U.S. patent application number 11/722908 was filed with the patent office on 2008-05-22 for method and a device for total spinal disc replacement.
Invention is credited to Andreas Appenzeller, Roger Buerki, Gregor Feigenwinter, Robert Frigg, Beat Lechmann, Paul W. Pavlov.
Application Number | 20080119932 11/722908 |
Document ID | / |
Family ID | 35998566 |
Filed Date | 2008-05-22 |
United States Patent
Application |
20080119932 |
Kind Code |
A1 |
Lechmann; Beat ; et
al. |
May 22, 2008 |
Method and a Device for Total Spinal Disc Replacement
Abstract
A method for total replacement of an affected intervertebral
disc through a dorsal approach comprising the steps of removing the
disc material of the affected intervertebral disc (3) and inserting
an intervertebral prosthesis (30) into the intervertebral disc
space via an extraforaminal path (23). An intervertebral prosthesis
(100), in particular an intervertebral disk prosthesis comprising
A) a first prosthetic component (101) having a first apposition
surface (107) disposed transversely to the central axis (103) B) a
second prosthetic component (102) having a second apposition
surface (108) disposed transversely to the central axis (103);
whereby C) said first and second prosthetic components (101;102)
are connected by means of an articulation (106); whereby D) when
viewed parallel to said central axis (103) said first and second
prosthetic components (101;102) have an elongated shape with a
major axis (127) and a transverse minor axis (128); E) said central
axis (103), major axis (127) and transverse minor axis (128)
intersecting each other and said central axis (103) and transverse
minor axis (128) defining a middle plane (126); F) said first and
second prosthetic component (101;102) have a cross-sectional area
orthogonal to said central axis (103) which is essentially oval or
elliptical; whereby G) said cross-sectional area comprises at least
two concavities (125;130) lying on different sides of said middle
plane (126) and on the same side of said major axis (127).
Inventors: |
Lechmann; Beat; (Grenchen,
CH) ; Frigg; Robert; (Bettlach, CH) ; Pavlov;
Paul W.; (Njimegen, NL) ; Buerki; Roger;
(Balsthal, CH) ; Feigenwinter; Gregor;
(Lampenberg, CH) ; Appenzeller; Andreas; (Biel,
CH) |
Correspondence
Address: |
STROOCK & STROOCK & LAVAN LLP
180 MAIDEN LANE
NEW YORK
NY
10038
US
|
Family ID: |
35998566 |
Appl. No.: |
11/722908 |
Filed: |
December 27, 2005 |
PCT Filed: |
December 27, 2005 |
PCT NO: |
PCT/CH05/00776 |
371 Date: |
June 27, 2007 |
Current U.S.
Class: |
623/17.11 |
Current CPC
Class: |
A61F 2/4425 20130101;
A61F 2002/30092 20130101; A61F 2002/30133 20130101; A61F 2310/00023
20130101; A61F 2002/30331 20130101; A61F 2002/443 20130101; A61F
2310/00179 20130101; A61F 2002/30601 20130101; A61F 2002/30125
20130101; A61F 2230/0008 20130101; A61F 2/4611 20130101; A61F
2210/0014 20130101; A61F 2002/30616 20130101; A61F 2002/4627
20130101; A61F 2220/0033 20130101; A61F 2310/00748 20130101; A61F
2230/0015 20130101; A61F 2310/00029 20130101; A61F 2002/30649
20130101; A61F 2310/0058 20130101; A61F 2002/30841 20130101 |
Class at
Publication: |
623/17.11 |
International
Class: |
A61F 2/44 20060101
A61F002/44 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 28, 2004 |
CH |
2160/04 |
Claims
1-15. (canceled)
16. An intervertebral prosthesis comprising; a first prosthetic
component having a first surface disposed transversely to a central
axis for contacting the end plate of a first adjoining vertebral
body and further comprising a first cross-sectional area which is
orthogonal to a central axis and elliptical in shape; a second
prosthetic component having a second surface disposed transversely
to the central axis for contacting the end plate of a second
adjoining vertebral body and further comprising a second
cross-sectional area which is orthogonal to the central axis and
elliptical in shape; wherein: said first and second prosthetic
components are connected by means of an articulation; wherein said
first and said second prosthetic components each have an elongated
shape with a major axis and a transverse minor axis when viewed
parallel to the central axis; and said central axis, major axis and
transverse minor axis intersect each other and said central axis
and said transverse minor axis defining a middle plane; whereby
said first and second cross-sectional areas comprise at least two
concavities on different sides of said middle plane and on the same
side of said major axis.
17. The intervertebral prosthesis as claimed in claim 1, wherein
said first cross-sectional area and said second cross-sectional
area are kidney shaped with an enlargement arranged essentially
symmetrical to said middle plane.
18. The intervertebral prosthesis as claimed in claim 1, wherein
said at least two concavities have an essentially semi-elliptical
or semi-oval shape.
19. The intervertebral prosthesis as claimed in claim 1, wherein
said at least two concavities are disposed essentially symmetrical
to said middle plane.
20. The intervertebral prosthesis as claimed in claim 1, wherein
said first and second prosthetic component has a length measured
parallel to said major axis and wherein each of said at least two
concavities has a width measured parallel to said major axis, said
width amounting to between fifteen percent and thirty-five percent
of said length.
21. The intervertebral prosthesis as claimed in claim 1, wherein
said first and second prosthetic component has a maximum width
measured parallel to said transverse minor axis and wherein each of
said at least two concavities has a depth measured parallel to said
transverse minor axis, said depth amounting to between three
percent and twenty-five percent of said maximum width.
22. The intervertebral prosthesis as claimed in claim 1, wherein
said first cross-sectional area and said second cross-sectional
area have an essentially elliptical periphery with a smaller radius
of curvature at the first subsidiary vertex than at the second
subsidiary vertex of said periphery.
23. The intervertebral prosthesis as claimed in claim 1, wherein
said first subsidiary vertex is on the same side of said major axis
as said at least two concavities.
24. The intervertebral prosthesis as claimed in claim 1, wherein
said first and second prosthetic components have a length measured
parallel to said major axis and a maximum width measured parallel
to said transverse minor axis, wherein the ratio of the length to
the maximum width is between 3:1 and 5:1.
25. An intervertebral prosthesis comprising: a first prosthetic
component having a first surface disposed transversely to a central
axis for contacting the end plate of a first adjoining vertebral
body and further comprising a first cross-sectional area which is
orthogonal to a central axis and elliptical in shape; a second
prosthetic component having a second surface disposed transversely
to the central axis for contacting the end plate of a second
adjoining vertebral body and further comprising a second
cross-sectional area which is orthogonal to the central axis and
elliptical in shape; wherein: said first and second prosthetic
components are connected by means of an articulation wherein said
articulation is configured as a ball-and-socket joint comprising: a
spherical cap connected to one of the first and second prosthetic
components and a spherical recess congruent to said spherical cap
in the other of said first and second prosthetic components.
26. The intervertebral prosthesis as claimed in claim 10, wherein
one of the first and second prosthetic components and the spherical
cap consist of a single piece.
27. The intervertebral prosthesis as claimed in claim 10, wherein
said intervertebral prosthesis comprises at least three pieces with
the spherical cap being the third piece attachable to one of said
first and second prosthetic components.
28. The intervertebral prosthesis as claimed in claim 12, wherein
said intervertebral prosthesis further comprises an articular shell
including a recess which is attachable to one of said first and
second prosthetic components as the third piece.
29. The intervertebral prosthesis as claimed in claim 13, wherein
the spherical cap and the articular shell consist of a material
comprising metal and plastic.
30. The intervertebral prosthesis as claimed in claim 13, wherein
the spherical cap and the articular shell consist of a
ceramic-to-ceramic material pairing.
31. The intervertebral prosthesis as claimed in claim 13, wherein
the surfaces of the spherical cap and of the recess are coated with
titanium carbide or with amorphous carbon.
32. The intervertebral prosthesis as claimed in claim 10, wherein
at least the spherical cap is made of a memory metal.
33. The intervertebral prosthesis as claimed in claim 10, wherein
at least the spherical cap is made of a material capable of
swelling.
34. The intervertebral prosthesis as claimed in any one of the
claims 10, wherein at least the spherical cap is made of a
flowable, thermosetting material.
35. The intervertebral prosthesis as claimed in claim 10, wherein
at least the spherical cap is made of a monomer, comonomer,
homopolymer, oligomer, or mixtures which contains a thermosetting,
flowable substance.
36. The intervertebral prosthesis as claimed in claim 20, wherein
the thermosetting, flowable substance is selected from the group
of: a) polyethylene glycols; b) n-vinylpyrrolidones; c) vinyls; and
d) styrenes.
37. The intervertebral prosthesis as claimed in claim 1 wherein
said first prosthetic component is selected from a first group of
at least two first prosthetic components.
38. The intervertebral prosthesis as claimed in claim 1, wherein
said second prosthetic component is selected from a second group of
at least two second prosthetic components.
39. The intervertebral prosthesis as claimed in claim 1, wherein
said first and second prosthetic component each comprise an
intermediate surface, said first and second intermediate surfaces
facing each other and at least the first intermediate surface being
provided with at least one cavity with an undercut being located at
a first lateral end of said first and second prosthetic components
and being capable of accepting an anchoring member of an implant
holder.
40. (canceled)
Description
[0001] Today the state of the art concerning total spinal disc
replacement device insertion is the anterior approach, i.e. true
anterior, anterolateral (oblique) or true lateral. The surgeon
decides between transperitoneal or retroperitoneal approaches,
depending on the treated level or his personal experience. However,
due to the presence of major vessels (e.g. aorta, vena cava) the
anterior approach to the spine is often performed in the presence
of vascular surgeons thereby causing extra costs.
[0002] In U.S. Pat. No. 6,719,794 GERBER a method for insertion of
an intervertebral fusion implant is disclosed. The removal of the
affected spinal disc as well as the insertion of the implant is
performed via a posterior approach offset from the midline of the
spine to the affected intervertebral disc. Disadvantageously, such
a transforaminal approach includes a partial dissection of the
facet joint.
[0003] A prosthetic device for transforaminal insertion into an
intervertebral space is known from US 2004/0225365 EISERMANN. This
known prosthesis comprises two components having an articulating
surface each in order to permit articulating motion between the
first and second components and consequently of the adjoining
vertebrae. The transforaminal path disclosed might cause potential
damage to important anatomical structures such as nerve roots,
dura, ligamentum flavum and interspinous ligaments.
[0004] Therefore, it is an object of the present invention to
provide a method for total spinal disc replacement device insertion
including a dorsal approach to the spine without having to dissect
the facet joint neither completely nor partially.
[0005] According to the method of the present invention the above
object is achieved by means of an extraforaminal approach including
an access portal in the Fibrocartilago Intervertebralis between the
anterior and posterior longitudinal ligaments for removing the
affected intervertebral disc as well as for insertion of a total
disc prosthesis.
[0006] The method according to the invention offers the following
specific advantages: [0007] A wide opening to the intervertebral
space compared to true posterior or transforaminal approaches is
achievable; [0008] The surgeon passes the neural structures and
does not have to dissect the facet joint; [0009] The detection of
the correct trajectory can be made with a visualisation of the
Processus Transversus; [0010] The patient is in prone position as
he would be for dorsal fixation procedures; and [0011] The surgeon
is used to patient positioning and incisions.
[0012] In a preferred embodiment the key element of the
extraforaminal approach to the spinal disc is a path in front of
the transverse processes (Processus Transversus).
[0013] In a further embodiment the method further comprises the
steps of:
A) Performing a dorsal incision extra-medially, i.e. apart from the
median longitudinal plane by targeting the Fascia
Lumbodorsalis;
B) Approaching the affected intervertebral disc with a Kirschner
wire;
C) Inserting along the Kirschner wire a trocar and a protection
sleeve to the affected intervertebral disc;
D) Cutting out an access portal of a width W and an area A into the
Fibrocartilago Intervertebralis with a cutting instrument;
E) Removing the disc material with a surgical device;
F) Cleaning the endplates of the adjacent upper and lower vertebral
body with a surgical device;
G) Opening or enlarging of the intervertebral space by using a
distractor;
H) Inserting an intervertebral prosthesis through the access portal
by means of an implant holder.
[0014] In another embodiment the disc material is removed with a
surgical device through a protection sleeve. This permits the
advantage that the use of a protection sleeve during removing the
disc material allows a better protection of the surrounding soft
tissue.
[0015] In a further embodiment the access portal is cut at a
distance X>0 apart from the anterior longitudinal ligament and
the posterior longitudinal ligament, therewith permitting the
advantage that the anterior longitudinal ligament and the posterior
longitudinal ligament remain intact in order to stabilize the
treated segment of the vertebra.
[0016] In still another embodiment the distance X amounts between 2
mm and 38 mm.
[0017] In a further embodiment the width W of the access portal is
between 8 mm and 36 mm.
[0018] In still a further embodiment the area A of the access
portal is between 24 mm.sup.2 and 684 mm.sup.2 and the height is
preferably between 3 and 19 mm.
[0019] In another embodiment the step of distracting of the
vertebral bodies adjoining the disc space to be treated is
performed through the protection sleeve.
[0020] In a further embodiment the distraction of the vertebral
bodies adjoining the disc space to be treated is performed by
slightly bending a distractor in order to keep the view to the
situs free for the surgeon.
[0021] In yet a further embodiment the total disc replacement
procedure is performed without dissecting the facet joints.
[0022] In another embodiment the total disc replacement procedure
is performed without dissecting the transverse processes.
[0023] In a further embodiment the access to the intervertebral
space to be treated is essentially straight. This allows the
advantage that due to the almost straight access the use of
essentially straight instruments e.g. for cleaning the endplates of
the adjacent vertebral bodies or other surgical actions is
possible.
[0024] In another embodiment the incision is reduced to a tube.
[0025] In a further embodiment the risk of damaging the neural
structures is reduced by means of passing (not approaching) the
spinal cord and locating, mobilising and marking the nerve
root.
[0026] It is a further object of the invention to provide an
intervertebral prosthesis having a contour when viewed orthogonally
to its central axis which has a minimal width but still an adequate
articulation area.
[0027] According to the invention the above object is achieved
through an intervertebral prosthesis which essentially comprises a
first and a second prosthetic component each having an apposition
surface disposed transversely to the central axis and apt for
contacting the end plate of an adjoining vertebral body each.
Furthermore, said first and second prosthetic components are
connected by means of an articulation. When viewed parallel to said
central axis said first and second prosthetic components have an
elongated shape with a major axis and a transverse minor axis,
whereby said central axis, major axis and transverse minor axis
intersect each other and said central axis and transverse minor
axis defining a middle plane. Said first and second prosthetic
component have a cross-sectional area orthogonal to said central
axis which is essentially oval or elliptical and said
cross-sectional area comprises at least a first and a second
concavity lying on different side of the middle plane and on the
same side of the major axis.
[0028] The intervertebral prosthesis according to the invention
offers the following specific advantages: [0029] the first and
second prosthetic components have a small width at their portions
towards their lateral ends but still an adequate width adjacent the
middle plane where the articulation is located, said small width
allowing an implantation by means of an extraforaminal access and
said adequate width adjacent the middle plane allowing the
configuration of an articulation adapted to the natural
intervertebral disc; [0030] un-necessary material on the first and
second prosthetic components (bone contact plates) is removed in
order to give special attention to the fact that the bony endplates
of the vertebral bodies change their shape at the location where
the prosthesis is situated during their degeneration, i.e. they
become more undulated over time; and [0031] possible osteophytes on
the posterior periphery of the vertebral endplates which the
surgeon decides not to remove are taken into consideration, i.e.
the intervertebral prosthesis can be positioned easier because the
prosthesis can be manipulated around the undulations.
[0032] In a preferred embodiment of the intervertebral prosthesis
said cross-sectional area of said first and second prosthetic
component is kidney shaped with an enlargement arranged essentially
symmetrical to said the middle plane.
[0033] In a further embodiment said at least two concavities have
an essentially semi-elliptical or semi-oval shape.
[0034] In another embodiment said at least two convavities are
disposed essentially symmetrical to said middle plane.
[0035] In still another embodiment said first and second prosthetic
component have a length H measured parallel to said major axis and
wherein each of said at least two concavities has a width W
measured parallel to said major axis, said width W amounting to
between 15% and 35% of said length H.
[0036] In yet another embodiment said first and second prosthetic
component have a maximum width B measured parallel to said
transverse minor axis and wherein each of said at least two
concavities has a depth T measured parallel to said transverse
minor axis, said depth T amounting to between 5% and 25% of said
maximum width B.
[0037] In a further embodiment said cross-sectional area of said
first and second prosthetic components has an essentially
elliptical periphery with a smaller radius of curvature at the
first subsidiary vertex than at the second subsidiary vertex of
said periphery.
[0038] In another embodiment said first subsidiary vertex is on the
same side of said major axis as said at least two concavities.
[0039] In a further embodiment, the ratio of the length H of the
prosthetic components to the width B thereof is between 3:1 and
5:1. The advantage of this design essentially is that in order to
implant the two prosthetic components in the intervertebral space
(intervertebral disk) it is only necessary to clear a narrow access
path such permitting an extraforaminal approach.
[0040] In yet a further embodiment said articulation is configured
as a ball-and-socket joint comprising a spherical cap connected to
one of the first and second prosthetic components and congruent to
said spherical cap a spherical recess in the other of said first
and second prosthetic components.
[0041] In another embodiment, the intervertebral prosthesis is
realised in two pieces, i.e. the spherical cap is made in one piece
with one of the two prosthetic components.
[0042] In a further embodiment, the intervertebral prosthesis is
realised in three pieces, so that the spherical cap 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 spherical cap may be realised 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 spherical cap highly
crosslinked polyethylene (X-UHMWPE), an alloy of cobalt and chrome,
or a ceramic material.
[0043] 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 spherical cap may be
realised using different materials, so that it is possible to
achieve optimal sliding properties for the articular surfaces.
[0044] In a further embodiment, the spherical cap 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.
[0045] In yet another embodiment a ceramic-to-ceramic articulation
is used. In a further embodiment the surfaces of the spherical cap
and the recess are coated with titanium carbide or with amorphous
carbon (ADLC) therewith permitting a substantial reduction of the
coefficient of friction.
[0046] In another embodiment, at least the spherical cap is made of
a memory metal or of a material capable of swelling (e.g.
hydrogels). In still another embodiment at least the spherical cap
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:
a) polyethylene glycols, preferably polyethylene
glycol(di)-acrylates; b) n-vinylpyrrolidones; and c) vinyls,
preferably vinyl alcohols; and d) styrenes.
[0047] The polymers thus obtained may be widely varied as regards
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.
[0048] 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 centre of the respective radii, i.e. the
center of rotation. By means of this embodiment the following
advantages may be achieved: [0049] the position of the centre of
rotation is adjustable in height as the two component parts may be
arranged in a modular manner; [0050] the components which may also
vary in the radius of the spherical cap, which makes it possible to
adjust the centre of rotation of the intervertebral prosthesis;
[0051] the position of the centre 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; [0052] the prosthetic components may also
take into account the articulation requirements of the motion
segment in that it is possible to include spherical caps having
different radiuses. Greater spherical cap 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; [0053] the
heights of the prosthetic components and the corresponding radiuses
of the articulating spherical cap of the intervertebral prosthesis
may vary and are thus adaptable to the dimensions of different
intervertebral spaces.
[0054] In yet a further embodiment said first and second prosthetic
component each comprise an intermediate surface, said first and
second intermediate surfaces facing each other. At least the first
or second intermediate surface is provided with at least one cavity
with an undercut being located at the first or/and second lateral
end of said first and second prosthetic components, said cavity
with an undercut being apt for acceptance of an anchoring member of
an implant holder.
[0055] The implant holder according to the invention is provided
with a sleeve and an anchoring member, e.g. a hook member being
insertable into the cavity and undercut and being displaceably
disposed in the central bore of the sleeve, said implant holder
further having a front end being provided with a fore-part which is
adapted to the lateral ends of the first and/or second prosthetic
component of an intervertebral prosthesis according to invention.
Furthermore, the implant holder is provided with a fastening
mechanism permitting to pull the anchoring member towards the
sleeve such pressing the lateral end of the intervertebral
prosthesis against the fore-part.
[0056] Further objects and advantages of the invention will become
apparent from the following description when read with reference to
the accompanying drawings which illustrate the method according to
the invention. In the drawings:
[0057] FIG. 1 is a cross-section through the spinal column
orthogonal to the longitudinal axis of the spinal column;
[0058] FIG. 2 is a plane view to the back of a patient in prone
position;
[0059] FIG. 3 is a plane view to the dorsal muscle configuration of
a patient;
[0060] FIG. 4 is a cross-section through the body of a patient
orthogonal to the longitudinal axis of the spinal column and seen
from cranial;
[0061] FIG. 5 is a perspective view to the lumbar part of the
spinal column whereby a Kirschner wire is inserted into the
affected spinal disc according to one step of an embodiment of the
method of the present invention;
[0062] FIG. 6 is a perspective view to the lumbar part of the
spinal column whereby a trockar and a protection sleeve are slid
over the Kirschner wire according to one step of an embodiment of
the method of the present invention;
[0063] FIG. 7 is a perspective view to the lumbar part of the
spinal column whereby a cutting device is slid through the
protection sleeve according to one step of an embodiment of the
method of the present invention;
[0064] FIG. 8 is a perspective view to the lumbar part of the
spinal column whereby an access portal is being cut into the
affected disc space;
[0065] FIG. 9 is a perspective view to the lumbar part of the
spinal column together with a distractor according to one step of
an embodiment of the method of the present invention;
[0066] FIG. 10 is a perspective view to the lumbar part of the
spinal column together with an intervertebral prosthesis and an
implant holder according to one step of an embodiment of the method
of the present invention;
[0067] FIG. 11 is a lateral view to the portion of the spinal
column together with the inserted intervertebral prosthesis;
[0068] FIG. 12 is a view from anterior to the portion of the spinal
column together with the inserted intervertebral prosthesis;
[0069] FIG. 13 is a top view of an embodiment of the intervertebral
prosthesis according to the invention;
[0070] FIG. 14 is a front view of the embodiment of FIG. 13;
[0071] FIG. 15 is a lateral view of the embodiment of FIGS. 13 and
14;
[0072] FIG. 16 is a perspective view of the second prosthetic
component of the embodiment of FIGS. 13-15;
[0073] FIG. 17 is a cross-section along the major axis of the
second prosthetic component of FIG. 16;
[0074] FIG. 18 is a magnified view of one lateral end of the second
prosthetic component of FIGS. 16 and 17;
[0075] FIG. 19 is a perspective view of the second prosthetic
component of FIGS. 16-18 together with the leading end of an
embodiment of the implant holder according to the invention;
and
[0076] FIG. 20 is a perspective view of the second prosthetic
component of FIGS. 16-18 together with a portion of the sleeve of
an embodiment of the implant holder according to the invention.
[0077] Description of the preferred method for replacement of a
spinal disc through an extraforaminal approach according to the
invention: [0078] 1. Performing a dorsal incision 12 approximately
7 cm extra-medial, i.e. apart from the median longitudinal plane 2
whereby the Fascia Lumbodorsalis is targeted in order to minimize
the muscular destruction (FIG. 3); [0079] 2. Approaching the
affected intervertebral disc 3 with a Kirschner wire 14 in an
extraforaminal path 23 in front of the processus transversus 6
whereby the use of X-ray control, e.g. an image intensifier is
mandatory (FIG. 5); [0080] 3. Inserting along the Kirschner wire 14
a trockar 15 and a protection sleeve 16 to the affected
intervertebral disc 3 passing the Processus Costalis 17 (FIG. 6);
[0081] 4. Cutting an access portal 9 of a width W and a height H
(FIG. 8) into the Fibrocartilago intervertebralis 18 apart from the
anterior longitudinal ligament 5 (FIG. 1) and the posterior
longitudinal ligament 4 (FIG. 1) with a cutting instrument 19 (FIG.
7); [0082] 5. Removing the disc material with curettes, rongeurs,
spoons lead through the protection sleeve 16, preferably with use
of an endoscope; [0083] 6. Cleaning the endplates of the adjacent
upper and lower vertebral body 10;11, particularly by use of
specific instruments like water jet or ultrasonic devices,
preferably with use of an endoscope; [0084] 7. Removing the
affected intervertebral disc 3 by slightly bending a distractor 20
in order to keep the view to the situs free for the surgeon,
whereby the distraction is performed through the protection sleeve
16 (FIG. 6) or a soft tissue retractor (FIG. 9); [0085] 8.
Inserting the intervertebral prosthesis 30 through the access
portal 9 by means of an implant holder 22 whereby the use of X-ray
control, e.g. an image intensifier in order to control the position
of the intervertebral prosthesis 30 is mandatory (FIG. 10).
[0086] A detailed description of an extraforaminal approach to
vertebral bodies in case of posterolateral fusion of vertebrae,
e.g. by securing bone grafts to the pedicles or transverse
processes by means of bone screws can be found in:
Watkins Melvin B.
"Posterolateral fusion of the lumbar and lumbosacral spine"
J Bone Joint Surg Am. 1953 October; 35-A(4):1014-8
Watkins Melvin B.
"Posterolateral fusion in pseudoarthrosis and posterior element
defects of the lumbosacral spine"
Clin Orthop Relat Res. 1964 July-August; 35:80-5.
[0087] FIGS. 11 and 12 illustrate the situation after completion of
the surgical process, i.e. an intervertebral prosthesis 30 has been
inserted between the two vertebral bodies 10;11. The intervertebral
prosthesis 30 shown comprises an upper and a lower apposition
member 24;25 the outer surfaces of which abut the end plates of the
vertebral bodies 10; 11. Furthermore, the intervertebral prosthesis
30 comprises an articulation 26 jointedly connecting the upper and
lower apposition member 24;25 such allowing articulating motion
between the two apposition members 24;25 and consequently of the
two adjoining vertebrae 10;11.
[0088] FIGS. 13-15 illustrate an embodiment of the intervertebral
prosthesis 100 comprising a first prosthetic component 101, a
second prosthetic component 102 and an articulation 106
articulatedly connecting said first and second prosthetic component
101;102. Opposite said articulation 106 the first and second
prosthetic component 101;102 comprise a first apposition surface
107, respectively a second apposition surface 108, whereby said
first apposition surface 107 is configured for abutting the base
plate of a first intervertebral body 10 contacting the
intervertebral prosthesis 100 on top and said second apposition
surface 108 is configured for abutting the cover plate of a second
intervertebral body 11 contacting the intervertebral prosthesis 100
at the bottom. The articulation 106 is configured as a
ball-and-socket joint, said ball-and-socket joint comprising a
spherical cap 112 at the second prosthetic component 102 and
congruent to said spherical cap 112 a spherical recess 111 in the
first prosthetic component 101.
[0089] Each of the first and second apposition surfaces 108;109 is
disposed transversely to the central axis 103. When viewed parallel
to said central axis 103 said first and second prosthetic
components 101;102 have an elongated shape with a major axis 127
and a transverse minor axis 128, whereby said central axis 103,
major axis 127 and transverse minor axis 128 intersect each other.
Said central axis 103 and said transverse minor axis 128 further
define a middle plane 126. Furthermore, said first and second
prosthetic component 101;102 have a cross-sectional area orthogonal
to said central axis 103 which is essentially elliptical and
comprises two concavities 125 lying on different sides of said
middle plane 126 and on the same side of said major axis 127.
[0090] The two concavities 125 are disposed symmetrically to said
middle plane 126 such that one of said two concavities 125 is
arranged in a first quadrant of a circle the centre of which
coincides with the point of intersection of the major axis 127, the
transverse minor axis 128 and the central axis 103 and the
circumference of which is tangent to the periphery 129 of said
cross-sectional area at the principal vertices. The second of said
two concavities 125 is arranged in a clockwise succeeding, second
quadrant of said circle. Furthermore, the two concavities 125 have
an essentially semi-elliptical shape and have a depth T measured
parallel to said transverse minor axis 128 amounting to about 5% of
the maximum width B of said first and second prosthetic components
101;102.
[0091] The first and second prosthetic component 101;102 each
comprise an intermediate surface 109; 110, said first and second
intermediate surfaces 109; 110 facing each other. As shown in FIGS.
16-18 the second intermediate surface 110 is provided with two
cavities 131 with an undercut 132 being located at the first and
second lateral end 133;134 of said first and second prosthetic
components 101;102 whereby said cavities 131 with undercut 132 are
apt for acceptance of an anchoring member 141 of an implant holder
22 (FIG. 19,20) whereby the surgeon may select the respective
cavity 133 in case of approaching the intervertebral space from the
left or from the right side.
[0092] FIGS. 19 and 20 illustrate an embodiment of the implant
holder 22 which is provided with a sleeve 140 and an anchoring
member 141, with a hook member at the front end. The anchoring
member 141 may be inserted into the cavity 131 and undercut 132 and
is displaceably disposed in the central bore of the sleeve 140. The
implant holder 22 further has a front end 142 being provided with a
fore-part 143 which is adapted to the lateral ends 133,134 (FIG.
16) of the first and/or second prosthetic component 101,102.
Furthermore, the implant holder 22 is provided with a fastening
mechanism (not shown) permitting to pull the anchoring member 141
into the sleeve 140 such pressing the lateral end 133 of the
intervertebral prosthesis against the fore-part 143. The sleeve 140
is curved in order to permit an insertion of the intervertebral
prosthesis 100 along an extraforaminal path.
* * * * *