U.S. patent application number 09/790751 was filed with the patent office on 2001-09-06 for threaded fusion cage anchoring device and method.
This patent application is currently assigned to Tegementa L.L.C.. Invention is credited to Ray, Charles D..
Application Number | 20010020185 09/790751 |
Document ID | / |
Family ID | 26721273 |
Filed Date | 2001-09-06 |
United States Patent
Application |
20010020185 |
Kind Code |
A1 |
Ray, Charles D. |
September 6, 2001 |
Threaded fusion cage anchoring device and method
Abstract
The present disclosure is directed to an anchoring device and
system for stabilizing adjacent vertebral joints. The anchoring
device includes an anchoring plate adapted to be secured to at
least one vertebral disc having a central portion, extended ends
portions and at least one lateral extension. The central portion
includes an anchoring nut for fastening the anchoring plate to a
vertebral implant and the end portions include anchoring screws for
fastening the anchoring plate to the at least one vertebral disc.
The vertebral implant is preferably a threaded fusion cage, wherein
the anchoring nut is rotatably fixed to both the anchoring plate
and the threaded fusion cage. The anchoring device preferably
includes the central portion and each extended end portion having
at least one locking tab for rotatably locking the anchoring nut
and anchoring screws. Additionally, the central portion further
includes a plurality of projecting detents along an outer periphery
thereof which mate with corresponding slots on the threaded fusion
cage. The present disclosure is also directed to a method of
implanting a vertebral implant.
Inventors: |
Ray, Charles D.;
(Williamsburg, VA) |
Correspondence
Address: |
Lawrence Cruz
Tyco Healthcare Group LP
150 Glover Avenue
Norwalk
CT
06856
US
|
Assignee: |
Tegementa L.L.C.
|
Family ID: |
26721273 |
Appl. No.: |
09/790751 |
Filed: |
February 22, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09790751 |
Feb 22, 2001 |
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09403866 |
Mar 3, 2000 |
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60044190 |
Apr 25, 1997 |
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Current U.S.
Class: |
623/17.11 |
Current CPC
Class: |
A61F 2/446 20130101;
A61F 2/4611 20130101; A61F 2002/30331 20130101; A61F 2002/30235
20130101; A61F 2002/449 20130101; A61F 2002/4627 20130101; Y10S
606/91 20130101; A61F 2230/0069 20130101; A61F 2002/30578 20130101;
A61F 2/442 20130101; A61F 2002/30774 20130101; A61F 2220/0033
20130101; A61F 2002/3085 20130101; A61F 2002/30593 20130101 |
Class at
Publication: |
623/17.11 |
International
Class: |
A61F 002/44 |
Claims
What is claimed is:
1. An anchoring device for use with a vertebral implant comprising:
an anchoring plate having a central portion and at least one
extended end portion; the central portion configured for attachment
to a vertebral implant; and each end portion including an anchoring
fastener, wherein the anchoring fastener is adapted to be joined to
a bony segment.
2. The anchoring device according to claim 1, including two
extended end portions.
3. The anchoring device according to claim 1, wherein the vertebral
implant is a threaded fusion cage.
4. The anchoring device according to claim 1, wherein the anchoring
fastener is a bone screw.
5. The anchoring device according to claim 1, wherein the central
portion and each extended end portion further includes a least one
locking tab.
6. The anchoring device according to claim 1, wherein the central
portion further includes a plurality of projecting detents along an
outer periphery thereof.
7. The anchoring device according to claim 1, wherein the anchoring
plate further includes at least one lateral extension.
8. A system for stabilizing adjacent vertebral portions comprising:
a vertebral implant adapted to be secured between adjacent
vertebral portions; an anchoring plate adapted to be secured to the
adjacent vertebral portions, the anchoring plate having a central
portion and extended ends portions; the central portion including
an anchoring nut for fastening the anchoring plate to the vertebral
implant; and the end portions including anchoring screws for
fastening the anchoring plate to the adjacent vertebral
portions.
9. The anchoring system according to claim 8, wherein the vertebral
implant is a threaded fusion cage.
10. The anchoring system according to claim 9, wherein the
anchoring nut is rotatably fixed to the anchoring plate and the
threaded fusion cage.
11. The anchoring system according to claim 8, wherein each end
portion is fixedly attached to a vertebral disc.
12. The anchoring system according to claim 8, wherein the central
portion and each extended end portion further includes at least one
locking tab.
13. The anchoring system according to claim 8, wherein the central
portion further includes a plurality of projecting detents along an
outer periphery thereof.
14. The anchoring system according to claim 8, wherein the
anchoring plate further includes at least one lateral
extension.
15. A method of implanting a vertebral implant comprising the steps
of: inserting a vertebral implant between adjacent vertebrae;
positioning an anchoring plate in a corresponding relationship to
the vertebral implant and the adjacent vertebrae, the anchoring
plate including a central portion and extended ends portions, the
central portion including an anchoring nut for fastening the
anchoring plate to the vertebral implant, and the end portions
including anchoring screws for fastening the anchoring plate to
portions of the adjacent vertebrae; fastening the anchoring nut to
the vertebral implant; and fastening the anchoring screws to the
portions of the adjacent vertebrae.
16. The method of implanting a vertebral implant according to claim
15, wherein the anchoring plate includes at least one locking tab
along an outer periphery of the central portion and the extended
end portions, and further including the step of positioning the
locking tabs into engagement with the anchoring nut and anchoring
screws.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This Patent Application claims the benefit of U.S.
Provisional Application No. 60/044,190 filed Apr. 25, 1997.
TECHNICAL FIELD
[0002] The present disclosure concerns devices and methods for
stabilizing fusion inserts placed for the purpose of fusing two
adjacent joints such as vertebrae of the spine, and more
particularly, to a threaded fusion cage anchoring device.
BACKGROUND OF THE RELATED ART
[0003] Degeneration of a joint such as a spinal segment by a
deterioration of the hard and soft tissues of the joint complex may
produce severe local or radiating pain when that segment is in
motion. Typically joint complexes consist of two bony structures
and an interposed flexible, movable portion. In the spine the bony
structures are the vertebrae and the movable portion is the
intervertebral disc. The disc is composed of a multilayered outer
ligamentous belt, the annulus, constructed in concentric
laminations rather like the plies of an automobile tire. In the
core of the disc there is a small mass of flexible fibrogel,
contained by the annulus ring. The fibrogel mass, the nucleus of
the disc, is a hydrogel which on absorbing water exerts a
substantial swelling pressure to lift the vertebra and balance the
forces applied against the disc by gravity and surrounding muscular
contractions. Therefore, the hydrogel is important for resisting
potentially disruptive forces applied to the vertebrae.
[0004] Unfortunately, as the disc degenerates, the internally
contained hydrogel begins to lose its water-binding ability and
shrinks. This shrinkage leads to a loosening of the annulus fibers
which permits an abnormal range of motion of the segment with
buckling and delamination of the overlapping plies. Tears in as few
as several layers of the approximately 12 to 20 concentric
laminations of the annulus may permit a herniation of the pressured
central nucleus material outward through the annulus defect.
[0005] Conventional procedures for treating degenerative vertebral
discs involve fusing the discs together to stop all motion of the
bone segments. The most efficient method of fusion places bone or a
bone inducing substance inside a supporting device surgically
implanted into the center of the disc. This supporting device
construct will obliterate the degenerated nucleus, hold the bone
material rigidly in position, protect the bone from collapse,
extrusion or invasion by residual soft tissues of the disc and
cause the opposing vertebrae to rapidly fuse together. The
preferred intervertebral fusion device is a vertebral fusion cage.
For example, U.S. Pat. No. 4,961,740 to Ray, contents of which are
incorporated herein, discloses threaded vertebral fusion cages. The
internal cavities of the cages are used to secure the bone graft
material and to permit bone growth through and across the
surgically emptied nucleus cavity between adjacent vertebrae.
[0006] As opposed to non-threaded fusion cages which are hammered
or tapped into position, insertion of threaded vertebral fusion
cages is made more efficient because the threaded outer surface
permits easy adjustment of the depth and penetration of the cage
into the disc space. The threaded outer surface also prevents
dislodgment or expulsion of the cage. In addition, the graft bone
packed within the threaded fusion cages presents or effuses through
these perforations and comes into intimate contact with the bone of
the adjacent vertebral bodies. When the cage is inserted into the
bored or tapped intervertebral bed, the lateral walls of the cage
are oriented horizontally and face the disc cavity. These lateral
cage walls are blocked (i.e., contains no apertures) and therefore
are a barrier against any potential ingrowth of residual disc
tissue into the contained graft area which could interfere with or
weaken the fusion formation of these adjacent vertebrae.
[0007] More recently, emphasis has been placed on securely fixating
the fusion cage implant within the vertebrae. During a fusion cage
implantation procedure, the surgeon may determine that sufficient
stabilization of the space has not been achieved by implantation of
the fusion cage alone. In such situations, additional
instrumentation to improve the stability of the vertebrae and cage
is required. Examples where additional stabilization procedures may
be used include: the vertebral bone is weak, the cages do not fit
tight enough in the vertebral space or the central concavity of the
disc space is too deep to achieve good cage penetration along the
anterior-posterior length of the disc space. In such cases, the
surgeon ordinarily would be forced to place additional fusion
instrumentation such as pedicle screws, rods or vertebral body
plates to prevent cage dislodgment and improve the opportunity for
a good fusion. This additional step in the surgical procedure
increases the complexity, potential hazards and cost of the
procedure. The embodiments of the present disclosure solve these
and other associated problems and provides a simple and easily
applied instrumentation to intraoperatively achieve increased cage
fixation and disc space stability.
SUMMARY
[0008] The present disclosure is directed to an anchoring device
and system for stabilizing adjacent vertebral joints. The anchoring
device includes an anchoring plate adapted to be secured to at
least one vertebral disc having a central portion, extended end
portions and at least one lateral extension. The central portion
includes an anchoring nut for fastening the anchoring plate to a
vertebral implant and the end portions include anchoring screws for
fastening the anchoring plate to the at least one vertebral disc.
The vertebral implant is preferably a threaded fusion cage, wherein
the anchoring nut is rotatably fixed to both the anchoring plate
and the threaded fusion cage.
[0009] The anchoring device preferably includes the central portion
and each extended end portion having at least one locking tab for
rotatably locking the anchoring nut and anchoring screws.
Additionally, the central portion further includes a plurality of
projecting detents along an outer periphery thereof which mate with
corresponding slots on the threaded fusion cage.
[0010] The present disclosure is also directed to a method of
implanting an anchoring device to at least one vertebral disc
having a vertebral implant. The method includes providing an
anchoring plate having a central portion and extended end portions.
The central portion includes an anchoring nut for fastening the
anchoring plate to a vertebral implant and at least one locking tab
along an outer periphery thereof. The end portions include
anchoring screws for fastening the anchoring plate to at least one
vertebral disc and at least one locking tab along an outer
periphery thereof. The method further includes: situating the
anchoring plate in a corresponding relationship to the at least one
vertebral disc and the vertebral implant; fastening the anchoring
nut to the vertebral implant; and fastening the anchoring screws to
the at least one vertebral disc. The locking tabs are then
positioned into engagement with the anchoring nut and anchoring
screws.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] The objects and features of the present disclosure, which
are believed to be novel, are set forth with particularity in the
appended claims. The present disclosure, both as to its
organization and manner of operation, together with further
objectives and advantages may best be understood by reference to
the following description, taken in connection with the
accompanying drawings, in which:
[0012] FIG. 1 is a view illustrating several adjacent spinal
segments and two anchoring devices according to the present
disclosure mounted to the spinal segments;
[0013] FIG. 2 is a bottom plan view of the anchoring device
according to the present disclosure;
[0014] FIG. 3 is a perspective view illustrating a posterior aspect
of a fusion cage and associated fusion cage inserting drive
shaft;
[0015] FIG. 4 is a plan view of an anchoring nut associated with
the anchoring device of the present disclosure; and
[0016] FIG. 5 is a bottom plan view illustrating an anchoring
device of an alternative embodiment according to the present
disclosure.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0017] The preferred embodiments of the apparatus and methods
disclosed herein are discussed in terms of orthopedic spinal fusion
procedures and instrumentation. It is envisioned, however, that the
disclosure is applicable to a wide variety of procedures including,
but, not limited to joint repair, non-union fractures, facial
reconstruction, spinal stabilization and the like. In addition, it
is believed that the present method and instrumentation finds
application in both open and minimally invasive procedures
including endoscopic and arthroscopic procedures wherein access to
the surgical site is achieved through a cannula or small
incision.
[0018] The following discussion includes a description of the
threaded fusion cage anchoring device utilized in performing a
spinal fusion followed by a description of the preferred method for
implanting the threaded fusion cage anchoring device in accordance
with the present disclosure.
[0019] Reference will now be made in detail to the preferred
embodiments of the disclosure, which are illustrated in the
accompanying figures. Turning now to the figures, wherein like
components are designated by like reference numerals throughout the
various figures, attention is first directed to FIGS. 1 and 2.
[0020] An anterior view of a fused vertebral section 10 including
two implanted anchoring devices 12 across three adjacent spinal
segments 14, 16 and 18 are generally shown at FIG. 1. The spinal
segments 14, 16 and 18, for instance, cervical spinal segments, are
separated by two interposed disc spaces 20 and 22. Threaded fusion
cages 24 are implanted between spinal segments 14 and 16 and spinal
segments 16 and 18 and across the interposed disc spaces 20 and 22,
respectively.
[0021] With particular reference to FIGS. 1-3, the anchoring device
12 of the present disclosure generally includes an anchoring plate
26, anchoring nut 28 and anchoring screws 30. Anchoring plate 26 is
generally in the shape of a figure-eight and includes a large
central bore 32 and extension arms 34. Each extension arm 34
includes at least one anchoring screw bore 36 for receiving
anchoring screw 30. The anchoring device 12 of the present
disclosure is preferably fabricated from a suitable biocompatible
rigid material such as titanium and/or alloys of titanium,
stainless steel, ceramic materials or rigid polymeric materials.
Anchoring plate 26 includes a fusion cage mating side 38 (bottom,
i.e., FIG. 2) and an anchoring nut mating side 40 (top, i.e., FIG.
1). The fusion cage mating side 38 includes projecting detents or
pins 42 for engaging slots 44 of fusion cage 24 (FIG. 3). The
projecting detents 42 are preferably located along the outer
periphery of central bore 32. The anchoring device 12 of the
present disclosure and associated threaded fusion cage 24 may
include any number of detents 42 and mating slots 44, wherein the
higher quantity of projecting detents 42 and mating slots 44
provide for an optimal fixed relationship between the fusion cage
24 and the anchoring plate 26 without a large angular change in the
implanted fusion cage 24 position. That is, the altering of the
number of slots 44 of fusion cage 24, as well as, the mating
projecting detents 42 of anchoring plate 26 will incrementally
alter the angular relationship between the anchoring plate 26 and
fusion cage 24. As such, minor angular changes in the orientation
of the anchoring plate 26 with respect to the fusion cage 24 is
beneficial so that the initial optimal depth of penetration of
implanted fusion cage 24 into the joint space need not be markedly
altered from the possible rotation attributable to the implantation
of anchoring device 12.
[0022] As best depicted in FIG. 1, the orientation or angular
displacement of the anchoring plate 26 relative to the longitudinal
axis of the spinal column, may be altered from 0 to 80 degrees as
needed to provide appropriate stability to the fusion cage 24
relative to the adjacent vertebrae. This broad angular displacement
assures a safe positioning of the anchoring plate 26 relative to
certain anatomical structures, such as, the vertebral end plate,
nearby traversing nerves or bony obstructions. In this regard, when
a pair of fusion cages 24 has been implanted at the same level, the
anchoring plates 26 are preferably set substantially parallel to
each other. Hence, having a broad angular displacement allows the
angulation between each anchoring plate 26 to be altered in order
to obtain optimal anchoring screw 30 placement in the vertebral
bodies. Similarly, when two single cages 24 or a pair of cages 24
are placed at adjacent spinal levels, the common angulation of the
anchoring plates 26 may be altered for optimal anchoring screw 30
placement into the adjacent vertebral bodies. Both the cages 24 and
anchoring plates 26 may be placed by an anterior or posterior
surgical approach to the lumbar spine. However, in the thoracic and
cervical spinal areas an anterior method alone is recommended.
[0023] With particular reference to FIGS. 1, 2 and 4, the anchoring
device 12 of the present disclosure is placed over the implanted
fusion cages 24 and attached to each fusion cage 24 with a threaded
anchoring nut 28 which screws into matching threads 46 inside the
inner periphery of fusion cage 24. Once installed, anchoring nut 28
is prohibited from loosening by a plurality of malleable nut
locking tabs 48 positioned on opposing sides of the central bore 32
of anchoring plate 26. The bending of the nut locking tabs 48 over
the anchoring nut 28 will engage at least one flat portion of the
anchoring nut collared head 50 and thereby prevent the anchoring
nut 28 from rotating and becoming loose. The extension arms 34 of
anchoring plate 26 include anchoring screw bores 36 through which
slotted head anchoring screws 30 are passed and tightened into the
vertebral bodies at convenient and safe locations. Similarly, the
anchoring screws 30 are prevented from unscrewing by a plurality of
malleable screw locking tabs 52 placed on opposing sides of the
anchoring screw bores 36 on extension arms 34. The screw locking
tabs 52 are oriented so that at least one of them will firmly mate
with at least one slot located on the head of anchoring screws 30
when locking tabs 52 are bent over anchoring screws 30.
[0024] The anchoring device 12 provides the additional support
needed to fully stabilize the fusion cage 24 relative to spinal
segments 14, 16 and 18. By crossing the interposed disc space 20
and 22 and attaching the anchoring screws 30 to the vertebral
bodies at an extended distance from fusion cage 24, a substantial
increase in mechanical fixation strength is provided. Essentially,
the anchoring device 12 keeps the vertebrae from moving apart and
therefore from distracting away from the fusion cage 24 as
postoperative spinal motions occur. Further, the anchoring plate 26
significantly improves the initial overall rigidity of the fusion
cage system.
[0025] With reference to FIG. 3, a fusion cage 24 inserting drive
shaft 54 for seating a threaded fusion cage 24 inside a bore made
between adjacent surfaces of a spinal segment is shown. A plurality
of slots 44 on the outer edge 62 of the fusion cage 24 match
projecting tabs 56 on drive shaft 54. The fusion cage 24 attaches
to a retractable central threaded coupler 58 which rotates freely
within the drive shaft 54. The fusion cage slots 44 mate with the
projecting tabs 56 of drive shaft 54. Upon rotation of drive shaft
54, the threaded coupler 58 engages the matching fusion cage
threads 46 located along an inner periphery of fusion cage 24. The
mated slots 44 and projecting tabs 56 are used to rotatably drive
the fusion cage 24 into position after which the threaded coupler
58 is unscrewed releasing both the drive shaft 54 and threaded
coupler 58 from the fusion cage 24. In the cases where positioning
of fusion cage 24 needs further adjustment, the drive shaft 54 may
be mated to the fusion cage 24 via projecting tabs 56 and slots 44
to torque the fusion cage 24 into a final position without the
necessity of firmly reattaching the threaded coupler 58 to the
fusion cage 24.
[0026] With particular reference to FIG. 5, an additional
embodiment of the anchoring plate 26 is shown, wherein like
components which correspond to those of previous embodiments
described herein are designated by like reference numerals.
Anchoring plate 26 further includes additional lateral extensions
or tangs 60 for further stabilizing the interposed disc spaces 20
and 22 by being forced into the spaces 20 and 22 as the anchoring
nut 28 is tightened onto anchoring plate 26 and into fusion cage
24. The space between the margins of lateral tangs 60 may
accommodate additional bone growth material such as cancellous or
soft bone from another human (allograft) or from the same patient
(autograft) which serves to provide a better fusion of spinal
segments 14, 16 and 18.
IMPLANTATION OF THE ANCHORING DEVICE
[0027] The implantation of the anchoring device 12 of the present
disclosure will now be described with respect to a single anchoring
device 12 although multiple anchoring devices 12 can be implanted
across one or more vertebral discs or spinal segments 14, 16 and
18. A standard surgical approach is used to gain access to the
surface of the vertebral bodies to be fused. This may consist of an
anterior approach in the neck and thoracic spine or an anterior or
posterior approach in the lumbar spine. One or more bores are
drilled into selected intervertebral spaces and tissue debris is
cleaned out therefrom. For some fusion cage implants, the bore may
be tapped to match the threaded portion of the fusion cages. In
other cases, a self-tapping fusion cage may be used and no
threading will be required.
[0028] As shown generally at FIG. 3, a threaded fusion cage 24
having slots 44 along its outer edge 62 is mated to projecting tabs
56 on the tip of the drive shaft 54, wherein the threaded coupler
58 is threaded onto the inner fusion cage threads 46 of fusion cage
24 to secure the fusion cage 24 to the drive shaft 54 during
insertion thereof within the intervertebral spaces. Next, the
fusion cage 24 is screwed into its optimal position in the prepared
intervertebral bore and the threaded coupler 58 and drive shaft 54
are detached.
[0029] The placement of anchoring device 12 is dependent upon the
actual location of the implanted fusion cage 24. If a single fusion
cage 24 or alternatively a pair of fusion cages 24 are implanted at
multiple vertebral levels, then the orientation of the anchoring
plates 26 will be in parallel pairs throughout the multiple fused
vertebral segments. The projecting detents 42 located along the
mating surface 38 of anchoring plate 26 mates with equivalently
spaced slots 44 located on the outer edge 62 of the implanted
fusion cage 24. A minor angular adjustment is made in the
orientation of the anchoring plate 26 and fusion cage 24 relative
to the longitudinal axis of the spine to maintain clearance of any
anatomical structures. This angular adjustment requires only a few
degrees of change from the initial position of the fusion cage 24.
The anchoring plate 26 may be bent slightly, before or after being
attached to the fusion cage 24, to conform with the curving surface
of the vertebral bodies or to establish clearance from other
adjacent structures.
[0030] Once an anchoring plate 26 is positioned over the implanted
fusion cage 24, the anchoring nut 28 is passed through the central
bore 32 of the anchoring plate 26 and screwed into the
corresponding mating fusion cage threads 46 portion of the
implanted fusion cage 24. Since the anchoring device 12 and fusion
cage 24 can include a plurality of projecting detents 42 and mating
slots 44, the anchoring plate 26 can be incrementally rotated to
bring the anchoring plate 26 into its most advantageous position
relative to the fusion cage 24 position. The rotation or adjusting
of the anchoring plate 26 with respect to the fusion cage 24 is
performed prior to tightening the anchoring nut 28 to the anchoring
plate 26 and fusion cage 24. Pilot holes or bores are then drilled
into the vertebrae through the anchoring screw bores 36 of
extension arms 34. The extension arms 34 are next fitted with
anchoring screws 30 of the appropriate length through bores 36
which are screwed and anchored into the vertebral bone. Both nut
locking tabs 48 and screw locking tabs 52 are bent over the edges
of anchoring nut 28 and the slots of anchoring screw 30,
respectively, to prevent either from loosening or unscrewing. Bone
inducing material is then packed inside fusion cage 24, through
central bore 32 and the center of anchoring nut 28. Alternatively,
bone inducing material may be packed into fusion cage 24 prior to
insertion.
[0031] With respect to the alternative embodiment of anchoring
device 12 depicted at FIG. 5, wherein like components and methods
correspond to those of previously described embodiments described
herein and are designated by like reference numerals. The
implantation of anchoring plate 26 further includes the addition of
bone inducing material laterally placed along fusion cage 24 prior
to attaching anchoring plate 26 to fusion cage 24.
[0032] It will be understood that various modifications may be made
to the embodiments disclosed herein. For example, the anchoring
device 12 of the present disclosure may include any number of nut
locking tabs 48 and screw locking tabs 52 to better secure each nut
28 and screw 30, respectively. Also, anchoring device 12 may
include one or more extension arms 34 radially displaced along an
angular relationship from central bore 32 which would provide
better stabilization of the anchoring device 12, fusion cage 24 and
associated bone segments 14, 16 and 18. Therefore, the above
description should not be construed as limiting, but merely as
exemplifications of preferred embodiments. Those skilled in the art
will envision other modifications within the scope and spirit of
the claims appended hereto.
* * * * *