U.S. patent application number 14/342984 was filed with the patent office on 2014-08-14 for apparatus for dilating bodily tissue and for monitoring neural activity in the dilated bodily tissue.
The applicant listed for this patent is SPINE WAVE, INC.. Invention is credited to Mark W. Bender, Lawrence M. Boyd, Matthew Penny.
Application Number | 20140228874 14/342984 |
Document ID | / |
Family ID | 47832568 |
Filed Date | 2014-08-14 |
United States Patent
Application |
20140228874 |
Kind Code |
A1 |
Boyd; Lawrence M. ; et
al. |
August 14, 2014 |
APPARATUS FOR DILATING BODILY TISSUE AND FOR MONITORING NEURAL
ACTIVITY IN THE DILATED BODILY TISSUE
Abstract
An apparatus is provided herein for dilating bodily tissue and
for monitoring neural activity in the distracted bodily tissue. In
one aspect of the invention, the apparatus includes a first dilator
having a tubular body with a distal end, a proximal end, and at
least one electrode mounted about a circumference thereof; and, a
second dilator having a tubular body of electrically-insulative
material, the tubular body having a distal end, a proximal end, and
a lumen extending therebetween sized to permit the second dilator
to subsequently telescopically slide over the first dilator and
come into overlapping coaxial alignment with the first dilator. A
discrete window is formed through the tubular body, at or near the
distal end, in communication with the lumen. With the second
dilator being in overlapping coaxial alignment with the first
dilator, the window is located to come into registration with at
least one electrode such that, upon rotation of the second dilator
relative to the first dilator, the window is positionally
adjustable about the circumference of the first dilator.
Advantageously, in addition to detecting the proximity of a nerve
to the first dilator, the apparatus permits determination of the
direction of the nerve from the first dilator. This facilitates
more efficient re-positioning of the apparatus for avoidance of
nerves, if a new path is necessary.
Inventors: |
Boyd; Lawrence M.; (Durham,
NC) ; Bender; Mark W.; (Gainesville, FL) ;
Penny; Matthew; (Holly Springs, NC) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SPINE WAVE, INC. |
Shelton |
CT |
US |
|
|
Family ID: |
47832568 |
Appl. No.: |
14/342984 |
Filed: |
September 7, 2012 |
PCT Filed: |
September 7, 2012 |
PCT NO: |
PCT/US2012/054051 |
371 Date: |
March 5, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61532668 |
Sep 9, 2011 |
|
|
|
Current U.S.
Class: |
606/191 |
Current CPC
Class: |
A61B 5/4893 20130101;
A61M 2025/0175 20130101; A61M 2025/0008 20130101; A61B 5/0492
20130101; A61B 90/02 20160201; A61M 29/00 20130101 |
Class at
Publication: |
606/191 |
International
Class: |
A61M 29/00 20060101
A61M029/00; A61B 5/0492 20060101 A61B005/0492; A61B 5/00 20060101
A61B005/00 |
Claims
1. An apparatus for dilating bodily tissue and for monitoring
neural activity in the distracted bodily tissue, said apparatus
comprising: a first dilator having a tubular body with a distal
end, a proximal end, and at least one electrode mounted about a
circumference thereof; and, a second dilator having a tubular body
of electrically-insulative material, said tubular body having a
distal end, a proximal end, and a lumen extending therebetween
sized to permit said second dilator to telescopically slide over
said first dilator and come into overlapping coaxial alignment with
said first dilator, a discrete window being formed through said
tubular body in communication with said lumen, wherein, with said
second dilator being in overlapping coaxial alignment with said
first dilator, said window being located to come into registration
with said at least one electrode such that, upon rotation of said
second dilator relative to said first dilator, said window is
positionally adjustable about the circumference of said first
dilator.
2. An apparatus as in claim 1, wherein said at least one electrode
is annular.
3. An apparatus as in claim 1, wherein said at least one electrode
includes a plurality of electrodes.
4. An apparatus as in claim 3, wherein said electrodes are evenly
spaced about the circumference of said first dilator.
5. An apparatus as in claim 1 further comprising a third dilator
having a tubular body with a distal end, a proximal end, and a
lumen extending therebetween sized to permit said third dilator to
telescopically slide over said second dilator and come into
overlapping coaxial alignment with said second dilator.
6. An apparatus as in claim 5, wherein, at least one channel
extends along an outer surface of said tubular body of said third
dilator.
7. An apparatus as in claim 6, wherein said at least one channel
extends from said proximal end of said tubular body.
8. An apparatus for monitoring neural activity in bodily tissue and
for dilating the monitored tissue, said apparatus comprising: a
first dilator having a tubular body with a distal end, a proximal
end, and a plurality of electrodes mounted at equal intervals about
a circumference thereof; and, means for separately monitoring
electrical activity of each of said electrodes.
9. An apparatus as in claim 8 further comprising a second dilator
having a tubular body of electrically-insulative material, said
tubular body having a distal end, a proximal end, and a lumen
extending therebetween sized to permit said second dilator to
telescopically slide over said first dilator and come into
overlapping coaxial alignment with said first dilator.
10. An apparatus as in claim 9, wherein said second dilator
includes a plurality of windows corresponding to said plurality of
electrodes.
11. A system for monitoring neural activity in bodily tissue and
for dilating the monitored tissue, said system comprising: a first
dilator having a tubular body of electrically-insulative material,
said tubular body having a distal end, a proximal end, and a
plurality of axially extending channels formed about a
circumference thereof extending from said proximal end towards said
distal end; and, a probe formed to be sequentially introduced in
said channels.
12. A system as in claim 11, wherein said tubular body further
having at least one transverse channel in communication with a
distal terminus of at least one said channel, said transverse
channel being transversely disposed relative to said channel in
communication therewith.
13. A system as in claim 12, wherein said transverse channel having
a radial expanse greater than a radial expanse of said channel and
extending a limited extent of said circumference of said tubular
body so as to not circumscribe said tubular body.
14. A system as in claim 11, wherein said channels are disposed at
four substantially equally spaced locations about the circumference
of said tubular body.
15. A system as in claim 11, further comprising a second dilator
having a tubular body of electrically-insulative material, said
tubular body having a distal end, a proximal end and a lumen
extending therebetween sized to permit said second dilator to
telescopically slide over said first dilator, a plurality of
channels being formed about a circumference of said tubular body of
said second dilator formed each to accommodate said probe.
16. A method of monitoring neural activity in bodily tissue,
comprising the steps of: introducing a first dilator into bodily
tissue having a tubular body of electrically-insulative material,
said tubular body having a distal end, a proximal end, and at least
one electrode mounted adjacent the distal end around a
circumference thereof; introducing a second dilator having a
tubular body of electrically-insulative material, said tubular body
having a distal end, a proximal end, and a lumen extending
therebetween sized to permit said second dilator to telescopically
slide over said first dilator, a discrete window being formed
through said tubular body of said second dilator adjacent the
distal end thereof in communication with said lumen, said window
being placed during introduction of said second dilator in coaxial
alignment with said electrode; electrifying said electrode to cause
current to flow through said window; rotating said second dilator
circumferentially about said first dilator; and monitoring nerve
activity radially as said window is rotated about the electrode on
said first dilator.
17. A method as in claim 16, wherein prior to introducing said
first dilator an initial probe is introduced through said bodily
tissue to said target site and nerve activity is monitored during
said introduction.
18. A method as in claim 17, wherein said first dilator comprises a
lumen extending axially therethrough for receipt therethrough of
said initial probe, and with said initial probe being in position
in said bodily tissue and serving as a guide wire, said first
dilator is telescopically placed over said initial probe with said
initial probe extending through said lumen.
19. A method of monitoring neural activity in bodily tissue,
comprising the steps of: introducing a first dilator into bodily
tissue, said first dilator having a tubular body of
electrically-insulative material, said tubular body having a distal
end, a proximal end, and a plurality of axially extending channels
formed about a circumference thereof extending from said proximal
end towards said distal end, each channel being formed to
accommodate said probe, said distal end of said first dilator being
placed adjacent a target site; attaching a probe to a
neuromonitoring device capable of electrifying said probe and
monitoring nerve proximity; introducing said probe sequentially
into each of said channels with a tip of said probe being placed
adjacent and exposed to said target site, electrifying the tip of
said probe and monitoring nerve activity at each channel, and
removing said probe from each channel thereafter; providing a
second dilator having a tubular body of electrically-insulative
material, said tubular body having a distal end, a proximal end and
a lumen extending therebetween sized to permit said second dilator
to telescopically slide over said first dilator, a plurality of
axially extending channels being formed about a circumference of
said tubular body of said second dilator extending from said
proximal end towards said distal end, each channel being formed
each to accommodate said probe; telescopically sliding said second
dilator axially over said first dilator with the distal end of said
second dilator being placed adjacent said target site; and
introducing said probe sequentially into each of said channels of
said second dilator with a tip of said probe being placed adjacent
and exposed to said target site, electrifying the tip of said probe
and monitoring nerve activity at each channel of said second
dilator, and removing said probe from each channel thereafter.
20. The method as in claim 19, wherein prior to introducing said
first dilator an initial probe is introduced through said bodily
tissue to said target site and nerve activity is monitored during
said introduction.
21. The method as in claim 19, wherein said first dilator comprises
a lumen extending axially therethrough for receipt therethrough of
said initial probe, and with said initial probe in position and
said bodily tissue and serving as a guide wire, said first dilator
is telescopically placed over said initial probe with said initial
probe extending through said lumen.
Description
CROSS-REFERENCES TO RELATED APPLICATIONS
[0001] This application is a National Stage Application under 35
U.S.C. .sctn.371 of PCT International Application No.
PCT/US2012/054051, filed Sep. 7, 2012, which claims priority to
Provisional Patent Application No. 61/532,668, filed Sep. 9, 2011,
the entire contents of which are incorporated by reference
herein.
FIELD OF THE INVENTION
[0002] The subject invention relates to apparatus and methods for
dilating bodily tissue and, more particularly, for monitoring
neural activity intraoperatively in bodily tissue being
dilated.
BACKGROUND OF THE INVENTION
[0003] Surgery requires the introduction of various instruments
into the body. Direct, or even close, engagement with nerves by
surgical instruments may result in nerve damage potentially leaving
a lasting deleterious effect on a patient. This concern becomes
greater where larger instruments must be introduced thus increasing
the potential for harmful engagement with a nerve.
[0004] Lateral access to the spine, in a direction transverse to
the anterior-posterior axis, may be desired for certain procedures,
for example, for vertebral interbody fusion. Lateral access,
however, requires passage through a psoas muscle which is located
on both sides of the spine. Increased nerve density within the
psoas muscle adds difficulty to the lateral access technique. To
avoid nerve contact, electromyography (EMG) techniques have been
utilized which intraoperatively monitor electrical activity to
evaluate nerve location. A basic EMG technique for intraoperative
neuromonitoring utilizes a monopolar probe which includes an
electrified tip that is insertable into bodily tissue. Current is
applied to the tip with a ground electrode attached to the skin.
Current is introduced through the probe and the activity of
surrounding nerves is monitored using electrodes placed on muscles
innervated by the nearby nerves (knows as myotomes). Activation of
a muscle action potential by the electrical stimulus threshold
value indicates proximity to a nerve. Such threshold levels are
known in the art. Upon detection of a nerve, the probe is
re-located with the process repeated to further evaluate proximity
of nerves. The intended goal is to locate a passage through the
bodily tissue at sufficient distance from surrounding nerves. The
described prior art technique provides a finding of how close a
nerve is located to the probe (determined by the current reading).
Other known art describes the specific location or direction of the
detected nerve relative to the probe. However, improvements in
determining nerve location as well as direction, particularly in
lateral access spinal surgery is desired.
SUMMARY OF THE INVENTION
[0005] An apparatus is provided herein for dilating bodily tissue
and for monitoring neural activity in the dilated bodily tissue. In
one aspect of the invention, the apparatus includes a first dilator
having a tubular body with a distal end, a proximal end, and at
least one electrode mounted about a circumference thereof; and, a
second dilator having a tubular body of electrically-insulative
material, the tubular body having a distal end, a proximal end, and
a lumen extending therebetween sized to permit the second dilator
to subsequently telescopically slide over the first dilator and
come into overlapping coaxial alignment with the first dilator. A
discrete window is formed through the tubular body, at or near the
distal end, in communication with the lumen. With the second
dilator being in overlapping coaxial alignment with the first
dilator, the window is located to come into registration with at
least one electrode such that, upon rotation of the second dilator
relative to the first dilator, the window is positionally
adjustable about the circumference of the first dilator.
Advantageously, with the subject invention, in addition to
detecting the proximity of a nerve to the first dilator, the
apparatus permits determination of the direction of the nerve from
the first dilator. This facilitates more efficient re-positioning
of the apparatus for avoidance of nerves, if a new path is
necessary.
[0006] In a further aspect of the subject invention, a plurality of
electrodes, spaced about the circumference of the first dilator,
may be used in place of the annular electrode. The electrodes are
independently electrified and monitored so as to permit evaluation
of each electrode relative to possible proximate nerves.
[0007] In yet a further aspect of the subject invention, an
electrode may be sequentially introduced about the circumference of
the first dilator to evaluate proximity of nerves.
[0008] As used herein, the term "distal", and derivatives thereof,
shall refer to a direction towards a patient, while the terminal
"proximal", and derivatives thereof, shall refer to a direction
away from a patient and towards the operating surgeon.
[0009] These and other aspects of the invention will be better
understood through a study of the following detailed description
and accompanying drawings.
BRIEF DESCRIPTION OF DRAWINGS
[0010] FIG. 1 is an exploded view of an apparatus formed in
accordance with the subject invention;
[0011] FIG. 1A shows an alternative clip useable with the subject
invention;
[0012] FIG. 2 is a top plan view of a first dilator formed in
accordance with the subject invention;
[0013] FIGS. 3, 3A, 4 and 4A depict a second dilator formed in
accordance with the subject invention;
[0014] FIGS. 5a-5c show the process of a monopolar probe being
inserted into a target site in accordance with the subject
invention;
[0015] FIGS. 6 and 7 depict the first and second dilators being
assembled together for use;
[0016] FIG. 8 is a top plan view of a third dilator formed in
accordance with the subject invention;
[0017] FIG. 8A is a top plan view of an alternative third dilator
formed in accordance with the subject invention;
[0018] FIG. 8B is a cross-sectional view taken along line 8B-8B of
FIG. 8A;
[0019] FIG. 9 is a cross-sectional view taken along line 9-9 of
FIG. 8;
[0020] FIG. 9A is an end view as seen along line 9A-9A of FIG.
8;
[0021] FIG. 10 is a top plan view of a fourth dilator formed in
accordance with the subject invention;
[0022] FIG. 11 is a cross-sectional view taken along line 11-11 of
FIG. 10;
[0023] FIG. 12 depicts a bulbous electrode useable in accordance
with the subject invention;
[0024] FIG. 13 depicts a plastic clip useable with the subject
invention;
[0025] FIGS. 14 and 15 show a variation of the subject invention
utilizing a plurality of electrodes with a discrete window formed
in the second dilator;
[0026] FIG. 16 shows a variation of the subject invention with the
first and second dilators being pre-assembled for use;
[0027] FIGS. 17 and 18 show a variation of the subject invention
using a plurality of electrodes with corresponding windows being
formed in the second dilator; and,
[0028] FIGS. 19-21 show a variation of the first dilator including
a plurality of channels with FIG. 20 being a cross-sectional view
taken along line 20-20 of FIG. 19 and FIG. 21 being an end view
taken along line 21-21 of FIG. 19.
DETAILED DESCRIPTION OF THE INVENTION
[0029] With reference to the Figures, various apparatuses and
techniques for dilating bodily tissue and for monitoring neural
activity in the dilated bodily tissue are shown. The apparatuses
are described herein for use with spinal lateral access surgery. As
will be appreciated by those skilled in the art, the apparatuses
may be utilized in other surgical applications, such as posterior
or posterior-lateral access spinal surgery, as well as, in surgical
applications in other parts of the body. The apparatuses provide
for the preparation of a working access channel to a target site by
sequentially dilating bodily tissue while permitting intraoperative
neural monitoring to evaluate proximity of the inserted apparatus
to surrounding nerves.
[0030] In a first embodiment, an apparatus 10 is provided which, as
shown in FIGS. 1 and 2, generally includes a first dilator 12
having a tubular body 14 with a distal end 16, a proximal end 18
and a lumen 20 extending therebetween. The lumen 20 is sized to
permit passage therethrough of the shaft of a monopolar probe or a
guide wire, as described below.
[0031] An annular electrode 22 is mounted about a circumference of
the tubular body 14, preferably in a position closer to the distal
end 16 than the proximal end 18. The tubular body 14 preferably
includes a rounded or tapered portion 24 at the distal end 16
surrounding the lumen 20 which acts as a wedge to allow for a
gradual dilation of bodily tissue as the first dilator 12 advances
into the bodily tissue. The electrode 22 may be located on or
proximally of the portion 24. To permit electrical flow from the
electrode 22 in a controlled manner, portions of the tubular body
14 adjacent to the electrode 22 may be formed with
electrically-insulative material. A conductor 26 may extend through
the tubular body 14 which is electrically coupled to the electrode
22 and includes an exposed portion 28 preferably located in
proximity to the proximal end 18. A layer of
electrically-insulative material 30 is provided on the conductor 26
to separate the electrode 22 from the exposed portion 28. With this
configuration, current applied to the exposed portion 28 may be
conducted through the conductor 26 and to the electrode 22 as
needed.
[0032] The first dilator 12 is preferably provided with a length of
at least 25.4 cm between the distal and proximal ends 16, 18 so as
to have sufficient length to extend from a target site inside of
the body with the proximal end 18 being exposed outside of the
body. Also, the first dilator 12 preferably has an outside diameter
of about 6 mm.
[0033] In the first embodiment, the apparatus 10 also includes a
second dilator 32 which, as shown in FIGS. 3 and 4, includes a
tubular body 34 having a distal end 36, a proximal end 38 and a
lumen 40 extending therebetween. A rounded or tapered portion 37 is
provided at the distal end 36 for easing dilation of bodily tissue
with advancement of the second dilator 32 into the bodily tissue.
The lumen 40 is sized to permit the second dilator 32 to
telescopically slide over the first dilator 12 and come into
overlapping coaxial alignment with the first dilator 12. To
facilitate this arrangement, it is preferred that the diameter of
the lumen 40 be formed slightly larger than the outer diameter of
the first dilator 12. It is also preferred that the second dilator
32 have a shorter length than the first dilator 12 with a length of
about 23 cm being provided between the distal and proximal ends 36,
38. In this manner, with the distal end 36 of the second dilator 32
being generally aligned with the distal end 16 of the first dilator
12, the first dilator 12 will extend proximally beyond the second
dilator 32. The second dilator 32 preferably has an outer diameter
of about 8 mm.
[0034] A discrete window 42 is formed through the tubular body 34
in communication with the lumen 40. The window 42 is located so as
to come into registration with the electrode 22 with the second
dilator 32 being in overlapping coaxial alignment with the first
dilator 12. With this arrangement, upon rotation of the second
dilator 32 relative to the first dilator 12, the window 42 is
positionally adjustable about the circumference of the first
dilator 12 and about the electrode 22. This allows for current
flowing out of the electrode 22 to be focused in a particular
radial direction into the surrounding tissues. The second dilator
32 is provided with a mark or other suitable indicia 44 at or
adjacent to the proximal end 38 which is axially aligned with the
window 42. In this manner, with the window 42 being located inside
of a patient and not being directly visually observable, the mark
44 provides for a visual indication of the angular position of the
window 42 about a central axis of the second dilator 32.
[0035] The window 42 may be formed with various configurations. As
shown in FIGS. 3 and 4, the window 42 may be polygonal (e.g.,
triangular). Intersecting corners may be rounded or otherwise
formed to avoid sharp angular transitions between sides of the
polygon. Alternatively, as shown in FIGS. 3A and 4A, the window 42
may be elliptical having a circular or oval shape.
[0036] The apparatus 10, utilizing the first and second dilators
12, 32, may be used as follows. In one procedure, a monopolar probe
46 is initially provided which includes a shaft 43 that terminates
in a sharpened tip 45, and a handle 47 mounted to the shaft 43. The
monopolar probe 46 is configured to be releasably attached to a
source of electricity 48 such as by a jack 50. A ground or
reference electrode 52 is attached to the patient's skin and also
electrically coupled to the source of electricity 48 such that with
the monopolar probe 46 being inserted into a patient, a closed
electrical circuit is defined between the monopolar probe 46 and
the ground electrode 52. Additional surface or needle electrodes
are placed on the muscle groups (myotomes) that are innervated by
the nerve roots around the particular spinal segments where the
surgeon is performing tissue dilation. It is preferred that the
source of electrical current 48 be provided with controls for
controlling the level of electrical output and measuring apparatus
for monitoring the level of the electrical output from the
electrodes on the various myotomes, particularly the magnitude of
current output.
[0037] Once initial preparations have been made, the tip 45 of the
monopolar probe 46 is caused to be inserted into a patient and
directed towards a target site (FIG. 5a). Fluoroscopy or other
radiological techniques may be used to guide the monopolar probe 46
to the target site. With lateral access spinal surgery, the
monopolar probe 46 is introduced in a lateral direction relative to
the spine, which is perpendicular to the anterior-posterior axis as
described in U.S. Pat. No. 4,545,374 issued to Robert E. Jacobson
on Oct. 8, 1985 and entitled "Method and Instruments for Performing
a Percutaneous Diskectomy" incorporated herein by reference in its
entirety. The tip 45 may be introduced into the body until close or
touching engagement with the psosas muscle (FIG. 5a). Using the
known technique of "mapping", the tip 45 of the monopolar probe 46
may be electrified with the tip 45 being positionally adjusted
about the surface of the psosas muscle to evaluate electrical
activity prior to insertion thereinto. Those skilled in the art
will recognize proximate neural presence based on variations in the
detected level of current. Where an acceptable site is located, the
monopolar probe 46 is advanced so as to pierce into the psosas
muscle (FIG. 5b) and into the target site (FIG. 5c). Electrical
levels in the muscle electrodes may be monitored during the
advancement of the monopolar probe 46. If neural presence is
detected, the monopolar probe 46 may be re-located. The advancement
of the tip 45 into the target site provides anchoring of the shaft
43 to the target site. Once secured, the source of electricity 48
may be decoupled from the monopolar probe 46, the handle 47 may be
removed with the shaft 43 of the monopolar probe 46 acting as a
guide wire to the target site.
[0038] Thereafter, the first dilator 12 is caused to telescopically
slide over the monopolar probe 46 with the shaft 43 passing into
the lumen 20. Preferably, the first dilator 12 is twisted or
rotated as it is being advanced in order to facilitate tissue
dissection. With the first dilator 12 having a greater outer
diameter than the shaft 43, tissue surrounding the apparatus 10 is
caused to dilate upon advancement of the first dilator 12 into the
body. The source of electricity 48 may be coupled to the first
dilator 12, particularly at the exposed portion 28, during
advancement of the first dilator 12 along the shaft 43. This
permits for intraoperative neural monitoring globally about the
shaft as the first dilator 12 is advanced. The first dilator 12 is
introduced with the distal end 16 coming into proximity with the
target site.
[0039] Thereafter, the second dilator 32 may be telescopically slid
over the first dilator 12 with advancement of the second dilator 32
into the body causing further dilation of surrounding bodily
tissue. The second dilator 32 is advanced with the distal end 36
coming generally into alignment with the distal end 16, as shown in
FIG. 6. In this position, the window 42 is in axial registration
with the electrode 22. The source of electricity 48 is coupled to
the exposed portion 28 of the first dilator 12 such as with a clip
54, 54A. As shown in FIG. 1, the clip 54 may be formed to
resiliently engage the first dilator 12 (e.g., having a spring clip
element), or, the clip 54A, as shown in FIG. 1A, may be manually
adjustable (e.g., a slide lock) to engage the first dilator 12. The
second dilator 32 is then caused to rotate about the first dilator
12 with the window 42 being positionally adjusted about the
electrode 22 (FIG. 7). This allows for a focused flow of current to
be controllably released from the electrode 22 about the
circumference of the apparatus 10. During a course of the rotation
of the second dilator 32 relative to the first dilator 12, the
level of electrical activity in the muscle electrodes is monitored.
If a sufficiently significant change in electrical activity (a
compound muscle action potential) is detected which indicates the
presence of a proximate nerve, the approximate distance of the
nerve from the apparatus 10 may be estimated by the current
magnitude of stimulation current and the direction of the detected
nerve from the apparatus 10 may be visually observed by the
position of the mark 44 corresponding to the location of the
observed change in electrical flow. With this information, the
surgeon may retract the apparatus 10 and re-position the monopolar
probe 46 in a direction away from the detected nerve at a distance
of at least that estimated by the observed electrical change. The
procedure may be repeated with the introduction in sequence of the
monopolar probe 46, the first dilator 12 and the second dilator 32,
as described above, to evaluate the proximity of any nerves
relative to the re-positioned assembly. If no proximate nerves are
detected, the procedure may continue. If, however, a proximate
nerve is detected, the process may be repeated until an acceptable
passage is detected.
[0040] To allow for additional dilation of the surrounding bodily
tissue, a third dilator 56, as shown in FIGS. 8 and 9, may be
provided having a tubular body 58 with a distal end 60, a proximal
end 62 and a lumen 64 extending therebetween. A rounded or tapered
portion 61 may be provided at the distal end 60 for easing dilation
of bodily tissue with advancement of the third dilator 56 into the
bodily tissue. The lumen 64 is sized to permit the third dilator 56
to telescopically slide over and come into coaxial alignment with
the second dilator 32. The larger outer diameter of the third
dilator 56, as compared to the outer diameter of the second dilator
32, provides for additional dilation of surrounding bodily tissue.
The third dilator 56 may be formed with a length of about 21 cm and
an outer diameter of about 12.5 mm. The third dilator 56 is
preferably shorter than the first and second dilators 12, 32 to
allow for access thereto while in a telescoped relationship.
[0041] It may be desired to intraoperatively monitor for neural
activity about the third dilator 56. The third dilator 56 is formed
of electrically-insulative material which does not permit the
passage therethrough of current which would emanate from the
electrode 22. To permit neural monitoring about the third dilator
56, a plurality of axially extending channels 66 may be formed
about the circumference of the tubular body 58, preferably at four
substantially equally spaced locations (FIG. 9A). It is preferred
that the channels 66 be generally straight and be located to be
accessible from towards the proximal end 62 with the third dilator
56 being located inside of a patient. The channels 66 may extend
from the proximal end 62. In use, as shown schematically in FIG. 1,
a monopolar probe 46 may be sequentially inserted into each of the
channels 66 with an electrical monitoring being conducted about the
distal end 60 at each site. With this arrangement, proximity to any
surrounding nerves may be evaluated, as well as the direction
towards such nerves. The spacing of the channels 66 allows for
evaluation of sectors or quadrants about the third dilator 56 to
obtain a general direction towards a detected nerve.
[0042] As shown in FIGS. 8 and 8A, the channels 66 may be formed to
terminate spaced from the distal end 60 of the tubular body 58. In
addition, as shown in FIGS. 8A and 8B, at the distal terminus of
one or more of the channels 66, a transverse channel 67 may be
provided which is disposed transversely to, and is in communication
with, the respective channel 66. The transverse channel 67 provides
a radial expanse extending from the distal terminus of the channel
66 which may provide for enhanced signal transmission from a
monopolar probe 46 disposed in the respective channel 66. The
transverse channel 67 may be of limited radial extent about the
circumference of the tubular body 58 so as to not circumscribe the
tubular body 58. Optionally, one or more of the transverse channels
67 may be extended to overlap two or more of the channels 66,
including having one transverse channel 67 circumscribe the
circumference of the tubular body 58 in being in communication with
all of the channels 66.
[0043] Additional dilators, such as fourth dilator 68 may then be
provided and formed in similar manner to the third dilator 56 but
at increasing diameters so as to provide for telescoping engagement
about the assembly 10 with ever-increasing dilation of surrounding
bodily tissue. Each dilator of greater diameter is also provided
with shorter length to permit access to components located
therewithin, yet the dilators must be provided with sufficient
length to extend from the body during use. The channels 66 may be
provided in each of the fourth dilator 68 and any additional outer
dilators to permit neural monitoring in the same manner as
described with respect to the third dilator 56. The fourth dilator
68 may also be formed to have expanded windows 67 similar to third
dilator 56 as described with respect to FIGS. 8 and 8A.
[0044] In an alternate procedure, a surgeon may choose to insert
the first dilator 12 without the use of the monopolar probe 46.
With this procedure, the first dilator 12 is inserted with the
distal end 16 being located adjacent to the target site.
Fluoroscopy or other radiological techniques may be used to guide
the first dilator 12 to the target site. The source of electricity
48 may be coupled to the first dilator 12, particularly at the
exposed portion 28, during advancement of the first dilator 12 into
the bodily tissue. This permits for intraoperative neural
monitoring as the first dilator 12 is advanced. Thereafter, to
secure the first dilator 12 at the set position, a conventional
guide wire is inserted through the lumen 20 and advanced into the
disc at the target site so as to provide an anchoring effect for
the assembly 10. Thereafter, the second dilator 32 and subsequent
dilators, are introduced and neural monitoring is conducted in the
same manner as described above.
[0045] As will be appreciated by those skilled in the art, the
electrode 22 may be formed of various configurations, such as
having a generally cylindrical shape (FIG. 7), with the outer
surface being generally flat, or with a bulbous shape, as shown in
FIG. 12. The electrode 22 may also have a tapered portion to match
the profile of the first dilator 12 (FIG. 2). In addition, the
electrode 22 may be attached to the tubular body 14 such as being
seated within a slot therein, or may be fixed by a plastic ring 70
mounted at the distal end 16 of the tubular body 14 (FIG. 13).
[0046] As will also be appreciated by those skilled in the art, the
electrode 22 may be replaced by a plurality of electrodes 72
circumferentially spaced, preferably equally, about the first
dilator 12 (FIGS. 14 and 15). Preferably, four equally-spaced
electrodes 72 are utilized. This version may be used in the same
fashion as described above with respect to the electrode 22, with
the electrodes 72 in this version being all simultaneously coupled
to the source of electricity 48. The window 42 is caused to be
rotated about the electrodes 72 in the same fashion as described
above.
[0047] With reference to FIG. 16, the first and second dilators 12,
32 may be assembled pre-insertion for collective insertion into the
body. Here, the first dilator 12 may include blunt-nosed tip 74 to
act as a leading end for insertion.
[0048] With the use of the plurality of electrodes 72, the
electrodes 72 may be configured to be separately electrified in
turn about the circumference of the first dilator 12. Here, the
first dilator 12 is useable in conjunction with the second dilator
32 in the same manner as described above, except that a window 76
is provided for each of the electrodes 72 (FIG. 17). During use,
with the second dilator 32 being located about the first dilator
12, the windows 76 are all in simultaneous registration with
corresponding electrodes 72 so as to simultaneously expose all of
the electrodes 72. Current is then caused to be sequentially
introduced into each of the electrodes 72 in turn. Electrical
activity is monitored to determine which, if any of the electrodes
72, develops a "hit" (electrical activity in one of the muscle
electrodes). The direction of the nerve is determined based on the
related electrode 72 which is electrified and the muscle in which
activity was noted. No adjustment (i.e., rotation) of the second
dilator 32 is necessary relative to the first dilator 12 for this
variation.
[0049] As a further variation, the second dilator 32 may be formed
completely solid, with no windows therein (FIG. 18). With this
arrangement, the electrodes 72 may be formed to be distally exposed
in the first dilator 12, such as shown in FIG. 18. This may be
achieved by extending the electrodes 72 into the portion 37 or the
blunt-nosed tip 74 so as to extend therefrom. Recesses 78 may be
formed in the portion 37 or the blunt-nosed tip 74 in which the
electrodes 72 may be seated and exposed without the electrodes 72
having to extend outwardly therefrom.
[0050] In an alternative arrangement as shown in FIGS. 19-21, a
first dilator 112 may be provided with the tubular body 114 being
of electrically-insulative material having the channels 66 formed
about a circumference thereof in the same manner as described with
respect to the third dilator 56 shown in FIGS. 8 and 8A. With this
arrangement, the first dilator 112 does not include any electrodes,
and the second dilator 32 may be completely eliminated. The first
dilator 112 may be introduced to the target site with or without
the use of the monopolar probe 46 as described hereinabove. With
the first dilator held in position, a monopolar probe 46 may be
sequentially inserted into the channels 66 of the first dilator 112
in the same manner as described above with respect to the third
dilator 56 to evaluate proximity of nerves in each of the four
quadrants. Thereafter, a third dilator 56 or fourth dilator 68 may
be used as described above as desired by the surgeon.
* * * * *