U.S. patent application number 13/891141 was filed with the patent office on 2014-01-30 for flexible stabilization device for dynamic stabilization of bones or vertebrae.
This patent application is currently assigned to Biedermann Technologies GmbH & Co. KG. The applicant listed for this patent is Biedermann Technologies GmbH & Co. KG. Invention is credited to Lutz Biedermann, Wilfried Matthis, Helmar Rapp.
Application Number | 20140031868 13/891141 |
Document ID | / |
Family ID | 36177294 |
Filed Date | 2014-01-30 |
United States Patent
Application |
20140031868 |
Kind Code |
A1 |
Biedermann; Lutz ; et
al. |
January 30, 2014 |
FLEXIBLE STABILIZATION DEVICE FOR DYNAMIC STABILIZATION OF BONES OR
VERTEBRAE
Abstract
A flexible stabilization device for dynamic stabilization of
bones or vertebrae is provided comprising a rod construct including
a rod made of an elastomeric material the rod having a first
connection section, a second connection section and a third section
therebetween, the first and second connection sections being
connectable with a bone anchoring device, respectively, and a
sleeve provided on at least a portion of the third section of the
rod such that at least the first and second connection sections are
exposed.
Inventors: |
Biedermann; Lutz;
(VS-Villingen, DE) ; Matthis; Wilfried; (Weisweil,
DE) ; Rapp; Helmar; (Deisslingen, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Biedermann Technologies GmbH & Co. KG; |
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US |
|
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Assignee: |
Biedermann Technologies GmbH &
Co. KG
Donaueschingen
DE
|
Family ID: |
36177294 |
Appl. No.: |
13/891141 |
Filed: |
May 9, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13425153 |
Mar 20, 2012 |
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13891141 |
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11642566 |
Dec 19, 2006 |
8157843 |
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13425153 |
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60753620 |
Dec 23, 2005 |
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Current U.S.
Class: |
606/255 |
Current CPC
Class: |
A61B 17/7037 20130101;
A61B 17/7004 20130101; A61B 17/702 20130101; A61B 17/7032 20130101;
A61B 17/7031 20130101 |
Class at
Publication: |
606/255 |
International
Class: |
A61B 17/70 20060101
A61B017/70 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 23, 2005 |
EP |
05028283 |
Claims
1. A flexible stabilization device for dynamic stabilization of
bones or vertebrae comprising: a rod assembly including a rod made
of an elastomeric material and structured such that its length is
adjustable, the rod configured to transmit compressive forces in
the axial direction, the rod having a first connection section, a
second connection section and a third section therebetween, the
first and second connection sections being connectable with a bone
anchoring device, respectively, and a sleeve provided on at least a
portion of the third section of the rod, the length of the sleeve
being smaller than a length of the rod, such that at least the
first and second connection sections are exposed.
2. A flexible stabilization device according to claim 1, wherein
the sleeve is made of an elastomeric material.
3. A flexible stabilization device according to claim 2, wherein
the elastic properties of the rod and the sleeve are different.
4. A flexible stabilization device according to claim 2, wherein
the elastomeric material of any one of the rod and the sleeve is a
biocompatible plastic material such as polyurethane or
polysilicone.
5. A flexible stabilization device according to claim 1, wherein
the inner wall of the sleeve is in contact with the surface of the
rod.
6. A flexible stabilization device according to claim 5, wherein
the inner wall of the sleeve has a structure which engages with a
structure on the surface of the rod.
7. A flexible stabilization device according to claim 1, further
comprising at least a first and a second bone anchoring device
connected with the rod assembly.
8. A flexible stabilization device according to claim 7, wherein at
least one of the bone anchoring devices is constructed so as to
allow a polyaxial connection between a shank of the bone anchoring
device and the rod.
9. A flexible stabilization device according to claim 1, wherein
the rod comprises a plurality of connection sections and a
plurality of sleeves therebetween.
10. A rod assembly for a flexible stabilization device, the rod
assembly comprising: a rod made of an elastomeric material, the rod
having a first connection section, a second connection section and
a third section therebetween; and a sleeve provided on at least a
portion of the third section of the rod such that at least the
first and second connection sections are exposed; wherein an inner
wall of the sleeve has a structure which engages with an inner
structure on a surface of the rod.
11. A rod assembly according to claim 10, wherein the sleeve is
made of an elastomeric material.
12. A rod assembly according to claim 11, wherein the elastic
properties of the rod and the sleeve are different.
13. A rod assembly according to claim 11, wherein the elastomeric
material of any one of the bar and the sleeve is a biocompatible
plastic material such as polyurethane or polysilicone.
14. A rod assembly according to claim 10, wherein the rod comprises
a plurality of connection sections and a plurality of sleeves
therebetween.
15. A flexible stabilization device for dynamic stabilization of
bones or vertebrae comprising: a rod assembly comprising: a rod
made of an elastomeric material and having a first connection
section, a second connection section and a third section
therebetween; and a sleeve provided on at least a portion of the
third section of the rod, the length of the sleeve being smaller
than a length of the rod, such that at least the first and second
connection sections are exposed; a bone anchoring device
connectable with any one of the first connection section and the
second connection section of the rod, the bone anchoring device
comprising: a shank portion configured to be anchored in a bone or
in a vertebra; a head portion having a recess including an opening,
the recess configured to receive a portion of any one of the first
connection section and the second connection section of the rod;
and a securing element configured to secure the portion in the
recess by pressure exerted on the portion.
16. A flexible stabilization device according to claim 15, wherein
the sleeve is made of an elastomeric material.
17. A flexible stabilization device according to claim 16, wherein
the elastic properties of the rod and the sleeve are different.
18. A flexible stabilization device according to claim 16, wherein
the elastomeric material of any one of the bar and the sleeve is a
biocompatible plastic material such as polyurethane or
polysilicone.
19. A flexible stabilization device according to claim 15, wherein
the inner wall of the sleeve is in contact with the surface of the
rod.
20. A flexible stabilization device according to claim 19, wherein
the inner wall of the sleeve has a structure which engages with a
structure on the surface of the rod.
21. A flexible stabilization device according to claim 15, wherein
at least on of the first bone anchoring device and the second bone
anchoring device is constructed so as to allow a polyaxial
connection between the shank thereof and the rod.
22. A flexible stabilization device according to claim 15, wherein
the rod comprises a plurality of connection sections and a
plurality of sleeves therebetween.
Description
CROSS-REFERENCE TO RELATED APPLICATION(S)
[0001] This application is a continuation of U.S. patent
application Ser. No. 13/425,153, filed Mar. 20, 2012, which is a
continuation of U.S. patent application Ser. No. 11/642,566, filed
Dec. 19, 2006, now U.S. Pat. No. 8,157,843, which claims the
benefit of U.S. Provisional Patent Application Ser. No. 60/753,620,
filed Dec. 23, 2005, and claims priority from European Patent
Application EP05028283, filed Dec. 23, 2005, the entire disclosures
of which are incorporated herein by reference.
BACKGROUND
[0002] The present disclosure relates to a flexible stabilization
device for the dynamic stabilization of bones or vertebrae.
[0003] A flexible stabilization device for stabilizing adjacent
vertebrae is known from EP 0 669 109 B1. In this stabilization
device monoaxial bone screws placed in adjacent vertebrae are
connected by an elastic strap. The strap is fastened to the bone
screws in a pre-stressed manner. A support body which is resistant
to compression surrounds the strap between the bone screws to
transmit compressive forces. The support body, the heads of the
bone screws and the elastic strap form a kind of joint allowing a
limited motion of the vertebrae.
[0004] US 2003/0220643 A1 discloses a device for connecting
adjacent vertebral bodies in which monoaxial pedicle screws are
interconnected by a spring. The spring allows spinal flexion and a
limited degree of lateral bending and axial rotation while
preventing spinal extension without the need of a transverse
member. A sleeve is placed over the spring. Impingement between the
sleeve and the pedicle screws assists the spring in preventing
spinal extension. The length of the spring is predetermined. An
adaptation in length by the surgeon is not possible.
[0005] WO 2004/105577 A2 discloses a spine stabilization system
with one or more flexible elements having an opening or slit in
form of a helical pattern. Adjustments of the system with regard to
its flexible characteristics are not possible during surgery.
[0006] A bone anchoring device comprising a monoaxial bone screw
and a flexible rod which is made of an elastic material is known
from EP 1 364 622 A2. The elastic characteristics of the bone
anchoring device are determined by material and the shape of the
rod which cannot be modified by the surgeon. Furthermore, the use
of monoaxial bone screws limits the possibility of adjustment of
the position of the shaft relative to the rod.
[0007] Based on the above, there is a need for a flexible
stabilization device for dynamic stabilization of bones or
vertebrae which allows modification of the elastic characteristics
of the device and at the same time the adaptation of the length of
the rod construct during the surgical operation.
SUMMARY OF THE INVENTION
[0008] A flexible rod assembly including an inner rod and outer rod
or sleeve made of an elastomeric material allows an adjustment of
the elastic characteristics of the stabilization device to a large
extent. By means of selection of a rod and a sleeve with
appropriate elastic properties which can be different from each
other an adaptation of the elastic properties of the rod construct
to the motion of a specific spinal segment is possible. In
particular, flexion and compression of the spine can be controlled
by means of the elastic properties of the inner rod, whereas
extension of the spine can be controlled by selection of an
appropriate sleeve. The separation of the damping with regards to
flexion/compression and extension movements results in a harmonic
behaviour of the vertebral segments under motion control of the
construct. As a consequence thereof loosening of the bone screws
can be prevented. Additionally, adjustment of the length of the
inner rod and of the sleeve is possible. Hence, a modular system is
provided which is allows adaptation at the time of surgery. In
combination with polyaxial screws the possibilities of adjustment
are further increased.
[0009] Further features and advantages of the disclosure will
become apparent and will be best understood by reference to the
following detailed description of embodiments taken in conjunction
with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1a shows a perspective exploded view of a rod construct
according to an embodiment of the disclosure.
[0011] FIG. 1b shows the rod construct of FIG. 1a in an assembled
state.
[0012] FIG. 2 shows an exploded view of a stabilization device
comprising the rod construct of FIG. 1a.
[0013] FIG. 3 schematically shows in an exploded view the
accommodation of the rod of FIG. 1a in the receiving part of a
polyaxial bone screw.
[0014] FIG. 4 shows a sectional view of the assembled parts of FIG.
3.
[0015] FIG. 5 schematically shows the assembled stabilization
device of FIG. 2 applied to adjacent vertebrae of the spinal
column.
[0016] FIG. 6a schematically shows the stabilization device of FIG.
5 with the spinal column in flexion.
[0017] FIG. 6b schematically shows the stabilization device of FIG.
5 with the spinal column in extension.
[0018] FIG. 7 schematically illustrates the directions of
displacement of the rod construct of FIG. 1b.
[0019] FIG. 8a schematically shows the rod construct in a state of
flexion according to FIG. 6a.
[0020] FIG. 8b schematically shows the rod construct in a state of
extension according to FIG. 6b.
[0021] FIGS. 9a and 9b show a further example of application of the
stabilization device in a top view.
[0022] FIG. 10 shows modification of the rod construct in
section.
DETAILED DESCRIPTION OF THE INVENTION
[0023] As shown in FIGS. 1a and 1b, the flexible stabilization
device includes a rod assembly including rod 20 made of an
elastomeric material and a sleeve 40 which is also made of an
elastomer material. In the embodiment shown, the rod 20 has a
cylindrical shape with a smooth surface. Due to the elastomer
material, the rod is partially or fully flexible. For example, the
rod 20 can be made of a biocompatible plastic material such as a
polymer on the basis of polyurethane, polysilicone or PEEK. A
particularly suitable material is Polycarbonate Urethane. The
material of the rod includes well-defined elastic properties and
the rod shows bending elasticity, compressive elasticity and
tensile elasticity.
[0024] The elastomeric material of the sleeve 40 can also be a
biocompatible plastic material such as a polymer on the basis of
polyurethane, polysilicone or PEEK which includes elastic
properties which can be selected independently of the elastic
properties of the rod 20. Also for the sleeve 40, Polycarbonate
Urethane is particularly suitable. The sleeve 40 has a tube-like
shape including a channel 41 the diameter of which is slightly
larger than the outer diameter of the rod 20 so that the rod 20 can
be inserted into the channel 41 as shown in FIG. 1b. The length of
the sleeve 40 is selected to be smaller than the length of the rod
20 such that a first connection section 20a and a second connection
section 20b of the rod 20 protrude from the channel 41 in the
assembled state as shown in FIG. 1b. A section 20c between the
first connection section 20a and the second connection section 20b
of the rod 20 is accommodated in the channel 41 of the sleeve 40.
Preferably the length of the sleeve 40 corresponds approximately to
the distance between the receiving parts of the bone anchoring
devices, or can be slightly larger.
[0025] With reference to FIGS. 2 to 4 the connection of the rod 20
with the receiving part 6 of a bone anchoring element 1 is
explained. Although the sleeve 40 is omitted in the illustration of
FIG. 3, for the purpose of describing the connection of the rod 20
with the receiving part 6, the sleeve 40 is placed on the rod 20
before the latter is secured to the respective receiving parts 6 of
the bone anchoring elements 1.
[0026] The bone anchoring element 1 in this embodiment is a
polyaxial bone screw having a shank 2 with a bone thread, a tip 3
at one end and a spherical head 4 at the opposite end. A recess 5
for engagement with a screwing-in tool is provided at the side of
the head 4 which is opposite to the shank. The receiving part 6 has
a first end 7 and a second end 8 opposite to the first end and a
longitudinal axis 9 intersecting the plane of the first end and the
second end. Coaxially with the longitudinal axis 9 a bore 10 is
provided which extends from the first end 7 to a predetermined
distance from the second end 8. At the second end 8 an opening 11
is provided the diameter of which is smaller than the diameter of
the bore 10. A spherical or otherwise tapering section 12 is
provided adjacent of the opening 11 which forms a seat for the
spherical head 4.
[0027] The receiving part 6 further has a U-shaped recess 13 which
starts at the first end 7 and extends in the direction of the
second end 8 to a predetermined distance from said second end 8. By
means of the U-shaped recess 13 two free legs 14, 15 are formed
extending towards the first end 7. Adjacent to the first end 7 the
receiving part 6 comprises an internal thread 16 on said legs 14,
15.
[0028] As can be seen in FIG. 3, a first pressure element 17 is
provided which has a cylindrical construction with an outer
diameter which is only slightly smaller than the inner diameter of
the bore 10 to allow the first pressure element 17 to be introduced
into the bore 10 of the receiving part 6 and to be moved in the
axial direction. On its lower side facing towards the second end 8,
the pressure element 17 includes a spherical recess 18 the radius
of which corresponds to the radius of the spherical head 4 of the
bone screw. On the opposite side, the first pressure element 17 has
a cylindrical recess 19 which extends transversely to the
longitudinal axis 9. The lateral diameter of this recess is
selected such that the connection section 20a or 20b with a
circular cross section, respectively, of the rod 20 which is to be
received in the receiving part 6 can be inserted into the recess 19
and guided laterally therein. The depth of the cylindrical recess
19 is selected such that in an assembled state when the connection
section 20a or 20b of the rod 20 is inserted and pressed against
the bottom of the U-shaped recess 13, the first pressure element 17
exerts a pressure on the head 5. Further the depth is preferably
about half of the diameter of the connection section 20a or 20b of
the rod 20. As can be seen in FIG. 3, the first pressure element 17
has a coaxial bore 21 for guiding a screwing-in tool
therethrough.
[0029] As shown in FIGS. 3 and 4, the bone anchoring element 1
further comprises a second pressure element 23 with a first end 24
and a second end 25. The width of the second pressure element 23 is
such that the second pressure element 23 can be inserted into the
U-shaped recess 13 of the receiving part 6. On opposite sides of
the second pressure element 23 two cylindrical projections 26 are
provided which fit into the space limited by the internal thread 16
to slide along the internal thread 16 when the second pressure
element 23 is inserted.
[0030] As can be seen in FIG. 2, the second pressure element 23
further includes a cylindrical recess 27 extending from the second
end 25 in the direction towards the first end 24 the cylinder axis
of which is perpendicular to that of the cylindrical projections
26. On the side of the second end 25, the cylindrical projections
26 include lower edges 26a. The diameter of the cylindrical recess
27 corresponds to the diameter of the connection section 20a or 20b
of the rod 20 and its depth to half or less than half of the
diameter of the connection section 20a or 20b.
[0031] The bone anchoring element 1 further includes an inner screw
30 which can be screwed-in between the legs 14, 15. The internal
thread 16 and the cooperating thread of the inner screw 30 can have
any known thread shape. Using a flat thread or a negative angle
thread can prevent splaying of the legs 14, 15.
[0032] The receiving part 6 and the first pressure element 17 can
have corresponding crimp bores 32, 33 on opposite sides by means of
which the screw 1, the receiving part 6 and the first pressure
element 17 can be loosely pre-assembled. As shown in FIGS. 3 and 4
the first pressure element 17 and the second pressure element 23
can have projections 22, 28, respectively, which can contribute to
the fixation of the elastic rod 20.
[0033] The other parts of the flexible stabilization device except
the rod 20 and the sleeve 40 can be made of the commonly used
biocompatible materials, such as stainless steel or titanium or any
other material suitable for a bone screw.
[0034] In use, at least two bone anchoring devices are anchored
into the bone. Next, the rod 20 and the sleeve 40 are selected and
combined to achieve the desired elastic properties of the flexible
stabilization device. If, for example, more than two vertebrae are
to be connected, different sleeves 40 having different elastic
properties can be selected and provided between different
vertebrae. In this way, the elastic properties of the stabilization
device can be adapted at the time of surgery. Preferably, the
sleeve 40 is selected to have a length corresponding to the
distance of the two receiving parts when the pedicle screws are
screwed into adjacent vertebrae. Since the rod 20 and the sleeve 40
are made of elastomeric material, shortening during surgery is
possible. Then, rod 20 with the sleeve 40 or, if more that one
motion segment shall be stabilized via a single rod 20, with a
plurality of sleeves 40 is inserted into the receiving parts 6 of
the bone anchoring elements. Preferably, in the balanced position
of the two adjacent vertebrae, the sleeve 40 is in contact with the
receiving parts 6.
[0035] Thereafter, the second pressure element 23 is inserted in
the receiving part 6 and the inner screw 30 is screwed-in between
the legs 14, 15. After adjusting the angular position of the bone
screw, the inner screw 30 is tightened. By the pressure exerted by
the inner screw 30 onto the second pressure element 23, the rod 20
is clamped between the first and the second pressure element 17, 23
and simultaneously the head 4 of the bone screw is locked in its
angular position.
[0036] Next, with reference to FIGS. 5 to 8b the elastic properties
of the flexible stabilization device are described. In FIG. 5 the
assembled stabilization device is shown with the rod 20 and the
sleeve 40 arranged to connect two polyaxial pedicle screws which
are placed in adjacent vertebrae W forming a motion segment. The
positions of the shanks of the pedicle screws are indicated by
dash-dotted lines. As can be seen in FIG. 5, the receiving parts 6
of the bone anchoring elements 1 have a distance x in the balanced
position in which the rod 20 and the sleeve 40 are in an unstressed
state.
[0037] FIG. 6a shows the stabilization device when flexion takes
place. During flexion, tensile stress is applied to the rod 20
resulting in an elongation of the rod 20. The distance between the
bone anchoring elements is increased to x+.DELTA.X.sub.1. The
increase .DELTA.X.sub.1 in the distance is limited by the restoring
force produced by the rod 20 due to its elastic properties. The
increase in the distance can be, for example, in the range of
approximately 1.5 mm. Hence, flexion/compression is controlled
mainly by the inner rod 20.
[0038] FIG. 6b shows the stabilization device when extension takes
place. During extension, a compressive force is applied to the rod
20 and the sleeve 40 by the receiving parts 6 of the bone anchoring
elements 1. The elasticity of the rod 20 and the sleeve 40 allows
the distance between the receiving parts 6 to decrease to a
distance x-.DELTA.x.sub.2. Due to the elastic properties of the rod
20 and the sleeve 40, a restoring force acts on the receiving parts
6 which limits the decrease of the distance. The distance can, for
example, decrease by approximately 0.5 mm. Hence, extension is
controlled by the compressibility of the inner rod 20 and is
limited by the sleeve.
[0039] In an alternative manner of application, the sleeve 40 can
be pre-compressed in the balanced state and/or the rod 20 can be
pre-stressed in the balanced state.
[0040] FIG. 7 illustrates the possible deformations which the rod
20 and the sleeve 40 can undergo. FIGS. 8a and 8b show the
deformation of the rod 20 and the sleeve 40 in flexion (FIG. 8a)
and in extension (FIG. 8b).
[0041] FIGS. 9a and 9b show an example of application of the
stabilization device. FIG. 9a shows two adjacent vertebrae V, V'
which are medio-laterally inclined with respect to each other in
the case of the presence of scoliosis. To dynamically stabilize and
correct such a motion, segment rods 200, 200' with different
sleeves 400, 400' can be used on the left side and on the right
side. The sleeve 400 used on the left side rod 200 has a length
which is greater than the length of sleeve 400' used on the right
side rod 200'. In this manner, it is possible to eliminate the
inclination of two vertebrae on the left side. In addition, the
outer diameter of the sleeve 400 can be different from that of the
sleeve 400' in order to have a different motion control with
respect to the left side and the right side.
[0042] Further modifications of the above described embodiments are
possible. In the embodiment described before, the sleeve 40 has the
shape of a hollow cylinder; however, different shapes of the sleeve
are possible. For example, a barrel-shape is possible. The length
of the sleeve can differ from the embodiment shown. The rod 20 may
also have a rectangular, square, oval or triangular cross-section
or any other appropriate shape of the cross-section. In this case,
the shape of the sleeve 40 is appropriately adapted. In particular,
it is possible to form the rod 20 and/or the sleeve 40 with the
shape varying in the longitudinal direction. The rod 20 and the
sleeve 40 can be formed to be highly flexible or hardly
flexible.
[0043] The surface of the rod 20 and/or the sleeve 40 can be
textured or structured. FIG. 10 shows an example of an inner rod
201 having a corrugated surface, with corrugations 300 provided in
the circumferential direction. The inner wall of the sleeve 401 has
corresponding corrugations cooperating with that of the rod. This
prevents or reduces a displacement of the sleeve relative to the
rod.
[0044] In the example of the bone anchoring element described
above, the connection of the shanks 2 of the bone anchoring
elements 1 to the respective receiving parts 6 is polyaxial.
However, it is also possible to provide a monoaxial connection.
[0045] For the inner screw 30, all known modifications can be used.
This includes also the use of an outer ring or nut.
[0046] In the embodiments described, the bone anchoring element 1
is introduced from the top into the receiving part 6. However, the
bone anchoring element 1 can also be introduced from the bottom of
the receiving part 6 if the receiving part 6 is constructed to
allow this.
[0047] The head of the bone anchoring element and the shaft can be
constructed as separate parts which can be connected.
[0048] The present disclosure is not limited to screws as bone
anchoring elements but can be realized with bone hooks or any other
bone anchoring element.
* * * * *