Abstract:
The present invention generally is directed toward a spinal fixation system whereby a coupling element allows the physician to selectively lock or unlock either the connection between the coupling element and a fastener, such as to allow for repositioning of the coupling element, or the connection between the coupling element and an elongate rod. The locking or unlocking of these connections may be made independently and as desired by the physician.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of U.S. patent application Ser. No. 12/688,437, filed Jan. 15, 2010, which is a continuation of U.S. patent application Ser. No. 11/957,039, filed Dec. 14, 2007, now issued as U.S. Pat. No. 7,909,873, which claims priority to U.S. provisional application 60/875,114 filed Dec. 15, 2006, and U.S. provisional application 60/875,173 filed Dec. 15, 2006, the disclosures of which are all being incorporated herein by reference in their entirety. This application is also a continuation-in-part of U.S. patent application Ser. No. 13/748,139, filed Jan. 23, 2013, which claims priority to U.S. patent application Ser. No. 13/331,676, filed Dec. 20, 2011, now issued as U.S. Pat. No. 8,382,837, which is a continuation of U.S. patent application Ser. No. 12/241,979, filed Sep. 30, 2008, now issued as U.S. Pat. No. 8,100,973, which is a continuation of U.S. patent application Ser. No. 11/105,783, filed Apr. 14, 2005, now issued as U.S. Pat. No. 7,465,318, which claims priority to U.S. provisional application 60/562,686, filed Apr. 15, 2004 and U.S. provisional application 60/604,800, filed Aug. 26, 2004, the disclosures of which are all being incorporated herein by reference in their entirety. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates generally to the field of orthopedic devices to treat fractured bone in the spine, and more particularly to an orthopedic instrument and implant system that can be used to facilitate bone cement treatment of a vertebral compression fracture. 
       BACKGROUND OF THE INVENTION 
       [0003]    There are many disease states that cause bone defects in the spinal column. For instance, osteoporosis and other metabolic bone conditions weaken the bone structure and predispose the bone to fracture. If not treated, certain fractures and bone defects of the vertebral body may produce intolerable pain, and may lead to the development of deformity and severe medical complications. 
         [0004]    Bone weakening may also result from benign or malignant lesions of the spinal column. Tumors often compromise the structural integrity of the bone and thus require surgical stabilization and repair of defects with biocompatible materials such as bone grafts or cements. Bone tumors of the spine are relatively common, and many cause vertebral compression fracture. 
         [0005]    More than 700,000 osteoporotic compression fractures of the vertebrae occur each year in the United States—primarily in the elderly female population. Until recently, treatment of such fractures was limited to conservative, non-operative therapies such as bed rest, bracing, and medications. 
         [0006]    One surgical technique for treating vertebral compression fracture can include injecting or filling the fracture bone or bone defect with biocompatible bone cement. A relatively new procedure known as “vertebroplasty” was developed in the mid 1980&#39;s to address the inadequacy of conservative treatment for vertebral body fracture. This procedure involves injecting radio-opaque bone cement directly into a fracture void, through a minimally invasive cannula or needle, under fluoroscopic control. The cement is pressurized by a syringe or similar plunger mechanism, thus causing the cement to fill the void and penetrate the interstices of a broken trabecular bone. Once cured, the cement stabilizes the fracture and eliminates or reduces pain. Bone cements are generally formulations of non-resorbable biocompatible polymers such as PMMA (polymethylmethacrylate), or resorbable calcium phosphate cements which allow for the gradual replacement of the cement with living bone. Both types of bone cements have been used successfully in the treatment of bone defects secondary to compression fractures of the vertebral body. 
         [0007]    One clinical issue associated with vertebroplasty is containment of the cement within the margins of the defect. For instance, an osteoporotic compression fracture usually compromises portions of the cortical bone creating pathways to cement leakage. Thus, there is a risk of cement flowing beyond the confines of the bone into the body cavity. Cement leakage into the spinal canal, for instance, can have grave consequences to the patient. 
         [0008]    Yet another significant risk associated with vertebroplasty is the injection of cement directly into the venous system, since the veins within the vertebral body are larger than the tip of the needle used to inject the cement. A combination of injection pressure and inherent vascular pressure may cause unintended uptake of cement into the pulmonary vessel system, with potentially disastrous consequences including embolism to the lungs. 
         [0009]    One technique which has gained popularity in recent years is a modified vertebroplasty technique in which a “balloon tamp” is inserted into the vertebral body via a cannula approach to expand or distract the fractured bone and create a void within the cancellous structure. Balloon tamps are inflated using pressurized fluid such as saline solution. The inflation of a balloon membrane produces a radial force on the bone and forms a cavity in the bone. When deflated and removed, the membrane leaves a cavity that is subsequently filled with bone cement. The formation of a cavity within the bone allows for the injection of more viscous cement material which may be relatively less prone to leakage. 
         [0010]    In certain instances, such as the treatment of acute or mobile fractures, the balloon is also effective at “reducing” the fracture and restoring anatomic shape to a fractured body. In particular, balloon dilatation in bone is maximally effective if the balloon device is targeted inferior to, or below, the fracture plane. In this instance, the balloon dilatation may distract, or lift, a fracture bone fragment, such as the vertebral body endplate. 
         [0011]    In other instances, such as chronic or partially healed fractures, balloons are less effective at “reducing” the fracture because radial forces are insufficient. Often the bone in an incompletely healing fracture is too dense and strong, and requires more aggressive cutting treatment, such as a drill or reamer tool to create a sufficient cavity. In these more challenging cases, the ability to inject bone cement into a cavity created by a balloon or a reamer in the vicinity of the fracture is typically sufficient to stabilize the bone and relieve pain, even in the absence of fracture reduction. 
         [0012]    One limitation to the use of such methods has been the difficulty in targeting the location at which the cavity should be created. Known techniques require access to the vertebral body using straight cutting and reaming tools which are only able to access a limited region of the vertebral body being treated, generally only within one side of the vertebral body. A cavity created using these techniques can only treat one side of a vertebral body being targeted, resulting in an uneven distribution of bone cement that cannot completely stabilize the vertebral body. As a result, multiple entry points on different sides of the vertebral body are generally required in order to provide a symmetrical distribution of bone cement around a central axis of the vertebral body. These multiple entry points significantly increase the time necessary for the procedure, the portion of the body being treated, and the amount of bone cement being injected, and as such can significantly increase the risks associated with treatment of a patient. 
       SUMMARY OF THE INVENTION 
       [0013]    The present invention is directed towards novel methods and devices for preparing a cavity in bone, deploying a cement-directing stent device, and injecting bone cement into the device. The methods and devices disclosed herein can allow a cavity to be created in a vertebral body along a curvilinear pathway, allowing for a substantially symmetrical distribution of bone cement over a central vertical axis of a vertebral body. This can allow a vertebral body to be successfully and completely stabilized from a single surgical access point and using a single stent device. 
         [0014]    One aspect of the invention can include a method of deploying a stent within an enlarged curvilinear void created in a bony structure. The method can include the steps of: inserting a distal end of a stent delivery system through a cannula and into a curvilinear void created in a bony structure, deploying a self-expanding cement-directing stent within the curvilinear void, wherein the self-expanding stent is releasably attached to the distal end of the stent delivery system, attaching a cement injecting syringe to the proximal end of the stent delivery system, injecting cement through the stent delivery system and into the stent, terminating the cement injection when the volume of cement injected exceeds the interior volume of the expanded stent, and releasing the stent from the stent delivery system. 
         [0015]    In one embodiment, the stent delivery system can include at least one of a proximal deployment mechanism, an internal flexible guidewire, and an internal flexible tube, such as a polymer extrusion. The self-expanding cement-directing stent can include a multifilament braided, polymer impregnated, self-expanding, cement-directing stent collapsed on the distal end of the guidewire and restrained in a collapsed condition by a tubular polymer sheath. The self-expanding cement-directing stent can be deployed by slideably uncovering the tubular sheath to release and expand the stent within an enlarged curvilinear void. The self-expanding cement-directing stent can be alternatively or further deployed by removing the internal flexible guidewire and/or the polymer extrusion. 
         [0016]    Alternatively, another method of stent deployment eliminates the need for the tubular sheath. The self-expanding cement-directing stent is maintained in a collapsed state solely by the internal flexible guidewire and/or the polymer extrusion. Once positioned in the enlarged curvilinear void, deployment of the self-expanding cement-directing stent can be accomplished solely by removing the internal flexible guidewire and/or the polymer extrusion. 
         [0017]    In one embodiment, the self-expanding cement-directing stent can be connectably attached to the proximal deployment mechanism by a hollow tube assembly. The stent can be released by actuating the proximal deployment mechanism. 
         [0018]    One aspect of the invention can include a method of deploying a stent within an enlarged curvilinear void created in a bony structure. The method can include the step of inserting a stent catheter assembly into an enlarged curvilinear void through a cannula and into the curvilinear void created in a bony structure, wherein the stent catheter assembly can include a proximal deployment mechanism, an internal flexible guidewire, a multifilament braided, polymer impregnated, self-expanding, cement-directing stent collapsed on the distal end of the guidewire and restrained in a collapsed condition by a tubular polymer sheath, and connectably attached to the distal end of the deployment mechanism by a hollow tube assembly. 
         [0019]    The method can further include the steps of deploying the self-expanding cement directing stent by slideably uncovering the tubular sheath to release and expand the stent within the enlarged void within the bony structure, removing the internal flexible guidewire, attaching a cement filled cement injecting syringe to the proximal deployment mechanism, injecting cement into the proximal deployment mechanism through the hollow tube assembly into the stent, pressurizing the cement to cause the complete filling of the stent interior, terminating the filling when the volume of cement injected exceeds the interior volume of the expanded stent, and releasing the stent from the hollow tube assembly. 
         [0020]    In one embodiment, the self-expanding cement-directing stent can include a multifilament braided, polymer impregnated, self-expanding, cement-directing stent. In one embodiment, the stent delivery system can include a handle and an elongate shaft. The stent can be releasably attached to a distal end of the elongate shaft. In one embodiment, the stent is further releasably attached at a distal end thereof, The stent can be released by actuating a user control mechanism on the handle. The elongate shaft can include at least one of an inner shaft, an outer shaft, a tubular sheath, a flexible guidewire, and an internal polymer extrusion. 
         [0021]    In one embodiment, prior to the deploying step the self-expanding cement-directing stent is collapsed on a distal end of at least one of the inner shaft, the guidewire, and the polymer extrusion. The self-expanding cement-directing stent can be deployed by retracting at least one of the inner or outer shaft, the flexible guidewire, and the polymer extrusion. 
         [0022]    In one embodiment, prior to the deploying step the self-expanding cement-directing stent can be restrained in a collapsed condition by the tubular sheath. The self-expanding cement-directing stent can be deployed by slideably retracting the tubular sheath to allow the stent to self-expand within the enlarged curvilinear void. In one embodiment, the deploying step includes actuating a rotating cam mechanism. 
         [0023]    The invention is also drawn to stent delivery systems and components thereof adapted for use with any of the methods described above. 
         [0024]    Another aspect of the invention can include a stent delivery system for deploying a stent within an enlarged curvilinear void created in a bony structure. The stent delivery system can include a handle and an elongate shaft adapted to releasably hold a self-expanding cement-directing stent at a distal end thereof. The elongate shaft can include a sheath and at least one of an inner and an outer shaft. The stent delivery system can also include at least one user control mechanism adapted to deploy the stent. 
         [0025]    In one embodiment, the at least one user control mechanism includes a rotating cam mechanism. Actuating the rotating cam mechanism can retract the sheath towards the handle. In one embodiment, actuating the rotating cam mechanism simultaneously extends the distal end of at least one of the inner and the outer shaft away from the handle. 
         [0026]    In one embodiment, a distal end of the handle can include an interface element adapted to releasably engage at least a portion of proximal end of a cannula. The stent delivery system can also include a stent release mechanism adapted to release the stent from the elongate shaft. 
         [0027]    Another aspect of the invention can include a user control mechanism for a stent delivery device. The user control mechanism can include a support element, at least one cam shaft helically positioned on the support element, a linear support sleeve, and at least one pin engaging the cam shaft and the linear support sleeve. The cam shaft and the linear support sleeve force the pin linearly along an axial extent of the user control mechanism upon a rotation of the support element. 
         [0028]    In one embodiment, the at least one pin is attached to an elongate shaft extending from a distal end of the user control element. The elongate shaft can include at least one of an inner shaft, an outer shaft, and a sheath. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0029]    In the drawings, like reference characters generally refer to the same parts throughout the different views. Also, the drawings are not necessarily to scale, emphasis instead generally being placed upon illustrating the principles of the invention. In the following description, various embodiments of the present invention are described with reference to the following drawings, in which: 
           [0030]      FIG. 1A  is a schematic side view of a stent including a plurality of holes, in accordance with one embodiment of the invention; 
           [0031]      FIG. 1B  is another schematic side view of the stent of  FIG. 1A ; 
           [0032]      FIG. 1C  is a schematic rear perspective view of the stent of  FIG. 1A , showing the plurality of holes; 
           [0033]      FIG. 1D  is a schematic front perspective view of the stent of  FIG. 1A , showing the plurality of holes; 
           [0034]      FIG. 1E  is another schematic rear perspective view of the stent of  FIG. 1A ; 
           [0035]      FIG. 1F  is another schematic front perspective view of the stent of  FIG. 1A ; 
           [0036]      FIG. 2A  is a schematic plan view of a delivery system for a stent, in accordance with one embodiment of the invention; 
           [0037]      FIG. 2B  is another schematic plan view of the delivery system of  FIG. 2A ; 
           [0038]      FIG. 2C  is a photograph of a delivery system inserted in a patient, in accordance with one embodiment of the invention; 
           [0039]      FIG. 2D  is a schematic side view of a cement filled stent inserted in a vertebral body, in accordance with one embodiment of the invention; 
           [0040]      FIG. 3A  is a schematic plan view of a delivery system and collapsed stent, in accordance with one embodiment of the invention; 
           [0041]      FIG. 3B  is a schematic perspective view of the handle of the delivery system of  FIG. 3A ; 
           [0042]      FIG. 3C  is a schematic plan view of the handle of the delivery system of  FIG. 3A ; 
           [0043]      FIG. 3D  is a schematic perspective view of the handle of the delivery system of  FIG. 3A , with the flexible guidewire (e.g., nitinol wire) retracted; 
           [0044]      FIG. 3E  is a schematic perspective view of the handle of the delivery system of  FIG. 3A , with the sheath retracted; 
           [0045]      FIG. 3F  is a schematic perspective view of the handle of the delivery system of  FIG. 3A , with the flexible guidewire (e.g., nitinol wire) and sheath retracted; 
           [0046]      FIG. 3G  is a schematic perspective view of a stent coupled to the delivery system of  FIG. 3A , with the sheath retracted; 
           [0047]      FIG. 3H  is a schematic perspective view of the handle of the delivery system of  FIG. 3A , with the sliding mechanism extended forward; 
           [0048]      FIG. 3I  is a schematic perspective view of the handle of the delivery system of  FIG. 3A , with the sliding mechanism retracted to an intermediate position; 
           [0049]      FIG. 3J  is a schematic perspective view of an expanded stent coupled to the delivery system of  FIG. 3A ; 
           [0050]      FIG. 3K  is a schematic perspective view of the handle of the delivery system of  FIG. 3A , with the inner core assembly (i.e., polymer extrusion and flexible guidewire) removed; 
           [0051]      FIG. 3L  is a schematic perspective view of the handle of the delivery system of  FIG. 3A , with a syringe attached; 
           [0052]      FIG. 3M  is a schematic perspective view of the handle of the delivery system of  FIG. 3A , with the cement piston inserted to push through additional cement; 
           [0053]      FIG. 3N  is a schematic perspective view of the handle of the delivery system of  FIG. 3A , with the cement piston removed; 
           [0054]      FIG. 3O  is a schematic perspective view of the handle of the delivery system of  FIG. 3A , with the locking mechanism unlocked; 
           [0055]      FIG. 3P  is a schematic perspective view of the rear of the handle of the delivery system of  FIG. 3A , with the locking mechanism unlocked; 
           [0056]      FIG. 4A  is a schematic side view of a handle for a delivery system with a rotational cam mechanism, in accordance with one embodiment of the invention; 
           [0057]      FIG. 4B  is a schematic side view of the handle of  FIG. 4A  after being turned; 
           [0058]      FIG. 4C  is a schematic end view of another handle for a delivery system with a rotational cam mechanism, in accordance with one embodiment of the invention; 
           [0059]      FIG. 4D  is a schematic side view of the handle of  FIG. 4C ; 
           [0060]      FIG. 4E  is a schematic plan view of the handle of  FIG. 4C ; 
           [0061]      FIG. 4F  is another schematic end view of the handle of  FIG. 4C ; 
           [0062]      FIG. 4G  is a schematic perspective view of a linear sleeve for the handle of  FIG. 4C ; 
           [0063]      FIG. 4H  is a schematic perspective view of a support element on a linear sleeve for the handle of  FIG. 4C ; 
           [0064]      FIG. 4I  is a schematic perspective view of the handle of  FIG. 4C ; 
           [0065]      FIG. 4J  is another schematic perspective view of the handle of  FIG. 4C ; 
           [0066]      FIG. 5  is a schematic side view of a handle for a delivery system with a rotational threaded mechanism, in accordance with one embodiment of the invention; 
           [0067]      FIG. 6  is a schematic side view of a handle for a delivery system with a geared mechanism, in accordance with one embodiment of the invention; 
           [0068]      FIG. 7  is a schematic side view of a handle for a delivery system with a sliding belt mechanism, in accordance with one embodiment of the invention; 
           [0069]      FIG. 8A  is a schematic perspective view of a handle for a delivery system with a triggering mechanism, in accordance with one embodiment of the invention; 
           [0070]      FIG. 8B  is a schematic perspective view of the interior cam mechanism of the handle of  FIG. 8A ; 
           [0071]      FIG. 9  is a schematic perspective view of a delivery system inserted in a cannula, in accordance with one embodiment of the invention; 
           [0072]      FIG. 10A  is a schematic end view of a handle for another delivery system, in accordance with one embodiment of the invention; 
           [0073]      FIG. 10B  is a schematic side view of the handle of  FIG. 10A ; 
           [0074]      FIG. 10C  is a schematic plan view of the handle of  FIG. 10A ; 
           [0075]      FIG. 11A  is a schematic perspective view of the handle of  FIG. 10A ; 
           [0076]      FIG. 11B  is a schematic perspective view of the handle of  FIG. 11A  after rotation of a rotating user control mechanism; 
           [0077]      FIG. 11C  is a schematic perspective view of the handle of  FIG. 11B  after removal of the top cap; 
           [0078]      FIG. 11D  is a schematic perspective view of the handle of  FIG. 11C  after depression of sliding of the stent release buttons; 
           [0079]      FIG. 12A  is a schematic sectional side view side view of a releasable attachment mechanism attached at a distal end of a collapsed stent, in accordance with one embodiment of the invention; 
           [0080]      FIG. 12B  is a schematic sectional side view of the releasable attachment mechanism of  FIG. 12A  after expansion of the stent; 
           [0081]      FIG. 12C  is a schematic sectional side view of the releasable attachment mechanism of  FIG. 12A  after detachment from the distal end of the stent; and 
           [0082]      FIG. 12D  is a schematic sectional side view of the releasable attachment mechanism of  FIG. 12A  injecting filler material into the stent after removal of the inner rod. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0083]    The present invention discloses methods and apparatus for introducing a stent into a curvilinear or other shaped cavity created within the cancellous bone of a fractured vertebral body or other bony structure. The invention also discloses methods and apparatus for injecting cement into the stent and into the surrounding cancellous bone through positioned exit holes in the stent. 
         [0084]    The methods and apparatus disclosed herein allow for a covered stent to be safely inserted into the vertebral body through the same entry profile as current vertebral compression fracture treatments. Once in place, the delivery apparatus can direct cement into the stent and through the designated holes into the vertebral body. This can allow for the controlled flow of cement away from the spinal canal and towards the anterior side of the vertebral body. Unlike cardiovascular stent delivery systems, the delivery systems disclosed herein have a positive attachment to the stent for cement injection and stent placement adjustability, thus increasing the stability, controllability, and safety of the system during surgical procedures. 
         [0085]    In one embodiment of the invention, expansion of a stent in response to retraction of an outer sheath covering the stent, and maintaining it in a collapsed configuration, is performed in an orthopedic rather than cardiovascular environment. In one embodiment, the delivery system may have certain features that exhibit some similarity to cardiovascular and endoscopic medical device designs, but may also have several mechanical additions specially designed and configured for orthopedic compatibility. 
         [0086]    In one embodiment, the delivery system is configured to compensate for stent foreshortening in a closed cavity environment. Foreshortening of a stent occurs when a stent is expanded from a radially collapsed configuration to a radially expanded configuration, with the expansion resulting in a reduction in length as the diameter of the stent is increased. This length reduction results in the expanded stent being retracted back from the distal wall of the cavity in which it is deployed, which in turn results in the expanded stent failing to completely fill the cavity in which it is deployed. The delivery systems disclosed herein therefore differ from the usual stent delivery systems that are used in vascular or duct environments where longitudinal space is available to allow foreshortening. 
         [0087]    In one embodiment, the stent can be attached to the distal tip of the delivery system and is not automatically released from the device during stent expansion. As a result, physicians are able to pull the stent out of the vertebral body during the surgical procedure, compress, recover with the outer sheath and redeliver the stent if the physician is not satisfied with the original placement. This recovery and redeployment can greatly increase the chances of correctly placing the stent in the most advantageous, and safe, position within a patient. 
         [0088]    In one embodiment of the invention, the delivery system has the ability to retract an outer sheath maintaining the stent in a collapsed configuration from a side portal in order to minimize the length of the delivery system. Cement injection back pressures significantly increase with longer cement injection channels. By incorporating a slit into the outer sheath to allow the outer sheath extrusion to pass over the shafts of the delivery system and be pulled sideways or linearly through the handle, the overall delivery system length can be reduced. This allows the cement to travel a shorter distance to fill the stent, and therefore reduces the injection pressure required to inject cement into the stent at substantially zero pressure. This reduction in injection pressure can increase the usability of the delivery system, while reducing the potential for failure of the injection process, and increasing the safety of the system. 
         [0089]    In one embodiment, the method of cement injection through the delivery systems disclosed herein may provide a safer and more efficient means of treating a vertebral compression fracture than current vertebral compression fracture treatments. In one embodiment, cement may be initially injected by a syringe through the inner shaft of the delivery system. The delivery system can direct the cement straight into the stent and through the designated outlet holes in the stent into the surrounding cancellous bone. Once injection with a syringe becomes difficult, for example as a result of the cement curing, a solid piston can be inserted into the inner shaft to deliver more cement. The inner lumen of the delivery system can, in one embodiment, hold approximately 1.5 cc of cement from the proximal to the distal end. The cement piston can also be used to completely clear the inner shaft of cement to prevent cement back flow out of the pedical. With the delivery system and stent attachment at the distal tip of the delivery system, cement injection becomes more controlled than in more traditional techniques of vertebroplasty and kyphoplasty. 
         [0090]    Stent 
         [0091]    In one embodiment of the invention, a stent can include a multifilament co-braided shaped structure and a self-expanding structure composite which is collapsible to an elongated tubular shape suitable to fit within a tubular sheath assembled to a novel delivery catheter. The outer wall of the stent can be impregnated in preferred regions with a polymer to form a thicker, relatively less permeable wall. The polymer impregnated co-braided wall is further perforated with holes or slots in preferred locations. An example cement directing stent for use with this invention is disclosed in U.S. Patent Publication No. 2005/0261781 A1 to Sennett et al., the disclosure of which is incorporated herein by reference in its entirety. The stent geometry is optimized to fit within a reamed or balloon-expanded cavity located approximately within the anterior ⅔ of a vertebral body. The cavity is formed by a sequential method using a number of specifically designed instruments. An example stent  100  is shown in  FIGS. 1A-1F . 
         [0092]    In one embodiment of the invention, the stent  100  can be sized to substantially conform to the dimensions of a predetermined cavity created within a vertebral body. The stent  100  can be configured to be collapsible, thus allowing delivery of the stent  100  through a relatively small diameter access cannula. The stent  100  can also have a self-restoring shape, allowing the stent to automatically expand to its original shape, corresponding substantially with the dimensions of the cavity into which it is inserted, without the need for inflation of the stent  100  by the injection of filler material or other fluids or substances. In one embodiment, the stent  100  may be self-restoring to an expanded configuration, at least because it is constructed, at least in part, from a shape-memory material, such as, but not limited to, nitinol. The stent  100  may be constructed, at least in part, as a braided structure  110 . 
         [0093]    In one embodiment, expansion of the stent  100  does not generate a distraction force on the end plates of the vertebral body and does not compact the interior cancellous bone structure of the vertebral body. Upon expansion of the stent  100  within the vertebral body, filler material (such as bone cement) can be injected into the stent  100  to at least partially fill the interior of the stent  100 . In one embodiment, the injection of filler material does not substantially alter the shape and dimensions of the stent  100 , other than to conform the stent, if necessary, to the shape of the cavity in which it is disposed. 
         [0094]    In one embodiment of the invention, the wall of the stent may include at least one hole  120  or permeable region allowing filler material to leave the interior of the stent  100  and enter the vertebral body. The at least one hole  120  or porous region can allow for the controlled and directed distribution of filler material within the vertebral body. The wall of the stent  100  may include a plurality of holes of various sizes and/or a plurality of regions of differing permeability, allowing for a greater or lesser escape of filler material in different directions. The wall of the stent  100  may also include at least one baffle or other non-permeable region preventing the escape of filler material in certain directions. In general, the total cross-sectional area of the holes exceeds that of a cement inlet hole  140 , to prevent excess back pressure or buildup of pressure in the interior of the stent. 
         [0095]    In one embodiment, the stent  100  may have a proximal region  130  that is configured to be releasably mounted to a delivery system and includes the inlet hole  140  to allow for the injection of cement. The stent  100  can also have a closed distal region  150  to be positioned away from the delivery system and to be placed against the distal end of the cavity in which it is placed. 
         [0096]    In one embodiment, the method of treating the patient may involve external reduction by extension, i.e. physical manipulation of the patient when placing the patient on the operating table before treatment of the vertebral fracture site. The method of treating the patient can also involve stabilizing the vertebral body, not distracting the upper and lower end plates using the stent as an expansion device. 
         [0097]    Delivery System 
         [0098]    An example of a delivery system can be seen in  FIG. 2A . The delivery system  200  can include a handle portion  205  at a proximal end, and a hollow elongate shaft  210  extending towards a distal end. A stent  215  can be releasably held at the distal end of the hollow elongate shaft  210 . 
         [0099]    In one embodiment of the invention, the delivery system  200  can be configured to releasably couple to a cannula that is inserted percutaneously from the posterior approach through the outer tissue of a patient and anchored into the bone of the vertebral body to a suitable depth. The hollow elongate shaft  210  can be configured to slidably extend through the cannula such that the stent  215  protrudes from the distal end of the cannula and into a curvilinear cavity formed within the vertebral body. The stent may be configured to extend at a specific angle, or along a predetermined arc, to conform to the axis of the cavity. In an alternative embodiment, the stent may extend straight out from the distal end of the hollow elongate shaft  210 . 
         [0100]    The flexibility and resiliency of the stent is well adapted for use in cavities having a variety of shapes, including curvilinear, cylindrical, tapered, conical, etc. The stent may be flexible, such that it may be deflected by the walls of the cavity and therefore conform substantially to the curvature or shape of the cavity when inserted. In a further alternative embodiment, the cavity may extend straight out from the distal end of the cannula, and no curvature or deflection of the stent is required for correct insertion of the stent into the cavity. 
         [0101]    In one embodiment, a flange  220  and key  225  may be fitted to the handle portion  205  of the delivery system  200  at the proximal end of the hollow elongate shaft  210 . The flange  220  may enable the delivery system to be releasably locked to the cannula to ensure stability of the delivery system  200  during the procedure. The key  225  may be configured to mate with a slot in the cannula to ensure that the delivery system  200  is inserted into the cannula in the correct circumferential orientation. In an alternative embodiment, the delivery system  200  may include a locking mechanism, latch, or other appropriate means of releasable engagement with the cannula. In a further alternative embodiment, no means of locking the delivery system  200  to the cannula may be required. 
         [0102]    In one embodiment, a sheath  230  may be used to releasably maintain the stent  215  in a collapsed configuration during insertion through the cannula and into the cavity. The collapsed configuration may be substantially the same diameter as the diameter of the hollow elongate shaft  210  (i.e. a diameter configured to fit slidably through the cannula). The sheath  230  may be a hollow elongate flexible tube of plastic, fabric, wire mesh, composite, metal or other appropriate material, that can slideably extend over the hollow elongate shaft  210  and stent  215  to hold the stent  215  at a set diameter substantially equal to the diameter of the hollow elongate shaft  210 . 
         [0103]    The proximal end  235  of the sheath  230  may extend through an exit hole  240  in the handle  205  of the delivery system  200 . An elongate slot may be inserted in a portion of the proximal end  235  of the sheath  230  to allow the sheath  230  to be pulled out through the exit hole  240  without tearing. In one embodiment, a handle may be placed on the end of the sheath  230  to assist in pulling the sheath  230  out through the exit hole  240 . 
         [0104]    In use, the sheath  230  is slid over the hollow elongate shaft  210  and stent  215  to hold the stent  215  in a collapsed configuration. Once the stent  215  has been inserted through the cannula and into the cavity, the sheath  230  can be pulled back through the exit hole  240  in the handle  205 . This retracts the sheath  230  back along the hollow elongate shaft  210  and off the stent  215 . The stent  215  is then free to self-expand to its original shape, which may, in one embodiment, conform substantially with the shape of the curvilinear cavity. In one embodiment, a marking  245  may be placed on the sheath  230  near the proximal end  235  to indicate to a user when the sheath  230  has been retracted far enough to uncover the stent  215 . 
         [0105]    In addition to the sheath  230 , or possibly in place of the sheath  230 , a polymer extrusion and/or a flexible guidewire  250  may be inserted through the handle  205  and hollow elongate shaft  210  to provide an internal force to extend the distal end of the stent  215  and assist in holding the stent  215  in a collapsed, or partially collapsed, configuration. The polymer extrusion may be an elongated hollow polymer shaft made of any flexible polymer such as PEBAX, Nylon PET or PTFE. The flexible guidewire  250  may be an elongate solid or hollow rod of stainless steel, aluminum, plastic, or another appropriate material, that may slideably extend through the hollow elongate shaft  210  of the delivery system  200 , with the distal end of the flexible guidewire  250  abutting against the interior distal end of the stent  215  to force the stent forward. 
         [0106]    In one embodiment, the flexible guidewire  250  may also include a guidewire handle  255  that can assist the user in pulling and pushing on the guidewire  250  as required. A mounting element  260  may be releasably connected to the end of the handle  205  with a bayonet retention feature or other attachment feature and through which the flexible guidewire  250  passes. The mounting element  260  may also be connected to the polymer extrusion that extends down to the stent  215  and is disposed coaxially between the flexible guidewire  250  and the hollow elongate shaft  210  of the delivery system  200 . This extrusion may be used, for example, to provide a smooth, low friction boundary between the guidewire  250  and the hollow elongate shaft  210 . The polymer extrusion may be of a length such that the extrusion also assists in maintaining the stent  215  in a collapsed configuration prior to insertion and deployment in the cavity. The mounting element  260  may be used to cover a luer lock, or other mounting feature, that may be used to releasably hold a syringe once the inner core assembly (i.e., polymer extrusion and guidewire  250 ) has been removed. 
         [0107]    The inner core assembly (i.e., polymer extrusion and guidewire  250 ) may provide multiple functions for the delivery system  200 . For example, the inner core assembly (i.e., polymer extrusion and guidewire  250 ) may be used to assist in maintaining the stent  215  in a collapsed configuration prior to insertion and deployment in the cavity. The inner core assembly (i.e., polymer extrusion and guidewire  250 ) may also be used to counteract any foreshortening of the stent  215  that may occur during expansion. 
         [0108]    In one embodiment, a sliding mechanism  265  can also be used to counteract foreshortening of the stent  215  as a result of expansion within the cavity. The sliding mechanism may be fixedly coupled to the hollow elongate shaft  210  of the delivery system  200 , and be slidably coupled to the handle  205  of the delivery system  200 . By sliding the sliding element  265  forward, the entire hollow elongate shaft  210  and attached stent  215  can be pushed forward, thus pushing the distal end of the expanded stent  215  towards the distal end of the cavity. After the stent  215  has been pushed to the end of the cavity, the sliding element  265  can be slid backwards by a small amount to counteract any foreshortening of the proximal end of the stent  215  that may result from the pushing process. A releasable locking mechanism  270 , including a spring mounted locking element  275 , can be used to ensure that the sliding element  265  is locked in place when not needed. In one embodiment, markings may be placed on the handle  205  to indicate the length of travel of the sliding element  265 . 
         [0109]    Once a stent  215  has expanded and been correctly positioned within a cavity, the stent  215  may be filled with cement, cement analogue, or other filler material, by fitting a syringe to the luer lock, or other locking mechanism at the proximal end of the hollow elongate shaft  210 , after the inner core assembly (i.e., polymer extrusion and guidewire  250 ) has been removed. The cement can then flow through the hollow elongate shaft  210  and into the interior of the stent  215 , after which it can flow into the vertebral body through the carefully positioned holes in the stent  215 . 
         [0110]    Once the stent has been filled, the stent can be released from the delivery system  200  and the system removed from the patient. A locking mechanism  280  may be included in the handle  205  of the delivery system  200  to releasably hold the stent  215  to the hollow elongate shaft  210 . The locking mechanism  280  may be attached to an elongate element that is attached at its distal end to the proximate end of the stent  215 . The locking mechanism  280  may also include a slider  285 , or a switch, clasp, or other user interface element, to unlock the stent  215  from the elongate element and/or hollow elongate shaft  210  once the stent has been correctly positioned and filled. In one embodiment, a pin  290  may be removably inserted into the locking mechanism  280  to ensure that the stent  215  is not released accidentally. 
         [0111]    It should be noted that at all steps of a method using the above-identified delivery system  200 , medical imaging techniques, such as fluoroscopy, may be used to image the interior of the vertebral body and confirm the location and status of the stent  215 , cement, and cavity. 
         [0112]    An example a delivery system  200  with the sheath  230  retracted and the stent  215  expended is shown in  FIG. 2B . An example of this delivery system  200  inserted into a patient can be seen in  FIG. 2C . A cross-section of a cement filled stent  215  inserted into a vertebral body  292  is shown in  FIG. 2D . In this figure, large arrows  294  indicate the direction of the cement leaving through holes  296  in the stent  215  in order to stabilize a fracture  298 . Small arrows correspond to areas of lower permeability of the stent  215 , through which nominal amounts of cement leave the stent  215  to further anchor the stent  215  and fill any remaining voids in the cavity. 
         [0113]    Method of Use 
         [0114]    An embodiment of the invention can include a method of using the delivery systems described herein to insert and deploy a stent device into a cavity created in a vertebral body. The cavity may be a curvilinear cavity. In an alternative embodiment, the cavity may be of any appropriate size and shape, with a stent selected to be configured to substantially conform to the size and shape of the cavity created. 
         [0115]    In one embodiment of the invention, a procedure for using the devices disclosed herein can be used to produce a curvilinear cavity within a vertebral body, and place a stent within the cavity created within the vertebral body. The stent can be a self-expanding, covered stent that allows interdigitation and prevents leakage of bone cement in undesired directions. In one embodiment, a single stent can be placed at a mid-line location of a vertebral body, rather than placing multiple stents on either side of the mid-line, thus reducing the time and fluoroscopy exposure require during a surgical implantation procedure. 
         [0116]    In one embodiment, the method of creating a cavity for within a vertebral body, or other bony body, can include first creating a posterior pathway to the vertebral body, using a extrapedicular or intrapedicular approach, with a Jamshidi needle and/or K-wire. This may be performed, for example, using a dual C-arm technique to place and medialize the Jamshidi needle/K-wire to the fullest extent. 
         [0117]    A working channel and trocar assembly can then be inserted along the pathway created by the Jamshidi needle/K-wire. This can be performed, for example, by locking the trocar into the working channel, inserting the working channel into the pathway, and tapping the assembly into place until the distal tip of the trocar and working channel extends, in one embodiment, 1-3 mm beyond the posterior wall of the vertebral body. The trocar can then be removed, leaving the open working channel in place. 
         [0118]    A curved pathway through the vertebral body can then be created using a curved drill. This may be achieved using any of the drill arrangements described herein. In one embodiment, the drill depth markings at the user interface are set to “0” mm prior to insertion into the working channel. The drill can then be locked into the working channel with the key facing in the medial direction, thus ensuring the correct direction of curvature of the drill within the vertebral body. The handle of the drill can then be rotated to advance the drill tip into the vertebral body, with fluoroscopy, or some other appropriate technique, used to determine when the desired depth of penetration is achieved. The drill can then be removed and the depth markings on the user interface recorded. In one embodiment, the drill tip is oriented in the contralateral anterior quadrant of the vertebral body, thus assuring proper cavity positioning and bilateral cement filling. 
         [0119]    In one embodiment, a larger cavity can then be created within the vertebral body by reaming out the hole created by the curved drill with a curved reamer. This may be achieved, for example, by first setting the depth markings on the user interface of the reamer to match those recorded for the drill depth, thus assuring that the reamer is positioned correctly within the vertebral body. The reamer can then be advanced fully into the pathway created by the drill and locked into the working channel, with the position of the reamer confirmed using fluoroscopy or some other appropriate technique. The blade of the reamer can then be opened, for example by rotating a portion of the handle of the reamer, and reaming can be carried out by rotating the handle. In one embodiment, the reamer may be stopped approximately 1-3 mm before approaching the distal tip of the working channel, with the position confirmed by fluoroscopy, or some other appropriate technique. The blade can then be closed (for example by rotating a portion of the handle in the opposite direction), and the reamer removed. In one embodiment, due to blade deflection, the cavity created by the reamer can have a slight taper from the distal end to the proximal end. 
         [0120]    Once a cavity has been created, a stent delivery system can be locked into the working channel to correctly position a stent within the vertebral body. Once the stent has been positioned, a sheath covering the stent can be removed to deploy and expand the stent, and cement can be injected into the stent by attaching a syringe to the proximal end of the delivery system. The desired amount of cement can be injected into the stent with fluoroscopy, or some other appropriate technique, being used to monitor the flow of cement into the stent. Once the requisite amount of cement has been injected, the stent can be released from the delivery system and the delivery system removed from the working channel, thus leaving the stent in place within the vertebral body. The working channel can then be removed and the access pathway sutured or otherwise closed. 
         [0121]    One example embodiment may include inserting a delivery system  200  into the cannula such that the covered stent is extended beyond the distal end of the cavity and into the curvilinear cavity. An example of a delivery system prior to insertion into a cannula is shown in  FIGS. 3A-3C . Once the delivery system  200  is fully inserted within the cannula, the delivery system  200  can engage with, and be locked in place by, a locking element associated with the cannula. In one embodiment of the invention, the delivery system  200  may be extended through the cannula until a user can feel resistance to the forward movement, indicating that the end of the collapsed stent is abutting against the distal end of the cavity created within the vertebral body. In an alternative embodiment, the length of the cavity may be carefully measured such that the end of the collapsed stent will automatically extend to the end of the cavity upon insertion of the delivery system  200 . In addition to these techniques, or in place of these techniques, representative fluoroscopic photos or movies, or use of other appropriate medical imaging techniques, may be taken to ensure the correct placement of the stent within the cavity. 
         [0122]    Once the stent has been correctly positioned within the cavity in its collapsed configuration, it may be expanded within the cavity. In one embodiment, the inner core assembly (i.e., polymer extrusion and guidewire  250 ) inserted through the center of the delivery system  200  and abutting against the distal end of the stent may be pulled back, for example by pulling on a handle  255  attached to the flexible guidewire  250  and twisting off the bayonet retention feature of the mounting element  260  attached to the polymer extrusion, thus relieving the force on the distal end of the stent that is assisting in maintaining the stent in a collapsed configuration. In one example embodiment, the flexible guidewire  250  and handle  255  may be pulled back by approximately two inches, or by a greater or lesser distance, as required. In an alternative embodiment, the flexible guidewire  250  and handle  255  may be removed completely. In a further alternative embodiment, there is no need for the inner core assembly (i.e., polymer extrusion and guidewire  250 ) to be inserted within the delivery system  200 , with the sheath  230  alone being sufficient to maintain the stent in a fully collapsed configuration. An example of a flexible guidewire  250  and handle  255  being retracted can be seen in  FIG. 3D . 
         [0123]    Once the force on the distal end of the stent, provided by the flexible guidewire  250  and/or polymer extrusion, has been removed, the stent is ready to be expanded. Expansion of the stent can be executed by retracting the sheath  230 , for example by pulling on a handle attached to the sheath, by a predetermined amount. A mark  245  may be placed on the sheath  230  to indicate when the sheath  230  has been pulled back by the correct amount. Retracting the sheath  230  removes the external restrictive force on the stent and allows it to self-expend to its preformed, free-state configuration. This may, in one embodiment of the invention, substantially conform to the size and shape of the cavity. An example of a sheath  230  after being retracted can be seen in  FIGS. 3E and 3F . In an alternative embodiment, the sheath  230  can be removed prior to the polymer extrusion being removed. An example of a stent  215  with the sheath  230  retracted but with the polymer extrusion remaining in place and extended to the distal end of the stent  215  can be seen in  FIG. 3G . 
         [0124]    In one embodiment of the invention, expansion of the stent  215  can also result in a certain amount of foreshortening at the distal end of the stent  215 . This foreshortening, which is caused by the increase in the diameter of the stent  215  as it expands resulting in a responsive decrease in the length of the stent  215 , may retract the end of the stent  215  slightly from the distal end of the cavity. This may be compensated for by providing a force to push the entire stent  215  forward until the distal end of the expanded stent  215  abuts against the distal end of the cavity. This may be achieved through the use of a sliding mechanism  265  that is configured to allow for the extension and retraction of the entire stent  215  and elongated shaft  210  arrangement along the axis of the shaft. By releasing the locking mechanism  270  on this sliding mechanism  265 , the stent  215  and elongated shaft  210  can be pushed forward by the required amount. The sliding mechanism  265  can then re-engage the locking mechanism to lock the stent at a final position. An example of the sliding mechanism  265  pushed forward within the handle  205  can be seen in  FIG. 3H . 
         [0125]    In one embodiment, forcing the expanded stent  215  forward may result a certain amount of foreshortening of the stent  215  at its proximal end (i.e. the end attached to the elongated shaft  210  of the delivery system  200 ). Here, after forcing the stent  215  forward using the sliding mechanism  265 , the sliding mechanism  265  may be retracted by a small amount to counteract any foreshortening at the proximal end of the stent  215 . Again, the sliding mechanism  265  may be locked into position once the stent  215  has been correctly positioned. As before, fluoroscopic images, or other appropriate medical images, may be taken to confirm the positioning and expansion of the stent at the distal end of the cavity. In one embodiment of the invention, the polymer extrusion may also be used to extend the expanded stent after foreshortening due to the expansion. An example of the sliding mechanism  265  retracted after being pushed forward within the handle  205  can be seen in  FIG. 3I . An example of a fully expanded stent  215  coupled to a hollow elongated shaft  210  with a sheath  230  retracted can be seen in  FIG. 3J . 
         [0126]    As mentioned above, the polymer extrusion can perform the function of collapsing the stent by stretching the stent out longitudinally or axially, by applying a force in that direction from within the stent. The proximal end of the stent is fixed to the elongate shaft  210  and the distal end of the stent is stretched and held in place by the polymer extrusion which is locked in position to the handle  205  by the mounting element  260 . With the stent collapsed, it can be moved easily down the working channel, thereby eliminating the need for a sheath in the delivery system. 
         [0127]    After correct positioning of the expanded stent  215 , the polymer extrusion can be removed completely from the delivery system  200  by releasing and retracting the mounting element  260  from the handle portion  205 . Removing the polymer extrusion leaves a hollow shaft  210  through the center of the delivery system  200  and into the interior of the expanded stent  215 . This hollow shaft can then be used for the injection of cement, or other material, into the stent. An example of the delivery system with the polymer extrusion removed can be seen in  FIG. 3K . 
         [0128]    Injection of cement into the stent may be performed by releasably connecting the end of a syringe  310  to the hollow shaft at the point vacated by the polymer extrusion mounting element  260 . In one embodiment of the invention, a 10 cc threaded syringe may be used, although in alternative embodiments, any appropriate injection device may be utilized. In one embodiment, the proximal end of the hollow shaft may include a luer lock  320 , or other releasable locking arrangement, that may engage the end of the syringe  310  and engage it with the hollow shaft  210 . An example of a syringe  310  attached to the handle  205  of the delivery system  200  can be seen in  FIG. 3L . Alternatively, instead of directly rigidly connecting the syringe  310  to the handle  205 , a rigid or flexible extension tube can be interdisposed between the syringe  310  and the handle  205 . The extension tube allows the physician to have his hands out of the fluoroscopic field and also provides the opportunity to reorient the syringe  310 , e.g., by forming an “elbow” or other angular connection, so that the syringe  310  is not fixedly cantilevered axially from the delivery system  200 . 
         [0129]    Once the syringe  310  is in place, the cement, or other material, such as a cement analogue, can be injected into the hollow shaft  210  of the delivery system  200  and into the expanded stent  215 . Injection of cement may be continued until the stent  215  is completely filled and cement flows out of the designated holes in the stent into the vertebral body. Once enough cement has flowed out of the stent  215  and into the vertebral body to provide the required level of interdigitation between the stent  215  and vertebral body, the injection can be stopped. Again, fluoroscopic images, or other appropriate medical images, may be taken to confirm that the stent has been filled and the required amount of cement has flowed out into the vertebral body at the correct positions. 
         [0130]    In one embodiment of the invention a cement piston  325  may be used to push additional cement in the hollow shaft  210  into the stent  215 , for example when high cement viscosity has resulted in incomplete filling of the cavity. This may be achieved by simply detaching the syringe  310 , and pushing the cement piston  325  back into the hollow shaft  210  to force the additional cement in the shaft  210  into the stent  215 . This may be important if the physician is not satisfied with the amount of cement filling prior to removal. In one embodiment, the hollow shaft  210  can hold 1.5 cc of cement, or other material, with the cement piston  325  capable of pushing any percentage of that volume into the stent  215 , as required. Once the correct amount of cement has been injected into the stent  215 , the cement piston  325  can again be removed. An example of the cement piston  325  forcing cement through the shaft  210  can be seen in  FIG. 3M . An example of the handle  205  of the delivery system  200 , after the cement piston  325  has been removed again, can be seen in  FIG. 3N . 
         [0131]    After the stent  215  has been filled with cement, and the correct amount of cement has exited the stent  215  through the exit holes to interdigitate with the vertebral body, the stent  215  can be released from the delivery system  200  and the delivery system  200  removed. In one embodiment of the invention, a locking mechanism  280  may be used to hold the stent  215  onto the delivery system  200 . This locking mechanism  280  may include any appropriate means of releasably engaging the proximal end of the stent, including, but not limited to, a clamping mechanism, a grasping mechanism, sliding mechanism, a pressure fit between an outer shaft, the proximal end of the stent, and the inner hollow shaft, or any other appropriate mechanism. In one embodiment, the locking element  285  may include a slide, switch, or other element at the proximal end of the delivery system, allowing the locking mechanism to disengage from the stent when required. A removable pin  290 , or other locking device, may be inserted into the delivery system  200  to ensure that the delivery system  200  is not disengaged from the stent  215  inadvertently, before the cement has been fully injected. An example of the locking mechanism  280  after the pin  290  has been removed and the locking mechanism  280  opened is shown in  FIGS. 3O and 3P . 
         [0132]    Once the stent has been released from the delivery system, the delivery system can be unlocked and removed from the cannula. After this, the cannula may be removed and the surgical incision closed. 
         [0133]    In an alternative embodiment, a delivery system including a handle adapted to move multiple components of the delivery system with a movement of a single user control mechanism can be used to deploy a stent within a cavity created within a vertebral body. This user control mechanism can include a mechanism such as, but not limited to, a rotating mechanism, a sliding mechanism, a trigger mechanism, or any other appropriate mechanical, electrical, and/or magnetic mechanism. 
         [0134]    Employing a user control mechanism to control a number of functions of the delivery system can both simplify and speed up the deployment process, while reducing the number of steps that need to be performed by a user during the deployment process. This can increase the efficiency of the delivery system while increasing the safety of the deployment methods for a patient being treated. In one embodiment, a user control mechanism can control the retraction of a sheath covering the stent, the movement of an inner shaft, and/or the movement of an outer shaft. The inner shaft can include, but is not limited to, a flexible guidewire, a hollow flexible shaft, and/or another appropriate elongate element configured to extend through the interior of an outer shaft. The outer shaft can include, but is not limited to, a hollow elongate shaft configured to releasably engage the stent at its distal end. 
         [0135]    In an alternative embodiment, additional and/or different functions of the delivery system can be controlled by a single user control mechanism. These functions can include, but are not limited to, injecting filler material such as cement into the stent, releasing the stent, locking, and/or unlocking, the delivery system to/from the cannula, curving the distal end of the flexible shaft to facilitate deployment of the stent within a curved cavity, and/or any other appropriate function of a stent delivery system. 
         [0136]    In one embodiment, a user control mechanism is adapted to retract the outer sheath of the elongate shaft of a delivery system to allow the stent to be fully deployed within a cavity in a vertebral body. At the same time, the inner and outer shafts of the elongate shaft are moved forward to compensate for any foreshortening of the stent during retraction of the sheath, as described above. This allows the stent to be deployed in its expanded configuration at the full distal extent of the cavity. The user control mechanism can be configured to move the sheath and the inner and outer shafts simultaneously in opposite directions by set amounts, with the sheath being retracted towards the handle of the delivery system while the inner and outer shafts are extended outwards away from the handle. 
         [0137]    The distance by which each of the sheath and the inner and outer shaft should be moved relative to each other is dependent upon factors that can include the size and shape of the stent and the cavity in which the stent is being deployed. For example, in one embodiment, the sheath can be retracted by a distance equal to or greater than the length of the stent to ensure that it is fully retracted from the stent in order to allow the stent to expand fully. The inner and outer shafts, in contrast, can be extended by a distance equal to the foreshortening of the stent as it expands from its collapsed configuration to its expanded configuration. In one embodiment, the inner and outer shafts can be extended out from the handle by the same distance. In an alternative embodiment, the inner shaft and the outer shaft can be extended out from the handle by different distances. 
         [0138]    Example user control mechanisms for moving multiple components of a delivery system can be seen in  FIGS. 4A-8B . 
         [0139]      FIGS. 4A and 4B  show a handle  400  for a delivery system with a rotational cam mechanism  410  before and after being rotated. The rotational cam mechanism  410  includes three separate slotted cam shafts wrapped helically on a support element  420  surrounding the central shaft  425  of the handle  400 . An outer grip  430  covers the support element  420  and central shaft  425  and engages with the support element  420 . Pins associated with each of the outer shaft, the inner shaft, and the sheath engage with the slotted cam shafts such that a rotation  435  of the support element  420  will force the pins axially along the central shaft of the delivery device in a direction and distance controlled by the angle and direction of each slotted cam shaft. 
         [0140]    More specifically, a first slotted cam shaft  440  engages with a first pin  445  attached to the outer shaft of a delivery system. A second slotted cam shaft  450  engages with a second pin  455  attached to the inner shaft of the delivery system. And, a third slotted cam shaft  460  engages with a third pin  465  attached to a sheath. As a result, as the outer grip  430  is rotated about the central shaft  425  of the handle  400 , the first pin  445  and second pin  455  will be forced axially forward  470  toward the distal end of the handle  400 , resulting in the inner shaft and outer shaft being extended outwards from the distal end of the handle  400  (and therefore compensating for any foreshortening of the stent during deployment). Simultaneously, the third pin  465  will be pulled axially rearwards  475  toward the proximal end of the handle  400 , resulting in the sheath being pulled rearwards  475  towards the handle  400  (and therefore exposing the stent). 
         [0141]    In one embodiment, the helical paths for each of the inner shaft and outer shaft have the same angle, resulting in the distal ends of the inner shaft and outer shaft each being forced forward  470  the same distance. In an alternative embodiment, the helix paths for each of the inner shaft and outer shaft may be different, resulting in the distal ends of the inner shaft and outer shaft being forced forward  470  by a different amount. In a further alternative embodiment, at least one of the inner shaft and outer shaft may be stationary. 
         [0142]    Additional axially slotted cam shafts can be located at the distal end of the first slotted cam shaft  440  and third slotted cam shaft  460 , allowing the first pin  445  and third pin  465  to remain in the same axial position while the second pin  455  is moved rearwards  475  by pulling the outer grip  430  rearwards  475  towards the proximal end of the handle  400  of the delivery system after the rotation of the outer grip is completed. By having axial slots of different lengths, the pins can be moved axially by different distances when the outer grip is pulled rearwards  475  towards the proximal end of the handle. For example, the first axial slotted cam shaft  480  (associated with the outer shaft) is shorter than the second axial slotted cam shaft  485  (associated with the sheath), so that when the outer grip  430  is pulled rearwards  475 , the second pin  455  is moved rearwards  475  along with the outer grip  430 , the first pin  445  remains stationary until it connects with the end  490  of the first axial slotted cam shaft  480 , after which it moves rearwards  475  along with the outer grip  430 , and the third pin  465  remains stationary throughout the entire axial rearward  475  motion of the outer grip  430 . In alternative embodiments, different lengths of axial cam shafts can be associated with any of the pins, allowing for different rearward travel distances, as desired. By moving the outer shaft back a certain distance after being pushed forward, while leaving the inner shaft extended, the stent can be stretched out and fully deployed without the distal end of the stent being pulled back from the distal end of the cavity. In an alternative embodiment, there are no axial cam shafts. 
         [0143]    In one example embodiment, the outer grip  430  can be rotated through approximately 120° to fully move the sheath, inner shaft, and outer shaft (and thus deploy the stent). In an alternative embodiment, a larger or smaller rotation of the outer grip  430 , for example between 90° and 360°, can be used. 
         [0144]    Another example of a handle  400  for a delivery system with a rotational cam mechanism  410  is shown in  FIGS. 4C-4J . In this embodiment, the delivery system includes a handle portion  400  and a hollow elongate shaft (not shown) extending from the distal end of the handle  400 . The hollow elongate shaft can include a distal end adapted to support and deploy a stent within a cavity created within a vertebral body. The hollow elongate shaft can include an inner shaft and an outer shaft adapted to engage a stent, releasably positioned at the distal end of the elongate shaft. A sheath can be positioned over the outer shaft and extend over the stent to maintain the stent in a collapsed configuration during insertion through the cannula and into the cavity. 
         [0145]    As with the embodiment of  FIGS. 4A and 4B , the rotational cam mechanism  410  includes three separate slotted cam shafts wrapped helically on a support element  420  surrounding the central shaft  425  of the handle  400 . An outer grip  430  covers the support element  420  and central shaft  425  and engages with the support element  420 . Pins  445 ,  455 ,  465  (associated with each of the outer shaft, the inner shaft, and the sheath) engage with the slotted cam shafts  440 ,  450 ,  460  such that a rotation  435  of the support element  420  will force the pins  445 ,  455 ,  465  axially along the central shaft of the delivery device in a direct and distance controlled by the angle and direction of each slotted cam shaft  440 ,  450 ,  460 . In one embodiment, the pins  445 ,  455 ,  465  are positioned within a linear support sleeve  492  that is configured to ensure that the pins  445 ,  455 ,  465  can only move axially, either forwards  470  or backwards  475 , along the length of the handle  400 . A schematic perspective view of the linear support sleeve  492  engaging one of the pins is shown in  FIG. 4G , with  FIG. 4H  showing the support element  420  positioned on the linear support sleeve  492 . 
         [0146]    A single axial slotted cam shaft  495  is located at the distal end of the first slotted cam shaft  440  and third slotted cam shaft  460 , allowing the first pin  445  and third pin  465  to moved rearwards  475  together. A removable cap  497  is placed on the proximal end of the handle  400  to cover a luer lock  498  adapted for engagement with a filler material delivery device, such a syringe. 
         [0147]    A stent release button  482  is located on the handle  400  to actuate disengagement of the stent from the elongate shaft once deployment and filling of the stent is completed. The stent release button  482  can be depressed and slid rearwards  475  towards the proximal end of the handle  400  (i.e. away from the elongate shaft) to release the stent from the elongate shaft. In an alternative embodiment, two stent release buttons located opposite each other on either side of the handle  400  can be used. In a further alternative embodiment, any appropriate user interface elements including, but not limited to, a dial, a switch, a sliding element, or a button, can be used to activate the detachment of the stent from the elongate shaft, and/or to perform any other required functions. 
         [0148]      FIG. 5  shows a handle  500  for a delivery system with a rotational threaded mechanism  510 . The rotational cam mechanism  510  includes two separate threads wrapped helically on a support element  520  surrounding the central shaft  525  of the handle  500 . An outer grip  530  covers the support element  520  and central shaft  525  and engages with the threads on the support element  520 . A first thread  540  is associated with the sheath of the delivery system, while a second thread  550  is associated with at least one of the inner shaft and outer shaft of the delivery system. A slotted control button  560  can provide a user control for additional functions of the delivery system. 
         [0149]    In operation, a rotation of the outer grip  530  will drive the sheath (associated with the first thread  540 ) in an axially rearward  575  direction, while the inner and/or outer shaft (associated with the second thread  550 ) will be driven in an axially forward  570  direction. The helical angle of each thread will determine how far each element is moved axially through the rotation of the outer grip  530 . In an alternative embodiment, larger or smaller helical angles can be used to move one or more elements by any required distance, as appropriate. In addition, more threads, at any required helical angle, can be incorporated into the rotational threaded mechanism  510  to control additional elements of the delivery system. 
         [0150]    In an alternative embodiment, a geared mechanism can be used to control the movement of the inner shaft, the outer shaft, the sheath, and/or any other appropriate element of the delivery system. The geared mechanism can include a number of gear arrangements, including any appropriately configured and sized gears to move the shafts and/or sheath in different directions and by different distances, as required sequentially or simultaneously. An example geared mechanism  610  can be seen in  FIG. 6 . 
         [0151]      FIG. 6  shows a handle  600  for a delivery system with a geared mechanism  610 . The geared mechanism  610  includes a first gear arrangement  620 , engaging the sheath, and a second gear arrangement  630  for controlling the movement of one of more of the inner and outer shafts. In operation, a pin  640  can be moved in a rearward direction  675  by a user, thus pulling the sheath rearwards  475  by a distance corresponding to the length of the slot  650 . The first gear arrangement  620  will be driven by the movement of the pin  640 , which will in turn drive the second gear arrangement  630  and push the inner shaft and/or outer shaft in a forward direction  670 . Through careful selection of the slot  650  and gearing arrangements  620 ,  630 , the sheath and the inner and/or outer shafts can be moved by any appropriate distance and in either the forward  670  or rearward  675  direction. Different gearing arrangements to drive additional and/or different elements can be used, as appropriate. In an alternative embodiment, a dial associated with a gearing element, or other appropriate user control, can be used instead of, or in addition to, the pin. 
         [0152]      FIG. 7  shows a handle  700  for a delivery system with a sliding belt mechanism  710 . The sliding belt mechanism  710  includes a sliding outer grip  720  that is coupled to an inner sliding belt arrangement  730  that forces an inner element  740  in a forward  770  direction as the sliding outer grip  720  is pushed in a rearward  775  direction by a user. 
         [0153]    More specifically, the sheath is attached to the sliding outer grip  720 , while the inner shaft and outer shaft are connected to the inner element  740 . By coupling the sheath, inner shaft, and/or outer shaft of the elongate shaft  750  to either the sliding outer grip  720  or the inner element  740 , each shaft and sheath can be moved forwards  770  or rearwards  775 , as required. The sliding belt mechanism can provide simultaneous movement of the shafts and/or sheath, but may also provide sequence in the movement of the shafts and/or sheath by delaying one function through the belt arrangement  730 . As before, a luer lock  760  can be placed at a proximal end of the handle  700  to provide a coupling element for a cement deliver device, such as a syringe. 
         [0154]      FIGS. 8A and 8B  show a handle  800  for a delivery system with a triggering mechanism  810 . The triggering mechanism  810  includes three separate slotted cam shafts positioned on a pair of cam plates  820  within a trigger  825  that is pivotably connected to a support element  830 . Pins associated with each of the outer shaft, the inner shaft, and the sheath of the elongate shaft  815  engage with the slotted cam shafts such that a closing of the trigger  825  will force the pins axially along the central shaft  835  of the delivery device in a direct and distance controlled by the angle and direction of each slotted cam shaft. This configuration can result in a simple mechanical delivery system that is easy to use. 
         [0155]    More specifically, a first slotted cam shaft  840  engages with a first pin  845  attached to the outer shaft of a delivery system. A second slotted cam shaft  850  engages with a second pin  855  attached to the inner shaft of the delivery system. And, a third slotted cam shaft  860  engages with a third pin  865  attached to a sheath. As a result, as the trigger  825  is closed by being pivoted  885  into the support element  830  about a pivot point  880 , the first pin  845  and second pin  855  will be forced axially forward  870  toward the distal end of the handle  800 , resulting in the inner shaft and outer shaft being extended outwards from the distal end of the handle  800  (and therefore compensating for any foreshortening of the stent during deployment). Simultaneously, the third pin  865  will be pulled axially rearwards  875  toward the proximal end of the handle  800 , resulting in the sheath being pulled rearwards  875  towards the handle  800  (and therefore exposing the stent). 
         [0156]    The first slotted cam shaft  840  includes a bend  890 , resulting in the first pin  845  (and therefore the outer shaft) being moved forward  870  initially before being moved in a rearward direction  875  during a second portion of the closing motion. In alternative embodiments, any one or more of the cam shafts can be curved, bent, and/or angled in any appropriate manner to produce the required forwards and/or rearward movement of each element of the delivery system. In a further alternative embodiment, none of the cam shafts include a bend. 
         [0157]    As before, a luer lock  895  can be placed at a proximal end of the handle  800  to provide a coupling element for a cement delivery device, such as a syringe. In one embodiment, a bump  892  on a rear portion of one or both of the cam plates  820  can engage and force the release of an end cap on the handle  800 , thus exposing the luer lock  895  and prompting the user to begin the next stem of the process. In an alternative embodiment, no bump is required, and the end cap of the handle  800  is instead removed manually. 
         [0158]    In one embodiment, the delivery system may include a locking mechanism adapted to releasably lock the delivery system within a cannula in a required circumferential orientation, to ensure the correct positioning of the stent within the cavity created within the vertebral body. In one embodiment, a spring loaded locking mechanism on the cannula may engage a portion of the handle of the delivery system to releasably lock it in place, with one or more buttons, switches, knobs, or other appropriate user elements, either on the cannula or on the handle of the delivery system, releasing the locking mechanism when the delivery system is to be removed. In one embodiment, the cannula can include a sliding element adapted to engage a protruding flange at a distal end of a handle of a delivery system to releasably lock the delivery device into the cannula. An example cannula  900  including a sliding element  910  for releasably engaging a protruding flange of a delivery system  920  can be seen in  FIG. 9 . In further embodiments, any other appropriate means of releasably locking the delivery system to the cannula in a required circumferential configuration can be used. 
         [0159]    In one embodiment, a key may be positioned on the hollow elongate shaft to mate with a slot in the cannula to ensure that the delivery system is inserted into the cannula in the desired orientation. In an alternative embodiment, at least a portion of the distal end of the handle of the delivery system can be configured to mate with a portion of the cannula, thus ensuring the positioning of the delivery system in the correct orientation. 
         [0160]    In one embodiment, as described above, the delivery system can be used to deploy a stent within a cavity created within a vertebral body, wherein the handle is adapted to control multiple components of the delivery system with a movement of a single user control mechanism, such as a rotation, sliding, or triggering of a user control mechanism. 
         [0161]    Another example delivery system  1000 , including a rotating user control mechanism  1040  on the handle  1010 , can be seen in  FIGS. 10A to 10C . The rotating user control mechanism can include, but is not limited to, a rotational cam mechanism or a rotational threaded mechanism. In an alternative embodiment, a gear mechanism, a sliding belt or triggering mechanism, or any other appropriate mechanism, as described herein, can be used in place of the rotating user control mechanism  1040  to move the inner shaft, outer shaft, and/or sheath, as required. 
         [0162]    As with certain other embodiments of the invention described herein, the delivery system  1000  includes a handle  1010 , an elongate shaft  1020 , including a key component  1025 , a top cap  1030 , and a number of user interface elements. The user interface elements include a rotating user control mechanism  1040  and two stent release buttons  1050 . In an alternative embodiment, a lesser or greater number of stent release buttons can be used. In one embodiment, the stent release buttons  1050  can be replaced by one or more switches, knobs, sliding elements and/or other appropriate user elements, or combinations thereof, as required. 
         [0163]    In one embodiment, one or more additional user input mechanisms  1060  can be incorporated into the handle  1010 . These user input mechanisms  1060  can include, but are not limited to, delivery system release mechanisms, stent deployment and/or release mechanisms, a mechanism for controlling the curvature of a distal end of one or more of the elongate shafts, or any other appropriate control, delivery, and/or deployment function control elements. In alternative embodiments, the user input mechanisms  1060  can include, but are not limited to, buttons, switches, dials, sliding elements, or other appropriate mechanical or electrical input elements. In one example embodiment, the user input mechanism  1060  is a delivery system release mechanism adapted to allow the delivery system  1000  to be unlocked and disengaged from a cannula or other working channel. Again, any other appropriate user element on the delivery system  1000  and/or cannula can be used to release the delivery system  1000  from the cannula upon completion of the stent deployment. In a further alternative embodiment, there are no additional user input mechanisms  1060 . 
         [0164]    A method of using the delivery system  1000 , in accordance with one embodiment of the invention, can be seen in  FIGS. 11A to 11D . This embodiment includes first inserting the delivery system  1000  into the cannula and locking it in position in a predetermined set orientation.  FIG. 11A  shows the delivery system  1000  in its initial configuration after insertion into a cannula (not shown). The rotating user control mechanism  1040  on the handle  1010  of the delivery system  1000  can then be rotated, resulting in the outer sheath of the elongate shaft being retracted while the inner and outer shafts are moved forward to compensate for any foreshortening of the stent during retraction of the sheath, as described above.  FIG. 11B  shows the delivery system  1000  after rotation of the rotating user control mechanism  1000 . 
         [0165]    Once the sheath has been retracted, the top cap  1030  of the handle  1010  can be removed, and a syringe or other cement deployment device can be attached to a luer lock  1070  (or other appropriate connection means) at the proximal end of the handle  1010 .  FIG. 11C  shows the handle  1010  with a top cap  1030  removed. Cement can then be injected through the delivery system  1000  and into the stent. Once the required amount of cement has been delivered into the stent, the syringe can be removed. 
         [0166]    The stent release buttons  1050  can then be depressed and slid towards the proximal end of the handle  1010  (i.e. away from the elongate shaft  1020 ) to release the stent from the elongate shaft  1020 .  FIG. 11D  shows the delivery system  1000  with the stent release buttons  1050  depressed and slid towards the proximal end of the handle  1010  to release the stent. The delivery system  1000  can then be safely removed by activating a delivery system release button, or other appropriate mechanism, to disengage the delivery system  1000  from the locking mechanism on the cannula, and removing the delivery system  1000  from the cannula while leaving the disengaged stent within the vertebral body. 
         [0167]    In one embodiment of the invention, a distal end of an elongate shaft can include a preformed curvature. The elongate shaft can include, but is not limited to, an inner shaft, an outer shaft, a tubular sheath, a flexible guidewire, and an internal polymer extrusion. The elongate shaft, or a portion thereof, can be constructed from a metal including, but not limited to, nitinol, steel, aluminum, or any other appropriate material such as, but not limited to, a plastic. The distal end of the elongate shaft can also include a slotted arrangement allowing the distal end of the elongate shaft to curve and/or preferentially buckle in a specified direction. This curving of the distal end of the elongate shaft can be controlled by a curvature control mechanism located, for example, within the handle of the delivery system. In an alternative embodiment, the elongate shaft can preferentially buckle in response to a force imposed on the distal end of the elongate shaft by the surrounding bone and/or tissue within the vertebral body. Example elongate shafts with preformed and controlled curvature and/or preferential buckling are described in the related U.S. patent application Docket No. SOT-004, entitled “Devices and Methods for Vertebrostenting,” and filed of even date herewith, and U.S. application Ser. No. 11/091,232, the disclosures of which are being incorporated herein by reference in their entirety. 
         [0168]    In one embodiment of the invention, a stent for use with the apparatus and methods described herein can include an attachment mechanism at a distal end thereof (i.e. at the end of the stent remote from the elongate shaft). This attachment mechanism can releasably attach to one or more elongate elements extending through the interior of the elongate shaft. 
         [0169]    In operation of one embodiment, the elongate element extending through the elongate shaft and attaching to the distal end of the stent can be used to hold the stent in a collapsed configuration prior to deployment in place of, or in addition to, a sheath. When the stent is ready to be deployed, the attached elongate element can be used to pull the distal end of the stent rearwards towards its proximate end (i.e. the end of the stent releasably attached to the distal end of the elongate shaft) in order to assist in expanding or to forcibly expand the stent. This may be advantageous in embodiments of the invention using a stiffer and/or thicker stent, that may benefit from additional external forces to assist in its expansion or to provide positive forces on the walls of a cavity in which it is inserted. For example, a stiffer stent, with a more substantive mesh structure, can be used to provide a jacking force to expand the size of a cavity and/or jack or push two walls of a collapsed vertebral body apart. In this embodiment, the self-expanding nature of the stent may not provide sufficient force in and of itself to provide a jacking force of desired magnitude. The additional force needed to allow the stent to jack the walls apart can be provided by the pulling force applied to the distal end of the stent by the releasably attached elongate element. After the stent has been expanded, the elongate element can be released from the stent and removed through the elongate shaft. 
         [0170]    The elongate element releasably attached to the distal end of the stent can also be advantageous in embodiments where a cavity has not been reamed out in the vertebral body, or other structure, but rather only a drill hole has been created in the vertebral body sufficient in size to receive the stent in a collapsed configuration. In this embodiment, the elongate element can be used to pull on the distal end of the stent and assist in expanding it into the body structure surrounding the drill hole. This method may be useful, for example, in the treatment of seriously degraded vertebral bodies, where the stent can be expanded into the surrounding degraded bony structure with nominal additional force. 
         [0171]    An example stent deployment method including a stent with an attachment mechanism at its distal end can be seen in  FIGS. 12A to 12D . In this embodiment, a stent  1205  is releasably attached at its proximal end  1210  to an elongate shaft  1215  including an inner shaft  1220  and an outer shaft  1225 . The means of releasably attaching the stent  1205  to the elongate shaft can include any of the mechanisms and methods described herein. 
         [0172]    A ferrule  1230  is placed against the interior wall of the distal end  1235  of the stent  1205 , with a locking ring  1240  holding the ferrule  1230  in place against the wall of the distal end  1235  of the stent  1205 , for example by a radial interference fit. The ferrule includes a hollow proximate end  1245  with two slots  1250  formed in the walls thereof. The slots  1250  are adapted to releasably engage an elongate attachment element  1255  with a pair of tangs  1260  at a distal end thereof. The tangs  1260  are bent in towards the central axis  1275  of the elongate attachment element  1255  such that the tips  1265  of the tangs  1260  can be extended into the hollow proximate end  1245  of the ferrule  1230 . In an alternative embodiment, a greater or lesser number of slots  1250  and corresponding tangs  1260  can be used. 
         [0173]    Once the tips  1265  of the tangs  1260  have been extended into the hollow proximate end  1245  of the ferrule  1230 , an inner rod  1270  is extended through the elongate attachment element  1255  to abut against the inner walls of the tangs  1260 . By pushing the inner rod  1270  forward towards the distal end  1235  of the stent  1205 , the inner rod  1270  pushes the ends of the tangs  1260  outwards from the central axis  1275  of the elongate attachment element  1255  such that the tips  1265  are forced into the slots  1250  in the ferrule  1230 . As a result, the elongate attachment element  1255  becomes releasably coupled to the ferrule  1230  and can therefore provide a pulling force to the distal end  1235  of the stent  1205 . 
         [0174]    In operation, the elongate attachment element  1255  is coupled to the ferrule  1230  prior to deploying the stent  1205  in the vertebral body. To facilitate insertion of the stent  1205  through the cannula, and into the vertebral body, the elongate attachment element  1255  is pushed forwards against the distal end  1235  of the stent  1205  to force the stent  1205  into a collapsed configuration, as shown in  FIG. 12A . In one embodiment a sheath can be extended over the stent  1205  to hold the stent  1205  in a collapsed configuration, with the sheath being retracted once the stent  1205  is in position within the vertebral body, as described above. In an alternative embodiment, no sheath is required, with the elongate attachment element  1255  providing sufficient force to maintain the stent  1205  in a collapsed configuration. 
         [0175]    Once the stent  1205  has been positioned correctly within the vertebral body, the elongate attachment element  1255  can be pulled back by a set amount, dependent upon the size and shape of the stent  1205 , thus pulling on the distal end  1235  of the stent  1205  and forcing it to expand to its deployed configuration, as shown in  FIG. 12B . Advantageously, as the distal end  1235  of the stent  1205  is pulled back, the proximal end  1210  of the stent can be advanced or pushed forward, in order to expand the stent  1205  while leaving a midpoint of the stent  1205  in essentially a fixed position in the cavity in the vertebral body. This coordinated action of retracting the distal end  1235  while advancing the proximal end  1210  can be accomplished using the types of mechanisms described above located in the handle. 
         [0176]    After the stent  1205  has been positioned in its deployed configuration, the inner rod  1270  can be pulled out from the elongate attachment element  1255 , as shown in  FIG. 12C . As the inner rod  1270  is pulled out, the tangs  1260  collapse back into their initial configuration (i.e. bent in towards the central axis  1275  of the elongate attachment element  1255 ). This in turn removes the tips  1265  of the tangs  1260  from the slots  1250  of the ferrule  1230 , thus disengaging the elongate attachment element  1255  from the ferrule  1230 . The elongate attachment element  1255  can then be pulled out from the ferrule, leaving the distal end  1235  of the stent  1205  free. 
         [0177]    In one embodiment, the elongate attachment element  1255  is a hollow needle adapted to inject cement into the stent  1205 . In operation, once the inner rod  1270  has been removed and the elongate attachment element  1255  detached from the ferrule  1230 , cement can be injected through the elongate attachment element  1255  and into the interior of the stent  1205  to fill the stent  1205 , as shown in  FIG. 12D . After the stent  1205  has been filled with cement to the volume required, the elongate attachment element  1255  can be removed and the stent  1205  detached from the elongate shaft. In an alternative embodiment, the elongate attachment element  1255  can simply be removed from the elongate shaft  1215  after deployment of the stent  1205 , with cement, or any other appropriate filler material, being injected thereafter into the stent  1205  directly through the inner shaft  1220  of the elongate shaft  1215 , or through a separate cement injection element. 
         [0178]    The elongate attachment element  1255 , elongate shaft  1215 , ferrule  1230 , locking ring  1240 , and inner rod  1270  can be constructed from materials including, but not limited to, a metal (e.g. nitinol, steel, aluminum, or any other appropriate metal), a plastic, and/or a composite material. 
         [0179]    In an alternative embodiment, the ferrule  1230  can be attached to the distal end  1235  of the stent  1205  by any other appropriate method, such as, but not limited to, being glued to, welded to, or otherwise attached to the stent  1205 . In further alternative embodiments, the elongate attachment element  1255  can be releasably attached to the ferrule by any appropriate mechanical, electrical, thermal, or magnetic connection means. 
         [0180]    In alternative embodiments of the invention, any appropriate material, or combination of materials, may be used for the components of the delivery system. Appropriate materials include, but are not limited to, stainless steel, aluminum, plastics, textiles (for the sheath), composite materials, or any combination thereof. The delivery system may be configured with all, or only some of, the components described herein, depending upon the specific requirements of the system. 
         [0181]    The delivery system may be configured to deliver cement, cement analogue, or other appropriate filler material, to any appropriate stent, bag, or other fillable device. In one embodiment, the stent need not have holes for the directed exit of the cement into the vertebral body. The delivery system may be configured to delivery a stent, or other device, to a cavity in any bony structure, and not just a vertebral body. Additionally, any appropriately shaped cavity may be treated with the above-mentioned delivery system and stents. 
         [0182]    It should be understood that alternative embodiments, and/or materials used in the construction of embodiments, or alternative embodiments, are applicable to all other embodiments described herein. 
         [0183]    The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The foregoing embodiments, therefore, are to be considered in all respects illustrative rather than limiting the invention described herein. Scope of the invention is thus indicated by the appended claims, rather than by the foregoing description, and all changes that come within the meaning and range of equivalency of the claims are intended to be embraced therein.