Patent Publication Number: US-2009222097-A1

Title: Nucleus implant and method of installing same

Description:
FIELD OF THE DISCLOSURE 
     The present disclosure relates generally to orthopedics and spinal surgery. More specifically, the present disclosure relates to nucleus implants. 
     BACKGROUND 
     In human anatomy, the spine is a generally flexible column that can take tensile and compressive loads. The spine also allows bending motion and provides a place of attachment for ribs, muscles and ligaments. Generally, the spine is divided into three sections: the cervical spine, the thoracic spine and the lumbar spine. The sections of the spine are made up of individual bones called vertebrae. Also, the vertebrae are separated by intervertebral discs, which are situated between adjacent vertebrae. 
     The intervertebral discs function as shock absorbers and as joints. Further, the intervertebral discs can absorb the compressive and tensile loads to which the spinal column may be subjected. At the same time, the intervertebral discs can allow adjacent vertebral bodies to move relative to each other a limited amount, particularly during bending, or flexure, of the spine. Thus, the intervertebral discs are under constant muscular and/or gravitational pressure and generally, the intervertebral discs are the first parts of the lumbar spine to show signs of “wear and tear”. 
     Facet joint degeneration is also common because the facet joints are in almost constant motion with the spine. In fact, facet joint degeneration and disc degeneration frequently occur together. Generally, although one may be the primary problem while the other is a secondary problem resulting from the altered mechanics of the spine, by the time surgical options are considered, both facet joint degeneration and disc degeneration typically have occurred. For example, the altered mechanics of the facet joints and/or intervertebral disc may cause spinal stenosis, degenerative spondylolisthesis, and degenerative scoliosis. 
     One surgical procedure for treating these conditions is spinal arthrodesis, i.e., spine fusion, which can be performed anteriorally, posteriorally, and/or laterally. The posterior procedures include in-situ fusion, posterior lateral instrumented fusion, transforaminal lumbar interbody fusion (“TLIF”) and posterior lumbar interbody fusion (“PLIF”). Solidly fusing a spinal segment to eliminate any motion at that level may alleviate the immediate symptoms, but for some patients maintaining motion may be beneficial. It is also known to surgically replace a degenerative disc or facet joint with an artificial disc or an artificial facet joint, respectively. Additionally, it is known to surgically remove nucleus pulposus material from within an intervertebral disc and replace the nucleus pulposus material with an artificial nucleus. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a lateral view of a portion of a vertebral column; 
         FIG. 2  is a lateral view of a pair of adjacent vertrebrae; 
         FIG. 3  is a top plan view of a vertebra; 
         FIG. 4  is a cross section view of an intervertebral disc; 
         FIG. 5  is a plan view of a first embodiment of a nucleus implant; 
         FIG. 6  is another plan view of the first embodiment of the nucleus implant; 
         FIG. 7  is a cross-section view of the first embodiment of the nucleus implant taken along line  7 - 7  in  FIG. 6 ; 
         FIG. 8  is a plan view of a second embodiment of a nucleus implant; 
         FIG. 9  is another plan view of the second embodiment of the nucleus implant; 
         FIG. 10  is a cross-section view of the second embodiment of the nucleus implant taken along line  10 - 10  in  FIG. 9 ; 
         FIG. 11  is a cross-section of a first embodiment of a set of nucleus implant injection tubes; 
         FIG. 12  is a cross-section of a second embodiment of a set of nucleus implant injection tubes; 
         FIG. 13  is a cross-section of a third embodiment of a set of nucleus implant injection tubes; 
         FIG. 14  is a flow chart of a first method of installing a nucleus implant; 
         FIG. 15  is a plan view of a third embodiment of a nucleus implant; 
         FIG. 16  is another plan view of the third embodiment of the nucleus implant; 
         FIG. 17  is a cross-section view of the third embodiment of the nucleus implant taken along line  17 - 17  in  FIG. 16 ; 
         FIG. 18  is a cross-section of a fourth embodiment of a set of nucleus implant injection tubes; 
         FIG. 19  is a cross-section of a fifth embodiment of a set of nucleus implant injection tubes; 
         FIG. 20  is a cross-section of a sixth embodiment of a set of nucleus implant injection tubes; 
         FIG. 21  is a cross-section of a seventh embodiment of a set of nucleus implant injection tubes; 
         FIG. 22  is a cross-section of an eighth embodiment of a set of nucleus implant injection tubes; 
         FIG. 23  is a flow chart of a second method of installing a nucleus implant; 
         FIG. 24  is a plan view of a fourth embodiment of a nucleus implant; 
         FIG. 25  is another plan view of the fourth embodiment of the nucleus implant; 
         FIG. 26  is a cross-section view of the fourth embodiment of the nucleus implant taken along line  26 - 26  in  FIG. 25 ; and 
         FIG. 27  is a flow chart of a third method of installing a nucleus implant. 
     
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS 
     A nucleus implant is disclosed. The nucleus implant can be configured to be installed within an intervertebral disc between an inferior vertebra and a superior vertebra. The nucleus implant can include an expandable core and an expandable chamber that can be disposed at least partially around the expandable core. The expandable chamber can be expanded from a deflated position to an inflated position. Further, a hardness of the expandable core, when inflated, can be greater than or equal to a hardness of the expandable chamber when inflated. 
     It will be noted that the chamber that is at least partially peripheral enables, when it is inflated, accurate positioning of the core. This implant provides a great mobility from one vertebra to another vertebra (rotation and/or flexion). Since the core is harder than the chamber it acts as a pivot, thereby making these movements easier. 
     In another embodiment, a nucleus implant is disclosed. The nucleus implant can be configured to be installed within an intervertebral disc between an inferior vertebra and a superior vertebra. The nucleus implant can include an expandable core and a toroid shaped expandable chamber that can be disposed at least partially around the expandable core. Moreover, a hardness of the expandable core, when inflated, can be greater or equal to than a hardness of the toroid shaped expandable chamber when inflated. 
     In yet another embodiment, a nucleus implant is disclosed. The nucleus implant can be configured to be installed within an intervertebral disc between an inferior vertebra and a superior vertebra. The nucleus implant can include an expandable core that can include an outer surface. Also, the nucleus implant can include a first toroid shaped expandable chamber that can be disposed at least partially around the expandable core and a second toroid shaped expandable chamber that can be disposed at least partially around the first toroid shaped expandable chamber. A hardness of the expandable core can be greater than or equal to a hardness of the first expandable chamber and the hardness of the first expandable chamber can be greater than or equal to a hardness of the second expandable chamber when the expandable core, the first expandable chamber, and the second expandable chamber are inflated. 
     In still another embodiment, a nucleus implant is disclosed. The nucleus implant can be configured to be installed within an intervertebral disc between an inferior vertebra and a superior vertebra. The nucleus implant can include an expandable core and a bowl shaped expandable chamber that can be disposed at least partially around the expandable core. A hardness of the expandable core when inflated can be greater than or equal to a hardness of the bowl shaped expandable chamber when inflated. 
     In yet still another embodiment, a nucleus implant is disclosed. The nucleus implant can be configured to be installed within an intervertebral disc between an inferior vertebra and a superior vertebra. The nucleus implant can include an expandable core that can include an outer surface and a U shaped expandable chamber that can be disposed at least partially around the expandable core. A hardness of the expandable core when inflated can be greater than or equal to a hardness of the U shaped expandable chamber when inflated. 
     In another embodiment, a method of installing a nucleus implant within an intervertebral disc between an inferior vertebra and a superior vertebra of a patient is disclosed. The method can include implanting the nucleus implant within the intervertebral disc. Further, the nucleus implant can include an expandable core and an expandable chamber at least partially around the expandable core. The method can also include inflating the expandable core and inflating the expandable chamber around the expandable core. A hardness of the expandable core when inflated can be greater than or equal to a hardness of the expandable chamber when inflated. 
     In yet another embodiment, a method of installing a nucleus implant within an intervertebral disc between an inferior vertebra and a superior vertebra of a patient is disclosed. The method can include implanting the nucleus implant within the intervertebral disc. The nucleus implant can include an expandable core, a first expandable chamber at least partially around the expandable core, and a second expandable chamber at least partially around the first expandable chamber. Moreover, the method can inflating the expandable core, inflating the first expandable chamber around the expandable core, inflating the second expandable chamber around the first expandable chamber. A hardness of the expandable core when inflated can be greater than or equal to a hardness of the first expandable chamber when inflated. Also, the hardness of the first expandable chamber when inflated can be greater than or equal to a hardness of the second expandable chamber when inflated. 
     In still yet another embodiment, a method of installing a nucleus implant within an intervertebral disc between an inferior vertebra and a superior vertebra of a patient is disclosed. The method can include implanting the nucleus implant within the intervertebral disc. The nucleus implant can include an expandable core and an expandable chamber at least partially around the expandable core. Additionally, the method can include inflating the expandable chamber and inflating the expandable core within the expandable chamber. A hardness of the expandable core when inflated can be greater than or equal to a hardness of the expandable chamber when inflated. 
     Description of Relevant Anatomy 
     Referring initially to  FIG. 1 , a portion of a vertebral column, designated  100 , is shown. As depicted, the vertebral column  100  includes a lumber region  102 , a sacral region  104 , and a coccygeal region  106 . As is known in the art, the vertebral column  100  also includes a cervical region and a thoracic region. For clarity and ease of discussion, the cervical region and the thoracic region are not illustrated. 
     As shown in  FIG. 1 , the lumbar region  102  includes a first lumber vertebra  108 , a second lumbar vertebra  110 , a third lumbar vertebra  112 , a fourth lumbar vertebra  114 , and a fifth lumbar vertebra  116 . The sacral region  104  includes a sacrum  118 . Further, the coccygeal region  106  includes a coccyx  120 . 
     As depicted in  FIG. 1 , a first intervertebral lumbar disc  122  is disposed between the first lumber vertebra  108  and the second lumbar vertebra  110 . A second intervertebral lumbar disc  124  is disposed between the second lumbar vertebra  110  and the third lumbar vertebra  112 . A third intervertebral lumbar disc  126  is disposed between the third lumbar vertebra  112  and the fourth lumbar vertebra  114 . Further, a fourth intervertebral lumbar disc  128  is disposed between the fourth lumbar vertebra  114  and the fifth lumbar vertebra  116 . Additionally, a fifth intervertebral lumbar disc  130  is disposed between the fifth lumbar vertebra  116  and the sacrum  118 . 
       FIG. 2  depicts a detailed lateral view of two adjacent vertebrae, e.g., two of the lumbar vertebra  108 ,  110 ,  112 ,  114 ,  116  shown in  FIG. 1 .  FIG. 2  illustrates a superior vertebra  200  and an inferior vertebra  202 . As shown, each vertebra  200 ,  202  includes a vertebral body  204 , a superior articular process  206 , a transverse process  208 , a spinous process  210  and an inferior articular process  212 .  FIG. 2  further depicts an intervertebral space  214  that can be established between the superior vertebra  200  and the inferior vertebra  202  by removing an intervertebral disc  216  (shown in dashed lines). 
     Referring to  FIG. 3 , a vertebra, e.g., the inferior vertebra  202  ( FIG. 2 ), is illustrated. As shown, the vertebral body  204  of the inferior vertebra  202  includes a cortical rim  302  composed of cortical bone. Also, the vertebral body  204  includes cancellous bone  304  within the cortical rim  302 . The cortical rim  302  is often referred to as the apophyseal rim or apophyseal ring. Further, the cancellous bone  304  is softer and weaker than the cortical bone of the cortical rim  302 . 
     As illustrated in  FIG. 3 , the inferior vertebra  202  further includes a first pedicle  306 , a second pedicle  308 , a first lamina  310 , and a second lamina  312 . Further, a vertebral foramen  314  is established within the inferior vertebra  202 . A spinal cord  316  passes through the vertebral foramen  314 . Moreover, a first nerve root  318  and a second nerve root  320  extend from the spinal cord  316 . 
     It is well known in the art that the vertebrae that make up the vertebral column have slightly different appearances as they range from the cervical region to the lumbar region of the vertebral column. However, all of the vertebrae, except the first and second cervical vertebrae, have the same basic structures, e.g., those structures described above in conjunction with  FIG. 2  and  FIG. 3 . The first and second cervical vertebrae are structurally different than the rest of the vertebrae in order to support a skull. 
     Referring now to  FIG. 4 , an intervertebral disc is shown and is generally designated  400 . The intervertebral disc  400  is made up of two components: the annulus fibrosus  402  and the nucleus pulposus  404 . The annulus fibrosus  402  is the outer portion of the intervertebral disc  400 , and the annulus fibrosus  402  includes a plurality of lamellae  406 . The lamellae  406  are layers of collagen and proteins. Each lamella  406  includes fibers that slant at 30-degree angles, and the fibers of each lamella  406  run in a direction opposite the adjacent layers. Accordingly, the annulus fibrosus  402  is a structure that is exceptionally strong, yet extremely flexible. 
     The nucleus pulposus  404  is the inner gel material that is surrounded by the annulus fibrosus  402 . It makes up about forty percent (40%) of the intervertebral disc  400 . Moreover, the nucleus pulposus  404  can be considered a ball-like gel that is contained within the lamellae  406 . The nucleus pulposus  404  includes loose collagen fibers, water, and proteins. The water content of the nucleus pulposus  404  is about ninety percent (90%) at birth and decreases to about seventy percent (70%) by the fifth decade. 
     Injury or aging of the annulus fibrosus  402  may allow the nucleus pulposus  404  to be squeezed through the annulus fibers either partially, causing the disc to bulge, or completely, allowing the disc material to escape the intervertebral disc  400 . The bulging disc or nucleus material may compress the nerves or spinal cord, causing pain. Accordingly, the nucleus pulposus  404  can be removed and replaced with an artificial nucleus. 
     DESCRIPTION OF A FIRST EMBODIMENT OF A NUCLEUS IMPLANT 
     Referring to  FIG. 5  through  FIG. 7 , an embodiment of a nucleus implant is shown and is designated  500 . As shown, the nucleus implant  500  includes an expandable core  502  that defines an outer surface  504 . In a particular embodiment, when inflated, the expandable core  502  can have a cross-section that is generally elliptical. Alternatively, the expandable core  502  can have a cross-section that is: generally circular, generally rectangular, generally square, generally triangular, generally trapezoidal, generally rhombic, generally quadrilateral, any generally polygonal shape, or any combination thereof. 
     As illustrated in  FIG. 5  and  FIG. 6 , an expandable chamber  506  can be disposed around the expandable core  502 . In a particular embodiment, as shown, the expandable chamber  506  can have a generally toroidal shape. The shape of the chamber enables, when expanded or inflated, automatic positioning of the core. Further, when expanded, or inflated, the expandable chamber  506  can have a cross-section that is generally shaped like a kidney bean. Alternatively, the expandable chamber  506  can have a cross-section that is: generally elliptical, generally circular, generally rectangular, generally square, generally triangular, generally trapezoidal, generally rhombic, generally quadrilateral, any generally polygonal shape, or any combination thereof. 
     The expandable chamber  506  can define an inner surface  508  and an outer surface  510 . In a particular embodiment, the inner surface  508  of the expandable chamber  506  can be attached to the outer surface  504  of the expandable core  502 , for example, by gluing. As such, proper placement of the expandable chamber  506  can be based on the placement of the expandable core  502 . Alternatively, the expandable chamber  506  can be separate from the expandable core  502  and the expandable chamber  506  may engage the expandable core  502  after the expandable chamber  506  is properly inflated. Alternatively, the core and the chamber may be made of one and the same element, for example, for the sake of convenience. 
     As depicted in  FIG. 5 , the nucleus implant can include a first injection tube  512  that extends from the outer surface  504  of the expandable core  502 . Further, the nucleus implant  500  can include a second injection tube  514  that extends from the outer surface  510  of the expandable chamber  506 . In a particular embodiment, each of the expandable core  502  and the expandable chamber  506  of the nucleus implant  500  is expandable from a respective deflated position, shown in  FIG. 5 , to one selected position among a plurality of inflated positions, shown in  FIG. 6 , up to a maximum inflated position. Further, after the expandable core  502  and the expandable chamber  506  are inflated, or otherwise expanded, the injection tubes  512 ,  514  can be removed, as depicted in  FIG. 6 . 
     In a particular embodiment, the nucleus implant  500  can include a first self-sealing valve (not shown) within the outer surface  504  of the expandable core  502 , e.g., adjacent to the first injection tube  512 . Moreover, the nucleus implant  500  can include a second self-sealing valve (not shown) within the outer surface  510  of the expandable chamber  506 , e.g., adjacent to the second injection tube  514 . The self-sealing valves can prevent the expandable core  502  and the expandable chamber  506  from leaking material after the expandable core  502  and the expandable chamber  506  are inflated and the injection tubes  512 ,  514  are removed. 
       FIG. 7  indicates that the nucleus implant  500  can be implanted within an intervertebral disc  600  between a superior vertebra  700  and an inferior vertebra  702 . More specifically, the nucleus implant  500  can be implanted within an intervertebral disc space  602  established within the annulus fibrosus  604  of the intervertebral disc  600 . The intervertebral disc space  602  can be established by removing the nucleus pulposus (not shown) from within the annulus fibrosus  604 . 
     In a particular embodiment, the expandable core  502  and the expandable chamber  506  can be inflated so the inner surface  508  of the expandable chamber  506  engages the outer surface of the expandable core  502  and the outer surface  510  of the expandable chamber  506  engages the annulus fibrosis  604 . The nucleus implant  500  can provide shock-absorbing characteristics substantially similar to the shock absorbing characteristics provided by the nucleus pulposus. Further, in a particular embodiment, the hardness of the expandable core  502  of the nucleus implant  500  is greater than or equal to the hardness of the material used to inflate the expandable chamber  506 , i.e., after the materials used to inflate the expandable core  502  and the expandable chamber  506  are cured. Alternatively, the viscosity of the material used to inflate the expandable core  502  is greater than or equal to the viscosity of the material used to inflate the expandable chamber  506 . As one example, the core has a hardness of 55 Shore D and the expandable chamber has a hardness of 40 Shore D. 
     Additionally, in a particular embodiment, the height of the expandable core  502  is greater than or equal to the height of the expandable chamber  506  when each is properly expanded within the intervertebral disc  600 . As shown in  FIG. 7 , the expandable core  502  and the expandable chamber  506  of the nucleus implant  500  can be configured to provide proper support and spacing between the superior vertebra  700  and the inferior vertebra  702 . 
     In a particular embodiment, the expandable core  502 , the expandable chamber  506 , or both the expandable core  502  and the expandable chamber  506  of the nucleus implant  500  can be inflated with one or more injectable extended use approved medical materials that remain elastic after curing. Further, the injectable extended use approved medical materials can include polymer materials that remain elastic after curing. 
     For example, the polymer materials can include polyurethane materials, polyolefin materials, polyether materials, silicone materials, or a combination thereof. Further, the polyolefin materials can include polypropylene, polyethylene, halogenated polyolefin, flouropolyolefin, or a combination thereof. The polyether materials can include polyetherketone (PEK), polyetheretherketone (PEEK), polyetherketoneketone (PEKK), polyaryletherketone (PAEK), or a combination thereof. Also, the silicone materials can include a silicone hydrogel. 
     In an alternative embodiment, the injectable extended use approved medical materials can include one or more fluids such as sterile water, saline, or sterile air. In alternative embodiments, the expandable core  502 , the expandable chamber  506 , or both the expandable core  502  and the expandable chamber  506  of the nucleus implant  500  can be inflated with one or more of the following: fibroblasts, lipoblasts, chondroblasts, differentiated stem cells or other biologic factor which would create a motion limiting tissue when injected into a bioresorbable motion limiting scaffold. 
     In a particular embodiment, the nucleus implant  500  can be installed using a posterior surgical approach, as shown. Further, the nucleus implant  500  can be installed through a posterior incision  606  made within the annulus fibrosus  604  of the intervertebral disc  600 . Alternatively, the nucleus implant  500  can be installed using an anterior surgical approach, a lateral surgical approach, or any other surgical approach well known in the art. 
     DESCRIPTION OF A SECOND EMBODIMENT OF A NUCLEUS IMPLANT 
     Referring to  FIG. 8  through  FIG. 10 , a second embodiment of a nucleus implant is shown and is designated  800 . As shown, the nucleus implant  800  includes an expandable core  802  that defines an outer surface  804 . In a particular embodiment, when inflated, or otherwise expanded, the expandable core  802  can have a cross-section that is generally elliptical. Alternatively, the expandable core  802  can have a cross-section that is: generally circular, generally rectangular, generally square, generally triangular, generally trapezoidal, generally rhombic, generally quadrilateral, any generally polygonal shape, or any combination thereof. 
     As illustrated in  FIG. 8  through  FIG. 10 , an expandable chamber  806  can be disposed around the expandable core  802 . In a particular embodiment, when expanded, or otherwise inflated, the expandable chamber  806  can have a generally inverted-bowl shape and the expandable chamber  806  can be draped, or otherwise placed, over the expandable core  802  as shown in  FIG. 10 . 
     The thus shaped chamber that is arranged around the core may enable accurate positioning of the core. The accuracy of the core positioning may be increased by inflating the chamber with a uniform pressure. 
     The expandable chamber  806  can define an inner surface  808  and an outer surface  810 . In a particular embodiment, the inner surface  808  of the expandable chamber  806  can be attached to the outer surface  804  of the expandable core  802 . As such, proper placement of the expandable chamber  806  can be based on the placement of the expandable core  802 . Alternatively, the expandable chamber  806  can be separate from the expandable core  802  and the expandable chamber  806  may engage the expandable core  802  after the expandable chamber  806  and the expandable core  802  are properly inflated. 
     As depicted in  FIG. 8 , the nucleus implant  800  can include a first injection tube  812  that extends from the outer surface  804  of the expandable core  802 . Further, the nucleus implant  800  can include a second injection tube  814  that extends from the outer surface  810  of the expandable chamber  806 . In a particular embodiment, each of the expandable core  802  and the expandable chamber  806  of the nucleus implant  800  is expandable from a deflated position, shown in  FIG. 8 , to one selected position among a plurality of inflated positions, shown in  FIG. 9 , up to a maximum inflated position. Further, after the expandable core  802  and the expandable chamber  806  are inflated, or otherwise expanded, the injection tubes  812 ,  814  can be removed, as depicted in  FIG. 9 . 
     In a particular embodiment, the nucleus implant  800  can include a first self-sealing valve (not shown) within the outer surface  804  of the expandable core  802 , e.g., adjacent to the first injection tube  812 . Moreover, the nucleus implant  800  can include a second self-sealing valve (not shown) within the outer surface  810  of the expandable chamber  806 , e.g., adjacent to the second injection tube  814 . The self-sealing valves can prevent the expandable core  802  and the expandable chamber  806  from leaking material after the expandable core  802  and the expandable chamber  806  are inflated and the injection tubes  812 ,  814  are removed. 
       FIG. 10  indicates that the nucleus implant  800  can be implanted within an intervertebral disc  900  between a superior vertebra  1000  and an inferior vertebra  1002 . More specifically, the nucleus implant  800  can be implanted within an intervertebral disc space  902  established within the annulus fibrosus  904  of the intervertebral disc  900 . The intervertebral disc space  902  can be established by removing the nucleus pulposus (not shown) from within the annulus fibrosus  904 . 
     In a particular embodiment, the expandable core  802  and the expandable chamber  806  can be inflated so the inner surface  808  of the expandable chamber  806  engages the outer surface of the expandable core  802  and the outer surface  810  of the expandable chamber  806  engages the annulus fibrosis  904 . Further, portions of the outer surface  810  of the expandable chamber  806  can engage the superior vertebra  1000  and an inferior vertebra  1002 . Moreover, when the expandable core  802  and the expandable chamber  806  are expanded, or otherwise inflated, a portion of the expandable chamber  806  is located between the expandable core  802  and the superior vertebra  1000 . 
     The nucleus implant  800  can provide shock-absorbing characteristics substantially similar to the shock absorbing characteristics provided by the nucleus pulposus. Further, in a particular embodiment, the hardness of the expandable core  802  of the nucleus implant  800  is greater than or equal to the hardness of the material used to inflate the expandable chamber  806 , i.e., after the materials used to inflate the expandable core  802  and the expandable chamber  806  are cured. Alternatively, the viscosity of the material used to inflate the expandable core  802  is greater than or equal to the material used to inflate the expandable chamber  806 . As shown in  FIG. 10 , the expandable core  802  and the expandable chamber  806  of the nucleus implant  800  can be configured to provide proper support and spacing between the superior vertebra  1000  and the inferior vertebra  1002 . 
     In a particular embodiment, the expandable core  802 , the expandable chamber  806 , or both the expandable core  802  and the expandable chamber  806  of the nucleus implant  800  can be inflated with one or more injectable extended use approved medical materials that remain elastic after curing. Further, the injectable extended use approved medical materials can include polymer materials that remain elastic after curing. 
     For example, the polymer materials can include polyurethane materials, polyolefin materials, polyether materials, silicone materials, or a combination thereof. Further, the polyolefin materials can include polypropylene, polyethylene, halogenated polyolefin, flouropolyolefin, or a combination thereof. The polyether materials can include polyetherketone (PEK), polyetheretherketone (PEEK), polyetherketoneketone (PEKK), polyaryletherketone (PAEK), or a combination thereof. Also, the silicone materials can include a silicone hydrogel. 
     In an alternative embodiment, the injectable extended use approved medical materials can include one or more fluids such as sterile water, saline, or sterile air. In alternative embodiments, the expandable core  802 , the expandable chamber  806 , or both the expandable core  802  and the expandable chamber  806  of the nucleus implant  800  can be inflated with one or more of the following: fibroblasts, lipoblasts, chondroblasts, differentiated stem cells or other biologic factor which would create a motion limiting tissue when injected into a bioresorbable motion limiting scaffold. 
     In a particular embodiment, the nucleus implant  800  can be installed using a posterior surgical approach, as shown. Further, the nucleus implant  800  can be installed through a posterior incision  906  made within the annulus fibrosus  904  of the intervertebral disc  900 . When the chamber has been inflated, the core is not able to get out through the incision  906  after its installation. This is because the bottom of the chamber having a generally inverted-bowl shape is placed between the incision and the core. Alternatively, the nucleus implant  800  can be installed using an anterior surgical approach, a lateral surgical approach, or any other surgical approach well known in the art. 
       FIG. 11  illustrates a first embodiment of an injection tube set  1100  that can be used in conjunction with the first nucleus implant  500  or second nucleus implant  800 , described above. As shown, the injection tube set  1100  includes a first injection tube  1102  and second injection tube  1104 . Further, the injection tubes  1102 ,  1104  are separate tubes. 
       FIG. 12  shows a second embodiment of an injection tube set  1200  that can be used in conjunction with the first nucleus implant  500  or second nucleus implant  800 , described above. As shown, the injection tube set  1200  can include a first injection tube  1202  and second injection tube  1204 . Further, the injection tubes  1202 ,  1204  can be positioned tangential to each other and the injection tubes  1202 ,  1204  can be disposed, or otherwise placed, within a jacket  1206 . In a particular embodiment, the jacket  1206  can protect the injection tubes  1202 ,  1204  and the jacket  1206  can facilitate insertion of a nucleus implant within an intervertebral disc. 
       FIG. 13  depicts a third embodiment of an injection tube set  1300  that can be used in conjunction with the first nucleus implant  500  or second nucleus implant  800 , described above. As shown, the injection tube set  1300  includes a first injection tube  1302  and second injection tube  1304  disposed around the first injection tube  1302 . In this particular embodiment, the first injection tube  1302  and the second injection tube  1304  can be coaxial or concentric. 
     DESCRIPTION OF A FIRST EMBODIMENT OF A METHOD OF INSTALLING A NUCLEUS IMPLANT 
     Referring to  FIG. 14 , an exemplary, non-limiting embodiment of a method of installing a nucleus implant is shown and commences at block  1400 . At block  1400 , a patient is secured on an operating table. For example, the patient can be secured in a supine position to allow an anterior approach to be used to access the patient&#39;s spinal column. Further, the patient may be placed in a “French” position in which the patient&#39;s legs are spread apart. The “French” position can allow the surgeon to stand between the patient&#39;s legs. Further, the “French” position can facilitate proper alignment of the surgical instruments with the patient&#39;s spine. In another particular embodiment, the patient can be secured in the supine position on an adjustable surgical table. 
     In one or more alternative embodiments, a surgeon can use a posterior approach or a lateral approach to implant an intervertebral prosthetic device. As such, the patient may be secured in a different position, e.g., in a prone position for a posterior approach or in a lateral decubitus position for a lateral approach. 
     Moving to block  1402 , the location of the affected disc is marked on the patient, e.g., with the aid of fluoroscopy. At block  1404 , the surgical area along spinal column is exposed. Further, at block  1406 , a surgical retractor system can be installed to keep the surgical field open. For example, the surgical retractor system can be a Medtronic Sofamor Danek Endoring™ Surgical Retractor System. 
     Proceeding to block  1408 , the annulus fibrosus of the affected disc is incised to expose the nucleus pulposus. Further, at block  1410 , the nucleus pulposus is removed to create an intervertebral disc space within the annulus fibrosus. At block  1412 , the nucleus implant is inserted within the intervertebral disc space of the annulus fibrosus. Further, at block  1414 , the expandable core is inflated. At block  1416 , the inflated core is aligned. Moving to block  1418 , the expandable chamber is inflated, or otherwise expanded, around the inflated core, thereby enabling positioning and retention of the core. Alternatively, the chamber may be inflated before the core. 
     At block  1420 , the first injection tube, i.e., the injection tube attached to the expandable core, can be removed. Continuing to block  1422 , the expandable core is sealed—if the expandable chamber is not self-sealing, e.g., with a self-sealing valve. At block  1424 , the second injection tube, i.e., the injection tube coupled to the expandable chamber, can be removed. Moreover, at block  1426 , the expandable chamber is sealed—if the expandable chamber is not self-sealing, e.g., with a self-sealing valve. At block  1428 , the material used to inflate, or expand, the expandable core and the expandable chamber can be cured. In a particular embodiment, the material can be allowed to cure naturally under the ambient conditions of the operating room. Alternatively, the material can be cured using an energy source. For example, the energy source can be a light source that emits visible light, infrared (IR) light, or ultra-violet (UV) light. Further, the energy source can be a heating device, a radiation device, or other mechanical device. 
     Proceeding to block  1430 , the annulus fibrosus is sutured. At block  1432 , the intervertebral space can be irrigated. Further, at block  1434 , the retractor system can be removed. At block  1436 , a drainage, e.g., a retroperitoneal drainage, can be inserted into the wound. Additionally, at block  1438 , the surgical wound can be closed. The surgical wound can be closed using sutures, surgical staples, or any other surgical technique well known in the art. Moving to block  1440 , postoperative care can be initiated. The method ends at state  1442 . 
     DESCRIPTION OF A THIRD EMBODIMENT OF A NUCLEUS IMPLANT 
     Referring to  FIG. 15  through  FIG. 17 , a third embodiment of a nucleus implant is shown and is designated  1500 . As shown, the nucleus implant  1500  includes an expandable core  1502  that defines an outer surface  1504 . In a particular embodiment, when inflated, the expandable core  1502  can have a cross-section that is generally elliptical. Alternatively, when inflated, the expandable core  1502  can have a cross-section that is: generally circular, generally rectangular, generally square, generally triangular, generally trapezoidal, generally rhombic, generally quadrilateral, any generally polygonal shape, or any combination thereof. 
     As illustrated in  FIG. 15  and  FIG. 16 , a first expandable chamber  1506  can be disposed around the expandable core  1502 . In a particular embodiment, as shown, the first expandable chamber  1506  can have a generally toroidal shape. Further, as shown in  FIG. 17 , the first expandable chamber  1506  can have a cross-section that is generally shaped like a kidney bean when the first expandable chamber  1506  is inflated. Alternatively, when inflated, the first expandable chamber  1506  can have a cross-section that is: generally elliptical, generally circular, generally rectangular, generally square, generally triangular, generally trapezoidal, generally rhombic, generally quadrilateral, any generally polygonal shape, or any combination thereof. 
     The first expandable chamber  1506  can define an inner surface  1508  and an outer surface  1510 . In a particular embodiment, the inner surface  1508  of the first expandable chamber  1506  can be attached to the outer surface  1504  of the expandable core  1502 . As such, proper placement of the first expandable chamber  1506  can be based on the placement of the expandable core  1502 . Alternatively, the first expandable chamber  1506  can be separate from the expandable core  1502  and the first expandable chamber  1506  may engage the expandable core  1502  after the first expandable chamber  1506  is properly inflated. 
     As depicted in  FIG. 15 , the nucleus implant  1500  can include a first injection tube  1512  that extends from the outer surface  1504  of the expandable core  1502 . Further, the nucleus implant  1500  can include a second injection tube  1514  that extends from the outer surface  1510  of the first expandable chamber  1506 . 
       FIG. 15  through  FIG. 17  further show that the nucleus implant  1500  can include a second expandable chamber  1516  that can be disposed around the first expandable chamber  1506 . In a particular embodiment, the second expandable chamber  1516  can have a generally toroidal shape. Further, when inflated, the second expandable chamber  1516  can have a cross-section that is generally shaped like a kidney bean. Alternatively, when inflated, the second expandable chamber  1516  can have a cross-section that is: generally elliptical, generally circular, generally rectangular, generally square, generally triangular, generally trapezoidal, generally rhombic, generally quadrilateral, any generally polygonal shape, or any combination thereof. 
     The second expandable chamber  1516  can define an inner surface  1518  and an outer surface  1520 . In a particular embodiment, the inner surface  1518  of the second expandable chamber  1516  can be attached to the outer surface  1510  of the first expandable chamber  1506  and the inner surface  1508  of the first expandable chamber  1506  can be attached to the outer surface  1504  of the expandable core  1502 . Alternatively, the second expandable chamber  1516  can be separate from the first expandable chamber  1506  and the expandable core  1502 . In such a configuration, the second expandable chamber  1516  can engage the first expandable chamber  1506  after the first expandable chamber  1506  and the second expandable chamber  1516  are properly inflated. An implant with several chambers may enable more fine adjustment of the position of the core than with a single chamber. 
     As illustrated in  FIG. 15 , the nucleus implant  1500  can include a third injection tube  1522  that extends from the outer surface  1520  of the second expandable chamber  1516 . In a particular embodiment, each of the expandable core  1502 , the first expandable chamber  1506 , and the second expandable chamber  1516  of the nucleus implant  1500  is expandable from a deflated position, shown in  FIG. 15 , to one selected position among a plurality of inflated positions, shown in  FIG. 16 , up to a maximum inflated position. Further, after the expandable core  1502 , the first expandable chamber  1506 , and the second expandable chamber  1516  are inflated, or otherwise expanded, the injection tubes  1512 ,  1514 ,  1522  can be removed, as depicted in  FIG. 16 . 
     In a particular embodiment, the nucleus implant  1500  can include a first self-sealing valve (not shown) within the outer surface  1504  of the expandable core  1502 , e.g., adjacent to the first injection tube  1512 . The nucleus implant  1500  can also include a second self-sealing valve (not shown) within the outer surface  1510  of the first expandable chamber  1506 , e.g., adjacent to the second injection tube  1514 . Further, the nucleus implant  1500  can include a third self-sealing valve (not shown) within the outer surface  1520  of the second expandable chamber  1516 , e.g., adjacent to the third injection tube  1522 . The self-sealing valves can prevent the expandable core  1502  and the expandable chambers  1506 ,  1516  from leaking material after the expandable core  1502  and the expandable chambers  1506 ,  1516  are inflated and the injection tubes  1512 ,  1514 ,  1522  are removed. 
       FIG. 17  indicates that the nucleus implant  1500  can be implanted within an intervertebral disc  1600  between a superior vertebra  1700  and an inferior vertebra  1702 . More specifically, the nucleus implant  1500  can be implanted within an intervertebral disc space  1602  established within the annulus fibrosus  1604  of the intervertebral disc  1600 . The intervertebral disc space  1602  can be established by removing the nucleus pulposus (not shown) from within the annulus fibrosus  1604 . 
     In a particular embodiment, the expandable core  1502 , the first expandable chamber  1506 , and the second expandable chamber  1516  can be inflated so the inner surface  1508  of the first expandable chamber  1506  engages the outer surface of the expandable core  1502  and the outer surface  1510  of the first expandable chamber  1506  engages the inner surface  1518  of the second expandable chamber  1516 . Further, the outer surface  1520  of the second expandable chamber  1516  can engage the annulus fibrosis  1604 . 
     The nucleus implant  1500  can provide shock-absorbing characteristics substantially similar to the shock absorbing characteristics provided by the nucleus pulposus. Further, in a particular embodiment, the hardness of the material used to inflate the expandable core  1502  of the nucleus implant  1500  is greater than or equal to the hardness of the material used to inflate the first expandable chamber  1506 , i.e., after the materials cure. Moreover, the hardness of the material used to inflate the first expandable chamber  1506  can be greater than or equal to the hardness of the material used to inflate the second expandable chamber  1516 , e.g., after those materials cure. 
     Arranging several expandable chambers around a core may result in an implant with hardness that varies more progressively from the core towards the periphery than with a single chamber. Thus, an implant with a very hard core and a very soft periphery may be obtained. Moreover, an implant with several variable hardness chambers may more easily spread the loads exerted at the vertebral level. In addition, the mobility of the thus arranged implant is better controlled. As one example, the core has a hardness of 55 Shore D, the first chamber has a hardness of 50 Shore D and the second chamber has a hardness of 40 Shore D. 
     Alternatively, the viscosity of the material used to inflate the expandable core  1502  of the nucleus implant  1500  can be greater than or equal to the viscosity of the material used to inflate the first expandable chamber  1506 . Also, the viscosity of the material used to inflate the first expandable chamber  1506  can be greater than or equal to the viscosity of the material used to inflate the second expandable chamber  1516 . 
     Additionally, the height of the expandable core  1502 , when expanded, can be greater than or equal to the height of the first expandable chamber  1506  when expanded. Also, the height of the first expandable chamber  1506 , when expanded, can be greater than or equal to the height of the second expandable chamber  1516  when expanded. As shown in  FIG. 17 , the expandable core  1502 , the first expandable chamber  1506 , and the second expandable chamber  1516  of the nucleus implant  1500  can be configured to provide proper support and spacing between the superior vertebra  1700  and the inferior vertebra  1702 . 
     In a particular embodiment, the expandable core  1502 , the first expandable chamber  1506 , the second expandable chamber  1516 , or a combination of the expandable core  1502 , the first expandable chamber  1506 , and the second expandable chamber  1516  of the nucleus implant  1500  can be inflated with one or more injectable extended use approved medical materials that remain elastic after curing. Further, the injectable extended use approved medical materials can include polymer materials that remain elastic after curing. 
     For example, the polymer materials can include polyurethane materials, polyolefin materials, polyether materials, silicone materials, or a combination thereof. Further, the polyolefin materials can include polypropylene, polyethylene, halogenated polyolefin, flouropolyolefin, or a combination thereof. The polyether materials can include polyetherketone (PEK), polyetheretherketone (PEEK), polyetherketoneketone (PEKK), polyaryletherketone (PAEK), or a combination thereof. Also, the silicone materials can include a silicone hydrogel. 
     In an alternative embodiment, the injectable extended use approved medical materials can include one or more fluids such as sterile water, saline, or sterile air. In alternative embodiments, the expandable core  1502 , the first expandable chamber  1506 , the second expandable chamber  1516 , or a combination of the expandable core  1502 , the first expandable chamber  1506 , and the second expandable chamber  1516  of the nucleus implant  1500  can be inflated with one or more of the following: fibroblasts, lipoblasts, chondroblasts, differentiated stem cells or other biologic factor which would create a motion limiting tissue when injected into a bioresorbable motion limiting scaffold. 
     In a particular embodiment, the nucleus implant  1500  can be installed using a posterior surgical approach, as shown. Further, the nucleus implant  1500  can be installed through a posterior incision  1606  made within the annulus fibrosus  1604  of the intervertebral disc  1600 . Alternatively, the nucleus implant  1500  can be installed using an anterior surgical approach, a lateral surgical approach, or any other surgical approach well known in the art. 
       FIG. 18  illustrates a first embodiment of an injection tube set  1800  that can be used in conjunction a nucleus implant, e.g., the third nucleus implant  1500  described herein. As shown, the injection tube set  1800  includes a first injection tube  1802 , a second injection tube  1804 , and a third injection tube  1806 . As shown, each injection tube  1802 ,  1804 ,  1806  can be tangentially connected to two other injection tubes such that a cross-section of the injection tube set  1800  is generally triangular. 
       FIG. 19  shows a second embodiment of an injection tube set  1900  that can be used in conjunction with a nucleus implant, e.g., the third nucleus implant  1500  described above. As shown, the injection tube set  1900  can include a first injection tube  1902 , a second injection tube  1904 , and a third injection tube  1906 . Each injection tube  1902 ,  1904 ,  1906  can be tangentially connected to two other injection tubes such that a cross-section of the injection tube set  1900  is generally triangular. Further, in a particular embodiment, a jacket  1908  can be disposed around the injection tubes  1902 ,  1904 ,  1906  along the length of the injection tubes  1902 ,  1904 ,  1906 . The jacket  1908  can protect the injection tubes  1902 ,  1904 ,  1906  and the jacket  1908  can facilitate insertion of a nucleus implant within an intervertebral disc. 
       FIG. 20  illustrates a third embodiment of an injection tube set  2000  that can be used in conjunction a nucleus implant, e.g., the third nucleus implant  1500  described herein. As shown, the injection tube set  2000  includes a first injection tube  2002 , a second injection tube  2004 , and a third injection tube  2006 . As shown, the first injection tube  2002  and the third injection tube  2006  can be tangentially connected to the second injection tube  2004  such that the cross-section of the injection tube set  2000  is generally flat. 
       FIG. 21  illustrates a fourth embodiment of an injection tube set  2100  that can be used in conjunction a nucleus implant, e.g., the third nucleus implant  1500  described herein. As shown, the injection tube set  2100  includes a first injection tube  2102 , a second injection tube  2104 , and a third injection tube  2106 . As shown, the first injection tube  2102  and the third injection tube  2106  can be tangentially connected to the second injection tube  2104  such that the cross-section of the injection tube set  2100  is generally flat. Further, in a particular embodiment, a jacket  2108  can be disposed around the injection tubes  2102 ,  2104 ,  2106  along the length of the injection tubes  2102 ,  2104 ,  2106 . The jacket  2108  can protect the injection tubes  2102 ,  2104 ,  2106  and the jacket  2108  can facilitate insertion of a nucleus implant within an intervertebral disc. 
       FIG. 22  depicts a fifth embodiment of an injection tube set  2200  that can be used in conjunction with a nucleus implant, e.g., the third nucleus implant  1500  described above. As shown, the injection tube set  2200  includes a first injection tube  2206 . A second injection tube  2204  can be disposed around the first injection tube  2206 . Further, a third injection tube  2202  can be disposed around the second injection tube  2204 . In this particular embodiment, the first injection tube  2206 , the second injection tube  2204 , and the third injection tube  2202  can be coaxial or concentric. 
     DESCRIPTION OF A SECOND EMBODIMENT OF A METHOD OF INSTALLING A NUCLEUS IMPLANT 
     Referring to  FIG. 23 , a second exemplary, non-limiting embodiment of a method of installing a nucleus implant is shown and commences at block  2300 . At block  2300 , a patient is secured on an operating table. For example, the patient can be secured in a supine position to allow an anterior approach to be used to access the patient&#39;s spinal column. Further, the patient may be placed in a “French” position in which the patient&#39;s legs are spread apart. The “French” position can allow the surgeon to stand between the patient&#39;s legs. Further, the “French” position can facilitate proper alignment of the surgical instruments with the patient&#39;s spine. In another particular embodiment, the patient can be secured in the supine position on an adjustable surgical table. 
     In one or more alternative embodiments, a surgeon can use a posterior approach or a lateral approach to implant an intervertebral prosthetic device. As such, the patient may be secured in a different position, e.g., in a prone position for a posterior approach or in a lateral decubitus position for a lateral approach. 
     Moving to block  2302 , the location of the affected disc is marked on the patient, e.g., with the aid of fluoroscopy. At block  2304 , the surgical area along spinal column is exposed. Further, at block  2306 , a surgical retractor system can be installed to keep the surgical field open. For example, the surgical retractor system can be a Medtronic Sofamor Danek Endoring™ Surgical Retractor System. 
     Proceeding to block  2308 , the annulus fibrosus of the affected disc is incised to expose the nucleus pulposus. Further, at block  2310 , the nucleus pulposus is removed to create an intervertebral disc space within the annulus fibrosus. At block  2312 , the nucleus implant is inserted within the intervertebral disc space of the annulus fibrosus. Further, at block  2314 , the expandable core is inflated. At block  2316 , the inflated core is aligned. Moving to block  2318 , the first expandable chamber is inflated, or otherwise expanded, around the inflated core. At block  2320 , the second expandable chamber is inflated, or otherwise inflated, around the first expandable chamber. 
     Proceeding to block  2322 , the first injection tube, i.e., the injection tube attached to the expandable core, can be removed. At block  2324 , the expandable core is sealed—if the expandable chamber is not self-sealing, e.g., with a self-sealing valve. At block  2326 , the second injection tube, i.e., the injection tube coupled to the first expandable chamber, can be removed. Moreover, at block  2328 , the first expandable chamber is sealed—if the first expandable chamber is not self-sealing, e.g., with a self-sealing valve. Further, at block  2330 , the third injection tube, i.e., the injection tube coupled to the second expandable chamber, can be removed. Moreover, at block  2332 , the second expandable chamber is sealed—if the second expandable chamber is not self-sealing, e.g., with a self-sealing valve. At block  2334 , the material used to inflate, or expand, the expandable core and the expandable chambers can be cured. In a particular embodiment, the material can be allowed to cure naturally under the ambient conditions of the operating room. Alternatively, the material can be cured using an energy source. For example, the energy source can be a light source that emits visible light, infrared (IR) light, or ultra-violet (UV) light. Further, the energy source can be a heating device, a radiation device, or other mechanical device. 
     Proceeding to block  2336 , the annulus fibrosus is sutured. At block  2338 , the intervertebral space can be irrigated. Further, at block  2340 , the retractor system can be removed. At block  2342 , a drainage, e.g., a retroperitoneal drainage, can be inserted into the wound. Additionally, at block  2344 , the surgical wound can be closed. The surgical wound can be closed using sutures, surgical staples, or any other surgical technique well known in the art. Moving to block  2346 , postoperative care can be initiated. The method ends at state  2348 . 
     DESCRIPTION OF A FOURTH EMBODIMENT OF A NUCLEUS IMPLANT 
     Referring to  FIG. 24  through  FIG. 26 , an embodiment of a nucleus implant is shown and is designated  2400 . As shown, the nucleus implant  2400  includes an expandable core  2402  that defines an outer surface  2404 . In a particular embodiment, when inflated, the expandable core  2402  can have a cross-section that is generally elliptical. Alternatively, when inflated, the expandable core  2402  can have a cross-section that is: generally circular, generally rectangular, generally square, generally triangular, generally trapezoidal, generally rhombic, generally quadrilateral, any generally polygonal shape, or any combination thereof. 
     As illustrated in  FIG. 24  through  FIG. 26 , an expandable chamber  2406  can be disposed around the expandable core  2402 . In a particular embodiment, as shown, the expandable chamber  2406  can be generally shaped like the letter “U” and the expandable chamber  2406  can be inflated, or otherwise expanded, around the expandable core  2402 . 
     The U-shaped chamber is particularly suited for avoiding the migration of the core towards the incision through which it has been inserted. This is because the U shape partially surrounding the core blocks this incision. This U shape is also advantageous when the intervertebral disc shape has, in a saggital plane, an obvious trapezoidal shape. An intermediate expandable chamber occupying the space between the core  2402  and the U chamber  2406  ( FIG. 24 ) may be envisaged. This additional arrangement may allow more accurate positioning of the core. 
     The expandable chamber  2406  can define a first surface  2408  and a second surface  2410 . In a particular embodiment, the first surface  2408  of the expandable chamber  2406  can be attached to the outer surface  2404  of the expandable core  2402 . As such, proper placement of the expandable chamber  2406  can be based on the placement of the expandable core  2402 . Alternatively, the expandable chamber  2406  can be separate from the expandable core  2402  and the expandable chamber  2406  may engage the expandable core  2402  after the expandable chamber  2406  is properly inflated. 
     As depicted in  FIG. 24 , the nucleus implant  2400  can include a first injection tube  2412  that extends from the outer surface  2404  of the expandable core  2402 . Further, the nucleus implant  2400  can include a second injection tube  2414  that extends from the second surface  2410  of the expandable chamber  2406 . In a particular embodiment, each of the expandable core  2402  and the expandable chamber  2406  of the nucleus implant  2400  is expandable from a deflated position, shown in  FIG. 24 , to one selected position among a plurality of inflated positions, shown in  FIG. 25 , up to a maximum inflated position. Further, after the expandable core  2402  and the expandable chamber  2406  are inflated, or otherwise expanded, the injection tubes  2412 ,  2414  can be removed, as depicted in  FIG. 25 . 
     In a particular embodiment, the nucleus implant  2400  can include a first self-sealing valve (not shown) within the outer surface  2404  of the expandable core  2402 , e.g., adjacent to the first injection tube  2412 . Also, the nucleus implant  2400  can include a second self-sealing valve (not shown) within the second surface  2410  of the expandable chamber  2406 , e.g., adjacent to the second injection tube  2414 . The self-sealing valves can prevent the expandable core  2402  and the expandable chamber  2406  from leaking material after the expandable core  2402  and the expandable chamber  2406  are inflated and the injection tubes  2412 ,  2414  is removed. 
       FIG. 26  indicates that the nucleus implant  2400  can be implanted within an intervertebral disc  2500  between a superior vertebra  2600  and an inferior vertebra  2602 . More specifically, the nucleus implant  2400  can be implanted within an intervertebral disc space  2502  established within the annulus fibrosus  2504  of the intervertebral disc  2500 . The intervertebral disc space  2502  can be established by removing the nucleus pulposus (not shown) from within the annulus fibrosus  2504 . 
     In a particular embodiment, the expandable core  2402  and the expandable chamber  2406  can be inflated so the first surface  2408  of the expandable chamber  2406  engages a portion of the outer surface of the expandable core  2402  and the second surface  2410  of the expandable chamber  2406  engages a portion of the annulus fibrosis  2504 . Further, portions of the outer surface  2410  of the expandable chamber  2406  can engage the superior vertebra  2600  and an inferior vertebra  2602 . Moreover, when the expandable chamber  2406  is expanded, or otherwise inflated, the expandable chamber  2406  at least partially surrounds the expandable core  2402 . As depicted in  FIG. 25 , the core  2402  is placed between the arms of the U formed by the chamber  2406 . 
     The nucleus implant  2400  can provide shock-absorbing characteristics substantially similar to the shock absorbing characteristics provided by the nucleus pulposus. Further, in a particular embodiment, the hardness of the material used to inflate the expandable core  2402  of the nucleus implant  2400  is greater than or equal to the hardness of the material used to inflate the expandable chamber  2406 , i.e., after the materials cure. Alternatively, the viscosity of the material used to inflate the expandable core  2402  is greater than or equal to the viscosity of the material used to inflate the expandable chamber  2406 . 
     Also, the overall height of the expandable core  2402  is greater than or equal to the overall height of the expandable chamber  2406  when inflated. As shown in  FIG. 26 , the expandable core  2402  and the expandable chamber  2406  of the nucleus implant  2400  can be configured to provide proper support and spacing between the superior vertebra  2600  and the inferior vertebra  2602 . 
     In a particular embodiment, the expandable core  2402 , the expandable chamber  2406 , or a combination of the expandable core  2402  and the expandable chamber  2406  of the nucleus implant  2400  can be inflated with one or more injectable extended use approved medical materials that remain elastic after curing. Further, the injectable extended use approved medical materials can include polymer materials that remain elastic after curing. 
     For example, the polymer materials can include polyurethane materials, polyolefin materials, polyether materials, silicone materials, or a combination thereof. Further, the polyolefin materials can include polypropylene, polyethylene, halogenated polyolefin, flouropolyolefin, or a combination thereof. The polyether materials can include polyetherketone (PEK), polyetheretherketone (PEEK), polyetherketoneketone (PEKK), polyaryletherketone (PAEK), or a combination thereof. Also, the silicone materials can include a silicone hydrogel. 
     In an alternative embodiment, the injectable extended use approved medical materials can include one or more fluids such as sterile water, saline, or sterile air. In alternative embodiments, the expandable core  2402 , the expandable chamber  2406 , or a combination of the expandable core  2402  and the expandable chamber  2406  of the nucleus implant  2400  can be inflated with one or more of the following: fibroblasts, lipoblasts, chondroblasts, differentiated stem cells or other biologic factor which would create a motion limiting tissue when injected into a bioresorbable motion limiting scaffold. 
     The material or materials used for generating the expansion of the core and the chamber can be different for the core and the chamber. This holds true for this or any of the embodiments described herein, particularly when the implant comprises a core and several chambers. 
     In a particular embodiment, the nucleus implant  2400  can be installed using a posterior surgical approach, as shown. Further, the nucleus implant  2400  can be installed through a posterior incision  2506  made within the annulus fibrosus  2504  of the intervertebral disc  2500 . Alternatively, the nucleus implant  2400  can be installed using an anterior surgical approach, a lateral surgical approach, or any other surgical approach well known in the art. 
     DESCRIPTION OF A THIRD EMBODIMENT OF A METHOD OF INSTALLING A NUCLEUS IMPLANT 
     Referring to  FIG. 27 , an exemplary, non-limiting embodiment of a method of installing a nucleus implant is shown and commences at block  2700 . At block  2700 , a patient is secured on an operating table. For example, the patient can be secured in a supine position to allow an anterior approach to be used to access the patient&#39;s spinal column. Further, the patient may be placed in a “French” position in which the patient&#39;s legs are spread apart. The “French” position can allow the surgeon to stand between the patient&#39;s legs. Further, the “French” position can facilitate proper alignment of the surgical instruments with the patient&#39;s spine. In another particular embodiment, the patient can be secured in the supine position on an adjustable surgical table. 
     In one or more alternative embodiments, a surgeon can use a posterior approach or a lateral approach to implant an intervertebral prosthetic device. As such, the patient may be secured in a different position, e.g., in a prone position for a posterior approach or in a lateral decubitus position for a lateral approach. 
     Moving to block  2702 , the location of the affected disc is marked on the patient, e.g., with the aid of fluoroscopy. At block  2704 , the surgical area along spinal column is exposed. Further, at block  2706 , a surgical retractor system can be installed to keep the surgical field open. For example, the surgical retractor system can be a Medtronic Sofamor Danek Endoring™ Surgical Retractor System. 
     Proceeding to block  2708 , the annulus fibrosus of the affected disc is incised to expose the nucleus pulposus. Further, at block  2710 , the nucleus pulposus is removed to create an intervertebral disc space within the annulus fibrosus. At block  2712 , the nucleus implant is inserted within the intervertebral disc space of the annulus fibrosus. Further, at block  2714 , the expandable chamber is inflated. Moving to block  2716 , the expandable core is inflated, or otherwise expanded, within the inflated expandable chamber. 
     At block  2718 , the first injection tube, i.e., the injection tube attached to the expandable core, can be removed. Continuing to block  2720 , the expandable core is sealed—if the expandable chamber is not self-sealing, e.g., with a self-sealing valve. At block  2722 , the second injection tube, i.e., the injection tube coupled to the expandable chamber, can be removed. Moreover, at block  2724 , the expandable chamber is sealed—if the expandable chamber is not self-sealing, e.g., with a self-sealing valve. At block  2726 , the material used to inflate, or expand, the expandable core and the expandable chamber can be cured. In a particular embodiment, the material can be allowed to cure naturally under the ambient conditions of the operating room. Alternatively, the material can be cured using an energy source. For example, the energy source can be a light source that emits visible light, infrared (IR) light, or ultra-violet (UV) light. Further, the energy source can be a heating device, a radiation device, or other mechanical device. 
     Proceeding to block  2728 , the annulus fibrosus is sutured. At block  2730 , the intervertebral space can be irrigated. Further, at block  2732 , the retractor system can be removed. At block  2734 , a drainage, e.g., a retroperitoneal drainage, can be inserted into the wound. Additionally, at block  2736 , the surgical wound can be closed. The surgical wound can be closed using sutures, surgical staples, or any other surgical technique well known in the art. Moving to block  2738 , postoperative care can be initiated. The method ends at state  2740 . 
     CONCLUSION 
     With the configuration of structure described above, the nucleus implant according to one or more of the embodiments provides a device that may be implanted to replace the nucleus pulposus within a natural intervertebral disc that is diseased, degenerated, or otherwise damaged. The nucleus implant can be disposed within an intervertebral disc space that can be established within an intervertebral disc by removing the nucleus pulposus. 
     The above-disclosed subject matter is to be considered illustrative, and not restrictive, and the appended claims are intended to cover all such modifications, enhancements, and other embodiments that fall within the true spirit and scope of the present invention. Thus, to the maximum extent allowed by law, the scope of the present invention is to be determined by the broadest permissible interpretation of the following claims and their equivalents, and shall not be restricted or limited by the foregoing detailed description.