Abstract:
A method of augmenting the nucleus pulposus of an intervertebral disc comprises forming a passage through an annulus fibrosus surrounding the nucleus pulposus and inserting a space creating device comprising a plurality of chambers. Without removing a portion of the nucleus pulposus, plurality of chambers are filled to expand the space creating device to create a space within the nucleus pulposus. The method further comprises injecting at least one biocompatible material into the space within the nucleus pulposus.

Description:
BACKGROUND 
       [0001]    Within the spine, the intervertebral disc functions to stabilize and distribute forces between vertebral bodies. The intervertebral disc comprises a nucleus pulposus which is surrounded and confined by the annulus fibrosus. Intervertebral discs are prone to injury and degeneration. For example, herniated discs typically occur when normal wear, or exceptional strain, causes a disc to rupture. Degenerative disc disease typically results from the normal aging process, in which the tissue gradually loses its natural water and elasticity, causing the degenerated disc to shrink and possibly rupture. 
         [0002]    Intervertebral disc injuries and degeneration are frequently treated by replacing or augmenting the existing disc material. Current methods and instrumentation used for treating the disc require a relatively large hole to be cut in the disc annulus to allow introduction of the implant. After the implantation, the large hole in the annulus must be plugged, sewn closed, or other wise blocked to avoid allowing the implant to be expelled from the disc. Besides weakening the annular tissue, creation of the large opening and the subsequent repair adds surgical time and cost. A need exists for devices, instrumentation, and methods for implanting an intervertebral implant using minimally invasive surgical techniques. 
       SUMMARY 
       [0003]    In one embodiment, a method of augmenting the nucleus pulposus of an intervertebral disc comprises forming a passage through an annulus fibrosus surrounding the nucleus pulposus and inserting a space creating device comprising a plurality of chambers. Without removing a portion of the nucleus pulposus, plurality of chambers are filled to expand the space creating device to create a space within the nucleus pulposus. The method further comprises injecting at least one biocompatible material into the space within the nucleus pulposus. 
         [0004]    In another embodiment, a device for supplementing a nucleus pulposus comprises an expandable central body comprising a cylindrical portion bounded by a pair of curved surfaces and adapted to receive a first biocompatible material. At least one of the pair of curved surfaces is adapted to penetrate a vertebral endplate adjacent the nucleus pulposus. The device also comprises an expandable ring member surrounding the cylindrical portion and adapted to receive a second biocompatible material. 
         [0005]    In another embodiment, a system for treating a nucleus pulposus of an intervertebral disc comprises a cannula adapted to access an annulus fibrosus of the intervertebral disc and a multi-chamber spacing device comprising at least three inflatable chambers. Each of the inflatable chambers is connected to at least one other of the inflatable chambers and the spacing device is collapsible for passage through the cannula. The system further comprises a catheter connected to the spacing device and extendable through the cannula. 
         [0006]    A system for treating a nucleus pulposus of an intervertebral disc comprises a cannula adapted to access an annulus fibrosus of the intervertebral disc and a multi-chamber spacing device comprising two connected and inflatable chambers One of the inflatable chambers is expandable along the annulus fibrosus. The system further comprises a catheter connected to the spacing device and extendable through the cannula. 
         [0007]    Additional embodiments are included in the attached drawings and the description provided below. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]      FIG. 1  is a sagittal view of a section of a vertebral column. 
           [0009]      FIGS. 2-5  are a sequence of superior views of a nucleus augmentation treatment. 
           [0010]      FIG. 6  is a superior view of a nucleus augmentation device implanted in the vertebral column. 
           [0011]      FIG. 7 . is a sagittal view of the nucleus augmentation device of  FIG. 6 . 
           [0012]      FIG. 8  is a perspective view of a nucleus augmentation device according to another embodiment of the disclosure. 
           [0013]      FIG. 9  is a cross-sectional view of the nucleus augmentation device of  FIG. 8 . 
           [0014]      FIGS. 10-18  are superior views of nucleus augmentation devices according to alternative embodiments of the disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0015]    The present disclosure relates generally to methods and devices for augmenting an intervertebral disc, and more particularly, to methods and devices for minimally invasive nucleus augmentation procedures. For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the embodiments, or examples, illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended. Any alterations and further modifications in the described embodiments, and any further applications of the principles of the invention as described herein are contemplated as would normally occur to one skilled in the art to which the invention relates. 
         [0016]    Referring first to  FIG. 1 , the reference numeral  10  refers to a vertebral joint section or a motion segment of a vertebral column. The joint section  10  includes adjacent vertebral bodies  12 ,  14 . The vertebral bodies  12 ,  14  include endplates  16 ,  18 , respectively. An intervertebral disc space  20  is located between the endplates  16 ,  18 , and an annulus  22  surrounds the space  20 . In a healthy joint, the space  20  contains a nucleus pulposus  24 . 
         [0017]    Referring now to  FIGS. 2-5 , in this embodiment, the nucleus  24  may be accessed by inserting a cannula  30  into the patient and locating the cannula at or near the annulus  22 . An accessing instrument  32 , such as a trocar needle, a K-wire, or a dilator is inserted through the cannula  30  and used to penetrate the annulus  22 , creating an annular opening  33 . With the opening  33  created, the accessing instrument  32  may be removed and the cannula  30  left in place to provide passageway for additional instruments. 
         [0018]    In this embodiment, the nucleus is accessed using a posterolateral approach. In alternative embodiments, the annulus may be accessed with a lateral approach, an anterior approach, a trans-pedicular/vertebral endplate approach or any other suitable nucleus accessing approach. Although a unilateral approach is described, a multi-lateral approach may be suitable. For example, a suitable bilateral approach to nucleus augmentation may involve a combination approach including an annulus access opening and an endplate access opening. 
         [0019]    It is understood that any cannulated instrument including a guide needle or a trocar sleeve may be used to guide the accessing instrument. 
         [0020]    In this embodiment, the natural nucleus, or what remains of it after natural disease or degeneration, may remain intact with no tissue removed. In alternative embodiments, partial or complete nucleotomy procedures may be performed. 
         [0021]    As shown in  FIG. 3 , a space creating device  36  having a catheter portion  38  and a multi-compartment or multi-chamber spacing portion  40  may be inserted through the cannula  30  and the annular opening  33  into the nucleus  24 . In this embodiment, the multi-compartment spacing portion  40  is a multi-compartment expandable device such as a balloon which may be formed of elastic or non-elastic materials. The space creating device  36  may be rolled or folded to minimize its size for insertion through the cannula  30 . 
         [0022]    The balloon can be of various shapes including conical, spherical, square, long conical, long spherical, long square, tapered, stepped, dog bone, offset, or combinations thereof. Balloons can be made of various polymeric materials such as polyethylene terephthalates, polyolefins, polyurethanes, nylon, polyvinyl chloride, silicone, polyetheretherketone, polylactide, polyglycolide, poly(lactide-co-glycoli-de), poly(dioxanone), poly(.epsilon.-caprolactone), poly(hydroxylbutyrate), poly(hydroxylvalerate), tyrosine-based polycarbonate, polypropylene fumarate or combinations thereof. Additionally, the expandable device may be molded or woven. 
         [0023]    In alternative embodiments, the space creating device may have multiple catheter portions with each separately feeding a different compartment of the spacing portion. 
         [0024]    Referring now to  FIG. 4 , the multi-compartment spacing portion  40  has two separate or substantially separate but attached lobes or chambers  42 ,  44 . Each of the compartments  42 ,  44  are connected to the catheter portion  38 . The catheter portion  38  is attached to a material delivery device  46 , such as a syringe, which may be filled with a biocompatible material  48 . The biocompatible material  48  may be pressurized and injected through the catheter portion  38  of the space creating device  36  to pressurize, inflate, and fill the compartments  42 ,  44  of the spacing portion  40 . As the compartments become filled, the spacing portion  40  may unroll or unfold from its minimized configuration. The filling of the spacing portion  40  may be controlled by a control mechanism  49 , such as a valve. The control mechanism  49  may control the total volume of the material injected into the spacing portion  40 , but may also control the volume of material injected into each of the compartments  42 ,  44 . The inflation medium may be injected under pressure supplied by a hand, electric, or other type of powered pressurization device. The internal balloon pressure may be monitored with a well known pressure gauge  50 . The pressure gauge  50  or a pressure limiter may be used to avoid over inflation or excessive injection. The rate of inflation and level of inflation of the spacing portion  40  can be varied between patients depending on disc condition. 
         [0025]    As the spacing portion  40  is gradually filled and inflated, the surrounding nucleus tissue may become displaced or stretched, creating a space  52 . The inflation may also cause the intradiscal pressure to increase. Both the pressure increase and the direct expansion of the spacing portion  40  may cause the endplates  16 ,  18  to distract. 
         [0026]    Referring now to  FIG. 5 , after the spacing portion  40  is inflated to the desired level, the catheter portion  38  is detached from the spacing portion  40  and removed from the patient. If the selected biocompatible material  48  is curable in situ, the catheter portion  38  may be removed during or after curing to minimize leakage. The opening  33  may be small enough, for example less than 3 mm, that it will close or close sufficiently that the spacing portion  40  will remain within the annulus. The use of an annulus closure device such as a suture, a plug, or a material sealant is optional. The cannula  30  may be removed and the minimally invasive surgical incision closed. 
         [0027]    Examples of biocompatible materials  48  which may be used for disc augmentation include natural or synthetic and resorbable or non-resorbable materials. Natural materials include various forms of collagen that are derived from collagen-rich or connective tissues such as an intervertebral disc, fascia, ligament, tendon, skin, or demineralized bone matrix. Material sources include autograft, allograft, xenograft, or human-recombinant origin materials. Natural materials also include various forms of polysaccharides that are derived from animals or vegetation such as hyaluronic acid, chitosan, cellulose, or agar. Other natural materials include other proteins such as fibrin, albumin, silk, elastin and keratin. Synthetic materials include various implantable polymers or hydrogels such as silicone, polyurethane, silicone-polyurethane copolymers, polyolefin, polyester, polyacrylamide, polyacrylic acid, polyvinyl alcohol, polyethylene oxide, polyethylene glycol, polylactide, polyglycolide, poly(lactide-co-glycolide), poly(dioxanone), poly(.epsilon.-caprolactone), poly(hydroxylbutyrate), poly(hydroxylvalerate), tyrosine-based polycarbonate, polypropylene fumarate or combinations thereof. Suitable hydrogels may include poly(vinyl alcohol), poly(acrylic acids), poly(methacrylic acids), copolymers of acrylic acid and methacrylic acid, poly(acrylonitrile-acrylic acid), polyacrylamides, poly(N-vinyl-2-pyrrolidone), polyethylene glycol, polyethyleneoxide, polyacrylates, poly(2-hydroxy ethyl methacrylate), copolymers of acrylates with N-vinyl pyrrolidone, N-vinyl lactams, polyurethanes, polyphosphazenes, poly(oxyethylene)-poly(oxypropylene) block polymers, poly(oxyethylene)-poly(oxypropylene) block polymers of ethylene diamine, poly(vinyl acetate), and sulfonated polymers, polysaccharides, proteins, and combinations thereof. 
         [0028]    The selected biocompatible material may be curable or polymerizable in situ. The biocompatible material may transition from a flowable to a non-flowable state shortly after injection. One way to achieve this transition is by adding a crosslinking agent to the biomaterial before, during, or after injection. The biocompatible material in its final state may be load-bearing, partially load-bearing, or simply tissue augmenting with minimal or no load-bearing properties. 
         [0029]    Proteoglycans may also be included in the injectable biocompatible material  48  to attract and/or bind water to keep the nucleus  24  hydrated. Regnerating agents may also be incorporated into the biocompatible material. An exemplary regenerating agent includes a growth factor. The growth factor can be generally suited to promote the formation of tissues, especially of the type(s) naturally occurring as components of an intervertebral disc. For example, the growth factor can promote the growth or viability of tissue or cell types occurring in the nucleus pulposus, such as nucleus pulposus cells and chondrocytes, as well as space filling cells, such as fibroblasts and connective tissue cells, such as ligament and tendon cells. Alternatively or in addition, the growth factor can promote the growth or viability of tissue types occurring in the annulus fibrosus, as well as space filling cells, such as fibroblasts and connective tissue cells, such as ligament and tendon cells. An exemplary growth factor can include transforming growth factor-β (TGF-β) or a member of the TGF-β superfamily, fibroblast growth factor (FGF) or a member of the FGF family, platelet derived growth factor (PDGF) or a member of the PDGF family, a member of the hedgehog family of proteins, interleukin, insulin-like growth factor (IGF) or a member of the IGF family, colony stimulating factor (CSF) or a member of the CSF family, growth differentiation factor (GDF), cartilage derived growth factor (CDGF), cartilage derived morphogenic proteins (CDMP), bone morphogenetic protein (BMP), or any combination thereof. In particular, an exemplary growth factor includes transforming growth factor β protein, bone morphogenetic protein, fibroblast growth factor, platelet-derived growth factor, insulin-like growth factor, or any combination thereof. 
         [0030]    Therapeutic or biological agents may also be incorporated into the biomaterial. An exemplary therapeutic or biological agent can include a soluble tumor necrosis factor α-receptor, a pegylated soluble tumor necrosis factor α-receptor, a monoclonal antibody, a polyclonal antibody, an antibody fragment, a COX-2 inhibitor, a metalloprotease inhibitor, a glutamate antagonist, a glial cell derived neurotrophic factor, a B2 receptor antagonist, a substance P receptor (NK1) antagonist, a downstream regulatory element antagonistic modulator (DREAM), iNOS, a inhibitor of tetrodotoxin (TTX)-resistant Na+-channel receptor subtypes PN3 and SNS2, an inhibitor of interleukin, a TNF binding protein, a dominant-negative TNF variant, Nanobodies™, a kinase inhibitor, or any combination thereof. These regenerating, therapeutic, or biological agents may promote healing, repair, regeneration and/or restoration of the disc, and/or facilitate proper disc function. 
         [0031]    In an alternative embodiment, the material delivery device  46  may contain an inflation medium instead of a biocompatible material. The inflation medium may be pressurized and injected through the catheter portion  38  of the space creating device  36  to pressurize and inflate the compartments  42 ,  44  of the spacing portion  40 . The inflation of the spacing portion  40  may be controlled by the control mechanism  49 . The inflation medium may be injected under pressure supplied by a hand, electric, or other type of powered pressurization device. The internal balloon pressure may be monitored with the pressure gauge  50 . The pressure gauge  50  or a pressure limiter may be used to avoid over inflation or excessive injection. The rate of inflation and level of inflation of the spacing portion  40  can be varied between patients depending on disc condition. The inflation medium may be a saline and/or radiographic contrast medium such as sodium diatrizoate solution sold under the trademark Hypaque by Amersham Health, a division of GE Healthcare (Amersham, UK). 
         [0032]    As the spacing portion  40  is gradually inflated, the surrounding nucleus tissue may become displaced or stretched, creating a space within the nucleus pulposus  24 . The inflation may also cause the intradiscal pressure to increase. Both the pressure increase and the direct expansion of the spacing portion  40  may cause the endplates  16 ,  18  to distract. 
         [0033]    In this alternative embodiment, the space creating portion  40  may be deflated and removed and the biocompatible material  48  injected into the space formed within the nucleus pulposus  24  and vacated by the space creating portion  40 . The material  48  may be injected after the space creating portion  40  has been deflated and removed or may be injected while the space creating portion  40  is being deflated and removed. For example, the biomaterial  48  may become increasingly pressurized while the pressure in the space creating portion  40  is lowered. In some procedures, the material  48  may be injected before the space creating portion  40  is removed. With the material  48  injected and the space creating portion  40  removed, the cannula  30  may be removed and the minimally invasive surgical incision closed. 
         [0034]    Any of the steps of the above described methods including expansion of the space creating portion  40  and filling the space created by the space creating portion  40  may be monitored and guided with the aid of imaging methods such as fluoroscopy, x-ray, computed tomography, magnetic resonance imaging, and/or image guided surgical technology such as a Stealth Station surgical navigation system (Medtronic, Inc., Minneapolis, Minn.) or a BrainLab system (Heimstetten, Germany). 
         [0035]    In another alternative embodiment, the space creating portion may be inflated with an inflation medium and the inflation medium replaced with a biocompatible material. The space creating portion filled with biocompatible material may be detached from the catheter portion and may remain in the nucleus  24  as an implant. 
         [0036]    Alternative space creating portions and space creating methods are described in the currently pending applications “Devices, Apparatus, and Methods for Improved Disc Augmentation” (Attorney Docket No. 31132.512) and “Devices, Apparatus, and Methods for Bilateral Approach to Disc Augmentation” (Attorney Docket No. 31132.513), both filed Apr. 27, 2006 and incorporated herein by reference. 
         [0037]    Referring now to  FIGS. 6-7 , in this embodiment, a multi-chamber spacing portion  60  comprises a central spherical chamber  62  and a ring or donut (torus) chamber  64 . The spherical chamber  62  and the ring chamber  64  may be molded together, bonded together, sewn together, or otherwised affixed to one another. The spacing portion  60  may be inserted into the nucleus pulposus and filled using any of the methods described above. The chambers  62 ,  64  may be independently filled with any of the materials described above. For example, the spherical chamber  62  may be filled with a material that becomes relatively hard such as polymethylmethacrylate (PMMA) bone cement. The ring chamber  64  may be filled with a material that remains relatively soft compared to the PMMA, such as silicone or polyurethane. In this embodiment, the spherical chamber  62  may be inflated first and the ring chamber  64  may inflated after the chamber  62  is inflated. As shown in  FIG. 7 , after inflation, the upper and lower surfaces of the spherical chamber  62  may extend outward beyond the ring chamber  64 . As the central spherical chamber  62  becomes filled and hardens, the upper and lower surfaces of the chamber  62  may penetrate the contacted endplate surfaces of the vertebral bodies  12 ,  14 , securing or anchoring the spacing portion  60  between the two endplates  16 ,  18 . In this embodiment, the spacing portion  60  may function as an anchored distractor. Penetration of the endplate is broadly understood to include piercing of the endplate, indentation of the endplate, deformation of the endplate, remodeling of the endplate over a period of time to conform to the spacing portion, or any other reaction of or change to the endplate as a result of high contract stress with the spacing portion. 
         [0038]    Referring now to  FIGS. 8-9 , in this embodiment, a multi-chamber spacing portion  70  comprises a central chamber  72  and a ring or donut (torus) chamber  74 . The central chamber  72  includes a cylindrical area  76  bounded by curved or domed surfaces  78 . The central chamber  72  and the ring chamber  74  may be molded together, bonded together, sewn together, or otherwised affixed to one another. The spacing portion  70  may be inserted into the nucleus pulposus and filled using any of the methods described above. The chambers  72 ,  74  may be independently filled with any of the materials described above. For example, the central chamber  72  may be filled with a material that becomes relatively hard such as polymethylmethacrylate (PMMA) bone cement. The ring chamber  74  may be filled with a material that remains relatively soft compared to the PMMA, such as silicone or polyurethane. In this embodiment, the central chamber  72  may be inflated first and the ring chamber  74  may inflated after the chamber  72  is inflated. As shown in  FIG. 8 , after inflation, the curved surfaces  78  of the chamber  72  may extend outward beyond the ring chamber  74 . As the central chamber  72  becomes filled and hardens, the upper and lower curved surfaces  78  of the chamber  72  may penetrate the contacted endplate surfaces of the vertebral bodies  12 ,  14 , securing the spacing portion  70  between the two endplates  16 ,  18 . The filled cylindrical area  76  of the central chamber  72  may provide greater axial support to the curved surfaces  78 , enhancing penetration of the central chamber into the endplates and resisting migration of the spacing portion  70 . Penetration of the endplate is broadly understood to include piercing of the endplate, indentation of the endplate, deformation of the endplate, remodeling of the endplate over a period of time to conform to the spacing portion, or any other reaction of or change to the endplate as a result of high contract stress with the spacing portion. 
         [0039]    Referring now to  FIG. 10 , in this embodiment, a multi-chamber spacing portion  80  comprises multiple clustered lobes  82 . The spacing portion  80  may be inserted into the nucleus pulposus and filled using any of the methods described above. The lobes  82  may be selectively filled to compensate for a particular patient&#39;s disc degeneration or injury. For example, lobes located in an area of significant disc degeneration may be filled with biocompatible material to restore natural disc height and elasticity. Lobes located closer to intact and hydrated nucleus tissue may be unfilled, underfilled, or filled with a softer material to blend the implant with the natural nucleus. Multiple lobes may provide the physician with greater flexibility in adapting to a particular patient&#39;s anatomy. 
         [0040]    Referring now to  FIG. 11 , in this embodiment, a multi-chamber spacing portion  90  comprises a central chamber  92  and an irregularly shaped chamber  94 . The central chamber  92  may be spherical or cylindrical as in the embodiments described above, although other shapes may be suitable. The chamber  94  is an irregular shape selected to conform to, or compensate for loss in, the surrounding nucleus tissue. The spacing portion  90  may be inserted into the nucleus pulposus and filled using any of the methods described above. The chambers  92 ,  94  may be independently filled with any of the materials described above. For example, the central chamber  92  may be filled with a material that becomes relatively hard such as polymethylmethacrylate (PMMA) bone cement. The irregular chamber  94  may be filled with a material that remains relatively soft compared to the PMMA, such as silicone or polyurethane. The irregular chamber  94  may be unfilled, underfilled, or filled with a softer material to blend the implant with the natural nucleus. The irregular shape may provide the physician with greater flexibility in adapting to a particular patient&#39;s anatomy. 
         [0041]    Referring now to  FIG. 12 , in this embodiment, a multi-chamber spacing portion  100  comprises a central chamber  102  and outer chambers  104 ,  106 . The central chamber  102  may be spherical or cylindrical as in the embodiments described above, although other shapes may be suitable. The outer chambers  104 ,  106  may be selectively filled to compensate for a particular patient&#39;s disc degeneration or injury. For example, chambers  104  may be filled with biocompatible material to restore natural disc function in areas of greater disc degeneration or injury. Chambers  106  may be unfilled or underfilled for areas requiring less augmentation. Multiple chambers may provide the physician with greater flexibility in adapting to a particular patient&#39;s anatomy. The spacing portion  100  may be inserted into the nucleus pulposus and filled using any of the methods described above. The chambers  102 ,  104 ,  106  may be independently filled with any of the materials described above. 
         [0042]    Referring now to  FIG. 13 , in this embodiment, a multi-chamber spacing portion  110  comprises a spherical central chamber  112  and a spherical outer chamber  114 , concentric with central chamber  112 . Although the chambers  112 ,  114  are described as spherical, other configurations may be suitable. The spacing portion  110  may be inserted into the nucleus pulposus and filled using any of the methods described above. The chambers  112 ,  114  may be independently filled with any of the materials described above. For example, the central chamber  112  may be filled with a material that becomes relatively hard such as polymethylmethacrylate (PMMA) bone cement. The irregular chamber  114  may be filled with a material that remains relatively soft compared to the PMMA, such as silicone or polyurethane. 
         [0043]    Referring now to  FIG. 14 , in this embodiment, a multi-chamber spacing portion  120  has a fusiform structure similar to a football. Other shapes such as ellipsoid may also be suitable. The spacing portion  120  includes chambers  122 ,  124 . The spacing portion  120  may be inserted into the nucleus pulposus and filled using any of the methods described above. The chambers  122 ,  124  may be independently filled with any of the materials described above. For example, the chambers  122 ,  124  may both be filled with polyurethane materials, however the chamber  122  may be underfilled or filled with a different type of polyurethane having a final hardness lower than that used for chamber  124 . In this way, the spacing portion  120  may be tailored toward a particular patient&#39;s anatomy. 
         [0044]    Referring now to  FIG. 15 , in this embodiment, a multi-chamber spacing portion  130  comprises a spherical central chamber  132  and an outer chamber  134  extending along the annulus  22  to occlude an annulus defect  136 . Although the chamber  132  is described as spherical, other configurations may be suitable. The spacing portion  130  may be inserted into the nucleus pulposus and filled using any of the methods described above. The chambers  132 ,  134  may be independently filled with any of the materials described above. For example, the central chamber  132  may be filled with a material that becomes relatively hard such as polymethylmethacrylate (PMMA) bone cement. The outer occluding chamber  134  may be filled with a material that also becomes relatively hard to prevent the migration of chamber  132  through the defect  136 . 
         [0045]    Referring now to  FIG. 16 , in this embodiment, a multi-chamber spacing portion  140  comprises an irregularly shaped central chamber  142  and an outer chamber  144  extending along the annulus  22  to occlude an annulus defect  136 . The spacing portion  140  may be inserted into the nucleus pulposus and filled using any of the methods described above. The chambers  142 ,  144  may be independently filled with any of the materials described above. For example, the central chamber  142  may be filled with a material that becomes relatively compliant or soft. The outer occluding chamber  144  may be filled with a material that also becomes relatively hard to prevent the migration of chamber  142  through the defect  136 . 
         [0046]    Referring now to  FIG. 17 , in this embodiment, a multi-chamber spacing portion  150  comprises three chambers  152 ,  154 ,  156 , serially arranged. The spacing portion  150  may be inserted into the nucleus pulposus and filled using any of the methods described above. The chambers  152 ,  154 ,  156  may be independently filled with any of the materials described above. The chambers  152 ,  154 ,  156  may also be filled, underfilled, or unfilled to achieve a desired result for a particular patient. The shape and number of the chambers depicted is merely exemplary and other shapes, configuration, and quantities of chambers may be suitable. 
         [0047]    Referring now to  FIG. 18 , in this embodiment, a multi-chamber spacing portion  160  comprises three chambers  162 ,  164 ,  166 , serially arranged. The spacing portion  160  may be inserted into the nucleus pulposus and filled using any of the methods described above. The chambers  162 ,  164 ,  166  may be independently filled with any of the materials described above. The chambers  162 ,  164 ,  156  may also be filled, underfilled, or unfilled to achieve a desired result for a particular patient. The shape and number of the chambers depicted is merely exemplary and other shapes, configuration, and quantities of chambers may be suitable. 
         [0048]    As used in this description, the term “filled” should be broadly construed describe those chambers that are not only completely filled, but also partially filled. It is understood that some chambers of a filled multi-chamber space creating device may be unfilled or partially filled. 
         [0049]    Although only a few exemplary embodiments have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible in the exemplary embodiments without materially departing from the novel teachings and advantages of this disclosure. Accordingly, all such modifications and alternative are intended to be included within the scope of the invention as defined in the following claims. Those skilled in the art should also realize that such modifications and equivalent constructions or methods do not depart from the spirit and scope of the present disclosure, and that they may make various changes, substitutions, and alterations herein without departing from the spirit and scope of the present disclosure. It is understood that all spatial references, such as “horizontal,” “vertical,” “top,” “upper,” “lower,” “bottom,” “left,” “right,” “anterior,” “posterior,” “superior,” “inferior,” “upper,” and “lower” are for illustrative purposes only and can be varied within the scope of the disclosure. In the claims, means-plus-function clauses are intended to cover the elements described herein as performing the recited function and not only structural equivalents, but also equivalent elements.