Patent Description:
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 <FIG>, each vertebra <NUM> includes a vertebral body <NUM> that supports a vertebral arch <NUM>. A median plane <NUM> generally divides vertebra <NUM> into two substantially equal lateral sides. Vertical body <NUM> has the general shape of a short cylinder and is anterior to the vertebral arch <NUM>. The vertebral arch <NUM> together with vertebral body <NUM> encloses a space termed the vertebral foramen <NUM>. The succession of vertebral foramen <NUM> in adjacent vertebrae <NUM> along the vertebral column define the vertebral canal (spinal canal), which contains the spinal cord. Vertebral arch <NUM> is formed by two pedicles <NUM> which project posteriorly to meet two laminae <NUM>. The two laminae <NUM> meet posteriomedially to form the spinous process <NUM>. At the junction of pedicles <NUM> and laminae <NUM>, six processes arise. Two transverse processes <NUM> project posterolaterally, two superior articular processes <NUM> project generally superiorly and are positioned superior to two inferior articular processes <NUM> that generally project inferiorly.

The vertebral foramen <NUM> is generally an oval shaped space that contains and protects the spinal cord <NUM>. Spinal cord <NUM> comprises a plurality of nerves <NUM> surrounded by cerebrospinal fluid (CSF) and an outermost sheath/membrane called the dural sac <NUM>. The CSF filled dural sac <NUM> containing nerves <NUM> is relatively compressible. Posterior to the spinal cord <NUM> within vertebral foramen <NUM> is the ligamentum flavum <NUM>. Laminae <NUM> of adjacent vertebral arches <NUM> in the vertebral column are joined by the relatively broad, elastic ligamentum flavum <NUM>.

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 <NUM><NUM> or an anterior-posterior (AP) dimension of the canal of less than <NUM>-<NUM> 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, 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 spinal cord 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 postoperatively.

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 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.

<CIT> relates to systems, apparatus and methods for ablation, resection, aspiration, collagen shrinkage and/or hemostasis of tissue and other body structures in open and endoscopic spine surgery.

<CIT> provides a method of and an apparatus for removing bone, capsule ligaments from a co-operating pair of superior and inferior articulating processes (also called facet joints) of the spine to create a path for postero-lateral endoscopic access to the vertebral foramen and to the epidural space of the spinal canal.

<CIT> discloses a method for treating stenosis in a spine which comprises percutaneously accessing the epidural space in a stenotic region of interest.

<CIT> represents the closest prior art and the preamble of claim <NUM> is based on this document.

<CIT> discloses a safety needle including an elongate, tubular needle and a safety probe movable therein between an extended position with a blunt distal end of the safety probe projecting distally of the needle distal end and a retracted position with the safety probe distal end disposed proximally of the needle distal end.

Further prior art is disclosed in <CIT>, <CIT>, <CIT>, <CIT> and <CIT>.

These and other needs in the art are addressed by a kit for treating spinal stenosis as it is defined in claim <NUM>.

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.

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 <FIG>, <FIG>, <FIG>, <FIG>, and <FIG> 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.

Referring again to <FIG>, vertebral foramen <NUM> contains a portion of the ligamentum flavum <NUM>, spinal cord <NUM>, and an epidural space <NUM> between ligamentum flavum <NUM> and spinal cord <NUM>. Spinal cord <NUM> comprises a plurality of nerves <NUM> surrounded by cerebrospinal fluid (CSF) contained within dural sac <NUM>. Nerves <NUM> normally comprise only a small proportion of the dural sac <NUM> volume. Thus, CSF filled dural sac <NUM> is somewhat locally compressible, as localized pressure causes the CSF to flow to adjacent portions of the dural sac. Epidural space <NUM> is typically filled with blood vessels and fat. The posterior border of the normal epidural space <NUM> generally defined by the ligamentum flavum <NUM>, which is shown in its normal, non-thickened state in <FIG>.

<FIG> illustrates a case of spinal stenosis resulting from a thickened ligamentum flavum <NUM>. Since vertebral foramen <NUM> is defined and surrounded by the relatively rigid bone its volume is essentially constant. Thus, thickening of ligamentum flavum <NUM> within vertebral foramen <NUM> can eventually result in compression of spinal cord <NUM>. In particular, the thickened ligamentum flavum <NUM> may exert a compressive force on the posterior surface of dural sleeve <NUM>. In addition, thickening of ligamentum flavum <NUM> may compress the blood vessels and fat occupying epidural space <NUM>.

Compression of spinal cord <NUM>, 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 <NUM> 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 <NUM>, methods, techniques, and devices described herein may be employed to reduce the compressive forces exerted by the thickened ligamentum flavum on spinal cord <NUM> and the blood vessels in epidural space <NUM> (e.g., decompress spinal cord <NUM> and blood vessels in epidural space <NUM>). In particular, compressive forces exerted by the thickened/enlarged ligamentum flavum <NUM> 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 <NUM> by excising portions of ligamentum flavum <NUM>. In particular, in some embodiments of the MILD procedure, the ligamentum flavum <NUM> is accessed, cut and removed ipsilaterally (i.e., on the same side of vertebral arch <NUM>) by a percutaneous cranial-caudal approach. Such an embodiment of the MILD procedure may be described hereinafter as Ipsilateral Approach MILD Procedure (ILAMP).

As shown in <FIG>, ligamentum flavum <NUM> is posteriorly apposed to spinal cord <NUM>. Thus, placement of tools within ligamentum flavum <NUM> to excise portions of ligamentum flavum <NUM> creates a risk of for inadvertent damage to the spinal cord <NUM>, dural sac <NUM>, and/or nerves <NUM>. Thus, in preferred embodiments of the procedures described herein, prior to insertion of tissue excision devices into the ligamentum flavum <NUM>, a gap is advantageously created between ligamentum flavum <NUM> and spinal cord <NUM> to provide a safety zone between ligamentum flavum <NUM> and spinal cord <NUM>.

<FIG> illustrates an enlarged cross-sectional view of a vertebral foramen <NUM> within a vertebra. Vertebral foramen <NUM> includes epidural space <NUM> and spinal cord <NUM> containing nerves <NUM> and CSF within dural sac <NUM>. Further, a thickened/enlarged ligamentum flavum <NUM> extends into vertebral foramen <NUM>. To reduce the risk of damage to dural sac <NUM> and spinal cord <NUM>, a safety zone <NUM> is created between ligamentum flavum <NUM> and dural sac <NUM>.

As previously described, spinal cord <NUM> comprises nerves <NUM> surrounded by CSF and is contained within dural sac <NUM>. Since more than <NUM>% of the volume of dural sac <NUM> in the lumbar region is filled by CSF, dural sac <NUM> is highly compressible. Thus, even when stenosis is causing compression of spinal cord <NUM>, in most cases it is possible to temporarily compress spinal cord <NUM> further. Thus, according to preferred embodiments, dural sac <NUM> is further compressed in the region of interest by injecting a fluid into epidural space <NUM> to create safety zone <NUM>. The fluid may be injected into the epidural space <NUM> with an insertion member, such as a needle. The presence of the injected fluid comprising safety zone <NUM> gently applies an additional compressive force to the outer surface of dural sac <NUM> so that at least a portion of the CSF within dural sac <NUM> is forced out of dural sac <NUM> in the region of interest, resulting in safety zone <NUM> between dural sac <NUM> and ligamentum flavum <NUM>.

According to some embodiments, dural sac <NUM> is compressed by injecting a standard radio-opaque non-ionic myelographic contrast medium or other imagable or nonimagable medium into epidural space <NUM> 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 <NUM> to at least a desired degree. The injected medium is preferably substantially contained within the confines of epidural space <NUM> extending to the margins of the dural sac <NUM>. The epidural space is substantially watertight and the fatty tissues and vascularization in epidural space <NUM>, 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 <NUM> column may be referred to hereinafter as "contrast-guided dural protection.

Once a safety zone <NUM> has been created, a tissue excision tool or device <NUM> may be inserted into the ligamentum flavum <NUM>. Device <NUM> may comprise any suitable device, tool or instrument for relieving stenosis caused by the thickened/enlarged ligamentum flavum <NUM> including without limitation, embodiments of tissue excision devices and tissue retraction devices described in more detail below. Further, as best illustrated in <FIG>, device <NUM> is inserted and positioned in the ligamentum flavum <NUM> on the same side (ipsilateral) of median plane <NUM> as device <NUM> percutaneously accesses the body, such that device <NUM> does not cross median plane <NUM>. In another embodiment, as best illustrated in <FIG>, device <NUM> is positioned in the ligamentum flavum <NUM> on the opposite side of median plane <NUM> as device <NUM> percutaneously accesses the body, such that device <NUM> crosses median plane <NUM>. In some embodiments, tissue excision device <NUM> may be guided by and advanced through a cannula toward the ligamentum flavum <NUM>. In other embodiments, a cannula is not be employed to guide device <NUM> as it is advanced toward ligamentum flavum <NUM>.

While it is preferred that the tip of device <NUM> remain within ligamentum flavum <NUM> as shown, the presence of safety zone <NUM> reduces the likelihood that dural sac <NUM> will be damaged, even if the tip of device <NUM> breaks through the anterior surface of ligamentum flavum <NUM>.

Because the present techniques are preferably performed percutaneously, certain aspects of the present invention may be facilitated by imaging. Imaging windows (e.g., a fluoroscopic window of access - FWA) may be employed to aid in performance of all or part of the procedures described herein. For instance, an imaging window may be employed to aid in insertion of device <NUM> into ligamentum flavum <NUM> as shown in <FIG>. Preferable imaging windows/views are described in more detail below.

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 <NUM> 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 expanded epidural space <NUM> will be readily visible using fluoroscopy or CT imaging. Thus, safety zone <NUM> created by the present contrast-guided dural compression techniques can reduce the risk of damage to dural sac <NUM> and spinal cord <NUM> during MILD procedures to remove or displace portions of ligamentum flavum <NUM> and/or laminae <NUM> 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 <NUM> 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 <NUM> 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 <NUM> 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 dural sac <NUM> in the manner described above and to remain sufficiently present in the region of interest for at least about <NUM> 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 lowviscosity fluid, thicken upon injection into the patient, and be returned to its lowviscosity 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 Omnipaque® <NUM> 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 <NUM> and spinal nerves <NUM>, 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 <NUM> after the MILD procedure dissipates relatively quickly. For example, in preferred embodiments, the gel would have sufficient viscosity to compress dural sac <NUM> 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 tom or cut, then gel could immediately serve to seal the site and prevent leakage of the cerebral spinal fluid.

Once safety zone <NUM> has been created, the margins of epidural space <NUM> are clearly demarcated by the injected medium and may be visualized radiographically if an imageable medium has been used. As mentioned above, percutaneous procedures can then more safely be performed on ligamentum flavum <NUM> and/or surrounding tissues with reduced potential for injuring dural sac <NUM> and spinal cord <NUM>.

A variety of suitable techniques and devices may be employed to reduce the size of the thickened/enlarged ligamentum flavum <NUM>, thereby decompressing spinal cord <NUM> as well as blood vessels contained within the epidural space <NUM>. Examples of suitable decompression techniques include without limitation, removal of tissue from ligamentum flavum <NUM>, laminectomy, laminotomy, and retraction and anchoring of ligamentum flavum <NUM>. In some embodiments, all or a portion of ligamentum flavum <NUM> is excised using a tissue excision device or tool (e.g., device <NUM>). Embodiments of tissue excision tools are described in more detail below.

Accessing ligamentum flavum <NUM> with a tissue excision device <NUM> to remove portions of ligamentum flavum <NUM> can present significant challenges. For instance, in some conventional approaches to correct stenosis caused by an enlarged ligamentum flavum, an incision is made in the back of the patient and then the muscles and supporting structures of the vertebral column (spine) are stripped away, exposing the posterior aspect of the vertebral column. Subsequently, the thickened ligamentum flavum is exposed by removal of a portion of vertebral arch <NUM>, often at lamina <NUM>, which encloses the anterior portion of the spinal canal (laminectomy). The thickened ligamentum flavum ligament can then be excised by sharp dissection with a scalpel or punching instruments. However, this approach is usually performed under general anesthesia and typically requires an extended hospital stay, lengthy recovery time and significant rehabilitation. Referring briefly to <FIG>, as another example, some MILD procedures access ligamentum flavum <NUM> percutaneously by boring a hole through the vertebral arch <NUM> of vertebra <NUM>, often through a lamina <NUM>. A cannula and/or device <NUM> may be passed through the bore and/or anchored to the bore to access ligamentum flavum <NUM> for excision. However, while such a MILD approach is minimally invasive and reduces recovery time, such an approach requires the additional step of boring a hole in the posterior of the vertebra <NUM> of interest. Thus, in some cases it will be preferable to employ a MILD that percutaneously accesses ligamentum flavum <NUM> without the need to cut or bore through the vertebrae.

<FIG> is a partial cross-sectional lateral view of a segment of a vertebral column <NUM>. The segment of vertebral column <NUM> illustrated in <FIG> includes three vertebrae 10a, 10b, and 10c. Each vertebra 10a, 10b, 10c includes a vertebral body 12a, 12b, 12c, that supports a vertebral arch 14a, 14b, 14c, respectively. Vertical body 12a, 12b, 12c is anterior to vertebral arch 14a, 14b, 14c, respectively. Each vertebral arch 14a, 14b, 14c together with vertebral body 12a, 12b, 12c, respectively, encloses a vertebral foramen 15a, 15b, 15c. The succession of vertebral foramen 15a, 15b, 15c in adjacent vertebrae 10a, 10b, 10c define vertebral canal <NUM> (spinal canal) that runs along the length of vertebral column <NUM>. Vertebral canal <NUM> contains the spinal cord (not shown in <FIG>).

As previously described, each vertebral arch 14a, 14b, 14c includes two pedicles 24a, 24b, 24c, which project posteriorly to meet two lamina 16a, 16b, 16c, respectively. It is to be understood that in this view, one pedicle has been removed from each vertebra 10a, 10b, 10c and only the cross-section of one lamina 16a, 16b, 16c is visible. The two lamina 16a, 16b, 16c meet posteriomedially to form the spinous process 18a, 18b, 18c, respectively.

Lamina 16a, 16b, 16c of adjacent vertebra 10a, 10b, 10c are connected by ligamentum flavum <NUM> (shown in cross-section). The relatively elastic ligamentum flavum <NUM> extends almost vertically from superior lamina to inferior lamina of adjacent vertebrae. In particular, ligamentum flavum <NUM> originates on the inferior surface of the laminae of the superior vertebrae and connects to the superior surface of the laminae of the inferior vertebrae. For instance, ligamentum flavum <NUM> originates on the inferior surface of lamina 16a of superior vertebra 10a and connects to the superior surface of lamina 16b of the inferior vertebra 10b. Thus, ligamentum flavum <NUM> spans an interlaminar space <NUM> (i.e., space between laminae of adjacent vertebrae). Interlaminar space <NUM> is generally the space between laminae of adjacent vertebrae in spinal column <NUM>.

Still referring to <FIG>, each lamina 16a, 16b, 16c comprises a relatively broad flat plate of bone that extends posteromedially and slightly inferiorly from pedicles 24a, 24b, 24c, respectively. Along the length of vertebral column <NUM>, the lamina 16a, 16b, 16c overlap like roofing shingles, with each lamina substantially parallel to and at least partially overlapping the adjacent inferior lamina. Further, the adjacent substantially parallel laminae are separated by the intervening ligamentum flavum <NUM> and interlaminar space <NUM>. For instance, lamina 16a is substantially parallel to and partially overlaps adjacent inferior lamina 16b and is separated from lamina 16b by ligamentum flavum <NUM> and interlaminar space <NUM>.

<FIG> illustrates vertebral column <NUM> as it may be oriented with the anterior side positioned down and posterior back surface <NUM> positioned upward, as may be encountered during a spinal procedure or surgery. In addition, in the embodiment illustrated in <FIG>, ligamentum flavum <NUM> is thickened/enlarged, resulting in spinal stenosis. In particular, the anterior portions of enlarged ligamentum flavum <NUM> are extending into spinal canal <NUM>, potentially exerting compressive forces on the spinal cord (not shown) that resides within spinal canal <NUM>.

As previously discussed, to relieve compressive forces on the spinal cord and hence relieve the associated symptoms of spinal stenosis, portions of ligamentum flavum <NUM> may be excised. However, to percutaneously excise portions of ligamentum flavum <NUM> via minimally invasive techniques, the innate structure of vertebral column <NUM> and each vertebra may present significant imaging challenges. For instance, lateral imaging windows/views of ligamentum flavum <NUM> substantially in the direction of the z-axis may be obscured by the various processes of the vertebrae (e.g., transverse processes, superior articular processes, inferior articular processes), the laminae of each vertebra, etc. Further, some anterior-posterior (A-P) imaging windows/views of ligamentum flavum <NUM> substantially in the direction of the x-axis may also be obscured by the laminae. In particular, in the A-P radiographic imaging planes substantially in the direction of the x-axis, the posterior edges of parallel laminae overlap and obscure ligamentum flavum <NUM> and interlaminar space <NUM>, particularly the anterior portions of ligamentum flavum <NUM> and interlaminar space <NUM> closest to spinal canal <NUM>. However, with an imaging window/view in a plane substantially parallel to the X-Y plane, at an angle θ generally in the direction of arrow <NUM>, and slightly lateral to the spinous process, interlaminar space <NUM> and ligamentum flavum <NUM> may be viewed without significant obstruction from neighboring laminae. In other words, imaging windows/views generally aligned with arrow <NUM> (<FIG>) allow a more direct view of interlaminar space <NUM> and ligamentum flavum <NUM> from the posterior back surface with minimal obstruction by the vertebrae, laminae in particular.

Typically, the long axes of the substantially parallel laminae (e.g., laminae 16a, <NUM>,b, 16c) and interlaminar spaces (e.g., interlaminar spaces <NUM>) are generally oriented between <NUM> and <NUM> degrees relative to posterior back surface <NUM>. Thus, preferably the imaging means (e.g., x-ray beam, fluoroscopy tube, etc.) is positioned generally in the direction represented by arrow <NUM>, where θ is substantially between <NUM> and <NUM> degrees relative to the anterior back surface <NUM>. In other words, the imaging means is positioned substantially parallel to the surface of the laminae. The resulting imaging window/view, termed "caudal-cranial posterior view" hereinafter, permits a clearer, more direct, less obstructed view of interlaminar space <NUM> and ligamentum flavum <NUM> from the general posterior back surface <NUM>. The caudal-cranial posterior view permits a relatively clear view of interlaminar space <NUM> and ligamentum flavum <NUM> in directions generally along the y-axis and z-axis. However, the caudal-cranial posterior view by itself may not provide a clear imaging window/view of interlaminar space <NUM> and ligamentum flavum <NUM> in directions generally along the x-axis. In other words, the caudal-cranial posterior view by itself may not provide a clear imaging window/view that can be used to accurately determine the posterior-anterior depth, measured generally along the x-axis, of a device across the ligamentum flavum <NUM>.

Thus, in preferred embodiments, an additional imaging window/view, termed "caudal-cranial posterior-lateral view" hereinafter, is employed to provide a clearer, unobstructed view of interlaminar space <NUM> and ligamentum flavum <NUM> in directions generally along the y-axis and z-axis. The caudal-cranial posterior-lateral view is generated by orienting an imaging means generally at an angle θ relative to outer surface of the patient and also angling such imaging means laterally in an oblique orientation, revealing a partial lateral view of interlaminar space <NUM> occupied by ligamentum flavum <NUM> on the anterior side of the lamina and posterior to the underlying dural sac (not shown) and spinal cord (not shown).

By employing at least one of the caudal-cranial posterior view and the caudal-cranial posterior-lateral views, relatively clear imaging windows/views of the interlaminar space <NUM> and ligamentum flavum <NUM> in directions along the x-, y-, and z-axes may be achieved.

<FIG> illustrates vertebral column <NUM> and an instrument <NUM>. Once unobstructed imaging windows/views of interlaminar space <NUM> and ligamentum flavum <NUM> are established in the manner described above, instrument <NUM> is employed to percutaneously access interlaminar space <NUM> and ligamentum flavum <NUM>. Instrument <NUM> may be any suitable device necessary to perform the MILD procedures described herein including without limitation a tissue excision device, a cannula employed to guide a tissue excision device, or combinations thereof. Tissue excision tools and devices are described in more detail below.

More specifically, using images of the interlaminar space <NUM> and ligamentum flavum <NUM> obtained from the desired direction(s), (e.g., caudal-cranial posterior view and the caudal-cranial posterior-lateral view), instrument <NUM> can be employed to penetrate the skin and soft tissue in the posterior back surface <NUM> of the patient. In preferred embodiments, the skin entry point for instrument <NUM> is between <NUM> and <NUM> inferior (caudal to) the posterior surface of the interlaminar space <NUM> of interest. For instance, if the portion of ligamentum flavum <NUM> between lamina 16a and lamina 16b is the area of interest, then instrument <NUM> may be inserted into the patient's back about <NUM> to <NUM> inferior to posterior surface <NUM> of interlaminar space <NUM>.

Referring now to <FIG>, instrument <NUM> is preferably initially inserted into the posterior tissue and musculature of the patient generally parallel to the longitudinal axis of spinal column <NUM>. In other words, the angle β between the posterior back surface <NUM> and instrument <NUM> is between <NUM> and <NUM> degrees when instrument <NUM> is initially inserted. Further, instrument <NUM> is preferably inserted into the posterior tissue and musculature of the patient on the same side (ipsilateral) of the median plane as the area of interest (e.g., the targeted portion of ligamentum flavum <NUM>), as best seen in <FIG>. Once instrument <NUM> is inserted into the posterior tissue and musculature of the patient, instrument <NUM> then may be oriented <NUM> to <NUM> degrees relative to the posterior back surface <NUM> in order to create a trajectory across ligamentum flavum <NUM> in the area of interest. It is to be understood that once instrument <NUM> is inserted into the patients posterior back surface <NUM>, the ends of instrument <NUM> are free to pivot about the insertion location in posterior back surface <NUM> in the general direction of the y-axis and the z-axis, and may be advanced posteriorly or anteriorly generally in the direction of the x-axis.

Once inserted into the posterior tissue and musculature of the patient, instrument <NUM> can be positioned to provide a trajectory across interlaminar space <NUM> in the area of interest, generally towards the anterior surface of the lamina superior to the area of interest. For example, if interlaminar space <NUM> between lamina 16a and lamina 16b is the area of interest, instrument <NUM> is positioned to provide a trajectory that will allow a cutting instrument to be inserted across interlaminar space <NUM> between lamina 16a and lamina 16b towards the anterior surface of lamina 16a (superior lamina).

By switching between the caudal-cranial posterior view and the caudal-cranial posterior-lateral view, or by viewing both the caudal-cranial posterior view and the caudal-cranial posterior-lateral view at the same time, instrument <NUM> can be advanced to ligamentum flavum <NUM> in the area of interest with more certainty than has heretofore been present. Once instrument <NUM> has reached ligamentum flavum <NUM>, portions of ligamentum flavum <NUM> may be excised with a tissue excision device so as to relieve pressure on the spinal nerves. If instrument <NUM> comprises a tissue excision tool, instrument <NUM> may be inserted into ligamentum flavum <NUM> to resect portions of ligamentum flavum <NUM>. However, if instrument <NUM> comprises a cannula, instrument <NUM> will be positioned adjacent the ligamentum flavum <NUM> in the region of interest and a tissue excision device may be advanced through instrument <NUM> toward ligamentum flavum <NUM> and inserted in ligamentum flavum <NUM> in the region of interest to retract tissue therefrom. In some embodiments, excision can be performed generally from posterior to anterior across interlaminar space <NUM> and then laterally along the anterior portion of ligamentum flavum <NUM> if desired. The actual depth of the tip of instrument <NUM> (or any tissue excision device passing through instrument <NUM> in the case instrument <NUM> is a cannula) in the general direction of the x-axis may be adjusted with guidance from the caudal-cranial posterior-lateral view and appropriate retraction/advancement of instrument <NUM> and appropriate adjustment of instrument <NUM> between <NUM> and <NUM> degrees relative to the posterior back surface <NUM><NUM>.

Referring to <FIG>, the tip of an exemplary tissue excision device <NUM> is shown schematically within ligamentum flavum <NUM>. Tissue excision device <NUM> may be the same device as instrument <NUM>, or may be a tool passed through instrument <NUM> if instrument <NUM> is a cannula. In particular, device <NUM> has accessed ligamentum flavum <NUM> according to the ILAMP method previously described. Thus, device <NUM> is positioned to excise portions of ligamentum flavum <NUM> on the same lateral side of median plane <NUM> as device <NUM> is percutaneously inserted. In other words, in the view shown in <FIG>, device <NUM> is inserted into the body on the right side of median plane <NUM> and enters ligamentum flavum <NUM> on the right side of median plane <NUM> to excise portions of ligamentum flavum <NUM> on the right side of median plane <NUM>. In <FIG>, device <NUM> does not cross median plane <NUM>.

<FIG> illustrates an embodiment of an alternative MILD method in which exemplary tissue excision device <NUM> is positioned to excise portions of ligamentum flavum <NUM> on the opposite lateral side of median plane <NUM> as device <NUM> is percutaneously inserted. More specifically, device <NUM> is inserted into the body on the rights side of median plane <NUM>, enters ligamentum flavum <NUM> on the right side of median plane <NUM>, but is positioned to excise portions of ligamentum flavum <NUM> on the left side of median plane <NUM>. In <FIG>, device <NUM> crosses median plane <NUM>.

In the manner described, portions of the ligamentum flavum can be excised by a percutaneous MILD procedure. In particular, with the approach described and as best illustrated in <FIG> and <FIG>, ligamentum flavum <NUM> can be accessed, and portions thereof removed via the interlaminar space on the same lateral side (ipsilateral) of median plane <NUM> as the entry point for instrument <NUM> (e.g., a cannula, a tissue excision tool, etc.). This approach may sometimes hereinafter be referred to as an Iplsilateral Approach MILD Procedure (ILAMP).

Embodiments of tissue excision tools, devices, and methods disclosed herein may take several forms and may be used according to the ILAMP method described above, or used according to alternative MILD procedures (e.g., MILD procedure schematically illustrated in <FIG>). One such alternative MILD procedure is disclosed in <CIT> (<CIT>). In the descriptions of the tissue excision devices below, the distal portions of the devices are described in detail. As used herein, the term "distal" refers 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.

<FIG> and <FIG> illustrate the distal portion of an embodiment of a tissue excision device <NUM> in an opened position. Tissue excision device <NUM> comprises an inner tubular member <NUM> coaxially disposed within and slidingly engaging an outer tubular member <NUM>. Inner and outer tubular members <NUM>, <NUM> share a central longitudinal axis <NUM>. Outer member <NUM> has an inner radius R1, as measured from axis <NUM>, and inner member <NUM> has an outer radius R2, as measured from axis <NUM>. In this embodiment, outer radius R2 is substantially the same or slightly less than inner radius R1 such that the outer surface of inner tubular <NUM> slidingly engages the inner surface of tubular <NUM>. Thus, outer tubular <NUM> and inner tubular <NUM> are permitted to move axially (i.e., along axis <NUM>) relative to each other. Tubulars <NUM>, <NUM> may be formed from any suitable hollow bodies including without limitation a hypotube, cannula, or catheter. Although tubulars <NUM>, <NUM> shown in <FIG> and <FIG> generally have a circular cross-section, in general, members <NUM>, <NUM> may have any suitable shape and cross-section including without limitation circular, oval, or rectangular.

Inner tubular <NUM> includes a central through bore <NUM> and a distal end <NUM>. Bore <NUM> runs the length of inner tubular <NUM> and provides a void or space that may be filled with tissue excised by device <NUM> (e.g., excised pieces of ligamentum flavum). Distal end <NUM> includes an upper member <NUM> and a lower member <NUM>. Distal end <NUM>, including upper member <NUM> and lower member <NUM>, completely extends from outer tubular <NUM> when device <NUM> is in the opened position as illustrated in <FIG> and <FIG>. Upper member <NUM> and lower member <NUM> are preferably integral with and formed from inner tubular <NUM>. In such embodiments, distal end <NUM> of inner tubular <NUM> may be formed into an upper member <NUM> and lower member <NUM> by any suitable means including without limitation casting or molding, laser cutting, machining, hot or cold working, or combinations thereof.

Lower member <NUM> comprises a fixed end 232a integral with inner tubular <NUM> and a cutting end 232b, including a cutting tip <NUM>, that cuts through tissue as lower member <NUM> is advanced through tissue. Cutting tip <NUM> preferably has a sharpened or beveled edge defined by an acute angle λ that is preferably between <NUM>° and <NUM>°. In the embodiment illustrated in <FIG> and <FIG>, lower member <NUM> is an extension of inner tubular <NUM> and thus is coaxial with outer tubular <NUM>. As previously mentioned, lower member <NUM> is preferably integral with inner tubular <NUM>. However, it should be understood that lower member <NUM> may alternatively be a distinct component that is mechanically coupled to inner tubular <NUM> at fixed end 232a. In such alternative embodiments, lower member <NUM> may be coupled to inner tubular <NUM> by any suitable means including without limitation, welding, pins, or combinations thereof. In addition, lower member <NUM> is a relatively rigid structure that experiences minimal flexing and bending as it is advanced through tissue. Further, it should be appreciated that in the embodiment illustrated in <FIG> and <FIG>, no portion of lower member <NUM> is located at a radial distance (as measured perpendicularly from axis <NUM>) greater than inner radius R1 of outer tubular <NUM>, even when device <NUM> is in the opened position.

Referring still to <FIG> and <FIG>, upper member <NUM> includes a fixed end 231a integral with inner tubular <NUM> and a cutting end 231b, including a cutting tip <NUM>, that cuts through tissue as upper member <NUM> is advanced through tissue. Cutting tip <NUM> preferably has a sharpened or beveled edge defined by an acute angle α that is preferably between <NUM>° and <NUM>°.

In addition, upper member <NUM> is disposed at an angle θ with respect to lower member <NUM>. When device <NUM> is in the fully opened position illustrated in <FIG> and <FIG>, angle θ is at a maximum, termed herein open angle θ<NUM>. In general, the angular separation of upper member <NUM> and lower member <NUM> results from the bending or flexing of upper member <NUM> in a resilient flexing region <NUM> near fixed end 231a. Specifically, when upper member <NUM> is manufactured, upper member <NUM> is shaped or plastically deformed at flexing region <NUM> so as to form open angle θ<NUM>. For an upper member <NUM> having a length between <NUM> (<NUM>")and <NUM> (<NUM>")(as measured from cutting tip <NUM> to fixed end 231a), open angle θ<NUM> is preferably between <NUM>° and <NUM>°, and more preferably between <NUM>° and <NUM>°.

Although flexing region <NUM> defines the opened position of upper member <NUM>, upper member <NUM> may be elastically flexed within or about flexing region <NUM>. Thus, upper member <NUM> may be described as being biased to the opened position, i.e. upper member <NUM> tends to return to open angle θ<NUM> whenever it is flexed to an angle θ that differs from open angle <NUM><NUM>.

As previously described, flexing region <NUM> is formed by plastically deforming, bending, or otherwise shaping upper member into the opened position shown in <FIG> and <FIG>. In alternative embodiments, upper member <NUM> may be a distinct component that is mechanically connected to inner tubular <NUM>. In such alternative embodiments, flexing region <NUM> may be formed by a pivotal connection between upper member <NUM> and inner tubular <NUM> that is biased opened, such as by a spring or the like. Thus, although upper member <NUM> elastically bends or flexes at flexing region <NUM> in the embodiments described herein, flexing region <NUM> may also be described as a pivoting region.

Referring still to <FIG> and <FIG>, upper member <NUM> extends inward (toward axis <NUM>) at a second angled or bent region <NUM>, forming a tooth <NUM> near cutting end 231b. The amount or degree of bending at angled region <NUM> is defined by an angle p relative to axis <NUM>. Angled region <NUM> preferably has an angle p between <NUM>° and <NUM>°, and more preferably between <NUM>° and <NUM>°. Further, angled region <NUM> preferably has a smoothly contoured outer surface to enhance the ability of distal end <NUM> to pass smoothly through tissue. In addition to its utility in excising tissue, the inclusion of angled region <NUM> extending radially beyond outer radius R3 of outer tubular <NUM> offers the potential for improved fluoroscopic visualization, and hence control, of distal end <NUM> of device <NUM>. For instance, under fluoroscopic visualization, angled region <NUM> may project beyond any shadowing generated by other portions of device <NUM>, such as a handle attached to device <NUM>, etc..

As best seen in <FIG>, upper member <NUM> is preferably slightly longer than lower member <NUM>. Thus, as upper member <NUM> and lower member <NUM> are preferably sized and shaped such that upper member <NUM> can "clamp down" and mate with lower member <NUM> when upper member <NUM> flexes about flexing region <NUM> toward lower member <NUM> in the direction of arrow <NUM>. Specifically, as upper member <NUM> flexes toward lower member <NUM>, tooth <NUM> moves toward and preferably ultimately engages free end 232b and cutting tip <NUM> of lower member <NUM>. It is to be understood that as upper member <NUM> pivots or flexes about flexing region <NUM> in the direction of arrow <NUM>, the angle θ between upper member <NUM> and lower member <NUM> decreases.

<FIG> schematically illustrate the transition of tissue excision device <NUM> from the opened position (<FIG>) to the closed position (<FIG>). As shown in <FIG>, tissue excision device <NUM> fully open. When device <NUM> is in the opened position, distal end <NUM> of inner tubular <NUM> is fully extended from outer tubular <NUM> and upper member <NUM> is biased away from lower member <NUM> and disposed at open angle θ<NUM> relative to lower member <NUM>. To close tissue excision device <NUM>, outer tubular <NUM> is advanced toward distal end <NUM> generally in the direction of arrow <NUM>. As outer tubular <NUM> advances over distal end <NUM>, the inner surface of outer tubular <NUM> engages the outer surface of upper and lower members <NUM>, <NUM>. In particular, the inner surface of outer tubular <NUM> engages the portions of upper member <NUM> that extend radially beyond the inner radius R2 of outer tubular <NUM>. As a result, the inner surface of outer tubular <NUM> exerts a force on the outer surface of upper member <NUM>, causing upper member <NUM> to elastically flex or pivot about flexing region <NUM> in the direction of arrow <NUM>. Consequently, the angle θ decreases, as best seen in <FIG>. As outer tubular <NUM> is advanced over distal end <NUM>, upper member <NUM> continues move toward lower member <NUM>. In <FIG>, tissue excision device <NUM> has achieved a fully closed position. When device <NUM> is in the fully closed position, upper member <NUM> and lower member <NUM> are completely disposed within outer tubular <NUM> and angle θ between upper member <NUM> and lower member <NUM> is at a minimum, termed herein closed angle θC. In particular, when device <NUM> is in the fully closed position, closed angle θC between upper member and lower member is preferably between <NUM>° and <NUM>°.

Referring briefly to <FIG>, another a tissue excision device <NUM> not falling within the scope of the appended claims, is schematically illustrated. Like device <NUM>, tissue excision device <NUM> comprises an inner tubular member <NUM> coaxially disposed within an outer tubular member <NUM>. Inner tubular <NUM> includes a distal end <NUM> having an upper member <NUM> and a lower member <NUM>. Upper member <NUM> includes a cutting tip <NUM> and lower member <NUM> includes a cutting tip <NUM>. Device <NUM> operates substantially the same as device <NUM>, with the exception that device <NUM> includes two movable members <NUM>, <NUM> that each operate similarly to upper member <NUM> of device <NUM>. When device <NUM> is in the opened position illustrated in <FIG>, both upper member <NUM> and lower member <NUM> extend radially beyond the inner radius of outer tubular <NUM>. (as measured from axis <NUM>). When device <NUM> is actuated into the closed position, upper member <NUM> and lower member <NUM> are urged toward each other as outer tubular <NUM> advances over distal end <NUM>.

<FIG> schematically illustrate the excision of a portion of tissue <NUM> by device <NUM>. A cannula (not shown) is employed to provide percutaneous access to tissue <NUM>. Tissue excision device <NUM> is insertable into and advanced through such a cannula to reach tissue <NUM>. <CIT> (<CIT>) discloses several tools, devices and methods for employing a portal to provide percutaneous access to a tissue of interest. The device <NUM> may be passed through such cannula in the opened position or closed position.

Regardless of the manner in which tissue excision device <NUM> reaches the tissue of interest (e.g., by portal or otherwise), prior to insertion into the tissue to be excised, device <NUM> is configured in the opened position as shown in <FIG>, <FIG>, and <FIG>. With device <NUM> in the opened position, the distal portion of tissue excision device <NUM> is advanced into tissue <NUM>, as best shown in <FIG>. Tissue <NUM> 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, distal end <NUM> of device <NUM> is preferably inserted into the stenotic ligamentum flavum <NUM>, preferably posterior to a safety zone <NUM>, in order to safely cut and remove portions of the thickened ligamentum flavum <NUM> (see <FIG> and <FIG>), thereby reducing the stenosis.

Still referring to <FIG> and <FIG>, as device <NUM> is inserted and advanced into tissue <NUM>, cutting tips <NUM>, <NUM> cut through tissue <NUM>. In addition, as device <NUM> is advanced into tissue <NUM>, portions of tissue <NUM> cut by cutting tips <NUM>, <NUM> slide into and fill at least a portion of bore <NUM> of inner tubular <NUM>. It is to be understood that the farther device <NUM> is advanced into tissue <NUM>, the more tissue <NUM> is cut, and the greater the amount of cut tissue <NUM> that will occupy inner bore <NUM>. Upper member <NUM>, including flexing region <NUM> and angled region <NUM>, as well as lower member <NUM> are preferably sufficiently rigid that the device does not inadvertently transition to the closed position as device <NUM> is advanced through the tissue. In other words, upper member <NUM> and lower member <NUM> are preferably sufficiently rigid and are configured such that the forces exerted on the outer surface of upper member <NUM> and lower member <NUM> by the surrounding tissue <NUM> as device <NUM> is advanced does not tend to move upper member <NUM> towards lower member <NUM>.

In some embodiments, distal end <NUM> is shaped and configured such that the forces exerted on the inner surfaces of distal end <NUM> by tissue entering bore <NUM> are substantially balanced by the forces acting on the outside surfaces of distal end <NUM>.

In other embodiments, the distance perpendicular to axis <NUM> between cutting tip <NUM> and cutting tip <NUM> is <NUM>% to <NUM>% of the diameter of bore <NUM>.

Once the desired amount of tissue has been cut by device <NUM> and disposed within inner bore <NUM>, outer tubular <NUM> is slid toward and over distal end <NUM>, thereby closing device <NUM> as previously described. As upper member <NUM> and lower member <NUM> move towards each other, tissue <NUM> within bore <NUM> is severed from the surrounding tissue <NUM>. For instance, tooth <NUM> and cutting tip <NUM> slice tissue extending axially from bore <NUM>, and annular cutting edge <NUM> of outer tubular <NUM> slices tissue extending radially from bore <NUM> between upper member <NUM> and lower member <NUM>. In some embodiments, cutting edge <NUM> of outer tubular <NUM> is sharpened or beveled to enhance the cutting ability of outer tubular <NUM>. Once device <NUM> has achieved the closed position, device <NUM> may be retracted from tissue <NUM> as best shown in <FIG>. The portion of tissue <NUM> contained within inner bore <NUM> is removed along with device <NUM>. Once device <NUM>, including a portion of tissue <NUM> within inner bore <NUM>, has been completely removed from the patient, resected tissue within bore <NUM> is removed from bore <NUM> (i.e.. bore <NUM> is emptied) so that device <NUM> may be reinserted into tissue <NUM> to continue to the cutting and removal of portions of tissue <NUM>.

Pieces of tissue <NUM> captured within inner bore <NUM> may be removed by simply opening device <NUM> and pulling the pieces of tissue from inner bore <NUM>. Device <NUM> may be opened from the closed position by retracting outer tubular <NUM> from inner tubular <NUM>, thereby extending distal end <NUM> from outer tubular <NUM>. As device <NUM> transitions to its opened position, upper member <NUM> and lower member <NUM> will separate and angle θ will increase, allowing the user to access inner bore <NUM>. In preferred embodiment, once outer tubular <NUM> is sufficiently retracted, upper member <NUM> will retake its initial open position with angle η and angle θ at their respective maximums. In other words, upper member <NUM> is sufficiently rigid to rebound to its original opened position once outer member <NUM> no longer restricts the radial movement of upper member <NUM> (i.e., upper member <NUM> acts like a spring).

In an alternative embodiment, a plunger or tissue ejector may be included with device <NUM>, <NUM> to physically eject the excised tissue <NUM> from inner bore <NUM>. For instance, a plunger <NUM> (<FIG>) may be included within device <NUM> to push cut tissue within inner bore <NUM> out through the openings in distal end <NUM>. Such embodiments are described in more detail below.

The process of inserting device <NUM> into tissue <NUM> in the opened position, closing device <NUM>, retracting device <NUM> in the closed position, opening device <NUM>, emptying inner bore <NUM>, and reinserting device <NUM> may be repeated until the desired amount of tissue <NUM> has been excised and removed. Referring briefly to <FIG>, when device <NUM> is employed to remove portions of thickened ligamentum flavum <NUM>, this process may be repeated until the spinal canal is adequately decompressed. Further, when device <NUM> is employed to remove portions of thickened ligamentum flavum <NUM>, the tips <NUM>, <NUM> of device <NUM> are preferably controlled to remain within ligamentum flavum <NUM> and not penetrate safely zone <NUM>. Nonetheless, safety zone <NUM> is preferably provided so that even an inadvertent penetration into epidural space <NUM> by device <NUM> will not result in damage to the dural sac <NUM> or nerves <NUM>.

The components of tissue excision device <NUM> (e.g., outer tubular <NUM>, inner tubular <NUM>, members <NUM>, <NUM>, etc.) may comprise any suitable material(s) including without limitation metals (e.g., stainless steel, titanium, etc.), non-metals (e.g., polymer, composites, etc.) or combinations thereof. The components of tissue excision device <NUM> are preferably manufactured from a durable biocompatible material such as titanium or stainless steel, but may alternatively be polymeric. In addition, members <NUM>, <NUM> each preferably comprise a relatively rigid material(s) capable of maintaining their shape and configuration when inserted into and advanced through tissue. Further, upper member <NUM> preferably comprises a resilient material having the ability to be repeatedly flexed from its initial opened position to its closed position (e.g., by pivoting about flexing region <NUM>) and vice versa without cracking or otherwise being damaged. Similarly, it is desirable that upper member <NUM> resume its initial opened position when device <NUM> is transitioned from closed to opened (e.g., as outer tubular <NUM> is retracted from distal end <NUM>, thereby allowing distal end <NUM> to extend from outer tubular <NUM>). Thus, it is also preferred that upper member <NUM> comprise a resilient material capable resuming its original configuration once external forces (e.g., force applied by outer tubular <NUM>) are removed.

In addition, the components of tissue excision device <NUM> 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 <NUM> may be assembled by any suitable method including without limitation welding, press fitting, or combinations thereof. Still further, the inner surface of inner tubular <NUM> may be roughened by knurling, sand blasting, bead blasting, plasma etching, or other suitable means to enhance the ability of inner bore <NUM> to enhance grasping and retention of excised portions of tissue.

Referring now to <FIG>, the invention further includes a multi-function tool <NUM> that provides both tissue-resection and sample clearance. In certain embodiments, the multi-function tool supports one-handed operation, thereby increasing usability by the physician. Tool <NUM> generally includes a housing <NUM> having a bore <NUM> therethrough and a guide tube <NUM>, trigger <NUM>, and plunger <NUM> reciprocably disposed in bore <NUM>. Housing <NUM> includes a body <NUM> with a grip <NUM> extending therefrom. Grip <NUM> is preferably ergonomically sized and shaped so that it can be easily and firmly grasped by a physician. Body <NUM> has a proximal end <NUM> and a distal end <NUM>.

A trigger chamber <NUM> is disposed within body <NUM> and includes a trigger opening <NUM> adjacent to grip <NUM>. Bore <NUM> preferably extends through housing <NUM> from proximal end <NUM> to distal end <NUM>, intersecting trigger chamber <NUM>. Bore <NUM> preferably includes a reduced diameter portion <NUM>, which extends from distal end <NUM> to trigger chamber <NUM>, and a larger diameter portion <NUM>, which extends from trigger chamber <NUM> to proximal end <NUM>.

Guide tube <NUM> is slidably received in bore <NUM>. In some embodiments, guide tube <NUM> may be the same component as outer tubular <NUM> described above with regard to tissue excision device <NUM> (<FIG>). Guide tube <NUM> is preferably sized so that its outer diameter is slightly less than the inside diameter of reduced diameter bore portion <NUM>. Guide tube <NUM> has a proximal end <NUM> and a distal end <NUM>. A sleeve <NUM> is preferably affixed to guide tube <NUM> at or near proximal end <NUM>. Sleeve <NUM> preferably includes a trigger-engaging means <NUM> for engaging trigger <NUM>, as described in detail below.

Disposed within guide tube <NUM> is a tissue-engaging means such as a tissue clamp <NUM>. Tissue clamp <NUM> may be a rod <NUM> having a proximal end <NUM> and a distal end <NUM>. In some embodiments, the distal end <NUM> may include a tissue excision device (e.g., tissue excision device <NUM>) as described elsewhere herein. The proximal end <NUM> of tissue clamp <NUM> may include a stop <NUM> or other means for preventing movement of tissue engaging means <NUM> relative to body <NUM>. Stop <NUM> may be rigidly affixed to tissue clamp <NUM> and may be held in place within body <NUM> by a pin <NUM>. In alternative embodiments, proximal end <NUM> is held in place within body <NUM> by welding, pinning, crimping, or any other suitable means.

Trigger <NUM> has an inner end <NUM> and an outer end <NUM>. Outer end <NUM> preferably includes a finger ring <NUM> or other similar ergonomic configuration that allows outer end <NUM> to be easily manually actuated toward grip <NUM>. The inner end <NUM> of trigger <NUM> preferably includes at least one arm <NUM>, which extends adjacent to and beyond guide tube <NUM>. In preferred embodiments, arm <NUM> slidably engages trigger-engaging member <NUM> on guide tube <NUM>. Trigger <NUM> is preferably pivotally mounted to housing <NUM> at a pivot point <NUM> between its inner and outer ends <NUM>, <NUM>. In certain embodiments, pivot point <NUM> is closer to inner end <NUM> than it is to outer end <NUM>, so that a mechanical advantage can be employed during operation of the tool. A rotation stop <NUM> is preferably provided within cavity <NUM> and positioned so that it prevents rotation of inner trigger end <NUM> beyond a certain point.

In certain embodiments, tissue clamp <NUM> is provided as a hollow tube or rod. In these embodiments, it is preferred to provide a tissue ejection system <NUM>. Tissue ejection system <NUM> may comprise yet another rod or tube <NUM> (also shown in phantom in <FIG>), which is coaxial with and slidably disposed within tissue clamp <NUM>. Rod <NUM> is initially positioned so that it extends out of the proximal end of tissue clamp <NUM> and its distal end <NUM> is disposed within tissue clamp <NUM> at a point that is slightly inward of the tissue resection means. Tissue ejection system <NUM> may include a plunger head <NUM> affixed to the proximal end of rod <NUM>. Plunger head <NUM> preferably includes a plunger body <NUM> having distal and proximal ends <NUM>, <NUM>, respectively, and a knob or button <NUM> affixed to proximal end <NUM> of plunger body <NUM>. A spring <NUM> or other biasing means is preferably mounted between the distal end <NUM> of plunger body <NUM> and stop <NUM>.

In some embodiments, the outer surface of plunger body <NUM> preferably includes an offset portion <NUM> defined at its ends by distal and proximal shoulders <NUM>, <NUM>, respectively. A pin <NUM> is provided in body <NUM> and positioned so that it engages offset portion <NUM>. While rod <NUM> is slidable within body <NUM>, its axial movement in the distal direction is limited by engagement of pin <NUM> with proximal shoulder <NUM> and in the proximal direction by distal shoulder <NUM>. Spring <NUM> is preferably configured such that it is slightly compressed when pin <NUM> engages distal shoulder <NUM>. Thus, plunger head <NUM> is normally urged in the proximal direction so that it extends beyond the proximal end <NUM> of the device.

In operation, when it is desired to resect tissue from within a patient, the present multi-function tool allows a surgeon to remove a desired amount of tissue efficiently and precisely. In many instances, the tissue that is to be resected lies beneath the skin, and possibly within or adjacent to bone. For example, when stenosis is caused by hypertrophy of the ligamentum flavum, it may be desirable to remove portions of the hypertrophied ligament. In such cases, access to the resection site may be provided by inserting a trocar and cannula (e.g., instrument <NUM> in <FIG>) through the skin and intervening soft tissue as described elsewhere herein. Once the tip of the device has reached the resection site, the trocar can be removed, leaving the cannula in place to serve as a portal to the site. In the case of a hypertrophied ligamentum flavum or other stenosis, it may be preferred to use an ipsilateral technique, as described elsewhere herein.

With the cannula in place, or not, the distal end of the present tool <NUM> is inserted to the resection site as shown in <FIG>. Depending on the inner diameter of the cannula, the tissue excision device on the end of tool <NUM> may or may not be open as it passes through the cannula. Because the distal end <NUM> of tissue clamp <NUM> includes a tissue excision device (e.g., device <NUM> shown in <FIG>) it will tend to engage, or "bite into" tissue as it advances out of the end of the cannula. When a desired amount of tissue has been engaged, up to the capacity of the excision device, that tissue can be resected by advancing guide tube <NUM> axially toward the distal end <NUM>. As it advances, guide tube <NUM> bears on the outer surface of the tissue excision device (e.g., outer surface of upper member <NUM> shown in <FIG>), urging the tissue excision device into a closed position. As the tissue excision device reaches the closed position, a segment of tissue is resected and retained within the tissue excision device (e.g., within bore <NUM> shown in <FIG>). Guide tube <NUM> is advanced by applying pressure in the proximal direction on the outer end <NUM> of trigger <NUM>. This causes trigger <NUM> to pivot around point <NUM>, which in turn causes arm <NUM> to urge sleeve <NUM> in the distal direction. As sleeve <NUM> and tube <NUM> move in the distal direction, arm <NUM> pivots and shifts relative to sleeve <NUM>. As the distal end <NUM> of the guide tube reaches the distal end <NUM> of the tissue clamp, it is prevented from advancing further by engagement with stop <NUM>.

The closed tool <NUM>, containing the segment of resected tissue, may then be pulled back, out of the cannula and emptied. To empty the tool <NUM>, trigger <NUM> is urged distally, thereby causing guide tube <NUM> to retract into tool <NUM>, which in turn allows the tissue excision device to open. Because it is not uncommon for the tissue segment to remain stuck within the device, tissue ejection system <NUM> may be used to discharge the tissue segment. Tissue ejection system <NUM> is actuated by applying pressure to knob <NUM>, urging it in the distal direction. As it advances, plunger body <NUM> advances within the bore or lumen of the tissue excision device (e.g., bore <NUM> shown in <FIG>), compressing spring <NUM>. The distal end <NUM> of the plunger advances, pushing the tissue segment out as it does so. Once the tissue segment has been ejected, removing pressure from know <NUM> will allow spring <NUM> to return the plunger to its normal position, advancing rod <NUM> in the proximal direction until distal shoulder <NUM> bears on pin <NUM>.

With the completion of these steps, tool <NUM> is ready to resect another tissue segment. It will be understood that the steps can be carried out in different sequences, depending on the desired objective. For example, tool <NUM> can be advanced to the desired resection site in a closed position, rather than an open position.

The ILAMP methods and techniques described herein allow spinal decompression to be performed percutaneously, avoiding the pain, lengthy recovery time, and risk associated with open surgery. In addition, the ILAMP methods and techniques described herein permit clearer, less obstructed imaging views of the interlaminar spaces and ligamentum flavum between the laminae in the areas of interest. Such improved imaging views offer the potential for enhanced accuracy and safety in the placement of tools within the ligamentum flavum proximal the epidural space and spinal cord. Further, the excision tools and devices described herein may be employed with the ILAMP methods, or alternative percutaneous methods, to excise portions of a thickened ligamentum flavum, thereby reducing spinal stenosis caused by such enlarged ligamentum flavum.

Claim 1:
A kit for treating spinal stenosis comprising:
a cannula (<NUM>); and
a tissue excision device (<NUM>) having a distal portion configured to be inserted through the cannula (<NUM>), the tissue excision device (<NUM>) having an open position and a closed position and comprising:
an outer tubular member (<NUM>);
an inner tubular member (<NUM>) slidably received within the outer tubular member (<NUM>), the outer tubular member (<NUM>) and the inner tubular member (<NUM>) sharing a central axis (<NUM>);
wherein the inner tubular member (<NUM>) has a fixed end (231a) and a distal end (<NUM>), the distal end (<NUM>) including an upper member (<NUM>) and a lower member (<NUM>); and
a longitudinal axis of the lower member (<NUM>) is fixed parallel to the central axis of the outer tubular member (<NUM>);
wherein the upper member (<NUM>) is biased away from the lower member (<NUM>) in the open position, the upper member (<NUM>) and the lower member (<NUM>) each having a distal cutting end (231b, 232b); and
wherein the upper member (<NUM>) comprises a bent region (<NUM>);
characterized in that
the bent region (<NUM>) forms a tooth (<NUM>) near the distal cutting end (231b) of the upper member (<NUM>), the tooth (<NUM>) comprising a cutting tip (<NUM>) configured such that the cutting tip (<NUM>) is angled toward the central axis (<NUM>) relative to the fixed end (231a) in the open position; and
the upper member (<NUM>) and the lower member (<NUM>) of the distal end (<NUM>) of the inner tubular member (<NUM>) extend from the outer tubular member (<NUM>) in the open position, wherein the outer tubular member (<NUM>) is configured to be advanced relative to the inner tubular member (<NUM>), engaging the distal end (<NUM>) of the inner tubular member (<NUM>) and causing the distal end (<NUM>) to be in the closed position.