Abstract:
A needle assembly  10  compromising an infusion needle  11  that includes a needle cannula  13  made of a superelastic material such as Nitinol. The needle cannula is cold-worked or heat annealed to produce a preformed bend  16  that can be straightened within passageway  21  of a coaxial outer cannula  12  for introduction into the body of a patient. Upon deployment from the outer cannula, the needle cannula substantially returns to the preformed configuration for the introduction or extraction of materials at areas lateral to the entry path of the needle assembly. The needle assembly can compromise a plurality of needle cannulae than can be variably arranged or configured for attaining a desired infusion pattern.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is divisional of U.S. patent application Ser. No. 12/255,990, filed Oct. 22, 2008, which is a continuation of U.S. patent application Ser. No. 11/281/151, filed Nov. 17, 2005, which is a continuation of U.S. patent application Ser. No. 10/678,774, filed Oct. 3, 2003, now abandoned, which is a continuation of U.S. patent application Ser. No. 10/201,112, filed Jul. 22, 2002, now abandoned, which is a continuation of U.S. patent application Ser. No. 09/668,067, filed Sep. 22, 2000, now U.S. Pat. No. 6,425,887 issued Jul. 30, 2002, which is a divisional of U.S. patent application Ser. No. 09/457,844, filed on Dec. 9, 1999, now U.S. Pat. No. 6,592,559 issued Jul. 15, 2003, which claims the benefit of U.S. Provisional Patent Application Ser. Nos. 60/111,624, filed Dec. 9, 1998 and 60/130,597 filed Apr. 22, 1999, each of which is hereby incorporated herein by reference. 
     
    
     TECHNICAL FIELD 
       [0002]    This invention relates generally to medical devices and more particularly to needles that are curved for indirect infusion access within the body. 
       BACKGROUND 
       [0003]    Medical procedures involving the vertebrae are typically complicated because of the preciseness required to avoid both neural damage and injury to major blood vessels, as well as the indirect path that is usually required to access the treatment site. 
         [0004]    This is certainly the case when performing a vertebroplasty, a procedure whereby bone cement, most commonly methyl methacrylate, is injected into a vertebral body to provide stabilization and/or pain relief in selected patients having a spinal condition such as osteolytic metastasis and myeioma, painful or aggressive hemangiome (benign lesions of the spine), or painful osteoporotic vertebral collapse. 
         [0005]    Standard treatment practice depends on the region of the spine being treated. For the cervical vertebrae, anterolateral access is used with a 15 gauge needle. The large vessels adjacent to the vertebra are laterally manipulated by the radiologist to provide an access site between the vessels and the pharyngolarynx. An upward access route is required because the needle must be introduced below the mandible. 
         [0006]    When accessing the thoracic or lumbar vertebrae, typically a large 10 gauge needle is used following a transpedicular or posterolateral approach. The transpedicular route is preferred to avoid spinal nerve injury and to decrease the probability of the cement leaking into tissues adjacent to the vertebral body. 
         [0007]    To obtain complete fill of a damaged vertebral body, it is often required that a second transpedicular access be made from the opposite side. A single infusion usually cannot fill the entire target area because the needle tip cannot be redirected from the original plane of entry. Continued infusion of cement from the first access site will usually not result in an adequate infusion due to the tendency of the material to set before it fills all of the affected area, thereby becoming a baffle to itself. Furthermore, the thick density of the marrow and structures, such as veins, usually acts to impede free flow of the cement within the vertebral body. 
         [0008]    Another concern during the procedure is accidental puncture of the these veins. Because vertebral veins lead directly to the lungs, there is a significant risk of pulmonary embolism if cement is accidentally introduced therein. 
         [0009]    The inability to adequately maneuver the needle cannula tip within a body or around structures is a major limitation of the straight needle. Additional needle sticks to complete a medical procedure result in discomfort to the patient and additional risk of leakage and other complications. 
         [0010]    To sufficiently access a vertebral body for complete infusion of cement, the needle tip must be capable of being deflected at significantly large angles from the original axis. This would require that the needle have a distal bend so that the needle could be rotated to selectively direct the material. 
         [0011]    Rigid curved needles are well known for suturing applications; however, adding anything more than a slight bend to an infusion needle limits its access path and ability to deeply penetrate tissue, especially bone. For example, a rigid curved needle is unsuitable for use in a vertebroplasty procedure where the needle cannula must be driven through the bone and deep into the vertebral body using a relatively straight approach and maintained in place to avoid additional damage to the entry site. While the initial needle access must be done with a straight needle of sufficient strength to penetrate bone, the ideal approach would be to direct a lateral infusion of cement following needle penetration, and then to withdraw the needle along its original path. 
         [0012]    Accomplishing this is problematic. The tissue density and resistance of the tissue to penetration at the treatment site can require that the inner infusion member be nearly as stiff as the outer piercing cannula. A certain degree of needle rigidity is required in order to be able to maneuver the needle and accurately direct flow of material. 
         [0013]    While stainless steel needles having a slight distal bend are known, the amount of needle curvature necessary to provide adequate lateral infusion is not possible—the needle plasticly deforms once inside the outer restraining cannula and hence is unable to return resiliently to its preformed shape. Thus, a second needle access would still be required to provide adequate filling. 
         [0014]    Other medical procedures present similar problems when a single straight needle is used. One example is tumor ablation where percutaneous ethanol injection is used to treat carcinoma of the liver and kidney. Originally introduced as a palliative treatment for inoperable hepatocellular carcinoma of the liver, ethanol injection has now been shown to have curative potential comparable to resection in many patients, especially for smaller tumors. 
         [0015]    Practice has been to inject ethanol directly into masses using a straight needle and to allow the ethanol to infuse from one or more side holes into the tissue. The problem is that the infusion may not penetrate any deeper than the needle tract; thus portions of the tumor are not effectively treated. It is desirable to provide a device for more effective infusion of ethanol into the tumor mass. 
       SUMMARY OF THE INVENTION 
       [0016]    The foregoing problems are solved and a technical advance is achieved in an infusion needle made of rigid superelastic material and having at least one performed bend along the distal portion of its length. The needle is used as an inner cannula coaxially with a second hollow cannula for restraining the inner needle cannula in a substantially straight orientation during percutaneous introduction to the target site, whereby the inner needle cannula is deployed to resiliently return to its preformed configuration. 
         [0017]    The ability of the preformed inner needle cannula to deflect laterally upon exiting the outer cannula allows the inner needle cannula to infuse or aspirate material at multiple points within different planes in the body as the inner infusion needle rotates about its longitudinal axis. This helps to reduce or eliminate the need for additional “sticks” with the outer cannula; it also allows the operator to make an entry from one direction, then to deploy the curved inner cannula to reach a site that cannot be accessed directly, such as where another structure lies along the access path, thereby blocking the target site. 
         [0018]    The preferred material for the inner cannula is a superelastic, shape memory alloy such as sold under the trademark Nitinol (Ni—Ti); however, there are other non Ni Ti alloys that may be used. A Nitinol alloy is desirably selected that has properties whereby the temperature at which the martensitic to austenitic phase change occurs is lower than the working temperature of the device (i.e. room temperature). 
         [0019]    As described in U.S. Pat. No. 5,597,378, incorporated herein by reference, a permanent bend may be heat set in a superelastic Nitinol cannula by maintaining the cannula in the desired final shape while subjecting it to a prescribed high temperature for a specific time period. The resulting cannula can be elastically manipulated far beyond the point at which stainless steel or other metals would experience plastic deformation. Nitinol and other superelastic materials when sufficiently deformed undergo a local phase change at the point of stress to what is called “stress-induced martensite” (SIM). When the stress is released, the material resiliently returns to the austenitic state. 
         [0020]    A second method of imparting a permanent bend to the needle material is by a process commonly known as “cold working.” Cold working involves mechanically overstressing or overbending the superelastic cannula. The material within the bending region undergoes a localized phase shift from austenite to martensite and does not fully return to its original shape. In the case of the cold-worked cannula, the result is a permanent curve about the bending zone which has been locked in to at least a partial martensitic crystalline state. 
         [0021]    In contrast, when heat treating is used, the entire heat-annealed cannula is in a austenitic condition, even in the curved region, and is only temporarily transformed to martensite under sufficient bending stresses. Therefore, the flexural properties of the annealed cannula vary little across its length. 
         [0022]    Conversely, the bend of a cold-worked cannula, which contains martensite, has increased resistance to deformation and therefore holds its shape better than the more flexible bend of the pure austenitic cannula This increased rigidity can be an advantage for certain clinical applications. 
         [0023]    In one aspect of the invention, an introducer trocar or stylet is used with either the outer or inner needle cannula, depending on the luminate size of the needle, to facilitate access to tissue and/or prevent coring tissue into the distal tip of the needle device. The infusion needle or inner cannula is introduced through the outer cannula after access has been established and the trocar or stylet is removed. 
         [0024]    Depending on the size of the cannulas, the degree of the preformed bend, or the method used to form the bend, the inner cannula or needle may slightly deform the outer cannula as the preformed bend present in the inner needle or cannula is constrained within the outer cannula. As a result, the outer cannula may be deflected a few degrees from its normal longitudinal axis at a point corresponding to the bend of the inner cannula. As the inner cannula is deployed from the outer cannula, the inner cannula deflects laterally until the entire region of the bend is unsheathed. The distal opening of the inner cannula is oriented at a large angle (preferably within the range of 60-90° from the original longitudinal axis when the inner needle is fully deployed. 
         [0025]    The ability of the inner cannula to deflect at a significant angle from the original longitudinal axis has great utility in a number of applications where straight access is required followed by redirection of the distal opening. This deflection permits access to a different site without the necessity of withdrawing and reintroducing the needle. 
         [0026]    A primary example of such a procedure is vertebroplasty in which infusion of the stabilizing cement with a straight needle often requires a second stick to provide complete filling to stabilize the vertebral body while avoiding damage to delicate structures such as veins. As with the standard single-needle procedure involving the thoracic or lumbar regions of the spine, a transpedicular approach is normally used whereby the larger outer needle cannula, such as a coaxial Jamshldi-type needle, is introduced into the damaged or diseased vertebral body. The outer needle includes an inner introducer trocar which is then replaced with a inner curved needle for infusion of the cement. 
         [0027]    The ability of the curved needle to deflect laterally and rotate to reach multiple planes gives it a significant advantages over straight needles which have a limited range of movement. Because of this additional range of movement, the curved needle can usually complete the vertebroplasty procedure with a single access of the vertebral body. This avoids additional discomfort and risks to the patient, which include complications from leakage of cement or inadvertent infusion into non-target areas. 
         [0028]    In addition to using the coaxial needle for infusion of cement as above, the device can also be adapted for aspirating material or serving as a conduit for the introduction of other devices. The apparatus may be used for a percutaneous corpectomy, a procedure which involves fusion and decompression of two or more vertebrae by first aspirating tissue from the damaged vertebral bodies, then introducing a prosthesis having a carbon fiber composite cage packed with bone graft material to serve as scaffolding for the affected vertebrae. Once the cage is properly positioned, methyl methacrylate or another suitable material is infused into the vertebral bodies to secure the prosthesis. The percutaneous corpectamy offers less trauma, and with the reinforcement cage, provides superior rigidity over a conventional corpectomy utilizing bone graft material alone. 
         [0029]    In another aspect of the invention, the coaxial needle can be adapted for paraspinal use to inject medicaments within the neural canal or epidural space as part of management and/or diagnosis of pain. Preferably, the outer cannula has a tip adapted for piercing soft tissue. This outer needle cannula, preferably about twenty-one (21) gauge, is introduced percutaneously parallel to the spinal column along with an internal stylet with matched bevel to prevent coring tissue into the distal opening. The stylet is removed and the curved needle, about twenty-five (25) gauge, is inserted into the outer cannula. The needle assembly is then maneuvered to contact a nerve root during a diagnostic procedure to help recreate pain symptoms of the patient. The inner infusion needle also includes a stylet which is situated within the passageway of the needle as it is directed to the target site. The stylet is then removed from the infusion needle and medicaments, commonly steroids such as celestone (injected with lidocaine), kenalog, or methylprednisone are introduced to the treatment site. The inner needle is then withdrawn into the outer sheathing cannula and both are withdrawn from the patient. 
         [0030]    Another use of the smaller gauge paraspinal needle is for diskography which consists of injecting a contrast agent (preferably nonionic contrast media) directly into the patient&#39;s disk to delineate the extent of any malformation or injury to the vertebral body. 
         [0031]    Yet another aspect of the invention solves the problem of infusion of ethanol into a tumor mass by utilizing a plurality of curved needle cannulae deployed within an cannula introduced into the tumor where the curved needle cannulae radiate outward into an umbrella-shaped configuration. Infusion can take place at multiple points within the tumor to provide wider dispersion of the ethanol. Following treatment, the curved needle cannulae are withdrawn into the cannula and the device is removed from the patient. 
         [0032]    In a related aspect, one or more needle cannulae are located proximal to the distal end of the infusion needle. These proximally-located cannulae allow infusion of medicaments at different points along the length of the device. By having multiple sets of needles arranged in the umbrella configuration, the volume of tissue treated is increased. The coaxial outer cannula includes a plurality of side apertures that allow the proximally-located needle cannulae to deploy after the infusion needle is placed at the desired location in the body and the outer cannula is withdrawn. An outer sheath over the coaxial outer cannula selectively exposes the side apertures to permit the appropriate alignment of needle cannulae and apertures when there are multiple rows of each. 
         [0033]    The invention has applicability in any clinical situation where a straight approach is dictated and there is a need to avoid an obstructing structure (a large vessel, bowel loop, etc.) in the entry path, or the need to redirect the approach to a more lateral pathway to infuse medicaments or aspirate, such as to drain an abscess. 
         [0034]    In addition to infusion or aspiration, the invention can provide a conduit for introducing and/or directing the path of other medical devices within the body such as radio-frequency ablation catheters or wire guides. This would allow a straight approach to a critical juncture whereafter the curved infusion needle can be deployed to precisely proceed to the desired anatomical site, especially in situations such as a luminal bifurcation or when access to an ostium is required. 
         [0035]    Another use of the invention is to place the infusion needle in a bronchoscope or colonoscope which can serve as the outer constraining device. Under visualization, the inner needle then can be directed to perform a biopsy or other type of procedure. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0036]      FIG. 1  is an isometric view of an illustrative embodiment of the curved needle inner cannula; 
           [0037]      FIG. 2  is a top view of an outer needle cannula with an introducer trocar and the inner curved needle cannula; 
           [0038]      FIG. 3  is a top view of the assembly of the inner curved needle cannula inside the outer needle cannula; 
           [0039]      FIG. 4  is an exploded isometric view of a second embodiment of the inner and outer cannula; 
           [0040]      FIG. 5  depicts a pictorial view of the inner cannula of  FIG. 4  with an introducer stylet; 
           [0041]      FIG. 6  is a side view of the inner cannula of  FIG. 4  being initially deployed from the outer cannula; 
           [0042]      FIG. 7  is a side view of the inner cannula of  FIG. 4  being further deployed from the outer cannula; 
           [0043]      FIG. 8  is a side view of the inner cannula of  FIG. 4  being still further deployed from the outer cannula; 
           [0044]      FIG. 9  is a partially sectional view depicting the apparatus of  FIG. 2  being introduced into a vertebral body; 
           [0045]      FIG. 10  is a partially sectional view similar to  FIG. 9 , depicting of the apparatus of  FIG. 2  infusing cement into a vertebral body. 
           [0046]      FIG. 11  is a broken, partially sectioned view similar to  FIGS. 9 and 10 , depicting of the apparatus of  FIG. 2  infusing additional cement into a vertebral body. 
           [0047]      FIG. 12  is an isometric view of a third embodiment of the apparatus; 
           [0048]      FIG. 13  is a side view of the multi-directional infusion needle illustrated in of  FIG. 12 ; 
           [0049]      FIG. 14  is a broken, side view of the needle of  FIG. 13  partially showing the needle deployed; 
           [0050]      FIG. 15  is a side view of a trocar introducer used with the embodiment of  FIG. 12 ; 
           [0051]      FIG. 16  is a side view of the proximal assembly portion of the apparatus illustrated in  FIG. 12 ; 
           [0052]      FIG. 17  is a side view of a fourth embodiment of the apparatus; 
           [0053]      FIG. 18  is a broken, partially-sectioned side view of the apparatus illustrated in  FIG. 17  prior to deployment; 
           [0054]      FIG. 19  is a transverse cross-sectional view of coaxial outer cannula depicted in  FIG. 17 ; 
           [0055]      FIG. 20  depicts cross-sectional views of two embodiments of coaxial outer cannula depicted in  FIG. 17 ; 
           [0056]      FIG. 21  is an isometric view of a fifth embodiment of the present apparatus; and 
           [0057]      FIG. 22  is an isometric view similar to that of  FIG. 21  showing the apparatus fully deployed. 
       
    
    
     DETAILED DESCRIPTION 
       [0058]      FIG. 1  depicts a needle assembly  10  comprising an infusion needle  11  with a preformed bend  16  for lateral infusion or aspiration of medicaments and other materials. As defined herein, the “needle assembly  10 ” can comprise infusion needle  11  alone or infusion needle  11  in combination with other components. The “infusion needle  11 ” as defined herein comprises one or more needle cannulae having a preformed bend  16 . 
         [0059]    The infusion needle  11  of  FIG. 1  is comprised of a superelastic alloy needle cannula  13 , preferably the alloy sold under the trademark Nitinol, that is soldered or otherwise affixed to a well-known needle hub  14  using one of a selected number of well-known techniques, including that of Hall described in U.S. Pat. No. 5,354,623 whose disclosure is expressly incorporated herein by reference, and a flange  23  which has a first tapered or pointed end  24  whose shape is readily distinguishable from the second, squared end  42 . 
         [0060]    First end  24  corresponds to the direction of preformed bend  16  in needle cannula  13  of infusion needle  11 . Bend  16  is formed in the Nitinol needle cannula  13  by either the well-known process of deforming the cannula under extreme heat for a prescribed period of time, which produces a cannula entirely in the austenitic state, or by cold working the cannula, which involves applying a large amount of mechanical stress to deflect the  15  cannula well beyond the desired amount of permanent bend. Cold working permanently locks a crystalline structure in the bending zone into at least a partial martensitic condition while the unstressed portions of the cannula remain in the austenitic state. 
         [0061]    Cold worked Ni—i alloys are discussed in “Linear Superelasticity In Cold-Worked Ni—Ti”, (Zadno and Duerig) pp. 414 to 419,  in Engineering Aspects of Shape Memory Alloys , Butterworth-Heineman, Boston, Mass. (Duerig et al, editors) which is incorporated herein by reference. In addition to Nitinol, superelastic or pseudoelastic copper alloys, such as Cu—Al—Ni, Cu—Al—Zi, and Cu—Zi, are available as alternative needle cannula materials. Flexible polymeric materials with sufficient rigidity for both deployment and shape memory to assume a desired curve may also be used in certain applications, either alone or in combination with reinforcing metal components such as a metal braid or tip. 
         [0062]    Preformed bend  16  of infusion needle  11  forms a distal portion of needle cannula  13 , preferably close to about 25% of the length of needle cannula  13  in the embodiment shown in  FIG. 1 . The large size of the infusion needle, preferably 10 to 18 gauge, makes this particular embodiment suitable for penetrating a vertebral body to perform a vertebroplasty or percutaneous corpectomy procedure. A more preferred range is 12 to 17 gauge, with the most preferred cannula size being 13 to 15 gauge. 
         [0063]    With regard to a vertebroplasty and corpectomy procedures, the larger gauge cannula has both the strength to penetrate dense bone material as well as a sufficient lumen diameter to aspirate material from the vertebral body and to infuse highly viscous bone cement, such as methyl methacrylate. The preferred preformed bend  16  of the infusion needle  11  has a constant radius. For the embodiment of  FIG. 1 , the preferred radius of distal bend  16  is approximately 3.0 cm for a 13 gauge needle, and approximately 2.5 cm for a 14 gauge needle. Although the illustrative embodiment has a constant bend radius, an increasing or decreasing radius bend could be employed for certain clinical applications. Furthermore, it is possible to introduce more than one bend into the superelastic cannula for applications requiring a special needle configuration. 
         [0064]    The primary purpose of using a Nitinol or other superelastic alloy cannula is that the cannula can be constrained into one shape during passage to the treatment site, then deployed into the preformed configuration without experiencing any plastic deformation. 
         [0065]      FIG. 2  depicts a pair of needles to be used coaxially in that manner, including the infusion needle  11  of  FIG. 1  and a coaxial outer cannula  12  for maintaining inner infusion needle  11  in a substantially straight configuration while being introduced to the treatment site. The embodiment depicted in  FIG. 2  is Jamshidi-type needle (Manan Inc., Northbrook, Ill.) which is a two-part needle assembly  43 , and is most commonly used for accessing dense, hard tissue such as bone, fibrous material, etc. Thus, it is well suited for penetrating the wall of a vertebral body wherein the infusion needle  11  can be deployed. 
         [0066]    The two-part needle assembly  43  includes a coaxial outer cannula  12  having a stainless steel cannula  19  with an inner passageway  21  that is sufficiently large to accommodate inner infusion needle  11 . For example, the standard 11 gauge Jamshidi-type needle suitable for accessing a vertebral body would be used with thirteen (13) gauge inner curved needle. Stainless steel cannula  19  is affixed proximally to a handle  26  and a connector hub  31  (shown in  FIG. 3 ). The connector hub  31  receives the second part of the two-part needle assembly  43 , the coaxial outer cannula introducer  52  which preferably comprises a trocar  25 . The trocar hub  27  locks into handle  26  of coaxial outer cannula  12 . The beveled tip  30  of trocar  25  extends approximately 5 mm beyond the distal tip  22  of coaxial outer cannula  12  and assists in penetration. Trocar  25  also serves to prevent the coaxial outer cannula  12  from coring a sample of bone or other material during access. 
         [0067]    After outer needle assembly  43  has been directed to the target site, trocar  25  is removed from coaxial outer cannula  12  and infusion needle  11  is inserted into passageway  21  of the coaxial outer cannula  12 , as shown in  FIG. 3 . To maintain openness of the infusion needle passageway  15  and to prevent tissue coring during deployment, an inner needle introducer stylet  46  can be introduced coaxially inside the infusion needle. Inner needle introducer stylet  45  includes a handle  83  and a shaft  46  which is made of a flexible, high-tensile. polymeric material such as polyetherethylketone (PEEK) to allow stylet  45  to assume the contour of preformed bend  16  after deployment. 
         [0068]    Inner infusion needle  11  straightens as it is loaded into coaxial outer cannula  12 . As the portion including preformed bend  16  of infusion needle  11  extends out from tip  22  of coaxial outer cannula  12  as depicted in  FIG. 3 , infusion needle  11  assumes the preformed shape due to the superelastic properties of needle cannula  13 . For infusion, inner needle introducer stylet  52 , which helps prevent coring of tissue into passageway  21  of coaxial outer cannula  12 , is removed. The tapered or “arrow” end  24  of flange  23  of proximal hub  14  corresponds with the deflection plane  29  of infusion needle  11 . 
         [0069]    By maneuvering flange  28 , the inner curved needle  13  can be rotated in either direction  28  to reorient the plane of deflection  29  and place the tip opening  17  at multiple locations within the area being treated. 
         [0070]    In  FIG. 3 , tip  17  is deflected at an angle  44  of approximately 60° to 70° from the device longitudinal axis  18 . This gives, for example, with a thirteen (13) gauge infusion needle  11 , a lateral reach, measured from tip  17  to longitudinal axis  18 , of nearly thirty (30) millimeters in any direction. 
         [0071]    While the degree of deflection required is determined by the application and desired lateral reach of the device, it is also limited by the size of the cannula if the permanent bend is cold worked into the material. Cold working provides a stiffer bend which can be advantageous in certain applications such as vertebroplasty and biopsy of dense tissue; it is more difficult to permanently deform a larger gauge Nitinol cannula without application of extreme heat. For the embodiments contemplated, the angle of deflection  44  can encompass a range of 30° to 110° , with a preferred range of 40 to 90° for most applications. 
         [0072]      FIG. 4  depicts a second version of the inner curved needle and sheathing outer needle adapted for use in the injection of medicaments, contrast media, or other non-viscous agents. The infusion needle  11  is comprised of a smaller gauge needle cannula  13 , preferably around twenty-five (25) gauge, mounted to a proximal hub  14 . The preformed bend  16  of individual needle cannula  13  has a slightly tighter radius than that illustrated in  FIGS. 1 through 3 . 
         [0073]    Still referring to  FIG. 4 , the coaxial outer cannula  12  includes a correspondingly sized needle cannula  19 , preferably around twenty-one (21) gauge, attached to a standard needle hub that is adapted to receive proximal hub  14  of infusion needle  11 . The embodiment of  FIG. 4  is used with a plurality of stylets that are inserted within both the inner and outer needles during their respective introduction into the body. The first is an outer cannula introducer stylet  52  that is inserted into the passageway  21  of coaxial outer cannula  12 . The coaxial outer cannula  12  and outer cannula introducer stylet  52  are inserted together into the patient. The stylet, which is preferably a stainless steel stylet wire  46  with an attached standard plastic needle hub  47 , prevents the coaxial outer cannula  12  from coring tissue into passageway  21  at distal tip  22 . 
         [0074]    Once coaxial outer cannula  12  is in position, outer cannula introducer stylet  52  is withdrawn from coaxial outer cannula  12  and infusion needle  11  and second introducer stylet  45  are inserted together into outer needle passageway  21 . The inner needle introducer stylet  45 , which is longer than outer cannula introducer stylet  52  in order to fit the longer infusion needle  11 , serves a similar function to the outer cannula introducer stylet  52  by preventing coring of tissue when infusion needle  11  is deployed from coaxial outer cannula  12 . 
         [0075]    As illustrated in  FIGS. 4 and 5 , proximal hub  14  of infusion needle  11  is adapted such that hub  53  of inner needle introducer stylet  45  locks together with proximal hub  14  to keep the two in alignment. This locking mechanism includes a molded protuberance  49  on hub  53  that fits within a recess  50  on proximal hub  14 . The purpose of maintaining alignment of hub  53  and proximal hub  14  is to match the beveled surface  51  at the tip of the inner needle introducer stylet  45 , shown in  FIG. 5 , with the beveled edge at the tip  17  of infusion needle  11 . 
         [0076]      FIGS. 6 through 8  depict the deployment of infusion needle  11  from within outer needle cannula  12 .  FIG. 6  shows infusion needle  11  during initial deployment from coaxial outer cannula  12 . The preformed bend  16  of the infusion needle  11  is constrained by the cannula  19 ; however, as illustrated in  FIG. 6 , preformed bend  16  may be of sufficient stiffness to slightly deform outer cannula  19  while infusion needle  11  is inside coaxial outer cannula  12 . Despite this slight deformation, coaxial outer cannula  12  is still substantially straight. 
         [0077]    As depicted in  FIG. 7 , stress preformed bend  16  places on outer cannula  19  relaxes as infusion needle  11  is further deployed and the angle of deflection  44  (measured from longitudinal axis  18  of coaxial outer cannula  12  to the opening at tip  17  of infusion needle  11 ) is increased. As infusion needle  11  is further deployed as depicted in  FIG. 8 , fully exposing preformed bend  16  to produce the largest angle of deflection  44 , the unstressed outer cannula returns to a straight configuration. 
         [0078]    The phenomenon depicted in  FIGS. 6 through 8  is most noticeable when using smaller gauge cannulae, such as shown in  FIGS. 4 and 5 . The larger gauge outer cannula of  FIGS. 1 to 3  is more resistant to deformation than that of  FIGS. 4 and 5 . Naturally, the tendency of the stressed outer cannula to deform is also very much dependent on the stiffness and radius of the preformed bend  16  as well as the thickness of the cannula wall and material used. To eliminate this deformation during introduction of the device into the body, stylet  45 , as depicted in  FIG. 5 , can be used as a stiffener until removed immediately before the portion having preformed bend  16  is deployed. 
         [0079]      FIGS. 9 through 11  depict the use of the device illustrated in  FIG. 3  to perform a vertebroplasty procedure on a pathological vertebral body  33  using a transpedicular approach. As depicted in  FIG. 9 , coaxial outer cannula  12  with introducer trocar  25  is introduced through the wall  38  and into the marrow  37  of the vertebral body  33 . The transpedicular route of access places the needle between the mammillary process  34  and accessory process  35  of the vertebral arch  55 . The vertebral arch  55  is attached posteriorly to the vertebral body  33  and together they comprise the vertebra  54  and form the walls of the vertebral foremen  36 . 
         [0080]    Once coaxial outer cannula  12  and inner introducer trocar  25  are within the internal region or marrow  37  of the vertebral body, trocar  25  is withdrawn from the coaxial outer cannula  12  and infusion needle  11  is inserted in its place.  FIG. 10  depicts infusion needle  11  infusing bone cement  41 , commonly methyl methacrylate, into vertebral body  33  to provide it with improved structural integrity. As depicted in  FIG. 11 , infusion needle  11  can be partially withdrawn or rotated to obtain more complete filling or to avoid the network of vertebral veins. Even though the vertebral body may not need to be completely filled, the density of marrow  37  would still necessitate a second transpedicular stick in the absence of the instant apparatus infusing cement within multiple planes within vertebral body  33 . Upon completion of the procedure, infusion needle  11  is withdrawn back into coaxial outer cannula  12  and both are removed from vertebral body  33 . 
         [0081]    The utility of the hollow, curved superelastic needles is certainly not limited to procedures involving the spine. Such needles are useful at many sites within the body that might require straight access by a needle, followed by indirect or lateral infusion, aspiration, or sampling. For example, the inner needle could be adapted to take biopsy samples from dense tissue, such as a breast lesion, especially where indirect access is might be desirable. 
         [0082]      FIG. 12  is an isometric view of hollow, curved superelastic needles in which needle assembly  10  comprises a multiple needle assembly  70  useful in infusion of ethanol or other medicaments into a tumor. In  FIG. 12 , needle assembly  10  comprises an infusion needle  11 , which includes a multiple needle assembly  70  comprising a plurality of needle cannulae  13 , each having a preformed bend  16 , a proximal assembly  58  for constraining the multiple needle assembly  70 , and a coaxial outer cannula  12  for introducing the multiple needle assembly  70  to its anatomical target. 
         [0083]    The multiple needle assembly  70  in  FIG. 13  includes a base cannula  56  affixed to a proximal hub  14  such as a standard female luer fitting. A plurality of needle cannulae  13  are manifolded into base cannula  56 , preferably evenly spaced in an umbrella configuration  75 , and affixed in place with a solder joint  57 . In the structure illustrated in  FIG. 12 , five needle cannulae  13  are used; from two to as many as appropriate for the given cannula size can be used. As with the other versions, needle cannulae  13  are preferably made of Nitinol that is either annealed or cold-worked to produce the preformed bend  16 . In the structure illustrated in  FIG. 12 , the coaxial outer cannula  12  has an outer diameter of approximately 0.072 inches and an inner diameter of around 0.06 inches, while the individual curved needle cannulae  13  have an outer diameter of 0.02 inches and an inner diameter of about 0.12 inches. As shown in  FIG. 14 , the tips  17  of the needle cannulae  13  may be beveled to better penetrate tissue. 
         [0084]    Deployment of curved needle cannulae  13  of multiple needle assembly  70  is depicted in  FIG. 14 . Needle cannulae  13  are restrained by coaxial outer cannula  12  until multiple needle assembly  70  is advanced, exposing the distal end portions of needle cannulae  13  at distal end  22  of coaxial outer cannula  12 , whereby they radiate outward to assume, when fully advanced, the umbrella configuration  75  shown in  FIG. 13 . 
         [0085]      FIG. 15  depicts a side view of an outer needle assembly comprising a coaxial outer cannula  12  and outer cannula introducer stylet  52  used in placement of the multiple needle assembly  70  of  FIGS. 12 through 14 . The outer cannula introducer stylet  52  is inserted into passageway  21  of coaxial outer cannula  12  with the male proximal hub  47  of the outer cannula introducer stylet  52  fitting into the female proximal hub  20  of coaxial outer cannula  12  when the outer cannula introducer stylet  52  is fully advanced. Outer cannula introducer stylet  52  includes a sharp tip  63 , such as the diamond-shape tip depicted, for penetrating tissue. 
         [0086]    The outer cannula introducer stylet  52  and coaxial outer cannula  12  may be introduced percutaneously into the liver or kidney and placed at the desired treatment location. The outer cannula introducer stylet  52  is then removed. The proximal assembly  58  with the preloaded multiple needle assembly is then advanced into the coaxial outer cannula  12  which remains in the patient. In the version illustrated in  FIGS. 12 through 15 , the coaxial outer cannula preferably has an outer diameter of about 0.095 inches and an inner diameter of about 0.076 inches, while the outer diameter of the inner stylet is preferably about 0.068 inches. 
         [0087]      FIG. 16  a side view of the proximal assembly  58  shown of  FIG. 12 . The Proximal assembly  58  includes a distal male adaptor  60  connected to an intermediate cannula  59  that is sufficiently large to accommodate multiple needle assembly  70 . At the proximal end of the intermediate cannula  59  is proximal assembly female adaptor  61  which is connected proximally to a proximal assembly hub  62 , such as a Tuohy-Borst adaptor. Proximal assembly hub  62  is utilized by the physician during manipulation of the device. 
         [0088]    The multiple needle assembly  70  of  FIG. 13  is loaded into lumen  64  at the proximal end  65  of the proximal assembly hub  62 , with the needle cannulae  13  remaining within intermediate cannula  59 . Distal end  66  of proximal assembly  58  with preloaded multiple needle assembly  70  is then inserted into proximal hub  20  of the coaxial outer cannula as depicted in  FIG. 12 . The multiple needle assembly  70  is then advanced from the proximal assembly  58  into the coaxial outer cannula  12  where it is deployed as depicted in  FIGS. 12 to 14 . Ethanol is infused into multiple needle assembly  70  via the proximal hub  14  of the infusion needle  11 . Following treatment, the multiple needle assembly  70  is withdrawn into coaxial outer cannula  12  and the entire needle assembly  10  is removed from the patient. 
         [0089]      FIGS. 21 and 22  depict a variation of needle assembly  10  of  FIG. 12  in which infusion needle  11  and coaxial outer cannula  12  are connected to a coaxial handle  76  used to advance and deploy multiple needle assembly  70  releasably from constraint of coaxial outer cannula  12 . As shown, coaxial handle  76  comprises a stationary outer component  77  that fits over base cannula  56  of multiple needle assembly  70  and attaches to proximal hub  20 . A slidable inner component  78  further comprises a thumb piece  79  used by the physician to advance or retract the coaxial outer cannula  12  as the slidable inner component  78  retracts into stationary outer component  77 . 
         [0090]    In  FIG. 21 , the needle assembly is depicted in the introducer position with the thumb piece  79  advanced fully forward within a slot  80  in outer slidable component  77 . 
         [0091]      FIG. 22  depicts the deployment state of needle assembly  10  in which thumb piece  79  has been moved to the most proximal position within slot  80 . In this position, coaxial outer cannula  12  is retracted to fully expose the plurality of needle cannulae  13  which can assume their unconstrained configuration with the preformed bends  16 . 
         [0092]    This type of handle can be used with both the multiple and single infusion needle where a introducer trocar or stylet is not required. Other well-known types of coaxial handles  76  include, but are not limited to, screw-type, rachet-type, or trigger-activated handles which allow coaxial outer cannula  12  to be longitudinally displaced relative to infusion needle  11 . To reduce the need for a trocar or stylet for facilitating tissue penetration, distal tip  22  of coaxial outer cannula  12  can be shaped into a needle point such as depicted, or into a non-coring point to help maintain an open outer cannula passageway  21 . 
         [0093]    A syringe or other reservoir container can be attached to proximal hub  14  as an infusate source or for collection of aspirated material. In addition, a reservoir, such as a syringe, can be incorporated internally within coaxial handle  76  of needle assembly  10  or integrally attached thereto. 
         [0094]    Another version of multiple needle assembly  70  is depicted in  FIGS. 17-20  whereby there are one or more groupings of proximally-located needles  73  in addition to the distally-located needles  74  that are similar to those illustrated in of  FIG. 12 . By locating the additional needle cannulae  13  proximal to those at the distal end, wider dispersal and coverage is attained for infusion of medicaments. 
         [0095]    In the version illustrated in  FIG. 17 , there is an arrangement of four needle cannulae comprising the distally-located needles  74 , while at least one other group comprising proximally-located needles  73  located along the length of infusion needle  11  provides for simultaneous infusion in a more proximal location. The needle cannulae  13  of the proximally-located and distally-located needles  73 ,  74  can vary in configuration, length, number, and how they are attached to a base cannula  56  such as that shown in  FIG. 13 . For example, individual needle cannulae  13  within an umbrella configuration  75  or between proximally-located and distally-located needles  73 ,  74  can be longer, or have a different radius than others, to vary the distribution pattern of the infusate. 
         [0096]    As depicted in  FIGS. 17 and 18 , each pair of oppositely-disposed needle cannulae  13  within a grouping of four proximally-located needles  73  are longitudinally offset with respect to the adjacent pair located ninety degrees (90° therefrom, as are the side apertures  67  from which they emerge. With regard to attachment, possibilities include, but are not limited to, having all needle cannulae  13  attaching to a single base cannula  56 ; dividing base cannula  56  such that a separate portion extends distally from the proximally-located needles  73  to join the distally-located needles  74 , or eliminating the base cannula  56  such that needle cannulae  13  of multiple needle assembly  70  are separate and run the length of infusion needle  11 . 
         [0097]    To constrain needle cannulae  13  for introduction along a single pathway into the body, a coaxial outer cannula  12  is used that has side apertures  67  in the cannula to permit the proximally-located needles  73  to deploy outward therethrough for lateral infusion.  FIG. 18  shows a sectioned view of the needle assembly of  FIG. 17  in which the needle cannulae  13  are constrained in the introduction position. An introducer cannula  68  is used to selectively expose side apertures  67  in versions where the arrangement of needles is such that individual needle cannulae  13  may prematurely exit a non-designated hole or row, preventing or delaying proper deployment of the multiple needle assembly  70 . By maintaining the introducer sheath over side apertures  67  until distally-located needles  73  are deployed, proper deployment of all needle cannulae  13  is easier. 
         [0098]      FIGS. 19 and 20  illustrate intraluminal guides  69  to help facilitate proper alignment of needle cannulae  13  with a designated side aperture  67 . In  FIG. 19 , a series of ridges  71  within passageway  21  of coaxial outer cannula  12  guide the needle cannulae  13  to align with a designated side aperture  67 .  FIG. 20  depicts an alternative intraluminal guide  69  in which the needle cannulae  13  travel longitudinally within grooves  72  formed in the inner wall of passageway  21 .