U.S. patent application number 16/842935 was filed with the patent office on 2020-12-10 for devices and methods for treating spinal cord tissue.
The applicant listed for this patent is Wake Forest University Health Sciences. Invention is credited to Louis C. Argenta, David L. Carroll, Nicole H. Levi, Jie Liu, Michael J. Morykwas, Stephen Tatter, William D. Wagner.
Application Number | 20200384168 16/842935 |
Document ID | / |
Family ID | 1000005037944 |
Filed Date | 2020-12-10 |
United States Patent
Application |
20200384168 |
Kind Code |
A1 |
Argenta; Louis C. ; et
al. |
December 10, 2020 |
DEVICES AND METHODS FOR TREATING SPINAL CORD TISSUE
Abstract
The present invention provides devices and methods that treat
damaged spinal cord tissue, such as spinal tissue damaged by
disease, infection, or trauma, which may lead to the presence of
swelling, compression, and compromised blood flow secondary to
interstitial edema.
Inventors: |
Argenta; Louis C.;
(Winston-Salem, NC) ; Carroll; David L.;
(Winston-Salem, NC) ; Levi; Nicole H.;
(Winston-Salem, NC) ; Liu; Jie; (Woodbury, MN)
; Morykwas; Michael J.; (Winston-Salem, NC) ;
Tatter; Stephen; (Winston-Salem, NC) ; Wagner;
William D.; (Clemmons, NC) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Wake Forest University Health Sciences |
Winston-Salem |
NC |
US |
|
|
Family ID: |
1000005037944 |
Appl. No.: |
16/842935 |
Filed: |
April 8, 2020 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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15700667 |
Sep 11, 2017 |
10632235 |
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16842935 |
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14458790 |
Aug 13, 2014 |
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15700667 |
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12248346 |
Oct 9, 2008 |
8834520 |
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14458790 |
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61088558 |
Aug 13, 2008 |
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61081997 |
Jul 18, 2008 |
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60978884 |
Oct 10, 2007 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61M 2210/1003 20130101;
A61M 1/0088 20130101; A61F 13/00021 20130101; A61M 1/0023
20130101 |
International
Class: |
A61M 1/00 20060101
A61M001/00; A61F 13/00 20060101 A61F013/00 |
Claims
1-10. (canceled)
11. A method for treating damaged spinal cord tissue with
sub-atmospheric pressure, comprising: placing a porous
bio-incorporable material at the damaged spinal cord tissue to
provide gaseous communication between pores of the porous
bio-incorporable material and the damaged spinal cord tissue;
creating a region about the damaged spinal cord tissue and the
porous bio-incorporable material for maintaining sub-atmospheric
pressure therein; operably connecting a vacuum source to the
region; and providing sub-atmospheric pressure from the vacuum
source to the region through the porous bio-incorporable material
to the damaged spinal cord tissue to treat the damaged spinal cord
tissue.
12. The method according to claim 11, wherein the porous
bio-incorporable material comprises at least two layers to provide
a multi-layer structure.
13. The method according to claim 11, wherein vacuum source is
operable to cycle on and off to provide alternating periods of
production and non-production of sub-atmospheric pressure.
14. The method according to claim 0, wherein the duty cycle may be
between 1 to 10 (on/off) and 10 to 1 (on/off).
15. The method according to claim 11, wherein vacuum source is
operable to provide a periodic waveform.
16. The method according to claim 0, wherein the periodic waveform
is a sine wave.
17. The method according to claim 11, wherein the porous
bio-incorporable material is sufficiently compliant so that when
the porous bio-incorporable material presses against the spinal
cord, the porous bio-incorporable material does not interfere with
spinal cord function.
18. The method according to claim 0, wherein the porous
bio-incorporable material is sufficiently firm so that the porous
bio-incorporable material does not collapse so much as to interfere
with spinal cord function.
19. The method according to claim 11, wherein the porous
bio-incorporable material is sufficiently firm so that the porous
bio-incorporable material does not collapse so much as to interfere
with spinal cord function.
20. The method according to claim 11, wherein the vacuum source
cooperates with the porous bio-incorporable material so that the
porous bio-incorporable material does not interfere with spinal
cord function upon providing the sub-atmospheric pressure from the
vacuum source.
Description
RELATED APPLICATIONS
[0001] This application is a continuation of U.S. application Ser.
No. 15/700,667, filed Sep. 11, 2017, which is a continuation of
U.S. application Ser. No. 14/458,790, filed Aug. 13, 2014, which is
a divisional of U.S. application Ser. No. 12/248,346, filed Oct. 9,
2008, which issued as U.S. Pat. No. 8,834,520, which claims the
benefit of priority of U.S. Provisional Application No. 60/978,884,
filed on Oct. 10, 2007, U.S. Provisional Application No.
61/081,997, filed on Jul. 18, 2008, and U.S. Provisional
Application No. 61/088,558, filed on Aug. 13, 2008, the entire
contents of which applications are incorporated herein by
reference.
FIELD OF THE INVENTION
[0002] The present invention relates generally to devices and
methods for treating damaged or compromised spinal cord tissue
using sub-atmospheric pressure and more particularly, but not
exclusively, to devices and methods for treating spinal cord tissue
that have experienced a recoverable or non-recoverable injury.
BACKGROUND OF THE INVENTION
[0003] The anatomy, physiology, and pathologic processes that
involve the spinal cord pose special concerns for the treatment of
damaged or compromised spinal cord tissue. The preservation of both
the three-dimensional structural anatomy and the microanatomical
relationships of neurons (whose function depends on specific
spatial relationships with other neurons and other supporting
cells), as well as the maintenance of properly oxygenated blood
flow and the homogeneous ground substance matrix in which the
neurons survive, are vital to the survival and function of spinal
cord tissues. Moreover, the inability of spinal cord cells to
regenerate emphasizes the need to maximize survival of every
possible neuron. For reasons such as these, treatment of both open
and closed space pathology in the spinal cord poses special
concerns.
[0004] Among the clinical problems that threaten survival of spinal
cord tissue, the control of spinal cord edema, infection, and blood
supply are central. The spinal cord responds to trauma and injury
by collecting a significant amount of interstitial edema. Because
the spinal cord is enclosed in a closed space (dura and the spinal
canal), edema results in compression and compromise of the blood
flow and nutritional performance of the spinal cord, which greatly
impairs physiological recovery of the spinal cord and often of
itself results in progression of compromise and death of the spinal
cord. Currently available treatments for reducing edema include
pharmacologic agents, such as glucocorticoids (Dexamethasone,
Prednisone, Methyl Prednisolone), diuretics, and extensive surgical
decompression. However, disadvantages to these treatments include
irregular and unpredictable results, complications of the drugs,
infection, and surgical complications.
[0005] The need for rapid and effective treatment is also vital due
to the disastrous consequences and high likelihood of rapid
propagation of infection and edema in the spinal cord. At present
there are few successful methods available to treat pathologies
affecting the intraspinal space, spinal cord parenchyma, and the
surrounding structures. Where tissues elsewhere in the body can be
treated with dressing changes, the spinal cord is not amenable to
this type of treatment because of its precarious structure,
propensity for infection, and potential for progression of injury.
There is evidence that inflammation and immunological response to
spinal cord trauma and other pathology are of equal or greater long
term consequences than the initial trauma or insult. The response
of the spinal cord to decreased blood flow secondary to edema
results in hypoxia and ischemia/reperfusion-mediated injury. These
injuries contribute to the neuropathological sequella, which
greatly contribute to the adverse outcome of spinal injury.
[0006] In addition, the spinal cord requires a continuous supply of
oxygenated blood to function and survive. Within a few minutes of
complete interruption of blood flow to the spinal cord,
irreversible spinal cord damage results. The spinal cord can,
however, remain viable and recover from reduced blood flow for more
prolonged periods. There is evidence that focal areas of the spinal
cord can remain ischemic and relatively functionless for days and
still recover. This finding has led to the concept of an ischemic
zone, termed the penumbra or halo zone, that surrounds an area of
irreversible injury. A secondary phenomena in the ischemic zone is
the release of excitotoxins that are released locally by injured
neurons, alterations in focal blood flow, and edema.
[0007] Vascular pathology of the spine may be a result of:
inadequate blood flow to the spinal cord cells from decreased
perfusion pressure, rupture of a blood vessel resulting in direct
injury to the local spinal cord area, or by compression of adjacent
tissue; intrinsic disease of the spinal cord blood vessels such as
atherosclerosis, aneurysm, inflammation, etc.; or a remote thrombus
that lodges in the spinal cord blood vessels from elsewhere such as
the heart.
[0008] In cases of intraspinal hemorrhage, the hemorrhage usually
begins as a small mass that grows in volume by pressure dissection
and results in displacement and compression of adjacent spinal cord
tissue. Edema in the adjacent compressed tissue around the
hemorrhage may lead to a mass effect and a worsening of the
clinical condition by compromising a larger area of spinal cord
tissue. Edema in the adjacent spinal cord may cause progressive
deterioration usually seen over 12 to 72 hours. The occurrence of
edema in the week following the intraspinal hemorrhage often
worsens the prognosis, particularly in the elderly. The tissue
surrounding the hematoma is displaced and compressed but is not
necessarily fatally compromised. Improvement can result as the
hematoma is resorbed, adjacent edema decreased, and the involved
tissue regains function.
[0009] Treatment of these conditions has been disappointing.
Surgical decompression of the spinal cord can be helpful in some
cases to prevent irreversible compression. Agents such as mannitol
and some other osmotic agents can reduce intraspinal pressure
caused by edema. Steroids are of uncertain value in these cases,
and recently hyperbaric oxygen has been proposed.
[0010] Thus, though the application of negative (or
sub-atmospheric) pressure therapy to wounded cutaneous and
subcutaneous tissue demonstrates an increased rate of healing
compared to traditional methods (as set forth in U.S. Pat. Nos.
5,645,081, 5,636,643, 7,198,046, and 7,216,651, as well as US
Published Application Nos. 2003/0225347, 2004/0039391, and
2004/0122434, the contents of which are incorporated herein by
reference), there remains a need for devices and methods
specifically suited for use with the specialized tissues of the
spinal cord.
SUMMARY OF THE INVENTION
[0011] The present invention provides devices and methods that use
sub-atmospheric (or negative) pressure to treat damaged spinal cord
tissue, such as spinal tissue damaged by disease, infection, or
trauma, for example, which may lead to the presence of swelling,
compression, and compromised blood flow secondary to interstitial
edema. For instance, the spinal cord may be damaged by blunt trauma
resulting in a recoverable or non-recoverable injury.
[0012] In one of its aspects the present invention provides a
method for treating damaged spinal cord tissue using
sub-atmospheric pressure. The method comprises locating a porous
material proximate the damaged spinal cord tissue to provide
gaseous communication between one or more pores of the porous
material and the damaged spinal cord tissue. The porous material
may be sealed in situ proximate the damaged spinal cord tissue to
provide a region about the damaged spinal cord tissue for
maintaining sub-atmospheric pressure at the damaged spinal cord
tissue. The porous material may be operably connected with a vacuum
system for producing sub-atmospheric pressure at the damaged spinal
cord tissue, and the vacuum system activated to provide
sub-atmospheric pressure at the damaged spinal cord tissue. The
sub-atmospheric pressure may be maintained at the damaged spinal
cord tissue for a time sufficient to decrease edema at the spinal
cord. For example, the sub-atmospheric pressure may be maintained
at about 25 mm Hg below atmospheric pressure. The method may also
include locating a cover over damaged spinal cord tissue and
sealing the cover to tissue proximate the damaged spinal cord
tissue for maintaining sub-atmospheric pressure at the damaged
spinal cord tissue. The cover may be provided in the form of a
self-adhesive sheet which may be located over the damaged spinal
cord tissue. In such a case, the step of sealing the cover may
include adhesively sealing and adhering the self-adhesive sheet to
tissue surrounding the damaged spinal cord tissue to form a seal
between the sheet and tissue surrounding the damaged spinal cord
tissue.
[0013] In another of its aspects the present invention provides an
apparatus for treating damaged spinal cord tissue. The apparatus
may include a porous bio-incorporable material, such as an
open-cell collagen, having pore structure configured to permit
gaseous communication between one or more pores of the porous
material and the spinal cord tissue to be treated. The
bio-incorporable nature of the porous material can obviate the need
for a second procedure to remove the porous material. (As used
herein the term "bio-incorporable" is defined to describe a
material that may be left in the patient indefinitely and is
capable of being remodeled, resorbed, dissolved, and/or otherwise
assimilated or modified.) The apparatus also includes a vacuum
source for producing sub-atmospheric pressure; the vacuum source
may be disposed in gaseous communication with the porous material
for distributing the sub-atmospheric pressure to the spinal cord
tissue. The porous material may have, at least at a selected
surface of the porous material, pores sufficiently small to prevent
the growth of tissue therein. In addition, the porous material may
have, at least at a selected surface of the porous material, a pore
size smaller than the size of fibroblasts and spinal cord cells,
and may have a pore size at a location other than the selected
surface that is larger than that of fibroblasts and spinal cord
cells. The pore size of the porous material may be large enough to
allow movement of proteins the size of albumin therethrough. Also,
the porous bio-incorporable material may include at least one
surface that is sealed to prevent the transmission of
sub-atmospheric pressure therethrough. The apparatus may also
include a cover configured to cover the damaged spinal cord tissue
to maintain sub-atmospheric pressure under the cover at the damaged
spinal cord tissue.
[0014] Thus, the present invention provides devices and methods for
minimizing the progression of pathologic processes, minimizing the
disruption of physiological spinal cord integrity, and minimizing
the interference with spinal cord blood flow and nutrition. By
decreasing spinal cord edema and intraspinal pressure the risk of
spinal cord herniation and compromise may be minimized. In
addition, the present invention facilitates the removal of
mediators, degradation products, and toxins that enhance the
inflammatory and neuropathological response of tissues in the
spinal cord.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] The foregoing summary and the following detailed description
of the preferred embodiments of the present invention will be best
understood when read in conjunction with the appended drawings, in
which:
[0016] FIG. 1 schematically illustrates a partial cross-sectional
view of an exemplary configuration of an apparatus of the present
invention in situ prior to the application of sub-atmospheric
pressure;
[0017] FIG. 2 schematically illustrates the partial cross-sectional
view of FIG. 1 as a sub-atmospheric pressure is being applied;
[0018] FIG. 3 schematically illustrates the partial cross-sectional
view of FIGS. 1 and 2 showing the effect of the applied
sub-atmospheric pressure on the tissues surrounding the spinal
cord;
[0019] FIG. 4 schematically illustrates a partial cross-sectional
view of a second exemplary configuration of the present invention
in situ comprising a rigid or semi-rigid cover disposed
subcutaneously over the spinal cord;
[0020] FIG. 5 schematically illustrates a partial cross-sectional
view of a third exemplary configuration of the present invention in
situ comprising a flexible cover disposed subcutaneously over the
spinal cord;
[0021] FIG. 6 illustrates the BBB score as a function of time for
control animals exposed to recoverable blunt trauma of the spinal
cord;
[0022] FIG. 7 illustrates the BBB score as a function of time for
animals exposed to recoverable blunt trauma of the spinal cord and
treated with sub-atmospheric pressure;
[0023] FIG. 8 illustrates the cross-sectional area of the spinal
cord as a function of time for control animals exposed to
non-recoverable blunt trauma of the spinal cord;
[0024] FIG. 9 illustrates the cross-sectional area of the spinal
cord as a function of time for animals exposed to non-recoverable
blunt trauma of the spinal cord and treated with sub-atmospheric
pressure; and
[0025] FIG. 10 schematically illustrates a porous material having a
multi-layer structure for use in a sub-atmospheric pressure
apparatus of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0026] Referring now to the figures, wherein like elements are
numbered alike throughout, the present invention relates to devices
and methods that use sub-atmospheric (or negative) pressure for
treating damaged spinal cord tissue, where "damaged" tissue is
defined to include tissue that is injured, compromised, or in any
other way impaired, such as damage due to trauma, disease,
infection, surgical complication, or other pathologic process, for
example. More specifically, the devices and methods of the present
invention can effect treatment of edema of the spinal cord
parenchyma secondary to any cause, such as the aforementioned
causes; treatment of any of the spaces surrounding the spinal cord,
including the subdural/epidural spaces; and, treatment of elevated
intraspinal pressure due to any cause, such as the aforementioned
causes.
[0027] An exemplary configuration of a sub-atmospheric spinal cord
treatment device 100 of the present invention may include a vacuum
source 30 for supplying sub-atmospheric pressure via a tube 20 to a
porous material 10 disposed proximate the spinal cord 7, FIGS. 1-3.
In this regard, the porous material 10 may be structured to deliver
and distribute sub-atmospheric pressure to the spinal cord 7. The
spinal cord treatment device 100 may be applied to a patient by
locating a porous material 10 proximate the damaged spinal cord
tissue 7 to provide gaseous communication between one or more pores
of the porous material 10 and the damaged spinal cord tissue 7. A
tube 20 may be connected to the porous material 10 at a distal end
22 of the tube 20, and the porous material 10 may be sealed in situ
by sutures 8 in the skin and subcutaneous tissues 2 to provide a
region about the damaged spinal cord tissue 7 for maintaining
sub-atmospheric pressure. The proximal end 24 of the tube 20 may be
attached to a vacuum source 30 to operably connect the porous
material 10 to the vacuum system 30 for producing sub-atmospheric
pressure at the damaged spinal cord tissue 7 upon activation of the
vacuum system 30.
[0028] Turning to FIG. 1 in greater detail, an exemplary
configuration of a sub-atmospheric spinal cord treatment device 100
of the present invention is illustrated in situ in a patient with
surrounding tissues shown in partial cross-section. The tissues
illustrated include the skin and subcutaneous tissue 2, muscle
tissue, such as the trapezius 3 and erector spinae 4, vertebrae 5,
transverse process 6, and the spinal cord 7. To provide access to
the spinal cord 7, a portion of the vertebrae 5 may be missing. For
instance, the spinous process may be absent due to surgical
dissection, disease, or injury. A porous material 10, such as an
open-cell collagen material, may be placed in the subcutaneous
space proximate the spinal cord tissue 7 to be treated with
sub-atmospheric pressure to decrease edema in the parenchymal
tissues and improve physiologic function, for example. In addition
to an open-cell collagen material, the porous material 10 may also
include a polyglycolic and/or polylactic acid material, a synthetic
polymer, a flexible sheet-like mesh, an open-cell polymer foam, a
foam section, a porous sheet, a polyvinyl alcohol foam, a
polyethylene and/or polyester material, elastin, hyaluronic acid,
alginates, polydiolcitrates, polyhyrdoxybutyrate,
polyhyrdoxyfumarate, polytrimethylenecarbonate,
polyglycerolsebecate, aliphatic/aromatic polyanhydride, or other
suitable materials, and combinations of the foregoing any of which
may be fabricated by electrospinning, casting, or printing, for
example. Such materials include a solution of chitosan (1.33%
weight/volume in 2% acetic acid, 20 ml total volume) which may be
poured into an appropriately sized mold. The solution is then
frozen for 2 hours at -70.degree. C., and then transferred to the
lyophylizer with a vacuum applied for 24 hours. The material may be
cross-linked by 2.5%-5% glutaraldehyde vapor for 12-24 hours (or by
ultraviolet radiation for 8 hours) to provide a cast porous
material 10.
[0029] Additionally, the porous material 10 may be made by casting
polycaprolactone (PCL). Polycaprolactone may be mixed with sodium
chloride (1 part caprolactone to 10 parts sodium chloride) and
placed in a sufficient volume of chloroform to dissolve the
components. For example, 8 ml of the solution may be poured into an
appropriately sized and shaped contained and allowed to dry for
twelve hours. The sodium chloride may then be leached out in water
for 24 hours.
[0030] It is also possible to use electrospun materials for the
porous material 10. One exemplary of a formulation and method for
making an electrospun porous material 10 was made using a
combination of collagen Type I:chondroitin-6-sulfate (CS):poly
1,8-octanediol citrate (POC) in a ratio of 76%:4%:20%: by weight.
Two solvents were utilized for the collagen/CS/POC. The CS was
dissolved in water and the collagen and POC were dissolved in
2,2,2-trifluoroethanol (TFE). A 20% water/80% TFE solution
(volume/volume) solution was then used. For electrospinning, the
solution containing the collagen:CS:POC mixture was placed in a 3
ml syringe fitted to an 18 Ga needle. A syringe pump (New Era Pump
Systems, Wantaugh, N.Y.) was used to feed the solution into the
needle tip at a rate of 2.0 ml/hr. A voltage of 10-20 kV was
provided by a high voltage power supply (HV Power Supply, Gamma
High Voltage Research, Ormond Beach. Fla.) and was applied between
the needle (anode) and the grounded collector (cathode) with a
distance of 15-25 cm. The material was then cross-linked with
glutaraldehyde (Grade II, 25% solution) and heat polymerized
(80.degree. C.) for 48 hours. It is also possible to electrospin
collagen Type I porous materials 10 starting with an initial
concentration of 80 mg/ml of collagen in
1,1,1,3,3,3-hexafluoro-2-propanol (HFP), then use the same
electrospinning conditions as the collagen:CS:POC combination.
[0031] An additional method for creating porous materials 10 is to
use thermal inkjet printing technologies. Bio-incorporable
materials such as collagen, elastic, hyaluronic acid, alginates,
and polylactic/polyglycolic acid co-polymers may be printed. As
examples, Type I collagen (Elastin Products Co., Owensville, Mo.)
dissolved in 0.05% acetic acid, then diluted to 1 mg/ml in water
can be printed, as can sodium alginate (Dharma Trading Co., San
Raphael, Calif.) 1 mg/ml in water. A mixture of Type I collagen
(2.86 mg/ml in 0.05% acetic acid) and polylactic/polyglycolic acid
(PURAC America, Blair, Nebr.) (14.29 mg/ml in tetraglycol (Sigma
Aldrich, St. Louis Mo.)) can also be printed. Hardware from a
Hewlett Packard 660c printer, including the stepper motors and
carriage for the cartridges, can be mounted to a platform. The
height of the hardware above the platform can then be adjusted for
printing in layers.
[0032] The porous material 10 may comprise pores sufficiently small
at the interface between the porous material 10 and the spinal cord
7 to prevent the growth of tissue therein, e.g., a pore size
smaller than the size of fibroblasts and spinal cord cells;
otherwise the porous material 10 may stick to the spinal cord 7 and
cause bleeding or trauma when the porous material 10 is removed. In
addition, the pore size at the interface between the porous
material 10 and the spinal cord 7 may be sufficiently small so as
to avoid the excessive production of granulation or scar tissue at
the spinal cord 7 which may interfere with the physiologic function
of the spinal cord 7. At the same time, the pore size of the porous
material 10 may be large enough to allow movement of proteins the
size of albumin therethrough to permit undesirable compounds to be
removed, such as mediators, degradation products, and toxins.
[0033] The porous material 10 may, however, have a larger pore size
(e.g., larger than that of fibroblasts and spinal cord cells)
interior to the porous material 10 or at any other location of the
porous material 10 that is not in contact with spinal cord tissue
7. For example, the porous material 110 may comprise a multi-layer
structure with a non-ingrowth layer 112 having a sufficiently small
pore size to prevent the growth of tissue therein for placement at
the spinal cord, and may have an additional layer 114 of a
different material that has a relatively larger pore size in
contact with the non-ingrowth layer 112.
[0034] Alternatively, the porous material 10 may be homogeneous in
composition and/or morphology. At a location away from the
interface with the spinal cord 7, the porous material 10 may have a
pore size sufficiently large to promote the formation of
granulation tissue at other tissues in the spaces surrounding the
spinal cord 7, such as promotion of granulation tissue in areas
where spinal cord disruption has occurred. In addition, the porous
material 10 may have a configuration in which one or more sides or
surfaces of the porous material 10 are sealed to prevent the
transmission of sub-atmospheric pressure through such a sealed
surface, while at the same time having at least one surface through
which sub-atmospheric pressure may be transmitted. Such a
configuration of the porous material 10 can present preferential
treatment of tissue on one side of the porous material 10 while not
treating the other side. For instance, the parenchyma of the spinal
cord 7 could be treated with the non-sealed interface on one side
of the porous material 10.
[0035] The porous material 10 may be comprised of a material that
needs to be removed after sub-atmospheric therapy is given, which
could require a second surgery. Alternatively, the porous material
10 may be comprised of a material that is bioabsorbable or degrades
harmlessly over time to avoid a second surgery, such as collagen.
In addition, the porous material 10 may comprise a non-metallic
material so that an MRI can be performed while the porous material
10 is in situ. The porous material 10 may also comprise a material
that is sufficiently compliant so that if it presses against the
spinal cord 7 the porous material 10 does not interfere with spinal
cord function. At the same time, the porous material 10 may
comprise a material that is sufficiently firm so that the porous
material 10 does not collapsed so much as to create a pull on, or
distortion of, the "normal spinal cord" that might interfere with
spinal cord function.
[0036] To deliver sub-atmospheric pressure to the porous material
10 for distribution to the spinal cord 7, a tube 20 may be
connected directly or indirectly in gaseous communication with the
porous material 10 at the distal end 22 of the tube 20. For
example, the distal end 22 of the tube 20 may be embedded in the
porous material 10 or may be placed over the porous material 10.
The distal end 22 of the tube 20 may also include one or more
fenestrations to assist in delivering the sub-atmospheric pressure
to the porous material 10 and the spinal cord 7. The tube 20 may
extend through an opening in the skin and subcutaneous tissue 2
which may be secured about the tube 20 with a suture 8 to assist in
providing a seal about the tube 20. The proximal end 24 of the tube
20 may be operably connected to a vacuum source 30, such as a
vacuum pump, to provide sub-atmospheric pressure that is
transmitted via the tube 20 to the porous material 10 and the
spinal cord 7.
[0037] The vacuum source 30 may include a controller 32 to regulate
the production of sub-atmospheric pressure. For instance, the
vacuum source 30 may be configured to produce sub-atmospheric
pressure continuously or intermittently; e.g. the vacuum source 30
may cycle on and off to provide alternating periods of production
and non-production of sub-atmospheric pressure. The duty cycle
between production and non-production may be between 1 to 10
(on/off) and 10 to 1 (on/off). In addition, intermittent
sub-atmospheric pressure may be applied by a periodic or cyclical
waveform, such as a sine wave. The vacuum source 30 may be cycled
after initial treatment to mimic a more physiologic state, such as
several times per minute. The sub-atmospheric pressure may be
cycled on-off as-needed as determined by monitoring of the pressure
in the spinal cord 7. In general, the vacuum source 30 may be
configured to deliver sub-atmospheric pressure between atmospheric
pressure and 75 mm Hg below atmospheric pressure to minimize the
chance that the sub-atmospheric pressure may result in bleeding
into the spinal cord 7 or otherwise be deleterious to the spinal
cord 7. The application of such a sub-atmospheric pressure can
operate to remove edema from the spinal cord 7, thus preserving
neurologic function to increase the probability of recovery and
survival in a more physiologically preserved state.
[0038] To assist in maintaining the sub-atmospheric pressure at the
spinal cord 7, a flexible cover/sheet 50 or rigid (or semi-rigid)
cover 40 may be provided proximate the spinal cord 7 to provide a
region about the spinal cord 7 where sub-atmospheric pressure may
be maintained, FIGS. 4, 5. Specifically, with reference to FIGS. 4
and 5, a cover 40, 50 may be provided over the spinal cord 7 and
porous material 10 by adhering the cover 40, 50 to tissues
proximate the spinal cord 7 to define an enclosed region 48, 58
about the spinal cord 7 and porous material 10. For instance, the
cover 40, 50 may be glued to the vertebrae 5, muscle tissue 4,
and/or other appropriate tissues using an adhesive 42, such as a
fibrin glue. The adhesive 42 may comprise an auto-polymerizing glue
and/or may desirably include a filler to provide the adhesive 42
with sufficient bulk to permit the adhesive 42 to conform to the
shapes of the potentially irregular surfaces which the adhesive 42
contacts. The adhesive 42 may be provided as a separate component
or as a portion of the cover 40, 50 to provide a self-adhesive
cover 40, 50. For instance, the cover 50 may comprise a flexible
self-adhesive sheet which includes a suitable adhesive on one or
more of its surfaces.
[0039] For the flexible cover 50, an outside edge or border of the
flexible cover 50 may be rolled under (or toward) the spinal cord
7. Alternatively, the flexible cover 50 may be curled out away from
the spinal cord 7 so that the underside of the cover 50 (that side
facing with the porous material 10) may then contact with the
vertebrae 5 and surrounding muscles and soft tissue, FIG. 5. If the
flexible cover 50 is rolled under the spinal cord 7, an adhesive 52
may then be applied to the outside of the cover 50 between the
cover 50 and the vertebrae 5, surrounding muscle and soft tissues
to help promote an airtight seal. If the flexible cover 50 is
curled away from the spinal cord 7, an adhesive may be applied to
the underside of the cover 50, between the cover 50 and the
vertebrae 5 and surrounding muscle and soft tissue to create an
airtight seal.
[0040] Sub-atmospheric pressure may be delivered under the cover
40, 50 by cooperation between the cover 40, 50 and the tube 20.
Specifically, the cover 40 (or flexible cover 50) may include a
vacuum port 43 to which the distal end 22 of the tube 20 connects
to provide gaseous communication between the tube 20 and the space
48 under the cover 40 over the spinal cord 7, FIG. 4.
Alternatively, the cover 50 (or cover 40) may include a
pass-through 52 through which the tube 20 passes so that the distal
end 22 of the tube 20 is disposed interior to, and in gaseous
communication with, the space 58 under the cover 50 over the spinal
cord 7, FIG. 5.
[0041] The cover 40, 50 may serve to further confine the
subcutaneous region about the spinal cord 7 at which
sub-atmospheric pressure is maintained. That is, as illustrated in
FIGS. 4 and 5, the cover 40, 50 provides an enclosed space/region
48, 58 about spinal cord 7 under the cover 40, 50, which can serve
to isolate the tissues exterior to the cover 40, 50 from exposure
to the sub-atmospheric pressure applied to the spinal cord 7. In
contrast, as illustrated in FIGS. 2 and 3, in the absence of a
cover, sub-atmospheric pressure delivered to the porous material 10
and spinal cord 7 may draw the surrounding tissues, such as muscles
3, 4, inward towards the tube 20 and porous material 10 along the
directions of the arrows shown in FIG. 2 resulting in the
configuration of tissues illustrated in FIG. 3. In this regard the
stretched and/or moved tissues, such as muscles 3, 4, can help to
confine the applied sub-atmospheric pressure to a region between
the muscles 4 and the spinal cord 7. In addition the covers 40, 50
may further protect the spinal cord 7 from exogenous infection and
contamination beyond the protection already afforded by the porous
material 10 and sutured skin 2. Likewise, the covers 40, 50 may
further protect surrounding tissues from the spread of infection
from the spinal cord 7 such as spinal cord abscesses, meningitis,
and spinal tissue infection.
[0042] In another of its aspects, the present invention also
provides a method for treating damaged spinal cord tissue using
sub-atmospheric pressure with, by way of example, the devices
illustrated in FIGS. 1-5. In particular, the method may comprise
locating a porous material 10 proximate the damaged spinal cord
tissue 7 to provide gaseous communication between one or more pores
of the porous material 10 and the damaged spinal cord tissue 7. The
porous material 10 may be sealed in situ proximate the damaged
spinal cord tissue 7 to provide a region about the damaged spinal
cord tissue 7 for maintaining sub-atmospheric pressure at the
damaged spinal cord tissue 7. In this regard, the muscles 3,4 and
subcutaneous tissues may be loosely re-approximated over top of the
porous material 10 with the tube 20 exiting through the skin 2 and
the skin 2 sutured closed. A further airtight dressing may
optionally be placed over the suture site to promote an airtight
seal. The porous material 10 may be operably connected with a
vacuum system 30 for producing sub-atmospheric pressure at the
damaged spinal cord tissue 7, and the vacuum system 30 activated to
provide sub-atmospheric pressure at the damaged spinal cord tissue
7. For example, the sub-atmospheric pressure may be maintained at
about 25 to 75 mm Hg below atmospheric pressure. The
sub-atmospheric pressure may be maintained at the damaged spinal
cord tissue 7 for a time sufficient to decrease edema at the spinal
cord 7 or to control spinal fluid leaks. In addition, the
sub-atmospheric pressure may be maintained at the damaged spinal
cord tissue 7 for a time sufficient to prepare the spinal cord
tissue 7 to achieve a stage of healing and diminution of bacterial
counts such that acceptance of secondary treatments (e.g., flaps,
skin grafts) can be successful. The method may be used for at least
4 hours, or can be used for many days. At the end of the vacuum
treatment, the sutures 8 may be removed and the skin 2 re-opened.
The porous material 10 may then be removed and the skin 2
re-sutured closed.
[0043] The method may also include locating a cover 40, 50 over the
damaged spinal cord tissue 7 and sealing the cover 40, 50 to tissue
proximate the damaged spinal cord tissue 7 for maintaining
sub-atmospheric pressure at the damaged spinal cord tissue 7. The
step of sealing the cover 40, 50 to tissue surrounding the damaged
spinal cord tissue 7 may comprise adhesively sealing and adhering
the cover 40, 50 to tissue surrounding the damaged spinal cord
tissue 7. The cover 50 may be provided in the form of a
self-adhesive sheet 50 which may be located over the damaged spinal
cord tissue 7. In such a case, the step of sealing the cover 50 may
include adhesively sealing and adhering the self-adhesive sheet 50
to tissue surrounding the damaged spinal cord tissue 7 to form a
seal between the sheet 50 and tissue surrounding the damaged spinal
cord tissue 7. In addition, the step of operably connecting a
vacuum system 30 in gaseous communication with the porous material
10 may comprise connecting the vacuum system 30 with the vacuum
port 42 of the cover 40.
EXAMPLES
[0044] Rat Spinal Cord Injuries and Sub-atmospheric Pressure
Exposure
[0045] Experiment 1
[0046] A series of experiments were conducted to determine the
effects of sub-atmospheric pressure on the spinal cord in rats post
contusion injury. In a first animal protocol, 250-300 gram Sprague
Dawley rats were obtained and the model of spinal contusion
developed and verified. The procedure for creating the injury and
assessing recovery was based upon the description of spinal cord
contusion injury in Wrathall, et al., Spinal Cord Contusion in the
Rat: Production of Graded, Reproducible, Injury Groups,
Experimental Neurology 88, 108-122 (1985). The surgical technique
was developed for exposing the spinal cord in the anesthetized rats
and consistent production of a contusion injury by dropping a
cylindrical 10 gram weight through a glass tube from a height of 5
cm. Half of the rats were untreated controls while the other half
had the area of contusion exposed to 4 hours of sub-atmospheric
pressure (25 mm Hg below atmospheric). However, the degree of
injury did not produce a significant injury in the control animals
(they recovered quickly), and thus it was not possible to compare
the treated animals to the control animals.
[0047] Experiment 2
[0048] A second protocol was developed in which a more severe
injury was inflicted on the spinal cord (a 10 gram weight was
dropped from a higher height--7.5 cm). Twenty-eight large (300
gram) Sprague Dawley rats were procured over time and allowed to
acclimate to housing conditions. On the day of surgery, the animals
were sedated and the back shaved and scrubbed for surgery. A
midline incision made over the spine was made extending through the
skin and subcutaneous tissue and the cutaneous maximus muscle and
fascia exposing the deeper back muscles. The paired muscles that
meet at the midline (trapezius and potentially latisimus dorsi)
were separated at the midline and retracted laterally. The deep
`postural` muscles such as the spinotrapezius and/or the
sacrospinal muscles that are attached to the bony structures of the
spine itself were also divided on the midline and retracted
laterally. This exposed the spinous process and potentially some of
the transverse processes. At the level of T7-T9, the spinous
processes and the small transversospinal muscles that extend
between two consecutive vertebra were removed, exposing the surface
(dura) of the spinal cord. A laminectomy was performed at T-8. The
spine was stabilized at T-7 and T-9 and a 10 gram weight was
dropped from a height of 7.5 cm to produce a moderate degree of
spinal cord injury based on the procedure of Wrathall, et al. Five
animals died on their respective day of initial surgery (three in
the control group and two in the vacuum treated group), and early
in the experiment one animal in the control group died two days
into the experiment, leaving 22 animals. By the end of the
experiment, eleven animals had been assigned randomly to each of
the control group and the 25 mm Hg vacuum group.
[0049] For the control rats, no treatment was provided, and the
injury was sutured closed. For the vacuum treated rats, a polyvinyl
alcohol vacuum dressing (Vacuseal Plus, Polymedics, Belgium) was
placed on the cord and the skin sutured closed, with the vacuum
tube extending through the incision. After 1 hour delay, a vacuum
(sub-atmospheric pressure) of 25 mm Hg below atmospheric pressure
was applied for 4 hours to each animal in the vacuum treatment
group. At the end of this time, the animals were re-sedated, the
vacuum dressings removed, and the skin incision re-sutured with
monofilament suture.
[0050] The incision sites were inspected daily. The animals were
examined for signs of ability to self void their bladders. Any
animal unable to void received manual assistance three times per
day at 8 hour intervals. The animals were examined daily for signs
of auto-cannibalism, pressure sores, and for degree of hydration
(pinch test). The animals were housed in soft shavings to minimize
potential for pressure sore development. Food was placed on the
bottom of cages to facilitate eating. Animals were examined daily
for recovery of motor function of hind limbs using a modified
Tarlov scoring system for each hind limb. (0=no movement, no weight
bearing; 1=slight movement, no weight bearing; 2=frequent movement,
no weight bearing; 3=weight bearing, 1-2 steps; 4=walking with
deficit; 5=walking with no deficit.) The animals were tested daily
on an inclined plane (angle at which they can no longer hold on and
slide off the plane), and for hind limb grip strength. The animals
were euthanized 14 days post surgery, and the spines removed and
examined histologically.
[0051] The results of the experiment are provided in Tables 1 and
2, with day "0" being the day of surgery. Several animals exhibited
minimal injury/deficit and may not have had an adequate injury
during weight drop. (Control animals 1, 2, 11 and treated animals
3, 9, 10. See Tables 1 and 2.) Two animals exhibited a severe/total
injury and did not recover. (Control animal 5 and treated animal 2.
See Tables 1 and 2.) This left a total of seven control and seven
treated animals believed to have an adequate injury but not a
severe/total injury.
[0052] For purposes of analysis, an animal was considered
"recovered" as of the day on which it achieved a score of at least
"4/4." Of the seven control animals, three had not recovered to at
least a score of 4/4 (right leg/left leg--walking with deficit) by
day eight post surgery. (Animals 3, 6, 7. Table 1.) Of the
remaining four control animals (animals 4, 8, 9, 10), three animals
reached a score of 4/4 on days 4, 6, and 13, and one reached a
score of 4/5 on day 7. Thus, the four control animals reached a
score of at least 4/4 in a mean of 7.5+/-3.35 days. For the treated
animals, all seven (animals 1, 4, 5, 6, 7, 8, 11) reached a score
of at least 4/4 in a mean of 5.14+/-1.24 days. Thus it is evident
that application of 25 mm Hg vacuum to the injured spine was able
to increase the rate of functional recovery (p=0.059).
TABLE-US-00001 TABLE 1 Control Time Post Surgery (days) 0 1 2 3 4 5
6 7 8 13 Animal 1 5/5 5/5 5/5 5/5 5/5 5/5 5/5 5/5 5/5 2 5/4 5/4 5/4
5/4 5/4 5/4 5/4 5/4 5/4 3 0/0 0/0 1/1 1/1 2/1 2/1 2/2 3/2 3/2 4 2/2
2/2 3/3 3/3 4/4 4/4 4/4 5/4 5/4 5 1/0 1/0 1/0 1/0 1/1 1/1 1/1 1/1
1/1 6 0/0 0/0 1/0 1/0 1/1 2/1 2/2 3/2 3/2 7 0/1 0/1 1/1 1/2 1/2 2/2
2/3 3/3 3/3 8 0/0 0/0 1/1 1/1 2/2 2/2 3/3 3/3 3/3 4/4 9 0/0 0/0 0/1
0/1 1/2 2/2 3/4 4/5 10 0/0 0/0 1/1 1/1 1/1 1/1 4/4 4/4 11 4/4 4/4
5/4 5/5 5/5
TABLE-US-00002 TABLE 2 Vacuum Treated Time Post Surgery (days) 0 1
2 3 4 5 6 7 8 13 Animal 1 1/1 1/2 1/2 2/2 3/4 4/4 4/4 4/4 4/4 2 0/0
0/0 0/0 1/0 1/0 1/0 1/1 1/1 1/1 3 4/4 4/5 5/5 5/5 5/5 5/5 5/5 5/5
5/5 4 0/0 2/0 2/1 3/2 3/3 4/3 4/4 5/4 5/5 5 2/1 2/1 3/2 3/3 4/4 5/5
5/5 5/5 5/5 6 2/3 3/3 3/4 4/4 5/5 5/5 5/5 5/5 5/5 7 1/0 1/0 1/1 2/3
3/4 4/5 5/5 5/5 5/5 8 1/0 1/0 2/1 3/2 3/2 3/2 4/3 5/4 5/4 5/4 9 3/4
5/5 4/4 5/5 5/5 10 4/4 4/4 4/4 5/5 5/5 11 0/0 0/0 1/1 2/2 3/3 3/3
4/4 4/4
[0053] Experiment 3
[0054] An additional protocol was developed in which a still more
severe injury was created that would result in a non-recoverable
(permanent) functional deficit. The contusion paradigm was based
upon techniques developed at the W.M. Keck Center for Collaborative
Neuroscience--The Spinal Cord Injury Project using the NYU spinal
cord contusion system. These systems (currently named "MASCIS") are
custom built and are available commercially through the Biology
Department at Rutgers University (W.M. Keck Center for
Collaborative Neuroscience, Piscataway, N.J.).
[0055] In the preceding experiments, animals were operated on
depending on weight, but in this experiment the animals were
operated on depending on age. Long Evans hooded rats were operated
on at 77 days of age to standardize the severity of injury. Between
one and six days before surgery, some of the animals were sedated
and transported to the Small Animal MRI Imaging Facility of Wake
Forest University School of Medicine, and the spinal cord was
scanned at the level of T9-T10 using a Bruker Biospin Horizontal
Bore 7 Tesla small animal scanner (Ettlingen, Germany). The animals
which were scanned were then allowed to recover from anesthesia in
a heated cage. On the day of surgery the animals were anesthetized,
and the backs of the animals were shaved and a depilatory cream
used. Using aseptic technique, a laminectomy was performed at the
level of T9-T10. The NYU spinal cord contusion system impactor was
used, and the cord was impacted at T9-T10 with a 10 gram rod
dropped from a height of 25 mm. Animals in the control group had
the incision sutured closed, and the animals were allowed to
recover in a heated cage. For treated animals, a polyvinyl alcohol
vacuum dressing (VersaFoam, Kinetic Concepts, Inc., San Antonio,
Tex.) was placed over the cord, the incision sutured closed, and 25
mm Hg vacuum, i.e. 25 mm Hg below atmospheric pressure, applied for
8 hours. After this time the treated animals were re-sedated, the
incision opened, the vacuum dressing removed, and the incision
re-sutured closed. If the animals received a post-surgery MRI, the
animal was scanned 8 hours post impaction.
[0056] Functional recovery was assessed with the BBB scale, a 22
point scale from the W.M. Keck Center for Collaborative
Neuroscience. (Table 3). The animals were monitored for 21 days,
then euthanized by lethal CO.sub.2 exposure. Bladders were
expressed daily, and the animals were monitored for signs of
auto-cannibalism, pressure sores, skin lesions, etc. Any animal
exhibiting signs of auto-cannibalization were removed from the
study and euthanized. Pressure sores and skin lesions were treated
as appropriate and with consultation of ARP veterinary staff.
Despite this care, in the course of this experiment, some animals
died, while others were excluded for other problems.
TABLE-US-00003 TABLE 3 BBB Locomotor Rating Scale Value Condition 0
No observable hind limb (HL) movement 1 Slight Movement of one or
two joints, usually the hip &/or knee 2 Extensive movement of
one joint or Extensive movement of one joint and slight movement of
one other joint 3 Extensive movement of two joints 4 Slight
movement of all three joints of the HL 5 Slight movement of two
joints and extensive movement of the third 6 Extensive movement of
two joints and slight movement of the third 7 Extensive movement of
all three joints of the HL 8 Sweeping with no weight support or
Plantar placement of the paw with no weight support 9 Plantar
placement of the paw with weight support in stance only (i.e. when
stationary) or Occasional, Frequent, or Consistent weight supported
dorsal stepping and no plantar stepping 10 Occasional weight
supported plantar; no front limb (FL)-HL coordination 11 Frequent
to consistent weight supported plantar steps and no FL-HL
coordination 12 Frequent to consistent weight supported plantar
steps and occasional FL- HL coordination 13 Frequent to consistent
weight supported plantar steps and frequent FL-HL coordination 14
Consistent weight supported plantar steps, consistent FL-HL
coordination and Predominant paw position during locomotion is
rotated (internally or externally) when it makes initial contact
with the surface as well as just before it is lifted off at the end
of stance or Frequent plantar stepping; consistent FL-HL
coordination; and occasional dorsal stepping 15 Consistent plantar
stepping and Consistent FL-HL coordination; and No toe clearance or
occasional toe clearance during forward limb advancement;
Predominant paw position is parallel to the body at initial contact
16 Consistent plantar stepping and Consistent FL-HL coordination
during gait; and Toe clearance occurs frequently during forward
limb advancement; Predominant paw position is parallel at initial
contact and rotated at lift off 17 Consistent plantar stepping and
Consistent FL-HL coordination during gait; and Toe clearance occurs
frequently during forward limb advancement; Predominant paw
position is parallel at initial contact and lift off 18 Consistent
plantar stepping and Consistent FL-HL coordination during gait; and
Toe clearance occurs consistently during forward limb advancement;
Predominant paw position is parallel at initial contact and rotated
at lift off 19 Consistent plantar stepping and Consistent FL-HL
coordination during gait; and Toe clearance occurs consistently
during forward limb advancement; Predominant paw position is
parallel at initial contact and lift off; and tail is down part or
all of the time 20 Consistent plantar stepping and Consistent
coordinated gait; consistent toe clearance' Predominant paw
position is parallel at initial contact and lift off; and Trunk
instability; Tail consistently up 21 Consistent plantar stepping
and Consistent coordinated gait; consistent toe clearance;
predominant paw position is parallel throughout stance; consistent
trunk stability; tail consistently up
[0057] For these studies of a permanent injury, 36 rats with the
dura intact completed the study and were analyzed. Eleven (11)
vacuum treated animals started the study, with one animal removed
at five weeks and one at eight weeks due to urinary tract
infections and kidney failure. Thus, 9 vacuum treated animals
completed the 12 week study. Twenty seven control animals started
and completed the study. The vacuum treated animals exhibited a
greater functional recovery (p<0.072) at 3 weeks post injury:
BBB Score=12.818+/-1.401 (n=11) vacuum treated versus
11.704+/-2.391 (n=27) control. The vacuum treated animals exhibited
a significantly greater functional recovery (p<0.001) at 4 weeks
post injury: BBB Score=13.625+/-1.303 (n=11) vacuum treated versus
11.500+/-0.707 control (n=27). FIGS. 6 and 7. The recovery of the
vacuum treated animals plateaued, and the recovery levels of the
control animals gradually approached the level of the vacuum
treated animals. FIGS. 6 and 7. (Note, some animals were studied
for three weeks (generally earlier in the study) while some were
observed for 12 weeks for functional recovery.)
[0058] In addition to the BBB assessments, two animals with intact
dura were analyzed for a change in the cross sectional area (e.g.,
in mm.sup.2) of the spinal cord by pre- and post-injury MRI scans
(with the post-injury scan performed post-treatment for the vacuum
treated animals) using the procedures listed above for this
experiment. Of the four animals produced for this analysis, only
one vacuum treated animal did not have any technical or impaction
error and could be used. Of the control animals, one had a minor
height error which occurred when the release pin of the spinal cord
contusion system was pulled from its housing; all other control
animals had significant impaction errors which precluded analysis
of the cross sectional area of the spinal cord. The machine
recorded height from which the weight was dropped for the vacuum
treated rat was 24.8 mm and for the control rat was 25.782 mm.
[0059] Turning to FIG. 8, the control animal showed a slight
increase in cross sectional area as the scans went down (tail-ward)
the spine. This was evident for both the pre-impaction scan and the
post-impaction scan. At both the above-injury and below-injury
sites, the cross sectional area was not significantly different
between the pre-impaction scan and the post-impaction scan. The
above-injury pre-impaction mean was 5.49 mm.sup.2+/-0.2 (n=5)
versus a post impaction mean of 5.32 mm.sup.2+/-0.23 (n=4):
p<0.211) (The below-injury pre-impaction mean was 6.81
mm.sup.2+/-0.25 (n=3) versus a post-impaction mean of 6.46
mm.sup.2+/-0.78 (n=4): p<0.464) However, at the site of
impaction, the post-impaction cross sectional area for the control
animal was significantly larger (p<0.001) than the pre-impaction
cross sectional area: mean of pre-impaction area of 5.63
mm.sup.2+/-0.24 (n=5 scans) versus mean post-impaction area of 6.43
mm.sup.2+/-0.32 (n=4 scans). This was most likely due to swelling
of the cord due to the limits of the dura, as the bone which would
be the limiting factor on diameter of the cord had been
removed.
[0060] Unlike the control animal, the vacuum treated animal did not
show an increase in mean diameter of the cord at the site of the
injury after vacuum treatment, FIG. 9. The mean pre-impaction area
at the level of the injury was 7.28 mm.sup.2+/-0.73 (n=4 scans)
versus a mean post-treatment area of 7.03 mm.sup.2+/-0.99 (n=4
scans) (p<0.73). The similarity in the size of the spinal cord
pre-impaction and post-treatment at the site of the injury was most
likely due to removal of fluid from within the dura, thus
maintaining the initial diameter of the cord.
[0061] The pre-impaction and post-treatment scans at the
above-injury area were similar (not significantly different). The
pre-impaction above-injury area was 7.79+/-0.64 (n=3 scans) versus
post-treatment of 8.33+/-1.11 (n=5 scans) (p<0.48). For the
scans of the vacuum treated animal below-injury, the post-treatment
cross sectional area of the cord was significantly larger than the
pre-impaction cross sectional area: Pre-impaction area of
7.61+/-0.43 (n=4 scans) versus post-treatment area of 10.76+/31
0.35 (n=4 scans), p<0.001. A possible explanation for the
increase in below-injury cross sectional area of the cord may be
attributable to venous congestion. Alternatively, the applied
vacuum may have actively withdrawn cerebrospinal fluid from around
the cord, allowing the cord to expand to fill the area of the
spinal canal within the vertebral bodies. This expansion would act
to minimize the intra-dura pressure and help to preserve cell
viability.
[0062] These and other advantages of the present invention will be
apparent to those skilled in the art from the foregoing
specification. Accordingly, it will be recognized by those skilled
in the art that changes or modifications may be made to the
above-described embodiments without departing from the broad
inventive concepts of the invention. It should therefore be
understood that this invention is not limited to the particular
embodiments described herein, but is intended to include all
changes and modifications that are within the scope and spirit of
the invention as set forth in the claims.
* * * * *