U.S. patent application number 15/203431 was filed with the patent office on 2016-10-27 for osteosynthetic implant with an embedded hinge joint.
The applicant listed for this patent is DePuy Synthes Products, Inc.. Invention is credited to Robert FRIGG.
Application Number | 20160310181 15/203431 |
Document ID | / |
Family ID | 4551326 |
Filed Date | 2016-10-27 |
United States Patent
Application |
20160310181 |
Kind Code |
A1 |
FRIGG; Robert |
October 27, 2016 |
Osteosynthetic Implant With An Embedded Hinge Joint
Abstract
An osteosynthesis implant includes at least one coupling in the
form of a swivel joint. Each swivel joint includes at least one
planar or annular swivel element and two connecting arms that
define a pivot axis. The coupling permits rotation about each pivot
axis. The implant and coupling may be formed of unitary
construction, or a separate coupling may be connectable to the
implant. The coupling may receive a bone fastener such as a bone
screw, or may be used in applications that require the coupling to
directly support portions of the body such as spinal features.
Inventors: |
FRIGG; Robert; (Bettlach,
CH) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
DePuy Synthes Products, Inc. |
Raynham |
MA |
US |
|
|
Family ID: |
4551326 |
Appl. No.: |
15/203431 |
Filed: |
July 6, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12984302 |
Jan 4, 2011 |
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15203431 |
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10735854 |
Dec 16, 2003 |
7887569 |
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12984302 |
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09714147 |
Nov 17, 2000 |
6663632 |
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10735854 |
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PCT/CH98/00208 |
May 19, 1998 |
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09714147 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61F 2002/30634
20130101; A61B 17/7035 20130101; A61B 17/8047 20130101; A61B
17/8052 20130101; A61F 2/4425 20130101; A61B 17/80 20130101 |
International
Class: |
A61B 17/80 20060101
A61B017/80; A61B 17/70 20060101 A61B017/70 |
Claims
1. (canceled)
2. A bone fixation system, comprising: a first coupler for coupling
a bone screw to a longitudinal support; a first screw guiding
member including a first screw receiving hole defining a first
screw axis, the first screw receiving hole being sized so that the
first bone screw may be inserted therein only along the first screw
axis; first and second pivot arms extending radially outward from
the first screw guiding member along a first pivot axis to connect
the first screw guiding member to the first coupler so that the
first screw guiding member can pivot relative to the first coupler
about the first pivot axis to pivot the first screw axis relative
to the first coupler; a second coupler for coupling a second bone
screw to the longitudinal support; a second screw guiding member
including a second screw receiving hole defining a second screw
axis, the second screw receiving hole being sized so that the
second bone screw may be inserted therein only along the second
screw axis; and third and fourth pivot arms extending radially
outward from the second screw guiding member along a second pivot
axis to connect the second screw guiding member to the second
coupler so that the second screw guiding member can pivot relative
to the second coupler about the second pivot axis to pivot the
second screw axis relative to the second coupler.
3. The system of claim 2, wherein the longitudinal support is a
rod, a longitudinal axis of the rod extending substantially
perpendicularly to the first and second screw axes.
4. The system of claim 2, wherein the first coupler includes a
first channel sized and shaped to receive the longitudinal support
therein.
5. The system of claim 4, further comprising a fastener in threaded
engagement with the first coupler to lock the longitudinal support
within the first channel.
6. The system of claim 2, wherein the first and second bone screws
are pedicle screws and wherein the longitudinal support is a spinal
support rod.
7. The system of claim 2, wherein the first screw receiving hole
and a head of the first bone screw are structured to create an
angularly stable connection between the first bone screw and the
first screw guiding member to lock the first bone screw at the
first screw axis.
8. The system of claim 2, wherein first screw guiding member
includes an outer ring coupled to the first and second pivot arms
and an inner ring coupled to the outer ring by fourth and fifth
pivot arms extending along a third pivot axis so that the inner
ring can pivot about the third pivot axis relative to the outer
ring.
9. The system of claim 8, wherein the third pivot axis is
substantially perpendicular to the first pivot axis.
10. A method for treating bone comprising the steps of: inserting
to a first target location within a living body a first coupler and
a first screw guiding member including a first screw receiving hole
defining a first screw axis, wherein first and second pivot arms
extend radially outward from the first screw guiding member along a
first pivot axis to connect the first screw guiding member to the
first coupler so that the first screw guiding member can pivot
relative to the first coupler about the first pivot axis; inserting
a first bone screw through the first screw receiving hole along the
first screw axis; locking the first bone screw to the first screw
guiding member to create an angularly stable connection
therebetween; pivoting the first screw guiding member to a desired
angle relative to the first coupler and inserting the first bone
screw into a first target portion of bone along a desired axis;
coupling the first coupler to a longitudinal support; inserting to
a second target location within the living body a second coupler
and a second screw guiding member including a second screw
receiving hole defining a second screw axis, wherein third and
fourth pivot arms extend radially outward from the second screw
guiding member along a second pivot axis to connect the second
screw guiding member to the second coupler so that the second screw
guiding member can pivot relative to the second coupler about the
second pivot axis; inserting a second bone screw through the second
screw receiving hole along the second screw axis; locking the
second bone screw to the second screw guiding member to create an
angularly stable connection therebetween; pivoting the second screw
guiding member to a desired angle relative to the second coupler
and inserting the second bone screw into a second target portion of
bone along a desired axis; and coupling the second coupler to the
longitudinal support.
11. The method of claim 10, wherein the step of coupling the first
coupler to the longitudinal support comprises inserting the rod
into a channel of the first coupler and tightening a threaded nut
over the channel.
12. The method of claim 11, wherein the first and second bone
screws are pedicle screws and wherein the longitudinal support is a
spinal support rod.
13. The method of claim 10, further comprising: locking a head of
the first bone screw in the screw guiding member to create an
angularly stable connection between the first bone screw and the
first screw guiding member with the first bone screw locked at the
first screw axis.
14. The method of claim 10, wherein first screw guiding member
includes an outer ring coupled to the first and second pivot arms
and an inner ring coupled to the outer ring by fourth and fifth
pivot arms extending along a third pivot axis, the method further
comprising pivoting the inner ring can pivot about the third pivot
axis relative to the outer ring.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of prior patent
application Ser. No. 09/714,147, filed Nov. 17, 2000, which in turn
is a continuation of the U.S. National Stage designation of
co-pending International Patent Application PCT/CH98/00208, filed
May 19, 1998, the entire contents of which are expressly
incorporated herein by reference thereto.
FIELD OF THE INVENTION
[0002] The invention relates to an implant with a coupling. More
particularly, the invention relates to osteosynthesis implants with
couplings having gimbal-type swivel joints.
BACKGROUND OF THE INVENTION
[0003] Angularly fixed longitudinal supports such as plates and
bars increasingly are used in osteosynthesis applications. Such
devices are particularly useful for treating fractures that are
located near joints, or for anchoring screws in the spinal column.
In applications that use short screws, the screws typically can be
inserted in the longitudinal support at a preset angle without
presenting problems. When longer screws are necessary, a fixed,
system-dependent orientation of the screw may be impractical or
unwieldy.
[0004] To facilitate the use of longer screws in regions such as
the spine, special ball joints have been developed. In addition, as
disclosed in German patent DE 195 48 395, bone plates have been
proposed with specially configured screw holes drilled therein for
accepting correspondingly shaped screw heads. The bone screw thus
may be locked in place in the bone plate in a relatively randomly
selectable orientation. But, the complexity, bulky nature, and
insufficient strength provided by the connections of these ball
joints and screw head-borehole configurations does not sufficiently
remedy the inherent problems encountered with fixed,
system-dependent orientations of screws.
[0005] Also disclosed in German patent DE 24 38 669 to Bezold is an
osteosynthesis bone plate with screw holes having a respective
spacing that can be manipulated using externally generated forces.
The screw holes are arranged in the form of lugs punched out of the
main body of the osteosynthesis plate and connected thereto merely
by elastic legs. In one embodiment, the legs are aligned along one
axis and connected to the lug diametrically relative to the axis.
When the lug is lifted out of the plane of the plate, the legs are
bent such that the rotational axis of the lug no longer coincides
with the vertical axis of either the lug itself or the screw hole.
Use in clinical applications thus is limited because as the lug is
turned, the center of the screw hole is undesirably shifted.
[0006] There exists a need for a bone plate with a coupling that
facilitates the use of a wide range of sizes of bone screws. There
further exists a need for a coupling that requires less space than
ball joints and provides simplicity in design and use.
Additionally, there is a need for a substantially flat swivel joint
for use in connecting implant components such as a bone screw and a
bone plate.
[0007] The present invention provides an implant and coupling
capable of furnishing these improvements, and advantageously has
application in a wide range of other implants unrelated to bone
screw support.
SUMMARY OF THE INVENTION
[0008] The present invention relates to an osteosynthesis implant
that includes a coupling comprising at least one annular element
having a pair of connecting members for coupling the annular
element to a surrounding structure. The connecting members provide
the annular element with a swiveling motion with respect to the
surrounding structure for alignment of the annular element during
insertion or implantation of the implant. The connecting members
also form a single coupling axis with the surrounding structure and
the annular element swivels about that coupling axis.
[0009] In one embodiment, the annular element defines a hole for
receiving a fastener and the surrounding structure is the implant.
Typically, the annular element has a generally circular
configuration and defines a generally cylindrical hole that extends
along a central axis. Also, the hole is generally perpendicular to
at least one of the top and bottom surfaces of the annular
element.
[0010] In another embodiment, the annular element has a top
surface, a bottom surface, and a first thickness defined between
the top and bottom surfaces, and the implant has a top implant
surface, a bottom implant surface, and a second thickness defined
between the top and bottom implant surfaces and the connecting
members have a connection thickness. Typically, the first thickness
of the annular element is less than or equal to the second
thickness of the implant and the connection thickness of the
connecting members is also less than or equal to the second
thickness of the implant.
[0011] In another embodiment, the coupling has inner and outer
annular elements where each element has a pair of connecting
members and the connecting members of the inner annular element are
coupled to the outer annular element and the connecting members of
the outer annular element are coupled to a surrounding structure.
This permits the inner annular element to be provided with a first
swiveling motion and the outer annular element to be provided with
a second swiveling motion. Also, the connecting members of the
inner annular element form a first coupling axis and the connecting
members of the outer annular element form a second coupling axis
that is positioned at an angle with respect to the first coupling
axis. The first and second coupling axes can be substantially
perpendicular to each other.
[0012] In another embodiment of the present invention, the inner
and outer annular elements, the connecting members and the implant
are all formed of unitary construction and each connecting member
is capable of exhibiting elastic deformation to permit the annular
element to swivel.
[0013] In another embodiment, the implant is an intervertebral
element having at least one surface that includes the surrounding
structure in which the inner and outer annular elements are
disposed so that more precise alignment can be provided. In an
exemplary embodiment, the intervertebral element has two parallel
surfaces, each of which provides the surrounding structure in which
the inner and outer annular elements are disposed. The two parallel
surfaces define a central longitudinal axis and the intervertebral
element has a first through-hole extending generally perpendicular
to the central longitudinal axis and has a second through-hole
extending generally perpendicular to the first through-hole.
[0014] In another exemplary embodiment. the intervertebral element
has top and bottom surfaces, each of which provide the surrounding
structure in which inner and outer annular elements are disposed,
In addition, the top and bottom surfaces are, typically, configured
as generally oval plates and are spaced apart from each other with
a central connector that is generally cylindrical, Furthermore, the
central connector is fixed to the inner annular elements, such that
swivelling of the plates is permitted while the inner annular
elements remain parallel to each other and the connecting members
of the inner annular element form a first coupling axis and the
connecting members of the outer annular element form a second
coupling axis that is generally perpendicular to the first coupling
axis. Typically, the implant is configured and dimensioned to be
received between two vertebral bodies.
[0015] In another embodiment of the present invention, the
surrounding structure in which inner and outer annular elements are
disposed is a fixation system for a longitudinal support. The
fixation system comprises a mounting head having a top surface and
bottom surface, a first head bore which extends from the top head
surface to the bottom head surface about a head bore longitudinal
axis and a second head bore which extends substantially
perpendicular to the first head bore. The second head bore is
configured and dimensioned to receive a longitudinal support and
the inner annular element includes a hole for a pedicle screw.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] 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:
[0017] FIG. 1A shows a cross-sectional view of an implant of the
present invention in which a swivel joint is integrated in a bone
plate;
[0018] FIG. 1B shows a top view of the implant of FIG. 1A;
[0019] FIG. 2 shows a top view of another implant of the present
invention in which a double-gimbaled swivel joint is integrated in
a bone plate;
[0020] FIG. 3 shows a partial, cross-sectional view of yet another
implant of the present invention in which swivel joints are
integrated in two femur plates and receive a hip screw;
[0021] FIG. 4A shows a partial cross-sectional view of an
additional implant of the present invention in which a swivel joint
is integrated in a vertebral fixation element;
[0022] FIG. 4B shows a side view of the implant of FIG. 4A;
[0023] FIG. 4C shows a top view of a swivel joint used in the
implant of FIG. 4A;
[0024] FIG. 5 shows a perspective view of another implant of the
present invention in which a swivel joint is integrated in a
vertebral unit;
[0025] FIG. 6 shows a cross-sectional view of yet another implant
of the present invention in which a vertebral unit is integrated
with a swivel joint;
[0026] FIG. 7 shows a side view of the implant of FIG. 6; and
[0027] FIG. 8 shows another side view of the implant of FIG. 6 with
the vertebral end plates disposed at an angle.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0028] The present invention relates to an osteosynthetic implant
or implant component having at least one swivel joint connected
thereto and preferably being in the form of a planar gimbal
articulation. The at least one swivel joint preferably includes a
planar, disc-shaped or annular swivel element having two flat,
bar-shaped connecting elements positioned along a common axis at
the outer perimeter of the swivel element. The connecting elements
or legs define axes of rotation. Each swivel joint includes at
least one swivel element that is rotatably connected to the implant
or implant component via the connecting elements. The inner swivel
element may be provided with a borehole generally perpendicular to
the plane of rotation defined by the axes of rotation of the swivel
element. The implant or implant component and the swivel joints may
be an integral unit, or connecting legs in the form of pivot shafts
may be positioned between the planar or annular swivel joint and
the implant in such a fashion that the swivel joint is
concentrically supported in a borehole of an osteosynthesis implant
component and is rotatable around the pivot axes.
[0029] The connecting elements may be dimensioned so that elastic
deformation thereof permits an angularly fixed rotation of the
swivel element relative to the implant or implant component. The
connecting legs are situated opposite each other along one axis,
with their outer lateral surfaces attached to the implant or
implant component while their inner faces are attached to a planar
or annular swivel joint.
[0030] In one preferred embodiment, the swivel joint includes two
nested, coplanar swivel elements, with each inner swivel element
being connected via two connecting elements to a corresponding
outer swivel element to permit rotation around a first axis.
Likewise, the outer swivel element is connected via two connecting
elements to the implant or implant component to permit rotation
around a second axis. The axis of rotation may extend between the
nested swivel elements along the plane in which the swivel elements
are situated, and the axes of rotation may be offset by 90.degree.
from each other. The swivel joint may be configured as a planar,
double-gimbal swivel joint. Thus, the two swivel elements are
gimbal-mounted within a single implant component borehole, with an
outer swivel element being rotatably supported in the borehole of
the osteosynthesis implant component and the inner swivel element
being rotatably supported in the borehole of the outer swivel
element.
[0031] The connecting elements may be shafts that are pivot-mounted
in at least one swivel element and in the implant or implant
component. In addition, the swivel elements and the implants or
implant components may be separated by slots extending to the
connecting elements. which may be in the form of generally arcuate
or circular segments.
[0032] The implant incorporating the swivel joint may be a
block-shaped bone plate, and the thickness of the swivel element
and connecting elements may be less than the thickness of the bone
plate, other implant, or the wall of an osteosynthesis implant
component accommodating the swivel joint. The swivel joint is
integrated with the bone plate.
[0033] In another preferred embodiment, the swivel joint is
integrated in a mounting head for connecting a pedicle screw to a
longitudinal support within a spinal vertebra fixation system. The
swivel joint includes at least one swivel element, with the
mounting head serving to connect the longitudinal support to the
pedicle screw. The swivel joint and mounting head may be an
integral unit. The implant may be configured as an intervertebral
unit or as a vertebra substitute. Such an intervertebral unit may
have a swivel joint integral with its top and bottom surfaces for
adapting to adjacent vertebra.
[0034] In a further preferred embodiment, two swivel joints are
attached by their inner swivel elements to the ends of a rod in a
direction generally perpendicular to their axes of rotation, with
one swivel element of each swivel joint being connected to a
vertebral end plate. The vertebral end plates contacting the
vertebrae are in the form of oval rings which are connected to
outer swivel elements and each outer swivel element, in turn, is
connected to each respective inner swivel element. Each of the two
vertebral end plates is connected to the rod by way of a swivel
joint, each rotatable around at least one axis of rotation.
[0035] The swivel joint may be configured for holding a bone
fastener. A bone screw or pedicle screw may extend through a
borehole in the swivel element, with the screw head bearing against
the swivel element, so that the swivel joint permits the screw head
to rotate within the bone plate or vertebral fixation system about
at least one axis. The borehole in the swivel element may be
tapered and a bone fastener such as a bone screw or pedicle screw
may have a correspondingly conical screw head so as to permit an
angularly fixed connection between the implant or implant component
and the bone fastener. Furthermore, the borehole in the swivel
element may be provided with internal threading to be engaged by
external threading on the screw head or shank of the bone screw or
pedicle screw, thus permitting an angularly fixed connection
between the implant or implant component and the bone fastener. The
threading may be tapered.
[0036] The bone screw or the pedicle screw may be provided with an
expandable head, and by means of a clamping screw, the parts of the
expandable screw head are pressed with a positive fit against the
wall of the borehole so as to permit an angularly fixed connection
between the implant or implant component and the bone fastener.
[0037] Referring to FIGS. 1A and 1B, bone fixation system 100
includes bone plate 3 with couplings 10 in the form of swivel
joints 49 mounted therein. In a preferred embodiment, bone plate 3
is provided with at least one screw hole 7 that extends from top
surface 13 to bottom surface 14 of bone plate 3 about a center axis
12 and serves to accommodate a fastener 1 such as a bone screw.
Screw hole 7 has an inner wall 7'. Swivel joint 49 including a
circular inner swivel element 4 and two coaxial inner connecting
legs 5. Inner connecting legs 5 connect inner swivel element 4 to
bone plate 3. Preferably, inner swivel element 4 has an annular
shape, with a central borehole 8' and an outer perimeter 9'. When
circular inner swivel element 4 with inner connecting legs 5 is
disposed in screw hole 7, two near semicircular slots 6 are defined
between wall 7' of bone plate 3 and perimeter 9' of inner swivel
element 4, the slots 6 being concentric with screw hole 7.
Preferably, slots 6 are milled into bone plate 3, although slots 6
may be formed otherwise. Inner connecting legs 5 and inner swivel
element 4 may be unitarily constructed from the same blank and are
integral parts of bone plate 3.
[0038] Inner swivel element 4 of swivel joint 49 has a thickness
T.sub.a defined vertically between upper swivel element surface 70
and lower swiveling element surface 72, and bone plate 3 has a
thickness T.sub.b defined vertically between top surface 13 to
bottom surface 14. Preferably, legs 5 have a thickness that is
substantially the same as thickness T.sub.a. In the preferred
embodiment, thickness T.sub.a of coupling 10 is less than the
thickness T.sub.b of plate 3.
[0039] As shown in FIGS. 1A and 1B, coupling 10 with inner
connecting legs 5 is in the form of a single gimbal or universal
joint. Coaxial connecting legs 5 of swivel joint 49 define an axis
of rotation 11 that is disposed transverse to the longitudinal
direction of bone plate 3. When a bone screw 1 is inserted into
central borehole 8' of inner swivel element 4 and screw head 2 of
bone screw 1 bears against upper swivel element surface 70, swivel
joint 49 permits rotation of inner swivel element 4 about axis of
rotation 11. Thus, bone screw 1 may be oriented at a desired angle
and screwed into a bone.
[0040] Turning now to FIG. 2, another preferred embodiment of
coupling 10 for use with a bone fixation system 100 is shown.
Swivel joint 50 is provided with a circular outer swivel element 16
having outer connecting legs 15. A circular inner swivel element 4
is coupled to circular outer swivel element 16 with inner
connecting legs 5, while circular outer swivel element 16 is
coupled to bone plate 3 with outer connecting legs 15. Two near
semicircular slots 74 are defined between perimeter 9' of inner
swivel element 4 and first perimeter 76 of outer swivel element 16.
Likewise, two near semicircular slots 17 are defined between second
perimeter 78 of outer swivel element 16 and wall 7' of bone plate
3. Outer connecting legs 15 are disposed coaxially about an axis
18, permitting outer swivel element 16 to rotate about axis 18.
[0041] In the embodiment of FIG. 2, axis 18 is disposed generally
parallel to the longitudinal direction of bone plate 3, while axis
11 is disposed generally transverse thereto. Thus, swivel joint 50
permits swivelling about two non-parallel axes 11, 18. Preferably,
axes 11, 18 are offset by about 90.degree. with respect to each
other, permitting double-gimbaled action. Inner swivel element 4,
inner connecting legs 5, outer connecting legs 15 and outer swivel
element 16 may be unitarily constructed as integral parts of bone
plate 3. Alternatively, inner connecting legs 5 and outer
connecting legs 15 may be pins or other suitable coupling elements.
If pins are used, the pins forming connecting legs 15 are supported
in bone plate 3 and inner swivel element 4, while the pins forming
legs 5 are supported in outer swivel element 16 and inner swivel
element 4.
[0042] Referring to FIG. 3, a bone fixation system 200 includes a
bone fastener in the form of a hip screw 19 along with upper and
lower bone plates 3, 26, each having a coupling 10. Hip screw 19
may enter bone plate 3 at an oblique angle, and thus may be
supported in bone plate 3 by means of a coupling 10 such that screw
head 20 of hip screw 19 bears against inner swivel element 4 of
coupling 10. Preferably, since hip screw 19 does not extend
perpendicular to bone plate 3, inner swivel element 4 is tilted in
the desired direction prior to implantation of hip screw 19.
However, angulation in vivo by a surgeon also may be achieved. A
coupling 10 suitable for use in bone fixation system 200, for
example, may be in the form of either swivel joint 49 or 50,
although embodiments of coupling 10 with more than two swivel
elements forming a swivel joint may also be used. Accordingly,
depending on the type of joint used, coupling 10 may include inner
connecting legs 5 for a single gimbal joint, or coupling 10 may
incorporate inner connecting legs 5 and outer connecting legs 15
for a double gimbal joint.
[0043] Since inner connecting legs 5 and outer connecting legs 15
preferably provide fixed connections between bone plate 3 and inner
swivel element 4, or between bone plate 3, inner swivel element 4
and outer swivel element 16, orientation of a coupling 10 in bone
plate 3 may generate a retractive force. It is desirabie to
minimize or eliminate such retractive forces, as by effectively
neutralizing the retractive forces through the use of an additional
coupling 10 in a bone plate 26. In particular, upper and lower bone
plates 3, 26 are placed one on top of the other, and shank 21 of
hip screw 19 is inserted through the integrated coupling 10 of each
plate. Additional tightening bone screws 24 may be used for
fastening the two bone plates 3, 26 to bone 25.
[0044] By moving bone plates 3, 26 relative to each other, it is
possible to adjust and fix the orientation of hip screw 19 in a
wide range of angles. Tightening bone screws 24 may be used to fix
bone plates 3, 26 in place, and additionally serve to fix the
orientation of hip screw 19. Shank 21 of hip screw 19 is inserted
in central boreholes 22, 23 of inner swivel elements 4 of couplings
10 which are provided in bone plates 26, 3, respectively. Due to
the use of two couplings 10, when bone plates 3, 26 are fastened,
forces transverse to longitudinal axis 27 of hip screw 19 are
avoided, notwithstanding the retractive force of inner connecting
legs 5 and outer connecting legs 15.
[0045] FIGS, 4A, 4B and 4C show another preferred embodiment of the
present invention in the form of a vertebral fixation system 300.
Coupling 10 is used to connect pedicle screw 29 to mounting device
34, which has a first end 80 and a second end 82. Preferably, first
end 80 of mounting device 34 is configured for threadable
engagement with a fastening nut 33, so that the location of
mounting device 34, and consequently the position of pedicle screw
29, may be fixed on a longitudinal support 32 that extends through
a borehole 86. A coupling 10 is disposed in second end 82 of
mounting device 34, and preferably coupling 10 includes an inner
swivel element 4, an outer swivel element 16, inner connecting legs
5, and outer connecting legs 15, as previously described herein.
Inner swivel element 4, outer swivel element 16, inner connecting
legs 5 as well as outer connecting legs 15 are all integrated with
mounting head 31.
[0046] A central longitudinal axis 35 extends between first end 80
and second end 82 of mounting device 34, preferably about the
center of a cavity 84 in mounting device 34. Pedicle screw 29 is
inserted through borehole 28, defined by inner swivel element 4,
until screw head 30 makes full contact with borehole 28. If pedicle
screw 29 does not extend parallel to longitudinal axis 35 of
mounting head 31, coupling 10 compensates for the change in angle.
The choice of design for coupling 10 dictates the permissible
angulation of pedicle screw 29. For example, when a swivel joint 50
having a dual-gimbal swivel joint is employed, it is possible to
rotate the pedicle screw 29 relative to mounting head 31 about two
axes 36, 37. Alternatively, if a coupling 49 with a single gimbal
swivel joint is used, the coupling only facilitates the rotation of
pedicle screw 29 about one axis relative to mounting head 31.
[0047] Referring to FIG. 5, another preferred embodiment of the
present invention is shown in the form of a spinal block, which may
serve as an intervertebral element or as a vertebra substitute.
Vertebral fixation system 400 includes a spinal unit 38 with a pair
of opposing couplings 10 disposed in the top surface 39 and bottom
surface 40. Couplings 10 include inner swivel elements 4, which
serve as the support surfaces for vertebral sections adjacent to
spinal unit 38 upon implantation. Inner swivel elements 4 may be
plate-like or annular, and thus may not include a central hole
therein. Spinal unit 38 preferably has the general form of a block,
further including a front surface 4i, rear surface 42, and two side
surfaces 43 and 44. A first through-hole 45 extends from front
surface 41 to rear surface 42, and a second through-hole 46 extends
between side surfaces 43 and 44.
[0048] Preferably, top surface 39 and bottom surface 40 of spinal
unit 38 are cambered so that the inner swivel elements 4 of the
pair of couplings 10 form the highest point of top surface 39 and
the lowest point of bottom surface 40. Advantageously, couplings 10
permit spinal unit 38 to be used even when the lower and upper
support surfaces in the spinal column (i.e., adjacent vertebral
bodies) are not parallel to one another. Couplings 10 may be
integrated into top surface 39 and bottom surface 40 of spinal unit
38, so that spinal unit 38 and couplings 10 are made of unitary
construction. With reference to FIG. 2, for example, each coupling
10 may include an inner swivel element 4 having two opposing,
coaxial, inner connecting legs 5 that permit rotation with respect
to outer swivel elements 16. Outer swivel elements 16 are connected
to spinal unit 38 with two opposing, coaxial, outer connecting legs
15 that permit rotation with respect to spinal unit 38. Preferably,
outer connecting legs 15 are offset by about 90.degree. with
respect to inner connecting legs 5. Thus, each inner swivel element
4 serves as a support surface for the parts of the spinal column
that are adjacent to and in contact with spinal unit 38.
Furthermore, each inner swivel element 4 preferably permits
rotation about two approximately perpendicular axes disposed
proximate top surface 39 and proximate bottom surface 40 of spinal
unit 38.
[0049] As shown in FIGS. 6-8 another preferred embodiment of the
present invention may serve as a spinal implant. Vertebral fixation
system 500 includes a pair of vertebral end plates 61 that each
have a centrally located coupling 10. Each coupling 10 includes two
nested swivel elements 4, 16 connected to each other via connecting
legs 5, 15, so that rotation of vertebral end plates 61 is
permitted. In the pre-rotation base position, swivel elements 4, 16
are disposed about a common plane formed by axes of rotation 11,
18, which extend parallel to the support surfaces of vertebral end
plates 61. Outer annular swivel elements 16 are connected to
vertebral end plates 61 with a pair of coaxial connecting legs 15
that generally define axis 11, such that rotation is permitted
about axis In addition, outer annular swivel elements 16 are
connected to inner swivel elements 4 with generally coaxial
connecting legs 5, such that rotation is permitted about axis 18.
Preferably, vertebral end plates 61 are in the form of oval rings
that define hollow areas 62 between the inner walls 88 of vertebral
end plates 61 and the perimeter 90 of outer swivel elements 16.
[0050] Moreover, each of the inner swivel elements 4 is attached to
one of ends 63, 64 of a central body 60, which may be cylindrical
and preferably is a rod. Rod 60 is disposed along central axis 87
which also is generally perpendicular to the plane formed by axes
of rotation 11, 18, and thus perpendicular to the pair of opposing,
inner swivel elements 4. Each of the two vertebral end plates 61 is
connected to rod 60 via a coupling 10 such that rotation is
permitted about two axes 11, 18. Referring in particular to FIGS.
7-8, vertebral end plates 61 are show in an initial state in FIG. 7
with a uniform spacing T.sub.c therebetween. The provision of a
coupling 10 in each of upper and lower vertebral end plates 61, and
the provision of a connection between each coupling 10 of the two
plates, permits vertebral fixation system 500 to angulate based on
forces applied to plates 61. For example, as shown in FIG. 8, the
generally uniform separation distance T.sub.c may be decreased by
an amount .delta . . . sub.1 in one region, while the separation
distance T.sub.c may be increased by an amount .delta . . . sub.2
in another region of system 500.
[0051] 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.
[0052] 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.
For example, in an alternate embodiment, more than two annular
swivel elements may be provided. In addition, the connecting legs
that couple the swivel elements to each other and also to an
implant may not be disposed generally perpendicular with respect to
each other. Still further, the swivel elements may be detachably
connectable to a bone plate, so that a surgeon can choose a
coupling with a suitable central bore hole size for receiving a
bone screw having a surgeon-selected diameter or configuration. In
yet another alternate embodiment, fastening elements such as bone
screws may be threadably engaged with one or more couplings.
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.
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