U.S. patent application number 11/686021 was filed with the patent office on 2008-09-18 for intervertebral implant component with three points of contact.
Invention is credited to Heather Cannon, Edwin Cham, Thierry Marnay.
Application Number | 20080228275 11/686021 |
Document ID | / |
Family ID | 39760072 |
Filed Date | 2008-09-18 |
United States Patent
Application |
20080228275 |
Kind Code |
A1 |
Cannon; Heather ; et
al. |
September 18, 2008 |
INTERVERTEBRAL IMPLANT COMPONENT WITH THREE POINTS OF CONTACT
Abstract
An intervertebral implant is made up of components which each
have an inner surface and an outer surface which engages an
adjacent vertebra and presents only three distinct points of
contact with a cortical rim of the vertebra. Preferably, the outer
surface has a footprint which is sized to be within that of the
cortical rim. In disclosed embodiments, the footprint can be
convexo-concave shaped, D shaped, or kidney shaped. The
intervertebral implant can be provided with upper and lower (or
first and second) components which engage adjacent first and second
vertebrae and which move relative to one another. The implant has
both the first and second outer surfaces sized to present a
respective footprint sufficient for two lateral-anterior and one
posterior points of contact with an adjacent cortical rim of the
respective first and second vertebra.
Inventors: |
Cannon; Heather; (West
Chester, PA) ; Cham; Edwin; (Schwenksville, PA)
; Marnay; Thierry; (Casielnau Le Lez, FR) |
Correspondence
Address: |
STITES & HARBISON PLLC
1199 NORTH FAIRFAX STREET, SUITE 900
ALEXANDRIA
VA
22314
US
|
Family ID: |
39760072 |
Appl. No.: |
11/686021 |
Filed: |
March 14, 2007 |
Current U.S.
Class: |
623/17.16 |
Current CPC
Class: |
A61F 2/4611 20130101;
A61F 2002/4627 20130101; A61F 2002/30884 20130101; A61F 2230/0034
20130101; A61F 2230/0015 20130101; A61F 2002/30187 20130101; A61F
2002/443 20130101; A61F 2002/30133 20130101; A61F 2002/30841
20130101; A61F 2002/4628 20130101; A61F 2/4425 20130101 |
Class at
Publication: |
623/17.16 |
International
Class: |
A61F 2/44 20060101
A61F002/44 |
Claims
1. An intervertebral implant component comprising: an outer surface
for engaging an adjacent vertebra and an inner surface; wherein
said outer surface is constructed to present only three distinct
points of contact for engaging a cortical rim of the adjacent
vertebra, and said outer surface has a footprint which is sized to
be within that of the cortical rim to be engaged.
2. (canceled)
3. An intervertebral implant component as claimed in claim 21
wherein said footprint of said outer surface is convexo-concave
shaped.
4. An intervertebral implant component as claimed in claim 1,
wherein said footprint of said outer surface is D shaped.
5. An intervertebral implant component as claimed in claim 1,
wherein said footprint of said outer surface is kidney shaped.
6. An intervertebral implant component as claimed in claim 1,
wherein said three points of contact of said footprint of said
outer surface with the cortical rim are two lateral-anterior points
and one posterior point.
7. An intervertebral implant component as claimed in claim 6,
wherein a footprint of said outer surface includes opposed ends
which provide the two lateral-anterior points of contact.
8. An intervertebral implant component as claimed in claim 1,
wherein said outer surface includes at least one vertebra engaging
protrusion.
9. An intervertebral implant component as claimed in claim 8,
wherein said at least one vertebra engaging protrusion includes a
protruding keel located adjacent a longitudinal end of said outer
surface.
10. An intervertebral implant component as claimed in claim 9,
wherein said keel is curved.
11. An intervertebral implant component as claimed in claim 1,
wherein said inner surface includes a pair of instrument receiving
cutouts extending to an adjacent outer edge thereof.
12. An intervertebral implant component as claimed in claim 11,
wherein said cutouts are angled centrally inwardly.
13. An intervertebral implant component as claimed in claim 12,
wherein said cutouts are dovetail shaped in cross section.
14. An intervertebral implant comprising: a first part which has a
first outer surface for engaging a first vertebra and a first inner
surface; a second part which has a second outer surface for
engaging a second vertebrae and a second inner surface; and said
first and second parts being moveable relative to one another;
wherein said first and second outer surfaces are sized to present a
respective footprint sufficient for only three points of contact
with an adjacent cortical rim of the respective first and second
vertebra to be engaged, said footprints also being sized to be
within that of the adjacent cortical rim to be engaged.
15. (canceled)
16. An intervertebral implant as claimed in claim 14, wherein said
footprints of said outer surfaces are convexo-concave shaped.
17. An intervertebral implant as claimed in claim 14, wherein said
footprints of said outer surfaces are D shaped.
18. An intervertebral implant as claimed in claim 14, wherein said
footprints of said outer surfaces are kidney shaped.
19. An intervertebral implant as claimed in claim 14, wherein said
three points of contact of each of said footprints of said outer
surfaces with the adjacent cortical rims are two lateral-anterior
points and one posterior point.
20. An intervertebral implant as claimed in claim 19, wherein each
of said footprints of said outer surfaces include opposed ends
which provide the two lateral-anterior points of contact.
21. An intervertebral implant as claimed in claim 14, wherein each
of said outer surfaces includes at least one vertebra engaging
protrusion.
22. An intervertebral implant as claimed in claim 21, wherein each
said at least one vertebra engaging protrusion includes a
protruding keel located adjacent a longitudinal end of the
respective said outer surface.
23. An intervertebral implant as claimed in claim 22, wherein each
said keel is curved.
24. An intervertebral implant as claimed in claim 14, wherein each
of said inner surfaces includes a pair of instrument receiving
cutouts extending to an adjacent outer edge thereof.
25. An intervertebral implant as claimed in claim 24, wherein each
of said cutouts is angled centrally inwardly.
26. An intervertebral implant as claimed in claim 25, wherein each
of said cutouts is dovetail shaped in cross section.
Description
BACKGROUND OF THE INVENTION
[0001] Historically, when it was necessary to completely remove a
disc from between adjacent vertebrae, the conventional procedure is
to fuse the adjacent vertebrae together. This "spinal fusion"
procedure, which is still in use today, is a widely accepted
surgical treatment for symptomatic lumbar degenerative disc
disease. However, reported clinical results vary considerably, and
complication rates are considered by some to be unacceptably
high.
[0002] More recently, there have been important developments in the
field of disc replacement, namely disc arthoplasty, which involves
the insertion of an artificial intervertebral disc implant into the
intervertebral space between adjacent vertebrae, and which allows
limited universal movement of the adjacent vertebrae with respect
to each other. The aim of total disc replacement is to remove pain
generation (caused by a bad disc), restore anatomy (disc height),
and maintain mobility in the functional spinal unit so that the
spine remains in an adapted sagittal balance. Sagittal balance is
defined as the equilibrium of the trunk with the legs and pelvis to
maintain harmonious sagittal curves. In contrast with fusion
techniques, total disc replacement preserves mobility in the motion
segment and mimics physiologic conditions.
[0003] One such intervertebral implant includes an upper part that
can communicate with an adjacent vertebrae, a lower part that can
communicate with an adjacent vertebrae, and an insert located
between these two parts. An example of this type of implant is
disclosed in U.S. Pat. No. 5,314,477 (Marnay).
[0004] While this and other known implants represent improvements
in the art of artificial intervertebral implants, there exists a
continuing need for improvements in this field.
BRIEF SUMMARY OF THE INVENTION
[0005] In accordance with the present invention, a component of an
intervertebral implant is provided with an inner surface and an
outer surface. The outer surface engages an adjacent vertebra and
presents only three distinct points of contact with a cortical rim
of the adjacent vertebra. Preferably, the outer surface has a
footprint which is sized to be within that of the cortical rim. In
disclosed embodiments, the footprint of the outer surface has a
major convex side and can be convexo-concave shaped, D shaped, or
kidney shaped.
[0006] Preferably, the three points of contact of the footprint of
the outer surface with the cortical rim are two lateral-anterior
points and one posterior point. In addition, the footprint of the
outer surface includes opposed ends which provide the two
lateral-anterior points of contact.
[0007] In a preferred embodiment, the outer surface of the
component includes at least one vertebra engaging protrusion. The
protrusion can include a protruding keel located adjacent an
opposed or longitudinal end, which keel may be curved.
[0008] Also in a preferred embodiment, the inner surface includes a
pair of cutouts extending to an adjacent outer edge thereof. The
cutouts are preferably angled centrally inwardly and dovetail
shaped in cross section.
[0009] Also in accordance with the present invention, an
intervertebral implant can be provided with upper and lower (or
first and second) components, each as described above and each of
which engages an adjacent first and second vertebrae. The implant
also includes a means for allowing the first and second components
to move relative to one another. The implant would have the outer
surfaces of both the first and second components sized to present a
respective footprint sufficient for only three points of contact
with an adjacent cortical rim of the respective first and second
vertebra.
[0010] It is an advantage of the present invention that a minimally
sized intervertebral implant is provided.
[0011] It is also an advantage of the present invention that the
intervertebral implant has only three points of contact made at the
cortical rim of the adjacent vertebrae.
[0012] It is a further advantage of the present invention that a
major convex-sided shape of the intervertebral implant presents a
small insertion size which can be inserted along an arc shaped
path.
[0013] Other features and advantages of the present invention are
stated in or apparent from detailed descriptions of presently
preferred embodiments of the invention found hereinbelow.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0014] FIG. 1 is a perspective exploded view of an implant in
accordance with the present invention.
[0015] FIG. 2 is a top plan view of the implant depicted in FIG. 1
adjacent a vertebra.
[0016] FIG. 3 is a top plan view of the implant depicted in FIG. 2
partially inserted into an intervertebral space.
[0017] FIG. 4 is a top plan view of the implant depicted in FIG. 2
fully inserted into an intervertebral space.
[0018] FIG. 5 is a left side view of the implant depicted in FIG. 2
inserted into an intervertebral space.
[0019] FIG. 6 is an anterior view of the implant depicted in FIG.
5.
[0020] FIG. 7 is a perspective exploded view of an alternatively
shaped implant of the present invention.
[0021] FIG. 8 is a perspective exploded view of an implant similar
to FIG. 1 but showing a modification of the invention.
[0022] FIG. 9 is a perspective view of a component of an
alternatively shaped implant of the present invention showing a
modification of the invention.
[0023] FIG. 10 shows the operative portion of an instrument used
for insertion of an implant according to the present invention.
[0024] FIG. 11 shows an implant having components as in FIG. 9
being engaged by the instrument depicted in FIG. 10.
DETAILED DESCRIPTION OF THE INVENTION
[0025] With reference now to the drawings in which like numerals
represent like elements throughout the views, an intervertebral
implant 10 according to the present invention is depicted in FIGS.
1-6. Broadly and as best shown in FIG. 1, implant 10 is formed of
three components or parts, an upper part 12, a lower part 14 and a
movable insert 16 allowing upper part 12 to move relative to lower
part 14. An opposed pair of convexities 18 are provided on
respective inner surfaces 19 of upper and lower parts 12 and 14
(though only convexity 18 for lower part 16 is shown), and
concavities 20 (only upper concavity 20 is shown) on opposite sides
of insert 16 which concavities 20 mate with adjacent convexities
18. Such parts 12, 14 and 16 in general and the motions provided
thereof are well known in the art, such as in USPA 2006/0116769
(Marnay et al.) which is herein incorporated by reference, and thus
need not be discussed further. It will be noted that it is also
known in the art that insert 16 could be a convexity extending
integrally from one part which mates with a concavity integrally in
the other part, so the separate depiction of an insert 16 for the
present invention is only exemplary of one type of movable insert
means known in the art.
[0026] Both upper and lower parts 12 and 14 each have an outer
surface 24. As known in the art, outer surfaces 24 are each
designed to contact an adjacent vertebrae, such as upper and lower
vertebrae 26 and 28 depicted in FIGS. 2-6. As shown in FIGS. 2-4,
vertebra 28 (and similar vertebrae in general) includes a
relatively rigid cortical rim 30 of bone which surrounds less rigid
cancellous bone 32. Prior art vertebral implants were designed to
cover cortical rim 30. However, such coverage results in multiple
points (or areas) of contact which are not needed. Thus, implant 10
of the present invention provides a more compact and hence easier
to insert implant which still has a good and sufficient contact
with the adjacent vertebrae.
[0027] It is thus a feature of the present invention that outer
surfaces 24 are designed or sized to provide three distinct points
(or small areas) of contact 34a, 34b and 34c (or collectively,
points 34) with the adjacent cortical rim 30 as shown in FIG. 4. It
will be appreciated that points of contact 34 shown in FIG. 4 are
those of outer surface 24 of upper part 12 which would contact
upper vertebra 26 (not shown) but in the same manner as the
underlying points of contact 34 of lower part 14 (which are not
seen because they are covered by upper part 12) contact lower
vertebra 28 which is shown. It will be noted that outer surface 24
also includes a series of small teeth or spikes 36 or other such
protrusions upstanding therefrom which serve to anchor upper and
lower parts 12 and 14 in place after implantation as well known in
the art.
[0028] As noted above, outer surface 24 is shaped with a major
convex side according to the present invention to present a
footprint so that only three points of contact 34 are provided
thereby. As the size of vertebrae vary depending on location and on
the individual user, implant 10 will be tailored to the individual
so that only three points of contact 34 are made. This sizing of
the footprint of outer surface 24 is conveniently determined by
choosing the footprint of outer surface 24 to be located within the
footprint of cortical rim 30 as shown. The points of contact 34 are
left and right lateral-anterior points 34a and 34c which are
preferably symmetrically located as shown, and a posterior point
34b. Conveniently, the footprint of the outer surface 24 includes
opposed ends which provide the left and right lateral-anterior
points 34a and 34c. Suitable footprints to provide the three points
34 of contact include: a) a convexo-concave footprint as shown by
implant 10 in FIGS. 1-4 (and by implant 210 in FIG. 8); b) a
D-shaped footprint as shown by implant 110 in FIG. 7; or c) a
kidney shaped footprint as shown by implant 310 in FIGS. 9 and
11.
[0029] The use of such a small footprint and only three points of
contact 34 with one being posterior or anterior also makes it
possible for implants 10, 110, 210 and 310 to have a relatively
narrow or small maximum width between left and right points 34a and
34c as evident from the three footprints discussed above. This
narrow maximum width, particularly where augmented by a
longitudinal concavity or inward bowing as with implants 10, 210
and 310, permits implants 10, 110, 210 and 310 to be inserted
between adjacent vertebrae 26 and 28 through a smaller incision
than if the implant spanned cortical rim 30 in all directions. In
FIGS. 2-4, it will also be appreciated that the size and shape of
implant 10 also makes the implanting of implant 10 from the angle
shown and along the path depicted easy to accomplish.
[0030] Implant 110 depicted in FIG. 7 discloses upper and lower
parts 112 and 114 having outer surfaces 124 which present a D
shaped footprint. As with FIG. 1, as noted above, insert 116 shows
the upper concavity thereof (opposite the similar lower concavity
thereof.
[0031] Depicted in FIG. 8 is an implant 210 which is also
convexo-concave shaped like implant 10. However, implant 210
includes a keel 262 extending from each of outer surfaces 224
adjacent an opposed or longitudinal end thereof, and preferably the
opposed end which is inserted last between vertebrae 26 and 28 (see
FIG. 3) with the opposite longitudinal end then preferably having a
slight chamfer to ease insertion. Each keel 262 serves to anchor
the associated upper and lower parts 212 and 214 of implant 210 in
place in a provided cutout or slot in adjacent vertebrae 26 and 28
after implantation as known in the art, in addition to the
anchoring provided by the small spikes 236 also shown in FIG. 8.
Keel 262 is depicted as curved or arced to match arced insertion
path along which implant 210 would be implanted between the
vertebrae (as shown by the three positions of implant 10 shown in
FIGS. 2-4); though if implant 262 is implanted along a straight
direction, keel 262 would instead be straight. If desired, two or
more keels positioned along an arc or straight line could also be
provided. The cutout required for keel 262 could be made in advance
of implantation, or keel 262 could be self-cutting having
chisel-like cutting edges at the introduction end as known in the
art.
[0032] In FIG. 9, an entire implant is identified by the numeral
310, although only lower part 314 thereof is shown in detail. The
upper part 312 is a mirror image thereof, and the insert the same
as the above described insert 16. Lower part 314 has an outer
surface 324 which presents a kidney shaped footprint as shown. Also
shown on lower part 314 are an opposed pair of cutouts 372 in inner
surface 319. Cutouts 372 are dovetail shaped, that is, the vertical
walls thereof are angled inwardly (or each toward the other cutout
372), and cutouts 372 are also preferably are longitudinally angled
centrally inwardly or converging toward one another (or toward
convexity 318) as they extend from the adjacent opposed end.
Cutouts 372 are provided so that an instrument with a pair of
matingly shaped engaging members can securely grasp lower part 314
(and similarly upper part 312) in order to insert implant 310
between vertebrae 26 and 28 as generally known in the art; and the
added security of having both the dovetails shape and convergence
allows cutouts 372 to be usable as well to reposition or even
remove implant 310 as required. Of course, cutouts 372 could also
be parallel to one another rather than converging if desired if
less holding power is needed with the instrument.
[0033] Depicted in FIGS. 10 and 11 is a portion of an insertion
instrument 400 which can be used for insertion of implant 310 (or
the other disclosed implants if they are provided with cutouts
372). Instrument 400 includes a base 402 attached to an inserter
shaft 403. Extending distally from base 402 (away from inserter
shaft 403) is a longitudinal fixed arm 404. Fixed arm 404 is shaped
with top and bottom laterally-inwardly directed projections 406a
and 406b. Projections 406 are designed to fit matingly in cutouts
372, and thus have a mating dovetail design. Laterally opposite to
fixed arm 404 is a movable arm 408 having top and bottom
laterally-inwardly directed projections 410a and 410b which are
similarly shaped as projections 406 but oppositely directed. Like
projections 406, projections 410 are designed to fit matingly in
cutouts 372 but on the opposite side of implant 310. As known in
the art, movable arm 408 is movable about a pivot 412 provided in
base 402 toward fixed arm 404, and this movement is accomplished by
a rod 414 guided in inserter shaft 403 which is forced against a
pin 416 integral with movable arm 408 and trapped in slot 418 of
base 402.
[0034] In use, instrument 400 is used to grasp implant 310 by
placing projections 406 and 410 on either sides of implant 310 and
adjacent respective cutouts 372. Then, by manipulation of rod 414,
movable arm 408 is moved towards fixed arm 404 so that projections
406 and 410 are received in and then locked in cutouts 372. Once
projections 406 and 410 are locked in place in cutouts 372, implant
310 is securely attached to base 402 so that implant 310 can be
inserted between vertebrae by manipulation of inserter shaft 403 as
known in the art.
[0035] While the present invention has been described with respect
to exemplary embodiments thereof, it will be understood by those of
ordinary skill in the art that variations and modifications can be
effected within the scope and spirit of the invention.
* * * * *