US20050240193A1 - Devices for creating voids in interior body regions and related methods - Google Patents

Abstract

Several embodiments of cutting tips for tools for creating voids in interior body regions are provided. The cutting tips provide for rotational and translational cutting. An actuator mechanism for deploying a cutting tip converts the rotational movement of a wheel into translational movement of a plunger rod. The actuator mechanism provides positive cutting action as the cutting tip is moved from a first, non-deployed position to a second, deployed position and from the second, deployed position to the first, non-deployed position. Methods of creating a void in bone provide one or more mechanical cutting tools that may be used in combination with one or more expandable void-creating structures to form a void of a desired size and configuration.

Description

RELATED APPLICATION
• This application claims the benefit of provisional U.S. Application Ser. No. 60/499,934, filed Sep. 3, 2003, and entitled “Mechanical Devices for Creating Voids in Interior Body Regions and Related Methods.”
FIELD OF THE INVENTION
• This invention relates generally to tools for creating cavities or voids in interior body regions. In particular, the invention relates to creating voids in bone for diagnostic or therapeutic purposes.
BACKGROUND OF THE INVENTION
• A minimally invasive method of forming a cavity or void within one of the body's solid organs, for both diagnostic and treatment purposes, is becoming increasingly important as radiological and other types of scanning techniques improve a physician's ability to view inside the body without having to make an incision.
• The most common solid organ currently making use of a minimally invasive technique to form a void is bone. Typically this is any pathological bone in the body with a fracture, osteoporosis, or a tumor. The most commonly used void-forming method for bones is the inflatable bone tamp, as described in U.S. Pat. Nos. 4,969,888 and 5,108,404. Void formation in this case is usually followed by filling with a filling substance like bone cement or a bone substitute.
• Mechanical methods are also available for making voids inside solid organs. Those solid organs include the brain, the kidneys, the spleen, the liver and bone. In the brain, for example, an abscess could be easily debrided and irrigated with a minimally invasive mechanical void technique. A fractured spleen could be approached with a minimally invasive technique, to make a small void to fill with gelfoam or some other coagulant to stop hemorrhage. An osteoporotic, fractured vertebral body or bone tumor could be approached by a minimally invasive mechanical system in order to create a cavity or void and then refill with a bone substitute. A demand exists for systems or methods that are capable of forming voids in bone and other interior body regions in safe and efficacious ways.
SUMMARY OF THE INVENTION
• The invention provides systems and methods for creating voids in interior body regions.
• One aspect of the invention provides a cutting tip for cutting or scraping bone. In one embodiment, a curette-type instrument at the end of a shaft can be mechanically angled into different positions to scrape material to form a void. In another embodiment, a mechanical device at the end of a shaft resembles a T-type configuration and allows both translational and rotational cutting to form a void. In a third embodiment, the cutting tip includes a turned and tapered trunk. In a fourth embodiment, the cutting tip includes a conical trunk. In a fifth embodiment, a sharp, stout, metal spring is provided on the end of a shaft. In a sixth embodiment, the distal end of a shaft carries two more fingers to grab tissue for extraction. In a seventh embodiment, a hinged void-forming device is carried by a shaft and allows for formation of a void, which may be of a rectangular or any other pre-determined shape.
• Another aspect of the invention provides an actuator mechanism for deploying a cutting tip. In one embodiment, rotational movement of a thumbwheel is converted to translational movement of a plunger rod. In an alternative embodiment, rotational movement of a control knob is converted to translational movement of a plunger rod through interaction of a series of gears.
• Another aspect of the invention provides a tool for creating voids in interior body regions. The tool comprises a shaft, a tip for contacting bone, and a hinge member coupling the tip to the shaft. The tip becomes uncoupled if the torque applied exceeds a maximum hinge torque. The shaft includes a region of weakness proximal to the tip along which the shaft will break if the torque applied exceeds a maximum shaft torque. The maximum hinge torque is greater than the maximum shaft torque.
• According to another aspect of the invention, a tool for creating voids in interior body regions comprises a shaft assembly including a lumen, a tip for contacting bone coupled to the shaft, and a rod slidable within the lumen. The rod is tethered to the tip.
• According to another aspect of the invention, a tool for creating voids in interior body regions comprises a shaft including a lumen, and a tip for contacting bone coupled to the shaft by a coupling element. The tip is additionally tethered to the shaft such that the tip remains tethered to the shaft if the coupling element becomes inoperable.
• According to another aspect of the invention, a tool for creating voids in interior body regions comprises a cannula and a shaft. The shaft has a handle and is sized and configured for passage through the cannula. A projection extends radially from the shaft to restrict forward advancement of the shaft within the cannula.
• Another aspect of the invention provides methods of creating a void in bone. The methods provide one or more mechanical cutting tools that may be used in combination with one or more expandable void-creating structures to form a void of a desired size and configuration.
BRIEF DESCRIPTION OF THE DRAWINGS
• FIG. 1 is a perspective view of a mechanical tool for creating voids in interior body regions and illustrating pivoting movement of the cutting tip in phantom.
• FIG. 2 is a perspective view of a bone treatment device.
• FIG. 3 is a perspective view illustrating insertion and use of the device ofFIG. 2 in a vertebra.
• FIG. 4 is a perspective view of an alternative embodiment of a cutting tip and illustrating pivoting movement of the tip in phantom.
• FIG. 5 is a front plan view of the tip shown inFIG. 4 and illustrating rotational movement of the cutting tip.
• FIG. 6 illustrates 180° rotational movement of the cutting tip in a vertebra to create a 180° void.
• FIG. 7 illustrates the shaft rotated 180° relative toFIG. 6 and the cutting tip again rotated 180° to form a 360° void.
• FIG. 8 is a side view of the tip shown inFIG. 4 and illustrating translational movement of the cutting tip in a sawing-like motion.
• FIG. 9 illustrates the translational movement of the cutting tip and formation of a void in a vertebra.
• FIG. 10 is a perspective view illustrating the use of a marker band to identify the position of the cutting tip in relation to the distal end of the cannula.
• FIG. 11 is a perspective view illustrating use of a stop to limit translational advancement of the shaft within a cannula.
• FIG. 12A is an enlarged view of a groove located on the shaft of the cutting tool.
• FIG. 12B is a perspective view of an alternative embodiment of a shaft in which a portion of the shaft is formed of a material of reduced strength and/or rigidity relative to the rest of the shaft.
• FIG. 13 is a perspective view of an alternative embodiment of a stop that limits translational and rotational movement of the shaft along and within the cannula.
• FIG. 13A is a perspective view of an alternative embodiment of a T-shaped slot that limits translation and rotational movement of the shaft along and within the cannula.
• FIG. 14 is a schematic view representing the preset size and configuration of a void formed by performing a full sweep motion of a cam follower along a cam surface.
• FIG. 15 is a perspective view of an alternative embodiment of a cutting tip and illustrating pivoting movement of the tip in phantom.
• FIG. 16 is a front plan view of the tip shown inFIG. 15 and illustrating rotational movement of the cutting tip.
• FIG. 17 is a perspective view of an alternative embodiment of a cutting tip and illustrating pivoting movement of the tip in phantom.
• FIG. 18 is a front plan view of the tip shown inFIG. 17 and illustrating rotational movement of the cutting tip.
• FIG. 19 is a sectional view of an actuator mechanism for deploying a cutting tip and showing placement of the tool in the user's hand.
• FIG. 20 is a close-up and partial sectional view of the thumbwheel, threaded cap, flange, and stop ofFIG. 19.
• FIG. 21 is a cut-away view of the tether and hinge mechanism of the cutting tip.
• FIG. 22 is a side sectional view of an alternative embodiment of an actuator mechanism in which a lever actuates movement of the plunger rod.
• FIG. 23 is a perspective view of a tool incorporating an alternative embodiment of an actuator mechanism.
• FIG. 24 is a top sectional view of an alternative embodiment of an actuator mechanism.
• FIG. 25 is a side sectional view of an alternative embodiment of an actuator mechanism and showing placement of the tool in the user's hand.
• FIG. 26 is a side partial section view illustrating an alternative embodiment of a mechanical bone cutting tool illustrating the cutting tip in a straightened or malleable state and retracted within a cannula.
• FIG. 27 is a view similar toFIG. 26 and illustrating advancement of the cutting tip beyond the distal tip of the cannula and the introduction of fluid to activate the cutting tip.
• FIG. 28 is a view similar toFIG. 27 and illustrating activation of the cutting tip to a predetermined configuration.
• FIG. 29 is a side view of an alternative embodiment of a cutting tip illustrating the cutting tip in a straightened or malleable state.
• FIG. 30 is a view similar toFIG. 29 illustrating the cutting tip in the activated state.
• FIG. 31 is a side view of an alternative embodiment of a cutting tip illustrating the cutting tip in a straightened or malleable state.
• FIG. 32 is a view similar toFIG. 31 illustrating the cutting tip in the activated state.
• FIG. 33 is a side view of an alternative embodiment of a cutting tip carried by a shaft and illustrating a dual lumen extending through the shaft into the cutting tip.
• FIG. 34 is a side view of an alternative embodiment of a cutting tip illustrating a throughbore extending through the cutting tip.
• FIG. 35A is a side view illustrating a pre-bent or formed cutting tip confined by a cannula.
• FIG. 35B is a side view similar toFIG. 35A illustrating the deployment of the pre-bent or formed cutting tip by extension of the tip beyond the cannula.
• FIG. 36 is a side view of an alternative embodiment of a mechanical void-creating device.
• FIG. 37 is a side view of an alternative embodiment of a mechanical void-creating device.
• FIG. 38 is a side view of an alternative embodiment of a mechanical void-creating device.
• FIG. 39 is a top view of the device shown inFIG. 38.
• FIG. 40 is a side view of an alternative embodiment of the device ofFIGS. 38 and 39 in which spring blades extend from the device.
• FIGS.41A-D illustrate a method of creating and filling a void in bone in which a first mechanical cutting tool is used to create a void in bone and a second mechanical cutting tool is used to expand and/or further define the void.
• FIGS.42A-E illustrate an alternative method of creating and filling a void in bone in which a first mechanical cutting tool is used to create a void in bone and a second mechanical cutting tool and then an expandable body are used to expand and/or further define the void.
• FIGS.43A-D illustrate an alternative method of creating and filling a void in bone in which a first expandable body is used to create a void in bone and a second expandable body is used to expand and/or further define the void.
• FIGS.44A-E illustrate an alternative method of creating and filling a void in bone in which a first expandable body is used to create a void in bone and a second expandable body and then a mechanical cutting tool are used to expand and/or further define the void.
• FIGS.45A-E illustrate an alternative method of creating and filling a void in bone in which a first expandable body is used to create a void in bone and a mechanical cutting tool and then a second expandable body are used to expand and/or further define the void.
• FIGS.46A-E illustrate an alternative method of creating and filling a void in bone in which an expandable body is used to create a void in bone and a first mechanical cutting tool and then a second mechanical cutting tool are used to expand and/or further define the void.
• FIGS.47A-E illustrate an alternative method of creating and filling a void in bone in which a first cutting tool is used to create a void in bone and an expandable body and then a second mechanical cutting tool are used to expand and/or further define the void.
• FIGS.48A-E illustrate an alternative method of creating and filling a void in bone in which a mechanical cutting tool is used to create a void in bone and a first expandable body and then a second expandable body are used to expand and/or further define the void.
DESCRIPTION OF THE PREFERRED EMBODIMENT
• Although the disclosure hereof is detailed and exact to enable those skilled in the art to practice the invention, the physical embodiments herein disclosed merely exemplify the invention that may be embodied in other specific structure. While the preferred embodiment has been described, the details may be changed without departing from the invention, which is defined by the claims.
• The systems and methods embodying the is invention can be adapted for use virtually in any interior body region, where the formation of a cavity or void within tissue is required for a therapeutic or diagnostic purpose. The preferred embodiments show the invention in association with systems and methods used to treat bones. This is because the systems and methods which embody the invention are well suited for use in this environment. It should be appreciated that the systems and methods which embody features of the invention can be used in other interior body regions, as well.
• Various embodiments of cutting tips are described below in detail. In each case their sizes and shapes could be produced to fit the ideal void to be formed, whether it is a void in a tibia or a vertebral body. In addition, these mechanical tools could be made of any bio-compatible metal (for example, but not limited to stainless steel, titanium, titanium alloys, tantalum, aluminum, aluminum alloys, or other metals) that has adequate shear and tensile strength to perform their void-forming function. Plastic polymers having suitable biomechanical properties may also be used for these tools. Alternatively, the tool may be plated or coated with a biocompatible material.
• I. Mechanical Cutting Tool
• A. Curette
• FIGS. 1-3 show atool10 capable of forming a cavity or void in a targeted treatment area. Thetool10 comprises ashaft12 having a proximal and a distal end, respectively14 and16. Theshaft12 preferable includes ahandle18 to aid in gripping and maneuvering theshaft12 through a pre-formed access path into bone. Thehandle18 can be made of any suitable material, e.g., any rigid polymer or metal or combination thereof, secured about theshaft12. Thehandle18 is desirably sized and configured to be securely and comfortably grasped by the physician.
• Theshaft12 carries a void-formingstructure20 at itsdistal end16. In the illustrated embodiment, thestructure20 takes the form of amulti-faceted cutting tip20. The cuttingtip20 may be adapted for use in various body regions, e.g., to create a void in bone. The cuttingtip20 may also serve to remove hard or soft tumors from tissue. As used in this specification, a cutting tip is a surface adapted to mechanically form a void in bone through contact with the bone, e.g., by cutting, shearing, scooping, shaving, sciving, dissecting, or scoring of the bone.
• The cuttingtip20 is hingedly coupled todistal end16 of theshaft12. The cuttingtip20 is desirably adapted to extend radially from theshaft12 and radially from the pre-formed access path to a diameter that is greater than a diameter of the access path. The cuttingtip20 can be made of any suitable biocompatible material, e.g., stainless steel, cobalt chromium, titanium and alloys or mixtures thereof. Theshaft12 and cuttingtip20 can alternatively be made of different materials (e.g. alloys of stainless steel with different strengths: 303 stainless steel, 304 stainless steel, 17-4 stainless steel, 17-7 stainless steel) and welded or otherwise bonded together. As will be described in detail later, an actuator, e.g., wheel22 (see also, e.g.,FIGS. 19 and 23), permits selective movement of the cuttingtip20 from a first, closed or non-deployed position to a second, open or deployed position.
• In the closed position (represented by solid lines inFIG. 1), the cuttingtip20 extends from thedistal end16 of theshaft12 along the axis S of theshaft12. In this position, theshaft12 can be easily passed through acannula23 or other instrument. The hinge mechanism permits pivoting of thetip20 at an angle A transverse to axis S ofshaft12 to the opened position (represented in phantom inFIG. 1). In a preferred embodiment, the cuttingtip20 is adapted to pivot and be selectively secured in any pivot position from 0-90° relative to the axis S of theshaft12.
• Desirably, the actuating mechanism provides positive, controlled movement in both directions (i.e., from the open, deployed position to the closed, non-deployed position and from the closed, non-deployed position to the open, deployed position) during all degrees of actuation. That is, the secured pivot position and angle A are maintained regardless of the rotational orientation of theshaft12. The actuator mechanism provides positive cutting action as the tip is actuated in either direction to provide bi-directional cutting. Actuation may be repeated so as to provide continuous cutting. The speed of actuation may be varied to vary the speed of cutting. The cuttingtip20 also permits translational (i.e., longitudinal) movement along the axis S of theshaft12 in a push-pull or sawing motion with the tip in the deployed position. The physician creates a desired void by repeated actuation, translational movement, or by performing a series of combined actuation and translational movements.
• In use, the cuttingtip20 is placed in the closed position extending from thedistal end16 of theshaft12, i.e., at a 0° angle A relative to axis S. Thetool10 may be introduced into a targeted treatment site through an open procedure. Desirably, thetool10 is introduced in a closed and minimally invasive procedure in which apercutaneous cannula23 is advanced into a desired treatment region, e.g., avertebral body37. Theshaft12 is then passed through thecannula23 and the cuttingtip20 is extended beyond the distal end of thecannula23. Alternatively, thecannula23 may be removed after introduction of thetool10. Fluoroscopy or other visualization techniques may be employed to aid in introducing thecannula23 and tool into the targeted treatment area. The cuttingtip12 is then pivoted to a desired position, i.e., preferably any position between 0-150°, and most preferably about 90°. Also, conceivably thetip20 could deploy in either direction without stopping in the non-deployed condition. Actuation may be repeated and theshaft12 advanced in fore and aft directions by pushing and pulling in a sawing-like motion to thereby create a void.
• If rotational cutting is desired, turning ofshaft12 is required to reposition thetip20 to continue cutting. In this case, the cuttingtip20 is returned to the closed position and theshaft12 turned or rotated to a new position. The cuttingtip20 is again pivoted to a desired angle A (open position) and theshaft12 again advanced in fore and aft directions using a push-pull motion. It is apparent that theshaft12 may be repositioned any number of times to produce a void of a desired configuration.
• With reference now toFIGS. 2 and 3, thecannula23 desirably incorporates a distal portion having a reduced profile. Thecannula23 includes alarge diameter portion25, a small diameterdistal portion27, and atransition portion29. Alternatively, thecannula23 may provide a taper between the large andsmall diameter portions25 and27 (not shown). Theshaft12 of thetool10 is desirably sized to fit within alumen31 extending through thecannula23, and may be of a constant or varying size.
• Desirably, the reduced distal tip diameter of thecannula23 will allow the tip of thetool10 to be inserted into the targeted bone, with a corresponding reduction in the size of the access path created in the bone. Thesmaller diameter section27 of thecannula23 will pass through the cortical wall into the bone, while thelarger diameter section25 can abut against the outside of the bone (sealing the opening, if desired), and will desirably stretch, but not tear, softer tissues.
• In a preferred embodiment, thesmaller diameter portion27 is desirably sized such that, when thelarger diameter portion25 abuts thecortical bone33 of thepedicle35, the distal end of thesmaller diameter portion27 extends through thepedicle35 and emerges into thevertebral body37 and enters intocancellous bone39. In this embodiment, thetool10 could be sized such that, when fully inserted into thecannula23, thedistal cutting tip20 would be prevented from contacting and/or breaching the anteriorcortical wall41 of thevertebral body37 or targeted bone.
• Other low profile bone access tools are described in U.S. patent application Ser. No. 09/952,014, filed Sep. 11, 2001, entitled “Systems and Methods for Accessing and Treating Diseased or Fractured Bone Employing a Guide Wire,” which is herein incorporated by reference.
• B. T-Tip Embodiment
• In many cases, it is desirable to cut in both a rotational as well as in a translational direction. In such cases, it is preferable that the rotational cutting motion reflects an ergonomic and natural motion for the physician.FIGS. 4-9 illustrate an embodiment of acutting tool100 having a cuttingtip120 which permits translational, rotational, or simultaneous translational and rotational movement of the cutting tip using an ergonomic and natural motion. The cutting tip is made from any suitable biocompatible material, e.g., stainless steel.
• AsFIG. 4 illustrates, the cuttingtip120 provides apivot region124 hingedly attached to ashaft112, e.g.,pivot pin126 passes throughhole128 inpivot region124 and intoshaft112. This arrangement permits a wide range of pivot motion allowing the cutting tip to pivot at virtually any desired angle. In a preferred embodiment, the cuttingtip120 is adapted to pivot from 0-90° relative to the axis S of theshaft112. Similar to the embodiment ofFIG. 1, the actuating mechanism is positive in both directions.
• Acollar130 divides thepivot region124 and atrunk region132 and provides additional strength and support to thecutting tip120. The maximum width (W) of thetrunk132 is parallel to the axis S of theshaft112 when thetip120 is deployed at 90° (illustrated in phantom inFIG. 4).
• Thetrunk132 carries acutting disc134 providing a dual rounded cutting surface extending on either side of thetrunk132, providing a 360° cutting surface. In a preferred embodiment, the diameter ofdisc134 is approximately the same as the diameter of theshaft112 so as to minimize stress on thetip120 during cutting and to provide ease of passage through a cannula.
• The tip includes a flat orstraight cutting surface136 along the tip of thedisc134 that provides greater ease in cutting bone on the pullback motion. When pushing, theshaft112 provides the strength and force for cutting.
• Thedisc134 andtrunk132 together provide a large surface contact area that enables thetip120 to take an aggressive bite into bone and gouge bone material in large chunks.
• The disc configuration allows rotational cutting in both clockwise and counterclockwise directions. With reference toFIG. 5, thetip120 is extended to a desired angle A, e.g., 90° along axis T. Theshaft112 is then rotated 0-90° in a first direction (represented by arrow138) relative to axis T. Theshaft112 can be rotated 0-90° in the opposite direction (represented by arrow140) relative to axis T to create a void extending 180° by a simple turning of the physician's wrist.
• FIG. 6 illustrates rotation of thecutting tip120 in bone, e.g., avertebra142, to create a 180° void. In many cases, it may be desirable to create a void extending 360°. AsFIG. 7 shows, after formation of a 180° void, theshaft112 may be rotated 180° and again aligned approximately along axis T. Theshaft112 is then rotated 0-90° in a first direction (represented by arrow144) relative to axis T. Theshaft112 can be rotated 0-90° in the opposite direction (represented by arrow146) relative to axis T to create a void extending 360°. The physician can monitor the position of thetip120 with use of fluoroscopy.
• The disc configuration also allows translational cutting in a push-pull or sawing motion as represented by arrows inFIGS. 8 and 9. In use, the physician may deliver translational and rotational forces simultaneously by pushing in and pulling out while simultaneously rotating a handle or alternating rotational and translational motions. In this manner, the physician controls rotational and translational movement of thecutting tip120 to create a void of desired size and shape, e.g., cylindrical.
• Desirably, as seen inFIG. 10, theshaft112 carries a boss or stop102 designed to limit forward, i.e., translational, motion of theshaft112 within acannula104. The diameter of thestop102 approximates the diameter of thecannula104 so that thestop102 rests against the face or top106 of thecannula104 to stop forward advancement of theshaft112 within thecannula104.
• Thestop102 is positioned on theshaft112 such that there is sufficient room to accommodate the physician's fingers wrapped around and under thehandle18. Thestop102 thus provides clearance between the physician's fingers and thepercutaneous access cannula104, preventing pinching or catching of the physician's fingers. Thestop102 stops insertion of theshaft112 to leave a comfortable working distance for the physician's hand when rotating the shaft112 (i.e., a sweeping cutting motion) or when using a push-pull cutting motion or a combination of both cutting motions. In a representative embodiment, thestop102 is positioned approximately 1.75 inches (about 4.5 cm.) from the base of thehandle18. By restricting or preventing further advancement of theshaft112, thestop112 prevents advancement of the shaft112 (and void-forming structure20) within the vertebral body. This prevents the possibility of puncturing or breaching the anterior cortical wall of the vertebra142 (see alsoFIG. 9).
• Desirably, amarker band101 is positioned distal of thestop102. As seen inFIG. 10, when theshaft112 is fully inserted into theaccess cannula104, themarker band101 is aligned with theface106 of thecannula104 as the cuttingtip120 is exiting thecannula104 into a bone, e.g., avertebra142. As shown inFIG. 11, when theshaft112 is fully inserted into thecannula104, thetip120 extends beyond the distal end103 of the cannula103.
• In a representative embodiment, themarker band101 is located approximately 3 cm. distal of thestop102. In this embodiment, when theshaft112 is fully inserted into the cannula104 (i.e., resting against the stop102), thetip120 extends approximately 3.5 cm. from the distal end103 of thecannula104 when thecutting tip120 is in the non-deployed position (i.e., aligned with the axis S of the shaft112), and approximately 3 cm. from the distal end103 of thecannula104 when thetip120 is in the deployed position (e.g., at 90°).
• In a preferred embodiment, agroove105 is positioned proximal thestop102. As best seen inFIG. 12, thegroove105 is a turned angular cut having an angle G with a radius R on theshaft112 to define a line of weakness on theshaft112. In a representative embodiment, thegroove105 is a 60° angular cut (i.e., G=approximately 60°) having a radius R of approximately 0.006 inch. The mean torque required for failure of theshaft112 at groove105 (the maximum shaft torque) is less than the torque required for failure of theshaft112 at pin126 (the maximum hinge torque) (see alsoFIG. 4), or more generally, of the cutting assembly itself. For example, it has been found that the mean torque required to scrape normal bone is approximately 2.0 in.-lb. In a representative embodiment, the mean torque required for failure of theshaft105 atgroove105 is approximately 7.3 in.-lb. and the mean torque required for failure atpin128 is 9.3 in.-lb. In the event that excessive torque is translated through theshaft112, thegroove105 results in theshaft112 breaking or severing at thegroove112 before thetip120 breaks or fails at thepivot region124. This provides an additional safety feature that allows theshaft112 andundeformed pivot region124 to be safely removed from thecannula104 without complications. Failure or deformation of thepivot region124 is avoided.
• It is contemplated that the region of weakness can also be formed by any of a variety of other suitable means that provide that theshaft112 will sever or break prior to thetip120 becoming uncoupled from the shaft112 (i.e., that provide that the maximum hinge torque is greater than the maximum shaft torque). For example, as shown inFIG. 12B, aportion111 of theshaft112 may be formed of a material of reduced strength and/or rigidity relative to the remaining portions113A and113B of theshaft112 to define a region of weakness. In one representative embodiment, shaft portions113A and113B are formed of a biocompatible metal andshaft portion111 is formed of a biocompatible plastic material.
• With reference toFIG. 13, theshaft112 may also carry a boss or stop102 with a tine or lug108 that selectively mates with a complementary slot or groove110 in acannula104 or other access device so as to limit rotational motion to a preset angle. In this arrangement, the slot or groove110 defines a cam surface. The tine or lug108 serves as a cam follower. The configuration of the cam surface and cam follower can vary, but preferably define a system in which a sweep of the cam follower across the full range of motion of the cam surface consistently creates a void of a predetermined size and shape.
• FIG. 13 shows an embodiment in which the cam surface takes the form of anelongated slot110 in the circumferential margin of thecannula104. The depth of reach is defined by the depth of the slot. That is, the length LS of the slot limits forward advancement of the stop102 (and therefore the shaft112) within thecannula104. The width WS of the slot is greater than the width WC of the lug ortine102 by a pre-determined amount. The angle of rotation is controlled by the extent of theslot110, i.e., the difference in width between theslot110 and the width of tine or lug108 (i.e., the difference between WS and WC). Because the depth of the reach and the angle of rotation are pre-determined and constant, a sweep of the full range of motion of the cam surface and the cam follower consistently creates a void of a predetermined size and shape. For example,FIG. 14 illustrates the formation of a pre-determined pie-shaped void having an angle A1. The pre-determined void has a length corresponding to the length LS ofslot110 as shown inFIG. 13. Theslot110 can be varied, e.g., by varying the width of theslot110 along its length, to form voids of a desired, pre-determined shape and size. For example,FIG. 13A illustrates an alternative embodiment of aslot110A in which theslot110A is generally T-shaped and adapted to form a pre-determined void biased such that the most forward portion is of greater volume, with each volume also being wedge shaped.
• In use, thetool100 is introduced into a targeted treatment site. Desirably, thetool100 is introduced in a closed and minimally invasive procedure in which apercutaneous cannula104 is advanced into a desired treatment region, e.g., a vertebral body. Introduction of the tool may be assisted by conventional visualization techniques, as previously described. Theshaft112 is then passed through thecannula104 and thecutting tip120 is extended beyond the distal end of thecannula104. The cuttingtip112 is then pivoted to the desired position, i.e., any position between 0-90°.
• The physician manipulates thecutting tip120 by sweeping theshaft112 along the full range of motion of the cam surface and cam follower. Thestop102 serves to limit translational movement of theshaft112 along thecannula104 and the lug ortine108 limits rotational movement of theshaft112 within thecannula104 to create a void of a pre-determined size and shape. Because the void created is of a consistent and pre-determined size and shape, visualization is not required during cutting and void formation. The need for fluoroscopy or other visualization techniques is thereby reduced, limiting the patient's exposure to radiation or dyes. Upon completion of the procedure, the cuttingtip112 is returned to the non-deployed position and thecannula104 andtool100 are withdrawn.
• C. Turned and Tapered Trunk Embodiment
• FIGS. 15 and 16 illustrate an alternative embodiment of atool200 for creating voids in interior body regions. In this embodiment, thetrunk232 is tapered and rotated 90° relative to the embodiment shown inFIGS. 4-9 so that the maximum width W of the trunk is perpendicular to the axis S of theshaft212 when thetip220 is deployed at a 90° angle A from the axis S of theshaft212.
• This arrangement minimizes the combined surface area of thedisc234 andtrunk232 in contact with the bone during scraping and cutting and thus minimizes transmission of significant force and stress to the hinge mechanism.
• Thedisc234 has a convexfront surface248 providing a dome-shape. Preferably, thedisc234 has a diameter that is approximately the same as the diameter of theshaft212, minimizing stress on thetip220 during cutting and providing ease of passage of thetip220 through a cannula. The domed configuration facilitates cutting and scraping of bone by producing leverage on the bone that allows thetip220 to roll out of the bone easily. The domed configuration allows the tip to easily release from bone and to disengage from the bone for easy withdrawal.
• Thedisc234 provides a 360° cutting surface and permits both translational and rotational movement of thecutting disc234 when deployed at the desired angle A, as previously described.
• D. Conical Trunk Configuration
• FIGS. 17 and 18 illustrate another alternative embodiment of atool300 for creating voids in interior body regions. In this embodiment, thetrunk332 is tapered similar to the embodiment ofFIGS. 15 and 16, but is conical.
• Thetrunk332 also carries a dome-shapeddisc334 allowing both translational and rotational cutting, similar to the embodiment ofFIGS. 15 and 16.
• The combined cutting surface of thedisc334 andtrunk332 is minimized and is designed to reduce the force and stress on the hinged mechanism by minimizing the contact area in the bone in all directions. The same profile (symmetrical cross-section of the conical trunk332) is presented to the bone regardless of whether pushing or pulling (translational) force, turning (rotational) force, or a combination of both forces is applied.
• II. Actuator Mechanism
• A. Thumbwheel Embodiment
• FIGS. 19-22 illustrate one embodiment of an actuator mechanism for use with a void-forming tool. The actuator mechanism converts rotational motion into translational movement to control the deployment of a cutting tip. By way of illustration and not limitation, the actuator mechanism is illustrated with the cuttingtip120 embodiment ofFIGS. 4-9.
• The actuator mechanism provides athumbwheel150, an insert orcap152,flange154,plunger rod156, androtational stop158. Thethumbwheel150,cap152,flange154,plunger rod156, and stop158 may be made of any suitable metal. The thumbwheel is seated in a free-floating manner in aslot160 withinhandle18. In a preferred embodiment, thehandle18 is made of a strong and durable polymer plastic.
• Thethumbwheel150 extends, at least in part, from thehandle18 for manipulation by the thumb or index finger of the user, as seen inFIG. 19. Thethumbwheel150 desirably includes grooves or knurls for easy grasping and manipulation. While thethumbwheel150 may be configured for manual manipulation, it is contemplated that the actuator may also be power-driven. Thecap152 is seated within thethumbwheel150 and is desirably threaded or otherwise adapted to engage thewheel150 so as to move with thewheel150. Thecap152 is connected, e.g., by welding, to theplunger rod156. The transmission ratio, and therefore the amount of torque delivered, may be controlled by altering the thread pitch of thecap152.
• Theplunger rod156 is sized and configured to be seated within theshaft112 and to extend beyond theshaft112 andthumbwheel150 through bores in thecap152 andthumbwheel150. In the illustrated embodiment, thethumbwheel150 andshaft112 are positioned offset on thehandle18 for placement of theshaft112 between the index and middle finger, as seen inFIG. 19. As shown inFIG. 21, the distal end of theplunger rod156 is coupled totether wire166. Thetether160 is looped to pass throughholes168 in cuttingtip120 belowpin126 and is swaged or welded to theplunger rod156. Movement ofplunger rod156 regulates pressure on thetether160 to actuate thetip120 between the deployed and non-deployed positions. Thetether160 will keep thetip120 attached toshaft112 in the event of breakage or failure ofpin126 to permit easy removal. This prevents parts from being left behind during removal, thereby providing an additional safety feature.
• While the illustrated embodiment shows thetip120 coupled to theshaft112 and additionally tethered to theshaft112 by arod156, it is contemplated that thetip120 may be additionally tethered to theshaft112 by any of a variety of ways to provide that thetip120 remains tethered to theshaft112 if the coupling element (e.g., pin126) becomes inoperable. For example, in an alternative embodiment, thetip120 is additionally tethered toshaft112 by a cable or pulley (not shown).
• Theflange154 is seated in aslot170 within thehandle18 and is coupled to theshaft112, e.g., by welding or by interference or compression fit. Desirably, theflange154 includes an offset bore such that there is only one way in which it may be seated withslot170. Theflange154 engages theshaft112 within thehandle18 and is sized and configured to essentially prevent rotational movement of theshaft112.
• In the illustrated embodiment, therod156 has arectangular end172 sized and configured to pass through a complementaryrectangular opening174 in thestop158. Thestop158 engages therod156 to prevent rotation of therod156 during actuation. Thestop158 is mounted to theplunger rod156 and seated exterior to and againstslot160. The arrangement of themetal stop158 against theplastic slot160 creates additional frictional forces to provide additional strength and reinforcement and serves to limit the amount of torque delivered to theplunger rod156.
• Rotation of thethumbwheel150 in a first direction advances theplunger rod156 in a first direction along theshaft112 to decrease tension onwire166 and actuate deployment of thecutting tip120. Rotation of thethumbwheel150 in the opposite direction advances the plunger rod in the opposite direction within theshaft112 and increases tension onwire166 to actuate movement of thecutting tip120 from the deployed to the non-deployed position. This arrangement converts the rotational movement of thethumbwheel150 into the translational movement of theplunger rod156.
• In an alternative embodiment, shown inFIG. 22, alever176 is hingedly attached to theplunger rod156. Movement of thelever176 in a first direction advances the plunger in a first direction to deploy thecutting tip120, and movement of thelever176 in the opposite direction advances theplunger156 in a second direction to move thecutting tip120 from the deployed to the non-deployed position. In this manner, thelever176 permits the physician to continuously and conveniently move thetip120 itself without moving theshaft112 to create a reciprocating cutting motion.
• B. Gear Embodiment
• FIGS. 23-25 illustrate an embodiment of an actuator similar to the embodiment ofFIGS. 19-21. The actuator provides a series of gears that interact to convert rotational motion to translational motion.
• Acentral gear178 is similar in configuration and function to thethumbwheel150 shown inFIGS. 19-21. Thecentral gear178 andshaft112 are centered along the bottom of thehandle18 for placement of theshaft112 between the middle and ring fingers.
• Control knobs180A and180B are provided at each end of thehandle18 for actuation by the user's thumb. Alternatively, thecontrol knobs180A and180B may be driven by a motor. Eachcontrol knob180A and180B defines a gear that actuates a correspondingintermediate gear182A or182B positioned between thecontrol knob180A or180B and thecentral gear178. Rotation of thecontrol knob180A or180B actuates the correspondingintermediate gear182A or182B and thecentral gear178. Rotational movement of the control knob180 is thereby converted into translational movement of theplunger rod156, similar to the previous embodiment.
• The symmetric design is designed for easy use by either the right or left hand. Further, the symmetric design allows easy rotation of thehandle18.
• In use, theshaft112 is advanced through acannula104. The cuttingtip120 is extended beyond the distal end of thecannula104. Acontrol knob180A or180B is rotated to deploy thecutting tip130 to the desired angle. The physician then creates a desired void by performing a series of translational and rotational movements of theshaft112. The physician then returns the cuttingtip120 to the non-deployed position.
• If desired, thehandle18 can then be rotated 180°. The opposingcontrol knob180A or180B is then manipulated to again deploy thecutting tip120 to a desired angle and another series of translational and rotational movements may be performed.
• Once the desired void is created, the physician returns thetip120 to the non-deployed position. Thetool100 is withdrawn from the patient. The physician then completes the procedure by filling the void with a bone cement or bone substitute, removing thecannula104, and closing the incision.
• The rate and/or force of cutting may be controlled by altering the transmission ratio. The force may be varied by varying the screw thread pitch or the transmission gear ratio. The rate of motion (i.e., speed of actuation) may be varied by manually or mechanically varying the speed of actuation.
• III. Alternative Embodiments of Mechanical Void Creators
• A. Shape Memory Alloys
• FIGS. 26-28 illustrate an embodiment of atool700 employing acutting tip720 formed of a shape memory alloy. Use of a shape memory alloy allows for a smaller instrument as the hinge mechanism is no longer needed to activate the tip. Smaller instruments are safer and can access smaller vertebral bodies located higher in the spine. Smaller instruments are also less invasive and are less traumatic to the patient, allowing for a faster recuperation time.
• Amalleable rod701 formed of a shape memory alloy, e.g., Nitinol, is provided. It is contemplated that therod701 may be of a variety of different diameters, tip configurations, and actuation angles. Therod701 has a malleable or straightened state (FIGS. 26 and 27) and an activated or articulated predetermined, desired state (FIG. 28). Therod701 is sized and configured for passage in a straightened or malleable state through acannula104 into a vertebra or any bone surface. Once inserted into the bone, therod701 returns to its predetermined, desired memory shape as a result of either the body temperature of the patient or by means of an electrical impulse (e.g., cooling, heat, voltage, etc.). For example, the distal end of therod701 is activated to an angle, e.g., 90°, to form an elbow defining a cutting tip, as shown inFIG. 28. In a representative embodiment, the length from the distal end of the rod to the bend is approximately 0.5 cm. Cutting of the bone is accomplished by a rotating motion or a push-pull motion or a combination of both motions, as previously described. Therod701 desirably includes alumen703 that permits introduction of a cooling or heating media (S), e.g., saline, to return therod701 to a straightened state allowing for easy withdrawal.
• In another embodiment, therod701 is formed from a shape memory alloy with an activation temperature that is equal to room temperature, i.e., therod701 is fully austenitic at room temperature. Therefore, therod701 is fully articulated to its predetermined shape at room temperature. Therod701 is chilled to a martensitic condition (malleable state) prior to insertion into bone, allowing for easy insertion. Therod701 articulates to the predetermined, desired position upon returning to room temperature. This ensures that the proximal end of thecutting tip720 attains full activation without depending on heat transfer from the distal end of the rod701 (which is in contact with the patient) or any outside means (e.g., heat, voltage, etc.). Alumen703 is provided in therod701 to facilitate the introduction of a cooling media (S), e.g., chilled saline, to deactivate the material and allow for easy withdrawal. In another alternative embodiment, the alloy is super-elastic and thecannula104 confines the pre-bent or formed cuttingtip720 until the activation mechanism deploys thecutting tip720 to extend beyond the cannula104 (seeFIGS. 35A and 35B).
• In another alternative embodiment, therod701 may be used to straighten thecannula104 which is formed of a shape memory alloy. In this embodiment, the cuttingtip720 is disposed on the shape memory cannula104 (not shown). Thecannula104 is educated to have a curved tip and therod701 is moveably disposed within thecannula104 to straighten thecannula104 by fully engaging therod701 within the cannula104 (i.e. by pushing the rod701) and to allow thecannula104 and cuttingtip720 to curve or articulate by pulling back on therod701. Desirably, therod701 is made of a rigid material, such as stainless steel.
• In another embodiment, the activation temperature of the alloy is set at a temperature higher than body temperature. In this embodiment, therod701 is malleable for insertion and withdrawal. Therod701 achieves full activation to its predetermined shape only through the application of heat or voltage. This permits control of the change of the state of therod701 from malleable to the predetermined shape, or any percentage there between, using a potentiometer or other suitable device.
• Therod701 may be attached to a handle by a standard square drive or Hudson-style orthopedic fitting on the proximal end (not shown). A torque-regulating handle could be mated to therod701 to allow for torque-limiting rotational scraping.
• In one embodiment, therod701 is fixedly attached or otherwise coupled to ahandle18 having an actuator mechanism. For example, in the illustrated embodiment, therod701 is coupled to athumbscrew152 and is driven by an actuator mechanism similar to the mechanism illustrated inFIGS. 19 and 20. Therod701 is actuated (moved in fore and aft directions) within thecannula104 by the actuator mechanism. This permits thecutting tip720 to be retracted (FIG. 26) in a malleable state within thecannula104 for easy insertion and withdrawal and then extended (FIG. 27) beyond the distal end of thecannula104 within bone and activated for use (FIG. 28).
• In a preferred embodiment, thehandle18 includes aluer fitting705. The fitting705 is sized and configured to mate with a complementary luer fitting707 on a fluid introduction device, e.g., asyringe709, to establish fluid communication between thelumen703 and thefluid introduction device709. Fluid, e.g., chilled or heated saline, may be introduced from thesyringe709 through therod lumen703 to control movement of therod701 between the malleable (deactivated) and activated states.
• In an alternative embodiment, shown inFIGS. 29 and 30, acutting tip720A of a desired configuration is formed at the distal end of themalleable rod701. Thetip720A may be a separate piece welded to therod701, or thetip720A may be carved or otherwise formed in therod701, e.g., by conventional machining techniques. In the illustrated embodiment, the cuttingtip720A is of a conical trunk and domed disc configuration similar to the embodiment illustrated inFIGS. 17 and 18. It is apparent, however, that the configuration of thecutting tip720A can be varied according to the procedure being performed and/or to accommodate individual anatomy. In one embodiment, theentire rod701, including thecutting tip720A, are formed of the shape memory alloy. Therod701 yields from a malleable state (FIG. 29) to the activated state (FIG. 30) as previously described. Therod701 desirably includes alumen703 to permit introduction of a fluid media to control movement between the deactivated and activated states, as also previously described.
• In an alternative embodiment, illustrated inFIGS. 31 and 32, thetip720A and adistal portion711 of therod701 are formed of a shape memory alloy. Arod body713 is formed of any suitable biocompatible, surgical grade material. Thedistal portion711, carrying thecutting tip720A, is welded or otherwise fixed to therod body713. Thedistal portion711 of therod701 yields from a malleable state (FIG. 31) to the activated state (FIG. 32). Therod701 desirably includes alumen703 to permit introduction of a fluid media to control movement between the deactivated and activated states. In an alternative embodiment, therod701 may include adual lumen714 so that fluid media can circulate through theshaft112 and desirably through the cutting tip720 (seeFIG. 33) In another alternative embodiment, therod701 may include athroughbore703A to accommodate more thermal flow (seeFIG. 34).
• B. Alternative Mechanical Void Creators
• FIG. 36 shows an alternative embodiment of amechanical tool400 for creating a void in an interior body region. Ashaft412 carries a sharp, stout,metal spring420 on the end of ashaft412. Theshaft412 can be rotated against the direction of thespring420 causing it to cut bone (or other tissue) in an expanding fashion. Thetool400 is sized and configured to be introduced through a cannula (not shown) with thespring420 extending beyond the cannula and theshaft412 rotated into the tissue a short distance at a time. Theshaft412 can then be withdrawn to remove any captured tissue. If no tissue is captured, thetool400 is reintroduced farther into the tissue and tissue removal is again attempted. Thetool400 may also be used to loosen tissue to allow better cutting and/or removal by other mechanical tools.
• FIG. 37 shows another embodiment of amechanical tool500 for creating a void in an interior body region. Two ormore fingers520 are carried on the distal end of ashaft512. Preferably, theshaft512 carries fourfingers520, twofingers520 facing each other. Thefingers520 are introduced into the tissue through a cannula (not shown), and then mechanically closed with a pulley-type system or other similar system to grab tissue for extraction. Desirably, thefingers520 are adapted to further expand as the size of the void increases. It is apparent that the length of thefingers520 may be chosen to suit the intended use and particular individual anatomy.
• FIGS. 38 and 39 show another embodiment of amechanical tool600 for creating a void in an interior body region. The tool includes a hinged void-creatingdevice620 carried on the distal end of theshaft612. The void-creatingdevice620 may be used to create a void or to loosen tissue to allow better cutting and removal by other mechanical tools.
• The void-creatingdevice620 provides for adjusting the height of thedevice620. Apositioning rod621 is coupled to thedevice620 for expanding and contracting thedevice620. The height may be adjusted by drawing in therod621 to increase the height H and pushing out on the rod to decrease the height H of thedevice620. Calibrated markings (not shown) may be provided on the rod handle to indicate the dimension of thedevice620 as therod621 is drawn back or advanced. The height H may also be chosen to suit the intended use and particular individual anatomy.
• FIG. 40 shows an embodiment similar toFIGS. 35 and 36, but additionally providing a spring blade or series ofspring blades623 for more aggressive cutting. Thespring blades623 are coupled to the last blades out of the cannula and desirably pre-bent to cut parallel to the end plates.
• IV. Creation of Voids in Bone
• Two or more different mechanical cutting tools of the type described may also be used in combination to form a cavity or void of a desired size and configuration in a targeted bone. In addition, one or more mechanical cutting tools may be used in combination with one or more expandable void-creating tools to form the desired void. Expandable structures for creating voids in bones are described in U.S. Pat. Nos. 4,969,888, 5,827,289, 5,972,015, 6,235,043, 6,248,110, and 6,607,544, all of which are herein incorporated by reference.
• Fracture reduction and deformity correction is influenced by a variety of factors, including, but not limited to, acuteness of the fracture, bone quality (e.g. osteoporosis, bone cancers, steroid-induced osteoporosis), and healing. In some fractures, expansion of the expandable structure may be distorted by a region or regions of hard bone. This results in a high pressure within the expandable structure and low volume of expansion media within the expandable structure. The use of a mechanical cutting tool to selectively break up the region of hard bone will allow the expandable structure to achieve a more consistent and reliable fracture reduction. Mechanical cutting or scraping tools will break bone, but an expandable structure is required for the en-masse endplate reduction and deformity correction.
• In use, an access path to bone is made using a conventional access cannula by techniques commonly known in the art. A first void creator, which may be a mechanical cutting tool or an expandable structure, is then introduced into a bone to create a void. The first void creator is then removed. A second void creator, which may be the same as or different from the first void creator, is then inserted into the bone to enlarge or further define the void to form a void of a desired size and configuration. The second void creator is then removed. If desired, a third void creator, which may be the same or different from the first and/or second void creators, may then be introduced to further enlarge and define the void and then removed. Desirably, a filling material, e.g., bone cement or bone substitute, is then injected or otherwise introduced into the void to fill the void.
• In one embodiment, illustrated inFIGS. 41A-41D, a firstmechanical cutting tool800A and a secondmechanical cutting tool800B, which may be different in size and/or configuration from thefirst cutting tool800A, are used to create avoid802 of a desired size and configuration. Anaccess cannula104 is percutaneously introduced to provide an access path into a bone, e.g., a vertebra142 (FIG. 41A). The firstmechanical cutting tool800A is introduced through thecannula104 into thecancellous bone39 of thevertebra142. The cuttingtip820A is manipulated in a series of longitudinal and/or rotational movements to create a void802 in the cancellous bone39 (FIG. 41B). Thefirst cutting tool800A is then removed. The secondmechanical cutting tool800B is then introduced and manipulated in a series of longitudinal and/or rotational movements (FIG. 41C). Thesecond cutting tool800B desirably has acutting tip820B of a different size and/or configuration to enlarge and/or otherwise further define the void802 created by thefirst tool800A. For example, in the illustrated embodiment, thesecond cutting tool800B has acutting tip820B of a greater height than thefirst cutting tip820A to enlarge thevoid802, but is of a similar configuration. Thesecond cutting tool800B is then removed. Afiller material804, e.g., bone cement or bone substitute, may then be introduced into the void802 to fill the void802 (FIG. 41D).
• Alternatively, as shown inFIGS. 42A-42E, after removal of thesecond cutting tool800B, anexpandable structure900 may be introduced through thecannula104 and expanded to enlarge and/or further define the void802 created by the first and second mechanical cutting tools802A and802B. While in the illustrated embodiment theexpandable structure900 takes the form of a balloon adapted to expand or form a void by compression of cancellous bone, theexpandable structure900 may be any suitable device which can be expanded to enlarge and/or further define the void. For example, theexpandable structure900 may also be a mechanical jack, retractor, or spring. Desirably, theexpandable structure900 has a collapsed condition permitting insertion of theexpandable structure900 through thecannula104 and an expanded condition in which theexpandable structure900 compactscancellous bone39 upon expansion within thecancellous bone39. Theexpandable structure900 is then removed. The void802 may then be filled, as previously described.
• In another embodiment, illustrated inFIGS. 43A-43D, a firstexpandable structure900A and a secondexpandable structure900B, which may be different in size and/or configuration from the firstexpandable structure900A, are used to create avoid802 of a desired size and configuration. Anaccess cannula104 is percutaneously introduced to provide an access path into a vertebra142 (FIG. 43A). The firstexpandable structure900A is introduced through thecannula104 in the collapsed condition into thecancellous bone39 of thevertebra142. Theexpandable structure900A is then expanded to create a void802 in cancellous bone39 (FIG. 43B). The firstexpandable structure900A is then removed. The secondexpandable structure900B is then introduced and expanded (FIG. 43C). The secondexpandable structure900B is desirably of a different size and/or configuration such that expansion of the secondexpandable structure900B enlarges and/or otherwise further defines the void802 created by the firstexpandable structure900A. For example, in the illustrated embodiment, the secondexpandable structure900B is of a larger volume, but is of a similar configuration. It is contemplated, however, that the secondexpandable structure900B may be of a different configuration than the firstexpandable structure900A. The secondexpandable structure900B is then removed. Afiller material804, e.g., bone cement or bone substitute, may then be introduced into the void802 to fill the void802 (FIG. 43D).
• Alternatively, as shown inFIGS. 44A-44E, after removal of the secondexpandable structure900B, if desired, amechanical cutting tool800 may be introduced through thecannula104 to enlarge and/or further define the void802 created by the first and secondexpandable structures900A and900B. Thecutting tool800 is then removed. The void802 may then be filled, as previously described.
• FIGS. 45A-45E illustrate another method of creating a void802 in bone of a desired size and configuration. Anaccess cannula104 is percutaneously introduced to provide an access path into a vertebra142 (FIG. 45A). A firstexpandable structure900A is introduced through thecannula104 in the collapsed condition into thecancellous bone39 of thevertebra142. Theexpandable structure900A is then expanded to create a void802 in cancellous bone39 (FIG. 45B). Because the reticulum of thecancellous bone39 may be somewhat dense, it may be difficult for theexpandable structure900A to sufficiently compact thecancellous bone39 to permit full expansion of theexpandable body900A. This may occur with older fractures or in normal bone that has been injured by trauma, but is not necessarily osteoporotic. In this case, theexpandable structure900A may expand preferentially in a given direction depending on the density of the reticulum, but is not able to expand to its full preformed shape, as seen inFIG. 45B. The firstexpandable structure900A is then removed.
• Amechanical cutting tool800 is then introduced (FIG. 45C). The cuttingtip820 is manipulated in a series of longitudinal and/or rotational movements to enlarge and/or otherwise further define the void802 created by theexpandable structure900A. Thecutting tool800 is then removed.
• If desired, a secondexpandable structure900B, which may be of a different size and/or configuration from the firstexpandable structure900A, is then introduced prior to filling the void802 (FIG. 45D). Use of thecutting tool800 to break or cut the reticulum and expand thevoid802 allows the secondexpandable structure900A to fully expand. The secondexpandable structure900A is then expanded to enlarge and/or otherwise further define the previously createdvoid802. The secondexpandable structure900B is then removed. Alternatively, instead of a secondexpandable structure900B, the firstexpandable structure900A may be reintroduced, re-expanded, and then removed. Afiller material804 may then be introduced into the void802 to fill the void (FIG. 45E).
• In an alternative method shown inFIGS. 46A-46E, anaccess cannula104 is percutaneously introduced to provide an access path into a vertebra104 (FIG. 46A). Anexpandable structure900 is introduced and expanded to create a void802 in cancellous bone39 (FIG. 46B). The firstexpandable structure900A is then removed.
• A firstmechanical cutting tool800A is then introduced (FIG. 46C). The cuttingtip820A is manipulated in a series of longitudinal and/or rotational movements to enlarge and/or otherwise further define the void802 created by theexpandable structure900. Thecutting tool800 is then removed.
• If desired, a secondmechanical cutting tool800B, which may be of a different size and/or configuration from the firstmechanical cutting tool800A, is then introduced prior to filling the void802 (FIG. 46D). The cuttingtip820B is manipulated in a series of longitudinal and/or rotational movements to enlarge and/or otherwise further define the void802 created by theexpandable structure900 andfirst cutting tool800A. Thesecond cutting tool800B is then removed. Afiller material804 may then be introduced into the void802 to fill the void802 (FIG. 46E).
• In an alternative method shown inFIGS. 47A-47E, a firstmechanical cutting tool800A is introduced and manipulated in a series of longitudinal and/or rotational movements to create avoid802. Thefirst cutting tool800A is then removed. Anexpandable structure900 is then introduced and expanded to enlarge and/or otherwise further define the void802 created by thefirst cutting tool800A. Theexpandable structure900 is then removed.
• If desired, a secondmechanical cutting tool800B, which may be of a different size and/or configuration from the firstmechanical cutting tool800A, is then introduced prior to filling thevoid802. The cuttingtip820B is manipulated in a series of longitudinal and/or rotational movements to enlarge and/or otherwise further define the void802 created by theexpandable structure900A and first cutting tool802A. The second cutting tool802B is then removed. Afiller material804 may then be introduced into the void802 to fill thevoid802.
• Alternatively, as seen inFIGS. 48A-48E, instead of a second mechanical cutting tool, a secondexpandable structure900B, is introduced and expanded to enlarge and/or otherwise further define the void created by the firstexpandable structure900A andfirst cutting tool800A.

Claims (9)

1. A tool for creating a void in interior body regions comprising

a shaft,

a tip for contacting bone, and

a hinge member coupling the tip to the shaft, the tip becoming uncoupled if the torque applied exceeds a maximum hinge torque,

the shaft including a region of weakness proximal to the tip along which the shaft will break if the torque applied exceeds a maximum shaft torque, and

the maximum hinge torque being greater than the

maximum shaft torque.

2. A tool as inclaim 1

wherein a scived portion of the shaft defines the region of weakness.

3. A tool as inclaim 1

wherein the region of weakness is an angular groove.

4. A tool as inclaim 3

wherein the angular groove is a turned angular cut of approximately 60°.

5. A tool as inclaim 1

wherein the shaft comprises a first material and a second material different than the first material, and

wherein the second material forms the region of weakness.

6. A tool as inclaim 5

wherein the second material comprises a plastic material.

7. A tool for creating a void in interior body regions comprising

a shaft assembly including a lumen,

a tip for contacting bone coupled to the shaft, and

a rod slidable within the lumen, the rod being tethered to the tip.

8. A tool for creating a void in interior body regions comprising

a shaft including a lumen, and

a tip for contacting bone coupled to the shaft by a coupling element,

the tip being additionally tethered to the shaft such that the tip remains tethered to the shaft if the coupling element becomes inoperable.

9. A tool for creating a void in interior body regions comprising

a cannula,

a shaft having a handle and sized and configured for passage through the cannula, and

a projection on the shaft distal of the handle and extending radially from the shaft,

the projection restricting forward advancement of the shaft within the cannula.

Images