Note: Descriptions are shown in the official language in which they were submitted.
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DUAL ANCHOR SPINAL IMPLANT APPARATUS
BACKGROUND
Spinal osteosynthesis devices for correcting deformations of the spine often
comprise at least one rod extending along a portion of the vertebral column of
tlie patient.
It is connected to the vertebrae by devices which can take various forms. In
particular, it
can pass through connectors which are themselves mounted on threaded
protrusions
carried by plates, bone anchoring screws or hooks which are placed opposite
the pedicles
or on the posterior arches or transverse processes of the vertebrae.
For osteosynthesis devices or systems fitted by a posterior approach,
anchoring the
rod on the vertebrae by means of hooks placed on a vertebra is particularly
indicated. To
this end, anchoring means have been conceived in which a hook connected to the
rod by a
connector, as indicated above, is connected to a second hook by means of a
smaller rod.
The second hook is placed at a distance from the first one on the same
vertebra or, if
appropriate, on another vertebra. Such means are described in particular in
document FR-
A-2 816 196. In said document, the rod of small diameter is tlireaded and is
inserted into a
hole in the head of the hook which bears the connector. In document FR-A-2 767
263, the
hook on which the spinal rod is fixed comprises, on its head, two channels:
one in which a
spinal rod is installed (therefore no connector is used here), the other in
which a smaller
rod is installed, which connects the hook to the other hook. The rods are
immobilized in
the head of the hook by threaded plugs. These means of fixation have the
disadvantage of
having relatively complex structures and of requiring, for their installation,
a number of
manoeuvres and a lengtll of time which it would be desirable to reduce.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of an embodiment of a spinal osteosynthesis
device.
FIG. 2 is a perspective view of the embodiment of FIG. 1 connected with
vertebral
bone.
FIG. 3 is a perspective view of the embodiment of FIG. 1 including additional
structure in a state of assembly.
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FIG. 4 is a perspective view of the einbodiment of FIG. 1 including additional
structure in a further state of assembly.
FIG. 5 is a perspective view of the embodiment of FIG. 1 with an embodiment of
an orthopedic longitudinal member connected thereto.
DESCRIPTION OF THE DISCLOSED EMBODIMENTS
For the purposes of promoting an understanding of the principles of the
invention,
reference will now be made to the embodiment illustrated in the drawings and
specific
language will be used to describe the same. It will nevertheless be understood
that no
limitation of the scope of the invention is thereby intended. Any such
alterations and
further modifications in the illustrated device, and any such further
applications of the
principles of the invention as illustrated herein, are contemplated as would
normally occur
to one skilled in the art to which the invention relates.
As will be seen from the figures, an embodiment of a spinal osteosynthesis
device
comprises a first hook 1 intended to be attached to a vertebral body, such as
at a lamina or
opposite a pedicle of a vertebra. The head 2 of hook 1, in the illustrated
embodiment of
hook 1, supports a threaded protrusion or shaft 3 which is substantially
perpendicular to
upper surface 4 of the head 2. Upper surface 4 may be substantially flat. Hook
1 includes
a blade 22, which is forked in the illustrated embodiment, connected to head
2. Hook 1
may also include one or more indentations 24, shown in the illustrated
embodiment as
adjacent upper surface 4. In a particular embodiment, two indentations 24 may
be
provided, one on each side of hook 1.
Shaft or protrusion 3 may be threaded as noted above or otherwise configured.
If it
is threaded, standard machine threads may be used, to accommodate a nut or
other locking
member. At a medial portion of the illustrated embodiment of shaft 3, a line
of lesser
resistance (e.g. weakened or small-diameter section) 18 is found. A head
portion 26 may
be placed on shaft 3. As shown in FIG. 1, head portion 26 can be placed at or
near the top
of shaft 3, and can be configured to accommodate a wrench or holding tool, as
with the
hexagonal configuration of the illustrated embodiment. Other configurations or
placements of head portion 26 may be used.
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A second hook 5 is provided for connection to a vertebral body, such as a
posterior
arch or to a transverse process of a vertebra, either the same vertebra to
which hook 1 is
attached or, if appropriate, a different vertebra. The illustrated embodiment
of hook 5
includes a blade portion 28, and a head 8 having a groove or channel 30
substantially
parallel to blade 28 and internal threads 32 bordering channe130. It will be
understood
that the channel 30 could have other angles with respect to blade 28, and
threads 32 could
be external, could be replaced by other surface configurations, or could be
removed in
other embodiments. As seen particularly in FIG. 1, in one embodiment head 8 of
hook 5
may have side surfaces 34 adjacent channe130 that are angled with respect to
channe130,
to assist the surgeon in inserting items into channel 30 from the side. Head 8
may also
have side indentations 36 adjacent channe130, that can be configured to
accommodate a
gripping, holding or positioning tool or other structure.
As is known, hooks 1, 5 can be connected via a rod 6 that in the illustrated
embodiment is of small diameter. The latter (i.e. rod 6), in the illustrated
embodiment, has
one of its ends 38 or a middle portion simply placed in groove 30 in the head
8 of the
second hook 5, where it is free in translation and in rotation before being
immobilized
there by a threaded plug or set screw 9. In the illustrated embodiment, middle
portion or
end 38 of rod 6 is substantially cylindrical. The other end 40 of rod 6 is
flattened (e.g.
with substantially flat upper surface 42 and lower surface 44) in the
illustrated
embodiment and has an aperture 10, which may be oblong with a length of the
order of 10
mm, for example. Shaft or protrusion 3 can be fitted through said aperture 10
in such a
way that the flattened end 40 of the rod 6 rests on the head 2 of the first
hook 1(e.g.
substantially flat lower surface 44 contacts substantially flat surface 4) and
end 40 can be
immobilized against head 2 by a locking member such as a nut, an example of
which will
be described further below. Rod 6 has a diameter generally of the order of 3
mm; it is
referred to as being "of small diameter" above simply by contrast to the rod
13 which
generally has a substantially greater diameter (of the order of 5.5 mm, for
example).
Figure 2 shows an example of a stage involved in fitting the disclosed
structure on
a vertebra 14 of the patient. Hook I is installed opposite a pedicle of the
vertebra 14, and
hook 5 on the transverse process of the same vertebra 14, it being understood
that this
arrangement is just one exaniple and that any other type of location of the
hooks on the
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vertebra is contemplated. Rod 6 connecting the two hooks 1, 5 may be arranged
as in
Figure 1. For example, aperture 10 of rod 6 may be placed over shaft 3 and
against or near
surface 4 of hook 1, and middle or end portion 38 of rod 6 may be placed in
channel 30 of
hook 5 by insertion through the top and/or side of channel 30. It will be
noted that the
oblong shape of aperture 10 allows the surgeon great latitude in positioning
rod 6 in the
best possible location without difficulty. Likewise, the angular and
translational position
of hook 5 can be established without difficulty.
Figure 3 shows an example of another stage of fitting the disclosed structure.
Rod
6 of small diameter has been immobilized on the hooks 1, 5, on the one hand by
the
threaded plug 9 screwed into groove 30 in the head 8 of the second hook 5,
and, on the
other hand, by a nut N fitted on the protrusion 3. This nut N comprises two
parts separated
by a line of lesser strength (not visible in Figure 4) which makes nut N
divisible. The
lower part 15 of nut N is designed with a conical (or spherical) upper surface
46 intended
to cooperate with the connector 11, as discussed below. The upper part 16 has
flat faces
allowing nut N to be tightened by means of a suitable tool. Thus, when upper
part 16 is
tightened, lower part 15 is forced against upper surface 42 of rod 6. Applying
sufficient
torque to upper part 16 or cutting or applying other force at the line of
lesser strength
causes a break or rupture at or near the line of lesser strength, separating
upper part 16
from lower part 15. In this way, upper part 16 can be removed while lower part
15 is
maintained securely against upper surface 42 of rod 6. Before or after rod 6
is
immobilized with respect to one or both of hooks 1, 5, it is preferable to cut
off its part
extending beyond the second hook 5 (e.g. at least part of end 38).
Figure 4 shows an example of another stage of fitting the disclosed structure,
in
which stage the upper part 16 of nut N fitted on the protrusion 3 has been
removed. All
that remains of nut N, therefore, is its lower part 15 which is ready to
receive the
connector 11.
Figure 5 shows an example of another stage of fitting the disclosed structure.
In
that embodiment, a spinal rod 13 has been connected to it. To do this, a
connector 11 is
provided. Connector 11 in one embodiment includes a longitudinal orifice 12
sized and
shaped to accommodate rod 13 and an aperture 48. In the illustrated
embodiment, orifice
12 has a longitudinal axis and is open below and/or to a side of that axis, so
that rod 13 can
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be inserted into orifice 12 longitudinally and/or laterally with respect to
that axis.
Aperture 48 is sized and configured to allow at least part of shaft 3 to be
inserted through
it. In a particular embodiinent, the height of connector 11 adjacent aperture
48 is such that
line of lesser resistance 18 extends above aperture 48.
5 Connector 11, in whose longitudinal orifice 12 the rod 13 has first been
fitted in
one embodiment, is placed on the protrusion 3 and over lower part 15 of nut N,
and then
claniped by a nut 17 which has the dual function of clamping connector 11 on
the
remaining part 15 of nut N and of wedging the rod 13 inside the connector 11.
In
particular embodiments, rod 13 is held between a portion of connector 11 (e.g.
a wall
defining orifice 12) and the remaining part 15 of nut N, and/or between a
portion of
connector 11 (e.g. a wall defining orifice 12) and upper surface 42 of rod 6.
After the nut
17 has been tightened, the part of the protrusion 3 emerging from it is, as is
customary,
broken or cut off by the surgeon along line of lesser resistance 18.
The example which has just been described and shown is of course non-limiting,
and various modifications can be made to it.
For example, the disclosed structure can be installed not on just one
vertebra, but
on two different vertebrae, in such a way as to form a sub-assembly of
vertebrae to which
the rod 13 is connected. The designs of the hooks 1, 5 can be modified
depending on the
site of installation envisaged. Further, the rod 6 can be connected to hook 5
by means
other than those shown.
The configuration of connector 11 can be different, in which case the
configuration
of the nut N and/or parts 15, 16 clamping the rod 6 on the head 2 of hook 1
can be
modified. It is not necessary for nut N or parts 15, 16 to be divisible.
In the example shown, end 40 of rod 6 with aperture 10 is flattened in one
embodiment in order to cooperate with a planar embodiment of upper surface 4
of hook 1,
but other designs are conceivable, for example a sphere-to-sphere contact
between the rod
6 and the hook 1.
In the example shown, protrusion 3 is made in one piece with hook 1 and
perpendicular to the latter's upper surface 4, but it can also be formed by a
separate
component connected to hook 1 in a way which allows protrusion 3 to be angled
with
respect to surface 4 of hook I inside a cone. This angulation, which is
normally of the
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order of at most 30 , can make it easier to fit connector 11, rod 13 or other
orthopedic
parts because it permits approximate or preliminary bending of rod 13 prior to
connection
with connector 11. If the configurations of the means for connecting
protrusion 3 to hook
1, and of nut N for immobilizing rod 6 on hook 1, so permit, this angulation
can, if
appropriate, persist after the construct has been immobilized. Means for
ensuring this
angulation are well known in the prior art, for example in document WO-A-
02/38061,
where they are applied to plates.
A spinal orthopedic construct by a posterior approach, with which the
disclosed
structures can be used, can, depending on the surgeon's preference and on its
location on
the spine, comprise only connection devices as disclosed herein, or
simultaneously
comprise one or more connection devices as disclosed herein and one or more
connection
devices of other types.
Thus, among other things apparatus is disclosed herein for connecting an
orthopedic rod of a spinal osteosynthesis device to a vertebra or to two
vertebrae, of which
embodiments may include a first hook provided with a threaded protrusion for
fitting a
connector in which an orthopedic rod is inserted, a second hook, a rod
connecting the two
hooks, and means for immobilizing the ends of the connecting rod on the hooks.
The end
of the connecting rod in contact with the first hoolc may be an oblong
aperture, and the
means for immobilizing this end on the head of the first hook may be formed by
a nut.
The nut can be a divisible nut, a lower part of which can cooperate with the
connector.
The protrusion can have an angulation with respect to the upper surface of the
first hook.
An end of the connecting rod may be flattened so as to cooperate with an upper
surface of
the head of the first hook. The head of the second hook can comprise a groove
for
insertion of an end of the connecting rod, and the means for immobilizing said
end in said
head can be formed by a threaded plug. Also disclosed is a spinal
osteosynthesis
apparatus including a rod, connectors, and structure for joining said
connectors to the
patient's vertebrae, and can be fitted by, for example, a posterior approach.
While the invention has been illustrated and described in detail in the
drawings and
foregoing description, the same is to be considered as illustrative and not
restrictive in
character, it being understood that all changes and modifications that come
within the
spirit of the invention are desired to be protected.
