reference will now be made in detail to the present preferred embodiments of the invention , examples of which are illustrated in the accompanying drawings . wherever possible , the same reference numbers ( optionally including different suffixes ) are used in the drawings and the description to refer to the same or like parts . fig2 , 3 , 5 , and 10 show examples of components that could be included in an embodiment of a system according to the present invention . as shown in fig2 , the system preferably includes at least one guide tube 10 having at least one inner lumen extending from a proximal end portion to a distal end portion . the distal end portion of the guide tube 10 preferably includes a releasable anchoring element 12 for releasably anchoring the distal end portion of the guide tube 10 in at least one vertebra . in the embodiment shown in fig2 , the anchoring element 12 is at least one thread on an outer surface of the guide tube 10 . the thread permits the guide tube 10 to be removably threaded into a hole bored in a vertebra . the guide tube 10 is preferably made of stainless , surgical steel but may be made of metal composites , ceramic composites , surgical polymers or surgical plastics . preferably , the guide tube 10 includes a suitable tracking element 14 configured to interact with a computer controlled surgical navigation system ( not shown ) using a detector for determining the position of the guide tube 10 with respect to a known reference in 3d space . by way of example only , the tracking element 14 could be at least one led emitter / reflector located on a proximal end portion of the guide tube 10 . the tracking element 14 could also be any structure that is capable of being detected / tracked by means of a surgical navigation system that uses any sonic , optical , electromagnetic , or other suitable technology known in the art . for example , the tracking element 14 is particularly capable of being used with a surgical navigation system constructed according to the teachings of u . s . pat . no . 5 , 383 , 454 ; pct application no . pct / u . s . 94 / 04530 ( publication no . wo 94 / 24933 ); and / or pct application no . pct / u . s . 95 / 12894 ( publication no . wo 96 / 11624 ), the disclosures of which are incorporated by reference . the guide tube 10 includes a lumen that extends from its proximal end portion to its distal end portion . preferably , the lumen is sized to allow for passage therethrough of at least one tool , such as the drilling tool 20 shown in fig3 . the drilling tool 20 preferably includes a bit 22 ( i . e ., burr ) configured to abrade soft tissue or bone , such as portions of an intervertebral disc or a vertebra . the bit 22 is preferably a high speed drill bit made of hardened surgical , stainless steel and optionally coated with teflon or other coatings to prevent aggregation or sticking of osseous material . the bit 22 is coupled to a flexible , rotatable drive member 24 , such as a cable , that is rotatably driven by an external motor ( not shown ) to rotate the bit 22 . the drive member 24 passes through a tubular member 26 that is preferably configured to be steerable . as shown in fig3 , the tubular member 26 includes a number of segments 28 a - 28 e . hinge members 30 a , 30 b , 30 c and 30 d couple adjacent pairs of the segments 28 a - 28 b , 28 b - 28 c , 28 c - 28 d , 28 d - 28 e together to permit relative pivotal movement of the segments in each of the pairs . an axially movable steering element 32 , such as a cable , passes freely through the segments 28 b - 28 e and has a distal end connected to the distal segment 28 a . axial movement of the steering element 32 causes bending at one or more of the hinge members 30 a - 30 d in a plane to vary the position of the distal end portion of the tubular member 26 with respect to the remainder of the tubular member 26 . this enables steerable movement of the drilling tool 20 , especially when the movement at the distal end portion is combined with rotation of the tubular member 26 and / or axial movement of the tubular member 26 . of course , there are many different ways in which the drilling tool 20 could be constructed to provide steering . a tracking element 34 could be provided on the drilling tool 20 to interact with a computer controlled surgical navigation system to determine the location of the bit 22 with respect to a known reference point . for example , the tracking element 34 could be provided on the steering element 32 and constructed like the tracking element 14 shown in fig2 . the drilling tool 20 is preferably made of surgical steel , but the drive member 24 and steering element 32 could be made of metal composites , surgical polymers , or other suitable materials . preferably , at least a portion of the drilling tool 20 is capable of being imaged with fluoroscopic imaging . the drilling tool 20 could be constructed to be connected to a stereotactic device that could be used to determine the position of the bit 22 . structure could be provided on the drilling tool 20 to remove materials with suction . for example , the drilling tool could include a lumen capable of being coupled to a suction source . for example , a flexible tube , such as surgical polymer tubing , could be provided in the tubular member and have an open end extending adjacent to the bit 22 . although the steerable drilling tool 20 is described below as being used in a spinal fusion procedure , the drilling tool 20 could be used in a number of different spinal or non - spinal procedures . the system according to the invention also preferably includes at least one inflatable balloon implant 40 shown in fig1 - 12 . the balloon implant 40 is configured to be filled with material to provide fusion in a cavity that is formed at least partially in an intervertebral disc , as described below . the balloon implant 40 is preferably made of a biodegradable substance such as collagen . the balloon implant 40 and the material used to fill it may include growth factors , such as bone morphogenic proteins or fibroplast growth factor , genetically modified cells for replacement therapy , or mesenchymal stem cells to further promote bony fusion . the system according to the present invention could include other components , such as a device for providing suction and / or irrigation of a surgical site . preferably , all or some of the components are made of permanent or disposable materials that are capable of being sterilized . the present invention also includes one or more preferred methods of fusing a spinal region . these procedures are explained with reference to the structural embodiments described above . however , it should be understood that the method of the invention could be practiced with structure other than that disclosed herein . in addition , the structure of the present invention could be used with processes other than those described herein . in one method according to the present invention , a patient is placed on an appropriate operating surface . optionally , imaging equipment , such as fluoroscopy , is used to visualize a region of the spine . small stab incisions are made in the back and a conventional drill is preferably used to drill a hole through corticle material on the outer surface of the pedicle of a vertebra . for the procedure shown in fig4 , a first hole is drilled in the pedicle of a first vertebra and a second hole is drilled in a pedicle of a second vertebra adjacent to the first vertebra . although fig4 - 11 show these holes as being substantially parallel to the plane of the disc , the holes are preferably angled from about 30 degrees to about 45 degrees with respect to the plane of the disc so that the axes of the holes form an angle having a vertex at the disc . a respective guide tube 10 a , 10 b is placed in contact with each of the vertebrae . preferably , each guide tube 10 a , 10 b is releasably anchored in the corresponding pedicle hole by engaging the threads on the guide tube 10 a , 10 b in the vertebrae . once the guide tubes 10 a and 10 b have been inserted , an x - ray , ct scan or other diagnostic scan could be used to localize the anatomical position of the tubes 10 a and 10 b , identify the best position for fusion and identify the best insertion points for subsequent instrumentation . after anchoring the guide tubes 10 a and 10 b , at least one of the guide tubes 10 a and 10 b is moved to thereby position one or more of the vertebrae . for example , as shown in fig5 , a distraction tool 50 is coupled to the guide tubes 10 a and 10 b to force the guide tubes 10 a and 10 b apart from one another and thereby distract one or more of the vertebrae away from the disc . the distraction tool 50 could be constructed in many different ways . for example , this device could have a ratchet adjustment . in addition to moving the guide tubes 10 a , 10 b toward or away from each other , one or more of the anchored guide tubes 10 a , 10 b could be rotated ( or translated ) to thereby rotate ( or translate ) one or more of the vertebrae . preferably , a computer - controlled surgical navigation device is used to determine the movement of the guide tubes , for example , by interacting with the tracking element 14 shown in fig2 . this preferably enables a surgeon to visualize the repositioning of the vertebrae . one or more steerable drilling tools 20 a and 20 b are inserted though the guide tubes 10 a and 10 b . the drive member 24 ( fig3 ) of each drilling tool 20 a , 20 b is rotated to thereby rotate each bit 22 . each drilling tool is moved further through the guide tubes 10 a and 10 b , as shown in fig7 , and the bit 22 abrades material in the respective vertebra , including medullary material spaced away from the disc . as shown in fig8 , each of the drilling tools 20 a and 20 b are preferable steered toward the disc , for example by axially moving the steering element 32 ( fig3 ), and the drilling tools 20 a and 20 b abrade at least a portion of the end plates of the disc between the vertebrae . the material abraded by the drilling tools 20 a and 20 b is preferably removed through one or both of the guide tubes 10 a , 10 b . for example , a suction and / or irrigation device could be passed into one of the tubes 10 a and 10 b , while one of the drill tools is passed through the other of the tubes 10 a and 10 b . the position of the distal end of the drilling tools 20 a and 20 b is preferably determined , for example , by using a computer controlled surgical navigation device that interacts with the tracking element 34 ( fig3 ). after abrasion of all material , the drilling tools 20 a and 20 b are pulled out of the tubes 10 a and 10 b , and the further removal of any remaining loose material occurs via suction , irrigation , flexible forceps , or other means for clearing such loose material . eventually , all of the interior of the disc , including its nucleus , is removed to form a cavity extending through the disc and preferably into portions of the adjacent vertebrae . preferably , none of the circumferential segments of the annulus fibrosis are abraded or removed during the procedure , such that at least a portion of the fibrosis extends around the cavity . in a preferred practice of the invention , the inflatable balloon implant 40 is preferably inserted into the cavity via one of the guide tubes 10 a and 10 b . the balloon is preferably filled with a contrast agent , as shown in fig1 , and the balloon is viewed with appropriate imaging equipment , such as a fluoroscope . one possible imaging agent that could be used to inflate the balloon is omnipaque . since the inflated balloon preferably fills the entire cavity , the imaging of the balloon can be used to evaluate whether the cavity is properly configured . it can also be used to ascertain proper anatomic alignment or position and to verify complete filling of the cavity . in the event that further material needs to be removed to enlarge the cavity , the implant 40 could be removed from the cavity , and abrasion with one or more of the steerable drilling tools could be continued . when the cavity is properly formed , a flowable fusion substance is preferably passed into the cavity via one of the guide tubes 10 a , 10 b . preferably , the fusion substance is a substance capable of solidfying such that it is no longer readily flowable . for example , the fusion substance could be a solidifying agent including polymethacrylate , such as methylmethacrylate or cranioplastic methacrylate , hydroxyapatite , another polymer , and / or a biological matrix . the flowable substance may include growth factors , such as bone morphogenic proteins or fibroplast growth factor , genetically modified cells for replacement therapy or mesenchymal stem cells to further promote bony fusion . in addition , the fusion substance could include antibiotics such as tobramycin , for example . in one possible practice of the invention , the balloon implant used for the imaging is removed from the cavity before the fusion substance alone is passed into the cavity . alternatively , the balloon implant 40 used for the imaging could be drained of the imaging agent and then filled with the fusion substance via one of the guide tubes 10 a , 10 b . in another alternate practice of the invention , the balloon implant 40 used for the contrast agent is removed from the cavity and another balloon implant is inserted in the cavity and filled with the fusion substance . filling a balloon implant with the fusion substance is preferred in order to contain the fusion substance and prevent migration into unintended areas , such as the area near the spinal chord . after passing the fusion substance into the cavity , the tubes 10 a and 10 b are removed from the vertebrae . fig1 shows the balloon implant 12 in place after being filled with the flowable agent and after solidification of the fusion substance . fig1 shows an alternate embodiment of a balloon implant 40 a that is configured to fill a relatively larger cavity extending into two adjacent discs positioned near a spinal fracture . in the preferred practice of the invention , the guide tubes 10 a , 10 b could be moved at various times during the procedure to reposition one or more of the vertebrae . for example , the movement shown in fig5 could take place after the cavity is fully formed . in addition , the vertebrae could be retained in their repositioned state until the fusion substance solidifies . fig1 - 17 show an alternative procedure like that shown in fig4 - 13 , but involving a single guide tube 10 . as shown in fig1 , the guide tube 10 is used to remove the inner material from a disc with suction applied though the guide tube 10 . as shown in fig1 - 17 , a balloon is inserted into a cavity formed in the disc and eventually filled with the fusion substance to fuse the spinal region . the method and apparatus according to the invention could be used for noninvasive or minimally invasive spinal disc distraction , rotation or translation and subsequent stabilization . the invention could be used for treatment of spinal disorders including , but not limited to , scoliosis , lordosis , kyphosis , spinal fractures , spinal instability , tumors , spinal degeneration due to disease , disc bulges , herniations , and tears . preferably , the invention will stabilize the spine and correct anatomic misalignment caused by the above disorders . for example , the movement of one or more of the guide tubes to reposition one or more vertebrae could be used to correct scoliosis prior to spinal fusion . the method and apparatus according to the present invention could be used for procedures in many different areas of the spine . although the invention has particular advantages in association with procedures for the lower spinal area , the invention could also be used for procedures for the thoracic area or the cervical area , for example . preferably , the present invention shortens the time a patient is being operated on by speeding up the repair of the spinal disorders and thereby reduces risks associated with pre - and post - operative complications . the invention also preferably decreases pain by decreasing pressure on nerve roots , improves mobility , and improves long - term alignment of the spine , thereby providing improved outcomes for spinal disorder patients . the invention could be used to fuse regions of various sizes . for example , the invention could be practiced to fuse two adjacent spinal discs or may be used across more than two . there are a variety of different ways in which the various instruments could be guided during a procedure . for example , stereotactic guidance could be used . it will be apparent to those skilled in the art that various modifications and variations can be made to the structure and methodology of the present invention without departing from the scope or spirit of the invention . in view of the foregoing , it is intended that the present invention cover modifications and variations of this invention provided they fall within the scope of the following claims and their equivalents .
a method and system for fusing a region in the spine involve the use of at least one guide tube to pass instruments and substances into the spinal region in a minimally invasive manner . in the preferred practice of the method , a guide tube is anchored to a vertebra and the guide tube is moved to thereby position the vertebra . a steerable drilling tool is passed through the guide tube and steered into position to abrade at least a portion of an intervertebral disc and thereby create a cavity in the disc . a flowable substance is passed into the cavity and permitted to solidify to establish fusion in the cavity . optionally , an uninflated balloon is inserted into the cavity and the balloon is filled with the flowable substance to contain the flowable substance .