Abstract:
An inter-vertebral disc prosthesis intended for percutaneous deployment comprises an expandable annular enclosure and an expandable nuclear enclosure. The expandable annular enclosure incorporates a reinforcing annular band along its periphery and is filled with in-situ curable rubber. The expandable nuclear enclosure is filled with a gas. The nuclear prosthesis further incorporates a novel, integrally molded sealing valve assembly and is stretchable and collapsible into a minimal profile for ease of insertion into a specially designed delivery cannula, and is inflation-assisted expandable into an inter-vertebral disc in which complete percutaneous nuclectomy has been performed.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This is a utility application claiming priority to U.S. Provisional Application Ser. No. 61/212,104 filed Apr. 7, 2009, and incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention generally relates to body-implantable devices. More particularly, the present invention relates to a percutaneously insertable and expandable inter-vertebral disc prosthesis. Specifically, the present invention comprises a novel nuclear prosthesis, a specially designed delivery apparatus, and a loading apparatus for loading the nuclear prosthesis within the delivery apparatus. 
     2. Description of the Related Art 
     The role of the inter-vertebral disc in spine biomechanics has been the subject of extensive research and is generally well understood. A typical native spinal unit is shown for exemplary purposes in  FIG. 22A . The functional spinal unit, or spinal motion segment  500  consists of two adjacent vertebrae  502  and  504 , the inter-vertebral disc  506  and the adjacent ligaments (not shown). The components of the disc are the nucleus pulposus  506   a , the annulus fibrosis  506   b , and the vertebral end-plates  506   c . These components act in synchrony and their integrity is crucial for optimal disc function. During axial loading of the normal native disc  506 , the pressure of the nucleus pulposus  506   a  rises, transmitting vertical force on the end plates  506   c  and outward radial stress on the annulus fibrosis  506   b , as shown by the direction arrows in  FIG. 22A . The vertical stress is transformed to tensile forces in the fibers of the annulus fibrosis  506   b . Because the gelatinous nucleus pulposus  506   a  is deformable but noncompressible, it flattens radially, and the annulus fibrosis  506   b  bulges and stretches uniformly. Flexion of the spine involves the compression of the anterior annulus fibrosis  506   b , as well as the nucleus pulposus  506   a . The nucleus pulposus  506   a  deforms and migrates, posteriorly stretching the annular fibers and expanding radially. Thus, the nucleus pulposus  506   a  and annulus fibrosis  506   b  function synergistically as a cushion by reorienting vertical forces radially in a centrifugal direction. 
     The native vertebral end plate  506   c  prevents the nucleus pulposus from bulging into the adjacent vertebral body by absorbing considerable hydrostatic pressure that develops from mechanical loading of the spine. The end plate  506   c  is a thin layer of hyaline fibrocartilage with subchondral bone plate, typically around 1 millimeter thick. The outer 30% of the end plate  506   c  consists of dense cortical bone and is the strongest area of the end plate  506   c . The end plate  506   c  is thinnest and weakest in the central region adjacent to the nucleus pulposus. 
     With aging and repetitive trauma, the components of the inter-vertebral disc  506  undergo biochemical and biomechanical changes and can no longer function effectively, resulting in a weakened inter-vertebral disc  506 . As the disc  506  desiccates and becomes less deformable, the physical and functional distinction between the nucleus pulposus  506   a  and the annulus fibrosis  506   b  becomes less apparent. Disc desiccation is associated with loss of disc space height and pressure. The annulus fibrosis  506   b  loses its elasticity. The apparent strength of the vertebral end-plates  506   e  decreases and vertebral bone density and strength are diminished. This leads the end-plates  506   c  to bow into the vertebral body, imparting a biconcave configuration to the vertebral body. Uneven stresses are created on the end plates  506   c , annulus fibrosis  506   b , ligaments (not shown), and facet joints (not shown), leading to back pain. At this point, the annulus fibrosis  506   b  assumes an inordinate burden of tensile loading and stress, and this further accelerates the process of degeneration of the annulus fibrosis  506   b . Fissuring of the annulus fibrosis  506   b  further diminishes its elastic recoil, preventing the annulus fibrosis  506   b  from functioning as a shock absorber. Leakage of the nuclear material can cause irritation of the nerve roots by both mechanical and biochemical means. Eventually, degenerative instability is created, leading to both spinal canal and neuroforaminal stenosis. 
     Historically, spine surgery consisted of simple decompressive procedures. The advent of spinal fusion and the proliferation of surgical instrumentation and implants has led to an exponential utilization of expensive new technologies. As an alternative to open surgical discectomy and fusion, Minimally Invasive Spinal Surgery (MISS) has been advocated. Thus far, the primary rationale for favoring the MISS approach has been to lessen postoperative pain, limit the collateral damage to the surrounding tissues, and hasten the recovery process rather than affect long term outcomes. Despite the lack of clear superiority and outcome data, these technologies have continued to flourish. 
     However, many spinal surgeons remain skeptical about the positive claims regarding MISS, citing certain drawbacks, including increase in operating room time, requirement for expensive proprietary instruments, increased cost, and the technically demanding nature of the procedure. Despite the advantage of a minimal incision approach, MISS requires an adequate decompression and/or fusion procedure in order to have results comparable to traditional open surgical approaches. 
     Ideally, a nuclectomy and implant insertion would be performed through a percutaneous posterolateral approach. Advantages of the percutaneous posterolateral approach over conventional open surgery and MISS include obviating the need for surgically exposing, excising, removing, or injuring interposed tissues; preservation of epidural fat; avoiding epidural scarring, blood loss, and nerve root trauma. Other advantages include minimizing “access surgery” and hospitalization costs, and accelerating recovery. A percutaneous procedure may be expeditiously used on an outpatient basis in selected patients. On the other hand, percutaneous insertion imposes a number of stringent requirements on the nuclear prosthesis and its method of delivery. 
     Several devices have been used to fill the inter-vertebral space void following discectomy in order to prevent disc space collapse. These devices generally fall into two categories: fusion prostheses and motion prostheses. Fusion prostheses intended for MISS insertion offer few if any advantages over those for open surgical technique. While these types of implants eliminate pathological motion, they also prevent normal biomechanical motion at the treated segment. Greater degrees of stress are transmitted above and below the treated segment, often leading to accelerated degeneration of adjacent discs, facet joints, and ligaments (adjacent level degeneration). 
     Motion prostheses generally aim at restoring disc height, shock absorption, and range of motion, thus alleviating pain. Artificial motion prostheses may be divided into two general types: the total disc prosthesis and the nucleus prosthesis. The total disc prosthesis is designed for surgical insertion, replacing the entire disc, while the nucleus prosthesis is designed for replacing only the nucleus pulposus, and generally may be inserted by open surgical or MISS methods. 
     Prior designs of motion nucleus prostheses include enclosures that are filled with a diverse variety of materials to restore and preserve disc space height while permitting natural motion. However, there are several shortcomings of prior nucleus motion prostheses designs. Some of the prior nucleus motion prostheses require surgical approaches for insertion that involve removal of a significant amount of structural spinal elements including the annulus fibrosis. Removal of these structural spinal elements causes destabilization of the spinal segment. Prior nuclear motion prosthesis designs also fail to provide the outer margin of the nuclear prosthesis with surface and structural properties that encourage native tissue ingrowth. Instead, such prostheses are made from generally non-porous materials that impede full incorporation of the nuclear prosthesis into the surrounding annular margin. 
     Some prior designs have annular bands along the outer periphery of the nucleus motion prostheses. However, prior annular bands are non-compliant. This is disadvantageous because it reduces the radial outer expansion required for load dampening. Thus, the load is transferred to the end plates of the vertebrae, which can withstand only limited deformation. The result is that the end plates eventually fail, resulting in loss of intradiscal pressure, accelerated degeneration, and subsidence of the nuclear prosthesis. Other prostheses do not have an annular band. These prostheses tend to exert untoward pressure on an already weakened annulus fibrosis. Particularly, such a prosthesis tends to protrude into a pre-existing annular tear. 
     Other designs fail to incorporate or use a central gas cushion with a valve system or assembly that does not leak. Still others concentrate the harder load bearing component of the nuclear prosthesis in the central aspect of the disc, predisposing the nuclear prosthesis to subsidence. Another problem with prior nuclear motion prostheses is the imprecise sizing and tailoring of the nuclear prosthesis. Over sizing places unnecessary stress on the already damages and degenerated annulus fibrosis, while under sizing of the nuclear prosthesis may result in inadequate contact with the inner wall of the annulus fibrosis, and possibly non-integration and migration of the nuclear prosthesis. Other designs of nucleus motion prostheses suffer draw backs such as bulkiness, inelasticity, inability to fold and pack the nuclear prosthesis into a delivery cannula or apparatus for percutaneous implantation into a patient. In fact, percutaneous delivery of a motion nucleus prosthesis heretofore, has been unavailable. 
     Applicants here propose to overcome the disadvantages of the prior designs of nucleus motion prostheses by providing a multi-compartment nuclear prosthesis having a semi-compliant annular reinforcement band disposed adjacent or contiguously around the periphery of a rubber filled annular enclosure. The annular enclosure nests a central, gas cushioned nuclear enclosure and an integrated sealing valve assembly. The nuclear prosthesis of the present invention is foldable to fit within a delivery apparatus, and is intended for percutaneous insertion into a nuclear space void following percutaneous total nuclectomy. Once percutaneously inserted, the nuclear prosthesis is expandable by an inflation-assisting device to provide cushioning and stability to a spinal segment weakened by degeneration. 
     SUMMARY OF THE INVENTION 
     The present invention overcomes the deficiencies of prior nuclear motion prostheses, offers several advantageous properties, and provides a system for sizing, forming, delivering, and deploying a nuclear prosthesis into the inter-vertebral disc space. The percutaneously implantable nuclear prosthesis, formed in accordance with the present invention, utilizes the advantages of both a textile prosthesis and a polymer prosthesis to create a compartmentalized composite structure, having characteristics closely resembling the properties of a healthy native inter-vertebral disc. The nuclear prosthesis is comprised of an annular structure and a nuclear structure. The annular structure comprises an annular enclosing layer which defines an annular enclosure, an annular reinforcement band adjacent the periphery of the annular enclosing layer, a sealing valve core disposed within the annular enclosure and adjacently attached to the annular enclosing layer, and in-situ curable rubber, which is injected into the annular enclosure. The nuclear structure comprises a nuclear enclosing layer which defines a nuclear enclosure and an indwelling catheter mounted and bonded to a neck portion of the nuclear enclosing layer, and extends distally into, and is enclosed within the nuclear enclosure. 
     Referring to  FIG. 22B  the structure of the nuclear prosthesis comprising the annular structure  11  filled with the deformable, but not compressible in-situ curable rubber and the nuclear structure  21  centrally located within the annular structure  11  and being filled with a compressible gas allows for the vertical and horizontal load stresses placed on the inter-vertebral disc space to be redirected inward, centrally toward the nuclear structure  21  (see direction arrows of  FIG. 22B ), instead of outward. Moreover, annular structure  11  has a biocompatible outer annular reinforcement band that encourages tissue in-growth of the native annulus fibrosis  506   b , thereby providing reinforcement to the native annulus fibrosis. 
     According to the present invention, there is provided a percutaneously insertable and detachable nuclear prosthesis having an annular enclosing layer that defines an annular enclosure. The annular enclosing layer is made of an annular tubular elastomeric membrane, is contiguous along its outer periphery with a textile annular reinforcement band, and incorporates a sealing valve core. Central to the annular enclosing layer is a nuclear enclosing layer defining a nuclear enclosure. The nuclear enclosing layer has a neck region. The neck region of the nuclear enclosing layer defines an open mouth that receives an indwelling catheter. The neck region is mounted on the indwelling catheter. The indwelling catheter is a tube that defines a lumen. The indwelling catheter is coupled to a sealing valve core which is disposed within the annular enclosure, and has its lumen plugged by a sealing plug after inflation within the inter-vertebral disc space. 
     The nuclear prosthesis is detachably mounted to a distal end of an inflation stylus and is loaded within a distal end of a delivery apparatus. The inflation stylus has three inflation tubes projecting from the distal end of the inflation stylus and slidably insertable through the sealing valve core of the sealing valve assembly. The sealing valve core is formed of a resilient material and has three pathways being defined by three parallel channels extended through the sealing valve core. Upon insertion of the three inflation tubes of the inflation stylus through the channels of the sealing valve core, the pathways take the form of cylindrical apertures in precise mating alignment with the inflation tubes of the inflation stylus to provide fluid-tight seal against and around the outer surfaces of the inflation tubes. The central inflation tube is a nuclear access tube that provides pressurized fluid to the nuclear enclosure. One of the outer tubes is an annular inlet tube that provides pressurized fluid to the annular enclosure through an inlet port provided in the sealing valve core. The other outer tube is an annular outlet tube that receives pressurized fluid from the annular enclosure through an outlet port provided in the sealing valve core. 
     The annular inlet tube and the annular outlet tube have side pores in the walls of the tubes adjacent the closed tips of the tubes whereby in-situ vulcanizing rubber flows through the side pore in the annular inlet tube into one end of the annular enclosure and back through the side pore of the annular outlet tube, and into the inflation stylus. After inflation of the annular enclosure and nuclear enclosure, the inflation stylus can be efficiently disengaged from the sealing valve core, and upon withdrawal thereof, the pathways return to an elongated slit or channel configuration to provide a fluid tight seal for the inflated nuclear prosthesis. 
     It is, therefore, a general object of the present invention to provide a nuclear prosthesis which exhibits an optimal overall combination of physical, viscoelastic, and other properties superior to previous designs of motion nucleus prostheses. 
     It is another object of the present invention to provide a nuclear prosthesis that is fundamentally reliable and durable, and utilizes the latest in surface modification technology to enhance the bio-compatibility, bio-durability, infection resistance, and other aspects of performance. 
     It is another object of the present invention to provide a nuclear prosthesis that reduces stress on the vulnerable central portions of the native vertebral end plates. 
     It is another object of the present invention to reduce the stress on the vulnerable central portions of the native vertebral end plates by providing a nuclear prosthesis that redirects the vector of forces caused by load stress inward, toward the core or center of the nuclear prosthesis. In this regard, the present invention provides a gas-filled central enclosure to aide in load bearing, cushioning, shock absorption and stabilization by directing the vector of forces toward the gas-filled central enclosure. The present invention redirects both lateral and vertical forces toward the gas-filled central enclosure, thereby providing protection to the vertebral end plates. The present invention accomplishes the redirection of vector forces by having a non-compliant annular reinforcement band along the outer periphery of the nuclear prosthesis, and a compressible gas filled central nuclear enclosure. 
     It is yet another object of the present invention to provide a nuclear prosthesis that provides reinforcement and structural support to the native annulus fibrosis. The annular reinforcement band of the present invention encourages native tissue in-growth of the native annulus fibrosis to provide added stabilization and reinforcement. 
     It is still another object of the present invention to provide a nuclear prosthesis wherein the compliance of the nuclear prosthesis increases progressively toward the center of the nuclear prosthesis. Each component of the nuclear prosthesis is tailored to provide suitable viscoelastic properties that contribute to the overall performance of the nuclear prosthesis. This arrangement is intended to relieve the stress on the native annulus fibrosis by redirecting the radial outer vector of forces centrally toward the nuclear enclosure. The nuclear prosthesis is thus rendered iso-elastic with respect to the spinal segment. 
     Yet another object of the present invention is to provide a nuclear prosthesis that has expansion tailorability. The nuclear prosthesis can be expanded to variable sizes to accommodate the dimensions of the evacuated nuclear space. The nuclear enclosing layer, annular enclosing layer and annular reinforcement band possess the ability to be first inflated or stretched to its unextended or working profile and then, there-beyond to a limited extent and/or controlled extent by the application of greater pressure. The controlled flexibility of the textile annular reinforcement band and the expansion of the annular and nuclear enclosures can accommodate a wider range of nuclear space dimensions, reducing the need to precisely match the nuclear prosthesis to the nuclear space as to size. 
     It is yet a further object of the present invention to provide an inflation-assisted expandable nuclear prosthesis that distracts the disc space, and supports and reinforces the annulus fibrosis while keeping the ligaments and facet joints in a taut condition. 
     It is another object of the present invention to provide a novel sealing valve assembly which has a sealing valve core integrally bonded to the annular enclosing layer within the annular enclosure, having a mounting region adapted on its inner margin for fluid tight bonding to an indwelling catheter lying within the nuclear enclosure. The sealing valve core of the sealing valve assembly is detachably connected to the tip of the delivery apparatus and is self-sealing upon removal of the inflation stylus. 
     It is another object of the present invention to provide a nuclear prosthesis which can be geometrically and elastically deformed to reduce its axial and transverse diameter through radial elongation, into a minimal profile for ease of insertion into the delivery apparatus, while minimizing the risks that could be associated with such flexibility. This is achieved by the components of the nuclear prosthesis being suitably configured and dimensioned to form a perfect mating fit to each other and to the nuclear enclosing layer. The annular reinforcement layer, annular enclosing layer and nuclear enclosing layer must cooperate in a synchronized fashion to achieve a precise folded and wrapped configuration. The folding of the nuclear prosthesis is further achieved by minimizing the combined thicknesses of the annular enclosing layer and nuclear enclosing layer and optimizing the longitudinal flexibility and radial compliance of the annular reinforcement band by careful selection of the type of bio-compatible yarn, the number of layers, the heat set conditions, and the angles at which braids are formed. The folding of the nuclear prosthesis is also aided by the selection and use of a semi-compliant medical balloon material for the annular and nuclear enclosing layers. 
     It is further an object of the present invention to provide a nuclear prosthesis that has a porous outer margin thereby facilitating the incorporation of the nuclear prosthesis into the nuclear space. 
     It is yet another object of the present invention to provide a delivery apparatus having an assembly of coaxial telescoping cannulas with the nuclear prosthesis disposed therein, and a method of delivering the nuclear prosthesis percutaneously to the nuclear space. The delivery apparatus houses and carries the folded nuclear prosthesis within its delivery cannula. The delivery cannula also houses and incorporates an inflation stylus defining three tubes in fluid communication with the three chambers or pathways of the sealing valve core of the nuclear prosthesis. Within the delivery cannula is a specially designed release cannula adjacent the sealing valve core to release the inflation stylus from the nuclear prosthesis. 
     A typical procedure for implantation of the nuclear prosthesis involves performing an initial percutaneous nuclectomy through a percutaneous access device, insertion of the delivery apparatus within the percutaneous access device, insertion of the delivery cannula carrying the nuclear prosthesis and deploying the nuclear prosthesis within the nuclear space void. In deployment, the annular and nuclear enclosures are expanded using any suitable fluid delivery system, allowing the nuclear prosthesis to assume a substantially discoid shape as the nuclear prosthesis radially and axially expands and substantially conforms to the shape of the nuclear space void. 
     The annular and nuclear enclosures are inflated simultaneously with a pressurized liquid until adequate disc space distraction is achieved and a predetermined pressure level within the nuclear prosthesis is achieved. The annular enclosure is inflated with an in-situ curable rubber, and the nuclear enclosure is inflated with a liquid such as saline. After curing of the in-situ curable rubber within the annular enclosure occurs, the liquid within the nuclear enclosure is replaced with a compressible gas. Nitrogen, carbon dioxide, or many other suitable gases can be used within the nuclear enclosure. At this point, the indwelling catheter is plugged with a sealing plug introduced into the indwelling catheter and pushed therein. The delivery cannula is detached from the sealing valve core by the release cannula, and the delivery apparatus is then removed. 
     These and other objects, aspects, features and advantages of the present invention will be clearly understood and explained with reference to the accompanying drawings and through consideration of the following detailed description. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a sectional side view of the annular structure of the nuclear prosthesis of the present invention; 
         FIG. 1A  is a sectional side view of the loading apparatus of the present invention with an inflated nuclear prosthesis of the present invention therein; 
         FIG. 1B  is a sectional side view of an inflated annular enclosing layer of the nuclear prosthesis of the present invention; 
         FIG. 1C  is a sectional side view of an inflated annular enclosing layer of the nuclear prosthesis of the present invention; 
         FIG. 1D  is a sectional top view of the delivery apparatus of the present invention with the nuclear prosthesis of the present invention loaded therein; 
         FIG. 2  is a sectional side view of an inflated annular enclosing layer and deflated nuclear enclosing layer of the nuclear prosthesis of the present invention; 
         FIG. 2A  is a sectional side view of the loading apparatus of the present invention with a partially deflated nuclear prosthesis of the present invention therein; 
         FIG. 2B  is a sectional side view of the annular enclosing layer of the nuclear prosthesis of the present invention in a partially stretched position during loading into the delivery apparatus; 
         FIG. 2C  is a sectional side view of the nuclear prosthesis of the present invention in a partially deflated state; 
         FIG. 2D  is a sectional top view of the delivery apparatus of the present invention with the nuclear prosthesis of the present invention loaded thereon; 
         FIG. 3  is a sectional side view of the nuclear prosthesis and the inflation stylus of the present invention; 
         FIG. 3A  is a sectional side view of the loading apparatus of the present invention showing the loading of a deflated nuclear prosthesis of the present invention onto the delivery apparatus of the present invention; 
         FIG. 3B  is a sectional side view of the annular enclosing layer of the nuclear prosthesis of the present invention in a fully stretched position during loading onto the delivery apparatus; 
         FIG. 3C  is a sectional side view of the nuclear prosthesis showing the folding of the annular enclosing layer around the nuclear enclosing layer when the nuclear prosthesis is deflated; 
         FIG. 3D  is a sectional top view of the delivery apparatus of the present invention with the nuclear prosthesis of the present invention loaded thereon and retracted therein, with the delivery apparatus disposed within an access cannula; 
         FIG. 4  is a sectional top view of the nuclear prosthesis and the inflation stylus of the present invention; 
         FIG. 5  is a sectional top partially exploded view of the sealing valve core of the sealing valve assembly of the nuclear prosthesis of the present invention; 
         FIG. 6  is a sectional top view of the sealing valve core of the sealing valve assembly of the nuclear prosthesis of the present invention; 
         FIG. 7  is a sectional top view of the sealing valve core of the sealing valve assembly of the nuclear prosthesis of the present invention; 
         FIG. 8  is a side view of the indwelling catheter and the mounting region of the nuclear enclosing layer of the nuclear prosthesis of the present invention; 
         FIG. 9  is a sectional side view of the annular enclosing layer, retaining ring and the layers of the annular reinforcement band of the nuclear prosthesis of the present invention; 
         FIG. 10  is a sectional side view of the inflation stylus of the present invention and the of the nuclear prosthesis of the present invention showing interaction of the nuclear access tube with the indwelling catheter; 
         FIG. 11  is a sectional top view of the inflation stylus of the present invention; 
         FIG. 11A  is a sectional top view of the inflation stylus of the present invention and the of the nuclear prosthesis of the present invention showing interaction of the tubes of the inflation stylus with the ports and pathways of the sealing valve core; 
         FIG. 11B  is a sectional top view of the inflation stylus of the present invention and the of the nuclear prosthesis of the present invention showing interaction of the tubes of the inflation stylus with the ports and pathways of the sealing valve core; 
         FIG. 12  is a side view of the release cannula of the delivery apparatus of the present invention interacting with the annular enclosing layer of the nuclear prosthesis of the present invention; 
         FIG. 13  is a side view along line  12 - 12  of  FIG. 12  showing the connection of the inflation stylus to the of the nuclear prosthesis of the present invention; 
         FIG. 14  is a sectional side view showing the connection of the inflation stylus to the of the nuclear prosthesis of the present invention; 
         FIG. 15  is a sectional side view showing the connection of the inflation stylus to the of the nuclear prosthesis of the present invention; 
         FIG. 16  is a sectional side view showing the annular enclosing layer folded around the nuclear enclosing layer when the is a sectional side view showing the connection of the inflation stylus to the of the nuclear prosthesis of the present invention is deflated; 
         FIG. 17  is a perspective view of the outer layer of the annular reinforcement band of the nuclear prosthesis of the present invention; 
         FIG. 18  is a perspective view of one of the middle layers of the annular reinforcement band of the nuclear prosthesis of the present invention; 
         FIG. 19  is a perspective view of the inner layer of the annular reinforcement band of the nuclear prosthesis of the present invention; 
         FIG. 20  is a sectional side view of the nuclear prosthesis of the present invention after delivery and inflation with fluid within the patient; 
         FIG. 21  is a sectional side view of the nuclear prosthesis of the present invention after delivery and inflation with fluid within the patient; 
         FIG. 22A  is a rear view of a native inter-vertebral disc space showing the direction of dispersion of typical horizontal and vertical load forces; and 
         FIG. 22B  is a rear view of an inter-vertebral disc space with the nuclear prosthesis of the present invention therein, showing redirection of dispersion of typical horizontal and vertical load forces by the nuclear prosthesis of the present invention. 
     
    
    
     DESCRIPTION OF THE INVENTION 
     Referring to  FIGS. 1 through 4  the nuclear prosthesis  10  of the present invention is disclosed. Nuclear prosthesis  10  comprises an annular structure  11  and a nuclear structure  21 . Annular structure  11  comprises an annular enclosing layer  12  defining an annular enclosure  14 , and nuclear structure  21  comprises a nuclear enclosing layer  22  defining a nuclear enclosure  24 . Nuclear enclosing layer  22  is disposed adjacent annular enclosing layer  12  in the central space defined by annular enclosing layer  12 , along an inner margin  16  thereof. Annular structure  11  of nuclear prosthesis  10  further comprises an annular reinforcement band  20  contiguous with or adjacent a peripheral or outer margin  18  of the inflatable annular enclosing layer  12  and a sealing valve core  28  of a sealing valve assembly  26 . Annular enclosing layer  12  incorporates the sealing valve core  28  and annular enclosure  14  filled in-situ with curable rubber. In its inflated state, nuclear prosthesis  10  is substantially discoid in shape, as shown in  FIGS. 20 and 21 . 
     Annular enclosure  14  is in communication with an inlet port  36   a  and an outlet port  38   a  of sealing valve core  28 . Nuclear structure  21  comprises nuclear enclosing layer  22 , which defines a discoid inflatable nuclear enclosure  24 , and an indwelling catheter  32 . A neck portion  22   a  of nuclear enclosing layer  22  is mounted on indwelling catheter  32 , which has a side-pore  32   a  and a closed tip  32   d  (see  FIG. 8 ). Nuclear enclosing layer  22  is filled in-situ with compressible gas and converges on a neck portion  22   a  adapted for fluid-tight bonding to indwelling catheter  32  (see  FIG. 8 ). Returning to  FIGS. 1 through 4 , indwelling catheter  32  includes a bulbous portion  32   b  on the proximal end thereof, which is adapted to be coupled within a sealing valve core  28  of sealing valve assembly  26  to a pressurized fluid for inflation of nuclear enclosure  24 . Bulbous portion  32   b  of indwelling catheter  32  is snap-secured and adhesively bonded to sealing valve core  28  so that a fluid-tight connection will be achieved. 
     Referring to  FIGS. 1D ,  2 D and  3 D, a delivery apparatus  200  is disclosed. Delivery apparatus  200  is coaxially and telescopically slidable within an access cannula  202 . A distal delivery cannula  204  of delivery apparatus  200  coaxially encloses a release cannula  206  (see  FIGS. 10 ,  11 A,  11 B and  12 ) and an inflation stylus  100 . Referring to  FIGS. 4 ,  11 ,  11 A and  11 B, inflation stylus  100  is a rigid tube with a triple lumen that terminates in three inflation tubes  102 ,  104  and  106 . Inflation tubes  102 ,  104  and  106  define inflation lumens therein, and are in fluid communication with annular enclosure  14  and nuclear enclosure  24  via sealing valve core  28 . The three inflation tubes are an annular inlet tube  102 , an annular outlet tube  104  and a nuclear access tube  106 . Annular inlet tube  102 , annular outlet tube  104  and nuclear access tube  106  project from the distal end of inflation stylus  100  and are detachably secured to three corresponding pathways  36   b ,  38   b  and  40 , respectively, within sealing valve core  28 . 
     Inflation tubes  102 ,  104  and  106  are adapted to mate with the three corresponding pathways  36   b ,  38   b  and  40 , respectively, of sealing valve core  28 . In order to couple inflation stylus  100  to sealing valve core  28 , inflation tubes  102 ,  104  and  106  are inserted through the inflation bores  36   c ,  38   c  and  40   a , respectively, which are disposed on the outer margin of sealing valve core  28  (see  FIGS. 12 through 14 ). Inflation tubes  102 ,  104  and  106  then extend into the slit-like pathways  36   b ,  38   b  and  40 , respectively. 
     A fluid-tight communication is formed between annular enclosure  14  through inlet port  36   a  and outlet port  38   a , and through annular inlet tube  102  and annular outlet tube  104 . Annular inlet tube  102  has a side pore  102   a , and annular outlet tube  104  has a side pore  104   a . Side pores  102   a  and  104   a  are located towards the closed distal ends of the annular inlet tube  102  and annular outlet tube  104 , respectively. Side pore  102   a  provides a fluid-tight communication with inlet port  36   a , and side pore  104   a  provides a fluid-tight communication with outlet port  38   a  of sealing valve core  28 . A third fluid-tight communication is formed between nuclear enclosure  24  and inflation stylus  100 , through nuclear access tube  106 , which terminates with an end bore  106   a . Nuclear access tube  106  slides through passage  40   a  and engages a proximal end  32   c  of indwelling catheter  32 . 
     Referring to  FIGS. 4 through 9 ,  11 A and  11 B, the design of sealing valve assembly  26  is disclosed. Sealing valve assembly  26  employs sealing valve core  28  which permits the passage of fluid through inlet port  36   a , outlet port  38   a  and indwelling catheter  32 , but prevents the flow of fluid through sealing valve core  28  when tubes  102 ,  104  and  106  are removed from pathways  36   b ,  38   b  and  40 , respectively. Sealing valve core  28  is formed of a resilient material and contains the three constricted slit-like pathways  36   b ,  38   b  and  40  for frictionally engaging the outer surfaces of inflation tubes  102 ,  104  and  106 , respectively, so that a predetermined force is required to withdraw inflation stylus  100  from sealing valve core  28 . Pathways  36   b ,  38   b  and  40  define passageways through which inflation tubes  102 ,  104  and  106 , respectively, may be inserted without imparting damage to sealing valve core  28 . 
     Sealing valve assembly  26  comprises sealing valve core  28 , indwelling catheter  32 , and a sealing plug (not shown). Sealing valve core  28  has the general cross-sectional configuration as inflated annular enclosure  14 , and is substantially concentric with inflated annular enclosing layer  12 . Sealing valve core  28  has an outside diameter which is slightly smaller than the diameter of inflated annular enclosure  14 , allowing for additional thickness contributed by annular enclosing layer  12  adjacently enclosing sealing valve core  28 . The additional thickness is crucial during loading nuclear prosthesis  10  onto delivery apparatus  200 . Sealing valve core  28  is preferably fabricated by molding from implantable grade elastomeric material (not shown), such that when an in-situ curable rubber such as RTV liquid silicon or other suitable RTV liquid elastomer is injected in-situ into annular enclosure  14 , a strong bond is formed between the thermoset silicon of sealing valve core  28  and in the in-situ cured rubber to create a unified load-bearing cushion. Preferably, both sealing valve core  28  and the in-situ curable rubber have a similar modulus of elasticity. 
     Referring to  FIGS. 11A and 11B , sealing valve core  28  detachably mounted on the distal end of inflation stylus  100  is shown. Inflation tubes  102 ,  104  and  106  at the distal end of inflation stylus  100  are inserted through pathways  36   b ,  38   b  and  40 , respectively, of sealing valve core  28 . In this configuration, side pore  102   a  of annular inlet tube  102  and side pore  104   a  of annular outlet tube  104  are in alignment with inlet port  36   a  and outlet port  38   a , respectively, of the sealing valve core  28 . Pathways  36   b ,  38   b  and  40  in sealing valve core  28  are substantially collapsible such that they take the form of three elongated slits prior to insertion of inflation tubes  102 ,  104  and  106  therein. 
     Upon insertion of inflation tubes  102 ,  104  and  106  through pathways  36   b ,  38   b  and  40 , respectively, detachable fluid-tight engagement is achieved between inflation tubes  102 ,  104  and  106  of inflation stylus  100 , and annular enclosing layer  12  and nuclear enclosing layer  22 . Pathways  36   b ,  38   b  and  40  frictionally engage the outer surfaces of inflation tubes  102 ,  104  and  106 , obviating the danger of leakage or dislodgement during the pressuring and inflation of nuclear prosthesis  10 , as will discussed in more detail hereinafter. 
     Referring to  FIGS. 5 through 9 ,  11 A and  11 B, sealing valve core  28  forms an annular slot  28   b , which extends the outer radial circumference of sealing valve core  28 . Therefore, annular slot  28   b  is adjacent both inner margin  16  of annular enclosing layer  12  and outer margin  18  of annular enclosing layer  12 . Sealing valve core  28  further forms a nuclear slot  28   a  within annular slot  28   b  along the surface of sealing valve core  28  adjacent inner margin  16  of enclosing layer  12 . Annular slot  28   b  and nuclear slot  28   a  are adapted to receive and retain inner margin  16  of annular enclosing layer  12 , respectively, as well as a surrounding retaining ring  30 . Thus, along inner margin  16 , annular slot  28   b  and nuclear slot  28   a  define a nuclear mounting region  28   d , which receives annular enclosing layer  12  and retaining ring  30  therein. Annular slot  28   b  is adapted to receive and retain outer margin  18  of annular enclosing layer, as well as retaining ring  30 . Therefore, along outer margin  18 , annular slot  28   b  defines an annular mounting region  28   c  for receiving and retaining outer margin  18  of enclosing layer and retaining ring  30 . The lateral ridges of annular slot  28   b  along outer margin  18  of annular enclosing layer  12  mate with a flat distal tip of release cannula  206  of delivery apparatus  200  such that when release cannula  206  is held stationary and inflation stylus  100  is retracted, release cannula  206  urges sealing valve core  28  to detach from inflation stylus  100 . 
     Referring to  FIGS. 2 ,  3 ,  4 , and  8 , nuclear structure  21  comprises nuclear enclosing layer  12 , nuclear enclosure  24  and indwelling catheter  32 . Nuclear enclosure  24  is defined by the inflatable nuclear enclosing layer  22 , which is bonded about the periphery of indwelling catheter  32 . Indwelling catheter  32  is comprised of a catheter body having a bulbous portion  32   b  disposed on the proximal end  32   c  of indwelling catheter  32 , which is affixed to inner margin  16  of annular enclosing layer  12 , and extends within sealing valve core  28 . Nuclear enclosing layer  22  is bonded to indwelling catheter  32  at a connector terminal  22   b . Connector terminal  22   b  is defined by neck portion  22   a  receiving and tightly bonding to the body of indwelling catheter  32  at a predetermined distance from proximal end  32   c  and bulbous portion  32   b  of indwelling catheter  32 , and a retaining collar  22   c  receiving and crimping to neck portion  22   a  and indwelling catheter  32  to provide a fluid-tight seal to nuclear enclosing layer  22 . 
     A fluid-tight seal is formed between indwelling catheter  32  and neck portion  22   a  of the nuclear enclosing layer  22  by applying a layer of adhesive material (not shown) between indwelling catheter  32  and neck portion  22   a  of nuclear enclosing layer  22  and crimping retaining collar  22   c  over indwelling catheter  32  and neck portion  22   a  to form the sealed connector terminal  22   b . Preferably, indwelling catheter  32  and the inner surface of neck portion  22   a  are thermally and chemically similar, allowing a permanent bond to be performed. 
     In a preferred embodiment, a polymeric insert (not shown) formed of a mutually bondable material may be interposed between the outer surface of indwelling catheter  32  and inner surface of neck portion  22   a  of nuclear enclosing layer  22  during the manufacturing process; thus providing for a more durable structural integrity of the attachment. The entire connector terminal  22   b  including retaining collar  22   c , which is placed around neck portion  22   a  of nuclear enclosing layer  22 , is then thermally processed and crimped to sealably bond neck portion  22   a  of nuclear enclosing layer  22  to indwelling catheter  32 . Retaining collar  22   c  tapers proximally for ease of insertion and bonding into nuclear slot  28   a  of nuclear mounting region  28   b . Indwelling catheter  32  is relatively stiff and may be formed from polyurethane or polyethylene material (not shown) and may include a braided or helically wound wire reinforcing layer (not shown) to resist kinking. In a preferred embodiment, indwelling catheter  32  is formed by extruding a plurality of layers (not shown), including a suitably bondable outer layer (not shown) into a tubular form. 
     A seal plug (not shown) is inserted into indwelling catheter  32  for obstructing the lumen of indwelling catheter  32  after inflation of nuclear enclosure  24  is complete. The seal plug is prevented from being dislodged from the lumen of indwelling catheter  32  by the constriction of the slit-like pathway  40  of sealing valve core  28  following retraction of inflation stylus  100 . 
     Referring to  FIGS. 1 through 3 , and  FIGS. 1B through 3C , annular enclosing layer  12  has a doughnut-configuration with a substantially concave inner margin  16  and a substantially convex outer margin  18 , providing for inward folding of the concave inner margin  16 , forming a substantially “C” shaped flat band upon deflation of nuclear prosthesis  10 . The substantially “C” shaped flat band configuration of the deflated annular enclosing layer  12  facilitates wrapping annular enclosing layer  12  around the collapsed nuclear enclosing layer  22  and indwelling catheter  32 . This configuration also provides for interlocking of nuclear enclosing layer  22  within annular enclosing layer  22  when nuclear prosthesis  10  is inflated. 
     Annular enclosing layer  12  is preferably made from a polymeric material and defines a fluid-tight annular enclosure  14 , which is inflatable with an in-situ curable rubber. Annular enclosing layer  12  is preferably semi-compliant. Desirable attributes of annular enclosing layer  12  are not necessarily identical to desirable attributes for medical balloon catheters (not shown), which are used extensively in medical applications such as angioplasty, valvuloplasty, urological procedures and tracheal or gastric intubation. 
     For example, non-compliance and high tensile strength are less crucial in the case of the present invention&#39;s annular enclosing layer  12  of nuclear prosthesis  10 . Annular enclosing layer  12  is not expected to be subjected to high bursting pressures because annular enclosing layer  12  is filled with curable in-situ rubber that is deformable, and because nuclear prosthesis  10  is contained within the confines of a closed space bordered by the native vertebral end-plates of the patient. Furthermore, annular enclosing layer  12  is disposed between annular reinforcement band  20  and nuclear enclosing layer  22 , which restrain over-inflation of annular enclosing layer  12 , thus further making non-compliance and high tensile strength less crucial. The thickness of the membrane (not shown) of which annular enclosing layer  12  is made need only be thick enough to provide a fluid-tight barrier to leakage of in-situ cured rubber. Accordingly, a thin membrane of 20 to 60 microns may be used to construct annular enclosing layer  12 . 
     On the other hand, long-term structural integrity, moisture resistance (to avoid degeneration and to provide some protection to the rubber within annular enclosure  14 ) is of paramount importance to ensure durability. Other desirable attributes include kink resistance, low wall thickness, low tendency for pinholing, and ease of bonding and coating to other compounds. 
     Referring to  FIGS. 4 through 9 ,  11 A and  11 B, sealing valve core  28  of the present invention is adapted to be disposed within annular enclosure  14  and is bondable to annular enclosing layer  12  by heat fusion, ultrasonic welding, hot mold bonding, crimping, or other similar bonding methods known in the art. Adhesive layers (not shown) may be used advantageously in combination to bond sealing valve core  28  of sealing valve assembly  26  to annular enclosing layer  12 , although when the polymer material (not shown) of which sealing valve core  28  of sealing valve assembly  26  and annular enclosing layer  12  are made are similar, adhesives may be unnecessary. 
     As annular enclosing layer  12  is made from semi-compliant material (not shown), inflating annular enclosure  14  tends to exert a peel-away force on the bond between annular enclosing layer  12  and sealing valve core  28  of sealing valve assembly  26 . To avoid this potential problem, nuclear slot  28   a  and annular slot  28   b  are formed along the surface of sealing valve core  28  adjacent inner margin  16  of annular enclosing layer  12 , and are adapted to receive a portion of inner margin  16  of annular enclosing layer  12  and a portion of inner layer  30   a  of retaining ring  30 . Annular slot  28   b  extends the radial circumference of sealing valve core  28 . On the surface of sealing valve core  28  adjacent outer margin  18  of annular enclosing layer  12 , annular slot  28   b  receives a portion of outer margin  18  and a portion of outer layer  30   b  of retaining ring  30 . In a preferred embodiment, the method of securing sealing valve core  28  of sealing valve assembly  26  to annular enclosing layer  12  includes the use of retaining ring  30  positioned over and crimped tightly around annular enclosing layer  12  such that inner layer  30   a  of retaining ring  30  is adjacent nuclear slot  28   a , and outer layer  30   b  of retaining ring  30  is adjacent annular slot  28   b . The entire connection of sealing valve core  28 , annular enclosing layer  12  and retaining ring  30  is then thermally pressed to form a sealably bonded sealing valve core  28  within annular enclosure  14  resistant to separation from annular enclosing layer  12  during inflation. 
     Preferably, both sealing valve core  28  and the in-situ curable rubber injected into annular enclosure  14  are comprised of the same rubber material. When the in-situ curable rubber injected in annular enclosure  14  during inflation of nuclear prosthesis  10  solidifies, it bonds to sealing valve core  28 . The result is that the distinction between sealing valve core  28  and the curable rubber disappears, and an integral annular enclosure  14  of unitary construction is created. 
     Referring to  FIGS. 4 ,  9 ,  10  and  17  through  19 , annular reinforcement band  20  is disclosed. Annular reinforcement band  20  of the present invention is preferably a semi-compliant multi-layered bio-compatible textile structure that provides a detent to maximal stretching of the circumference of nuclear prosthesis  10 . Various parameters and properties of annular reinforcement band  20  may be adjusted to provide longitudinal flexibility and stretch, radial compliance, and kink resistance of annular reinforcement band  20 . Such variations include varying the materials from which the fibers making up the layers  20   a ,  20   b  and  20   c  of annular reinforcement band  20  are formed, varying fiber density, varying fiber denier, varying braiding angles, varying the number of strands per filament, and varying heat-set conditions. These parameters are tailored to provide the desirable function required of a particular layer of annular reinforcement band  20 , depending on the layer&#39;s position in annular reinforcement band  20 . Generally, outer layers  20   a  should be substantially less compliant, and compliance the annular reinforcement band  20  should increase through intermediate layers  20   b  and inner layer  20   c.    
     In a preferred embodiment, annular reinforcement band  20  is a three-dimensional structure that is formed by extending and interlocking at least one yarn of each layer of annular reinforcement band  20  with the adjacent layers. The multi-layered textile annular reinforcement band  20  shows a gradation of properties between its inner layers and outer layers. Referring to  FIG. 9  and  FIGS. 17 through 19 , at least one, and preferably more than one outer layers  20   a  are preferably made of a warp knitted pattern of biocompatible fibers. This gives outer layers  20   a  of annular reinforcement band  20  the advantage of velour, high porosity surface, enhancing tissue in-growth, as well as resisting unraveling. The fibers of outer layers  20   a  may be of low denier and may be textured or non-textured. 
     At least one, and preferably more than one intermediate layers  20   b  may be formed from biocompatible fibers forming a plurality of loops which follow helical or spiral paths, which may also be wavy or serpentine, contributing to the compliance of annular reinforcement band  20 . The fibers of intermediate layers  20   b  preferably include monofilaments of larger denier formed of durable material, such as polyethylene teraphthlate in braided or jersey patterns providing a load-bearing component, resistant to torsion and overstretching. The fibers in intermediate layers  20   b  may be chosen to perform a gradation of properties between the mid or equatorial region of annular reinforcement band  20  towards the upper and lower axial margins thereof. In a preferred embodiment, the equatorial section of annular reinforcement band  20  is formed of monofilaments that are thicker, stronger and less compliant filaments, with tapering of these properties towards the upper and lower margins of annular reinforcement band  20 . This renders annular reinforcement band  20  more resistant to kinking during stretching and radial compression of nuclear prosthesis  10  necessary to load nuclear prosthesis  10  within delivery apparatus  200 . 
     Inner layer  20   c  of annular reinforcement band  20  is formed from more compliant and thinner biocompatible yarn. In one embodiment, inner layer  20   c  may include a fusible fiber (not shown) having a low melting temperature, heat-fusing annular reinforcement band  20  to an innermost layer of intermediate layers  20   b  and annular enclosing layer  12 , enhancing ravel and fray resistance. In the preferred embodiment, annular reinforcement band  20  is not bonded to annular enclosing layer  12 . 
     In the preferred embodiment of the present invention, synthetic yarns (not shown) which are not degraded by the body are used to form the textile annular reinforcement band  20 . The yarns may be of the monofilament, multifilament or spun type, used in different combinations. Monofilaments are preferred in intermediate layers  20   b , providing for a lower volume structure with comparable strength to the fiber bundles of the multifilament fibers. Multifilaments are preferred along inner layer  20   c  and outer layers  20   a  to increase flexibility. The yarns may be flat, textured, twisted, shrunk, or pre-shrunk. As discussed above, the yarn type and yarn denier for a particular layer of the textile annular reinforcement band  20  may be chosen to meet the design requirements of annular reinforcement band  20 . 
     Referring to  FIGS. 2 ,  3  and  4 , nuclear enclosing layer  22  is essentially a discoid multilayered medical balloon which is fabricated by forming a plurality of polymeric layers (not shown) that converge on neck portion  22   a  of connector terminal  22   b , adapted for fluid-tight bonding to indwelling catheter  32 . Conventional balloon fabricating techniques are utilized to form a composite nuclear enclosing layer  22  of different polymeric materials (not shown) that are subjected to a stretch blow-molding operation in a heated mold (not shown). The resulting nuclear enclosing layer  22  of the present invention provides superior burst strength, superior abrasion resistance, and superior structural integrity, without significantly impairing the overall compressibility and gas-cushioning function of nuclear prosthesis  10 . 
     Long-term maintenance of a gas cushion in an inflated state is perhaps the most demanding requirement of nuclear enclosure  24 . Various approaches may be taken, including melt-blending the materials making up nuclear enclosing layer  22  and the use of multilayer fiber reinforced balloon structures (not shown) to make nuclear enclosing layer  22 . 
     Referring to  FIGS. 2 ,  3 ,  4  and  8 , nuclear enclosing layer  22  has a neck portion  22   a  which is bonded to indwelling catheter  32 , forming a secure connector terminal  22   b . Indwelling catheter  32  has a proximal end  32   c  including bulbous portion  32   b  which is adapted to be coupled to nuclear access tube  106  inflation stylus  100 , which is inserted through pathway  40  in sealing valve core  28  of sealing valve assembly  26 . Bulbous portion  32   b  defines a bulbous portion that snaps into a corresponding bulbous region  32   e  in sealing valve core  28 . Bulbous portion  32   b  is sealingly affixed to the corresponding bulbous portion  32   e  of sealing valve core  28 , forming a fluid-tight bond with sealing valve core  28 . Proximal end  32   c  of indwelling catheter  32  is in fluid communication with the distal end of nuclear access tube  106 , within sealing valve core  28 . 
     Nuclear enclosing layer  22  is sealingly mounted on the shaft of indwelling catheter  32 . Preferably, neck portion  22   a  of nuclear enclosing layer  22  is thermally or meltably bonded to indwelling catheter  32 . Connector terminal  22   b  and indwelling catheter  32  are all preferably made of melt compatible material. Connector terminal  22   b  may utilize a tie layer or “retaining collar”  22   c  formed of mutually bondable material that is slipped over neck portion  22   a  of nuclear enclosing layer  22 . Retaining collar  22   c  is heated and crimped to simultaneously meltably join neck portion  22   a  of nuclear enclosing layer  22 , retaining collar  22   c , and indwelling catheter  32 , making connector terminal  22   b  a permanent fluid-tight seal. 
     Indwelling catheter  32  defines a lumen with side pore  32   a  therein located proximal to closed tip  32   d  of indwelling catheter  32 . After inflating nuclear prosthesis  10  within the nuclear space void of a patient, the lumen of indwelling catheter  32  can be permanently obstructed by a small sealing plug (not shown) introduced through proximal end  32   c  of indwelling catheter  32 , and pushed into position with a guidewire (not shown) or other suitable positioning device. Pathway  40  of sealing valve core  28  collapses upon removal of inflation stylus  100 , preventing back-up of the sealing plug within indwelling catheter  32 . 
     Referring to  FIGS. 1D ,  2 D and  3 D, delivery apparatus  200  is disclosed. Prior to insertion of delivery apparatus  200  into the patient, a percutaneous access device (not shown) provides an access way or annular fenestration (not shown) into the inter-vertebral disc space of the patient, which is held open by an access cannula  202 . Any percutaneous access device used for minimally invasive percutaneous procedures can be used to create the annular fenestration. Generally, such percutaneous access devices comprise a plurality of telescopically arranged cannulas (not shown). After creation of the annular fenestration, delivery apparatus  200  can be delivered within access cannula  202 . Delivery apparatus  200  comprises a delivery cannula  204  with nuclear prosthesis  10  loaded therein, and a release cannula  206 . Delivery apparatus  200 , including nuclear prosthesis  10  and delivery cannula  204  which houses nuclear prosthesis  10  is provided, assembled and hermetically sealed so that loading or handling of nuclear prosthesis  10  is unnecessary during insertion and inflation thereof within the nuclear space void of the patient. 
     Still referring to  FIGS. 1D ,  2 D, and  3 D, delivery apparatus  200  of the present invention has oval inner and outer cross-section conforming to the cross sections of access cannula  202 . Delivery apparatus  200  comprises a delivery cannula  204  having a wall of uniform thickness defining a cylindrical inner passage having a substantially oval cross section, and a substantially oval release cannula  206  located within the oval, cylindrical inner passage of delivery cannula  204 . Inflation stylus  100  is slidably received within the oval release cannula  206 . 
     Delivery apparatus  200  is slidably received internally of the access cannula  202 , and is selectively extendible and retractable relative to access cannula  202  to facilitate proper placement of nuclear prosthesis  10  through the annular fenestration into the disc space void. 
     Referring to  FIGS. 10 through 11B , delivery cannula  204  of delivery apparatus  200  encloses release cannula  206 , which is telescopically slidable over inflation stylus  100 . As previously discussed, inflation stylus  100  includes three inflation tubes  102 ,  104  and  106  extending from its tip. Inflation tubes  102 ,  104  and  106  are frictionally engaged to pathways  36   b    38   b  and  40  (respectively) of sealing valve core  28 . In a preferred embodiment, nuclear access tube  106  has a bulbous ridge  106   b  formed at its mid aspect that mates with a corresponding bulbous region  40   b  formed along passageway  40 . The frictional engagement, as well as the engagement of bulbous ridge  106   b  with the bulbous region  40   b  provides a firm attachment of inflation stylus  100  to sealing valve core  28 , while allowing inflation tubes  102 ,  104  and  106  to be withdrawn when sufficient force is applied to it. 
     The amount of force required to withdraw inflation stylus  100  from nuclear prosthesis  10  may be chosen by selecting the rigidity and modulus of elasticity forming sealing valve core  28  as well as selecting the size and geometry of the pathways  36   b ,  38   b  and  40  and bulbous ridge  106   b . Generally, the amount of force required to release inflation stylus  100  from sealing valve core  28  must be more than the maximum inflation pressure experienced at the connection during inflation of nuclear prosthesis  10 . It may be difficult to precisely control the force required to withdraw inflation stylus  100  from sealing valve core  28 . 
     As may be appreciated, if this force is too great, sealing valve core  28  may be dislodged through the annulotomy, possibly causing tearing of the native annulus fibrosis. If the force required to withdraw inflation stylus  100  from sealing valve core  28  is too small, inflation stylus  100  may become prematurely detached from sealing valve core  28  during pressurizing and inflation of nuclear prosthesis  10 . 
     Referring to  FIGS. 10 through 12 , in a preferred embodiment, the release of inflation stylus  100  from sealing valve core  28  is obtained by utilizing release cannula  206  placed coaxially around inflation stylus  100 . Release cannula  206  has a thick wall and a diameter smaller than the outer diameter of sealing valve core  28 , such that its distal end engages sealing valve core  28  to, in effect, push sealing valve core  28  away from inflation stylus  100 . A screw drive mechanism (not shown) is threadedly engaged with and coupled to the proximal end (not shown) of inflation stylus  100  and release cannula  206  to achieve smooth, efficient, and predictable disengagement of inflation stylus  100  from the sealing valve core  28 . 
     The screw drive mechanism provides a mechanical advantage for withdrawing inflation stylus  100  from sealing valve core  28  at a controlled rate. A coupler (not shown) at the proximal end of inflation stylus  100  is adapted to engage the proximal end (not shown) of release cannula  206  to controllably extend and retract inflation stylus  100  and control its maximum travel. This can be done while the tip of release cannula  206  holds sealing valve core  28  stationary within annular enclosure  14 . The extension and retraction capabilities of inflation stylus  100  (in unison or independent of release cannula  206 ) facilitate proper deployment and detachment of nuclear prosthesis  10  within the nuclear space void. Withdrawal of inflation stylus  100  may be achieved by merely turning a knob (not shown) on the screw drive mechanism, which causes inflation stylus  100  to retract axially with respect to release cannula  206 , while sealing valve core  28  is held in place by the tip of release cannula  206 , thereby selectively screw-engaging or disengaging release cannula  206 . 
     The retracting motion continues until inflation tubes  102 ,  104  and  106  are completely disengaged from pathways  36   b ,  38   b  and  40 , respectively, of sealing valve core  28 . The screw drive mechanism may include a worm drive (not shown) that mates with teeth (not shown) formed on the exterior surface of inflation stylus  100  and release cannula  206 . Clearly, a wide variety of mechanical linkages are available to extend and retract inflation stylus  100  and release cannula  206 . It is particularly advantageous to provide a mechanism which allows independent, as well as linked and coordinated movements. 
     The knob may also be rotationally twisted in one direction during the loading of nuclear prosthesis  10  into delivery apparatus  200 . In this case, release cannula  206  and inflation stylus  100  are retracted as one unit into delivery apparatus  200 , pulling nuclear prosthesis  10  through a loading apparatus  300  and progressively radially compressing nuclear prosthesis  10  to a reduced-radius state until it is fully loaded within delivery cannula  204  of delivery apparatus  200 . When the knob is rotationally twisted in the opposite direction, release cannula  206  and inflation stylus  100  extend as one unit extruding nuclear prosthesis  10  from the tip of delivery cannula  204  to achieve predictable and controlled incremental deployment within the nuclear space void. 
     Referring to  FIGS. 1A ,  2 A and  3 A, loading apparatus  300  has a first loading block  302  and a second loading block  304  traversed by mirror-image funnel-shaped passageways  306  and  308 , respectively. The distal end of delivery apparatus  200  fits snugly but slidably within loading port  316  at a front end of first loading block  302 . The apposing ends of first loading block  302  and second loading block  204  have the general size and configuration of an inflated nuclear prosthesis  10 . Each funnel shaped passageway  306  and  308  of first loading block  302  and second loading block  304 , respectively tapers down within each loading block  302  and  304  to a second, smaller configuration which has the general cross-sectional oblong configuration of delivery cannula  204  of delivery apparatus  200 , and runs for a short distance in loading blocks  302  and  304 , forming a smooth transition with the inner margin of delivery cannula  204  at the loading port  316  of first loading block  302 . 
     Funnel passageways  306  and  308  of loading apparatus  300  define a tapered diamond-shaped space that geometrically and plastically deforms nuclear prosthesis  10  from a generally round, inflated configuration, as it is being deflated and pulled in opposing directions (as indicated by direction arrows  400  and  402 ) of the radial axis through the tapered funnel shaped passageways  306  and  308 , and then loaded into delivery cannula  204  of delivery apparatus  200 , which has been inserted into loading port  316  of first loading block  302 . 
     Referring to  FIGS. 1A through 3C , as nuclear prosthesis  10  is pulled and stretched in opposing directions  400  and  402  within the diamond-shaped passageway defined by funnel shaped passageways  306  and  308 , nuclear prosthesis is progressively radially approximated to a reduced-radius state. Simultaneously, annular enclosure  14  is deflated, approximating inner margin  16  and outer margin  18  of annular enclosing layer  12  into the thin substantially “C” shaped configuration, which assumes a more acute curvature as nuclear prosthesis  10  is stretched. 
     Annular enclosing layer  12  is stretched in a radial direction diametrically opposite to loading port  316  and delivery apparatus  200  by a traction band  322  removably wrapped around annular enclosing layer  12  at a position diametrically opposite the position of loading port  316 . In one embodiment, removable traction band  322  is a rubber band. However, any suitable band made of any suitable material can be used as traction band  322 , so long as it allows for removable attachment to annular enclosing layer  12  and is capable of stretching nuclear prosthesis  10  in a direction diametrically opposite the direction delivery apparatus  200  stretches nuclear prosthesis  10 . As nuclear prosthesis  10  reaches the small end of the diamond-shaped passageway defined by funnel shaped passageways  306  and  308 , annular enclosing layer  12  is wrapped tightly and folded compactly around nuclear enclosing layer  22  and indwelling catheter  32 , into the smallest possible cross-section, and is withdrawn into delivery cannula  204  of delivery apparatus  200 . The folded nuclear prosthesis  10  fits loosely within delivery cannula  204 , allowing achievement of unhindered deployment into the nuclear space void. 
     The inner surfaces of loading blocks  302  and  304  are preferably lined with a water-soluble lubricious hydrophilic coating (not shown) to lubricate the contact surfaces between loading blocks  302  and  304  and nuclear prosthesis  10  during loading thereof onto delivery apparatus  200 . 
     During the loading process, nuclear prosthesis  10  is deflated, stretched and radially compressed so as to adopt a low-profile configuration within the delivery cannula. Referring to  FIGS. 3A and 3D , folded nuclear prosthesis  10  is shown releasably attached to the distal end of inflation stylus  100 , which is surrounded by release cannula  206  and housed within the delivery cannula  204 . Delivery apparatus  200  passes through access cannula  202 . As previously discussed, nuclear prosthesis  10  is secured to inflation stylus  100 , by way of inflation tubes  102 ,  104  and  106  projecting from the distal tip of inflation stylus  100  and inserted into corresponding passageways  36   b ,  38   b  and  40 , respectively, in sealing valve core  28  of nuclear prosthesis  10 . When the inflation stylus  100 —release cannula  206  assembly is retracted within delivery cannula  204 , the loaded nuclear prosthesis  10  is pulled into the delivery cannula  204 . 
     It should be appreciated by one skilled in the art that once the deflated nuclear prosthesis  10  is delivered into the nuclear space void, an inflation-assisting device (not shown) or fluid delivery apparatus (not shown) introduces the in-situ curable rubber into annular enclosure  14  and the liquid and/or gas into nuclear enclosure  24 . It should be understood to one of ordinary skill in the art that any device, apparatus and/or system suitable for injecting fluid can be used to inflate nuclear prosthesis  10  could be used. Furthermore, fluid can be injected into nuclear prosthesis  10  manually using a syringe (not shown) connected to the tubes  102 ,  104  and  106  of inflation stylus  100 . 
     Although the invention has been described with reference to specific embodiments, this description is not meant to be construed in a limited sense. Various modifications of the disclosed embodiments, as well as alternative embodiments of the invention will become apparent to persons skilled in the art upon the reference to the description of the invention. It is therefore contemplated that the appended claims will cover such modifications that fall within the scope of the invention.