U.S. patent number RE42,626 [Application Number 10/629,788] was granted by the patent office on 2011-08-16 for multidirectional adaptable vertebral osteosyntsis device with reduced space requirement.
This patent grant is currently assigned to Medicrea Technologies. Invention is credited to Jean Taylor, Bernard Villaret.
United States Patent |
RE42,626 |
Taylor , et al. |
August 16, 2011 |
Multidirectional adaptable vertebral osteosyntsis device with
reduced space requirement
Abstract
A vertebral osteosynthesis device includes at least two bone
anchoring elements (1) in the vertebral bone structures
respectively (S, L5.), a longitudinal linking member (2) between
the bone anchoring elements, and connector links (3) between the
bone anchoring elements and said linking members. Each bone
anchoring element includes a bond fixing part (4), a head (5) to be
gripped by a screwing device, a threaded shaft (7) extending the
grip head, and a clamping element (8) to be screwed on said shaft
to lock together the connector link, the longitudinal linking
member and the corresponding bone anchoring element; the threaded
shaft (7) is provided at its end with a hinge ball joint (11) in a
housing (12) of the grip head (5), enabling a multidirectional
adjustment of the shaft (7) and a positioning of the connector link
(3) adapted to the vertebral segment configuration (S, L5, . . .
Lw) receiving the bone anchoring elements.
Inventors: |
Taylor; Jean (Cannes,
FR), Villaret; Bernard (Croix-Chapeau,
FR) |
Assignee: |
Medicrea Technologies (La
Rochelle, FR)
|
Family
ID: |
11041500 |
Appl.
No.: |
10/629,788 |
Filed: |
June 3, 1998 |
PCT
Filed: |
June 03, 1998 |
PCT No.: |
PCT/FR98/01119 |
371(c)(1),(2),(4) Date: |
March 02, 2000 |
PCT
Pub. No.: |
WO98/55038 |
PCT
Pub. Date: |
December 10, 1998 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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Reissue of: |
09445176 |
Mar 2, 2000 |
6267765 |
Jul 31, 2001 |
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Foreign Application Priority Data
Current U.S.
Class: |
606/86A |
Current CPC
Class: |
A61B
17/7014 (20130101); A61B 17/7007 (20130101); A61B
17/7037 (20130101); A61B 17/701 (20130101); A61B
17/7047 (20130101); A61B 17/7052 (20130101); A61B
17/7041 (20130101); A61B 17/8061 (20130101) |
Current International
Class: |
A61F
5/00 (20060101) |
Field of
Search: |
;606/61,60,69,72,73,86A,261,219,59,151,217,277,258
;411/383,388,389,397 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Philogene; Pedro
Attorney, Agent or Firm: Young & Thompson
Claims
What is claimed is:
1. Spinal osteosynthesis device comprising at least two
bone-anchoring elements (1; 31) for anchoring in respective bodies
(S, L5) of the bone structure of the spine, at least one member (2;
16) for longitudinally connecting the bone-anchoring elements, and
shackles (3) for connecting the bone-anchoring elements together,
each bone-anchoring element comprising a head (5; 33) for grasping
with a screwing tool (6), a threaded shank (7) extending the head
for grasping, and a tightening element (8) which can be fitted onto
this shank to immobilize the assembly comprising the connector
shackle, the longitudinal connecting member and the corresponding
bone-anchoring element, characterized in that the threaded shank
(7) has a ball end (11) for articulation in a housing (12) of a
spherical cup (57) of the head (5) for grasping, allowing the shank
(7) to be oriented in many directions, and allowing the connecting
shackle (3) to be positioned to suit the configuration of the
vertebral segment (S, L5, . . . L2) receiving the bone-anchoring
element, and in that the ball (11) and .[.the cup (57).]. .Iadd.an
exterior surface of the head .Iaddend.have respective centres of
rotation (R1, R2) which are separated by a distance (S), giving the
device, when tightened using the tightening element (8), by bearing
against the .[.spherical cup (57).]. .Iadd.exterior surface
.Iaddend.of the head (5) for grasping, a function of returning the
bone-anchoring element by transverse force, the connector shackle
for this purpose having a spherical bearing surface (55)
articulated to a portion of the spherical surface of the cup (57)
of the head (5) of the bone-anchoring element.
2. Device according to claim 1, characterized in that the threaded
shank (7) and the connecting shackle (3) are equipped with means
for immobilizing the shank and its ball (11) in terms of rotation
once the threaded shank has been introduced into a corresponding
through-hole (10) through the shackle.
3. Device according to claim 2, characterized in that .[.the.].
said means .Iadd.for immobilizing .Iaddend..[.comprise.].
.Iadd.comprises .Iaddend.at least one rotation-stopping
geometry.[., preferably two, namely.]. .Iadd.comprising .Iaddend.a
first rotation-stopping geometry (13) formed on a collar (14)
arranged between the ball and the contiguous end of the threaded
shank (7), and a second, female, rotation-stopping geometry (15)
formed on the interior edge of the hole (10) in the shackle (3),
this second rotation-stopping geometry being designed to press
against the first rotation-stopping geometry once the shackle has
been fitted on the threaded shank.
4. Device according to claim 1, characterized in that the opposite
end of the threaded shank (7) to the ball (11) consists of a male
shape (21).[., for example a half-moon shape,.]. designed to
cooperate with a complementary female shape (23) of a tool (6) so
as to immobilize the ball in terms of rotation while the tightening
element (8) is being screwed onto the threaded shank (7).
5. Device according to claim 1, characterized in that the ball (11)
is held in .[.its.]. .Iadd.the .Iaddend.housing (12) by assembling
.[.(for example screwing, crimping, welding, etc.).]. the edge of
the .[.latter.]. .Iadd.housing .Iaddend.around the ball.
6. Device according to claim 1, characterized in that since the
surface of the cup (57) of the head (5) is hemispherical and
interrupted in the polar region to receive the ball (11), the
associated spherical surface (55) of the shackle (3) at least
partially covers the hemispherical surface of the cup, so as to
produce either an effect of returning the bone-anchoring element
(4) towards the axis, when coverage is total, as far as the equator
of the cup, or a slight return, roughly maintaining the initial
angular position of the bone-anchoring element, when coverage is
only partial.
7. Device according to claim 6, characterized in that the
connecting shackle (3) has a conical bearing surface (56) for the
tightening element (8), this surface being connected to the said
spherical surface (55).
8. Device according to claim 1, characterized in that it further
comprises at least one bone-anchoring element (31) comprising a
threaded anchoring shank (32), a head (33) which has a transverse
collar (34) and a shape (35) for grasping, for screwing, and a
threaded shank (7) extending the head, the assembly being all of
one piece.
9. Device according to claim 1, characterized in that the threaded
shank (7) has a narrowed portion (18) delimiting two threaded
regions (17) and (19) of this shank and constituting an initiator
for breakage once the tightening element has been assembled and
fitted on the connecting shackle, this narrowed portion therefore
allowing the shank (7) to be broken.
10. Device according to claim 1, characterized in that the member
for longitudinally connecting the bone-anchoring elements (1) is a
vertebral rod (2) passing through the shackles (3) for connecting
to the bone-anchoring elements.
11. Device according to claim 1, characterized in that the member
for longitudinally connecting the bone-anchoring elements (1) and
(31) is a plate (16) in which there are formed cylindrical and/or
oblong openings (41, 43) delimiting possible locations for the
bone-anchoring elements and through which the threaded shanks (7)
on which the immobilizing tightening elements (8) are fitted pass,
and in that the openings in the plate (16) have a similar outline
to that of the hole (10) in the connecting shackle (3) so as
likewise to fulfil a function of returning the bone-anchoring
element.
12. Device according to claim 1, characterized in that it comprises
a system for transversely connecting the bone-anchoring elements
(1), this system being formed of a pair of dished elements (58, 59)
each of one piece with a tab (61, 62), the relative position and
therefore the separation between the dished elements being
adjustable for example by means of a screw-nut assembly (63, 64)
passing through an elongate slot (65) in one tab (61) and a tapped
hole in the second tab (62).
13. A system for installing bone anchoring element, comprising: a
spinal osteosynthesis device comprising at least two bone-anchoring
elements (1; 31) for anchoring in respective bodies (S, L5) of the
bone structure of the spine, at least one member (2; 16) for
longitudinally connecting the bone-anchoring elements, and shackles
(3) for connecting the bone-anchoring elements together, each
bone-anchoring element comprising a head (5; 33) for grasping with
a screwing tool (6), a threaded shank (7) extending the head for
grasping, and a tightening element (8) which can be fitted onto
this shank to immobilize the assembly comprising the connector
shackle, the longitudinal connecting member and the corresponding
bone-anchoring element, characterized in that the threaded shank
(7) has a ball end (11) for articulation in a housing (12) of a
spherical cup (57) for the head (5) for grasping, allowing the
shank (7) to be oriented in many directions, and allowing the
connecting shackle (3) to be positioned to suit the configuration
of the vertebral segment (S, L5, . . . L2) receiving the
bone-anchoring element, and in that the ball (11) and .[.the cup
(57).]. .Iadd.an exterior surface of the head .Iaddend.have
respective centers of rotation (R1, R2) which are separated by a
distance (S), giving the device, when tightened using the
tightening element (8), by bearing against the .[.spherical cup
(57).]. .Iadd.exterior surface .Iaddend.of the head (5) for
grasping, a function of returning the bone-anchoring element by
transverse force, the connector shackle for this purpose having a
spherical bearing surface (55) articulated to a portion of the
spherical surface of the cup (57) of the head (5) of the
bone-anchoring element; and a tool (6) for angularly positioning
the threaded shank (7) and its ball (11) in the shackle (3) or the
plate (16), comprising a sleeve (24) mounted to slide axially
inside a socket (25), the end of which has a female shape (9) for
screwing the tightening element while the end of the sleeve is
provided with a female shape (20) designed to fit over a terminal
male shape (21) of the threaded shank (7) so as to immobilize the
threaded shank in terms of rotation in the position corresponding
to the rotation-stopping geometry while the tightening element is
being fitted using a cavity (9) of the socket (25).
.Iadd.14. Spinal osteosynthesis device comprising: at least two
bone-anchoring elements; and means for longitudinally connecting
the at least two bone-anchoring elements; each of the at least two
bone-anchoring elements comprising: a head shaped so as to allow
grasping with a screwing tool; a threaded shank extending from the
head, and a tightening element which can be fitted onto the
threaded shank to immobilize an assembly comprising the means for
longitudinally connecting and a corresponding one of said at least
two bone-anchoring elements, wherein the threaded shank has a ball
end for articulation in a housing of a spherical cup of the head,
allowing the shank to be selectively oriented with respect to the
head, and wherein the threaded shank and the means for
longitudinally connecting are constructed and arranged so that the
shank and the ball are prevented from rotating once the threaded
shank has been introduced into a corresponding through-hole through
the means for longitudinally connecting..Iaddend.
.Iadd.15. Device according to claim 14, wherein the threaded shank
comprises a first rotation-stopping geometry arranged between the
ball and an opposite end of the threaded shank, and a second,
female, rotation-stopping geometry is formed on an interior edge of
the through-hole in the means for longitudinally connecting, this
second rotation-stopping geometry being designed to press against
the first rotation-stopping geometry once the means for
longitudinally connecting has been fitted on the threaded
shank..Iaddend.
.Iadd.16. Device according to claim 14, characterized in that an
end of the threaded shank opposite the ball comprises a male shape
designed to cooperate with a complementary female shape of a tool
so as to allow immobilization of the ball in terms of rotation
while the tightening element is being screwed onto the threaded
shank..Iaddend.
.Iadd.17. Device according to claim 14, wherein the threaded shank
has a narrowed portion delimiting two threaded regions of the
shank, the narrowed portion constituting an initiator for breakage
once the tightening element has been assembled and fitted on the
means for longitudinally connecting, this narrowed portion
therefore allowing the shank to be broken..Iaddend.
.Iadd.18. Device according to claim 14, wherein the threaded shank
comprises two rotation-stopping geometries formed on a collar
arranged between the ball and an opposite end of the threaded
shank, and a two female rotation-stopping geometries are formed on
an interior edge of the through-hole in the means for
longitudinally connecting, the two rotation-stopping geometries of
the through-hole being designed to press against the two
rotation-stopping geometries of the threaded shank once the means
for longitudinally connecting has been fitted on the threaded
shank..Iaddend.
.Iadd.19. The spinal osteosynthesis device of claim 14, wherein the
means for longitudinally connecting the at least two bone-anchoring
elements comprises: a shackle corresponding to each of the at least
two bone-anchoring elements; and a member that interconnects a
plurality of the shackles..Iaddend.
.Iadd.20. The spinal osteosynthesis device of claim 14, wherein the
means for longitudinally connecting the at least two bone-anchoring
elements comprises: a plate comprising a plurality of apertures,
each of the apertures sized and shaped so as to allow engagement
with a respective one of the bone-anchoring elements..Iaddend.
.Iadd.21. The spinal osteosyntheses device of claim 16, wherein
each of the male end of the threaded shank and the complementary
female end of the tool comprise a half-moon shape..Iaddend.
.Iadd.22. The spinal osteosyntheses device of claim 17, wherein the
narrowed portion of the threaded shank comprises a
rotation-stopping geometry..Iaddend.
.Iadd.23. The spinal osteosyntheses device of claim 22, wherein the
end of the threaded shank opposite the ball comprises a male shape
designed to cooperate with a complementary female shape of a tool
so as to allow immobilization of the ball in terms of rotation, and
wherein a cross-sectional shape of the male shape is the same as a
cross-sectional shape of the narrowed portion of the threaded shank
with the rotation-stopping geometry..Iaddend.
.Iadd.24. A spinal osteosynthesis device comprising: at least two
bone-anchoring elements; and an interconnecting element that
interconnects the at least two bone-anchoring elements; each of the
at least two bone-anchoring elements comprising: a head shaped so
as to allow grasping with a screwing tool; a threaded shank
pivotably connected to the head, the threaded shank terminating in
a ball positioned in a socket on the head; and a tightening element
which can be fitted onto the threaded shank to immobilize an
assembly comprising the interconnecting element and a corresponding
one of said at least two bone-anchoring elements, wherein the
threaded shank and the interconnecting element are constructed and
arranged so that the shank and the ball are prevented from rotating
once the threaded shank has been introduced into a corresponding
through-hole in the interconnecting element..Iaddend.
.Iadd.25. A spinal osteosynthesis device comprising: at least two
bone-anchoring elements, each comprising a head having a shape to
allow grasping with a screwing tool, a threaded shank extending
from the head, the threaded shank terminating in a ball that is
pivotally disposed in a socket in the head, and a tightening
element that can be threaded onto the shank; at least one
longitudinal member; and shackles structured to engage the at least
one longitudinal member and the at least two bone-anchoring
elements, each said shackle comprising an aperture through which
the threaded shank can pass; wherein the head of each said
bone-anchoring element has a hemispherical outer surface, a
spherical center of which lies as a distance from a spherical
center of the socket in the head, each said shackle having a
surface that conforms to the hemispherical outer surface of the
head, such that when the tightening element is threaded onto the
threaded shank to urge the conforming surface of the shackle
against the hemispherical outer surface of the head, the threaded
shackle is forced into an alignment position with respect to the
head..Iaddend.
Description
FIELD OF THE INVENTION
The subject of the present invention is a spinal, particularly
dorso-lumbar, osteosynthesis device.
More specifically, the invention is aimed at a device of the type
comprising at least two bone-anchoring elements for anchoring into
bone structures of the spine, a member for longitudinally
connecting the bone-anchoring elements, and shackles for connecting
the bone-anchoring elements and the members for connecting the
screws; each bone-anchoring element comprises an anchor for
anchoring into the bone, a head for grasping by a screwing tool, a
threaded shank extending the head for grasping and a tightening
element which can be mounted on this shank to lock together the
connector, the longitudinal connecting member and the corresponding
bone-anchoring element.
BACKGROUND OF THE INVENTION
Multivertebral, particularly dorso-lumbar, osteosynthesis combines
the use of screws or hooks connected together by plates or
rods.
The use of plates with appropriate recesses allows the screws a
certain amount of travel and allows them to slide along an axis.
This is useful when fitting screws which diverge in the sagittal
plane.
The use of longitudinal connecting members such as rods for example
also allows the bone-anchoring elements, for example screws, to
slide along the principal axis of the longitudinal connecting
member, and allows screws which diverge in the horizontal plane to
be brought onto the same antero-posterior line, and this is by
virtue of derotation effects imparted on the rods about an
apicocaudal axis, that is to say in the horizontal plane.
However, the bending of the rod that this manoeuvring this must be
performed between two vertebral segments which are a sufficient
distance apart. Furthermore, one or more successive bending
operations are performed only in the same frontal plane. This then
results in a deformation transposed into another plane, orthogonal
to the first.
The adjusting of the pedicle-screws/rod pair may lead to very high
stresses in the system before it is definitely locked.
Special-purpose instruments have therefore been conceived.
Pedicle screws in which the threaded shank is extended rearwards
have also been developed, so that the descent of the rod as far as
the vertebral implantation base of the screw can be guided, segment
by segment.
The other benefit of this type of extended pedicle implant is that
it allows equal use either of a plate or of a rod.
There are deformations whose radius of curvature may be short, in
one or two segments, but, nonetheless, combined in the three
planes, sagittal, horizontal and frontal. Simply bending a rod in a
single plane, bringing this rod gradually alongside or performing
an overall derotation movement, is then no longer suitable.
This is because the reduction by rotation of the rod in the event
of bending in two planes is prohibited by the laws of
mechanics.
Reduction of a deformation with a large radius, under such
conditions, is in three planes, but is not in any way sequential,
and can even less be said to be selective.
These short deformations, which can be reduced partially, have to
be considered segment by segment and especially plane by plane
before any reduction manoeuvre, particularly partial, can be
envisaged.
One vertebra which is off-set in isolation in the frontal sagittal
and horizontal planes has to be brought into a condition such that
it can undergo reduction in just one plane if necessary, or even
with a view to be secured as it is to the adjacent segment under no
stress other than the stress induced by neutralization.
To meet these requirements, pedicle screws equipped with a "ball
joint" system have been designed and developed.
Thus, the head of a screw may be capped by a U-shaped element thus
dubbed a "tulip" which acquires mobility about the principal axis
of the screw.
The travel obtained makes it possible, within certain limits, to
get around the consequences of an angular offset in the horizontal
and/or frontal plane of the pedicle alignment.
This being the case, the bending of the rod is no longer a ruse for
roughly aligning a poorly frontally aligned setup.
The surgeon is thus freed of this enormous burden and can implant
the pedicle screws along the axis imposed by the topography of the
pathological vertebra.
Regional sagittal vertebral statics are observed by virtue of a
bending in one plane, aimed at restoring sagittal equilibrium.
Various mechanical solutions are proposed, particularly by
successively fitting together elements which culminate in the
securing of the screw/ball/rod triplet.
Geometrically complex recesses and the fitting-together of a series
of elements allow the advantages of the above described
screw/ball-jointed tulip element to be reproduced.
In spite of the considerable progress that this alternative
represents, it is appropriate that a critical analysis be made of
it, and this analysis can be summarized in three points: 1. The
multi-axis U-shaped screws firstly do not allow rod/plate
interchangeability, or if they do this entails disassembly rather
akin to the "nesting Russian doll" principle.
Furthermore, reduction of an anterolisthesis requires the use of
screws with a U, the arms of which are extended backwards, at the
expense of requiring far more space. Finally, in order not to
stress the tightening elements during traction manoeuvres, use of a
special-purpose reduction instrument is recommended but entails
stressing the pedicle in tension; all of which cause preliminary
weakening. 2. The use of successive spacing pieces may prove
tricky, increasing the number of manoeuvres.
The mechanically reliable nature of the immobilization assumes a
perfect fit, although such fit is uncertain under operating
conditions (firstly the constraints imposed by the process, the
interposition of tissue, poor visual inspection, etc.) where the
implant is embedded.
The absence of rotational locking between the anchoring part and
the multi-axis ball also makes dismantling difficult and sometimes
impossible. 3. The special-purpose instruments required involve
just as many unknowns which add to the operating time, requiring
medical auxiliaries training, and finally make maintenance more
involved.
SUMMARY OF THE INVENTION
According to the invention, the threaded shank has a ball end for
articulation in a housing of a spherical cup of the head for
grasping, allowing the shank to be orientated in many directions,
and allowing the connecting shackle to be positioned to suit the
configuration of the vertebral segment receiving the bone-anchoring
elements, and the ball and the cup have respective centres of
rotation which are separated by a distance, giving the device, when
tightened using the tightening element, by bearing against the
upper part of the head for grasping, a function of returning the
bone-anchoring element by transverse force, the connector shackle
for this purpose having a spherical bearing surface articulated to
a portion of the spherical surface of the cup of the head of the
bone-anchoring element.
Depending on the physical characteristics of the connecting
shackle, either the surface contact immobilizes the bone-anchoring
element and allows the orientation of the bone-anchoring element to
be maintained, or the connecting shackle bears against the upper
part of the head for grasping, giving the device, upon tightening
of the element, a transverse return function.
Thus, among other advantages, the device according to the invention
allows the implant to be orientated in many directions using a
system which requires a very small amount of space, and allows the
bone-anchoring elements to be used either with rods or with
plates.
According to one feature of the invention, the threaded shank and
the connecting shackle are equipped with means for immobilizing the
shank and its ball in terms of rotation once the threaded shank has
been introduced into the corresponding through-hole through the
shackle.
According to another feature of the invention, the said means
comprise at least one rotation-stopping geometry formed between the
ball and the contiguous end of the threaded shank, and a second
rotation-stopping geometry formed on the interior edge of the hole
in the shackle, this second geometry being designed to press
against the first geometry once the connecting shackle has been
slid along the threaded shank.
According to another feature of the invention, the device also
comprises at least one bone-anchoring element comprising an
anchoring shape, a head with a transverse collar and a shape for
grasping, for screwing and a threaded shank extending the head, the
assembly being all of one piece.
BRIEF DESCRIPTION OF THE DRAWINGS
Other particular features and advantages of the invention will
emerge from the description which will follow, which is given with
reference to the appended drawings which illustrate two embodiments
thereof by way of non-limiting examples.
FIG. 1 is a partial perspective view prior to assembly, on an
enlarged scale, of a first embodiment of the spinal osteosynthesis
device according to the invention.
FIG. 2 is a partial perspective view of the device of FIG. 1,
showing, on an enlarged scale, a bone-anchoring element with two
screw threads and a corresponding shackle for connection to a
vertebral rod, not depicted, it being possible for this
bone-anchoring element to be, in particular, a screw or a hook.
FIG. 3 is a perspective view on an enlarged scale of the device of
FIGS. 1 and 2 assembled and fitted to a vertebral segment.
FIG. 4 is an anterolateral elevation view of a dorsolumbar segment
with an osteosynthesis device according to the invention, during
fitting, some of the connecting shackles with which a vertebral rod
is equipped being slipped over the threaded shanks of the
corresponding bone-anchoring elements which have already been
anchored in the vertebral bony structures.
FIG. 5 is a posterior view of the dorso-lumbar segment of FIG. 4
and of the corresponding device, installed.
FIG. 6 is anterolateral view of the device of FIG. 5, showing the
lumbar lordosis provided by bending the vertebral rod.
FIG. 7 is a plan view of a one-piece bone-anchoring element without
ball, with which the osteosynthesis device according to the
invention may be equipped.
FIG. 8 is a view in elevation from behind of a device with a plate
for connecting the bone-anchoring elements and mounted on a
dorso-lumbar segment.
FIG. 9 is a view in elevation in a sagittal plane of the device
with a plate of FIG. 8, comprising a bone-anchoring element like
the one in FIG. 6.
FIG. 10 is a view partly in elevation and partly in section on an
enlarged scale of the assembly of a bone-anchoring element, a
connecting shackle and a tightening element according to the
embodiment of FIGS. 1 to 4, for returning the bone-anchoring
element to the axis of the tightening element.
FIG. 11 is a diagrammatic view in elevation on a smaller scale than
FIG. 10, of the whole of the corresponding device, illustrating the
angular return of the bone-anchoring element to the axis of the
tightening element and of the threaded rod during tightening.
FIG. 12 is a part view similar to FIG. 10 of an alternative form of
the device, which is modified so as practically not to provide any
appreciable angular return of the bone-anchoring element during
tightening.
FIG. 13 is a perspective view on an enlarged scale, of a second
embodiment of the connecting shackle of FIG. 2.
FIG. 14 is a view in elevation on an enlarged scale of a second
embodiment of a bone-anchoring element of the device.
FIG. 15 is a view partly in elevation and partly in section of one
embodiment of a system for transversely connecting two
bone-anchoring elements, with which the device of FIGS. 1 to 14 may
be equipped.
FIG. 16 is a view from above of the transverse connecting system of
FIG. 15.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The spinal osteosynthesis device illustrated in FIGS. 1 to 6
comprises several bone-anchoring elements, consisting, in the
example described, of elements 1 for anchoring into the bone of the
respective vertebrae, a member for longitudinally connecting the
bone-anchoring elements 1, which member consists of a vertebral rod
2, and shackles 3 for connecting the bone-anchoring elements 1 to
the vertebral rods 2, there being one shackle 3 per bone-anchoring
element 1. Each element 1 comprises a tapered bone-anchoring
threaded shank 4, a head 5 for grasping with a screwing tool 6, a
mechanical threaded shank 7 extending the head 5. The device is
supplemented by a nut 8 which can be screwed onto the threaded
shank 7 to lock together the connecting shackle 3, the vertebral
rod 2 and the corresponding bone-anchoring element 1.
The head 5 for grasping has a shape which can cooperate with a
screwing tool 6, for example a hexagonal outline as depicted,
designed to cooperate with a female hexagonal cavity 9 of the tool
6.
The shank 7 has a ball end 11 for articulation in a hemispherical
housing 12 of the head 5, in which housing this ball 11 can be held
by various assembly techniques, particularly by crimping, welding,
etc. The approximately hemispherical housing 12 allows the ball 11
to turn and be mobile in all planes, thus allowing the threaded
shank 7 to be orientated in many directions.
The latter and the connecting shackle 3 are fitted with means for
immobilizing the shank 7 and its ball 11 in terms of rotation while
the nut 8 is being tightened or slackened once the shank 7 has been
introduced into a corresponding through-hole 10 through the
connecting shackle 3. In the embodiment depicted, these means
comprise at least one male rotation-stopping geometry 13 formed on
a collar 14 arranged between the ball 11 and the contiguous end of
the shank 7, and at least one second, female, rotation-stopping
geometry illustrated as a flat 15 formed on the interior edge of
the hole 10 in the shackle 3. This second flat 15 is designed to
press against the first flat 13 once the shackle 3 has been slid
along the threaded shank 7.
As a preference, the collar 14 thus has two diametrically opposed
rotation-stopping geometries 13, just one of these geometries 13
being visible in the drawings. The collar 14 thus equipped with the
two geometries 13 can fit into the corresponding connecting shackle
3 if the fixture is being used with a vertebral rod 2 or into a
plate 16 having similar rotation-stopping geometries (edges of the
holes 38, 41, 43 in FIGS. 8 and 9) 13 (FIGS. 8 and 9) if a plate 16
is being used in place of the rod 2 as a member for longitudinally
connecting the screws 1.
Beyond the collar 14, the shank 7 has a first cylindrical threaded
portion 17, a narrowed portion 18 constituting a break initiator, a
second cylindrical threaded portion 19 extended by a plain end part
21 constituting a male shape with an appropriate profile, for
example a half-moon profile with a rotation-stopping geometry,
hereinafter known as the flat 22 (FIG. 2). This male shape 21 is
designed to be able to cooperate with a complementary female shape
20 of the tool 6 formed in the end of a sleeve 24 mounted to slide
axially inside a socket 25 at the end of which the hexagonal female
cavity 9 is arranged (FIG. 1).
The narrowed portion 18 preferably has a rotation-stopping geometry
identical to the fiat 22. This arrangement allows the ball 11 to be
immobilized in terms of rotation during an operation of withdrawing
the implant, using the tool 6.
Fitting the male shape 21 with its rotation-stopping geometry which
may be a flat 22, into the mating female shape 20 with the flats 22
and 23 pressing one against the other, allows the threaded shank 7
to be immobilized in terms of rotation while the nut 8 is being
screwed onto the threaded portions 19 and 17 of the shank 7.
Furthermore, once fitting is complete it is at the narrowed portion
18 that the shank 7 is broken into two parts so that the threaded
portion 19 can be removed. Thus, only the threaded portion 17 forms
an integral part of the permanent fixture, the second portion 19
having the function only of guiding the descent of the nut 8 as far
as the shackle 3 (FIG. 3). During the descent of the nut 8, the
fact that the male 22 and female 23 flats of the sleeve 24 are
fitted together immobilizes the ball 11 in its housing 12 in terms
of rotation.
The connecting shackle 3 consists of two branches 26, 27 bent one
over onto the other and separated by a longitudinal slit 28, the
hole 10 for the passage of the shank 7 thus being formed in the
branches 26, 27 one on each side of the slit 28. The two branches
26, 27 are connected by one or two rounded connecting pieces 29
which delimit one or two cylindrical housings 31 into which one or
two cylindrical rods 2 can be introduced (FIG. 13).
FIGS. 10 and 11 illustrate in greater detail the embodiment of the
device which has just been described with reference to FIGS. 1 to
3.
Specifically, they show that the sphere or ball 11 of the
bone-anchoring element 1 and the spherical cup 57 have respective
centres of rotation R1 and R2 which are distinct and separated by a
distance S. The surface of the cup 57 of the head 5 is
hemispherical and interrupted in its polar region to receive the
ball 11, and the associated spherical surface 55 of the shackle 3,
with the same radius of curvature as the surface of the
hemispherical cup 57, completely covers the latter.
The pressing on the upper part of the head 5 for grasping gives the
connecting shackle 3/bone-anchoring element 1 system a function of
returning the latter to the axis XX of the tightening nut 8 and of
the threaded shank 7 during the tightening manoeuvre using the
element 8. Specifically, during this manoeuvre, the element 8 (nut
for example), the skirt 8a of which rests against the conical wall
56 of the recess in the nut 8, produces a tensile force F (FIG. 10)
which causes a torque C (FIG. 11) which returns the bone-anchoring
element 4 towards the longitudinal axis XX of the tightening
element 8 and of the threaded shank 7 as the result of a force
which is orthogonal to this axis.
In the embodiment illustrated in FIG. 12, the spherical surface 55a
only partially covers the spherical surface of the cup 57 because
the spherical bearing surface 55a is interrupted significantly
before the equator of the cup 57. Thus, the tensile force F
produced by tightening the nut 8, immobilizes the connecting
shackle 3 by surface contact, while at the same time maintaining
the orientation of the bone-anchoring element 1.
This possibility of operating using different connectors capable of
varying the realignment allows corrections to be planned without
having to resort to additional tools.
FIG. 13 illustrates one embodiment of the connecting shackle 3a in
which this shackle comprises, on each side of the hole 10, two
rounded connecting pieces 29, 29a delimiting two respective
housings 31, 31a designed to receive longitudinal connecting
members such as vertebral rods.
FIG. 14 illustrates a second embodiment of the bone-anchoring
element, here consisting of a blade-type hook 60 replacing the
threaded shank 4 of the previous embodiment, the remainder of the
device incidentally being similar to the one in FIGS. 1 and 2,
particularly the head 5 for grasping using a screwing tool 6 and
the threaded shank 7. The blade-type hook 6 consists, in the way
known per se, of two pincers 60a, 60b with curved ends and
adjustable relative separation.
FIGS. 15 and 16 illustrate one possible embodiment of a system for
transversely connecting the bone-anchoring elements (1 or 31 or
60). This connecting system is formed of a pair of flared dished
elements 58, 59, the bottoms of which are pierced with an opening
66 for the passage of the threaded shank 7. Each dished element 58,
59 is made of one piece with a respective transverse tab 61, 62,
the relative position and therefore the separation between the
dished elements being adjustable. Adjustment may be achieved for
example by means of a screw/nut assembly 63, 64 passing through an
elongate slot 65 in one tab 61 and a tapped hole in the other tab
62. Each dished element 58, 59 is interposed between a connecting
shackle 3 (or 3a) and a corresponding tightening element 8 which
screws into the dished part, resting against its conical wall 67,
68 via its conical skirt 8a.
The ability to orientate the bone-anchoring element 1 with respect
to the axis XX, with return (FIGS. 10, 11) or without angular
return (FIG. 12) can also be achieved with a similar geometrically
complex cavity made in a plate such as 16 (FIGS. 8 and 9, orifice
41, 43).
Once the threaded shank 4 has already been applied to the structure
of a vertebra, for example a lumbar vertebra, the shank 7 is
orientated towards the corresponding connector 3 already mounted on
a vertebral rod 2. Once this has been performed, the tool 6 Allows
the shank 7 to be immobilized in terms of rotation using the sleeve
24 while the outer socket 25 allows the tightening element 8 to be
screwed as far as its position which immobilizes the assembly, the
rotation stopping geometry or geometries 13 of the collar 14
pressing against the corresponding rotation-stopping geometry or
geometries 15 of the shackle 3.
FIG. 4 illustrates a reduction manoeuvre. The vertebral rod 2 has
been bent in the sagittal plane to reproduce the curvature of the
lordosis that it is desired to re-establish. The connecting
shackles 3 are slipped onto the rod 2 which, via the shackles 3, is
guided step by step but without effort, because the ball 11 of each
bone-anchoring element 1 allows the extra-pedicle threaded shank 7
to be directed towards the shackle 3 before the rod 2 starts to be
brought into contact with the spinal column--namely in the example
depicted a dorso-lumbar segment: sacrum S and lumbar vertebrae L5,
L4, L3, L2. The descent of the shackle 3 along the threaded shank 7
which constitutes the mobile part of the implant, occurs by virtue
of the tightening element 8 (nut), using the wrench which consists
of the tool 6 which prevents the ball 11 from turning on itself as
explained earlier. The shackle 3 via its underside meets the
appropriately orientated collar 14, the two rotation-stopping
geometries 22 (flats) 23 meeting, thus immobilizing the ball 11.
Specifically, once it is facing the flat 15 of the shackle 3, the
collar 14 can no longer turn about its axis. When the two
rotation-stopping geometries--the male one 22 and the female one
15--are facing one another, the ball 11 immobilizes itself. The
implant has become a single-axis implant.
In the lombosacral set-up illustrated in FIG. 6, involving the
sacrum S and the first four lumbar vertebrae, it can be seen that
the physiological lordosis has been restored by curving the rod 2
in the sagittal plane, the extra-pedicle portions consisting of the
shanks 7 being orientated correspondingly to adapt to this
curvature. Once the set-up has been locked, the posterior portion
19 of each threaded shank 7 is easily broken by virtue of the
reduction in cross section formed by the break-initiator region 18.
Post-operative X-ray examinations of patients exhibiting lumbar
scoliosis make it possible to check that, by virtue of the
osteosynthesis device according to the invention, the pedicle
implants 1, seen face-on, are not in the same plane and that the
lumbar lordosis (side-on) has been restored satisfactorily with, in
particular, the reappearance of physiological discal asymmetry,
which is essential for creating anatomically correct
conditions.
FIG. 7 illustrates a second bone-anchoring element 31 (in this
example, a screw) which can be used in a device which is not an
embodiment according to the invention when this device comprises a
plate 16 (FIGS. 8 and 9) or connecting shackles 3.
The bone-anchoring element 31 comprises a threaded anchoring rod
32, a head 33 which has no ball thus making the screw a one-piece
screw. The head 33 consists of a transverse collar 34 and a shape
35 for grasping for screwing with an appropriate tool, for example
a hexagonal shape. A threaded shank 7 similar to the one of the
bone-anchoring element 1 extends the head 33, the assembly being of
one piece. Facing the sacrum S the plate 16 has an end part with a
circular hole for the passage of a single bone-anchoring element
31, and then, in the region of L5, has a second elongate portion 39
in which there is formed an oblong hole 41 which allows the
position of a bone-anchoring element 31 to be adjusted
correspondingly between two positions; finally, the plate 16 has a
third part 42 of elongate shape in which there is made an oblong
passage 43 delimiting three possible positions for the
bone-anchoring element 1 depending on the adjustment needed, by
virtue of three cut-outs formed on the edges of the passage 43.
The plate 16 which is intended for three spinal segments or stages,
S, L5, L4, for example, may be replaced with a plate suited to a
different number of stages. For example, in the three-stage set-up
of FIGS. 8 and 9, just one bone-anchoring element is multiaxial,
and therefore has a ball 11, the other bone-anchoring elements 31
being monoaxial. Each hole (41 . . . ) in the plate 16 may have the
same profile as the hole 10 in the connecting shackle 3 for the
passage of the bone-anchoring element (FIG. 10). This profile makes
it possible to fulfil a function of returning the bone element
towards the longitudinal axis of the tightening element and of the
threaded shank 7 by means of a force orthogonal to this axis. The
collar 34 located in the extension of the intra-pedicle portion of
the bone-anchoring element 1 is stationary (FIGS. 8 and 9). It may
beneficially provide good support against the vertebra using a
so-called "bracket" effect, whereas a bone-anchoring element 1 can
beneficially be used to reduce, at segment level, an angle between
two contiguous boney structures of the spine.
The multi-axis screw 1 is left free to move at the beginning of the
fitting of the tightening element 8 along the threaded shank 7.
Next, the sleeve 24 with its half-moon shape 23 immobilizes the
ball 11. Using an appropriate movement, the bone-anchoring element
1 is thus positioned in one of the three orifices of the oblong
hole 43. The prebending of the plate 16 allows the vertebra L4 to
reposition itself in lordosis with respect to the underlying
vertebra, without compromising the locking of the plate
16/bone-anchoring element 1 pair, because of the tolerance afforded
by the ball 11.
It is possible to use a plate for just two boney structures of the
lumbar spine. Prebending this plate allows the vertebra to be
tilted in the posterior direction and therefore allows
physiological discal asymmetry to be recreated, particularly in the
case of the surgical treatment of the so-called "flat back"
condition.
Aside from the technical advantages already mentioned, the spinal
osteosynthesis device according to the invention exhibits the
following advantages: the bone-anchoring element 1, 31 is guided by
an instrument 6 which instantly normalizes the axis of the pedicle
4, 32 of the bone-anchoring element 1 and its multi-axis extension
7. There is a possibility for reduction that is either monoplanar
or combined in all three planes. Certain operating sequences can be
avoided. Vertebral reduction by antero-posterior traction using the
bone-anchoring element, directly, without additional instruments.
The orientability of the system can be either maintained or
neutralized with equal ease according to the peri-operative
requirements by virtue of the dimensional and functional
characteristics of the connecting shackles 3 (the combination of
the spherical bearing surface 55 or 55a with the spherical cup
57).
* * * * *