U.S. patent application number 10/619180 was filed with the patent office on 2005-01-20 for insertion instrument for cervical prostheses.
This patent application is currently assigned to Cervitech, Inc.. Invention is credited to Keller, Arnold.
Application Number | 20050015095 10/619180 |
Document ID | / |
Family ID | 34062520 |
Filed Date | 2005-01-20 |
United States Patent
Application |
20050015095 |
Kind Code |
A1 |
Keller, Arnold |
January 20, 2005 |
Insertion instrument for cervical prostheses
Abstract
Insertion instrument for a multi-part intervertebral
endoprosthesis (9) which comprises two closure plates (91, 92) and
a sliding core (93) arranged between these, said insertion
instrument having a handgrip part (21, 31), gripping members which
hold the closure plates between them, and a force-receiving part
for applying an insertion force to the intervertebral
endoprosthesis (9), the gripping members being guided movably
toward and away from one another via a hinge (4) and being able to
be tensioned against the intervertebral endoprosthesis (9),
projections (51, 52) pointing in the tensioning direction (12) or
recesses for holding the intervertebral endoprosthesis (9) with
form-fit being provided on the gripping members, and a block (61)
guided in the longitudinal axis direction (10) and with an abutment
surface (62) being provided which can be moved by means of an
actuating device (7) so as to bear on the intervertebral
endoprosthesis (9) and, in its forward position, secures the
intervertebral endoprosthesis (9) against the projections (51 52)
or recesses.
Inventors: |
Keller, Arnold; (Kayhude,
DE) |
Correspondence
Address: |
Barry E. Bretschneider
Morrison & Foerster LLP
Suite 300
1650 Tysons Boulevard
McLean
VA
22101
US
|
Assignee: |
Cervitech, Inc.
Rockaway
NJ
|
Family ID: |
34062520 |
Appl. No.: |
10/619180 |
Filed: |
July 15, 2003 |
Current U.S.
Class: |
606/99 |
Current CPC
Class: |
A61F 2002/4628 20130101;
A61F 2/4603 20130101; A61F 2002/4622 20130101; A61F 2002/30616
20130101; A61F 2002/30904 20130101; A61F 2/4611 20130101; A61F
2002/443 20130101 |
Class at
Publication: |
606/099 |
International
Class: |
A61B 017/58 |
Claims
1. An insertion instrument for a multi-part intervertebral
endoprosthesis comprising: two closure plates and a sliding core
arranged between the closure plates, an insertion instrument
comprising a handgrip part, gripping members which hold the closure
plates between them a hinge, a force-receiving part for applying an
insertion force to the intervertebral endoprosthesis, projections
pointing in a tensioning direction or recesses for holding the
intervertebral endoprosthesis with a form-fit formed on the
gripping members, and a block guided in the longitudinal axis
direction and provided with an abutment surface (62) is provided
which configured to be movable by an actuating device so as to bear
on the intervertebral endoprosthesis and, in a forward position, so
as to secure the intervertebral endoprosthesis against the
projections or recesses, wherein the gripping members are
configured to be guided movably toward and away from one another
via the hinge and to be tensioned against the intervertebral
endoprosthesis.
2. The insertion instrument according to claim 1, wherein the
insertion instrument is designed as a forceps, whose jaw parts form
the gripping parts.
3. Insertion The insertion instrument according to claim 1 or 2,
wherein the actuating device is a rod with a handle arranged in the
rear area of the handgrip part.
4. The insertion instrument according to claim 3, wherein the rod
is provided with a screw thread and is guided in a counter thread
which is fixed on the instrument and arranged in the hinge.
5. The insertion instrument according to claim 2, wherein the
actuating device is guided through the hinge.
6. The insertion instrument according to claim 1 or 2, wherein the
handle is designed as a strike head.
7. The insertion instrument according to claim 1 or 2, further
comprising a locking device provided for securing the handgrip
parts in the position when pressed together, the locking device
having a guide for the actuating device.
8. The insertion instrument according to claim 1 or 2, wherein the
projections are arranged on jaw inserts which are fastened
releasably on the jaw parts.
9. The insertion instrument according to claim 7, wherein the
actuating device is a rod with a handle arranged in the rear area
of the handgrip part.
10. The insertion instrument according to claim 8, wherein the
actuating device is a rod with a handle arranged in the rear area
of the handgrip part.
11. The insertion instrument according to claim 4, further
comprising a locking device provided for securing the handgrip
parts in the position when pressed together, the locking device
having a guide for the actuating device.
12. The insertion instrument according to claim 8, further
comprising a locking device provided for securing the handgrip
parts in the position when pressed together, the locking device
having a guide for the actuating device.
Description
[0001] The invention relates to an insertion instrument for a
multi-part intervertebral endoprosthesis which comprises two
closure plates and a sliding core arranged between these, said
insertion instrument having a handgrip part, gripping members which
hold the closure plates between them, and a force-receiving part
for applying an insertion force to the intervertebral
endoprosthesis.
[0002] For inserting intervertebral prostheses, an insertion
instrument is known (EP-A-1 306 064) which, at its front end, has
two prosthesis holders for receiving in each case a prosthesis
plate and which consist of two gripping members which are connected
rigidly to one another and which hold the plates between them by
friction. For very small implants, of the kind which are used in
the area of the cervical spine and which have to be positioned very
precisely, this may be too unreliable.
[0003] The object of the invention is to make available an improved
instrument for implantation of intervertebral prostheses which is
adapted in particular to the requirements of implantation in
confined conditions, as apply in particular in the area of the
cervical spine.
[0004] The solution according to the invention lies in an insertion
instrument with the features of claim 1. Advantageous developments
are the subject of the dependent claims.
[0005] In the case of an insertion instrument for a multi-part
intervertebral endoprosthesis, in particular a cervical prosthesis,
which comprises two closure plates and a sliding core arranged
between these, said insertion instrument having a handgrip part,
gripping members which hold the closure plates between them, and a
force-receiving part for applying an insertion force to the
intervertebral endoprosthesis, the invention provides that the
gripping members are guided movably toward and away from one
another via a hinge and are able to be tensioned against the
intervertebral endoprosthesis, projections pointing in the
tensioning direction or recesses for holding the intervertebral
endoprosthesis with a form-fit are formed on the gripping members,
and a block guided in the longitudinal axis direction and with an
abutment surface is provided which can be moved to the
intervertebral endoprosthesis by means of an actuating device and,
in its forward position, secures the intervertebral endoprosthesis
against the projections or recesses. When the forceps-like
insertion instrument is closed, the gripping members connected to
one another via a hinge move toward one another and engage with a
form-fit via their projections (or recesses) in corresponding
depressions (or elevations) of the intervertebral endoprosthesis
and thus tension the latter in a direction transverse to the
longitudinal axis of the insertion instrument. The longitudinally
movably guided block can be moved toward the intervertebral
endoprosthesis until its abutment surface bears on the
intervertebral endoprosthesis and secures the latter against the
projections (or recesses). In this way, the intervertebral
endoprosthesis is also tensioned in the longitudinal direction. It
is thus held by the insertion instrument in a manner free of play
and in a precise position. By virtue of the block bearing firmly on
the intervertebral endoprosthesis, considerable forces, such as
arise when striking the intervertebral endoprosthesis into place,
can also be safely transmitted. Since these considerable forces are
transmitted via the block and its abutment surface, the projections
(or recesses) do not have to take up these forces. They can be of
fairly small dimension and therefore made very fine, as is desired
for precise positioning, without having to take into consideration
the high force transmission when striking the intervertebral
endoprosthesis home. In addition, by bearing on the intervertebral
endoprosthesis, the block ensures that the latter does not
inadvertently turn and that its individual elements do not open. By
virtue of the invention, the intervertebral endoprosthesis can thus
be held easily, safely and with precise positioning on the
insertion instrument and inserted.
[0006] A number of terms are explained below:
[0007] The longitudinal axis of the forceps is understood as the
center line which is the angle bisector between the handgrip parts
of the forceps halves and the jaw parts of the forceps halves.
[0008] The tensioning direction is understood as the direction in
which the gripping members move toward one another. The opposite
direction is the spreading direction. These directions are
generally approximately transverse to the longitudinal axis of the
insertion instrument.
[0009] A form-fit hold is understood as meaning that the
projections engage in correspondingly shaped receiving openings of
the intervertebral endoprosthesis, or vice versa. Viewed in the
direction of the longitudinal axis, the projections grip into an
undercut.
[0010] The insertion instrument is preferably designed as a
forceps, whose jaw parts form the gripping members. This permits a
space-saving construction and easy handling, which is of advantage
particularly in the confined conditions in the area of the cervical
spine.
[0011] To make it simpler to use, the actuating device has a rod
with a handle arranged in the rear area of the handgrip part. This
allows the operating surgeon to use the actuating device without
awkward maneuvering. Because of the small space available in the
case of cervical prostheses, this is of particular importance when
removing the insertion instrument after introduction of the
intervertebral endoprosthesis, when the block has to be moved back.
For this purpose, the rod is expediently provided with a screw
thread and is guided in a counterthread which is fixed on the
instrument and arranged preferably in the hinge. Thus, by turning
in one direction, the block can be guided toward the intervertebral
endoprosthesis and thus secure it, whereas, by turning in the
opposite direction, the block is moved away and releases the
intervertebral endoprosthesis for the purpose of removal of the
insertion instrument. The screw device also has the advantage of
being self-locking, with the result that a separate securing device
for protection against inadvertent displacement is not necessary.
However, a screw device is not absolutely necessary, and, instead,
other preferably self-locking actuating devices can also be
provided.
[0012] In a particularly advantageous construction, the actuating
device is guided through the hinge. This is not only a particularly
space-saving design, it also guarantees a near-center arrangement.
This arrangement ensures that the insertion instrument does not
deviate to the side even under high forces when struck. A high
degree of positioning precision when inserting the intervertebral
endoprosthesis is achieved in this way.
[0013] It is expedient for the actuating device to have a strike
head at its handgrip end. In this way, via the actuating device and
the block, it is possible to act directly on the intervertebral
endoprosthesis so as to bring it to its implantation site. For this
purpose, it is expedient for the handle itself to be designed as a
strike head. This permits a space-saving construction, which is of
considerable value particularly in the confined conditions in the
area of the cervical spine.
[0014] In order to ensure that the insertion instrument does not
inadvertently spring open, even when acted upon by considerable
force, a locking device is expediently provided for securing the
handgrip parts in the position when pressed together, said locking
device having a guide for the actuating device. This ensures that
the actuating device does not deflect outward under high loads,
particularly when the strike head is arranged far to the rear. The
locking device can be provided at the rear end of the handgrip
parts in a manner known per se. It is important that it is
sufficiently strongly dimensioned to withstand the loads which
occur during striking but can nevertheless be easily released for
removing the instrument.
[0015] In an expedient embodiment, the projections or recesses are
arranged on jaw inserts which are fastened releasably on the jaw
parts. This means that, if necessary, it is easy to exchange the
jaw inserts together with the projections or recesses arranged
thereon, in order to adapt the insertion instrument to other types
or sizes of intervertebral endoprostheses.
[0016] The invention is explained below with reference to the
drawing in which an advantageous illustrative embodiment is shown,
and where:
[0017] FIG. 1 shows an overall view of the insertion instrument
according to the invention, seen from above, with an intervertebral
endoprosthesis;
[0018] FIG. 2 shows an overall view of the insertion instrument
according to the invention seen from below;
[0019] FIG. 3 shows an enlarged detail view of a jaw part of the
insertion instrument, in a longitudinal axis section;
[0020] FIG. 4 shows a detail view of the other jaw insert; and
[0021] FIG. 5 shows a detail view of the insertion instrument with
an intervertebral endoprosthesis arranged thereon.
[0022] The illustrative embodiment, shown in the figures, of an
insertion instrument according to the invention is a forceps,
labeled as a whole by reference number 1. It is used for inserting
cervical prostheses 9 into the intervertebral space of two adjacent
vertebral bodies of the cervical spine (not shown).
[0023] The forceps 1 is made up of two forceps halves 2, 3 which
are connected to one another movably via a pivot hinge 4. In their
rear area, the forceps halves 2, 3 have a respective handgrip part
21, 31 and in their front area they have a respective jaw part 22,
32. The pivot hinge 4 is arranged at the transition between the
handgrip parts 21, 31 and the jaw parts 22, 32. It is formed by a
pin 42 on the forceps half 2 (in FIG. 1 it extends upward from the
plane of the drawing), which pin 42 is mounted in a matching
opening 43 in the central area of the other forceps half 3. The
bearing pin 42 has a through-bore 44 which runs from the handgrip
area of the forceps halves 2, 3 to the jaw area. It will be
discussed in more detail later. The pivot hinge 4 allows the
handgrip parts 21, 31 of the forceps halves 2, 3 to be moved toward
one another so that the jaw parts 22, 32 close, and vice versa.
[0024] The jaw parts 22, 32 function as gripping members. In the
front area, on their mutually facing inner surfaces, they each have
two projections 51, 52 pointing in the tensioning direction 12.
These projections are not arranged directly on the jaw parts 22,
32, but instead on jaw inserts 53 which are secured exchangeably,
by means of a screw (not shown), in a corresponding recess on the
outer surfaces of the jaw parts 22, 32. Each jaw insert 53 has a
projection 51 and a projection 52. The projection 51 is formed like
a pin and is located in the upper area of the jaw insert 53, while
the projection 52 is formed like a small plate and is located in
the lower area of the jaw insert 53. The dimensions and arrangement
of the projections 51, 52 are adapted to corresponding receiving
openings on the cervical prostheses 9 to be received. This will be
explained in more detail later.
[0025] Arranged on the jaw part 22 there is a guide rail 60 which
holds a block 61 such that the latter is longitudinally
displaceable in the forward and rearward directions on the forceps
half 2. The guide rail 60 is designed as an elongate hole in the
jaw insert 53 of the jaw part 32. A grub screw arranged laterally
in the block 61 engages in the oblong hole forming the guide rail
60 and guides the block in the longitudinal direction. Instead of
the oblong hole, other guide elements can also be provided which
allow the block 61 to be guided in forward and rearward movement in
the longitudinal direction, for example a dovetail guide. At its
front end, the block 61 is provided with an abutment surface 62
designed to cooperate with the cervical prosthesis 9.
[0026] The block 61 is engaged by an actuating device 7 which
extends from the rear area of the block 61 via the through-bore 44
and into the area between the handgrip parts 21, 31. The actuating
device 7 comprises a coupling element 70 for connection to the
block 61, which, in the illustrative embodiment shown, is a
vertebra support suitable for transmitting shear forces, and it
moreover comprises a rod 71 and a handle 72 for actuation. Provided
in the front area of the rod 71 there is an external thread 73
which cooperates with a complementary internal thread (not shown)
in the through-bore 44 of the pin 42 as an instrument-fixed guide.
By turning the handle 72, it is thus possible for the rod 71, and
with it the block 61 via the coupling element 70, to be moved
backward and forward along the guide rail 60. The handle 72 is
designed as a rotatable knob which, on its outer circumference 74,
has a suitable surface finish, for example a coarse ribbing 75, to
allow the operating surgeon a good grip.
[0027] The rear end of the handle 72 is provided with a convex
bulge 76. It serves as a strike head for the actuating device 7.
Impulses acting on the bulge 76 of the strike head are transmitted
by this via the rod 71 of the actuating device 7, the
shear-resistant vertebral support 70 and the block 61, to the
latter's abutment surface 62.
[0028] A locking device 8 for the handgrip parts 21, 31 is provided
in the rear area of the forceps 1. This locking device 8 comprises
a pivotably movable catch element 83 and a locking pawl 84 (which
are arranged opposite one another on the handgrip parts 21, 31), a
release device 81, a base 82 and a spring 87. The rear end of the
handgrip part 21 is designed as a fork, the locking pawl 84 being
formed by a beveling of the base of the fork. The catch element 83
is mounted by the base 82 in the plane enclosed by the handgrip
parts 21, 31. The spring 87 is designed as a leaf spring and acts
on that end of the catch element 83 mounted in the base 82 in such
a way that it is pressed forward to the locking pawl 84. Starting
from the base 82, the catch element 83 has a wide area and a narrow
area. In its narrow area, the catch element 83 has, on its front
face, a toothing 86 into which, when the forceps 1 is closed, the
locking pawl 84 engages and is locked, so that the handgrip parts
21, 31 cannot move away from one another and, as a result, the
insertion instrument 1 is safeguarded against inadvertently
springing open. In this way, it is possible for even substantial
loads, for example hammer strikes, to be applied to the bulge 76 on
the forceps 1 without any fear of inadvertent opening and without
the operating surgeon needing to secure the handgrip parts 21, 31
by manual force against undesired opening. To open the forceps 1
after implantation has been carried out, the catch element 83 is
pivoted rearward by applying rearward pressure on the release
element 81, by which means the locking pawl 84 is freed from the
catch element 83, and the handgrip parts 21, 31 thus move apart
from one another under the action of the spring 11. With the
forceps 1 in the opened state, the catch element 83 is pivoted
rearward counter to the force of the spring 87. Provided in the
wide area of the catch element 83 there is a guide 85 which is
designed as an oblong hole and which is used to hold the rod 71,
even when the forceps 1 is open, in a defined position in the
longitudinal axis 10 and to avoid deflection of the rod 71 even
under high loads.
[0029] Also fixed on the handgrip part 31 there is a leaf spring 11
which is guided round the rod 71 to the other handgrip part 21.
With the forceps 1 closed, this leaf spring 11 is tensioned and has
the effect that, after release of the catch elements 82 83, the
insertion instrument 1 automatically opens to permit removal.
[0030] The cooperation with the cervical prosthesis 9 will be
described now with reference to FIGS. 3 and 5. The cervical
prosthesis 9 consists of an upper closure plate 91 and a lower
closure plate 92, with a pivot [sic] element 93 arranged between
them. The cervical prosthesis 9 is intended for implantation in the
interspace between two adjacent vertebrae of a human cervical
spine. The top closure plate 91 is secured to the upper vertebra
and the bottom closure pate 92 is secured to the lower vertebra. To
arrange the cervical prosthesis 9 securely on the forceps 1 for
insertion into the intervertebral space, the top and bottom closure
plates 91, 92 have receiving openings on their lateral flanks in
the area of their front flange 94, 95. The receiving opening on the
top closure plate 91 is designed as a bore 97 with an additional
countersink. The receiving opening on the bottom closure plate 92
is designed as a slit 96. In its flange-side area, the sliding core
93 is likewise provided with a slit 96' which is arranged in such a
way that it is flush with the slit 96 of the bottom closure plate
92. The slits 96, 96' thus result in a continuous groove.
[0031] To receive the cervical prosthesis 9 with the forceps 1, the
cervical prosthesis 9 is brought into the area between the jaw
parts 22, 32 and the forceps 1 is closed, as a result of which the
jaw parts 22, 32 move toward one another. In so doing, the
projections 51, 52 engage in the corresponding receiving openings
of the two closure plates 91, 92, the pins 51 engaging in the bore
97 and the small plates 52 engaging in the slits 96, 96'. In this
way, the cervical prosthesis 9, in the tensioning direction, is
held free from play on the forceps 1. The different design of the
projections 51, 52 and of the receiving openings configured as
bores 97 and slits 96 ensures that the cervical prosthesis 9 can be
held on the forceps 1 only with the correct orientation. If, as in
the illustrated embodiment, the forceps 1 is additionally provided
with a marking 14 for the top, this virtually eliminates the
possibility of incorrect implantation as a result of incorrect
orientation of the cervical prosthesis 9. After the cervical
prosthesis 9 has in this way been received in the correct
orientation on the forceps 1, the rod 71 can be moved forward via
the actuating device 7 by turning the handle 72, with the result
that the block 61 comes to lie, from the rear, with its abutment
surface 62 on the flange 94, 95 of the cervical prosthesis 9. In
doing so, the block 61 tensions the cervical prosthesis 9 against
the projections 51, 52 and thus orients the cervical prosthesis 9
in a defined position. Any play existing in the longitudinal axis
direction between the projections 51, 52 and the bores 97 and the
slits 96 is compensated in this way. The cervical prosthesis 9 is
thus held securely and in a precise position on the forceps 1. In
addition, the fact that the block 61 bears on the flanges 93, 94 of
the two closure plates 91, 92 ensures that the two closure plates
91, 92 do not move away from one another at their front end. This
eliminates the possibility of the cervical prosthesis 9 opening,
which would prevent successful introduction into the intervertebral
space.
[0032] It is furthermore made possible to implant cervical
prostheses of different height without making changes to the
forceps 1. FIG. 3b shows a cervical prosthesis 9' which has a
thicker sliding core 93'. Like the sliding core 93, it is provided
with a slit 96" which is flush with the slit 96 of the bottom
closure plate 92. This configuration of the receiving opening on
the bottom closure plate 92 as a slit 96 and its continuation as
slit 96" in the sliding core 93' ensure that the thicker cervical
prosthesis 9' can be gripped and securely held with the same
forceps 1 without changing the arrangement of the projections 51,
52. The positioning precision is in this case guaranteed by the
pin-like projections 51 which engage in the bores 97.
[0033] If necessary, however, it is also possible to provide other
jaw inserts 53' which have a different arrangement of the
projections 51', 52', as is shown in FIG. 4. In this way, the
forceps 1 can be adapted to other intervertebral endoprostheses,
for example to particularly small ones for treatment of
children.
[0034] With its abutment surface 62, the block 61 affords a
sufficiently large force transmission surface for transmitting to
the cervical prosthesis 9 the impulses applied to the bulge 76
acting as the strike head. The great advantage of this is that the
projections 51, 52, which have been finely dimensioned in the
interest of precise positioning, do not have to transmit the strike
forces, so that the risk of bending or even breaking of the
projections 51, 52 as a result of overloading is excluded, by
virtue of the block 61 and its abutment surface 62 assuming the
role of force transmission.
[0035] The forceps 1 according to the invention allows the cervical
prosthesis 9 to be arranged with precise positioning and without
any risk of its being the wrong way round on the forceps 1, thereby
preventing any undesired opening of the cervical prosthesis 9.
Moreover, by virtue of the block 61 with the abutment surface 62,
it also permits transmission of forces even in the case of forceps
1 of small dimensions. In this way, reliable implantation of the
prosthesis is guaranteed. The small dimensioning of the forceps 1
also has the advantage that it gives the operating surgeon good
access to and a good overall view of the implantation site.
* * * * *