach
a protective cover to the prosthetic implant and the tool may then
be attached to the protective cover. Embodiments of the invention
which make use of this indirect attachment will be described in
more detail below.
[0058] The filamentary member attachment means on the prosthetic
implant may comprise a lug on the main body portion of the implant
around which a cable or other filamentary member can be looped.
Alternatively, or also, the filamentary member attachment means may
comprise a bore in the main body portion of the implant through
which a cable can be threaded.
[0059] The adjustable filamentary member attachment means on the
tool may comprise a mooring peg on the tool. The mooring peg may be
mounted on a carriage which is movable axially within the body of
the tool to tension the cable. Alternatively the adjustable
filamentary member attachment means on the tool may comprise a
spring loaded arm on the tool. The arm may be mounted on a carriage
which is movable axially within the body of the tool to tension the
cable or other filamentary member.
[0060] The cable or other filamentary member may be an endless
cable which may be looped around or threaded through the
filamentary member attachment means. Alternatively, a length of
cable may be used and secured to each filamentary member attachment
means by any convenient means, such as a tie, clip, or knot. Any
convenient number of cables or other filamentary members may be
used and any convenient number of attachment means on the
prosthetic implant and on the surgical tool may be employed. For
example, in one preferred embodiment of the invention, the
prosthetic implant is an acetabular cup comprising three means.
Each filamentary member attachment means is preferably spaced
evenly from an adjacent filamentary member attachment means around
the rim of the cup. The surgical tool may also comprise three
adjustable filamentary member attachment means. Each of these
adjustable filamentary member attachment means is preferably spaced
evenly around the circumference of the tool from an adjacent
filamentary member attachment means. The filamentary member is
preferably an endless stainless steel cable which passes from a
first filamentary member attachment means on the cup to a first
corresponding adjustable filamentary member attachment means on the
tool and then on to successive respective second and third
attachment means on the implant and on the tool, returning in an
endless loop to the first filamentary member attachment means on
the cup.
[0061] The surgical tool and prosthetic implant of the invention
have a number of significant advantages over the prior art. The use
of a cable or other filamentary member to provide, directly or
indirectly, means for securing the implant to the insertion tool
means that any compromise in the structural and functional
integrity of the implant as a result of the attachment is
minimised. The diameter of the cable may be quite small, for
example from about 0.5 mm to about 2 mm, and the means for
attachment of the cable to the implant may be correspondingly
small. For example, a bore of from about 0.5 mm to about 2 mm in
the rim of a prosthetic acetabulum of cobalt chrome will not
compromise the strength of the implant to any serious degree.
Similarly, the provision of lugs having sufficient protrusion to
allow a cable of from about 0.5 mm to about 2 mm diameter to be
looped therearound on the outer surface of the acetabulum, adjacent
the rim thereof, will not interfere to any serious degree with the
positioning of the implant in the bone cavity.
[0062] The use of a cable or other filamentary member to secure the
implant to the tool also has the advantage that the visibility of
the attachment area by the surgeon is maintained at a significantly
high degree. It is often important for the surgeon to be able to
see clearly the position of the implant with respect to the bone
surface or cavity.
[0063] The surgical tool of the invention may further be provided
with means for tensioning the cable or other filamentary member
after attachment of the cable to the tool to bring the first end
surface of the tool to bear upon the implant. For example, the
first end surface of the tool may comprise one or more flanges for
bearing on the rim of an acetabular cup. The adjustable filamentary
member attachment means on the tool may comprise one or more
mooring pegs on the tool, the or each mooring peg being mounted on
a carriage which is movable axially within the body of the tool to
tension the cable. Alternatively the adjustable filamentary member
attachment means on the tool may comprise a spring loaded arm on
the tool, the or each arm being mounted on said carriage.
Preferably, the carriage is carried on a screw-threaded member
mounted axially within the body.
[0064] When used, the protective cover may be a disposable
protective cover, or it may be reusable after appropriate
sterilisation. The protective cover is preferably of a rigid
material, for example polyethylene. Preferably, the protective
cover is provided with a number of holes, through which the cable
is threaded for attachment to the main body portion of the
prosthetic implant. The main body portion of the prosthetic implant
may comprise one or more lugs, around which the cable may be looped
for attachment of the main body portion to the protective cover by
means of the cable. Alternatively, or also, the main body portion
of the prosthetic implant may be provided with one or more bores
through which the cable may be threaded for attachment of the main
body portion to the protective cover by means of the cable.
[0065] The means for attachment of the tool to the protective cover
may comprise a shaped plug on one end of the tool, the plug being
receivable within a corresponding socket provided on the protective
cover. Preferably, a biased locating pin is provided on the tool,
the pin being locatable within a corresponding opening provided on
the protective cover, the biasing urging the pin into the opening
to prevent rotation between the insertion tool and the implant so
that rotational forces can be applied to the implant by means of
the tool when the implant is positioned or impacted.
[0066] Alternatively, or also, the means for attachment of the tool
to the protective cover may comprise means on the tool for
attachment of the cable thereto. In this case, there may further be
provided means for tensioning the cable after attachment of the
cable to the tool to bring the first end surface of the tool to
bear upon the protective cover. The means on the tool for
attachment of the cable may comprise one or more mooring pegs on
the tool, the or each mooring peg being mounted on a carriage which
is movable axially within the body of the tool to tension the
cable. Alternatively the means for attachment of the cable may
comprise one or more spring loaded arms being mounted on said
carriage. Preferably, the carriage is carried on a screw-threaded
member mounted axially within the body.
[0067] When a protective cover is used in the implant of the
invention, there is no necessity to manufacture surgical tools of
different sizes to correspond to different sizes of acetabular cup
or sheath. It is sufficient that the protective cover comprise a
receiving area for the surgical tool. When a tensioned cable is
used to grip the prosthetic implant the attachment provided is
robust in lateral and axial directions, whilst allowing the surgeon
to retain good visibility of the implant during the surgical
procedure.
[0068] When a tensioned cable is used to effect direct attachment
between the implant and the tool, the surgeon is allowed not only a
good degree of rotational and axial control over the implant whilst
inserting the implant, but also the surgeon is able to extract the
implant if he is not satisfied with its orientation after initial
insertion.
[0069] When any of the embodiments of the invention are applied to
the implantation of a prosthetic acetabular cup comprising a
polyethylene unit and a metal shell, it is not necessary for the
polyethylene liner unit to be snapped or screwed into the metal
shell after it has been seated in the acetabulum. A result of this
is that the polyethylene liner unit may be factory fitted reducing
the risk of damage to the unit during fitting.
4. BRIEF DESCRIPTION OF THE DRAWINGS
[0070] FIG. 1 shows an isometric view of a first form of surgical
tool and, in disassembled state, a first prosthetic implant in
accordance with the invention and a protective cover therefor.
[0071] FIG. 2 shows a cross-section along the axis of the surgical
tool of FIG. 1.
[0072] FIG. 3 shows an isometric view of the prosthetic implant of
FIG. 1 and its protective cover when assembled.
[0073] FIG. 4 shows a side view of the main body portion of the
prosthetic implant of FIGS. 1 and 3.
[0074] FIG. 5 shows a partial cross-section on line A-A of FIG.
4.
[0075] FIG. 6 shows an isometric, partly cut away view of a second
form of surgical tool and a second assembled and protected
prosthetic implant according to the invention.
[0076] FIG. 7 shows a plan view from above of the main body portion
of the prosthetic implant of FIG. 6 when disassembled from its
disposable protective cover.
[0077] FIG. 8 is an isometric view of a third form of surgical tool
in accordance with the invention in its closed condition.
[0078] FIG. 9 is an isometric view of the surgical tool of FIG. 8
in its open condition.
[0079] FIG. 10 is a perspective view on a slightly enlarged scale
of a further form of prosthetic implant according to the invention
for use with the surgical tool of FIGS. 8 and 9.
[0080] FIG. 11 is a further perspective view, taken, fro, a
slightly different angle of the prosthetic implant of FIG. 10.
[0081] FIG. 12 is a further perspective view of the prosthetic
implant of FIGS. 11 and 12 with the protective cover raised.
[0082] FIG. 13 is a plan view of a further form of prosthetic
implant according to the invention.
[0083] FIG. 14 is a cross section on line B-B of FIG. 13.
[0084] FIG. 15 is a similar cross section to that of FIG. 14 with a
protective cover in place to protect the articulating surface of
the prosthetic implant of FIGS. 13 and 14.
5. DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0085] Referring to FIG. 1, there is shown a surgical tool 1 having
an elongate body 2 and a first end surface 3 for bearing on a
prosthetic implant 4.
[0086] Prosthetic implant 4 comprises a main body portion 5 which
is an acetabular cup manufactured from cobalt chrome and intended
for use as part of a metal on metal articulating joint. The inner
articulating surface Sa of acetabular cup 5 is highly polished and
is covered (when the implant is assembled in readiness for
implantation in a prepared acetabular socket of a patient) by a
disposable protective cover 6 which is manufactured from a plastics
material such as polyethylene.
[0087] As will be apparent from the foregoing description, the
provision of a disposable protective cover is a preferred feature
of the invention. With the tool and prosthetic implant depicted in
FIG. 1, the disposable protective cover 6 may, if desired, be
omitted. In this case, end surface 3 of tool 1 would be provided
with one or more flanges (not shown), or would itself be of
sufficient diameter, to bear directly on the rim of acetabular cup
5 when assembled.
[0088] When prosthetic implant 4 is assembled in readiness for
implantation, a cable 7 secures disposable protective cover 6 to
acetabular cup 5 by means of lugs 8 on acetabular cup 5 and holes 9
through disposable protective cover 6.
[0089] Cable 7 is made of stainless steel. However, any suitable
material, such as a suitable synthetic fibre, may be used for
manufacture of the cable 7. The cable may be a continuous cable, as
is shown in FIG. 1. Compression clip 10 secures the two free ends
of cable 7 together in the prosthetic implant of FIG. 1.
Alternatively, cable 7 may be formed from a series of individual
loops or lengths of cable.
[0090] In the embodiment of the invention shown in FIG. 1, three
cable loops are depicted. It will be readily understood by those
skilled in the art that any other practical number of cable loops
(e.g. 4, 5 or 6) could alternatively be used.
[0091] Tool 1 comprises mooring pegs 11 for attachment of cable 7.
Mooring pegs 11 are movably mounted in slots 12 on elongate body
2.
[0092] Referring to FIG. 2, it can be seen that mooring pegs 11 are
mounted on a carriage 13 which is carried on screw-threaded member
14. By rotating knob 15 at the top of tool 1, carriage 13 can be
made to move up or down from its intermediate position, i.e. the
position shown in FIG. 1.
[0093] FIG. 3 shows prosthetic implant 4 when assembled with its
protective cover 6 held in place by means of cable 7 so as protect
polished surface 5'. It is intended that the implant 4 will be
supplied to customers in assembled form. However, implant 4 may
alternatively be assembled by a surgeon about to use it. Disposable
protective cover 6 is placed over the rim of acetabular cup 5 and
each respective loop 17 of cable 7 is hooked over a respective lug
8 of acetabular cup 5. The disposable protective cover 6 is secured
to acetabular cup 5 by drawing cable 7 through holes 9 so as to
tighten each loop 17 around its respective lug 8. Disposable
protective cover 6 has on its uppermost surface a raised portion or
peg 19 which is receivable within a corresponding cavity 20 in the
body 2 of tool 1. Disposable protective cover 6 may further have on
its underside, in the orientation depicted, a peripheral portion of
reduced thickness surrounding a downwardly projecting portion for
receipt within the rim 16 of acetabular cup 5, but this is not
shown in the drawings.
[0094] FIG. 4 shows a side view of the acetabular cup 5 and one of
the lugs 8. FIG. 5 is a cross-section on line A-A of FIG. 4 and
shows lug 8 on acetabular cup 5.
[0095] Referring back now to FIGS. 1, 2 and 3, in use of the tool
1, the surgeon will attach the assembled prosthetic implant 4 to
the tool 1 simply by bringing the disposable protective cover 6
into contact with the end surface 3 of tool 1, so that raised
portion or peg 19 is received within cavity 20, and looping each
respective loop of cable 7 around each respective receiving mooring
peg 11. Rotation of knob 15 in a clockwise direction causes
carriage 13 to slide upwardly and tension each loop of cable 7.
[0096] Once the prosthetic implant 4 is securely attached to the
tool 1, the surgeon may then insert the prosthetic implant 4 into a
surgically prepared acetabular cavity in a hip of the patient upon
whom the surgical operation is being performed. When the prosthetic
implant 4 is located to the surgeon's satisfaction, he simply
rotates knob 15 in an anti-clockwise direction to release the
tension on cable 7. He then unloops cable 7 from mooring pegs 11
and withdraws tool 1 from the operating area.
[0097] To detach disposal protective cover 6 and cable 7 from
acetabular cup 5, the surgeon may either unhook the cable 7 from
each lug 8 of acetabular cup 5 or he may simply cut cable 7 and
pull the cut cable through the holes 9 of disposable protective
cover 6.
[0098] Referring now to FIG. 6, there is shown a second form of
surgical tool 101 having an elongate body 102 and a first end
portion 103 for engagement with a prosthetic implant 104. 105 which
is an acetabular cup manufactured from cobalt chrome and intended
for use as part of a metal on metal articulating joint. The
articulating surface of acetabular cup 105 is covered by a
disposable protective cover 106 which is manufactured from a
suitable plastics material, such as polyethylene.
[0099] A cable 107 secures disposable protective cover 106 to
acetabular cup 105 by means of tunnels 108 in the rim 116 of
acetabular cup 105 and holes 109 through disposable protective
cover 106. Tunnels 108 cannot be seen in FIG. 6 but their ends are
visible in FIG. 7, which shows a plan view of the acetabular cup
component 105 of prosthetic implant 104. Each tunnel 108 follows a
roughly C-shaped path extends the short distance between a
corresponding pair of adjacent pair of adjacent tunnel ends as
illustrated in FIG. 7. Cable 107 is tensioned by means of a clip
107a to ensure tight registry between protective cover 106 and cup
105.
[0100] Referring back to FIG. 6, the first end portion 103 is
shaped to fit through a corresponding aperture 118 in disposable
protective cover 106 and so that it can then be rotated through a
quarter turn so as to secure tool 101 to protective cover 106 in
bayonet and socket fashion. First end portion 103 is located on the
end of a barrel 119 which is rotatable inside elongate body 102 by
means of knob 120. Locating pin 111 is provided to secure tool 101
with respect to the disposable protective cover 106 and is
receivable within either of corresponding openings 120a in
disposable protective cover 106. Pin 111 is retractable from
opening 120 by manual pressure applied to lift pin 111 towards its
retracted position. Pin 111 is biased towards its unretracted
position by means of a coil spring (not shown) housed within
chamber 121.
[0101] In use of the tool 101, the surgeon will attach the
assembled prosthetic implant 104 to the tool 1 simply by passing
the end portion 103 through socket 118 of disposable protective
cover 106 and rotating the barrel 119 of tool 101 through a quarter
turn using knob 120 so that the tool 101 is secured to the
prosthetic implant 104 by means of the bayonet and socket action.
Then biased locating pin 111 can be caused to snap into a
corresponding one of the openings 120a.
[0102] Once the prosthetic implant 104 is securely attached to the
tool 101, the surgeon may then insert the prosthetic implant 104
into a surgically prepared acetabular cavity of the patient. When
the prosthetic implant 104 is located to the surgeon's
satisfaction, he simply pulls locating pin 111 upwardly to release
it from opening 120 and rotates elongate body 102 by a quarter turn
before withdrawing tool 101 from the operating area.
[0103] To detach disposal protective cover 106 and cable 107 from
acetabular cup 105, the surgeon must cut cable 107 and pull the cut
cable through the holes 109 of disposable protective cover 106.
[0104] Referring to FIG. 8, there is shown a third form of surgical
tool 201 having an elongate hollow body 202 and a first end 203 for
engagement with a prosthetic implant. Towards its other end, body
202 has a handle portion 204 which is surmounted by a rotatable
knob 205 attached to the upper end of an internally threaded stub
shaft (not shown). Below handle portion 204 is a barrel portion 206
within which is slidably located a carriage 207 having an upwardly
extending externally threaded projection (not visible in FIG. 8)
which is screw threadedly engaged with the internally threaded stub
shaft of rotatable knob 205. By rotating knob 205, carriage 207 can
be caused to slide axially up or down within barrel portion 206 as
desired. At its lower end carriage 207 is provided with an axial
bore which receives an upwardly projecting peg mounted in a bottom
part 210 of tool 201.
[0105] Carriage 207 is provided with three radial slots whose upper
ends open into the axial bore in the bottom of carriage 207. In
addition each radial slot has associated with it a chordal slot
which extends downwardly and inwardly into the carriage 207 so as
to provide a pair of bearing surfaces one on either side of each
radial slot. Arms 208 having a lower hooked first end 209 are
pivotally mounted near their upper ends upon carriage 207 by means
of stub members which bear on the bearing surfaces provided by the
chordal slots. At a short distance the stub members, each arm 208
is pivotally biased outwardly away from carriage 207 by means of a
coil spring trapped between arm 208 and carriage 207. When carriage
207 moves down into barrel portion 206, however, the top of the
axial peg in the bottom part 210 impinges upon inward projections
on the upper ends of arms 208 so as to cause the arms 208 to swing
inwardly until the lower hooked ends 209 are received within
cut-out portions 211. On the other hand, as carriage 207 is caused
to slide axially up within barrel portion 206, the inward
projections on the upper ends of arms 108 no longer impinge on the
axial peg within bottom part 210 so that the springs can cause arms
208 to pivot outwardly upon their stub members.
[0106] Slots 212 in barrel portion 206 allow this pivoting movement
to occur and rounded enlarged portions 213 permit the stub members
to pass through during assembly of the tool 201.
[0107] At the first end 203 of tool 201 there is an axial peg 214
and an axially offset auxiliary peg 215.
[0108] FIGS. 10 to 12 illustrate an acetabular implant suitable for
use with the surgical tool 201. This comprises an acetabular cup
216 and a protective cover 217 made from high density polyethylene.
Acetabular cup 216 is made of cobalt chrome with a highly polished
inner bearing surface 218 and an outer texturised surface 219 which
is intended to promote bone ingrowth following implantation in a
patient's hip and which is coated with hydroxyapatite. In addition,
the outer surface 219 is provided with two pairs of ribs 220 which
are intended to bite into the bone surrounding the patient's
acetabular cavity during the implantation operation so as to
prevent unwanted rotation of the implant, particularly during the
early stages of the post-operative recuperation period.
[0109] Protective cover 217 is retained in place on acetabular cup
216 by means of cable 221. This passes through holes 222 in
protective cover 217 and through tunnels (not shown) which follow a
substantially C-shaped path through the wall of the acetabular cup
216. Protective cover 217 has on its upper side an axial bore 223
to receive peg 214 of surgical tool 201 and also an axially offset
bore 224 to receive peg 215 of surgical tool 201.
[0110] The ends of cable 221 are secured to one another by means of
sleeve 225. As can perhaps best be seen from FIG. 12 a first end
portion is threaded upwards through sleeve 225, is then doubled
back on itself to form a first loop projecting upwardly from the
upper end of sleeve 225 and passed back down through sleeve 225,
and is led around sleeve 225, before the first free end is passed
through the first loop. In a similar way the other end portion of
the cable 221 is passed downwardly through sleeve 225, is doubled
back on itself to form a second loop projecting downwardly from the
lower end of sleeve 225 and passed back up through sleeve 225, and
is led around sleeve 225, before the second free end is passed
through the second loop. The four portions of cable passing through
sleeve 225 are a snug fit therein. Up applying tension to the cable
221, the first and second loops are tightened and so tighten their
grip upon the respective free ends of cable 221 to secure the cable
221 into a continuous loop.
[0111] In use, a surgeon takes surgical tool 201 with the carriage
207 in its end position nearest end 203 so that arms 208 are fully
retracted and fits peg 214 into bore 223 and peg 215 into bore 224.
Next he loops the three upstanding loops of cable 221 each over a
respective hooked end 209 of an arm 208. He then rotates knob 205
clockwise to cause carriage 207 to slide axially up barrel portion
206. In so doing the upper ends of arms 208 come out of engagement
with the axial peg of bottom part 210 and the springs bias arms 208
outwardly towards the position of FIG. 9. In so doing the hooked
ends 209 pull upwardly on cable 221 and tighten it. When the knob
can no longer be readily rotated by hand the cable 221 is taut and
holds acetabular cup 216 and its protective cover 217 firmly on the
end 203 of tool 201.
[0112] After the acetabular cup has been seated in the surgically
prepared cavity in the patient's hip to the satisfaction of the
surgeon, he then rotates knob anticlockwise to move carriage 207
back to its start position, thereby slackening the tension in cable
221 and enabling him to disengage tool 201 from the operative area.
When the tool 201 has been removed, he cuts cable 221 and withdraws
it from the tunnels in acetabular cup 216 through which it has been
threaded and removes protective cover 217 in readiness for
insertion of the ball on the patient's femur (or the ball head of a
femoral prosthesis) into the acetabular cup 216 and closure of the
surgical wound.
[0113] Instead of using a stainless steel cable 221 it is
alternatively possible to use a synthetic fibrous material of high
strength such as Kevlar.TM. monofilament.
[0114] FIGS. 14 to 16 illustrate another form of acetabular implant
302 according to the invention. This comprises an outer metal cup
member 302, which is made, for example, of cobalt chrome, and an
inner liner 303 made of high density polyethylene which is intended
to provide the bearing surface of the ball head of a femoral
prosthesis. Surrounding the upper rim of the inner surface of
cup-member 302 is an inwardly projecting lip 304 below which is an
adjacent circumferential ridge 305. Inner liner 303 has a
peripheral ledge on its upper face which substantially conforms in
dimensions to lip 304. It also has a circumferential groove
corresponding to ridge 305. Liner 303 is press fitted in the
factory into acetabular cup member 302 with the circumferential
ledge on liner 303 engaged under the lip 304 and with ridge 305
engaged in the corresponding circumferential groove in liner
303.
[0115] Three short tunnels 306 each of which follows a generally
C-shaped path are formed between the three adjacent pairs of tunnel
openings which are visible in FIG. 14. These tunnels are provided
for the passage of a closed loop of cable, similar to cable 221,
for retaining a protective cover 307 which is intended to protect
the inner surface of liner 303 during implantation by a surgeon.
This protective cover 307 has an axial bore 308, similar to bore
223 of protective cover 217, and also an axially offset bore (not
shown) similar to bore 224 of protective cover 217, to enable the
implant 301 to be used with the surgical tool 201.
[0116] Instead of using one continuous loop of cable 221, it is
alternatively possible to use three separate continuous loops of
cable or Kevlar.TM. monofilament, one for each tunnel 306.
* * * * *