U.S. patent application number 16/676583 was filed with the patent office on 2020-05-28 for implant for cartilage repair.
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, Leif RYD.
Application Number | 20200163771 16/676583 |
Document ID | / |
Family ID | 42989216 |
Filed Date | 2020-05-28 |
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United States Patent
Application |
20200163771 |
Kind Code |
A1 |
BAKE; Nina ; et al. |
May 28, 2020 |
IMPLANT FOR CARTILAGE REPAIR
Abstract
A medical implant for cartilage repair at an articulating
surface of a joint. The implant includes an implant body and at
least one extending post. The implant body has an articulate
surface configured to face the articulating part of the joint and a
bone contact surface configured to face the bone structure of a
joint. A cartilage contact surface connects the articulate and the
bone contact surfaces and is configured to contact the cartilage
surrounding the implant body in a joint. The cartilage contact
surface has a coating that includes bioactive material.
Inventors: |
BAKE; Nina; (Lidingo,
SE) ; RYD; Leif; (Malmo, SE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
EPISURF IP-MANAGEMENT AB |
Stockholm |
|
SE |
|
|
Assignee: |
EPISURF IP-MANAGEMENT AB
Stockholm
SE
|
Family ID: |
42989216 |
Appl. No.: |
16/676583 |
Filed: |
November 7, 2019 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13699090 |
Jan 17, 2013 |
10470885 |
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PCT/EP2011/058484 |
May 24, 2011 |
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16676583 |
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61347650 |
May 24, 2010 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61F 2002/30156
20130101; A61F 2002/30878 20130101; A61F 2310/00976 20130101; B33Y
80/00 20141201; A61F 2002/30113 20130101; A61F 2002/30125 20130101;
A61F 2230/0008 20130101; A61F 2/28 20130101; A61F 2002/30962
20130101; A61F 2230/0021 20130101; A61F 2230/0023 20130101; A61F
2002/30154 20130101; A61F 2310/00928 20130101; A61F 2230/0006
20130101; A61F 2230/0093 20130101; A61F 2002/30299 20130101; A61F
2/30942 20130101; A61F 2310/00796 20130101; A61F 2002/30929
20130101; A61F 2310/00179 20130101; A61F 2310/00161 20130101; A61F
2310/00407 20130101; A61F 2002/30948 20130101; A61F 2310/00011
20130101; A61F 2/30756 20130101 |
International
Class: |
A61F 2/28 20060101
A61F002/28; A61F 2/30 20060101 A61F002/30 |
Foreign Application Data
Date |
Code |
Application Number |
May 24, 2010 |
EP |
10163721.3 |
Claims
1: A medical implant (1) for cartilage repair at an articulating
surface of a joint, comprising a contoured, substantially plate
shaped, implant body (n) and at least one extending post (8), where
said implant body has: a) an articulate surface (3) configured to
face the articulating part of the joint; b) a bone contact surface
(6) configured to face the bone structure of a joint, where the
bone contact surface (6) is provided with the extending post (8),
said articulate (3) and bone contact (6) surfaces facing mutually
opposite directions; and c) a cartilage contact surface (7),
connecting the articulate (3) and the bone contact (6) surfaces,
which is configured to contact the cartilage surrounding the
implant body (11) in a joint characterized in that the cartilage
contact surface (7) has a coating substantially consisting of a
bioactive material.
2: The medical implant of claim 1, wherein said bioactive material
is any of hydroxyapatite (HA), titanium (Ti),titanium alloys, bone
morphogenetic protein (BMP), beta tricalcium phosphate (TCP), alfa
tricalcium phosphate (TCP), collagens, fibronectin, osteonectin,
calcium sulphate, calcium phosphate, calcium aluminates, calcium
silicates, calcium carbonates or bioactive glass, fluoro compounds
or combinations thereof.
3: The medical implant of claim 1, wherein the bioactive material
is capable of stimulating cartilage growth and regeneration.
4: The medical implant of claim 3, wherein the bioactive material
is any of hydroxyapatite (HA), titanium (Ti), bone morphogenetic
protein (BMP) and/or beta tricalcium phosphate (TCP).
5: The medical implant of claim 1, wherein said bioactive material
is hydroxyapatite (HA).
6: The medical implant according to claim 1, wherein said bone
contact surface (6) is coated or partly coated with bioactive
material.
7: The medical implant according to claim 1, wherein said extending
post is coated or partly coated with bioactive material.
8: The medical implant according to claim 6, wherein said bioactive
material of the bone contact surface (6) and/or extending post (8)
is any of hydroxyapatite (HA), titanium (Ti), bone morphogenetic
protein (BMP), beta tricalcium phosphate (TCP), collagens,
fibronectin, osteonectin, calcium sulphate, calcium phosphate,
calcium aluminates, calcium silicates, calcium carbonates,
bioactive glass or bisphosphonates, or combinations thereof.
9: The medical implant according to claim 1, wherein said extending
post is not coated with bioactive material.
10: The medical implant according to claim 1, wherein said
articulate surface (3) substantially corresponds to the curvature
of the articulating surface at the site of the diseased
cartilage.
11: The medical implant according to claim 1, wherein the coating
of the cartilage contact surface (7) and/or bone contact surface
(6) and/or extending post (8) consists of more than 95%
hydroxyapatite according to XRD.
12: The medical implant according to claim 1, wherein the bone
contact surface or the cartilage contact surface or both has a
double coating, comprising an inner coating of titanium and a
surface coating of hydroxyapatite and/or tricalcium phosphate.
13. (canceled)
14: Use of a medical implant according to claim 1 for the purpose
of stimulating cartilage regeneration.
15: Use according to claim 13 wherein the bioactive material is any
of hydroxyapatite (HA), titanium (Ti), titanium alloys, bone
morphogenetic protein (BMP), beta tricalcium phosphate (TCP), alfa
tricalcium phosphate (TCP), collagens, fibronectin, osteonectin,
calcium sulphate, calcium phosphate, calcium aluminates, calcium
silicates, calcium carbonates or bioactive glass, fluoro compounds
or combinations thereof.
16: Use according to claim 15 wherein the bioactive material is
hydroxyapatite (HA) or titanium (Ti).
17: A method of designing an implant (1) for cartilage repair in an
articulating surface of a joint, comprising the steps of: I.
determining physical parameters for cartilage damage in a joint and
generating design parameters for an implant (1) and its placement
comprising: a) obtaining image data representing a three
dimensional image of a bone member of the joint; b) identifying in
the obtained image data and individual cartilage damage in an
articulate surface of the bone member; c) determining based on the
obtained image data the location of the individual cartilage
damage; i) determining based on the obtained image data the size
and shape of the individual cartilage damage; j) determining a
cartilage damage site based on the determined size and shape of the
cartilage damage; k) determining based on the obtained image data
the surface contour curvature of the individual cartilage damage
site (92) and/or the subchondral bone in the joint in the
predetermined area comprising the individual cartilage damage site;
l) determining a representation of a healthy surface contour
curvature comprising the individual cartilage damage site m)
selecting an implant (1) to fit the individual cartilage damage
site wherein the implant (1) has; a cross sectional area adapted to
fit the surface area of the cartilage damage site an articulate
surface (3) intended to align with the articular cartilage surface
in the joint, based on the healthy surface contour curvature a
cartilage contact surface (7), connecting the articulate (3) and a
bone contact (6) surface, which is configured to contact the
cartilage surrounding the implant body (11) the individual joint
and wherein the cartilage contact surface (7) is designed to have a
coating substantially consisting of a bioactive material. II.
generating design parameters of the implant (1), comprising the
following steps; c. generating the contact points for a cartilage
contact surface (7) of an implant body (11) dependent on said
determined surface contour curvature of the cartilage and/or the
subchondral bone in the joint in a predetermined area comprising
and surrounding the site of cartilage damage, such that said
cartilage contact surface (7) of the implant body (11) fits to said
surface contour of the cartilage or the subchondral bone in the
joint. d. generating the design parameters for where bioactive
material is to be placed on the implant body (11) depending on the
design of the cartilage contact surfaces.
18: A method of designing an implant (1) for cartilage repair in an
articulating surface of a joint according to claim 17 wherein the
bioactive material is any of hydroxyapatite (HA), titanium (Ti),
bone morphogenetic protein (BMP), beta tricalcium phosphate (TCP),
collagens, fibronectin, osteonectin, calcium sulphate, calcium
phosphate, calcium aluminates, calcium silicates, calcium
carbonates, bioactive glass or bisphosphonates, or combinations
thereof.
19: A method of designing an implant (1) for cartilage repair in an
articulating surface of a joint according to claim 1 wherein the
techniques for obtaining images, of either the cartilage or the
underlying bone or both may are selected from X-rays, optical
coherence tomography, SPECT, PET, MR and ultrasound imaging
techniques and computed tomography.
20-21. (canceled)
Description
FIELD OF THE INVENTION
[0001] This invention relates in general to the field of orthopedic
implants. More particularly the present invention relates to a
medical implant for cartilage repair at an articulating surface in
a joint such as a knee, hip, toe and shoulder.
BACKGROUND
General Background
[0002] Traumatic and overuse disorders of the joints of the body is
a common problem. The weight-bearing and articulating surfaces of
for example knees and other joints, are covered with a layer of
soft tissue that typically comprises a significant amount of
hyaline cartilage. The cartilage is prone to damage due to disease,
injury or chronic wear and causes much suffering in terms of pain
or disability to move freely. It is therefore important to have
efficient means and methods for repairing damaged cartilage in
joints in for example knees. Large knee prostheses on the market
are successful in relieving pain but there is a limit in the
lifetime of the prostheses of 10-15 years.
[0003] These large prostheses have lead to the 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 as thin plates, or a head, with a hard surface for
facing the articulate side of the joint and a bone contacting
surface for facing the bone below the damaged part of cartilage.
Generally, the shape and the curvature of the articulate surface of
the implant are designed to be similar to the shape and the
curvature of the part of the joint where the implant is inserted.
Such implants are often designed with a contoured surface head and
may also have one or several extending posts in the shape of a peg
or a rod projecting from the bone contacting side underneath the
surface head for fastening the implant to the bone in a first
fixation in connection with the implant surgery.
Specific Background
[0004] In the surgical operation of implanting such small implants
it is critical that the implant is positioned in a precise manner,
this first fixation is called the primary fixation and it provides
a mechanical attachment of the implant directly after implantation.
Primary mechanical fixation can be further reinforced with a
secondary fixation of the implant to the bone tissue as the implant
integrates with the underlying bone. A firm secondary fixation is
promoted by coating the implant with an osteoinductive, bioactive
material, for example hydroxyapatite, also called hydroxylapatite
or HA, on the parts of the implant contacting the bone. The bone
then grows into and/or onto the implant and is in this way fixated
additionally to the bone.
[0005] Although this kind of small implant has widened the
repertoire for the orthopedic surgeons when it comes to repairing
smaller cartilage damages in the joints, there are unwanted
scenarios in the surgery of these small implants. When an implant
is inserted to replace damaged cartilage in a joint, a small space
may arise between a peripheral edge of the implant and the
adjoining cartilage. It has been observed that joint fluid may
enter the small space between the implant and the cartilage, and
flow into gaps between the bone and the implant. This may lead to a
stopped or delayed integration between the bone and the implant. It
may even lead to the undermining of the implant and to the
detachment of the implant. Another problem that may arise is that
the cartilage in the immediate vicinity of the implant may slide in
relation to the implant, such that it is twisted, slides over the
edge onto the top of the implant or is pressed down such that the
edge and surface of the implant projects above the surface of the
cartilage. This in turn may lead to irregular cartilage formation
and wear damages to both the cartilage in the vicinity of the
implant and to the cartilage on the opposing joint surface.
Prior Art
[0006] Examples of prior art which discloses implants where
bioactive material is used on the bone contacting side of the
implant to promote bone to grow onto the implant is found in the
following patent publications.
[0007] EP2116210 A1 from Diamorph describes an implant component
and a method for producing an implant using functionally graded
sintered material composed of at least 4 layers. A top layer
comprises 100 wt % biocompatible wear resistant material whereas
the bone contacting side of the implant comprises bioactive
material, preferably hydroxyapatite (see FIG. 2 and the abstract).
The functionally graded material between the top layer and the bone
contacting side comprises gradually increasing amounts of bioactive
material towards the bone contacting surface.
[0008] WO2009135889 A1 from Diamorph describes an implant device
for an articulating surface in a joint such as a knee, elbow or
shoulder. In this piece of prior art there is shown an implant that
has a primary fixation means in the shape of an extending post that
comprises bioactive ceramic material. Other surfaces comprising
bioactive material are facing the bone underlying the cartilage
(page 4 line 10-11).
[0009] WO2007/014164 A2 describes a method for implanting a
prosthetic articular surface in a joint (e.g. a knee).
Hydroxyapatite material (HA) is described as an alternative of a
biocompatible and osteoinductive [046] material on the surface of
the bone contacting portion of the implant [042], [045].
[0010] US2004/0002766 A1 relates to metallic orthopedic implants
having surfaces of a thin, dense, highly wear-resistant coating of
diffusion-hardened oxidation or nitridation layer in addition to
surfaces coated with one or more bioceramic or bone growth
promoting materials such as one or more apatite compounds. The
apatite coating is applied on bone contacting areas. The
publication shows that the bioceramics may be applied to different
sites on the implant, and it is preferred that the bioceramics are
applied to areas of maximum contact with bone, as it is intended to
promote maximum bone in-growth and on-growth [0090]. EP 1277450 A2
shows a prosthetic implant for the repair and regeneration of
tissue.
OBJECT OF THE INVENTION
General Object
[0011] The general object of the invention is to solve the problem
of providing an implant for cartilage repair at an articulate
surface of a joint that enables the implant to integrate well with
healthy cartilage as well as with underlying bone. A more specific
object and a partial problem to be solved is to provide an implant
that reduces or blocks joint fluid from entering into the interface
between the implant and the underlying bone.
SUMMARY OF THE INVENTION
[0012] The invention is based on the findings that some bioactive
substances, e.g. hydroxyapatite (HA), bone morphogenetic protein
(BMP), beta tricalcium phosphate (TCP) or alfa tricalcium phosphate
(TCP) has the ability to stimulate cartilage growth and
regeneration, in addition to the previously well known ability to
stimulate growth in bone tissue. In order to solve the above stated
problems the inventors have designed an implant with a cartilage
contacting rim coated with a bioactive material, e.g. HA, TCP
and/or BMP, and thereby achieved an implant with a potential for
better fixation in the joint and a longer life time.
[0013] In a first aspect, the inventive concept comprises a medical
implant (1) for cartilage repair at an articulating surface of a
joint, comprising a contoured, substantially plate shaped implant
body (11) and at least one extending post (8). The implant body has
an articulate surface (3) configured to face the articulating part
of the joint and a bone contact surface (6) configured to face the
bone structure of a joint, where the bone contact surface (6) is
provided with the extending post (8) and said articulate (3) and
bone contact (6) surfaces face mutually opposite directions. A
cartilage contact surface (7) connects the articulate (3) and the
bone contact (6) surfaces and is configured to contact the
cartilage surrounding the implant body (11) in a joint. The
cartilage contact surface (7) has a coating substantially
consisting of a bioactive material.
[0014] In an embodiment of the invention the bioactive material is
any of hydroxyapatite (HA), titanium (Ti), titanium alloys, bone
morphogenetic protein (BMP), beta tricalcium phosphate (TCP),
collagens, fibronectin, osteonectin, calcium sulphate, calcium
phosphate, calcium aluminates, calcium silicates, calcium
carbonates or bioactive glass, or combinations thereof. In an
aspect of the invention the bioactive material is capable of
stimulating cartilage growth and regeneration. Preferably the
bioactive material is any of hydroxyapatite (HA), titanium (Ti),
bone morphogenetic protein (BMP) and/or beta tricalcium phosphate
(TCP), most preferably the bioactive material is hydroxyapatite
(HA).
[0015] Further varieties of the inventive concept comprise such an
implant comprising any of the following optional individual or
combinable aspects:
[0016] The bone contact surface (6) is coated or partly coated with
bioactive material.
[0017] The extending post is coated or partly coated with bioactive
material.
[0018] The bioactive material of the bone contact surface (6) and
or extending post (8) is any of hydroxyapatite (HA), titanium (Ti),
bone morphogenetic protein (BMP), beta tricalcium phosphate (TCP),
collagens, fibronectin, osteonectin, calcium sulphate, calcium
phosphate, calcium aluminates, calcium silicates, calcium
carbonates, bioactive glass or bisphosphonates, or combinations
thereof.
[0019] The extending post is not coated with bioactive
material.
[0020] The articulate surface (3) substantially corresponds to the
curvature of the articulating surface at the site of the diseased
cartilage.
[0021] The coating of the cartilage contact surface (7) and/or bone
contact surface (6) and/or extending post (8) consists of more than
95% hydroxyapatite according to XRD.
[0022] The bone contact surface or the cartilage contact surface or
both has a double coating, comprising an inner coating of titanium
and a surface coating of hydroxyapatite and/or tricalcium
phosphate.
BRIEF DESCRIPTION OF THE FIGURES
[0023] The present invention will be further explained below with
reference to the accompanying drawings, in which:
[0024] FIG. 1a shows a sectional view of an exemplifying embodiment
of the implant of the present invention with the cartilage contact
surface coated with hydroxyapatite.
[0025] FIG. 1b shows a sectional view of an exemplifying embodiment
of the implant of the present invention with both the bone contact
and the cartilage contact surfaces coated with hydroxyapatite.
[0026] FIG. 1c is shows a sectional view of an exemplifying
embodiment of the implant of the present invention with the bone
contact and the cartilage contact surface and also the extending
post coated with hydroxyapatite.
[0027] FIG. 1d shows a perspective view of an implant according to
FIG. 1a and shows an embodiment of the present invention having a
hydroxyapatite coating on the cartilage contact surface.
[0028] FIG. 2 shows a schematic view of the coated implant
according to the invention inserted in the bone and cartilage
surface of a joint.
[0029] FIG. 3 shows a photo of the coated implant according to the
invention inserted in the bone and cartilage surface of a
joint.
[0030] FIG. 4 shows a close up view in a photo of the coated
implant according to the invention inserted in the bone and
cartilage surface of a joint.
[0031] FIG. 5 shows a photo of the coated implant according to the
invention inserted in the bone and cartilage surface of a
joint.
[0032] FIG. 6 shows a photo of the coated implant according to the
invention inserted in the bone and cartilage surface of a
joint.
DETAILED DESCRIPTION OF THE INVENTION
Introduction
[0033] The present invention relates to a new medical implant for
replacing or repairing damaged, diseased or injured cartilage in an
articulating surface of a joint. The implant has a cartilage
contact surface, intended to contact the cartilage in a joint,
which is coated with a bioactive material capable of stimulating
cartilage growth and regeneration. The implant alleviates problems
discussed in the background, by promoting cartilage on-growth to
the implant. By this feature the implant becomes more integrated
with the cartilage surface, yielding a more stabilized interaction
and firmer attachment between the implant and the cartilage.
Thereby cartilage damage in the vicinity of the implant is
decreased. Also the entering of joint fluid between the implant,
cartilage and bone is reduced or prevented. In addition, a smoother
transition between the cartilage and the implant may be obtained,
leading to lesser wear on the opposing surface of the joint as the
cartilage and the implant works as an integrated mechanical
entity.
The Implant Structure
Implant Structure in General
[0034] FIG. 1a shows an exemplifying embodiment of an implant 1
according to the present invention. The implant 1 comprises a
contoured, substantially plate shaped implant body 11 and an
extending post 8 extending from the implant body 11. The implant
body 11 has an articulate surface 3, configured to face the
articulating part of the joint, and a bone contact surface 6,
configured to face the bone structure of the joint. Between these
surfaces of the plate shaped body 11 of the implant 1 there is a
cartilage contact surface 7, on the rim or border that connects the
articulate and the bone contact surfaces. The cartilage contact
surface 7 is configured to face or contact the cartilage, and
optionally also the bone, surrounding the implant when the implant
is inserted in a joint such as a knee, toe, hip, elbow or shoulder.
The cartilage contact surface is coated with a bioactive material,
such as a hydroxyapatite coating.
[0035] The implant is placed in the joint after removal of the
damaged cartilage and optionally, but preferably, formation of a
recess in the bone under the cartilage damage, e.g. by reaming. The
implant is secured in the bone first by primary attachment, by
means of the extending post 8 which fits in a drill hole in the
bone. The implant is also secured by a long-term secondary fixation
mechanism where cartilage and/or bone tissue is grown into and/or
onto the parts of the implant coated with bioactive material.
Details of the Implant Structure
Implant Body
[0036] The implant 1 comprises a contoured, substantially plate
shaped implant body 11. The implant body 11 has a thin, plate-like
design, meaning that its cross-sectional distance 9 is larger or
even substantially larger than its thickness 4, e.g. at least 1.5
times larger. The plate can vary in size and shape and may be
adjusted to the size and shape of the damaged cartilage tissue and
to the needs of particular treatment situations. For instance the
cross-section of the implant body 11 may have a circular or roughly
circular, oval, triangular, square or irregular shape, preferably a
shape without sharp edges. The size of the implant 1 may also vary.
The surface area of the implant body 11 varies in different
realizations of the invention between 0.5 cm.sup.2 and 20 cm.sup.2,
between 0.5 cm.sup.2 and 15 cm.sup.2, between 0.5 cm.sup.2 and 10
cm.sup.2 or between about 1-10 cm.sup.2, preferably between 0.5
cm.sup.2 and 5 cm.sup.2. In general, small implants are preferred
since they have a smaller impact on the joint at the site of
incision and are also more easily implanted which leads to smaller
open surgical procedures. The primary factor for determining the
size of the implant is however the nature of the lesion in the
cartilage to be repaired. The thickness 4 of the implant body 11 is
between 1 mm and about 10 mm, preferably between about 2 mm and 5
mm. The thickness of the implant body 11 should on the whole
preferably match the thickness of the original cartilage layer,
possibly also adapted to adjust for the recess in the bone, used
for anchorage of the implant or formed as a part of the disease
process. The articulate surface and the cartilage surrounding the
implant have, because of the prepared precise fit of the implant in
the implant site, corresponding heights.
Articulate Surface
[0037] The implant body 11 has an articulate surface 3 configured
to face the articulating part of the joint. The articulate surface
3 comprises a biocompatible metal, metal alloy or ceramic. More
specifically it can consist of 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 3
comprises a cobalt chrome alloy (CoCr), pyrolytic carbon stainless
steel, or a ceramic material.
[0038] It should also be understood that the articulate surface 3
may also be further surface treated in order to e.g. achieve an
even more durable surface or a surface with a lower friction
coefficient. Such treatments may include, for example, polishing,
micro machining, heat treatment, precipitation hardening or
depositing a suitable surface coating.
Bone Contact Surface
[0039] The implant body 11 has a bone contact surface 6, configured
to face or contact the bone structure of the joint. In one
embodiment the bone contact surface 6 comprises a biocompatible
metal, metal alloy or ceramic, such as any of the metals, metal
alloys or ceramic described above for the articulate surface 3.
Preferably the bone contact surface 6 comprises a cobalt chrome
alloy (CoCr) or stainless steel.
[0040] In one embodiment the bone contact surface 6 comprises, or
in one specific embodiment is coated with, a bioactive material. In
an alternative embodiment of the invention the bone contact surface
does not comprise a bioactive material and/or is uncoated.
[0041] The bioactive material of the bone contact surface, if
present, preferably stimulates bone to grow into and/or onto the
implant surface. Several bioactive 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 bioactive materials include bioactive glass, bioactive ceramics
and biomolecules such as collagens, fibronectin, osteonectin and
various growth factors, e.g. bone morphogenetic protein (BMP). A
commonly used bioactive material in the field of implant technology
is the bioactive ceramic 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.
Thus, HA coatings have been developed for medical implants to
promote bone attachment. Other bioactive ceramics include calcium
sulphate, calcium phosphate, calcium aluminates, calcium silicates,
calcium carbonates or combinations thereof, or 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.
[0042] The bioactive materials described above have an anabolic
effect on the bone i.e. stimulates bone growth. 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 21 and/or the extending post can also be
modified with bisphosphonates. Bisphosphonates are substances that
inhibit the catabolic process of bone. One way to bind the
bisphosphonate to the surface is by coating it with HA, which it
readily binds to. The implant can also simply be immersed in a
bisphosphonate solution or linked with some other biocompatible
molecule e.g. carbodiimides, N-hydroxysuccinimide (NHS)-esters,
fibrinogen, collagen etc.
[0043] The bone contact surface may also be further modified with
fluoro compounds to enhance the bioactivity of the surface.
[0044] In one embodiment the bone contact surface 6 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 bone, is preferably a HA coating
containing more than 95% HA or 95-99.5% HA, or a coating comprising
tricalcium phosphate (TCP) in combination with HA. 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 and/or soluble HA and/or TCP
would eventually shed or dissolve.
Cartilage Contact Surface
[0045] Between the articulate surface 3 and the bone contact
surface 6 of the plate shaped body 11 there is a cartilage contact
surface 7 on the rim or border which connects the articulate and
the bone contact surfaces. The cartilage contact surface 7 is
configured to face or contact the cartilage surrounding the implant
and optionally also the bone underlying the cartilage layer when
the implant is inserted in a joint for example in the knee. The
cartilage contact surface 7 is coated with a bioactive material,
such as any of bioactive materials described above for the bone
contact surface 6. Preferably the bioactive material is capable of
stimulating cartilage growth, regeneration and attachment. The
bioactive surface promotes adhesion of the implant to the
surrounding cartilage surface. Such bioactive materials include
hydroxyapatite (HA), titanium (Ti), bone morphogenetic protein
(BMP) or beta tricalcium phosphate (TCP), separately or in
combination. In a preferred embodiment the bioactive material of
the cartilage contact surface 3 is hydroxyapatite (HA) and/or beta
tricalcium phosphate (TCP).
[0046] In one embodiment the cartilage contact surface 7 is coated
with a double coating, such as described for the bone contact
surface 6 above. Such double coating may for instance comprise an
inner coating comprising titanium (Ti). The second, outer coating,
that is configured to contact the bone, is preferably a HA coating
containing more than 95% HA or 95-99.5% HA, or a coating comprising
tricalcium phosphate (TCP), or a combination of HA and TCP.
[0047] Using a bioactive material such as hydroxyapatite as a
coating on the cartilage contact surface 7 of the implant has the
effect that the implant, after insertion at the implant site with
primary fixation, is fixated by a secondary fixation mechanism
where the cartilage grows together with the bioactive coating of
the implant, creating a smooth sealed surface without any holes or
where joint fluid can pass. This would lead to an implant that
stays in the right place and that is not prone to be undermined by
joint fluids. Also, the smooth surface, where the implant and the
surrounding cartilage may act as an integrated mechanical entity,
reduces or prevents wear damage on the surface of the opposing side
of the joint.
[0048] The height 4 of the cartilage contact surface 7 corresponds
to at least 75% of the thickness of the cartilage at the site of
implant insertion in the joint. More preferably the height 4 of the
cartilage contact surface 7 corresponds to the height of the
cartilage surrounding the implant site plus the height of an area
reamed out from the underlying bone in order to fit and fix the
implant. The height 4 of the cartilage contact surface 7 may vary
between said extremes. Typically the height 4 of the cartilage
contact surface 7 is between 0.5 and 8 mm, preferably between 1 and
5 mm.
[0049] The bioactive coating on the cartilage contact surface 7 is
preferably provided all the way around the cartilage contact
surface 7 on the rim of the plate shaped implant body 11. The
coating is intended to be in direct contact with the surrounding
cartilage and bone of a joint once the implant is implanted in the
cartilage of a joint, for example a knee. The coating covers
60-100%, more preferably 80-100% and most preferably 90-100% of the
cartilage contacting surface 7. In another embodiment the surface
is coated such that the height 4 all around the rim of the implant
body 11 is 80-100%, preferably 90-100% covered, counting from the
bone contact surface 6 and upwards. In still another embodiment the
coating covers most of the cartilage contact surface 7, except for
an uncoated section 0.5-1 mm at the top of the height 4, adjacent
to the articulate surface 3. By keeping the section closest to the
articulate surface uncoated shedding of the bioactive material onto
the cartilage surface surrounding the implant is prevented/reduced,
thereby reducing the risk of wear from the shed material onto the
joint surfaces.
[0050] The coating technique used is thermal spraying; in
particular, air plasma spraying is the method which is used for
producing these hydroxyapatite coatings on the implant. Another
alternative is Vacuum Plasma Spray coating (VPS). In a
hydroxyapatite embodiment the coating contains more than 95%
hydroxyapatite by XRD after heating of alternatively the coating or
the hydroxyapatite coating contains 95-99.5% hydroxyapatite.
Extending Post
[0051] The implant body 11 may have one or several extending posts
8 which extend from the bone contact surface 6. In order to promote
an immediate attachment of the implant to the bone as it is
implanted into the body, the extending post 8 is used for
immediate, mechanical attachment, called primary fixation. The
extending post 8 has a physical structure in the form of for
example a cylinder or other shapes such as one or more of a small
screw, peg, keel, barb or the like. The implant body 11 and the
extending post(s) 8 may be manufactured as a single, integral piece
or as separate pieces that are joined by some kind of attachment
means, e.g. glue or by a threaded joint.
[0052] The primary fixation means 4 may comprise e.g. the metal,
metal alloy or ceramic, as in the articulate surface 3.
[0053] The extending post 8 can in one aspect of the invention be
coated with a bioactive material such as described for the bone
contact surface 6 above. In another aspect of the invention the
extending post is uncoated.
[0054] In one embodiment the extending post 8 comprises uncoated
titanium (Ti) and the cartilage contact surface 7 are coated with
hydroxyapatite (HA) or a double coating with an inner coating
comprising titanium (Ti) and an outer coating comprising HA,
tricalcium phosphate (TCP), or a combination of HA and TCP.
[0055] An implant which does not have a coating on the extending
post 8, and thus lacks a secondary fixation of the extending post,
is suitable for repairing a cartilage damage in for example a hip
joint where a lot of pressure is applied on the placed implant and
where there is a need for an implant which reduces the risk for
tensions when the mechanical pressure is high. By avoiding coating
of the extending post, the extending post is thus not attached to
the bone; the mechanical forces are in this way not directed into
the bone part through the extending post (which may lead to
tensions in the bone structure). The mechanical forces are directed
to the bone through the implant head only which reduces the risk
for tensions in the bone on the implant site.
Manufacturing of the Implant
[0056] An implant according to the present invention may be
manufactured in predetermined, standard shapes and sizes or be
tailor made for specific patients. A variety of manufacturing
processes are conceivable, including, casting, molding, sintering
or turning/cutting a blank e.g. with laser etc.
[0057] In one embodiment the implant according to the present
invention the articulate surface 3 may be formed in a way so that
it substantially corresponds to the curvature of the articulating
surface at the site of the diseased cartilage and such that it is
adapted to a particular individual and its cartilage damage.
Techniques for obtaining such 3D images, of either the cartilage or
the underlying bone or both may also include X-rays, optical
coherence tomography, SPECT, PET, MR and ultrasound imaging
techniques. The 3D images are used for measuring the reconstruction
of the bone and the thickness and/or curvature of the cartilage and
for determining the position, size and contour of damaged cartilage
or cartilage loss.
[0058] A technique for making these tailor made implants is
selective laser sintering (SLS). SLS is an additive manufacturing
technique that uses a high power laser (for example, a carbon
dioxide laser) to fuse small particles of plastic, metal (Direct
metal laser sintering), ceramic, or glass powders into a mass
representing a desired 3-dimensional object. The laser selectively
fuses powdered material by scanning cross-sections generated from a
3-D digital description of the part (for example from a CAD file or
scan data) on the surface of a powder bed. After each cross-section
is scanned, the powder bed is lowered by one layer thickness, a new
layer of material is applied on top, and the process is repeated
until the part is completed. Or, the 3D surfaces are formed with a
high precision lathe, a machine in which work is rotated about a
horizontal axis and shaped by a fixed tool. The 3D surfaces can
also be reamed using the digital data.
[0059] Manufacturing of an implant according to the invention may
be performed using the design method according to the invention
(see below) in combination with using a technique for making the
implant is selected from selective laser sintering (SLS) (see
above).
Design Method of the Implant
[0060] A method of designing an implant (1) for cartilage repair in
an articulating surface of a joint, comprising the steps of: [0061]
I. determining physical parameters for cartilage damage in a joint
and generating design parameters for an implant (1) and its
placement comprising: [0062] a) obtaining image data representing a
three dimensional image of a bone member of the joint; [0063] b)
identifying in the obtained image data and individual cartilage
damage in an articulate surface of the bone member; [0064] c)
determining based on the obtained image data the location of the
individual cartilage damage; [0065] d) determining based on the
obtained image data the size and shape of the individual cartilage
damage; [0066] e) determining a cartilage damage site based on the
determined size and shape of the cartilage damage; [0067] f)
determining based on the obtained image data the surface contour
curvature of the individual cartilage damage site (92) and/or the
subchondral bone in the joint in the predetermined area comprising
the individual cartilage damage site; [0068] g) determining a
representation of a healthy surface contour curvature comprising
the individual cartilage damage site [0069] h) selecting an implant
(1) to fit the individual cartilage damage site wherein the implant
(1) has; [0070] a cross sectional area adapted to fit the surface
area of the cartilage damage site [0071] an articulate surface (3)
intended to align with the articular cartilage surface in the
joint, based on the healthy surface contour curvature [0072] a
cartilage contact surface (7), connecting the articulate (3) and a
bone contact (6) surface, which is configured to contact the
cartilage surrounding the implant body (11) the individual joint
and wherein the cartilage contact surface (7) is designed to have a
coating substantially consisting of a bioactive material. [0073]
II. generating design parameters of the implant (1), comprising the
following steps; [0074] a. generating the contact points for a
cartilage contact surface (7) of an implant body (11) dependent on
said determined surface contour curvature of the cartilage and/or
the subchondral bone in the joint in a predetermined area
comprising and surrounding the site of cartilage damage, such that
said cartilage contact surface (7) of the implant body (11) fits to
said surface contour of the cartilage or the subchondral bone in
the joint. [0075] b. generating the design parameters for where
bioactive material is to be placed on the implant body (11)
depending on the design of the cartilage contact surfaces.
[0076] In another embodiment regarding the method of designing an
implant (1) for cartilage repair in an articulating surface of a
joint the bioactive material is any of hydroxyapatite (HA),
titanium (Ti), bone morphogenetic protein (BMP), beta tricalcium
phosphate (TCP), collagens, fibronectin, osteonectin, calcium
sulphate, calcium phosphate, calcium aluminates, calcium silicates,
calcium carbonates, bioactive glass or bisphosphonates, or
combinations thereof.
[0077] The techniques for obtaining images according to the method
of the invention, of either the cartilage or the underlying bone or
both may be selected from X-rays, optical coherence tomography,
SPECT, PET, MR, ultrasound imaging techniques and CT (computed
tomography).
PRACTICAL EXAMPLE OF THE INVENTION
Example 1
[0078] Implants 1 according to the invention were tested on adult
sheep, approximately 1.5 years old; [0079] Defects in the medial
femoral condyles in the knee of the sheep were created. [0080]
Implants were inserted to replace the created defect areas in the
medial femoral condyles. [0081] Implants were retrieved and checked
by taking histological preparations from the implant site after 6
weeks and after 3 months from insertion. An exact series of
equipment, able to cut through metal as well as bone, was used. En
bloc samples were retrieved, showing a cross-section of the
implantation site (see FIGS. 2 and 3). Light microscopy revealed
good integration of the implants to the bone. It was also observed
that the surrounding cartilage 71 had reacted with close adherence
to the HA containing surface of the implant. This suggests that HA
attracts also cartilage and promotes a biological activity.
Example 2
[0082] Implants 1 according to the invention were tested on adult
sheep, approximately 1.5-3 years old; [0083] Defects in the medial
femoral condyles in the knee of the sheep were created. [0084]
Implants were inserted to replace the created defect areas in the
medial femoral condyles.
[0085] The sheep was killed six weeks after insertion of the
implant and then the implants were retrieved and checked by taking
histological preparations from the implant. FIG. 4 shows a close up
view in a photo of the coated implant according to the invention
inserted in the bone 42 and cartilage surface of a joint in a
sheep. FIG. 4 shows the implant body 11 in black and shows the
close contact of the implant head with the surrounding cartilage
40. Cartilage 40 surrounding the implant body 11 is adhered to the
implant body 11.
Example 3
[0086] Implants 1 according to the invention were tested on adult
sheep, approximately 1.5-3 [0087] Defects in the medial femoral
condyles in the knee of the sheep were created. [0088] Implants
were inserted to replace the created defect areas in the medial
femoral condyles.
[0089] FIG. 5 shows an implant 1 in a sheep which was killed 6
months after insertion of the implant in the bone and cartilage in
the joint of a sheep. The arrow 50 is pointing at the border above
where HA is no longer present on the implant body 11. From FIG. 6,
which is an enhancement of the implant body area in FIG. 3, it can
be seen that the HA coated part (below the arrow 50 boarder) of the
implant body 11 is in close contact with bone 42 and cartilage
40.
* * * * *