PATENT ABSTRACT
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.

PATENT DESCRIPTION
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a Division of U.S. Ser. No. 10/674,031, filed Sep. 29, 2003, now U.S. Pat. No. 7,488,337 issued Feb. 10, 2009, which claims the benefit of U.S. Provisional application Ser. No. 60/414,766, filed Sep. 30, 2002. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates generally to methods and apparatus for bone, tissue and duct dilatation, for example in surgically treating bone deformities and bones suffering from or predisposed to fracture or to collapse, particularly spinal fractures such as those commonly resulting from osteoporosis. In the example of bone treatment, an inflatable balloon element in accordance with the present invention is inserted into an interior region, cavity or passage of a damaged, collapsed, or deformed bone segment; and, thereafter the balloon element is inflated to form, enlarge or support the interior bone region thereby to effect a desirable realignment of the damaged bone segment with adjacent bone portions. In alternative embodiments of this invention, following the dilatation step, the balloon element may be collapsed and withdrawn from the interior bone region utilizing the special methods and apparatus of this invention or, in some embodiments, the dilated balloon element may be left in place, and the cavity or the interior of the dilated balloon element may be filled with a suitable support material. The present invention has particular application in, but is not limited to, treatment of vertebral body compression fractures. 
     BACKGROUND OF THE INVENTION 
     A number of diseases, illnesses and other medical conditions are treatable at least in part by dilatation of a bone, tissue or duct. For example, medical conditions and/or physical injuries can lead to or predispose a bone to deformity, such as a fracture. A familiar example is osteoporosis, in which bones lose calcium and break more easily. The human spinal column, comprised of interconnected vertebrae or vertebral bodies, has proven to be especially susceptible to the effects of osteoporosis. A vertebral body weakened by osteoporosis can fracture from a fall, or simply during routine activities. When a vertebral body fractures, it can collapse and change the shape of the spine. The damaged portion of the spine becomes shorter, and the rest of the spine above the broken vertebral body bends forward. As additional vertebral fractures occur, the spine shortens further, increasingly forcing the individual into a hunched-over posture. 
     As taught by U.S. Pat. No. 6,066,154 (Reiley et al.), which is incorporated herein by reference, it is known in the art to use an inflatable balloon-like device to treat certain bone conditions, resulting from osteoporosis, avascular necrosis, bone cancer and the like, that predispose a bone to, or lead to, fracture or collapse. A particularly common application is in the treatment of vertebral body compression fractures resulting from osteoporosis. 
     Typical treatment of such conditions includes a series of steps which a surgeon or health care provider can perform to form a cavity in an interior region of pathological bone, including but not limited to osteoporotic bone, osteoporotic fractured metaphyseal and epiphyseal bone, osteoporotic vertebral bodies, fractured osteoporotic vertebral bodies, fractures of vertebral bodies due to tumors especially round cell tumors, avascular necrosis of the epiphyses of long bones, especially avascular necrosis of the proximal femur, distal femur and proximal humerus and defects arising from endocrine conditions. 
     The method typically further includes the steps of making an incision in the skin (usually one incision, but a second small incision may also be required if a suction egress is used) followed by the placement of a guide pin which is passed through the soft tissue down to and into the bone. 
     The method of the Reiley &#39;154 patent further includes the steps of drilling the bone to be treated to form a cavity or passage in the bone, following which an inflatable balloon-like device is inserted into the cavity or passage where it is inflated. The inflation of the inflatable device causes a compacting of the cancerous bone and bone marrow against the inner surface of the cortical wall of the bone to further enlarge the cavity or passage. The inflatable device is then deflated and then is completely removed from the bone. The art further teaches that a smaller inflatable device (a starter balloon) can be used initially, if needed, to initiate the compacting of the bone marrow and to commence the formation of the cavity or passage in the cancellous bone and marrow. After this has occurred, a larger, inflatable device can be inserted into the cavity or passage to further compact the bone marrow in all directions. 
     At this point in accordance with Reiley &#39;154, a flowable biocompatible filling material, such as methylmethacrylate cement or a synthetic bone substitute, is directed into the bone cavity or passage that has been formed and enlarged, and the filling material is allowed to set to a hardened condition to provide ongoing structural support for the bone. Following this latter step, the insertion instruments are removed from the body and the incision in the skin is covered with a bandage. 
     A related U.S. Pat. No. 6,048,346 (Reiley et al.), which is also incorporated herein by reference, teaches an improved mechanical bone cement injection assembly, which is described as constituting an improvement over prior art devices that operated “similar to a household caulking gun” in that it facilitates greater control over the placement of cement and other flowable liquids into an interior region of a bone. 
     Another inflatable apparatus intended for deployment into interior body regions is described in U.S. Pat. No. 5,972,015 (Scribner et al.), which is also incorporated herein by reference. The Scribner &#39;015 patent describes a catheter tube extending along a first axis in conjunction with an expandable structure having an expanded geometry oriented about a second axis, not aligned with the first axis, so as to treat an asymmetrically-shaped interior body region or where the access channel cannot be aligned with the body region to be treated. A particular application of this technology is stated to be for the fixation of fractures or other osteoporotic and non-osteoporotic conditions of human and animal bones, specifically for treating a human lumbar vertebra. 
     Two somewhat earlier patents describing similar apparatus and methods for treating vertebral body compression fractures and the like using an inflatable balloon-like element inserted into the bone cavity are U.S. Pat. Nos. 5,108,404 (Scholten et al.) and 4,969,888 (Scholten et al.), both of which are also incorporated herein by reference. 
     Numerous problems remain, however, with the prior art apparatuses and methods. For successful expansion of a fractured vertebral body, an expandable element inserted into the vertebral cavity must be capable of being inflated to a relatively large working diameter of about 12 mm-25 mm, starting with a relatively short balloon working length, e.g., about 12 mm-25 mm, sized to fit inside the vertebral cavity, at very high working pressures on the order of 200-400 psi or higher. It has been found that the use of lower inflation pressure in such applications results in only a partial, incomplete expansion of the fractured vertebral body. When that partially-expanded vertebral body is subsequently filled with cement or comparable material, which then hardens, there is a permanent remaining spinal deformity at that vertebral body. Not only must the expandable/inflatable element in the vertebral cavity be capable of inflation to very high pressure without potentially disastrous rupture in order to fully expand a collapsed/fractured vertebral body, in addition the inflated element must resist puncture by hard, sharp cancellous bone and surface irregularities around the outer edges of the vertebral cavity. Standard materials commonly used in the prior art for constructing the expandable, balloon-like element used to expand bone cavities cannot be safely inflated to very high pressures on the order of 200-400 psi or higher, and, when inflated, typically do not have a high degree of puncture resistance. 
     One possible approach to improve the strength of the balloon-like elements to make them better able to withstand very high inflation pressures would be to use thicker balloon walls and/or to make these elements out of stiffer, stronger materials. There are several reasons, however, why these seemingly straightforward solutions have not proven successful in practice. One is the need to limit the balloon wall thickness and the need to maintain balloon wall flexibility to facilitate access to, and withdrawal from, a bone cavity. 
     In treating a vertebral fracture, for example, the vertebral cavity is typically accessed by drilling a small hole and locating a short, hollow, metallic tubular element (canula) through the left or right pedicle portion (or sometimes both) of the vertebral arch (see, e.g., FIG. 2 of U.S. Pat. No. 5,972,015, which shows the left and right pedicle portions 42 of vertebral arch 40, and FIG. 6 of the same patent which shows an access hole for catheter tube 50 and expandable structure 56 through one pedicle portion 42 into the interior volume 30 of reticulated cancellous, or spongy, bone 32). Because pedicle portion 42 shown in FIGS. 2 and 6 of the Scribner &#39;015 patent is relatively small and is itself readily susceptible to fracture if its structural integrity is impaired by too large a hole, it is crucial to keep the diameter of the hole, therefore also of the canula, to a minimum, typically no larger than about 4-5 mm. The canula helps to protect surrounding bone portions from abrasion and from expansion forces while inserting or removing the catheter shaft or while inflating the balloon element. 
     Thus, conventional practice has been to fold or wrap the balloon-like element relatively tightly around the end of a catheter shaft in order to keep the maximum diameter of the unit at the balloon end small enough to fit through the canula of a small-diameter pedicle hole. If a balloon-like expandable element was fabricated having relatively thick walls and/or made from a relatively stiff, less flexible material, such an element might well be inflatable to a higher pressure, but it generally could not be wound tightly enough about the distal end of a catheter shaft to fit through a narrow-diameter pedicle hole. 
     Even assuming that it were possible somehow to wrap a relatively thick-walled and/or stiff balloon element sufficiently tightly to facilitate insertion of the device through a narrow-diameter pedicle hole, it then would be virtually impossible using prior art technology to remove or withdraw the balloon element through the same hole or canula following dilatation. The reason is that, after a cycle of inflation and deflation inside the vertebral cavity, a thick-walled/relatively inflexible balloon element cannot be refolded or rewrapped in-situ to a sufficiently small diameter to be capable of being withdrawn through the canula without the use of excessive force which might crack or break the pedicle. 
     In another example, a balloon catheter according to the present invention can be used to treat congenital obstructions of the nasal lacrimal duct. This procedure requires inserting an inflatable element at the distal end of a catheter through the very narrow and sensitive lacrimal duct, inflating the balloon to compress the obstruction and open the passageway, deflating the balloon, and thereafter removing the deflated balloon element through the lacrimal duct. Following inflation, however, the balloon element may not return to its pre-inflation profile making withdrawal difficult. 
     These and other deficiencies in and limitations of the prior art approaches to treating bone deformities, such as vertebral body compression fractures, and other medical treatments involving inserting, inflating, and thereafter deflating and removing a balloon element through a relatively narrow body passageway are largely if not completely overcome with the apparatus and methods of this invention for bone, tissue and duct dilatation. 
     OBJECTS OF THE INVENTION 
     Accordingly, a general object of the present invention is to provide improved apparatus and methods for bone, tissue and duct dilatation. 
     Another general object of the present invention is to provide improved inflatable balloon-like elements for dilatation of interior bone regions, tissue portions, or duct segments in combination with balloon withdrawal systems and methods of using the same. 
     Still another general object of the present invention is to provide inflatable balloon-like elements able to expand to relatively large diameters, to withstand relatively high inflation pressures, and to resist damage by hard, sharp cancellous bone for use in dilating an interior region of a damaged bone. 
     A specific object of the present invention is to provide apparatus and methods for more effectively treating vertebral body compression fractures. 
     Another specific object of the present invention is to provide apparatus and methods for removing congenital obstructions of the nasal lacrimal duct. 
     Another specific object of the present invention is to provide inflatable balloon-like elements for dilatation of an interior region of a damaged bone capable of expansion to inflated working diameters of about 12 mm-25 mm, starting with relatively short balloon working lengths sized to fit inside a vertebral or other bone or body cavity, at working pressures of about 200-400 psi or higher. 
     Still another specific object of the present invention is to provide inflatable balloon structures, capable of inflation to high working pressures, which are relatively easily introduced into the interior region of a bone, tissue or duct through a small diameter opening, on the order of about 4 to about 5 mm or less in diameter or width, and which balloon structures are capable of being collapsed to a very small diameter following inflation to facilitate withdrawal after use. 
     Yet another specific object of the present invention is to provide active or passive balloon wrapping or tensioning assemblies, or both for use in conjunction with inflatable balloon structures according to the present invention to facilitate insertion of a balloon structure through a narrow diameter opening or passageway and/or withdrawal of a balloon structure through a narrow diameter opening or passageway following an inflation-deflation cycle. 
     Another specific object of the present invention is to provide assemblies comprising in combination an inflatable balloon element, a catheter shaft connected to the balloon element to provide a working fluid for inflating the balloon element and for withdrawing the fluid to deflate the balloon element, and at least a balloon tensioning and/or wrapping device or both for stretching the balloon element and/or folding, pleating or wrapping the balloon element to facilitate insertion and/or removal of the balloon element through a narrow diameter duct, access channel or canula typically having an opening of about 4 to 5 mm or less. 
     Other objects and advantages of the present invention will in part be obvious and will in part appear hereinafter. The invention accordingly comprises, but is not limited to, the apparatus and related methods, involving the several steps and the various components, and the relation and order of one or more such steps and components with respect to each of the others, as exemplified by the following description and the accompanying drawings. Various modifications of and variations on the apparatus and methods as herein described will be apparent to those skilled in the art, and all such modifications and variations are considered within the scope of the invention. 
     SUMMARY OF THE INVENTION 
     The present invention provides for the fabrication, deployment, inflation, deflation and withdrawal of very high-pressure, puncture- and abrasion-resistant balloon catheters that are capable of being relatively easily introduced and withdrawn through a hole or canula in the pedicle of a spine, or through the lacrimal duct, and in similar body treatment applications. In other embodiments of the present invention, the balloons, expansion elements, and balloon catheters described herein function to increase the surface area of dilation in order to more readily compress cancellous or other bone matter thereby to expand a vertebral or other bone element, to compress or remove a lacrimal duct obstruction, and in similar medical treatment applications. 
     Balloon catheter designs described herein provide for either active or passive axial tension on the balloon or expansion element, or an assembly for wrapping the balloon element, or both. Tension and/or wrapping may be needed for both insertion and withdrawal, but has been found to be primarily needed for in-situ tensioning/wrapping prior to withdrawal where one does not have the benefit of being able to wrap the balloon down with one&#39;s fingers as is commonly done prior to insertion. 
     In accordance with the present invention, a balloon or expansion element may be mounted on the distal end of a hollow tube which may be either metal or plastic. These devices need not be flexible/bendable as is common with standard balloon catheters because the devices of the present invention typically are not intended to be snaked through the tortuous path of a blood vessel. The proximal end of the balloon is bonded to or integrally connected with the tube at or near the distal end of the tube to create a fluid passage through the tube to the interior of the balloon element. The distal end of the balloon can be configured in several different ways. 
     In one embodiment, the distal end of the balloon is sealed off either by integral manufacturing of a sealed end balloon, for example in accordance with U.S. Pat. No. 5,411,477, which is incorporated herein by reference, or by sealing or potting the distal balloon neck. This end is left unattached and an axially-oriented push rod is used to push against the sealed end of the balloon causing tension and axial elongation or movement of the balloon during deflation, which causes the balloon to form a number of longitudinal pleats or folds which substantially reduces the profile of the deflated balloon allowing it to be more easily withdrawn. The fact that the distal end is not attached makes this embodiment easier to manufacture and reduces the chance of a leak point by eliminating a glue or bond joint. 
     In an alternative embodiment, the distal end of the balloon can be attached to the push rod by adhesive or thermal bonding if desired. The push rod can be rotated and pushed to produce an even tighter re-wrap of the balloon. Both active and passive rotation of the push rod can be used. 
     The push rod can be spring loaded anywhere along the shaft, preferably at the back (proximal) end of the catheter inside a suitable manifold where the force, distance and other important parameters can be easily controlled, permanently set, or be made adjustable by the device user. The force can be active or passive, it can be adjusted so that there is always an axial load on the balloon or only a load when the balloon is inflated and deflated. Once the balloon is stretched a predetermined amount the tension is released. The removal of constant tension during sterilization, storage, etc. can be important to prevent creep or weakening of the balloon and at the bond areas. A method of passive tension, but with an active preparation before using it, may be the most desirable approach for many applications. 
     The push rod itself can be a compressive spring or a spring can be incorporated anywhere along the length of the push rod or machined as part of the rod. Alternatively, the design can be fabricated such that there is no push rod, but the hollow tube has a spring section either attached or integrally formed somewhere along its length inside the balloon, and the balloon is attached to this rod at one or both ends. The tension can also be provided by hydraulic or pneumatic actuation on the back end of the device, or a pneumatic bladder can be inflated in the back. 
     An adjustable position/tension rod may be preferred in some applications in which the balloon may be inflated to very high pressure beyond its elastic limit where permanent axial and radial deformation may occur. Such deformation would require the catheter design to accommodate this growth to insure that enough tension and axial displacement takes place to fold the balloon down. 
     In all of these designs, inflation of the balloon will cause the balloon to fill up in diameter while causing the overall length of the balloon to shorten, which will push or compress the shaft. The tension is designed to allow the balloon to fully expand. As the balloon is deflated, the tension in the shaft pushes the distal end in the distal direction and begins folding or collapsing the balloon and may also assist in more rapid deflation of the balloon. In another embodiment, elastomeric tubing can be placed over the balloon to help it refold and to protect the balloon from damage. The balloon can also be coated to help improve its puncture and abrasion resistance. 
     In still another embodiment of the present invention, a balloon that is longer than the length necessary to fill a bone or similar body cavity can be used, and the canula can be designed so as to restrict any expansion thereby creating an absolute maximal dilation region for each and every application without wasting space for the balloon transitions or requiring multiple length balloons for treating various size vertebral or other bone or body cavities. All that would be necessary is to have available several balloon diameters or a more compliant balloon, but of only one length. In this embodiment, it is also envisioned to size or position the canula such that the distal end may extend partially into the cavity to be dilated so as to further control balloon length and area of dilation. 
     In still another embodiment, after dilating a balloon or inflation element in accordance with this invention, the rod structure is removed, the balloon is filled with cement or a cement-like material that cures and hardens in situ and left in place as an implant. After removing the canula, the long proximal neck can be cut off to separate the proximal end of the catheter from the filled balloon element. In another variation, a hollow push rod could be left in place during cement filling of the balloon to act as a vent tube, which would be removed after the balloon is full of cement. 
     In yet another embodiment of this invention, multi-lumen balloon elements, for example as described in my U.S. Pat. Nos. 5,342,301; 5,569,195; and 5,624,392, which are incorporated herein by reference, may be used as the balloon elements for the catheters of this invention. 
     Other specific embodiments of the present invention include the following: 
     (1) An assembly adapted for bone, tissue and/or duct dilatation of a living being comprising in combination: a hollow tube; an inflatable and deflatable balloon element having proximal and distal ends in fluid communication with the hollow tube; and, balloon tensioning and/or balloon wrapping device(s) for stretching the balloon element and/or folding, pleating or wrapping the balloon element to facilitate insertion and/or removal of the balloon element through a narrow diameter duct, access channel or cannula. 
     (2) An assembly according to paragraph (1) above in which said balloon element is capable of being inflated to a working diameter of about 12 mm to about 25 mm. 
     (3) An assembly according to paragraph (1) above in which said balloon element is capable of being inflated to a working pressure of about 200-400 psi over a relatively short balloon working length. 
     (4) An assembly according to paragraph (1) above in which said balloon element is stretched and/or folded, pleated or wrapped to a diameter of about 4-5 mm or less for insertion through and/or removal from said duct, access channel or canula. 
     (5) An assembly according to paragraph (1) above in which said balloon tensioning and/or balloon wrapping device(s) is/are selected from the group consisting of active and passive tensioning and wrapping devices. 
     (6) An assembly according to paragraph (1) above in which, upon inflation to its working pressure, the balloon element maintains a high degree of puncture and abrasion resistance. 
     (7) An assembly according to paragraph (1) above in which the balloon element is mounted on the distal end of the hollow tube, and the proximal end of the balloon element is bonded to or integrally connected with an end of the tube to create a passage through the tube to the interior of the balloon element. 
     (8) An assembly according to paragraph (7) above in which the distal end of the balloon element is sealed, and the assembly further comprises a rod element running through the passage of the tube and the interior of the balloon element to the sealed distal end of the balloon element. 
     (9) An assembly according to paragraph (8) above in which axial force can be applied manually or automatically to push the rod element against the sealed distal end of the balloon element causing tension and axial elongation of the balloon element. 
     (10) An assembly according to paragraph (9) above in which the rod element is not attached to the balloon element. 
     (11) An assembly according to paragraph (9) above in which the rod element is attached to or otherwise engages the balloon element. 
     (12) An assembly according to paragraph (11) above in which wherein rotational force can be applied manually or automatically to rotate the rod element from its free-standing position causing the balloon element at least in part to wrap around the rod element. 
     (13) An assembly according to paragraph (9) above in which wherein said rod element is spring loaded to apply axial tensioning and elongation to the balloon element. 
     (14) An assembly according to paragraph (11) above in which said rod element is spring loaded to apply rotational tensioning to the balloon element. 
     (15) An assembly according to paragraph (11) above in which said rod element is spring loaded to apply both automatic axial and rotational tensioning to the balloon element. 
     (16) An assembly according to paragraph (9) above in which said rod element comprises a compressive or rotational spring element. 
     (17) An assembly according to paragraph (7) above in which said hollow tube comprises a compressive spring element. 
     (18) An assembly according to paragraph (1) above in which the balloon tensioning and/or wrapping device is hydraulically or pneumatically actuated. 
     (19) An assembly according to paragraph (8) above in which said rod element is adjustable in length. 
     (20) An assembly according to paragraph (1) above including elastomeric tubing placed over said balloon element. 
     (21) An assembly according to paragraph (1) above in which wherein the exterior of said balloon element is coated with a material to improve puncture and abrasion resistance. 
     (22) An assembly according to paragraph (11) above including at least a cannula element wherein at least one end of the balloon element extends into or completely through said cannula element when the balloon element is positioned in a cavity to be dilated. 
     (23) An assembly according to paragraph (22) above in which said cannula element is adapted to restrict expansion forces of the balloon element during inflation. 
     (24) An assembly according to paragraph (8) above in which, after the balloon element is inserted in a cavity to be dilated and inflated to working pressure for a sufficient period of time, the interior of the inflated balloon element is filled in situ with a cement material. 
     (25) An assembly according to paragraph (24) above in which the rod element is removed before the balloon element is filled with a cement material. 
     (26) An assembly according to paragraph (24) above in which the rod element has a hollow interior to act as a vent for working fluid while the balloon element is filled with a cement material, and is removed before the cement hardens. 
     (27) An assembly according to paragraph (24) above in which the hollow tube is detached from the balloon element after the balloon element is filled with the cement material. 
     (28) An assembly according to paragraph (1) above in which said balloon element comprises a multi-lumen balloon. 
     (29) An assembly according to paragraph (11) above in which said rod element is spring loaded to apply automatic axial tensioning to the balloon element and is adapted for optional manual rotational tensioning of the balloon element. 
     (30) An assembly according to paragraph (1) above including a pre-curved guidewire in the interior of the balloon element. 
     (31) An assembly according to paragraph (8) above in which said rod element comprises concentric inner and outer tubular members which are rotatable relative to one another and said balloon element is attached to or engages one of said tubular members whereby rotational forces can be applied to cause the balloon element at least in part to wrap around one of said tubular members. 
     (32) An assembly according to paragraph (8) above in which wherein said rod element is pre-curved and consists essentially of a material having memory properties. 
     (33) An assembly according to paragraph (1) above in which said balloon element is pre-curved. 
     (34) An assembly according to paragraph (1) above in which said balloon element consists essentially of a non-elastomeric material. 
     (35) A method for treating a living being for bone, tissue and/or body duct dilatation comprising the sequential steps of: inserting an inflatable balloon element in an uninflated state into an interior region, cavity or passage of a damaged, collapsed or deformed bone, tissue or duct through a first narrow diameter opening or passageway to position the balloon element at a body location requiring dilatation; inflating the balloon element with a working fluid to a working pressure and for a time period sufficient to substantially completely dilate the interior region, cavity or passage to substantially restore its normal size, shape and/or alignment; deflating the balloon element by withdrawing the working fluid; during and/or subsequent to said deflating step, stretching and/or folding, pleating or wrapping the balloon element to reduce its profile; and, withdrawing the previously-inflated balloon element through a narrow diameter opening or passageway, which may be the same as or different than said first narrow diameter opening or passageway. 
     (36) A method according to paragraph (35) above in which said balloon element is inflated to a working diameter of about 12 mm to about 25 mm during the inflating step. 
     (37) A method according to paragraph (35) above in which said balloon element is inflated to a working pressure of about 200-400 psi over a relatively short balloon working length during the inflating step. 
     (38) A method according to paragraph (1) above in which said balloon element is stretched and/or folded, pleated or wrapped to a diameter of about 4-5 mm or less for the steps of inserting and/or withdrawing the balloon element. 
     (39) A method according to paragraph (35) above in which said balloon element is stretched and/or folded, pleated or wrapped using at least a balloon tensioning and/or balloon wrapping device selected from the group consisting of active and passive tensioning and wrapping devices. 
     (40) A method according to paragraph (35) above in which, following inflation to its working pressure, the balloon element maintains a high degree of puncture and abrasion resistance. 
     (41) A method according to paragraph (35) above including the step of applying a vacuum to the inflated balloon element during the deflating step to assist with withdrawal of the working fluid. 
     (42) A method according to paragraph (35) above in which the balloon element is mounted on the distal end of a hollow tube, and the proximal end of the balloon element is bonded to or integrally connected with an end of the tube to create a passage through the tube to the interior of the balloon element. 
     (43) A method according to paragraph (42) above in which the distal end of the balloon element is sealed. 
     (44) A method according to paragraph (43) above in which a rod element passes through the tube and the interior of the balloon element to the sealed end of the balloon element. 
     (45) A method according to paragraph (44) above including the step of applying axial force manually or automatically to said sealed end of the balloon element through said rod element during and/or subsequent to the deflating step causing tension and axial elongation of the balloon element. 
     (46) A method according to paragraph (45) above in which the rod element is not attached to the balloon element. 
     (47) A method according to paragraph (45) above in which the rod element is attached to or otherwise engages the balloon element. 
     (48) A method according to paragraph (47) above including the step of applying rotational force manually or automatically to said rod element during and/or subsequent to the deflating step causing the balloon element at least in part to wrap around the rod element. 
     (49) A method according to paragraph (45) above in which said rod element is spring loaded to apply axial tensioning and elongation to the balloon element. 
     (50) A method according to paragraph (48) above in which said rod element is spring loaded to apply rotational tensioning to the balloon element. 
     (51) A method according to paragraph (35) above in which the balloon tensioning and/or wrapping device is hydraulically or pneumatically actuated. 
     (52) A method according to paragraph (44) above in which said rod element is adjustable in length, said method further comprising the step of adjusting the length of said rod element such that said rod element applies an axial tensioning to the balloon element during the deflating step. 
     (53) A method according to paragraph (35) above including the step of coating the exterior of the balloon element with a coating to improve puncture and abrasion resistance. 
     (54) A method according to paragraph (35) above in which, upon inserting the balloon element into an interior region, cavity or passage, at least one end of the balloon element extends into or completely through a cannula element positioned in one of the narrow diameter openings or passageways. 
     (55) A method according to paragraph (35) above in which said balloon element comprises a multi-lumen balloon. 
     (56) A method according to paragraph (47) above in which said rod element is spring loaded to automatically apply axial tensioning to the balloon element during the deflating step, said method further comprising the step of applying manual rotational tensioning to the balloon element during and/or subsequent to the deflating step. 
     (57) A method according to paragraph (35) above including the steps of positioning a guidewire through the interior region, cavity or passage to be dilated, and using the guidewire to position the balloon element during the inserting step. 
     (58) A method according to paragraph (57) above in which said guidewire is pre-curved. 
     (59) A method according to paragraph (44) above in which said rod element is pre-curved and fabricated from a material having memory properties. 
     (60) A method according to paragraph (35) above in which said balloon element is pre-curved. 
     (61) A method according to paragraph (35) above in which said balloon element consists essentially of a non-elastomeric material. 
     (62) A method for treating a living being for bone or tissue dilatation comprising the sequential steps of: providing a dilatation apparatus able to fit through a narrow opening, said dilatation apparatus comprising an inflatable balloon element in fluid communication with a hollow tube, and a rod element running through the interior of the hollow tube and the inflatable balloon element, wherein said balloon element is uninflated and is wrapped, folded, pleated or stretched at least in part about said rod element to reduce the profile of the balloon portion of the dilatation apparatus; inserting the dilatation apparatus into an interior region, cavity or passage of a damaged, collapsed or deformed bone or tissue region through a first narrow diameter opening or passageway to position the balloon element at a body location requiring dilatation; inflating the balloon element through the hollow tube with a working fluid to a working pressure and for a time period sufficient to substantially completely dilate the interior region, cavity or passage to substantially its normal size, shape and/or alignment; and, filling the inflated balloon element in situ through the hollow tube with a cement material. 
     (63) A method according to paragraph (62) above including the further steps of removing the rod element before filling the balloon element with cement material and detaching the hollow tube from the balloon element after it is filled with cement. 
     (64) A method according to paragraph (62) above in which the rod element has a hollow interior which is used for venting working fluid from the balloon element while it is being filled with cement material. 
     (65) A method according to paragraph (64) above including the steps of removing the rod element and detaching the hollow tube from the balloon element after it is filled with cement. 
     (66) A method according to paragraph (62) above in which said balloon element is inflated to a working diameter of about 12 mm to about 25 mm during the inflating step. 
     (67) A method according to paragraph (62) above in which said balloon element is inflated to a working pressure of about 200-400 psi over a relatively short balloon working length during the inflating step. 
     (68) A method according to paragraph (62) above in which said balloon element is wrapped, folded, stretched and/or pleated about said rod element such that the balloon portion of the dilatation apparatus has a diameter of about 4-5 mm or less for the inserting step. 
     (69) A method according to paragraph (62) above in which said balloon element comprises a multi-lumen balloon. 
     (70) A method according to paragraph (62) above including the steps of positioning a guidewire through the interior region, cavity or passage to be dilated, and using the guidewire to position the balloon element during the inserting step. 
     (71) A method according to paragraph (62) above in which said guidewire is pre-curved. 
     (72) A method according to paragraph (62) above in which said rod element is pre-curved and fabricated from a material having memory properties. 
     (73) A method according to paragraph (62) above in which said rod element is pre-curved and fabricated from a material having memory properties. 
     (74) A method according to paragraph (62) above in which said balloon element consists essentially of a non-elastomeric material. 
     (75) A method for treating a living being for dilatation of a section of a body duct to relieve a collapse or blockage condition comprising the sequential steps of: providing a dilatation apparatus able to fit through a narrow opening, said dilatation apparatus comprising an inflatable balloon element in fluid communication with a hollow tube, and a rod element running through the interior of the hollow tube and the inflatable balloon element, wherein said balloon element is uninflated and is wrapped, folded, pleated or stretched at least in part about said rod element to reduce the profile of the balloon portion of the dilatation apparatus; inserting the dilatation apparatus into a body duct to be dilated to position the balloon element at a duct section requiring dilatation; inflating the balloon element through the hollow tube with a working fluid to a working pressure and for a time period sufficient to substantially completely dilate the duct section to substantially its normal size; deflating the balloon element by withdrawing the working fluid; during and/or subsequent to said deflating step, stretching and/or folding, pleating or wrapping the balloon element to reduce its profile; and, withdrawing the dilatation apparatus including the previously-inflated balloon element from the treated duct. 
     (76) A method according to paragraph (75) above in which said balloon element is inflated to a working diameter of about 12 mm to about 25 mm during the inflating step. 
     (77) A method according to paragraph (75) above in which said balloon element is inflated to a working pressure of about 200-400 psi over a relatively short balloon working length during the inflating step. 
     (78) A method according to paragraph (75) above in which said balloon element is stretched and/or folded, pleated or wrapped to a diameter of about 4-5 mm or less for the steps of inserting and/or withdrawing the balloon element. 
     (79) A method according to paragraph (75) above in which said balloon element is stretched and/or folded, pleated or wrapped using at least a balloon tensioning and/or balloon wrapping device selected from the group consisting of active and passive tensioning and wrapping devices. 
     (80) A method according to paragraph (75) above including the step of applying a vacuum to the inflated balloon element during the deflating step to assist with withdrawal of the working fluid. 
     (81) A method according to paragraph (75) above in which the distal end of the balloon element is sealed, said method further comprising the step of applying axial force manually or automatically to said sealed end of the balloon element through said rod element during and/or subsequent to the deflating step causing tension and axial elongation of the balloon element. 
     (82) A method according to paragraph (81) above in which the rod element is not attached to the balloon element. 
     (83) A method according to paragraph (81) above in which the rod element is attached to or otherwise engages the balloon element. 
     (84) A method according to paragraph (83) above including the step of applying rotational force manually or automatically to said rod element during and/or subsequent to the deflating step causing the balloon element at least in part to wrap around the rod element. 
     (85) A method according to paragraph (81) above in which said rod element is spring loaded to apply axial tensioning and elongation to the balloon element. 
     (86) A method according to paragraph (84) above in which said rod element is spring loaded to apply rotational tensioning to the balloon element. 
     (87) A method according to paragraph (75) above in which the balloon tensioning and/or wrapping device is hydraulically or pneumatically actuated. 
     (88) A method according to paragraph (75) above in which said rod element is adjustable in length, said method further comprising the step of adjusting the length of said rod element such that said rod element applies an axial tensioning to the balloon element during the deflating step. 
     (89) A method according to paragraph (84) above in which said rod element is spring loaded to automatically apply axial tensioning to the balloon element during the deflating step, said method further comprising the step of applying manual rotational tensioning to the balloon element during and/or subsequent to the deflating step. 
     (90) A method according to paragraph (75) above in which said rod element comprises concentric inner and outer tubular members which are rotatable relative to one another, and said balloon element is attached to or engages one of said tubular members, said method further comprising the step of rotating said tubular members relative to one another during an/or subsequent to the deflating step to cause the balloon element to wrap at least in part around one of said tubular members. 
     These and other variations and embodiments of the apparatus of this invention, and different applications for and methods of using such apparatus, will be apparent from the drawings and the following description of the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is a schematic elevation view of apparatus according to a first embodiment of the present invention designed for automatic tensioning of a balloon element using a spring tensioning system located at the proximal (external) end of the device to facilitate withdrawal through a small diameter canula from a bone cavity following dilatation and subsequent deflation. In  FIG. 1A , the catheter is shown in a neutral position as it would be for shipping and storage prior to use. The cap portion is loose, and there is no compression of the spring element. The balloon element is shown extended, pleated and/or folded for compactness. 
         FIG. 1C  is an end view of the apparatus of  FIG. 1A  as seen from the distal end. 
         FIG. 1B  is a cross-sectional view of the device as shown in  FIG. 1C  taken along line  1 B- 1 B. 
         FIG. 2A  is a schematic elevation view of the same apparatus shown in  FIG. 1A , except that in  FIG. 2A  the cap has been screwed down resulting in at least partially compressing the spring element in preparation for using the device. The balloon element remains extended and folded and/or pleated. 
         FIG. 2C  is an end view of the apparatus of  FIG. 2A  as seen from the distal end. 
         FIG. 2B  is a cross-sectional view of the device as shown in  FIG. 2C  taken along line  2 B- 2 B. 
         FIG. 3A  is a schematic elevation view of the same apparatus shown in  FIGS. 1A and 2A , except that in  FIG. 3A  pressurized fluid has been introduced to fully inflate the balloon element. As a consequence of the balloon being inflated, it expands in diameter and shortens in length causing the rod/disc elements to be displaced toward the proximal end of the apparatus thereby further compressing the spring element. 
         FIG. 3C  is an end view of the apparatus of  FIG. 3A  as seen from the distal end. 
         FIG. 3B  is a cross-sectional view of the device as shown in  FIG. 3C  taken along line  3 B- 3 B. 
         FIG. 4A  is a schematic elevation view of the same apparatus shown in  FIGS. 1A ,  2 A and  3 A, except that in  FIG. 4A  dilatation pressure has been removed and, optionally, a vacuum may be applied to the fluid inlet/outlet conduit to withdraw fluid from the formerly inflated balloon element thereby collapsing it. As the balloon element is deflated, the compressed spring element exerts a force on the disc and rod pushing them axially toward the distal end of the apparatus. This results in stretching and tensioning the balloon element thereby assisting in collapsing, folding and/or pleating the balloon element for easier withdrawal from the dilated bone cavity. 
         FIG. 4C  is an end view of the apparatus of  FIG. 4A  as seen from the distal end. 
         FIG. 4B  is a cross-sectional view of the device as shown in  FIG. 4C  taken along line  4 B- 4 B. 
         FIG. 5A  is a schematic elevation view of apparatus according to a second embodiment of the present invention designed for manual tensioning and optional rotation (twisting and wrapping) of a balloon element to facilitate withdrawal through a small diameter canula from a bone cavity following dilatation and subsequent deflation. In  FIG. 5A , the catheter is shown in a neutral position as it would be for shipping and storage prior to use. The cap is loose, the balloon element is prefolded and/or pleated, and, optionally, wrapped around a push rod extending along the longitudinal axis of the device. The sealing gasket is not compressed, and the push rod is in a forward position (toward the distal end of the device). In one variation of this embodiment of the invention, the push rod may be attached to the distal tip of the balloon element or otherwise capable of engaging the balloon element to enable twisting the balloon element to wrap it around the push rod as described further below. 
         FIG. 5C  is an end view of the apparatus of  FIG. 5A  as seen from the distal end. 
         FIG. 5B  is a cross-sectional view of the device as shown in  FIG. 5C  taken along line  5 B- 5 B. 
         FIG. 6A  is a schematic elevation view of the same apparatus shown in  FIG. 5A , except that in  FIG. 6A  the cap has been tightened and the sealing gasket compressed in preparation for use to prevent pressurized inflation fluid from leaking out of the proximal end of the device. 
         FIG. 6C  is an end view of the apparatus of  FIG. 6A  as seen from the distal end. 
         FIG. 6B  is a cross-sectional view of the device as shown in  FIG. 6C  taken along line  6 B- 6 B. 
         FIG. 7A  is a schematic elevation view of the same apparatus shown in  FIGS. 5A and 6A , except that in  FIG. 7A  pressurized fluid has been used to fully inflate the balloon element. As a consequence of the balloon being inflated, it expands in diameter and shortens in length causing the push rod to be displaced toward the proximal end of the apparatus. 
         FIG. 7C  is an end view of the apparatus of  FIG. 7A  as seen from the distal end. 
         FIG. 7B  is a cross-sectional view of the device as shown in  FIG. 7C  taken along line  7 B- 7 B. 
         FIG. 8A  is a schematic elevation view of the same apparatus shown in  FIGS. 5A ,  6 A and  7 A, except that in  FIG. 8A  dilatation pressure has been removed and, optionally, a vacuum may be applied to the fluid inlet/outlet conduit to withdraw fluid from the formerly inflated balloon element thereby collapsing it. As the balloon is being deflated, or after deflation, axial force is manually applied to the proximal end of the push rod to push it toward the distal end of the device thereby assisting with stretching and refolding or repleating the balloon for easier withdrawal through the canula from a dilated bone cavity. 
         FIG. 8C  is an end view of the apparatus of  FIG. 8A  as seen from the distal end. 
         FIG. 8B  is a cross-sectional view of the device as shown in  FIG. 8C  taken along line  8 B- 8 B. 
         FIG. 9A  is a schematic elevation view of the same apparatus shown in  FIGS. 5A ,  6 A and  7 A, except that in  FIG. 9A  the push rod is attached to or engages the balloon and, as the formerly inflated balloon is being deflated, or after deflation, rotational force is manually applied to the proximal end of the push rod to rotate the push rod resulting in wrapping the deflated balloon around the push rod to further reduce the balloon profile for easier withdrawal through the canula from a dilated bone cavity. 
         FIG. 9C  is an end view of the apparatus of  FIG. 9A  as seen from the distal end. 
         FIG. 9B  is a cross-sectional view of the device as shown in  FIG. 9C  taken along line  9 B- 9 B. 
         FIG. 10A  is a schematic elevation view of apparatus according to a third embodiment of the present invention designed for automatic tensioning of a balloon element to facilitate withdrawal through a small diameter canula from a bone cavity following dilatation and subsequent deflation. The apparatus of  FIG. 10A  is configured substantially similar to that shown in  FIG. 1A  except that the inflation/deflation port in  FIG. 10A  has been integrated into the cap/proximal end structure thereby eliminating the Y-element or side branch in  FIG. 1A  which served as the fluid inlet/outlet conduit. 
         FIG. 10C  is an end view of the apparatus of  FIG. 10A  as seen from the distal end. 
         FIG. 10B  is a cross-sectional view of the device as shown in  FIG. 10C  taken along line  10 B- 10 B. 
         FIG. 11A  is a schematic elevation view of the same apparatus shown in  FIG. 10A , except that in  FIG. 11A  the cap has been screwed down and pressurized fluid has been introduced to fully inflate the balloon element. As a consequence of screwing down the cap and inflating the balloon, the spring element has been compressed. 
         FIG. 11C  is an end view of the apparatus of  FIG. 11A  as seen from the distal end. 
         FIG. 11B  is a cross-sectional view of the device as shown in  FIG. 11C  taken along line  11 B- 11 B. 
         FIG. 12A  is a schematic elevation view of the same apparatus shown in  FIGS. 10A and 11A , except that in  FIG. 12A  dilatation pressure has been removed and, optionally, a vacuum may be applied to the inflation/deflation port to withdraw fluid from the formerly inflated balloon element thereby collapsing it. As the balloon element is deflated, the compressed spring element exerts a force on the disc and rod pushing them axially toward the distal end of the apparatus. This results in stretching and tensioning the balloon element thereby assisting in collapsing, folding and/or pleating the balloon element for easier withdrawal from the dilated bone cavity. 
         FIG. 12C  is an end view of the apparatus of  FIG. 12A  as seen from the distal end. 
         FIG. 12B  is a cross-sectional view of the device as shown in  FIG. 12C  taken along line  12 B- 12 B. 
         FIG. 13A  is a schematic elevation view of apparatus according to a fourth embodiment of the present invention for automatic tensioning of an adjustable length balloon element to facilitate withdrawal through a small diameter canula from a bone cavity following dilatation and subsequent deflation. In this embodiment, the balloon element is designed longer than necessary to fill the bone cavity being treated, and an adjustable clamp, nut, collar or similar element is used to help maintain a precise balloon length and to resist expansion forces during balloon inflation. The apparatus of  FIG. 13A  is otherwise shown configured substantially similar to that of  FIG. 1A  with cap and spring elements to effect automatic tensioning of the balloon element upon deflation. In  FIG. 13A , the cap portion is loose, and there is no compression of the spring element. 
         FIG. 13C  is an end view of the apparatus of  FIG. 13A  as seen from the distal end. 
         FIG. 13B  is a cross-sectional view of the device as shown in  FIG. 13C  taken along line  13 B- 13 B. 
         FIG. 14A  is a schematic elevation view of the same apparatus shown in  FIG. 13A , except that in  FIG. 14A  the cap has been screwed down resulting in at least partially compressing the spring element in preparation for using the device. The balloon element remains extended and folded and/or pleated. 
         FIG. 14C  is an end view of the apparatus of  FIG. 14A  as seen from the distal end. 
         FIG. 14B  is a cross-sectional view of the device as shown in  FIG. 14C  taken along line  14 B- 14 B. 
         FIG. 15A  is a schematic elevation view of the same apparatus shown in  FIGS. 13A and 14A , except that in  FIG. 15A  pressurized fluid has been introduced to inflate the distal end balloon element. As a consequence of the balloon being inflated, inflation forces try to push the canula backward (toward the proximal end) and/or to pull the catheter out. The adjustable nut or comparable element prevents such undesirable movements. 
         FIG. 15C  is an end view of the apparatus of  FIG. 15A  as seen from the distal end. 
         FIG. 15B  is a cross-sectional view of the device as shown in  FIG. 15C  taken along line  15 B- 15 B. 
         FIG. 16A  is a schematic elevation view of the same apparatus shown in  FIGS. 13A ,  14 A and  15 A, except that in  FIG. 16A  dilatation pressure has been removed and, optionally, a vacuum may be applied to the fluid inlet/outlet conduit to withdraw fluid from the formerly inflated balloon element thereby collapsing it. As the balloon element is deflated, the compressed spring element exerts a force on the disc and rod pushing them axially toward the distal end of the apparatus. This results in stretching and tensioning the balloon element thereby assisting in collapsing, folding and/or pleating the balloon element for easier withdrawal from the dilated bone cavity. 
         FIG. 16C  is an end view of the apparatus of  FIG. 16A  as seen from the distal end. 
         FIG. 16B  is a cross-sectional view of the device as shown in  FIG. 16C  taken along line  16 B- 16 B. 
         FIG. 17A  is a schematic elevation view of apparatus according to a fifth embodiment of the present invention designed for automatic tensioning and optional manual rotation (twisting and wrapping) of a balloon element to facilitate withdrawal through a small diameter canula from a bone cavity following dilatation and subsequent deflation. In this configuration, the rod passes through the disc and is attached to the disc and to the balloon element. In  FIG. 17A , the catheter is shown in a neutral position as it would be for shipping and storage prior to use. The cap portion is loose, and there is no compression of the spring element. The balloon element is shown extended, pleated and/or folded for compactness. 
         FIG. 17C  is an end view of the apparatus of  FIG. 17A  as seen from the distal end. 
         FIG. 17B  is a cross-sectional view of the device as shown in  FIG. 17C  taken along line  17 B- 17 B. 
         FIG. 18A  is a schematic elevation view of the same apparatus shown in  FIG. 17A , except that in  FIG. 18A  the cap has been screwed down resulting in at least partially compressing the spring element in preparation for using the device. The balloon element remains extended and folded and/or pleated. 
         FIG. 18C  is an end view of the apparatus of  FIG. 18A  as seen from the distal end. 
         FIG. 18B  is a cross-sectional view of the device as shown in  FIG. 18C  taken along line  18 B- 18 B. 
         FIG. 19A  is a schematic elevation view of the same apparatus shown in  FIGS. 17A and 18A , except that in  FIG. 19A  pressurized fluid has been introduced to fully inflate the balloon element. As a consequence of the balloon being inflated, it expands in diameter and shortens in length causing the rod/disc elements to be displaced toward the proximal end of the apparatus thereby further compressing the spring element. 
         FIG. 19C  is an end view of the apparatus of  FIG. 19A  as seen from the distal end. 
         FIG. 19B  is a cross-sectional view of the device as shown in  FIG. 19C  taken along line  19 B- 19 B. 
         FIG. 20A  is a schematic elevation view of the same apparatus shown in  FIGS. 17A ,  18 A and  19 A, except that in  FIG. 20A  dilatation pressure has been removed and, optionally, a vacuum may be applied to the fluid inlet/outlet conduit to withdraw fluid from the formerly inflated balloon element thereby collapsing it. As the balloon element is deflated, the compressed spring element exerts a force on the disc and rod pushing them axially toward the distal end of the apparatus. This results in stretching and tensioning the balloon element thereby assisting in collapsing, folding and/or pleating the balloon element for easier withdrawal from the dilated bone cavity. 
         FIG. 20C  is an end view of the apparatus of  FIG. 20A  as seen from the distal end. 
         FIG. 20B  is a cross-sectional view of the device as shown in  FIG. 20C  taken along line  20 B- 20 B. 
         FIG. 21A  is a schematic elevation view of the same apparatus shown in  FIGS. 17A ,  18 A,  19 A and  20 A, except that in  FIG. 21A  the rod is attached to or engages the balloon and, as the formerly inflated balloon is being deflated, or after deflation, rotational force is manually applied to the proximal end of the rod to rotate the rod resulting in wrapping the deflated balloon around the rod to further reduce the balloon profile for easier withdrawal through the canula from a dilated bone cavity. 
         FIG. 21C  is an end view of the apparatus of  FIG. 21A  as seen from the distal end. 
         FIG. 21B  is a cross-sectional view of the device as shown in  FIG. 21C  taken along line  21 B- 21 B. 
         FIG. 22A  is a schematic elevation view of apparatus according to a sixth embodiment of the present invention designed for automatic tensioning of a balloon element using a spring tensioning system located at the distal (internal) end of the device to facilitate withdrawal through a small diameter canula from a bone cavity following dilatation and subsequent deflation. In  FIG. 22A , the catheter is shown in a neutral position as it would be for shipping and storage prior to use. The cap portion is loose, and there is little or no compression of the spring element. The balloon element is shown extended, pleated and/or folded for compactness. 
         FIG. 22C  is an end view of the apparatus of  FIG. 22A  as seen from the distal end. 
         FIG. 22B  is a cross-sectional view of the device as shown in  FIG. 22C  taken along line  22 B- 22 B. 
         FIG. 22D  is an enlarged cross-sectional view of the distal end of the device as shown in  FIG. 22B  to better illustrate details of the spring tensioning system at the balloon end of the apparatus. 
         FIG. 23A  is a schematic elevation view of the same apparatus shown in  FIG. 22A , except that in  FIG. 23A  the cap has been screwed down resulting in at least partially compressing the spring element and applying axial tension to the balloon in preparation for using the device. The balloon element remains extended and folded and/or pleated. 
         FIG. 23C  is an end view of the apparatus of  FIG. 23A  as seen from the distal end. 
         FIG. 23B  is a cross-sectional view of the device as shown in  FIG. 23C  taken along line  23 B- 23 B. 
         FIG. 23D  is an enlarged cross-sectional view of the distal end of the device as shown in  FIG. 23B  to better illustrate details of the spring tensioning system at the balloon end of the apparatus. 
         FIG. 24A  is a schematic elevation view of the same apparatus shown in  FIGS. 22A and 23A , except that in  FIG. 24A  pressurized fluid has been introduced to fully inflate the balloon element. As a consequence of the balloon being inflated, it expands in diameter and shortens in length thereby further compressing the spring element. 
         FIG. 24C  is an end view of the apparatus of  FIG. 24A  as seen from the distal end. 
         FIG. 24B  is a cross-sectional view of the device as shown in  FIG. 24C  taken along line  24 B- 24 B. 
         FIG. 24D  is an enlarged cross-sectional view of the distal end of the device as shown in  FIG. 24B  to better illustrate details of the spring tensioning system at the balloon end of the apparatus. 
         FIG. 25A  is a schematic elevation view of the same apparatus shown in  FIGS. 22A ,  23 A and  24 A, except that in  FIG. 25A  dilatation pressure has been removed and, optionally, a vacuum may be applied to the fluid inlet/outlet conduit to withdraw fluid from the formerly inflated balloon element thereby collapsing it. As the balloon element is deflated, the compressed spring element exerts a force on the rod pushing it axially toward the distal end of the apparatus. This results in stretching and tensioning the balloon element thereby assisting in collapsing, folding and/or pleating the balloon element for easier withdrawal from the dilated bone cavity. 
         FIG. 25C  is an end view of the apparatus of  FIG. 25A  as seen from the distal end. 
         FIG. 25B  is a cross-sectional view of the device as shown in  FIG. 25C  taken along line  25 B- 25 B. 
         FIG. 25D  is an enlarged cross-sectional view of the distal end of the device as shown in  FIG. 25B  to better illustrate details of the spring tensioning system at the balloon end of the apparatus. 
       Similar to the embodiments of  FIGS. 5-9  and  17 - 21 , the embodiment of FIGS.  22 - 25  can readily be adapted to add a rod rotation/balloon wrapping capability if the rod is equipped with a rotation-resisting element and the rod engages or can engage the end of the balloon. 
         FIGS. 26A-26D  show schematic cross-sectional views of a vertebral segment with a V-shaped catheter access channel formed through both pedicle portions and the cancellous bone being treated in accordance with one embodiment of the present invention. 
         FIGS. 27A-27D  show schematic cross-sectional views of a vertebral segment with a V-shaped catheter access channel formed through both pedicle portions and the cancellous bone being treated in accordance with another embodiment of the present invention. 
         FIGS. 28A-28E  show schematic cross-sectional views of a vertebral segment with a U-shaped catheter access channel formed through both pedicle portions and the cancellous bone being treated in accordance with still another embodiment of the present invention. 
         FIG. 29  shows a schematic cross-sectional view of a vertebral segment with a U-shaped catheter access channel formed through both pedicle portions and the cancellous bone being treated in accordance with still another embodiment of the present invention. 
         FIG. 30  shows a schematic cross-sectional view of a vertebral segment with a U-shaped catheter access channel formed through both pedicle portions and the cancellous bone being treated with a catheter apparatus using a pre-curved guidewire in accordance with another embodiment of the present invention. 
         FIG. 31  is a schematic side view of a pre-curved balloon element designed for use in some embodiments of the present invention. 
         FIG. 32  is a schematic cross-sectional view of a vertebral segment with a catheter access channel formed through only one pedicle portion being treated with a catheter apparatus using a pre-curved guidewire in accordance with another embodiment of the present invention. 
         FIG. 33  is a schematic cross-sectional view of a vertebral segment with catheter access channels formed through both pedicle portions for treatment with two catheter apparatuses in accordance with still another embodiment of the present invention. 
         FIG. 34A  is a schematic elevation view of apparatus according to still another embodiment of the present invention designed for wrapping a balloon or inflation element to facilitate withdrawal through a small diameter canula from a bone cavity or through a small diameter duct following dilatation and subsequent deflation. The apparatus of  FIG. 34A  is configured somewhat similar to that shown in  FIG. 10A  except that in  FIG. 34A  there is a fixed inner shaft and the balloon is wrapped by rotating the outer shaft. This can be accomplished with or without tensioning of the balloon or inflation element. 
         FIG. 34C  is an end view of the apparatus of  FIG. 34A  as seen from the distal end. 
         FIG. 34B  is a cross-sectional view of the device as shown in  FIG. 34C  taken along line  34 B- 34 B. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       FIGS. 1-4  illustrate a dilatation balloon tensioning apparatus according to a first embodiment of the present invention. The balloon dilatation catheter apparatus  10  in  FIGS. 1A-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  FIG. 1B , 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  FIGS. 1A-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  FIGS. 1A 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  FIGS. 1A-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  FIGS. 2A-2C , catheter apparatus  10  of  FIGS. 1A-1C  is shown with cap element  24  screwed down resulting in at least partially compressing spring element  22  in preparation for use. In  FIGS. 3A-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  FIGS. 4A-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 . 
       FIGS. 5-9  illustrate a dilatation balloon tensioning apparatus according to a second embodiment of the present invention. The balloon dilatation catheter apparatus  110  in  FIGS. 5A-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  FIG. 5B , 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  FIGS. 5A-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  FIG. 5C , 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  FIGS. 6A-6C , catheter apparatus  110  of  FIGS. 5A-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  FIGS. 7A-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  FIGS. 8A-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  FIGS. 9A-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  FIG. 9C , thereby further reducing the profile of the deflated balloon. 
       FIGS. 10-12  illustrate a dilatation balloon tensioning apparatus according to a third embodiment of the present invention. The balloon dilatation catheter apparatus  210  in  FIGS. 10A-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  FIG. 10B , 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  FIGS. 10A-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  FIG. 10C , 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  FIGS. 10A-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  FIGS. 11A-11C , catheter apparatus  210  of  FIGS. 10A-10C  is shown with cap element  224  screwed down resulting in at least partially compressing spring element  222  in preparation for use. Also in  FIGS. 11A-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  FIGS. 12A-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 . 
       FIGS. 13-16  illustrate a dilatation balloon tensioning apparatus according to a fourth embodiment of the present invention. The balloon dilatation catheter apparatus  310  in  FIGS. 13A-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  FIG. 13B , 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  FIGS. 13A-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  FIGS. 13A 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  FIGS. 13A-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  FIGS. 14A-14C , catheter apparatus  310  of  FIGS. 13A-13C  is shown with cap element  324  screwed down resulting in at least partially compressing spring element  322  in preparation for use. In  FIGS. 15A-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  FIG. 15B , 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  FIGS. 16A-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. 
       FIGS. 17-21  illustrate a dilatation balloon tensioning apparatus according to a fifth embodiment of the present invention. The balloon dilatation catheter apparatus  410  in  FIGS. 17A-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  FIG. 17B , 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  FIGS. 17A-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  FIGS. 17A 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  FIGS. 17A-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  FIGS. 18A-18C , catheter apparatus  410  of  FIGS. 17A-17C  is shown with cap element  424  screwed down resulting in at least partially compressing spring element  422  in preparation for use. In  FIGS. 19A-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  FIGS. 20A-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  FIGS. 21A-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  FIG. 21C , thereby further reducing the profile of the deflated balloon. 
       FIGS. 22-25  illustrate a dilatation balloon tensioning apparatus according to a sixth embodiment of the present invention. The balloon dilatation catheter apparatus  510  in  FIGS. 22A-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  FIG. 22B , 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  FIGS. 22A-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  FIGS. 22A 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 .  FIG. 22D  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  FIG. 22D , 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  FIGS. 23A-23D , catheter apparatus  510  of  FIGS. 22A-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  FIGS. 24A-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  FIG. 24D ), thereby further compressing spring element  522 . 
     In  FIGS. 25A-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.  FIGS. 26-33  illustrate various specific applications of apparatus and methods according to this invention in treating vertebral fractures. 
     For example,  FIGS. 26A-26D  schematically illustrate the treatment of a partially collapsed vertebral segment with an apparatus according to one embodiment of this invention.  FIG. 26A  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  FIG. 26A , 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  FIG. 26B , a catheter guidewire  67  may then be threaded through the V-shaped passageway. As shown in  FIG. 26C , 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  FIG. 26D , 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. 
       FIGS. 27A-27D  generally correspond respectively to  FIGS. 26A-26D , as described above, except that in  FIGS. 27A-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  FIG. 27C , 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  FIG. 27D , 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. 
       FIGS. 28A-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  FIG. 28A , 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  FIG. 28B , canula elements  73  and  74  are positioned respectively in the passages through left pedicle portion  84  and right pedicle portion  86 . As seen in  FIG. 28C , a guidewire  87  may then be positioned in the passageway through the vertebral segment  80 . As seen in  FIG. 28D , 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  FIG. 28E , upon inflation of balloon element  89 , only the middle portion inside interior region  82  can fully expand. As seen in  FIG. 29 , 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. 
       FIG. 30  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  FIG. 30 , 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. 
       FIG. 31  schematically illustrates a pre-curved balloon element specially designed for use with a catheter apparatus according to this invention. 
       FIG. 32  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. 
       FIG. 33  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. 
       FIGS. 34A-34C  illustrate yet another embodiment of the present invention.  FIG. 34A  is a schematic elevation view of a balloon dilatation apparatus  610  in some respects comparable to the balloon dilatation apparatus  210  of  FIG. 10A . As best seen in the sectional view of  FIG. 34B , 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.