TISSUE MODIFICATION DEVICES

[0001] This patent application claims priority as a continuation-in-part of U.S. patent application Ser. No. 11/952,934, titled “TISSUE REMOVAL DEVICES AND METHODS” (filed Dec. 7, 2007). This patent application also claims priority to U.S. Provisional Patent Application Ser. No. 61/080,647, filed Jul. 14, 2008, and U.S. Provisional Patent Application Ser. No. 61/081,685, filed Jul. 17, 2008. These applications are herein incorporated by reference in their entirety.

[0002] All publications and patent applications mentioned in this specification are herein incorporated by reference in their entirety as if each individual publication or patent application was specifically and individually indicated to be incorporated by reference.

[0003] The present invention relates generally to medical/surgical devices and methods. More specifically, the present invention relates to flexible tissue modification devices and methods of modifying tissue using such devices, particularly for treatment of spinal stenosis.

[0004] A significant number of surgical procedures involve modifying tissue in a patient's body, such as by removing, cutting, shaving, abrading, shrinking, ablating or otherwise modifying tissue. Minimally invasive (or “less invasive”) surgical procedures often involve modifying tissue through one or more small incisions or percutaneous access, and thus may be more technically challenging procedures. Some of the challenges of minimally invasive tissue modification procedures include working in a smaller operating field, working with smaller devices, and trying to operate with reduced or even no direct visualization of the tissue (or tissues) being modified. For example, using arthroscopic surgical techniques for repairing joints such as the knee or the shoulder, it may be quite challenging to modify certain tissues to achieve a desired result, due to the required small size of arthroscopic instruments, the confined surgical space of the joint, lack of direct visualization of the surgical space, and the like. It may be particularly challenging in some surgical procedures, for example, to cut or contour bone or ligamentous tissue with currently available minimally invasive tools and techniques. For example, trying to shave a thin slice of bone off a curved bony surface, using a small-diameter tool in a confined space with little or no ability to see the surface being cut, as may be required in some procedures, may be incredibly challenging or even impossible using currently available devices.

[0005] One area of surgery which would likely benefit from the development of less invasive techniques is the treatment of spinal stenosis. Spinal stenosis occurs when nerve tissue and/or the blood vessels supplying nerve tissue in the spine become impinged by one or more structures pressing against them, causing symptoms. The most common form of spinal stenosis occurs in the lower (or lumbar) spine and can cause severe pain, numbness and/or loss of function in the lower back and/or one or both lower limb.

[0006] FIG. 1 is a top view of a vertebra with the cauda equina (the bundle of nerves that extends from the base of the spinal cord) shown in cross section and two nerve roots branching from the cauda equina to exit the central spinal canal and extend through intervertebral foramina on either side of the vertebra. Spinal stenosis can occur when the spinal cord, cauda equina and/or nerve root(s) are impinged by one or more tissues in the spine, such as buckled or thickened ligamentum flavum, hypertrophied facet joint (shown as superior articular processes in FIG. 1), osteophytes (or “bone spurs”) on vertebrae, spondylolisthesis (sliding of one vertebra relative to an adjacent vertebra), facet joint synovial cysts, and/or collapse, bulging or herniation of an intervertebral disc. Impingement of neural and/or neurovascular tissue in the spine by one or more of these tissues may cause pain, numbness and/or loss of strength or mobility in one or both of a patient's lower limbs and/or of the patient's back.

[0007] In the United States, spinal stenosis occurs with an incidence of between 4% and 6% (or more) of adults aged 50 and older and is the most frequent reason cited for back surgery in patients aged 60 and older. Patients suffering from spinal stenosis are typically first treated with conservative approaches such as exercise therapy, analgesics, anti-inflammatory medications, and epidural steroid injections. When these conservative treatment options fail and symptoms are severe, as is frequently the case, surgery may be required to remove impinging tissue and decompress the impinged nerve tissue.

[0008] Lumbar spinal stenosis surgery involves first making an incision in the back and stripping muscles and supporting structures away from the spine to expose the posterior aspect of the vertebral column. Thickened ligamentum flavum is then exposed by complete or partial removal of the bony arch (lamina) covering the back of the spinal canal (laminectomy or laminotomy). In addition, the surgery often includes partial or complete facetectomy (removal of all or part of one or more facet joints), to remove impinging ligamentum flavum or bone tissue. Spinal stenosis surgery is performed under general anesthesia, and patients are usually admitted to the hospital for five to seven days after surgery, with full recovery from surgery requiring between six weeks and three months. Many patients need extended therapy at a rehabilitation facility to regain enough mobility to live independently.

[0009] Removal of vertebral bone, as occurs in laminectomy and facetectomy, often leaves the affected area of the spine very unstable, leading to a need for an additional highly invasive fusion procedure that puts extra demands on the patient's vertebrae and limits the patient's ability to move. Unfortunately, a surgical spine fusion results in a loss of ability to move the fused section of the back, diminishing the patient's range of motion and causing stress on the discs and facet joints of adjacent vertebral segments. Such stress on adjacent vertebrae often leads to further dysfunction of the spine, back pain, lower leg weakness or pain, and/or other symptoms. Furthermore, using current surgical techniques, gaining sufficient access to the spine to perform a laminectomy, facetectomy and spinal fusion requires dissecting through a wide incision on the back and typically causes extensive muscle damage, leading to significant post-operative pain and lengthy rehabilitation. Thus, while laminectomy, facetectomy, and spinal fusion frequently improve symptoms of neural and neurovascular impingement in the short term, these procedures are highly invasive, diminish spinal function, drastically disrupt normal anatomy, and increase long-term morbidity above levels seen in untreated patients.

[0010] Therefore, it would be desirable to have less invasive methods and devices for modifying target tissue in a spine to help ameliorate or treat spinal stenosis, while inhibiting unwanted damage to non-target tissues. Ideally, such techniques and devices would reduce neural and/or neurovascular impingement without removing significant amounts of vertebral bone, joint, or other spinal support structures, thereby avoiding the need for spinal fusion and, ideally, reducing the long-term morbidity resulting from currently available surgical treatments. It may also be advantageous to have minimally invasive or less invasive tissue modification devices capable of treating target tissues in parts of the body other than the spine. At least some of these objectives will be met by the present invention.

[0011] Described herein are improved devices for modifying tissue and methods of using them. These devices may be included as part of a system for modifying tissue. In general, these devices include a plurality of blades positioned on (or formed from) rungs that are flexibly connected. The rungs are typically rigid, somewhat flat and wider than they are long (e.g., rectangular). The rungs may be arranged, ladder like, to a flexible substrate, or between two or more cables. Different sized rungs may be used. The blades (on the rungs) may be arranged in a staggered arrangement. A tissue-collection or tissue capture element (e.g., chamber, bag, or the like) may be used to collect the cut or modified tissue.

[0012] Any of the devices described herein may be used as part of a tissue decompression (e.g., spinal decompression) method to modify tissue such as soft tissue (e.g., ligamenum flavum, etc.) and hard tissue (e.g., bone). In particular, these devices may be used as part of a spinal decompression technique within a spinal foramen.

[0013] The devices described herein may be used as part of a guide-based access and decompression system, including those previously described in any of the following patent applications and provisional patent applications, each of which is herein incorporated by reference in its entirety: U.S. patent application Ser. No. 11/250,332, titled “DEVICES AND METHODS FOR SELECTIVE SURGICAL REMOVAL OF TISSUE” (filed Oct. 15, 2005), U.S. patent application Ser. No. 11/251,199, titled “DEVICES AND METHODS FOR TISSUE ACCESS” (Oct. 15, 2005), U.S. patent application Ser. No. 11/375,265, titled “METHODS AND APPARATUS FOR TISSUE MODIFICATION” (filed Mar. 13, 2006), U.S. patent application Ser. No. 11/405,848, titled “MECHANICAL TISSUE MODIFICATION DEVICES AND METHODS” (filed Apr. 17, 2006), U.S. patent application Ser. No. 11/429,377, titled “FLEXIBLE TISSUE RASP” (filed May 4, 2006), U.S. patent application Ser. No. 11/538,345, titled “ARTICULATING TISSUE CUTTING DEVICE” (filed Oct. 3, 2006), U.S. patent application Ser. No. 11/687,548, titled “TISSUE REMOVAL WITH AT LEAST PARTIALLY FLEXIBLE DEVICES” (filed Mar. 16, 2007), U.S. patent application Ser. No. 11/687,558, titled “FLEXIBLE TISSUE REMOVAL DEVICES AND METHODS” (filed Mar. 16, 2007), U.S. patent application Ser. No. 11/870,370, titled “PERCUTANEOUS SPINAL STENOSIS TREATMENT” (filed Oct. 10, 2007), and U.S. patent application Ser. No. 12/127,535, titled “GUIDEWIRE EXCHANGE SYSTEMS TO TREAT SPINAL STENOSIS” (filed May 27, 2008).

[0014] In particular, the devices described herein may use a guidewire-based system that is configured so that the device may be pulled into position and/or tensioned so as to be urged against a tissue, and thereby modify the tissue. This configuration may be referred to as a bimanual system, since both ends (e.g., the proximal end and the distal end of the device) may be tensioned or pulled to modify the tissue. Tissue may be modified by removal or smoothing of the tissue, and may be performed by pulling the devices described herein through the tissue so that the working surface (e.g., the blades on the rungs) contacts one or more tissue surfaces.

[0015] In general, the tissue-modification devices described herein have an elongate, flexible body that includes a plurality of connected rungs. At least some of the rungs include one or more cutting edges (e.g., blades), that may project from the rung. The rungs may be connected by a flexible material that extends along the length of the device. These devices are typically configured so that they can be used in the narrow region of a spinal foramen. Thus, the devices may be substantially flat. For example, the devices may be substantially ribbon-shaped. These devices may also include a distal attachment site for a guidewire. Thus, a guidewire may be used to pull a device from the distal end of the device into position, and may also be used to tension the device so that it is urged against the tissue.

[0016] For example, described herein are flexible tissue-modification devices for removing tissue from a patient comprising: a flexible elongate body having an axial length, a width and a thickness. The elongate body in this example includes a plurality of rungs that are flexibly connected, wherein each rung extends at least partially across the width of the body. The axial length is greater than the width, and the width is greater than the thickness, and at least one cutting edge on two or more of the rungs.

[0017] The rungs may be sufficiently rigid that they do not deflect when tension is applied to urge the device against the tissue. For example, the rungs may be formed of a metal, alloy, polymer, or other appropriate material(s), particularly those that are relatively rigid.

[0018] The elongate body of the device may be formed by the connected rungs, and may be substantially straight (e.g., linear), curved, or substantially non-linear in the proximal-to-distal (e.g., along the length of the device) direction.

[0019] The rungs may be shaped as rectangles, squares, ovals, trapezoids, or the like. In particular, the rungs may have an axial length that is less than the width of the rungs. Rungs are typically flat, so that the thickness (or height) of the rungs is less than the width and/or length of the rung. Any of these dimensions may vary for different rungs along the length of the device. For example, rungs nearer the proximal end may be thicker, and rungs at either the proximal or distal ends may be narrower or wider.

[0020] The rungs may be connected directly to each other, or may be separated. For example, a rung may be directly connected to an adjacent rung via a hinged joint or other movable joint, allowing the device to be flexible along its length. In some variations some or all of the rungs are separated from each other by a spacer. Adjacent rungs may be connected to each other by one or more connectors. For example, a connector may be a flexible connector such as a mesh or woven material. As mentioned, the connector may be a hinged joint. In some variations, the connector comprises at least one cable.

[0021] Any of the tissue modification devices described herein may include one or more guidewire couplers at the distal end of the device. A guidewire coupler typically engages with a portion (e.g., the proximal end) of the guidewire to secure the guidewire to the guidewire coupler. The guidewire coupler may be configured so that a portion of the guidewire (such as the proximal end of the guidewire) is held securely in the distally located guidewire coupler. The guidewire coupler may releasably hold the guidewire in position. The guidewire is typically held by the guidewire coupler so that when engaged, the guidewire and the guidewire coupler do not move relative to each other. Additionally, the guidewire may be typically held so that pulling on the distal end region of the guidewire results in pulling the device from its distal end, i.e. pulling the device from where the guidewire is coupled via the guidewire coupler. Thus, the coupler may engage the guidewire with sufficient strength and stability to allow the device to be positioned within the body by drawing on the distal end of the guidewire.

[0022] The tissue modification devices (or systems including the devices) may also include a handle or a handle attachment region at the proximal end of the device. A handle may be for manual manipulation (e.g., pulling) of the device. The handle may be removable or non-removably attached to the device.

[0023] In some variations, the devices also include at least one protective side guard extending along the length of the flexible elongate body. The protective side guard may be a shield or barrier that prevents the edges of the device (e.g., the edges of the rungs) from scraping tissue as the device is drawn proximally/distally, particularly when modifying tissue. For example, the protective side guard may be a polymeric (e.g. flexible) material having a smooth, atraumatic outer surface.

[0024] As mentioned, any of these devices may also include at least one spacer between adjacent rungs. A spacer may be a ball, tube, washer, or the like. The spacer may be any appropriate size, to provide an appropriate distance between adjacent rungs. In some variations multiple spacers are used between rungs. For example, multiple spacers may be placed on the sides of the rungs. In some variations, the spacers are linked to the rest of the device by a hollow or passage. For example, a spacer may be threaded between rungs on the connector(s) linking the rings. A spacer may also attach to other structures. For example, in variations in which a collection region is provided, the spacer may connect to a collection bag.

[0025] One or more cutting edges may be included on each rung. The cutting edge may be part of a blade. In some variations of the tissue modification devices, the cutting edge(s) on the rung or rungs project from the surface of the rung. For example, a blade may be formed by a portion of the rung that extends up (e.g., out of the plane of the tissue modification device). The blade or cutting edge may be oriented so that it optimally cuts tissue as the device is urged against the target tissue. For example, the blade may be oriented so the blade is perpendicular to the long axis (the length) of the device. The blade may be shaped (e.g., flat, pointed, or the like). The shape and orientation of the blade may help steer the device as it is urged against the tissue.

[0026] Cutting edges may be arranged on the device (e.g., on any of the rungs, or any plurality of rungs) in any appropriate manner. For example, cutting edges (e.g., blades) may be arranged so that there are more or fewer blades in some regions than in others. In some variations, the density of cutting edges increases along the length of the tissue modification device such that there are fewer cutting edges near the distal end of the device, and the number of blades increases along the length, proceeding proximally; the number or density (distribution) of blades may then decrease again towards the proximal end of the region that will engage the tissue. In general, the descries described herein may be used as two stroke devices, so that the device may modify tissue both as it is drawn distally (e.g., forward) and as it is drawn proximally (backwards). Thus, the tissue modification device may be adapted to modify tissue in both directions. Alternatively, in some variations, the device may be adapted so that it does not substantially modify tissue when drawn in one direction, but only when moved in the opposite direction. For example, cutting edges may be shielded or protected on one side by including a blunting region.

[0027] The cutting edges on adjacent rungs of the tissue modification device may be axially offset from each other. Offsetting the axial position of the blades (or cutting edges) may enhance cutting by presenting a wider effective cutting surface. Thus, relatively narrow (or pointed) blades/cutting edges may be used to cut a region of tissue that is wider than the blade/cutting surface width.

[0028] The cutting edge may generally be positioned on the rung (and therefore on the device) so that it is not immediately adjacent to the edges of the device. For example, the cutting edge may be positioned on the rung spaced from the edge of the rung. For example, the cutting edge may be spaced approximately 0.5 mm, or greater than 0.5 mm.

[0029] In some variations the tissue modification devices may include blades of different shapes and sizes on the same device. Blades may have different heights (e.g., projecting from the rung), widths, shapes, etc. Different shaped/sized blades may also be arranged along the length of the tissue modification device (e.g., along the tissue modification surface or side of the device). For example, in some variations, blades at the more proximal end of the tissue modification device may be more closely spaced and may have a lower profile than blades more distally. Alternatively, the blades near the ends (e.g. proximal and distal ends) of the tissue modification region of the device may be less closely spaced and have a slightly higher profile than blades along the center of the length of the device. These arrangements may help overcome stiction when using the device to modify tissue. For example, the tissue modification device could have blades with graduated profiles so that the blades near the ends (proximal and distal) permit a “running start” for the tissue modification from the larger blades. In some variations, the profile of the blades near one or both ends (e.g., the distal end) have a lower profile than blades near the middle of the tissue modification device

[0030] In some variations, the tissue modification device may also include one or more ramps or projections that are not cutting edges, that project from one or more of the rungs. Ramp regions may project from one or more rungs and may have increasing profile(s) towards the center of the tissue modification region. A ramp or ramp region may dilate the region to be modified. In some variations the maximum height of the ramp may be the same or slightly greater than the height of any blades.

[0031] Any of the devices described herein may also include a tissue collection region for collecting tissue cut by the device. The tissue collection region may communicate with the rungs, so that it forms behind the rungs (e.g., away from the cutting face of the device). Examples of tissue collection regions are described in greater detail below, but may be configured so that they have a fixed minimum volume. Tissue may enter the tissue collection region by passing through or around the rungs. For example, in variations in which the rungs are spaced apart, tissue may pass into the tissue collection region by passing between the rungs. In some variations the rungs include one or more channels or passages that may guide tissue into the tissue collection region. The tissue collection region may be removable (e.g., to empty or swap out when full), replaceable, or emptyable, so that the device can be re-used or used after emptying the tissue collection region.

[0032] Also described herein are flexible tissue-modification devices for removing tissue from a patient that include at least two flexible elongate cables, wherein the cables extend substantially adjacent to each other from the proximal end of the device to the distal end of the device, a plurality of rungs, wherein each rung extends between the cables, and at least one cutting edge on two or more of the rungs. Any of the features described above may be included in this variation as well. For example, the width of a rung extending between the flexible elongate cables may be greater than the length of that rung extending proximally to distally.

[0033] In variations in which the rungs are connected via a connector such as a plurality of cables, the distal ends of such flexible elongate cables may be secured together. Similarly, the proximal ends of the flexible elongate cables may also (or alternatively) be secured together.

[0034] Also described herein are methods of modifying tissue. For example, in some variations, the methods include the steps of: passing a flexible tissue-modification device at least partially around a target tissue, wherein the flexible tissue-modification device is configured as any of the flexible tissue-modification devices described herein (e.g., comprises a flexible elongate body having a width and a thickness, a plurality of rungs that are flexibly connected, wherein each rung at least partially extends across the width of the body, and at least one cutting edge on two or more of the rungs); moving the tissue-modification device against the target tissue by pulling the tissue-modification device from at least one end of the device; and cutting the target tissue with the cutting edges on the rungs of the tissue-modification device.

[0035] The step of passing the flexible tissue-modification device at least partially around the target tissue may include passing a guidewire at least partially around the target tissue and pulling the flexible tissue-modification device around the target tissue using the guidewire.

[0036] In some variations, the method also includes collecting cut tissue into a tissue collection portion of the tissue-modification device.

[0037] In any of the methods described herein, the tissue may be modified to decompress one or more spinal nerves. For example, the method may include the steps of removing or modifying tissue within a spinal foramen.

[0038] The step of moving the tissue-modification device against the target tissue may include applying tension to both the proximal end and the distal end of the tissue-modification device to drive the tissue-modification device against the target tissue. The method may also include the step of detecting neuronal tissue near the flexible tissue-modification device. For example, one or more electrodes may be used to determine the proximity of a nerve to the cutting surface(s) of the device.

[0039] Any of the methods described herein may include a step of sensing a change in the tissue type (e.g., from hard to soft tissue) during operation. For example, the method may include the step of sensing a change in the resistance to movement. In general, the tactile feel of the tissue being cut may change between hard and soft tissues, and this feel may be sensed either automatically (using one or more sensors that are sensitive to changes in resistance to motion of the device) or manually (e.g., a user may feel more of a “kick”).

[0040] As mentioned, any of the devices described herein may include a tissue collection region. In particular, tissue collection regions having a fixed open volume or a fixed minimum open volume are described. For example, described herein are flexible tissue-modification devices for removing tissue from a patient, comprising: a flexible elongate body extending proximally and distally along a length, further having an anterior surface, wherein the anterior surface extends at least partially proximally and partially distally; a plurality of cutting edges communicating with the anterior surface; and a tissue collection region configured to store tissue cut by the plurality of cutting edges, the tissue collection region having a fixed minimum open space and one or more vias allowing tissue cut from the cutting edge into the open space, wherein the open space of the tissue collection region is formed between the anterior surface and a posterior substrate separated from the anterior surface by a thickness.

[0041] A minimum open space may allow tissue to be driven into the tissue collection region without requiring substantial force. Thus, in some variations the device is configured so that the minimum open volume formed as the space between the anterior surface and the posterior substrate (which forms a second surface) is relatively constant even when the devices are flexed along their length as they are pulled against a target tissue (e.g., within a spinal foramen). The minimum open volume may be determined by the size of the opening. For example, the anterior surface and the posterior surface formed by the posterior substrate may be separated by a minimum distance of between about 0.5 mm and about 5 mm.

[0042] The posterior substrate may be secured in parallel to the anterior (tissue cutting) surface. In some variations, the posterior substrate is a relatively rigid elongate substrate extending at least partially proximally and partially distally. The posterior substrate may extend the same distance as the anterior surface, so that the tissue collection region underlies all of the cutting edges. In some variations, the posterior substrate is formed so that it does not inhibit the flexing or bending (the flexibility) of the elongate body. In some variations, the posterior substrate is formed of an expandable material that allows the posterior substrate to expand as the tissue collection region is filled.

[0043] The posterior substrate may be coupled to the anterior surface. For example, the posterior substrate may be coupled to the anterior surface by a plurality of connectors linking the anterior surface to the posterior substrate. The connectors may be rigid, to maintain the minimum open volume. In some variations, the posterior surface is connected to the device so that it may be extendable in the posterior/anterior direction, along the length of the device. The device may be configured so that the posterior surface moves along the length (proximally/distally) as the device is flexed. For example, the posterior substrate may be extendable in the proximal and distal axis. For example, the posterior substrate may be coupled to the flexible elongate body by an expandable connector that allows the posterior substrate to extend or contract proximally and distally as the tissue-modification device is flexed. The expandable connector may be a spring, an elastic region, or the like.

[0044] In some variations, the posterior substrate comprises an accordion region, which may expand/contract as it is flexed. The expansion may occur along the length of the device. In some variations, the posterior substrate may expand open to increase the volume of the tissue collection region above the minimum open volume. In some variations the volume of the tissue collection region is relatively constant (and is approximately fixed minimum open volume).

[0045] The plurality of cutting edges may be blades, and these cutting edges may project from the anterior surface.

[0046] A via through which tissue may pass into the tissue collection region may be an opening or a channel through the anterior surface. For example, a via may be a channel formed at the base of a cutting edge or blade. In some variations the via is an opening formed in the anterior surface which is adjacent to the blade extending from the anterior surface.

[0047] As described above, in some variations the device includes a plurality of connected rungs. Thus, the anterior surface may comprise a plurality of rigid rungs that are flexibly connected.

[0048] Any of the device variations including a tissue collection region having a fixed minimum open space or volume may include a guidewire attachment region, as mentioned above, and/or a handle or handle attachment region in communication with the proximal end of the flexible elongate body.

[0049] For example, in some variations a device for modifying tissue is a flexible elongate tissue-modification device including: a flexible elongate body having a length and a width, the body extending distally and proximally along the length, wherein the length is greater than the width; a plurality of rungs that are flexibly connected, wherein each rung extends across the width of the body; at least one cutting edge on two or more of the rungs; and a tissue collection region adjacent to the rungs, wherein the tissue collection region has a minimum open space defined by the space between the rungs and a tissue collection substrate that extends at least partially proximally and distally. The tissue collection region comprises a plurality of connectors connecting the tissue collection substrate with the rungs.

[0050] Also described herein are methods of removing tissue from a patient, the method comprising: passing a flexible tissue-modification device having a tissue collection region at least partially around a target tissue, wherein the flexible tissue-modification device comprises a flexible elongate body having an anterior surface extending proximally and distally, a plurality of cutting edges communicating with the anterior surface and a tissue collection region having a minimum open space in communication with the cutting edges; moving the tissue-modification device against the target tissue by pulling the tissue-modification device from at least one end of the device; cutting the target tissue with the cutting edges; and collecting the cut tissue into the open space of the tissue collection region. The step of passing the flexible tissue-modification device at least partially around the target tissue may include passing a guidewire around the target tissue, and pulling the flexible tissue-modification device around the target tissue using the guidewire. These methods may also be used to decompress spinal tissue. For example, the target tissue may comprise tissue within a spinal foramen.

[0051] The step of moving the tissue-modification device against the target tissue may include applying tension to both the proximal end and the distal end of the tissue-modification device to drive the tissue-modification device against the target tissue.

[0052] In some variations, the method also includes the step of sensing neuronal tissue near the flexible tissue-modification device.

[0053] In some of the tissue-modification devices described herein, the devices have a first configuration and can be converted to and locked in a second configuration. The first and second configurations may refer to the configuration of the devices in the proximal-distal axis. The first configuration may be linear (e.g., relatively un-curved) and the second configuration may be curved or bent. In both configurations (the first and second), the device may still be flexible along its length (e.g., proximally to distally) in at least one direction (e.g., anterior/posterior).

[0054] For example, a flexible tissue-modification device for removing tissue from a patient may include: a flexible elongate body having a length, a width and a thickness, wherein the length is greater than the width, and the width is greater than the thickness, an anterior surface extending proximally and distally across the width of the flexible elongate body; a plurality of cutting edges communicating with the anterior surface, wherein the flexible tissue-modification device is convertible from a first configuration, in which the anterior surface has a first proximal to distal shape, and a second configuration in which the anterior surface has a second proximal to distal shape; and a lock for locking the proximal to distal shape of the anterior surface of the tissue-modification device.

[0055] The device may also include a cable extending proximally and distally in the device that is configured to change the proximal to distal shape of the anterior surface when tension is applied to the cable. As mentioned, the first proximal to distal shape of the anterior surface may be linear. The second proximal to distal shape of the anterior surface may be bent or curved. For example, the second proximal to distal shape may be C-shaped, S-shaped, etc.

[0056] As mentioned, any of these devices may include a guidewire coupler at the distal end of the flexible elongate body, and/or a handle or handle attachment region in communication with the proximal end of the flexible elongate body. As described above, the anterior surface may include a plurality of flexibly connected rungs, wherein each rung extends across the width of the flexible elongate body. Any of these devices may also include a tissue collection region, particularly a tissue collection region having a fixed minimum space.

[0057] For example, described herein are flexible tissue-modification devices for removing tissue from a patient that include a flexible elongate body having a length, a width and a thickness, wherein the length is greater than the width, and the width is greater than the thickness; a plurality of rungs that are flexibly connected, wherein each rung extends across the width of the body and forms an anterior surface; at least one cutting edge on two or more of the rungs; wherein the flexible tissue-modification device is convertible from a first configuration, in which the anterior surface has a first proximal to distal shape, and a second configuration, in which the anterior surface has a second proximal to distal shape; and a lock for locking the proximal to distal shape of the anterior surface of the tissue-modification device.

[0058] The devices described herein may also include a cable extending proximally and distally in the device that is configured to change the proximal to distal shape of the anterior surface by applying tension to the cable.

[0059] Methods of removing tissue from a patient may include using tissue modification devices that can be converted between different proximal-to-distal shapes, such as those described above. For example, described herein are methods of removing tissue from a patient comprising: passing a flexible tissue-modification device at least partially around a target tissue, wherein the flexible tissue-modification device comprises a flexible elongate body having an anterior surface extending proximally and distally, and a plurality of cutting edges communicating with the anterior surface; wherein the anterior surface of the flexible tissue-modification device is convertible between a first proximal to distal shape and a second proximal to distal shape; converting the anterior surface of the tissue modification device from a first proximal to distal shape to a second proximal to distal shape; locking the anterior surface in the second proximal to distal shape; moving the tissue-modification device against the target tissue by pulling the tissue-modification device from at least one end of the device; and cutting the target tissue with the cutting edges.

[0060] The step of converting the anterior surface of the tissue modification device from a first proximal to distal shape to a second proximal to distal shape may include converting the anterior surface from a linear shape to a curved shape, such as a C-shape or an S-shape, or the like.

[0061] In some variations, the step of passing the flexible tissue-modification device at least partially around the target tissue comprises: passing a guidewire around the target tissue; and pulling the flexible tissue-modification device around the target tissue using the guidewire.

[0062] Any of the methods for modifying tissue, including the methods in which the tissue modification device changes shape, may include collecting cut tissue by the cutting edges of the tissue-modification device into a tissue collection portion of the tissue-modification device.

[0063] The step of moving the tissue-modification device against the target tissue typically comprises applying tension to both the proximal end and the distal end of the tissue-modification device to drive the tissue-modification device against the target tissue.

[0105] Various embodiments of tissue modification devices and systems, as well as methods for making and using tissue modification devices and systems, are provided herein. In general, a flexible tissue-modification device as described herein is configured to remove tissue from a patient. In particular, these tissue-modification devices may be configured to decompress spinal stenosis. These devices typically include a flexible elongate body that extends proximally to distally (proximal/distal), and is configured to be inserted into a patient so that it extends around the target tissue, so that it can be bimanually pulled against the target tissue by applying tension to either end of the device. Thus, the device may be extended into, through, and/or around a spinal foramen. The device is flexible in at least one plane. For example, in variations in which the device has an elongated ribbon shape that is long and flat with a width greater than the thickness, the device includes a first major surface (e.g., a front) and a second major surface (a back), and has edges (minor surfaces) between the first and second major surfaces. The first major surface may be referred to as the anterior or front surface and the second major surface may be referred to as the posterior or back surface. The devices described herein may be flexible along the anterior and posterior surfaces, and the anterior or front surface may include one or more cutting edges configured to cut tissue as the anterior surface of the device is urged against a tissue. The posterior surface may be configured to shield or protect non-target tissue.

[0106] The tissue modification devices described herein also typically include one or more of the following features: all or a portion of the device maybe formed of flexibly connected rungs or links; the devices may include a tissue capture region having a fixed minimum volume; and the device may be configured so that the major/minor surfaces may have non-linear shapes along their length, or may be stitched between linear and non-linear shapes. A tissue modification device may include one or more of these features in any combination. Each of these features is described and illustrated in greater detail below.

[0107] Although much of the following description and accompanying figures generally focuses on surgical procedures in spine, in alternative embodiments, devices, systems and methods of the present invention may be used in any of a number of other anatomical locations in a patient's body. For example, in some embodiments, the flexible tissue modification devices of the present invention may be used in minimally invasive procedures in the shoulder, elbow, wrist, hand, hip, knee, foot, ankle, other joints, or other anatomical locations in the body. Similarly, although some embodiments may be used to remove or otherwise modify ligamentum flavum and/or bone in a spine to treat spinal stenosis, in alternative embodiments, other tissues may be modified to treat any of a number of other conditions. For example, in various embodiments, treated tissues may include but are not limited to ligament, tendon, bone, tumor, cyst, cartilage, scar, osteophyte, inflammatory tissue and the like. Non-target tissues may include neural tissue and/or neurovascular tissue in some embodiments or any of a number of other tissues and/or structures in other embodiments. In one alternative embodiment, for example, a flexible tissue modification device may be used to incise a transverse carpal ligament in a wrist while inhibiting damage to the median nerve, to perform a minimally invasive carpal tunnel release procedure. Thus, various embodiments described herein may be used to modify any of a number of different tissues, in any of a number of anatomical locations in the body, to treat any of a number of different conditions.

[0108] In some variations, a tissue modification device is formed from a plurality of flexibly connected rungs. As used herein, a rung may also be referred to as a link or crosspiece. A rung may be stiff (e.g., made of a relatively rigid material) or flexible. The rungs may be connected to or may form the anterior (front) major surface. At least some of these rungs include one or more cutting edges, which may be configured as blades. The cutting edges may be formed as part of the rung, or attached to the rung.

[0109] Individual rungs may have any appropriate shape. For example, a rung may have a rectangular shape, an oval shape, a trapezoidal shape, or the like. In general, the rung is relatively flat (e.g., having a thickness that is substantially less than the length and width). A rung may be smooth, rough or some combination. Different rungs in the same device may be different shapes and sizes, as illustrated below. A rung may be directly or indirectly connected to adjacent rungs.

[0110] Rungs are flexibly connected to adjacent rungs and/or to another portion of the tissue modification device. A connector, such as a cable, wire, chain, string, sheet, ribbon, mesh, fabric, or the like, may be used to connect adjacent rungs. The connector may be flexible, or stiff. A connector may extend only between adjacent rungs, or it may extend along all or a portion of the length of the device so that multiple rungs may be attached to the same connector. More than one connector may be used to connect adjacent rungs. For example, rungs may be connected between two parallel wires. In some variations, the rungs are directly connected to adjacent rungs by a hinge joint or the like. Combinations of connectors and direct connections between rungs may be used.

[0111] In some variations, rungs may be separated from each other by a space. The space may be an opening. In some variations, one or more spacers are used to separate adjacent rungs. The spacing between adjacent rungs may be different. In variations including one or more tissue collection regions, the spaces between rungs may provide a passage (or via) between the cutting surface on the anterior-facing surface of the rung, on which a cutting edge may be located (or may extend from) and the tissue collection region.

[0112] For example, FIG. 2A illustrates one variation of a tissue modification device having a plurality of rungs. FIG. 2A is a partially exploded, perspective view illustrating enlargements of various regions. The tissue-modification device shown in FIG. 2A is flexible and includes individual rungs that may articulate relative to each other. This device includes two parallel cables 201, 201′ and a plurality of rungs 205, 205′, 206, 203 extend between the cables. The cables are the connectors that link adjacent rungs. In this example, the two cables are joined at the proximal 233 and distal 235 regions. In some variations, the cable is joined at the proximal and distal ends, or is formed from a single cable; in some variations the two cables are separate. At least a portion of the cable is flexible. Any appropriate cable may be used, including metal or polymeric cables. Cables may be single-filament or formed of multiple filaments. The portion of the cable towards the distal end of the device, as shown in this example, may be hinged, and the links between distal and proximal sections may be connected in flexible junctions.

[0113] In some embodiments, the links or rungs 205, 205′, 206, 203 spanning the cables have different shapes and sizes. The rungs 203 in the central region each include one or more cutting edges 211 projecting from the anterior (target tissue facing) surface. These cutting rungs 203 may form a tissue modifying region of the device. The cutting edges shown are triangular or pointed, although any appropriate shape may be used. Further, these cutting edges may be oriented in any desired manner; the orientation of the cutting edges may help steer or guide the device as it is urged against a target tissue to cut the tissue. In this example the cutting edges are oriented in parallel with the long axis (the distal/proximal axis) of the device.

[0114] In some embodiments, the rungs may have varying widths along the length of the tissue modification device. For example, the rungs toward the distal end of the device may have a small width, while rungs towards the proximal end of the device may have a larger. For example, the small width may be on the order of 4 to 6 mm, while the large width may be on the order of 6 to 8 mm. Thus, there may be an intermediate region along the length of the tissue modification device over which the width of the device (approximately the width of the rungs in some variations) transitions from relatively narrow to relatively wider. In some embodiments, there may be rungs of a medium width in the center portion of the device. These transition rungs may include cutting edges or may alternatively be non cutting rungs.

[0115] In one variations, as shown in FIG. 2B, the cutting edges may have different heights on different rungs. For example, in FIG. 2B the cutting edges on the rungs toward the center of the device 298 may have a first height, while the cutting edges on the rungs toward the proximal 299 and/or distal 299′ ends of the device may have a second height. The first height may be larger than the second height, allowing the device to cut first a shallow cut, and then a deeper cut as the device is pulled along against tissue. The cutting edges in this configuration may function to provide a smooth transition as the device is pulled along against tissue and the sequentially higher cutting edges begin to engage with the tissue. Alternatively, the second height may be larger than the first height.

[0116] In some variations, the cutting edges are formed from the material forming the rung, and the cutting edge (e.g., blade) is machined as part of the rung. For example, a rung may have an initial thickness measuring the height of the rung and the blade. The material at this initial thickness is machined (or otherwise removed) to form a series of blades projecting from the surface of the rung. Alternatively, the cutting edges may be cut out of the surface of the rung, and bent out of the surface of the rung such that the cutting edge or blade is substantially perpendicular to the rung. The cutting edge may be cut by Wire EDM machining (Electrical Discharge Machining), or any other suitable process. In some embodiments, the cutting edges or blades may be manufactured separately and connected to the rung.

[0117] In FIG. 2A the rungs are threaded onto the cables by openings or channels formed in the rung. For example, a tissue-modification device such as the one shown in FIG. 2A may be formed by threading the various components (e.g., rungs, spacers, etc.) onto the cable(s) connecting them. In some variations (described in greater detail below), a tissue collection region may be connected below the rungs. In some variations the rungs may be rings, or may include space for tissue collection or a tissue-collection region.

[0118] In some embodiments, as shown in FIG. 2C, crimping elements 272, 272′ may also be threaded onto the cables by openings or channels formed in the crimping elements. Once in place, the elements may be crimped to the cable or fixed to the cable in any other suitable fashion, such as by welding. The crimping elements fixed to the cable function to hold the rungs and other various components in place, and may further function to avoid loading the proximal and/or distal portions and/or ends of the tissue modification device.

[0119] The cables or rungs in one or more regions along the device may be covered or protected. For example, in FIG. 2C, the proximal portions of the tissue modification device includes a protector region, such as a solid material or covering element over the cables. Thus, the tissue modification device may have a solid proximal end protector region or portion 274. This solid portion may be a polymer extrusion, or any other suitable material in any suitable configuration.

[0120] A widener or ramp region or regions may also be included as part of the tissue modification device. For example, FIG. 2D shows one variation of a tissue modification device having ramp regions 288, 288′ at the proximal and distal portions of the tissue modification device. In some embodiments, the ramp begins towards the proximal and/or distal ends of the device, at a height approximately flush with the device, and increase. For example, the height may increase to approximately the height of any blades or cutting surfaces, or slightly higher. In some embodiments, the height of the ramp increases to a height approximately equal to or just below the height of the blades. The ramp may function to provide a smooth transition as the device is pulled along against tissue and the cutting edges begin to engage with the tissue. The ramp may extend across multiple rungs, a single rung, or may be coupled to the cables of the device. The ramp may be a solid structure, or a ribbed structure (as shown in FIG. 2D).

[0121] Rungs 203 with cutting edges 211, may extend over a portion of the length of the device. As illustrated in FIG. 2A, the device may include two or more rungs with cutting edges or blades 203 (e.g., “cutting rungs”). In this example, these cutting rungs 203 are separated by a gap formed by spacing elements 209 between the rungs. These spacing elements are also attached to the connector 201, 201′ that flexibly connects the rungs. In FIG. 2A the spacers are threaded on the two parallel cables. The sizes of the connectors and/or spacing elements 209 may be varied to change the spacing between the rungs, and also the longitudinal shape (curvature) of the device, as described in greater detail, below.

[0122] In addition to the cutting rungs 203, other rungs may also be included that do not have a cutting surface. For example, linking rungs 205, 205′ may be used. In FIG. 2A distal linking rungs 205 are shown removed from the device, but may be included. These rungs may protect the cable, and/or the tissue, and may be different sizes. Nearer to the distal end 235 of the device shown in FIG. 2A, smaller rungs 206 may be used to house the cable or cables connecting the rungs. These rungs 206 may be shaped to allow the device to be flexible in one or more direction (e.g., up/down relative to the major surface), while limiting the flexibility in other directions.

[0123] In some embodiments, the cutting rungs, non-cutting rungs, spacing elements, or any other suitable portion of the device may include a tracking element. For example, a tracking element may be disposed in the distal end of the device, such that the tip of the device may be tracked as it is inserted into a patient and/or moved within the patient. Alternatively, the device may include multiple tracking elements disposed along the length of the device, or multiple tracking elements disposed along a portion of the length of the device (for example along the cutting region of the device). In some embodiments, the tracking element is a material that is detectable by an imaging system. Some examples of suitable tracking elements include echogenic materials or substances (i.e. configured to form an echogenic surface) detectable by an ultrasound system, and radio-opaque materials detectable by a radiograph system, such as a fluoroscope. Alternatively, the tracking element may be configured to be detectable by an MRI or Infrared system. In some embodiments the tracking element is preferably a coil configured to be detected by an electromagnetic tracking or navigation system. For example, the devices described herein may incorporate a tracking system such as the AXIEM™ Electromagnetic Tracking Technology, e.g., the StealthStation® AXIEM™ (Medtronic Navigation, Louisville, Colo. USA). In some embodiments, the device is configured to generate an electromagnetic field around a patient's target anatomy that can be tracked to triangulate the positioning of devices having tracking elements.

[0124] The proximal end 233 of the device shown in FIG. 2A includes a handle 231 which may be permanently or removeably attached to the proximal end. The distal end 235 shown in FIG. 2A includes a guidewire coupler 237 that is flexibly attached to the distal end of the device. A guidewire coupler is configured to attach to a guidewire (e.g., one end of a guidewire) so that the device can be manipulated, at least in part, by pulling on the guidewire after the guidewire has been secured to the device. For example, in some variations a guidewire may be inserted into the body from a first location outside of the body, then passed around the target tissue (e.g., around a spinal foramen) and out of the body from a second position. The distal end of the guidewire may then be coupled to the flexible tissue modification device (such as the one shown in FIG. 2A) and pulled through the body until the tissue modifying region of the device, e.g., the portion of the device including cutting rungs 203, is positioned opposite the target tissue. In some variations the guidewire used includes a tip region that is enlarged and may engage the guidewire coupler. For example, the guidewire may have a proximal end with a flange or ball. This enlarged region may be configured to fit into an opening on the guidewire coupler 242 so that the guidewire can be pulled distally from outside of the patient. In some variations the distal end of the device may be completely withdrawn, so that it can be grasped and manipulated. In other variations, the distal end of the tissue-modification device remains coupled to the guidewire, and the guidewire may be grasped to manipulate the distal end of the tissue-modification device. A handle may be attached to the guidewire.

[0125] The overall tissue-modification device shown in FIG. 2A has an elongate body formed of the plurality of substantially rigid rungs. This variation has a length (an axial length, from proximal to distal) and a width. The length of the device is longer than the width of each rung. In some embodiments, the ratio of the length of the device to the width of each rung is greater than five. Alternatively, in some embodiments, the ratio may be greater than ten. The device is also relatively thin; in this variation the thickness is smaller than the width of each rung. In some embodiments, the ratio of the width of each rung to the thickness of each rung is greater than two. Alternatively, in some embodiments, the ratio may be greater than five. The use of two cables for the device shown in FIG. 2A allows the articulation of the links.

[0126] The distal end of the device 235 (including the guidewire coupler region) is hinged, as is the connection to the proximal end 252. In some variations the couplings at the proximal and distal regions allow rotation of the connection with respect to the tissue modification region such that torque (twisting motion) is not transferred to the tissue modification region. For example, FIG. 3A illustrates one variation of the distal end of the tissue modification device in which the distal end includes a guidewire coupler 237 that is rotatably connected to the tissue modification device, more specifically to cable 201, by connector 301. Alternatively, the distal end, including a guidewire coupler, may be rigidly attached to the cable, as shown in FIG. 3B. The distal ends of the cable include rungs 206 (as shown in FIG. 2A), protector portion, or links that cover the cable, and may help prevent damage to tissue by presenting a relatively atraumatic surface.

[0127] In FIG. 2A, the flexible portion of the device formed by connected rungs or links is joined to the proximal end of the device, which may be less flexible, and may include a handle or an attachment region for a handle. This interface between the links forming the flexible region and the proximal end is shown as joint 252. The proximal joint 252 near the proximal end 233 is a ball joint 207 to which the cables are attached. The ball joint allows the rotation of the handle and/or proximal portion of the device with respect to the tissue modification region of the device. Thus, the proximal handle may be rotated along the long axis of the tissue modification device, but will not substantially torque the tissue modification region of the device.

[0128] The variation shown in FIG. 2A may also include a proximal connecting region 262 near the proximal end 233 of the device to which the handle 231 is attached. This connecting region may be relatively stiff (or inflexible), or it may also be flexible.

[0129] As mentioned, in operation, the device is urged against the target tissue and may be moved in the proximal/distal direction to modify (e.g., cut) the target tissue. For example, both the proximal and distal ends of the tissue-modification device may be pulled to urge the device against the target tissue, and may each be alternately pulled to a greater degree than the other handle to slide the device over the target tissue, allowing the cutting edges to cut and modify the target tissue. In this example, as the blade(s) cut the tissue, a moment is generated between the tip of the blade and the base of the blade, on the rung, where the cable runs through the rung. Thus, in some variations, the base of the blade rung must be sufficiently wide to resist rotating about the length of the cable. Furthermore, it may be advantageous to include fixed rigid sections.

[0130] As mentioned, the rungs forming the device may be flexibly connected by hinges between the rungs. The connections shown in FIG. 2A are flexible connections, and individual rungs are not directly connected, but are instead connected via a cable. Since the cable is flexible, the flexion point is concentrated between rung and mating ferrule (spacer).

[0131] FIG. 4 shows a portion of a tissue modification device similar to that shown in FIG. 2A. In FIG. 4, the cutting rungs each include a plurality of cutting edges. These cutting edges are again shown as oriented along the long axis of the device, although other orientations may be used. The cutting edges may be offset from each other along the long axis of the device, so a wider cutting area is formed. In addition the cutting edges may be spaced from the sides of the rungs, allowing the edges of the tissue modification device to be relatively atraumatic. FIG. 4 also illustrates spacers between each rung or link, on either side of the device (i.e., on each of the cables). In FIG. 4, different spacers are shown, including relatively long ferrules 401, and bead-like spacers 403. The different spacers may modify the flexibility of the device.

[0132] FIG. 5A illustrates a portion of the proximal end of the tissue modification device shown in FIG. 2A in which the cables are attached to the joint 207 by coils 501 that permit the cables to flex during operation. In some variations, these coils may be springs.

[0133] In some variations, as shown in FIG. 5B, the rungs forming the device may be flexibly connected by hinges between the rungs without spacers. The connections shown in FIG. 5B are flexible connections. Individual rungs are not directly connected, but are instead connected via a cable. Since the cable is flexible, the flexion point is concentrated between each rung. The length of each rung may be designed such that every transition point between each rung is a hinge point. As shown in FIG. 5B, the rungs may be configured such that a pair of rungs defines an opening between them. This opening may provide a location through which tissue may travel and/or be collected.

[0134] In some embodiments, as shown in FIGS. 6-8A, a tissue-modification device may include flexibly connected rungs or links that do not require the connection by a proximal-distal cable illustrated in FIG. 2A. For example, FIGS. 6-8A show various methods of flexibly connecting rungs or links. In FIG. 6, two adjacent cutting rungs are joined together so that they may move relative to each other as the device is flexed. In this example the devices are hinged. FIGS. 7 and 8A illustrate alternative variations similar to FIG. 6. In FIGS. 6-8B, the adjacent rungs or links are directly connected to each other and can be bent or moved as illustrated by the arrows. As shown in FIG. 8B, the devices can be bent (at least partially). In FIG. 8B, the hinged region may be formed by bending two regions of the adjacent links over each other. In these variations, a separate connector (e.g., cable, etc.) is not necessary to allow adjacent links to flex. Alternatively, the hinged regions may include a hinge pin (not shown).

[0135] FIGS. 9A-9D illustrate another alternative method of connecting adjacent rungs or links to allow flexion or provide flexibility. FIGS. 9A-9D show an embodiment in which adjacent links are connected via a woven ribbon to which the rungs are secured. A portion of flexible material is shown in FIG. 9A. Any appropriate (flexible) material, including meshes, woven, non-woven, and polymeric materials may be used. For example, the flexible material could be made from several materials, for example: stainless steel, aramid fibers, carbon fibers, glass fibers etc. Rungs can be attached to the flexible material by any appropriate method. For example, FIG. 9B shows a rung having downward-pointed edges configured to either pierce the woven ribbon or to be bent around the connector material, as illustrated in FIGS. 9C and 9D. The bottom side of the material and/or rungs can be softened by molding a polymer 904 to the material, as illustrated in FIG. 9H. The material may be formed into a ribbon or band shape. Additional rungs (of different or similar dimensions), may also be secured to the connector material forming the device.

[0136] FIGS. 9E and 9F show another variation in which the downward-pointed edges of the rungs penetrate the material and pass through it so that they can be and secured to it. For example, In FIG. 9E, the downward pointing edges pierce the material (though the material may also include pre-formed holes). The downward-pointed regions can then be bent back up to secure the rung to the connector material. Other means for fastening the rung to the connector material may also be used. In the example shown in FIGS. 9E-9G, the edge of the rungs is not concurrent with the edge of the tissue-modification device. FIG. 9G shows a portion of an exemplary tissue-modification device including a flexible connector connecting multiple rungs having cutting edges extending from them. In FIG. 9, the rungs are spaced from the edge of the tissue cutting device, and an atraumatic edge 903 is included along the outer periphery (along the major surface).

[0137] Spacing the rungs from the edge in this manner may reduce the risk of side cutting. Other variations, including variations having a connector cable(s), the cable and rungs can be protected on the side by a separate tube like elements on the edges that are interlaced with the rungs and the cable, as illustrated in FIGS. 10 and 11. In FIG. 10, for example, the cables 1001, 1001′ on either sides of the device are covered by a protective cover 1003. Rungs 1005 span the distance between the two cables. FIG. 11 shows a slightly higher magnification of the tissue modification region of the device shown in FIG. 10. In FIG. 11, the cutting edges 1101 are shown extending from the rungs.

[0138] The blade rung “ladder” design described above for the tissue modification devices having flexibly linked rungs may include spaces between the rungs. In some variations the tissue cutting region may also include holes or openings. These spaces between the rungs, holes, and/or openings may form part of a tissue capture region, or may act as vias or channels to direct cut tissue into a tissue capture region. As the tissue modification region modifies and/or removes the tissue, at least a portion of (and preferably the majority of) the cut tissue may be lodged between the cutting edges or blades and/or between the rungs of the device, such that the captured tissue is removed from the patient along with the device as the device is removed from the patient. Alternatively, in some variations, the space between the rungs may channel cut tissue into a tissue capture region. As the cutting edges (e.g., the triangular “teeth” shown in some of the figures, above) cut the tissue, the tissue may be driven into a tissue capturing or collection region. In some variations, the edge of the adjacent rung may shear the tissue as the device is urged against the tissue and moved. In some variations, the edge of the rung may also be sharp, or may include a sharp region. Thus, tissue may pass through the blade rungs and into a tissue collection region. The (typically upward) pressure of urging the device against the target tissue may therefore aide in packing the tissue into a tissue capture region. In some embodiments, the device may have elements to aid in the movement of the cut tissue. For example, the rungs may be designed such that two adjacent rungs function as a one way valve, allowing the tissue to enter through the space between the rungs, and then kept between or below the rungs and prevented from moving back out. Each rung may include a flap or a wing that couples to a flap or wing of an adjacent rung to function as a one way valve. The rungs may alternatively be designed in any other suitable fashion.

[0139] In general, a tissue capture region may require some amount of force or pressure to drive the cut tissue into the capture region. This may be particularly true for expandable tissue capture regions, such as an expandable bag that is attached behind the tissue modification region (e.g., behind or within the rungs including cutting edges). As the tissue fills the area below the blades, the bag may expand to accommodate the increase volume. Increased pressure may be required to ‘pack’ the tissue into the tissue cutting region.

[0140] In some applications it would be beneficial to provide pre-expanded tissue capture regions, or tissue capture regions having a minimum volume that is fixed. The fixed minimum volume typically refers to a fixed open volume. Fixed minimum volume tissue capture regions typically include a minimum open volume, but this open volume may be increased as the device is operated; for example, the volume may be expandable from the fixed minimum open volume. Alternatively, the total volume of the tissue capture region maybe fixed or predetermined. Having a fixed minimum open volume allows tissue to enter the tissue capture region without having to apply additional force to drive the tissue into the tissue capture region.

[0141] In some variations a tissue collection region having a fixed minimum open space may be defined by the space between the openings into the tissue collection region (which may be the rungs of the tissue modification region) and a tissue collection substrate. The tissue collection substrate is typically spaced apart from the tissue modification side of the rungs by a thickness that forms the open space. The tissue collection region may have a length that extends at least along the tissue modification region of the tissue modification device (e.g., the cutting rungs in variations including rungs), but may extend further proximally/distally.

[0142] For example, FIGS. 12A-12C illustrate one variation of a tissue modification device including a tissue collection region having a fixed minimum open space. FIG. 12A shows a cross-section along the long (distal/proximal) axis of the device. In this variation the device includes a plurality of flexibly connected rungs 1205 that are connected by a connector (a cable 1215). The rungs in the tissue modification region include cutting edges 1209. A tissue collection region 1219 (illustrated in FIG. 12B) is formed between the top of the rungs 1205 and a tissue collection substrate 1211. In this example, the tissue collection substrate 1211 is a semi-rigid substrate element that extends along the proximal/distal length of the device. In some embodiments, the substrate element may additionally include guiding features to move and/or position the tissue in a desired direction, such as toward the outer portions of the device, beneath the non-cutting rungs. For example, a guiding element may be one or more ridges in the substrate that are arrow or chevron shaped, with the vertex of the shape pointed toward the outer regions of the device. The distal end of this variation also includes a guidewire coupler or coupling region 1252, and individual links 1205 may be separated by spacers (shown as ferrules) 1245.

[0143] FIG. 12B shows a cross-section through one of the rung elements 1205 shown in FIG. 12A. In this variation, the rung 1205 includes two channels 1216 and 1216′ through which the cables 1215 (FIG. 12A) may pass. The top (anterior) of the rung includes a plurality of cutting edges 1209. Within the rung 1205 is a fixed open volume 1219 that is formed between the top of the rung and a tissue collection substrate 1211 on the bottom of the rung. The tissue collection substrate may be secured within the rung by loops or straps 1223 that extend across the bottom of the rung. FIG. 12C shows a top view of the tissue modification device of FIGS. 12A and 12B.

[0144] The tissue-collection substrate portion of the tissue modification device shown in FIGS. 12A-12C is slideable within the rungs (e.g., along the straps of the rungs). One end of the tissue collection substrate may be fixed (e.g., near the distal end of the device) and the other end may include an elastic or spring element 1272 that allows the tissue-collection substrate to slide as the tissue modification device is bent during operation. FIGS. 13A-13D illustrate variations of tissue-collection substrates that may be used. For example, in FIG. 13A, the tissue collection substrate 1211 is a semi-rigid sheet of material as shown in FIG. 12A-12C. The tissue-collection substrate may be formed of any appropriate material, including metals or alloys (e.g., stainless steel, titanium, NiTi, aluminum, etc.), plastics (e.g., PEAK, PET, PP, EP, PET, etc.), and elastic materials (e.g., urethanes, silicones, etc.). Other materials may also be used. Since the overall device (including the tissue collection substrate) is flexible at least in the plane forming the major surfaces, the tissue collection substrate may be bendable. Thus, when more rigid materials are used (e.g., metals) to form the substrate, the substrate may be relatively thin.

[0145] FIGS. 12D-12G illustrate another variation of a tissue modification device including a tissue collection region having a fixed minimum open space. FIG. 12D shows a perspective view of a portion of a tissue modification device including a tissue collection region 1262. This tissue collection region has sides and a bottom region, and includes a channel through which connectors (shown as cables 1266, 1266′ in FIG. 12D) may pass. The tissue collection region may be a single, flexible piece, as indicated in FIG. 12D, or it may be a plurality of pieces linked by the connector. In this variation, the tissue collection region also includes spaced into which rungs may fit so that the connectors may pass through the rungs. This is also apparent from the top view shown in FIG. 12E. FIGS. 12F and 12G illustrate sectional views taken through a portion of the tissue modification device including a cutting run (shown in FIG. 12F) and a portion of the tissue modification device that is between adjacent cutting rungs (shown in FIG. 12G).

[0146] Alternatively, the tissue collection region may include projections that project into a space or slot formed on the rungs; the connectors may pass through these projections and through the rungs. IN addition, spacers (e.g., ferrles, beads, etc.) may be used between the rungs.

[0147] In some variations, the substrate may be configured to expand/contract as the tissue modification device is flexed. For example, as described above, in some variations the tissue collection substrate may be connected at one (or both) axial ends via a spring or elastic member. FIGS. 13B1 to 13B3 illustrate a side view of another variation of a substrate that is configured to accordion along its length as the device it is attached to is flexed. For example, when the tissue modification device is flexed or bent in a first direction the substrate may contract or accordion closed, as shown in FIG. 13B1. In the relaxed state the substrate is ‘neutral’, with folds that may be expanded or contracted, as shown in FIG. 13B2. When the tissue modification device is bent in a second direction the substrate may expand or accordion open, as shown in FIG. 13B3.

[0148] In an alternative variation the substrate is expandable, and includes rigid edge with an expandable element between, as illustrated in FIG. 14A. In this variation the rigid portion may be secured to the tissue collection device (e.g., to the links of a tissue collection device), and the expandable portion may be made of a mesh or thin plastic material. FIG. 14B shows just the rigid portion of one variation of this embodiment, in which the rigid frame 1401 surrounding an expandable portion 1403 includes cross-struts 1407. Substrates including expandable regions may be useful to allow the tissue collection region to expand even beyond the minimum fixed volume, allowing the collection of additional tissue even after the minimum fixed volume is filled.

[0149] In general, the tissue collection substrate may be held to the tissue modification device by one or more connectors linking the tissue collection substrate to the rung. In FIGS. 12A-12C the tissue collection region is bounded by the tissue collection substrate that is secured to the link via a strap or loop that is formed by the rung. In some variations the connectors are not part of the rungs, but are separate elements. For example, FIGS. 15A-15C illustrate variations in which the tissue collection substrate is secured to the device by a cable or rod connector between each rung and the tissue collection substrate. In some variations, the connector is formed as a part of the tissue collection substrate. FIG. 15A shows a cross-section through a flexible tissue modification device having rungs 1501 and a tissue collection region 1509 that is formed between the top of the rung 1501 and a substrate 1511 that is secured to the rung by a pair of cables 1515, 1515′ or rods. FIG. 15C shows a similar variation in which the substrate is secured to the rung by connectors that may swing or slide. As described, the rung shown may be flexibly connected via one or more cables 1503, 1503′. In all of these examples of tissue collection regions there is a minimum open volume that has a fixed minimum, so that, even when flexed, the tissue collection region has a non-collapsible open space so that tissue can enter the space. In some variations this minimum fixed space is formed by a separation of between about 2 and about 6 mm between the rung forming the top of the space and the substrate.

[0150] FIG. 15B shows a cross-section through the tissue modification region of a tissue modification device including rung and tissue collection design shown in FIG. 15A. As before, the tissue collection substrate in this example is shown axially connected to the device via a spring 1511.

[0151] In operation, tissue cut by the blades may be collected into the tissue collection regions described. As mentioned, openings between the rungs may act as channels or vias through which cut tissue may pass into the collection region(s). In some variations, the tissue modification device may include openings adjacent to the cutting edge(s) through which tissue may pass. Although the examples described above include tissue collection regions having a fixed minimum open volume as part of a tissue modification device comprising a plurality of rungs, a fixed minimum open volume tissue collection region may be incorporated as part of any tissue collection region, even those not having rungs.

[0152] Other examples of tissue capturing mechanisms which may be used are described, for example, in U.S. patent application Ser. No. 11/687,558 (titled “FLEXIBLE TISSUE REMOVAL DEVICES AND METHODS”), filed on Mar. 16, 2007, and U.S. patent application Ser. No. 11/687,548 (titled “TISSUE REMOVAL WITH AT LEAST PARTIALLY FLEXIBLE DEVICES”), filed on Mar. 16, 2007, and U.S. patent application Ser. No. 11/952,934 (titled “TISSUE REMOVAL DEVICES AND METHODS”), filed on Dec. 7, 2007; these references are all incorporated by reference herein.

[0153] As mentioned above, the spacing and orientation of the cutting edges of the tissue modification devices may be arranged to optimize performance. For example, FIG. 16A to 16C illustrate one arrangement of cutting edges (blades) in which adjacent rungs have blades that are offset from each other. Offsetting the blade in this manner may allow them to more uniformly cut as the device is operated to modify tissue. Blade density may be important when it comes to cutting both soft tissue and bone. To improve the density and allow for material to pass through blade teeth, the leading and following blades may be interdigitated. FIGS. 16A-16C show the interdigitation of a set of blades. The first rung 1601 (Rung-A) cuts a leading path and the second rung 1603 (Rung-B) cuts a following path. This arrangement of cutting edges and rungs may help maximize the material removal for one cut stroke. FIG. 16C is a side view of Rung-A directly in front of Rung-B.

[0154] In addition to the substantially linear tissue modification devices described above, any of these tissue-modification devices may also be configured to have a non-linear shape (e.g., axial shape) and/or be shape-morphing devices that can convert between linear and non-linear shapes. Non-linear devices may be pre-formed into a curved or bent shape (such as “s”- shaped, or serpentine, device or “c”-shaped devices, or the like). Alternatively, a non-linear device may be a shape-morphing device that can be changed from a linear to a non-linear shape, either before or during use of the device to modify tissue.

[0155] The phrase ‘linear’ and ‘non-linear’ shapes typically refer to the shape of the device along the major (distal/proximal) axis, when looking down on the major (tissue-modifying) surface.

[0156] For example, FIG. 17A illustrates a device having an S-shape (or serpentine) shape. This is a non-linear device (since the major surface does not travel in a line, but is curved). The device can be constructed using the cable (or wire) rung design, as illustrated in FIG. 18. In FIG. 18, the links are separated by one or more spacers that are unequal in length from one side of the device (e.g., one cable) to the other. This difference in spacing causes the device to curve, as shown. For example, the side of a device with a larger radius of curvature may include spacers such as relatively long ferrules 401 (shown in FIG. 4), and the side of a device with a smaller radius of curvature may include bead-like spacers 403 (shown in FIG. 4). Curved devices may have a wider stroke length when cutting the tissue, and may therefore cut a wider region of tissue. For given stroke length, the amplitude (peak to peak of the curve) becomes the effective width of the device, producing a kerf wider than the individual rung.

[0157] Additionally the devices can be deployed into the spine in a linear configuration and then changed to a non linear configuration. This conversion in shape may be achieved in-situ by pulling on a cable on one side of the rung more than the other side. Alternatively, you can pull both sides with the same tension in combination with variably compressible ferrules/spacers between the rungs in selected locations. For example to achieve a concave curve to the device on the right side, the right side would have more compressible ferrules (elastomeric) than the left side. Once the new non-linear shape was achieved, the cable wire(s) could be locked in position near the proximal end and/or handle. If desired, the cables could be readjusted to form a linear shape to the device prior to device removal. For example, a device may be increased in width by shift parallel links from an oblique angle to perpendicular with the cable, shown in the images below.

[0158] In some variations, the shape-morphing devices may be transitioned between a first straight (e.g., linear) configuration and a second straight configuration, with the first configuration being narrower than the second configuration. Two examples of this are shown in FIGS. 17B-17C and 17D-17E. In FIG. 17B the tissue modification device has a relatively narrow profile and can be expanded into a wider profile as illustrated in FIG. 17C. The rungs in FIG. 17B are initially diagonal, relative to the parallel cables flexibly connecting them. By pulling on one of the cables, one side of the device to which the rungs are connected, may be pulled to align the rungs perpendicular to the long axis of the device. Since the rungs are relatively rigid, this will expand the width of the tissue modification device, as indicated in FIG. 17C.

[0159] FIGS. 17D and 17E illustrate a similar variation, in which the tissue modification device may be expanded from a first linear configuration, in which the rungs are chevron-shaped when viewed from the top as in FIG. 17D, to a second linear configuration that is wider, in which the rungs can be pulled so that they are perpendicular to the long axis (proximal/distal axis) of the device, as illustrated in FIG. 17E. In this variation, a cable, pull wire, or the like may be connected to the rungs to convert them from the first to the second shapes. The rungs may be adapted (e.g., hinged) for conversion. In some variations each run is actually a two rungs that are joined end-to-end.

[0160] Any of the tissue modification devices described herein may be used to decompress one or more spinal regions, as mentioned above. In particular, any of these devices may be used to decompress nerve roots placed within the spinal anatomy along various paths, including those shown in FIGS. 19A-19C. Because these devices are flexible, and may be appropriately sized and shaped to fit within a neural forman, these devices may be used to accesses appropriate regions of the spine from a single access point (e.g., from the patient's midline or near-midline region). The procedure may be used to decompress spinal nerve roots on the unilateral or bilateral side from the access point. A probe or guide may be introduced into the spinal epidural space (or along or just within the ligamentum flavum) at an appropriate spinal level using image guidance and/or tracking (e.g., electromagnetic tracking). Introduction may be either via percutaneous puncture or open laminotomy.

[0161] As shown in FIG. 19A, the device may be used to decompress an ipsilateral or contralateral proximal nerve (in a lateral recess). A guide may be deployed immediately cephalad to the caudal segment pedicle on the appropriate side (e.g., location 1810). This access point can be confirmed radiographically. If neural structures adjacent to the guide cannot be directly visualized, the relationship of these structures to the guide or tissue modification devices can be determined using electrical stimulation, ultrasound imaging, endoscopic mean or other techniques. In some variations, once the guide is deployed and optional neural localization is complete, a guidewire is passed via the cannulated guide. The guidewire can be sharp on its distal end and penetrate the skin dorsolaterally after exiting the foramen. The guidewire may includes a wire exchange tip on its proximal end, as mentioned above. As shown in FIG. 19A, the guidewire may be threaded along a path from location 1810 to where it exits through the foramen, as shown by at least one of arrows 1812 (for ipsilateral decompression of the nerve root origin at the disk level) and 1814 (for contralateral decompression of the nerve root origin at the disk level). In some embodiments, the probe/guide is removed once the guidewire has been positioned.

[0162] Next, a flexible tissue modification device is attached to the proximal wire exchange tip, and a distal handle may be secured to the distal wire tip. The device can then be introduced into the epidural space and then into the lateral recess by careful upward force applied to the distal handle. In some embodiments, the device is pulled by the guidewire on the path through the spinal anatomy. As described above, suitable paths include paths shown by arrows 1812 and 1814 to decompress the nerve root origin at disk level. Once the device is in place as confirmed visually or radiographically, bimanual reciprocating strokes may be utilized to decompress dorsal impinging bone or soft tissue at the nerve root origin. In some embodiments, approximately 30-40 reciprocating strokes are required to complete the decompression. This may be confirmed radiographically or with palpation by instruments. The device may then be detached and the wire removed.

[0163] The probe/guide may be reinserted to decompress the ipsilateral or contralateral distal (foraminal) portion of the nerve root, so that the same (or a different) tissue modification device may be used to decompress another region of the spine (or nerve root) using the same access or entry site. Thus, a guide may be deployed immediately caudal to the caudal segment pedicle on the appropriate side. The guide may be deployed in the same access point (location 1810) as described above. Transforaminal positioning and the relationship to neural elements can again be confirmed visually, radiographically, and/or with electrical stimulation, ultrasound or alternative means. Once appropriate localization is confirmed, the guidewire can be passed and probe/guide removed. As shown in FIG. 19A, the guidewire may be threaded along a path from location 1810 to where it exits through the foramen, as shown by at least one of arrows 1816 (for ipsilateral decompression along the nerve root) and 1818 (for contralateral decompression along the nerve root). A handle is attached to the distal guidewire and the tissue modification device to the proximal exchange tip. The device is then introduced into the spine (e.g., the epidural space, or the region anterior to the posterior edge of the ligamentum flavum) with careful upward force applied to the distal handle. In some embodiments, the device is pulled by the guidewire on the path through the spinal anatomy. As described above, and as shown in FIG. 19A, suitable paths include paths shown by arrows 1816 and 1818 to decompress along the nerve root. The foraminal decompression is performed using bimanual reciprocating strokes to remove impinging bone and soft tissue. In some embodiments, approximately 30-40 strokes are required to decompress the root. Confirmation of decompression may be done radiographically or using instruments to palpate along the root. The device can then be detached and the guidewire removed.

[0164] As shown in FIG. 19B, the devices described herein can used to decompress the ipsilateral or contralateral (not shown), or both, regions adjacent the level proximal to the nerve root (lateral recess). A guide may be deployed in the same access point (location 1810) as described above. Transforaminal positioning and the relationship to neural elements are once again confirmed visually, radiographically, and/or with electrical stimulation, ultrasound or alternative means. Once appropriate localization is confirmed, the guidewire may be passed and the probe/guide removed. As shown in FIG. 19B, the guidewire can then be threaded along a path from location 210 to where it exits through the foramen, as shown by arrow 220 (for ipsilateral decompression of the adjacent nerve root origin). A handle can be attached to the distal guidewire and the guidewire can then be attached to the distal end of one of the tissue modification devices described herein. The device can then be introduced into the spine by pulling on the guidewire. In some embodiments, the decompression device is pulled by the guidewire on the path through the spinal anatomy as illustrated in FIG. 19A, 19B, or 19C. As described above, and as shown in FIG. 19B, suitable paths include the path shown by arrow 1820 the adjacent nerve root origin. The lateral recess decompression may be performed using bimanual reciprocating strokes to remove impinging bone and soft tissue. In some embodiments, approximately 30-40 strokes are required to decompress the nerve. Confirmation of decompression may be done radiographically or using instruments to palpate along the root.

[0165] As shown in FIG. 19C, a probe/guide may be used to introduce a tissue modification device as described herein to decompress the central canal. The guide may be deployed in the same access point (location 1810) as described above. Once appropriate localization is confirmed, the guidewire may be passed and probe/guide removed. As shown in FIG. 5, the guidewire can be threaded along a path from location 1810 to where it exits through the intralaminar window, as shown by arrow 1822 (not the adjacent foramen). A handle may be attached to the distal guidewire and, the tissue modification device may be coupled to the proximal end of the guidewire. The device can then be introduced into the epidural space by pulling the distal end of the guidewire on the path through the spinal anatomy, drawing the device into position adjacent the target tissue in the spinal canal. As described above, and as shown in FIG. 19C, suitable paths include the path shown by arrow 1822 to decompress tissue associated with the central canal and may be effective in treating patients with central spinal stenosis. The decompression may be performed using bimanual reciprocating strokes to remove impinging bone and soft tissue. In some embodiments, approximately 30-40 strokes are required to decompress the root. Confirmation of decompression may be done radiographically or using instruments to palpate along the nerve.

[0166] In some embodiments, the probe, guide, or guidewire may also include a tracking element or plurality of tracking elements. The tracking element may be similar to the tracking element of the tissue modification device. As described above, in some embodiments the tracking element is a material that is detectable by an imaging system, while in some embodiments the tracking element is preferably a coil configured to be detected by an electromagnetic tracking or navigation system.

[0167] Any of the procedures described herein can be done in combination with other techniques including an open or minimally invasive decompression procedure where tools such as rongeurs and powered drills are used to remove tissue primarily around the proximal end of nerve root (lateral recess). Such techniques may include laminotomies, etc.

[0168] Although various illustrative embodiments are described above, any of a number of changes may be made to various embodiments without departing from the scope of the invention as described by the claims. For example, the order in which various described method steps are performed may often be changed in alternative embodiments, and in other alternative embodiments one or more method steps may be skipped altogether. Optional features of various device and system embodiments may be included in some embodiments and not in others. Therefore, the foregoing description is provided primarily for exemplary purposes and should not be interpreted to limit the scope of the invention as it is set forth in the claims.