WO2002019930A2

WO2002019930A2 - Tools and methods for creating cavities in bone

Info

Publication number: WO2002019930A2
Application number: PCT/CH2001/000526
Authority: WO
Inventors: Stuart Weikel; Nisra Thongpreda; Mike Lehmicke; Douglas Kephart; Sean Kerr; Larry Binder
Original assignee: Synthes Ag Chur; Synthes (U.S.A.)
Priority date: 2000-09-01
Filing date: 2001-08-31
Publication date: 2002-03-14
Also published as: KR20030040436A; WO2002017794A8; MXPA03001805A; AU2001283749A1; WO2002017794A1; BR0113680A; CA2420688A1; JP2004514470A; US20040133208A1; US20020032447A1; AU2001286924A1; AR030595A1; WO2002019930A3; EP1408841A1; US6679886B2; WO2002017794A9; ZA200301517B; CN1449262A; US7476226B2; US20040087956A1

Abstract

The invention provides new tools and methods for creating cavities in cancellous bone, for example but not limited to vertebroplasty, and for treating these cavities by injecting appropriate treatment materials, i.e., bone paste, cemment, autograft, allograft, etc. The tools include a prove that introduces a passageway to the cancellous area, a cannula which expands the hole in the bon e and provides a passegeway for a tamp of flexible curette to push or tamp back the cancellous structure to from the cavity, and a syringe which fills the cavity with appropriate treatment material. These tools advantageously work together.

Description

TOOLS AND METHODS FOR CREATING CAVITIES IN BONE

The invention relates to tools and procedures, which, in use, form cavities in interior body regions of bones, particularly in vertebrae, for diagnostic or therapeutic purposes according to the definition of claims 1 and 2 to 5.

Certain diagnostic or therapeutic procedures require the formation of a cavity in a bone mass. This procedure can be used to treat any bone, for example, bone which due to osteoporosis, avascular necrosis, cancer, or trauma, is fractured or is prone to compression fracture or collapse. These conditions, if not successfully treated, can result in deformities, chronic complications, and an overall adverse impact upon the quality of life.

For example, as described in U.S. Patents 4,969,888, 5,108,404, and 5,827,389, an expandable body is deployed to form a cavity in cancellous bone tissue, as part of a therapeutic procedure that fixes fractures or other abnormal bone conditions, both osteoporotic and non-osteoporotic in origin. The expandable body compresses the cancellous bone to form an interior cavity. The cavity receives a filling material, which provides renewed interior structural support for cortical bone.

U.S. Patent 5,062,845 described a surgical tool for preparing a graft site between opposing vertebra. The tool has a distal end with external dimensions sized to be passed through the patient's anatomy to a point of entry on the spine. At each incremental extension, the surgeon rotates the handle so that the blades cut out a large chamber equal to the size of the diameter of the extended extendable blades located on the distal end of the tool. After each such cut, the handle turned to progressively increase the diameter of the cutting edges of blades until a chamber of desired size (up to the diameter of the fully extended blades) is formed. Intermittently, between enlarging the diameter of the cavity, the surgeon may retract the blades and remove the tool to flush the cavity being formed. The extension and retraction of the blades.

U.S. Patent 5,512,037 describes a percutaneous surgical retractor having an outer sleeve with an open beveled configuration and having an angle defining a leading edge on the distal end of the outer sleeve to facilitate percutaneous insertion of the retractor; a blade slidable within said outer sleeve between at least a deployed position extending beyond the distal end of the outer sleeve and a retracted position disposed within the outer sleeve, the blade having a deployable memory curved distal end.

The invention provides new tools and methods for creating cavities in cancellous bone, for example but not limited to vertebroplasty, and for treating these cavities by injecting appropriate treatment materials, i.e., bone paste, cement, autograft, allograft, etc. The tools include a probe that introduces a passageway to the cancellous area, a cannula which expands the hole in the bone and provides a passageway for a tamp or flexible curette to push or tamp back the cancellous structure to form the cavity, and a syringe which fills the cavity with appropriate treatment material. These tools advantageously work together.

The probe is a long slender body with a sharp tip and a handle. The outer diameter of the long slender body is sufficient to fit inside the cannula. The tip of the probe may contain a drilling tip, a sharp point, a serrated edge, or a combination thereof. In a preferred embodiment, the probe has a changeable sharp tip firmly held by a probe sheath that provides strength and gently sloping surfaces useful for wedging or pushing away bone.

In use, the cannula may be pre-loaded onto the probe so that the handle of the probe need not be removed to insert the cannula. The probe guides the cannula, while the cannula enlarges the hole in the bone and is firmly anchored in this hole. Once the cannula is in its desired position, the probe may be removed by withdrawing it out f the end of the cannula not engaged with the bone.

The cannu)a is a guiding tube with a cutting edge on the distal end thereof, and is essentially a long cylindrical tube which guides and holds the tamp in place while the tamp is being used to form the cavity. The cannula preferably has a handle to facilitate rotation and working of the cannula into the bone. More preferably, the cannula has a handle with a hole extending there through that is in alignment with and continuous with the hole extending through body. The cannula body preferably is tubular with the hole extending the entire length of the tube. The hole is advantageously, but not necessarily, circular.

The hole is configured and adapted so that other tools, such as those described herein, may be inserted into the bone through the cannula hole. It is further preferred that the hole in the cannula allows the bone tamp to be freely rotatable. In a preferred embodiment, the interior wall of the cannula defines an open cylinder having an inner diameter between about 3 and about 7 mm, more preferably between about 3 and about 6 mm, and most preferably between about 4.2 and about 5 mm. In one embodiment, the exterior wall of the cannula defines a cylinder that is between about 5 and about 9 mm. In a more preferred embodiment, the outer diameter of the cannula is between about 6 and about 8 mm, most preferably between about 6 and about 7 mm.

The cannula may be made of a metal, for example a surgical steel alloy, an elastomer, or any other material suitable for surgical devices. The cannula can be constructed, for example, using standard flexible, medical grade plastic materials, like vinyl, nylon, polyethylenes, ionomers, polyurethane, and polyethylene tetraphthalate (PET). The cannula can also include more rigid materials to impart greater stiffness and thereby aid in its manipulation and torque transmission capabilities. More rigid materials that can be used for this purpose include stainless steel, nickel-titanium alloys (NITENOL material), and other metal alloys.

In a preferred embodiment, the distal end of the cannula is adapted to cut through skin, tissue, and bone. In one embodiment, for example, the distal end of the cannula has a serrated edge. The end is advantageously circular to ease cutting into the bone. In addition, the cannula may also have a widely spaced thread disposed on the exterior body that assists in inserting the cannula into the bone. The threaded cannula also may be used to anchor the cannula into the bone of facilitate removal of the cannula when desired.

The tamp is sized and adapted to pass through the cannula and into the cancellous portion of the bone. In one embodiment, where the tamping mechanism is then carefully expanded and rotated to form the cavity. The tamp has a body which is approximately advantageously, but not necessarily, a long cylinder. In one embodiment the an outer diameter or widest portion of the long body is between about 3 and about 7 mm, preferably between about 4 and about 6 mm, and more preferably between about 4 and about 4.5 mm at the point where the body enters the bone. In one embodiment the diameter or dimensions of the long body is essentially unchanging along the length of the body. The body may be solid or hollow. In many embodiments, there is a groove along one side of the body, wherein a wire or a rod may pass. This wire or rod may be used to control the deployment of the tamping mechanism.

In a preferred embodiment, the tamping mechanism is sized to create cavities wherein the largest radial dimension measured from the axis of the body is between about 4 and about 24 millimeters, preferably between about 6 and about 20 millimeters, more preferably between 8 and 16 millimeters.

This body and the tamping mechanism may be made of metal, for example a surgical steel alloy, an elastomer, or any other material suitable for surgical devices. The body and/or the tamping mechanism can be constructed, for example, using standard flexible, medical grade plastic materials, like vinyl, nylon, polyethylenes, ionomers, polyurethane, and polyethylene tetraphthalate (PET). The body can also include more rigid materials to impart greater stiffness and thereby aid in its manipulation and torque transmission capabilities. More rigid materials that can be used for this purpose include stainless steel, nickel-titanium alloys (NITENOL™), and other metal alloys.

The body typically has the appearance of a long rod or tube. The tamp is designed to have its distal end pass through a cannula and through a passageway cut into the bone. The tamping mechanism, which is on the distal end of the body, therefore also passes through the cannula and into the bone. The other end of the tamp body is controlled by the physician.

The body advantageously may have markings along its length so that the physician may quickly and easily determine the depth at which the tamp reaches into the bone. The physician is able to freely slide the tamp axially within the guide cannula to deploy it in the targeted treatment area.

The physician-controlled end of the body contains a handle and a controlling mechanism by which the tamping mechanism may be deployed during tamping and retracted or un- deployed for removal of the tamp from the bone. While a motor may be used to effect rotation, it may be preferable in certain uses to manually rotate the tamp so that, for example, the physician may feel how easily the tamp is rotated. The handle may be removable, but when tamping this handle should be fixed to the body. This handle is preferably sized and shaped to facilitate easy handling and rotation - that is, sized and shaped like a screwdriver handle. Alternatively, the handle may be shaped like a pistol grip, where squeezing the grip effects a rotation of the tamp. There may be a locking nut to hold the body of the tamp to the handle.

The tamp controlling mechanism controls the deployment of the tamping mechanism on the distal end of the body. Therefore, most embodiments of the tamp provide a control mechanism which runs alongside, or within, the tamp body. The controlling mechanism may move a rod, or extend a wire, or the like, wherein the rod or wire controls the degree to which the tamping mechanism is or may be deployed. In some embodiments, the controlling mechanism provides precise positioning of the tamp. In other embodiments, the controlling mechanism limits the range of motion in which the tamp may move, preferably gradually limiting the range of motion until the tamp is securely held in a single position.

Any method or device may be used to control the deployment of the tamping mechanism. In one embodiment, the controlling mechanism is a fine thread and a collar, whereby rotating the collar relative to the handle of the tamp causes the tamping mechanism to expand, contract, or otherwise be deployed, such as by advancing or retracting the sheath around the tamping mechanism, advancing a rod or similar device to limit the range of motion of the tamp, or the like. Alternatively, the controlling mechanism may limit the expansion or contraction of the tamping mechanism. Preferably, this thread has interruptions, such as flat sides cut at regular intervals, which interact with a locking pin and/or a bearing located within the collar. The locking pin or bearing, when in alignment with the interruptions of the threaded body, moves into the interruption to at least partially resist further turning of the collar. Preferably, the interruptions provide an audible click. As the collar is rotated further, the locking pin or bearing moves out of the interruption.

In practice the controlling mechanism may in fact move the body of the tamp, relative to the handle such that the rod or wire, which may be fixed to the handle, appears to advance or retract when viewed at the distal end of the body. Alternatively, the controlling mechanism may cause the tamp to expand, contract, or otherwise be deployed by moving the tamp itself. In either example, the collar may be fixed to the handle in a manner that allows for rotation of the collar about the handle while restricting the collar from moving along the longitudinal axis of the handle. In one embodiment, the tamp uses a directional tip, i.e., a flapper, attached to the distal end of the tamp as the tamping mechanism. The flapper may be hinged on one end to allow movement of the flapper relative to the body in one plane. In this embodiment, the flapper is hinged, and connected thereby, to the distal end of the cylindrical body so that the distal end of the flapper can be displaced out of alignment with the body so that when the flapper is rotated out of alignment with the body it provides a greater effective radius at the distal end of the tamp. Thus, when the tamp is rotated the flapper can displace cancellous tissue away from the tamp.

In a preferred embodiment, the flapper is hinged, and connected thereby, to the distal end of the tamp body so that the distal end of the flapper can displace itself out of alignment with the body to its maximum extent, and wherein the control rod when extended limits the effective radius at the distal end of the tamp. .

In one embodiment, the flapper may move about the hinge, when unimpeded by the cannula or by the controlling mechanism, through an arc ranging from 0 degrees to between about 60 degrees and about 150 degrees, preferably to between about 80 degrees and about 120 degrees, and most preferably to about 90 degrees, with an angle of 0 denoting alignment with the tamp body. In a preferred embodiment, the range of motion of the flapper can be gradually limited by the control mechanism. For example, as the physician turns the collar as described above, the range of motion of the flapper is restricted from returning to alignment with the tamp until eventually the control mechanism securely holds the flapper in a single position. As mentioned above, it is most preferred that the final position of the flipper is about 90 degrees, although a final position in the ranges noted above may also be suitable.

While the flapper may be configured and adapted to cut the cancellous tissue, compact or tamp it, or both, in one preferred embodiment the flapper has a blunt tip that primarily compacts the tissue. The flapper may be curved or may have curved edges to further promote tamping back cancellous tissue when the tamp is rotated. In some applications, cutting may be preferred over tamping. Thus, the flapper may be configured and adapted to suit the particular application or desired result, such as by using a more aggressive flapper shape to cut tissue instead of tamp it. For instance, in one embodiment the edges of the flapper are designed to cut cancellous material when the flapper is rotated. A preferred flapper is a curved cup-type shape. The flapper may also be a cylindrical rod shape, or a flattened cylindrical or oval shape, a curved propeller-type shape, or a paddle shape. This flapper tip also may be rounded to minimize cutting.

In one embodiment of the tamp with a flapper having a range of motion as described above, there is a rod which passes up a groove in the side of the tamp or, alternatively, up a groove inside the body of the tamp. In this embodiment, the rod is part of the controlling mechanism which, when in its retracted mode, does not interfere with the movement of the flapper. In its fully extended mode, the rod impinges on the flapper on one side of the hinge, which causes the flapper to be displaced from its alignment with the tamp body toward the other side of the hinge to its greatest extent. When the rod is in an intermediate position, the flapper can move from a point somewhat displaced from its alignment with the tamp body where the rod is impinging on the flapper to a point of maximum displacement from its alignment with the tamp body. It is preferred that the linkage is a single part to maintain simplicity in design and use.

Another tamp embodiment employs a expandable ring made from memory metal, i.e., a superelastic nickel titanium alloy such as NITENOL . The expandable ring has a preformed shape so that when the memory metal or NITENOL body is retracted into the body of the tamp there is no expanded ring, and as the NITENOL body exits from the body of the tamp an expanding ring is formed. The structure comprises a ribbon of resilient inert memory metal, which is bent back upon itself and preformed with resilient memory to form a ring. This expandable ring is the tamping mechanism.

The expandable ring may be formed into any desired shape. It also may be symmetrical about an axis or asymmetrical, depending upon the desired performance of the tamp.

Moreover, the expandable ring may be formed such that a portion or side of the ring expands more than another so that the ring appears to be off-center from the longitudinal axis of the tamp body. In one embodiment, the ring is oval in shape, while in another the ring is D-shaped. In other embodiments, the expandable ring forms a polygon, which may have regular or irregular sides and angles.

In a preferred embodiment, the memory metal is in the form of a flattened ribbon. In another preferred embodiment, the edges of the expanding memory metal ring are blunted and/or curved to minimize cutting and to maximize displacement of the cancellous tissue during rotation. Manipulation of the ribbon, i.e., expanding and contracting as well as rotating, when inside bone tamps creates a cavity in the cancellous bone.

In one preferred embodiment, called the symmetrical ring embodiment, the expandable ring when in its fully expanded position forms a ring-like structure with a point on the distal end of the body. In a variation of this embodiment, the ring forms a hexagonal-type structure with one point on the distal portion of the ring and a second point near the body of the tamp. In another embodiment, the ring when in its fully expanded position forms a circular or oval structure, or flattened version thereof. In a third embodiment, the ring forms a rounded triangle, where the radius of each corner of the triangle is beneficially at least 3 millimeters. In these embodiments, the deployment of the ring can be effected by either a wire which allows deployment and retraction of the ribbon outside the body of the tamp, wherein feeding wire in expands the ring and pulling wire out retracts the tube, or in the case of preformed tubes by pushing the tube outside the body, for example with a rod, wherein as more of the ribbon extends past the body of the tube, the ring or other structure will grow or expand in size or length. The option of feeding and retracting wire is preferred.

In a particularly preferred embodiment, the ring forms an asymmetrical ring. In practice, this ring may form a shape of a "D". In this embodiment, one end of the ribbon forming the ring may be attached to a rod while the other end runs back towards the handle. The controlling mechanism in this embodiment controls the expansion of the loop. Of course, the "D" shape of the asymmetric loop is pre-formed. In its fully withdrawn position, the ring is sufficiently compact to fit into the tamp body.

The cannula, tamping body, and/or tamping mechanism may have disposed thereon one or more radiological markers. The markers are made from known radiopaque materials, like platinum, gold, calcium, tantalum, and other heavy metals. The markers permit radiologic visualization of the loop structure, tamp body, and/or cannula within the targeted treatment area.

The systems and methods embodying the invention can be adapted for use virtually in any interior body region, where the formation of a cavity 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. 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 most bone structure, including but not limited to the vertebra.

The invention also provides directions for using a selected tool according to a method comprising the steps of deploying the tool inside bone and manipulating the structure to cut cancellous bone and form the cavity. The method for use can also instruct filling the cavity with a material, such as, e.g., bone cement, autograft material, allograft material, synthetic bone substitute, a medication, or a flowable material that sets to a hardened condition.

Fig. 1 is two views, 90 degrees apart in perspective, of a probe body, and a view of the probe tip from a forward perspective;

Fig. 2 is three views, two of which are 90 degrees apart in perspective, of a probe handle;

Fig. 3 is a view of a assembled probe body and handle and of a probe tip;

Fig. 4 is a view of a the distal end of a operational probe;

Fig. 5 is a view of a probe extending through a cannula;

Fig. 6 is a view of a cannula;

Fig. 7 is a view of a cannula;

Fig. 8 is a view of a cleaning, or flushing, bar.

Fig. 9 is two views, 90 degrees apart in perspective, of a bone tamp of the memory metal ring embodiment; Fig. 10 is three views of a memory metal ring at different levels of deployment;

Fig. 11 is four views of a memory metal ring at different levels of deployment;

Fig. 12 is a view of a bone tamp of the memory metal ring embodiment;

Fig. 13 is a view of a collar controlling mechanism with threads;

Fig. 14 is an expanded view of a memory metal ring;

Fig. 15 is a view of a bone tamp of the rod and memory metal filament for use with the asymmetric memory metal ring embodiment;

Fig. 16 is two views, 90 degrees apart in perspective, of a bone tamp of the flapper embodiment;

Fig. 17 is a view of a flapper only partially deployed;

Fig. 18 is a view of a flapper only partially deployed;

Fig. 19 is a view of a flapper only partially deployed;

Fig. 20 is a view of a flapper that is not deployed;

Fig. 21 is a view of a bone tamp of the flapper embodiment that is not deployed;

Fig. 22 is five views of details of the flapper and hinge;

Fig. 23 is a view of details of a directional tip flapper;

Fig. 24 is a view of the distal end of a bone tamp of the flapper embodiment that is fully deployed;

Fig. 25 is three views of a bone tamp of the flapper embodiment; Fig. 26 is six views of a bone tamp of the flapper embodiment;

Fig. 27 is a view of a bone tamp of the flapper embodiment with a rongeur handle;

Fig. 28 is a view of a syringe-type device for displacing materials through the cannula;

Fig. 29 is two views of a bone tamp of the memory metal ring embodiment as it would appear in a vertebra; and

Fig. 30 is a view of a threaded cannula.

Fig. 1 contains 2 drawings of a probe sleeve 10, Fig. 1A of a top view, Fig. 1 B of a side view, and Fig. 1C of a forward perspective looking only at the distal end. The probe sleeve is adapted to have the probe tip fit 12 slidingly therein. The distal end of the probe tip 12 extends past the distal end of the probe sleeve 10 by a predetermined and variable distance. In one embodiment, the distal end of the probe sleeve 10 is beveled. The sleeve 10 extends from the probe tip for a distance ranging from about 0.05 to about 0.5 millimeters, say about 0.1 to 0.2 millimeters, at a sharp angle, for example between about 30 degrees and about 90 degrees, preferably between about 45 degrees and about 75 degrees, more preferably between about 55 and about 65 degrees, wherein the angle is measured from an imaginary line running axially with the probe sleeve 10. This provides a strong surface that may face shearing action from bone during insertion. The angle of the bevel is then changed to a more gentle angle, say between about 5 and about 45 degrees, preferably between about 15 and about 35 degrees, and maintains approximately this angle until the outer diameter of the probe sleeve 10 is matched. This provides a gentle surface 16 for displacing bone during insertion. When viewed at another angle, the probe sleeve is even more gently angles, with the angle ranging from about 5 to about 30 degrees, providing another gently sloping surface 13 to displace bone. There is a distance scale 18 on the exterior of the probe sleeve 10. Finally, there is a hole 20 in the sleeve. This hole contains a bearing 22 or set screw 22 which locks the probe tip into the probe sleeve. The hole may be beveled to allow the bearing or screw to move to disassemble the probe.

Fig. 2 contains several perspective drawings of a handle 24 for the probe sleeve shown in Fig. 1. The handle has a probe collar 26 which, when in its downward position as shown, locks the bearing 22 into place, thereby securing the probe tip 12 (not shown). The probe tip 12 has a groove sized and positioned to accept a portion of the bearing 22, thereby preventing the probe tip 12 from moving axially in the probe sleeve 10. The probe collar 26 has a groove 28 on its interior surface, wherein if the groove 28 is slid to intersect the bearing 22 then the bearing 22 will disengage from the probe tip 12 and the probe tip 12 can be slid axially. A spring 30 provides downward force on the probe collar 26, so to disengage the probe tip 12 the physician must overcome the force of the spring and slide the collar up toward the handle 22.

The probe tip 12 can be seen in its entirety in Fig. 3, though the groove in which the bearing 22 sits can not be seen. Also shown in Fig. 3 is a probe sleeve 10 and a handle 24 and set screw 22. A close-up of the distal end of the probe sleeve 10 and probe tip 12, after assembly, is shown in Fig. 4. It can be seen that in this embodiment the probe tip has a point formed by making a diagonal cut 32 through the round probe tip. Other methods and shapes for forming a point are equally acceptable.

Fig. 5 shows the probe assembly of Fig. 4 passing through a cannula 34. The cannula 34 has optionally threads 36, a cutting edge 38, and a handle 40.

The cannula 34 of Fig. 5 is more clearly shown in the drawing of Fig. 6. Details of the cutting edge 38 show that there are cutting surfaces 42 set at an angle of 30 degrees, though the angle could range from 20 degrees to about 80 degrees, preferably between about 30 degrees and about 50 degrees, edges with a pitch of about 7.5 millimeters on a

5.4 millimeter outer diameter cannula. The threads 36, when present, are beneficially raised between about 0.05 and about 0.5, say about 0.2 to about 0.3, millimeters above the body of the cannula body 34. The cannula body 34 can have an outer diameter of between about 3 and about 7 millimeters, preferably between about 4 and 6 millimeters, more preferably between about 5 and 5.5 millimeters. The cannula 34 is a tube, where the wall of the tube is between about 0.2 and about 1 millimeter, preferably between about 0.3 and about 0.6 millimeters, in thickness.

Fig. 7 shows a cannula 34 without threads. In this cannula, the handle 40 is a bar handle as opposed to a circular handle of the cannula of Fig. 6. This cannula body 34 has an outer diameter of about 4.8 millimeters. The angle of the cutting surfaces 42 is about 50 degrees. The bar handle may be preferred in some instances because there may need to be a significant amount of torque put on the cannula while edging or cutting the cannula into the bone.

Fig. 8 shows a displacement rod for the cannula where the tolerance between the displacement rod and the cannula is between about 0.1 and about 0.5 millimeters. These displacement rods are used to remove debris from the cannula. Similar rods are used for the bone tamp body.

Fig. 9 shows two views of a memory metal expanding ring bone tamp. The body 44 is shown to be substantially cylindrical, but the cross section may be of almost any type. The body 44 in this embodiment is about 4.2 plus or minus about 0.2 millimeters in outer diameter. The size of the body is not important so long as the body 44 and the ring 46, when retracted, pass through the interior diameter of the cannula. There is a distance scale 48 set in millimeter increments. The length of the body 44 is about 190 millimeters, but this length can vary. The memory metal loop 46 is shown in the expanded position where it has a diameter of about 10 millimeters and a length of about 15 millimeters. The range of expansion for an expanding ring tamp is beneficially between about 4 to about 24 millimeters, preferably between about 6 and about 20 millimeters, more preferably between about 8 and about 16 millimeters.

In this embodiment the collar 50 has a bearing/set screw 52 that slides in channel 54. The mechanism by which the collar is advanced or retracted includes but is not limited to sliding, turning a threaded collar, or even squeezing a pistol grip. Channel 54 is firmly anchored to handle 56. Therefore, when the collar 50 with its bearing or set screw 52 slides in channel 54, the collar 50 and body 44 moves relative to the handle 56. By sliding the collar toward the ring 46, the ring 46 is retracted into the body. The controlling mechanism for the memory metal loop involves withdrawing the memory metal loop 46 into the body 44. In its fully withdrawn state, the memory metal loop 14 shall not exceed past the body 10 by more than about 4 millimeters, say no more than about 2.5 millimeters. The ring 46 is firmly fixed to the handle 56. The push button 58, under a force exerted by spring 60, and tapered bushing 62, keep the rod or wire 64 which is continuous with the memory metal ring 46 firmly fixed to the handle 56. Depressing the push button 58 allows the rod to slide, loosening the gripping force between the rod and the handle. This push button is used when disassembling the tamp for cleaning. Note that a set screw 66 can be used to lock the push button to prevent accidentally releasing the ring assembly.

The physician can expand the memory metal loop 46 by pulling back the collar 50. There is advantageously in collar 50 a thumb hold to give good control over this slidable collar. The collar is held in place by friction, the thumb-force, and optionally with a set screw. The channel 54 has a discrete beginning and end, therefore limiting the amount the body 44 can be slid relative to the handle 56. The channel 54 may have side-facing depressions or grooves which with a twist allow the collar to be "locked" in one of several pre-selected positions.

The shape of the ring 46 is pre-set into the memory metal as is known in the industry. One such shape, shown in Fig. 10, is a rounded triangular shape. Fig. 10 shows how the ring 46 expands as it exits from the body 44. Fig. 11 shows another embodiment where the ring 46 is oval.

Fig. 12 shows another embodiment of an expanding ring bone tamp.

Fig. 13 is an embodiment of the collar 50 where collar movement is affected by rotating the collar on threads 68. The threads 68 advantageously have flat portions 70 made thereon such that the thread can be readily locked, or so that a spring-loaded bearing may make an audible click, as the collar is rotated and the bearing (not shown) passes over the flattened zone. The finer control given by threads allows for partial deployment of the tamping mechanism.

Fig. 14 is a close-up view of the loop 46. In one embodiment, these loops are symmetrical. However, an asymmetric ring is used in another embodiment. In such an embodiment, shown in Fig. 15, one end of the material used to form the ring is supported at least partially by a rod 72 as it extends out of the body 44. The metal is then looped around to form a loop 46 and fed back through the body 44. Control of the deployment of such a loop can be effected either by feeding and withdrawing the ribbon or, more preferably, by moving the body 44 relative to the rod 72. A groove (not shown) along the rod 72 passing back to the handle or along the body 44 allows the ribbon to be easily fed back to the collar or handle where it may be secured.

In each of these embodiments, the material used for the loop is a resilient material, such as a suitable steel or plastic. In an exemplary embodiment, a shape memory material, such as Nitinol, is used for the loop.

Fig. 16 shows a flapper embodiment of a bone tamp. This tamp has the collar 50 with the threads 68. The body 44 of this embodiment has a groove cut therein where the rod 74 passes. If the rod 74 is not encased by the body 44 but just runs in an open groove, it is advantageous to have slidable tie-downs that positively hold the rod 74 against the body 44 in several pre-selected positions. There is a stop 78 that prevents the rod 74 from being over-extended. The rod 74 pushes the flapper 80. In Fig. 16, the rod is fully extended and the flapper is extended out of alignment with the body 44 by about 90 degrees. The set screws or bearings 82 hold the base 84 of the rod 74 withing the collar 50. There is a channel 86 in the base 84 which allows the collar to be rotated without rotating the body 44 or the rod 74. The flapper is held on by at least two points which form a hinge.

The control exhibited by the threaded controlling mechanism is such that the flapper can be only partially deployed, as is shown in Fig.s 17 to 19. Fig. 20 and Fig. 21 show the flapper in its un-deployed position. Note that in Fig. 21 the collar 50 is well back from the stops 78. Fig. 22 shows details of the hinge 88 and blunted flapper 80. Fig. 23 shows a blow-up of a directional flapper 80,where rotating in one direction increases the tamping effect and rotating in the opposite direction increases erosion of the cancellous material. Fig. 24 more clearly shows one type of interaction between the rod 74 and the flapper 80, where the rod slides against and displaces the flapper.

Fig. 25 shows an embodiment of the flapper tamp wherein pulling a metal or plastic wire attached directly to the flapper causes the flapper to move out of alignment with the shaft.

Fig. 26 shows another embodiment of the flapper bone tamp. In this embodiment, the opposite end of the flapper is slidingly engaged at point 90 to the body 44, as well as being hinged at point 88. Fig. 27 shows an embodiment of the flapper bone tamp in which the flapper deploys in response to squeezing a pistol-type grip, also known as a ronguer.

Fig. 28 shows a syringe adapted to fit a tube which is extendable through the cannula. The syringe is adapted to deliver material as necessary for treatment of the formed cavity. Examples of the delivered material include polymethylmethacrylate (PMMA) or other bone filler material. In some embodiments between about 100 psi and about 1500 psi must be generated to inject the treatment material at a ^' sufficient rate. The syringe is advantageously threaded so that turning the threaded portion results in displacement of a plunger and resultant controlled high pressure delivery of material. This structure allows the syringe to deliver the material in a controlled and discrete fashion at a desired pressure.

Fig. 29 shows the deployment of a ring-type bone tamp with the ring made of a shape memory metal. The releasing of the ring corresponds to withdrawing of the body partially from the cancellous area.

Fig. 30 shows a threaded cannula, where the threads are raised from the body to assist in axially moving the cannula through bone.

Of course, the smaller diameter the tools, the less damage is made during entry. These tools have small diameter - for example, the bone tamps most preferably have an outer diameter in the body of between about 4 millimeters and about 6 mm. The cannula has an outer diameter that is typically at least about 1 millimeter greater than this. Size is therefore very important in view of inadvertent damage during ingress and egress of the tools.

In use, the bone tamp body 44 is used for axial and rotational movement within a cannula 34. The physician is able to freely slide the body 44 axially within the guide sheath of the cannula body 34. As a secondary precaution, when fully confined by the cannula, the loop structure, if projecting a significant distance beyond the distal end of the bone tamp body, is collapsed by the surrounding cannula.

During normal operation, the body of the bone tamp collapses the memory metal ring structure. When free of the body of the bone tamp, the loop structure springs open to assume its normal dimension. The physician can operate the collar 50 to alter the dimension of the ring 46 at will.

The physician is also able to rotate the deployed loop structure by rotating the handle. Rotation of the loop structure tamps back, and to some extent slices through surrounding tissue mass. Rotation is preferably manual, as tamping the bone requires better "feel" than does simply cutting away tissue.

The tool is particularly useful for, but is not limited in its application to, vertebrae. The tools can be deployed equally as well in long bones and other bone types.

The vertebra includes a vertebral body, which extends on the anterior side of the vertebra. The vertebral body includes an exterior formed from compact cortical bone. The cortical bone encloses an interior volume of reticulated cancellous, or spongy, bone(also called medullary bone or trabecular bone).

The vertebral body is generally in the shape of an oval disk. Access to the interior volume of the vertebral body can be achieved, for example, by wedging and/or cutting through hard bone. Such wedging and/or cutting can be achieved, for example, with a probe and cannula as described here.

When the bone tamp is deployed outside the cannula in the cancellous bone, the physician operates the controlling mechanism in the manner previously described to obtain a desired dimension for the loop structure or the desired deployment of the flapper. The physician manually rotates the loop structure or flapper through surrounding cancellous bone. The rotating structure cuts and tamps back cancellous bone and thereby forms a cavity.

Synchronous rotation and operation of the controlling mechanism to enlarge the dimensions of the tamping structure during the procedure allows the physician to achieve a create a cavity of desired dimension.

The procedure for use of these tools is as follows. First, the probe is constructed with the probe tip extending beyond the probe body by a predetermined length. The handle is attached to the probe. Alternatively, the cannula is pre-loaded around the probe if the handle on the probe is non-removable. The probe is advanced through the bone, i.e., vertebral body, preferably through percutaneous approach to the desired depth. The handle is removed, leaving the probe body in place, and the cannula is slipped over the probe (if it has not been preloaded thereon). The depth markings may be used to determine the depth of penetration. The cannula is advanced down the probe shaft and is threaded or worked into the pedicle or vertebral body. Then, the probe is removed while the cannula remains in place. The bone tamp is inserted through the cannula and then the tamping mechanism is deployed therein, with appropriate retraction of the deployment and/or rotation as needed, to create the void space. When the cavity is of the desired shape and size, the tamping mechanism is retracted so that the bone tamp can be withdrawn through the cannula. Then, optionally, a void filler is placed into the cavity via the cannula using the syringe of Fig. 28 or any other suitable device. The flush bar may be used at any time to make sure the body of the cannula remains clean and obstruction- free, and also may be used to displace treatment material that adheres to the cannula into the cavity. Finally, the cannula is removed.

A single use of any one of the tools creates contact with surrounding cortical and cancellous bone. This contact can damage the tools, creating localized regions of weakness, which may escape detection. In addition, exposure to blood and tissue during a single use can entrap biological components on or within the tools.

The tools described here allow for replacement of each component, and especially easy replacement of those components which contact bone. The tools also are easy to clean and disassemble. The tools may be used only once and then discarded. If so, use of plastics is preferred for many tool structures.

While it is apparent that the invention disclosed herein is well calculated to fulfill the objects stated above, it will be appreciated that numerous modifications and embodiments may be devised by those skilled in the art. Therefore, one skilled in the art would appreciate that such modifications and embodiments fall within the scope of the present invention.

Claims

1. Device for creating cavities in a bone comprising a longitudinal body having a distal end and a physician-controlled end whereby said longitudinal body is provided with a tamping mechanism.

2. Device according to claim 1 , characterized in that

A) said longitudinal body comprises a controlling mechanism extending along said longitudinal body; and

B) said tamping mechanism is situated at the distal end of said longitudinal body and being expandable transversely to said longitudinal body during tamping and retractable or contractible for removal of the tamping mechanism from the bone by means of said controlling mechanism; whereby

C) in the contracted state said tamping mechanism does not protrude over the widest portion of said longitudinal body.

3. Probe for introducing a passageway to the cancellous area of a bone comprising a longitudinal body having a distal end and a physician-controlled end whereby a sharp tip is provided at the distal end of said longitudinal body.

4. Cannula for guiding surgical instruments comprising a longitudinal hollow body having a distal end and physician-controlled end whereby a cutting edge is provided at the distal end.

5. Syringe-type device having a longitudinal hollow body with a distal end and a physician- controlled end and a plunger being axially displaceable within said hollow body whereby said distal end is adapted to fit a tube which is extendable through a cannula.