U.S. patent application number 11/182677 was filed with the patent office on 2005-11-10 for apparatus for connecting a bone fastener to a longitudinal rod.
This patent application is currently assigned to Synthes USA. Invention is credited to Donath, Raoul, Frigg, Robert.
Application Number | 20050251141 11/182677 |
Document ID | / |
Family ID | 4358118 |
Filed Date | 2005-11-10 |
United States Patent
Application |
20050251141 |
Kind Code |
A1 |
Frigg, Robert ; et
al. |
November 10, 2005 |
Apparatus for connecting a bone fastener to a longitudinal rod
Abstract
A device for connecting a bone fastener to a longitudinal rod
has two bores spaced a distance apart and generally parallel axes.
A holding member may be associated with one bore, the holding
member configured to engage a bone fastener such as a bone screw or
pedicle hook. A rod coupling member may be associated with the
other bore, the coupling member configured to engage a longitudinal
rod. The holding member and rod coupling member both are configured
to articulate within their respective bores, thus allowing the rod
and rod coupling, as well as the holding member and bone fastener,
to rotate about both bore axes. The holding member and rod coupling
member also separately lockable to allow independent locking of the
bone fastener and the rod to the connector, thus preventing or
enabling relative rotation as desired.
Inventors: |
Frigg, Robert; (Bettlach,
CH) ; Donath, Raoul; (Grenzach-Wyhlen, DE) |
Correspondence
Address: |
JONES DAY
222 EAST 41ST STREET
NEW YORK
NY
10017-6702
US
|
Assignee: |
Synthes USA
|
Family ID: |
4358118 |
Appl. No.: |
11/182677 |
Filed: |
July 15, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11182677 |
Jul 15, 2005 |
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10372345 |
Feb 24, 2003 |
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6945972 |
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10372345 |
Feb 24, 2003 |
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PCT/CH00/00449 |
Aug 24, 2000 |
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Current U.S.
Class: |
606/301 ;
606/264; 606/266; 606/278; 606/291; 606/328; 606/330 |
Current CPC
Class: |
A61B 17/8038 20130101;
A61B 17/7044 20130101; A61B 17/8047 20130101; A61B 17/7041
20130101 |
Class at
Publication: |
606/061 |
International
Class: |
A61B 017/58 |
Claims
1. A connector for connecting a bone fastener to a rod, the
connector comprising: a coupling portion having top and bottom
surfaces and first and second bores, each bore having a
longitudinal axis, the axes separated by a distance; and a rod
coupler associated with the second bore and comprising a rod
receiving portion having an axis, a tab segment, and a bore
engaging portion having a bottom end with an increased portion, the
increased portion having a dimension greater than that of the
second bore, wherein: the increased portion prevents the rod
coupler from passing through the coupling portion when the rod
coupler is inserted into the second bore; and the tab segment
contacts the top surface of the coupling portion such that the rod
coupler is axially fixed with respect to the coupling portion when
the rod coupler is inserted into the second bore.
2. The connector of claim 1 wherein the rod coupler is rotatable
about the second bore longitudinal axis.
3. The connector of claim 1 wherein the rod coupler is rotatable
about the first bore longitudinal axis.
4. The connector of claim 1 wherein the increased portion comprises
a conical flange and the second bore comprises a corresponding
conical recess adjacent to the bottom surface of the coupling
portion.
5. The connector of claim 4 wherein the conical flange and conical
recess have corresponding engagement surfaces, and at least one of
the engagement surfaces comprises serrations configured to prevent
relative rotation between the flange and the bore.
6. The connector of claim 1 wherein the rod receiving portion has
first and second vertical legs configured to receive a rod, the rod
coupler further having locked and unlocked positions.
7. The connector of claim 1 wherein the rod receiving portion
comprises a channel having a longitudinal axis, a top end distal
from the bore engaging portion and a bottom end opposite the top
end, the channel longitudinal axis coaxial with the rod receiving
portion axis, the channel top end being open to allow a rod to be
introduced into the rod receiving portion by pressing the rod
through the channel top end in a direction substantially parallel
to the second bore axis.
8. The connector of claim 1 wherein the first and second bore
longitudinal axes are substantially parallel.
9. The connector of claim 1 further comprising a locking member
having a rod coupler engaging portion.
10. The connector of claim 1 further comprising a holding member
associated with the first bore and configured to engage the bone
fastener and to connect the bone fastener to the coupling
portion.
11. The connector of claim 10 wherein the holding member is
rotatable about the second bore longitudinal axis.
12. The connector of claim 10 wherein the holding member comprises
top and bottom surfaces and a wall, the wall having at least one
vertical slot disposed therein and intersecting one of the top and
bottom surfaces.
13. The connector of claim 10 wherein the rod coupler and the
holding member each have locked and unlocked positions independent
of each other.
14. The connector of claim 10 wherein the holding member comprises
a head portion of the bone fastener.
15. The connector of claim 10 wherein the holding member has a bore
configured to accept the bone fastener, the holding member further
having locked and unlocked positions.
16. The connector of claim 15 wherein the rod coupler is rotatable
360 degrees within the second bore when the holding member is in
the locked position with a bone fastener.
17. The connector of claim 15 further comprising a tensioner sized
and configured to engage the holding member in the locked position
wherein the holding member is immobilized with respect to the
coupling portion and the bone fastener is immobilized within the
holding member.
18. The connector of claim 17 wherein the tensioner comprises a
head portion of the bone fastener.
19. The connector of claim 17 wherein the holding member bore has a
conical profile and internal threads and the tensioner further
comprises a conical outer profile and external threads
corresponding to those of the holding member bore.
20. The connector of claim 17 wherein the holding member is
configured to be resiliently displaceable such that the holding
member having an outer spherical surface expands to engage the
coupling first bore having an inner spherical surface to configure
the holding member in the locked position when the tensioner
engages the bore.
21. The connector of claim 10 wherein the coupling portion first
bore comprises a substantially spherical inner surface and the
holding member comprises a substantially spherical outer surface
configured to slide within the spherical bore inner surface such
that the holding member is rotatable within the first bore about
multiple axes.
22. The connector of claim 21 wherein the holding member is
slidable within the spherical bore inner surface about axes both
parallel and perpendicular to the first bore axis.
23. The connector of claim 1 wherein the bone fastener comprises a
bone screw or hook.
24. A connector for connecting a bone fastener to a rod, the
connector comprising: a coupling portion having top and bottom
surfaces and first and second bores, each bore having an axis, the
axes separated by a distance; and a rod coupler associated with the
second bore and comprising a rod receiving portion and a bore
engaging portion, the bore engaging portion having a bottom flange
and an increased portion, the increased portion being between the
bottom flange and the rod receiving portion, the flange and
increased portion each having a dimension greater than that of the
second bore such that the flange prevents the rod coupler from
passing through the coupling portion when the rod coupler is
inserted into the second bore and the increased portion contacts
the top surface of the coupling portion such that the rod coupler
is axially fixed with respect to the coupling portion when the rod
coupler is inserted into the second bore.
25. The connector of claim 24 further comprising a bone fastener
connected to the coupling portion via the first bore.
26. The connector of claim 25 wherein the bone fastener comprises a
bone screw or hook.
27. The connector of claim 24 wherein the rod receiving portion
comprises first and second vertical legs configured to receive a
rod placed there between.
28. The connector of claim 27 further comprising a rod locking
member configured to engage a top portion of each of the first and
second vertical legs to hold the rod between the rod locking member
and a top surface of the connector.
29. The connector of claim 28 wherein the rod locking member
comprises threads configured to engage corresponding threads in the
top portion of at least one of the first and second vertical
legs.
30. The connector of claim 24 further comprising a holding member
associated with the first bore and configured to engage a bone
fastener.
31. The connector of claim 30 wherein the holding member has a bore
configured to receive the bone fastener, the holding member further
having an unlocked position in which it is free to rotate within
the first bore, and a locked position in which it is immobilized
within the first bore.
32. The connector of claim 30 wherein the connector further
comprises a tensioner configured to engage the holding member and
to lock the holding member in position such that the holding member
is immobilized within the first bore.
33. The connector of claim 32 wherein when the holding member
engages the bone fastener, the tensioner engages the holding
member, and the rod coupler engages a rod, the rod and rod coupler
are rotatable 360 degrees about both the first and second bore
longitudinal axes.
34. The connector of claim 32 wherein the tensioner comprises
external threads configured to engage corresponding internal
threads in the holding member bore.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This is a continuation of co-pending U.S. application Ser.
No. 10/372,345, filed Feb. 24, 2003, now U.S. Pat. No. ______,
which is a continuation of International Patent Application No.
PCT/CH00/00449, filed Aug. 24, 2000, the entire contents of both
are expressly incorporated herein by reference thereto.
FIELD OF THE INVENTION
[0002] The invention relates to spinal fixation systems and, in
particular, to a device for adjustably connecting a bone fastener
to a longitudinal rod.
BACKGROUND OF THE INVENTION
[0003] In posterior treatment of spinal deformities, pedicle screws
or hooks are used to connect vertebral bodies to a longitudinal
rod. Prior to implantation, the longitudinal rod is shaped in a
particular form so as to correct the deformity of the vertebral
column. This technique has proved successful and has been
considered state of the art.
[0004] Despite the development of new connecting techniques, such
as the use of jaws with polyaxial bearings to connect the screws
and the longitudinal rod, the intra-operative connection of the two
elements remains problematic, particularly in cases of heavy spinal
deformities. The problem lies in the fixed distance between the
head of the pedicle screw and the longitudinal carrier. In other
words, the polyaxial bearing of the screw head within the
connecting jaw allows for variable screw angles, but not for
variable distances between the screw head and longitudinal rod
carrier. A variable distance between the screw head or the end
portion of the hook and the longitudinal rod carrier is desirable,
because achieving 100 percent alignment of the vertebral column
relative to the longitudinal rod is not always possible.
[0005] It is accordingly an object of the invention to provide an
apparatus for connecting a pedicle screw or a pedicle hook to a
longitudinal rod that has a polyaxial bearing for the pedicle screw
or pedicle hook and a pivotable connection between the connector
and the longitudinal rod that can be locked in any desired
position.
SUMMARY OF THE INVENTION
[0006] The invention relates to a device for connecting a bone
fastener to a longitudinal rod. The device comprises a connector
that includes a coupling portion having two bores. Each bore has a
longitudinal axis, and the axes are separated by a predetermined
distance. The connector also has a holding member associated with
the first bore configured to engage the bone fastener to connect
the fastener to the coupling. A rod coupler is associated with the
second bore and comprises a bore engaging portion, a rod receiving
portion, and preferably a locking member having a rod coupler
engaging portion. The connector is configured so the rod and rod
coupler may be rotated about the first bore longitudinal axis. In
one embodiment, the holding member may be rotated about the second
bore axis. In another embodiment, the rod coupler may be rotated
about the second bore longitudinal axis. In yet another embodiment,
the first and second bore axes are substantially parallel.
[0007] The holding member may comprise top and bottom surfaces and
a wall having at least one vertical slot, the slot intersecting
either the top or bottom surface. The holding member may have a
bore configured to engage a bone fastener, and may also have locked
and unlocked positions. A tensioner may be provided to engage the
holding member bore to lock the holding member, rendering the
holding member immobilized with respect to the coupler first bore,
and immobilizing the bone fastener within the holding member.
[0008] The holding member and tensioner are configured so that when
the tensioner engages the holding member to render it locked, the
longitudinal rod and rod coupler may rotate 360 degrees within the
second bore. In one embodiment, the tensioner may comprise the head
of a bone fastener such as a bone screw or pedicle hook.
Alternatively, the holding member may comprise the head of a bone
fastener.
[0009] The coupling portion first bore may comprise a substantially
spherical inner surface and the holding member may comprise a
correspondingly substantially spherical outer surface configured to
slide within the inner surface. This configuration allows the
holding member to rotate within the first bore about multiple axes,
which may include axes both parallel and perpendicular to the first
bore axis.
[0010] The holding member bore may have a conical profile and
internal threads, and the tensioner may have a corresponding
conical outer profile and external threads which mate with those of
the bore. The holding member may be resiliently displaceable so
that upon engagement with the tensioner, the holding member outer
spherical surface may expand to engage the coupling first bore
inner surface, configuring the holding member in the locked
position. The holding member may have at least one slot configured
to render the holding member resiliently displaceable.
[0011] The rod receiving portion may have at least one vertical leg
configured to accept the longitudinal rod, and the rod coupler may
have locked and unlocked positions. The rod coupler and holding
member may, independent of each other, be configured in their
respective locked or unlocked positions.
[0012] The rod receiving portion may comprise a channel having a
longitudinal axis, a top distal from the bore engaging portion, and
a bottom end opposite the top end. The channel longitudinal axis
may be coaxial with that of the rod receiving portion. The top end
of the channel may be open to allow a longitudinal rod to be
introduced into the receiving portion by pressing the rod into the
channel top end in a direction substantially parallel to the second
bore axis.
[0013] The rod coupler bore engaging portion may comprise a bottom
end having an increased portion having a dimension greater than
that of the second bore, preventing the rod coupler from passing
all the way through the coupling when the coupler is inserted into
the bore. This increased portion may comprise a conical flange, and
the second bore may have a corresponding conical recess adjacent
the bottom surface of the coupling. The conical flange and recess
may have corresponding engagement surfaces, and at least one of the
engagement surfaces may have serrations to prevent relative
movement of the flange and coupling bore.
[0014] An alternative embodiment of the connector may be provided
for connecting a bone screw to a rod, the connector having a
coupling with first and second bores separated by a predetermined
distance, each bore having a longitudinal axis. A holding member
may be associated with the first bore, and may be capable of
engaging a bone screw. A rod coupler may be associated with the
second bore, and may have a bore engaging portion and a rod
receiving portion. The rod coupler may be rotatable about the
second bore longitudinal axis.
[0015] The holding member and coupling first bore may have
corresponding spherical surfaces configured to allow the holding
member to rotate within the first bore about multiple axes.
[0016] The connector may also have a tensioner which may engage the
holding member and immobilize the bone screw with respect to the
holding member. The connector may be configured so that when the
holding member engages the bone screw and the tensioner engages the
holding member, and the rod coupler engages the longitudinal rod,
the rod and rod coupler may be rotated 360 degrees within the
second bore.
[0017] The rod coupler may be provided with first and second
vertical legs to receive a longitudinal rod. A rod locking member
may also be provided to engage a top portion of each of the first
and second legs to retain the rod within the rod coupler along a
direction perpendicular to a longitudinal axis of the rod. The rod
locking member may have threads which engage corresponding threads
in the top portion of at least one of the first and second vertical
legs of the rod coupler.
[0018] The first and second legs may each have a top end distal
from the coupling, where the top ends are open to allow a rod to be
introduced into the rod receiving portion by pressing the rod
between the legs in a direction substantially parallel to the
second bore axis. The rod receiving portion of the rod coupler may
form a channel configured to allow a rod to be introduced into the
rod receiving portion by threading the rod into the channel in a
direction substantially perpendicular to the second bore axis.
[0019] The connector may also have a tensioner configured to engage
the holding member to immobilize the bone screw with respect to the
holding member. The holding member may be radially expandable so
that when engaged by the tensioner, the holding member spherical
surface expands to engage the inner surface of the coupling first
bore, thus locking the holding member to the coupling.
[0020] The rod locking member and rod coupler of this embodiment
may be configured to engage the rod so that the rod may not move
with respect to the rod coupler or rod locking member. The rod
locking member and rod coupler may also be configured so that the
rod is held between the rod locking member and a top surface of the
connector. The rod coupler bore engaging portion may comprise a
bottom end having an increased portion having a dimension greater
than that of the second bore, wherein when the rod coupler is
inserted into the second bore, the increased portion prevents the
rod coupler from passing through the coupling. The increased
portion may comprise a conical flange, and the second bore may have
a corresponding conical recess adjacent to a bottom surface of the
coupling. The conical flange and conical recess may have
corresponding engaging surfaces, at least one of which may have
serrations to prevent relative movement between the flange and
bore.
[0021] The rod coupler bore engaging portion may further comprise a
top end opposite the bottom end, the bore engaging portion further
may comprise a second increased portion located between the bore
engaging portion top and bottom ends, the second increased portion
having a dimension greater than that of the second bore, wherein
when the rod coupler is inserted into the second bore, the first
and second increased portions couple the rod coupler to the second
bore. The rod coupler bore engaging portion may have at least one
slot between the first and second increased portions, the at least
one slot making at least part of the bore engaging portion
resiliently displaceable to allow the second increase portion to be
accepted within the second bore.
[0022] In yet another embodiment of the invention, a connector for
connecting a bone screw to a rod has a coupling portion with first
and second bores, each bore having a longitudinal axis, the axes
separated by a predetermined distance. The first bore is associated
with the bone screw, and the second bore is associated with a rod
coupler. The rod coupler has an articulating portion and a rod
receiving portion. The articulating portion is configured to be
rotatably and axially slidably receivable within the second bore.
The rod receiving portion has at least one vertical leg configured
to receive the rod in a direction substantially perpendicular to
the second bore longitudinal axis. When the rod engages the rod
coupler, the rod may be selectively rotated about the first bore
longitudinal axis. The rod coupler may comprise a cap configured to
engage the top end of the at least one vertical leg to retain the
longitudinal rod in at least one direction perpendicular to the rod
longitudinal axis.
[0023] The connector of this embodiment may further comprise a
holding member associated with the first bore and configured to
receive the bone screw. The holding member may have a bore
configured to accept the bone screw, the holding member further
having an unlocked position in which it is free to rotate within
the first bore, and a locked position in which it is immobilized
within the first bore. A tensioner may be provided to engage the
holding member and configure the holding member in the locked
position whereby the holding member is immobilized within the first
bore. The tensioner may comprise external threads configured to
engage internal threads of the holding member bore.
[0024] The connector is configured such that when the holding
member engages the bone fastener, and the tensioner engages the
holding member, and the rod coupler engages the rod, the rod and
rod coupler may be rotated 360 degrees about both the first and
second bore longitudinal axes.
[0025] The first bore of the connector may have a substantially
spherical inner surface and the holding member may have a
substantially spherical outer surface configured to be slidably
received within the first bore. The holding member may further be
radially expandable such that when the tensioner engages the
holding member bore, the holding member spherical outer surface
expands to engage the inner spherical surface of the coupling first
bore, thus locking the holding member to the coupling.
[0026] The holding member bore may have a conical profile and
internal threads, and the tensioner may have a conical outer
profile and external threads corresponding to the holding member
bore.
[0027] The rod coupler may comprise a channel having a top end
distal from the coupling portion and a bottom end proximal to the
coupling portion, the channel top end being open to allow a rod
having an axis substantially parallel to the channel axis to be
introduced into the rod engaging portion by pressing the rod
through the channel top end in a direction substantially parallel
to the second bore axis.
[0028] The connector articulating portion may comprise an increased
portion having a dimension greater than that of the second bore,
such that when the rod coupler is inserted into the second bore,
the increased portion prevents the rod coupler from passing through
the coupling. The increased portion may comprise a conical flange,
and the second bore may have a corresponding conical recess
adjacent to the coupling portion bottom surface. The conical flange
and bore may have corresponding engagement surfaces, and at least
one engagement surface comprises serrations to prevent relative
rotation between the flange and bore.
[0029] The holding member may have top and bottom surfaces and a
wall. The wall may have at least one vertical slot intersecting at
least the jaw top surface so that when the tensioner engages the
holding member, the holding member expands along the at least one
slot.
BRIEF DESCRIPTION OF THE DRAWINGS
[0030] The features and advantages of the invention will become
more apparent upon consideration of the following detailed
description, taken in conjunction with the accompanying drawings,
in which like reference characters refer to like parts throughout,
and in which:
[0031] FIG. 1 is an exploded view of a first embodiment of the
invention;
[0032] FIG. 2 is a sectional view of a second embodiment of the
invention of FIG. 1, showing a fastener holding member formed
integrally with a bone fastener, a tensioner, a holding member
expansion feature, and a rod coupler;
[0033] FIG. 3 is a sectional view of a third embodiment of the
invention, showing the fastener holding member formed integrally
with a pedicle hook; and
[0034] FIG. 4 is a sectional view of a fourth embodiment of the
invention, showing an alternative arrangement of the longitudinal
rod coupler.
DETAILED DESCRIPTION OF THE INVENTION
[0035] FIGS. 1 and 2 show a coupling 3, a fastener holding member
10, a tensioner 12 for releasably fixing a bone fastener 2, a rod
coupler 13, and a rod locking element 33 configured for releasably
fixing a longitudinal rod 1 to coupling 3. Coupling 3 has a
longitudinal axis 30, a top surface 5 configured to contact
longitudinal rod 1, a bottom surface 6, and a fastener coupling
bore 7 which connects top and bottom surfaces 5, 6. Fastener
coupling bore 7 further has an axis 11 that is substantially
perpendicular to the coupling longitudinal axis 30. In addition,
coupling 3 has a rod coupling bore 19 which connects top and bottom
surfaces 5, 6 and has an axis 14 which is substantially parallel to
fastener coupling bore axis 11. The fastener and rod coupling bores
7, 19 are separated by a distance 31 measured along the coupling
longitudinal axis 30.
[0036] The rod coupling bore 19 is configured to slidingly receive
a cylindrical articulating portion 130 of longitudinal rod coupler
13 such that coupler 13 may rotate within the bore 19 about the rod
coupling bore axis 14. The bottom end portion 16 of rod coupler 13
comprises an increased-diameter flange portion 35, configured to
mate with a corresponding recess 27 in the rod coupling bore 19, so
that when articulating portion 130 is inserted into the rod
coupling bore 19, the coupler flange portion 35 axially engages the
rod coupler recess 27, preventing further axial movement in the
insertion direction of rod coupler 13 with respect to coupling
3.
[0037] The fastener coupling bore 7 may comprise a partial
spherical profile, the top and bottom portions of the sphere being
intersected and cut by coupling 3 top and bottom surfaces 5,6. The
fastener holding member 10 may have a partial spherical outer
surface profile designed to correspond to the fastener coupling
bore 7 inner surface. The corresponding spherical surfaces allow
the fastener holding member 10 to be received in the fastener
coupling bore 7 so that the holding member 10 is fully pivotable
within the bore (i.e., it may rotate about any one of, or
combination of, three orthogonal axes).
[0038] The fastener holding member 10 may further comprise top and
bottom surfaces 20, 21 positioned adjacent top and bottom surfaces
5, 6 respectively. Holding member 10 may further comprise a conical
bore 23 having a conical internal screw thread 24 and an axis 230
that when installed is concentric to fastener coupling bore axis
11.
[0039] The fastener holding member 10 further may be configured so
that its angular position within the fastener coupling bore 7 is
lockable. Such a configuration may allow the user to lock the
position of the associated fastener 2 in the desired pivot
position, immobilizing it with respect to coupling 3. This locking
feature may be effected by providing a radial expansion feature
within holding member 10, so that when the desired holding
member/fastener position is obtained at least a portion of the
holding member 10 spherical surface may be expanded to contact or
interfere with fastener coupling bore 7, the frictional contact
between surfaces preventing further relative movement. This radial
expansion feature may be provided in the form of at least one
vertical slot 101 located in holding member 10 between the holding
member outer spherical surface and conical bore surface 23. The at
least one slot 101 may extend along a portion of the height of
holding member 10, and may be parallel to holding member bore axis
230. The slot or slots 101 may intersect the top end surface 20 of
holding member 10, but not the bottom end surface 21.
Alternatively, the slot or slots 101 may intersect the bottom end
surface 20, but not the top end surface 21. In one embodiment, the
fastener holding member 10 comprises a series of parallel vertical
slots evenly spaced about the circumference of the holding member
10, each slot intersecting one of the top or bottom end surfaces
20, 21 of holding member 10.
[0040] A tensioner 12 may be provided to radially expand holding
member 10 to its aforementioned locked position. The tensioner 12
may comprise a frustoconical outer surface 120 corresponding to the
holding member conical bore 23 and further may be provided with a
conical external screw thread 25 corresponding to the holding
member bore threads 24. The tensioner 12 may have an adjustment end
121 and a leading end 122, the adjustment end 121 comprising a
connection 123 suitable for engagement with a standard driving
tool. Because the conical shape of tensioner 12, adjustment end 121
has a larger outer diameter than leading end 122. Under this
arrangement, holding member 10 may be expanded by threadably
driving the tensioner 12 into the bore so that the larger diameter
adjustment end 121 enters a relatively smaller diameter portion of
the holding member conical bore 23, forcing open the at least one
vertical slot 101 in the holding member 10. Such expansion of the
at least one slot 101 may be sufficient to press the holding member
10 outer surface against the fastener coupling bore 7, fixing
holding member 10 to coupling bore 7 and coupling 3, as previously
described.
[0041] In one embodiment, tensioner 12 itself comprises head
portion 8 of bone fastener 2. In an alternative embodiment, holding
member 10 comprises head portion 8 of bone fastener 2. Bone
fastener 2 may be a bone screw 9 or a pedicle hook 90. Where
tensioner 12 is integral to head portion 8 of bone fastener 2, bone
fastener 2 may be releasably fixed to coupling 3 by threadably
driving head portion 8 into holding member 10, the corresponding
conical surfaces 23, 120, threads 24, 25, and at least one slot 101
serving to expand holding member 10 and fix fastener 2 to the
fastener coupling bore 7.
[0042] A longitudinal rod coupler 13 is used to receive and engage
the longitudinal rod 1. The rod coupler 13 may have an articulating
portion 130 that is configured to be rotatable and axially slidable
within rod coupling bore 19, and which has an axis 131 that, when
coupler 13 is engaged with coupling 3, is substantially coaxial to
the rod coupling bore axis 14. Rod coupler 13 may also have a rod
receiving portion 132 which, in one embodiment, comprises a channel
17 having a channel axis 32 oriented substantially perpendicular to
the rod coupling bore axis 14. Channel 17 may have at least one
vertical leg 137 configured to retain the longitudinal rod in at
least a direction substantially perpendicular to the rod
longitudinal axis 4.
[0043] The longitudinal rod coupler 13 may have a top end 15,
adjacent to which channel 17 is open. The longitudinal rod coupler
13 may also have a bottom end 16 opposite the top end 15, and
adjacent to the coupling bottom surface 6. The bottom end 16 may
comprise an increased portion 35 having a diameter greater than the
diameter of the rod coupling bore 19, so that when the rod coupler
13 is inserted into the rod coupling bore 19, the increased portion
35 prevents the rod coupler 13 from passing through the coupling
bore 19 completely. Where the bottom end 16 comprises an increased
portion 35, the bottom surface 6 of the coupling 3 may comprise a
corresponding recess 27 configured to engage the increased portion
35. In one embodiment, the increased portion may comprise a conical
flange 26, and coupling 3 may comprise a correspondingly conical
recess 27. To prevent post-installation rotation between coupling 3
and rod coupler 13, at least one of the conical flange 26 or
coupling recess 27, or both, may comprise serrations 28.
[0044] Channel 17 may be configured so that it is open at the top
end 15 of the longitudinal rod coupler 13. To capture the
longitudinal rod 1 within the rod coupler channel 17, a rod locking
element 33 may be provided. In one embodiment, rod locking element
33 comprises a locking cap 133. Cap 133 may comprise internal
threads 134 configured to engage corresponding external threads 34
formed in the top end 15 of the rod coupler 13. Upon insertion of
the longitudinal rod 1 in the channel 17, locking cap 133 may be
threaded onto the coupler top end 15 and rotated until a bottom
surface 135 of the cap engages the longitudinal rod 1, thereby
sandwiching longitudinal rod 1 between cap 133 and top surface 5 of
coupling 3. To release longitudinal rod 1, locking cap 133 may be
unscrewed and disengaged from the rod coupler top end 15.
[0045] In one embodiment, the portion of coupling 3 comprising
fastener coupling bore 7 is recessed so that when a longitudinal
rod 1 is engaged with coupling 3, and a bone fastener 2 and
tensioner 12 are fully engaged in holding member 10, the fastener,
tensioner and holding member are sufficiently recessed within
coupling 3 that coupling 3 and rod 1 may be rotated without
interference 360 degrees about the rod coupling bore axis 14.
[0046] FIG. 2 shows an alternative embodiment in which the fastener
holding member 10 comprises the head portion 8 of bone fastener 2,
which, in this embodiment, is a bone screw 9. In this embodiment,
the bottom end 16 of longitudinal rod coupler 13 comprises a
conical flange 26, configured to be received in a complementary
inner cone 27 formed in the rod coupling bore 19 of coupling 3.
Additionally, an at least partially circumferential tab segment 29
is provided on the rod coupler articulating portion adjacent the
channel. This tab segment is adapted to engage the top surface 5 of
coupling 3 when the rod coupler is inserted into the rod coupling
bore 14. When the tab segment 29 engages the top surface 5 of
coupling 3, it fixes rod coupler 13 axially with respect to
coupling 3 and prevents rod coupler 13 from backing out of the rod
coupling bore 19. The inner diameter of the rod coupling bore 19
may be only slightly larger than the outer diameter of the
articulating portion 130. The articulation portion 130 may,
therefore, comprise at least one vertical slot 36 to allow the
articulating portion 130 to be compressed so that tab segment 29
can pass through the bottom surface 6 of the coupler and though the
bore 19.
[0047] FIG. 3 shows an alternative embodiment of the rod coupler 13
in which the holding member 10 comprises the head portion 8 of the
bone fastener 2, which, in this embodiment, is a pedicle hook 90.
In this embodiment the head portion of the pedicle hook 90
comprises the spherically-shaped holding member 10.
[0048] FIG. 4 shows a further embodiment of the coupling 3 in which
channel 17 is open at the top end 15 to permit a longitudinal rod 1
to be inserted laterally into the longitudinal rod coupler 13 (i.e.
in a direction perpendicular to the rod longitudinal axis 4). A
sleeve 360, including a rod engaging surface 361, and two side
walls 37 extending parallel to the rod coupling bore axis 14, is
placed over the rod receiving portion 132 (in this case channel 17)
at the top end 15 to fix the longitudinal rod 1 relative to the
longitudinal rod coupler 13. The sleeve 360 is then held in place
by a nut 38 which may be screwed onto an external screw thread 34
on the channel top end 15. Thus the longitudinal rod 1 is retained
between the top surface 5 of coupling 3 and rod engaging surface
361 of the sleeve 360. The side walls 37 provide lateral fixation.
In this embodiment, conical flange 26 comprises radially aligned
teeth (e.g., serrations 28), which secure rod coupler 13 and
coupling 3 against relative rotational movement.
[0049] Accordingly, it should be understood that the embodiments
disclosed herein are merely illustrative of the principles of the
invention. Various other modifications may be made by those skilled
in the art that will embody the principles of the invention and
fall within the spirit and the scope thereof.
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