Title: Fixing element and ancillary for stabilizing vertebrae
Abstract: The invention concerns an osteosynthesis system, comprising at least a linking element in the form of a rod, at least two fixing elements each capable of being anchored in a vertebra, and a locking screw. The invention is characterized in that the base of the head has a general horse-saddle shape, and the head has guide means for an independent closure component designed to be fixed on the head after the linking element has been positioned in the fork of the head, said closure component being generally U-shaped whereof the branches are urged to co-operate with the branches of-the fork-shaped part of the head and whereof the base comprises an internal thread for co-operating with the locking screw and the guide means provided on the head is formed by an arc-shaped shoulder on the outer side surfaces of the fork-shaped part. The invention also concerns an ancillary and an element for fixing such a system.
Patent Number: 6,911,030 Issued on 06/28/2005 to Vanacker, et al.
| Inventors:
|
Vanacker; Gerard (Saint Maur, FR);
Zeller; Reinhard (Boulogne, FR)
|
| Assignee:
|
Spinevision S.A. (FR)
|
| Appl. No.:
|
019715 |
| Filed:
|
June 30, 2000 |
| PCT Filed:
|
June 30, 2000
|
| PCT NO:
|
PCT/FR00/01872
|
| 371 Date:
|
March 15, 2002
|
| 102(e) Date:
|
March 15, 2002
|
| PCT PUB.NO.:
|
WO01/01873 |
| PCT PUB. Date:
|
January 11, 2001 |
Foreign Application Priority Data
| Current U.S. Class: |
606/61 |
| Intern'l Class: |
A61B 017/58 |
| Field of Search: |
606/61,72,73
|
References Cited [Referenced By]
U.S. Patent Documents
| 5562663 | Oct., 1996 | Wisnewski et al.
| |
| 5696321 | Dec., 1997 | Igarashi et al.
| |
| 5899901 | May., 1999 | Middleton.
| |
| Foreign Patent Documents |
| 41 07 480 | Sep., 1992 | DE.
| |
| 0 346 521 | Dec., 1989 | EP.
| |
| 0 535 623 | Apr., 1993 | EP.
| |
| 0 879 579 | Nov., 1998 | EP.
| |
Primary Examiner: Dawson; Glenn K.
Assistant Examiner: Davis; D. Jacob
Attorney, Agent or Firm: Bachman & LaPointe, P.C.
Claims
1. A system for osteosynthesis on the vertebral column for stabilization of vertebrae comprising:
at least one rod-shaped linkage element;
at least two fixation means to be anchored into a vertebra;
each said fixation means having a head in the shape of a fork having two branches,
said two branches defining a reception space closely in the form of a U for receiving
the at least one rod-shaped linkage element;
said head having a bottom in the shape of a horse saddle;
a blocking screw to be screwed in the reception space to fix the at least one
linkage element between the two branches of the fork shaped head;
an independent closure to be fixed on the head after positioning the at least
one linkage element in the fork of the head;
said independent closure part being in the general shape of a U with branches
cooperating with the branches of the fork shaped part of the head;
said closure part having a bottom which comprises a threading for cooperation
with the blocking screw; and
guide means for positioning said closure part on said head, said guide means
including inclined undercut portions in external lateral surfaces of the forked
shaped part of the head forming arched shoulders.
2. A system for osteosynthesis according to claim 1, further comprising said
closure part having complementary shoulders and said closure part being anchored
by contacting transverse surfaces of the shoulders during tightening of the blocking screw.
3. A system for osteosynthesis according to claim 2, wherein the shoulders provided
on the lateral surfaces of the fork shaped head part are in the shape of an arc
of a circle.
4. A system for osteosynthesis according to claim 2, wherein the closure part
shoulders have inclined contact surfaces converging towards the threading for receiving
the blocking screw.
5. A system according to claim 1, further comprising said head having a longitudinal
axis and said independent closure being movable relative to said head about an
axis transverse to said longitudinal axis.
6. A system according to claim 1, wherein said independent closure part branches
comprise arms formed from a flexible material and wherein said arms are flexed
to set the closure part on the head.
7. A system according to claim 1, wherein said independent closure part branches
comprise arms formed from a shape memory material and wherein said closure part
is set on the head by subjecting the arms to a temperature which causes the arms
to fold back into an anchoring position.
8. A system according to claim 1, wherein the head has a plurality of cut-outs
for allowing passage of an instrument.
9. A system according to claim 1, wherein the shoulders on said head are formed
by an arc.
10. A system for osteosynthesis on the vertebral column for stabilization of
vertebrae comprising:
at least one rod-shaped linkage element;
at least two fixation means to be anchored into a vertebra;
each said fixation means having a head in the shape of a fork having two branches,
said two branches defining a reception space closely in the form of a U for receiving
the at least one rod-shaped linkage element;
said head having a bottom in the shape of a horse saddle;
a blocking screw to be screwed in the reception space to fix the at least one
linkage element between the two branches of the fork shaped screw head;
an independent closure part;
said head having a guide means for said independent closure part to be fixed
on the head after positioning the at least one linkage element in the fork of the
head;
said independent closure part being in the general shape of a U with branches
cooperating with the branches of the fork shaped part of the head;
said closure part having a bottom which comprises a threading for cooperation
with the blocking screw;
said guide means provided on the head being formed by an arched shoulder on external
lateral surfaces of the fork shaped part of the head;
said head being prolonged by a lower part in the shape of a hook for setting
in place a pedicle; and
said hook comprising a flexible lamina for temporary maintenance.
11. A fixing element to be anchored onto a vertebra for osteosynthesis instrumentation,
said fixing element comprising:
a head in the shape of a fork having two branches, said two branches defining
a reception space closely in the form of a U for receiving a linkage element;
said head having a bottom in the general shape of a horse saddle;
an independent closure part;
said head further having guide means for said independent closure part capable
of being fixed on the head after said linkage element has been positioned in the
fork of the head;
said closure part being in the general form of a U with branches co-operating
with the fork branches;
said closure part having a bottom which comprises a threading for co-operation
with a blocking screw; and
said guide means being formed by inclined undercuts in external lateral surfaces
of the fork shaped part of the head, said undercuts forming a pair of arched shoulders.
12. A fixing element according to claim 11, wherein the closure has a complementary
shoulders and is anchored by contacting transverse surfaces of the shoulders during
tightening of the blocking screw.
13. A fixing element according to claim 12, wherein the shoulders provided on
lateral surfaces of the fork shaped part of the head are in the form of an arc
of a circle, allowing a degree of freedom for the linkage element relative to a
fixation implant on a vertebral column.
14. A fixing element according to claim 12, wherein the closure part shoulders
have inclined contact surfaces converging on the threading.
15. A fixing element according to claim 11, wherein said independent closure
part branches comprise arms formed from a flexible material and wherein said arms
are flexed to set the closure part on the head.
16. A fixing element according to claim 11, wherein said independent closure
part branches comprise arms formed from a shape memory material and wherein said
closure part is set on the head by subjecting the arms to a temperature which causes
the arms to fold back into an anchoring position.
17. A fixing element according to claim 11, wherein the head has a plurality
of cut-outs for allowing passage of an instrument.
18. A fixing element to be anchored onto a vertebra for osteosynthesis instrumentation,
said fixing element comprising:
a head in the shape of a fork having two branches, said two branches defining
a reception space closely in the form of a U for receiving a linkage element;
said head having a bottom in the shape of a horse saddle;
said head further having guide means for an independent closure part capable
of being fixed on the head after said linkage element has been positioned in the
fork of the head;
said closure part being in the general shape of a U with branches cooperating
with the fork branches;
said closure part having a bottom which comprises a threading for cooperation
with a blocking screw;
said guide means being formed by an arched shoulder on external lateral surfaces
of the fork shaped part of the head;
a lower part in the form of a hook for setting in place on the vertebra; and
said hook comprising a flexible lamina for temporary fixation maintenance.
Description
BACKGROUND OF THE INVENTION
The present invention relates to the domain of spinal osteosynthesis intended
for surgery of the vertebral column, to correct malformations of the degenerative
or idiopathic, neuromuscular or tumoral, or of the traumatological type.
In prior art, it is known how to use an instrumentation comprising implants to
be fixed on the bone, by screwing or by hooks and linkage elements enabling the
surgeon to apply constraints for straightening or stabilising the vertebral column.
As an example, the European patent EP626828 describes such a system enabling
osteosynthesis
on the vertebral column, together with a linkage element between this system and
the tools used for assembly and/or disassembly. This prior art document describes
a device for osteosynthesis on the vertebral column, in particular for stabilising
the vertebrae, comprising:
- at least one linkage element in the shape of a rod.
- at least two fixation elements each able to be anchored in a vertebra,
these means having a head of the forked shape type whose two branches define a
reception space closely U-shaped for the linkage element,
- a tightening screw able to be screwed in the reception space to fix
the linkage element between the two branches of the fork-shaped screw head,
- the head whose bottom of the reception space is shaped in the form of
a concave cup corresponding with a tilting bushing element fitted between the bottom
of the reception space and the linkage element, the bushing element whose bearing
surface opposite the reception space bottom is of a complementary convex shape,
characterised in that the tilting bushing element is provided with a hemispherical
bearing surface corresponding with the bottom of the reception space. This element
is provided with a cut-out open from the tightening screw side in order to receive
the linkage element in the form of a rod. The tilting bushing is maintained against
the bottom of the reception space in such a way that it can tilt just as well in
a plane parallel to the median plane of the reception space as in a perpendicular plane.
Patent PCT WO9101691 is also known, describing a device for straightening
and propping up a vertebral column, constituted of screwed implants or hooks linked
by at least two rods integrated together through the intermediary of connection
and linkage elements. These rods are introduced longitudinally in grooves perpendicular
to the screw, provided for this purpose in the body of the implants or hooks, then
blocked in the bottom of the grooves. Integralisation of the rods is obtained with
a threaded cross tie. A deformation by approaching the sides of the groove, set
in the body of the implants or hooks, in order to obtain blocking of the rod in
the bottom of the groove, is obtained through a system of cylindrical screw and
conical threaded nut.
Patent WO9514437 is also known, revealing an implant comprising a part destined
for anchoring the bone and a body for fixation on a rod, comprising two lateral
branches defining a channel, this implant also comprising a threaded plug adapted
in order to be screwed on the internal walls of the two branches. Another patent
PCT WO9410944 describes a device comprising a connection element set between a
rod or other longitudinal implant, and a bone fixation screw placed in the degenerative
vertebra. This connection element comprises a ring with dimensions such that the
rod can pass through. The ring is provided with screws for fixing the rod and extends
radially thanks to a cylindrical arm designed to be fixed to the fixation screw
of the bone and tightened on the screw. The arm and the ring constitute a single
part. This device allows the surgeon to avoid deforming the rod further when the
latter is in the presence of non-aligned vertebral pedicles, leaving the surgeon
total freedom to choose the placing of the two axes of the fixation screw of the
bone and the rod.
The problem of devices of prior art is that of maintenance of the orientation
decided by the surgeon at the time of the definitive fixation and of the dissociation
between the positioning of the linkage element and the insertion of the bone implant.
In the devices comprising a tightening screw, the tightening of this screw has
a tendency to modify the relative orientation of the linkage rods and the fixation element.
Another problem is that of adjusting the setting of the screws during the
realignment stage of the vertebral column by rotation of the correction rod. This
correction rod crosses through numerous vertebral implants, for example 10 to 15
implants and/or vertebral screws. Generally, each of these implants comprises a
blocking screw. This blocking screw must be sufficiently tightened to avoid slipping
from the vertebral implant, but not too tight in order to allow rotation of the
rod without excessive friction. The adjustment of the degree of screwing of each
of these blocking screws is a fastidious and delicate operation.
SUMMARY OF THE INVENTION
The aim of the invention is to avoid these inconveniences by proposing a system
and an implant making it possible to preserve the degree of correction decided
by the surgeon during the operations of definitive fixation and tightening of blocking
screws of the linkage element. The aim is also to allow rotation of the rod during
its rotational manoeuvring, with minimum friction independent of the degree of
tightening of the blocking screw.
Thus, the aim of the invention concerns in its most general form a device for
osteosynthesis on the vertebral column, in particular for the stabilisation of
vertebrae, comprising:
- at least one linkage element in the form of a rod, or plate,
- at least two means of fixation each able to be anchored into a vertebra,
these means having a head in the shape of a fork whose two branches define a reception
space closely in the form of a "U" for the linkage element,
- a blocking screw capable of being screwed in the reception space to
fix the linkage element positioned between the two branches of the forked shape
screw head, characterised in that the bottom of the head has the general shape
of a horse saddle, in that the head has a guide means for an independent closure
part capable of being fixed on the head after positioning the linkage element in
the fork of the head, said closure part being in the general form of a "U" with
branches coming into co-operation with the branches of the part in the shape of
a "Y" fork for the head, and whose bottom comprises a threading for co-operation
with the blocking screw and in that the guide means provided on the head are formed
by an arched shoulder on the external lateral surfaces of the fork shaped part.
The horse-saddle shape can be described as an inverse hyperbolic paraboloid,
according to a particular embodiment but it is not limited to a shape engendered
by a second degree equation corresponding to a hyperbolic paraboloid.
This embodiment makes it possible first of all to insert the fixation, means
on the vertebral column, then the linkage elements possibly at the same time as
the closure part, then to adjust the correction independently from the locking
element, and when the optimum correction has been obtained, to block each implant
by the blocking screws. The tightening of the blocking screws does not modify the
orientation of the fixation means because of the degree of freedom of movement
of the closure part relative to the body of the fixation means.
The closure part has two lateral branches which are flexibly malleable, with
an arched shoulder on the interior surfaces. The dimensions and shapes of branches
and shoulders are determined in such a way as to allow the setting of the closure
part by flexible spacing of the branches and the interlocking of the shoulders.
The final locking of the closure part and the implant is produced by tightening
the blocking screw. The guide means of the closure part on the head is formed by
a complementary arched shoulder provided on the external lateral surfaces of the
fork-shaped part. This arched shoulder allows rotation of the closure part relative
to the head of the implant.
A variant consists of producing a closure part having a shape memory. Such a
part
has spread arms at rest, to allow setting on the fork-shaped part. When it is in
position on the head of the hook, a modification of temperature makes the arms
fold back into an anchoring position on the fork.
According to a preferred embodiment, the shoulders have contact surfaces
converging closely towards the threading intended to receive the blocking screw.
According to a variant, the position of the closure part is fixed relative
to the head fork. The shoulder or the interlocking means, according to this variant,
do not allow a degree of rotational freedom of the closure part.
The angle of convergence is not very critical. It is only important that the
contact surfaces should be oriented towards the bottom of the closure part. However,
an angle of about ten degrees relative to the transversal plane would already make
it possible to obtain a satisfactory guiding.
According to an embodiment variant, the head is prolonged by a lower part
in the shape of a hook for maintaining the vertebral column for the setting on
a pedicle, vertebra lamina or transverse process, said hook comprising a flexible
lamina for temporary maintenance of the fixation.
The invention surely relates to the system comprising the components as a whole
(correction rod, implants, closure parts, blocking screws). Nonetheless it also
relates to the fixation element capable of being anchored onto a vertebra, for
the osteosynthesis instrumentation. This fixation element can be used with linkage
elements other than rods, for example a linkage element with a trapezoid or variable
cross-section, or laminae, in particular laminae having linkage zones of circular cross-section.
The invention also concerns an ancillary for the implementation of a system for
osteosynthesis according to the invention characterised in that it presents two
jaws which come to lodge in the cut-outs provided on the head of the implant, and
a device exerting a force on the rod to ensure its lateral and/or vertical displacement,
with the intention of enabling the positioning of the rod in the fork. This effort
can be exerted on the rod through the intermediary of the closure part with which
the ancillary co-operates during the phase of setting the rod in place in the fork
of the implant. The co-operation can be carried out by temporary screwing of the
ancillary in the threading of the closure part.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will be better understood by reading the following description
of the attached drawings wherein:
FIG. 1 shows a longitudinal cross-section of an embodiment of an osteosynthesis
system according to the invention;
FIG. 2 shows a diagram from the side of the system according to the invention, and
FIGS. 3 and 4 show a view of the implant according to two perpendicular faces.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)
The osteosynthesis system according to the present invention comprises a linkage
element (
1), an implant (
2) with a complementary closure part (
3),
and a blocking screw (
13).
The rod (
1) will not be described in greater detail since it belongs to
the present state of the art and can take diverse forms. In the example given,
it is formed of a metallic rod with a circular cross-section.
The implant has a fork shaped head (
5), with two lateral arms (
6,
7) defining a space intended to receive the linkage element (
1).
The bottom (
8) of the fork is generally horse-shoe shaped, with a concave
curve in the transversal plane corresponding to the plane of FIG. 1, and a convex
curve in the complementary plane.
The radius of the concave curve corresponds closely to the external radius of
the guiding element (
1). The latter thus comes into contact following a
semi-peripheral line. This contact according to a line and not according to an
annular surface allows a degree of pivoting freedom, and at the same time ensures
more efficient blocking after tightening than in the case of a simple pinpoint contact.
The closure part (
3) has a general "U" shape, with two arms (
10,
11) and a bottom with a threading (
12) to receive a blocking screw.
The arms (
10,
11) have a spacing allowing the head to be put into
place. At their lower extremity the arms (
10,
11) have arched shoulders
(
14,
15) with an upper inclined surface (
16,
17).
These arched shoulders (
14,
15) co-operate with the complementary
guide means (
20,
21) provided on the head (
5). These guide
means also have an inclined arched contact surface (
22,
23), and
co-operate with the complementary contact surfaces (
14,
15) when
the closure part is set in place on the head (
5). They then ensure a guiding
allowing pivoting of the closure part along a transversal axis (
24) and
ensure the locking of the closure part (
3) on the head (
5), and thus
the blocking of the rod (
1) after tightening the screw (
13).
FIG. 2 is a side view showing that the rod (
1) has a degree of freedom
tilting around a transversal axis (
24). This makes it possible to give the
implant independence, and to position the implant by means of the hook (
26)
on the pedicle, and independently to search for the best orientation of the rod
(
1) without interference between these two restrictions. The horse-shoe
shape and the mobility of the closure part make it possible to adapt the locking
and to avoid de-rotation or displacement of the rod during tightening of the screw (
13).
The hook (
26) defines a "U-shaped" space (
27) for linkage with
the lamina of a vertebra. In order to ensure temporary maintenance, a flexible
lamina (
28) is set inside this "U" space and ensures a temporary maintenance
on the bone in such a way that there is no risk of the lamina of the hook disturbing
the spinal cord or any other structure. The flexible lamina (
28) pushes
back the hook in a posterior direction relative to the patient, and avoids lesions
of the noble tissues during the phase of correction by rotation of the rod.
FIGS. 3 and 4 show side views of the implant, without the closure part.
The implant has two cut-outs (
30,
31) allowing the passage of an
instrument with two jaws to lodge in the cut-outs (
30,
31), and a
device exerting an effort on the rod to ensure its lateral and/or vertical displacement,
in order to allow the positioning of the rod in the fork through the intermediary
of the closure part (
3). In this case, one part of the instrument is integrated
temporarily with the closure part with the aid of a screw introduced in the threading
(
12) of the closure part (
3).
The invention is described above as a non-limiting example. It is understood
that those skilled in the art can produce diverse variants, in particular by replacing
the hook by a pedicle screw, or a vertebral screw for inserting on the anterolateral
face of the vertebral column.
*
