U.S. patent application number 11/468601 was filed with the patent office on 2006-12-28 for intervertebral prosthesis.
This patent application is currently assigned to SPINALMOTION, INC.. Invention is credited to Malan deVilliers, Ulrich R. Hahnle.
Application Number | 20060293754 11/468601 |
Document ID | / |
Family ID | 32031274 |
Filed Date | 2006-12-28 |
United States Patent
Application |
20060293754 |
Kind Code |
A1 |
deVilliers; Malan ; et
al. |
December 28, 2006 |
Intervertebral Prosthesis
Abstract
An intervertebral prosthesis for insertion between adjacent
vertebrae includes a first prosthesis plate and a second prosthesis
plate. The first and second prosthesis plates each comprise a
midline, an engagement surface to engage a first vertebra and a
bearing surface disposed opposite the engagement surface. The
bearing surfaces of the first and second plates are arranged to
cooperate to form an articulate joint. A first region of serrations
is disposed on the engagement surface of the first plate on one
side of the midline of the first plate, and a second region of
serrations is disposed on the engagement surface of the first plate
on an opposite side of the first plate midline. Each region
comprises at least several serrations, and each serration comprises
a base attached to one of the plates and tapers from the base to a
tip.
Inventors: |
deVilliers; Malan; (Irene,
Gauteng, ZA) ; Hahnle; Ulrich R.; (Mountain View,
CA) |
Correspondence
Address: |
TOWNSEND AND TOWNSEND AND CREW, LLP
TWO EMBARCADERO CENTER
EIGHTH FLOOR
SAN FRANCISCO
CA
94111-3834
US
|
Assignee: |
SPINALMOTION, INC.
201 San Antonio Circle, Ste 115
Mountain View
CA
|
Family ID: |
32031274 |
Appl. No.: |
11/468601 |
Filed: |
August 30, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11084224 |
Mar 18, 2005 |
|
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11468601 |
Aug 30, 2006 |
|
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PCT/IB03/01529 |
Apr 24, 2003 |
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11084224 |
Mar 18, 2005 |
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Current U.S.
Class: |
623/17.14 |
Current CPC
Class: |
A61F 2002/30364
20130101; A61F 2220/0033 20130101; A61F 2310/00029 20130101; A61F
2002/30899 20130101; A61F 2002/30841 20130101; A61F 2310/00017
20130101; A61F 2220/0025 20130101; A61F 2002/30369 20130101; A61F
2230/0065 20130101; A61F 2002/30904 20130101; A61F 2220/0016
20130101; A61F 2310/00179 20130101; A61F 2002/30662 20130101; A61F
2250/0098 20130101; A61F 2310/0088 20130101; A61F 2002/302
20130101; A61F 2002/3008 20130101; A61F 2002/443 20130101; A61F
2/4425 20130101; A61F 2/4611 20130101; A61F 2002/30785 20130101;
A61F 2002/30884 20130101; A61F 2002/30822 20130101; A61F 2002/30528
20130101; A61F 2/30771 20130101; A61F 2002/30332 20130101 |
Class at
Publication: |
623/017.14 |
International
Class: |
A61F 2/44 20060101
A61F002/44 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 19, 2002 |
ZA |
ZA 2002/7517 |
Claims
1. An intervertebral prosthesis for insertion between adjacent
vertebrae, the prosthesis comprising: a first prosthesis plate
comprising a midline, an engagement surface to engage a first
vertebra and a bearing surface disposed opposite the engagement
surface; a second prosthesis plate comprising a midline, an
engagement surface to engage a second vertebra and a bearing
surface disposed opposite the engagement surface, wherein the
bearing surfaces of the first and second plates are arranged to
cooperate to form an articulate joint; a first region of serrations
disposed on the engagement surface of the first plate on one side
of the midline of the first plate; and a second region of
serrations disposed on the engagement surface of the first plate on
an opposite side of the first plate midline; and wherein each
region comprises at least several serrations and each serration
comprises a base attached to one of the plates and tapers from the
base to a tip.
2. The prosthesis according to claim 1 wherein the serrations of
the first region are parallel to the serrations of the second
region.
3. The prosthesis according to claim 1 wherein the serrations of
the first and second regions are parallel to the midline.
4. The prosthesis according to claim 1 wherein the serrations of
the first and second regions are symmetrically disposed about the
midline.
5. The prosthesis according to claim 1 further comprising a core
located between the plates, the core comprising a first surface
adapted to engage the bearing surface of the first plate and a
second surface adapted to engage the bearing surface of the second
plate, wherein the first surface of the core and the bearing
surface of the first plate comprise cooperating spherical
surfaces.
6. The prosthesis according to claim, 5 wherein second surface of
the core and the bearing surface of the second plate comprise
cooperating spherical surfaces.
7. A prosthesis according to claim 1 further comprising a fin to
anchor the first plate in the first vertebra, the fin disposed
along the midline between the rows of serrations disposed on the
first plate, the fin adapted to enter a cut in the first
vertebra.
8. The prosthesis according to claim 7, wherein holes are formed
transversely through the fin.
9. The prosthesis according to claim 1, wherein the bearing surface
of each plate is bounded by an annular rim, wherein the annular
rims are arranged to contact one another at a predetermined limit
of articulate movement of the plates.
10. The prosthesis according to claim 1, wherein the bearing
surface of each plate is bounded by an annular rim having a groove
formed thereon, wherein the grooves are adapted to connect to a
placement instrument while the prosthesis is inserted into the
intervertebral space.
11. An intervertebral prosthesis for insertion between adjacent
vertebrae, the prosthesis comprising: a first prosthesis plate
comprising a midline, an engagement surface to engage a first
vertebra and a bearing surface disposed opposite the engagement
surface; a second prosthesis plate comprising a midline, an
engagement surface to engage a second vertebra and a bearing
surface disposed opposite the engagement surface, wherein the
bearing surfaces of the first and second plates are arranged to
cooperate to form an articulate joint; a first region of serrations
disposed on the engagement surface of the first plate on one side
of the midline of the first plate; a second region of serrations
disposed on the engagement surface of the first plate on an
opposite side of the first plate midline; a third region of
serrations disposed on the engagement surface of the second plate
on one side of the midline of the second plate; a fourth region of
serrations disposed on the engagement surface of the second plate
on an opposite side of the second plate midline; and wherein each
region comprises at least several serrations and each serration
comprises a base attached one of the plates and tapers from the
base to a tip.
12. The prosthesis according to claim 11 wherein the serrations of
the third and fourth regions are identical the serrations of the
first and second regions, respectively.
13. The prosthesis according to claim 11 wherein the serrations of
the first region are parallel to the serrations of the second
region and the serrations of the third region are parallel to the
serrations of the fourth region.
14. The prosthesis according to claim 11 wherein the serrations of
the first region and the serrations of the second region are
parallel to the first plate midline and the serrations third region
and the serrations of the fourth region are parallel to the second
plate midline.
15. The prosthesis according to claim 11 wherein the serrations of
the first and second regions are symmetrically disposed about the
first plate midline and the serrations of the third and fourth
regions are symmetrically disposed about the second plate
midline.
16. The prosthesis according to claim 11 further comprising a core
located between the plates, the core comprising a first surface
adapted to engage the bearing surface of the first plate and a
second surface adapted to engage the bearing surface of the second
plate, wherein the first surface of the core and the bearing
surface of the first plate comprise cooperating spherical
surfaces.
17. The prosthesis according to claim, 11 wherein second surface of
the core and the bearing surface of the second plate comprise
cooperating spherical surfaces.
18. A prosthesis according to claim 11 further comprising: a first
fin to anchor the first plate in the first vertebra, the fin
disposed along the midline between the regions of serrations
disposed on the first plate, the fin adapted to enter a cut in the
first vertebra; and a second fin to anchor the second plate in the
second vertebra, the fin disposed along the midline between the
regions of serrations disposed on the second plate, the fin adapted
to enter a cut in the second vertebra.
19. The prosthesis according to claim 18, wherein holes are formed
transversely through the fins.
20. The prosthesis according to claim 11, wherein the bearing
surface of each plate is bounded by an annular rim, wherein the
annular rims are arranged to contact one another at a predetermined
limit of articulate movement of the plates.
21. The prosthesis according to claim 11, wherein the bearing
surface of each plate is bounded by an annular rim having a groove
formed thereon, wherein the grooves are adapted to connect to a
placement instrument while the prosthesis is inserted into the
intervertebral space.
Description
CROSS-REFERENCES TO RELATED APPLICATIONS
[0001] The present application is a continuation of U.S. patent
application Ser. No. 11/084,224 (Atty. Docket No. 022031-001710US),
filed on Mar. 18, 2005, which is a continuation-in-part of
PCT/IB2003/001529 (Atty. Docket No. 022031-001700PC), filed on Apr.
24, 2003, designating the United States, which claimed priority
from South African Application No. 2002/7517, filed on Sep. 19,
2002; the full disclosures of which are incorporated herein by
reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] This invention relates to an intervertebral prosthesis.
[0004] In the event of damage to a spinal disc it is known practice
to implant an intervertebral prosthesis surgically to replace the
damaged organ. Several types of prosthesis for this purpose are
known and in common use.
[0005] One type of known intervertebral prosthesis is sold by
Waldemar Link GmbH & Co under the trademark LINK.RTM. SB
Charite. This prosthesis includes upper and lower prosthesis plates
which locate against and engage the adjacent vertebral bodies, and
a low friction core between the plates. The core has upper and
lower convexly curved surfaces and the plates have corresponding,
concavely curved recesses which cooperate with the curved surfaces
of the core. This allows the plates to slide over the core to allow
required spinal movements to take place. The curved recesses in the
plates are surrounded by annular ridges which locate, at the limit
of sliding movement of the plates over the core, in opposing
peripheral channels surrounding the curved surfaces of the
core.
[0006] This type of configuration is also described in European
Patent Publication Nos. EP 0 560 140 and EP 0 560 141 (both
Waldemar Link GmbH & Co). However a drawback of such
configurations is that the provision of the peripheral ribs and
channels limits the areas available for bearing and sliding contact
between the plates and core, and accordingly the loads which can be
transmitted by the prosthesis. As a result of the relatively small
bearing areas, it is believed that at least the core will be
subject to rapid wear and have a relatively short life-span.
[0007] EP 0 560 141 also describes one alternative arrangement in
which the curved surfaces of the core carry opposing, elongate keys
that locate in elongate grooves in the plates and another
alternative arrangement in which the plates have opposing elongate
keys that locate in elongate grooves in the opposite curved
surfaces of the core. These key and groove arrangements allow the
plates to slide freely over the core, within the limits of the
length of the grooves, in one plane only. Although allowance is
made for some lateral play of the keys in the grooves, very little
sliding movement of the plates over the core can take place in the
orthogonal vertical plane, and this is considered to be a serious
drawback of this design.
[0008] 2. Description of the Background Art
[0009] European Patent Publication Nos. EP 0 560 140 and EP 0 560
141 have been discussed above. U.S. Patent Publication Nos.
US2002/0035400 and US2002/0128715 describe intervertebral
prostheses with center-posts received in passages in a core. The
core possesses an annular flange structure engaged by extensions on
the plates.
BRIEF SUMMARY OF THE INVENTION
[0010] According to the invention there is provided an
intervertebral prosthesis for insertion between adjacent vertebrae,
the prosthesis comprising upper and lower prosthesis plates
locatable against the respective vertebrae and having opposing,
concavely curved recesses therein and a core located between the
plates, the core having opposed, convexly curved surfaces received
in the recesses of the plates to allow the plates to slide in
articulated manner over the core, characterized in that: [0011] the
opposed surfaces of the core and the recesses of the plates have
cooperating spherical curvatures, [0012] the recess of a plate
surrounds a locating peg projecting centrally from the base of the
recess, and [0013] the peg locates loosely in an opening located
centrally in a curved surface of the core, whereby the plates can
slide over the core in all directions while the peg holds the core
captive.
[0014] In some embodiments, only one of the plates, typically the
operatively lower plate, includes a peg. In other embodiments, both
plates include pegs, the pegs opposing one another and locating
loosely in respective openings located centrally in the opposed
curved surfaces of the core. In each embodiment it is preferred
that each peg and the opening in which it locates are conical in
shape.
[0015] According to another aspect of the invention there is
provided a prosthesis plate for use in a prosthesis as summarized
above, the prosthesis plate having a coarse surface locatable
against a vertebra, an oppositely facing concavely curved surface
which is complemental in shape to a convexly curved surface of a
core of the prosthesis, characterized in the concavely curved
surface of the plate has a spherical curvature and in that the
plate includes a conical locating peg extending centrally from the
concavely curved surface, the peg being locatable loosely in a
central opening in the convexly curved surface of the core.
[0016] According to yet another aspect of the invention there is
provided a core for use in the prosthesis, the core comprising a
one piece plastics body having operatively upper and lower curved
surfaces, characterized in that the curved surfaces of the body are
spherically curved and at least one of the surfaces has a central,
conical opening therein dimensioned to receive a conical locating
peg of a prosthesis plate loosely.
[0017] Other features of the invention are set forth in the
appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] The invention will now be described in more detail, by way
of example only, with reference to the accompanying drawings in
which:
[0019] FIG. 1 shows a cross-sectional view of a prosthesis plate
used in a prosthesis according to the invention;
[0020] FIG. 2 shows a plan view of the prosthesis plate seen in
FIG. 1;
[0021] FIG. 3 shows a cross-sectional view of a core used in a
prosthesis according to the invention;
[0022] FIG. 4 shows a plan view of the core seen in FIG. 3;
[0023] FIG. 5 shows a cross-sectional view of an intervertebral
prosthesis according to a first embodiment of the invention in a
neutral condition before articulation has taken place;
[0024] FIG. 6 shows the prosthesis of FIG. 5 articulated to a limit
position; and
[0025] FIG. 7 shows a cross-sectional view of an intervertebral
prosthesis according to a second embodiment of the invention.
DETAILED DESCRIPTION OF THE INVENTION
[0026] The prosthesis plate 10 seen in FIGS. 1 and 2 may be formed
from titanium, typically being formed in one piece of grade 5
titanium. Other suitable materials include titanium nitrides,
cobalt chrome alloys, and ceramics. The prosthesis plate includes a
major surface 12 which is machined to a coarse, serrated finish 14.
Projecting from the surface 12 is an elongate fin 16 pierced by
transverse holes 18. The opposite surface of the plate 10 is formed
with a recess 20 surrounding a projecting conical peg 22 of round
cross-section at the centre of the recess. The recess is bounded by
an annular rim 24. The surface 26 of the recess is concavely,
spherically curved and has a titanium nitride finish.
[0027] A first embodiment of prosthesis of the invention, indicated
generally by the numeral 28 in FIGS. 5 and 6, includes a pair of
identical prosthesis plates 10 arranged in opposition to one
another. The prosthesis 28 also includes a core 30 illustrated in
FIGS. 3 and 4. The core is made in one piece of a low friction
plastics material, in this case a polyethylene known as Orthosol,
but a variety of other high molecular weight polyethylenes might
also find use. Alternatively, the core could be composed of a
metal, such as cobalt chrome, or of a ceramic. The core is
generally in the form of a circular, doughnut-shaped toroid and has
identical upper and lower surfaces 32 which are convexly,
spherically curved. The upper and lower surfaces 32 are formed
centrally with conical openings 34, in this case forming the
opposite ends of a circular cross-section passage 36 passing
axially and centrally through the body of the core.
[0028] The core surfaces 32 and recess surface 26 have the same
radius of curvature which is, in this case, 18 mm.
[0029] In the assembled prosthesis 28, the plates 10 are arranged
in opposition to one another with the core 30 located between them.
The pegs 22 of the plates locate in the openings 34, i.e. in the
ends of the passage 36. The combined length of the pegs is less
than the length of the passage 36, so the inner ends of the pegs
are spaced apart from one another by a short distance 38, as shown
in FIG. 5. The transverse dimension of each peg is, at all points
along the length of the peg, considerably less than the diameter of
the passage 36 at the corresponding point along the length of the
passage.
[0030] The cooperating spherical surfaces 26 and 32 and the
relative dimensions of the pegs 22 and the passage 36 allow the
plates 10 to slide or articulate over the core through a fairly
large range of angles and in all directions or degrees of freedom,
including rotation about the central axis.
[0031] At a predetermined limit of articulated movement of the
plates relative to the core, the rims 24 of the plates contact with
one another as indicated by the numeral 40 in FIG. 6. Further
articulation of the prosthesis 28 beyond this point is not
possible. At the limit of articulation, the pegs 22 also come into
abutment with the side of the passage 36, as also illustrated in
FIG. 6.
[0032] It will also be noted in FIG. 6 that the openings 34 at the
ends of the passage 36 are defined by similar cone angles to the
pegs 22, so that contact between the pegs and the sides of the
openings takes place complementally over virtually the entire
length of each peg.
[0033] Throughout the range of possible articulation, the pegs 22
remain in the passage 36 and prevent the core from separating
laterally from the plates 10. In other words, the core is held
captive by the pegs during all possible articulations which can
take place. In the illustrated embodiment, the plates 10 are
limited to 12.degree. of articulation before the rims 24 abut one
another, i.e. 12.degree. is the maximum articulation which can take
place.
[0034] In the prosthesis 28 described above, the pegs 22 locate in
a passage 32 which passes right through the core 30. It will
however be understood that in other embodiments, the pegs could
merely locate in blind recesses or openings in the opposite
surfaces of the core without such openings actually being joined to
one another to form a continuous passage.
[0035] FIG. 7 illustrates a prosthesis according to a second
embodiment of the invention in a view similar to that of FIG. 5. In
FIG. 7, components corresponding to components illustrated in the
earlier Figures are indicated by the same reference numerals.
[0036] The lower prosthesis plate 10 in FIG. 7 is identical to the
prosthesis plates of the first embodiment. However, the upper
prosthesis plate, designated 10.1, has no central peg. Instead, the
surface 26 is continuously, spherically curved. In all other
respects the plate 10.1 is identical to the plate 10.
[0037] In the assembled prosthesis 50, the core is held captive by
the action of the single peg 22 carried by the lower prosthesis
plate 10. The core 30 is identical to the core described previously
but once again it will be appreciated that core could have a blind
recess in its downwardly facing, curved surface 32 only to receive
the single peg 22.
[0038] The prosthesis 28, 50 is surgically implanted between
adjacent spinal vertebrae in place of a damaged disc. Those skilled
in the art will understand that the adjacent vertebrae are forcibly
separated from one another to provide the necessary space for
insertion. The plates 10, 10.1 are slipped laterally into place
between the vertebrae with their fins 16 entering slots cut in the
opposing vertebral surfaces to receive them.
[0039] After insertion of the core between the opposing plates, the
vertebra are allowed to move together to hold the assembled
prosthesis in place.
[0040] The surfaces 12 of the plates 10, 10.1 locate against the
opposing vertebrae and, with passage of time, firm connection
between the plates and the vertebrae will be achieved as bone
tissue grows over the serrated finish. Bone tissue growth will also
take place about the fins 16 and through the holes 18 therein,
further enhancing the connection which is achieved.
[0041] Referring to FIGS. 3 and 4, the core 30 used in the
embodiments described above is formed with narrow, angularly
spaced, blind passages which accommodate titanium pins 42. The core
itself is transparent to X-radiation and so would normally be
invisible in a post-operative X-ray examination. The pins 42 serve
as radiographic markers and enable the position of the core 30 to
be ascertained during such examination.
[0042] Annular grooves 44 are provided in the plates 10, 10.1 to
facilitate holding and manipulation of the prosthesis by
appropriate instruments during placement into the intervertebral
disc space.
[0043] Compared to known prostheses, the prostheses 28, 50
described above have a number of advantages, as follows: [0044] 1.
The peg or pegs 22 hold the core captive and prevent it from
slipping out sideways. [0045] 2. At a predetermined maximum limit
of articulation, the rims 24 contact one another to prevent further
articulation. At the same time, the peg or pegs 22 contact the
sides of the openings 34, also preventing further articulation.
[0046] 3. An acceptable bearing area of the plates on the core is
obtained with the central peg/central opening configurations
described above. This is particularly advantageous compared to
prior art prostheses where the core has peripheral channels on its
upper and lower surfaces to receive peripheral rims on the plates
at the limit of articulation.
[0047] In practice, it may happen that there is imperfect alignment
of the prosthesis plates. In the case of very poor alignment, the
dual peg configuration of FIGS. 5 and 6 gives rise to the
possibility that the pegs 22 are laterally offset from one another
by a substantial distance. This can in turn lead to the undesirable
consequence that the range of articulation which can be
accommodated is unduly limited, and attempts to articulate past the
limit could result in damage to the core by the misaligned pegs. In
the embodiment of FIG. 7 the single peg can be received centrally
by the core, thereby avoiding this potential problem.
[0048] The principles of the invention are applicable to prosthetic
disc implants for lumbar vertebrae as well as cervical vertebrae.
In the latter case, the fins 16 will typically be omitted.
[0049] While the present invention has been described with respect
to particular embodiments and specific examples thereof, it should
be understood that other embodiments may fall within the spirit and
scope of the invention. Therefore, the scope of the invention is
limited solely by the claims and their full range of
equivalents.
* * * * *