U.S. patent application number 12/606901 was filed with the patent office on 2010-05-06 for flexible linking piece for stabilising the spine.
Invention is credited to Regis Le Couedic, Denis Pasquet.
Application Number | 20100114169 12/606901 |
Document ID | / |
Family ID | 8852866 |
Filed Date | 2010-05-06 |
United States Patent
Application |
20100114169 |
Kind Code |
A1 |
Le Couedic; Regis ; et
al. |
May 6, 2010 |
FLEXIBLE LINKING PIECE FOR STABILISING THE SPINE
Abstract
Embodiments described herein relate to a connecting member for
maintaining the spacing between at least two anchor members screwed
into vertebrae and methods for stabilizing the spine using a
connecting member. One embodiment of a connecting member can
include a first rigid portion formed of a first material, a second
rigid portion formed of the first material and a connecting body
comprising a second material that is more elastically deformable
than the first material.
Inventors: |
Le Couedic; Regis;
(Bordeaux, FR) ; Pasquet; Denis; (Pessac,
FR) |
Correspondence
Address: |
SPRINKLE IP LAW GROUP
1301 W. 25TH STREET, SUITE 408
AUSTIN
TX
78705
US
|
Family ID: |
8852866 |
Appl. No.: |
12/606901 |
Filed: |
October 27, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10333881 |
Jan 24, 2003 |
7641673 |
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PCT/FR01/02426 |
Jul 25, 2001 |
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12606901 |
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Current U.S.
Class: |
606/264 ;
606/279 |
Current CPC
Class: |
A61B 17/7004 20130101;
A61B 17/7032 20130101; A61B 17/7031 20130101 |
Class at
Publication: |
606/264 ;
606/279 |
International
Class: |
A61B 17/70 20060101
A61B017/70; A61B 17/88 20060101 A61B017/88 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 25, 2000 |
FR |
00/09706 |
Claims
1. A method of stabilizing a spinal segment of a body comprising:
securing a first anchor to a first vertebra, the first anchor
including a head portion and a bone attachment portion; securing a
second anchor to a second vertebra, the second anchor including a
head portion and a bone attachment portion; implanting a connecting
member into the body, wherein the connecting member comprises: a
first rigid portion formed of a first material comprising; a first
rod portion adapted to secure in a head portion of a first anchor;
and a first wall having a larger radius than the first rod portion;
a second rigid portion formed of the first material comprising: a
second rod portion adapted to secure in a head portion of a second
anchor; and a second wall having a larger radius than the second
rod portion; and a connecting body having a first end abutting the
first wall and a second end abutting the second wall, wherein the
connecting body comprises a second material that is more
elastically deformable than the first material; positioning the
connecting body between the head portion of the first anchor and
the head portion of the second anchor; and positioning the first
rigid portion within the head portion of the first anchor and the
second rigid portion in the head portion of the second anchor.
2. The method of claim 1, wherein the first wall and second wall
each comprise at least one protrusion that abuts the connecting
body.
3. The method of claim 2, wherein the first rigid portion partially
overlaps said connecting body.
4. The method of claim 1, wherein the first rigid portion defines
an opening passing from the first wall through the first rigid
portion and open to an end of the first rod portion and the second
rigid portion defines an opening passing from the second wall
through the second rigid rod portion and open to and of the second
rod portion.
5. The method of claim 1, further comprising positioning the first
rigid portion and second rigid portion from the top of the first
anchor and second anchor respectively.
6. The method of claim 1, further comprising: securing the first
rigid portion to the head portion of the first anchor by engaging a
first locking member to a the head portion of the first anchor; and
securing the second rigid portion to the head portion of the second
anchor by engaging a second locking member to a the head portion of
the second anchor;
7. The method of claim 1, wherein the head portion of each of the
first and second anchors includes a slot adapted to receive the
first rigid portion and second rigid portion respectively.
8. The method of claim 1, wherein the connecting body has a greater
cross-sectional area than the first rod portion and the second rod
portion.
9. The method of claim 7, wherein the first rigid portion and
second rigid portion are formed of a biocompatible metal and the
connecting body comprises a polymer.
10. A connecting member comprising: a first rigid portion formed of
a first material comprising; a first portion adapted to secure in a
head portion of a first anchor; and a first wall having a larger
radius than the first rod portion; a second rigid portion formed of
the first material comprising: a second portion adapted to secure
in a head portion of a second anchor; and a second wall having a
larger radius than the second rod portion; and a connecting body
having a first end abutting the first wall and a second end
abutting the second wall, wherein the connecting body comprises a
second material that is more elastically deformable than the first
material.
11. The connecting member of claim 10, wherein the first wall and
second wall each comprise at least one protrusion that abuts the
connecting body.
12. The connecting member of claim 11, wherein the first rigid
portion partially overlaps said connecting body.
13. The connecting member of claim 10, wherein the first rigid
portion defines an opening passing from the first wall through the
first rigid portion and open to an end of the first rod portion and
the second rigid portion defines an opening passing from the second
wall through the second rigid rod portion and open to and of the
second rod portion.
14. The connecting member of claim 10, wherein the first material
is a biocompatible metal and the second material is a polymer.
15. The connecting member of claim 10, wherein the connecting body
is substantially symmetrical about a longitudinal axis.
16. The connecting member of claim 10, wherein the first rigid
portion and the second rigid portion are cylindrical.
17. A spinal stabilization system comprising: a first anchor
coupled to a first vertebra, the first anchor having a head
portion; a second anchor coupled to a second vertebra, the second
anchor having a head portion; a connecting member comprising: a
first rigid portion formed of a first material comprising; a first
portion secured in a head portion of a first anchor; and a first
wall having a larger radius than the first rod portion; a second
rigid portion formed of the first material comprising: a second
portion secured in a head portion of a second anchor; and a second
wall having a larger radius than the second rod portion; and a
connecting body having a first end abutting the first wall and a
second end abutting the second wall, wherein the connecting body
comprises a second material that is more elastically deformable
than the first material.
18. The spinal stabilization system of claim 17, wherein the first
wall and second wall each comprise at least one protrusion that
abuts the connecting body.
19. The spinal stabilization system of claim 18, wherein the first
rigid portion partially overlaps said connecting body.
20. The spinal stabilization system of claim 17, wherein the first
rigid portion defines an opening passing from the first wall
through the first rigid portion and open to an end of the first
rigid portion and the second rigid portion defines an opening
passing from the second wall through the second rigid portion and
open to an end of the second rigid portion.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of and claims priority
under 37 CFR 1.53(b) to U.S. patent application Ser. No.
10/333,881, filed Jan. 24, 2003, entitled "Flexible Linking Piece
for Stabilising the Spine" by inventors Regis LeCouedic and Denis
Pasquet, which claims priority under 35 U.S.C. 371 to International
Application No. PCT/FR01/02426, filed Jul. 25, 2001, entitled
"Flexible Linking Piece for Stabilising the Spine" by inventors
Regis LeCouedic and Denis Pasquet, which claims benefit of priority
to French Application No. 00/09706 entitled "Flexible Linking Piece
for Stablising the Spine" by inventors Regis LeCouedic and Denis
Pasquet, filed Jul. 25, 2000, all of which are incorporated herein
by reference.
TECHNICAL FIELD
[0002] This disclosure relates to a connecting member for
maintaining the spacing between at least two anchor members which
are interconnected by said connecting member.
BACKGROUND
[0003] Systems for stabilizing the vertebral column by bracing at
least two consecutive vertebrae by means of anchor members fixed
into said vertebrae and connected by rigid connecting rods are well
known in the art. Systems of this kind are generally coupled
systems such that two consecutive vertebrae are interconnected by
two substantially parallel rods fixed one on each side of the
spinous processes. The anchor members are screwed into the
posterior portions of the vertebrae and pass through the pedicles
and a substantial portion of the vertebral bodies and therefore
provide a fixed and durable connection.
[0004] The above stabilizing systems are routinely used to
consolidate several consecutive vertebrae. Thus the vertebrae are
interconnected by rigid rods over a substantial length of the
vertebral column. Such assemblies hold the vertebrae correctly
relative to each other; however, they considerably stiffen the
spine in terms of bending. It has been shown that a more flexible
stabilizing system, which confers greater relative mobility on the
vertebrae, is beneficial in some pathologies.
BRIEF SUMMARY
[0005] A first object of embodiments described herein is to provide
a connecting member for maintaining the spacing of existing anchor
members while at the same time allowing relative mobility of said
anchor members.
[0006] To achieve the above object, a connecting member in
accordance with one embodiment, adapted to maintain the spacing
between at least two anchor members screwed into vertebrae,
comprises at least two rigid rod-forming parts made of a first
material and each having a fixing, first portion adapted to be
fixed into an anchor member and a fastening, second portion, said
rods being aligned with each other and said fastening portions
facing each other, and a connecting body that is made entirely from
a second material that is more elastically deformable than said
first material and interconnects the facing fastening portions of
said rigid parts so that said connecting body is able to deform
elastically, whereby the vertebrae, which are held spaced from each
other, are movable relative to each other.
[0007] Thus a feature of the connecting member lies in the way the
two rigid parts are fastened together by means of an elastically
deformable connecting body which imparts relative mobility to the
rigid parts when under stress, with the reaction force to the
stress being proportional, within certain limits, to the
deformation of the connecting body. As a result, the connecting
member can be bent by stresses in directions that are not parallel
to the axis of the connecting member; it can also be stretched or
contracted by opposing forces acting parallel to the axis of the
connecting member.
[0008] Consequently, the two anchor members, when at rest, are
interconnected by the connecting member with its fixing portions
fastened to the anchor members, and can be moved relative to each
other by forces proportional to the movement.
[0009] Said rigid parts are preferably mechanically connected
together by a single connecting body providing the whole of said
mechanical connection. In this way a single member provides the
connection between the rigid parts at the same time as controlling
relative movement of the rigid parts. Also, in a particular
embodiment, said connecting body consists entirely of a single
second material to simplify assembly and to impart homogeneous
mechanical properties to it.
[0010] The connecting member of an embodiment has n rigid parts
with n-1 connecting bodies disposed between them along the
longitudinal axis of said member, each rigid part situated between
two connecting bodies having one fixing, first portion and two
fastening, second portions, there being one fastening, second
portion at each end of said fixing, first portion, and said
fastening, second portions being connected respectively to said two
connecting bodies, and the rigid parts at the two ends of said
member advantageously have respective single fastening, second
portions connected to the connecting bodies, whereby said
connecting member is adapted to interconnect n anchor members.
[0011] Thus, by virtue of this feature, the connecting member
maintains the spacing between all the anchor members that it
interconnects, each of which can be fixed to a respective vertebra,
to align them. Each rigid part is fixed to an anchor member and,
between successive anchor members, there is a connecting body that
interconnects the two fastening portions. Thus a single connecting
member stabilizes several vertebrae, which reduces the time to
assemble the stabilizing system as a whole and consequently the
operating time. Also, by virtue of this feature, the connecting
member stabilizes several consecutive vertebrae by connecting them
together, while at the same time making them highly flexible and
conferring on them a high degree of relative compressibility in the
longitudinal direction.
[0012] In a preferred embodiment, each of said fastening portions
of said rigid parts that said connecting body interconnects has a
fastening wall to which said connecting body is adapted to adhere.
Thus no additional fixing member is needed and the adhesive
properties of the second material to the fastening wall are
sufficient to connect them.
[0013] In one particular embodiment, said fastening wall has
openings adapted to cooperate with asperities on said connecting
body to increase the surface area of contact between said wall and
said body.
[0014] Obviously, providing openings in a wall increases the
surface area of that wall, which increases the contact area between
the two materials if one of the materials can be molded onto the
wall of the other material. The increase in contact area increases
the connecting forces between said connecting body and said
fastening portions. Also, the static friction forces of the
material of the connecting member on said two members are increased
in a corresponding manner and these forces are added to the
connecting forces.
[0015] Said second material of which said connecting body is made
is advantageously obtained by polymerization. In this way, the
connecting body can easily be hot molded onto the fastening walls
if the material is polymerized beforehand, or it can be formed in
situ if the rate of polymerization of the monomers constituting
said second material is sufficiently low to provide the time
necessary for completing the assembly.
[0016] In a preferred embodiment, said first material of which said
rigid parts are made is a titanium alloy. It is therefore easy to
form openings in said fastening wall to which said connecting body
is able to adhere.
[0017] In another preferred embodiment, the section of said rigid
rod-forming parts is circular, which facilitates the manufacture of
the member. Also, if prior art circular section connecting rods are
to be replaced by connecting rods described herein without making
it necessary to replace the anchor members, it is necessary for
said rigid parts to have sections identical to the sections of the
prior art connecting rods.
[0018] The present disclosure also provides a vertebral
stabilization system for fastening together at least two vertebrae
each having a median plane substantially perpendicular to the axis
of the spine of which they form a part and a posterior wall
defining a posterior median plane of said spine, said system
comprising at least two anchor members each adapted to be fixed
into the posterior wall of a respective vertebra so that a line
which intersects said two anchor members is substantially parallel
to said axis of the spine, which system further comprises at least
one connecting member whose two rigid parts are adapted to
interconnect said two anchor members so that the axis of said
connecting member is substantially parallel to said axis of the
spine, whereby said vertebrae, which are interconnected via their
posterior portions, present relative mobility along said axis of
said spine.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] Other features and advantages of various embodiments will
emerge on reading the following description of particular
embodiments, which is given by way of non-limiting example and with
reference to the accompanying drawings, in which:
[0020] FIG. 1 is a diagrammatic perspective view of a connecting
member in accordance with an embodiment,
[0021] FIG. 2 is a diagrammatic view in axial section of the
connecting member in accordance with an embodiment,
[0022] FIG. 3 is a perspective view showing anchor members
connected by the connecting member,
[0023] FIG. 4 is a side elevation view of a vertebral column
showing two consecutive vertebrae into which there are screwed
anchor members interconnected by a connecting member in accordance
with an embodiment, and
[0024] FIG. 5 is a perspective view showing a connecting member
having two connecting bodies and three rigid parts.
DETAILED DESCRIPTION
[0025] The various portions of a connecting member are described
initially with reference to FIG. 1.
[0026] The connecting member 10 has two cylindrical rigid parts 12
and 14. Each rigid part 12, 14 has a fixing, first portion 16, 18
and a fastening, second portion 20, 22 forming an enlargement. The
facing fastening portions 20 and 22 are connected together by a
connecting body 24 so that the rigid parts 12 and 14 are in axial
alignment. The connecting member 10 is therefore circularly
symmetrical about the axis A.
[0027] How the two rigid parts 12 and 14 are fastened together is
described below with reference to FIG. 2.
[0028] The connecting body 24 is a plastics material body obtained
by polymerization. The material of the body is chosen from
materials which are more elastically deformable than the material
of said rigid parts 12, 14 and, most importantly, whose elastic
properties are of the same order of magnitude as those of the
posterior ligaments that hold the spine together.
[0029] Organic silicon compounds constitute polymers whose
mechanical properties can be determined by the choice of their
basic components, in particular by their degree of substitution,
the nature of the substituents, and their molecular weight, and
whose elastic behavior predominates over its plastic behavior. They
therefore constitute a family of materials suitable for
interconnecting the two rigid parts 12 and 14. Also, these polymers
can adhere strongly to materials of inorganic composition. Thus the
connecting body 24 provides good means for fastening together the
rigid parts 12, 14, which are generally made of titanium alloy.
[0030] Nevertheless, the polymer materials that can be used are not
limited to organic silicon compounds, and any other material having
comparable properties could be suitable.
[0031] The material of the connecting body 24 is adapted to adhere
to the fastening walls 20' and 22' of said fastening second
portions 20, 22. However, to increase the adhesion, openings 30, 32
are formed in the fastening walls 20, 22 of the fastening, second
portions and are adapted to cooperate with asperities 26, 28 on the
connecting body 24 which are inserted into the openings 30, 32.
[0032] This feature increases the contact area between the two
materials and thereby increases the connecting force between them
in a direction normal to said surface of contact and creates static
friction forces which are additional to the adhesion force.
[0033] A connection of the above kind is obtained either by
injecting the polymer while hot between the two rigid parts 12 and
14 held facing each other in a mold, or by cold molding the mixture
of monomers between the two rigid parts 12 and 14, if the speed of
the reaction is sufficiently low. The asperities 26, 28 are
therefore formed in situ, when the polymer liquid or paste inserted
into the openings 26, 28 solidifies after cooling or after a
chemical reaction. Obviously, the connecting body 24 consists of
the polymer disposed between the rigid parts 12 and 14, more
specifically between the fastening walls 20' and 22', and, in order
to retain the polymer between the facing portions while it is in
the liquid state, the walls of the mold must necessarily surround
the space between and in line with the two rigid parts 12, 14.
[0034] In a particular embodiment (not shown) the openings 30, 32
formed in the fastening walls 20' and 22' open onto the outside
wall of the rigid parts 12 and 14 so that the liquid polymer
penetrates entirely into the openings 30, 32 without it being
possible for air to be trapped therein. This reinforces the
fastening of the connecting body 24 to the rigid parts 12, 14.
[0035] Also, the openings 30, 32, which are shown as parallel to
the longitudinal axis of the connecting member in FIG. 2, can be
oblique to that longitudinal axis and/or not rectilinear. These
configurations increase the static friction forces of the polymer
on the rigid parts, which fastens them together more strongly.
[0036] Now that the manner in which the two rigid parts are
fastened together has been described, movement of the rigid parts
relative to each other is described with reference to FIG. 1.
[0037] Given the circular symmetry of the rigid parts 12 and 14 and
the connecting body 24, and the nature of the material of the
connecting body 24, the connecting member 10 is able to bend in all
directions in a plane Pp perpendicular to the axis A of the
connecting member when the two first portions are immobilized.
Bending of the connecting member 10 compresses one edge of the
connecting body 24 and stretches the diametrally opposite edge,
whereas the rigid parts 12 and 14 retain their shape. Because the
material of the connecting body 24 is elastically deformable, when
the stresses causing the bending are removed, the connecting member
10 returns to its original state in which the rigid parts 12 and 14
are in axial alignment.
[0038] Also, the rigid parts 12 and 14 can move relative to each
other in opposite directions along the longitudinal axis A to
compress or stretch the connecting body 24.
[0039] The relative movement of the two rigid parts 12 and 14 can
occur in directions other than the directions described above, but
the connecting member is principally loaded in bending, tension and
compression, as described in more detail below.
[0040] Deformation of the connecting member connected with relative
movement of the anchor members 42 and 44 is described next with
reference to FIG. 3.
[0041] FIG. 3 shows the connecting member 10 whose two rigid parts
12 and 14 interconnect the two anchor members 42 and 44. The two
anchor members 42 and 44 are parallel to each other in a common
axial plane Pa.
[0042] Each anchor member 42, 44 has a threaded shank 46 with a
U-shaped head 48 at the top whose inside wall is threaded so that a
screw-forming member 50 can be screwed into it. Thus the first
portions 16 and 18 of the rigid parts 12 and 14 are accommodated in
the heads 48 of the respective anchor members 42 and 44 and are
locked to them by tightening the screw-forming members 50.
[0043] As a result, when the threaded shanks 46 of the anchor
members move towards each other due to the effect of opposite
forces T and -T in the plane Pa and substantially parallel to the
axis A the anchor members 42 and 44 deform the connecting member,
which bends.
[0044] The bending of the connecting member 10 compresses the lower
edge 52 of the connecting body 24 and stretches the diametrally
opposite upper edge 54, while the rigid parts 12 and 14 retain
their shape. Because the material of the connecting body 24 is
elastically deformable, when the stress is removed the connecting
member reverts to its original rectilinear shape and the threaded
shanks of the anchor members 46 return to their former relative
position.
[0045] The mechanism of elastic bending of the connecting member 10
and the anchor members 42, 44 described above is the same if the
threaded shanks 46 of the anchor members 42 and 44 move away from
each other, the connecting member bending with the opposite
curvature.
[0046] Also, the anchor members 42 and 44 are movable in
translation relative to each other along the axis A, their relative
movement stretching or compressing the connecting body 24.
[0047] The use of the connecting member 10 in a vertebral
stabilization system for fastening together at least two vertebrae
V1 and V2 is described below with reference to FIG. 4.
[0048] The vertebrae V1, V2 each have respective median planes PV1,
PV2 substantially perpendicular to the axis Ar of the spine of
which they form part, and respective posterior walls PPV1, PPV2
defining a posterior median plane PPr of said spine.
[0049] The stabilizing system includes at least two anchor members
42 and 44 respectively screwed into the posterior walls PPV1, PPV2
of the vertebrae V1, V2, so that a line L that intersects the two
anchor members 42 and 44 is substantially parallel to said axis Ar
of the spine. The two first portions 16 and 18 of the connecting
member 10 interconnect the two anchor members 42 and 44. As a
result, the vertebrae V1 and V2, which are interconnected in their
posterior portions, possess relative mobility along the axis Ar of
the spine.
[0050] Thus when the spine is stretched, the vertebrae V1 and V2
move away from each other in opposite directions E and -E, which
causes the threaded shanks 46 to move away from each other,
deforming the connecting member 10, and in particular its
connecting body 24. This is because the connecting body is
compressed both longitudinally and at the upper edge 54. The
deformed connecting member has it concave side facing away from the
spine.
[0051] When the spine is bent, the inverse effect occurs and the
vertebrae V1 and V2 move towards each other, which induces
deformation of the connecting member with its concave side facing
toward the spine.
[0052] The connecting body is then subjected to longitudinal
extension of its upper edge 54 and possibly to compression of its
lower edge 52.
[0053] It will be understood that the connecting member 10 achieves
greater relative mobility of the vertebrae compared to the prior
art connecting rods, which cannot be compressed longitudinally.
[0054] In a particular embodiment as shown in FIG. 5, the
connecting member has three rigid rod-forming parts 12, 14, 15 and
two connecting bodies 24.sub.1, 24.sub.2 interconnecting the three
rigid parts 12, 14, 15. To this end, the central rigid part 15
includes a fixing, first portion and two fastening, second
portions, with one fastening, second portion on each side of said
fixing, first portion. The fastening, second portions are connected
to the two connecting bodies 24.sub.1, 24.sub.2. The other two
rigid parts 12, 14, situated at the two ends of the connecting
member, have a single fastening, second portion connected to the
connecting bodies.
[0055] The connecting member therefore maintains the spacing
between three anchor members that it interconnects, which are fixed
to three substantially equidistant vertebrae, to align them. Each
rigid part of the connecting member is fixed to an anchor member so
that there are respective elastically deformable connecting bodies
between the pairs of vertebrae. In this way, a single connecting
member stabilizes three vertebrae, which reduces the time needed to
assemble the stabilizing system as a whole and consequently the
operating time. Also, because the three vertebrae are
interconnected by a single connecting member, their mobility
relative to each other is better controlled.
[0056] It goes without saying that providing connecting members
having more than three rigid parts connected together by
elastically deformable connecting bodies would not depart from the
scope of the invention.
* * * * *