U.S. patent application number 09/941153 was filed with the patent office on 2002-06-27 for multidirectional pivoting bone screw and fixation system.
Invention is credited to Crandall, Dennis, Morrison, Matthew M., Strohkirch, Terrance.
Application Number | 20020082599 09/941153 |
Document ID | / |
Family ID | 24097327 |
Filed Date | 2002-06-27 |
United States Patent
Application |
20020082599 |
Kind Code |
A1 |
Crandall, Dennis ; et
al. |
June 27, 2002 |
Multidirectional pivoting bone screw and fixation system
Abstract
A double-jointed bone bolt for use in an apparatus for
maintaining vertebra in a desired relationship. The apparatus has a
rod that extends substantially along the spine and one or more bone
bolts. At least one of the bone bolts is double jointed. The
double-jointed bolt has a mounting portion with a hook or coarse
threads to engage a vertebra, and the mounting portion is attached
to a pivot post in a manner that allows the pivot post to be
rotatable about a common axis in respect to the mounting portion.
The pivot post of the bone bolt is then pivotally attached to a
connector portion of the bone bolt that has machine threads upon
which a surgeon may attach a clamp. The clamp has a second bolt and
an arm. The second bolt holds the rod and the arm to the clamp. The
second bolt has a first channel to attach to the rod, while the arm
has a second channel to attach the double-jointed bone bolt.
Inventors: |
Crandall, Dennis; (Mesa,
AZ) ; Morrison, Matthew M.; (Cordova, TN) ;
Strohkirch, Terrance; (Cordova, TN) |
Correspondence
Address: |
John V. Daniluck
Woodard, Emhardt, Naughton, Moriarty and McNett
Bank One Center/Tower
111 Monument Circle, Suite 3700
Indianapolis
IN
46204-5137
US
|
Family ID: |
24097327 |
Appl. No.: |
09/941153 |
Filed: |
August 28, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09941153 |
Aug 28, 2001 |
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09526435 |
Mar 15, 2000 |
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6309391 |
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Current U.S.
Class: |
606/256 ;
606/278 |
Current CPC
Class: |
A61B 17/7035 20130101;
A61B 17/7041 20130101; A61B 17/7049 20130101 |
Class at
Publication: |
606/61 |
International
Class: |
A61B 017/58 |
Claims
We claim:
1. A bolt for connecting a vertebra to a longitudinal member,
comprising: a mounting portion, said mounting portion having means
for engaging a vertebra; a pivot post, said mounting portion and
said pivot post being engaged to one another so as to be rotatable
about a connection axis; a connector portion pivotally attached to
said connector post, said connector portion having machine
threads.
2. The bolt of claim 1, including means for attaching a wrench to
said mounting portion.
3. The bolt of claim 1, where said mounting portion has a proximal
end and said pivot post has a distal end, and the proximal end of
said mounting portion and the distal end of said post have mutually
engageable male and female contacts, and wherein said contacts are
adapted to allow said pivot post to rotate in respect to said
mounting portion.
4. The bolt of claim 1, including a snap ring operably connecting
said mounting portion and said post.
5. The bolt of claim 1, wherein said mounting portion has a length
and said means for engaging are coarse threads disposed over at
least a portion of the length of said mounting portion.
6. An apparatus for maintaining vertebra in a desired relationship,
comprising: a rod having a first longitudinal axis extending
substantially along the spine; a bone bolt, said bone bolt
including a mounting portion, a pivot post and connector portion,
said mounting portion having means for engaging a vertebra; said
mounting portion and said pivot post being engaged to one another
so as to be rotatable about a connection axis; said connector
portion pivotally attached to said pivot post, and said connector
portion having machine threads and a second longitudinal axis; and
a clamp, said clamp including a second bolt and an arm, said second
bolt having a first channel for receiving a portion of the rod and
a portion with a third longitudinal axis, said arm joined to said
second bolt, said arm having a second channel for receiving the
machine threads of said bone bolt.
7. The assembly of claim 6, wherein said second bolt engages said
rod at a first longitudinal position and said bone bolt is spaced
from said first longitudinal position along the first longitudinal
axis.
8. The assembly of claim 6, wherein the second channel in said arm
is offset from said third longitudinal axis along the first
longitudinal axis.
9. The assembly of claim 6, including a nut rotatably threaded over
the machine threads of said bone bolt and rotatably connected to
the arm of said clamp.
10. The assembly of claim 6, wherein the second longitudinal axis
of said connector portion of said bone bolt is offset from the
third longitudinal axis of said portion of said clamp along the
first longitudinal axis of said rod.
11. The assembly of claim 6, wherein said arm has a centerline and
the second channel of said arm is laterally offset from the
centerline toward said rod.
12. The assembly of claim 6, wherein said arm has a centerline and
the second channel of said arm is laterally offset from the
centerline away from said rod.
13. The assembly of claim 6, wherein said arm has a centerline and
the second channel of said arm resides in the same plane as the
centerline.
14. The assembly of claim 6, wherein said arm may be fixedly
connected in a plurality of positions about said third longitudinal
axis.
15. The assembly of claim 6, wherein said clamp includes a rod
interface washer positioned over a portion of the second bolt,
between the first channel and the arm, said rod interface washer
being fixed against rotation relative to said bolt.
16. The assembly of claim 15, wherein said arm and said interface
washer have mating male protrusions and female cavities on at least
a portion of their surfaces such that, when pressed together, the
protrusions and cavities facilitate the engagement of said rod
interface washer to said arm, preventing rotation of said arm
relative to said rod interface washer.
17. The bolt of claim 6, where said mounting portion has a proximal
end and said pivot post has a distal end, and the proximal end of
said mounting portion and the distal end of said post have mutually
engageable male and female contacts, and wherein said contacts are
adapted to allow said pivot post to rotate in respect to said
mounting portion.
18. The bolt of claim 17, including a snap ring operably connecting
said mounting portion and said post.
19. The assembly of claim 17, wherein said clamp includes a rod
interface washer positioned over a portion of the second bolt,
between the first channel and the arm, said rod interface washer
being fixed against rotation relative to said bolt.
20. The assembly of claim 19, wherein said arm and said interface
washer have mating male protrusions and female cavities on at least
a portion of their surfaces such that, when pressed together, the
protrusions and cavities facilitate the engagement of said rod
interface washer to said arm, preventing rotation of said arm
relative to said rod interface washer.
21. The assembly of claim 20, wherein said arm may be fixedly
connected in a plurality of positions about said third longitudinal
axis.
Description
[0001] This application is a continuation of and claims priority to
U.S. patent application No. 09/526,435, filed Mar. 15, 2000, which
is incorporated herein by reference.
BACKGROUND
[0002] Spinal implant systems provide a rod for supporting the
spine and properly positioning components of the spine for various
treatment purposes. Bolts or screws are typically secured into the
vertebrae for connection to a supporting rod. These bolts must
frequently be positioned at various angles due to the anatomical
structure of the patient, the physiological problem to be treated,
and the preference of the physician. It is difficult to provide
secure connection between the spinal support rod and these
connecting bolts at various angles, and where there are differing
distances between the rod and bolts and different heights relative
to these components.
SUMMARY OF THE INVENTION
[0003] In one aspect, this invention is a bolt for connecting a
vertebra to a longitudinal member. The bolt has a mounting portion
with a hook or coarse threads to engage a vertebra. The mounting
portion is attached to a pivot post in a manner that allows the
pivot post to be rotatable about a common axis in respect to the
mounting portion of the bolt. The pivot post is then pivotally
attached to a connector portion that has machine threads upon which
a surgeon may attach other structures.
[0004] In another aspect, this invention is an apparatus for
maintaining vertebra in a desired relationship. The apparatus has a
rod that extends substantially along the spine and one or more bone
bolts. At least one of the bone bolt has a mounting portion with a
hook or coarse threads to engage a vertebra, and the mounting
portion is attached to a pivot post in a manner that allows the
pivot post to be rotatable about a common axis in respect to the
mounting portion of the bolt. The pivot post of the bone bolt is
then pivotally attached to a connector portion of the bone bolt
that has machine threads upon which a surgeon attaches a clamp. The
clamp, also a part of this embodiment of the invention, has a
second bolt and an arm. The second bolt holds the rod and the arm
to the clamp. The second bolt has a first channel to hold the rod
while the arm has a second channel to hold the bone bolt.
[0005] It is an object of this invention to provide a connection
assembly that will allow connection between a spinal support rod to
a vertebra at a variety of angles relative to the vertical, taken
when the patient is lying down.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] FIG. 1 is a perspective view of one embodiment of the
present invention.
[0007] FIGS. 2-4 are respectively top, side, and cross-sectional
views of a clamp that may be used in one embodiment of the present
invention.
[0008] FIGS. 5-8 are respectively, top, side, end, and
cross-sectional views of a clamp bolt that may be used in one
embodiment of the present invention.
[0009] FIGS. 9-10 are respectively end and side views of a stop
that may be used in one embodiment of the present invention.
[0010] FIGS. 11-14 are respectively end cross-sectional, top, side,
and side cross-sectional views of an arm that may be used in one
embodiment of the present invention.
[0011] FIGS. 15-17 are respectively end, side, and top views of a
washer that may be used in one embodiment of the present
invention.
[0012] FIGS. 18, 19 are top views of alternative embodiments for an
arm in the practice of the present invention.
[0013] FIG. 20 is a side view of a nut that may be used in one
embodiment of the present invention.
[0014] FIG. 21 is an exploded view of a bone bolt in one embodiment
of the present invention.
[0015] FIG. 22 is a cross-sectional view of a mounting portion of a
bone bolt according to one embodiment of the present invention.
[0016] FIGS. 23 and 24 are respectively side and top views of a
connecting portion of a bone bolt according to one embodiment of
the present invention.
[0017] FIGS. 25 and 26 are respectively front and side views of a
pivot post in a bone bolt according to one embodiment of the
present invention.
[0018] FIG. 27 is a top view of a snap ring for a bone bolt
according to one embodiment of the present invention.
[0019] FIG. 28 is a side view of a bone bolt according to one
embodiment of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0020] Specific language is used in the following description to
publicly disclose the invention and to convey its principles to
others. No limits on the breadth of the patent rights based simply
on using specific language are intended. Also included are any
alterations and modifications to the description that should
normally occur to one of average skill in this technology.
[0021] A bone bolt 1 according to one embodiment of the invention
is shown as part of a larger spinal implant system in FIG. 1. Bone
bolt 1 is shown attached to a clamp 2 with the longitudinal axis
L1, and clamp 2 is shown attached to a spinal implant rod 3 with a
longitudinal axis L2. Clamp 2 includes a clamp bolt 4, an arm 5, a
rod interface washer 6, a set screw 7, and a nut 12. Clamp bolt 4
has an aperture 8 for receiving rod 3, and while the aperture is
shown closed around rod 3, it will nevertheless be understood that
an open-sided aperture may also be used to permit top-loading of
rod 3 into clamp 2. Set screw 7 is inserted through a threaded
opening 9 and into aperture 8 in clamp bolt 4 so as to allow set
screw 7 to push against rod 3. Arm 5 has a bore 10 for receiving
bone bolt 1. Arm 5 is simultaneously tightened to clamp 2 when set
screw 7 is tightened against rod 3. As set screw 7 pushes against
rod 3, rod 3 pushes against rod interface washer 6, which pinches
arm 5 between rod interface washer 6 and stop 11. In this manner,
set screw 7 acts as a compression member to tighten clamp 2 and
achieve substantial fixation of arm 5 to rod 3.
[0022] Details of clamp bolt 4 are shown in FIGS. 2-8. Clamp bolt 4
can be subdivided into bolt head portion 13, bolt shaft portion 14,
washer seat portion 15 and washer stop portion 16. Threaded
openings 9a & 9b, and aperture 8 reside in bolt head portion
13. Threaded openings 9a & 9b open into aperture 8 at an
oblique angle A4 with respect to longitudinal axis L1 to allow set
screw 7 (FIG. 1) to force spinal rod 3 toward the distal end 17 of
aperture 8. Clamp bolt 4 is substantially symmetrical about
longitudinal axis L1 such that threaded openings 9a and 9b are
substantially mirror images. Bolt shaft portion 14 is generally
cylindrical in shape and is sized to accept the eye 18 (FIGS. 13
& 14) of arm 5. Arm 5 is then held on shaft portion 14 by
attaching stop 11 (shown in isolation in FIGS. 9 & 10) to the
end 19 of shaft portion 14, either by welding or some other
suitable means. As an alternative, shaft portion 14 may include
threads and stop 11 may be correspondingly threaded onto shaft
portion 14 to hold arm 5 in position. In this alternative design,
stop 11 may be the compressive member utilized to tighten clamp 2
onto rod 3 instead a set screw threaded into bolt head portion
13.
[0023] Clamp bolt 4 also preferably includes washer seat portion 15
and washer stop portion 16. A washer seat portion 15 that is
substantially rectangular in cross-section is currently preferred,
but washer seat portion 15 can be of any suitable shape that may
interlock with a complementary shape in rod interface washer 6
(FIGS. 1, 15, 16 & 17) to prevent rod interface washer 6 from
rotating in relation to clamp bolt 4. As shown, a washer stop 16 is
generally provided in clamp bolt 2 by placing a raised edge in bolt
head portion 13. Washer stop 16 prevents rod interface washer 6
from being inadvertently removed from clamp 2.
[0024] Details of arm 5 are shown in FIGS. 11-14. Arm 5 includes a
flange portion 20, and a collar portion 21. Flange portion 20 has
an eye 18, and as previously presented, clamp bolt 4 attaches to
arm 5 by placing the shaft portion 14 of clamp bolt 4 through eye
18 and then attaching stop 11 on end 19 of shaft portion 14. The
medial face 22 of flange portion 20 also includes a connection
surface 23. Connection surface 23 preferably includes structure for
facilitating the engagement of arm 5 against rotational movement
relative to rod interface washer 6. This engagement structure is
preferably a plurality of variable angle ridges that radiate from
the rotational center of eye 18. In other words, the structure is a
set of interlocking teeth that can generally be characterized as
male protrusions and complementary female cavities that upon
interlock, prevent rod interface washer 6 from rotating in respect
to arm 5.
[0025] Referring to FIGS. 12, 18 and 19; collar portion 21 of arm 5
has a bore 10. Bore 10 may assume various orientations in relation
to the centerline 24 of arm 5. FIG. 12 depicts bore 10 offset from
centerline 24 toward the stop (not shown) of clamp bolt 4.
Optionally, bore 10 can be offset from centerline 24 toward the
clamp aperture 8 (not shown) of clamp bolt 4, as shown in FIG. 19,
or bore 10 can be placed in the same plane as centerline 24, as
shown in FIG. 18. It being understood that the alternative arm
designs may permit even a smaller total width of clamp 2 by
bringing bone bolt 1 closer to the rod 3.
[0026] Referring to FIG. 20, there is shown nut 12, which is
preferably used to threadably engage bone bolt 1 (not shown) to arm
5, and prevent bone bolt 1 from moving longitudinally along
longitudinal axis L3 with respect to arm 5. Nut 12 has as set of
internal threads 32 to mate with the machine threads 60 on bone
bolt 1 and a set of locking tabs 33 on the proximal face 34 of nut
12 to firmly hold nut 12 upon bone bolt 1 once nut 12 is threaded
into place. The distal face 35 of nut 12 also includes an annular
collar 36. Annular collar 36 is integrally connected to nut 12, and
has a channel 70 that opens into internal threads 32. The end 39 of
collar 36 terminates in an annular rim 37 that laterally projects
beyond the diameter of annular collar 36, and forms an annular
groove 71 between annular rim 37 and distal face 35 of nut 12.
[0027] Referring back to FIGS. 11-14, arm 5 is preferably adapted
to rotatably secure nut 12 by annular rim 37 and annular collar 36.
The proximal face 72 of collar portion 21 of arm 5 includes a
semicircular cavity 38 around the entrance of bore 10 that is sized
to accept annular collar 36 and annular rim 37. By fitting collar
36 and rim 37 into cavity 38, annular rim 37 rides against
semi-circular lip 40, on the roof of cavity 38; opening 70 and
internal threads 32 of nut 12 are axially aligned with bore 10 of
arm 5; and nut 12 is rotatably secured to arm 5. In other words,
nut 12 is free to rotate about axis 41 or axis L3, but nut 12 is
substantially fixed against movement along longitudinal axis L3
(Figs. 11 & 13) relative to arm 5 because annular rim 37 rides
against semi-circular lip 40 in one direction and proximal face 72
in the other. In one preferred embodiment, nut 12 is temporarily
held in semicircular cavity 38 by slightly bending corners 73 &
74 of lip 40 against annular rim 37. Bending these corners will
temporarily hold nut 12 in arm 5 until the surgeon threads nut 12
onto bone bolt 1, and will not significantly hinder the surgeon's
rotation of nut 12 around bone bolt 1.
[0028] Details of rod interface washer 6 are shown in FIGS. 15, 16
& 17. Rod interface washer 6 can be any of several suitable
shapes, including the circle that is depicted. The medial face 25
of the rod interface washer 6 has an engagement surface, which
preferably includes an engagement groove 26 that accepts a
cylindrical spinal implant rod (such as rod 3 in FIG. 1).
Engagement groove 26 preferably runs across the entire face of
medial face 25. Rod interface washer 6 also has a central opening
27 that corresponds to the cross-sectional shape of previously
presented washer seat portion 15 in clamp bolt 4. In the currently
preferred embodiment, both washer seat portion 15 and opening 27
are substantially square. Although, this shape could vary from many
possible shapes that would similarly prevent rod interface washer 6
from rotating in respect to clamp bolt 4. To assist in this regard,
it is also preferable that rod interface washer have a guide groove
28 to accept bolt head portion 13 of clamp bolt 4 to further lock
clamp bolt 4 and rod interface washer 6 together. It should be
noted that guide groove 28 and engagement groove 26 are preferably
placed in such a manner that orients aperture 8 substantially
parallel to groove 26. This placement helps insure that spinal rod
3 will be held in the connector assembly in a direction that is
substantially perpendicular to clamp bolt 4, and in turn, also
substantially perpendicular to set screw 7.
[0029] Rod interface washer 4 also includes connection surface 29
on the lateral face 30 of rod interface washer 6. Connection
surface 29 preferably includes structure for facilitating the
engagement of rod interface washer 6 against rotational movement
relative to arm 5. This engagement structure is preferably a
plurality of variable angle ridges 31 that radiate from the
rotational center of rod engagement washer 6, similar to those
previously described on the medial face 22 on flange 20 of arm 5.
Variable angle ridges 31 are sized to mate with the similar
variable angle ridges 23 on arm 5. Referring to FIGS. 13 and 15,
both sets of ridges consist of alternating male protrusions and
female cavities. Hence, once placed together, these interlocking
ridges prevent rod engagement washer 6 from rotating in respect to
arm 5. And although radiating ridges are shown to facilitate the
fixation of these two parts, it is also contemplated that other
structures could serve this function. For example, it is also
contemplated that one could use any number of interlocking male and
female structures such as rounded bumps or knurling and mating
cavities. The locking engagement of connection surface 23 with
connection surface 29 may occur at any of a plurality of angles.
More specifically, the angle between longitudinal axis L3 of bone
bolt 1 and the longitudinal axis L2 of rod 3 may be adjusted to
meet the requirements of the patient's anatomy.
[0030] Details of bone bolt 1 can be seen in FIGS. 21-28. Bone bolt
1 includes a mounting portion 42, a pivot post 43, and a connector
portion 44. The distal end of mounting portion 21 has a set of
coarse threads 45. Coarse threads 45 have a thread convolution for
engaging cancellous bone and terminate in a tapered tip 46. Tapered
tip 46 helps align bone bolt 1 into a predrilled opening in a
vertebra and also helps coarse threads 45 to gradually engage and
advance into the vertebra upon rotation of mounting portion 21. In
this regard, although coarse threads are shown as a means for
engaging a vertebra, it is also contemplated that a hook, mounted
on the end of mounting portion 42, could also be used as an
alternative means to engage a vertebra. The proximal end 47 of
mounting portion 42 terminates in hex-headed drive portion 49. The
inside of hex-headed drive portion 49 includes an annular
receptacle 48, and the inner wall of receptacle 48 has an annular
groove 50. (FIG. 22) Annular receptacle 48 is sized to accept hub
51 of pivot post 43 (FIGS. 25 & 26), and annular groove 50 is
sized to accept snap ring 52. (FIG. 27) Pivot post 43 is shown in
isolation in FIGS. 25 & 26. Pivot post 43 has a hub 51 and an
ear 53 with a channel 55. Hub 51 preferably has a circular
cross-section and is circumscribed by an annular groove 54. Hub 51
is sized to freely rotate about longitudinal axis L4 inside
receptacle 48 of the mounting portion 42 of bone bolt 1. During
assembly in one preferred embodiment, snap ring 52 (FIG. 27) is
placed partly inside annular groove 54 before hub 51 is inserted
into receptacle 48. Then, upon insertion into receptacle 48, snap
ring 52 partially expands into annular groove 50, and thereby
rotatably connects pivot post 53 to the proximal end 47 of mounting
portion 42.
[0031] A top and side view of the connector portion 44 of bone bolt
1 is shown in FIGS. 23 & 24. Most of the longitudinal length of
connector portion 44 is circumscribed with machine threads 60. The
lower end 57 of connector portion 44 terminates with a pair of ears
56 that are diametrically opposite of each other at the radial
perimeter of end 57. Each of the ears 56 includes an aperture or
channel 58 for insertion of pin 59 (FIG. 21). During assembly, pin
59 is inserted through aperture 58 in one ear, then through channel
55 in pivot post 43, and then through aperture 58 in the other ear.
Thusly joined to mounting portion 42 and pivot post 43, the
connector portion 44 of bolt 1 may be pivoted around pin 59 as
depicted by arc A5, and may also be rotated around longitudinal
axis 1A of the mounting portion 42, as depicted by arc A6. (FIG.
28)
[0032] Referring back to FIG. 1, a typical construct in the use of
this invention typically has two or more largely identical rods, 1
and 61, and at least two or more bone bolts 1, 62-64 attached to
each rod by clamps 2, 65-67. And optionally, the rods may be joined
by one or more cross-linking members 68 & 69. An example of a
suitable cross-linking member is described in U.S. Pat. No.
5,947,966 to Drewry et al, the disclosure of which is specifically
incorporated into this specification by reference. And although
each of the clamps and bone bolts shown in this figure are
identical, it is further contemplated that other clamps and bone
bolts could be incorporated in a common construct in the use of
this invention. For example, one could also use the clamps and bone
bolts described in U.S. Pat. Nos. 5,643,263 and 5,885,285 to
Simonson, the disclosures of which are specifically incorporated
into this specification by reference with one or more of the bone
bolts described herein.
[0033] Clamp 2 is depicted in FIGS. 2-4, less set screw 7, which
has been removed for clarity along with rod 3 and bone bolt 1. The
clamp is used by placing spinal rod 3 through aperture 8. The
connector portion 44 of bone bolt 1 is then threaded through bore
10 and nut 12 of clamp 2 as the surgeon desires. Arm 5 and the
variable angle ridges 31 on the rod interface washer 6 are then
interlocked with the variable angle ridges 23 on arm 5, and the
assembly is tightened by threading set screw 7 into either of the
threaded openings 9, (or by optionally turning stop 11 around
connector portion 44 as described in an alternative embodiment).
Upon entering aperture 8, set screw 7 contacts the spinal rod and
forces the spinal rod toward interface washer 6. The spinal rod
then contacts rod interface washer 6, and engages groove 26. As one
continues turning set screw 7, rod interface washer 6 presses
flange portion 20 of arm 5 against stop 11. The variable angle
surfaces, item 23 on arm 5 and item 31 on rod interface washer 6,
firmly engage each other and prevent rod interface washer 6 from
rotating in relation to arm 5, which further locks arm 5 in
relation to clamp bolt 4 because rod interface washer 6 cannot
rotate in relation to clamp bolt 4. Adjustments can be made by
loosening set screw 5 then re-tightening the set screw when the
preferred position has been located. The surgeon can adjust the
longitudinal position of bone bolt 1 by rotating nut 12 as the
surgeon desires. The set screws 7 shown in FIG. 1 are of a type
that shear at 75 when the appropriate amount of torque has been
placed on set screw 7. Such set screws are now well-known in this
art.
[0034] Referring to FIGS. 1 & 2, one may note some additional
features of this invention by noting the locations of various
longitudinal axes. L1 is the longitudinal axis of a portion of
clamp 2. L2 is the longitudinal axis of rod 3, and L3 is the
longitudinal axis of both connector portion 44 of bolt 1 and bore
10 in arm 5. In this regard, one may not that L3 is offset from L1
a distance D1. In other words, clamp 2 will contact rod 3 at 76,
and L3 or bore 10 is spaced from 76 a distance D1 along rod 3. In
many circumstances involving patient anatomy, distance D1 may help
the surgeon place clamp 2 and/or bone bolt 1 in a manner that
avoids interfering with the patient's anatomy, such as the facet
joints of the spine.
[0035] While the invention has been illustrated and described in
detail, this is to be considered as illustrative and not
restrictive of the patent rights. The reader should understand that
only the preferred embodiments have been presented and all changes
and modifications that come within the spirit of the invention are
included if the following claims or the legal equivalent of these
claims describes them.
* * * * *