U.S. patent application number 09/246274 was filed with the patent office on 2002-01-24 for protection device.
Invention is credited to ALLEYNE, NEVILLE.
Application Number | 20020010466 09/246274 |
Document ID | / |
Family ID | 26849557 |
Filed Date | 2002-01-24 |
United States Patent
Application |
20020010466 |
Kind Code |
A1 |
ALLEYNE, NEVILLE |
January 24, 2002 |
PROTECTION DEVICE
Abstract
A spinal protection device is provided which minimizes the
formation of post-operative adhesions. The protection device may
comprise a fenestrated shield, and may be positioned such that
contact between the shield and the spinal dura is substantially
avoided.
Inventors: |
ALLEYNE, NEVILLE; (LA JOLLA,
CA) |
Correspondence
Address: |
KNOBBE MARTENS OLSON & BEAR LLP
620 NEWPORT CENTER DRIVE
SIXTEENTH FLOOR
NEWPORT BEACH
CA
92660
US
|
Family ID: |
26849557 |
Appl. No.: |
09/246274 |
Filed: |
February 8, 1999 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09246274 |
Feb 8, 1999 |
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08769508 |
Dec 19, 1996 |
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5868745 |
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08769508 |
Dec 19, 1996 |
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08440363 |
May 12, 1995 |
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5611354 |
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08440363 |
May 12, 1995 |
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08152433 |
Nov 12, 1993 |
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08152433 |
Nov 12, 1993 |
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07975106 |
Nov 12, 1992 |
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Current U.S.
Class: |
606/279 ;
606/86R |
Current CPC
Class: |
A61B 17/00 20130101;
Y10S 606/907 20130101; Y10S 606/91 20130101; A61B 90/00 20160201;
A61B 2090/0816 20160201; A61B 17/70 20130101 |
Class at
Publication: |
606/61 |
International
Class: |
A61F 002/30 |
Claims
What is claimed is:
1. A biocompatible protection device to prevent the postoperative
formation of adhesions comprising: a shield adapted to cover a bony
dissection in the spine of a vertebrate, said shield comprising
attachment ports for attaching said shield to bone, said shield
also comprising fenestrations.
2. The protection device of claim 1, wherein said shield comprises
an elongate concavity for maintaining said shield away from the
spinal dura following installation.
3. The protection device of claim 1, wherein said shield is
substantially pliable.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority to is a continuation of
U.S. Patent Application Ser. No. 08/769,508, now U.S. Patent No.
5,868,745, filed Dec. 19, 1996, which is a continuation of U.S.
Patent Application Ser. No. 08/440,363, filed May 12, 1995, now
U.S. Patent No. 5,611,354, which is a continuation of U.S. Patent
Application Ser. No. 08/152,433, filed Nov. 12, 1993, abandoned,
which is a continuation-in-part of U.S. Patent Application No.
07/975,106 filed Nov. 12, 1992, now U.S. Patent No. 5,437,672. The
disclosures of U.S. Patent Nos. 5,868,745, 5,611,354, and 5,437,672
are hereby incorporated by reference in their entireties.
BACKGROUND OF THE INVENTION
[0002] Adhesions commonly form between an organ and surrounding
connective tissue and bone after a surgical procedure. Following
surgical trauma, connective tissue surrounding the organ
proliferates to from a fibrous mass that binds the organ to
neighboring organs, viscera, muscle, or bone. Depending on the type
of surgery and the location of the incision, the adhesions may
produce negligible discomfort or severe pain. However, adhesion
formation can significantly complicate subsequent surgical
procedures at the same or adjacent sites. Repeat surgical
procedures are fairly frequent in the back, cardiac, abdomen and
cranium. The presence of post-operative adhesions from a prior
surgery complicates the second surgery because the contacts between
the target organ and the neighboring bone and connective tissue
must be carefully dissected away before the surgeon can initiate
the corrective surgical procedure. The surgeon risks damaging the
target organ during the dissection and the time required for the
dissection procedures adds to the total time that the patient is
under general anesthesia.
[0003] An unfortunate consequence of modern back surgery, whether
lumbar, thoracic, or cervical surgery, is the formation of
post-operative scar tissue. Scar formation surrounding the dura and
nerve roots oftentimes will compress the nerve roots and cauda
equina, thereby producing neural complications such as persistent
low back pain, sciatica, and/or bowel and bladder dysfunction.
Multiple revision operations may prove necessary due to recurrent
disk herniation, post-operative spinal stenosis (iatrogenic or
acquired), or because of exuberant epidural fibrosis.
[0004] Scar tissue formation after laminectomies and laminotomies
for disk excision or a decompressive laminectomy for spinal
stenosis present both surgeon and patient with an additional
post-operative concern. Laminectomies and laminotomies frequently
remove bone tissue and leave the dura exposed. Post laminectomy
scar tissue, also termed epidural fibrosis, is primarily formed
from fibrous connective tissue and develops in the post-operative
hematoma that forms between the paraspinous muscles and the dura.
The dura is relatively thin and can easily be injured during
surgery. In particular, the dura is susceptible to damage during
revision surgery when scar tissue adheres to the dura making it
difficult for the surgeon to perform an adequate neurolysis. Thus,
a method is needed for protecting the dura from scar tissue
adhesion.
[0005] At the present time, methods to minimize the amount of scar
tissue include the use of autogenous fat grafts, gelatin foams or
sponges, or microfibullary collagen as an interposing protective
layer between the spinal dura and the adjacent viscera. Other
biological substances and chemical compounds that have been tested
experimentally for their usefulness in animals include bone grafts,
microfibrillar collagen, elastase, polyethylene, mylar, dacron,
teflon and methylmethacrylate.
[0006] Autogenous fat grafts have been used following laminectomies
as early as 1964. The fat is placed over the exposed dura after
removal of the lamina or a portion of the lamina. The fat provides
a protective barrier for the dura, and may limit scar formation
between the muscle and the dural tissue. However, fat grafts are
known to frequently adhere to the dura. These adhesions complicate
revision surgery because they require tedious dissection by the
orthopaedic or neurosurgeon. Fat grafts are preferably harvested
from a sight close to the surgical incision, such as the subdermal
areolar tissue bed. However, unless the patients are overweight,
fat harvesting from nearby locations is not always possible,
particularly in multiple laminectomy procedures. Further, fat
harvesting may require a second incision. The incisions at the
secondary locations may sometimes lead to complications such as
hematoma formation or dimpling in the skin.
[0007] Other substances are used where fat grafts are not possible
or desired. Gelatin foam (such as Gelfoam.RTM. sponge, supplied by
Upjohn Company Inc., Kalamazoo, Mich.), or polylactic acid (PLA) is
a useful substitute for autogenous fat grafts. This material is
also placed over the dura to reduce scar formation. There is some
controversy concerning the preference of gelatin foams or sponges
versus fat; however, neither is optimal. Like fat, gelatin foams or
sponges may move out of position following surgery. Furthermore,
while fat and gelatin foams may form a barrier between the visceral
tissue and the dura, there is a propensity for both fat and gelatin
foam or sponge to adhere to the dura. Neither fat nor gelatin foam
provides adequate physical protection to the cauda equina.
[0008] A mechanical barrier that would provide support to the
spinal dura as well as reduce scar formation is needed. U.S. patent
No. 4,013,078 to Feild discloses a device for preventing adhesions
between the patient's dura and spinal nerves and other anatomic
structures following spinal surgery. The device includes a conduit
sheath of teflon or silicone that is positioned in close proximity
to the nerve root. Like the previous protective overlay substances,
such a device is invasive to the neuroforamen and anchors directly
to the dura. This in turn would promote adhesions between the dura
and the protecting device creating unnecessary complications for
revision surgery.
[0009] In order to minimize the surgical time for dissection,
minimize nerve injury and minimize dural tears a spinal cord
protection device should be simple to insert, non-invasive to the
dura and maintain a distance from the neural tissues. Preferably,
anchoring means should contact bone instead of tissue prone to scar
formation to minimize post-operative epidural fibrosis. Finally,
the optimal mechanical device is readily contoured to provide a
customized mechanical barrier to prevent dural or nerve root
injury. Preferably, the device is adaptable in design to
accommodate other surgical devices used in back surgery. Such a
device is provided in the detailed description of this
invention.
[0010] Adhesions also form between the heart and the anterior
thoracic skeleton following cardiac surgery. In particular,
adhesions form between the posterior surface of the sternum and the
anterior surfaces of the heart. Repeat open heart surgeries are
complicated by adhesion formation because the scar tissue must be
dissected away before the sternum can be cut lengthwise and before
the anterior thoracic skeleton can be retracted to expose the
heart. For example, it is estimated that there are at least 250,000
coronary artery bypass graft surgeries done each year in the United
States. Approximately 20% of these surgeries are revision
surgeries. Adhesions form between the greater vessels of the heart
and the posterior surface of the sternum. The adhesions make the
separation of the pericardium from the sternum difficult and thus
create severe complications during revision surgeries. It is
estimated that 2 to 4% of the revision surgeries end in fatality as
a result of adhesion-induced complications. Therefore, there is a
need for a device that minimizes adhesion formation. The present
device fulfills this need. Moreover, the device is simple to
insert, easy to remove and prevents the formation of adhesions
between the heart and the posterior surface of the sternum.
SUMMARY OF THE INVENTION
[0011] The present invention comprises methods and apparatus for
spinal protection following spinal surgeries. In one embodiment,
the invention comprises a biocompatible protection device
comprising a shield adapted to cover a bony dissection in the spine
of a vertebrate. The shield may include attachment ports and
fenestrations.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 is a right-front perspective view of the preferred
embodiment, showing the arched shield and attachment arms;
[0013] FIG. 2 is a bottom plan view showing the arched shield and
attachment arms of FIG. 1; FIG. 3A is a partial perspective view of
lumbar vertebrae illustrating the bony dissection associated with a
laminectomy;
[0014] FIG. 3B is a partial perspective view, similar to FIG. 3A,
showing use of the shield device to cover the laminectomy defect in
accordance with the present invention;
[0015] FIG. 3C is a partial perspective view showing the use of an
elongated shield device to cover a laminectomy defect associated
with two vertebrae;
[0016] FIG. 4A is a partial perspective view of lumbar vertebrae
illustrating the bony dissection associated with a
hemilaminectomy;
[0017] FIG. 4B is a partial perspective view, similar to FIG. 4A,
showing use of the shield device to cover the hemilaminectomy
defect in accordance with the present invention;
[0018] FIG. 5 is a partial side perspective view of the lumbar
vertebrae showing another preferred embodiment of the present
invention;
[0019] FIG. 6 is a sectional view taken substantially along the
line 6-6 of FIG. 5, showing the positioning of the arched shield in
accordance with a preferred embodiment of the present
invention;
[0020] FIG. 7 is a top plan view showing an exemplary cardiac
protector device of this invention;
[0021] FIG. 8A is a longitudinal cross-section of the device taken
substantially along the line 8-8 of FIG. 7 illustrating the curved
shield embodiment;
[0022] FIG. 8B is a longitudinal cross-section of the device
illustrating the flat shield embodiment;
[0023] FIG. 9 is a transverse cross-section of the device taken
substantially along the line 9-9 of FIG. 7 illustrating the
longitudinal guide;
[0024] FIG. 10 is a perspective view illustrating the position of
the device relative to the heart and the anterior thoracic
skeleton; and
[0025] FIG. 11 is an exploded perspective view further illustrating
the position of the device relative to the heart and rib cage.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0026] Back surgery including laminectomies, hemilaminectomies
spinal stenosis surgery, and diskectomies, including
microdiskectomies, involve the removal of vertebral bone tissue to
gain access to the spinal foramen. This bone removal leaves the
spinal dura exposed and unprotected. Following surgery, scar tissue
frequently forms between the dura and the surrounding tissue.
Research indicates that the epidural scar is principally formed
from fibroblasts derived from the damaged erector spinae muscles
that overlay the laminectomy site (LaRocca, et al. J. Bone Joint
Surg. 56B:545-550,1974). These cells form adhesions that bind the
muscle tissue to the fragile dura. As a result of adhesion
formation, spinal mobility is reduced and the adhesions often lead
to pain and slow post-operative recovery. The device of this
invention advantageously operates to prevent adhesion formation and
to physically protect the dura, now exposed by surgery. In
addition, the device of this invention facilitates future revision
surgery.
[0027] While this invention will be discussed as it relates to
spinal surgery, it is contemplated within the scope of this
invention that the shield of this invention is suitable as a
protective covering for any bony dissection in a vertebrate.
Therefore, while a preferred embodiment of this invention relates
to the use of the shield to cover a bony dissection of a vertebrae,
the shield device could similarly be used to cover a bony
dissection associated with open heart surgery, the bony dissection
of the cranium, or the like. Those with skill in the art of
orthopaedics or neurosurgery will be able to generate formed
shields, anchorable to bone, that will accommodate bony dissections
in a variety of skeletal tissues.
[0028] FIG. 1 provides an exemplary drawing of a preferred
embodiment of this invention. The invention provides a formed
shield 10 adapted to fit onto at least one vertebral facet (not
shown in FIG. 3) to cover the bony dissection associated with a
hemilaminectomy procedure, a laminectomy procedure or the like. As
diagrammed in FIG. 1, a main body 11 of the shield 10 is molded or
formed preferably as an arch or semi-cylinder. The arch flattens
out on each side of the main body 11, forming a pair of support
planes 12. The support planes 12 provide a surface area suitable
for resting the shield 10 against the vertebral bone. The arched
contours of the main body 11 prevent contact of the main body 11
with the spinal dura or nerve roots, thereby minimizing further
trauma to the spinal dura and preventing the formation of adhesions
and scar tissue between the underside of the device and the spinal
dura.
[0029] As will be discussed in the context of FIGS. 4 and 5, the
removal of vertebral bone along the spinal column leaves the cauda
equina susceptible to physical trauma. Products such as gelatin
foam or fat do not provide a sufficient barrier to prevent
potential physical trauma. The shield 10 of the present invention
advantageously rests on bone to minimize the contact between the
device and the spinal dura and surrounding neural tissues. Such
reduced contact minimizes adhesion formation between the neural
tissues and the device itself.
[0030] In a preferred embodiment of this invention, a plurality of
fenestrations 14 are formed in the surface of the shield 10. It is
contemplated within the scope of this invention that the
fenestrations 14 may take any number of forms or shapes, and those
depicted in the figures are to be viewed as exemplary The
fenestrations 14 are distributed across the surface of the shield
10 and are designed to prevent the retention of fluid within the
vertebral canal. Absent such openings, liquids such as cerebral
spinal fluid, blood, and irrigation fluid associated with surgery
could potentially accumulate beneath the shield 10 and create
harmful pressure on the cauda equina and associated neural tissue.
Following surgery the fenestrations 14 serve as out-flow ports to
relieve pressure associated with the accumulation of fluid beneath
the device during the healing process. Optionally, the
fenestrations 14 may be covered with a filter, mesh, or the like
(not shown), to prevent the extension of scar tissue formation into
the fenestrations 14 while permitting the passage of fluid through
the shield 10.
[0031] In another preferred embodiment of this invention, the
device is associated with a surgical drain (not shown) to further
facilitate fluid egress from the surgical site. Such surgical
drains are well known in the art and it is contemplated that the
device of this invention is adapted to accommodate a drain or in
another embodiment a drain is directly incorporated into the
device.
[0032] When positioned correctly over the bony dissection, it is
unlikely that the shield 10 would move. Thus, although not
necessary to the function of the present invention, it is
understood that most surgeons would likely prefer to anchor the
shield 10 in place following surgery.
[0033] The attachment means contemplated for use with the shield 10
of the present invention can take any number of forms. In a
preferred embodiment, the attachment is to bone. Bone attachment
contemplated within the scope of this invention include, but are
not limited to, both attachment to adjacent spinous processes and
lateral attachments such as to facets, transverse processes,
articulating processes or the like. It is desirable that no contact
is made with the neural elements. Preferably, the attachment means
does not extend into the spinal canal or neuroforamen to an extent
that would make contact with the dura or nerve roots likely.
[0034] In a preferred embodiment, the attachment means is a pair of
attachment arms 16 attached to the main body 11 of the shield 10.
Preferably, each of the attachment arms 16 comprise a rod 17 that
is attached to and extends, at an acute angle, from the main body
11 of the shield 10. In this embodiment, the rods 17 are used to
attach the shield 10 to an inferior or superior spinous process
(see FIGS. 4A and 4B). The actual attachment to the spinous process
may take any form known in the art. In a preferred embodiment the
rods 17 terminate in a pair of attachment flags 18. As shown in
FIG. 1, the flags 18 are provided with a plurality of pin holes 19
to facilitate their attachment to an adjacent spinous process. In
another embodiment, the attachment means is through the use of
surgical wire, staples or the like. The pins, wire or other
attachment means contemplated within this invention, whether in the
form of the rods 17 or otherwise, are prepared from surgical steel,
tungsten, titanium or other suitable materials. FIG. 2 clearly
illustrates the manner in which the attachment means laterally
extend beyond the "footprint" of the main body 11.
[0035] Advantageously, the fenestrations 14 may also serve as
attachment means. For example, suture or wire is useful for
attaching the shield 10 to bone by being passed through the
fenestrations 14, binding the shield 10 to adjacent bone.
Similarly, it is contemplated that in such cases where necessary,
the shield 10 is stabilized to cartilage ligament or adjacent
muscle tissue. In either case, the fenestrations 14 ably serve as
anchoring points over the entire surface of the shield 10, as
required.
[0036] The actual dimensions of the shield 10 will vary depending
on the particular surgical procedure. In a preferred embodiment,
the device is prepared in a size and shape to accommodate a
laminectomy. Laminectomies are used for spinal stenosis surgery,
for central disk herniation, for an osteophyte centrally, for
intradural tumors or for other conditions such as epidural
abscesses. Laminectomies result in the exposure of the right and
left nerve root axilla and the central cauda. The application of
the device to a bony dissection following a laminectomy procedure
is illustrated in FIG. 3A, 3B and 3C.
[0037] FIG. 3A is an illustration of a laminectomy of the fifth
lumbar vertebrae. A spinal cord 24 is schematically depicted,
surrounded by a vertebral column composed of individual lumbar
vertebrae 26, and the sacrum 28. Although the shape of the
individual vertebrae 28 does vary, each are composed of a
transverse process 30 and a spinous process 32.
[0038] A preferred application of the shield 10 is provided in FIG.
3B. The shield 10 is positioned over the laminectomy site and the
attachment arms 16, terminating here, in attachment flags 18, are
used to attach the device to the spinous process 32 of the fourth
lumbar vertebrae 26. In addition to the attachment arms 16, in this
embodiment, a set of four attachment pins 20 are used to anchor the
four corners of the shield 10 in place to the surrounding vertebrae
tissue.
[0039] FIG. 3C illustrates another preferred embodiment of the
invention. In FIG. 3C, the shield 10 is designed to span a
laminectomy defect involving two vertebrae. Attachment arms 16 and
attachment flags 18 are similarly positioned on the shield 10 of
FIG. 3C. In this embodiment, the shield 10 is adapted to span at
least two vertebrae. It is contemplated that the shield 10 is
prepared in a length and width to accommodate laminectomies
involving three or more vertebrae.
[0040] In the embodiment illustrated in FIGS. 3A and 3B, it is
contemplated that the overall length of the shield 10 will be at
least as long as a lateral length l of the lamina surface of the
vertebrae 26 containing the laminotomy defect, and wide enough to
stably mate with the remaining lateral lamina surfaces of bone
following the laminectomy procedure. Therefore, it is contemplated
that the overall length of the shield 10 for use in spanning one
laminectomy defect (or hemilaminectomy defect, see FIGS. 4A and 4B)
ranges in size from about 2.0 cm to 6.0 cm and preferably between
2.5 cm to 4.5 cm, with a final width ranging from about 1.5 cm to
4.5 cm, and preferably between about 2.0 cm to 3.5 cm.
[0041] Customization of the final size and shape of the shield 10
by the surgeon will produce a size suitable for each individual
patient. The optimal thickness of the shield 10 will vary depending
on the plasticity or moldability of the device, which in turn will
depend on the choice of shield material. However, it is
contemplated that a preferred thickness of the shield 10 should be
approximately 0.5 mm to 8 mm and more preferably, about 0.5 mm to 5
mm.
[0042] FIG. 4A provides an illustration of the bony dissection
associated with a hemilaminectomy. Since the dissection for a
hemilaminectomy is smaller than that of a laminectomy, it is
contemplated that the surgeon, using a scalpel, or the like will be
able to readily customize the shield 10 as sized for the
laminectomy to overlie the exposed dura after a hemilaminectomy
procedure. An example of a customized shield l0a contemplated for
use in a hemilaminectomy is provided in FIG. 4B. The customized
shield l0a is attached to the vertebrae 26 using the set of
attachment pins 20. Alternatively, it is contemplated that the
shield 10 of FIG. 1 could be customized for a hemilaminectomy by
removing one of the attachment arms 16. The remaining attachment
arm 16 serves as an attachment means to anchor the shield 10 to a
superior or an inferior spinous process.
[0043] It is further contemplated that the overall length of the
shield 10 can be varied to accommodate laminectomies or
hemilaminectomies involving more than one vertebrae. Thus, for
example, in a laminectomy procedure involving the third, fourth and
fifth lumbar vertebrae, the shield is preferably about 6.0 cm to
about 12 cm in length and more preferably about 6.5 cm to about 9
cm in length. The width is preferably about 2.0 cm to 5.0 cm and
more preferably about 2.0 cm to 3.5 cm.
[0044] As illustrated in FIG. 1, the main body 11 of the shield 10
preferably has an arch shape, and height h that prevents contact
between the spinal dura and the surface of the shield 10.
Preferably, the height h of the arch is between about 0.2 cm and
4.5 cm from the support planes 12, although within this range, it
is contemplated that the shield 10 will be manufactured in at least
two separate ranges of arch heights.
[0045] It is further contemplated that the arch height h can be
varied to accommodate other medical devices known in the art. In a
particularly preferred embodiment, the height h of the arch is
between about 0.2 cm to 1.5 cm, or about one-half the height of an
adjacent spinous process when positioned on the patient, and is
used with medical devices such as a Dynamic Transverse Traction
("DTT") unit or other instrumentation systems employing a plurality
of pedicle screws 34, (see FIG. 5) such as the Steffee-VSP system
(AcroMed Corporation), Isola instrumentation (AcroMed Corporation,
Cleveland, Ohio), or the like. The use of the shield 10 with such a
device is illustrated in FIG. 5 in side view and in FIG. 6 in
cross-section.
[0046] DTTs are particularly useful where lumbar segmental
instability is a problem. The pedicle screws 34 and transverse rods
36 associated with these devices tend to restrict the placement of
a spinal cord protective device over the spinal canal. The shield
10 that is suitable for a DTT device, or the like, preferably has a
height h smaller than the dimension of the height between the DTT
construct and the exposed dura. The reduced arch size permits the
positioning of the spinal cord protection device beneath the
pedical screws 34 and the transverse rods 36 without impingement In
such a case, the shield 10 is anchored to the vertebrae 26 through
the fenestrations 14. Alternatively, the shield 10 may be anchored
at its periphery to the adjacent facets or spinous processes 32
above or below the decompression, using anchoring pins together
with the anchoring means associated with the fenestrations 14.
[0047] It is contemplated that the shield 10 of this invention may
be prepared from any number of materials known in the art. It is
contemplated that the device could be prepared from surgical steel
including a woven metal fiber or other similar material. In a
preferred embodiment of this invention, the device is prepared from
a thermoplastic polymer such as polypropylene, polyethylene,
polymethacrylate or the like. Other materials contemplated for use
in this invention include, but are not limited to, tungsten,
titanium, polytetrafluoroethylene, silicone, bioerodable polylactic
acid, hydroxylapatite, regenerated collagen or the like. Those with
skill in the art of medical devices will be readily able to select
and formulate a composition having the preferred characteristics
herein described.
[0048] Preferably, the material is biocompatible and is capable of
being cut with a standard surgical tool, such as a scalpel, knife
or scissors to permit customization of the device in the operating
room to the shape and size of the bone defect for each individual
patient. Methods for manufacturing the device of this invention
will depend on the choice of material. Those with skill in the art
of manufacturing implantable medical devices will be readily able
to use the description of the invention provided herein to produce
the contemplated spinal cord protection device. Thus, the device of
this invention can be tooled, molded, heat pressed or the like. It
is further contemplated that, depending on the selection of
material for manufacturing the device of this invention, the device
may have some pliability, such that the surgeon can customize the
device to fit the desired bony dissection and, in addition, the
shield 10 can be further bent or molded by the surgeon to
accommodate the particular topography of the patient's spine.
[0049] The device of this invention may be prepared from a solid
sheet of material, or the device can advantageously be prepared as
a laminate. For those embodiments where the device is a composite
of laminated sheets, it is possible to include or incorporate a
radiopaque material as a laminated sheet into the device. Similarly
the shield material can be impregnated with a radiopaque substance
or incorporate a radiopaque material into the edges of the device.
Suitable radiopaque materials include metals or halogenated
compounds such as iodinated or brominated compounds. Other
compounds include barium containing substances, renografin or
commercially available, Isovue.RTM. (Squibb Diagnostics, Princeton,
N.J.). Thus, the polymers contemplated for use in preparing the
shield of this invention are preferably halogenated or are prepared
in combination with halogenated polymers.
[0050] The presence of a radiopaque material in the shield 10
permits visualization of the shield 10 by X-ray radiation or the
like. In situations where the patient's back pain persists or where
revision surgery is contemplated, the surgeon is able to determine
the position of the shield device of this invention prior to or
during the revision surgery. The radiopaque substance also allows
the surgeon to verify the location of the bone dissection as
determined from the position of the shield.
[0051] It is further contemplated that the shield 10 of the
invention can advantageously be impregnated with, or otherwise
positioned in place in association with, a drug suitable for
inhibiting the formation of adhesions. Therefore, in another
preferred embodiment, the shield contains an absorptive,
saturatable or impregnatable material suitable for acting as a
carrier for an adhesion-inhibiting substance. Suitable
adhesion-inhibiting drugs contemplated for use in association with
the shield 10 of this invention include, but are not limited to,
heparin salts and analogs of heparin salts, such as Pentosan
Polysulfate ("PPS", available, for example, from Sigma Chemical
Company, St. Louis, Mo.) or the like, or growth factor inhibitors
or other compounds recognized in the art to inhibit adhesion
formation. Further, compounds such as gelatin foams such as
Gelfoam.RTM. sponge or Avitene.RTM. (MedChem, Inc. Woodburn, Mass.)
can additionally be used together with the shield 10 of this
invention to further reduce the incidence of adhesions following
surgery.
[0052] One of the important advantages of this invention, over
gelatin foams and other materials used in the art, is that the
device facilitates revision surgery. Revision surgery is
complicated by the formation of adhesions to the spinal dura.
Dissections of adhesions and scar formation increase the time the
patient must be under anaesthesia. Moreover, dissection of the scar
tissue can result in inadvertent pierces or tears in the dura and
the release of spinal fluid into the surgical area that can further
complicate surgery. The spinal cord protection device prevents
adhesions with the dura. During revision surgery, the surgeon can
cut through the muscle and facia to the device quickly without the
potential of piercing or tearing the spinal dura.
[0053] To further facilitate revision surgery, it is contemplated
that in another preferred embodiment of this invention, the shield
10 is colored. It is contemplated that the selected dye will
contrast in color with bone, blood or internal tissues, and thus
further facilitate revision surgery since the surgeon can rapidly
identify the shield 10 during the dissection process. Thus,
contrasting colors contemplated for use with this device include
shades of blue, green, black, purple, yellow, orange or the
like.
[0054] While this invention is described in association with lumbar
vertebrae, it is contemplated that the shield 10 of this invention
is suitable for the cervical and thoracic regions of the spine as
well. Further, as disclosed supra, the shield 10 is contemplated
for use in any location in the body associated with a bony
dissection.
[0055] The shield 10 of the present invention is contemplated to be
commercially available in a number of different sizes, shapes and
include various attachment means. The shields preferably are
packaged in separate sterile packaging and can be arranged on a
tray that includes single and multiple protector devices in
different sizes and embodiments.
[0056] An exemplary surgical procedure employing the shield 10 of
this invention is provided in Example 1, below. This procedure is
only exemplary. Surgeons skilled in the art of orthopaedics and
neurosurgery will be readily able to adapt their surgical
techniques and surgical procedures to include the use of this
shield and in particular, those surgeons skilled in spinal surgery
will readily appreciate the variations discussed herein that do not
detract from the scope of this invention.
[0057] In another aspect of this invention, the device is
positioned between a target organ or tissue and the dermis to
protect that organ or tissue from damage during the accessing stage
of a subsequent surgical procedure. The protector device is
positioned over the organ or tissue and is preferably anchored to
bone, cartilage or muscle. When revision surgery is necessary, the
surgeon can rapidly access the protector device without the risk of
nicking or damaging the underlying organ or tissue. The protector
device can then be removed to expose the target tissue or
organ.
[0058] It is contemplated that the device will also facilitate
revision surgery by minimizing post-operative adhesion formation.
Post-operative adhesion formation complicates a wide variety of
revision surgeries. As discussed above, these adhesions make
dissection tedious because the adjacent bone or tissue is now
adhered to the target organ. This increases the likelihood that the
organ will be inadvertently damaged during the surgical procedure.
The presence of adhesions dramatically increases the time that a
person is under anesthesia. The present invention overcomes these
problems by creating a barrier that minimizes adhesion formation
between adjacent tissue plans and protects the surgical area from
damage during the accessing phase of a subsequent revision
surgery.
[0059] One application of the adhesion inhibitor of the present
invention is following open heart surgery. Adhesions form between
the pericardium and the posterior surface of the sternum following
a variety of open-heart cardiac procedures that disrupt the
pericardium and the linings of the greater vessels of the heart. In
particular, children who have congenital cardiac defects often
require multiple surgical procedures over their lifetimes. In
addition, a significant percentage of individuals who receive
cardiac bypass surgery will require a second cardiac procedure
months or years after their original bypass surgery. A common
problem associated with these surgeries is that adhesions form
between the posterior portion of the sternum and the anterior
portion of the pericardium of the heart following surgery. These
adhesions complicate subsequent surgeries because the heart is
affixed to the sternum during the second sternotomy procedure. The
surgeon must tediously dissect both pericardial adhesions and
adhesions forming between the greater vessels of the heart and the
sternum before performing the sternotomy.
[0060] Adhesions are particularly a problem for those revision
cardiac surgeries that employ portions of the internal mammary
artery for bypass tissue. Since the internal mammary artery has a
higher degree of patency than the saphenous vein, or other veins of
the lower extremity typically used for the bypass procedure, the
dissection process required to release the heart from the sternum
in a revision surgery is relatively complex. However, for a number
of other reasons, the internal mammary artery is the vessel of
choice for current bypass surgeries. These dissections are an
obligate step of the revision surgery and increase the amount of
time required to perform the second surgery and complicate the
surgical procedure by increasing the risk that the heart will be
inadvertently lacerated, nicked or otherwise damaged. The
lacerations or nicks to the heart and greater vessels may result in
serious complications or catastrophic results.
[0061] An example of the type of adhesion-minimizing protector
device contemplated in this invention is illustrated in FIG. 7.
This device is adapted to facilitate repeat open heart surgeries.
The body of the device 40, also known as a shield, is preferably
substantially oblong in shape. It is also contemplated that the
device can be substantially circular or substantially rectangular
in shape; however, as illustrated in FIG. 7, the edges of the
device are preferably rounded and smoothed to reduce abrasion and
bruising of the surrounding tissue after implantation. Thus, the
use of the term "substantially oblong" is used herein to mean that
the overall conformation of the anterior surface of the device is
generally similar to a geometric oblong.
[0062] In one embodiment, the device is generally flat (FIG. 8B)
such that both its anterior surface 42 (see FIG. 11), that is
adjacent to the sternum, and the posterior surface 44, that portion
of the device that is adjacent the heart, form a substantially flat
plane. In another embodiment, illustrated in FIG. 8A, the body of
the device is curved along at least one axis, such that the body
forms a portion of the face of a cylinder, with the posterior
surface 44 of the device forming a concavity. The concavity is
preferably slight such that the longitudinal edges 46 of the device
are minimally raised relative to a central longitudinal line 48
that spatially divides the device lengthwise. The arch height h of
the device is defined as the distance between the plane which
connects the opposing longitudinal edges 46 of the device and the
parallel plane tangent to the device at the central longitudinal
line 48. It is anticipated that the degree of curvature or
concavity will be no more than that required for the device to rest
comfortably between the heart and the sternum.
[0063] Anchoring means are preferably provided along the edges of
the device 40. In one embodiment of this device, the anchoring
means comprise fenestrations or anchoring ports 50 (see FIG. 7).
Preferably, the anchoring ports are large enough to accommodate
suture or wire. It is contemplated that the cardiac protector
device will be anchored to the central anterior portion of the
thoracic skeleton. Thus, the device can be anchored to bone,
cartilage, muscle or supportive elements associated with the
central anterior portion of the thoracic skeleton, including the
sternum. The anchoring means stabilize the device and prevent it
from moving with the normal pulsation of the heart. Further, the
anchoring means prevent the device from moving during normal
thoracic movement. It is contemplated that enough anchoring ports
are provided to permit the device to be anchored in place
irrespective of the position of the device relative to the sternum.
While FIG. 7 provides one example of a device having fenestrations
circumscribing the periphery of the apparatus; it is further
contemplated that the fenestrations can be limited to the cranial
and caudal aspects of the device. A method for attaching the device
in place following open heart surgery is provided in Example 2.
[0064] In one embodiment of the cardiac protector device, a
longitudinal guide 52 extends along the length of the anterior
surface of the device following the central longitudinal line 48.
This longitudinal guide is positioned beneath the sternum along the
sternotomy line. In the embodiment illustrated in FIG. 7 and by
cross-section in FIG. 9, the guide forms a longitudinal cutting
guide extending along the length of the device. The longitudinal
guide advantageously facilitates revision surgery by providing a
recess to further distance the device from the sternum midline.
This recess facilitates the positioning of the oscillating saw, or
other equivalent surgical tool, along the sternum. Thus, the
longitudinal guide serves as a groove for the surgeon to follow as
he or she cuts through the sternum. An exemplary surgery using a
cardiac protector device having a longitudinal guide is provided in
Example 3.
[0065] The dimensions of the device may vary in length such that
the device extends the full length of the sternum, or alternatively
the device may be just a few inches in length. Therefore, it is
contemplated that the device will range in length l from about 3.0
to 10 inches and more preferably from about 4.0 to 8.5 inches. The
width w of the device is preferably from about 0.5 to 4.0 inches
and more preferably from about 1.0 to 3.0 inches. The thickness of
the device may vary from 0.125 to 0.5 inches and preferably from
between 0.125 to 0.375 inches. In those embodiments where the body
of the device is curved, the arch height h of the device is
preferable no greater than 0.5 inches.
[0066] The dimensions can be selected and readily optimized by one
of skill in the art in view of the disclosure herein, depending
upon the particular surgical site and patient size. It is further
contemplated that the dimensions of the apparatus may be scaled
down even further to accommodate infant and pediatric applications
for cardiac procedures were multiple surgeries are likely.
[0067] The body of the cardiac protection device 40 is preferably
prepared from a biocompatible material that is capable of being cut
with a standard surgical tool, such as a scalpel, knife, or
scissors (such as a Mayo or Metsenbaum type scissor) to permit
customization of the device in the operating room. In a
particularly preferred embodiment, the device is sufficiently
malleable so that the device can be molded and contoured by the
surgeon at the time of the surgery to accommodate the coronary
artery bypass graft employing the internal mammary artery as its
primary vessel. Alternatively, the device can be preformed in its
final configuration from any of a variety of materials such as
stainless steel, injection moldable polymers, and the like as will
be apparent to one of skill in the art.
[0068] Preferably, the device is prepared from a thermoplastic
polymer such as polypropylene, polyethylene, polymethacrylate or
the like. It is further contemplated that the device, once formed,
is somewhat flexible. Therefore, other materials also contemplated
for use in this invention include, but are not limited to,
silicone, bioerodable polylactic acid, poly-HEMA, or the like.
Those with skill in the art will be able to select a suitable
biocompatible material.
[0069] It is also contemplated that even more flexible materials
will be selected for other protection device applications,
including between adjacent soft tissue planes. These devices are
then suitable for minimizing adhesion formation following abdominal
surgery, urogenital surgery, tendon surgery, hip surgery or the
like.
[0070] In yet another embodiment of this device, the device is
provided without anchoring ports. In this embodiment, the device is
prepared from a material that can be punctured by a sharp object to
permit the surgeon to form his or her own anchoring ports during
the surgical procedure.
[0071] It is further contemplated that the device can be tooled,
molded, heat pressed or the like. The methods of manufacturing the
device will depend on the choice of material. Those with skill in
the art of manufacturing implantable medical devices will be
readily able to use this description of the contemplated invention
together with the figures to produce the protector device of this
invention.
[0072] Like the spinal cord protection device, it is contemplated
that the cardiac protection device can be prepared from a solid
sheet of material, or the device can be prepared as a laminate. A
radiopaque material is preferably incorporated into the device
either as a laminate or the radiopaque substance can be impregnated
either throughout the device or along the periphery. Suitable
radiopaque materials are disclosed in the discussion relating to
the spinal cord protection device (supra) . FIG. 7 illustrates a
preferred embodiment having a radiopaque material such as barium or
the like incorporated into the device as a peripheral ring 54.
[0073] It is further contemplated that the body of the device, like
the spinal cord protection device described above, can be
impregnated with, coated with, or otherwise positioned in place in
association with a drug or other substance suitable for inhibiting
the formation of adhesions. Suitable adhesion-inhibiting drugs
contemplated for use in association with the cardiac protection
device include, but are not limited to, heparin salts and analogs
of heparin salts, such as Pentosan Polysulfate, hyaluronic acid,
dextran, growth factor inhibitors, or other compounds recognized in
the art to inhibit adhesion formation such as gelatin foams, or the
like.
[0074] Like the spinal cord protection device, it is contemplated
that the body of the cardiac protection device is colored to
contrast with the color of bone, fascia, blood and heart tissue.
Thus, contrasting colors contemplated for use with this device
include shades of blue, green, black, purple, yellow, pink, or the
like.
[0075] Particular embodiments of the invention will be discussed in
detail and reference has been made to possible variations within
the scope of the invention. There are a variety of alternative
adaptations and surgical procedures available to those of skill in
the art which would similarly permit one to successfully produce
and use the intended embodiments of this invention.
EXAMPLE 1
[0076] Laminectomy and Decompression Surgery involving the Surgical
Positioning of the Spinal Cord Protection Device
[0077] The surgical tools disclosed herein are standard surgical
equipment well known to those skilled in the art of orthopaedic and
neurosurgery. The patient is positioned on an Andrew's frame or
operating table and prepped and draped in the fashion standard for
back surgery. The incision is made over the spinous process of the
area to be decompressed. The incision is carried down through the
dorsal lumbar fascia and the fascia is then incised down to the
spinal lamina junction. Dissection is continued out to the tips of
the transverse processes and is accomplished using the
electrocautery and Cobb dissection tool. Self retaining retractors
are then placed into the wound to allow clear visualization of the
structures which have been denuded of their soft tissue. Further
meticulous soft tissue dissection is performed with the removal of
the supraspinous ligament and the interspinous ligament for the
vertebral levels to be addressed in the surgery process.
Intraoperative lateral x-ray confirms the position at the
appropriate level. A Lexzell rongeur is then used to remove the
bone of the spinous process 32 and that portion of the lamina 40
(see FIG. 3A). A Kerrison rongeur is used to remove bone from the
lamina as well as ligamentum flavum and epidural fat.
[0078] The dissection is carried out to the facet joints. If nerve
root entrapment, either by disk or soft tissue is noted lateral to
the facet, then a partial medial facetectomy is performed. The
origin of the nerve roots are then identified and traced into their
corresponding neural foramen.
[0079] A neural foraminal probe is placed into the neural foramen
at each level and if it is met with any impedance, a partial
foraminotomy is performed at each level to facilitate the passage
of the probe. Once this is completed, hemostasis is achieved using
the Malis bipolar coagulator or electrocautery device.
[0080] Dissection into the neural foramen many times can result in
increased instability by weakening the facet region. In order to
minimize this, a 4 mm burr is used to do the dissection in the
opening of the neural foramen to minimize the destruction with the
Kerrison rongeur. The operative area is then irrigated and suction
dried, and once again hemostasis is achieved using electrocautery
and a Malis bipolar coagulator.
[0081] Following the corrective surgery to the spinal column, the
spinal cord protection shield 10 is positioned over the laminectomy
defect (see FIG. 3B). Customization of the shield 10 is performed
with a scalpel and scissors thereby molding the shield 10 to
conform with the individual contours of the spinal column. The
angle of the attachment arms relative to the protector device is
adjusted by manually deforming the attachment arms to facilitate
their attachment to an adjacent spinous process. The arms are
sutured in place onto the spinous process and the fenestrations on
the shield body are additionally used to suture the device in place
(see FIG. 3B). The wound is closed using standard operating
procedures, a drain is preferably placed into the wound and, as one
example of wound closure, the wound is closed in layers using a #1
Vicryl (Ethicon, Piscataway, N.J.) suture for the dorsal lumbar
fascia, a 2-0 Vicryl for the deep subcutaneous tissue, and a 3-0
subcuticular stitch.
EXAMPLE 2
[0082] Method for inserting the Cardiac Protection Device
[0083] Those with skill in the art of heart surgeries will
recognize that there are a variety of surgical methods recognized
in the art for performing cardiac surgeries and that each surgeon
is familiar with his or her own preferred surgical strategy. This
Example is intended only to teach one with skill in the art how the
device of this invention can be incorporated into one physician's
particular surgical procedure.
[0084] The patient is positioned in a supine manner on the
operating table and the chest, upper abdomen and lower extremities
are prepped for surgery. After the patient has been prepped a
sterile drape is applied to the chest, lower extremities, abdomen
and the perineum. The chest and lower extremities are draped out
separately and kept sterile through the entire procedure to
facilitate vein harvesting in the lower extremities. One team of
physicians opens the heart and a second team harvests the graft of
the saphenous vein from the lower extremity. The vein is usually
harvested in toto. The chest is opened using an oscillating saw
along the midportion of the sternum. Once the sternum is divided,
the anterior portion of the chest is opened to expose the anterior
portions of the right and left chest cavities. The surgeon then
performs the bypass procedure.
[0085] When the surgical procedure is complete, the cardiac
protection device is attached to the posterior aspect of the
sternum. Preferably the device incorporates an adhesion-inhibiting
compound such as a heparin analog, or the like. The attachment is
accomplished as the lateral aspects of the sternum are brought
together. The device is attached to the sternum by running
anchoring sutures or wires through the sternum to the device at its
periphery. No more than one or two securing stitches positioned at
the cranial and caudal aspects of the device are generally required
to position the device in place. The sternum halves are wired
together and the incision is closed using standard procedures for
cardiac surgery wound closure
EXAMPLE 3
[0086] Method for accessing the Heart with a Cardiac Protection
Device in place
[0087] The following method is useful for accessing the thoracic
cavity for a revision cardiac bypass surgery in a patient having a
cardiac protection device in place. Once the sternum is exposed, a
Stryker sternal saw (such as a straight Stryker sternal saw
(298-97-100) or a half moon Stryker sagittal saw (2108-137)
(Stryker Medical Supply) is positioned along the manubrium of the
sternum with the blade positioned between the sternum and the
cardiac protection device. The half moon Stryker sagittal saw is
preferably used in revision coronary artery bypass surgery. The
longitudinal guide in the device is used as a path to move the saw
down the sternum. The sutures are clipped to separate the device
from the sternum and the rib cage is separated to expose the
thoracic cavity. The protector device is removed to expose the
heart.
[0088] While particular embodiments of the invention have been
described in detail, it will be apparent to those skilled in the
art that these embodiments are exemplary rather than limiting, and
the true scope of the invention is that defined in the following
claims.
* * * * *