US20090131867A1 - Steerable vertebroplasty system with cavity creation element - Google Patents

Abstract

Methods and devices for augmenting bone, such as in performing vertebroplasty are disclosed. A bone cement injection needle is provided, having a laterally deflectable distal end. The distal end may be provided with a cavity creation element, such as an inflatable balloon. Systems are also disclosed, including the steerable injection needle, introducer and stylet. The system may additionally include a cement delivery gun, one-time use disposable cement cartridges and a cement mixing chamber. Methods are also disclosed.

Description

• This application is a continuation-in-part of U.S. patent application Ser. No. 11/941,764 filed Nov. 16, 2007, the disclosure of which is incorporated by reference herein in its entirety.
• The present invention relates to bone augmentation devices and procedures. In particular, the present invention relates to steerable injection devices and systems for introducing conventional or novel bone cement formulations such as in performing vertebroplasty.
BACKGROUND OF THE INVENTION
• According to the National Osteoporosis Foundation ten million Americans have osteoporosis, and an estimated 34 million with low bone mass are at risk of developing osteoporosis (http://www.nof.org/osteoporosis/diseasefacts.htm). Called the “silent disease,” OSP develops slowly over a number of years without symptoms. Eighty percent of those affected are women, particularly petite Caucasian and Asian women, although older men and women of all races and ethnicities are at significant risk.
• In the United States, 700,000 people are diagnosed with vertebral compression fractures as a result of OSP each year. Morbidity associated with vertebral fractures includes severe back pain, loss of height and deformity, all of which negatively affect quality of life.
• Once microfracture of the vertebra begins, there is little the clinician can do except palliative medical treatment using analgesics, bed rest and/or restriction of activity. With time, the microfractures widen at one level and without surgical intervention, the fractures cascade downward with increasing kyphosis or “hunching” of the back. Once a mechanical lesion develops, surgery is the only option. Vertebroplasty or kyphoplasty are the primary minimally-invasive surgical procedures performed for the treatment of compression-wedge fractures due to OSP.
• Vertebroplasty stabilizes the collapsed vertebra by injecting polymethylmethacrylate (PMMA) or a substantially equivalent bone cement into cancellous bone space of the vertebrae. Besides providing structural support to the vertebra, the exothermic reaction of PMMA polymerization is said to kill off the nociceptors or pain receptors in the bone, although no proof of this hypothesis has been provided in the literature. This procedure is typically performed as an outpatient procedure and requires only a short-acting local or general anesthetic. Once the surgical area of the spine is anesthetized, the physician inserts one or two needles through small skin incisions into either the pedicle (uni-transpedicular) or the pedicles of the vertebral body i.e., bi-transpedicular. PMMA is injected through the needle and into the cancellous-bone space of the vertebra.
• Kyphoplasty mirrors the vertebroplasty procedure but has the additional step of inserting and expanding a nylon balloon in the interior of the vertebral body. Expansion of the balloon under pressure reduces the compression fracture and creates a cavity. After withdrawal of the balloon, PMMA is injected into the cavity to stabilize the reduction. The kyphoplasty procedure may restore the vertebral body height. Kyphoplasty is an in-patient surgery that requires hospitalization and a general anesthetic. Kyphon Inc. claims over 275,000 spinal fractures have been treated using their PMMA derivative and their “balloon” kyphoplasty procedure worldwide (Sunnyvale, Calif., Sep. 5, 2006, (PR NEWSWIRE) Kyphon study 2006).
• Bone cement for both vertebroplasty and kyphoplasty procedures currently employ variations of standard PMMA in a powder and a methyl methacrylate monomer liquid. When the powder and liquid monomer are mixed, an exothermic polymerization takes place resulting in the formation of a “dough-like” material, which is then inserted into the cancellous bone space. The dough, when hardened, becomes either the reinforcing structure or the grout between the bone and prosthesis.
• The average clinical in vivo life of the PMMA grout is approximately 10 years due to corrosion fatigue of either the bone-cement/prosthesis and/or the bone cement/bone interfaces. Jasty et al. (1991) showed that in cemented total hip replacements: “Fractures in the cement mantle itself were found on cut sections around all prostheses which had been in use for over three years.” Jasty et al. also noted: “In general, specimens less than 10 years in situ showed small incomplete fractures while the specimens in place more than 10 years all showed large complete cement mantle fractures.”
• When an implant fails, a revision becomes mandatory. After removal of the cement and hardware, a cemented arthroplasty can be repeated if enough cancellous bone matrix exists to grip the new PMMA. Alternatively, cement-less prosthesis can be installed. Such a revision, however, can only be applied to total joint replacement failures. For vertebroplasty and/or kyphoplasty, a classical screw and plate internal fixation with autograft fusion is necessary.
• Despite advances in the foregoing procedures, there remains a need for improved bone cement delivery systems which enable rapid and controllable deployment of bone cement for the treatment of conditions such as vertebral compression fractures.
SUMMARY OF THE INVENTION
• There is provided in accordance with one aspect of the present invention, a steerable vertebroplasty device having a cavity creation element. The vertebroplasty device comprises an elongate tubular body, having a proximal end, a distal end, and a central lumen extending therethrough. A deflectable zone is provided on the distal end of the tubular body, for deflection through an angular range. A handle is provided on the proximal end of the tubular body, having a deflection control thereon. A cavity creating element may be carried by the deflectable zone. In one embodiment, the cavity creating element is an inflatable balloon, in communication with a proximal inflation port by way of an elongate inflation lumen extending throughout the length of the tubular body.
• The deflection control may comprise a rotatable element, such as a knob rotatable about the longitudinal axis of the handle.
• The distal end of the tubular body is provided with at least one exit port in communication with the central lumen. The exit port may open in a lateral direction, an axial direction, or along an inclined surface positioned distally of a transition point between the longitudinal side wall of the tubular body and the distal end of the distal tip.
• Further features and advantages of the present invention will become apparent to those of skill in the art in view of the detailed description of preferred embodiments which follows, when considered together with the attached drawings and claims.
BRIEF DESCRIPTION OF THE DRAWINGS
• FIG. 1 is a perspective view of a steerable injection needle in accordance with one aspect of the present invention.
• FIG. 2 is a perspective view of an introducer in accordance with one aspect of the present invention.
• FIG. 3 is a perspective view of a stylet in accordance with one aspect of the present invention.
• FIG. 4 is a side elevational view of the steerable injection needle moveably coaxially disposed within the introducer, in a substantially linear configuration.
• FIG. 5 is a side elevational view of the assembly ofFIG. 4, showing the steerable injection needle in a curved configuration.
• FIG. 6 is a side elevational schematic view of another steerable injection needle in accordance with the present invention.
• FIG. 7A is a schematic view of a distal portion of the steerable needle ofFIG. 6, shown in a linear configuration.
• FIG. 7B is a schematic view as inFIG. 7A, following proximal retraction of a pull wire to laterally deflect the distal end.
• FIG. 8 is a schematic view of a distal portion of a steerable needle, having a side port.
• FIG. 9A is a schematic view of a distal portion of a steerable needle, positioned within an outer sheath.
• FIG. 9B is an illustration as inFIG. 9A, with the distal sheath partially proximally retracted.
• FIG. 9C is an illustration as inFIG. 9B, with the outer sheath proximally retracted a sufficient distance to fully expose the deflection zone.
• FIGS. 10A-10C illustrate various aspects of an alternative deflectable needle in accordance with the present invention.
• FIGS. 11A through 11C illustrate various aspects of a further deflectable needle design in accordance with the present invention.
• FIGS. 12 and 13 illustrate a further variation of the deflectable needle design in accordance with the present invention.
• FIG. 14 is a side elevational cross section through the proximal handle of the deflectable needle illustrated inFIG. 13.
• FIG. 15 is a cross sectional detail view of the distal tip of the steerable needle illustrated inFIG. 13.
• FIGS. 15A through 15H illustrate various views of alternative distal tip designs.
• FIGS. 16A and 16B are schematic illustrations of the distal end of a steerable injection device in accordance with the present invention, having a cavity creating element thereon.
• FIGS. 16C and 16D are alternative cross sectional views taken along theline16C-16C inFIG. 16A, showing different inflation lumen configurations.
• FIGS. 17A and 17B illustrate an alternative steerable injection device having a cavity creation element thereon.
• FIGS. 18A and 18B are schematic views of a bone cement delivery system in accordance with the present invention.
• FIGS. 19A through 19F show stages in the method of accomplishing vertebroplasty in accordance with present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
• The present invention provides improved delivery systems for delivery of a bone cement or bone cement composite for the treatment of vertebral compression fractures due to osteoporosis (OSP), osteo-trauma, and benign or malignant lesions such as metastatic cancers and myeloma, and associated access and deployment tools and procedures.
• The primary materials in the preferred bone cement composite are methyl methacrylate and inorganic cancellous and/or cortical bone chips or particles. Suitable inorganic bone chips or particles are sold by Allosource, Osteotech and LifeNet (K053098); all have been cleared for marketing by FDA The preferred bone cement also may contain the additives: barium sulfate for radio-opacity, benzoyl peroxide as an initiator, N,N-dimethyl-p-toluidine as a promoter and hydroquinone as a stabilizer. Other details of bone cements and systems are disclosed in U.S. patent application Ser. No. 11/626,336, filed Jan. 23, 2007, the disclosure of which is hereby incorporated in its entirety herein by reference.
• One preferred bone cement implant procedure involves a two-step injection process with two different concentrations of the bone particle impregnated cement. To facilitate the implant procedure the bone cement materials are packaged in separate cartridges containing specific bone cement and inorganic bone particle concentrations for each step. Tables 1 and 2, infra, list one example of the respective contents and concentrations in Cartridges1A and1B for the first injection step, and Cartridges2A and2B for the second injection step.
• The bone cement delivery system generally includes at least three main components: 1) stylet; 2) introducer cannula; and 3) steerable injection needle. SeeFIGS. 1-3. Packaged with the system or packaged separately is a cement dispensing pump. The complete system also preferably includes at least one cement cartridge having at least two chambers therein, and a spiral mixing nozzle.
• The stylet is used to perforate a hole into the pedicle of the vertebra to gain access to the interior of the vertebral body.
• The introducer cannula is used for bone access and as a guide for the steerable injection needle. The introducer cannula is sized to allow physicians to perform vertebroplasty or kyphoplasty on vertebrae with small pedicles such as the thoracic vertebra T5 as well as larger vertebrae. In addition, this system is designed for uni-transpedicular access and/or bi-pedicular access.
• Once bone access has been achieved, the steerable injection needle can be inserted through the introducer cannula into the vertebra. The entire interior vertebral body may be accessed using the steerable injection needle. The distal end of the needle can be manually shaped to any desired radius within the product specifications. The radius is adjusted by means of a knob on the proximal end of the device.
• The hand-held cement dispensing pump may be attached to the steerable injection needle by a slip-ring luer fitting. The pre-filled 2-chambered cartridges (1A and1B, and2A and2B) are loaded into the dispensing pump. As the handle of the dispensing pump is squeezed, each piston pushes the cartridge material into the spiral mixing tube. The materials are mixed in the spiral mixing nozzle prior to entering the steerable injection needle. The ratio of diameters of the cartridge chambers determines the mixing ratio for achieving the desired viscosity.
• The bone cement implant procedures described herein use established vertebroplasty and kyphoplasty surgical procedures to stabilize the collapsed vertebra by injecting bone cement into cancellous bone.
• The preferred procedure is designed for uni-transpedicular access and may be accomplished under either a local anesthetic or short-duration general anesthetic. Once the area of the spine is anesthetized, an incision is made and the stylet is used to perforate the vertebral pedicle and gain access to the interior of the vertebral body. The introducer cannula is then inserted and acts as a guide for the steerable injection needle.
• Injection of the preferred bone cement involves a two-step procedure. The pre-filled Cartridges1A and1B are loaded into the dispensing pump. As the dispensing pump handle is squeezed, each piston pushes material into the spiral mixing tube. The diameter of each chamber may be utilized to determine the mixing ratio for achieving the desired viscosity.
• The first step involves injecting a small quantity of PMMA with more than about 35%, e.g., 60% inorganic bone particles, onto the outer periphery of the cancellous bone matrix, i.e., next to the inner wall of the cortical bone of the vertebral body. The cement composite is designed to harden relatively quickly, forming a firm but still pliable shell. This shell is intended to prevent bone marrow/PMMA content from being ejected through any venules or micro-fractures in the vertebral body wall. The second step of the procedure involves a second injection of PMMA with an approximately 30% inorganic bone particles to stabilize the remainder of the weakened, compressed cancellous bone.
• Alternatively, the steerable needle disclosed herein and discussed in greater detail below, can be used in conventional vertebroplasty procedures, using a single step bone cement injection.
• Injection control for the first and second steps is provided by a 2 mm ID flexible injection needle, which is coupled to the hand operated bone cement injection pump. The 60% (>35%) and 30% ratio of inorganic bone particle to PMMA concentrations may be controlled by the pre-filled cartridge sets1A and1B, and2A and2B. At all times, the amount of the injectate is under the direct control of the surgeon or intervention radiologist and visualized by fluoroscopy. The introducer cannula is slowly withdrawn from the cancellous space as the second injection of bone cement begins to harden, thus preventing bone marrow/PMMA content from exiting the vertebral body. The procedure concludes with closure of the surgical incision with bone filler. In vitro and in vivo studies have shown that the 60% (>35%) bone-particle impregnated bone cement hardens in 2-3 minutes and 30% bone-particle impregnated bone cement hardens between 4 to 10 minutes.
• Details of the system components will be discussed below.
• There is provided in accordance with the present invention a steerable injection device that can be used to introduce any of a variety of materials or devices for diagnostic or therapeutic purposes. In one embodiment, the system is used to inject bone cement, e.g., PMMA or any of the bone cement compositions disclosed elsewhere herein. The injection system most preferably includes a tubular body with a steerable (i.e., deflectable) distal portion for introducing bone cement into various locations displaced laterally from the longitudinal axis of the device within a vertebral body during a vertebroplasty procedure.
• Referring toFIG. 1, there is illustrated a side perspective view of asteerable injection needle10 in accordance with one aspect of the present invention. Thesteerable injection needle10 comprises an elongatetubular body12 having aproximal end14 and adistal end16. Theproximal end14 is provided with a handle ormanifold18, adapted to remain outside of the patient and enable introduction and/or aspiration of bone cement or other media, and control of the distal end as will be described herein. In general,manifold18 is provided with at least oneinjection port20, which is in fluid communication with a central lumen (not illustrated) extending throughtubular body12 to at least onedistal exit port22.
• The manifold18 is additionally provided with acontrol26 such as a rotatable knob, slider, or other moveable control, for controllably deflecting adeflection zone24 on thedistal end16 of thetubular body12. As is described elsewhere herein, thedeflection zone24 may be advanced from a relatively linear configuration as illustrated inFIG. 1 to a deflected configuration throughout an angular range of motion.
• Referring toFIG. 2, there is illustrated an elongatetubular introducer30, having aproximal end32, adistal end34 and an elongatetubular body36 extending therebetween. A central lumen38 (not shown) extends between aproximal access port40 and adistal access port42.
• The central lumen38 has an inside diameter which is adapted to slideably axially receive thesteerable injection needle10 therethrough. This enables placement of thedistal end34 adjacent a treatment site within the body, to establish an access pathway from outside of the body to the treatment site. As will be appreciated by those of skill in the art, theintroducer30 enables procedures deep within the body such as within the spine, through a minimally invasive and/or percutaneous access. Thesteerable injection needle10 and/or other procedure tools may be introduced intoport40, through lumen38 and out ofport42 to reach the treatment site.
• Theproximal end32 ofintroducer30 may be provided with ahandle44 for manipulation during the procedure.Handle44 may be configured in any of a variety of ways, such as having aframe46 with at least afirst aperture48 and asecond aperture50 to facilitate grasping by the clinician.
• Referring toFIG. 3, there is illustrated a perspective view ofstylet60.Stylet60 comprises aproximal end62, adistal end64 and anelongate body66 extending therebetween. Theproximal end62 may be provided with astop68 such as a grasping block, manifold or other structure, to facilitate manipulation by the clinician. In the illustrated embodiment, theblock68 is configured to nest within arecess70 on the proximal end of theintroducer30.
• As will be appreciated by those of skill in the art, thestylet60 has an outside diameter which is adapted to coaxially slide within the central lumen onintroducer30. Whenblock68 is nested withinrecess70, adistal end64 ofstylet60 is exposed beyond thedistal end34 ofintroducer30. Thedistal end64 ofstylet60 may be provided with apointed tip72, such as for anchoring into the surface of a bone.
• Referring toFIG. 4, there is illustrated a side elevational view of an assembly in accordance with the present invention in which asteerable injection needle10 is coaxially positioned within anintroducer30. Theintroducer30 is axially moveably carried on thesteerable injection needle10. In the illustration ofFIG. 4, theintroducer30 is illustrated in a distal position such that it covers at least a portion of thedeflection zone24 oninjection needle10.
• FIG. 5 illustrates an assembly as inFIG. 4, in which theintroducer30 has been proximally retracted along theinjection needle10 to fully expose thedeflection zone24 oninjection needle10. In addition, thecontrol26 has been manipulated to deflect thedeflection zone24 through an angle of approximately 90°. Additional details of the steerable needle will be discussed below.
• FIG. 6 illustrates a schematic perspective view of an alternate steerable vertebroplasty injector, according to one embodiment of the invention. Thesteerable injector700 includes a body orshaft portion702 that is preferably elongate and tubular,input port704,adjustment control706, and handleportion708. Theelongate shaft702 preferably has a firstproximal portion710 and a seconddistal portion712 which merge at atransition point714.Shaft702 may be made of stainless steel, such as 304 stainless steel, Nitinol, Elgiloy, or other appropriate material. Alternatively, thetubular body702 may be extruded from any of a variety of polymers well known in the catheter arts, such as PEEK, PEBAX, nylon and various polyethylenes. Extrudedtubular bodies702 may be reinforced using metal or polymeric spiral wrapping or braided wall patterns, as is known in the art.
• Theshaft702 defines at least one lumen therethrough that is preferably configured to carry a flowable bone cement prior to hardening.Proximal portion710 ofshaft702 is preferably relatively rigid, having sufficient column strength to push through cancellous bone.Distal portion712 ofshaft702 is preferably flexible and/or deflectable and reversibly actuatable between a relatively straight configuration and one or more deflected configurations or curved configurations as illustrated, for example, inFIG. 5, as will be described in greater detail below. Thedistal portion712 ofshaft702 may include a plurality oftransverse slots718 that extend partially circumferentially around thedistal portion712 of theshaft702 to provide a plurality of flexion joints to facilitate bending.
• Input port704 may be provided with a Luer lock connector although a wide variety of other connector configurations, e.g., hose barb or slip fit connectors can also be used.Lumen705 ofinput port704 is fluidly connected tocentral lumen720 ofshaft702 such that material can flow from a source, throughinput port704 intocentral lumen720 of theshaft702 and out the open distal end or out of a side opening ondistal portion712.Input port704 is preferably at least about 20 gauge and may be at least about 18, 16, 14, or 12 gauge or larger in diameter.
• Input port704 advantageously allows for releasable connection of thesteerable injection device700 to a source of hardenable media, such as a bone cement mixing device described herein. In some embodiments, a plurality ofinput ports704, such as 2, 3, 4, or more ports are present, for example, for irrigation, aspiration, introduction of medication, hardenable media precursors, hardenable media components, catalysts or as a port for other tools, such as a light source, cautery, cutting tool, visualization devices, or the like. A first and second input port may be provided, for simultaneous introduction of first and second bone cement components such as from a dual chamber syringe or other dispenser. A mixing chamber may be provided within theinjection device700, such as within the proximal handle, or within thetubular shaft702
• A variety of adjustment controls706 may be used with the steerable injection system, for actuating the curvature of thedistal portion712 of theshaft702. Preferably, theadjustment control706 advantageously allows for one-handed operation by a physician. In one embodiment, theadjustment control706 is a rotatable member, such as a thumb wheel or dial. The dial can be operably connected to a proximal end of an axially movable actuator such aspull wire724. SeeFIG. 7A. When the dial is rotated in a first direction, a proximally directed tension force is exerted on thepull wire724, actively changing the curvature of thedistal portion712 of theshaft702 as desired. The degree of deflection can be observed fluoroscopically, and/or by printed or other indicium associated with thecontrol706. Alternative controls include rotatable knobs, slider switches, compression grips, triggers such as on a gun grip handle, or other depending upon the desired functionality.
• In some embodiments, theadjustment control706 allows for continuous adjustment of the curvature of thedistal portion712 ofshaft702 throughout a working range. In other embodiments, the adjustment control is configured for discontinuous (i.e., stepwise) adjustment, e.g., via a ratcheting mechanism, preset slots, deflecting stops, a rack and pinion system with stops, ratcheting band (adjustable zip-tie), adjustable cam, or a rotating dial of spring loaded stops. In still other embodiments, theadjustment control706 may include an automated mechanism, such as a motor or hydraulic system to facilitate adjustment.
• The adjustment control may be configured to allow deflection of thedistal portion712 through a range of angular deviations from 0 degrees (i.e., linear) to at least about 15°, and often at least about 25°, 35°, 60°, 90°, 120°, 150°, or more degrees from linear.
• In some embodiments, the length X of the flexibledistal portion712 ofshaft702 is at least about 10%, in some embodiments at least about 15%, 25%, 35%, 45%, or more of the length Y of theentire shaft702 for optimal delivery of bone cement into a vertebral body. One of ordinary skill in the art will recognize that the ratio of lengths X:Y can vary depending on desired clinical application. In some embodiments, the maximum working length ofneedle702 is no more than about 15″, 10″,8″,7″,6″, or less depending upon the target and access pathway. In one embodiment, when the working length ofneedle702 is no more than about 8″, the adjustabledistal portion712 of shaft has a length of at least about 1″ and preferably at least about 1.5″ or 2″.
• FIGS. 7A-B are schematic perspective views of a distal portion ofshaft702 of a steerable vertebroplasty injector, according to one embodiment of the invention. Shown is the preferably rigidproximal portion710 and deflectabledistal portion712. Thedistal portion712 ofshaft702 includes a plurality oftransverse slots718 that extend partially circumferentially around thedistal portion712 of theshaft702, leaving a relatively axiallynon-compressible spine719 in the form of the unslotted portion of the tubular wall.
• In some embodiments, theslots718 can be machined or laser cut out of the tube stock that becomesshaft702, and each slot may have a linear, chevron or other shape. In other embodiments, thedistal portion712 ofshaft702 may be created from an elongate coil rather than a continuous tube.
• Slots718 provide small compression hinge joints to assist in the reversible deflection ofdistal portion712 ofshaft702 between a relatively straightened configuration and one or more curved configurations. One of ordinary skill in the art will appreciate that adjusting the size, shape, and/or spacing of theslots718 can impart various constraints on the radius of curvature and/or limits of deflection for a selected portion of thedistal portion712 ofshaft702. For example, thedistal portion712 ofshaft702 may be configured to assume a second, fully deflected shape with a relatively constant radius of curvature throughout its length. In other embodiments, thedistal portion712 may assume a progressive curve shape with a variable radius of curvature which may, for example, have a decreasing radius distally. In some embodiments, the distal portion may be laterally displaced through an arc having a radius of at least about 0.5″, 0.75″, 1.0″, 1.25″, or 1.5″ minimum radius (fully deflected) to ∞ (straight) to optimize delivery of bone cement within a vertebral body. Wall patterns and deflection systems for bendable slotted tubes are disclosed, for example, in U.S. Patent Publication No. 2005/0060030 A1 to Lashinski et al., the disclosure of which is incorporated in its entirety by reference herein.
• Still referring toFIGS. 7A-B, apull wire724 resides within thelumen720 ofshaft702. Thedistal end722 of thepull wire724 is preferably operably attached, such as by adhesive, welding, soldering, crimping or the like, to an inner side wall of thedistal portion712 of theshaft702. Preferably, the attachment point will be approximately 180° offset from the center of theaxially extending spine719. Proximal portion ofpull wire724 is preferably operably attached toadjustment control706. Theadjustment control706 may be configured to provide an axial pulling force in the proximal direction toward the proximal end ofpull wire724. This in turn exerts a proximal traction on thedistal portion712 ofshaft702 operably attached todistal end722 ofpull wire724. The slotted side of the tubular body shortens under compression, while thespine side719 retains its axial length causing thedistal portion712 ofshaft702 to assume a relatively curved or deflected configuration. In some embodiments, a plurality of pull wires, such as two, three, four, ormore pull wires724 may be present within thelumen720 with distal points of attachment spaced axially apart to allow thedistal portion712 ofshaft702 to move through compound bending curves depending on the desired bending characteristic. Distal axial advance of the actuator will cause a deflection in an opposite direction, by increasing the width of theslots718.
• Adistal opening728 is provided onshaft702 in communication withcentral lumen720 to permit expression of material, such as bone cement, from theinjector700. Some embodiments may include a filter such asmesh812.Mesh structure812 can advantageously control cement output by controlling bubbles and/or preventing undesired large or unwieldy aggregations of bone cement from being released at one location and thus promote a more even distribution of bone cement within the vertebral body. Themesh812 may be created by a laser-cut crisscrossing pattern within distal end as shown, or can alternatively be separately formed and adhered, welded, or soldered on to thedistal opening728. Referring toFIG. 8, thedistal shaft portion712 may also include anend cap730 or other structure for occludingcentral lumen720, and adistal opening728 on the sidewall ofshaft702.
• In some embodiments, thedistal shaft712 can generate a lateral force of at least about 0.125 pounds, 0.25 pounds, 0.5 pounds, 1 pound, 1.5 pounds, 2 pounds, 3 pounds, 4 pounds, 5 pounds, 6 pounds, 7 pounds, 8 pounds, 9 pounds, 10 pounds, or more by activatingcontrol706. This can be advantageous to ensure that thedistal portion712 is sufficiently navigable laterally through cancellous bone to distribute cement to the desired locations. In some embodiments, thedistal shaft712 can generate a lateral force of at least about 0.125 pounds but no more than about 10 pounds; at least about 0.25 pounds but no more than about 7 pounds; or at least about 0.5 pounds but no more than about 5 pounds.
• In some embodiments, thedistal portion712 of shaft702 (or end cap730) has visible indicia, such as, for example, a marker visible via one or more imaging techniques such as fluoroscopy, ultrasound, CT, or MRI.
• FIGS. 9A-C illustrate in schematic cross-section another embodiment of adistal portion734 of asteerable injection device740. Thetubular shaft736 can include adistal portion734 made of or containing, for example, a shape memory material that is biased into an arc when in an unconstrained configuration. Some materials that can be used for the distalcurved portion734 include Nitinol, Elgiloy, stainless steel, or a shape memory polymer. Aproximal portion732 of theshaft736 is preferably relatively straight as shown. Also shown isend cap730, distallateral opening728 andmesh812.
• The distalcurved portion734 may be configured to be axially movably received within an outertubular sheath738. Thesheath738 is preferably configured to have sufficient rigidity and radial strength to maintain the curveddistal portion734 ofshaft732 in a relatively straightened configuration while the outertubular sheath738 coaxially covers the curveddistal portion734.Sheath738 can be made of, for example, a metal such as stainless steel or various polymers known in the catheter arts. Axial proximal withdrawal of thesheath738 with respect totubular shaft736 will expose an unconstrained portion of the shape memorydistal end734 which will revert to its unstressed arcuate configuration. Retraction of thesheath738 may be accomplished by manual retraction by an operator at the proximal end, retraction of a pull wire attached to a distal portion of thesheath738, or other ways as known in the art. The straightening function of theouter sheath738 may alternatively be accomplished using an internal stiffening wire, which is axially movably positionable within a lumen extending through thetubular shaft736. The length, specific curvature, and other details of the distal end may be as described elsewhere herein.
• In another embodiment, as shown inFIGS. 10A-C,tubular shaft802 of a steerable vertebroplasty injector may be generally substantially straight throughout its length in its unstressed state, or have a laterally biased distal end. A distally facing orside facing opening810 is provided for the release of a material, such as bone cement. In this embodiment,introducer800 includes an elongatetubular body801 with alumen805 therethrough configured to receive the tubular shaft (also referred to as a needle)802.Introducer800 can be made of any appropriate material, such as, stainless steel and others disclosed elsewhere herein.Needle802 may be made of a shape memory material, such as nitinol, with superelastic properties, and has an outside diameter within the range of between about 1 to about 3 mm, about 1.5-2.5 mm, or about 2.1 mm in some embodiments.
• Introducer800 includes a needle-redirectingelement804 such as an inclined surface near its distal end. Needle-redirectingelement804 can be, for example, a laser-cut tang or a plug having a proximal surface configured such that whenneedle802 is advanced distally intointroducer800 and comes in contact with the needle-redirectingelement804, adistal portion814 ofneedle802 is redirected out an exit port806 ofintroducer800 at anangle808, while proximal portion816 ofneedle802 remains in a relatively straightened configuration, as shown inFIG. 10B. Bone cement can then be ejected fromdistal opening810 on the end or side ofneedle802 within bone1000.Distal opening810 may be present at the distal tip of the needle802 (coaxial with the long axis of the needle802) or alternatively located on a distal radial wall ofneedle802 as shown inFIG. 10C. In some embodiments, theangle808 is at least about 15 degrees and may be at least about 30, 45, 60, 90, 105 degrees or more with respect to the long axis of theintroducer800.
• The illustrated embodiment ofFIGS. 10A-C and other embodiments disclosed herein are steerable through multiple degrees of freedom to distribute bone cement to any area within a vertebral body. For example, theintroducer800 andneedle802 can both rotate about their longitudinal axes with respect to each other, andneedle802 can move coaxially with respect to theintroducer800, allowing an operator to actuate the injection system three dimensionally. Thedistal portion814 ofneedle802 can be deflected to a position that is angularly displaced from the long axis of proximal portion816 of needle without requiring a discrete curved distal needle portion as shown in other embodiments herein.
• FIGS. 11A-C illustrate another embodiment of a steerable vertebroplasty injector.FIG. 11A schematically showshandle portion708,adjustment control706, andelongate needle shaft702, includingproximal portion710,distal portion712, andtransition point714.FIG. 11B is a vertical cross-section through line A-A ofFIG. 11A, and showsadjustment control706 operably connected to pullwire724 such as through a threaded engagement. Also shown isinput port704, andproximal portion710 anddistal portion712 ofneedle shaft702.FIG. 11C illustrates a cross-sectional view ofdistal portion712 ofshaft702. Thedistal end722 ofpull wire724 is attached at anattachment point723 to thedistal portion712 ofshaft702. Proximal retraction onpullwire724 will collapsetransverse slots718 and deflect the injector as has been discussed. Also shown is an inner tubular sleeve709, which can be advantageous to facilitate negotiation of objects or media such as bone cement, through the central lumen of theneedle shaft702.
• The interior sleeve709 is preferably in the form of a continuous, tubular flexible material, such as nylon or polyethylene. In an embodiment in which theneedle702 has an outside diameter of 0.095 inches (0.093 inch coil with a 0.001 inch thick outer sleeve) and an inside diameter of 0.077 inches, the interior tubular sleeve709 may have an exterior diameter in the area of about 0.074 inches and an interior diameter in the area of about 0.069 inches. The use of this thinwalled tube705 on the inside of theneedle shaft702 is particularly useful for guiding a fiber through theneedle shaft702. Theinterior tube705 described above is additionally preferably fluid-tight, and can be used to either protect the implements transmitted therethrough from moisture, or can be used to transmit bone cement through the steerable needle.
• In some embodiments, an outer tubular coating or sleeve (not shown) is provided for surrounding the steerable needle shaft at least partially throughout the distal end of the needle. The outer tubular sleeve may be provided in accordance with techniques known in the art and, in one embodiment, is a thin wall polyester (e.g., ABS) heat shrink tubing such as that available from Advanced Polymers, Inc. in Salem, N.H. Such heat shrink tubings have a wall thickness of as little as about 0.0002 inches and tube diameter as little as about 0.010 inches. The outer tubular sleeve enhances the structural integrity of the needle, and also provides a fluid seal and improved lubricity at the distal end over embodiments withdistal joints718. Furthermore, the outer tubular sleeve tends to prevent the device from collapsing under a proximal force on a pull wire. The sleeve also improves pushability of the tubular members, and improves torque transmission.
• In other embodiments, instead of a slotted tube, the needle shaft of a vertebroplasty injection system may include a metal or polymeric coil. Steerable helical coil-type devices are described, for example, in U.S. Pat. Nos. 5,378,234 or 5,480,382 to Hammerslag et al., which are both incorporated by reference herein in their entirety.
• An interior tubular sleeve (not illustrated) may be provided to facilitate flow of media through the central lumen as described elsewhere in the application. In some embodiments, a heat-shrink outer tubular sleeve as described elsewhere in the application is also provided to enhance the structural integrity of the sheath, provide a fluid seal across the chevrons or slots, as well as improve lubricity.
• The steerable injection needle (also referred to as the injection shaft) may have an outside diameter of between about 8 to 24 gauge, more preferably between about 10 to 18 gauge, e.g., 12 gauge, 13 gauge (0.095″ or 2.41 mm),14 gauge, 15 gauge, or16 gauge. In some embodiments, the inside diameter (luminal diameter) of the injection needle is between about 9 to 26 gauge, more preferably between about 11 to 19 gauge, e.g., 13 gauge, 14 gauge, 15 gauge, 16 gauge, or 17 gauge. In some embodiments, the inside diameter of the injection needle is no more than about 4 gauge, 3 gauge, 2 gauge, or 1 gauge smaller than the outside diameter of the injection needle.
• The inside luminal diameter of all of the embodiments disclosed herein is preferably optimized to allow a minimal exterior delivery profile while maximizing the amount of bone cement that can be carried by the needle. In one embodiment, the outside diameter of the injection needle is 13 gauge (0.095″ or 2.41 mm) with a 0.077″ (1.96 mm) lumen. In some embodiments, the percentage of the inside diameter with respect to the outside diameter of the injection needle is at least about 60%, 65%, 70%, 75%, 80%, 85%, or more.
• Referring toFIGS. 12 and 13, there is illustrated a modification of thesteerable injection needle10, in accordance with the present invention. Theinjection needle10 comprises an elongatetubular shaft702, extending between aproximal portion710 and adistal portion712. Theproximal portion710 is carried by aproximal handle708, which includes adeflection control706 such as a rotatable knob or wheel. Rotation of thecontrol706 causes a lateral deflection or curvature of thedistal steering region24 as has been discussed.
• Input port704 is in fluid communication with adistal opening728 on adistal tip730, by way of an elongatecentral lumen720.Input port704 may be provided with any of a variety of releasable connectors, such as a luer or other threaded or mechanically interlocking connector known in the art. Bone cement or other media advanced throughlumen720 under pressure may be prevented from escaping through the plurality ofslots718 in thesteering region24 by the provision of a thin flexible tubular membrane carried either by the outside oftubular shaft702, or on the interior surface definingcentral lumen720.
• Referring toFIG. 14, thehandle708 is provided with an axially orientedcentral bore732 having a first,female thread733 thereon. Aslider734 having a second complementary male thread735, is threadably engaged with thecentral bore732. Rotation of theknob706 relatively to theslider734 thus causes theslider734 to distally advance or proximally retract in an axial direction with respect to thehandle708. Theslider734 is mechanically linked to thepull wire724, such as by the use of one or more set screws orother fastener740.
• Slider734 is provided with at least one axially extending keyway orspline742 for slideably engaging a slide dowel pin744 linked to thehandle708. This allows rotation of therotatable control706, yet prevents rotation of theslider734 while permitting axial reciprocal movement of theslider734 as will be apparent to those of skill in the art. One or more actuating knob dowel pins746 permits rotation of therotatable control706 with respect to thehandle708 but prevents axial movement of therotatable control706 with respect to thehandle708.
• Referring toFIG. 15, the distal end of theshaft702 may be provided with any of a variety ofdistal opening728 orientations ordistal tip730 designs, depending upon the desired functionality. In the illustrated embodiment, thedistal tip730 is provided with anannular flange748 which may be slip fit into the distal end of thetubular body702, to facilitate attachment. The attachment of thedistal tip730 may be further secured by welding, crimping, adhesives, or other bonding technique.
• In general, thedistal tip730 includes aproximal opening750 for receiving media from thecentral lumen720, and advancing media throughdistal opening728.Distal opening728 may be provided on a distally facing surface, on a laterally facing surface, or on an inclined surface of thedistal tip730.
• Referring toFIGS. 15A and 15B, there is illustrated adistal tip30 having a singleinclined opening728 thereon. In any of the designs disclosed herein, one or two or three or four or moredistal ports728 may be provided, depending upon the desired clinical performance. In the illustrated embodiment, the distal tip includes a roundeddistal end750 which transitions either smoothly or through an angular interface with aninclined portion752. Thedistal opening728 is positioned distally of atransition754 at the proximal limit of theinclined surface752. This configuration enables thedistal opening728 to have a distal axially facing component, as compared to an embodiment having a side wall opening. See, for example,FIG. 8.
• Referring toFIG. 15B, thetip730 can be considered to have a centrallongitudinal axis770. Theaperture728 may be considered as residing on anaperture plane772, which intersects the distal most limit and the proximal most limit of theaperture728.Aperture plane772 intersects the longitudinal axis at an angle θ. In an embodiment having a side wall aperture, theaperture plane772 andlongitudinal axis770 would be parallel. In an embodiment having a completely distally facing aperture, theaperture plane772 would intersect thelongitudinal axis770 at an angle of 90°.
• In the illustrated embodiment, theinclined aperture728 is defined by anaperture plane772 intersecting thelongitudinal axis770 at an angle θ which is at least about 5°, often at least about 15°, and in many embodiments, at least about 25° or more. Intersection angles within the range of from about 15° to about 45° may often be used, depending upon the desired clinical performance.
• Referring toFIGS. 15C and 15D, an alternatedistal tip730 is illustrated. In this configuration, thedistal opening728 is in the form of asculpted recess756 extending axially in alignment with at least a portion of thecentral lumen720.Sculpted recess756 may be formed in any of a variety of ways, such as by molding, or by drilling an axial bore in an axial direction with respect to thetip730. Thesculpted recess756 cooperates with thetubular body702, as mounted, to provide adistal opening728 having an inclined aspect as well as an axially distally facing aspect with respect to the longitudinal axis of the steerable needle.
• Referring toFIGS. 15E and 15F, there is illustrated adistal tip730 having a plurality of distally facingapertures728. In the illustrated embodiment, four distal apertures are provided. Thedistal apertures728 may be provided on the roundeddistal end750, or on aninclined surface752 as has been discussed.
• Referring toFIGS. 15G and 15H, there is illustrated an alternativedistal tip730. In this configuration, anopening728 is oriented in a distally facing direction with respect to the longitudinal axis of the needle. The distal opening of the central lumen is covered by at least one, preferably two, and, as illustrated, fourleaflets758 to provide a collet like configuration. Each of theadjacent leaflets758 is separated by aslot760 and is provided with a living hinge or otherflexible zone762.
• In use, thedistal tip730 may be distally advanced through soft tissue, cortical or cancellous bone, with thedistal opening728 being maintained in a closed orientation. Following appropriate positioning of thedistal tip30, the introduction of bone cement or other media under pressure through thecentral lumen720 forces thedistal opening728 open by radially outwardly inclining eachleaflet758 about itsflection point762. This configuration enables introduction of the needle without “coring” or occluding with bone or other tissue, while still permitting injection of bone cement or other media in a distal direction.
• Any of the forgoing or other tip configurations may be separately formed and secured to the distal end of thetubular body702, or may be machined, molded or otherwise formed integrally with thetube702.
• Alternatively, a distal opening aperture may be occluded by a blunt plug or cap, which prevents coring during distal advance of the device. Once positioned as desired, the distal cap may be pushed off of the distal end of the injector such as under the pressure of injected bone cement. The deployable cap may take any of a variety of forms depending upon the injector design. For example, it may be configured as illustrated inFIG. 15A, only without theaperture728. Theflange748 is slip fit within the distal end of the injector body, and retained only by friction, or by a mild bond which is sufficient to retain thecap730 during manipulation of the injector, but insufficient to resist the force of injected bone cement. Thedeployable cap730 may be made from any of a variety of materials, such as stainless steel, Nitinol, or other implantable metals; any of a wide variety of implantable polymers such as PEEK, nylon, PTFE; or of bone cement such as PMMA. Alternatively, any of a variety of bioabsorbable polymers may be utilized to form thedeployable cap730, including blends and polymers in the PLA-PGLA absorbable polymer families.
• As a further alternative, coring during insertion of an injector having a distal opening may be prevented by positioning a removable obturator in the distal opening. The obturator comprises an elongate body, extending from a proximal end throughout the length of the injector to a blunt distal tip. The obturator is advanced axially in a distal direction through the central lumen, until the distal tip of the obturator extends slightly distally of the distal opening in the injector. This provides a blunt atraumatic tip for distal advance of the injector through tissue. Following positioning of the injector, the obturator may be proximally withdrawn from the central lumen, and discarded. The obturator may be provided with any of a variety of structures for securing the obturator within the central lumen during the insertion step, such as a proximal cap for threadably engaging a complementary luer connector on the proximal opening of the central lumen.
• In accordance with another aspect of the present invention, there is provided a combination device in which a steerable injector is additionally provided with a cavity formation element. Thus, the single device may be advanced into a treatment site within a bone, expanded to form a cavity, and used to infuse bone cement or other media into the cavity. Either or both of the expansion step and the infusion step may be accomplished following or with deflection of the distal portion of the injector.
• Referring toFIGS. 16A and 16B, thedistal portion302 of asteerable injector300 having a cavity formation element320 thereon is schematically illustrated. Thesteerable injector300 includes a relatively rigidproximal section304 and adeflectable section306 as has been discussed elsewhere herein. The lateral flexibility ofdistal section306 may be accomplished in any of a variety of ways, such as by the provision of a plurality of transverse chevrons orslots308.Slots308 may be machined or laser cut into appropriate tube stock, such as stainless steel or any of a variety of rigid polymers.
• Theslots308 oppose a column strength element such as anaxially extending spine310, for resisting axial elongation or compression of the device. Apull wire312 axially moveably extends throughout the length of the tubular body, and is secured with respect to the tubular body distally of thetransverse slots308. The proximal end of the pull wire is operatively connected to a control on a proximal handpiece or manifold. The control may be any of a variety of structures, such as a lever, trigger, slider switch or rotatable thumb wheel or control knob. Axial proximal traction (or distal advance) of thepull wire312 with respect to the tubular body causes a lateral deflection of thedistal steering section306, by axial compression or expansion of thetransverse slots308 relative to thespine310.
• Adistal aperture314 is in communication via acentral lumen316 with the proximal end of thesteerable injector300. Any of a variety of tip configurations may be used such as those disclosed elsewhere herein. The proximal end of thecentral lumen316 may be provided with a luer connector, or other connection port to enable connection to a source of media such as bone cement to be infused. In the illustrated embodiment, theaperture314 faces distally from thesteerable injector302, although other exit angles may be used as will be discussed below.
• Thesteerable injector300 is optionally provided with a cavity forming element320, such as aninflatable balloon322. In the illustrated embodiment, theinflatable balloon322 is positioned in the vicinity of the steerabledistal section306. Preferably, the axial length of a distal leadingsegment307 is minimized, so that theballoon322 is relatively close to the distal end of thesteerable injector300. In this embodiment, the plurality oftransverse slots308 are preferably occluded, to prevent inflation media from escaping into thecentral lumen316 or bone cement or other injectable media from escaping into theballoon322. Occlusion of thetransverse slots308 may be accomplished in any of variety of ways, such as by positioning a thin tubular membrane coaxially about the exterior surface of the tubular body and heat shrinking or otherwise securing the membrane across the openings. Any of a variety of heat shrinkable polymeric sleeves, comprising high density polyethylene or other materials, are well known in the catheter arts. Alternatively, a tubular liner may be provided within thecentral lumen316, to isolate the central lumen from thetransverse slots308.
• Theballoon322 is secured at adistal neck309 to the leadingsegment307 as is understood in the balloon catheter arts. Thedistal neck309 may extend distally from the balloon, as illustrated, or may invert and extend proximally along the tubular body. In either event, thedistal neck309 of theballoon322 is preferably provided with anannular seal324 either directly to thetubular body301 or to a polymeric liner positioned concentrically about the tubular body, depending upon the particular device design. This will provide an isolated chamber withinballoon322, which is in fluid communication with a proximal source of inflation media by way of aninflation lumen326.
• In the illustrated embodiment, theballoon322 is provided with an elongate tubular proximal neck which extends throughout the length of thesteerable injector300, to a proximal port or other site for connection to a source of inflation media. This part can be blow molded within a capture tube as is well understood in the balloon catheter arts, to produce a one piece configuration. Alternatively, the balloon can be separately formed and bonded to a tubular sleeve. During assembly, the proximal neck orouter sleeve328 may conveniently be proximally slipped over thetubular body301, and secured thereto, as will be appreciated by those of skill in the catheter manufacturing arts.
• Referring toFIG. 16C, theinflation lumen326 may occupy an annular space between theouter sleeve328 and thetubular body301. This may be accomplished by sizing the inside dimension of theouter sleeve328 slightly larger than the outside dimension of thetubular body301, by an amount sufficient to enable the desired inflation flow rate as will be understood in the art. Alternatively, referring toFIG. 16D, adiscrete inflation lumen326 may be provided while the remainder of theouter sleeve328 is bonded or snuggly fit against thetubular body301. This may be accomplished by positioning an elongate mandrel (not illustrated) between theouter sleeve328 and thetubular body301, and heat shrinking or otherwise reducing theouter sleeve328, thereafter removing the mandrel to leave thediscrete inflation lumen326 in place. Alternatively, any of a variety of internal inflation lumen may be devised, within thecentral lumen316 oftubular body301.
• Referring toFIGS. 17A and 17B, there is illustrated an alternative embodiment in which thedistal aperture314 is provided on a side wall of the tubular body. One or two or three or moredistal apertures314 may be provided in any of the embodiments disclosed herein, depending upon the desired clinical performance. In the illustrated embodiment, thedistal aperture314 is provided on the inside radius of curvature of thesteerable section306, as illustrated inFIG. 17B. Theaperture314 may alternatively be provided on the opposite, outside radius of curvature, depending upon the desired clinical performance.
• As a further alternative, the distal aperture orapertures314 may be provided in any of a variety of configurations on a distal cap or tip, adapted to be secured to the tubular body.
• The steerable injection systems described above are preferably used in conjunction with a mixing and dispensing pump for use with a multi-component cement. In some embodiments, a cement dispensing pump is a hand-held device having an interface such as a tray or chamber for receiving one or more cartridges. In one embodiment, the pump is configured to removably receive a double-barreled cartridge for simultaneously dispensing first and second bone cement components. The system additionally includes a mixing chamber, for mixing the components sufficiently and reproducibly to fully automate the mixing and dispensing process within a closed system.
• Bone cement components have conventionally been mixed, such as by hand, e.g., in mixing bowls in the operating room, which can be a time-consuming and unelegant process. The devices disclosed herein may be used with conventional bone cement formulations, such as manually mixed liquid-powder PMMA formulations. Alternatively, the use of a closed mixing device such as a double-barreled dispensing pump as disclosed herein is highly advantageous in reducing bone cement preparation time, preventing escape of fumes or ingredients, ensuring that premature cement curing does not occur (i.e., the components are mixed immediately prior to delivery into the body), and ensuring adequate mixing of components.
• Two separate chambers contain respective materials to be mixed in a specific ratio. Manual dispensing (e.g., rotating a knob or squeezing a handle) forces both materials into a mixing nozzle, which may be a spiral mixing chamber within or in communication with a nozzle. In the spiral mixing nozzle, all or substantially all mixing preferably occurs prior to the bone cement entering the steerable injection needle and, subsequently, into the vertebra. The cement dispensing hand pump may be attached to the steerable injection needle permanently, or removably via a connector, such as slip-ring Luer fittings. A wide range of dispensing pumps can be modified for use with the present invention, including dispensing pumps described in, for example, U.S. Pat. Nos. 5,184,757, 5,535,922, 6,484,904, and Patent Publication No. 2007/0114248, all of which are incorporated by reference in their entirety.
• Currently favored bone cement compositions are normally stored as two separate components or precursors, for mixing at the clinical site shortly prior to implantation. As has been described above, mixing of the bone cement components has traditionally been accomplished manually, such as by expressing the components into a mixing bowl in or near the operating room. In accordance with the present invention, the bone cement components may be transmitted from their storage and/or shipping containers, into a mixing chamber, and into the patient, all within a closed system. For this purpose, the system of the present invention includes at least one mixing chamber positioned in the flow path between the bone cement component container and the distal opening on the bone cement injection needle. This permits uniform and automated or semi-automated mixing of the bone cement precursors, within a closed system, and thus not exposing any of the components or the mixing process at the clinical site.
• Thus, the mixing chamber may be formed as a part of the cartridge, may be positioned downstream from the cartridge, such as in-between the cartridge and the proximal manifold on the injection needle, or within the proximal manifold on the injection needle or the injection needle itself, depending upon the desired performance of the device. The mixing chamber may be a discrete component which may be removably or permanently coupled in series flow communication with the other components of the invention, or may be integrally formed within any of the foregoing components.
• In general, the mixing chamber includes an influent flow path for accommodating at least two bone cement components. The first and second incoming flow path are combined, and mixing structures for facilitating mixing of the components are provided. This may include any of a variety of structures, such as a helical flow path, baffles and or additional turbulence inducing structures.
• Tables 1-2 below depict the contents and concentrations of one exemplary embodiment of bone cement precursors. Chambers1A and1B contain precursors for a first cement composition for distribution around the periphery of the formed in place vertebral body implant with a higher particle concentration to promote osteoinduction, as discussed previously in the application. Chambers2A and2B contain precursors for a second cement composition for expression more centrally within the implanted mass within the vertebral body, for stability and crack arresting, as discussed previously in the application.
• One of ordinary skill in the art will recognize that a wide variety of chamber or cartridge configurations, and bone cements, can be used with the present injection system. For example, in one embodiment, a first cartridge includes pre-polymerized PMMA and a polymerization catalyst, while a second cartridge includes a liquid monomer of MMA as is common with some conventional bone cement formulations.
• In some embodiments, the contents of two cartridges can be combined into a single cartridge having multiple (e.g., four) chambers. Chambers may be separated by a frangible membrane (e.g.,1A and2A in a first cartridge and1B and2B in a second cartridge, each component separated by the frangible membrane or other pierceable or removable barrier). In other embodiments, contents of the below cartridges can be manually pre-mixed and loaded into the input port of the injection system without the use of a cement mixing dispenser.

• TABLE 1
  Chamber 1A

  Methyl methacrylate (balance)	Hydroquinone (~75 ppm)(stabilizer)
  N,N-dimethyl-p-toluidine	Sterile bone particles (≧35 wt. %)
  (~0.9%)(catalyst
  for polymerization)
  Barium sulfate
  (~20 wt. %)(radio-opacifier)

  Chamber 1B

  Benzoyl peroxide	Physiological saline or poppy seed oil
  (~2%)(activator for	(balance)
  polymerization)

• TABLE 2
  Chamber 2A

  Methyl methacrylate (balance)	Hydroquinone (~75 ppm)(stabilizer)
  N,N-dimethyl-p-toluidine	Sterile bone particles (~30 wt. %)
  (~0.9%)(catalyst
  for polymerization)
  Barium sulfate
  (~20 wt. %)(radio-opacifier)

  Chamber 2B

  Benzoyl peroxide	Physiological saline or poppy seed oil
  (~2%)(activator for	(balance)
  polymerization)

• As illustrated inFIGS. 18A and 18B, in one embodiment, a system or kit for implanting bone cement includes at least some of the following components: a stylet configured to perforate a hole into the pedicle of the vertebral body; anintroducer cannula800 for providing an access pathway to the treatment site, asteerable injection needle700 to deliver bone cement to a desired location, and, acement dispensing pump910 preferably configured to accommodate one or two or moredual chamber cartridges1200 as well as a mixingnozzle995.
• The stylet may have a diameter of between about 0.030″ to 0.300″, 0.050″ to about 0.200″ and preferably about 0.100″ in some embodiments. Theintroducer cannula800 is between about 8-14 gauge, preferably between about 10-12 gauge, more preferably 11 gauge in some embodiments. Theintroducer cannula800, which may be made of any appropriate material, such as stainless steel (e.g., 304 stainless steel) may have a maximum working length of no more than about 12″, 8″, or 6″ in some embodiments. One or two or more bone cement cartridges, each having one or two or more chambers, may also be provided. Various other details of the components have been described above in the application.
• One embodiment of a method for delivering bone cement into a vertebral body is now described, and illustrated inFIGS. 19A-F. The method involves the general concept of vertebroplasty and kyphoplasty in which a collapsed or weakened vertebra is stabilized by injecting bone cement into cancellous bone.
• The cement implantation procedure is designed for uni-transpedicular access and generally requires either a local anesthetic or short-duration general anesthetic for minimally invasive surgery. Once the area of the spine is anesthetized, as shown inFIGS. 19A-B, the physician inserts astylet1302 to perforate alumen1304 into thepedicle wall1300 of the vertebra1308 to gain access to the interior of thevertebral body1310. As illustrated inFIG. 19C, theintroducer cannula800 is then inserted through thelumen1304 for bone access as well as acting as the guide for thesteerable injection needle700. Theintroducer cannula800 is sized to allow physicians to perform vertebroplasty or kyphoplasty on vertebrae withsmall pedicles1300 such as the thoracic vertebra (e.g., T5) as well as larger vertebrae. In addition, this system and method is advantageously designed to allow uni-transpedicular access as opposed to bi-pedicular access, resulting in a less invasive surgical procedure.
• Once bone access has been achieved, as shown inFIG. 19C thesteerable injection needle700 such as any of the devices described above can be inserted through theintroducer cannula800 and into the vertebra1308. Theentire interior1310 of the target vertebral body may be accessed using thesteerable injection needle800. Thedistal end712 of theneedle700 can be laterally deflected, rotated, and/or proximally retracted or distally advanced to position the bone cement effluent port at any desired site as previously described in the application. The radius can be adjusted by means of an adjustment control, such as a knob on the proximal end of the device as previously described.
• The actual injection procedure may utilize either one or two basic steps. In a one step procedure, a homogenous bone cement is introduced as is done in conventional vertebroplasty. The first step in the two step injection involves injection of a small quantity of PMMA with more than about 35%, e.g., 60% particles such as inorganic bone particles onto the periphery of the treatment site, i.e., next to the cortical bone of the vertebral body as shown inFIG. 19D. Thisfirst cement composite1312 begins to harden rather quickly, forming a firm but still pliable shell, which is intended to minimize or prevent any bone marrow/PMMA content from being ejected through any venules or micro-fractures in the vertebral body wall. The second step in the procedure involves an injection of a bolus of a second formulation of PMMA with a smaller concentration such as approximately 30% inorganic bone particles (second cement composite1314) to stabilize the remainder of the weakened, compressed cancellous bone, as illustrated inFIG. 19E.
• Injection control for the first and second steps is provided by an approximately 2 mm inside diameterflexible introducer cannula800 coupled to a bone cement injection pump (not shown) that is preferably hand-operated. Two separate cartridges containing respective bone cement and inorganic bone particle concentrations that are mixed in the 60% and 30% ratios are utilized to control inorganic bone particle to PMMA concentrations. The amount of the injectate is under the direct control of the surgeon or interventional radiologist by fluoroscopic observation. Theintroducer cannula800 is slowly withdrawn from the cancellous space as the bolus begins to harden, thus preventing bone marrow/PMMA content from exiting the vertebral body1308. The procedure concludes with the surgical incision being closed, for example, withbone void filler1306 as shown inFIG. 19F. Both the high and low bone cement particleconcentration cement composites1312,1314 harden after several minutes. In vitro and in vivo studies have shown that the 60% bone-particle impregnated bone cement hardens in 2-3 minutes and 30% bone-particle impregnated bone cement hardens between 4 to 10 minutes.
• The foregoing method can alternatively be accomplished utilizing the combination steerable needle ofFIG. 16A, having a cavity formation structure320 thereon. Once thesteerable injector300 has been positioned as desired, such as either with deflection as illustrated inFIG. 19C, or linearly, the cavity forming element320 is enlarged, such as by introducing inflation media under pressure into theinflatable balloon322. The cavity forming element320 is thereafter reduced in cross sectional configuration, such as by aspirating inflation media from theinflatable balloon322 to produce a cavity in the adjacent cancellous bone. Thesteerable injector300 may thereafter by proximally withdrawn by a small distance, to position thedistal opening314 in communication with the newly formed cavity. Bone cement or other media may thereafter be infused into the cavity, as will be appreciated by those skill in the art.
• At any time in the process, whether utilizing an injection needle having a cavity formation element or not, the steerable injector may be proximally withdrawn or distally advanced, rotated, and inclined to a greater degree or advanced into its linear configuration, and further distally advanced or proximally retracted, to position thedistal opening314 at any desired site for infusion of additional bone cement or other media. More than one cavity, such as two, or three or more, may be sequentially created using the cavity formation element, as will be appreciated by those of skill in the art.
• The aforementioned bone cement implant procedure process eliminates the need for the external mixing of PMMA powder with MMA monomer. This mixing process sometimes entraps air in the dough, thus creating porosity in the hardened PMMA in the cancellous bone area. These pores weaken the PMMA. Direct mixing and hardening of the PMMA using an implant procedure such as the above eliminates this porosity since no air is entrapped in the injectate. This, too, eliminates further weakening, loosening, or migration of the PMMA.
• While described herein primarily in the context of vertebroplasty, one of ordinary skill in the art will appreciate that the disclosed injection system can be used or modified in a wide range of clinical applications, such as, for example, other orthopedic applications such as kyphoplasty, treatment of any other bones, pulmonary, cardiovascular, gastrointestinal, gynecological, or genitourinary applications. While this invention has been particularly shown and described with references to embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the invention. For all of the embodiments described above, the steps of the methods need not be performed sequentially and the individual components of the devices may be combined permanently or be designed for removable attachment at the clinical site.

Claims (9)

1. A steerable vertebroplasty device, comprising:

an elongate, tubular body, having a proximal end, a distal end, and a central lumen extending therethrough;

a deflectable zone on the distal end of the tubular body, deflectable through an angular range;

a handle on the proximal end of the tubular body; and

a deflection control on the handle; and

a cavity creating element carried by the deflectable zone.

2. A steerable vertebroplasty device as inclaim 1, wherein the deflection control comprises a rotatable element.

3. A steerable vertebroplasty device as inclaim 1, wherein the distal end comprises a distally facing exit port in communication with the central lumen.

4. A steerable vertebroplasty device as inclaim 1, wherein the distal end comprises a laterally facing exit port in communication with the central lumen.

5. A steerable vertebroplasty device as inclaim 1, further comprising an actuator extending axially between the deflection control and the deflectable zone.

6. A steerable vertebroplasty device as inclaim 5, wherein the actuator comprises an axially moveable element.

7. A steerable vertebroplasty device as inclaim 1, wherein the cavity creating element comprises an inflatable balloon.

8. A steerable vertebroplasty device as inclaim 7, wherein the inflatable balloon is disposed proximally of an exit port on the tubular body.

9. A steerable vertebroplasty device as inclaim 1, wherein the tubular body comprises a proximal zone and a distal, deflectable zone separated by a transition, and the transition is at least about 15% of the length of the tubular body from the distal end.

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