US20070027464A1 - Device for resecting spinal tissue - Google Patents

Abstract

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.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS
• 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.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
• Not Applicable.
BACKGROUNDField of the Invention
• 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.
Field of the Invention
• 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.
Background of the Invention
• 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 inFIG. 1, eachvertebra10 includes avertebral body12 that supports avertebral arch14. Amedian plane210 generally dividesvertebra10 into two substantially equal lateral sides.Vertical body12 has the general shape of a short cylinder and is anterior to thevertebral arch14. Thevertebral arch14 together withvertebral body12 encloses a space termed thevertebral foramen15. The succession ofvertebral foramen15 inadjacent vertebrae10 along the vertebral column define the vertebral canal (spinal canal), which contains the spinal cord.
• Vertebral arch14 is formed by twopedicles24 which project posteriorly to meet twolaminae16. The twolaminae16 meet posteriomedially to form thespinous process18. At the junction ofpedicles24 andlaminae16, six processes arise. Twotransverse processes20 project posterolaterally, two superiorarticular processes22 project generally superiorly and are positioned superior to two inferiorarticular processes25 that generally project inferiorly.
• Thevertebral foramen15 is generally an oval shaped space that contains and protects thespinal cord28.Spinal cord28 comprises a plurality ofnerves34 surrounded by cerebrospinal fluid (CSF) and an outermost sheath/membrane called thedural sac32. The CSF filleddural sac32 containingnerves34 is relatively compressible. Posterior to thespinal cord28 withinvertebral foramen15 is theligamentum flavum26.Laminae16 of adjacentvertebral arches14 in the vertebral column are joined by the relatively broad,elastic ligamentum flavum26.
• 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 mm₂or 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.
SUMMARY OF THE INVENTION
• 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.
BRIEF DESCRIPTION OF THE DRAWINGS
• For a more complete understanding of the invention, reference is made to the accompanying drawings, wherein:
• FIG. 1 is cross-section of the spine viewed from the space between two vertebrae, showing the upper surface of one vertebra and the spinal canal with the dural sac and a normal (un-stenosed) ligamentum flavum therein;
• FIG. 2 is an illustration of the same section asFIG. 1, showing the spinal canal with the dural sac and a thickened ligamentum flavum therein;
• FIG. 3 is an enlarged cross-section of a vertebral foramen, showing a safety zone created by compression of the dural sac;
• FIG. 4 is the cross-section ofFIG. 3, showing a tissue excision tool positioned in the ligamentum flavum;
• FIGS. 5-9 are a series of illustrations showing tissue excision by a tissue-excision tool constructed in accordance with a first embodiment of the invention;
• FIGS. 10-14 are a series of illustrations showing tissue excision by a tissue-excision tool constructed in accordance with a second embodiment of the invention;
• FIGS. 15 and 17 are sequential illustrations showing removal of tissue from a tissue-excision tool by a tissue-removal device constructed in accordance with an embodiment of the invention;
• FIGS. 16 and 18 are end views of the tissue-removal device ofFIGS. 15 and 17, respectively;
• FIG. 19 shows an alternative embodiment of a grasping needle with a corkscrew shape;
• FIG. 20 is a perspective view of a tissue-excision tool constructed in accordance with a third embodiment of the invention;
• FIGS. 21 and 22 are enlarged cross-sectional and perspective views, respectively, of the grasping device ofFIG. 20 in its retracted position;
• FIGS. 23 and 24 are enlarged cross-sectional and perspective views, respectively, of the grasping device ofFIG. 20 in its extended position;
• FIG. 25 is a schematic illustration of one embodiment of a double-ended ligament anchor being deployed in a ligamentum flavum;
• FIG. 26 shows the device ofFIG. 25 after full deployment;
• FIG. 27 is a perspective view of an entire tool constructed in accordance with preferred embodiments;
• FIG. 28 is an enlarged cross-sectional view of the distal tip of the tool ofFIG. 27 with the aperture partially opened;
• FIG. 29 is a cross-sectional view of the handle end of the tool ofFIG. 27;
• FIG. 30 is cross-section of another embodiment of a tissue-removal device;
• FIG. 31 is a perspective view of the distal portion of an embodiment of a tissue excision device in an open position;
• FIG. 32 is an end-view of the tissue excision device ofFIG. 31;
• FIG. 33 is a perspective view of the tissue excision device ofFIG. 31 transitioning from the open position to the closed position; and
• FIGS. 34 and 35 are sequential schematic illustrations showing the excision of tissue by the tissue excision tool illustrated inFIG. 31.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
• 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 inFIGS. 1 and 3 to aid in understanding the descriptions that follow. The x-, y-, and z-axes have been assigned as follows. The x-axis is perpendicular to the longitudinal axis of the vertebral column and perpendicular to the coronal/frontal plane (i.e., x-axis defines anterior vs. posterior relationships). The y-axis runs substantially parallel to the vertebral column and perpendicular to the transverse plane (i.e., y-axis defines superior vs. inferior relationships). The z-axis is perpendicular to the longitudinal axis of the vertebral column and perpendicular to the median/midsagittal plane (i.e., z-axis defines the lateral right and left sides of body parts). The set of coordinate axes (x-, y-, and z-axes) are consistently maintained throughout although different views of vertebrae and the spinal column may be presented.
• 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 toFIG. 1,vertebral foramen15 contains a portion of the ligamentum flavum26,spinal cord28, and anepidural space27 between ligamentum flavum26 andspinal cord28.Spinal cord28 comprises a plurality ofnerves34 surrounded by cerebrospinal fluid (CSF) contained withindural sac32.Nerves34 normally comprise only a small proportion of thedural sac32 volume. Thus, CSF filleddural sac32 is somewhat locally compressible, as localized pressure causes the CSF to flow to adjacent portions of the dural sac.Epidural space27 is typically filled with blood vessels and fat. The posterior border of the normalepidural space27 generally defined by theligamentum flavum26, which is shown in its normal, non-thickened state inFIG. 1.
• FIG. 2 illustrates a case of spinal stenosis resulting from a thickenedligamentum flavum26. Sincevertebral foramen15 is defined and surrounded by the relatively rigid bone its volume is substantially constant. Thus, thickening of ligamentum flavum26 withinvertebral foramen15 can eventually result in compression ofspinal cord28. In particular, the thickenedligamentum flavum26 may exert a compressive force on the posterior surface ofdural sleeve32. In addition, thickening of ligamentum flavum26 may compress the blood vessels and fat occupyingepidural space27.
• Compression ofspinal cord28, 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 theepidural space27 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 flavum26, methods, techniques, and devices described herein may be employed to reduce the compressive forces exerted by the thickened ligamentum flavum onspinal cord28 and the blood vessels in epidural space27 (ergo, decompressspinal cord28 and blood vessels in epidural space27). In particular, compressive forces exerted by the thickened/enlarged ligamentum flavum26 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 flavum26 by excising portions of ligamentum flavum26. In particular, in some embodiments of the MILD procedure, the ligamentum flavum26 is accessed, cut and removed ipsilaterally (i.e., on the same side of vertebral arch14) 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 inFIGS. 1 and 2,ligamentum flavum26 is posteriorly apposed tospinal cord28. Thus, placement of tools within ligamentum flavum26 to excise portions of ligamentum flavum26 creates a risk of for inadvertent damage to thespinal cord28,dural sac32, and/ornerves34. Thus, in preferred embodiments of the procedures described herein, prior to insertion of tissue removal tools into theligamentum flavum26, a gap is advantageously created between ligamentum flavum26 and spinal cold28 to provide a safety zone between ligamentum flavum26 andspinal cord28.
• FIG. 3 illustrates an enlarged cross-sectional view of avertebral foramen15 within a vertebra.Vertebral foramen15 includesepidural space27 andspinal cord28 containingnerves34 and CSF withindural sac32. Further, a thickened/enlarged ligamentum flavum26 extends intovertebral foramen15. To reduce the risk of damage todural sac32 andspinal cord28, asafety zone40 is created between ligamentum flavum26 anddural sac32.
• As previously described,spinal cord28 comprisesnerves34 surrounded by CSF and is contained withindural sac32. Since more than 90% of the volume ofdural sac32 in the lumbar region is filled by CSF,dural sac32 is highly compressible. Thus, even when stenosis is causing compression ofspinal cord28, in most cases it is possible to temporarily compressspinal cord28 further. Thus, according to preferred embodiments,dural sac32 is further compressed in the region of interest by injecting a fluid intoepidural space27 to createsafety zone40. The presence of the injected fluid comprisingsafety zone40 gently applies an additional compressive force to the outer surface ofdural sac32 so that at least a portion of the CSF withindural sac32 is forced out ofdural sac32 in the region of interest, resulting insafety zone40 betweendural sac32 andligamentum flavum26.
• According to some embodiments,dural sac32 is compressed by injecting a standard radio-opaque non-ionic myelographic contrast medium or other imagable or non-imagable medium intoepidural space27 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 compressdural sac32 to at least a desired degree. The injected medium is preferably substantially contained within the confines ofepidural space27 extending to the margins of thedural sac32. The epidural space is substantially watertight and the fatty tissues and vascularization inepidural space27, 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 protectingspinal cord28 column may be referred to hereinafter as “contrast-guided dural protection.”
• Once asafety zone40 has been created, atool100, such as the tissue excision devices and tissue retraction devices described below, may be inserted into theligamentum flavum26, as illustrated inFIG. 4.Tool100 may comprise any suitable device, tool, or instrument for relieving stenosis caused by the thickened/enlarged ligamentum flavum26 including without limitation, embodiments of tissue excision devices and tissue retraction devices described in more detail below. Further, as best illustrated inFIG. 4,tool100 is positioned in theligamentum flavum26 on the opposite side ofmedian plane210 astool100 percutaneously accesses the body, such thattool100 crossesmedian plane210. In another embodiment,tool100 is inserted and positioned in theligamentum flavum26 on the same side (ipsilateral) ofmedian plane210 astool100 percutaneously accesses the body, such thattool100 does not crossmedian plane210.
• While it is preferred that the tip oftool100 remain within ligamentum flavum26 as shown, the presence ofsafety zone40 reduces the likelihood thatdural sac32 will be damaged, even if the tool breaks through the anterior surface of ligamentum flavum26.
• For insertion oftool100, 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 inFIG. 4. The fluoroscopic plane of projection is preferably but not necessarily oriented 20-40 degrees from normal (AP projection).
• 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 space27 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.
• Injectable Medium
• If desired, the injected medium can be provided as a re-absorbable water-soluble gel, so as to better localizesafety zone40 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 ofdural sac32 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 isOmnipaque® 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 tospinal cord28 andspinal nerves34, 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 ondural sac32 after the MILD procedure dissipates relatively quickly. For example, in preferred embodiments, the gel would have sufficient viscosity to compressdural sac32 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
• Aftersafety zone40 has been created, the margins ofepidural space27 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 onligamentum flavum26 and/or surrounding tissues without injuringdural sac32 ornerves34 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 flavum26 and/orlamina16 are excised using a percutaneous tissue excision device or probe100, which may hereinafter be referred to as the MILD device. As shown schematically inFIG. 4, adevice100 may be placed parallel to the posterior and lateral margin of thesafety zone40 with its tip in theligamentum flavum26.
• 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 inFIG. 4 and as illustrated inFIG. 5,device100 maybe a coaxial excision system50 with a sharpened or blunt tip that is placed obliquely into the thickenedligamentum flavum26 posterior tosafety zone40 under fluoroscopic guidance. The needle is preferably placed parallel to the posterior margin of the canal. Excision system50 is preferably manufactured from stainless steel, titanium or other suitable durable biocompatible material. As shown inFIGS. 5-10, an outer needle orcannula51 has an opening oraperture52 on one side that is closed during insertion by aninner occluding member54.Aperture52 is readily visible under imaging guidance. Onceneedle51 is positioned in the ligamentum flavum or other tissue removal site, inner occludingmember54 is removed or retracted so that it no longer closes aperture52 (FIG. 6).Aperture52 is preferably oriented away from the epidural space so as to further protect the underlying structures from injury during the surgical procedure. If it was not already present in the tool, a tissue-engagingmeans56 is inserted throughouter needle51 toaperture52 so that it contacts adjacent tissue, e.g., the ligamentum flavum, viaaperture52.
• Tissue-engagingmeans56 may be a needle, hook, blade, tooth or the like, and preferably has at least one flexible barb orhook58 attached to its shaft. Thebarb58 or barbs may extend around approximately 120 degrees of the circumference of the shaft.Barbs58 are preferably directed towards the proximal end of the tool. When tissue-engagingmeans56 is retracted slightly,barbs58 allow it to engage a segment of tissue. Depending on the configuration ofbarbs58, the tissue sample engaged by tissue-engagingmeans56 may be generally cylindrical or approximately hemispherical. Onceneedle56 has engaged the desired tissue, inner occluding means54, 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 means54 also functions as a cutting means in this embodiment. In alternative embodiments, such asFIGS. 10-14 discussed below, a cylindrical outer cuttingelement60 may extended overouter needle51 and used in place of occludingmember54 to excise the tissue sample.
• Referring still toFIGS. 5-9, once the tissue sample has been cut, tissue-engagingneedle56 can be pulled back throughouter needle51 so that the segment of tissue can be retrieved and removed from the barbs (FIG. 8). The process or engaging and resecting tissue may be repeated (FIG. 9) until the canal is adequately decompressed.
• Referring briefly toFIGS. 10-14, in other embodiments, a tissue-engaginghook64 can be used in place ofneedle56 and anouter cutting member60 can be used in place of inner occludingmember54.Hook64 may comprise a length of wire that has been bent through at least about 270°, more preferably through 315°, and still more preferably through about 405°. Alternatively or in addition,hook64 may comprise Nitinol™, or any other resilient metal that can withstand repeated elastic deflections. In the embodiment illustrated,hook64 includes at least onebarb58 at its distal end. In some embodiments,hook64 is pre-configured in a curvilinear shape and is retained withintool100 by outer cuttingmember60. When cuttingmember60 is retracted, the curved shape ofhook64 urges its outer end to extend outward throughaperture52. If desired, hook64 can be advanced toward the distal end oftool100, causing it to extend farther into the surrounding tissue. In some embodiments,hook64 is provided with acamming surface66.Camming surface66 beats on the edge of opening52 ashook64 is advance or retracted and thereby facilitates retraction and retention ofhook64 as it is retracted into the tool. In these embodiments,hook64 may not extend throughaperture52 until it has been advanced sufficiently forcamming surface66 to clear the edge of the opening.Hook64 may alternatively be used in conjunction with aninner occluding member54 in the manner described above. As above, hook64 can be used to retrieve the engaged tissue from the distal end of the tool.
• In still other embodiments, the tissue-engaging means may comprise a hook or tooth or the like that engages tissue viaaperture52 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 inouter cannula51 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 traversesaperture52 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 oftool100 remains within the ligamentum flavum and does not penetrate thesafety zone40. Nonetheless,safety zone40 is provided so that even an inadvertent penetration of the tool into the epidural space will not result in damage to the thecal sac. Regardless of the means by which the tissue is engaged and cut, it is preferably retrieved from the distal end of the tool so that additional tissue segments can be excised without requiring that the working tip of the tool be repositioned. A tissue-removal device such as that described below is preferably used to remove the tissue from the retrieval device between each excision.
• Tissue Removal
• Each piece of tissue may be removed frombarbs58 by pushing tissue-engagingmeans56 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,needle56 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 ofneedle56 proximal to the barbs.
• In an exemplary embodiment, shown inFIGS. 15-18, the tissue removal device may include ascraper120 that includes a keyhole slot having awide end122 and a narrow end124. To remove a tissue sample fromneedle56 orhook64, the tissue-engaging device with a mass of excisedtissue110 thereon can be retracted (pulled toward the proximal end of the tool) throughwide end122 of the slot and then re-inserted (pushed toward the distal end of the tool) through narrow end124 of the slot. Narrow end124 is large enough to allow passage of the barbed needle, but small enough to remove the tissue mass as the needle passes through. The removed tissue can exit the tool through anopening113 in the tool body. By shuttling the tissue-engaging device throughscraper120 in this manner, each excised segment oftissue110 can be removed from the device, readying the device for another excision.
• In an alternative embodiment shown inFIG. 30, the tissue removal device may be constructed such that tissue is removed from the tissue-engaging device by retracting the tissue-engaging device through narrow end124 of the slot. As above, narrow end124 is large enough to allow passage of the shaft of the tissue-engaging device, but small enough to remove the tissue mass as the needle passes through. If the tissue-engaging device is constructed of a tough material, the barbs or the like will cut through the tissue and/or deform and release the tissue. As above, the removed tissue can exit the tool through anopening113 in the tool body. By shuttling the tissue-engaging device throughscraper120 in this manner, each excised segment oftissue110 can be removed from the device, readying the device for another excision.
• In another alternative embodiment (not shown) an alternative mechanism for removing the tissue segment fromneedle56 includes an adjustable aperture in a disc. After the tissue-bearing needle is pulled back through the aperture, the aperture is partially closed.Needle56 andflexible hooks58 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 inFIG. 19 works by screwing into the ligamentum flavum in the manner that a corkscrew is inserted in a cork. After the screw engages a segment of tissue, outer cuttingelement60 slides over the needle, cutting a segment of tissue in a manner similar to that of the previous embodiment. In some embodiments, the cutting element can be rotated as it cuts.
• In other embodiments, shown inFIGS. 20-22, cannulatedscalpel51 houses a graspingdevice70 that includes at least one pair of arcuate,closable arms72.Closable arms72 may be constructed in any suitable manner. One technique for creating closable arms is to provide a slottedsleeve74, as shown. Slottedmember74 preferably comprises anelongate body75 with at least oneslot76 that extends through its thickness but does not extend to either end of the body.Slot76 is preferably parallel to the longitudinal axis of the sleeve. On either side ofslot76, astrip77 is defined, withstrips77 being joined at each end ofsleeve74. It is preferred that the width of eachstrip77 be relatively small. In some embodiments, it may be desirable to construct slottedmember74 from a portion of a hollow tube or from a rectangular piece that has been curved around a longitudinal axis. The inner edge of each strip that lies alongslot76 forms an opposingedge78. The width of the piece is the total of the width ofstrips77 andslot76.
• Advancing one end ofsleeve74 toward the other end ofsleeve74 causes eachstrip77 to buckle or bend. Ifstrips77 are prevented from buckling inward or if they are predisposed to bend in the desired direction, they will bend outward, thereby formingarcuate arms72, which extend throughaperture52 of cannulatedscalpel51, as shown inFIG. 21. As they move away from the axis ofbody75,arms72 move apart in a direction normal to the axis ofbody75. Likewise, moving the ends ofsleeve74 apart causesarms72 to straighten and to move together and inward toward the axis of the device, as shown inFIG. 22. As the arms straighten, opposingedges78 close and a segment of tissue can be capture between them. Tissue within the grasping device may then be resected or anchored via the other mechanisms described herein.
• Closable arms72 may include on their opposingedges78 ridges, teeth, or other means to facilitate grasping of the tissue. In other embodiments, edges78 may be sharpened, so as to excise a segment of tissue as they close. In these embodiments,closable arms72 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.
• Oncearms72 have closed on the tissue, ifarms72 have not cut the tissue themselves, the tissue can be excised using a blade such as cuttingelement60 above. The excised tissue can be removed from the inside ofneedle51 using a tissue-engaginghook64 or other suitable means. The process of extending and closingarms72, 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.
• Ligament Retraction
• 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, aretraction device90 as shown inFIG. 23 is used to retract and compress the thickened soft tissues around the posterior aspect of the spinal canal, thereby increasing the available space for the dural sac and nerves. In the embodiment shown,retraction device90 is a double-headed anchor that includes at least one distal retractable tissue-engagingmember91 and at least one proximal tissue-engagingmember92, each of which are supported on abody94.Retraction device90 is preferably constructed from an implantable, non-biodegradable material, such as titanium or stainless steel, but may alternatively be polymeric or any other, suitable material. In certain preferred embodiments,body94 is somewhat flexible. In some instances, flexibility inbody94 may facilitate the desired engagement ofbarbs91,92.Barbs91,92 may comprise hooks, arms, teeth, clamps, or any other device capable of selectively engaging adjacent tissue.Barbs91,92 may have any configuration that allows them to engage the ligamentum flavum and/or surrounding tissue. Similarly,barbs91,92 may be covered, sheathed, pivotable, retractable, or otherwise able to be extended from a first position in which they do not engage adjacent tissue to a second position in which they can engage adjacent tissue.
• FIG. 23 shows schematically the distal and proximalretractable arms91,92 of apreferred ligament anchor90. The proximal end of the anchor preferably includes a threaded connector96 or other releasable mechanism that attaches to asupport rod100.Ligament anchor90 may be attached to asupport shaft112 and sheathed in aguide housing114. The distal andproximal barbs91,92 are prevented byguide housing114 from engaging surrounding tissue. Housing102 is preferably a metal or durable plastic guide housing.
• 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 bysupport shaft112.Distal barbs91 are unsheathed and optionally expanded by pulling back guide housing102, as shown inFIG. 23.Distal barbs91 are secured in the ligamentum flavum by pulling back on thesupport shaft112. Withbarbs91 engaging the tissue, the ligamentum flavum is retracted posteriorly by pulling back onsupport shaft112. While maintaining traction on the now-retracted ligament,proximal barbs92 are uncovered and expanded by retractingguide housing114, as shown inFIG. 24.Barbs92 are preferably positioned in thesoft tissues116 in the para-spinal region so that the device is firmly anchored behind the posterior elements of the spinal canal. Once the proximal end of the anchor is engaged,support shaft112 may be detached frombody94 as shown inFIG. 24. In this manner, the posterior margin95 of the ligamentum flavum can be held in a retracted position, thereby expanding the canal. The procedure can then be repeated on adjacent portions of the ligamentum flavum until it is sufficiently retracted.
• In an alternative embodiment the proximal end ofligament anchor90 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 ofretraction devices90. 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.
• Whileretraction device90 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 mm²or 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 mm²in an average male is considered severe spinal stenosis. The present devices and techniques are anticipated to cause an increase in canal area of 25 mm²per anchor or 50 mm²total. 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 mm²or even30 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.
• Mild
• The minimally invasive ligament decompression (MILD) devices and techniques described herein allow spinal decompression to be performed percutaneously, avoiding the pain and risk associated with open surgery. Through the provision of a safety zone, the present devices and techniques offer reduced risk of spinal cord damage. In addition to improving nerve function, it is expected that decompression of the spinal canal in the manner described herein will result in improved blood flow to the neural elements by reducing the extrinsic pressure on the spinal vasculature. For these reasons, it is believed that spinal decompression performed according to the present invention will be preferable to decompression operations performed using currently known techniques.
• Dural Shield
• 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.
• FIGS. 31-33 illustrate the distal portion of an embodiment of atissue excision device200 in an open position.Tissue excision device200 comprises aninner tubular230 coaxially disposed within and slidingly engaging anouter sleeve210.Inner tubular230 andsleeve210 both share a centrallongitudinal axis250.Sleeve210 has an inner radius R₁(not shown), as measured fromaxis250, andinner tubular230 has an outer radius R₂(not shown), as measured fromaxis250. In this embodiment, outer radius R₂is substantially the same or slightly less than inner radius R₁such that the outer surface of inner tubular230 slidingly engages the inner surface ofsleeve210. Thus,sleeve210 andinner tubular230 are permitted to move axially (i.e., along axis250) relative to each other.Sleeve210 andinner tubular230 may be formed from any suitable hollow bodies including without limitation a hypotube, cannula, or catheter. Althoughsleeve210 and inner tubular230 shown inFIGS. 31-33 generally have a circular cross-section, ingeneral sleeve210 andinner tubular230 may have any suitable shape and cross-section including without limitation circular, oval, or rectangular.
• Inner tubular230 includes a central cavity or through bore240 (FIG. 32) that runs the length ofinner tubular230. In addition, a cuttinghead250 is disposed at the distal end ofinner tubular230. In this embodiment, cuttinghead250 is formed integrally with inner tubular230 such as by casting, molding, or machining. However, in different embodiments, cuttinghead250 may be manufactured separately frominner tubular230 and then fixed to the distal end of inner tubular230 by any suitable means, such as welding.
• Cuttinghead250 preferably comprises abody252 and three cuttingarms253 extending axially frombody252. In this embodiment,body252 is integral with and essentially an extension ofinner tubular230. Since eacharm253 extends axially frombody252, eacharm253 may be described as including a fixed end253aintegral withbody252 and afree end253bgenerally distal tobody252. Although each of the embodiments illustrated herein show cuttinghead250 with three cuttingarms253, in different embodiments, cuttinghead250 may include any suitable number of cuttingarms253 including without limitation two, three, four, or more.
• Arms253 are preferably integral withbody252 andinner tubular230. In such embodiments,arms253 may be formed by any suitable means including without limitation casting or molding, laser cutting, machining, or combinations thereof. However, it should be understood thatarms253 may alternatively be distinct components that are mechanically coupled tobody252 and inner tubular230 generally at fixed end253a. In such alternative embodiments,arms253 may be connected toinner tubular230 by any suitable means, including without limitation welding, pins, or combinations thereof.
• As best shown inFIG. 32, bore240 is contiguous with a tissue-receivingspace263 defined betweenarms253 inside cuttinghead250. Tissue-receivingspace253 and bore240 accommodate tissue excised by device200 (e.g., excised pieces of ligamentum flavum). In some embodiments, one or more of the surfaces that define tissue-receivingspace263 inside cuttinghead250 may include ridges, knurling or other textured surface features264 thereon so as to further improve grasping and retention of tissue betweenarms253.Textured surface feature264 may be formed by any suitable means including without limitation knurling, sand blasting, bead blasting, plasma etching, or combinations thereof. Likewise, the inner surface of inner tubular230 may be roughened to enhance the ability ofinner bore240 to enhance grasping and retention of excised portions of tissue.
• Referring again toFIGS. 31-33, eacharm253 preferably terminates in a cutting or tissue-grasping member. In the embodiment shown inFIGS. 31 and 32, two aims terminate incutters251 and a third arm terminates in a sharp anchoring tip154 that extends beyond the distal ends ofcutters251. Eachcutting edge251 preferably has a sharpened or beveled edge adapted to slice through tissue. In addition, in this embodiment, anchoring tip254 includes atissue grasping member257 that extends radially inward and helps grasp tissue and retain tissue within tissue-receivingspace263. In this embodiment,tissue grasping member257 is a tooth. However, in different embodiments, one or more tissue grasping members may comprise teeth, barbs, or the like.Tooth257 preferably has sharpened edges to enhance cutting of tissue. In general,arms253 may be any desired length.
• Cuttinghead250 is constructed so thatarms253 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 betweenarms253, termed herein as an “open position”. As shown inFIGS. 31 and 32, cuttinghead250 is in an open position. Specifically when cuttinghead250 is in an open position, cuttinghead250 is extended fromsleeve210 andfree ends253bof eacharm253 are radially spaced apart. Consequently, any tissue within tissue-receivingspace263 is not pinched or firmly grasped byarms253 and tissue is allowed to enter tissue-receivingspace263 via the gap betweenfree ends253bofarms253.
• Referring now toFIGS. 31 and 33, cuttinghead250 is transitioned to a closed position by advancingsleeve210 axially relative to cuttinghead250 toward cutting ends253bofarms253 in the direction ofarrow270. Specifically, eacharm253 preferably includes afrustoconical chamfer255 on its outer surface. The surface of eachfrustoconical chamfer255 extends radially beyond inner radius R₁ofsleeve210. In the opened position (FIG. 31), cuttinghead250 is extended fromsleeve210 and thussleeve210 does not engagefrustoconical chamfer255. Thus, eachfrustoconical chamfer255 is generally flee to extend radially beyond inner radius R₁of sleeve210 (i.e.,sleeve210 does engagechamfers255 nor restrict arms253). However, whensleeve210 is advanced toward cutting ends253bit engages the portions offrustoconical chamfer255 that radially extend beyond inner radius R₁ofsleeve210, thereby tending to forcearms253 together. Assleeve210 is advanced further towards cutting ends253b,sleeve210 continues to bear onchamfers255 andarms253 are brought closer together. Cuttinghead250 achieves the closed position whenarms253 contact each other and/or when each radially outermost portions orridge260 of eachfrustoconical chamfer255 is disposed withininner tubular230. At this point, cutting ends253bof eacharm253 are at their closest relative to each other. In some embodiments, cutting ends253bmay engage adjacent cutting ends253b.
• In the reverse manner,device200 and cuttinghead250 can be transitioned from the closed position to the open position. In general,sleeve210 may be moved axially relative to cuttinghead250 by any suitable manner including without limitation a threaded engagement withinner tubular230, a trigger mechanism, or combinations thereof.
• In the embodiments described herein, aims253 are normally open. In other words,arms253 are biased to the open position such that cuttinghead250 will assume the open position when no forces are acting to push arms153 together. Thus, to transitiondevice200 and cuttinghead250 to the closed position, compressive forces, namelysleeve210 acting on eachfrustoconical chamfer255, are necessary to pushaims253 together. Further, sincearms253 are biased open, cuttinghead253 will automatically assume the open position illustrated inFIG. 31 assleeve210 is retracted and cuttinghead253 extendsflom sleeve210. However, in other embodiments (not illustrated),arms253 may be biased closed and transitioned to an open position by providing an inner wedge between eacharm253 that urges the arms apart as it moves axially relative toarms253.
• Tissue Excision and Removal
• FIGS. 34 and 35 schematically illustrate the excision of a portion oftissue126 bydevice200. In some embodiments, a portal or cannula (not shown) may be employed to provide percutaneous access totissue126. For instance,tissue excision device200 may be inserted into and advanced through such a portal or cannula to reachtissue126. U.S. application Ser. No. 11/461,020 filed concurrently herewith, which is hereby incorporated herein by reference in its entirety, discloses several tools, devices and methods for employing a portal to provide percutaneous access to a tissue of interest. If a portal or cannula is used to guidedevice200,device200 may be passed through such cannula in the opened position or closed position.
• Regardless of the manner in whichtissue excision device200 reaches the tissue of interest (e.g., by portal or otherwise), prior to insertion into the tissue to be excised,device200 is configured in the open position as shown inFIGS. 31 and 32. Withdevice200 in the opened position, the distal portion oftissue excision device200 is advanced intotissue126, as best shown inFIG. 34.Tissue126 may be any type of tissue to be excised and removed from a patient including without limitation, soft tissue, fat, muscle, or bone. When used to treat spinal stenosis caused by a thickened ligamentum flavum, cuttinghead250 ofdevice200 is preferably inserted into thestenotic ligamentum flavum26, preferably posterior to asafety zone40, in order to safely cut and remove portions of the thickened ligamentum flavum26 (seeFIGS. 2 and 3), thereby reducing the stenosis.
• Still referring toFIGS. 34 and 35, asdevice200 is inserted and advanced intotissue126, portions oftissue126 slide into and fill at least a portion of tissue-receivingspace263 betweenarms253 within cuttinghead250. It is to be understood that thefarther device200 is advanced intotissue126, the greater the amount oftissue126 that will occupy tissue-receivingspace263. As tissue-receivingspace263 fills, some excess tissue within tissue-receivingspace263 may be pushed intobore240 ofinner tubular230.Arms253 are preferably rigid such that cuttinghead250 does not inadvertently transition to the closed position asdevice200 is advanced through the tissue. In other words,arms253 are preferably rigid so that the forces exerted on the outer surface ofarms253 by the surroundingtissue126 asdevice200 is advanced do not tend to movearms253 towards each other.
• Once a desired amount of tissue has filled tissue-receivingspace263 and bore240,device200 may be transitioned to the closed position by advancingsleeve210 toward cutting ends253band over cuttinghead250 as previously described. Asarms253 move towards each other, the portions oftissue126 within tissue-receivingspace263 and bore240 are severed from the surroundingtissue126. Specifically, the sharpened or beveled edges ofcutters251 andtooth257 slice tissue extending axially from tissue-receivingspace263, while an annular cutting edge211 ofsleeve210 slices tissue extending radially from tissue-receivingspace263 betweenarms253. Cutting edge211 ofsleeve210 is preferably sharpened to enhance the cutting ability ofsleeve210 as it moves relative to cuttinghead250. In addition, the severedtissue126 contained within tissue-receivingspace263 is grasped byarms253. Specifically,arms253 exert compressive forces on thetissue126 within tissue-receivingspace263, the textured surface features264 on the inner surface ofarms253 grips thetissue126 within tissue-receivingspace263, andtooth257 graspstissue126 within tissue-receivingspace263 and restricts it from sliding axially out of cuttinghead250 between cutting ends253b.
• Oncedevice200 has achieved the closed position,device200 maybe retracted fromtissue126 as best shown inFIG. 35. The portion oftissue126 contained within tissue-receivingspace263 and bore240 is removed along withdevice200. Oncedevice200, including a portion oftissue126 within tissue-receivingspace263 and bore240, has been completely removed from the patient, resected tissue within tissue-receivingspace263 and bore240 is removed fromdevice200 so thatdevice200 may be reinserted intotissue126 to continue to the cutting and removal of portions oftissue126.
• Pieces oftissue126 captured within tissue-receivingspace263 and bore240 may be removed by simply openingdevice200 and pulling the pieces of tissue from tissue-receivingspace263 and bore240.Device200 may be opened from the closed position by retractingsleeve210 from cuttinghead250 as previously described. Asdevice200 transitions to its opened position,arms253 will separate, allowing the user to access tissue-receivingspace263 andinner bore240.
• In an alternative embodiment, a plunger or tissue ejector may be included withdevice200 to physically eject the excisedtissue126 from tissue-receivingspace263 andinner bore240. For instance, a plunger (not shown) may be included withindevice200 to push cut tissue in tissue-receivingspace263 andinner bore240 axially out through the opening between cutting ends253bofarms253.
• The process of insertingdevice200 intotissue126 in the opened position, closingdevice126, retractingdevice200 in the closed position,opening device200, emptying tissue-receivingspace263 and bore240, and reinsertingdevice200 may be repeated until the desired amount oftissue126 has been excised and removed. Referring briefly toFIG. 3, whendevice200 is employed to remove portions of thickened ligamentum flavum26, this process may be repeated until the spinal canal is adequately decompressed. Further, whendevice200 is employed to remove portions of thickened ligamentum flavum26, the cutting ends253bof eacharm253 ofdevice200 are preferably controlled to remain within ligamentum flavum26 and not penetratesafety zone40. Nonetheless,safety zone40 is preferably provided so that even an inadvertent penetration intoepidural space27 bydevice200 will not result in damage to thedural sac32 ornerves34.
• The components of tissue excision device200 (e.g.,arms253,tooth257, 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 oftissue excision device200 are preferably manufactured from a durable biocompatible material such as titanium or stainless steel, but may alternatively be polymeric. In addition,arms253 each preferably comprise a relatively rigid material(s) capable of maintaining their shape and configuration when inserted into and advanced through tissue. Further,arms253 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 eacharm253 to return to its original configuration once external forces (e.g., force applied by sleeve210) are removed.
• In addition, the components oftissue excision device200 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 oftissue excision device200 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.

Claims (17)

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.

2. The device ofclaim 1 wherein the outer sleeve has an inner surface at a radius R₁and at least one arm has an outer frustoconical surface that extends radially to a distance greater than the radius R₁when the device is in the open position.

3. The device ofclaim 2 wherein the inner surface of the outer sleeve engages a radially outermost portion of the frustoconical surface when the device is in the closed position.

4. The device ofclaim 1 wherein each arm has a fixed end integral with the inner tubular and a free end.

5. The device ofclaim 4 wherein the free end of at least one arm includes a tissue grasping member.

6. The device ofclaim 5 wherein said tissue grasping member comprises a tooth extending radially inwards.

7. The device ofclaim 5 wherein the free end of at least one arm comprises a cutter having a beveled edge adapted to slice tissue.

8. The device ofclaim 6 wherein each arm has an axial length from the fixed end to the free end, and wherein the axial length of the at least one arm comprising the tooth is greater than the axial length of the other arms.

9. The device ofclaim 1 wherein at least one arm has an inner surface that includes a textured surface feature.

10. The device ofclaim 9 wherein the textured surface feature comprises ridges or knurling.

11. The device ofclaim 1 wherein the at least three arms define a tissue receiving space that is contiguous with a through bore of the inner tubular.

12. The device ofclaim 1 wherein each arm has a fixed end and a free end and wherein the free end of each arm engages the flee end of at least one other arm when the device is in the closed position.

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 ofclaim 13 wherein a portion of the patient's ligamentum flavum occupies the region of interest, and wherein step c) comprises inserting the tissue excision device into the ligamentum flavum in the region of interest, step d) comprises cutting at least a portion of the ligamentum flavum in the region of interest, and step e) comprises removing at least a portion of the cut ligamentum flavum.

15. The method ofclaim 13 further comprising the steps of compressing the dural sac in the region of interest by injecting a fluid to form a safety zone and establish a working zone in the region of interest, the safety zone lying between the working zone and the dural sac.

16. The method ofclaim 13 further comprising the step of emptying the cut tissue from the tissue excision device.

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.

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