U.S. patent application number 10/456535 was filed with the patent office on 2004-04-08 for device for fixing bones in relation to one another.
Invention is credited to Hess, Martin, Schlapfer, Fridolin, Tagwerker, Konrad.
Application Number | 20040068258 10/456535 |
Document ID | / |
Family ID | 4358161 |
Filed Date | 2004-04-08 |
United States Patent
Application |
20040068258 |
Kind Code |
A1 |
Schlapfer, Fridolin ; et
al. |
April 8, 2004 |
Device for fixing bones in relation to one another
Abstract
A device for fixation of vertebral bodies including a
longitudinal support with a central axis and n anchoring elements
(2.ltoreq.i.ltoreq.n). Each anchoring element having a longitudinal
axes, a front end, and a back end. The longitudinal axis of each
anchoring elements may be arranged at an angle of between
65.degree. and 115.degree. relative to the central axis of the
longitudinal support, while the anchoring elements are designed to
abut the back end. The anchoring elements may be shaped in the form
of a blade toward the front end.
Inventors: |
Schlapfer, Fridolin;
(Leimen, CH) ; Hess, Martin; (Holstein, CH)
; Tagwerker, Konrad; (Basel, CH) |
Correspondence
Address: |
JONES DAY
51 Louisiana Aveue, N.W
WASHINGTON
DC
20001-2113
US
|
Family ID: |
4358161 |
Appl. No.: |
10/456535 |
Filed: |
June 9, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10456535 |
Jun 9, 2003 |
|
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PCT/CH00/00654 |
Dec 8, 2000 |
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Current U.S.
Class: |
606/261 ;
606/311 |
Current CPC
Class: |
A61B 17/7025 20130101;
A61B 17/8625 20130101; A61B 17/70 20130101; A61B 2017/00858
20130101 |
Class at
Publication: |
606/061 |
International
Class: |
A61B 017/58 |
Claims
What is claimed is:
1. A device for fixation of bones, especially vertebral bodies,
relative to one another, comprising: A) a longitudinal support (1)
with a central axis (2); and B) n anchoring elements (3.i)
(2.ltoreq.i.ltoreq.n) with the longitudinal axes (4), one front end
each (5) and one back end each (6), whereby C) the longitudinal
axes (4) of the anchoring elements (3.i) are arranged at an angle
of between 65.degree. and 115.degree. relative to the central axis
(2) of the longitudinal support (1); and D) at least one of the
anchoring elements (3.j) (1.ltoreq.j.ltoreq.n) is designed in the
shape of a blade, characterized by the fact that: E) at the back
end (6) at least the anchoring element (3.j) comprises receiving
means (7) for the longitudinal support (1) with stopping means (8;
34) for reversibly securing the connection between the longitudinal
support (1) and anchoring element (3.j), and the secured connection
does not permit any relative movement between the longitudinal
support (1) and anchoring element (3.j), as well as taking up
forces and moments in all three axial directions of a
three-dimensional coordinate system.
2. The device according to claim 1, wherein at least the one
anchoring element (3.j) (1.ltoreq.j.ltoreq.n) is designed in the
shape of a blade abutting the back end (6) of the anchoring element
(3.j).
3. The device according to claim 2, wherein the stopping means (8)
can be operated from the back end (6) of at least the one anchoring
element (3.j).
4. The device according to claim 3, wherein the receiving means (7)
is open at the side so that the longitudinal support (1) can be
inserted into the receiving means (7) transverse to the
longitudinal axis (4).
5. The device according to claim 3, wherein the receiving means (7)
is open from the back end (6) so that the longitudinal support (1)
can be inserted into the receiving means (7) parallel to the
longitudinal axis (4).
6. The device according to claim 5, wherein at least one anchoring
element (3.j) comprises a transport device (15) for inserting the
anchoring element (3.j) into a bone parallel to the longitudinal
axis (4).
7. The device according to claim 6, wherein the transport device
(15) is designed as a transport screw (16).
8. The device according to claim 7, wherein the transport screw
(16) comprises a screw tip (17), a screw shaft (18), a threaded
segment (21) that abuts the screw tip (17), and drive means (19),
and the drive means (19) can be operated from the back end (6) of
the anchoring element (3.j).
9. The device according to claim 8, wherein at least one anchoring
element (3.j) has a through hole (20) coaxially and the transport
screw (16) can be accommodated in this hole (20) in such a way that
the screw tip (17) and threaded segment (21) protrude axially over
the front end (5) of the anchoring element (3.j).
10. The device according to claim 8, wherein at least one anchoring
element (3.j) has a through hole (20) coaxially and the transport
screw (16) can be accommodated in this hole (20), whereby the
threaded segment (21) is integrated into the anchoring element
(3.j) and over a part of its circumference protrudes radially over
the anchoring element (3.j) vertical to the longitudinal axis
(4).
11. The device according to claim 10, wherein the back end (6) of
at least one of the anchoring elements (3.j) has a coaxial cone
segment (23).
12. The device according to claim 11, wherein the cone segment (23)
has a concentric threaded hole (24) that is open at the end
axially.
13. The device according to claim 11, wherein a concentric pin (25)
with external threading axially abuts the cone segment (23) at the
end.
14. The device according to claim 10, wherein the receiving means
(7) comprise a coaxial ball head (26) that abuts the back end (6)
of the anchoring element (3.j) at the end.
15. The device according to claim 14, wherein the anchoring element
(3.j) has an anchoring segment (27) that has at least one blade (9)
and abuts the back end (6) over a length (L), whereby said blade
has an essentially rectangular cross-section with a thickness (D)
and a width (B) and the blade (9) has a first transverse axis (22)
parallel to the long sides of the cross-section.
16. The device according to claim 14, wherein the anchoring element
(3.j) has an anchoring segment (27) that has at least one blade (9)
and abuts the back end (6) over a length (L), whereby said blade,
when viewed from above, converges toward the front end (5).
17. The device according to claim 14, wherein the anchoring element
(3.j) has an anchoring segment (27) that has at least one blade (9)
and abuts the back end (6) over a length (L), whereby said blade,
when viewed from above, diverges toward the front end (5).
18. The device according to claim 14, wherein the anchoring element
(3.j) has an anchoring segment (27) that has at least one blade (9)
and abuts the back end (6) over a length (L), whereby said blade,
when viewed from above, converges to a point (14) at the front end
(5).
19. The device according to claim 14, wherein the anchoring element
(3.j) has an anchoring segment (27) that has at least one blade (9)
and abuts the back end (6) over a length (L), whereby said blade,
when viewed from above, slopes down downward on one side at the
front end (5).
20. The device according to claim 14, wherein the anchoring element
(3.j) has an anchoring segment (27) that has at least one blade (9)
and abuts the back end (6) over a length (L), whereby said blade,
when viewed from above, is convex at the front end (5).
21. The device according to claim 20, wherein the anchoring element
(3.j) has an anchoring segment (27) that has at least one blade (9)
and abuts the back end (6) over a length (L), whereby said blade,
when viewed in longitudinal section, converges to a tip at the
front end (5).
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of the U.S. national
stage designation of copending International Patent Application
PCT/CH00/00654, filed Dec. 8, 2000, the entire content of which is
expressly incorporated herein by reference thereto.
FIELD OF THE INVENTION
[0002] The present invention relates generally to orthopaedic
fasteners, and in particular to a device for fixation of vertebral
bodies.
BACKGROUND OF THE INVENTION
[0003] Instabilities in spinal-column motion segments that may be
caused by vertebral fractures, degenerative changes, etc. often
require that the segments in question be fused. In order to ensure
the immobilization of the segments to be fused as required for bone
fusion, the corresponding segments are often stabilized with a
fixation system. Fixation systems may either be inserted and
anchored from the posterior, whereby the anchoring is done by means
of bone screws in the pedicles, or from the anterior or
antero-lateral, in which case the anchoring is done by means of
bone screws in the vertebral bodies.
[0004] The quality with which fixation systems are anchored is
heavily dependent on the quality of the bone structures. This is
especially true of antero-laterally anchored fixation systems. The
greater the degree of osteoporosis, the greater the danger that the
bone screws will cut through the bone when subjected to even small
loads. The use of thick screws reduces the risk of cutting through
the bone. However, overly thick screws should be avoided lest there
be excessive destruction of the bone structure in the vertebral
body.
[0005] Known approaches in the related art for reducing the risk of
the anchoring elements cutting through the bone are presented in DE
296 00 879 and in WO 00/10473. These publications deal basically
with a hollow screw that is screwed into the vertebral body. The
hollow screw does not need to displace a great deal of bone,
because a peg of bone maybe left in place in the center of screw.
However, when the hollow screw is being screwed in, the vascular
supply to the peg of bone left in the center may be impaired, which
may lead to complications, especially in osteoporotic bones. Also,
in bones with still-functioning repair mechanisms, the hollow screw
may be so heavily in-grown that it may be difficult to remove it if
the area is to be inspected or, if removed, it will do serious
damage to the bone (in some cases, for example, it has proved to be
impossible to remove hollow screws inserted into the cervical
vertebral column).
[0006] In connection with the surgical treatment of fractures in
long bones, intramedullary stabilization techniques have been
developed that, with modification, may also be successfully
employed in the spinal column to solve the problem of anchoring
anterior and antero-lateral spinal-column fixation systems.
Intramedullary pins, for instance, may be used to splint fractured
tubular bones by providing an intramedullary connection between the
proximal portion of the broken tubular bone and its distal portion.
Because of its geometry, however, the intramedullary pin can
withstand only minor rotational and axial loads. This may not be
potentially problematic as long as the fractured bone is able under
axial load to maintain its height and the fracture is more or less
diaphyseal. As soon as multi-fragment fractures arise, however, the
intramedullary pin typically has to be anchored proximally and
distally. In this way, the intramedullary pin can provide not only
splinting but, as in the case of the spinal column, may act as a
proximately and distally anchored longitudinal support that can
transfer forces and moments at all levels from proximal to distal.
In the case of the intramedullary pin, the anchoring implants may
be screws that are run transversely through the bone and the
intramedullary pin on the proximal and distal sides. In patients
with osteoporosis and in cases where the fractures lie close to the
joint, anchoring the intramedullary pin with screws is often not a
satisfactory approach. Also, spiral-twisted blade-shaped implants
known in the related art and as used in clinical practice are not
particularly suitable for use on spinal column.
SUMMARY OF THE INVENTION
[0007] The present invention relates to the fixation of bones, and
in particular to the fixation of vertebral bodies. In one
embodiment, the present invention is comprises a longitudinal
support with a central axis and n anchoring elements
(2.ltoreq.i.ltoreq.n). Each anchoring element having a longitudinal
axes, a front end, and a back end. The longitudinal axis of each
anchoring elements may be arranged at an angle of between
65.degree. and 115.degree. relative to the central axis of the
longitudinal support, while the anchoring elements are designed to
abut the back end. The anchoring elements may be shaped in the form
of a blade toward the front end. The angle-variable connection of
the anchoring elements may be achieved by virtue of the fact that
at the back end each anchoring element comprises means for
receiving the longitudinal support with attachment means that can
be controlled from the back end for reversibly locking the
connection between the longitudinal support and the anchoring
element. The locked connection may prevent relative movement
between the longitudinal support and the anchoring element and
takes up forces and moments in all three axial directions of a
three-dimensional coordinate system.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] Preferred features of the present invention are disclosed in
the accompanying drawings, wherein similar reference characters
denote similar elements throughout the several views, and
wherein:
[0009] FIG. 1 is a top view of an embodiment of the device
according to the invention;
[0010] FIG. 2 is a side view of the embodiment of the device
according to the invention shown in FIG. 1;
[0011] FIG. 3 is a side view of another embodiment of the device
according to the invention;
[0012] FIG. 4 is a perspective view of an embodiment of the
anchoring element;
[0013] FIGS. 5a to 5g are top views of various embodiments of the
anchoring element;
[0014] FIGS. 6a and 6b are side views of various embodiments of the
anchoring element;
[0015] FIGS. 7a to 7e are cross-sections of anchoring elements of
various embodiments of the anchoring element;
[0016] FIGS. 8a and 8b are perspective views of twisted anchoring
segments in various embodiments of the anchoring element;
[0017] FIGS. 9a and 9b are perspective views of anchoring segments
consisting of multiple blades in various embodiments of the
anchoring element;
[0018] FIG. 10 is a perspective view of an embodiment of a
spiral-shaped anchoring element that is equipped with a transport
screw;
[0019] FIG. 11 is a perspective view of another embodiment of a
3-blade anchoring element that is equipped with a transport
screw;
[0020] FIG. 12 is a perspective view of another embodiment of an
anchoring element that is equipped with a transport device;
[0021] FIG. 13 is a perspective view of an implantable anchoring
element with a transport device;
[0022] FIG. 14a is a perspective view of an embodiment of the
anchoring element with a surface structure;
[0023] FIG. 14b is a perspective view of another embodiment of the
anchoring element with a surface structure;
[0024] FIG. 14c is a perspective view of an embodiment of the
anchoring element with transverse-running holes;
[0025] FIG. 15 is a perspective view of an embodiment of an
anchoring element that is equipped with a threaded bush;
[0026] FIGS. 16a and 16b are perspective views of devices for
anchoring a transport device for inserting the anchoring
element;
[0027] FIGS. 17a and 17b are perspective views of another device
for anchoring a transport device for inserting the anchoring
element;
[0028] FIG. 18 is a cross-section through a vertebral body with an
implanted anchoring element; and
[0029] FIG. 19 is a view of a cut-out of a spinal column with an
implanted device as described by the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0030] FIGS. 1 and 2 show an embodiment of the device according to
the invention that comprises an anchoring element 3 with receiving
means 7 for a longitudinal support 1 at the back end 6 of the
anchoring element 3. The receiving means 7 consists of a receiving
head 10 that is essentially circular-cylindrical and is coaxial
with a longitudinal axis 4 of the anchoring element 3, with a
channel 11 that is open toward the back end 6 to receive the
longitudinal support 1. In this case, the longitudinal support 1 is
received in such a way that its central axis 2 runs vertical to the
longitudinal axis 4. In an area between the front end 5 and the
receiving head 10, the anchoring element 3 contains an anchoring
segment 27, which is designed as an essentially parallelepiped
blade 9. Viewed vertically with respect to the longitudinal axis 4,
the blade 9 has a rectangular cross-section with a width B and a
thickness D. At the front end 5 of the anchoring element 3, the
width B of the blade 9 converges to a point 14. Moreover, external
threading 12 that is concentric to the longitudinal axis 4 on the
receiving head 10 and a nut 13 that can be screwed onto this
external threading 12 are arranged at the back end 6 of the
anchoring element 3 as immobilizing means 8 so that when the nut 13
is tightened, the longitudinal support 1 is axially clamped in the
channel 11, thereby locking the anchoring element 3 to the
longitudinal support 1.
[0031] The embodiment shown in FIG. 3 of the device according to
the invention encompasses an anchoring element 3, which has as an
anchoring segment 27 a spiral-shaped blade 9 that is coaxial to the
longitudinal axis 4. At the back end 8 of the anchoring element 3,
coaxial to the longitudinal axis 4, are located a cone segment 23
that abuts the anchoring segment 27 and, also attached coaxially
thereto, a threaded pin 25. The receiving means 7 consists
essentially of a connecting element 36 with a hole in it, wherein
the longitudinal support 1 is mounted so as to be able to move
coaxially with respect to the central axis 2 (FIG. 2) and can be
secured in place with a stop screw 35. Running next to the
longitudinal support 1 in connecting element 36 is a cavity 38 in
the shape of a hollow sphere that runs through the connecting
element 36, in which a slotted tensioning element 37 in the shape
of a two-base spherical segment is mounted. The tensioning element
37 is equipped with an inner cone 39, in which the cone segment 23
can be received in the anchoring element 3. Because the anchoring
element 3 and the connecting element 36 are connected by means of
the tensioning element 37 that can be rotated in the cavity around
three axes that are vertical to one another, the angle between the
central axis 2 of the longitudinal support 1 and the longitudinal
axis 4 of the anchoring element 3 can be varied. With a nut 13 that
can be screwed onto the threaded pin 25 at the end, the cone
segment 23 is pulled into the inner cone 39 of the tensioning
element 37, thus expanding said segment radially. In the cavity 38,
clamping is done in such a way that the anchoring element 3 is
locked in the connecting element 36. Such a connection between the
longitudinal support 1 and a pedicle screw as an anchoring element
3 is described in EP 0 599 847. Instead of the cone segment 23 and
the threaded pin 25, at the back end 6 of the anchoring element 3
there can be a ball head that can be connected to the longitudinal
support 1 by means of a device to connect a longitudinal support 1
to an anchoring element 3 that is designed as a pedicle screw, as
disclosed in WO 98/52482.
[0032] FIG. 4 shows an embodiment of the anchoring segment 27 that
abuts the back end 6 of the anchoring element 3.j over a length L.
The anchoring segment 27 consists essentially of a flat blade 9
that has a length L, a width B, and a thickness D. Length L and
thickness D enclose the lateral surfaces 32 of the blade. When
viewed vertically with respect to the longitudinal axis 4, the
cross-section of the blade 9 encompasses a first transverse axis
29, which runs in the plane of the lateral surfaces 32 and is
vertical with respect to the longitudinal axis 4, and a second
transverse axis 30, which is vertical with respect to the lateral
surfaces 32 and with respect to the longitudinal axis 4. The ratio
of width B to thickness D is basically between 1 and 14 and
preferably between 3 and 6. Owing to this ratio of width B to
thickness D, the implant can be inserted into a vertebral body
without major destruction of the bone. The blade 9 is then aligned
in the bone with allowance for the action of load. If the blade 9
is implanted in a vertebral body in such a way that the first
transverse axis 29 runs parallel to the longitudinal axis of the
spinal column, the blade 9 has great resistance to bending stress
but is in an unfavorable position with respect to cutting through
the bone. If, however, the blade 9 is implanted in the vertebral
body in such a way that the second transverse axis 30 runs parallel
to the longitudinal axis of the spinal column, the blade 9 is
placed in a more favorable position as regards cutting through the
bone, although this is achieved at the expense of reduced
resistance to bending.
[0033] For example, the blade 9 can be designed as follows:
[0034] a) in the shape of a parallelepiped with a length L, a
thickness D, and a width B (FIG. 5a);
[0035] b) in the shape of a wedge with a width B that converges
toward the front end 5 (FIG. 5b);
[0036] c) in the shape of a wedge with a width B that diverges
toward the front end 5 (FIG. 5c);
[0037] d) viewed from the top, the blade 9 is designed to be convex
at the front end 5 (FIG. 5d);
[0038] e) viewed from the top, the blade 9 tapers to a point 14
with even or uneven sides (FIG. 5e);
[0039] f) viewed from the top, the blade 9 is beveled on one side
at the front end 5 (FIG. 5f);
[0040] g) viewed from the top, the blade 9 is rounded on one side
at the front end 5 (FIG. 5g);
[0041] h) in a longitudinal section running parallel to the lateral
surfaces 32, the blade 9 tapers to a point at the front end 5 with
even or uneven sides (FIG. 6a);
[0042] i) in a longitudinal section running parallel to the lateral
surfaces 32, the blade 9 is beveled on one side at the front end 5
(FIG. 6b);
[0043] j) in a cross-section that is a vertical with respect to the
longitudinal axis 4, both of the lateral edges of the blade 9 that
lie in the lateral surfaces 32 taper into a point (FIG. 7a);
[0044] k) in a cross-section that is a vertical with respect to the
longitudinal axis 4, a lateral edge of the blade 9 that lies in a
lateral surface 32 tapers into a point (FIG. 7b);
[0045] l) in a cross-section that is a vertical with respect to the
longitudinal axis 4, a lateral edge of the blade 9 that lies in a
lateral surface 32 is beveled (FIG. 7c);
[0046] m) in a cross-section that is a vertical with respect to the
longitudinal axis 4, both lateral edges of the blade 9 that lie in
the lateral surfaces 32 are equally beveled (FIG. 7d); and
[0047] n) in a cross-section that is a vertical with respect to the
longitudinal axis 4, the two lateral edges of the blade 9 that lie
in the vertical surfaces 32 are beveled in diametrically opposed
ways (FIG. 7e).
[0048] FIGS. 8a and 8b show two embodiments of a twisted blade 9.
FIG. 8a shows a blade 9 that is twisted by an angle of twist a over
length L around an edge of the blade 9 that encloses length L and
abuts one of the lateral surfaces 32. FIG. 8b show the blade 9 that
is twisted by a angle of twist .alpha. over length L around the
longitudinal axis 4 as well. The twisting can be left-handed or
right-handed. For twisting length Lv and angle of twist .alpha.,
the lead of the twist can be defined as follows:
Lead S=Lv.degree.360.degree./.alpha.['].
[0049] In cases where the blade 9 is designed in shape of this kind
of spiral, a lead of between 60 mm and 300 mm and preferably
between 100 mm and 240 mm is advantageous.
[0050] FIG. 9a shows another embodiment of the anchoring element 3
with a combination of blades 9. The anchoring element 3 comprises
an anchoring segment 27 with two blades 9 that are connected by a
hollow 28 that is arranged coaxially with regard to the
longitudinal axis 4 over the entire length of the anchoring element
3. In this case the two blades 9 are arranged in such a way that
their first transverse axes 29 lie in one plane. A hole 20 runs
through the hollow 28 concentrically with respect to the
longitudinal axis 4.
[0051] The embodiment of the anchoring element 3 that is shown in
FIG. 9b is another combination of multiple blades 9 that comprises
three blades 9 arranged in the shape of a star. The one lateral
surfaces 32 (FIG. 4) of the three blades 9 are connected to a
coaxial hollow cylinder 28 parallel to the longitudinal axis 4,
whereby the first transverse axes 29 of the blades 9 enclose the
central angles .beta., .gamma., .delta.. In the embodiment depicted
here, the central angles is .beta., .gamma., .delta. are equal,
i.e., .beta.=.gamma.=.delta., while in other embodiments the blades
9 can be arranged with different central angles as required by the
given situation. An anchoring element 3 that comprises three or
more blades 9 can also be designed in the shape of a spiral.
[0052] In the case of intramedullary-pin systems, the blade-shaped
anchoring implant is hammered in. Hammering in or near the spinal
column is not recommended since there is the danger that vital
neurologic and vascular structures may be damaged.
[0053] Possible ways of inserting the anchoring element 3 in a
controlled manner using a transport device 15 are depicted in FIGS.
10-13. The transport device 15 shown in FIG. 10 includes a
transport screw 16 with a screw tip 17, a screw shaft 18, a
threaded segment 21 adjacent to the screw tip 17, and a drive means
19, whereby the drive means 19 can be operated from the back end 6
of the anchoring element 3. The transport screw 16 is able to turn
freely relative to the anchoring element 3. If the transport screw
16 is turned by means of the screwdriver 49, it screws through the
bone and pulls the anchoring element 3 along with it.
[0054] As shown in FIGS. 10 and 11, the threaded segment 21 can be
integrated into the anchoring segment 27, whereby the threads
protrude radially over the thickness D of the blade or protrude
over the anchoring segment 27 at the front end 5 of the anchoring
element 3. Moreover, the threaded segment 21 may protrude over only
part of length L or over the entire length L. The advantages of
this transport device 15 lie in the fact that the transport screw
16 pulls the anchoring segment 27 directly into the bone. There is
the disadvantage, however, that in the middle of the spinal column
the bone is very porous, so that the transport screw 16 may pull
out and the transport device could fail.
[0055] In FIG. 12 the transport device 15 includes a transport
screw 16, which is located in the hole 20 in the hollow 28,
protrudes over the front end 5 of the anchoring element 3, and can
be anchored in the counter corticalis. Instead of being anchored in
the counter corticalis by means of threading, as in the case of
transport screw 16, other elements such as pegs 46 (FIGS. 16a and
16b) or hooks 47 (FIGS. 17a and 17b), etc., with extensions can
also be used. At the back end 6 of the anchoring element 3, the
transport device 15 has an extension 63 that is connected to the
transport screw 16, protrudes coaxially over the anchoring element
3 over length segment A, and has an abutment 15 at the end, so that
an expanding device 51 can be inserted between the abutment 50 and
the back end 6 of the anchoring element 3 and the anchoring segment
27 can be forced into the bone by opening the expanding device 51.
In this embodiment of the transport device 15 the transport screw
16 is anchored in the bone from the outset. The drawback, however,
is the expensive instrumentation required by the limited space in
which the work may be performed.
[0056] The U-shaped auxiliary device 48 that is symbolically
depicted in FIG. 13 is anchored by means of, e.g., bone screws 52
in the cortex layer as an abutment in order to force the anchoring
segment 27 at the back end 6 of the anchoring element 3 into the
bone by means of an expanding device 51. Here additional drilling
of the vertebral bodies may be required in order to anchor the
auxiliary device 48.
[0057] Compared to bone screws as well as hollow screws, in the
blade 9 the anchor strength may be relatively low in the
longitudinal axis 4. The transport devices 15 shown in FIGS. 10-12
may increase the anchoring strength.
[0058] FIGS. 14a-14c show ways, without limitation, in which the
design of the surface of the blade 9 may be altered to increase
anchoring strength in the longitudinal axis 4:
[0059] a) A saw-toothed design of the surface of blade 9 that is
enclosed by length L and width B (FIG. 14a), whereby the steep
sides of the teeth of the saw are directed away from the front end
5 of the anchoring element 3; or 3
[0060] b) A fish-scale-like design of the surface of blade 9 that
is enclosed by length L and width B (FIG. 14b), whereby the sides
of the scales, which are steep in this case as well, are directed
away from the front end 5 of the anchoring element 3.
[0061] In this case, the saw-toothed or fish-scale-like design may
be applied to only one of the surfaces enclosed by length L and
width B, or it can be applied to both of these surfaces; or it can
encompass only a portion of length L, or it can extend over the
entire length L.
[0062] c) Instead of a mechanical lock, it is also possible to use
a biological lock. As FIG. 14c shows, in this case multiple holes
62 run through the blade 9 vertically with respect to the surfaces
enclosed by length L and width B, so that the bone can grow through
the holes 62.
[0063] In the embodiment shown in FIG. 15, a threaded bush 40 with
external threading 41 is located at the back end 6 of the anchoring
element 3. The threaded bush 40 includes a coaxial hole 42, which
can slide over a cylindrical pin 43 that is arranged between the
anchoring segment 27 and the cone end segment 23. Like the
transport screw 18 (FIGS. 10-12), this threaded bush 40 also helps
to increase the anchoring strength of the anchoring element 3 in
the bone. This embodiment can be used in combination with the
versions shown in FIGS. 10-14.
[0064] FIGS. 16a and 16b show devices for anchoring the transport
device 16 (FIG. 12) in the counter corticalis that can be used
instead of a transport screw 15 (FIG. 12). This is a hollow
cylindrical peg 46 that is designed to be elastically radial from
its first end 56 and its second end 57 by coaxial slots 56 in the
radial direction (FIG. 16a). In the embodiment shown in FIG. 16a,
the radial expansion of the peg 48 is accomplished by means of two
expanding cones 53 that are coaxially arranged on an also-coaxial
threaded rod 54 and that can be pushed against one another by the
external threading on the threaded rod and by corresponding
internal threading in the expanding cones 53. As FIG. 16b shows,
instead of the expanding cones 53 a wedge element 58 can also be
used to expand the peg 46 radially. A peg 46 is shown here that has
coaxially penetrating slots 55 only from the second end 57, so that
the expansion of the peg 46 is accomplished by pulling the wedge
element 58 inward coaxially by means of the threaded rod 54.
Instead of being made of 4 parts, as shown in FIG. 16b, the wedge
element 58 can also be composed of 1, 2, or 3 parts.
[0065] Another device for anchoring the transport device 16 (FIG.
12) in the counter corticalis is shown in FIG. 17a and 17b. This is
a hook 47 that expands radially relative to the longitudinal axis 4
of the anchoring element 3 (FIG. 1), tapers toward its tip 61, and
is forced together radially both before and during installation by
a coaxially arranged bush 59. The hook 47 is inserted by means of a
coaxial rod 60. After the hook 47 is inserted, bush 59 is pulled
off of the hook 47 over its end opposite the tip 61, whereupon the
hook 47 elastically expands radially and is thus anchored in the
counter corticalis.
[0066] FIG. 18 shows a cross-section through a vertebral body 63
with an inserted anchoring element 3 that passes through the
vertebral body 63 with a longitudinal axis 4 that runs transverse
to the longitudinal axis of the spinal column.
[0067] FIG. 19 shows a side view of several vertebral bodies 63
with an implanted device according to the invention which, in this
embodiment, comprises a telescoping longitudinal support 1 with a
central axis 2 that runs parallel to the longitudinal axis of the
spinal column and two anchoring elements 3.
[0068] In use the present invention may provide a spinal-column
fixation device that can be attached to the vertebral bodies by
means of spiral-twisted, blade-like anchoring elements and that
takes into account the following additional considerations:
[0069] a) the anchoring implants may be inserted before the
longitudinal support is inserted, thus obviating the need for
complicated targeting devices and for aligning the anchoring
elements specifically with the longitudinal support;
[0070] b) the longitudinal support may be placed at the end of the
anchoring implant;
[0071] c) connections between the longitudinal support and
anchoring implant may be polyaxial, play-free, and angularly
stable, and may be locked and unlocked; and
[0072] d) it should be possible to insert the anchoring elements
with a transport device, thereby avoiding the uncontrolled
hammering.
[0073] Depending on the design of the receiving means, the angle
between the longitudinal supports of the anchoring elements and the
central axis of the longitudinal support may be fixed, may be
varied around an axis, or may be adjusted polyaxially. The surface
of the blade may also be designed in different ways on a side that
is enclosed by length L and width B or on the two sides that are
enclosed by length L and width B. For example, without limitation,
the surface(s) of the blade may comprise:
[0074] a) a smooth surface;
[0075] b) saw-toothed;
[0076] c) fish-scale-like;
[0077] d) arrow-like teeth;
[0078] e) rough surface (for example, etched, plasma-coated,
radiated); or
[0079] f) holes (biological locking by virtue of the bone growing
through the holes).
[0080] In this regard the surface structures may be applied on one
side, on both sides, or only partially on the surface of the blade.
The different blade designs can be combined with the different
surfaces.
[0081] The anchoring element may be hammered in, or inserted into a
vertebral body with the aid of a transport device. Uncontrolled
hammering on the spinal column is generally not recommended (there
is the risk of damaging neurologic and vascular structures).
Suitable transport systems include, without limitation, the
following:
[0082] a) a transport screw is integrated into the blade (at the
tip);
[0083] b) an element (screw, pin, hook, etc. with extension)
anchored in the counter-corticalis serves as an abutment so that
the blade can be pulled into the bone; or
[0084] c) a device is anchored in the corticalis in order to force
the anchoring element into the bone.
[0085] Compared to the devices that are anchored to the vertebrae
by means of screws, the invention may provide the following
properties:
[0086] 1) Resistance to cutting through the bone may be increased,
while at the same time the amount of bone displaced may be
reduced:
[0087] Same load-bearing surface area per unit of length:
[0088] Implant with 2 bone screws per vertebra with a minor
diameter of d=5 mm; Load-bearing surface area per unit of surface
area: 2.times.d.times.length/length=10 mm2/mm Displacement per unit
of length: 2.times.d2.times.Pi/4.times.length/length=39 mm2/mm
[0089] Implant with blade-shaped anchoring element per vertebra
with width B=10 mm, core in the middle with a diameter of d=5 mm,
and a blade thickness of D=1.2 mm: Load-bearing surface area per
unit of surface area: 2.times.d.times.length/length=10 mm2/mm
Displacement per unit of length:
((B-d).times.H+d2.times.Pi/4.times.length/length=25.6 mm2/mm
[0090] This shows that there is thus a reduction in displacement
(excluding the threading) of 34% with the same load-bearing surface
area.
[0091] Same displacement per unit of length (excluding
threading):
[0092] Implant with 2 bone screws per vertebra with a minor
diameter of d=5 mm; Displacement per unit of length:
2.times.d2.times.Pi/4.times.leng- th/length=39 mm2/mm Load-bearing
surface area per unit of length: 2.times.d.times.length/length=10
mm2/mm
[0093] Implant with blade-shaped anchoring element per vertebra
with width B=7 mm, core in the middle with a diameter of d=5 mm,
and a blade thickness of D=1.2 mm: Displacement per unit of length:
((B-d).times.H+d2.times.Pi/4.times.length/length=39 mm2/mm
Load-bearing surface area per unit of length: ((39
mm2-d2.times.Pi/4/H+d).times.length- /length=21 mm2/mm.
[0094] This shows that the load-bearing surface area is increased
by 110% while displacement remains the same.
[0095] 2. Devices that are anchored in the vertebral bodies with
screws require at least 2 bone screws per vertebra or one bone
screw combined with a clasp-like base in order to provide the
rotational stability required for fusion. A blade-shaped anchoring
element may be anchored in the bone in a rotationally stable
manner, therefore providing the rotational stability required for
successful fusion of the vertebral bodies being bridged, and thus
offers the following advantages:
[0096] Devices that are connected to the spinal column cranially
and caudally by one blade-shaped anchoring element apiece may be
inserted higher up the spinal column than the bulky screw-anchored
implants;
[0097] The fact that the number of anchoring elements required per
vertebra may be reduced to one may make it faster and simpler to
insert implants based on blade-shaped anchoring elements.
[0098] In one embodiment, the device for fixation of bones may
comprise:
[0099] 1. A) a longitudinal support (1) with a central axis (2);
and B) n anchoring elements (3.i) (2.ltoreq.i.ltoreq.n) with the
longitudinal axes (4), one front end each (5) and one back end each
(6), whereby C) the longitudinal axes (4) of the anchoring elements
(3.i) are arranged at an angle of between 65.degree. and
115.degree. relative to the central axis (2) of the longitudinal
support (1); and D) at least one of the anchoring elements (3.j)
(1.ltoreq.j.ltoreq.n) is designed in the shape of a blade,
characterized by the fact that: E) at the back end (6) at least the
anchoring element (3.j) comprises receiving means (7) for the
longitudinal support (1) with stopping means (8; 34) for reversibly
securing the connection between the longitudinal support (1) and
anchoring element (3.j), and the secured connection does not permit
any relative movement between the longitudinal support (1) and
anchoring element (3.j), as well as taking up forces and moments in
all three axial directions of a three-dimensional coordinate
system.
[0100] 2. The device according to 1, wherein at least the one
anchoring element (3.j) (1.ltoreq.j.ltoreq.n) is designed in the
shape of a blade abutting the back end (6) of the anchoring element
(3.j).
[0101] 3. The device according to 1 or 2, wherein the stopping
means (8) can be operated from the back end (6) of at least the one
anchoring element (3.j).
[0102] 4. The device according to one of 1-3, wherein the receiving
means (7) is open at the side so that the longitudinal support (1)
can be inserted into the receiving means (7) transverse to the
longitudinal axis (4).
[0103] 5. The device according to one of 1-3, wherein the receiving
means (7) is open from the back end (6) so that the longitudinal
support (1) can be inserted into the receiving means (7) parallel
to the longitudinal axis (4).
[0104] 6. The device according to one of 1-5, wherein at least one
anchoring element (3.j) comprises a transport device (15) for
inserting the anchoring element (3.j) into a bone parallel to the
longitudinal axis (4).
[0105] 7. The device according to 6, wherein the transport device
(15) is designed as a transport screw (16).
[0106] 8. The device according to 7, wherein the transport screw
(16) comprises a screw tip (17), a screw shaft (18), a threaded
segment (21) that abuts the screw tip (17), and drive means (19),
and the drive means (19) can be operated from the back end (6) of
the anchoring element (3.j).
[0107] 9. The device according to 8, wherein at least one anchoring
element (3.j) has a through hole (20) coaxially and the transport
screw (16) can be accommodated in this hole (20) in such a way that
the screw tip (17) and threaded segment (21) protrude axially over
the front end (5) of the anchoring element (3.j).
[0108] 10. The device according to 8, wherein at least one
anchoring element (3.j) has a through hole (20) coaxially and the
transport screw (16) can be accommodated in this hole (20), whereby
the threaded segment (21) is integrated into the anchoring element
(3.j) and over a part of its circumference protrudes radially over
the anchoring element (3.j) vertical to the longitudinal axis
(4).
[0109] 10. The device according to 8, wherein at least one
anchoring element (3.j) has a through hole (20) coaxially and the
transport screw (16) can be accommodated in this hole (20), whereby
the threaded segment (21) is integrated into the anchoring element
(3.j) and over a part of its circumference protrudes radially over
the anchoring element (3.j) vertical to the longitudinal axis
(4).
[0110] 11. The device according to one of 1-10, wherein the back
end (6) of at least one of the anchoring elements (3.j) has a
coaxial cone segment (23).
[0111] 12. The device according to 11, wherein the cone segment
(23) has a concentric threaded hole (24) that is open at the end
axially.
[0112] 13. The device according to 11, wherein a concentric pin
(25) with external threading axially abuts the cone segment (23) at
the end.
[0113] 14. The device according to one of 1-10, wherein the
receiving means (7) comprise a coaxial ball head (26) that abuts
the back end (6) of the anchoring element (3.j) at the end.
[0114] 15. The device according to one of 1-14, wherein the
anchoring element (3.j) has an anchoring segment (27) that has at
least one blade (9) and abuts the back end (6) over a length (L),
whereby said blade has an essentially rectangular cross-section
with a thickness (D) and a width (B) and the blade (9) has a first
transverse axis (22) parallel to the long sides of the
cross-section.
[0115] 16. The device according to one of 1-14, wherein the
anchoring element (3.j) has an anchoring segment (27) that has at
least one blade (9) and abuts the back end (6) over a length (L),
whereby said blade, when viewed from above, converges toward the
front end (5).
[0116] 17. The device according to one of 1-14, wherein the
anchoring element (3.j) has an anchoring segment (27) that has at
least one blade (9) and abuts the back end (6) over a length (L),
whereby said blade, when viewed from above, diverges toward the
front end (5).
[0117] 18. The device according to one of 1-14, wherein the
anchoring element (3.j) has an anchoring segment (27) that has at
least one blade (9) and abuts the back end (6) over a length (L),
whereby said blade, when viewed from above, converges to a point
(14) at the front end (5).
[0118] 19. The device according to one of 1-14, wherein the
anchoring element (3.j) has an anchoring segment (27) that has at
least one blade (9) and abuts the back end (6) over a length (L),
whereby said blade, when viewed from above, slopes down downward on
one side at the front end (5).
[0119] 20. The device according to one of 1-14, wherein the
anchoring element (3.j) has an anchoring segment (27) that has at
least one blade (9) and abuts the back end (6) over a length (L),
whereby said blade, when viewed from above, is convex at the front
end (5).
[0120] 21. The device according to one of 1-20, wherein the
anchoring element (3.j) has an anchoring segment (27) that has at
least one blade (9) and abuts the back end (6) over a length (L),
whereby said blade, when viewed in longitudinal section, converges
to a tip at the front end (5).
[0121] 22. The device according to one of 1-20, wherein the
anchoring element (3.j) has an anchoring segment (27) that has at
least one blade (9) and abuts the back end (6) over a length (L),
whereby said blade, when viewed in longitudinal section, is
attached at the front end (5) on one side.
[0122] 23. The device according to one of 1-22, wherein the
anchoring element (3.j) has an anchoring segment (27) that has at
least one blade (9) and abuts the back end (6) over a length (L),
whereby said blade, when viewed in cross-section, narrows to a
point on at least one lateral surface (32).
[0123] 24. The device according to one of 1-22, wherein the
anchoring element (3.j) has an anchoring segment (27) that has at
least one blade (9) and abuts the back end (6) over a length (L),
whereby said blade, when viewed in cross-section, is attached on
one side on at least one lateral surface (32).
[0124] 25. The device according to one of 1-24, wherein the
anchoring element (3.j) has an anchoring segment (27) that has at
least one blade (9) and abuts the back end (6) over a length (L),
whereby said blade is twisted over length (L) around an edge that
abuts one lateral surface (32).
[0125] 26. The device according to one of 1-24, wherein the
anchoring element (3.j) has an anchoring segment (27) that has at
least one blade (9) and abuts the back end (6) over a length (L),
whereby said blade is twisted over length (L) around the
longitudinal axis (4).
[0126] 27. The device according to one of 1-26, wherein the
anchoring element (3.j) has an anchoring segment (27) that has two
blades (9) and abuts the back end (6) over a length (L).
[0127] 28. The device according to 27, wherein, when viewed in
cross-section, the blades (9) lie in one plane.
[0128] 29. The device according to 27 or 28, wherein, parallel to
the longitudinal axis (4), the blades (9) are separated by a
rod.
[0129] 30. The device according to 29, wherein the rod is a hollow
(28) that is drilled parallel to the longitudinal axis (4).
[0130] 31. The device according to one of 1-26, wherein the
anchoring element (3.j) has an anchoring segment (27) that has
three or more blades (9) and abuts the back end (6) over a length
(L) and the anchoring segment (27) has a star-shaped
cross-section.
[0131] 32. The device according to one of 1-26, wherein the
anchoring element (3.j) has an anchoring segment (27) has three or
more blades (9) and abuts the back end (6) over a length (L),
whereby the blades (9), viewed in the cross-section of the
anchoring segment (27), are arranged with unequal central
angles.
[0132] 33. The device according to one of 1-32, wherein the
anchoring element (3.j) has a coaxial hollow (28) with a hole (20)
that is also coaxial and penetrates the anchoring element (3.j)
from the front end (5) to the back end (6).
[0133] 34. The device according to one of 1-26, wherein the
anchoring element (3.j) has an anchoring segment (27) that has at
least one blade (9) and abuts the back end (6) over a length (L)
and at least the one blade (9) has a sawtooth surface structure,
whereby the steep sides of the saw-teeth are oriented toward the
back end (6) of the anchoring element (3.j).
[0134] 35. The device according to 34, wherein the surface
structure is attached on one side.
[0135] 36. The device according to 34, wherein the surface
structure is attached on both sides.
[0136] 37. The device according to one of 1-33, wherein the
anchoring element (3.j) has an anchoring segment (27) that has at
least one blade (9) and abuts the back end (6) over a length (L)
and at least the one blade (9) has a fish-scale-like surface
structure, whereby the steep sides of the scales are oriented
toward the back end (6) of the anchoring element (3.j).
[0137] 38. The device according to 37, wherein the surface
structure is attached on one side.
[0138] 39. The device according to 37, wherein the surface
structure is attached on both sides.
[0139] 40. The device according to one of 15-30 or 33-39, wherein
the anchoring segment (27), when viewed in cross-section section,
has two blades (9) that lie in one plane and that are separated by
a hollow (28) coaxially to the longitudinal axis (4), whereby the
blades (9) have a thickness (D) of between 0.8 and 2 mm and a width
(B) of between 2.5 mm and 4.5 mm and the hollow cylinder (28) has a
diameter (d) of between 3 and 7 mm.
[0140] 41. The device according to one of 15-40, wherein the ratio
of the width (B) to the thickness (D) is basically between 1 and
14.
[0141] 42. The device according to 41, wherein the ratio of the
width (B) to the thickness (D) is basically between 3 and 6.
[0142] 43. The device according to one of 15-42, wherein at least
one blade (9) is designed in the shape of a spiral.
[0143] 44. The device according to 43, wherein at least one blade
(9) has a lead S of between 60 and 300 mm.
[0144] 45. The device according to 44, wherein at least one blade
(9) has a lead S of between 100 and 240 mm.
[0145] 46. The device according to one of 43-45, wherein the
twisting angle a over length (L) of the blades (9) is between 0 and
360.degree..
[0146] 47. The device according to one of 43-45, wherein the
twisting angle a over length (L) of the blades (9) is between 0 and
180.degree..
[0147] 48. The device according to one of 43-45, wherein the
twisting angle a over length (L) of the blades (9) is between 0 and
45.degree..
[0148] 49. The device according to one of 43-45, wherein the
twisting angle a over length (L) of the blades (9) is between 45
and 90.degree..
[0149] 50. The device according to one of 15-49, wherein at least
one blade (9) is twisted in the shape of a spiral and the twist
runs clockwise.
[0150] 51. The device according to one of 15-49, wherein at least
one blade (9) is twisted in the shape of a spiral and the twist
runs counter-clockwise.
[0151] While various descriptions of the present invention are
described above, it should be understood that the various features
can be used singly or in any combination thereof. Therefore, this
invention is not to be limited to only the specifically preferred
embodiments depicted herein. Further, it should be understood that
variations and modifications within the spirit and scope of the
invention may occur to those skilled in the art to which the
invention pertains. Accordingly, all expedient modifications
readily attainable by one versed in the art from the disclosure set
forth herein that are within the scope and spirit of the present
invention are to be included as further embodiments of the present
invention. The scope of the present invention is accordingly
defined as set forth in the appended claims.
* * * * *