U.S. patent application number 11/193278 was filed with the patent office on 2006-08-17 for spinal ligament modification devices.
This patent application is currently assigned to X-Sten, Inc.. Invention is credited to Donald Schomer, Murray D. Solsberg, Bryce Way.
Application Number | 20060184175 11/193278 |
Document ID | / |
Family ID | 35787466 |
Filed Date | 2006-08-17 |
United States Patent
Application |
20060184175 |
Kind Code |
A1 |
Schomer; Donald ; et
al. |
August 17, 2006 |
Spinal ligament modification devices
Abstract
A method for treating stenosis in a spine comprises
percutaneously accessing the epidural space in a stenotic region of
interest, compressing the thecal sac in the region of interest to
form a safety zonem, inserting a tissue removal tool into tissue in
the working zone, using the tool to percutaneously reduce the
stenosis; and utilizing imaging to visualize the position of the
tool during at least a part of the reduction step. A tissue
excision system for performing percutaneous surgery, comprises a
cannula comprising a tissue-penetrating member having a distal end
defining an aperture on one side thereof, an occluding member
slidably received on or in the cannula and closing the aperture
when the occluding member is adjacent the cannula distal end, means
for engaging adjacent tissue via the aperture, and cutting means
for resecting a section of the engaged tissue.
Inventors: |
Schomer; Donald; (Englewood,
CO) ; Solsberg; Murray D.; (Englewood, CO) ;
Way; Bryce; (US) |
Correspondence
Address: |
CONLEY ROSE, P.C.
P. O. BOX 3267
HOUSTON
TX
77253-3267
US
|
Assignee: |
X-Sten, Inc.
Englewood
CO
|
Family ID: |
35787466 |
Appl. No.: |
11/193278 |
Filed: |
July 29, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60592099 |
Jul 29, 2004 |
|
|
|
Current U.S.
Class: |
606/83 |
Current CPC
Class: |
A61B 2017/320008
20130101; A61B 2017/320064 20130101; A61B 10/0275 20130101; A61B
17/0401 20130101; A61B 17/320016 20130101; A61B 2017/0427 20130101;
A61B 17/3401 20130101; A61B 2017/0412 20130101; A61B 17/1671
20130101; A61B 17/32053 20130101; A61B 10/0233 20130101; A61B
17/3478 20130101; A61B 2017/0419 20130101; A61B 2017/06176
20130101; A61B 2017/00349 20130101; A61B 2017/06052 20130101; A61B
17/0482 20130101; A61B 2017/00261 20130101; A61B 2017/32004
20130101; A61B 2017/0437 20130101; A61B 10/0283 20130101; A61B
17/320783 20130101; A61B 17/32002 20130101; A61B 2010/045
20130101 |
Class at
Publication: |
606/083 |
International
Class: |
A61B 17/32 20060101
A61B017/32 |
Claims
1. A device for removing tissue from a stenosed spine, comprising:
a cannula having a side aperture proximal its distal end; an
elongate body housed within said cannula and comprising two
radially extendable arms constructed such that radially extending
said arms causes them to extend outward through said side aperture
and retracting said arms causes them to close.
2. The device according to claim 1 wherein said arms each include
an opposing edge and at least one opposing edge includes teeth or
ridges.
3. The device according to claim 1 wherein said opposing edges
comprise cutting blades.
4. The device according to claim 1, further including an outer
cutting element slidably mounted on one of said cannula and said
body.
5. The device according to claim 1, further including a retractable
tissue-retrieval device.
6. The device according to claim 1 wherein said tissue-retrieval
device can be extended into said cannula to engage a tissue sample,
retracted for removal of the tissue sample, and re-extended into
the outer needle.
7. The device according to claim 1 wherein said tissue-retrieval
device comprises a barb.
8. The device according to claim 1, further including means for
removing tissue from the tissue-engaging device.
9. The device according to claim 1 wherein said tissue removing
means comprises a keyhold slot.
10. The device according to claim 1 wherein said elongate body has
first and second ends and wherein said arms are predisposed to
extend outwardly when said first and second ends are brought
together.
11. The device according to claim 1 wherein said elongate body has
first and second ends and wherein said arms are prevented from
buckling inwardly when said first and second ends are brought
together.
12. The device according to claim 1 wherein said elongate body
comprises an azimuthal portion of a hollow tube with a longitudinal
slot extending partially between its ends.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims benefit of U.S. application Ser. No.
60/592,099 filed Jul. 29, 2004, and entitled "Device for
Percutaneous Treatment of Spinal Stenosis," which is incorporated
herein by reference in its entirety.
TECHNICAL FIELD OF THE INVENTION
[0002] The present invention relates to a minimally invasive
method, device and system for treating spinal disorders using
imaging guidance. This invention also relates to devices used to
reduce stenosis and increase the cross-sectional area of the spinal
canal and to devices used to treat excess fat within the spinal
canal or epidural lipomatosis. This invention also relates to
methods, devices, therapies and medications used to treat disorders
that involve the epidural space.
BACKGROUND OF THE INVENTION
[0003] The spine comprises a stack of vertebrae with an
intervertebral disc between adjacent vertebrae. As shown in FIG. 1,
each vertebra 10 includes a vertebral body 12 that supports a bony
ring 14. The bony ring 14 consists of laminae 16, spinous process
18, transverse processes 20, superior articular processes 22, and
pedicles 24. Together with vertebral body 12, these vertebral
components define the spinal canal. The laminae 16 are joined in
the midline by the spinous process 18. In the cervical and thoracic
region the dural sac 32 contains the spinal cord, which comprises
nerves 34 surrounded by cerebrospinal fluid. The fluid-filled sac
is therefore compressible. The ligamentum flavum 26 is an elastic
yellow ligament connecting the laminae of adjacent vertebrae.
[0004] In degenerative conditions of the spine, narrowing of the
spinal canal (stenosis) can occur. Lumbar spinal stenosis is often
defined as a dural sac cross-sectional area less than 100 mm.sub.2
or an anteroposterior (AP) dimension of the canal of less than
10-12 mm for an average male.
[0005] The source of most cases of lumbar spinal stenosis is
thickening of the ligamentum flavum. Spinal stenosis may also be
caused by subluxation, facet joint hypertrophy, osteophyte
formation, underdevelopment of spinal canal, spondylosis deformans,
degenerative intervertebral discs, degenerative spondylolisthesis,
degenerative arthritis, ossification of the vertebral accessory
ligaments and the like. A less common cause of spinal stenosis,
which usually affects patients with morbid obesity or patients on
oral corticosteroids, is excess fat in the epidural space. The
excessive epidural fat compresses the dural sac, nerve roots and
blood vessels contained therein and resulting in back and leg pain
and weakness and numbness of the legs. Spinal stenosis may also
affect the cervical and, less commonly, the thoracic spine.
[0006] Patients suffering from spinal stenosis are typically first
treated with exercise therapy, analgesics and anti-inflammatory
medications. These conservative treatment options frequently fail.
If symptoms are severe, surgery is required to decompress the canal
and nerve roots.
[0007] To correct stenosis in the lumbar region, an incision is
made in the back and the muscles and supporting structures are
stripped away from the spine, exposing the posterior aspect of the
vertebral column. The thickened ligamentum flavum is then exposed
by removal of the bony arch (lamina) covering the back of the
spinal canal (laminectomy). The thickened ligament can then be
excised with sharp dissection with a scalpel or punching
instruments such as a Kerison punch that is used to remove small
chips of tissue. The procedure is performed under general
anesthesia. Patients are usually admitted to the hospital for
approximately five to seven days depending on the age and overall
condition of the patient. Patients usually require between six
weeks and three months to recover from the procedure. Many patients
need extended therapy at a rehabilitation facility to regain enough
mobility to live independently.
[0008] Much of the pain and disability after an open laminectomy is
due to the tearing and cutting of the back muscles, blood vessels
and supporting ligaments and nerves that occurs during the exposure
of the spinal column. Also, because these spine stabilizing back
muscles and ligaments are stripped and cut off, the spine these
patients frequently develop spinal instability
post-operatively.
[0009] Minimally invasive techniques result in less post-operative
pain and faster recovery compared to traditional open surgery.
Percutaneous interventional spinal procedures can be performed with
local anesthesia, thereby sparing the patient the risks and
recovery time required with general anesthesia. Another advantage
is that there is less damage to the paraspinal muscles and
ligaments with minimally invasive techniques reducing pain and
preserving these important stabilizing structures.
[0010] Various techniques for minimally invasive treatment of the
spine are known. Microdiscectomy is performed by making a small
incision in the skin and deep tissues to create a portal to the
spine. A microscope is then used to aid in the dissection of the
adjacent structures prior to discectomy. The recovery for this
procedure is much shorter than traditional open discectomies.
Percutaneous discectomy devices with fluoroscopic guidance have
been used successfully to treat disorders of the disc but not to
treat spinal stenosis or the ligamentum flavum directly.
Arthroscopy or direct visualization of the spinal structures using
a catheter or optical system have also been proposed to treat
disorders of the spine including spinal stenosis however these
devices still use miniaturized standard surgical instruments and
direct visualization of the spine similar to open surgical
procedures. These devices and techniques are limited by the small
size of the canal and these operations are difficult to perform and
master. Also these procedures are painful and often require general
anesthesia. The arthroscopy procedures are time consuming and the
fiber optic systems are expensive to purchase and maintain.
[0011] In addition, because the nerves of the spine pass through
the core of the spine directly in front of the ligamentum flavum,
any surgery, regardless of whether is open or percutaneous includes
a risk of damage to those nerves.
[0012] Hence, it remains desirable to provide a simple method and
device for treating spinal stenosis and other spinal disorders
without requiring open surgery. It is further desired to provide a
system whereby the risk of damage to the thecal sac containing the
spinal nerves can be reduced.
SUMMARY OF THE INVENTION
[0013] The present invention provides a method, device and system
for treating spinal stenosis or other spinal disorders using image
guidance in combination with percutaneous techniques. The present
system is referred to as a minimally invasive ligament
decompression (MILD) device. In some embodiments, the present
invention provides a means for compressing the thecal sac within
the epidural space so as to provide a safety zone in which further
surgical procedures may be performed without risk of damaging
nearby tissues or the thecal sac itself.
[0014] In further embodiments, the present method comprises the
steps of a) percutaneously accessing the epidural space in a region
of interest with image guidance; b) at least partially compressing
the thecal sac in the region of interest by injecting a fluid into
the epidural space to form a safety zone; c) percutaneously
accessing a working zone in at least one of the ligamentum flavum
and overlying dorsal tissues with image guidance, where the safety
zone lies between the working zone and thecal sac; d) inserting a
tissue removal tool into the working zone; e) using the tool remove
tissue so as to reduce the stenosis; and f) utilizing at least one
imaging system to identify tissues for removal. By way of example,
radiologic imaging may be used to safely guide the tool(s) to
target tissues and visualize the position of the tool during at
least part of the process.
[0015] In preferred embodiments, the device provides an anchored
pathway to the working zone so that excised tissue can be shuttled
out of the area for successive extractions without time consuming
repositioning of the tool(s). In other embodiments, the tool can be
repositioned as often as is necessary to achieve the desired
modifications. In still other embodiments, the present invention
includes percutaneous methods for placing a retractable anchor in
the ligamentum flavum and attaching it to the fascia or bone so as
to retract the ligamentum flavum, thus expanding the spinal canal.
In still other embodiments, the invention includes a percutaneous
mechanical suture system and method for placing a stitch in the
ligament and then anchoring the stitch so as to retract the
ligamentum flavum. The laminotomy site can serve as a site for a
bone anchor and/or flange for a suture to anchor the ligament.
[0016] Particular embodiments of the invention include a method for
treating stenosis in a spine, the spine including a thecal sac and
a canal and an epidural space therebetween, wherein the stenosis
determines a region of interest in the spine. The method may
comprise the steps of a) percutaneously accessing the epidural
space in the region of interest, b) compressing the thecal sac in
the region of interest by injecting a fluid to form a safety zone
and establish a working zone, with the safety zone lying between
the working zone and the thecal sac, c) inserting a tissue removal
tool into tissue in the working zone, d) using the tool to
percutaneously reduce the stenosis. It is preferred to use at least
one imaging system to visualize the position of the tool during at
least a part of step d).
[0017] Step d) may include 1) engaging adjacent tissue in the
working zone, 2) excising the engaged tissue, 3) removing the
resulting tissue section from the working zone, and 4) repeating
steps 1) through 3) until a desired amount of tissue has been
removed. The removed tissue may comprise a portion of the
ligamentum flavum, fat, and/or bone. Alternatively, the step d) may
include i) providing an anchor having first and second
tissue-engaging ends, ii) engaging the ligamentum flavum with the
first tissue-engaging end, iii) using the engaged first end to pull
at least a portion of the ligamentum flavum into a desired
position, and iv) using the second tissue-engaging end to anchor
the anchor such that the ligamentum flavum is retained in a desired
position. The anchor may be anchored to paraspinous tissue or to
other bone.
[0018] The invention also relates to an injectable fluid, which may
include a contrast agent and may have a temperature-dependent
viscosity such that it is more viscous at 37.degree. C. than at
30.degree. C.
[0019] The tool of steps c) and d) may include an outer cannulated
scalpel or needle, a tissue-engaging means, and a cutting or
resecting element and may further include means for removing tissue
from the tissue-engaging means. The tissue-engaging means may
comprise a resilient hook.
[0020] Some embodiments of the invention may take the form of a kit
for performing a procedure on a spine, in which the kit includes an
insertion member for accessing the epidural space, and an
expandable device adapted to be inserted into the epidural space by
the insertion member and expanded so as to compress a portion of
the thecal sac and provide a safety zone within the epidural space.
The expandable device may comprise a volume of a contrast medium,
such as a radio-opaque non-ionic myelographic contrast medium,
and/or may comprise a volume of a medium that is injectable at
ambient temperatures and more viscous at body temperature. The
contrast medium may include a bioactive agent and/or a steroid.
[0021] The kit may further include a surgical device, which in turn
may comprise a hollow cannulated scalpel or outer needle having a
side aperture proximal its distal end, and an elongate body housed
within the outer needle and comprising two radially extendable arms
constructed such that radially extending the arms causes them to
extend outward through the side aperture and retracting said arms
causes them to close. In other embodiments, the kit may comprise
means for engaging the ligamentum flavum and means for resecting a
section of the ligamentum flavum and the means for resecting may in
turn comprise a trocar, a barbed member coaxially received within
the trocar, and a blade. In other embodiments, the surgical device
may comprise means for engaging a first anatomical structure and
means for affixing the first anatomical structure to a second
anatomical structure. Alternatively, the surgical device may
comprise means for engaging the ligamentum flavum and soft tissues
in the Para spinal region of the patient so as to anchor the
ligamentum flavum, and/or means for engaging and retracting the
ligamentum flavum and means for anchoring the retracted ligamentum
flavum.
[0022] In still other embodiments, a percutaneous tool for treating
a stenosed spine by removing tissue therefrom, comprises an
cannulated scalpel, a first tissue-engaging means housed within the
cannulated scalpel, and a cutting element configured to resect a
sample of tissue that is engaged by the first tissue-engaging
means. The cannulated scalpel may include a side aperture through
which the first tissue-engaging means engages the tissue and the
tool may further include a second tissue-engaging device that is
adapted to remove the resected tissue sample from the first
tissue-engaging device. The second tissue-engaging device may
comprise a keyhole slot.
[0023] In still other embodiments, a device for removing tissue
from a stenosed spine may comprise a hollow outer needle having a
side aperture proximal its distal end, an elongate body housed
within the outer needle and comprising two radially extendable arms
constructed such that radially extending the arms causes them to
extend outward through said side aperture and retracting the arms
causes them to close. Each arm may include an opposing edge and at
least one opposing edge may include teeth or ridges or the opposing
edges may comprise cutting blades.
[0024] In certain embodiments, the present percutaneous tissue
excision system may include an inner needle having one or more
barbs extending around 120 degrees of its circumference. The
barb(s) may be directed toward the proximal end of the needle. The
tool may further include an occluding member that closes a side
aperture in the cannula may include a distal cutting edge adapted
to cut tissue. The tool may further comprise an outer cutting
member. The tissue-engaging components of the device preferably
comprise a resilient metal that can withstand repeated elastic
deflections.
[0025] In yet further other embodiments, a method for preventing
leakage of cerebrospinal fluid from an opening in a thecal sac in a
spine may comprise accessing the epidural space in the vicinity of
the opening and inserting a volume of fluid into the epidural
space, where the fluid thickens as it attains body temperature such
that the fluid blocks the opening in the thecal sac.
[0026] In further embodiments, a bone cutting device can be used to
access the ligamentum flavum and epidural space, to perform a
laminotomy or to allow placement of a cannula. Using a cannula
fixed within (extending through) the lamina, a cutting device can
be inserted into and removed from the ligamentum flavum and/or
epidural space. Real-time use of fluoroscopy or other imaging means
during the subsequent MILD procedure can be minimized with the
appropriate placement of tools following use of the bone cutting
device. The laminotomy creates a portal and gives a steady purchase
for instruments and instrument exchange. In addition, either the
laminotomy site or the neighboring tissue, including bone and/or
other tissue, can be used as an anchoring site for sutures or other
tissue-engaging means.
BRIEF DESCRIPTION OF THE DRAWINGS
[0027] For a more complete understanding of the invention,
reference is made to the accompanying drawings, wherein:
[0028] FIG. 1 is an illustration of a vertebra showing the spinal
canal with the thecal sac and a normal (un-stenosed) ligamentum
flavum therein;
[0029] FIG. 2 is an illustration of a vertebra showing the spinal
canal with the thecal sac and a thickened ligamentum flavum
therein;
[0030] FIG. 3 is an enlarged cross-section of the spine of FIG. 2,
showing a safety zone created by compression of the thecal sac;
[0031] FIG. 4 is the enlarged cross-section of FIG. 3, showing a
tissue removal tool positioned in the ligamentum flavum;
[0032] FIGS. 5-9 are a series of illustrations showing tissue
excision by a tissue-excision tool constructed in accordance with a
first embodiment of the invention;
[0033] FIGS. 10-14 are a series of illustrations showing tissue
excision by a tissue-excision tool constructed in accordance with a
second embodiment of the invention;
[0034] FIGS. 15 and 17 are sequential illustrations showing removal
of tissue from a tissue-excision tool by a tissue-removal device
constructed in accordance with an embodiment of the invention;
[0035] FIGS. 16 and 18 are end views of the tissue-removal device
of FIGS. 15 and 17, respectively;
[0036] FIG. 19 shows an alternative embodiment of a grasping needle
with a corkscrew shape;
[0037] FIG. 20 is a perspective view of a tissue-excision tool
constructed in accordance with a third embodiment of the
invention;
[0038] FIGS. 21 and 22 are enlarged cross-sectional and perspective
views, respectively, of the grasping device of FIG. 20 in its
retracted position;
[0039] FIGS. 23 and 24 are enlarged cross-sectional and perspective
views, respectively, of the grasping device of FIG. 20 in its
extended position;
[0040] FIG. 25 is a schematic illustration of one embodiment of a
double-ended ligament anchor being deployed in a ligamentum
flavum;
[0041] FIG. 26 shows the device of FIG. 25 after full
deployment;
[0042] FIG. 27 is a perspective view of an entire tool constructed
in accordance with preferred embodiments;
[0043] FIG. 28 is an enlarged cross-sectional view of the distal
tip of the tool of FIG. 27 with the aperture partially opened;
[0044] FIG. 29 is a cross-sectional view of the handle end of the
tool of FIG. 27;
[0045] FIG. 30 is cross-section of a tissue-removal device
constructed in accordance with an alternative embodiment of the
invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0046] The epidural space is the space between the ligamentum
flavum and the thecal sac. This space is filled with blood vessels
and fat. The nerves contained within the thecal sac are normally
surrounded by cerebrospinal fluid (CSF). When the ligamentum flavum
hypertrophies, the blood vessels that supply the nerves of the
cauda equina are compressed. This results in ischemic pain termed
spinal claudication. The nerve roots may also be compressed
resulting in back and/or leg pain.
[0047] Referring again to FIG. 1, the posterior border of the
normal epidural space 30 is formed by the normally thin ligamentum
flavum 26 and posterior epidural fat (not shown). Ligamentum flavum
26 extends from the lamina above the interspinous space to the
lamina below the interspinous space. The dural sleeve (thecal sac)
32 contains nerve roots 34 surrounded by cerebrospinal fluid. The
nerve roots 34 normally comprise only a small proportion of the
thecal sac volume.
[0048] In FIG. 2, spinal stenosis is present. Ligamentum flavum 26
is markedly thickened, compressing the posterior margin of dural
sleeve 32. As shown in FIG. 2, the posterior margin of the dural
sleeve 32 is apposed to the ligamentum flavum and the epidural
space is only a potential space. Because more than 90% of the
volume of the thecal sac in the lumbar region is filled by CSF, the
thecal sac is highly compressible. Thus, even though stenosis may
be causing compression of the thecal sac (and associated pain or
discomfort), in most instances it will be possible to temporarily
compress the thecal sac further. Thus, according to preferred
embodiments of the invention, thecal sac 32 is compressed in a
region of interest by applying pressure to the outside of the sac
so that at least a portion of the CSF is forced out of the region
of interest.
Creation of Safety Zone
[0049] According to certain embodiments, thecal sac 32 is
compressed by injecting a standard radio-opaque non-ionic
myelographic contrast medium or other imagable or non-imagable
medium into the epidural space in the region of interest. This is
preferably accomplished with a percutaneous injection. The result
is illustrated in FIG. 3. The presence of the fluid gently
compresses and displaces the dural sleeve 32 in the region of
interest, creating a safety zone 40 between thecal sac 32 and
ligamentum flavum 26. Sufficient injectable fluid is preferably
injected to displace the CSF out of the region of interest and
compress the thecal sac to at least a desired degree. The injected
medium is preferably substantially contained within the confines of
the epidural space extending to the margins of the nerve root
sleeves. The epidural space is substantially watertight and the
fatty tissues and vascularization in the epidural space, combined
with the viscous properties of the preferred fluids, serve to
substantially maintain the injected medium in the desired region of
interest. This novel method for protecting the neural column may be
referred to hereinafter as "contrast-guided dural protection."
[0050] Once a safety zone 40 has been created, a tool 100, such as
the tissue excision devices and tissue retraction devices described
below, can be inserted into the ligamentum flavum 26, as
illustrated in FIG. 4. While it is preferred that the tip of the
tool remain within the ligament as shown, the presence of safety
zone 40 ensures that the thecal sac will not be damaged even if the
tool breaks through the anterior surface of ligament 26. For
insertion of the tool, a fluoroscopic window of access (FWA) is
defined by the inferior margin of the lamina (contra lateral to the
point of instrument entry in the soft tissues) and the dorsal
margin of the contrast material that defines the epidural space.
This FWA is roughly orthogonal to the long axis of the cutting
instrument, which parallels the inferior surface of the lamina as
in FIG. 4. The fluoroscopic plane of projection is preferably but
not necessarily oriented 20-45 degrees from normal (AP
projection).
[0051] Because the present techniques are preferably performed
percutaneously, certain aspects of the present invention can be
facilitated by imaging. In this context, the spine can be imaged
using any suitable technology, including but not limited to 2D, 3D
fluoroscopy, CT, MRI, ultrasound or with direct visualization with
fiber optic or microsurgical techniques. Stereotactic or
computerized image fusion techniques are also suitable. Fluoroscopy
is currently particularly well-suited to the techniques disclosed
herein. Fluoroscopic equipment is safe and easy to use, readily
available in most medical facilities, relatively inexpensive. In a
typical procedure, using direct biplane fluoroscopic guidance and
local anesthesia, the epidural space is accessed adjacent to the
surgical site as described above.
[0052] If the injected medium is radio-opaque, as are for example
myelographic contrast media, the margins of the expanded epidural
space will be readily visible using fluoroscopy or CT imaging.
Thus, the safety zone created by the present contrast-guided dural
compression techniques can reduce the risk of damage to the spinal
cord during procedures to remove or displace portions of the
ligamentum flavum and/or laminae in order to treat spinal
stenosis.
Injectable Medium
[0053] If desired, the injected medium can be provided as a
re-absorbable water-soluble gel, so as to better localize the
safety zone at the site of surgery and reduce leakage of this
protective layer from the spinal canal. An injectable gel is a
significant improvement on prior epidural injection techniques. The
gel is preferably substantially more viscid than conventional
contrast media and the relatively viscid and/or viscous gel
preferably tends to remain localized at the desired site of
treatment as it does not spread as much as standard liquid contrast
media that are used in epidurography. The injected gel is
preferably sufficiently viscous that it remains substantially
within the local epidural space. This results in more uniform
compression on the thecal sac and less leakage of contrast out of
the canal. In addition, preferred embodiments of the gel are
re-absorbed more slowly than conventional contrast media, allowing
for better visualization during the course of the surgical
procedure.
[0054] In some embodiments, a contrast agent can be included in the
gel itself, so that the entire gel mass is imagable. In other
embodiments, an amount of contrast can be injected first, followed
by the desired amount of gel, or an amount of gel can be injected
first, followed by the desired amount of contrast. In this case,
the contrast agent is captured on the surface of the expanding gel
mass, so that the periphery of the mass is imagable.
[0055] Any standard hydrophilic-lipophilic block copolymer
(Pluronic) gel such as are known in the art would be suitable and
other gels may be used as the injectable medium. The gel preferably
has an inert base. In certain embodiments, the gel material is
liquid at ambient temperatures and can be injected through a small
bore (such as a 27 gauge needle). The gel then preferably becomes
viscous when warmed to body temperature after being injected. The
viscosity of the gel can be adjusted through the specifics of the
preparation. The gel or other fluid is preferably sufficiently
viscid or viscous at body temperature to compress and protect the
thecal sac in the manner described above and to remain sufficiently
present in the region of interest for at least about 30 minutes.
Thus, in some embodiments, the injected gel attains a viscosity
that is two, three, six or even ten times that of the fluids that
are typically used for epidurograms.
[0056] In certain embodiments, the injected medium undergoes a
reversible change in viscosity when warmed to body temperature so
that it can be injected as a low-viscosity fluid, thicken upon
injection into the patient, and be returned to its low-viscosity
state by cooling. In these embodiments, the injected medium is
injected as desired and thickens upon warming, but can be removed
by contacting it with a heat removal device, such as an aspirator
that has been provided with a cooled tip. As a result of localized
cooling, the gel reverts to its initial non viscous liquid state
and can be easily suctioned up the cooled needle or catheter.
[0057] An example of a suitable contrast medium having the desired
properties is Omnipaque.RTM. 240 available from Nycomed, New York,
which is a commercially available non-ionic iodinated myelographic
contrast medium. Other suitable injectable media will be known to
those skilled in the art. Because of the proximity to the spinal
nerves, it is preferred not to use ionic media in the injectable
medium. The preferred compositions are reabsorbed relatively
rapidly after the procedure. Thus any residual gel compression on
the thecal sac after the MILD procedure resolves relatively
quickly. For example, in preferred embodiments, the gel would have
sufficient viscosity to compress the thecal sac for thirty minutes,
and sufficient degradability to be substantially reabsorbed within
approximately two hours.
[0058] The injected contrast medium further may further include one
or more bioactive agents. For example, medications such as those
used in epidural steroid injection (e.g. Depo medrol, Celestone
Soluspan) may be added to the epidural gel to speed healing and
reduce inflammation, scarring and adhesions. The gel preferably
releases the steroid medication slowly and prolongs the
anti-inflammatory effect, which can be extremely advantageous.
Local anesthetic agents may also be added to the gel. This prolongs
the duration of action of local anesthetic agents in the epidural
space to prolong pain relief during epidural anesthesia. In this
embodiment the gel may be formulated to slow the reabsorption of
the gel.
[0059] The present gels may also be used for epidural steroid
injection and perineural blocks for management of acute and chronic
spinal pain. Thrombin or other haemostatic agents can be added if
desired, so as to reduce the risk of bleeding.
[0060] In some embodiments, the gel may also be used as a
substitute for a blood patch if a CSF leak occurs. The gel may also
be used as an alternative method to treat lumbar puncture
complications such as post-lumbar puncture CSF leak or other causes
of intracranial hypotension. Similarly, the gel may be used to
patch postoperative CSF leaks or dural tears. If the dural sac were
inadvertently torn or cut, then gel could immediately serve to seal
the site and prevent leakage of the cerebral spinal fluid.
Percutaneous Tissue Excision
[0061] After safety zone 40 has been created, the margins of the
epidural space are clearly demarcated by the injected medium and
can be visualized radiographically if an imagable medium has been
used. As mentioned above, percutaneous procedures can now safely be
performed on the ligamentum flavum and/or surrounding tissues
without injuring the dural sac or nerves and the spinal canal can
be decompressed using any of several techniques. Suitable
decompression techniques include removal of tissue from the
ligamentum flavum, laminectomy, laminotomy, and ligament retraction
and anchoring.
[0062] In some embodiments, all or a portion of the ligamentum
flavum and/or lamina are excised using a percutaneous tissue
excision device or probe 100, which may hereinafter be referred to
as the MILD device. As shown schematically in FIG. 4, a device 100
may be placed parallel to the posterior and lateral margin of the
safety zone 40 with its tip in the ligamentum flavum 26.
[0063] Preferred embodiments of the present tissue excision devices
and techniques can take several forms. In the discussion below, the
distal ends of the tools are described in detail. The construction
of the proximal ends of the tools, and the means by which the
various components disclosed herein are assembled and actuated,
will be known and understood by those skilled in the art.
[0064] By way of example, in the embodiment shown in FIG. 4 and as
illustrated in FIG. 5, device 100 may be a coaxial excision system
50 with a sharpened or blunt tip that is placed obliquely into the
thickened ligamentum flavum 26 posterior to safety zone 40 under
fluoroscopic guidance. The needle is preferably placed parallel to
the posterior margin of the canal. Excision system 50 is preferably
manufactured from stainless steel, titanium or other suitable
durable biocompatible material. As shown in FIGS. 5-10, an outer
needle or cannula 51 has an opening or aperture 52 on one side that
is closed during insertion by an inner occluding member 54.
Aperture 52 is readily visible under imaging guidance. Once needle
51 is positioned in the ligamentum flavum or other tissue removal
site, inner occluding member 54 is removed or retracted so that it
no longer closes aperture 52 (FIG. 6). Aperture 52 is preferably
oriented away from the epidural space so as to further protect the
underlying structures from injury during the surgical procedure. If
it was not already present in the tool, a tissue-engaging means 56
is inserted through outer needle 51 to aperture 52 so that it
contacts adjacent tissue, e.g. the ligamentum flavum, via aperture
52.
[0065] Tissue-engaging means 56 may be a needle, hook, blade, tooth
or the like, and preferably has at least one flexible barb or hook
58 attached to its shaft. The barb 58 or barbs may extend around
approximately 120 degrees of the circumference of the shaft. Barbs
58 are preferably directed towards the proximal end of the tool.
When needle 56 is retracted slightly, barbs 58 allow it to engage a
segment of tissue. Depending on the configuration of barbs 58, the
tissue sample engaged by needle 56 may be generally cylindrical or
approximately hemispherical. Once needle 56 has engaged the desired
tissue, inner occluding means 54, which is preferably provided with
a sharpened distal edge, is advanced so that it cuts the engaged
tissue section or sample loose from the surrounding tissue. Hence
occluding means 54 also functions as a cutting means in this
embodiment. In alternative embodiments, such as FIGS. 10-14
discussed below, a cylindrical outer cutting element 60 may
extended over outer needle 51 and used in place of occluding member
54 to excise the tissue sample.
[0066] Referring still to FIGS. 5-9, once the tissue sample has
been cut, tissue-engaging needle 56 can be pulled back through
outer needle 51 so that the segment of tissue can be retrieved and
removed from the barbs (FIG. 8). The process or engaging and
resecting tissue may be repeated (FIG. 9) until the canal is
adequately decompressed.
[0067] Referring briefly to FIGS. 10-14, in other embodiments, a
tissue-engaging hook 64 can be used in place of needle 56 and an
outer cutting member 60 can be used in place of inner occluding
member 54. Hook 64 may comprise a length of wire that has been bent
through at least about 270.degree., more preferably through
315.degree., and still more preferably through about 405.degree..
Alternatively or in addition, hook 64 may comprise Nitinol.TM., or
any other resilient metal that can withstand repeated elastic
deflections. In the embodiment illustrated, hook 64 includes at
least one barb 58 at its distal end. In some embodiments, hook 64
is pre-configured in a curvilinear shape and is retained within
tool 100 by outer cutting member 60. When cutting member 60 is
retracted, the curved shape of hook 64 urges its outer end to
extend outward through aperture 52. If desired, hook 64 can be
advanced toward the distal end of tool 100, causing it to extend
farther into the surrounding tissue. In some embodiments, hook 64
is provided with a camming surface 66. Camming surface 66 bears on
the edge of opening 52 as hook 64 is advance or retracted and
thereby facilitates retraction and retention of hook 64 as it is
retracted into the tool. In these embodiments, hook 64 may not
extend through aperture 52 until it has been advanced sufficiently
for camming surface 66 to clear the edge of the opening. Hook 64
may alternatively be used in conjunction with an inner occluding
member 54 in the manner described above. As above, hook 64 can be
used to retrieve the engaged tissue from the distal end of the
tool.
[0068] In still other embodiments, the tissue-engaging means may
comprise a hook or tooth or the like that engages tissue via
aperture 52 by being rotated about the tool axis. In such
embodiments (not shown) and by way of example only, the
tissue-engaging means could comprise a partial cylinder that is
received in outer cannula 51 and has a serrated side edge. Such a
device can be rotated via a connection with the tool handle or
other proximal device. As the serrated edge traverses aperture 52
tissue protruding into the tool via the aperture is engaged by the
edge, whereupon it can be resected and retrieved in the manner
disclosed herein.
[0069] In preferred embodiments, the working tip of tool 100
remains within the ligamentum flavum and does not penetrate the
safety zone 40. Nonetheless, safety zone 40 is provided so that
even an inadvertent penetration of the tool into the epidural space
will not result in damage to the thecal sac. Regardless of the
means by which the tissue is engaged and cut, it is preferably
retrieved from the distal end of the tool so that additional tissue
segments can be excised without requiring that the working tip of
the tool be repositioned. A tissue-removal device such as that
described below is preferably used to remove the tissue from the
retrieval device between each excision.
Tissue Removal
[0070] Each piece of tissue may be removed from barbs 58 by pushing
tissue-engaging means 56 through an opening that is large enough to
allow passage of the flexible barbs and supporting needle but
smaller than the diameter of the excised tissue mass. This pushes
the tissue up onto the shaft, where it can be removed with a
slicing blade or the like or by sliding the tissue over the
proximal end of the needle. Alternatively, needle 56 can be removed
and re-inserted into the tool for external, manual tissue
removal.
[0071] It is expected that in some embodiments, approximately 8-10
cores or segments of tissue will be excised and pushed up the shaft
towards the hub during the course of the procedure. Alternatively,
a small blade can be used to split the tissue segment and thereby
ease removal of the segment from the device. If desired, a blade
for this purpose can be placed on the shaft of needle 56 proximal
to the barbs.
[0072] In an exemplary embodiment, shown in FIGS. 15-18, the tissue
removal device may include a scraper 120 that includes a keyhole
slot having a wide end 122 and a narrow end 124. To remove a tissue
sample from needle 56 or hook 64, the tissue-engaging device with a
mass of excised tissue 110 thereon can be retracted (pulled toward
the proximal end of the tool) through wide end 122 of the slot and
then re-inserted (pushed toward the distal end of the tool) through
narrow end 124 of the slot. Narrow end 124 is large enough to allow
passage of the barbed needle, but small enough to remove the tissue
mass as the needle passes through. The removed tissue can exit the
tool through an opening 113 in the tool body. By shuttling the
tissue-engaging device through scraper 120 in this manner, each
excised segment of tissue 110 can be removed from the device,
readying the device for another excision.
[0073] In an alternative embodiment shown in FIG. 30, the tissue
removal device may be constructed such that tissue is removed from
the tissue-engaging device by retracting the tissue-engaging device
through narrow end 124 of the slot. As above, narrow end 124 is
large enough to allow passage of the shaft of the tissue-engaging
device, but small enough to remove the tissue mass as the needle
passes through. If the tissue-engaging device is constructed of a
tough material, the barbs or the like will cut through the tissue
and/or deform and release the tissue. As above, the removed tissue
can exit the tool through an opening 113 in the tool body. By
shuttling the tissue-engaging device through scraper 120 in this
manner, each excised segment of tissue 110 can be removed from the
device, readying the device for another excision.
[0074] In another alternative embodiment (not shown) an alternative
mechanism for removing the tissue segment from needle 56 includes
an adjustable aperture in a disc. After the tissue-bearing needle
is pulled back through the aperture, the aperture is partially
closed. Needle 56 and flexible hooks 58 then can pass through the
partially closed aperture but the larger cylinder of tissue cannot.
Thus the tissue segment is pushed back onto the shaft. The tissue
segment can either be pulled off the proximal end of the shaft or
cut off of it. A small blade may be placed just proximal to the
barbs to help cut the tissue segment off the shaft. The variable
aperture can formed by any suitable construction, including a pair
of metal plates with matching edges that each define one half of a
central opening. The two pieces may be held apart by springs. The
aperture may be closed by pushing the two edges together. In other
embodiments, this process can be mechanically automated by using a
disc or plate with an opening that is adjustable by a variety of
known techniques, including a slit screw assembly or flexible
gaskets.
Alternative Tissue Excision Devices
[0075] Other cutting and/or grasping devices can be used in place
of the system described above. For example, embodiments of the
grasping mechanism include but are not limited to: needles with
flexible barbs, needles with rigid barbs, corkscrew-shaped needles,
and/or retaining wires. The corkscrew-shaped needle shown in FIG.
19 works by screwing into the ligamentum flavum in the manner that
a corkscrew is inserted in a cork. After the screw engages a
segment of tissue, outer cutting element 60 slides over the needle,
cutting a segment of tissue in a manner similar to that of the
previous embodiment. In some embodiments, the cutting element can
be rotated as it cuts.
[0076] In other embodiments, shown in FIGS. 20-22, cannulated
scalpel 51 houses a grasping device 70 that includes at least one
pair of arcuate, closable arms 72. Closable arms 72 may be
constructed in any suitable manner. One technique for creating
closable arms is to provide a slotted sleeve 74, as shown. Slotted
member 74 preferably comprises an elongate body 75 with at least
one slot 76 that extends through its thickness but does not extend
to either end of the body. Slot 76 is preferably parallel to the
longitudinal axis of the sleeve. On either side of slot 76, a strip
77 is defined, with strips 77 being joined at each end of sleeve
74. It is preferred that the width of each strip 77 be relatively
small. In some embodiments, it may be desirable to construct
slotted member 74 from a portion of a hollow tube or from a
rectangular piece that has been curved around a longitudinal axis.
The inner edge of each strip that lies along slot 76 forms an
opposing edge 78. The width of the piece is the total of the width
of strips 77 and slot 76.
[0077] Advancing one end of sleeve 74 toward the other end of
sleeve 74 causes each strip 77 to buckle or bend. If strips 77 are
prevented from buckling inward or if they are predisposed to bend
in the desired direction, they will bend outward, thereby forming
arcuate arms 72, which extend through aperture 52 of cannulated
scalpel 51, as shown in FIG. 21. As they move away from the axis of
body 75, arms 72 move apart in a direction normal to the axis of
body 75. Likewise, moving the ends of sleeve 74 apart causes arms
72 to straighten and to move together and inward toward the axis of
the device, as shown in FIG. 22. As the arms straighten, opposing
edges 78 close and a segment of tissue can be capture between them.
Tissue within the grasping device may then be resected or anchored
via the other mechanisms described herein.
[0078] Closable arms 72 may include on their opposing edges 78
ridges, teeth, or other means to facilitate grasping of the tissue.
In other embodiments, edges 78 may be sharpened, so as to excise a
segment of tissue as they close. In these embodiments, closable
arms 72 may also be used in conjunction with a hook, barbed needle,
pincers or the like, which can in turn be used to retrieve the
excised segment from the device.
[0079] Once arms 72 have closed on the tissue, if arms 72 have not
cut the tissue themselves, the tissue can be excised using a blade
such as cutting element 60 above. The excised tissue can be removed
from the inside of needle 51 using a tissue-engaging hook 64 or
other suitable means. The process of extending and closing arms 72,
excising the tissue, and removing it from the device can be
repeated until a desired amount of tissue has been removed.
[0080] If desired, this cycle can be repeated without repositioning
the device in the tissue. Alternatively, the tool can be rotated or
repositioned as desired between excisions. It is possible to rotate
or reposition the tool during an excision, but it is expected that
this will not generally be preferred. Furthermore, it is expected
that the steps of tissue excision and removal can be accomplished
without breaching the surface of the ligament, i.e. without any
part of the device entering the safety zone created by the injected
fluid. Nonetheless, should the tool leave the working zone, the
safety zone will reduce the risk of injury to the thecal sac.
Ligament Retraction
[0081] In some embodiments, the spinal canal may also be enlarged
by retracting the ligamentum flavum, either with or without
concurrent resection. Retraction is preferably but not necessarily
performed after dural compression has been used to provide a safety
zone. In addition, the dural compression techniques described above
have the effect of pressing the ligamentum flavum back out of the
spinal canal and thereby making it easier to apply a restraining
means thereto.
[0082] Thus, in preferred embodiments, after a safety zone is
created by epidural injection of contrast medium or gel, a
retraction device 90 as shown in FIG. 23 is used to retract and
compress the thickened soft tissues around the posterior aspect of
the spinal canal, thereby increasing the available space for the
dural sac and nerves. In the embodiment shown, retraction device 90
is a double-headed anchor that includes at least one distal
retractable tissue-engaging member 91 and at least one proximal
tissue-engaging member 92, each of which are supported on a body
94. Retraction device 90 is preferably constructed from an
implantable, non-biodegradable material, such as titanium or
stainless steel, but may alternatively be polymeric or any other
suitable material. In certain preferred embodiments, body 94 is
somewhat flexible. In some instances, flexibility in body 94 may
facilitate the desired engagement of barbs 91, 92. Barbs 91, 92 may
comprise hooks, arms, teeth, clamps, or any other device capable of
selectively engaging adjacent tissue. Barbs 91, 92 may have any
configuration that allows them to engage the ligamentum flavum
and/or surrounding tissue. Similarly, barbs 91, 92 may be covered,
sheathed, pivotable, retractable, or otherwise able to be extended
from a first position in which they do not engage adjacent tissue
to a second position in which they can engage adjacent tissue.
[0083] FIG. 23 shows schematically the distal and proximal
retractable arms 91, 92 of a preferred ligament anchor 90. The
proximal end of the anchor preferably includes a threaded connector
96 or other releasable mechanism that attaches to a support rod
100. Ligament anchor 90 may be attached to a support shaft 112 and
sheathed in a guide housing 114. The distal and proximal barbs 91,
92 are prevented by guide housing 114 from engaging surrounding
tissue. Housing 102 is preferably a metal or durable plastic guide
housing.
[0084] The distal end of the device is preferably positioned in the
ligamentum flavum under fluoroscopic guidance. If desired, an
accessway through the lamina may be provided using an anchored
cannula or the like. The device is held in position by support
shaft 112. Distal barbs 91 are unsheathed and optionally expanded
by pulling back guide housing 102, as shown in FIG. 23. Distal
barbs 91 are secured in the ligamentum flavum by pulling back on
the support shaft 112. With barbs 91 engaging the tissue, the
ligamentum flavum is retracted posteriorly by pulling back on
support shaft 112. While maintaining traction on the now-retracted
ligament, proximal barbs 92 are uncovered and expanded by
retracting guide housing 114, as shown in FIG. 24. Barbs 92 are
preferably positioned in the soft tissues 116 in the para-spinal
region so that the device is firmly anchored behind the posterior
elements of the spinal canal. Once the proximal end of the anchor
is engaged, support shaft 112 may be detached from body 94 as shown
in FIG. 24. In this manner, the posterior margin 95 of the
ligamentum flavum can be held in a retracted position, thereby
expanding the canal. The procedure can then be repeated on adjacent
portions of the ligamentum flavum until it is sufficiently
retracted.
[0085] In an alternative embodiment, the proximal end of ligament
anchor 90 may be adapted to engage the lamina. This may be
accomplished by having the arm posterior to the lamina or by using
the laminotomy and suturing the device to the lamina there. A
knotted or knotless system or a suture plate can be used.
[0086] A second embodiment of the present method uses a plurality
of retraction devices 90. In this embodiment, the retraction device
is inserted through one lamina in an oblique fashion, paralleling
the opposite lamina. After the distal anchor is deployed, the
retraction device is pulled back and across the ligamentum flavum,
thereby decompressing the opposite lateral recess of the spinal
canal. This is repeated on the opposite side. This same device can
also be deployed with a direct approach to the lateral recess with
a curved guide housing.
[0087] While retraction device 90 is describe above as a
double-headed anchor, it will be understood that other devices can
be used. For example sutures, barbed sutures, staples or the like
can be used to fasten the ligament in a retracted position that
reduces stenosis.
[0088] Using the percutaneous methods and devices described herein,
significant reductions of stenosis can be achieved. For example, a
dural sac cross-sectional area less than 100 mm.sup.2 or an
anteroposterior (AP) dimension of the canal of less than 10-12 mm
in an average male is typically considered relative spinal
stenosis. A dural sac cross-sectional area less than 85 mm.sup.2 in
an average male is considered severe spinal stenosis. The present
devices and techniques are anticipated to cause an increase in
canal area of 25 mm.sup.2 per anchor or 50 mm.sup.2 total. With
resection and/or retraction of the ligamentum flavum, the
cross-sectional area of the dural sac can be increased by 10
mm.sup.2, and in some instances by as much as 20 mm or even 30
mm.sup.2. Likewise, the present invention can result in an increase
of the anteroposterior dimension of the canal by 1 to 2 mm and in
some instances by as much as 4 or 6 mm. The actual amount by which
the cross-sectional area of the thecal sac and/or the
anteroposterior dimension of the canal are increased will depend on
the size and age of the patient and the degree of stenosis and can
be adjusted by the degree of retraction of the ligament.
MILD
[0089] The minimally invasive ligament decompression (MILD) devices
and techniques described herein allow spinal decompression to be
performed percutaneously, avoiding the pain and risk associated
with open surgery. Through the provision of a safety zone, the
present devices and techniques offer reduced risk of spinal cord
damage. In addition to improving nerve function, it is expected
that decompression of the spinal canal in the manner described
herein will result in improved blood flow to the neural elements by
reducing the extrinsic pressure on the spinal vasculature. For
these reasons, it is believed that spinal decompression performed
according to the present invention will be preferable to
decompression operations performed using currently known
techniques.
Dural Shield
[0090] In some embodiments (not shown), a mechanical device such as
a balloon or mechanical shield can also be used to create a
protective guard or barrier between the borders of the epidural
space and the adjacent structures. In one embodiment a durable
expandable device is attached to the outside of the percutaneous
laminectomy device, preferably on the side opposite the cutting
aperture. The cutting device is inserted into the ligamentum flavum
with the expandable device deflated. With the aperture directed
away from the spinal canal, the expandable device is gently
expanded via mechanical means or inflated with air or another
sterile fluid, such as saline solution, via a lumen that may be
within or adjacent to the body of the device. This pushes the
adjacent vital structures clear from the cutting aperture of the
device and simultaneously presses the cutting aperture into the
ligament. As above, the grasping and cutting needles can then be
deployed and operated as desired. The balloon does not interfere
with tissue excision because it is located on the side opposite the
cutting aperture. The cutting needle may be hemispherical
(semi-tubular) in shape with either a straight cutting or a
sawing/reciprocating blade or may be sized to be placed within the
outer housing that separates the balloon from the cutting
aperture.
[0091] In another embodiment, a self-expanding metal mesh is
positioned percutaneously in the epidural space. First the epidural
space is accessed in the usual fashion. Then a guide catheter is
placed in the epidural space at the site of the intended surgical
procedure. The mesh is preferably compressed within a guide
catheter. When the outer cover of the guide catheter is retracted,
the mesh expands in the epidural space, protecting and displacing
the adjacent dural sheath. At the conclusion of the surgical
procedure, the mesh is pulled back into the guide sheath and the
assembly removed. The mesh is deformable and compresses as it is
pulled back into the guide catheter, in a manner similar to a
self-expanding mesh stent. There are many commercially available
self-expanding stents approved and in use in other applications.
However, using a self-expandable mesh as a device within the
epidural space to protect and displace the thecal sac is novel.
[0092] While preferred embodiments of this invention have been
shown and described, modifications thereof can be made by one
skilled in the art without departing from the scope or teaching of
this invention. For example, the means by which the safety zone is
formed may be varied, the shape and configuration of the tissue
excision devices may be varied, and the steps used in carrying out
the technique may be modified. Accordingly, the invention is not
limited to the embodiments described herein, but is only limited by
the claims that follow, the scope of which shall include all
equivalents of the subject matter of the claims. Likewise, the
sequential recitation of steps in a claim, unless explicitly so
stated, is not intended to require that the steps be performed in
any particular order or that a particular step be completed before
commencement of another step.
* * * * *