Cortical rim-supporting interbody devices

Abstract

An inflatable central distractor is inserted into the disc space between two vertebral endplates. Peripheral balloons are inserted into the disc space surrounding the central inflatable distractor. The peripheral balloons and the central inflatable distractor are simultaneously expanded so that the peripheral balloons surround the central inflatable distractor as it expands, and so that the central inflatable distractor and the peripheral balloons, when expanded, contribute to pushing the adjacent vertebral endplates apart.

Description

[Technical Field]

[0001] To treat low back pain, surgeons remove the degenerated disc and insert a fusion cage into the intervertebral space. To minimize the invasiveness of the fusion procedure, more recent efforts have focused on forming the fusion cage in situ by flowing a hardenable material into a balloon placed in the intervertebral space.

[0002] Subsidence of implanted interbody cages is a known risk in fusion and occurs more frequently in patients with low bone mineral density. Hou and Yuan, Spine Journal, 12, 3, 249-256 (2012), investigated the structural properties of lumbar endplates and reported that the peripheral endplates, particularly in the posterolateral region near the pedicle, were significantly stronger than the central region. They also concluded that as disc degeneration increased, the central region became weaker, while minimal strength changes were observed in the peripheral region. [Background technology]

[0003] U.S. Patent Publication No. 2004 / 0230309 (DePuy Spine) discloses an orthopedic device for implantation between adjacent vertebrae, comprising an arcuate balloon and a hardenable material within the balloon. In some embodiments, the balloon has a footprint that substantially corresponds to the periphery of the vertebral endplate. An inflatable device is inserted into the intervertebral space through a cannula and oriented such that upon inflation, the natural angle between the vertebrae is at least partially restored. At least one component selected from the group consisting of a load-bearing component and an osteobiologic component is directed to the inflatable device through fluid communication means.

[0004] U.S. Patent No. 8,007,535 (Hudgins) discloses an injectable annular ring useful for treating deteriorated intervertebral discs. In use, the annular ring can be collapsed or folded so that it can be placed through a small opening into a prepared intervertebral space within the annulus using minimally invasive techniques. The expansion or spreading of the annulus in the intervertebral space provides an internal cavity bounded by the annulus in direct contact with the vertebral endplates. When the internal volume of the annulus is injected or filled with a load-bearing, hardenable material, the filled annulus maintains the intervertebral space and prevents the annulus from being expelled from the internal cavity through the small annular opening.

[0005] U.S. Patent No. 6,332,894 (Stalcup) discloses an orthopedic implant for implantation between adjacent vertebrae in the spine, comprising a generally annular bag and a hardened polymer within the bag. A method for fusing adjacent vertebrae in the spine includes the steps of forming an access hole in the annulus of the disc between the adjacent vertebrae, removing nucleus material within the disc to form a cavity surrounded by the annulus, placing a generally annular bag within the cavity and filling the bag with a polymer, and injecting bone particles into the cavity surrounded by the annular bag and allowing the polymer to harden.

[0006] U.S. Published Patent Application No. 2003-0028251 (Mathews) discloses a method and apparatus for preparing an intervertebral space and forming an interbody device therein. The apparatus includes a distractor having an extendable portion that can be positioned in the intervertebral space to distract the space. The extendable portion also provides a form around or against which an interbody device of a first material is placed. A second material may be placed into the intervertebral space previously occupied by the distractor.

[0007] U.S. Published Patent Application No. 2005-0119752 (Williams) discloses apparatus and methods for manufacturing devices for treating degenerative and / or traumatic intervertebral discs. Artificial discs and disc components may include artificial nuclei and / or artificial annuli, which may be composed of shape-memory materials synthesized to achieve desired mechanical and physical properties. Artificial nuclei and / or annuli according to the present invention may comprise one or more hollow bodies that can be filled with a hardenable material for deployment. Hollow bodies according to the present invention may comprise one or more partitions to define one or more chambers and may comprise means for directing the flow of material within the hollow body. Figure 19a of Williams discloses a two-balloon design with a central balloon and a peripheral balloon. Summary of the Invention [Means for solving the problem]

[0008] According to one embodiment of the present invention, a method of forming an interbody fusion cage is disclosed. A central distractor is inserted into the intervertebral space between the vertebral endplates. Peripheral balloons are inserted into the intervertebral space such that they are wrapped around the central inflatable distractor. The central distractor and peripheral balloons are expanded such that the peripheral balloons surround the central inflatable distractor as it expands, and such that the central distractor and peripheral balloons, when expanded, contribute to pushing the adjacent vertebral endplates apart.

[0009] According to another embodiment of the present invention, a method for introducing an interbody fusion cage into an intervertebral space is disclosed. In the method, a deflated central distractor coupled to first and second guidewires is inserted into the intervertebral space between the vertebral endplates. The first peripheral balloon, having a guidewire lumen extending through its inner diameter, is slid into the intervertebral space along the guidewire so that the first peripheral balloon is adjacent to the central distractor. The second peripheral balloon, having a guidewire lumen extending through its inner diameter, is slid into the intervertebral space along the guidewire so that the second peripheral balloon is adjacent to the central distractor.

[0010] In a further embodiment, a method for forming an interbody fusion cage is disclosed. A central distractor is inserted into an intervertebral space between vertebral endplates via a first lumen. The distal end of the first lumen is guided into the intervertebral space, while the proximal end extends outside the patient's body. A peripheral balloon is inserted into the intervertebral space via a second lumen having a proximal end and a distal end. The distal end of the second lumen is guided into the intervertebral space, while the proximal end of the second lumen extends outside the patient's body. The proximal end of the first lumen is coupled to the proximal end of the second lumen. The peripheral balloon and central distractor are expanded by filling the peripheral balloon with a hardenable material and filling the central distractor with a bioinert fluid. Once the hardenable material has hardened, the first and second lumens are decoupled, and the central distractor is retracted from the intervertebral space, leaving a central void.

[0011] In yet a further embodiment, an apparatus for forming an intervertebral fusion device is disclosed. A central distraction device is attached to a first guidewire and a second guidewire. A first peripheral balloon assembly is provided including a concentric guidewire and a peripheral balloon having an inflation lumen. The guidewire lumen extends through an inner diameter of the first peripheral balloon, and the inflation lumen extends from the first peripheral balloon to an external inflation point. A second peripheral balloon assembly is provided including a concentric guidewire and a peripheral balloon having an inflation lumen. The guidewire lumen extends through an inner diameter of the second peripheral balloon, and the inflation lumen extends from the second peripheral balloon to an external inflation point. The first guidewire extends through the guidewire lumen of the first peripheral balloon, and the second guidewire extends through the guidewire lumen of the second peripheral balloon.

[0012] In another embodiment, a novel intervertebral fusion device is provided. An outer balloon is configured to fill the disc space when inflated. A first lumen is connected to the outer balloon. An inner balloon is enclosed within the outer balloon, the inner balloon being smaller than the outer balloon. A second lumen is disposed within the first lumen and connected to the inner balloon. The inner balloon is configured such that a horseshoe or toroidal shape is formed between the inner and outer balloons when inflated.

[0013] In yet another embodiment, an intervertebral fusion device configured for insertion into an intervertebral space between vertebral endplates is provided, wherein an inflatable peripheral balloon is operatively associated with means for filling the inflatable peripheral balloon with a hardenable material such that the inflatable peripheral balloon defines a substantially toroidal shape having an open cavity, and a central distractor is disposed within the open cavity and operatively associated with means for expanding the central distractor such that a distraction force is provided against the vertebral endplates by the inflatable peripheral balloon and biological fluid within the cavity.

[0014] In a further embodiment, a method for forming an intervertebral fusion device is provided. At least one inflatable balloon is introduced into the intervertebral space in an uninflated state. The inflatable balloon is filled with a curable material via at least one fluid communication device so that the balloon defines a substantially toroidal shape with an open cavity substantially in the center of the vertebral endplate. The cavity is simultaneously filled with a bioinert fluid, such that at least a portion of the overall distraction force is provided by both the balloon and the fluid in the cavity, distributing the distraction force across a majority of the vertebral endplate area throughout the range of distraction. The fluid is then removed from the cavity after the curable material in the balloon has hardened. The cavity is then filled with an osteogenic material.

[0015] In yet a further embodiment, a method for forming an intervertebral fusion device is provided, comprising: introducing a balloon assembly including an inner balloon disposed within an outer balloon into an intervertebral space, the inner and outer balloons being in an uninflated state; filling the outer balloon with a curable material via at least one fluid communication means such that the outer surface of the outer balloon contacts the upper and lower vertebral endplates; and filling the inner balloon such that the outer surface of the inner balloon contacts the inner surface of the outer balloon only in the regions where the outer surface of the outer balloon contacts the upper and lower endplates, forming a substantially toroidal shape within the volume containing the curable material. [Brief explanation of the drawings]

[0016] [Figure 1A] 1 shows a step-by-step process for fabricating an in situ formed device. [Figure 1B] 1 shows a step-by-step process for fabricating an in situ formed device. [Figure 1C] 1 shows a step-by-step process for fabricating an in situ formed device. [Figure 1D] 1 shows a step-by-step process for fabricating an in situ formed device. [Figure 1E] 1 shows a step-by-step process for fabricating an in situ formed device. [Figure 1F] 1 shows a step-by-step process for fabricating an in situ formed device. [Figure 1G] 1 shows a step-by-step process for fabricating an in situ formed device. [Figure 1H] 1 shows a step-by-step process for fabricating an in situ formed device. [Figure 1I] 1 shows a step-by-step process for fabricating an in situ formed device. [Figure 1J] 1 shows a step-by-step process for fabricating an in situ formed device. [Figure 1K] 1 shows a step-by-step process for fabricating an in situ formed device. [Figure 1L] 1 shows a step-by-step process for fabricating an in situ formed device. [Figure 2] 1 shows an annular peripheral balloon of the present invention. [Figure 3A] 1 shows a flowchart of a sending method. [Figure 3B] 1 shows a flowchart of a sending method. [Figure 3C] 2 shows a flowchart of the delivery method of the present invention. [Figure 4] 10 shows a cross-sectional view of MIS delivery of a deflated balloon with a track. [Figure 5] FIG. 1 shows a perspective view of an inflated balloon with tracks. [Figure 6A] 1 shows a cross section of a track. [Figure 6B] 1 shows a cross section of a track. [Figure 6C] 1 shows a cross section of a track. [Figure 7] 1 shows a balloon used as a light source. [Figure 8] 1 shows an assembly for placing an instrument into a lumen. [Figure 9A] 1 shows a track with a cut. [Figure 9B] 9B shows a cross-sectional view of the cutout of FIG. 9A. [Figure 9C] 9B shows a cross-sectional view of the cutout of FIG. 9A. [Figure 9D] 9B shows a cross-sectional view of the cutout of FIG. 9A. [Figure 9E] 9B shows a cross-sectional view of the cutout of FIG. 9A. [Figure 10] Shown is an inflated balloon with magnetic wheels on its track. [Figure 11A] 1 shows a cross section of the magnetic wheel / track engagement. [Figure 11B] 1 shows a cross section of the magnetic wheel / track engagement. [Figure 12] 1 shows an inflated balloon with a docking port for docking a device. [Figure 13]10 illustrates a method for introducing a distraction device and a fusion device into the intervertebral space without the use of a cannula. [Figure 14] A, B, and C show how the peripheral and central balloons are introduced into the intervertebral space. [Figure 15] 1 illustrates an intervertebral fusion device according to one embodiment of the present invention. [Figure 16A] 1 illustrates a cam assembly that can be used as a distraction device according to one embodiment of the present invention. [Figure 16B] 16B shows the cam of FIG. 16A in a collapsed configuration. [Figure 16C] 16B shows the cam of FIG. 16A fully rotated. [Figure 16D] 16B shows the slider of the cam assembly shown in FIG. 16A. [Figure 16E] 16B shows the slider of the cam assembly shown in FIG. 16A. [Figure 16F] 16B shows the slider of the cam assembly shown in FIG. 16A. [Figure 17] 1 illustrates a bellows assembly that can be used as a distraction device according to one embodiment of the present invention. [Figure 18A] 1 illustrates a spooling device that can be used as a distraction device according to one embodiment of the present invention. [Figure 18B] 1 illustrates a spooling device that can be used as a distraction device according to one embodiment of the present invention. [Figure 18C] 1 illustrates a spooling device that can be used as a distraction device according to one embodiment of the present invention. [Figure 18D] FIG. 10 shows a spooled ribbon placed between the vertebral endplates. DETAILED DESCRIPTION OF THE INVENTION

[0017] The present invention relates to intervertebral fusion devices and methods and apparatus for creating and delivering intervertebral fusion devices. In embodiments of the invention, an expandable central distractor is at least partially bounded by expandable peripheral distractors. The expandable central and peripheral distractors are simultaneously expanded so that each is positioned within the disc space to support a portion of the distraction load. As used herein, simultaneous expansion includes simultaneously expanding the central and peripheral distractors at the same or different expansion rates, as well as expanding the central and peripheral distractors in stages.

[0018] In accordance with a method embodiment of the present invention, in a first step, and now referring to FIG. 1A, a surgeon removes at least the nucleus pulposus portion of the disc targeted for removal.

[0019] In a second step, and now referring to FIG. 1B, a central inflatable distractor and peripheral balloons are inserted into the disc space and positioned in its central region. Typically, in this position, the peripheral balloons encase the central inflatable distractor so that the inner surface of the peripheral balloons contacts the outer periphery of the inflated distractor. As used herein, a balloon refers to a pressure vessel having at least one fluid communication means for pressurizing it by inflating it with a fluid or gas or by packing it with a discrete solid mass, which can exist in a collapsed configuration (negligible / small enclosed volume) or an expanded form (significant enclosed volume) when pressurized. Balloon materials can be made from any of a wide variety of polymers, woven or nonwoven fibers, fabrics, metals such as stainless steel, titanium, or nitinol, metal mesh, and carbon.

[0020] In some embodiments, the balloons can be introduced individually into the intervertebral space, with the central balloon first partially inflated to seat in the notch formed by the upper and lower concave vertebral endplate surfaces. At least one peripheral balloon is then introduced using at least one guidewire attached to the central balloon. The guidewire is used to precisely position each balloon. In other embodiments, the central and peripheral balloons are locked together to maintain their position relative to each other. In yet other embodiments, the interdiscal position of the balloons is locked in place via a locking system external to the body.

[0021] In a third step, and now referring to FIG. 1C , as disclosed in U.S. Patent Application Publication No. 20180271576, the central inflatable distractor is inflated, thereby separating the vertebral endplates to a specified height. In some embodiments, the central and peripheral balloons share the distraction load by inflating simultaneously, i.e., simultaneously or in stepped pressure intervals. The central and peripheral balloons provide lift to a majority of the endplates, meaning greater than 50% of the available endplate area, and preferably 100% of the available area (not including intact annular fibrosis). This has the added benefits of i) maximizing the endplate lift surface, thus minimizing the lift force acting on the endplates, ii) locating some of the lift force at the strongest part of the bone (the cortical margin), and iii) allowing for greater lift in patients with greater resistance to vertebral distraction.

[0022] In some embodiments, the peripheral balloons can be inflated first to a lower pressure to eliminate any kinks or pinch points that may impinge when the central balloon is inflated, thereby simplifying the insertion process by reducing the need for precise orientation and positioning of the device.

[0023] In yet another embodiment, an inflation controller can be used to enable efficient lift by leveraging creep deformation while eliminating the risk of endplate fracture caused by inflating the balloons too quickly. The inflation controller can consist of a motor-driven syringe pump and an in-line pressure sensor coupled to the peripheral and central balloons. The pressure reading is used as input to control the injection volume, thereby maintaining a constant pressure and force within the intervertebral space. Spinal tissues are known to exhibit creep characteristics, whereby they become elongated when exposed to a constant tensile stress. Therefore, applying a constant force will expand the intervertebral space.

[0024] In the fourth step, and now referring to FIG. 1D , the curable material is poured into the peripheral balloon. The balloon expands around the inflated central distractor to reach circumferentially around the central distractor and to contact the vertebral endplates separated by the central distractor. Essentially, the filled peripheral balloon and the filled central distractor occupy all of the available void space within the interbody cavity. In some embodiments, the peripheral balloon is pre-inflated with a bio-inert fluid, such as saline, to verify the inflated position and structural integrity of the peripheral balloon. The bio-inert fluid may have a radiopaque additive to aid in visualization using fluoroscopy. The peripheral balloon is then deflated and re-inflated with the curable material, or subjected to a controlled infusion of the curable material that replaces the initial fluid at a constant rate, thereby maintaining the pressure and shape of the inflated peripheral balloon. Suitable curable materials include two-component self-curing materials, such as PMMA, silicone, urethane, epoxy, and acrylic resins (e.g., dental resins). A possible acrylic resin consists of a combination of BISGMA (bisphenol-A-glycidyl methacrylate) and TEGMA (triethylene glycidyl methacrylate) mixed with a solution of BPO (benzoyl peroxide) in NMP (N-methyl-2-pyrrolidone) and DMPT (N,N-dimethyl-p-toluidine) in PEGDA 300 (polyethylene glycol diacrylate, Mn 258). Other suitable materials are disclosed in U.S. Pat. No. 9,333,091 B1, the relevant portions of which are incorporated herein. Other possible materials include composites using supercooled metals, which are flowed into a location of low stress and then intentionally stressed to solidify and fuse metal particles, electrorheological materials, and magnetorheological materials.

[0025] In the fifth step, and now referring to Figure 1E, the surgeon waits while the curable material hardens. In some cases, such as when using conventional PMMA, this wait time can be 5 to 20 minutes. In some embodiments, the surgeon can accelerate the hardening of the curable material through various energy means, including heat, chemical accelerators, light, electricity, moisture, or vibration. In some embodiments, the curable material is not self-hardening but remains fluid until an external energy stimulus is used to initiate hardening. Such materials require the application of a cure initiator, such as radiation (e.g., light), heat, vibration, moisture, or electrical energy, to bring about hardening. Possible materials include cyanoacrylates, one-part epoxies, heat-cured urethanes, single-component silicones, and acrylic resins. One such resin uses CQ (camphorquinone), NMP, 4EDMAB (ethyl 4-dimethylaminobenzoate), and PEGDA. This resin polymerizes under blue light via the following mechanism: a photoinitiator is activated using excitation light, the active photoinitiator and a tertiary amine (hydrogen donor) form free radicals, and the free radicals polymerize the monomer. The use of such curable materials provides unlimited flexibility and alleviates the time pressure for adjusting the components before curing. According to a feature of the present invention, the curable material may be hybrid, i.e., primarily cured on demand via external stimuli but also employing a longer duration of self-cure, meaning that the material cures over time with or without the addition of materials or energy, thereby ensuring that any fluids remaining uncured in the initial cure ultimately harden. Possible materials include combinations of the above self-cure materials with external energy-initiated materials. One such chemical and photoinitiated material uses a combination of BISGMA / TEGMA mixed with a solution of BPO, CQ, and NMP, and a solution of 4EDMAB, DMPT, and PEGDA. In another embodiment, the hardenable material remains flowable only in the presence of an external modifying environment, such as heat or electric current, and once the external input is removed (and the interbody space is allowed to return to its natural state), the material hardens. Possible materials include those with low melting temperatures or low glass transition temperatures.In yet another embodiment, the curable material in the peripheral balloons can be cured by UV light transmitted through the central distractor. Other suitable inflation and curing materials and techniques are disclosed in U.S. Patent Application Publication No. 20190008649, relevant portions of which are incorporated herein by reference.

[0026] In the fifth step, and now referring to FIG. 1F, the material in the peripheral balloons is fully cured and the central distractor is deflated.

[0027] In a sixth step, and now referring to FIG. 1G, the retracted central distractor is withdrawn, thereby creating a horseshoe-shaped structure that supports the intervertebral space. This horseshoe provides support along the cortical edges of the vertebrae while simultaneously creating an access point to the center of the intervertebral space. In some embodiments, the central distractor is not removed, but instead is made of a biocompatible or resorbable material.

[0028] In a seventh step, and now referring to FIG. 1H, a tube is inserted through the access point created in step 6 and positioned near the center of the intervertebral space. Implant material is then poured through the tube and into the intervertebral space, thereby filling the void with the implant. In FIG. 1I, the implant filling tube is removed.

[0029] Referring now to FIG. 1E, an instrument for forming an intervertebral fusion device is provided in accordance with one embodiment of the present invention. The distraction device includes a first tube 21 having a distal end portion 23 and an inflatable distractor 1, e.g., a central balloon, attached thereto. In the embodiment shown in FIG. 1E, the central balloon 1 is filled with a bioinert fluid. According to one aspect of the present invention, a threaded connector 120 can engage the tube 21 near the proximal end portion. As shown in FIG. 1J, the connector 120 can include a handle 130 and a threaded neck 132 extending from the handle 130. A tubing channel extends through the handle 130 and the neck 132, through which the first tube 21 extends. The distraction device further includes a second tube 25 having a distal end portion 27 and an inflatable distractor 3, e.g., a peripheral balloon, attached thereto. In the embodiment shown in FIG. 1E, the peripheral balloon 3 is filled with a hardenable material and has a height sized to span the intervertebral space.

[0030] According to one aspect of the present invention, a threaded connector 121 can engage with the second tube 25 near its proximal end portion. Similar to connector 120, connector 121 can include a handle 134 and a threaded neck 136 extending from the handle 134. A tubing channel extends through the handle 134 and the neck 136, through which the second tube 25 extends. Connectors 120 and 121 are matingly shaped so that, when connected, their respective tubing channels are adjacent to one another, positioning tubes 21 and 25 adjacent to one another, as shown in FIG. 1L. As shown in FIG. 1K, a threaded coupling component 122 is provided to couple with connectors 121 and 120, thereby securely attaching the proximal ends of first and second tubes 21 and 25. This arrangement fixes the position of central balloon 1 relative to peripheral balloon 3, keeping the relative positions of the balloons stable regardless of forces encountered within the intervertebral space when the balloons are inserted and inflated. The connecting components 122 can be removed while keeping the peripheral balloons 3 in place to allow removal of the central balloon 1 after the peripheral balloons 3 have hardened.

[0031] In an alternative configuration, connector 121 can engage a pair of tubes near their proximal end portions. The distal end of each tube can be connected to peripheral balloon 3 such that one tube can be used to inject material into peripheral balloon 3 and the other tube can be used to remove material from peripheral balloon 3. In some embodiments, tube 25 can include two or more lumens.

[0032] In experiments, it was observed that the substantially spherical or puck-shaped central balloon self-positioned in a stable manner relative to the central notch formed by the concave shapes of the upper and lower endplates. However, the peripheral balloons, in the absence of a fixation mechanism, tended to be expelled from the annulus at areas of defect or weak fiber. With the coupling mechanism between the central and peripheral balloons, the stability of the central balloon secured the peripheral balloons in the correct position.

[0033] In some embodiments, the distraction device may be locked or secured to an external fixation surface, such as an operating table or a location on the patient's body, to help secure the position of the central balloon 1 and the peripheral balloons 3 within the disc space. In one embodiment, a locking arm 123 is provided that can be attached to either the connectors 120 and 121, the threaded coupling component 122, or the tubes 21 and 25, and the fixation surface 127. The locking arm 123 can include one or more lockable, articulating leg segments 123a and 123b. Thus, the locking arm 123 can be locked at any position and angle. The locking arm 123, in cooperation with the tubes 21 and 25, is believed to help secure the position of the central balloon 1 and the peripheral balloons 3 within the disc space, prevent movement due to any forces during inflation, and overcome any tendency of the balloons to escape through the disc space entrance foramen or a weak spot in the disc annulus.

[0034] Referring to FIG. 1D, a balloon assembly for treating an intervertebral space is provided, comprising: a) an inflated distractor 1 having an outer periphery 2 and sized to expand the intervertebral space, the inflated distractor 1 being filled with a bioinert fluid; and b) an inflated fusion balloon 3 forming a shape having an outer periphery 4 and an inner surface 5, the fusion balloon being filled with a hardenable material, the inner surface of the fusion balloon contracting the outer periphery of the inflated distractor, the balloon wrapping around the distractor, the balloon forming an annular shape defining a lumen, and the inflated distractor being positioned in the lumen.

[0035] In accordance with one aspect of the present invention, and referring now to FIG. 1F, a balloon assembly for treating an intervertebral space is provided, comprising: a) a deflated distractor 1 having an outer periphery; and b) an inflated fusion balloon 3 forming a shape having an outer periphery 4 and an inner surface 5 defining an inner cavity 7, the fusion balloon 3 being filled with a hardening material, the fusion balloon 3 being sized to distract the intervertebral space, and the deflated distractor 1 being positioned within the inner cavity of the balloon.

[0036] One purpose of the expandable distractor 1, in conjunction with the fusion or peripheral balloon 3, is to distract the collapsed disc space to a desired height that restores the physiological spatial relationship of the adjacent intervertebral bodies. The expandable distractor may be provided in multiple sizes to accommodate the appropriate disc height. In some expanded embodiments, the expandable distractor has a cylindrical shape with an annular middle portion between two end faces. In some expanded embodiments, the space within the annular middle portion is filled with a bioinert distraction fluid, such as saline. In some embodiments, the expandable distractor includes a central balloon that is inflated using an osteogenic material and defined by a mesh bag that is not removed from the lumen. In some embodiments, this balloon or mesh bag is resorbable over time. The end faces may have a roughened outer surface or a high-friction coating or jacket to better grip the vertebral endplates. In some embodiments, the end faces are substantially parallel to each other in the expanded state. In other examples, the end faces are angled so that the expanded balloon assumes a wedge shape, thereby causing the anterior height of the expanded device to be greater than the posterior height of the expanded device. This allows the device to restore lordosis when the interbody fusion device is used in either the lumbar or cervical regions of the spine. Preferably, the wedge shape creates a tilt angle of 5 to 20 degrees, more preferably 5 to 15 degrees. In still other examples, the end faces are angled so that the expanded balloon assumes a wedge shape along the coronal plane, thereby causing unequal lateral heights on either side of the centerline of the expanded device. This allows the device to correct scoliosis and restore spinal straightness in the coronal plane. In some embodiments, the central balloon may be comprised of multiple sections or balloons whose pressures are separately controlled and used to restore the correct angle in at least one anatomical plane relative to adjacent vertebral endplates, providing better spinal alignment.

[0037] In at least one embodiment, the fusion device includes at least two compartmental peripheral balloons and at least one compartmental central balloon, so that when pressure is controlled separately for each compartment, the fusion device has full adjustability in three dimensions: linearly along the superior-inferior axis and rotationally about both the anterior-posterior and lateral axes.

[0038] In any of the disclosed embodiments, the central inflatable distractor can be made from balloon materials disclosed in U.S. Patent Application Publication No. 20040230309, the relevant portions of which are incorporated by reference. The central inflatable distractor can be made by using an intermediate size lumen and forming one end into a larger balloon by pressurizing the lumen inside a mold, then compressing the other end to a smaller size (able to fit through a small diameter cannula) by folding or reflowing the excess material into the smaller diameter lumen and trimming the excess material.

[0039] The peripheral balloon can be made of any conventional material used for medical balloons. In some embodiments, the balloon can be non-porous. In other embodiments, the balloon can be porous to allow some cement to escape, thereby allowing support to bond to adjacent tissue. In some embodiments, the peripheral balloon is resorbable over time. The upper and lower surfaces of the peripheral balloon can have roughened outer surfaces to better grip the vertebral endplates. These roughened outer surfaces can include, for example, multiple teeth. In other embodiments, it can be encapsulated in a stent or other porous or osteoconductive jacket, which provides a surface for bone to penetrate and grow around, thereby adding further stability to the implant. In some embodiments, the stent or porous jacket is made of an osteogenic material. In other embodiments, it is made of metal, a shape-memory material such as nitinol, a polymer, or other rigid material. In some embodiments, the peripheral balloon can be composed of multiple sections or balloons whose pressures are independently controlled and used to restore the correct angle to adjacent vertebral endplates relative to each other, providing better spinal alignment. Peripheral inflatable devices can be made by using an intermediate size lumen and forming one end into a larger balloon by pressurizing the lumen inside a mold, then compressing the other end to a smaller size (able to fit through a small diameter cannula) by folding or reflowing the excess material into a smaller diameter lumen and trimming the excess material.

[0040] In one embodiment, the peripheral balloons are made of an elastic material, which allows the balloon to conform as it expands into the space between the central inflatable distractor and the viable annulus. In another embodiment, the balloons are non-elastic and form a predetermined shape when inflated. The predetermined shape can be a horseshoe shape, which can be beneficial because it allows structural support to extend around the periphery of the central inflatable distractor and rest on the cortical margin. The predetermined shape can also include either parallel end faces or end faces that are angled relative to one another, which can be beneficial because it allows the peripheral balloons to contribute to the final distraction and relative positioning of the vertebrae.

[0041] In another embodiment, the central balloon may be completely contained within a larger balloon, as shown in FIG. 15 . In this embodiment, the outer balloon 210 may be made of a compliant or incompliant material. The outer balloon 210 is connected to a lumen 212 and can be expanded to fill the interbody space by inflating it with either a bio-inert fluid, such as saline, or a hardenable material that passes through the space between the lumens 212 and 215. The outer balloon 210 includes an upper wall 216 having an outer surface and an inner surface, and a lower wall 217 having an outer surface and an inner surface. In one embodiment, the outer balloon 210 expands sufficiently to contact the remaining annulus along its circumference, thereby assuming the shape of the vacated interbody cavity. The outer surface of the upper wall 216 contacts the upper vertebral endplate, and the outer surface of the lower wall 217 contacts the lower vertebral endplate. In accordance with the present invention, the inner balloon 214 is completely enclosed within the outer balloon 210. The inner balloon 214 is connected to a lumen 215 that is inflated with a bio-inert fluid, such as saline. The inner balloon 214 is made from a non-compatible material and is sized so that when expanded, it contacts the inner surface of the balloon wall 216 and constricts the inner surface of the lower balloon wall 217. The horizontal footprint of the inner balloon is smaller than that of the outer balloon such that there is a horseshoe-shaped space 220 between them. The space 220 is eventually filled with a hardenable material and hardened to provide rigid fusion support at the vertebral cortical margins.

[0042] Lumen 215 provides a port for introducing osteogenic material into the central balloon. The balloon material may be cut or dissolved from the lumen after the material in space 220 has hardened to access the endplates for fusion, or the balloon material may be resorbable over time.

[0043] In another embodiment, the peripheral balloon forms a substantial horseshoe shape. The horseshoe shape is advantageous because it provides a large surface area for resting on the cortical margins of the adjacent intervertebral bodies and its open ends allow both withdrawal of the central, deflated distractor and delivery of the bone graft into the cavity. Preferably, the peripheral balloon is made of a shape-memory material that assumes the shape of a horseshoe in its relaxed form. In another embodiment, however, the horseshoe-shaped peripheral balloon is made of a conventional polymer without shape-memory properties, and the balloon is simply manually wrapped around the central inflatable distractor prior to its delivery into the disc space so that it already has a substantial horseshoe shape as it enters the disc space. In another embodiment, the peripheral balloon is introduced separately from the central balloon, but guidelines guide the peripheral balloon to wrap around the central balloon in a substantially horseshoe shape.

[0044] In these horseshoe-shaped embodiments, the curable material may be introduced into the peripheral balloon via a third tube, the distal end of which is positioned within the peripheral balloon. The distal end of this third tube is initially inserted fully into the peripheral balloon, filling the distal portion of the peripheral balloon first. As the curable material fills the distal portion of the peripheral balloon, the distal end of the third tube is withdrawn proximally from the peripheral balloon at the same rate as the filling. This third tube thereby ensures complete filling of the peripheral balloon. In other embodiments, the curable material can simply flow freely into the proximal end opening of the peripheral balloon to fill the peripheral balloon.

[0045] In one embodiment, the peripheral balloon forms an annular shape. An annular peripheral balloon can be achieved using the technique disclosed in FIG. 4 of the Stalcup. The Stalcup technique may simply need to be modified by adding a central inflatable distractor at the distal end of the Stalcup's first filling hose. Such an annular embodiment is shown herein in FIG. 2. The annular peripheral balloon possesses holes that allow for the passage and withdrawal of both the central inflatable distractor and the graft filling tube. The advantage of an annular balloon is that it provides a slightly wider surface area of ​​contact with the intervertebral body than a horseshoe-shaped peripheral balloon, thereby reducing stress on the structural support. An annular balloon also provides more uniform support, thereby reducing stress non-uniformities.

[0046] In some embodiments, the system can be used without a peripheral balloon, allowing the cement to fully conform to the remaining anatomy. In this embodiment, a catheter can be used to evenly deposit the hardenable material. This catheter can be steerable and independent of the central balloon, or can be guided around the central expandable distractor via a guidance system around the central expandable distractor, and can be used to guide tools and implants into the disc space. These tools can be used to inspect the disc space, perform additional disc and annulus removal, and place implants. In another embodiment, an expanding foam containing the hardenable material can be used instead of a peripheral balloon. These configurations may be less preferred because they rely on a substantially intact and rigid annulus to accommodate the pressure of the expanding peripheral distractor.

[0047] In some embodiments, the system can be used without a central balloon, instead using peripheral balloons for the entire distraction before curing. In this configuration, the balloons are made of a non-elastic material to ensure an internal cavity is formed for the bone graft to fill. In some embodiments, the peripheral balloons form a central sealed cavity into which pressurized fluid or gas can be injected to apply a distraction force to the endplates.

[0048] The hardenable material filling the peripheral balloon forms a structural material capable of withstanding the physiological axial loads of the spinal cord. In some embodiments, the hardenable material may be a conventional bone cement, such as PMMA cement, or a moldable bone cement. In other embodiments, the hardenable material may be a low-viscosity cement similar to common dental cement, which offers the advantage of allowing the hardenable material to flow easily through small lumens. In some embodiments, the hardenable material self-hardens from a chemical reaction when the components are mixed, hardening after a set time. In other embodiments, it is cured by reaction with light or other energy input, hardening only when an external stimulus is applied, extending the time it takes to set the balloon in the desired position but providing the advantage of shortening the hardening time when selected to initiate the hardening process. In a preferred embodiment, the hardenable material uses a combination of self-hardening and external energy curing, providing the advantage of greater control over hardening time while ensuring that all materials eventually harden.

[0049] The graft deposited into the cavity can be any osteogenic material suitable for bone fusion. The amount of graft needed to fill the cavity can be estimated from the volume of fluid in the central distractor when in its expanded configuration. This allows the surgeon to prepare the appropriate amount of graft and avoid over- or under-filling the cavity.

[0050] The delivery methods and implantations described herein may be suitable for both complete and partial discectomies (ie, the annulus and ligaments are intact).

[0051] In some embodiments, it may be convenient to house each of the tubes associated with the balloon within a larger cannula, which may facilitate minimally invasive insertion of the tubes into the patient. Thus, in accordance with the present invention, there is provided a delivery cannula having a proximal end and a distal end, Here, each tube is substantially received within the delivery cannula such that the distal end of the first tube protrudes from the distal end of the delivery cannula and the distal end of the second tube protrudes from the distal end of the delivery cannula.

[0052] In some embodiments, a delivery cannula is not used. A guidance system, such as an over-the-wire guidewire, can be used instead. The balloon is inserted after the guidance system to ensure that it passes only through the desired anatomical pathway without damaging nerves or other delicate anatomical structures. In some embodiments, the inflation device requires a protective sheath to prevent damage during insertion into the intervertebral space. The advantage of not using a delivery cannula is that the outer diameter of the components entering the intervertebral space through the body can be minimized, thereby reducing invasiveness. Over-the-wire entry can be used with any approach, such as anterior, lateral, posterior, or through Kambin's triangle.

[0053] In some embodiments, the implant material may be HEALOS FX™, a flowable collagen-based material available from DePuy Spine, Raynham, Massachusetts, USA.

[0054] In some embodiments, the implant material may include an osteogenic agent. In some embodiments, the osteogenic agent is a growth factor. As used herein, the term "growth factor" encompasses any cellular product that regulates the proliferation or differentiation of other cells, particularly connective tissue progenitor cells. Growth factors that may be used in accordance with the present invention include, but are not limited to, members of the fibroblast growth factor family, including acidic and basic fibroblast growth factors (FGF-1 and FGF-2) and FGF-4; members of the platelet-derived growth factor (PDGF) family, including PDGF-AB, PDGF-BB, and PDGF-AA; members of the insulin-like growth factor (IGF) family, including EGF, VEGF, IGF-I, and -II; the TGF-β superfamily, including TGF-β 1, 2, and 3; osteogenic morphogenetic factors (OIFs), angiogenin, endothelin, hepatocyte growth factor, and keratinocyte growth factor (EGF). cytogenetic growth factors, members of the bone morphogenetic proteins (BMPs) BMP-1, BMP-3, BMP-2, OP-1, BMP-2A, BMP-2B, BMP-7 and BMP-14 including HBGF-1 and HBGF-2, growth differentiation factors (GDFs), members of the hedgehog family of proteins including Indian, Sonic and Desert hedgehog, ADMP-1, osteogenic members of the interleukin (IL) family, rhGDF-5, members of the colony stimulating factor (CSF) family including CSF-1, G-CSF and GM-CSF, and isoforms thereof.

[0055] In some embodiments, a platelet concentrate is provided as the bone-forming agent. In one embodiment, the growth factors released by the platelets are present in an amount at least two-fold (e.g., four-fold) greater than the amount found in the blood from which the platelets were collected. In some embodiments, the platelet concentrate is autologous. In some embodiments, the platelet concentrate is platelet-rich plasma (PRP). PRP is advantageous because it contains growth factors that can restimulate bone growth and its fibrin matrix provides a suitable scaffold for new tissue growth.

[0056] In some embodiments, the bone forming agent comprises an effective amount of a bone morphogenetic protein (BMP), which beneficially increases bone formation by promoting the differentiation of mesenchymal stem cells (MSCs) into osteoblasts and their proliferation.

[0057] In some embodiments, about 1 ng to about 10 mg of BMP is administered into the target intervertebral space. In some embodiments, about 1 microgram (m) to about 1 mg of BMP is administered into the target intervertebral space.

[0058] In many preferred embodiments, the bone forming agent is a porous matrix, preferably injectable.

[0059] The porous matrices of the present invention may contain porous or semi-porous collagen, extracellular matrix, metals (such as Ti, Ti64, CoCr, and stainless steel), polymers (such as PEEK, polyethylene, polypropylene, and PET), resorbable polymers (such as PLA, PDA, PEO, PEG, PVA, and capralactides), bone substitutes (such as TCP, HA, and CaP), autografts, allografts, xenografts, and / or blends thereof. The matrices may be oriented to allow flow from the bone attachment site to the suction port. Matrices may be layered with various densities, pore structures, and materials to allow for increased stem filtering at the desired location through density, pore size, affinity, and flow control (laminar, turbulent, and / or tortuous pathways).

[0060] In some embodiments, the porous matrix is ​​a mineral. In one embodiment, the mineral comprises calcium and phosphorus. In some embodiments, the mineral is selected from the group consisting of calcium phosphate, tricalcium phosphate, and hydroxyapatite. In one embodiment, the average porosity of the matrix is ​​about 20 to about 500 μm, e.g., about 50 to about 250 μm. In another embodiment of the invention, in situ porosity is created in the injected matrix to create a porous framework in the interbody space. Once in situ porosity is created in the space, the surgeon can inject other therapeutic compounds into the porosity, thereby treating surrounding tissue and enhancing the remodeling process of the target tissue.

[0061] In some embodiments, the mineral is administered in granular form. It is believed that administration of the granular mineral promotes the formation of bone growth around the mineral, allowing osseointegration to occur.

[0062] In some embodiments, the mineral is administered in the form of a hardenable paste, in which case the paste solidifies in vivo, thereby providing immediate post-treatment mechanical support to the interbody space.

[0063] In another embodiment, the therapeutic agent is delivered to the target space via an injectable absorbable or non-absorbable cement. The therapeutic agent is formulated using bioabsorbable macrosphere technology, allowing it to release bone-forming agents. The cement provides the initial stability required to treat pain in the target tissue. In some embodiments, the cement is selected from the group consisting of calcium phosphate, tricalcium phosphate, and hydroxyapatite. In other embodiments, the cement is any hard biocompatible cement, including PMMA, processed autologous and allograft bone. Hydroxyapatite is a preferred cement due to its strength and biological profile. Tricalcium phosphate may also be used alone or in combination with hydroxyapatite, especially when some degree of resorption is desired in the cement.

[0064] In some embodiments, the porous matrix comprises a resorbable polymeric material.

[0065] In some embodiments, the bone forming agent comprises an injectable liquid precursor that results in the in situ formation of a mineralized collagen composite. In some aspects, the injectable liquid precursor comprises: a) a first formulation comprising an acid-soluble type I collagen solution (preferably about 1 mg / ml to about 7 mg / ml collagen); and b) a second formulation comprising liposomes containing calcium and phosphate.

[0066] Combining an acid-soluble collagen solution with calcium and phosphate-loaded liposomes results in a liposome / collagen liquid precursor that forms a mineralized collagen gel when heated from room temperature to 37°C.

[0067] In some embodiments, liposomes are loaded with dipalmitoylphosphatidylcholine (90 mol%) and dimyristoylphosphatidylcholine (10 mol%). These liposomes are stable at room temperature, but when heated above 35°C, they form calcium phosphate minerals as a result of the release of encapsulated salts at the lipid chain melting transition. One such technique is disclosed in Pederson, Biomaterials 24:4881-4890 (2003), the specification of which is incorporated herein by reference in its entirety.

[0068] Alternatively, in situ mineralization of collagen can be achieved by increasing the temperature achieved by other types of reactions, including, but not limited to, chemical, enzymatic, magnetic, electrical, vibration, focused ultrasound, light, or atomic. Suitable sources include light, chemical reactions, enzyme-controlled reactions, and electrical wires embedded in the material. Further illustrating the electrical wire approach, a wire can first be embedded in the cavity, heated to create calcium deposits, and then withdrawn. In some embodiments, the wire can be a shape-memory material, such as nitinol, that can be shaped. Alternatively, an electrically conductive polymer can be selected as the temperature-raising element. The polymer is heated to form collagen, and then subjected to breakdown and resorption in situ, thereby providing a space adjacent to the mineralized collagen for bone formation.

[0069] In some embodiments, the osteoconductive material comprises calcium and phosphorus. In some embodiments, the osteoconductive material comprises hydroxyapatite. In some embodiments, the osteoconductive material comprises collagen. In some embodiments, the osteoconductive material is in particulate form.

[0070] Specific matrices may be incorporated into the device to provide load-bearing properties, allow directed bone formation, and / or control the density of the regenerated bone (cortical vs. cancellous) or allow cell formation for soft tissue attachment. The nanotubes or nanocrystals may be generally axially oriented to provide load-bearing capacity and capillary wicking of blood flow, further enhancing directed bone formation. Biocompatible nanotubes can currently be produced from either carbon or titanium, or bone substitutes including Ca, HA, and TCP.

[0071] In one embodiment, the bone forming agent is a plurality of ex vivo osteoprogenitor cells. Such live cells introduced into the interbody space have the ability to at least partially complement in situ derived stem cells in generating new bone for the interbody space.

[0072] In some embodiments, these cells are obtained from another human individual (allograft), while in other embodiments, the cells are obtained from the same individual (autograft). In some embodiments, the cells are harvested from bone tissue, while in others, the cells are harvested from non-bone tissue (and may be, for example, mesenchymal stem cells, chondrocytes, or fibroblasts). In others, autologous bone cells (such as from the knee, hip, shoulder, finger, or ear) may be used.

[0073] In one embodiment, when ex vivo living cells are selected as the additional therapeutic agent or substance, the living cells comprise mesenchymal stem cells (MSCs). MSCs offer particular advantages for administration to the interbody space because they are believed to more easily survive the relatively harsh environment present within the space, possess a desirable level of plasticity, and have the ability to proliferate and differentiate into desired cells.

[0074] In some embodiments, the mesenchymal stem cells are obtained from bone marrow, such as autologous bone marrow. In others, the mesenchymal stem cells are obtained from adipose tissue, preferably autologous adipose tissue.

[0075] In some embodiments, the mesenchymal stem cells injected into the interbody space are provided in an unconcentrated form, such as fresh bone marrow. In others, they are provided in a concentrated form. If provided in a concentrated form, they may be uncultured. Uncultured, unconcentrated MSCs can be easily obtained by centrifugation, filtration, or immunoabsorption. If filtration is selected, the method disclosed in U.S. Pat. No. 6,049,026 ("Muschler"), the specification of which is incorporated herein by reference in its entirety, can be used. In some embodiments, a matrix used to filter and concentrate the MSCs is also administered to the interbody space.

[0076] In some embodiments, bone cells (which may be derived from either allogeneic or autologous sources) or mesenchymal stem cells may be genetically engineered to produce osteoinductive osteoanabolic agents, which may be selected from the list of growth factors provided herein. The production of these osteoinductive agents may result in bone growth.

[0077] Recent studies have shown that plasmid DNA does not induce the inflammatory response caused by the use of viral vectors. Genes encoding bone (anabolic) agents, such as BMPs, may be effective when injected into unconnected, resorbing bone. In addition, overexpression of any of the growth factors provided herein, or other agents that can limit local osteoclast activity, may have a positive effect on bone growth. In one embodiment, the plasmid contains the genetic code for human TGF-β or erythropoietin (EPO).

[0078] Thus, in some embodiments, the additional therapeutic agent is selected from the group consisting of live cells and plasmid DNA.

[0079] The matrix may be made from a hydrogel or may incorporate a hydrogel as a component of the final structure. Hydrogels may be used to enhance and strengthen packing, improve handling characteristics, or increase vacuum pressure. Increased vacuum pressure may be used to determine proper hydration / stem cell filtration.

[0080] In all cases, excess bone marrow aspirate may be collected and mixed with added graft bulking agents containing collagen, such as HEALOS™ and HEALOS FX™, each available from DePuy Spine Inc, Raynham, Mass., USA.

[0081] Referring now to Figure 3A, a flow diagram of some preferred methods of practicing the present invention is provided. Generally, this figure discloses the steps of removing disc tissue to form an intervertebral space (702) (a major discectomy), inserting a central inflatable distractor into the intervertebral space (704), expanding the central inflatable distractor (706), inserting peripheral balloons into the intervertebral space (708), introducing a curable material into the peripheral balloon (710), and separating the peripheral balloon from its second delivery tube (712).

[0082] In step 706 above, the expanding step can include injecting a flowable support material (instead of saline) into the central expandable distractor (714). The flowable support material can be selected from the group consisting of grafts, hydrogels, hardenable materials, artificial disc materials, autografts, and allografts. This injection step can be followed by separating the central expandable distractor from its (first) delivery tube so that it can remain in the intervertebral space (716).

[0083] In some embodiments, step (712) may be followed by the further step (718) of retracting the central expandable distractor and removing it from the disc space to create a lumen. In one embodiment, step (718) may be followed by step (720) of filling the lumen with a flowable support material. The flowable support material may be selected from the group consisting of an implant, a hydrogel, a curable material, an artificial disc material, an autograft, and an allograft.

[0084] In another embodiment, removal of the central expandable distractor (step 718) may be followed by placing an instrument into the lumen (step 722) and performing a task with the instrument (step 724).

[0085] Introduction of an instrument into the lumen may be accomplished by utilizing tracks located on the inner surface of the peripheral balloon. The instrument may be selected from the group consisting of a camera, light, scraper, suction, irrigation, file, knife, grasper, burr, and rotary cutter. The task may be selected from the group consisting of inspection, disc removal, and endplate preparation. Performance of the task may be followed by the step of a) filling the lumen with a flowable support material.

[0086] The peripheral balloon may then be separated from its delivery tube by cutting, unscrewing, or rupturing.

[0087] Referring now to Figure 3B, a flow chart of some other preferred methods of practicing the present invention is provided. Generally, this figure discloses the steps of removing disc tissue to create a disc space (major discectomy) (802), inserting a central inflatable distractor into the disc space (804), expanding the central inflatable distractor (806), inserting peripheral balloons into the disc space (808), introducing a hardenable material into the peripheral balloon (810), and separating the peripheral balloon from its second delivery tube (812). Expanding the central inflatable distractor (step 806) may be followed by placing an instrument into the disc space (814) and performing a task using the instrument (816).

[0088] The placement of the instruments into the intervertebral space can be achieved by utilizing tracks located on the outer surface of the central inflatable distractor. The instruments can be placed on both sides of the central inflatable distractor. The instruments may be selected from the group consisting of a camera, a light, a scraper, a suction, an irrigation, a file, a knife, a grasper, a burr, and a rotary cutter. The task may be selected from the group consisting of an inspection, a disc removal, an endplate preparation, an annulus cut, an ALL cut, a PLL cut, and direct decompression. The performance of the task may be followed by step d) inserting a peripheral balloon into the intervertebral space. The delivery of this balloon can also be achieved by using tracks.

[0089] The curable material of step (810) may be selected from the group consisting of an implant, a hydrogel, a curable material, an artificial disc material, an autograft, and an allograft.

[0090] The separation in step 812 may be accomplished by cutting, unscrewing, or breaking apart the parts.

[0091] In some embodiments, the separation of step (812) may be followed by injecting (818) the support material into the first device.

[0092] The support material of step (818) may be selected from the group consisting of an implant, a hydrogel, a curable material, an artificial disc material, an autograft, and an allograft.

[0093] In some embodiments, the injection of step (818) may be followed by separating (820) the central inflatable distractor from its delivery tube (so that it may remain in the intervertebral space).

[0094] One embodiment of a method for forming an interbody fusion cage according to the present invention is shown in FIG. 3C. The method includes, at step 310, performing a bulk discectomy, i.e., removing disc tissue to form an intervertebral space. At step 315, an expandable peripheral device and an expandable central distractor are inserted into the intervertebral space. In some embodiments, the expandable peripheral device and the expandable central distractor may be inserted simultaneously, or in other embodiments, sequentially. In some embodiments, the expandable central distractor includes a first tube having a distal end portion and an expandable central distractor attached to the distal end portion of the first tube. Similarly, the expandable peripheral distractor includes a second tube having a distal end portion and an expandable peripheral distractor attached to the distal end portion of the second tube. In some embodiments, the distal ends of the central distractor tube and the peripheral distractor tubes are joined together after step 315.

[0095] In one embodiment, the peripheral and central devices may be expanded simultaneously or in stages at step 325. Alternatively, the peripheral devices may be partially expanded with a bioinert expansion material, as in step 320, prior to step 325 to reduce the risk of pinch points caused when the central device is expanded. At step 330, the expansion material in the peripheral devices may be replaced with a support material. In some embodiments, the peripheral devices may then be subjected to an external stimulus to harden the support material at step 335. In embodiments where the central and peripheral devices are coupled to one another, they may be decoupled at step 340.

[0096] In some embodiments, at step 345, the central device may be retracted and removed from the disc space after step 340. In other embodiments, the central device may be removed from the disc space immediately after step 325. Then, at step 350, the void created by removal of the central device may be filled with support material.

[0097] 4, an embodiment of a balloon having a track associated therewith is provided. Balloon 52 is connected to balloon catheter 53 via connection / release point 55. Track 57 wraps around the periphery of the balloon. The device is disposed within delivery cannula 59.

[0098] Referring now to FIG. 5, a perspective view of a deployed balloon 52 having a track 57 is provided. A balloon catheter 53 extends from the proximal portion of the balloon. The track 57 has a central groove 59 for docking with an instrument. In some embodiments, the track 57 can also be used to introduce and precisely position peripheral balloons. The concave nature of the vertebral endplates allows an inflated or partially inflated central distractor to self-center in the disc space, providing fixation stability when the peripheral balloons are inserted.

[0099] Figures 6A-6C disclose different track cross sections: Figure 6A discloses a double-sided track; Figure 6B discloses a single-sided track; and Figure 6C discloses a track with a trapezoidal cross section.

[0100] 7 discloses an embodiment in which a central balloon 61 is used as a light source. The balloon is attached to a light delivery catheter 65 housed within a delivery catheter 63. Light is delivered from a light source 67 into the light delivery catheter 65 and then into the balloon 61. In some embodiments, the fluid used to inflate the central balloon can contain light-reflecting particles (not shown), such as titanium dioxide, to better disperse the light. The light makes it easier to inspect the intervertebral space. In some embodiments, the light is used to harden a hardenable material in the peripheral balloons.

[0101] FIG. 8 discloses the step of inserting an instrument 71 into the lumen via a track 73 located on the inner surface 75 of a peripheral balloon 77 .

[0102] Figure 9A discloses an embodiment of a track 81 with cutouts 83. These cutouts provide a means for securing devices. Figure 9B discloses a cross section of cutouts 83. Figure 9C discloses a cross section of a T-shaped track cutout 85. Figure 9D discloses a cross section of a winding track cutout 87. Figure 9E discloses a cross section of a C-shaped track cutout 89.

[0103] Figure 10 discloses an embodiment showing a means for transporting an instrument along a track 91 on a central inflatable balloon 93. A number of magnetic wheels 95 are shown moving along the track. These wheels can be used to transport the instrument back and forth through the intervertebral space.

[0104] Figure 11A shows details of how the magnetic wheel 101 can be attached to the track. The wheel has a central magnet 103 that contacts a central rail 105 of the track 107. This overlap keeps the equipment aligned.

[0105] FIG. 11B shows another embodiment of wheel-truck engagement, where the truck has a pair of side rails 109 that keep the wheels engaged.

[0106] 12 shows a pair of docking ports 111 disposed on either side of a central inflatable balloon 113. An instrument 115 may have a distal docking ball 117 for reception by the docking ports. In this case, the instrument has an articulating scraper 119 attached to it for scraping tissue in the intervertebral space.

[0107] FIG. 13 discloses a method for introducing the injection and fusion device over the wire. A guidewire 1310 guides the distraction and fusion device into the disc space, thereby avoiding the risk of damaging nerves or other sensitive anatomical structures. Connection points are embedded in the distraction and fusion device assembly, keeping the device aligned with the guidewire as it passes through the body and into the disc space. In some embodiments, a protective cover 1330 prevents damage to the inflation device 1320 as it passes through body tissue, the disc annulus, and the collapsed endplates.

[0108] 14A-14C show a process for introducing the central and peripheral balloons into the exact intervertebral space location, with each balloon moving independently within the intervertebral space, allowing for a larger inflation device, a smaller path through the body, or a combination of the two. A guidewire 124 is attached to and inserted into the central inflation device. The peripheral balloons 125 slide into position over the guidewire, surrounding the central balloon, forming a roughly annular, dual-peripheral balloon system. A peripheral balloon inflation lumen 126 extends from the peripheral balloon to an inflation point outside the patient's body. The dual set of concentric lumens allows the guidewire to pass through and the balloons to inflate. The lumens may be removed after the peripheral balloons have hardened.

[0109] FIG. 16A discloses an alternative embodiment of a distraction device according to the present invention that utilizes one or more cam assemblies to distract intervertebral bodies. Each cam assembly may include first and second cams 140, each having a lower end that slidably engages a lower track 137 and an upper end that engages an upper track 138. As shown in FIG. 16B, the cams 140 are positioned substantially parallel to the major axes of the tracks 137 and 138 during insertion into the intervertebral space. The thin aspect ratio of the cams 140 facilitates insertion into the intervertebral space in a minimally invasive manner. Once inserted, the one or more cam assemblies can be positioned as desired and then rotated via actuation or expansion means, such as a pull line 144, gear, rotating shaft, or belt, to provide lift, as shown in FIG. 16C. In FIG. 16A, the pull line 144 is routed through a hole 145 in the lower track 137 and directed through an access point using a cannula 146. A cannula may be used to provide the necessary counterforce to keep the track 137 in place as the pull line is pulled. The rotation of the cam 140 can be controlled using the upper and lower grooved tracks 138 and 137. The tracks 137 and 138 also distribute the distraction load from the cam 140 over a wider surface, thereby reducing the risk of vertebral endplate damage. An additional set of mating grooves 141 and rails (not shown) can be provided in the center of each cam 140 and lower track 137 to further control alignment. If the cam assembly includes multiple lower tracks 137, they can be linked together using a rigid linkage 142 that slides along slots 143 that can be positioned along the edges of the lower tracks 137, as shown in FIG. 16D. This allows multiple lower tracks 137 to be minimally invasively inserted end-to-end into the line and then rotated to seat with their long sides touching, as shown in FIGS. 16E and 16F. The collapsed track / cam assemblies may be secured together during insertion using pins 139.

[0110] In some embodiments, one or more cam assemblies can be used in the central space of the peripheral balloons and can remain permanently in the disc space or can be removed after the peripheral balloons have hardened. In other embodiments, cam assemblies can be positioned around the periphery of the disc space and provide distraction alone or in conjunction with a central distraction balloon. In still other embodiments, the cam assemblies can be spaced through the disc space and used without other distraction devices.

[0111] FIG. 17 discloses yet another embodiment of a distraction device that utilizes one or more metal bellows to distract vertebral units. The bellows body or chamber 401 is made of a thin-walled metal, such as titanium, containing a plurality of pleats. When pneumatic fluid, hydraulic fluid, or small discrete chunks of solid material (such as beads) are inserted under pressure into the bellows inlet 402, the metal expands vertically, exerting a distraction force on the vertebral endplates. The distraction force is transmitted along the bellows upper surface 403 to the upper vertebral endplate and along the bellows lower surface 404 to the lower vertebral endplate. As the metal expands, it plastically deforms, thereby resisting collapse back to its original compressed shape. The space around the bellow(s) is filled with bone graft, and the expanded bellow(s) provide a support structure while bone fusion is forming. The bellows can provide support via a plastically deforming structure, fluid pressure within the bellows structure, a hardened material within the bellows structure, or some combination thereof. Multiple bellows can be used to distribute lift and / or increase the distraction force applied to the vertebral endplates. The bellows can be inserted minimally invasively by taking advantage of the thin aspect ratio of one side of the bellows. In some embodiments, the walls of the bellows contain pores that allow fusion through the device to the endplates when the device is expanded with osteogenic material or matrix.

[0112] In some embodiments, one or more bellows can be used in the central space of the peripheral balloons and can remain in the disc space permanently or can be removed after the peripheral balloons have hardened. In other embodiments, bellows can be positioned around the periphery of the disc space and can provide distraction alone or in conjunction with a central distraction balloon. In still other embodiments, bellows can be spaced through the disc space and used without other distraction devices.

[0113] 18A-18C disclose yet another embodiment of a distraction device that utilizes an elongated ribbon spooling mechanism to distract the intervertebral bodies. The spooling mechanism includes one or more ribbons 501 that are fed through a fixed base 510 at a proximal end. The ribbons 501 may be made of a polymeric material or metal and, in some embodiments, are primarily uniaxially flexible due to their thinness. Each ribbon 501 is fed along a linkage arm 502 that is itself pivotally coupled at its proximal end to the fixed base 510 and at its distal end to a guide linkage 503. The guide linkage 503 includes first and second guide arms 513, each including a guide post 504 extending approximately perpendicularly from the respective guide arm 513. The ribbons are pulled under tension toward the base 510. As the ribbons pass over the guide posts 504, they are redirected perpendicular to the reel 507. Ribbon tension is maintained, allowing the ribbons to be wound onto the reel in a controlled manner. The rotor 505 extends from the base 510 through the ribbon reel 507 and is driven by a drive mechanism (not shown) to drive the ribbon reel 507. In some embodiments, the rotor 505 engages with the ribbon reel 507 via a mechanical linkage, such as a convex-concave connection or a ball-and-socket type linkage. In the embodiment shown in FIGS. 18A-18C, the rotor 505 engages with the ribbon reel 507 by a geometry on the distal end of the rotor 505 mating with a geometry 506 on the distal end of the ribbon reel 507. The guide linkage 503 connects to the ribbon reel 507 via a bearing 508 with a pin joint 518. The bearing 508 is positioned on the ribbon reel 507 with a retaining ring 509 but is free to rotate along the longitudinal axis of the ribbon reel.

[0114] When in the interbody space, as shown in FIGS. 18A and 18B, the linkage arms 502, guide linkages 503, and ribbon 501 can be collapsed along with the rotor 505, allowing the device to be inserted minimally invasively. The fixed base 510 can be advanced distally, causing the linkage arms 502 and guide linkages 503 to rotate at the pin joints 518, creating distance between themselves and the rotor 505, as shown in FIG. 18C. The rotor 505 is then driven from the proximal end, thereby winding the ribbon 501 onto the reel. The distraction distance can be controlled by the amount of ribbon wound and / or the thickness of each ribbon material. One or more ribbons 501 are then cut at the guide linkages 503, and the base 510, rotor 505, guide linkages 503, and linkage arms 502 are retracted, leaving the wound ribbons 501 and ribbon reels 507 in the interbody space to provide a support structure for bone fusion. In some embodiments, the cavity left through the center of the reel when the rotor is retracted collapses in the absence of the rotor, creating flatter upper and lower surfaces for the wound ribbon, thereby creating a larger constricted area between the ribbon and the vertebral endplates, as shown in Figure 18D. Bone graft is then filled into the remaining cavity in the interbody space.

[0115] While what has been shown and described is believed to be the most practical embodiment, it will be apparent that deviations from the specific designs and methods described and illustrated may be suggested to those skilled in the art and used without departing from the spirit and scope of the present invention. For example, the curable material of any of the disclosed embodiments may be radiopaque and / or include tantalum marker beads to facilitate alignment with fluoroscopic scans. Markers may also be provided on the peripheral or central balloon.

[0116] The present invention is not limited to the particular constructions described and illustrated, but should be constructed to cohere with all modifications that may fall within the scope of the appended claims.

[0117] [Embodiment] (1) A method of forming an interbody fusion cage, comprising: inserting a central distractor into the intervertebral space between the vertebral endplates; inserting peripheral balloons into the intervertebral space such that the peripheral balloons are wrapped around the central inflatable distractor; expanding the central distractor and the peripheral balloons such that as the central distractor expands, the peripheral balloons surround the central distractor and such that the central distractor and the peripheral balloons, when expanded, contribute to pushing adjacent vertebral endplates apart; A method comprising: (2) The method of claim 1, further comprising simultaneously expanding the central distractor and the peripheral distractors. (3) The method of claim 2, wherein simultaneously expanding the central distractor and the peripheral distractors comprises expanding the central distractor and the peripheral distractors in a stepwise manner. (4) The method of claim 1, further comprising inflating the peripheral balloons before inflating the central distractor and the peripheral balloons. (5) The method of embodiment 1, wherein expanding the peripheral balloon comprises inflating the peripheral balloon with a bioinert fluid.

[0118] (6) The method of claim 1, wherein expanding the central distractor and the peripheral balloons comprises inflating the central distractor with a bioinert fluid. (7) The method of embodiment 1, wherein expanding the peripheral balloon includes inflating the peripheral balloon with a hardenable material. (8) The method of claim 7, wherein inflating the peripheral balloon with a hardenable material includes removing the bioinert fluid from the peripheral balloon and re-inflating the peripheral balloon with a hardenable material. (9) The method of embodiment 7, wherein inflating the peripheral balloon with the hardenable material comprises injecting the hardenable material into the peripheral balloon at a constant pressure, thereby maintaining the pressure and shape of the inflated peripheral balloon while forcing out the bioinert fluid. 10. The method of claim 1, wherein the hardenable material is a low viscosity cement.

[0119] (11) The method of claim 1, wherein the curable material is radiopaque. 12. The method of claim 1, wherein the curable material comprises tantalum marker beads. 13. The method of claim 1, further comprising retracting the central distractor after the curable material has cured. (14) The method of claim 1, wherein the central distractor comprises a mesh bag, and further comprising filling the central distractor with osteogenic material. 15. The method of claim 1, wherein the curable material is self-curing.

[0120] 16. The method of claim 1, further comprising adding an external curing initiator to the curable material. 17. The method of claim 14, wherein the external cure initiator comprises at least one of heat, radiation, electrical energy, light, vibration, and humidity. 18. The method of claim 17, wherein the curing initiator comprises UV light transmitted through the central distractor. (19) A method for introducing an interbody fusion cage into an intervertebral space, comprising: inserting a retracted central distractor coupled to first and second guidewires into the intervertebral space between the vertebral endplates; sliding a first peripheral balloon into the disc space so that the first peripheral balloon is adjacent to the central distractor, the first peripheral balloon having a guidewire lumen extending through an inner diameter along the guidewire; sliding a second peripheral balloon into the disc space adjacent to the central distractor, the second peripheral balloon having a guidewire lumen extending through an inner diameter along the guidewire; A method comprising: (20) A method of forming an interbody fusion cage, comprising: inserting a central distractor through a first lumen into an intervertebral space between vertebral endplates and guiding a distal end of the first lumen into the intervertebral space while a proximal end extends outside the body; inserting a peripheral balloon through a second lumen into the intervertebral space between the vertebral endplates and guiding a distal end of the second lumen into the intervertebral space while a proximal end extends outside the body; coupling the proximal end of the first lumen to the proximal end of the second lumen; expanding the peripheral balloons and the central distractor, wherein expanding the peripheral balloons comprises filling them with a hardenable material and expanding the central distractor comprises filling them with a bio-inert fluid; separating the first lumen and the second lumen after the hardenable material has hardened; retracting the central device from the intervertebral space, leaving a central void; A method comprising:

[0121] (21) The method of embodiment 20, further comprising filling the central void with an osteogenic material. (22) The method of embodiment 20, further comprising connecting the combined first and second lumens to an exterior surface. (23) A device for forming an intervertebral fusion device, comprising: a central distraction device including a first lumen, the first lumen having a distal end portion and a proximal end portion, the central distraction device including an expandable distractor attached to the distal end portion; a peripheral distraction device including a second lumen, the second lumen having a distal end portion and a proximal end portion, the second lumen including an inflatable balloon attached to the distal end portion; a coupling device configured to couple the proximal end of the first lumen to the proximal end of the second lumen; An apparatus comprising: (24) The device of embodiment 23, further comprising a first connecting member and a second connecting member disposed at a proximal end portion of each of the first lumen and the second lumen, the first connecting member and the second connecting member being configured to couple with the coupling component. (25) The device of embodiment 23, further comprising an inflation controller connected to the first inflation lumen and the second inflation lumen.

[0122] (26) The device of embodiment 23, further comprising a locking arm configured to connect at a proximal end to one of the first connecting member and the second connecting member and at a distal end to a rigid surface. (27) The device of claim 26, wherein the locking arm is articulated. (28) A device for forming an intervertebral fusion device, comprising: a first guidewire and a second guidewire; a central distraction device attached to the first guidewire and the second guidewire; a first peripheral balloon assembly including a peripheral balloon having a concentric guidewire lumen and an inflation lumen, the guidewire lumen extending through an inner diameter of the first peripheral balloon and the inflation lumen extending from the first peripheral balloon to an external inflation point; a second peripheral balloon assembly including a peripheral balloon having a concentric guidewire lumen and an inflation lumen, the guidewire lumen extending through an inner diameter of the second peripheral balloon and the inflation lumen extending from the second peripheral balloon to an external inflation point; Equipped with The device, wherein the first guidewire extends through the guidewire lumen of the first peripheral balloon and the second guidewire extends through the guidewire lumen of the second peripheral balloon. (29) The device of embodiment 28, further comprising an inflation controller connected to the first inflation lumen and the second inflation lumen. (30) An intervertebral fusion device, an outer balloon configured to fill the disc space when inflated; a first lumen connected to the outer balloon; an inner balloon enclosed within the outer balloon, the inner balloon being smaller than the outer balloon; a second lumen disposed within the first lumen and connected to the inner balloon; Equipped with An intervertebral fusion device, wherein the inner balloon is configured such that when inflated, a horseshoe or toroidal shape is formed between the inner and outer balloons.

[0123] (31) An intervertebral fusion device configured to be inserted into an intervertebral space between vertebral endplates, comprising: an inflatable peripheral balloon; means for filling the inflatable peripheral balloon with a curable material such that the inflatable peripheral balloon defines a substantially toroidal shape having an open cavity; a central distractor disposed within the open cavity; means for expanding the central distractor such that the inflatable peripheral balloon and fluid within the cavity provide a distraction force against the vertebral endplates; 1. An intervertebral fusion device comprising: 32. The device of claim 31, wherein the central distractor comprises a bellows having a plurality of pleats and including a thin-walled metal chamber having a fluid inlet. 33. The device of claim 32, wherein the wall of the bellows comprises a plurality of pores. (34) A method for forming an intervertebral fusion device, comprising: introducing at least one inflatable balloon into the disc space in an uninflated configuration; filling the at least one inflatable balloon with a hardenable material via at least one fluid communication device while simultaneously filling the cavity with a bioinert fluid so that the at least one balloon defines a substantially toroidal shape with an open cavity substantially in the center of the vertebral endplate, whereby at least a portion of the overall distraction force is provided by both the at least one balloon and the fluid within the cavity, and the distraction force is distributed across a majority of the vertebral endplate area throughout the range of distraction; removing the fluid from the cavity after the curable material in the at least one inflatable balloon has cured; filling the cavity with osteogenic material; A method comprising: (35) The method of embodiment 34, wherein the at least one inflatable balloon and the fluid communication device are inserted into the intervertebral space through a cannula having an inner diameter of less than 6 mm.

[0124] (36) The method of embodiment 34, wherein the at least one inflatable balloon and the fluid communication device are inserted into the intervertebral space along a wire in a manner requiring a path of less than 6 mm in diameter through the expanded tissue. (37) The method of embodiment 34, wherein the at least one inflatable balloon and the fluid communication device are inserted into the intervertebral space along a path that passes through Kambin's triangle. (38) The method of embodiment 34, wherein osteogenic material is inserted into the intervertebral space prior to insertion of the at least one inflatable balloon, and the osteogenic material is displaced to the edge of the intervertebral space upon insertion and expansion of the balloon. (39) The method of embodiment 34, further comprising introducing a central inflatable balloon into the intervertebral space and positioning the central inflatable balloon within the cavity, wherein filling the cavity with fluid comprises filling the central inflatable balloon with fluid. (40) The method of embodiment 39, wherein the central inflatable balloon is removed before filling the cavity with osteogenic material.

[0125] (41) The method of embodiment 39, wherein the central inflatable balloon is resorbable and left in situ, and the osteogenic material is added to at least one of the area inside the central inflatable balloon or the area surrounding the central inflatable balloon. (42) The method of embodiment 39, wherein the central inflatable balloon includes a light source, and further comprising initiating curing of the curable material using the light source contained within the central inflatable balloon. 43. The method of claim 39, wherein the central inflatable balloon is filled with a fluid containing titanium dioxide light-scattering particles. (44) The method of embodiment 34, further comprising filling the at least one inflatable balloon with a bio-inert fluid to define a substantially toroidal shape having an open cavity prior to filling the at least one inflatable balloon with the curable material, and removing the bio-inert fluid from the at least one inflatable balloon prior to filling with the curable material. (45) The method of embodiment 44, wherein after the at least one inflatable balloon is filled with a bio-inert fluid, the hardenable material is inserted via a first fluid communication means while the bio-inert fluid is removed via a second fluid communication means, thereby maintaining a constant pressure within the at least one inflatable balloon.

[0126] (46) The method of embodiment 34, wherein the at least one inflatable balloon is made of thin-walled metal having pleats that plastically deform and expand when pressurized. (47) A method for forming an intervertebral fusion device, comprising: introducing a balloon assembly into the intervertebral space, the balloon assembly including an inner balloon disposed within an outer balloon, the inner and outer balloons being in an uninflated state; filling the outer balloon with a curable material via at least one fluid communication means such that the outer surface of the outer balloon contacts the upper and lower vertebral endplates; filling the inner balloon such that the outer surface of the inner balloon contacts the inner surface of the outer balloon only in the region where the outer surface of the outer balloon contacts the superior end plate and the inferior end plate, thereby forming a substantially toroidal shape within a volume containing the curable material; A method comprising:

Claims

1. 1. An apparatus for forming an intervertebral fusion cage, comprising: a central distraction device including a first lumen, the first lumen having a distal end portion and a proximal end portion, the central distraction device including an inflatable distractor attached to the distal end portion of the first lumen; a peripheral distraction device including a second lumen, the second lumen having a distal end portion and a proximal end portion, the peripheral distraction device including an inflatable balloon attached to the distal end portion of the second lumen; a coupling device configured to couple the proximal end portion of the first lumen to the proximal end portion of the second lumen; Equipped with a first connecting member and a second connecting member disposed at a proximal end portion of each of the first lumen and the second lumen, the first connecting member and the second connecting member being configured to couple with the coupling device; the first lumen extends through a first tube channel extending through the first connecting member; the second lumen extends through a second tube channel that extends through the second connecting member; When the first connecting member and the second connecting member are coupled to the coupling device and connected to each other, the first tube channel and the second tube channel are adjacent to each other and the outer circumferential surfaces of the first lumen and the second lumen are disposed adjacent to each other; With the first connecting member and the second connecting member connected to the coupling device, the inflatable distractor of the central distraction device and the inflatable balloon of the peripheral distraction device are inserted into the intervertebral space, and when the inflatable balloon envelops the inflated inflatable distractor and the inner surface of the inflatable balloon is in contact with the outer surface of the inflated inflatable distractor, a hardenable material is poured into the inflatable balloon, and then the hardenable material in the inflatable balloon hardens to form the intervertebral fusion cage, and the inflatable distractor is deflated and pulled out of the intervertebral space.

2. The device of claim 1 , further comprising an inflation controller connected to the first lumen and the second lumen.

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