U.S. patent application number 17/532161 was filed with the patent office on 2022-03-17 for insulated pedicle access system and related methods.
The applicant listed for this patent is NuVasive, Inc.. Invention is credited to Jared Arambula, Eric Finley, Albert Kim, Scot Martinelli, Albert Pothier, Thomas Scholl.
Application Number | 20220079495 17/532161 |
Document ID | / |
Family ID | 1000005988687 |
Filed Date | 2022-03-17 |
United States Patent
Application |
20220079495 |
Kind Code |
A1 |
Scholl; Thomas ; et
al. |
March 17, 2022 |
Insulated Pedicle Access System and Related Methods
Abstract
A pedicle access system including a cannula, a stylet, and a
removable T-handle. The pedicle access system may be used to
percutaneously approach the pedicle, initiate pilot hole formation,
and conduct a stimulation signal to the target site for the
purposes of performing a pedicle integrity assessment during the
pilot hole formation. To do this, the cannula and stylet are locked
in combination and inserted through an operating corridor to the
pedicle target site, using the T-handle to facilitate easy movement
and positioning of the cannula/stylet combination. A stimulation
signal may be applied during pilot hole formation to conduct the
pedicle integrity assessment. In a significant aspect, the T-handle
may be detached from the cannula/stylet combination to facilitate
the use of various surgical tools as necessary.
Inventors: |
Scholl; Thomas; (San Diego,
CA) ; Kim; Albert; (San Diego, CA) ; Finley;
Eric; (Lancaster, CA) ; Pothier; Albert; (San
Diego, CA) ; Martinelli; Scot; (San Diego, CA)
; Arambula; Jared; (San Diego, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
NuVasive, Inc. |
San Diego |
CA |
US |
|
|
Family ID: |
1000005988687 |
Appl. No.: |
17/532161 |
Filed: |
November 22, 2021 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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15786760 |
Oct 18, 2017 |
11213236 |
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17532161 |
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|
14338154 |
Jul 22, 2014 |
10517502 |
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15786760 |
|
|
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|
13109981 |
May 17, 2011 |
8784330 |
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14338154 |
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11448237 |
Jun 6, 2006 |
7942826 |
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13109981 |
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60687947 |
Jun 6, 2005 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61B 5/24 20210101; A61B
17/1671 20130101; A61B 5/05 20130101; A61N 1/0551 20130101; A61B
5/4893 20130101; A61B 5/296 20210101; A61B 5/4504 20130101; A61B
2017/0046 20130101; A61B 5/389 20210101 |
International
Class: |
A61B 5/296 20060101
A61B005/296; A61B 5/05 20060101 A61B005/05; A61B 5/24 20060101
A61B005/24; A61B 5/389 20060101 A61B005/389; A61B 5/00 20060101
A61B005/00; A61B 17/16 20060101 A61B017/16 |
Claims
1. A method comprising: making an insulated pedicle access system
available for use, the insulated pedicle access system including: a
stylet having a handle and a needle attached to the handle; and a
cannula coupled to the handle such that the needle extends through
the cannula; advancing a distal end of the insulated pedicle access
system into a bone as part of forming a pilot hole; after the
advancing, unlocking the stylet from the cannula; and after the
unlocking removing the stylet from the cannula while leaving the
cannula positioned in the pilot hole.
2. The method of claim 1, further comprising: deploying a guide
wire into the pilot hole through the cannula; after deploying the
guide wire, removing the cannula; and advancing a pedicle screw
along the guide wire and into the bone.
3. The method of claim 1, further comprising: placing an electrical
stimulation source in electrical communication with the needle; and
delivering an electrical stimulation current from the electrical
stimulation source to monitor integrity of the bone.
4. The method of claim 1, wherein prior to unlocking the stylet
from the cannula: two or more protrusions of the stylet resist
movement of the cannula relative to the stylet in a direction
parallel to a length of the cannula.
5. The method of claim 1, wherein the insulated pedicle access
system further includes: a lock collar having: an interior lumen; a
first set of protrusions extending into the interior lumen; and a
second set of protrusions extending into the interior lumen;
6. The method of claim 5, wherein unlocking the stylet from the
cannula includes: manipulating the lock collar such that the first
and second set of protrusions transition from engaging with
engagement tabs to no longer engaging with the engagement tabs.
7. The method of claim 6, wherein the engagement tabs extend
perpendicularly from the handle.
8. The method of claim 1, wherein making an insulated pedicle
access system available for use includes assembling the insulated
pedicle access system.
9. The method of claim 8, further comprising: inserting the needle
into the cannula such that a coupler of the cannula enters a space
defined by the stylet handle and medial indentations of the handle
are aligned with but not yet engaging the coupler.
10. The method of claim 9, further comprising: manipulating a lock
collar such that the medial indentations engage with the
coupler.
11. A method comprising: making a stylet available for use, the
stylet comprising: a needle a proximal region and a distal region,
the distal region including a shaped tip; a handle portion
connected to the needle; and at least two engagement tabs extending
from the handle portion, making a cannula available for use, the
cannula comprising: an elongated shaft having a proximate end and a
distal end and an interior lumen; and a coupling element positioned
at the proximate end of the elongated shaft, the coupling element
having a proximal region and a distal region, wherein the proximal
region including an engagement region, wherein the at least two
engagement tabs are dimensioned to receive the cannula coupling
element engagement region, and wherein the engagement tabs have one
or more protrusions the one or more protrusions having geometry
complementary to the shape of the engagement region; decoupling the
stylet from the cannula such that the one or more protrusions cease
resisting movement of the engagement region relative to the stylet
in a direction parallel to the stylet's length; after decoupling
the stylet from the cannula, removing the stylet from the cannula;
inserting a guide wire through the cannula; and after inserting the
guide wire, advancing a pedicle screw along the guide wire and into
the bone.
12. The method of claim 11, further comprising: assembling an
insulated pedicle access system by inserting the needle into the
cannula; and advancing the insulated pedicle access system into a
bone as part of forming a pilot hole.
13. The method of claim 11, further comprising: placing an
electrical stimulation source in electrical communication with the
needle; and delivering an electrical stimulation current from the
electrical stimulation source to monitor bone integrity.
14. A method comprising: advancing a distal portion of an insulated
pedicle access system into a bone as part of forming a pilot hole;
and unlocking a stylet of the insulated pedicle access system from
a cannula of the pedicle access system; and removing the stylet
from the cannula while leaving the cannula positioned in the pilot
hole.
15. The method of claim 14, further comprising: deploying a guide
wire into the pilot hole through the cannula; after deploying the
guide wire, removing the cannula; and advancing a pedicle screw
along the guide wire and into the bone.
16. The method of claim 14, further comprising: placing an
electrical stimulation source in electrical communication with the
stylet; and delivering an electrical stimulation current from the
electrical stimulation source to the bone to monitor integrity the
bone.
17. The method of claim 14, wherein prior to unlocking the stylet
from the cannula: two or more protrusions of the stylet resist
movement of the cannula relative to the stylet in a direction
parallel to a length of the cannula.
18. The method of claim 14, wherein the insulated pedicle access
system further includes: a lock collar having: an interior lumen; a
first set of protrusions extending into the interior lumen; and a
second set of protrusions extending into the interior lumen;
19. The method of claim 18, wherein unlocking the stylet from the
cannula includes manipulating the lock collar such that the first
and second sets of protrusions transition from engaging with
engagement tabs to no longer engaging with the engagement tabs; and
wherein the engagement tabs extend perpendicularly from the
handle.
20. The method of claim 14, further comprising: prior to advancing
the distal portion, inserting the needle into the cannula such that
a coupler of the cannula enters a space defined by the stylet
handle and medial indentations of the handle are aligned with but
not yet engaging the coupler; and manipulating a lock collar such
that the medial indentations engage with the coupler.
Description
CROSS-REFERENCES TO RELATED APPLICATIONS
[0001] The present application is a continuation of U.S. patent
application Ser. No. 15/786,760, filed Oct. 18, 2017, which is a
continuation of U.S. patent application Ser. No. 14/338,154, filed
Jul. 22, 2014, which is a continuation of U.S. patent application
Ser. No. 13/109,981, filed May 17, 2011, now issued as U.S. Pat.
No. 8,784,330 (the contents being incorporated herein by
reference), which is a continuation of U.S. patent application Ser.
No. 11/448,237, filed Jun. 6, 2006, now issued as U.S. Pat. No.
7,942,826 (the contents being incorporated by reference), which
claims priority from U.S. Provisional Patent Application No.
60/687,947, filed Jun. 6, 2005 (the contents being incorporated
herein by reference).
BACKGROUND OF THE INVENTION
I. Field of the Invention
[0002] The present invention relates to a system and methods aimed
at accessing a pedicle in preparation for the placement of pedicle
screws.
II. Discussion of the Prior Art
[0003] An emerging trend in spinal surgery is to perform surgery in
a minimally invasive or minimal access fashion to avoid the trauma
of so-called open or "direct access" procedures. A specific area of
interest is in the placement of pedicle screws, which are typically
employed to effect posterior fixation in spinal fusion procedures.
While great strides are being made in this area, a risk exists (as
it does in open procedures) that the pedicle may become breached,
cracked, or otherwise compromised during the procedure. If the
pedicle (or more specifically, the cortex of the medial wall,
lateral wall, superior wall and/or inferior wall) is breached,
cracked, or otherwise compromised, the patient may experience pain
or neurologic deficit due to unwanted contact between the pedicle
screw and exiting nerve roots. This often necessitates revision
surgery, which can be painful and costly, both in terms of recovery
time and hospitalization.
[0004] Some attempts to minimize the risk of a pedicle breach
involve capitalizing on the insulating characteristics of bone and
the conductivity of the exiting nerve roots themselves to perform
pedicle integrity assessments. That is, if the wall of the pedicle
is breached, a stimulation signal applied to the pedicle screw
and/or the pilot hole (prior to screw introduction) will cause the
various muscle groups coupled to the exiting nerve roots to
contract. If the pedicle wall has not been breached, the insulating
nature of the pedicle will prevent the stimulation signal from
innervating the given nerve roots such that the associated muscle
groups will not twitch. Traditional EMG monitoring systems may be
employed to augment the ability to detect such innervation.
[0005] One period during a pedicle screw procedure in which the
risk of a pedicle breach is prevalent is during the initial access
of the pedicle. Typically, initial access to a pedicle may be
achieved by inserting a needle to the target site and driving the
needle point into the pedicle, creating a pilot hole. Due to the
size and shape of the typical needle, however, manipulation and
maneuvering of the needle may be awkward or difficult, increasing
the risk of complication. Additionally, the pedicle may be breached
and nerve damage done during the initial drive of the needle into
the pedicle, before a pedicle integrity test assessment may be
performed.
[0006] A problem that may arise when various medical instruments
are electrified and used with traditional EMG monitoring systems is
that different instruments may produce different EMG stimulation
thresholds. For example, an electrified needle may exhibit a
threshold stimulation of approximately 5-6 mA, while a bone screw
placed in the same location may exhibit a threshold stimulation of
approximately 16-20 mA. This can be problematic in that an
electrified needle may tend to indicate a breach in the pedicle
wall when in fact the pedicle wall is intact.
[0007] The present invention is directed at eliminating, or at
least improving upon, the shortcomings of the prior art.
SUMMARY OF THE INVENTION
[0008] The present invention provides a pedicle access system that
facilitates ease of handling and can achieve dynamic pedicle
integrity testing while forming a pilot hole.
[0009] According to a broad aspect of the present invention the
pedicle access system includes a cannula, a stylet, and a removable
T-handle. The pedicle access system of the present invention may be
used to percutaneously approach the pedicle, initiate pilot hole
formation, and conduct a stimulation signal to the target site for
the purposes of performing a pedicle integrity assessment during
the pilot hole formation. To do this, the cannula and stylet are
locked in combination and inserted through an operating corridor to
the pedicle target site, using the T-handle to facilitate easy
movement and positioning of the cannula/stylet combination. A
stimulation signal may be applied during pilot hole formation to
conduct the pedicle integrity assessment. In a significant aspect
of the present invention, the T-handle may be detached from the
cannula/stylet combination to facilitate the use of various
surgical tools as necessary.
[0010] The cannula includes a coupling element and an elongated
shaft. An interior lumen extends through the cannula from a first
opening in the coupling element to a second opening in the distal
region of the elongated shaft. The elongated shaft may be composed
of a conductive material, such as metal. A polymeric coating
blankets or otherwise encapsulates a majority of the exterior
surface of the elongated shaft, such that the elongated shaft
includes an insulated region and an uninsulated region. The
elongated shaft may incorporate one or more diameter changes along
its length.
[0011] The coupling element comprises three sections. First, a
proximal region is dimensioned to engage with the stylet. The
proximal region may also include at least one tab member protruding
in a generally lateral direction. The tab member functions to lock
the cannula and stylet in position together. Second, a center
section is dimensioned to engage with the T-handle. At least one
cutout may be provided in the exterior surface of the center
section. The cutout functions to secure the T-handle to the
cannula/stylet combination, or optionally to the cannula only.
Finally, there is a base portion having a circumference greater
than that of the center section such that a ledge is formed at the
interface of the center section and the base portion.
[0012] The stylet comprises a locking cap and a needle element. The
locking cap has a similar size and shape as the center section. The
locking cap contains a generally cylindrical aperture dimensioned
to receive the generally cylindrical top section of the cannula.
Furthermore, the locking cap includes at least one longitudinal
channel and at least one lateral channel that interact with the tab
member as a means to secure the stylet and cannula in place.
[0013] The longitudinal channel has a length dimension
corresponding to the length of the generally cylindrical aperture
and a width dimension sufficient to accommodate the length of the
tab member. The lateral channel extends generally perpendicularly
from the proximal end of the longitudinal channel, such that
together the channels form a generally half-T shape. The
longitudinal channel and the lateral channel, along with a ridge
positioned on at least one edge of the lateral channel interact
with the tab member on the cannula to lock the stylet and cannula
together. Additionally, the locking cap may include a ramped
surface to facilitate engagement with the T-handle.
[0014] The proximal portion of the needle element may be attached
to the interior of the locking cap. The elongated shaft of the
needle element extends distally from the proximal portion, with a
significant portion protruding from the opening of the generally
cylindrical aperture. The needle element is dimensioned to be
inserted through the interior lumen of the cannula. When fully
inserted, a distal portion of the needle element may protrude
slightly from the bottom opening of the cannula. The needle element
may be composed of a conductive material, such as metal, or a
non-conductive material with one or more embedded conductive
elements at or near the distal end capable of being communicatively
linked with a pedicle integrity testing system.
[0015] To combine the cannula and stylet, the needle element is
inserted into the interior lumen of the cannula through the opening
in the coupling element. The locking cap is positioned such that
its longitudinal channels are aligned with the tab members of the
cannula. The proximal region of the cannula is received into the
aperture on the locking cap, and the tab members pass through the
longitudinal channels. Insertion is complete when the proximal
region is fully received by the aperture, leaving the locking cap
in an "unlocked" position. In the unlocked position, the tab
members are positioned at the proximal ends of the longitudinal
channels. In this position the locking cap and center section of
the cannula are not aligned. To lock the stylet in place in the
cannula, the locking cap is rotated until it is aligned with the
center section. As the lateral channels rotate around the tab
members, the ridges may be deformed when they contact the tab
members. When the locking cap and center section align, the ridges
may clear the tab members and regain their original forms, thereby
preventing inadvertent rotation back to the unlocked position.
[0016] The T-handle includes a grip region, an aperture for
engaging the cannula or cannula/stylet combination, and a locking
mechanism for securing the T-handle to the cannula. The T-handle
aperture is dimensioned to snugly receive both the locking cap and
the center section of the cannula when they are aligned in the
locked position. The locking mechanism preferably comprises a lever
having one end integrated into the aperture wall and a free end
extending therefrom. The majority of the lever (excluding the free
end) may be the same thickness as the aperture wall and does not
protrude, interiorly or exteriorly, from the aperture wall. In its
"natural" state, the free end does protrude into the aperture
space. The free end is dimensioned to engage the cutout in the
center section of the cannula. The interior surface of the free end
may be slightly ramped. The ramped portion works in concert with
the ramped surface of the locking cap to force the free end out of
its natural state so the locking cap and the center section can fit
into the T-handle aperture. When the locking cap and center section
are fully inserted into the T-handle aperture, the locking
mechanism aligns with the cutout in the cannula, returns to its
natural state, and locks the T-handle to the cannula. Optionally,
the T-handle may be cannulated.
[0017] In an alternative aspect of the present invention, the
pedicle access system may be provided with a stylet, a cannula and
a lock collar. Any part of the stylet and/or cannula may be coated
with a nonconductive insulative coating to prevent shunting of
electrical current.
[0018] In a further alternative aspect of the present invention,
the pedicle access system may be provided with a retractable
insulation sheath dimensioned to cover the electrically conductive
cannula and stylet needle. The retractable insulation sheath is
adapted to electrically insulate the pedicle access system as it is
advanced along an operative corridor to a bony structure. As the
needle element is introduced into the bony structure (e.g. a
pedicle) during pilot hole formation, the insulation sheath
retracts to remain outside the bone and prevent electrical current
intended for the pilot hole from shunting to surrounding
tissue.
[0019] In a significant aspect of the present invention, the
pedicle access system may be used in combination with
neurophysiology monitoring systems and methods to conduct pedicle
integrity assessments while achieving initial access to the pedicle
and forming a pilot hole. The neurophysiology system performs
pedicle integrity assessments by determining the amount of
electrical communication between a stimulation signal and the
adjacent nerve root. The pedicle access system may be coupled with
the neurophysiology system by attaching an electric coupling device
to the uninsulated region of the cannula.
[0020] In another significant aspect of the present invention, the
pedicle access system may be used in cooperation with spinal
fixation systems that require access to pedicle target sites and
need pilot holes, as the cannula may be used to guide parts of the
surgical fixation system to the target site.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] Many advantages of the present invention will be apparent to
those skilled in the art with a reading of this specification in
conjunction with the attached drawings, wherein like reference
numerals are applied to like elements and wherein:
[0022] FIG. 1 is a plan view of an example of a pedicle access
system according to one embodiment of the present invention;
[0023] FIG. 2 is a perspective view of a cannula forming part of
the pedicle access system of FIG. 1;
[0024] FIG. 3 is a perspective view of a coupling element forming
part of the cannula of FIG. 2;
[0025] FIG. 4 is a perspective view of a stylet forming part of the
pedicle access system of FIG. 1;
[0026] FIG. 5 is a perspective view of a locking cap forming part
of the stylet of FIG. 4;
[0027] FIG. 6 is a perspective view of the distal portion of the
stylet of FIG. 4 protruding from the distal region of the cannula
of FIG. 2;
[0028] FIG. 7 is a perspective view of the distal portion of the
stylet of FIG. 4 protruding from the distal region of the cannula
of FIG. 2, with the distal region of the cannula having an
uninsulated portion;
[0029] FIG. 8 is a perspective view of the distal portion of the
stylet of FIG. 4 protruding from the distal region of the cannula
of FIG. 2, with the distal region of the cannula having a
directional electrode;
[0030] FIGS. 9-10 are plan and perspective views, respectively, of
the stylet of FIG. 4 partially inserted into the cannula of FIG.
2;
[0031] FIG. 11 is a is a plan view of the stylet of FIG. 4 fully
inserted into the cannula of FIG. 2 in an unlocked position;
[0032] FIG. 12 is perspective view of the locking cap of the fully
inserted stylet of FIG. 11, shown in an unlocked position;
[0033] FIG. 13 is a perspective view of the cannula and stylet
combination in the unlocked position of FIG. 11;
[0034] FIGS. 14-15 are perspective and plan views, respectively, of
the cannula and stylet combination of FIG. 13 in the locked
position;
[0035] FIGS. 16-17 are perspective views of a T-handle forming part
of the pedicle access system of FIG. 1;
[0036] FIG. 18 is a perspective view of the pedicle access system
of FIG. 1 with the cannula and stylet combination of FIG. 13 fully
inserted and locked in the T-handle;
[0037] FIG. 19 is an exploded perspective view of a pedicle access
system according to an alternative embodiment of the present
invention;
[0038] FIG. 20 is a perspective view of the assembled pedicle
access system of FIG. 19;
[0039] FIGS. 21-22 are plan and perspective views, respectively, of
a cannula forming part of the pedicle access system of FIG. 20;
[0040] FIGS. 23-24 are plan and perspective views, respectively, of
a coupling element forming part of the cannula of FIG. 21;
[0041] FIG. 25 is a perspective view of a stylet forming part of
the pedicle access system of FIG. 20;
[0042] FIG. 26 is a perspective view of a handle forming part of
the stylet of FIG. 25;
[0043] FIG. 27 is a perspective view of the pedicle access system
of FIG. 20 including an enlarged view of a distal region
thereof;
[0044] FIGS. 28-30 are perspective, top plan and bottom plan views,
respectively, of a lock collar forming part of the pedicle access
system of FIG. 20;
[0045] FIG. 31 is an exploded perspective view of a pedicle access
system according to a further alternative embodiment of the present
invention;
[0046] FIGS. 32-33 are perspective views of an assembled pedicle
access system of FIG. 31;
[0047] FIG. 34 is a front view of the pedicle access system of FIG.
32;
[0048] FIGS. 35-36 are side and perspective views, respectively, of
a cannula forming part of the pedicle access system of FIG. 31;
[0049] FIGS. 37-38 are side and perspective views, respectively, of
a coupling element forming part of the cannula of FIG. 35;
[0050] FIG. 39 is a perspective view of a stylet forming part of
the pedicle access system of FIG. 31;
[0051] FIG. 40 is a perspective view of a needle forming part of
the stylet of FIG. 39;
[0052] FIGS. 41-42 are perspective and plan views, respectively, of
a handle forming part of the stylet of FIG. 39;
[0053] FIGS. 43-44 are perspective and plan views, respectively, of
a lock collar forming part of the pedicle access system of FIG.
31;
[0054] FIG. 45 is a bottom plan view of a handle of FIG. 46 in
engagement with a lock collar of FIG. 43;
[0055] FIG. 46 is a perspective view of a retractable insulation
sheath forming part of the pedicle access system of FIG. 31;
[0056] FIG. 47 is a perspective view of an insulation tube forming
part of the retractable insulation sheath of FIG. 46;
[0057] FIG. 48 is a perspective view of a retraction tube forming
part of the retractable insulation sheath of FIG. 46;
[0058] FIGS. 49-50 are perspective views of a sheath attachment
element forming part of the pedicle access system of FIG. 31;
and
[0059] FIG. 51 is a perspective view of an example of a
neurophysiology system capable of connecting to the pedicle access
systems of FIGS. 1, 19 and 31 to conduct pedicle integrity
tests.
[0060] FIGS. 52-53 are side and perspective views, respectively, of
a cannula forming part of the pedicle access system of FIG. 51;
[0061] FIG. 53A are cross-sectional views taken along lines 53A-53A
in FIG. 53 illustrating the relative size of the insulated and
non-insulated regions of the cannula of FIGS. 51-53; and
[0062] FIG. 54 is a perspective view of an example of a
neurophysiology system capable of connecting to the pedicle access
systems of FIGS. 1, 19, and 31 to conduct pedicle integrity
tests.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0063] Illustrative embodiments of the invention are described
below. In the interest of clarity, not all features of an actual
implementation are described in this specification. It will of
course be appreciated that in the development of any such actual
embodiment, numerous implementation-specific decisions must be made
to achieve the developers' specific goals, such as compliance with
system-related and business-related constraints, which will vary
from one implementation to another. Moreover, it will be
appreciated that such a development effort might be complex and
time-consuming, but would nevertheless be a routine undertaking for
those of ordinary skill in the art having the benefit of this
disclosure. The insulated pedicle access system and related methods
disclosed herein boast a variety of inventive features and
components that warrant patent protection, both individually and in
combination.
[0064] FIG. 1 illustrates an example of a pedicle access system 10
according to one embodiment of the present invention. The pedicle
access system 10 includes a cannula 12, a stylet 14, and a T-handle
16. As will be described with greater detail below, the pedicle
access system 10 may be used to percutaneously approach the
pedicle, initiate pilot hole formation, and conduct a stimulation
signal to the target site for the purposes of performing a pedicle
integrity assessment during formation of the pilot hole. To do
this, the cannula 12 and stylet 14 may be lockingly mated to form a
cannula/stylet combination 15 which may be inserted through an
operating corridor to the pedicle target site, using the T-handle
16 to facilitate easy movement and positioning of the
cannula/stylet combination 15. The cannula/stylet combination 15
may be driven into the bone at the target site to form a pilot hole
while a stimulation signal is applied to the pedicle access system
10 and conducted to the target site to assess the integrity of the
pedicle during hole formation. The T-handle 16 may be detached from
the cannula/stylet combination 15 to facilitate the use of various
surgical tools (such as by way of example only a forceps, mallet,
or needle driver) after proper positioning of the cannula 12 and
stylet 14. Additionally, removal of the T-handle after proper
positioning of the cannula/stylet combination 15 provides a less
obstructed view of the operating corridor and surgical target site.
As shown and described herein, the cannula 12 and stylet 14 are
generally cylindrical in shape. However, it should be understood
that cannula 12 and stylet 14 may be provided in any suitable shape
having any suitable cross-section (e.g. generally oval or
polygonal) without deviating from the scope of the present
invention.
[0065] FIG. 2 illustrates an example of a cannula 12 forming part
of pedicle access system 10. Cannula 12 includes a coupling element
18 and an elongated shaft 20. An interior lumen extends through the
cannula 12 from a first opening 22 located at a proximal region 30
of the coupling element 18 to a second opening 24 located at a
distal end 21 of the elongated shaft 20. Elongated shaft 20 may be
composed of any conductive material such as metal, for example. A
polymeric coating is provided on a substantial portion of the
exterior surface of elongated shaft 20 such that elongated shaft 20
comprises an insulated portion 26 and an uninsulated portion 28.
Although elongated shaft 20 is shown having a single uniform
diameter, it will be appreciated that one or more diameter changes
may be incorporated along the elongated shaft 20 without deviating
from the scope of the present invention.
[0066] With reference to FIG. 3, coupling element 18 comprises a
proximal region 30, a center section 32, and a base portion 34.
Proximal region 30 is dimensioned to engage with the stylet 14
(described below). Proximal region 30 may include at least one tab
member 36 that protrudes in a generally lateral direction from the
proximal region 30. By way of example only, as shown in FIG. 3
proximal region 30 includes two tab members 36 positioned opposite
one another and adjacent to first opening 22. As will be described
in greater detail below, tab members 36 function to lock the
cannula 12 and stylet 14 together. Center section 32 is dimensioned
to be received within T-handle aperture 66 (FIG. 16) as described
in further detail below. Center section 32 may be provided with at
least one cutout 38 dimensioned to receive a locking mechanism 68
(FIG. 16) incorporated into T-handle 16 to secure the T-handle 16
to the cannula/stylet combination 15, or optionally to the cannula
12 only. The base 34 has a circumference that is greater than the
circumference of center section 32, such that a ledge 39 is formed
at the interface of center section 32 and the base portion 34. The
ledge 39 engages the rim 72 of T-handle 16 so as to minimize
potential stress on a T-handle locking mechanism 68 discussed
below.
[0067] FIG. 4 illustrates an example of a stylet 14 forming part of
the pedicle access system 10. Stylet 14 includes a locking cap 40
and a needle element 42. Locking cap 40 has a similar size and
shape to center section 32, and is similarly dimensioned to be
received within T-handle aperture 66, discussed below. Locking cap
40 includes a distal end 44 and a proximal end 46. As illustrated
in FIG. 5, locking cap 40 includes a generally cylindrical aperture
48 having an opening at distal end 44 and extending in a proximal
direction at least partially the length of locking cap 40.
Generally cylindrical aperture 48 is dimensioned to receive the
generally cylindrical proximal region 30 of cannula 12.
Furthermore, locking cap 40 includes at least one longitudinal
channel 50 (defined by an axis extending through the proximal and
distal ends 46, 44 respectively) and at least one lateral channel
52 extending generally perpendicularly from longitudinal channel
50. Longitudinal channel 50 and lateral channel 52 each extend from
an exterior surface 54 through an interior surface 56 into aperture
48. Preferably, the number of longitudinal channels 50 and lateral
channels 52 correspond to the number of tab members 36 on cannula
12. By way of example only (and as shown in FIGS. 3-5), cannula 12
includes two tab members 36 and stylet 14 includes two longitudinal
channels 50 and two lateral channels 52.
[0068] Longitudinal channel 50 initiates at the distal end 46 and
has a length corresponding to the length of the generally
cylindrical 48. Lateral channel 52 initiates at the proximal end of
longitudinal channel 50 and extends generally perpendicularly
therefrom such that together the longitudinal and lateral channels
50, 52 form a generally half-T shape. Longitudinal channel 50 and
lateral channel 52 function to interact with the tab 36 on cannula
12, so as to lock the stylet 14 and cannula 12 together.
Longitudinal channel 50 has a width dimension sufficient to
accommodate the length of tab member 36 and lateral channel 52 has
a height dimension sufficient to accommodate the height of tab
member 36 (best viewed in FIG. 12). A ridge 58 (shown in FIG. 12)
may be positioned along the distal-most edge 53 and/or
proximal-most edge 55 of the lateral channel 52 to engage with tab
member 36 and provide a locking means for the cannula/stylet
combination 15. Additionally, a portion of exterior surface 54
adjacent to proximal end 46 may comprise a ramped surface 49 such
that the circumference of distal end 44 is slightly greater than
the circumference of proximal end 46, so as to facilitate
engagement with the T-handle 16.
[0069] The needle element 42 comprises an elongated shaft 41 having
a proximal region 43 and a distal region 45. The proximal region 43
may be attached to the interior of locking cap 40 between proximal
end 46 and aperture 48. Elongated shaft 41 extends distally from
proximal region 43 with a significant portion protruding generally
perpendicularly from the opening of aperture 48. Needle element 42
is dimensioned to be inserted through the interior lumen of cannula
12. The distal region 45 generally includes a distal portion of
elongated shaft 41 and a shaped tip 47 having any form or shape
capable of being driven into the pedicle to create a pilot hole. By
way of example only, shaped tip 47 may have a beveled or double
diamond form. As illustrated in FIG. 6, when needle element 42 is
fully inserted into cannula 12, at least a portion of distal region
45 (including shaped tip 47) may protrude slightly from the second
opening 24 of cannula 12. Due to the insulated nature of cannula
12, the portion of needle element 42 that protrudes from cannula 12
effectively constitutes a stimulation region 60. The stimulation
region 60 may include the distal region 45 and/or the shaped tip
47.
[0070] According to a further aspect of the present invention, any
part of the needle element 42 (e.g. the elongated shaft 41, distal
region 45 and/or shaped tip 47) may be provided with a coating to
insulate and therefore limit or reduce the stimulation region 60 to
a desired configuration. For example, the distal tip 47 may have an
insulation coating to effectuate a stimulation region 60 consisting
of the portion of the distal region 45 of the needle element 42
between the insulated cannula 12 and the insulated distal tip 47.
Alternatively, the entirety of needle element 42 may be provided
with an insulative coating and the distal region 21 of cannula 12
may be provided with (for example) one or more uninsulated portions
29 (FIG. 7) and/or one or more directional electrodes 31 (FIG. 8)
forming a stimulation region 61. These alternative arrangements
serve to mitigate an apparent phenomenon in which certain
geometries (e.g. points and edges) tend to generate significantly
higher current densities and therefore are much more efficient at
exciting a nearby nerve, even through bone tissue. As a result,
instrumentation having these geometries may show a lower
stimulation threshold (and thus causing an EMG monitoring system to
indicate a breach in an intact pedicle) unless this phenomenon is
otherwise compensated for.
[0071] Needle element 42 may be composed of a conductive material,
such as metal. Alternatively, needle element 42 may be composed of
a non-conductive material with one or more embedded conductive
elements at or near the distal end (e.g. distal region 45 and/or
shaped tip 47) capable of being communicatively linked with a
pedicle integrity testing system.
[0072] FIGS. 9-15 illustrate the formation of the cannula/stylet
combination 15. In FIGS. 9-10 stylet 14 is introduced into cannula
12. Needle element 42 of stylet 14 is inserted into the interior
lumen of cannula 12 through the first opening 22 of coupling
element 18. The locking cap 40 of stylet 14 is positioned such that
its longitudinal channels 50 are aligned with the tab members 36 of
cannula 12. The proximal region 30 of cannula 12 is received into
the aperture 48 of locking cap 40, and the tab members 36 pass
through the longitudinal channels 50 as insertion of needle element
42 progresses. Insertion is complete when the proximal portion 30
is fully received by aperture 48, leaving the locking cap 40 in the
"unlocked" position illustrated in FIGS. 11-13. As mentioned above,
the distal region 45 of needle element 42 including shaped tip 47
(and the stimulation region 60) may protrude from the second
opening 24 of the elongated shaft 20 of cannula 12 when stylet 14
is fully inserted, shown in FIG. 11. In the unlocked position, tab
members 36 are positioned at the proximal end of longitudinal
channels 50 where the channels intersect lateral channels 52. At
this point, the corresponding shapes of the locking cap 40 of
stylet 14 and center section 32 of cannula 12 are out of alignment.
To lock stylet 14 in place and complete the combination, the
locking cap 40 is rotated until it is aligned with the center
section 32 as illustrated in FIGS. 14-15. As the lateral channels
52 rotate around the tab members 36, ridges 58 come into contact
with the tab members 36. The ridges may not pass the tab members 36
if the locking cap 40 is not rotated with enough force to deform
the ridges 58. Once the ridges 58 have deformed, the rotation may
continue towards the final position. The locking cap 40 and center
section 32 become aligned and the ridges 58 may clear the tab
members 36 and regain their original forms, thereby preventing
inadvertent rotation of the locking cap 40 back to the unlocked
position.
[0073] FIG. 16 illustrates an example of a T-handle 16 forming part
of the pedicle access system 10. T-handle 16 includes a grip region
64, an aperture 66 for engaging the cannula 12 or cannula/stylet
combination 15, and a locking mechanism 68 for securing the
T-handle to the cannula 12. Grip region 64 may be provided in any
number of suitable shapes and sizes that may aid the user in
holding and manipulating the pedicle access system 10 during use.
The T-handle aperture 66 is dimensioned to snugly receive both the
locking cap 40 and center section 32 when they are aligned in the
locked position as described above. The locking mechanism 68
preferably comprises a lever having one end that is integrated into
the aperture wall and a free end 70 extending therefrom. The
majority of the locking mechanism 68 (excluding free end 70) may
comprise the same thickness as the aperture wall and does not
protrude, interiorly or exteriorly, from the aperture wall. In its
"natural" state, the interior surface of free end 70 protrudes into
the aperture 66 space. The interior surface of free end 70 is
dimensioned to engage the cutout 38 in the center section 32 of
cannula 12. Furthermore, as illustrated in FIG. 17, the interior
surface of free end 70 may be slightly ramped, such that the edge
further from the aperture opening protrudes further into the
aperture than the edge closer to the aperture opening. The ramped
portion works in concert with the ramped surface 49 at the proximal
end 46 of locking cap 40 to force the free end 70 out of its
natural state as the locking cap 40 of stylet 14 and center section
32 of cannula 12 are received into the T-handle aperture 66. When
the locking cap 40 and center section 32 are fully inserted into
the T-handle aperture 66, as illustrated in FIG. 18, the interior
surface of free end 70 aligns with the cutout 38 in the center
section 32 and free end 70 returns to its natural state, thus
locking the T-handle 16 to the cannula 12. Furthermore, as the
locking cap 40 and center section 32 are fully inserted into the
T-handle aperture 66, the ledge 39 engages the rim 72. This
interaction functions to minimize potential stress on the T-handle
locking mechanism 68 by increasing the surface area that receives
force applied by the user. To remove the T-handle 16, the free end
70 may be lifted to disengage with the cutout 38, and the T-handle
may be pulled off. Optionally, T-handle 16 may be cannulated (not
shown) such that an interior lumen extends from an opening on the
top of the handle into the aperture 66.
[0074] FIGS. 19-20 illustrate an example of a pedicle access system
110 according to an alternative embodiment of the present
invention. The pedicle access system 110 includes a cannula 112, a
stylet 114, and a lock collar 116. As described above in relation
to pedicle access system 10, pedicle access system 110 may be used
to percutaneously approach the pedicle, initiate pilot hole
formation, and conduct a stimulation signal to the target site for
the purposes of performing a pedicle integrity assessment during
formation of the pilot hole. To do this, the cannula 112 and stylet
114 may be lockingly mated and inserted through an operating
corridor to the pedicle target site, using the handle portion 140
of the stylet 114 to facilitate easy movement and positioning of
pedicle access system 110. The pedicle access system 110 may be
driven into the bone at the target site to form a pilot hole while
a stimulation signal is applied and conducted to the target site to
assess the integrity of the pedicle during hole formation. As shown
and described herein, the cannula 112 and stylet 114 are generally
cylindrical in shape. However, it should be understood that cannula
112 and stylet 114 may be provided in any suitable shape having any
suitable cross-section (e.g. generally oval or polygonal) without
deviating from the scope of the present invention.
[0075] FIGS. 21-22 illustrate an example of a cannula 112 forming
part of pedicle access system 110. Cannula 112 includes a coupling
element 118 and an elongated shaft 120. An interior lumen extends
through the cannula 112 from a first opening 122 located at a
proximal region 130 of the coupling element 118 to a second opening
124 located at a distal end 121 of the elongated shaft 120.
Elongated shaft 120 may be composed of any conductive material such
as metal, for example. A polymeric coating may be provided on a
substantial portion of the exterior surface of elongated shaft 120
such that elongated shaft 120 comprises an insulated portion 126
and an uninsulated portion 128 (the edge of the coating and thus
the boundary between portions 126, 128 represented by callout 127
in FIGS. 21-22). Elongated shaft 120 may include any number of
diameter changes incorporated along its length without deviating
from the scope of the present invention. In the alternative,
elongated shaft 120 may be provided with a uniform diameter along
its length.
[0076] With reference to FIGS. 23-24, coupling element 118
comprises a proximal region 130, a center section 132, and a distal
portion 134. Proximal region 130 includes an engagement region 131
dimensioned to engage with the handle portion 140 of the stylet 114
(as described in further detail below). The engagement region 121
may be provided in any suitable geometric configuration to allow
for secure mating with the engagement tabs 144 of the handle 140.
By way of example only, the coupling element 118 is shown in FIGS.
23-24 having a hexagonal engagement region 131, however other
shapes are possible. Proximal region 130 may include at least one
tab member 136 that protrudes in a generally lateral direction from
the proximal region 130. By way of example only, as shown in FIG.
24 proximal region 130 includes two tab members 136 positioned
opposite one another and adjacent to first opening 122. Tab members
136 may be utilized to attach supplemental instruments and/or
apparatuses to the cannula 112. Center section 132 may be provided
with a diameter that is larger than the diameters of the proximal
region 130 and distal portion 134, and may be provided with a
plurality of ridges 133 and/or other features for the purpose of
providing a suitable gripping area for a user. The distal portion
134 is dimensioned to engage with the elongated shaft 120 of the
cannula 112.
[0077] FIG. 25 illustrates an example of a stylet 114 forming part
of the pedicle access system 110. Stylet 114 includes a handle
portion 140 and a needle element 142. Handle portion 140 may (by
way of example) resemble a T-handle for providing a user with a
suitable gripping means. Handle portion 140 may be provided with a
pair of engagement tabs 144 extending distally from handle portion
140. Engagement tabs 144 extend generally perpendicularly from the
handle 140 and generally parallel to one another such that the
engagement tabs 144 collectively form an interior space 146.
Interior space 146 is dimensioned to receive the proximal region
130 of the coupling element 118 of the cannula 112. Each engagement
tab 144 is provided with a medial (inwardly-facing) indentation 148
and a lateral (outwardly-facing) indentation 150. Medial
indentations 148 are dimensioned to engage the engagement region
131 of the coupling element 118, described above. For this reason,
the medial indentations 148 may be provided with any geometry
complementary to the shape of the engagement region 131 such that
when mated, the engagement tabs 144 (via the medial indentations
148) will prevent movement of the engagement region 131, in effect
locking the cannula 112 in place relative to the stylet 114. The
lateral indentations 150 are dimensioned to interact with the first
and second protrusions 170, 172 of the lock collar 116 described in
further detail below.
[0078] The needle element 142 comprises an elongated shaft 152
having a proximal region 154 and a distal region 156. The proximal
region 154 may be attached to the interior of handle portion 140.
Elongated shaft 152 extends distally from proximal region 154 and
generally perpendicularly from the handle 140. Needle element 142
is dimensioned to be inserted through the interior lumen of cannula
112. The distal region 156 generally includes a distal portion of
elongated shaft 152 and a shaped tip 158 having any form or shape
capable of being driven into the pedicle to create a pilot hole. By
way of example only, shaped tip 158 may have a beveled or double
diamond form. As illustrated in FIG. 27, when needle element 142 is
fully inserted into cannula 112, at least a portion of distal
region 156 (including shaped tip 158) may protrude slightly from
the second opening 124 of cannula 112. Due to the insulated nature
of cannula 112, the portion of needle element 142 that protrudes
from cannula 112 effectively constitutes a stimulation region 160.
The stimulation region 160 may include the distal region 152 and/or
the shaped tip 158.
[0079] According to a further aspect of the present invention, any
part of the needle element 142 (e.g. the elongated shaft 152,
distal region 156 and/or shaped tip 158) may be provided with a
coating to insulate and therefore limit or reduce the stimulation
region 160 to a desired configuration. For example, the distal tip
158 may have an insulation coating to effectuate a stimulation
region 160 consisting of the portion of the distal region 156 of
the needle element 142 between the insulated cannula 112 and the
insulated distal tip 158. This coating serves to mitigate an
apparent phenomenon in which certain geometries (e.g. points and
edges) tend to generate significantly higher current densities and
therefore are much more efficient at exciting a nearby nerve, even
through bone tissue. As a result, instrumentation having these
geometries may show a lower stimulation threshold (and thus causing
an EMG monitoring system to indicate a breach in an intact pedicle)
unless this phenomenon is otherwise compensated for.
[0080] Needle element 142 may be composed of any conductive
material, such as metal. Alternatively, needle element 142 may be
composed of a non-conductive material with one or more embedded
conductive elements at or near the distal end (e.g. distal region
156 and/or shaped tip 158) capable of being communicatively linked
with a pedicle integrity testing system.
[0081] With reference to FIGS. 28-30, a lock collar 116 is provided
to lockingly mate the cannula 112 and the stylet 114. Lock collar
116 has a generally cylindrical overall shape, and includes a
proximal portion 162, a distal portion 164 and an interior lumen
166 extending therethrough. The proximal portion 162 may have a
diameter greater than that of the distal portion 164 and is
provided with a plurality of friction elements 168 to allow a user
to grasp and turn the lock collar 116. The distal portion 164
includes a generally oval-shaped opening 170 providing access to
the lumen 166. The opening 170 further includes a pair of opposing
first protrusions 172 and a pair of opposing second protrusions 174
located along the inside edge of opening 170. First protrusions 172
are located 180.degree. from one another and are positioned at the
long ends of the oval-shaped opening 170. Second protrusions 174
are positioned at the narrow sides of the oval-shaped opening 170
(and thus are located at 90.degree. intervals from the first
protrusions 172 and 180.degree. from one another). First and second
protrusions 172, 174 are each dimensioned to engage the lateral
indentations 150 provided on the engagement tabs 144 of the handle
140, described above.
[0082] The interior lumen 166 is dimensioned to receive both of the
engagement tabs 144 of the handle 140. Initially, the pedicle
access system 110 of the present invention may be provided with the
locking collar 116 attached to the stylet 114 in an initial
position. This initial position is defined by the first protrusions
172 resting in the lateral indentations 150 of the engagement tabs
144 of the handle 140. Upon insertion of the needle element 142
into the cannula 112, the distal region 130 of the coupling element
118 of cannula 112 will enter the space 146 of the handle 140 such
that the medial indentations 148 are aligned with (but not yet
engaging) the engagement region 131 of the coupling element 118. At
this point, a user would then rotate the lock collar 116 90.degree.
to a second position such that the second protrusions 174 rest in
the lateral indentations 150. Due to the oval-shaped nature of the
opening 170, upon rotation of the lock collar 116, the engagement
tabs 144 will be forced toward one another, and the medial
indentations 148 will come in contact with and positively engage
the engagement region 131. As noted previously, this positive
engagement prevents the cannula 112 from moving. At the same time,
the lock collar 116 serves to lock the engagement tabs 114 in
place, effectively locking the cannula 112 and the stylet 114
together. The pedicle access system 110 is now ready for use.
[0083] FIGS. 31-34 illustrate an example of a pedicle access system
210 according to a further alternative embodiment of the present
invention. The pedicle access system 210 includes a cannula 212, a
stylet 214, a lock collar 216 and a retractable insulation sheath
217. As described above in relation to pedicle access systems 10
and 110, pedicle access system 210 may be used to percutaneously
approach the pedicle, initiate pilot hole formation, and conduct a
stimulation signal to the target site for the purposes of
performing a pedicle integrity assessment during formation of the
pilot hole. To do this, the cannula 212 and stylet 214 may be
lockingly mated and inserted through an operating corridor to the
pedicle target site, using the handle portion 240 of the stylet 214
to facilitate easy movement and positioning of pedicle access
system 210. The pedicle access system 210 may be driven into the
bone at the target site to form a pilot hole while a stimulation
signal is applied and conducted to the target site to assess the
integrity of the pedicle during pilot hole formation. The
retractable insulation sheath 217 functions to ensure maximum
efficiency of the stimulation signal as by limiting or preventing
shunting of the signal during pilot hole formation. As shown and
described herein, the cannula 212, stylet 214 and retractable
insulation sheath 217 are generally cylindrical in shape. However,
it should be understood that cannula 212, stylet 214 and sheath 217
may be provided in any suitable shape having any suitable
cross-section (e.g. generally oval or polygonal) without deviating
from the scope of the present invention.
[0084] The retractable insulation sheath 217 functions to ensure
maximum efficiency of the stimulation signal as by limiting or
preventing shunting of the signal during pilot hole formation. With
specific reference to FIGS. 32-34, this is accomplished by
providing a tubular insulation member 274 slideably mated with a
housing member 276 described in greater detail below. In an initial
position (shown in FIGS. 33-34), the tubular insulation member 274
is fully extended such that it extends at least to the tip 258 of
the stylet 214. Upon formation of a pilot hole in a pedicle (or
other piece of bone), the stylet 214 will advance into the bone
while the insulation sheath remains outside the bone (a position
shown by way of example in FIG. 32). Due to the insulative
properties of the sheath 217, the electrical current when supplied
will be directed into the pilot hole by the uninsulated portion of
the cannula 212 and stylet 214 while prevented from shunting
outside of the hole by the sheath 217.
[0085] FIGS. 35-36 illustrate an example of a cannula 212 forming
part of pedicle access system 210 of the present invention. Cannula
212 includes a coupling element 218 and an elongated shaft 220. An
interior lumen extends through the cannula 212 from a first opening
222 located at a proximal region 230 of the coupling element 218 to
a second opening 224 located at a distal end 221 of the elongated
shaft 220. Elongated shaft 220 may be composed of any conductive
material such as metal, for example. Elongated shaft 220 may
include any number of diameter changes incorporated along its
length without deviating from the scope of the present invention.
In the alternative, elongated shaft 220 may be provided with a
uniform diameter along its length.
[0086] With reference to FIGS. 37-38, coupling element 218
comprises a proximal region 230, a center section 232, and a distal
portion 234. Proximal region 230 includes an engagement region 231
dimensioned to engage with the handle portion 240 of the stylet 214
(as described in further detail below). The engagement region 231
may be provided in any suitable geometric configuration to allow
for secure mating with the engagement tabs 144 of the handle 140.
By way of example only, the coupling element 218 is shown in FIGS.
37-38 having a plurality of triangular-shaped indentations 233,
however other shapes are possible. Proximal region 230 may include
at least one tab member 236 that protrudes in a generally lateral
direction from the proximal region 230. By way of example only, as
shown in FIG. 38 proximal region 230 includes two tab members 236
positioned opposite one another and adjacent to first opening 222.
Tab members 236 may be utilized to attach supplemental instruments
and/or apparatuses to the cannula 212. Center section 232 may be
provided with a diameter that is larger than the diameters of the
proximal region 230 and distal portion 234, and may be provided
with a plurality of ridges 235 and/or other features for the
purpose of providing a suitable gripping area for a user. The
distal portion 234 is dimensioned to engage with the elongated
shaft 220 of the cannula 212 and may further be provided with a
recess 237 for engagement with the sheath attachment element 292,
described in further detail below.
[0087] FIG. 39 illustrates an example of a stylet 214 forming part
of the pedicle access system 210. Stylet 214 includes a handle
portion 240 and a needle element 242. Referring to FIGS. 41-42, the
handle portion 240 may (by way of example) resemble a T-handle for
providing a user with a suitable gripping means. By way of example
only, the handle portion 240 may have a substantially hollow
interior that is not fully enclosed. Handle portion 240 includes an
aperture 243 and a pair of engagement tabs 244 extending distally
from handle portion 240. Aperture 243 is dimensioned to allow
passage of the needle element 242 from the handle portion 240.
Engagement tabs 244 extend generally perpendicularly from the
handle 240 and generally parallel to one another such that the
engagement tabs 244 collectively form an interior space 246.
Interior space 246 is dimensioned to receive the proximal region
1230 of the coupling element 218 of the cannula 212. Each
engagement tab 244 is provided with a medial (inwardly-facing)
protrusion 248. Medial protrusions 248 are dimensioned to engage
the engagement region 231 of the coupling element 218, described
above. For this reason, the medial protrusions 248 may be provided
with any geometry complementary to the shape of the engagement
region 231 such that when mated, the engagement tabs 244 (via the
medial protrusions 248) will prevent movement of the engagement
region 231, in effect locking the cannula 212 in place relative to
the stylet 214.
[0088] With reference to FIG. 40, the needle element 242 comprises
an elongated shaft 252 having a proximal region 254 and a distal
region 256. The proximal region 254 includes an attachment element
257 configured to attach to the interior of handle portion 240. The
attachment element 257 is also configured to provide a point of
contact for an electrical stimulation source (e.g. a clip attached
to an electrical source). Elongated shaft 252 extends distally from
proximal region 254 and generally perpendicularly from the handle
240 (and through aperture 243). Needle element 242 is dimensioned
to be inserted through the interior lumen of cannula 212. The
distal region 256 generally includes a distal portion of elongated
shaft 252 and a shaped tip 258 having any form or shape capable of
being driven into the pedicle to create a pilot hole. By way of
example only, shaped tip 258 may have a beveled or double diamond
form. When needle element 242 is fully inserted into cannula 212,
at least a portion of distal region 256 (including shaped tip 258)
may protrude slightly from the second opening 224 of cannula
212.
[0089] Needle element 242 may be composed of any conductive
material, such as metal. Alternatively, needle element 242 may be
composed of a non-conductive material with one or more embedded
conductive elements at or near the distal end (e.g. distal region
256 and/or shaped tip 258) capable of being communicatively linked
with a pedicle integrity testing system. Although shown as separate
parts, the stylet 214 is preferably provided as a single unit, with
the needle element 242 and attachment element 257 molded in place
in the handle 240.
[0090] With reference to FIGS. 43-44, a lock collar 216 is provided
to lockingly mate the cannula 212 and the stylet 214. Lock collar
216 has a generally cylindrical overall shape, and includes a
proximal portion 262, a distal portion 264 and an interior lumen
266 extending therethrough. The proximal portion 262 may have a
diameter greater than that of the distal portion 264 and is
provided with a plurality of friction elements 268 to allow a user
to grasp and turn the lock collar 216. The distal portion 264
includes a generally oval-shaped opening 270 providing access to
the lumen 266. The opening 270 further includes a pair of opposing
protrusions 272 located along the inside edge of opening 270.
Protrusions 272 are located 180.degree. from one another and are
positioned approximately midway between the "long ends" and the
"narrow sides" of the oval-shaped opening 270. Protrusions 272 are
dimensioned to engage the sides of engagement tabs 244 of the
handle 240, described above.
[0091] The interior lumen 266 is dimensioned to receive both of the
engagement tabs 244 of the handle 240. Initially, the pedicle
access system 210 of the present invention may be provided with the
locking collar 216 attached to the stylet 214 in an initial
position. This initial position is defined by the protrusions 272
resting alongside the engagement tabs 244 of the handle 240. The
engagement tabs 244 at this point are disposed in the "long ends"
of the oval-shaped opening 270. Upon insertion of the needle
element 242 into the cannula 212, the distal region 230 of the
coupling element 218 of cannula 212 will enter the space 246 of the
handle 240 such that the medial protrusions 248 are aligned with
(but not yet engaging) the engagement region 231 of the coupling
element 218. At this point, a user would then rotate the lock
collar 216 90.degree. to a second position such that the
protrusions 272 rest in against the engagement tabs 244 and the
engagement tabs 244 rest in the "narrow sides" of the oval-shaped
opening 270, as shown in FIG. 45. Due to the oval-shaped nature of
the opening 270, upon rotation of the lock collar 216, the
engagement tabs 244 will be forced toward one another, and the
medial protrusions 248 will come in contact with and positively
engage the engagement region 231. As noted previously, this
positive engagement prevents the cannula 212 from moving. At the
same time, the lock collar 216 serves to lock the engagement tabs
214 in place, effectively locking the cannula 212 and the stylet
214 together. The pedicle access system 210 is now ready for
use.
[0092] According to a further aspect of the present invention, the
pedicle access system 210 may be provided with a retractable
insulation sheath 217 to electrically insulate the cannula 212 and
stylet 214. The insulation sheath 217 may be composed of a
non-conductive material or coated with a non-conductive polymer
coating to insulate the sheath 217. This prevents shunting of
electrical current during pilot hole formation, increasing the
efficiency with which the stimulation current is delivered to the
target area. Referring to FIG. 46, the insulation sheath 217
includes an insulation tube 274 and a housing member 276. As seen
in FIG. 47, the insulation tube comprises a cannulated, elongated
and generally cylindrical member having a proximal end 278 and a
distal end 280. The proximal end 278 includes at least one tab 282
configured to slideably engage the housing member 276 as set forth
below. In the example shown in FIG. 47, the insulation tube 274
includes a pair of tabs 282 positioned opposite one another,
however any number of tabs 282 may be provided without departing
from the scope of the invention. The distal end 280 may be provided
with a generally tapered surface 284 to allow for an improved
interface with the bone.
[0093] Referring to FIGS. 46 & 48, the housing member 276
comprises an elongated generally cylindrical member having a
proximal end 286, a distal end 287 and an interior lumen 288. The
proximal end 286 includes a shaped engagement feature 289 (e.g. a
recess as shown) dimensioned to engage a sheath attachment element
292 described in further detail below. The housing member 276
further includes at least one elongated track 290 in the form of a
cutout section extending substantially the length of the housing
member 276. The track 290 is dimensioned to slideably receive the
tabs 282 of the insulation tube 274 such that the insulation tube
274 is allowed to migrate within the lumen 288.
[0094] With reference to FIGS. 49-50, an example of a sheath
attachment element 292 is shown. The sheath attachment element 292
may be provided as a generally cylindrical member having an
interior lumen 293. Sheath attachment element 292 is dimensioned to
provide a snap-fit engagement with both the housing member 276 and
the coupling element 218 of cannula 212. The lumen 293 is provided
with a first ridge 294 near a distal end for secure engagement with
recess 289 of the housing member 276. Similarly, the lumen 293 is
provided with a second ridge (not shown) near a proximal end for
engagement with recess 237 of the coupling element 218 (FIG. 37).
During assembly of the pedicle access system 210, the retractable
insulation sheath 217 may be provided with the sheath attachment
element 292 mated to the housing member 276. The cannula 212 is
then inserted into the insulation sheath 217 and sheath attachment
element 292 will then engage the coupling element 218, thus
securely attaching the insulation sheath 217 to the pedicle access
system 210.
[0095] In use, the pedicle access system 210 is provided with the
insulation tube 274 in a first, fully extended position (e.g. FIG.
33). The insulation tube 274 will remain in this position as the
pedicle access system 210 is advanced through an operative corridor
to a bony target site (e.g. a pedicle). Upon initial engagement
with the bony structure, the tip 258 of the needle element 242 and
the distal end 280 of the insulation tube 274 may contact the bone
at approximately the same time. At this point the user may want to
begin monitoring the integrity of the pilot hole formation by using
a stimulation signal as described below. As the needle 242 is
advanced into the bone, forming a pilot hole, the distal end 280
remains engaged to the outside surface of the bone. At the same
time, the proximal end 278 (including tabs 282) of the insulation
tube will advance proximally along the track 290 of the housing
member 276. Due to the insulated nature of insulation tube 274, the
portion of needle element 242 and cannula 212 that protrude from
insulation tube 274 effectively constitute a stimulation region 260
(FIG. 32). As the needle 242 and cannula 212 are advanced into the
bony structure (and the insulation tube 274 remains on the outside
of the bony structure), the stimulation region 260 becomes larger.
Upon completion of the pilot hold formation, the needle 242 and
cannula 212 are withdrawn from the bony structure, and the pedicle
access system 210 may be removed from the operative corridor. A
spring (not shown) or other control mechanism may be provided to
limit the extent of migration of the insulation tube 274 and/or
provide a means for the insulation tube 274 to bias toward
returning to the fully extended position upon removal of the needle
242 from the pilot hole in the pedicle.
[0096] In a significant aspect of the present invention, the
pedicle access systems 10, 110 and 210 described above may be used
in combination with neurophysiology monitoring systems and methods
to conduct pedicle integrity assessments while achieving initial
access to the pedicle. By way of example only, the pedicle access
systems 10, 110 and 210 may be used in combination with the system
and methods shown and described in commonly owned and co-pending
Int'l Patent App. Ser. No. PCT/US02/22247, filed on Jul. 11, 2002,
the contents of which are hereby incorporated by reference into
this disclosure as set forth herein in its entirety.
[0097] With reference to FIG. 51, an example of one such
neurophysiology system 300 includes a display 301, a control unit
302, a patient module 304, an EMG harness 306, including eight
pairs of EMG electrodes 308 and a return electrode 310 coupled to
the patient module 304, and a host of surgical accessories 312,
including an electric coupling device 316 capable of being coupled
to the patient module 304 via one or more accessory cables 314.
[0098] The neurophysiology system 300 performs pedicle integrity
assessments by determining the amount of electrical communication
between a stimulation signal and the adjacent nerve root. To do
this, a stimulation signal is applied to the pilot hole or pedicle
screw via one of the surgical accessories 312. The EMG electrodes
308, positioned over the appropriate muscles, measure the EMG
responses corresponding to the stimulation signal. The relationship
between the EMG response and the stimulation signal is then
analyzed by the system and the results are conveyed to the user on
the display 301. The basic theory underlying the pedicle integrity
test is that given the insulating character of bone, a higher
stimulation current (or current density) is required to evoke an
EMG response when the stimulation signal is applied to an intact
pedicle as opposed to a breached pedicle. Thus, if EMG responses
are evoked by stimulation currents (or current densities) lower
than a predetermined safe level, the surgeon may be alerted that
there is a possible breach. The neurophysiology system may be
provided with software capable of compensating for multiple safe
stimulation thresholds based on different current densities being
applied to the pedicle by certain geometries of different
instruments.
[0099] The pedicle access systems 10, 110 and 210 described above
may be combined to and used in conjunction with the neurophysiology
system 300 by attaching (not shown) the electric coupling device
314 to (for example) the uninsulated region 28 of the cannula 12 of
pedicle access system 10. The electric coupling device 314 may
comprise a number of possible embodiments which permit the device
to attach and hold a surgical tool (such as the pedicle access
system 10) while allowing transmission of a stimulation signal to
the tool. One such electric coupling device 314 utilizes a
spring-loaded plunger to hold the surgical tool and transmit the
stimulation signal. The plunger 318 is composed of a conductive
material such as metal. A nonconductive housing 320 partially
encases the plunger rod 318 about its center. Extending from the
housing 320 is an end plate 324. An electrical cable 326 connects
the electric coupling device 314 to neurophysiology system 300. A
spring (not shown) is disposed within the housing 320 such that in
a natural or "closed" state the plunger 318 is situated in close
proximity to the endplate 324. Exerting a compressive force on the
spring (such as by pulling the cable 326 while holding the housing
320) causes a gap between the end plate 324 and the plunger 318 to
widen to an "open" position, thereby allowing insertion of a
surgical tool between the end plate 324 and plunger 318. Releasing
the cable 326 allows the spring to return to a "closed" position,
causing the plunger 318 to move laterally back towards the endplate
such that a force is exerted upon the surgical tool and thereby
holds it in place between the endplate 324 and the plunger 318.
Thereafter the electrical stimulus may be passed from the
neurophysiology system 300 through the cable 326 and plunger 318 to
the surgical tool.
[0100] Alternatively, the electrical coupling device may be
embodied in the form of a clip 328. The clip 328 is comprised of
two prongs hingedly coupled at a coupling point 330 such that the
clip 328 includes an attachment end 332 and a non-attachment end
334. A stimulation electrode 336 is disposed on the attachment end
332 and communicates with an electric cable 326 extending from the
non-attachment end 334 to the neurophysiology system 300. In a
"closed" position the prong ends at the attachment end 332 touch.
Depressing the prongs at the non-attachment end 334 in a direction
towards each other causes a gap to form between the prong ends at
the attachment end 332. Positioning the "opened" attachment end 332
over a desired surgical tool (such as the pedicle access system 10)
and releasing the force on the non-attachment end 334 causes the
attachment end 332 to pinch tight on the surgical tool and thereby
allow the electrical stimulus to pass from neurophysiology system,
through the stimulation electrode 336, to the surgical tool.
[0101] The pedicle access system 10 may thus be used to safely
access the pedicle and safely form a pilot hole. To do this, the
cannula 12, stylet 14, and T-handle 16 are preferably all combined
and locked together as described above. Using the T-handle 16 to
control the movement and positioning of the pedicle access system
10, the surgeon may position the stimulation point on the desired
target site. Next, the electric coupling device 116 may be attached
to the uninsulated region 28 of cannula 12 and the T-handle 16 may
be removed to facilitate the use of a tool such as a needle driver.
Stimulation signals are delivered to the pedicle access system 10
and emitted from the stimulation region 60 as it is being driven in
to the bone, forming the pilot hole. Should the neurophysiology
system 300 report a potential breach of the pedicle, pilot hole
formation may be halted and any steps deemed to be necessary by the
surgeon, based on his or her professional judgment, may be taken to
correct the problem. Alternatively, the electric coupling device
316 may be attached before positioning the pedicle access system
10, and the neurophysiology system 300 may be employed to monitor
the proximity of any nerves during positioning.
[0102] In another significant aspect of the present invention, the
pedicle access system 10 may be used in conjunction with spinal
fixation systems that require access to pedicle target sites and
need pilot holes, including but not limited to those systems shown
and described in commonly owned and co-pending U.S. patent
application Ser. No. 11/031,506 filed Jan. 6, 2005, and commonly
owned and co-pending Int'l Patent App. Ser. No. PCT/US05/032300
filed Sep. 8, 2005. After positioning the pedicle access system 10
on the desired pedicle target site and safely forming a pilot hole
as described above, the T-handle 16 and stylet 14 may be unlocked
and removed from the cannula 12, leaving the cannula 12 positioned
in the pilot hole. Guide wires subsequently used by the spinal
fixation systems may then be safely deployed to the pilot hole
through the cannula 12. Once the guide wire is in position the
cannula 12 may be removed from the target site and the surgeon may
commence use of the surgical fixation system.
[0103] While the invention is susceptible to various modification
and alternative forms, specific embodiments thereof have been shown
by way of example in the drawings and are herein described in
detail. It should be understood, however, that the description
herein of specific embodiments is not intended to limit the
invention to the particular forms disclosed, but on the contrary,
the invention is to cover all modifications, equivalents, and
alternatives falling within the scope and spirit of the invention
as defined herein.
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