U.S. patent application number 10/738652 was filed with the patent office on 2005-06-23 for anti-backout arthroscopic uni-compartmental prosthesis.
Invention is credited to Bertram, Morton III.
Application Number | 20050137713 10/738652 |
Document ID | / |
Family ID | 34677425 |
Filed Date | 2005-06-23 |
United States Patent
Application |
20050137713 |
Kind Code |
A1 |
Bertram, Morton III |
June 23, 2005 |
Anti-backout arthroscopic uni-compartmental prosthesis
Abstract
An improved uni-compartmental implant has a shaft having a
proximal end attached to a head and a distal end, and one or more
raised portions spaced apart along the shaft to resist back-out.
The length between the head and distal end is preferably less than
50 mm, the distal end of the shaft has a diameter on the order of 2
to 3 mm, the proximal end of the shaft has a diameter on the order
of 2 to 4 mm, and the head has a diameter ranging from 4 mm or less
to 20 mm or more, making the device suitable for knee arthroscopy
and other applications. The shaft and/or raised portions may
include a bone-ingrowth or bone-ongrowth surface, and the shaft
and/or raised portions may be made of a fiber-metal. The head
portion is preferably ceramic, though a chrome-cobalt alloy,
titanium, or other bio-compatible material may be used. The head
portion may have a bi-convex shape, a plano-convex shape, or a
concave-convex shape.
Inventors: |
Bertram, Morton III;
(Naples, FL) |
Correspondence
Address: |
John G. Posa
Gifford, Krass, Groh, Sprinkle,
Anderson & Citkowski, P.C.
280 N. Old Woodward Ave., Suite 400
Birmingham
MI
48009-5394
US
|
Family ID: |
34677425 |
Appl. No.: |
10/738652 |
Filed: |
December 17, 2003 |
Current U.S.
Class: |
623/23.44 ;
623/20.3 |
Current CPC
Class: |
A61F 2002/3895 20130101;
A61F 2002/30892 20130101; A61F 2002/30616 20130101; A61F 2002/30878
20130101; A61F 2310/00029 20130101; A61F 2310/00179 20130101; A61F
2250/0039 20130101; A61F 2310/00796 20130101; A61F 2002/30327
20130101; A61F 2310/00023 20130101; A61F 2/30767 20130101; A61F
2230/0067 20130101; A61F 2/30965 20130101; A61F 2002/4635 20130101;
A61F 2002/30884 20130101; A61F 2002/30205 20130101; A61F 2/38
20130101; A61F 2/30771 20130101; A61F 2/4618 20130101; A61F 2/30756
20130101; A61F 2002/30759 20130101 |
Class at
Publication: |
623/023.44 ;
623/020.3 |
International
Class: |
A61F 002/30; A61F
002/38 |
Claims
I claim:
1. A uni-compartmental implant, comprising: a shaft having a
proximal end attached to a head and a distal end; and one or more
raised portions spaced apart along the shaft to resist
back-out.
2. The uni-compartmental implant of claim 1, wherein the length
between the head and distal end is less than 50 mm.
3. The uni-compartmental implant of claim 1, wherein the distal end
of the shaft has a diameter on the order of 2 to 3 mm.
4. The uni-compartmental implant of claim 1, wherein the proximal
end of the shaft has a diameter on the order of 2 to 4 mm.
5. The uni-compartmental implant of claim 1, wherein the shaft
includes a bone-ingrowth or bone-ongrowth surface.
6. The uni-compartmental implant of claim 1, wherein the raised
portions include a bone-ingrowth or bone-ongrowth surface.
7. The uni-compartmental implant of claim 1, wherein the shaft is
made of a fiber-metal.
8. The uni-compartmental implant of claim 1, wherein the raised
portions are made of a fiber-metal.
9. The uni-compartmental implant of claim 1, wherein the head
portion is ceramic.
10. The uni-compartmental implant of claim 1, wherein the head
portion is constructed of a chrome-cobalt alloy or other
bio-compatible alloy.
11. The uni-compartmental implant of claim 1, wherein the head
portion has a bi-convex shape.
12. The uni-compartmental implant of claim 1, wherein the head
portion has a plano-convex shape.
13. The uni-compartmental implant of claim 1, wherein the head
portion has a concave-convex shape.
14. The uni-compartmental implant of claim 1, wherein the head
portion has a diameter ranging from 2 mm to 20 mm.
Description
FIELD OF THE INVENTION
[0001] This invention relates generally to joint-related prosthetic
devices and, in particular, to an arthroscopic, uni-compartmental
prosthesis.
BACKGROUND OF THE INVENTION
[0002] Due in part to an aging population that wishes to remain
active, arthritis of the knee is approaching epidemic proportions
in the U.S. Another factor is obesity, since the knees bear much of
increased weight in the body. It is estimated that approximately
750,000 surgical procedures are done in the U.S each year for knee
problems, including total-knee replacements, partial-knee
replacements, and arthroscopic procedures.
[0003] Quite often, patients treated with knee arthroscopy for
arthritis of the knee do very poorly. There are a number reasons
for this, but the low rate of success is largely due to the fact
that these patients have a small area of their cartilage which is
denuded of cartilage and they continue to have pain. Although the
area of cartilage eburnation is not large enough to warrant joint
replacement procedure, it is large enough to cause continued
problems and significant patient dissatisfaction.
[0004] Uni-compartmental knee procedures have therefore become more
popular in recent years. One reason is that smaller incisions are
now used, to the extent that uni-compartmental knees are now
carried out through a so-called minimally invasive approach. Still,
however, in many case this involves a 4-inch incision, significant
soft tissue dissection, and significant morbidity for the
patient.
[0005] To improve these procedures, various implants and techniques
are being devised. One of many is disclosed in Published U.S.
Patent Application 2002/0099446 A1. This reference discloses a
knee-joint prosthesis comprising at least one femoral component and
at least one tibial component. The femoral component includes a
first portion adapted for fixable attachment to a distal end of a
femur and a second portion formed with a bearing surface. The
femoral component is sized so as to permit attachment to the femur
of a patient without severing at least one the cruciate ligaments.
The tibial component has a first surface that is adapted to
cooperate with a patient's tibia, while a second surface of the
tibial component is adapted to cooperate with the femoral
component. The tibial component is sized so as to permit attachment
to the patient's tibia without severing at least one of the
cruciate ligaments.
[0006] Despite advances such as these, however, the need remains
for an improved implant, preferably one that resists back-out.
SUMMARY OF THE INVENTION
[0007] This invention resides in an improved uni-compartmental
implant including a shaft having a proximal end attached to a head
and a distal end, and one or more raised portions spaced apart
along the shaft to resist back-out. The length between the head and
distal end is preferably less than 50 mm, the distal end of the
shaft has a diameter on the order of 2 to 3 mm, the proximal end of
the shaft has a diameter on the order of 2 to 4 mm, and the head
has a diameter ranging from 4 mm or less to 20 mm or more, making
the device suitable for knee arthroscopy and other
applications.
[0008] The shaft and/or raised portions may include a bone-ingrowth
or bone-ongrowth surface, and the shaft and/or raised portions may
be made of a fiber-metal. The head portion is preferably ceramic,
though a chrome-cobalt alloy, titanium, or other bio-compatible
material may be used. The head portion may have a bi-convex shape,
a plano-convex shape, or a concave-convex shape.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIG. 1 is a drawing that illustrates a preferred embodiment
of the invention.
[0010] FIG. 2 is a drawing that illustrates an alternative head
design;
[0011] FIG. 3 is a drawing that illustrates a different alternative
head design; and
[0012] FIG. 4 is a drawing that illustrates yet a further
alternative head design.
DETAILED DESCRIPTION OF THE INVENTION
[0013] FIG. 1 illustrates a preferred embodiment of the invention.
The implantable device, shown generally at 100, includes a shaft
portion 102 having a head portion 104 and one or more raised
portions 106 to resist pull-out. In terms of dimensions, the length
of the device is preferably on the order of 25 mm, though length in
excess of this, or on the order of 10 mm or less, may be more
appropriate depending upon the application. The distance between
the raised portions, "D" is preferably a few millimeters; for
example, between 5 and 10 millimeters, depending upon the number
used and other considerations.
[0014] The shaft portion 102 preferably tapers from a diameter at
"B" of 3 mm, or less, to a diameter at "A" of 2.5 mm, or
thereabouts. The head 104 will preferably be offered in different
diameters, such as 4, 6, 8, 10, 15, and 20 mm, and so forth, in
which case smaller-diameter heads may have smaller dimensions of A
and B, and larger-diameter heads may have larger dimensions of A
and B. Smaller dimensions may use less raised portions 106, whereas
larger dimensions may use more of them.
[0015] Although the head portion 104 is generally shown as a
bi-convex shape, other head geometries may be appropriate, such as
plano-convex, concave-convex, and different radii of curvature,
whether concave or convex surfaces are used. In addition, although
the edge of the bi-convex surfaces of the head 104 are shown in the
drawing as smoothly transitioning through a smaller radius, the
sharp edge may alternatively be used. FIGS. 2-4 show three possible
alternative head configurations.
[0016] In terms of materials, the head portion may be made of any
appropriate bio-compatible material, such as chrome cobalt or
titanium, though in the preferred embodiment, ceramic is used. The
shaft 102 and raised portions 106 preferably include some type of
porous ingrowth or ongrowth surface such as hydroxyapetitite, and
such surfaces may be used in conjunction with raised bumps to
further assist in preventing backout. Although a metallic shaft in
raised portions may be used, when available, a fibermetal one is
the preferred technology.
[0017] The inventor has also devised a way to perform a procedure
arthroscopically without large incisions so that we could take care
of these patchy areas of ebumated bone within an isolated condyle
in the knee. The procedure could be done on the lateral or medial
side, and if the technique was altered slightly, it could even be
applied to the patellofemoral groove. The technique would involve a
variation of a procedure known as the OATS procedure. In this
procedure, osteoarticular transfer of tissue is performed by using
essentially a trephine to core out a plug of bad bone where the
cartilage has been worn away or eburnated and then an area of the
knee is harvested that has articular cartilage covering it but is
not needed, for instance, the inner portion of the patellofemoral
groove or inner portion of the medial and lateral femoral condyle
along the intercondylar notch. These tissue plugs, which contain
bone and cartilage, are then transferred over to this area. This
procedure has had moderate success. It is mostly used for young
people who have isolated articular defects.
[0018] According to this invention, the OATS procedure is converted
to an arthroplasty technique where, instead of a plug of bone and
cartilage, the plug of FIG. 1 is instead used. The area of defect
would be isolated, identified, and measured, then a guide wire
would be placed centrally into the defect. Over the guide wire, a
cannulated reamer would be placed that we would ream to a specified
depth. This would establish the canal size for the `stem` of the
prosthesis. We would then over-ream with a secondary reamer which
would then establish the size for the `rounded head` of the
prosthesis. At this point, the prosthesis could be either press
fitted or cemented into place in the defect.
[0019] I believe that this technique would have significant
advantages over the OATS procedure since this would be more rigidly
fixed and it would be sealing the defect with cement and/or cobalt
chrome. It would be more applicable for the elderly population as
they have more of a geographic ebumation of bone as opposed to
small circumscribed lesions that are applicable to the OATS
procedure. I would envision that for a typical arthritic knee, one
would need multiple plugs of cobalt chrome that could be placed in
these areas. With relative ease, the surgeon could place as many as
four or five of these circular plugs in the knee to take care of
the eburnated areas where the bone is exposed. An inventory would
be maintained that would come in different diameter sizes and stem
lengths for the prostheses. They could easily be used in a right or
a left knee and each prosthesis implanted would be a separate
charge. They are relatively small; therefore, they would not occupy
a large amount of shelf space at the hospital or in the local
distributor's office. The instrumentation would be easy to design
and would fit very nicely in a self-contained unit.
[0020] In rare situations, we would find eburnated bone on the
tibial side. This would obviously be more difficult to reach
because of the anatomy of the knee. However, it is conceivable that
lesions within the anterior two-thirds of the knee on the tibial
plateau could easily be re-surfaced in a manner such as I just
described. These plugs will actually be more flat as opposed to a
slightly rounded plug that would be used on the femoral side.
* * * * *