U.S. patent application number 15/324379 was filed with the patent office on 2017-06-22 for surgical joint implant and a bone-mountable rig.
This patent application is currently assigned to Episurf IP-Management AB. The applicant listed for this patent is EPISURF IP-MANAGEMENT AB. Invention is credited to Nina BAKE, Richard LILLIESTR LE.
Application Number | 20170172744 15/324379 |
Document ID | / |
Family ID | 51205363 |
Filed Date | 2017-06-22 |
United States Patent
Application |
20170172744 |
Kind Code |
A1 |
BAKE; Nina ; et al. |
June 22, 2017 |
SURGICAL JOINT IMPLANT AND A BONE-MOUNTABLE RIG
Abstract
A surgical joint implant has a cap in the form of at least two
intersecting circles of the same diameter having an articular outer
surface and an inner surface for bone adhesion. At the center of
each circle a peg, for bone insertion into a hole of a nominal
diameter, extends. One peg is slightly larger than said nominal
diameter, to achieve an interference fit and the other peg is
slightly thinner, to achieve a slide fit. A tubular drill rig open
at both ends and having an interior circumference corresponding to
the outer shape of the implant, can be mounted over the bone
surface to be repaired. It accommodates a double drill for
drilling, at the same time, a shallow hole of the diameter of the
intersecting circle and a deeper narrow hole at the center of the
circle of said nominal diameter.
Inventors: |
BAKE; Nina; (Lidingo,
SE) ; LILLIESTR LE; Richard; (Stockholm, SE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
EPISURF IP-MANAGEMENT AB |
Stockholm |
|
SE |
|
|
Assignee: |
Episurf IP-Management AB
Stockholm
SE
|
Family ID: |
51205363 |
Appl. No.: |
15/324379 |
Filed: |
July 9, 2014 |
PCT Filed: |
July 9, 2014 |
PCT NO: |
PCT/EP2014/064760 |
371 Date: |
January 6, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61F 2002/30331
20130101; A61F 2002/30897 20130101; A61F 2002/3013 20130101; A61B
17/1767 20130101; A61B 2034/108 20160201; A61F 2/38 20130101; A61F
2002/30878 20130101; A61B 17/17 20130101; A61B 34/10 20160201; A61F
2/30 20130101; A61F 2/4657 20130101; A61B 17/154 20130101; A61F
2002/30891 20130101; A61F 2/30756 20130101; A61B 17/15 20130101;
A61F 2/36 20130101; A61F 2002/30892 20130101 |
International
Class: |
A61F 2/30 20060101
A61F002/30; A61B 17/17 20060101 A61B017/17 |
Claims
1. Surgical The surgical joint implant having a cap with an
articular outer surface and an inner surface adapted for bone
adhesion, said cap having at least first and second pegs extending
from said inner surface for anchoring said implant in a bone,
characterized in that said at least first and second pegs have the
same nominal diameter and that the diameter of said first peg
deviates positively from said nominal diameter to provide an
interference fit in relation to said nominal diameter and in that
said second peg deviates negatively from said same nominal diameter
to provide a clearance fit in relation to said same nominal
diameter.
2. The surgical joint implant according to claim 1, wherein said
first peg deviates from said nominal diameter to provide a force
fit in relation to said nominal diameter.
3. The surgical joint implant according to claim 1, wherein said
second peg deviates from said nominal diameter to provide a slide
fit in relation to said nominal diameter.
4. The surgical joint implant according to claim 1, wherein a third
peg which deviates from said nominal diameter to provide a slide
fit in relation to said nominal diameter.
5. The surgical joint implant according to claim 1, wherein said
cap has the form of two intersecting circles of the same diameter,
said first and second pegs being disposed at the centers of the
respective circles.
6. The surgical joint implant according to claim 4, wherein the cap
has the form of three intersecting circles of the same diameter,
said first, second and third pegs being disposed at the centers of
the respective circles.
7. The surgical joint implant according to claim 1, wherein one of
the pegs is significantly longer than the others.
8. The surgical joint implant according to claim 1, wherein said
articular outer surface is individually custom-formed.
9. The surgical joint implant according to claim 1, wherein said
inner surface adapted for bone adhesion and the surfaces of said
pegs have an outer layer of a substance that promotes bone
growth.
10. A rig for correct drilling and insertion of a surgical joint
implant as claimed in claim 1, having a hollow tubular shell open
at both ends, wherein the interior of said shell defines at least
first and second intersecting right circular cylinders of equal
diameter.
11. The rig according to claim 10, wherein the interior of said
shell defines first, second and third intersecting right circular
cylinders of equal diameter.
12. The rig according to claim 10, wherein an arcuate wall is
selectively insertable into said shell interior to complete the
full circumference, as desired, one of said right circular
cylinders.
13. The rig according to claim 10, wherein the bone-engaging end of
said hollow tubular shell is shaped to conform to the shape of the
joint surface in which the implant is to be inserted.
14. The rig according to claim 10, wherein said rig is provided
with multiple holes for pins anchoring the rig securely in place on
the surface to be repaired.
Description
[0001] The present invention relates to a surgical joint implant
and a bone-mountable rig for correct drilling and insertion of such
a surgical joint implant. The implant according to the invention is
intended for repair of the surface of a joint of a human or
animal.
[0002] It is intended that the implants of the present invention
may be tailor-made to the patient and the damage to her joint to be
repaired. This individually shaped implant can be made by the
method described in Application No. PCT/EP2014/064749, reference
No. IPQ6028, filed by the same applicant and having the same filing
date. This co-pending application filed together herewith is hereby
incorporated by reference.
[0003] The advantages of implants over knee replacement have
stimulated a further development of smaller implants that can be
implanted with less invasive surgery. In this development there has
also been an effort to achieve small joint implants, suitable for
repair of a small cartilage injury that have a minimal influence on
the surrounding parts of the joint. In the current development,
such small implants are designed with an implant body that may be
formed as a mushroom cap with a hard surface to face the
articulating side of the joint and a bone contacting surface
engaging the bone below the damaged part of cartilage. The shape
and the curvature of the articulating surface of the implant may be
designed to be a reconstitution of the shape and the curvature of
the part of the joint when it was undamaged. Such implants are
usually designed as mushrooms with an implant body or head and with
a peg or a rod projecting from the bone contacting side of the
implant body for anchoring the implant into the bone.
[0004] WO2007/014164 A2 describes a kit comprising a plurality of
small joint implants having different predetermined shapes
described as circle, oval, L-shape and triangular shape and tools
for placing the implants and a method for placing the implant in a
joint, e.g. in the knee or other joints where there is a need for
repair of a cartilage and/or bone damage. In this piece of prior
art each implant shape has a specific guide tool which corresponds
to the shape of the implant.
[0005] The cartilage damage is repaired by choosing the most
suitable implant from the different shapes mentioned above. The
corresponding guide tool is selected and is used for faster reaming
of the area where the implant is to be placed. A drill is used for
drilling a hole to accept the post extending from the bone
contacting side of the implant. In the end, the implant is placed
on the area reamed or drilled out for the implant. Although it is
the intention that the guide tool shall be used for the preparation
of the placement of the implant it is also said that the use of the
guide tool is optional, see passage sections [019, 020].
THE ADVANTAGES OF THE INVENTION
[0006] The aim of the present invention is to solve a complex of
difficulties encountered when attempting to repair damaged joints
using surgical implants. For a number of different types of joint
damage, a circular implant mushroom cap with a central anchoring
stem or peg of smaller diameter is preferably used. The deeper
small diameter central hole for the central anchoring peg and the
shallower larger diameter hole for the implant cap having the new
joint repair surface can be accurately drilled at the same time
where a circular double drill is preferably used. A double drill
has a central small diameter bit and further up a larger diameter
drill cutting surface. An example of such a drill used together
with the drilling rig of the invention is shown in FIG. 4. Such
drills are commonly used in other areas for inlaid discs and for
countersinking screws.
[0007] But the area of the joint damage may not be easily covered
by a single circular implant if the damaged area is elongate or is
irregular or large in shape. Instead of using a number of separate
implants or an implant requiring complicated bone removal
techniques, using several different drills and tools, the surgical
implant and the rig according to the present invention provide an
exceptionally simple solution which also utilizes a single rig
anchored in place for the entire pre-drilling and drilling
operation. The same double-drill, the same pre drilling guide
socket and the same depth adjustment socket is used for all
drillings. This is made possible by a rig which permits shifting of
the guide socket or adjustment socket from one side to the other
side (or the other sides) of the hollow shell interior between
drillings. A shiftable interior arcuate wall can also be inserted
in each position to provide a complete circular cylinder for
holding the pre-drilling guide socket for each drilling.
[0008] According to one embodiment, this will simply create two
identical peg holes and an exactly excavated cavity to fit an
implant in the form of two intersecting circles of the same
diameter. Merely removing the insert wall in the cylindrical
interior then creates a shell, already securely rigged in location,
for a gauge for the oblong implant with at least two pegs. A
handled gauge in the shape of the implant is inserted after
drilling to check that the proper drilling depth has been reached.
After all drillings have been made and depth checked, the drilling
rig is removed.
[0009] The implant should comprise a biocompatible metal, metal
alloy, ceramic or polymeric material. More specifically it may
comprise any metal or metal alloy used for structural applications
in the human or animal body, such as stainless steel, cobalt-based
alloys, chrome-based alloys, titanium-based alloys, pure titanium,
zirconium-based alloys, tantalum, niobium and precious metals and
their alloys. If a ceramic is used as the biocompatible material,
it can be a biocompatible ceramic such as aluminium oxide, silicon
nitride or yttria-stabilized zirconia. Preferably the articulate
surface comprises a cobalt chrome alloy (CoCr) or stainless steel,
diamond-like carbon or a ceramic.
[0010] The implant according to one embodiment of the present
invention has two parallel pegs of the same nominal diameter, but
with one being slightly larger than the diameter of the hole to
provide an interference fit. The other peg of the same nominal
diameter is very slightly smaller than the diameter of the hole to
provide a slide fit. This relationship will provide secure
anchoring of the implant by virtue of the interference fit. The
slide fit peg will prevent rotation of the implant and will not
give rise to problematic stresses between the pegs which might be
the case with two interference fits. This implant and rig will also
make is easier to insert and make sure that the implant cap seats
securely in place against the bottom of the shallow wide hole
drilled into the bone. This is very important in making sure that
the implant is held securely by bone growth without cavities.
[0011] The present invention also contemplates as a first
alternative a surgical implant having two pegs, but it is also
contemplated according to the invention an implant having three or
more pegs and an implant form comprising three or more intersecting
circles. In this case the drill guide insert wall is shifted
between three or more different arcuate depressions in the interior
of the rig.
SHORT DESCRIPTION OF THE DRAWINGS
[0012] The implant and rig of the invention will be described below
with reference to a non-limiting example shown in the accompanying
drawings of which,
[0013] FIG. 1 shows a two-pegged implant,
[0014] FIG. 2 shows a rig according to the invention for a two
pegged implant. The rig is mounted in place on a femoral
condyle.
[0015] FIG. 3a shows a three-pegged implant having the form of
three identical intersecting circles.
[0016] FIG. 3b shows from above a rig with wall insert for a
three-peg implant.
[0017] FIG. 4 shows a double drill for use with the drilling rig
according to the invention.
[0018] FIG. 5a shows a pre-drilling guide socket.
[0019] FIG. 5b shows a drilling depth adjustment socket.
DETAILED DESCRIPTION
[0020] FIG. 1 shows one exemplary implant according to the present
invention, in this case for use in the repair of a damaged condylar
surface of the human femur. It is contemplated that in certain
applications of the invention the outer surface of cap 3 of the
implant 1 will be shaped to conform to the undamaged shape of the
patient's condyle. Standard sized and shaped implants will also be
covered by the scope of the main claim. Such implants can also be
used for many different joint surfaces in, for example, the joints
of the hip, knee, toe and shoulder.
[0021] The implant 1 has a cap 3 with on its outside 41 a new joint
surface and on its inside, in this particular embodiment, a ridge
47 which lodge in a drilled groove as will be explained below. The
implant cap has the shape of two intersecting circles of the same
diameter. Typical implants according to the invention may have a
cap with two intersecting circles of diameter 15 mm. Other shapes
which may be suitable are 17+17 mm, 20+20 mm and 25+25 mm. At the
center of each circle there extends a peg 48, 49. Each peg has, in
this particular embodiment, a narrower end 48a, 49a to aid in
directing the pegs correctly into drilled holes in the condyle, as
will be explained in more detail below.
[0022] In this case, the first peg 48 is longer than the second peg
49, but they can also be of the same length. According to the
invention, both pegs are of the same nominal diameter, but the
first peg 48 is slightly larger than the nominal diameter,
providing an interference fit shaft of said nominal diameter. An
anchoring interference fit between hard metal and living bone
requires a greater differential than an interference fit between
two metal elements. How much larger than the nominal diameter the
first peg is will be a matter of clinical testing and revision. In
this context involving a metal shaft in a hole in living bone and
in the appended claims the term interference fit in relation to a
nominal hole diameter is deemed to include positive differences up
to and including approximately +11% increase in diameter over the
nominal diameter. To get a very secure grip between a hole of a
diameter of 4 mm in living bone and a peg of one of the materials
described in the paragraph above, the peg should have a diameter of
between ca 4.1 and 4.4 mm. An interference fit between hard metal
and living bone requires a significantly larger difference than
between a shaft and a hole of hard metal for example. The
differential between the first peg diameter and the hole should not
be so great as to require excessive force to put it in place with
the risk of cracking in the bone. The second peg 49 has a diameter
of the same nominal diameter but falling within the standard
definitional boundaries for a clearance fit, i.e. almost of the
same diameter but very slightly smaller. This relationship will
ensure that the implant is securely anchored, is fairly easy to
install, and will not give rise to problematic stresses between the
pegs, either during implantation or thereafter.
[0023] FIG. 2 shows an example of a rig according to the present
invention which is used for all of the hole preparation. The rig
comprises an elongated hollow shell 51 having the form of two
intersecting (overlapping) right circular cylinders 52, 53 of the
same diameter. The rig can be formed to conform to the shape of the
bone and cartilage area of the patient to be repaired or can be a
standard rig. The rig is held securely in place on the condylar
surface in this case by pins (not shown) driven in through holes
61, to hold the rig securely in place throughout the entire
drilling process.
[0024] After the pins have been driven in, the cutting and drilling
process can begin, with a wall insert 55 inserted in one end of the
hollow shell, leaving an entire first right circular cylinder 52 at
one end of the hollow tubular shell. At this time the surgeon may
insert into the first right circular cylinder a depth adjustment
socket 505 (FIG. 5b) and then a sharp cylindrical hand knife, sized
exactly to the interior of the adjustment socket 505, make a
preliminary circular sharp edged cut through the cartilage down to
the bone. A circular bare bone area is left after this cartilage
removal.
[0025] In one embodiment, the surgeon uses a 17/4 mm double drill
as shown schematically in FIG. 4. It has a central narrow 4 mm
diameter bit 401, and a wider 17 mm diameter cutting bit 402. The
outer lateral surface 403 of the double drill conforms to a height
adjustment socket placed inside the wall insert, which securely
holds the double drill to drill, in the same operation, a central 4
mm hole for the first peg 48 and a much shallower surrounding bore
17 mm in diameter in this example. A pre-drilling of the initial
part of the peg hole in the bone can be made using a guide socket
501 (FIG. 5a). This improves the exact placement of the
simultaneous drilling of the peg hole and the circular bare-bone
area with the double drill (FIG. 3). After removing the drill, and
flushing out organic matter, the surgeon then slides the wall
insert 53 out and inserts it in on the other side of the hollow
shell, creating a complete right circular cylindrical guide hole on
the opposite side of the hollow shell.
[0026] The surgeon then inserts the adjustment socket and uses the
same cylindrical knife in the newly created guide hole, to make a
circular excision of the cartilage (not a complete circle since the
intersecting portion has already been removed in the previous
step). The in this embodiment 17/4 mm double drill is then used
again first with the guide socket 501 to pre-drill the peg hole and
then with the adjustment socket 505 to double-drill the peg hole to
its full depth and create the bare-bone circle , i.e. the 4 mm hole
for the second peg and a second surrounding shallow bore which is
of course also 17 mm in diameter.
[0027] These two drilling operations have created 4 mm peg holes
and a space in the bone to exactly accommodate in this case a 17+17
implant of the invention. The wall insert 53 is then completely
removed. A handle-equipped gauge corresponding to the intersecting
circular forms making up the implant, is used to make sure that the
holes have been drilled to the proper depth in the bone. The rig is
then removed and the implant pegs are inserted into their holes.
For the cap of the implant to lodge exactly in the in this case
17+17 shallow cavity removed from the surface of the bone it is
usually necessary to carefully tap the cap, preferably on top of
the first peg, with interference fit, with a hammer via a special
mandrel. The first, slightly thicker peg, is tapped down into its
hole while the second peg, slightly narrower, slides easily into
its hole. The larger diameter part of the 17/4 mm drill in this
example has a rim to excavate a peripheral slot slightly deeper
than the 17 mm shallow cavity, to accommodate the peripheral ridge
47 of the implant, helping to hold the implant securely in place
during healing and subsequent loading during use.
[0028] Thus the rig, which can be form-fitted to the shape of the
individual patient's condyle in this example, is placed over the
damaged area of the condyle and is anchored securely in place, in
this particular non-limiting example, by driving in four pins (not
shown) into holes 61 in the condyle shaped lower end of the rig 50.
It is now securely in place for the entire drilling operation,
which be simplified greatly and made much more exact and less
dependent on the artistry of the surgeon, which may vary from day
to day.
[0029] After drilling of the holes, the pins are pulled out and the
rig is removed from the site, for implantation of the implant and
reconstitution of the joint with the new implant.
[0030] It will be understood by the person skilled in the art that
the rig as claimed can be supplemented with for example an insert
sleeve to make one of the right circular cylinders of a small
diameter, e.g. from 17 to 15 mm in diameter, to accommodate an
implant having the form of two intersecting circles of slightly
different diameters, for example 15+17 millimeters.
[0031] It will of course also be possible, within the scope of the
invention to create an implant in the form of three, or more,
intersecting circles, to cover bone damage of more irregular
shape.
[0032] One such three-circle implant 101 is shown from below in
FIG. 3a showing three pegs 148, 149 and 150. In this example peg
148 has an interference fit diameter in relation to the common
nominal diameter of all three pegs and the other two pegs 149 and
150 have clearance fit diameters in relation to the common nominal
diameter.
[0033] The rig for this three-circle implant is shown from above in
FIG. 3b. The rig is held in place on the bone by pins (not shown)
inserted through holes 161. The wall insert 155, completes the
first right circular cylinder 152 covering the remaining portions
of the other two right circular cylinders. When the first circular
drilling has been made the wall insert 155 is pulled out, rotated
120 degrees and is inserted again to provide a drill guide for the
next circle drilling with the same double drill, which in one
embodiment can be the same 17/4 drill used together with the
two-circle rig. After rotation 120 degrees again and drilling, a
three pegged implant is inserted. As stated above, this insert has
one peg which is of interference fit dimension in relation to its
nominal diameter (in this case 4 mm) and the other two pegs are of
clearance fit.
[0034] The implant has a bone contact surface on the underside, on
the sides of the cap and on the pegs, which will be in direct
contact with the bone tissue when the implant is in place. In one
embodiment the bone contact surface comprises a biocompatible
metal, metal alloy or ceramic, such as any of the metals, metal
alloys or ceramic described above for the articulate surface.
Preferably the bone contact surface comprises a cobalt chrome alloy
(CoCr), a titanium alloy, titanium or stainless steel.
[0035] In one specific non-limiting embodiment the bone contact
surface comprises, or in one specific non-limiting embodiment is
coated with, a material that promotes osseointegration. In an
alternative embodiment of the invention the bone contact surface
does not comprise such a material and/or is uncoated.
[0036] The bioactive material or the material that promotes
osseointegration of the bone contact surface, if present,
preferably stimulates bone to grow into or onto the implant
surface. Several materials that have a stimulating effect on bone
growth are known and have been used to promote adherence between
implants and bone. Examples of such prior art materials include
bioactive glass, bioactive ceramics and biomolecules such as
collagens, fibronectin, osteonectin and various growth factors. A
commonly used material in the field of implant technology is
hydroxyapatite (HA), chemical formula
Ca.sub.10(PO.sub.4).sub.6(OH).sub.2. HA is the major mineral
constituent of bone and is able to slowly bond with bone in vivo.
HA coatings have been developed for medical implants to promote
bone attachment. Another bioactive material commonly used in prior
art is bioactive glass. Bioactive glasses, generally comprising
SiO.sub.2, CaSiO.sub.3, P.sub.2O.sub.5, Na.sub.2O and/or CaO and
possibly other metal oxides or fluorides, are able to stimulate
bone growth faster than HA.
[0037] The fixation of the implant can also be improved by
decreasing the catabolic processes i.e. decrease the amount of bone
resorption next to the implant. The bone contact surface and/or the
extending post can also be modified with bisphosphonates.
[0038] In one embodiment the bone contact surface is coated with a
double coating. Such double coating may for instance comprise an
inner coating comprising titanium (Ti). The second, outer coating,
that is configured to contact the cartilage and or bone, is
preferably a hydroxyapatite and/or beta tricalcium phosphate (TCP)
coating. By this design even more long-term fixation of the implant
is achieved, since bone in- or on-growth to the implant is further
stimulated by the titanium, even if the more brittle hyroxyapatite
would eventually shed/dissolve.
[0039] The bone contact surface may also be further modified with
fluoro compounds or acid etching to enhance the bioactivity and the
osseointegration of the surface. Another method to facilitate
osseointegration is blasting of the bone contact surface.
[0040] FIG. 4 shows an exemplary 4/17 double drill for use with the
multiple circle rigs described above (or with a previously known
single circle rig). The double drill has a 4 mm central bit 401 for
creating the hole for the peg and a wider cutting surface 402 for
creating the 17 mm shallow hole. One of the advantages of the
invention is that the same double drill can be used for single,
double or triple (or more) intersecting circle shaped implants,
used twice or three times as the case may be for the two
embodiments shown here.
* * * * *