US 20070027464 A1
A device for excising tissue. In an embodiment, the device comprises an outer sleeve. In addition, the device comprises an inner tubular member slidingly received within the outer sleeve. Further the device comprises a cutting head connected to a distal end of the inner tubular, wherein the cutting head comprises at least three aims extending axially from the inner tubular. Still further, the device has an open position in which the cutting head extends from the outer sleeve, and a closed position in which the cutting head is at least partially disposed within the sleeve.
1. A device for excising tissue, comprising:
an outer sleeve;
an inner tubular member slidingly received within the outer sleeve;
a cutting head on a distal end of the inner tubular;
wherein the cutting head comprises at least three arms extending axially from the inner tubular;
wherein the device has an open position in which the cutting head extends from the outer sleeve, and a closed position in which the cutting head is at least partially disposed within the sleeve; and
wherein the arms are biased away flom each other when the device is in the opened position.
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13. A method for treating stenosis in a spine of a patient having a median plane, the spine including a spinal canal having a posterior surface, a dural sac and an epidural space between the posterior surface and dural sac, the location of the stenosis determining a region of interest in the spine, comprising the steps of:
a) positioning a tissue excision device adjacent the region of interest, wherein the tissue excision device comprises:
an outer sleeve;
an inner tubular member slidingly received within the outer sleeve;
a cutting head connected to a distal end of the inner tubular;
wherein the cutting head comprises at least three arms extending axially from the inner tubular;
wherein the device has an open position in which the cutting head extends from the outer sleeve, and a closed position in which the cutting head is at least partially disposed within the sleeve.
b) opening the tissue excision device by extending the cutting head from the outer sleeve;
c) inserting the tissue excision device into tissue in the region of interest;
d) closing the tissue excision device by advancing the outer sleeve over the cutting head; and
e) retracting the tissue excision device from the tissue in the region of interest.
14. The method of
15. The method of
16. The method of
17. A kit for performing a procedure on a spine, the spine including an epidural space containing a dural sac, the lit comprising:
an insertion member for accessing the epidural space;
a volume of a contrast medium adapted to be inserted into the epidural space by the insertion member and expanded so as to compress a portion of the thecal sac and provide a safety zone within the epidural space; and
a tissue excision device comprising:
an outer sleeve;
an inner tubular member slidingly received within the outer sleeve;
a cutting head connected to a distal end of the inner tubular;
wherein the cutting head comprises at least three arms extending axially from the inner tubular;
wherein the device has an open position in which the cutting head extends from the outer sleeve, and
a closed position in which the cutting head is at least partially disposed within the sleeve.
This application claims benefit of U.S. provisional application Ser. No. 60/704,224 filed Jul. 29, 2005, and entitled “Device for Resecting Spinal Tissue,” which is hereby incorporated herein by reference in its entirety. This application also claims benefit of U.S. provisional application Ser. No. 60/747,166 filed May 12, 2006, and entitled “Percutaneous Tissue Excision Devices and Methods,” which is hereby incorporated herein by reference in its entirety.
The present invention relates generally to minimally invasive methods, devices and systems for treating spinal disorders using imaging guidance. More particularly, the present invention relates to devices and methods to reduce stenosis and increase the cross-sectional area of the spinal canal available for the spinal cord. Still more particularly, the present invention relates to devices and methods to percutaneously excise portions of an enlarged ligamentum flavum.
The present invention relates generally to a minimally invasive method, device and system for treating spinal disorders using imaging guidance. More particularly, this invention relates to devices and tools that provide a percutaneous portal to tissues in a region of interest. Still more particularly, this invention relates to devices and tools that provide percutaneous portals to tissue through bone.
The vertebral column (spine, spinal column, backbone) forms the main part of the axial skeleton, provides a strong yet flexible support for the head and body, and protects the spinal cord disposed in the vertebral canal, which is formed within the vertebral column. The vertebral column comprises a stack of vertebrae with an intervertebral disc between adjacent vertebrae. The vertebrae are stabilized by muscles and ligaments that hold the vertebrae in place and limit the movements of the vertebrae.
As illustrated in
Vertebral arch 14 is formed by two pedicles 24 which project posteriorly to meet two laminae 16. The two laminae 16 meet posteriomedially to form the spinous process 18. At the junction of pedicles 24 and laminae 16, six processes arise. Two transverse processes 20 project posterolaterally, two superior articular processes 22 project generally superiorly and are positioned superior to two inferior articular processes 25 that generally project inferiorly.
The vertebral foramen 15 is generally an oval shaped space that contains and protects the spinal cord 28. Spinal cord 28 comprises a plurality of nerves 34 surrounded by cerebrospinal fluid (CSF) and an outermost sheath/membrane called the dural sac 32. The CSF filled dural sac 32 containing nerves 34 is relatively compressible. Posterior to the spinal cord 28 within vertebral foramen 15 is the ligamentum flavum 26. Laminae 16 of adjacent vertebral arches 14 in the vertebral column are joined by the relatively broad, elastic ligamentum flavum 26.
In degenerative conditions of the spine, narrowing of the spinal canal (stenosis) can occur. Lumbar spinal stenosis is often defined as a dural sac cross-sectional area less than 100 mm2 or an anteroposterior (AP) dimension of the canal of less than 10-12 mm for an average male.
The source of many cases of lumbar spinal stenosis is thickening of the ligamentum flavum. Spinal stenosis may also be caused by subluxation, facet joint hypertrophy, osteophyte formation, underdevelopment of spinal canal, spondylosis deformans, degenerative intervertebral discs, degenerative spondylolisthesis, degenerative arthritis, ossification of the vertebral accessory ligaments and the like. A less common cause of spinal stenosis, which usually affects patients with morbid obesity or patients on oral corticosteroids, is excess fat in the epidural space. The excessive epidural fat compresses the dural sac, nerve roots and blood vessels contained therein and resulting in back and leg pain and weakness and numbness of the legs. Spinal stenosis may also affect the cervical and, less commonly, the thoracic spine.
Patients suffering from spinal stenosis are typically first treated with exercise therapy, analgesics and anti-inflammatory medications. These conservative treatment options frequently fail. If symptoms are severe, surgery is required to decompress the canal and nerve roots.
In some conventional approaches to correct stenosis in the lumbar region, an incision is made in the back and the muscles and supporting structures are stripped away from the spine, exposing the posterior aspect of the vertebral column. The thickened ligamentum flavum is then exposed by removal of a portion of the vertebral arch, often at the laminae, covering the back of the spinal canal (laminectomy). The thickened ligamentum flavum ligament can then be excised by sharp dissection with a scalpel or punching instruments such as a Kerison punch that is used to remove small chips of tissue. The procedure is performed under general anesthesia. Patients are usually admitted to the hospital for approximately five to seven days depending on the age and overall condition of the patient. Patients usually require between six weeks and three months to recover from the procedure. Further, many patients need extended therapy at a rehabilitation facility to regain enough mobility to live independently.
Much of the pain and disability after an open laminectomy results from the tearing and cutting of the back muscles, blood vessels, supporting ligaments, and nerves that occurs during the exposure of the spinal column. Also, because the spine stabilizing back muscles and ligaments are stripped and detached from the spine during the laminectomy, these patients frequently develop spinal instability post-operatively.
Minimally invasive techniques offer the potential for less post-operative pain and faster recovery compared to traditional open surgery. Percutaneous interventional spinal procedures can be performed with local anesthesia, thereby sparing the patient the risks and recovery time required with general anesthesia. In addition, there is less damage to the paraspinal muscles and ligaments with minimally invasive techniques, thereby reducing pain and preserving these important stabilizing structures.
Various techniques for minimally invasive treatment of the spine are known. Microdiscectomy is performed by making a small incision in the skin and deep tissues to create a portal to the spine. A microscope is then used to aid in the dissection of the adjacent structures prior to discectomy. The recovery for this procedure is much shorter than traditional open discectomies. Percutaneous discectomy devices with fluoroscopic guidance have been used successfully to treat disorders of the disc but not to treat spinal stenosis or the ligamentum flavum directly. Arthroscopy or direct visualization of the spinal structures using a catheter or optical system have also been proposed to treat disorders of the spine including spinal stenosis, however these devices still use miniaturized standard surgical instruments and direct visualization of the spine similar to open surgical procedures. These devices and techniques are limited by the small size of the canal and these operations are difficult to perform and master. In addition, these procedures are painful and often require general anesthesia. Further, the arthroscopy procedures are time consuming and the fiber optic systems are expensive to purchase and maintain.
Still further, because the nerves of the spinal cord pass through the spinal canal directly adjacent to and anterior to the ligamentum flavum, any surgery, regardless of whether open or percutaneous, includes a risk of damage to the nerves of the spinal cord.
Hence, it remains desirable to provide simple methods, techniques, and devices for treating spinal stenosis and other spinal disorders without requiring open surgery. It is further desired to provide a system whereby the risk of damage to the dural sac containing the spinal nerves may be reduced.
These and other needs in the art are addressed in one embodiment by a device for excising tissue. In an embodiment, the device comprises an outer sleeve. In addition, the device comprises an inner tubular member slidingly received within the outer sleeve. Further the device comprises a cutting head connected to a distal end of the inner tubular, wherein the cutting head comprises at least three arms extending axially from the inner tubular. Still further, the device has an open position in which the cutting head extends from the outer sleeve, and a closed position in which the cutting head is at least partially disposed within the sleeve.
These and other needs in the art aye addressed in another embodiment by a method for treating stenosis in a spine of a patient having a median plane, the spine including a spinal canal having a posterior surface, a dural sac and an epidural space between the posterior surface and dural sac, the location of the stenosis determining a region of interest in the spine. In an embodiment, the method comprises the step of positioning a tissue excision device adjacent the region of interest, wherein the tissue excision device comprises an outer sleeve, an inner tubular member slidingly received within the outer sleeve, and a cutting head connected to a distal end of the inner tubular, the cutting head including at least three arms extending axially from the inner tubular. In addition, the method comprises the step of opening the tissue excision device by extending the cutting head from the outer sleeve. Further, the method comprises the step of inserting the tissue excision device into tissue in the region of interest. Still further, the method comprises the step of closing the tissue excision device by advancing the outer sleeve over the cutting head. Moreover, the method comprises the step of retracting the tissue excision device from the tissue in the region of interest.
These and other needs in the art are addressed in another embodiment by a kit for performing a procedure on a spine, the spine including an epidural space containing a dural sac. In an embodiment, the kit comprises an insertion member for accessing the epidural space. In addition, the kit comprises a volume of a contrast medium adapted to be inserted into the epidural space by the insertion member and expanded so as to compress a portion of the thecal sac and provide a safety zone within the epidural space. Further, the kit comprises a tissue excision device comprising an outer sleeve, an inner tubular member slidingly received within the outer sleeve, a cutting head connected to a distal end of the inner tubular, wherein the cutting head comprises at least three arms extending axially from the inner tubular.
Thus, embodiments described herein comprise a combination of features and advantages intended to address various shortcomings associated with certain prior devices. The various characteristics described above, as well as other features, will be readily apparent to those skilled in the art upon reading the following detailed description of the preferred embodiments, and by referring to the accompanying drawings. It should be appreciated by those skilled in the art that the conception and the specific embodiments disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the embodiments described herein. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims.
For a more complete understanding of the invention, reference is made to the accompanying drawings, wherein:
The following discussion is directed to various embodiments of the invention. Although one or more of these embodiments may be preferred, the embodiments disclosed should not be interpreted, or otherwise used, as limiting the scope of the disclosure, including the claims. In addition, one skilled in the art will understand that the following description has broad application, and the discussion of any embodiment is meant only to be exemplary of that embodiment, and not intended to intimate that the scope of the disclosure, including the claims, is limited to that embodiment
For purposes of this discussion, the x-, y-, and z-axes are shown in
It is to be understood that the median/midsagittal plane passes from the top to the bottom of the body and separates the left and the right sides of the body, and the spine, into substantially equal halves (e.g., two substantially equal lateral sides). Further, it is to be understood that the frontal/coronal plane essentially separates the body into the forward (anterior) half and the back (posterior) half, and is perpendicular to the median plane. Still further, it is to be understood that the transverse plane is perpendicular to both the median plane and coronal plane and is the plane which divides the body into an upper and a lower half.
The Spinal Canal and Spinal Stenosis
Referring again to
Compression of spinal cord 28, particularly in the lumbar region, may result in low back pain as well as pain or abnormal sensations in the legs. Further, compression of the blood vessels in the epidural space 27 that houses the nerves of the cauda equina may result in ischemic pain termed spinal claudication.
In order to relieve the symptoms associated with a thickened or enlarged ligamentum flavum 26, methods, techniques, and devices described herein may be employed to reduce the compressive forces exerted by the thickened ligamentum flavum on spinal cord 28 and the blood vessels in epidural space 27 (ergo, decompress spinal cord 28 and blood vessels in epidural space 27). In particular, compressive forces exerted by the thickened/enlarged ligamentum flavum 26 may be reduced by embodiments of a minimally invasive ligament decompression (MILD) procedure described herein. In some embodiments, the MILD procedure may be performed percutaneously to reduce the size of ligamentum flavum 26 by excising portions of ligamentum flavum 26. In particular, in some embodiments of the MILD procedure, the ligamentum flavum 26 is accessed, cut and removed ipsilaterally (i.e., on the same side of vertebral arch 14) by a percutaneous cranial-caudal approach. Such an embodiment of the MILD procedure may be described hereinafter as Ipsilateral Approach MILD Procedure (ILAMP).
Creation of Safety Zone
As shown in
As previously described, spinal cord 28 comprises nerves 34 surrounded by CSF and is contained within dural sac 32. Since more than 90% of the volume of dural sac 32 in the lumbar region is filled by CSF, dural sac 32 is highly compressible. Thus, even when stenosis is causing compression of spinal cord 28, in most cases it is possible to temporarily compress spinal cord 28 further. Thus, according to preferred embodiments, dural sac 32 is further compressed in the region of interest by injecting a fluid into epidural space 27 to create safety zone 40. The presence of the injected fluid comprising safety zone 40 gently applies an additional compressive force to the outer surface of dural sac 32 so that at least a portion of the CSF within dural sac 32 is forced out of dural sac 32 in the region of interest, resulting in safety zone 40 between dural sac 32 and ligamentum flavum 26.
According to some embodiments, dural sac 32 is compressed by injecting a standard radio-opaque non-ionic myelographic contrast medium or other imagable or non-imagable medium into epidural space 27 in the region of interest. This is preferably accomplished with a percutaneous injection. Sufficient injectable fluid is preferably injected to displace the CSF out of the region of interest and compress dural sac 32 to at least a desired degree. The injected medium is preferably substantially contained within the confines of epidural space 27 extending to the margins of the dural sac 32. The epidural space is substantially watertight and the fatty tissues and vascularization in epidural space 27, combined with the viscous properties of the preferred fluids, serve to substantially maintain the injected medium in the desired region of interest. This novel method for protecting spinal cord 28 column may be referred to hereinafter as “contrast-guided dural protection.”
Once a safety zone 40 has been created, a tool 100, such as the tissue excision devices and tissue retraction devices described below, may be inserted into the ligamentum flavum 26, as illustrated in
While it is preferred that the tip of tool 100 remain within ligamentum flavum 26 as shown, the presence of safety zone 40 reduces the likelihood that dural sac 32 will be damaged, even if the tool breaks through the anterior surface of ligamentum flavum 26.
For insertion of tool 100, a fluoroscopic window of access (FWA) is defined by the inferior margin of the lamina (contra lateral to the point of instrument entry in the soft tissues) and the dorsal margin of the contrast material that defines the epidural space. This FWA is roughly orthogonal to the long axis of the cutting instrument, which parallels the inferior surface of the lamina as in
Because the present techniques are preferably performed percutaneously, certain aspects of the present invention may be facilitated by imaging. In this context, the spine can be imaged using any suitable technology, including without limitation, 2D fluoroscopy, 3D fluoroscopy, CT, MRI, ultrasound or with direct visualization with fiber optic or microsurgical techniques. Stereotactic or computerized image fusion techniques are also suitable. Fluoroscopy is currently particularly well-suited to the techniques disclosed herein. Fluoroscopic equipment is safe and easy to use, readily available in most medical facilities, relatively inexpensive. In a typical procedure, using direct biplane fluoroscopic guidance and local anesthesia, epidural space 27 is accessed for injection of contrast media adjacent to the surgical site.
If the injected medium is radio-opaque, as are for example myelographic contrast media, the margins of the expanded epidural space will be readily visible using fluoroscopy or CT imaging. Thus, the safety zone created by the present contrast-guided dural compression techniques can reduce the risk of damage to the spinal cord during procedures to remove or displace portions of the ligamentum flavum and/or laminae in order to treat spinal stenosis.
If desired, the injected medium can be provided as a re-absorbable water-soluble gel, so as to better localize safety zone 40 at the site of surgery and reduce leakage of this protective layer from the vertebral/spinal canal. An injectable gel is a significant improvement on prior epidural injection techniques. The gel is preferably substantially more viscid than conventional contrast media and the relatively viscid and/or viscous gel preferably tends to remain localized at the desired site of treatment as it does not spread as much as standard liquid contrast media that are used in epidurography. This may result in more uniform compression of dural sac 32 and less leakage of contrast out of the vertebral/spinal canal. In addition, preferred embodiments of the gel are re-absorbed more slowly than conventional contrast media, allowing for better visualization during the course of the surgical procedure.
In some embodiments, a contrast agent can be included in the gel itself, so that the entire gel mass is imagable. In other embodiments, an amount of contrast can be injected first, followed by the desired amount of gel, or an amount of gel can be injected first, followed by the desired amount of contrast. In this case, the contrast agent is captured on the surface of the expanding gel mass, so that the periphery of the mass is imagable.
Any standard hydrophilic-lipophilic block copolymer (Pluronic) gel such as are known in the art would be suitable and other gels may be used as the injectable medium. The gel preferably has an inert base. In certain embodiments, the gel material is liquid at ambient temperatures and can be injected through a small bore (such as a 27 gauge needle). The gel then preferably becomes viscous when warmed to body temperature after being injected. The viscosity of the gel can be adjusted through the specifics of the preparation. The gel or other fluid is preferably sufficiently viscid or viscous at body temperature to compress and protect the thecal sac in the manner described above and to remain sufficiently present in the region of interest for at least about 30 minutes. Thus, in some embodiments, the injected gel attains a viscosity that is two, three, six or even ten times that of the fluids that are typically used for epidurograms.
In certain embodiments, the injected medium undergoes a reversible change in viscosity when warmed to body temperature so that it can be injected as a low-viscosity fluid, thicken upon injection into the patient, and be returned to its low-viscosity state by cooling. In these embodiments, the injected medium is injected as desired and thickens upon warming, but can be removed by contacting it with a heat removal device, such as an aspirator that has been provided with a cooled tip. As a result of localized cooling, the gel reverts to its initial non viscous liquid state and can be easily suctioned up the cooled needle or catheter.
An example of a suitable contrast medium having the desired properties is OmnipaqueŽ 240 available from Nycomed, New York, which is a commercially available non-ionic iodinated myelographic contrast medium. Other suitable injectable media will be known to those skilled in the art. Because of the proximity to spinal cord 28 and spinal nerves 34, it is preferred not to use ionic media in the injectable medium. The preferred compositions are reabsorbed relatively rapidly after the procedure. Thus any residual gel compression on dural sac 32 after the MILD procedure dissipates relatively quickly. For example, in preferred embodiments, the gel would have sufficient viscosity to compress dural sac 32 for thirty minutes, and sufficient degradability to be substantially reabsorbed within approximately two hours.
The injected contrast medium further may further include one or more bioactive agents. For example, medications such as those used in epidural steroid injection (e.g. Depo medrol, Celestone Soluspan) may be added to the epidural gel to speed healing and reduce inflammation, scarring and adhesions. The gel preferably releases the steroid medication slowly and prolongs the anti-inflammatory effect, which can be extremely advantageous. Local anesthetic agents may also be added to the gel. This prolongs the duration of action of local anesthetic agents in the epidural space to prolong pain relief during epidural anesthesia. In this embodiment the gel may be formulated to slow the reabsorption of the gel.
The present gels may also be used for epidural steroid injection and perineural blocks for management of acute and chronic spinal pain. Thrombin or other haemostatic agents can be added if desired, so as to reduce the risk of bleeding.
In some embodiments, the gel may also be used as a substitute for a blood patch if a CSF leak occurs. The gel may also be used as an alternative method to treat lumbar puncture complications such as post-lumbar puncture CSF leak or other causes of intracranial hypotension. Similarly, the gel may be used to patch postoperative CSF leaks or dural tears. If the dural sac were inadvertently torn or cut, then gel could immediately serve to seal the site and prevent leakage of the cerebral spinal fluid.
Percutaneous Tissue Excision
After safety zone 40 has been created, the margins of epidural space 27 are clearly demarcated by the injected medium and can be visualized radiographically if an imagable medium has been used. As mentioned above, percutaneous procedures can now safely be performed on ligamentum flavum 26 and/or surrounding tissues without injuring dural sac 32 or nerves 34 and the spinal canal can be decompressed using any of several techniques. Suitable decompression techniques include removal of tissue from the ligamentum flavum, laminectomy, laminotomy, and ligament retraction and anchoring.
In some embodiments, all or a portion of ligamentum flavum 26 and/or lamina 16 are excised using a percutaneous tissue excision device or probe 100, which may hereinafter be referred to as the MILD device. As shown schematically in
Preferred embodiments of the present tissue excision devices and techniques can take several forms. In the discussion below, the distal ends of the tools are described in detail. The construction of the proximal ends of the tools, and the means by which the various components disclosed herein are assembled and actuated, will be known and understood by those skilled in the art.
By way of example, in the embodiment shown in
Tissue-engaging means 56 may be a needle, hook, blade, tooth or the like, and preferably has at least one flexible barb or hook 58 attached to its shaft. The barb 58 or barbs may extend around approximately 120 degrees of the circumference of the shaft. Barbs 58 are preferably directed towards the proximal end of the tool. When tissue-engaging means 56 is retracted slightly, barbs 58 allow it to engage a segment of tissue. Depending on the configuration of barbs 58, the tissue sample engaged by tissue-engaging means 56 may be generally cylindrical or approximately hemispherical. Once needle 56 has engaged the desired tissue, inner occluding means 54, which is preferably provided with a sharpened distal edge, is advanced so that it cuts the engaged tissue section or sample loose from the surrounding tissue. Hence occluding means 54 also functions as a cutting means in this embodiment. In alternative embodiments, such as
Referring still to
Referring briefly to
In still other embodiments, the tissue-engaging means may comprise a hook or tooth or the like that engages tissue via aperture 52 by being rotated about the tool axis. In such embodiments (not shown) and by way of example only, the tissue-engaging means could comprise a partial cylinder that is received in outer cannula 51 and has a serrated side edge. Such a device can be rotated via a connection with the tool handle or other proximal device. As the serrated edge traverses aperture 52 tissue protruding into the tool via the aperture is engaged by the edge, whereupon it can be resected and retrieved in the manner disclosed herein.
In preferred embodiments, the working tip of tool 100 remains within the ligamentum flavum and does not penetrate the safety zone 40. Nonetheless, safety zone 40 is provided so that even an inadvertent penetration of the tool into the epidural space will not result in damage to the thecal sac. Regardless of the means by which the tissue is engaged and cut, it is preferably retrieved from the distal end of the tool so that additional tissue segments can be excised without requiring that the working tip of the tool be repositioned. A tissue-removal device such as that described below is preferably used to remove the tissue from the retrieval device between each excision.
Each piece of tissue may be removed from barbs 58 by pushing tissue-engaging means 56 through an opening that is large enough to allow passage of the flexible barbs and supporting needle but smaller than the diameter of the excised tissue mass. This pushes the tissue up onto the shaft, where it can be removed with a slicing blade or the like or by sliding the tissue over the proximal end of the needle. Alternatively, needle 56 can be removed and re-inserted into the tool for external, manual tissue removal.
It is expected that in some embodiments, approximately 8-10 cores or segments of tissue will be excised and pushed up the shaft towards the hub during the course of the procedure. Alternatively, a small blade can be used to split the tissue segment and thereby ease removal of the segment from the device. If desired, a blade for this purpose can be placed on the shaft of needle 56 proximal to the barbs.
In an exemplary embodiment, shown in
In an alternative embodiment shown in
In another alternative embodiment (not shown) an alternative mechanism for removing the tissue segment from needle 56 includes an adjustable aperture in a disc. After the tissue-bearing needle is pulled back through the aperture, the aperture is partially closed. Needle 56 and flexible hooks 58 then can pass through the partially closed aperture but the larger cylinder of tissue cannot. Thus the tissue segment is pushed back onto the shaft. The tissue segment can either be pulled off the proximal end of the shaft or cut off of it. A small blade may be placed just proximal to the barbs to help cut the tissue segment off the shaft. The variable aperture can formed by any suitable construction, including a pair of metal plates with matching edges that each define one half of a central opening. The two pieces may be held apart by springs. The aperture may be closed by pushing the two edges together. In other embodiments, this process can be mechanically automated by using a disc or plate with an opening that is adjustable by a variety of known techniques, including a slit screw assembly or flexible gaskets.
Alternative Tissue Excision Devices
Other cutting and/or grasping devices can be used in place of the system described above. For example, embodiments of the grasping mechanism include but are not limited to: needles with flexible barbs, needles with rigid barbs, corkscrew-shaped needles, and/or retaining wires. The corkscrew-shaped needle shown in
In other embodiments, shown in
Advancing one end of sleeve 74 toward the other end of sleeve 74 causes each strip 77 to buckle or bend. If strips 77 are prevented from buckling inward or if they are predisposed to bend in the desired direction, they will bend outward, thereby forming arcuate arms 72, which extend through aperture 52 of cannulated scalpel 51, as shown in
Closable arms 72 may include on their opposing edges 78 ridges, teeth, or other means to facilitate grasping of the tissue. In other embodiments, edges 78 may be sharpened, so as to excise a segment of tissue as they close. In these embodiments, closable arms 72 may also be used in conjunction with a hook, barbed needle, pincers or the like, which can in turn be used to retrieve the excised segment from the device.
Once arms 72 have closed on the tissue, if arms 72 have not cut the tissue themselves, the tissue can be excised using a blade such as cutting element 60 above. The excised tissue can be removed from the inside of needle 51 using a tissue-engaging hook 64 or other suitable means. The process of extending and closing arms 72, excising the tissue, and removing it from the device can be repeated until a desired amount of tissue has been removed.
If desired, this cycle can be repeated without repositioning the device in the tissue. Alternatively, the tool can be rotated or repositioned as desired between excisions. It is possible to rotate or reposition the tool during an excision, but it is expected that this will not generally be preferred. Furthermore, it is expected that the steps of tissue excision and removal can be accomplished without breaching the surface of the ligament, i.e. without any part of the device entering the safety zone created by the injected fluid. Nonetheless, should the tool leave the working zone, the safety zone will reduce the risk of injury to the thecal sac.
In some embodiments, the spinal canal may also be enlarged by retracting the ligamentum flavum, either with or without concurrent resection. Retraction is preferably but not necessarily performed after dural compression has been used to provide a safety zone. In addition, the dural compression techniques described above have the effect of pressing the ligamentum flavum back out of the spinal canal and thereby making it easier to apply a restraining means thereto.
Thus, in preferred embodiments, after a safety zone is created by epidural injection of contrast medium or gel, a retraction device 90 as shown in
The distal end of the device is preferably positioned in the ligamentum flavum under fluoroscopic guidance. If desired, an accessway through the lamina may be provided using an anchored cannula or the like. The device is held in position by support shaft 112. Distal barbs 91 are unsheathed and optionally expanded by pulling back guide housing 102, as shown in
In an alternative embodiment the proximal end of ligament anchor 90 may be adapted to engage the lamina. This may be accomplished by having the arm posterior to the lamina or by using the laminotomy and suturing the device to the lamina there. A knotted or knotless system or a suture plate can be used.
A second embodiment of the present method uses a plurality of retraction devices 90. In this embodiment, the retraction device is inserted through one lamina in an oblique fashion, paralleling the opposite lamina. After the distal anchor is deployed, the retraction device is pulled back and across the ligamentum flavum, thereby decompressing the opposite lateral recess of the spinal canal. This is repeated on the opposite side. This same device can also be deployed with a direct approach to the lateral recess with a curved guide housing.
While retraction device 90 is describe above as a double-headed anchor, it will be understood that other devices can be used. For example sutures, barbed sutures, staples or the like can be used to fasten the ligament in a retracted position that reduces stenosis.
Using the percutaneous methods and devices described herein, significant reductions of stenosis can be achieved. For example, a dural sac cross-sectional area less than 100 mm2 or an anteroposterior (AP) dimension of the canal of less than 10-12 mm in an average male is typically considered relative spinal stenosis. A dural sac cross-sectional area less than 85 mm2 in an average male is considered severe spinal stenosis. The present devices and techniques are anticipated to cause an increase in canal area of 25 mm2 per anchor or 50 mm2 total. With resection and/or retraction of the ligamentum flavum, the cross-sectional area of the dural sac can be increased by 10 mm2, and in some instances by as much as 20 mm2 or even 30 mm2. Likewise, the present invention can result in an increase of the anteroposterior dimension of the canal by 1 to 2 mm and in some instances by as much as 4 or 6 mm. The actual amount by which the cross-sectional area of the thecal sac and/or the anteroposterior dimension of the canal are increased will depend on the size and age of the patient and the degree of stenosis and can be adjusted by the degree of retraction of the ligament.
The minimally invasive ligament decompression (MILD) devices and techniques described herein allow spinal decompression to be performed percutaneously, avoiding the pain and risk associated with open surgery. Through the provision of a safety zone, the present devices and techniques offer reduced risk of spinal cord damage. In addition to improving nerve function, it is expected that decompression of the spinal canal in the manner described herein will result in improved blood flow to the neural elements by reducing the extrinsic pressure on the spinal vasculature. For these reasons, it is believed that spinal decompression performed according to the present invention will be preferable to decompression operations performed using currently known techniques.
In some embodiments (not shown), a mechanical device such as a balloon or mechanical shield can also be used to create a protective guard or barrier between the borders of the epidural space and the adjacent structures. In one embodiment a durable expandable device is attached to the outside of the percutaneous laminectomy device, preferably on the side opposite the cutting aperture. The cutting device is inserted into the ligamentum flavum with the expandable device deflated. With the aperture directed away from the spinal canal, the expandable device is gently expanded via mechanical means or inflated with air or another sterile fluid, such as saline solution, via a lumen that may be within or adjacent to the body of the device. This pushes the adjacent vital structures clear from the cutting aperture of the device and simultaneously presses the cutting aperture into the ligament. As above, the grasping and cutting needles can then be deployed and operated as desired. The balloon does not interfere with tissue excision because it is located on the side opposite the cutting aperture. The cutting needle may be hemispherical (semi-tubular) in shape with either a straight cutting or a sawing/reciprocating blade or may be sized to be placed within the outer housing that separates the balloon from the cutting aperture.
In another embodiment, a self-expanding metal mesh is positioned percutaneously in the epidural space. First the epidural space is accessed in the usual fashion. Then a guide catheter is placed in the epidural space at the site of the intended surgical procedure. The mesh is preferably compressed within a guide catheter. When the outer cover of the guide catheter is retracted, the mesh expands in the epidural space, protecting and displacing the adjacent dural sheath. At the conclusion of the surgical procedure, the mesh is pulled back into the guide sheath and the assembly removed. The mesh is deformable and compresses as it is pulled back into the guide catheter, in a manner similar to a self-expanding mesh stent. There are many commercially available self-expanding stents approved and in use in other applications. However, using a self-expandable mesh as a device within the epidural space to protect and displace the thecal sac is novel.
Tissue Excision Devices
Embodiments of tissue excision tools, devices, and methods disclosed herein may take several forms and may be used in accordance with the MILD method described above, or used according to alternative procedures such as the ipsilateral approach minimally invasive ligament decompression procedure (ILAMP method) disclosed in U.S. application Ser. No. 11/382,349, which is hereby incorporated herein by reference in its entirety.
In the descriptions of the tissue excision devices below, the distal portions of the devices are described in detail, distal referring to positions that are relatively closer to the region of interest (e.g., the thickened portion of the ligamentum flavum to be decompressed). An exemplary embodiment of a proximal end for the tissue excision devices, including an actuation means, is also described below. However, it is to be understood that embodiments of tissue extraction devices described herein may be used with a variety of proximal ends and a variety of actuation means that are known and understood by those skilled in the art.
Inner tubular 230 includes a central cavity or through bore 240 (
Cutting head 250 preferably comprises a body 252 and three cutting arms 253 extending axially from body 252. In this embodiment, body 252 is integral with and essentially an extension of inner tubular 230. Since each arm 253 extends axially from body 252, each arm 253 may be described as including a fixed end 253 a integral with body 252 and a free end 253 b generally distal to body 252. Although each of the embodiments illustrated herein show cutting head 250 with three cutting arms 253, in different embodiments, cutting head 250 may include any suitable number of cutting arms 253 including without limitation two, three, four, or more.
Arms 253 are preferably integral with body 252 and inner tubular 230. In such embodiments, arms 253 may be formed by any suitable means including without limitation casting or molding, laser cutting, machining, or combinations thereof. However, it should be understood that arms 253 may alternatively be distinct components that are mechanically coupled to body 252 and inner tubular 230 generally at fixed end 253 a. In such alternative embodiments, arms 253 may be connected to inner tubular 230 by any suitable means, including without limitation welding, pins, or combinations thereof.
As best shown in
Referring again to
Cutting head 250 is constructed so that arms 253 can be brought together so as to grasp tissue therebetween, termed herein as a “closed position”, and moved apart so as to release tissue and/or allow the entry of tissue between arms 253, termed herein as an “open position”. As shown in
Referring now to
In the reverse manner, device 200 and cutting head 250 can be transitioned from the closed position to the open position. In general, sleeve 210 may be moved axially relative to cutting head 250 by any suitable manner including without limitation a threaded engagement with inner tubular 230, a trigger mechanism, or combinations thereof.
In the embodiments described herein, aims 253 are normally open. In other words, arms 253 are biased to the open position such that cutting head 250 will assume the open position when no forces are acting to push arms 153 together. Thus, to transition device 200 and cutting head 250 to the closed position, compressive forces, namely sleeve 210 acting on each frustoconical chamfer 255, are necessary to push aims 253 together. Further, since arms 253 are biased open, cutting head 253 will automatically assume the open position illustrated in
Tissue Excision and Removal
Regardless of the manner in which tissue excision device 200 reaches the tissue of interest (e.g., by portal or otherwise), prior to insertion into the tissue to be excised, device 200 is configured in the open position as shown in
Still referring to
Once a desired amount of tissue has filled tissue-receiving space 263 and bore 240, device 200 may be transitioned to the closed position by advancing sleeve 210 toward cutting ends 253 b and over cutting head 250 as previously described. As arms 253 move towards each other, the portions of tissue 126 within tissue-receiving space 263 and bore 240 are severed from the surrounding tissue 126. Specifically, the sharpened or beveled edges of cutters 251 and tooth 257 slice tissue extending axially from tissue-receiving space 263, while an annular cutting edge 211 of sleeve 210 slices tissue extending radially from tissue-receiving space 263 between arms 253. Cutting edge 211 of sleeve 210 is preferably sharpened to enhance the cutting ability of sleeve 210 as it moves relative to cutting head 250. In addition, the severed tissue 126 contained within tissue-receiving space 263 is grasped by arms 253. Specifically, arms 253 exert compressive forces on the tissue 126 within tissue-receiving space 263, the textured surface features 264 on the inner surface of arms 253 grips the tissue 126 within tissue-receiving space 263, and tooth 257 grasps tissue 126 within tissue-receiving space 263 and restricts it from sliding axially out of cutting head 250 between cutting ends 253 b.
Once device 200 has achieved the closed position, device 200 maybe retracted from tissue 126 as best shown in
Pieces of tissue 126 captured within tissue-receiving space 263 and bore 240 may be removed by simply opening device 200 and pulling the pieces of tissue from tissue-receiving space 263 and bore 240. Device 200 may be opened from the closed position by retracting sleeve 210 from cutting head 250 as previously described. As device 200 transitions to its opened position, arms 253 will separate, allowing the user to access tissue-receiving space 263 and inner bore 240.
In an alternative embodiment, a plunger or tissue ejector may be included with device 200 to physically eject the excised tissue 126 from tissue-receiving space 263 and inner bore 240. For instance, a plunger (not shown) may be included within device 200 to push cut tissue in tissue-receiving space 263 and inner bore 240 axially out through the opening between cutting ends 253 b of arms 253.
The process of inserting device 200 into tissue 126 in the opened position, closing device 126, retracting device 200 in the closed position, opening device 200, emptying tissue-receiving space 263 and bore 240, and reinserting device 200 may be repeated until the desired amount of tissue 126 has been excised and removed. Referring briefly to
The components of tissue excision device 200 (e.g., arms 253, tooth 257, etc.) may comprise any suitable material(s) including without limitation metals (e.g., stainless steel, titanium, etch), non-metals (e.g., polymer, composites, etc.) or combinations thereof. The components of tissue excision device 200 are preferably manufactured from a durable biocompatible material such as titanium or stainless steel, but may alternatively be polymeric. In addition, arms 253 each preferably comprise a relatively rigid material(s) capable of maintaining their shape and configuration when inserted into and advanced through tissue. Further, arms 253 preferably comprises a resilient material having the ability to be repeatedly flexed between the open position and closed position without cracking or otherwise being damaged. Such a resilient material also enables each arm 253 to return to its original configuration once external forces (e.g., force applied by sleeve 210) are removed.
In addition, the components of tissue excision device 200 may be manufactured by any suitable methods. Examples of suitable methods include casting or molding, machining, laser cutting, EMD, or combinations thereof. In some embodiments, cutting edges or tips may be electro polished to for sharpening. The components of tissue excision device 200 may be assembled by any suitable method including without limitation welding, press fitting, or combinations thereof.
While preferred embodiments of this invention have been shown and described, modifications thereof can be made by one skilled in the art without departing from the scope or teaching of this invention. For example, the means by which the safety zone is formed may be varied, the shape and configuration of the tissue excision devices may be varied, and the steps used in carrying out the technique may be modified. Accordingly, the invention is not limited to the embodiments described herein, but is only limited by the claims that follow, the scope of which shall include all equivalents of the subject matter of the claims. Likewise, the sequential recitation of steps in a claim, unless explicitly so stated, is not intended to require that the steps be performed in any particular order or that a particular step be completed before commencement of another step.