U.S. patent application number 11/722903 was filed with the patent office on 2008-05-01 for intervertebral prosthesis.
Invention is credited to Andreas Appenzeller, Robert Frigg, Beat Lechmann.
Application Number | 20080103597 11/722903 |
Document ID | / |
Family ID | 35998566 |
Filed Date | 2008-05-01 |
United States Patent
Application |
20080103597 |
Kind Code |
A1 |
Lechmann; Beat ; et
al. |
May 1, 2008 |
Intervertebral Prosthesis
Abstract
Intervertebral prosthesis (1), in particular intervertebral disk
prosthesis, with a central axis (6) and comprising A) a first
prosthetic component (2) having a first apposition surface (4) and
a first inner surface (7), both being disposed transversely to the
central axis (6) and having a spherical recess (11); B) a second
prosthetic component (3) having a second apposition surface (5) and
a second inner surface (8) both being disposed transversely to the
central axis (6) and having a calotte (9) congruent with said
recess (11); C) the first and second prosthetic components (2;3)
being connectable in an articulated manner by means of the calotte
(9) which may be slidably received in the recess (11); whereby D)
the first and second prosthetic components (2;3) have a width B and
a length H each being transverse to the central axis (6), said
first and second prosthetic components (2;3) further comprise a
longitudinal axis L.sub.1, respectively L.sub.2 extending parallel
to the respective length H; and whereby E) the length H is greater
than the width B, such that the prosthetic components (2;3) may be
put into a position in the intervertebral space in which the two
longitudinal axes L.sub.1 and L.sub.2 intersect each other at an
angle .alpha.>0.degree. when being projected in a plane being
orthogonal to the central axis (6).
Inventors: |
Lechmann; Beat; (Grenchen,
CH) ; Frigg; Robert; (Bettlach, CH) ;
Appenzeller; Andreas; (Biel, CH) |
Correspondence
Address: |
STROOCK & STROOCK & LAVAN LLP
180 MAIDEN LANE
NEW YORK
NY
10038
US
|
Family ID: |
35998566 |
Appl. No.: |
11/722903 |
Filed: |
December 27, 2005 |
PCT Filed: |
December 27, 2005 |
PCT NO: |
PCT/CH05/00774 |
371 Date: |
June 27, 2007 |
Current U.S.
Class: |
623/17.16 |
Current CPC
Class: |
A61F 2002/30841
20130101; A61F 2002/30601 20130101; A61F 2220/0033 20130101; A61F
2230/0015 20130101; A61F 2002/30616 20130101; A61F 2002/4627
20130101; A61F 2/4611 20130101; A61F 2002/30092 20130101; A61F
2310/00023 20130101; A61F 2310/00029 20130101; A61F 2310/00748
20130101; A61F 2002/30649 20130101; A61F 2002/30133 20130101; A61F
2310/00179 20130101; A61F 2002/443 20130101; A61F 2/4425 20130101;
A61F 2230/0008 20130101; A61F 2002/30331 20130101; A61F 2210/0014
20130101; A61F 2002/30125 20130101; A61F 2310/0058 20130101 |
Class at
Publication: |
623/17.16 |
International
Class: |
A61F 2/44 20060101
A61F002/44 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 28, 2004 |
CH |
2160/04 |
Claims
1. An intervertebral disk prosthesis comprising: a first prosthetic
component with a first width, a first length and a first
longitudinal axis, the first prosthetic component comprising a
first apposition surface disposed transversely to a central axis
for contacting an end plate of a first adjoining vertebral body and
further comprising a first inner surface disposed transversely to
the central axis and having a spherical recess; a second prosthetic
component with a second width, second length and a second
longitudinal axis, the second prosthetic component comprising a
second apposition surface disposed transversely to the central axis
for contacting an end plate of a second adjoining vertebral body
and further comprising a second inner surface disposed transversely
to the central axis and having a calotte congruent with said recess
wherein the calotte can be slidably received in the recess;
wherein: the first and second prosthetic components are connectable
in an articulated manner by means of the calotte being slidably
received in the recess; and the first length is greater than the
first width such that the first and second prosthetic components
are in position in the intervertebral space in which the first and
second longitudinal axes intersect each other at an angle greater
than zero degrees when being projected in a plane being orthogonal
to the central axis.
2. The intervertebral prosthesis as claimed in claim 1, wherein the
ratio of the first length to the first width is between 3:1 and
5:1.
3. The intervertebral prosthesis as claimed in claim 1, wherein one
of the first and second prosthetic components and the calotte
consist of one piece.
4. The intervertebral prosthesis as claimed in claim 1, wherein
said intervertebral prosthesis consists of at least three pieces
with the calotte being the third piece attachable to one of said
first and second prosthetic components.
5. The intervertebral prosthesis as claimed in claim 1, wherein
said intervertebral prosthesis consists of at least three pieces
and comprises an articular shell including the recess which is
attachable to one of said first and second prosthetic components as
a third piece.
6. The intervertebral prosthesis as claimed in claim 5, wherein the
calotte and the articular shell consist of a material pairing of
metal and plastic.
7. The intervertebral prosthesis as claimed in claim 5, wherein the
calotte and the articular shell consist of a ceramic-to-ceramic
material pairing.
8. The intervertebral prosthesis as claimed in claim 1, wherein the
surfaces of the calotte and of the recess are coated with titanium
carbide or with an amorphous carbon.
9. The intervertebral prosthesis as claimed in claim 1, wherein at
least the calotte is made of a memory metal.
10. The intervertebral prosthesis as claimed in claim 1, wherein at
least the calotte is made of a material capable of swelling.
11. The intervertebral prosthesis as claimed in claim 1, wherein at
least the calotte is made of a flowable, thermosetting
material.
12. The intervertebral prosthesis as claimed in claim 11, wherein
at least the calotte is made of a monomer, comonomer, homopolymer,
oligomer, or mixture which contains a thermosetting, flowable
substance.
13. The intervertebral prosthesis as claimed in claim 12, wherein
the thermosetting, flowable substance is selected from the group
of: a) polyethylene glycols; b) n-vinylpyrrolidones; c) vinyls; and
d) styrenes.
14. The intervertebral prosthesis as claimed in claim 1, wherein
said first prosthetic component is selected from a group of at
least two first prosthetic components.
15. The intervertebral prosthesis as claimed in claim 1, wherein
said second prosthetic component is selected from a group of at
least two second prosthetic component.
16. A method of implanting an intervertebral disk prosthesis into
an intervertebral space, which comprises a first and a second
prosthetic component articulately connectable with each other and
which presents a central axis extending coaxially or parallel to
the longitudinal axis of a vertebral column, comprising the steps
of: implanting the first prosthetic component via a first access
into a first intervertebral region that is transverse to the
central axis of the intervertebral prosthesis, the first prosthetic
component having a first width and a first length, wherein the
first length is greater than the first width; implanting the second
prosthetic component via a second access into a second
intervertebral region that is transverse to the central axis of the
intervertebral prosthesis; the second prosthetic component having a
second width and a second length, the second length being greater
than the second width; wherein the longitudinal axes of the first
and second prosthetic components extend parallel to the first
length and intersect each other at an angle greater than zero
degrees; and coupling the second prosthetic component to the first
prosthetic component in an articulated manner during the
implantation.
17. The method as claimed in claim 16, wherein the two accesses are
located posteriorly.
18. The method as claimed in claim 16, wherein the first access is
located transforaminally.
19. The method as claimed in claim 16, wherein the second access is
located extraforaminally.
20. (canceled)
21. The method as claimed in claim 16, wherein the first access and
second access each have one entrance point that is spaced apart
from the sagittal axis extending centrally in an antero-posterior
direction in such a way that the longitudinal axes of the two
implanted prosthetic components form an angle greater than zero
degrees.
22. The method as claimed in claim 21, wherein the angle is in a
range of between 25.degree. and 120.degree..
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This Application is a national stage application under 35
U.S.C. 371 based on International Application Serial No.
PCT/CH2005/000774 filed on Dec. 27, 2005 for "INTERVERTEBRAL
PROSTHESIS".
FIELD OF INVENTION
[0002] The invention relates to an intervertebral prosthesis, in
particular to an intervertebral disk prosthesis.
DESCRIPTION OF RELATED ART
[0003] In recent years, intervertebral prostheses have gained wide
acceptance in vertebral column surgery. These prostheses are
inserted anteriorly or antero-laterally between the vertebral
bodies in place of the intervertebral disk. This implantation
technique represents a certain risk, as the access leads through
the abdominal region. There is a risk that greater vessels in the
region of the anterior lumbar column may be injured. From a
biomechanical point of view, the anterior access has the
disadvantage that the anterior longitudinal ligament of the
vertebral column has to be partially or entirely dissected in order
to enable the insertion of the prosthesis. This dissection will
result in a certain instability of the vertebral column and may, in
the worst case, facilitate a ventral migration of the prosthesis.
In order to reduce the risk of a migration of the prosthesis,
different anchoring means are used which fix the prosthesis on the
cover plates of the adjacent vertebral bodies.
[0004] An intervertebral prosthesis of this type is known from WO
01/01893 MARNAY. This known prosthesis comprises two plates having
a ball-and-socket joint and two differently shaped projections for
anchoring the prosthesis in two vertebrae. In said document it is
also proposed to minimize the height of the prosthesis during
insertion in that the two components are made to engage with each
other. Despite the provided fixation means, there is a risk for the
prosthesis to migrate back along the insertion channel.
SUMMARY OF THE INVENTION
[0005] The invention is intended to provide a remedy for this. The
present invention is directed to an intervertebral prosthesis which
for implantation purposes is decomposable into two parts and which
is inserted into the intervertebral space via transforaminal and/or
extraforaminal accesses. The articulation of the intervertebral
prosthesis preferably consists of a spherical calotte and a
corresponding spherical recess. During the implantation of the two
prosthetic components, which are implanted separately into the
intervertebral space via the two separate accesses, the two
longitudinal axes of the prosthetic components cross each other in
the intervertebral space. By freely selecting the angle .alpha.
between the longitudinal axes of the two prosthetic components, the
position of the point of intersection can be adjusted in a sagittal
direction with the insertion points remaining unchanged. This
adjustment may be planned preoperatively by means of CT or X-ray
photographs or may be defined intraoperatively by means of guide
wires and/or templates.
[0006] The advantages achieved by the invention reside essentially
in the fact that due to the intervertebral prosthesis of the
invention: [0007] an individual adjustment of the intervertebral
prosthesis for any pair of vertebral bodies is possible. Thus, an
individual anatomy of the motion element can be taken into account;
[0008] the individual segmental motion sequences may be
preoperatively taken into account and defined by the surgeon;
[0009] an uncomplicated and secure operation technique is made
possible compared to implants which are inserted into the
intervertebral space in a completely assembled state; [0010] the
risk of an antero-posterior and/or lateral migration of the
prosthesis due to flexion/extension or lateral bending of the
spinal column is minimized; [0011] the natural intervertebral disk
has to be only partially removed, i.e. in order to implant the two
prosthetic components in the intervertebral space (intervertebral
disk) it is only necessary to clear two paths of a width B and a
length H, so that only the apposition surfaces of the two
prosthetic components are in bone contact with the respective end
plates. The rest of the intervertebral disk remains in situ and
prevents the intervertebral prosthesis from migrating laterally
and/or antero-posteriorly once the two prosthetic components have
been implanted.
[0012] In a preferred embodiment, the ratio of the length H of the
prosthetic components to the width B thereof is between 3:1 and
5:1. The advantages of this design essentially are that in order to
implant the two prosthetic components in the intervertebral space
(intervertebral disk) it is only necessary to clear two narrow
paths of a width B and a length H.
[0013] In another embodiment, the intervertebral prosthesis is
realized in two pieces, i.e. the calotte is made in one piece with
one of the two prosthetic components.
[0014] In a further embodiment, the intervertebral prosthesis is
realized in three pieces, so that the calotte forming the third
piece is connectable with one of the two prosthetic components. The
advantage of this design is to be seen essentially in the fact that
the plate and the calotte may be realized by using different
materials, so that it is possible to achieve optimal sliding
properties for the articular surfaces. Preferred materials for the
plates are titanium or a titanium alloy as well as PEEK or coated
variants, and for the calotte highly crosslinked polyethylene
(X-UHMWPE), an alloy of cobalt and chrome, or a ceramic
material.
[0015] In again a further embodiment, the intervertebral prosthesis
is realised in at least three pieces and comprises an articular
shell including the recess, whereby said articular shell is
attachable to one of said first and second prosthetic components as
a third piece. The advantage of this design is to be seen
essentially in the fact that the plate and the calotte may be
realised using different materials, so that it is possible to
achieve optimal sliding properties for the articular surfaces.
[0016] In a further embodiment, the calotte and the articular shell
consist of a material combination made of metal and plastic. The
advantages of this embodiment are that it is possible to use proven
combinations of joint replacement materials such as, for example,
highly crosslinked polyethylene (X-UHMWPE) and an alloy of cobalt
and chrome. Further advantages are to be seen in the fact that low
frictional forces are achievable for the relative displacement of
the articular surfaces and that a compensation of axial impact
loads can be achieved.
[0017] In yet another embodiment a ceramic-to-ceramic articulation
is used.
[0018] In a further embodiment the surfaces of the calotte and the
recess are coated with titanium carbide or with amorphous carbon
(ADLC) therewith permitting a substantial reduction of the
coefficient of friction.
[0019] In another embodiment, at least the calotte is made of a
memory metal or of a material capable of swelling (e.g.
hydrogels).
[0020] In still another embodiment at least the calotte is made of
a flowable, thermosetting material. The monomers, comonomers,
homopolymers, oligomers, or mixtures which contain such
thermosetting, flowable substances may suitably be selected from
the group of:
[0021] a) polyethylene glycols, preferably polyethylene
glycol(di)-acrylates;
[0022] b) n-vinylpyrrolidones; and
[0023] c) vinyls, preferably vinyl alcohols; and
[0024] d) styrenes.
[0025] The polymers thus obtained may be widely varied as regards
to their elasticity. The advantages of these designs are to be seen
essentially in the fact that due to the reduced volume of the
joint, the insertion of the intervertebral prosthesis becomes less
invasive, the increased volume being best suited for achieving an
optimal articular function.
[0026] In a further embodiment the first prosthetic component is
selected from a first kit of at least M.gtoreq.2 first prosthetic
components and the second prosthetic component is selected from a
second kit of at least N.gtoreq.2 second prosthetic components.
Said first and second kit may comprise first and second prosthetic
components being provided with different heights, articulation
radii or locations of the center of the respective radii, i.e. the
center of rotation. By means of this embodiment the following
advantages may be achieved [0027] the position of the center of
rotation is adjustable in height as the two component parts may be
arranged in a modular manner; [0028] the components which may also
vary in the radius of the calotte, which makes it possible to
adjust the center of rotation of the intervertebral prosthesis;
[0029] the position of the center of rotation, the angulation, and
the portion of translatory motion of the intervertebral prosthesis
may be freely selected within a relatively wide range, the portion
of translatory motion being the portion of movement measured
transversely to the central axis of the prosthetic components
relative to each other; [0030] the prosthetic components may also
take into account the articulation requirements of the motion
segment in that it is possible to include calottes having different
radiuses. Greater calotte radiuses have a higher portion of
translatory motion during deflection, which on the flexion of a
patient's spine puts increased pressure on the facet joints and
leads to an accelerated degeneration thereof; [0031] the heights of
the prosthetic components and the corresponding radiuses of the
articulating calotte of the intervertebral prosthesis may vary and
are thus adaptable to the dimensions of different intervertebral
spaces.
[0032] The method of implanting an intervertebral prosthesis into
the intervertebral space according to the invention comprises the
steps of:
[0033] A) implanting a first prosthetic component via a first
access into the intervertebral region transversely to the central
axis of the intervertebral prosthesis;
[0034] B) implanting the second prosthetic component of the
intervertebral prosthesis via a second access, which is different
from the first access, into the intervertebral region transversely
to the central axis of the intervertebral prosthesis, whereby the
two prosthetic components, when measured transversely to the
central axis each have a width B and a length H>B and the
longitudinal axes L.sub.1 and L.sub.2 of the first and second
prosthetic components which extend parallel to the length H
intersect each other at an angle .alpha.>0; and
[0035] C) coupling the second prosthetic component to the first
prosthetic component in an articulated manner during the
implantation.
[0036] Depending on the type of embodiment of the method of the
invention, at least one access is located transforaminally or
extraforaminally. The transforaminal access is known and
established in vertebral column surgery. Due to the extraforaminal
access it is possible to have large openings towards the
intervertebral disk space without adversely affecting the ventral
or the dorsal ligaments or the neural structures.
[0037] In a preferred embodiment the two accesses are located
posteriorly.
[0038] In another embodiment the first access is located
transforaminally.
[0039] In still another embodiment the second access is located
extraforaminally.
[0040] In a further embodiment the intervertebral disk located in
the spacing between the two vertebral bodies is removed only to
such an extent that the entire apposition surfaces of the two
prosthetic components designed for abutment onto the bone have full
bone contact with the end plate of the respective vertebral
body.
[0041] In yet a further embodiment the two accesses each have one
entrance point E which is spaced apart from the sagittal axis
extending centrally in an antero-posterior direction in such a way
that the longitudinal axes L.sub.1 and L.sub.2 of the two implanted
prosthetic components form an angle .alpha.. Preferably, the angle
.alpha. is in a range of between 25.degree. and 120.degree..
[0042] In the following, the invention and improvements of the
invention will be illustrated in greater detail with reference to
the partially diagrammatic representations of a plurality of
embodiments of the intervertebral prosthesis according to the
invention.
[0043] In the drawings:
[0044] FIG. 1 is a perspective view of one embodiment of the
intervertebral prosthesis of the invention;
[0045] FIG. 2 is a top view of the embodiment of the intervertebral
prosthesis of the invention shown in FIG. 1;
[0046] FIG. 3 is a top view of the embodiment of the intervertebral
prosthesis of the invention shown in FIG. 1 similar to FIG. 2 yet
with different angles .alpha., different distances A and a point of
intersection S dislocated along the sagittal axis 10.
[0047] The embodiment shown in FIG. 1 comprises essentially an
intervertebral prosthesis 1 which consists of two prosthetic
components 2;3 having rectangular apposition surfaces 4;5. Said two
prosthetic components 2;3, which have a length H and a width B, are
releasably connected with each other by means of a joint 14. The
joint 14 consists of a calotte 9 and a corresponding recess 11. In
this embodiment, the radius of the calotte 9 is greater than the
width B of the prosthetic component 3 but smaller than the length H
of said prosthetic component 3, the length H being four to five
times longer than the width B. This design feature leads to
different overall inclinations of the longitudinal axes
L.sub.1;L.sub.2 of the two prosthetic components 2;3 relative to
each other, depending on the magnitude of the angle .alpha.
(.alpha.=the angle between the longitudinal axes L.sub.1;L.sub.2 in
a plane extending orthogonally to the central axis 6). The optimal
articular function is achieved at an angle .alpha. of 90 degrees.
With said angle .alpha. being 90 degrees, the angle of inclination
is twice as great as with an angle .alpha. of 0 degrees.
[0048] The embodiment shown in FIG. 2 comprises a first and a
second prosthetic component 2;3, which are longitudinal members
having longitudinal axes L.sub.1 and L.sub.2, and a sagittal axis
10. The longitudinal axes L.sub.1;L.sub.2 of the two prosthetic
components 2;3 have a point of intersection S and form an angle
.alpha.. The distance A between the entrance points E, which are
disposed symmetrically with respect to the sagittal axis 10 and
which mark the points of insertion of the two prosthetic components
2;3 into the intervertebral space, and the point of intersection S
varies for different angles .alpha. formed by the longitudinal axes
L.sub.1 and L.sub.2 (FIGS. 3 and 4).
[0049] The two cross-sections shown in FIGS. 3 and 4 each comprise
two prosthetic components 2 and 3 with their respective
longitudinal axes L.sub.1 and L.sub.2. Due to the different angles
.alpha. caused by the modification of the positions of the
longitudinal axes L.sub.1 and L.sub.2 relative to each other, the
point of intersection S is displaced along the sagittal axis 10,
whereas the positions of the entrance points E remain unchanged as
the distance A increases. According to the appreciation given in
specialised literature, the variant shown in FIG. 3 having a point
of intersection S disposed dorsally with respect to the center of
the end plates of the vertebral bodies is advantageous as compared
to the variant shown in FIG. 4 having a point of intersection S
disposed frontally with respect to the center of the end
plates.
Description of the Surgical Method:
[0050] In the following the surgical method permitting the
implantation of an intervertebral prosthesis 1 will be described
with reference to FIG. 2:
[0051] a) Prior to the implantation, the intervertebral disk is
prepared as required by the size of the prosthetic components 2;3.
Instead of removing the entire intervertebral disk, it is only
necessary to clear two paths which are large enough so that the two
apposition surfaces 4;5 of the intervertebral prosthesis 1 may be
in direct contact with the cover plates of the vertebral bodies. To
this effect, the intervertebral space (intervertebral disk) is
removed only to such an extent that the entire application surfaces
of the two prosthetic components have bone contact with their
respective end plate. The rest of the intervertebral disk remains
in situ and prevents the intervertebral prosthesis from migrating
laterally once the two prosthetic components 2;3 have been
implanted.
[0052] b) Subsequent to the preparation of the two implantation
canals in the intervertebral disk the implantation of the two
prosthetic components 2;3 is performed via the two postero/lateral
accesses 12;13. It is preferred to first implant one prosthetic
component 2;3, whereupon the implantation of the other prosthetic
component 2;3 is carried out. As soon as the two corresponding
articulation centers (calotte 9-recess 11) are located in the point
of intersection S of the two longitudinal axes L.sub.1 and L.sub.2,
the two prosthetic components 2;3 may be connected with each other
by means of the joint 14 which is composed by the calotte 9 and the
recess 11. Due to the intervertebral disk portions remaining
laterally of the two prosthetic components 2;3 and the coupling of
the calotte 9 with the recess 11, the intervertebral prosthesis 1
is securely lodged in the intervertebral space. The center of
rotation is located in the central sagittal plane and may vary
anteriorly or posteriorly, the central sagittal plane being the
plane extending antero-posteriorly through the patient's body and
intersecting said body centrally.
[0053] For the implantation, two transforaminal or extraforaminal
accesses 12;13 may be used, which are known and established in
vertebral column surgery. Once the coupling has been effected, the
two prosthetic components 2;3 form a unit which admits inclinations
of the end plates of adjacent vertebral bodies relative to each
other.
[0054] Due to the posterior implantation technique of the
intervertebral prosthesis 1, the ventral ligament structures of the
vertebral column remain intact and are not impaired in their
function of stabilising the vertebral column. In addition, the
intact ventral ligament structure reduces the risk of a ventral
migration of the intervertebral prosthesis 1 and of endangering
ventral structures in the region of the vertebral column. The same
technique of surgical treatment may also be applied anteriorly, in
particular in the higher lumbar and thoracolumbar regions.
Anatomical circumstances preclude a strictly anterior insertion, as
the access is obstructed by the aorta and the vena cava. Also in
this case, the ventral structures of the fibrous ring as well as
the anterior longitudinal ligament remain intact.
* * * * *