Method of implanting a curable implant material

Abstract

A method of replacing a nucleus pulposus material wherein curable nucleus pulposus material is injected into a balloon in an intervertebral space

Claims

1. A method of replacing a nucleus pulposus in an intervertebral disc, comprising of the steps of: a) removing the nucleus pulposus from the intervertebral disc to create a space, b) inserting into the space a first balloon comprising an inlet port and an outlet port and a second separate, adjacent balloon comprising an inlet port and an outlet port, c) conducting a first fluid comprising a radiopaque agent through the inlet port of the first balloon and into the first balloon to substantially fill the space, and d) conducting a second fluid comprising a curable implant material into the second balloon to inflate the second balloon and displace the first fluid through the outlet port of the first balloon to provide simultaneous deflation of the first balloon and inflation of the second balloon carried out under substantially constant pressure, wherein the first and second balloons are laterally disposed beside each other during step b).

2. The method of claim 1 wherein the amount of the first fluid conducted into the first balloon is measured prior to step d).

3. The method of claim 1 further comprising: e) curing the implant material.

4. The method of claim 3 wherein the inlet and outlet ports are removed from the second balloon after step e).

5. The method of claim 1 further comprising the step, between steps c) and d), of: e) fluoroscopically assessing the first balloon.

6. The method of claim 1, wherein an outer surface of the first balloon abuts the space.

7. The method of claim 1, wherein an outer surface of each of the first balloon and the second balloon abuts the space.

8. A method of replacing a nucleus pulposus in an intervertebral disc, comprising the steps of: a) removing the nucleus pulposus from the intervertebral disc to create a space, b) inserting into the space a first balloon comprising an inlet port and an outlet port and a second separate, laterally adjacent balloon comprising an inlet port and an outlet port, c) conducting a first fluid comprising a radiopaque agent through the inlet port of the first balloon and into the first balloon to substantially fill the space, and d) conducting a second fluid comprising a curable implant material into the second balloon to displace the first fluid through the outlet port of the first balloon, wherein the simultaneous deflation of the first balloon and inflation of the second balloon is carried out under substantially constant pressure, so that when the first balloon is deflated the second balloon occupies substantially the same space as the first balloon had occupied, so that the simultaneous deflation/inflation of the balloons is carried out in a manner so as to maintain a disc height spacing created by the first balloon.

Description

DESCRIPTION OF THE FIGURES

(1) FIG. 1 discloses a cross-section of a damaged intervertebral disc.

(2) FIG. 2 discloses a cross-section of an intervertebral disc having a majority of the nucleus pulposus removed.

(3) FIG. 3 discloses a cannula inserted into the disc of FIG. 2 through a hole in the annulus fibrosus.

(4) FIG. 4 discloses a single balloon inserted into the disc of FIG. 3 through the cannula.

(5) FIG. 5 discloses filling the balloon of FIG. 4 with a radiopaque agent.

(6) FIG. 6 discloses displacing the radiopaque agent of FIG. 5 with a nucleus replacement material.

(7) FIG. 7 discloses the balloon of FIG. 6 completely filled with nucleus replacement material.

(8) FIG. 8 discloses the balloon of FIG. 7 having its ports removed.

(9) FIG. 9 discloses a dual balloon device inserted into the disc of FIG. 3 through the cannula.

(10) FIG. 10 discloses filling the trial balloon of FIG. 9 with a radiopaque agent.

(11) FIG. 11 discloses the implant balloon of FIG. 10 filled with nucleus replacement material and a deflated trial balloon.

(12) FIG. 12 discloses a side view of a functional spinal unit, wherein the disc space therein has a balloon of the present invention having multiple stacked (empty) chambers.

(13) FIG. 13 discloses the balloon of FIG. 12 filled to create the lordosis, wherein the chambers increase in length at higher locations in the disc space.

(14) FIG. 14 discloses a side view of a functional spinal unit, wherein the disc space therein has a balloon of the present invention having multiple stacked (filled) chambers to create the lordosis, wherein the chambers increase in length at higher locations in the disc space.

DETAILED DESCRIPTION OF THE INVENTION

(15) For the purposes of the present invention, a discectomy involves the removal of at least a portion of the nucleus pulposus of a degenerated disc. Often, the entire nucleus pulposus is removed. Frequently, a small amount of tissue from the annulus fibrosus portion of the intervertebral disc is removed as well, thereby leaving a central disc space surrounded by the remaining portion of the annulus fibrosus.

(16) FIG. 1 discloses a cross section of a damaged intervertebral disc.

(17) In performing a preferred method of the present invention, first, a discectomy is performed by creating a hole in the annulus fibrosus of the degenerating disc, inserting a tissue removal instrument (such as rongeurs) into the hole, and removing nucleus pulposus tissue from the central portion of the disc. The resulting structure is that shown in FIG. 2, wherein a portion of the nucleus pulposus is removed. Now referring to FIG. 3, a cannula 1 is inserted into the hole in the annulus fibrosus.

(18) In some embodiments, the device comprises a single balloon.

(19) Now referring to FIG. 4, the single balloon device of the present invention is inserted into the cannula. The device comprises a balloon 3 having an inlet port 5 and a outlet port 7. Now referring to FIG. 5, trial material 9 is flowed through the inlet port and into the balloon to fill the balloon with trial material. In one embodiment, the trial material is saline comprising a radiopaque agent. Now referring to FIG. 6, once the trial material 9 has been used to assess the disc space, the outlet port is opened and nucleus replacement material 11 is flowed into the balloon, thereby displacing the trial material 9. In FIG.6, the nucleus replacement material has displaced about half of the trial material from the balloon. Now referring to FIG. 7, the filling of the balloon with nucleus replacement material continues until the balloon is completely filled with nucleus replacement material. Now referring to FIG. 8, once the balloon is completely filled with nucleus replacement material, the outlet port and the inlet port are removed.

(20) In some embodiments, the device comprises two balloons.

(21) Now referring to FIG. 9, next, the device comprising both a trial balloon and an implant balloon is inserted directly into the disc cavity, preferably by being delivered through a minimally invasive cannula. The inlet and outlet ports for each balloon are shown exiting the cannula.

(22) Now referring to FIG. 10, next, the trial balloon is then inflated to conform to the cleared disc space cavity.

(23) Next, the volume of the intradiscal cavity is obtained by monitoring either the volume of material injected into the balloon, or the pressure in comparison to known balloon expansion values. Intra-operative imaging is then performed to determine the coronal, saggital, and axial placement of the device, as well as the size, angle and geometry of the cleared disc space. The intra-operative imaging may include the use of a C-arm, cineradiography or image guided surgery.

(24) Next, the surgeon makes an intraoperative determination as to whether an adequate intradiscal cavity has been created. If the surgeon determines that the intradiscal cavity is insufficient (for example, the disc space is located to the left of center), the surgeon deflates and removes the device, performs additional discectomy, and then again ascertains the disc space clearance with the trial balloon portion of the device.

(25) Based upon the surgeon's assessment of the amount, size and shape of the disc space cleared, the surgeon can select the appropriate disc treatment procedure, including the injection or insertion of nuclear and annular augmentation materials, disc replacement devices or fusion devices.

(26) Now referring to FIG. 11, if the surgeon decides to replace the nucleus with a nucleus replacement material, the surgeon then fills the implant balloon with a curable nucleus replacement material while deflating the trial balloon. The surgeon then allows the curable material to cure, thereby producing the desired implant.

(27) Therefore, in preferred embodiments, there is provided a method for replacing a nucleus pulposus, comprising the steps of:

(28) a) performing a discectomy to create a disc space;

(29) b) inserting a device comprising a deflated trial balloon and a deflated implant balloon into the disc space;

(30) c) expanding the deflated trial balloon,

(31) d) assessing the disc space via the inflated trial balloon,

(32) e) deflating the trial balloon while inflating the implant balloon with a curable nucleus replacement material; and

(33) f) curing the curable nucleus replacement material.

(34) The above steps will now be discussed in greater detail.

(35) In a preferred embodiment of the present invention, at least a portion of each of the nucleus pulposus and the annulus fibrosus is removed with a disc removal instrument to create a disc space DS. Suitable disc removal instruments include rongeurs, trephines, burrs and curettes. In some embodiments, the method includes removing at least a portion of the nucleus pulposus, wherein the removal step includes creating a vacuum or providing irrigation. In some embodiments, the irrigation is provided by the same cannulated instrument that delivers and expands the balloon. In some embodiments, the method includes removing at least a portion of the nucleus pulposus, wherein the removal step is achieved via chemical dissolution of the nucleus pulposus.

(36) Next, the device comprising the trial balloon and implant balloon is inserted into the disc space in a deflated form. The device comprises: a) a trial balloon having a lumen and comprising a first expandable material, and b) a trial tube having a proximal end portion, a distal end portion, and a throughbore (not shown), c) an implant balloon having a lumen and comprising a second expandable material, and d) an implant tube having a proximal end portion, a distal end portion, and a throughbore (not shown),
wherein the trial balloon lumen is connected to the distal end portion of the trial tube and is in fluid communication with its throughbore, and
wherein the implant balloon lumen is connected to the distal end portion of the implant tube and is in fluid communication with its throughbore.

(37) In some embodiments, and as shown, the device is inserted into the disc space through a cannula. So as to avoid further damage to the annulus, preferably, the cannula is sized to be smaller than the annular opening created in the disc. In other embodiments, the device is inserted without the aid of a cannula.

(38) The balloons can be delivered to the disc space by any suitable means, e.g., in deflated form retained within or upon the end of a rigid or semi-rigid rod or tube.

(39) In some embodiments, the balloons may also be inserted through a hole created in an endplate of an adjacent vertebra above or below the target disc. The balloons may also be inserted into the disc space via a posterior, anterior or anterolateral approach.

(40) Once positioned within the disc space, either centrally within the annular shell or at the edge of the annular rim, a suitable gas (e.g., nitrogen or carbon dioxide), liquid or other flowable expansion medium can be delivered through the tube in order to inflate the trial balloon in situ in a substantially radial, axial and/or longitudinal direction. In some embodiments, beads or other solid media are selected to be the expansion medium and are simply packed into the balloon through the tube.

(41) Next, the trial balloon is expanded while in the disc space. Preferably, the trial balloon is expanded with radio-opaque media (not shown), such as a radio-opaque gas or liquid, or with radio-opaque beads. Once expanded, the trial balloon may be imaged intra-operatively in order to determine the size, shape and location of the disc space. The trial balloon is only partially expanded in the disc space. Preferably, the trial balloon is expanded to completely fill the disc space.

(42) Next, the surgeon makes an intraoperative determination as to whether an adequate intradiscal cavity has been created. In some embodiments, this determination is made by either pressure assessment, fluoroscopic assessment or volumetric assessment. If the surgeon determines that the intradiscal cavity is insufficient (for example, the disc space is located to the left of center), the surgeon deflates and removes the device, performs additional discectomy, and then again ascertains the disc space clearance with the trial balloon portion of the device.

(43) Based upon the surgeon's assessment of the amount, size and shape of the disc space cleared, the surgeon can select the appropriate disc treatment procedure, including the injection or insertion of nuclear and annular augmentation materials, disc replacement devices or fusion devices.

(44) If, through the assessment, the surgeon has decided that sufficient disc space has been cleared, the surgeon then opens the exit port of the trial balloon and deflates the trial balloon (by, for example, providing suction through the exit port) while simultaneously filling the implant balloon with curable implant material. The simultaneously deflation of the trial balloon and inflation of the implant balloon is carried out under constant pressure or volume, so that when the trial balloon is deflated the implant balloon occupies substantially the same space as the trial balloon had occupied. Preferably, the simultaneous deflation/inflation of the balloons is carried out in a manner so as to maintain the disc height spacing created by the trial balloon. In some preferred embodiments, the implant balloon is filled through the injection of a plurality of discrete amounts of curable implant material. The injection of a plurality of discrete amounts of curable implant material allows the surgeon to accurately fill the balloon in a highly controlled manner. Once the implant balloon is completely filled, the cannulae connected with the balloons are removed. Optionally, the trial balloon may be removed as well. The material in the implant balloon is then allowed to cure.

(45) Therefore, in accordance with the present invention, there is provided a device for replacing a nucleus pulposus in an intervertebral disc, comprising;

(46) a) a first catheter having a first inlet tube having a proximal end opening and a distal end opening and a first outlet tube,

(47) b) a first balloon having an inlet port and an outlet port, wherein the inlet port is connected to the distal end opening of the first inlet tube and the outlet port is connected to the first outlet tube, and

(48) c) a first injection device containing a flowable radiopaque material, the first injection device connected to the proximal end opening of the inlet catheter.

(49) d) a second catheter having a second inlet tube having a proximal end opening and a distal end opening and a second outlet tube,

(50) e) a second balloon having an inlet port and an outlet port, wherein the inlet port is connected to the distal end opening of the second inlet tube, and

(51) f) a second injection device containing a curable nucleus replacement material, the injection device connected to the proximal end opening of the second inlet tube.

(52) Also in accordance with the present invention, there is provided a device for device for replacing a nucleus pulposus in an intervertebral disc, comprising;

(53) a) a first inlet catheter having a proximal end opening and a distal end opening,

(54) b) a first outlet catheter,

(55) c) a first balloon having an inlet port and an outlet port, wherein the inlet port is connected to the distal end opening of the first inlet catheter and the outlet port is connected to the first outlet catheter, and

(56) d) a first injection device containing a flowable radiopaque material, the first injection device connected to the proximal end opening of the inlet catheter.

(57) e) a second inlet catheter having a proximal end opening and a distal end opening,

(58) f) a second balloon having an inlet port and an outlet port, wherein the inlet port is connected to the distal end opening of the second inlet catheter, and

(59) g) a second injection device containing a curable nucleus replacement material, the injection device connected to the proximal end opening of the second inlet catheter.

(60) It may sometimes occur that the surgeon expands the trial balloon and decides that additional height is needed. Therefore, in some embodiment, there is provided a device comprising multiple, vertically arranged balloons. When such a balloon is provided, the surgeon fills the base balloon, and then has the option of filling the superior balloon in order to create more height in the trial or implant balloon. The provision of multiple balloons in the same device avoids the need to replace the undersized balloon and associated catheter with larger ones when the need for additional fill has been determined. In some embodiments, the plurality of balloons may take the form of stacked baffles. In some embodiments, the different balloons within the same disc are provided with different pressures or different compressible materials in order to obtain different properties for different balloons within the same disc. For example, in one embodiments, some but not all of the balloons may be provided with particles that resist shear and dampen axial forces. In some embodiments, the balloons that are closer to the endplates are stiffer than those further away from the endplates. In some embodiments thereof, the stacking could be produced via multiple chambers of the same balloon.

(61) In the lumbar region of the spine, the natural positioning of the vertebral endplates is such that the intervening disc has a wedged shape and provides a lordotic curvature to the spine. Therefore, it would be desirable for the implant balloon of the present invention to expand into a wedged shape that mimics the lordotic curvature of the spine. In other embodiments, the lordotic curvature is attained by implanting at least two balloons in a vertically arranged manner whereby the shape and spatial arrangement of the two balloons form a wedged shape and impart a lordotic curvature to the spine.

(62) In some embodiments thereof, the lordosis could be produced via multiple chambers of the same balloon. Now referring to FIG. 12, there is provided a balloon of the present invention having multiple stacked (empty) chambers which has been inserted into the disc space. Now referring to FIG. 13, there is provided a balloon of the present invention having multiple stacked chambers which have been filled to create the desired lordosis. In this particular embodiment, the chambers increase in length at higher locations in the disc space. Now referring to FIG. 14, there is provided a balloon of the present invention having multiple stacked chambers which have been filled to create the desired lordosis. In this particular embodiment, the chambers decrease in length at higher locations in the disc space.

(63) In some embodiments, ultrasound is used to assess the shape of the expanded balloon. In these embodiments, the expandable device (such as a balloon) is expanded within the disc space and ultrasound is then used to assess its shape. In some embodiments, the surgeon carries out an ultrasound-based assessment of the balloon after injecting the radiopaque material and before injecting the curable nucleus replacement material. The ultrasound assessment may be carried out with or without the balloon in place. If there is an intact annulus, the balloon may be used to pressurize the voided space and ultrasound may then be used to assess that pressurized space.

(64) Each expandable device or membrane of the present invention (such as a balloon) has at least one lumen, an inside surface, and an outer surface. Also, each balloon has an upper side, a lower side, an anterior side and a posterior side. The trial balloon is typically expanded by passing an expansion medium, such as a fluid or beads, through the lumen to fill the balloon. The implant balloon is typically expanded by filling it with a curable implant material.

(65) Suitable materials for preparing balloons of the present invention may include those that are presently used for such purposes as balloon angioplasty. Suitable materials provide an optimal combination of such properties as compliance, biostability and biocompatability, and mechanical characteristics such as elasticity and strength. Balloons can be provided in any suitable form, including those having a plurality of layers and those having a plurality of compartments when expanded. A useful device will include the balloons, together with a delivery catheter (optionally having a plurality of lumens extending longitudinally therewith), and fluid or gas pressure means.

(66) The balloons are typically made of an expandable material such as a plastic or elastomeric material. Examples thereof include silicone, polyurethane, polyethylene terephthalate, polycarbonate, thermoplastic elastomers and copolymers such as ether-ketone polymers such as poly(etheretherketone). Such polymeric materials can be used in either unsupported form, or in supported form, e.g., by the integration of fibers therein. In addition, the balloons may be made out of any of a wide variety of woven or nonwoven fibers, fabrics, metal mesh such as woven or braided wires, and carbon. Biocompatible fabrics or sheet material such as ePTFE and Dacron may also be used.

(67) In a particularly preferred embodiment, the balloons comprise a material selected from the group consisting of polyolefin copolymers, polyethylene, polycarbonate, polyethylene terephthalate, ether-ketone polymers, woven fibers, nonwoven fibers, fabrics and metal mesh.

(68) A radio-opaque material may be mixed with the expandable material to provide a radio-opaque balloon having imaging capability. The radio-opaque material may be provided in the form of a filler, particles, wires or shapes. Suitable radio-opaque materials include barium, barium sulfate, calcium or metallic materials.

(69) The balloons can include markers commonly used in image guided surgery to allow three dimensional reconstruction of the cleared disc space as compared to a preoperatively obtained reconstructed MRI and/or CT. The markers are preferably located upon the outside surface of the balloon. The markers may have spatially varying sizes, shapes or concentrations.

(70) Because volume controlled systems are preferred embodiments of the present invention, in some embodiments, the expandable material of the balloon can be a non-compliant material that expands to a predetermined size. In some preferred embodiments, the distraction of the disc space is accomplished by such an inflatable, rigid (non-compliant) balloon. The non-compliant balloon can be delivered in deflated form to the interior of the annulus and thereafter inflated in order to distract the disc space and provide a spaced region for the delivery of the implant material. The balloon is preferably of sufficient strength and of suitable dimensions to distract the space to a desired extent and to maintain the space in distracted position for a sufficient period of time.

(71) In one embodiment, at least the implant balloon has a wedged shape so that the height of the anterior portion of the expanded device is greater than the height of the posterior portion of the expanded device. This allows the surgeon to restore lordosis when the intervertebral implant is used in either the lumbar or cervical regions of the spine. Preferably, the wedged shape produces an angle of between 5 and 20 degrees, more preferably between 5 and 15 degrees.

(72) In preferred embodiments, the height of the medial portion of at least the implant balloon is greater than the height of either lateral portion of the implant balloon. This geometry more closely mimics the natural doming of the disc space.

(73) In some embodiments, the device can comprise at least one balloon of semicircular, circular, cylindrical, bilateral, or a generally crescent (or banana-like) shape. Upon inflation, each balloon can have a footprint that substantially corresponds to (but is smaller than) a rim of a vertebral endplate, wherein the anterior area height is greater than said posterior area height. More preferably, upon expansion, at least a portion of the balloon has a generally cylindrical shape thereby defining an axial dimension and a radial dimension.

(74) In some preferred embodiments, the balloons may also be used to distract the cleared disc space. When inflated, a non-compliant balloon may provide rigid walls (e.g., when they are fiber-supported or bellows-supported) that are sufficiently strong to distract the space. An inflatable device providing sufficient strength and dimensions for distraction can be prepared using conventional materials. In one embodiment, the uninflated balloon can be delivered to the center of the annular shell, and thereafter inflated to expand the annular shell and in turn, distract the space. Preferably, the expansion medium is injected in an amount sufficient to distract the space.

(75) As used herein, the word distraction will refer to the separation of the intervertebral joint surfaces to a desired extent, without rupture of their binding ligaments. Distraction can be accomplished by any suitable means including, for example, hydrostatic means. In one embodiment, the trial balloon is used as a distraction device. By the use of distraction, the disc space can be sufficiently re-established to achieve any desired final dimensions and position. Optionally, and preferably, the means used to accomplish distraction also serves the purpose of forming one or more barriers (e.g., balloons) for the flowable expansion media. If distraction is desired, then the disc space can be distracted prior to and/or during either a discectomy itself and/or delivery of a flowable expansion medium.

(76) A constricted disc space is generally on the order of 3 to 4 mm in height. Suitable distraction means are capable of providing on the order of about 3 atmospheres to about 4 atmospheres, (or on the order of about 40 psi to about 60 psi) of force in order to distract that disc space to on the order of 8 to 12 mm in height. Preferably, when used for distraction, the balloon of the present invention is designed to withstand at least 1 MPa of pressure, more preferably at least 2 MPa, more preferably at least 3 MPa.

(77) Distraction may occur via a multitude of steps or iterations, thereby allowing the soft tissue to relax, thus reducing the risk of soft tissue damage.

(78) Preferably, the expansion media of the in situ formed device can be delivered percutaneously (e.g., through a cannula having a diameter of no more than 6 mm, preferably no more than 2 mm). However, the expansion media of the in-situ formed device can also be delivered in cannulae of much larger dimension (such as up to 18 mm, or through a Craig needle). More preferably, the expansion media of the in-situ formed device is delivered into the disc space in the form of an injectable fluid.

(79) It has been reported in the literature that balloons inserted into the disc space may be subject to retropulsion. Therefore, in some embodiments of the present invention, and particularly those that include distraction, upon expansion, the inflatable implant balloon forms an upper surface having a first plurality of teeth projecting outwards from the upper surface. Upon expansion of the device, these teeth will project in the direction of the upper endplate and, upon complete expansion of the device, will engage the endplate to from a secure interlock with the endplate and resist retropulsion.

(80) In some embodiments, the implant balloon can be coated with an adhesive such as a protein activated sealant, or a sealant that becomes adhesive when wetted or activated.

(81) Preferably, the teeth are made of a stiff non-resorbable material, such as polyetheretherketone (PEEK). Preferably, the teeth have a height of between 0.5 mm and 1.5 mm, and have a triangular cross-section.

(82) In some embodiments of the present invention, upon expansion, the inflatable implant balloon forms an upper surface formed of a material having a high coefficient of friction. Upon expansion of the device, the high coefficient of friction of the upper and lower surfaces will cause a drag upon any movement of the upper surface and therefore keep the device in place and resist retropulsion.

(83) Preferably, the high friction upper and lower surfaces of the implant balloon device are made from a material selected from a group consisting of polyether block copolymer (PEBAX), ABS (acrylonitrile butadiene styrene); ANS (acrylonitrile styrene); Delrin; PVC (polyvinyl chloride); PEN (polyethylene napthalate); PBT (polybutylene terephthalate); polycarbonate; PEI (polyetherimide); PES (polyether sulfone); PET (polyethylene terephthalate); PETG (polyethylene terephthalate glycol), high and medium melt temperature: polyamides, aromatic polyamides, polyethers, polyesters, Hytrell, polymethylmethacrylate, polyurethanes: copolymers, EVA (ethylene vinyl acetate) or ethylene vinyl alcohol; low, linear low, medium and high density polyethylenes, latex rubbers, FEP, TFE, PFA, polypropylenes, polyolefins; polysiloxanes, liquid crystal polymers, inomers, Surlins, silicone rubbers, SAN (styrene acrylonitrile), nylons: 6, 6/6, 6/66, 6/9, 6/10, 6/12, 11, all PEBAXs 12; polyether block amides; and thermoplastic elastomers.

(84) Balloons of the present invention can be made using materials and manufacturing techniques used for balloon angioplasty devices. U.S. Pat. No. 5,807,327 (Green) discloses balloons that may be used in the present invention. The materials disclosed by Green for the formation of the balloon include tough non-compliant layer materials (col. 8, lines 18-36 of Green) and high coefficient of friction layer materials (col. 8, lines 42-54 of Green).

(85) Generally, the balloon is deliverable through a cannula having an inside diameter of between 3 mm and 18 mm, preferably between 4 mm and 12 mm, more preferably between 5 mm and 10 mm.

(86) In some preferred embodiments, a cannula having an inner diameter of no more than 6 mm, is inserted into the disc space.

(87) In some embodiments in which the surgeon desires to minimize the size of the incision, the balloon is preferably deliverable through a cannula having an inside diameter of between 0.5 mm and 6 mm, preferably between 1 mm and 4 mm, more preferably between 2 mm and 3 mm.

(88) In some embodiments, the present invention can be used to provide gradual correction of a scoliotic disc. The degree of curvature can be gradually changes over time by, for example, pumping up the balloons with a syringe.