fig1 - 4 illustrate a dilatation balloon tensioning apparatus according to a first embodiment of the present invention . the balloon dilatation catheter apparatus 10 in fig1 a - 1c generally comprises a proximal end catheter sleeve portion 12 , a middle sleeve portion 14 , and a balloon or inflation element 16 at or near the distal end of the catheter . as best seen in fig1 b , proximal end catheter sleeve portion 12 comprises a branched or y - shaped element , of which one arm or branch 18 comprises a tubular shell with external threads 25 at its proximal end , and the second arm or branch 20 comprises a fluid inlet / outlet conduit for introducing pressurized fluid 40 into catheter 10 for inflating balloon 16 or for withdrawing fluid 40 after a dilatation procedure . the tubular shell of branch 18 comprises a region adjacent to the threaded region for housing a spring element 22 . cap element 24 has internal threads and is sized to mate with the external threads 25 at the proximal end of branch 18 . as seen in fig1 a - 1c , the cap element 24 is loosely threaded onto branch 18 , and there is no compression of spring element 22 , the condition in which catheter 10 would ordinarily be shipped and stored . balloon element 16 is shown extended , and , as seen in fig1 a and 1c , is preferably pleated or folded for compactness . balloon elements suitable for use with the various catheter designs described herein may be elastomeric or non - elastomeric , depending on the particular application , and may be fabricated from various conventional balloon catheter materials , for example the various catheter and balloon materials taught by u . s . pat . no . 5 , 499 , 973 , which is incorporated herein by reference . it is also within the scope of this invention to coat the exterior of the balloon elements to prevent or minimize damage or rupture from sharp bones . it is also within the scope of this invention to cover the balloon elements with elastomeric tubes both to help squeeze and deflate the balloons during deflation and to resist damage from surrounding bone . at the distal end of the region for housing spring element 22 ( i . e ., at the end opposite from where the cap 24 is threaded onto branch 18 ), a disc element or circular fitting 30 is sized to slide inside the region housing spring element 22 so as to compress the spring element by displacement in the proximal direction or to decompress the spring element by displacement in the distal direction . associated with disc element 30 is axially moveable rod element 34 ( which may or may not be physically connected to disc element 30 ) which runs axially through the interior of the catheter from the distal side of disc element 30 to the sealed tip portion 28 of balloon 16 . rod element 34 may or may not be physically connected to or may or may not engage balloon tip portion 28 . rod element 34 operating in conjunction with disc element 30 thus can act like a piston to alternately compress and allow decompression of spring element 22 . also shown in fig1 a - 1c , although it is typically not attached to catheter apparatus 10 , is a small diameter canula 26 which provides a channel for the catheter apparatus through a bone portion into the bone interior . balloon element 16 must be able to slide through the hollow interior of canula 26 during insertion of the catheter and , more importantly , during removal of the catheter after the balloon has undergone an inflation / deflation cycle . in fig2 a - 2c , catheter apparatus 10 of fig1 a - 1c is shown with cap element 24 screwed down resulting in at least partially compressing spring element 22 in preparation for use . in fig3 a - 3c , pressurized fluid 40 has been introduced through branch 20 , through a part of the interior of proximal sleeve portion 12 , and through the interior of middle sleeve portion 14 to fully inflate balloon 16 . as balloon 16 is inflated , it expands in diameter and shortens in length causing rod 34 to move in a proximal direction , thereby displacing disc element 30 in a proximal direction and further compressing spring element 22 . in fig4 a - 4c , dilatation pressure is removed and fluid is withdrawn from balloon 16 and from the interior of catheter 10 through fluid inlet / outlet branch 20 . in a preferred embodiment , a vacuum may be applied to the proximal end of branch 20 to assist in withdrawing fluid and fully collapsing balloon 16 . as balloon 16 becomes deflated , the force exerted by the compressed spring element 22 becomes greater than the force exerted by the collapsing balloon . eventually this results in displacing disc element 30 toward the distal end of the catheter , in turn driving rod 34 in the distal direction , and thereby stretching and tensioning balloon 16 . this automatic tensioning of the balloon element upon deflation assists in collapsing , folding and / or pleating the balloon to minimize its lateral profile for easier withdrawal through the small diameter interior channel of canula 26 . fig5 - 9 illustrate a dilatation balloon tensioning apparatus according to a second embodiment of the present invention . the balloon dilatation catheter apparatus 110 in fig5 a - 5c generally comprises a proximal end catheter sleeve portion 112 , a middle sleeve portion 114 , and a balloon or inflation element 116 at the distal end of the catheter . as best seen in fig5 b , proximal end catheter sleeve portion 112 comprises a branched or y - shaped element , of which one arm or branch 118 comprises a tubular shell with external threads 125 at its proximal end , and the second arm or branch 120 comprises a fluid inlet / outlet conduit for introducing pressurized fluid 140 into catheter 110 for inflating balloon 116 or for withdrawing fluid 140 after a dilatation procedure . the tubular shell of branch 118 comprises a region adjacent to the threaded region for housing a sealing gasket 122 or similar compressible sealing element having a centrally located aperture . cap element 124 includes a centrally - located axial bore 127 to accommodate a push rod 134 , and also has internal threads sized to mate with the external threads 125 at the proximal end of branch 118 . as seen in fig5 a - 5c , cap element 124 is loosely threaded onto branch 118 , rod 134 is forward ( toward the distal end of the catheter ), and there is no compression of sealing gasket 121 , the condition in which catheter 110 would ordinarily be shipped and stored . balloon element 116 is shown extended , as best seen in fig5 c , and is preferably pleated or folded for compactness . push rod 134 , having a knob portion 136 at its proximal end , is slidably positioned inside the catheter and is sized to extend axially the full length of catheter 110 . push rod 134 extends through the central bore 127 of cap 124 , through the sealing gasket 121 , which acts like a bushing for supporting and centering rod 134 , through the interior of sleeves 112 and 114 , and through the interior of balloon 116 to the sealed tip portion 128 . in one variation of this invention embodiment , rod 134 may be connected to or capable of engaging tip portion 128 to facilitate twisting or wrapping balloon element 116 about rod 134 following a dilatation and deflation cycle . in fig6 a - 6c , catheter apparatus 110 of fig5 a - 5c is shown with cap element 124 screwed down and tightened thereby compressing sealing gasket 121 to form a fluid - tight seal at the sealing gasket and around rod 134 in preparation for using the catheter , while still permitting rod 134 to slide through the gasket aperture . in fig7 a - 7c , pressurized fluid 140 has been introduced through branch 120 to fully inflate balloon 116 . as balloon 116 is inflated , it expands in diameter and shortens in length causing rod 134 to slide in a proximal direction . in fig8 a - 8c , dilatation pressure is removed and fluid is withdrawn from balloon 116 and from the interior of catheter 110 through branch 120 . in a preferred embodiment , a vacuum may be applied to the proximal end of branch 20 to assist in withdrawing fluid and in fully collapsing balloon 116 . as balloon 116 becomes deflated , axial force is manually applied to the proximal end of rod 134 to push it toward the distal end of the catheter thereby assisting with stretching and refolding or repleating the balloon into a set of small folds or pleats to create a smaller diameter profile for easier withdrawal of the deflated balloon through canula 126 . in fig9 a - 9c , in addition to using rod 134 to stretch the deflated balloon 116 , a rotational force ( as indicated by arrows 142 ) is applied to knob 136 to rotate rod 134 causing balloon element 116 to be wrapped around rod 134 , as best seen in fig9 c , thereby further reducing the profile of the deflated balloon . fig1 - 12 illustrate a dilatation balloon tensioning apparatus according to a third embodiment of the present invention . the balloon dilatation catheter apparatus 210 in fig1 a - 10c generally comprises a proximal end catheter sleeve portion 212 , a middle sleeve portion 214 , and a balloon or inflation element 216 at the distal end of the catheter . as best seen in fig1 b , proximal end catheter sleeve portion 212 comprises a tubular shell portion 218 with external threads 225 at its proximal end and a region adjacent to the threaded region for housing a spring element 222 . cap element 224 includes a centrally - located axial bore 227 through which fluid 240 can be introduced to or withdrawn from catheter 210 , and also has internal threads sized to mate with the external threads 225 at the proximal end of the shell portion 218 . a gasket , seal , or o - ring 229 , or a similar fluid - sealing element , having a centrally - located aperture , is disposed at the proximal end of the region of shell portion 218 which houses spring 222 . as seen in fig1 a - 10c , cap element 224 is loosely threaded onto shell portion 218 , and there is no compression of spring 222 , the condition in which catheter 220 would ordinarily be shipped and stored . balloon element 216 is shown extended , as best seen in fig1 c , and is preferably pleated or folded for compactness . at the distal end of the region for housing spring element 222 ( i . e ., at the end opposite from where the cap 224 is threaded onto branch 218 ), a disc element or circular fitting 230 is sized to slide inside the region housing spring element 222 so as to compress the spring element by displacement in the proximal direction or to decompress the spring element by displacement in the distal direction . associated with disc element 230 is axially moveable rod element 234 ( which may or may not be physically connected to disc element 230 ) which runs axially through the interior of the catheter from the distal side of disc element 230 to the sealed tip portion 228 of balloon 216 . rod element 234 may or may not be physically connected to or may or may not engage balloon tip portion 228 . rod element 234 operating in conjunction with disc element 230 thus can act like a piston to alternately compress and allow decompression of spring element 222 . also shown in fig1 a - 10c , although it is typically not attached to catheter apparatus 210 , is a small diameter canula 226 which provides a channel for the catheter apparatus through a bone portion into the bone interior . balloon element 216 must be able to slide through the hollow interior of canula 226 during insertion of the catheter and , more importantly , during removal of the catheter after the balloon has undergone an inflation / deflation cycle . in fig1 a - 11c , catheter apparatus 210 of fig1 a - 10c is shown with cap element 224 screwed down resulting in at least partially compressing spring element 222 in preparation for use . also in fig1 a - 11c , pressurized fluid 240 has been introduced through axial bore 227 , through the interior of proximal sleeve portion 212 , and through the interior of middle sleeve portion 214 to fully inflate balloon 216 . as balloon 216 is inflated , it expands in diameter and shortens in length causing rod 234 to move in a proximal direction , thereby displacing disc element 230 in a proximal direction and further compressing spring element 222 . in fig1 a - 12c , dilatation pressure is removed and fluid 240 is withdrawn from balloon 216 and from the interior of catheter 210 through axial bore 227 . in a preferred embodiment , a vacuum may be applied to the proximal end of axial bore 227 to assist in withdrawing fluid and fully collapsing balloon 216 . as balloon 216 becomes deflated , the force exerted by the compressed spring element 222 becomes greater than the force exerted by the collapsing balloon . eventually this results in displacing disc element 230 toward the distal end of the catheter , in turn driving rod 234 in the distal direction , and thereby stretching and tensioning balloon 216 . this automatic tensioning of the balloon element upon deflation assists in collapsing , folding and / or pleating the balloon to minimize its lateral profile for easier withdrawal through the small diameter interior channel of canula 226 . fig1 - 16 illustrate a dilatation balloon tensioning apparatus according to a fourth embodiment of the present invention . the balloon dilatation catheter apparatus 310 in fig1 a - 13c generally comprises a proximal end catheter sleeve portion 312 , a middle sleeve portion 314 , and a balloon or inflation element 316 at or near the distal end of the catheter . as best seen in fig1 b , proximal end catheter sleeve portion 312 comprises a branched or y - shaped element , of which one arm or branch 318 comprises a tubular shell with external threads 325 at its proximal end , and the second arm or branch 320 comprises a fluid inlet / outlet conduit for introducing pressurized fluid 340 into catheter 310 for inflating balloon 316 or for withdrawing fluid 340 after a dilatation procedure . the tubular shell of branch 318 comprises a region adjacent to the threaded region for housing a spring element 322 . cap element 324 has internal threads and is sized to mate with the external threads 325 at the proximal end of branch 318 . as seen in fig1 a - 13c , the cap element 324 is loosely threaded onto branch 318 , and there is no compression of spring element 322 , the condition in which catheter 310 would ordinarily be shipped and stored . balloon element 316 is shown extended , and , as seen in fig1 a and 13c , is preferably pleated or folded for compactness . at the distal end of the region for housing spring element 322 ( i . e ., at the end opposite from where the cap 324 is threaded onto branch 318 ), a disc element or circular fitting 330 is sized to slide inside the region housing spring element 322 so as to compress the spring element by displacement in the proximal direction or to decompress the spring element by displacement in the distal direction . associated with disc element 330 is axially moveable rod element 334 ( which may or may not be physically connected to disc element 330 ) which runs axially through the interior of the catheter from the distal side of disc element 330 to the sealed tip portion 328 of balloon 316 . rod element 334 may or may not be physically connected to or may or may not engage balloon tip portion 328 . rod element 334 operating in conjunction with disc element 330 thus can act like a piston to alternately compress and allow decompression of spring element 322 . also shown in fig1 a - 13c is a canula element 326 . in this embodiment of the invention , however , the canula element 326 does more than just provide a channel through a bone for inserting or removing the catheter apparatus . in this embodiment , the distal section of catheter sleeve portion 312 includes external threads 336 . the proximal end of canula 326 is not open , as was the case for the previously described invention embodiments . instead , canula 326 is sealed at its proximal end by a plate member 337 having a threaded central bore 338 , the threads being sized to mate with external threads 336 . thus , by turning canula 326 around the axis of sleeve portion 312 , the position of canula 326 can be adjusted relative to balloon 316 by axial movement along the threaded portion of sleeve 312 . in this embodiment of the present invention , balloon element 316 is designed to be longer than the maximum length needed to fill the bone cavity being treated . by adjusting the position of canula 326 along the distal threaded portion of sleeve 312 , a surgeon can expose a length of balloon element 316 just sufficient to fill a given bone cavity before inserting the balloon into the bone cavity and inflating it . in this way , a standard catheter apparatus with a standardized balloon element in accordance with the present invention can be easily customized for each application thereby avoiding the need to prepare and stock a multiplicity of balloon lengths . in fig1 a - 14c , catheter apparatus 310 of fig1 a - 13c is shown with cap element 324 screwed down resulting in at least partially compressing spring element 322 in preparation for use . in fig1 a - 15c , pressurized fluid 340 has been introduced through branch 320 , through a part of the interior of proximal sleeve portion 312 , and through the interior of middle sleeve portion 314 to fully inflate the exposed portion of balloon 316 . as seen best in fig1 b , the proximal end of balloon 316 is constrained from expanding beyond the internal diameter of canula 326 by the walls of canula 326 . as balloon 316 is inflated , at least in part , it expands in diameter and shortens in length causing rod 334 to move in a proximal direction , thereby displacing disc element 330 in a proximal direction and further compressing spring element 322 . in fig1 a - 16c , dilatation pressure is removed and fluid is withdrawn from balloon 316 and from the interior of catheter 310 through fluid inlet / outlet branch 320 . in a preferred embodiment , a vacuum may be applied to the proximal end of branch 320 to assist in withdrawing fluid and fully collapsing balloon 316 . as balloon 316 becomes deflated , the force exerted by the compressed spring element 322 becomes greater than the force exerted by the collapsing balloon . eventually this results in displacing disc element 330 toward the distal end of the catheter , in turn driving rod 334 in the distal direction , and thereby stretching and tensioning balloon 316 . this automatic tensioning of the balloon element upon deflation assists in collapsing , folding and / or pleating the balloon to minimize its lateral profile for easier withdrawal . fig1 - 21 illustrate a dilatation balloon tensioning apparatus according to a fifth embodiment of the present invention . the balloon dilatation catheter apparatus 410 in fig1 a - 17c generally comprises a proximal end catheter sleeve portion 412 , a middle sleeve portion 414 , and a balloon or inflation element 416 at or near the distal end of the catheter . as best seen in fig1 b , proximal end catheter sleeve portion 412 comprises a branched or y - shaped element , of which one arm or branch 418 comprises a tubular shell with external threads 425 at its proximal end , and the second arm or branch 420 comprises a fluid inlet / outlet conduit for introducing pressurized fluid 440 into catheter 410 for inflating balloon 416 or for withdrawing fluid 440 after a dilatation procedure . the tubular shell of branch 418 comprises a region adjacent to the threaded region for housing a spring element 422 . cap element 424 has internal threads and is sized to mate with the external threads 425 at the proximal end of branch 418 . as seen in fig1 a - 17c , the cap element 424 is loosely threaded onto branch 418 , and there is no compression of spring element 422 , the condition in which catheter 410 would ordinarily be shipped and stored . cap element 424 further includes a centrally - located axial bore 427 to accommodate a rod element 434 as hereinafter described . balloon element 416 is shown extended , and , as seen in fig1 a and 17c , is preferably pleated or folded for compactness . push rod 434 , having a knob portion 436 at its proximal end , is slidably positioned inside the catheter and is sized to extend axially the full length of catheter 410 . push rod 434 extends through the central bore 427 of cap 424 , through a sealing gasket 421 , which acts like a bushing for supporting and centering rod 434 , through the center of spring element 422 and the interior of sleeves 412 and 414 , and through the interior of balloon 416 to the sealed tip portion 428 . in one variation of this invention embodiment , rod 434 may be connected to or capable of engaging tip portion 428 to facilitate twisting or wrapping balloon element 416 about rod 434 following a dilatation and deflation cycle . at the distal end of the region for housing spring element 422 ( i . e ., at the end opposite from where the cap 424 is threaded onto branch 418 ), a disc element or circular fitting 430 is sized to slide inside the region housing spring element 422 so as to compress the spring element by displacement in the proximal direction or to decompress the spring element by displacement in the distal direction . disc element 430 has a centrally - located axial bore to accommodate axially moveable rod element 434 . rod element 434 may or may not be physically connected to balloon tip portion 428 . rod element 434 operating in conjunction with disc element 430 thus can act like a piston to alternately compress and allow decompression of spring element 422 . also shown in fig1 a - 17c , although it is typically not attached to catheter apparatus 410 , is a small diameter canula 426 which provides a channel for the catheter apparatus through a bone portion into the bone interior . balloon element 416 must be able to slide through the hollow interior of canula 426 during insertion of the catheter and , more importantly , during removal of the catheter after the balloon has undergone an inflation / deflation cycle . in fig1 a - 18c , catheter apparatus 410 of fig1 a - 17c is shown with cap element 424 screwed down resulting in at least partially compressing spring element 422 in preparation for use . in fig1 a - 19c , pressurized fluid 440 has been introduced through branch 420 , through a part of the interior of proximal sleeve portion 412 , and through the interior of middle sleeve portion 414 to fully inflate balloon 416 . as balloon 416 is inflated , it expands in diameter and shortens in length causing rod 434 to move in a proximal direction , thereby displacing disc element 430 in a proximal direction and further compressing spring element 422 . in fig2 a - 20c , dilatation pressure is removed and fluid is withdrawn from balloon 416 and from the interior of catheter 410 through fluid inlet / outlet branch 420 . in a preferred embodiment , a vacuum may be applied to the proximal end of branch 420 to assist in withdrawing fluid and fully collapsing balloon 416 . as balloon 416 becomes deflated , the force exerted by the compressed spring element 422 becomes greater than the force exerted by the collapsing balloon . eventually this results in displacing disc element 430 toward the distal end of the catheter , in turn driving rod 434 in the distal direction , and thereby stretching and tensioning balloon 416 . this automatic tensioning of the balloon element upon deflation assists in collapsing , folding and / or pleating the balloon to minimize its lateral profile for easier withdrawal through the small diameter interior channel of canula 426 . in fig2 a - 21c , in addition to using rod 434 to stretch the deflated balloon 416 , a rotational force ( as indicated by arrows 442 ) is applied to knob 436 to rotate rod 434 causing balloon element 416 to be wrapped around rod 434 , as best seen in fig2 c , thereby further reducing the profile of the deflated balloon . fig2 - 25 illustrate a dilatation balloon tensioning apparatus according to a sixth embodiment of the present invention . the balloon dilatation catheter apparatus 510 in fig2 a - 22d generally comprises a proximal end catheter sleeve portion 512 , a middle sleeve portion 514 , and a balloon or inflation element 516 at or near the distal end of the catheter . as best seen in fig2 b , proximal end catheter sleeve portion 512 comprises a branched or y - shaped element , of which one arm or branch 518 comprises a tubular shell with external threads 525 at its proximal end , and the second arm or branch 520 comprises a fluid inlet / outlet conduit for introducing pressurized fluid 540 into catheter 510 for inflating balloon 516 or for withdrawing fluid 540 after a dilatation procedure . cap element 524 has internal threads and is sized to mate with the external threads 525 at the proximal end of branch 518 . as seen in fig2 a - 22d , the cap element 524 is loosely threaded onto branch 518 , and there is no compression of a spring element 522 , located inside balloon 516 , the condition in which catheter 510 would ordinarily be shipped and stored . balloon element 516 is shown extended , and , as seen in fig2 a and 22c , is preferably pleated or folded for compactness . an axially moveable rod element 534 having a head portion 530 at its proximal end runs axially through the interior of the catheter from the distal side of cap element 524 to the sealed tip portion 528 of balloon 516 . rod element 534 may or may not be physically connected to balloon tip portion 528 . the head portion 530 of rod 534 moves axially within a region in the interior of branch 518 as rod 534 slides toward or away from tip portion 528 . at the distal end of rod 534 and located inside balloon 516 is a spring tensioning system comprising a spiral spring element 522 wrapped around at least a portion of rod 534 . fig2 d is an enlarged view of the balloon end of the catheter which better shows spring element 522 spiraling around the distal end of rod 534 . as best seen in fig2 d , the distal end of rod 534 in one embodiment may comprise two telescoping rod sections consisting of a hollow tubular section 546 and a smaller - diameter section 547 sized to slidably fit inside the hollow interior of section 546 and terminating in a bulbous rod tip 548 . spring element 522 is a spiral spring having a diameter smaller than the outer diameter of rod section 546 but larger than the outer diameter of rod section 547 . spring element 522 is not secured at either end but occupies a region bounded at the proximal end by the distal end of rod section 546 and at the distal end by the proximal surface of rod tip 548 . in fig2 a - 23d , catheter apparatus 510 of fig2 a - 22d is shown with cap element 524 screwed down resulting in at least partially compressing spring element 522 by the distal movement of rod section 546 relative to rod section 547 , in preparation for use . in fig2 a - 24d , pressurized fluid 540 has been introduced through branch 520 , through a part of the interior of proximal sleeve portion 512 , and through the interior of middle sleeve portion 514 to fully inflate balloon 516 . as balloon 516 is inflated , it expands in diameter and shortens in length causing further inward telescoping of rod section 547 into rod section 546 ( as best seen in fig2 d ), thereby further compressing spring element 522 . in fig2 a - 25d , dilatation pressure is removed and fluid is withdrawn from balloon 516 and from the interior catheter 510 through fluid inlet / outlet branch 520 . in a preferred embodiment , a vacuum may be applied to the proximal end of branch 520 to assist in withdrawing fluid and fully collapsing balloon 516 . as balloon 516 becomes deflated , the force exerted by the compressed spring element 522 becomes greater than the force exerted by the collapsing balloon . eventually this results in an outward telescoping of rod section 547 out of rod section 546 driven by the decompression of spring element 522 , and thereby stretching and tensioning balloon 516 . this automatic tensioning of the balloon element upon deflation assists in collapsing , folding and / or pleating the balloon to minimize its lateral profile for easier withdrawal through the small diameter interior channel of canula 526 . apparatus according to the present invention can be utilized in a variety of ways . as previously discussed , a principal intended application for the apparatus and methods of this invention is in treating vertebral fractures by dilating the interior of a vertebral element using a balloon catheter . fig2 - 33 illustrate various specific applications of apparatus and methods according to this invention in treating vertebral fractures . for example , fig2 a - 26d schematically illustrate the treatment of a partially collapsed vertebral segment with an apparatus according to one embodiment of this invention . fig2 a schematically illustrates a cross - section of a vertebral segment 60 comprising an interior region 62 filled with cancellous , or spongy , bone , and left and right pedicle portions 64 and 66 respectively . as seen in fig2 a , straight - line access holes have been drilled or otherwise created through pedicle portions 64 and 66 and into the adjacent cancellous bone in interior region 62 so as to meet and form a v - shaped passageway from the exterior of vertebral segment 60 through interior region 62 . as shown in fig2 b , a catheter guidewire 67 may then be threaded through the v - shaped passageway . as shown in fig2 c , a catheter apparatus 68 according to the present invention is introduced into the v - shaped passageway along guidewire 67 so as to position all of the uninflated balloon element 69 of the catheter apparatus inside interior region 62 . as shown in fig2 d , once balloon element 69 is properly positioned in region 62 , the balloon element can be inflated , expanding against the surrounding cancellous bone and thereby restoring the shape and size of the vertebral segment close if not identical to its pre - injury configuration . following this procedure , balloon element 69 is deflated and its lateral profile is reduced by stretching , tensioning , folding or pleating the balloon element utilizing the automatic or manual tensioning and / or twisting techniques previously described for a catheter apparatus in accordance with this invention . once the lateral profile of balloon element 69 is sufficiently reduced , catheter apparatus 68 , including balloon element 69 , can be easily withdrawn from the vertebral segment . fig2 a - 27d generally correspond respectively to fig2 a - 26d , as described above , except that in fig2 a - 27d , after the v - shaped passageway is created through vertebral segment 60 , canula elements 70 and 71 are inserted respectively into the passages through pedicle portions 64 and 66 . as seen in fig2 c , the catheter apparatus 78 used with this embodiment of the invention includes a balloon element 79 which is longer than the length of the v - shaped passageway through interior region 62 . as a result , a proximal - end portion of balloon element 79 remains in canula 70 and a distal - end portion of balloon element 79 is in canula 71 . as seen in fig2 d , when balloon element 79 is inflated , only the middle portion of the balloon which is inside region 62 can fully inflate . the inflation of the proximal and distal ends of balloon element 79 is constrained by the inner walls respectively of canula elements 70 and 71 . the canula elements 70 and 71 prevent the expansion forces exerted by the inflated balloon inside the passages through pedicle portions 64 and 66 from rupturing these relatively fragile bones . fig2 a - 28e schematically illustrate a cross - section of a vertebral segment 80 comprising an interior region 82 filled with cancellous bone , and left and right pedicle portions 84 and 86 respectively . as seen in fig2 a , a curved passageway has been created through left pedicle portion 84 , through the cancellous bone in region 82 , and through the right pedicle portion 86 to form a u - shaped channel from the exterior of vertebral segment 80 through interior region 82 . as shown in fig2 b , canula elements 73 and 74 are positioned respectively in the passages through left pedicle portion 84 and right pedicle portion 86 . as seen in fig2 c , a guidewire 87 may then be positioned in the passageway through the vertebral segment 80 . as seen in fig2 d , a catheter 88 in accordance with the present invention , having a balloon element 89 , may then be positioned along guidewire 87 such that a middle portion of balloon element 89 is in interior region 82 . balloon element 89 is shown longer than the entire passageway through vertebral segment 80 . as a result , when balloon element 89 is in place , a proximal - end portion of balloon element 89 extends completely through canula element 73 in left pedicle portion 84 and a distal - end portion of balloon element 89 extends completely through canula element 74 in right pedicle portion 86 . in a variation of this embodiment , balloon element 89 may be fabricated so as to be pre - curved for easier placement and better fit when inflated inside the u - shaped channel . as seen in fig2 e , upon inflation of balloon element 89 , only the middle portion inside interior region 82 can fully expand . as seen in fig2 , while balloon element 89 is in place and inflated , the proximal and distal ends of balloon element 89 are outside vertebral segment 80 and therefore accessible to the surgeon &# 39 ; s hands 81 or to instruments . fig3 schematically illustrates a cross section of a vertebral segment 160 being treated with a catheter apparatus 162 which utilizes a pre - curved internal guidewire 163 but without a spring tensioning element according to another embodiment of the present invention . the pre - curved guidewire 163 , fabricated for example from nitinol or other material having “ memory ” properties , assists in properly positioning the balloon element 169 in the preformed channel through the cancellous bone . in one variation of this invention embodiment , balloon element 169 may be fabricated as a relatively thinner , more flexible balloon which can be fully inflated at relatively lower pressures inside vertebral segment 160 . a more flexible balloon will have more uniform contact with the surrounding cancellous bone resulting in more surface area for expansion during inflation and the application of inflation forces at the interior locations where such forces are needed for expanding the bone mass . in another variation of this invention embodiment , following a balloon inflation cycle , balloon element 169 can be deflated and guidewire 163 can be utilized similar to the push rods previously described for applying tension to the deflated balloon element to assist with removal through the small - diameter canula 165 . if the balloon element 169 is of a thinner , more flexible construction than those previously described , less tensioning is required for removal . in addition , in the embodiment illustrated in fig3 , external tensioning can be applied to the distal end of the catheter , for example by simply pulling on the distal end , to assist in reducing the profile of the deflated balloon element for easier withdrawal . alternatively or additionally , tensioning could be applied to the distal end of the catheter by twisting it . in still another variation in accordance with this invention , balloon element 169 could be left in place in the interior of vertebral segment 160 , and the cavity inside the balloon could be inflated and filled with cement for permanent support of the damaged vertebral element . during this procedure the push rod , if hollow , could be used as a vent tube that is removed after the balloon is filled with cement . the balloon walls would contain the liquid cement during the setting period thereby preventing leakage through bone fractures causing medical problems . even after the cement is set , the balloon walls would prevent direct contact between the cement and the surrounding bone or tissue . for this embodiment , the long proximal neck of the balloon would be cut off after filling the balloon with cement and after removing the canula . fig3 schematically illustrates a pre - curved balloon element specially designed for use with a catheter apparatus according to this invention . fig3 schematically illustrates a cross section of a vertebral segment 170 being treated with a catheter apparatus 172 utilizing a pre - curved guidewire 173 according to another embodiment of the present invention . fig3 schematically illustrates a cross section of a vertebral segment 180 being treated with two catheter apparatuses 182 and 192 according to another embodiment of the present invention . in still another embodiment of this invention , the catheter balloon element for expanding a damaged bone region may be a multi - lumen balloon as described in u . s . pat . nos . 5 , 342 , 301 and 5 , 569 , 195 , which patents are incorporated herein by reference . use of a multi - lumen balloon can be of particular value where even using the spring tension or manual wrapping techniques described above will not allow production of a desired size and / or pressure balloon because the balloon profile is simply too large to fit in the canula . instead , by using a multi - lumen balloon , one can achieve both large diameters and higher pressures because each individual balloon can hold higher pressures with thinner walls . even more important is that the cone or transition regions of the multi - lumen balloons are much thinner and much more flexible . for example , one could utilize a balloon element comprising four balloons / lumens with or without a central lumen for the shaft . alternatively , with a 5 - lumen multi - lumen balloon configuration , the shaft can pass through the central fifth lumen created by the four outside lumens or the shaft can pass through one of the four outside lumens . as an alternative to a true multi - lumen catheter balloon construction , this embodiment of the invention could be practiced with many of the benefits of a multi - lumen balloon using several individual balloons in a side - by - side multiple balloon configuration . the individual balloons could be bonded together or , preferably , one could put an elastomeric or non - elastomeric sleeve over the group of individual balloons to keep them aligned during placement at the intended site , inflation and removal after the inflation cycle . the multi - lumen and multiple balloon embodiments of this invention as described above may be practiced with straight balloons or with pre - curved balloons configured for easier placement and better fit inside a curved catheter access channel . fig3 a - 34c illustrate yet another embodiment of the present invention . fig3 a is a schematic elevation view of a balloon dilatation apparatus 610 in some respects comparable to the balloon dilatation apparatus 210 of fig1 a . as best seen in the sectional view of fig3 b , this embodiment of the invention utilizes a stationary inner shaft or rod element 634 secured at its distal end to the tip 628 of inflation or balloon element 616 and a rotatable outer shaft 614 . rod element 634 runs through a central longitudinal channel in the catheter to the tip 628 of balloon element 616 . outer shaft 614 is connected at its distal end to inflation or balloon element 616 and at its proximal end to a rotatable sleeve element 612 , which may advantageously include outward projections 615 to assist with manual rotation of the sleeve element and the connected outer shaft 614 . the proximal end of sleeve element 612 is designed with a lip portion 613 to receive and rotatably hold the distal end of a catheter inlet conduit 624 through which a fluid 640 can be introduced to inflate the balloon element 616 . a gasket , seal , or o - ring 629 , or a similar fluid - sealing element , having a centrally - located aperture , is seated between the end of conduit 624 and the lip portion 613 of sleeve element 612 . this embodiment of the present invention is especially useful in duct dilatation applications , for example in treating the lacrimal duct . in such applications , the inflation or balloon element 616 of apparatus 610 is positioned inside a duct that requires dilatation , for example to improve fluid drainage . prior to insertion into the duct , the balloon element 616 can be tightly wrapped around the rod element 634 to reduce its profile and to facilitate insertion with minimal tissue damage or trauma . once properly positioned , the balloon can be unwrapped by rotating sleeve element 612 , for example using projections 615 , either clockwise or counterclockwise as appropriate . after it is positioned and unwrapped , balloon element 616 can be inflated with fluid 640 supplied from a pressurized fluid source through the hollow central channel running from the proximal end of inlet conduit 624 to the interior of the balloon element 616 . the balloon element may be inflated to a desired size and / or a desired inflation pressure , depending on the elastic or inelastic nature of the balloon material , maintained fully inflated for a desired length of time , such as one to ten minutes , and then deflated by disconnecting the fluid source and / or withdrawing the fluid , for example by applying a vacuum . this inflation cycle may be repeated two or more times as appropriate for treating the duct dysfunction . following this medical procedure , the balloon or dilatation element is deflated and sleeve element 612 is again rotated either clockwise or counterclockwise in order to rewrap the deflated balloon element 616 tightly around rod element 634 to reduce its profile for removal from the duct . projections 615 can be especially useful during this step to put additional twisting ( rotational ) forces on the deflated balloon element to obtain a tight wrap . projections 615 can be held manually to maintain a tight wrap of the deflated balloon element or they can be used to secure this wrapped position such as with an elastic or other holding element . the rewrapped balloon element can then be relatively easily withdrawn from the duct with little or no trauma to surrounding tissue . it will be apparent to those skilled in the art that other changes and modifications may be made in the above - described apparatus for adjustable epidermal tissue ingrowth cuffs and methods for using that apparatus without departing from the scope of the invention herein , and it is intended that all matter contained in the above description shall be interpreted in an illustrative and not a limiting sense .
apparatus and methods are disclosed for medical treatment comprising bone , tissue or duct dilatation using inflatable dilatation elements together with apparatus and techniques for tensioning , stretching , folding , and / or wrapping the dilatation elements externally as well as in situ to facilitate insertion , positioning and withdrawal procedures .