Patent Publication Number: US-2009222093-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 plan view of a third embodiment of a nucleus implant; 
         FIG. 12  is another plan view of the third embodiment of the nucleus implant; 
         FIG. 13  is a cross-section view of the third embodiment of the nucleus implant taken along line  13 - 13  in  FIG. 12 ; 
         FIG. 14  is a plan view of a fourth embodiment of a nucleus implant; 
         FIG. 15  is another plan view of the fourth embodiment of the nucleus implant; 
         FIG. 16  is a cross-section view of the fourth embodiment of the nucleus implant taken along line  16 - 16  in  FIG. 15 ; and 
         FIG. 17  is a plan view of a fifth embodiment of a nucleus implant; 
         FIG. 18  is another plan view of the fifth embodiment of the nucleus implant; 
         FIG. 19  is a cross-section view of the fifth embodiment of the nucleus implant taken along line  19 - 19  in  FIG. 18 ; and 
         FIG. 20  is a flow chart of a 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. Further, the nucleus implant can include a solid core and an expandable chamber that can be disposed at least partially around the solid core. The expandable chamber can be expanded from a deflated position to an inflated position. 
     It will be noted that the chamber that is at least partially arranged around the core enables, when it is inflated, accurate positioning of the core. This implant provides mobility from one vertebra to another vertebra (rotation/flexion). The solid core of the implant makes easy the insertion of the latter in an intervertebral disc. Further, the solid core enables the implant to have certain features/properties (such as hardness) before the expansion of the chamber. This is because it is rather difficult to obtain these features/properties only when inflating the core and the chamber. 
     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 a solid core that can include an outer surface. Also, the nucleus implant can include a toroid shaped expandable chamber that can be disposed at least partially around the solid core. The toroid shaped expandable chamber can include an inner surface and an outer surface. Further, the inner surface of the toroid shaped expandable chamber can engage the outer surface of the solid core and the outer surface of the toroid shaped expandable chamber can engage an annulus fibrosus of an intervertebral disc. 
     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 a solid core that can include an outer surface. Moreover, the nucleus implant can include a first toroid shaped expandable chamber that can be disposed at least partially around the solid core. The first toroid shaped expandable chamber can include an inner surface and an outer surface. The inner surface of the first toroid shaped expandable chamber can engage the outer surface of the solid core. The nucleus implant can also include a second toroid shaped expandable chamber that can disposed at least partially around the first toroid shaped expandable chamber. The second toroid shaped expandable chamber can include an inner surface and an outer surface. Further, the inner surface of the second expandable chamber can engage the outer surface of the first toroid shaped expandable chamber. Also, the outer surface of the second toroid shaped expandable chamber can engage an annulus fibrosus of the intervertebral disc. 
     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. Moreover, the nucleus implant can include a solid core that can include an outer surface. The nucleus implant can also include a bowl shaped expandable chamber that can be disposed at least partially around the solid core. The bowl shaped expandable chamber can include an inner surface and an outer surface. The inner surface of the bowl shaped expandable chamber is configured to engage the outer surface of the solid core and the outer surface of the bowl shaped expandable chamber can engage an annulus fibrosus of the intervertebral disc, the superior vertebra, the inferior vertebra, or a combination thereof. 
     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. Additionally, the nucleus implant can include a solid core that can include an outer surface. The nucleus implant can also include a U shaped expandable chamber that can be disposed at least partially around the solid core. The U shaped expandable chamber can include a first surface and a second surface. The first surface of the U shaped expandable chamber can engage the outer surface of the solid core and the second surface of the U shaped expandable chamber can engage an annulus fibrosus of the intervertebral disc. 
     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. The nucleus implant can include a solid core and an expandable chamber at least partially around the solid core. Further, the method can include inflating the expandable chamber around the solid core. The expandable chamber can include an outer surface that engages an annulus fibrosus of the intervertebral disc when the expandable chamber is inflated. Further, a hardness of the solid core is greater than or equal to a hardness of the expandable chamber. 
     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 a solid core  502  that defines an outer surface  504 . In a particular embodiment, the solid core  502  can have a cross-section that is generally elliptical. Alternatively, the solid 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 solid core  502 . In a particular embodiment, as shown, the expandable chamber  506  can have a generally toroidal shape. The shape of the chamber may enable, when expanded or inflated, the automatic positioning of the core. Further, 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 solid core  502 . As such, proper placement of the expandable chamber  506  can be based on the placement of the solid core  502 . Alternatively, the expandable chamber  506  can be separate from the solid core  502  and the expandable chamber  506  may engage the solid core  502  after the expandable chamber  506  is properly inflated. Alternately, the core and the chamber may be made of one and the same element, for example, for the sake of easiness. 
     As depicted in  FIG. 5 , the nucleus implant  500  can include an injection tube  512  that extends from the outer surface  510  of the expandable chamber  506 . In a particular embodiment, the expandable chamber  506  of the nucleus implant  500  is expandable from a 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 chamber  506  is inflated, or otherwise expanded, the injection tube  512  can be removed, as depicted in  FIG. 6 . 
     Additionally, the nucleus implant  500  can include a core holder  514  that extends from the surface of the solid core  502 . The core holder  514  can be used to position the nucleus implant  500  and hold the nucleus implant  500  in the proper position while the expandable chamber  506  is inflated. Moreover, the core holder  514  can be removed after the expandable chamber  506  is inflated. In a particular embodiment, the nucleus implant  500  can include a self-sealing valve (not shown) within the outer surface  510  of the expandable chamber  506 , e.g., adjacent to the injection tube  512 . The self-sealing valve can prevent the expandable chamber  506  from leaking material after the expandable chamber  506  is inflated and the injection tube  512  is 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 chamber  506  can be inflated so the inner surface  508  of the expandable chamber  506  engages the outer surface of the solid 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 solid 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 that material is cured. Additionally, the height of the solid core  502  can be greater than or equal to the height of the expandable chamber  506  when fully expanded. As shown in  FIG. 7 , the solid 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 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, and silicone materials. Further, the polyolefin materials can include polypropylene, polyethylene, halogenated polyolefin, and flouropolyolefin. The polyether materials can include polyetherketone (PEK), polyetheretherketone (PEEK), polyetherketoneketone (PEKK), and polyaryletherketone (PAEK). 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 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. 
     Forming a hole in the core of the implant may facilitate its manipulation. Further, such a hole may be used for introducing additional elements/other materials such as a temporary radiographic marker. 
     Description of a Second Embodiment of a Nucleus Implant 
     Referring to  FIG. 8  through  FIG. 10 , an embodiment of a nucleus implant is shown and is designated  800 . As shown, the nucleus implant  800  includes a solid core  802  that defines an outer surface  804 . In a particular embodiment, the solid core  802  can have a cross-section that is generally elliptical. Alternatively, the solid 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. 
     Further, the solid core  802  of the nucleus implant  800  can be formed with a hole  805 . In a particular embodiment, the hole  805  is formed in the center of the solid core  802 . Moreover, the hole  805  can have a generally cylindrical shape. Alternatively, the hole  805  can have a generally prismatic shape. Moreover, the hole  805  can have a generally polyhedral shape. 
     As illustrated in  FIG. 8  and  FIG. 9 , an expandable chamber  806  can be disposed around the solid core  802 . In a particular embodiment, as shown, the expandable chamber  806  can have a generally toroidal shape. The shape of the chamber may enable, when expanded or inflated, the automatic positioning of the core. Further, the expandable chamber  806  can have a cross-section that is generally shaped like a kidney bean. Alternatively, the expandable chamber  806  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  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 solid core  802 . As such, proper placement of the expandable chamber  806  can be based on the placement of the solid core  802 . Alternatively, the expandable chamber  806  can be separate from the solid core  802  and the expandable chamber  806  may engage the solid core  802  after the expandable chamber  806  is properly inflated. 
     As depicted in  FIG. 8 , the nucleus implant  800  can include an injection tube  812  that extends from the outer surface  810  of the expandable chamber  806 . In a particular embodiment, 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 chamber  806  is inflated, or otherwise expanded, the injection tube  812  can be removed, as depicted in  FIG. 9 . 
     Additionally, the nucleus implant  800  can include a core holder  814  that extends from the surface of the solid core  802 . The core holder  814  can be used to position the nucleus implant  800  and hold the nucleus implant  800  in the proper position while the expandable chamber  806  is inflated. Moreover, the core holder  814  can be removed after the expandable chamber  806  is inflated. The toroidal shape of the chamber that is arranged around the core may enable accurate positioning of the core. In a particular embodiment, the nucleus implant  800  can include a self-sealing valve (not shown) within the outer surface  810  of the expandable chamber  806 , e.g., adjacent to the injection tube  812 . The self-sealing valve can prevent the expandable chamber  806  from leaking material after the expandable chamber  806  is inflated and the injection tube  812  is 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 chamber  806  can be inflated so the inner surface  808  of the expandable chamber  806  engages the outer surface of the solid core  802  and the outer surface  810  of the expandable chamber  806  engages the annulus fibrosis  904 . 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 solid 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 that material is cured. Additionally, the height of the solid core  802  can be greater than or equal to the height of the expandable chamber  806  when fully expanded. As shown in  FIG. 10 , the solid 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 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, and silicone materials. Further, the polyolefin materials can include polypropylene, polyethylene, halogenated polyolefin, and flouropolyolefin. The polyether materials can include polyetherketone (PEK), polyetheretherketone (PEEK), polyetherketoneketone (PEKK), and polyaryletherketone (PAEK). 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 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 . 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. 
     Description of a Third Embodiment of a Nucleus Implant 
     Referring to  FIG. 11  through  FIG. 13 , a third embodiment of a nucleus implant is shown and is designated  1100 . As shown, the nucleus implant  1100  includes a solid core  1102  that defines an outer surface  1104 . In a particular embodiment, the solid core  1102  can have a cross-section that is generally elliptical. Alternatively, the solid core  1102  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. 11  and  FIG. 12 , a first expandable chamber  1106  can be disposed around the solid core  1102 . In a particular embodiment, as shown, the first expandable chamber  1106  can have a generally toroidal shape. Further, as shown in  FIG. 13 , the first expandable chamber  1106  can have a cross-section that is generally shaped like a kidney bean. Alternatively, the first expandable chamber  1106  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  1106  can define an inner surface  1108  and an outer surface  1110 . In a particular embodiment, the inner surface  1108  of the first expandable chamber  1106  can be attached to the outer surface  1104  of the solid core  1102 . As such, proper placement of the first expandable chamber  1106  can be based on the placement of the solid core  1102 . Alternatively, the first expandable chamber  1106  can be separate from the solid core  1102  and the first expandable chamber  1106  may engage the solid core  1102  after the first expandable chamber  1106  is properly inflated. 
     As depicted in  FIG. 11 , the nucleus implant  1100  includes a first injection tube  1112  that extends from the outer surface  1110  of the first expandable chamber  1106 . In a particular embodiment, the first expandable chamber  1106  of the nucleus implant  1100  is expandable from a deflated position, shown in  FIG. 11 , to one selected position among a plurality of inflated positions, shown in  FIG. 12 , up to a maximum inflated position. Further, after the first expandable chamber  1106  is inflated, or otherwise expanded, the first injection tube  1112  can be removed, as depicted in  FIG. 12 . 
       FIG. 11  through  FIG. 13  further show that the nucleus implant  1100  can include a second expandable chamber  1116  that can be disposed around the first expandable chamber  1106 . In a particular embodiment, as shown, the second expandable chamber  1116  can have a generally toroidal shape. Further, as shown in  FIG. 13 , the second expandable chamber  1116  can have a cross-section that is generally shaped like a kidney bean. Alternatively, the second expandable chamber  1116  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  1116  can define an inner surface  1118  and an outer surface  1120 . In a particular embodiment, the inner surface  1118  of the second expandable chamber  1116  can be attached to the outer surface  1110  of the first expandable chamber  1106  and the inner surface  1108  of the first expandable chamber  1106  can be attached to the outer surface  1104  of the solid core  1102 . Alternatively, the second expandable chamber  1116  can be separate from the first expandable chamber  1106  and the solid core  1102 . In such a configuration, the second expandable chamber  1116  can engage the first expandable chamber  1106  after the first expandable chamber  1106  and the second expandable chamber  1116  are properly inflated. 
     As illustrated in  FIG. 11 , the nucleus implant  1100  includes a second injection tube  1122  that extends from the outer surface  1120  of the second expandable chamber  1116 . In a particular embodiment, the second expandable chamber  1116  of the nucleus implant  1100  is expandable from a deflated position, shown in  FIG. 11 , to one selected position among a plurality of inflated positions, shown in  FIG. 12 , up to a maximum inflated position. Further, after the second expandable chamber  1116  is inflated, or otherwise expanded, the second injection tube  1122  can be removed, as depicted in  FIG. 12 . 
     Additionally, the nucleus implant  1100  can include a core holder  1124  that extends from the surface of the solid core  1102 . The core holder  1124  can be used to position the nucleus implant  1100  and hold the nucleus implant  1100  in the proper position while the first expandable chamber  1106  and the second expandable chamber  1116  are inflated. Moreover, the core holder  1124  can be removed after the first expandable chamber  1106  and the second expandable chamber  1116  are inflated. An implant with several chambers surrounding a core may enable more fine adjustment of the position of a core than with a single chamber. 
     In a particular embodiment, the nucleus implant  1100  can include a first self-sealing valve (not shown) within the outer surface  1110  of the first expandable chamber  1106 , e.g., adjacent to the first injection tube  1112 . Further, the nucleus implant  1100  can include a second self-sealing valve (not shown) within the outer surface  1120  of the second expandable chamber  1116 , e.g., adjacent to the second injection tube  1122 . The self-sealing valves can prevent the expandable chambers  1106 ,  1116  from leaking material after the expandable chambers  1106 ,  1116  are inflated and the injection tubes  1112 ,  1122  are removed. 
       FIG. 13  indicate that the nucleus implant  1100  can be implanted within an intervertebral disc  1200  between a superior vertebra  1300  and an inferior vertebra  1302 . More specifically, the nucleus implant  1100  can be implanted within an intervertebral disc space  1202  established within the annulus fibrosus  1204  of the intervertebral disc  1200 . The intervertebral disc space  1202  can be established by removing the nucleus pulposus (not shown) from within the annulus fibrosus  1204 . 
     In a particular embodiment, the first expandable chamber  1106  can be inflated so the inner surface  1108  of the first expandable chamber  1106  engages the outer surface of the solid core  1102  and the outer surface  1110  of the first expandable chamber  1106  engages the inner surface  1118  of the second expandable chamber  1116 . Further, the outer surface  1120  of the second expandable chamber  1116  can engage the annulus fibrosis  1204 . 
     The nucleus implant  1100  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 solid core  1102  of the nucleus implant  1100  is greater than or equal to the hardness of the material used to inflate the first expandable chamber  1106 , i.e., after that material is cured. Further, the hardness of the material used to inflate the first expandable chamber  1106  is greater than or equal to the hardness of the material used to inflate the second expandable chamber  1116 , e.g., after those materials cure. 
     Arranging several expandable chambers around a core may result in an implant with a 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 such an arranged implant may be better controlled. In 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. 
     Arranging several expandable chambers around a core enables to obtain an implant, the hardness of which 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 enables to more easily spread the loads exerted at the level of the vertebras. In addition, the mobility of the thus arranged implant is better controlled. By way of 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 
     Additionally, the height of the solid core  1102  can be greater than or equal to the height of the first expandable chamber  1106  when fully expanded. Also, the height of the first expandable chamber  1106  when fully expanded can be greater than or equal to the height of the second expandable chamber  1116  when fully expanded. As shown in  FIG. 13 , the solid core  1102 , the first expandable chamber  1106 , and the second expandable chamber  1116  of the nucleus implant  1100  can be configured to provide proper support and spacing between the superior vertebra  1300  and the inferior vertebra  1302 . 
     In a particular embodiment, the first expandable chamber  1106 , the second expandable chamber  1116 , or a combination of the first expandable chamber  1106  and the second expandable chamber  1116  of the nucleus implant  1100  can be inflated with one or more injectable extended use approved medical materials that remain elastic after curing. It will be appreciated that the material or materials used for injection can be different for the two chambers. 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 first expandable chamber  1106 , the second expandable chamber  1116 , or a combination of the first expandable chamber  1106  and the second expandable chamber  1116  of the nucleus implant  1100  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  1100  can be installed using a posterior surgical approach, as shown. Further, the nucleus implant  1100  can be installed through a posterior incision  1206  made within the annulus fibrosus  1204  of the intervertebral disc  1200 . Alternatively, the nucleus implant  1100  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 Fourth Embodiment of a Nucleus Implant 
     Referring to  FIG. 14  through  FIG. 16 , an embodiment of a nucleus implant is shown and is designated  1400 . As shown, the nucleus implant  1400  includes a solid core  1402  that defines an outer surface  1404 . In a particular embodiment, the solid core  1402  can have a cross-section that is generally elliptical. Alternatively, the solid core  1402  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. 14  through  FIG. 16 , an expandable chamber  1406  can be disposed around the solid core  1402 . In a particular embodiment, as shown, the expandable chamber  1406  can have a generally inverted-bowl shape and the expandable chamber  1406  can be draped, or otherwise placed, over the solid core  1402  and inflated or expanded, as shown in  FIG. 16 . 
     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 or substantially uniform pressure. 
     The expandable chamber  1406  can define an inner surface  1408  and an outer surface  1410 . In a particular embodiment, the inner surface  1408  of the expandable chamber  1406  can be attached to the outer surface  1404  of the solid core  1402 . As such, proper placement of the expandable chamber  1406  can be based on the placement of the solid core  1402 . Alternatively, the expandable chamber  1406  can be separate from the solid core  1402  and the expandable chamber  1406  may engage the solid core  1402  after the expandable chamber  1406  is properly inflated. 
     As depicted in  FIG. 14 , the nucleus implant  1400  can include an injection tube  1412  that extends from the outer surface  1410  of the expandable chamber  1406 . In a particular embodiment, the expandable chamber  1406  of the nucleus implant  1400  is expandable from a deflated position, shown in  FIG. 14 , to one selected position among a plurality of inflated positions, shown in  FIG. 15 , up to a maximum inflated position. Further, after the expandable chamber  1406  is inflated, or otherwise expanded, the injection tube  1412  can be removed, as depicted in  FIG. 15 . 
     Additionally, the nucleus implant  1400  can include a core holder  1414  that extends from the surface of the solid core  1402 . The core holder  1414  can be used to position the nucleus implant  1400  and hold the nucleus implant  1400  in the proper position while the expandable chamber  1406  is inflated. Moreover, the core holder  1414  can be removed after the expandable chamber  1406  is inflated. In a particular embodiment, the nucleus implant  1400  can include a self-sealing valve (not shown) within the outer surface  1410  of the expandable chamber  1406 , e.g., adjacent to the injection tube  1412 . The self-sealing valve can prevent the expandable chamber  1406  from leaking material after the expandable chamber  1406  is inflated and the injection tube  1412  is removed. 
       FIG. 16  indicates that the nucleus implant  1400  can be implanted within an intervertebral disc  1500  between a superior vertebra  1600  and an inferior vertebra  1602 . More specifically, the nucleus implant  1400  can be implanted within an intervertebral disc space  1502  established within the annulus fibrosus  1504  of the intervertebral disc  1500 . The intervertebral disc space  1502  can be established by removing the nucleus pulposus (not shown) from within the annulus fibrosus  1504 . 
     In a particular embodiment, the expandable chamber  1406  can be inflated so the inner surface  1408  of the expandable chamber  1406  engages the outer surface of the solid core  1402  and the outer surface  1410  of the expandable chamber  1406  engages the annulus fibrosis  1504 . Further, portions of the outer surface  1410  of the expandable chamber  1406  can engage the superior vertebra  1600  and an inferior vertebra  1602 . Moreover, when the expandable chamber  1406  is expanded, or otherwise inflated, a portion of the expandable chamber  1406  is located between the solid core  1402  and the superior vertebra  1600 . 
     It will be appreciated that in a particular embodiment, the arrangements of the implant of  FIGS. 13 and 16  may be assembled within the same implant. Thus, for example, the inverted-bowl shaped chamber  1406  may be formed of a first chamber having an inverted-bowl shape and a second peripheral chamber similar to the chamber  1116  of  FIG. 13  and that peripherally surrounds this first chamber. The advantages related to each of both implants of  FIGS. 13 and 16  may thus be obtained with a single implant. 
     The nucleus implant  1400  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 solid core  1402  of the nucleus implant  1400  is greater than or equal to the hardness of the material used to inflate the expandable chamber  1406 , i.e., after that material is cured. As shown in  FIG. 16 , the solid core  1402  and the expandable chamber  1406  of the nucleus implant  1400  can be configured to provide proper support and spacing between the superior vertebra  1600  and the inferior vertebra  1602 . 
     In a particular embodiment, the expandable chamber  1406  of the nucleus implant  1400  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 chamber  1406  of the nucleus implant  1400  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  1400  can be installed using a posterior surgical approach, as shown. Further, the nucleus implant  1400  can be installed through a posterior incision  1506  made within the annulus fibrosus  1504  of the intervertebral disc  1500 . Alternatively, the nucleus implant  1400  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 Fifth Embodiment of a Nucleus Implant 
     Referring to  FIG. 17  through  FIG. 19 , an embodiment of a nucleus implant is shown and is designated  1700 . As shown, the nucleus implant  1700  includes a solid core  1702  that defines an outer surface  1704 . In a particular embodiment, the solid core  1702  can have a cross-section that is generally elliptical. Alternatively, the solid core  1702  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. 17  through  FIG. 19 , an expandable chamber  1706  can be disposed around the solid core  1702 . In a particular embodiment, as shown, the expandable chamber  1706  can be generally shaped like the letter “U” and the expandable chamber  1706  can be inflated, or otherwise expanded, around the solid core  1702 . 
     The U-shaped chamber may be 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 conceals this incision. This U-shape is also advantageous when the intervertebral disc shape has, in a sagittal plane, an obvious trapezoidal shape. A U-shape enables the chamber to suitably occupy the space on three sides of the core. It is to be noted that an intermediate expandable chamber occupying the space between the core  1702  and the U chamber  1706  ( FIG. 17 ) may be envisaged. This additional arrangement may result in more accurate positioning of the core. 
     The expandable chamber  1706  can define a first surface  1708  and a second surface  1710 . In a particular embodiment, the first surface  1708  of the expandable chamber  1706  can be attached to the outer surface  1704  of the solid core  1702 . As such, proper placement of the expandable chamber  1706  can be based on the placement of the solid core  1702 . Alternatively, the expandable chamber  1706  can be separate from the solid core  1702  and the expandable chamber  1706  may engage the solid core  1702  after the expandable chamber  1706  is properly inflated. 
     As depicted in  FIG. 17 , the nucleus implant  1700  can include an injection tube  1712  that extends from the second surface  1710  of the expandable chamber  1706 . In a particular embodiment, the expandable chamber  1706  of the nucleus implant  1700  is expandable from a deflated position, shown in  FIG. 17 , to one selected position among a plurality of inflated positions, shown in  FIG. 18 , up to a maximum inflated position. Further, after the expandable chamber  1706  is inflated, or otherwise expanded, the injection tube  1712  can be removed, as depicted in  FIG. 18 . 
     Additionally, the nucleus implant  1700  can include a core holder  1714  that extends from the surface of the solid core  1702 . The core holder  1714  can be used to position the nucleus implant  1700  and hold the nucleus implant  1700  in the proper position while the expandable chamber  1706  is inflated. Moreover, the core holder  1714  can be removed after the expandable chamber  1706  is inflated. In a particular embodiment, the nucleus implant  1700  can include a self-sealing valve (not shown) within the second surface  1710  of the expandable chamber  1706 , e.g., adjacent to the injection tube  1712 . The self-sealing valve can prevent the expandable chamber  1706  from leaking material after the expandable chamber  1706  is inflated and the injection tube  1712  is removed. 
       FIG. 19  indicates that the nucleus implant  1700  can be implanted within an intervertebral disc  1800  between a superior vertebra  1900  and an inferior vertebra  1902 . More specifically, the nucleus implant  1700  can be implanted within an intervertebral disc space  1802  established within the annulus fibrosus  1804  of the intervertebral disc  1800 . The intervertebral disc space  1802  can be established by removing the nucleus pulposus (not shown) from within the annulus fibrosus  1804 . 
     In a particular embodiment, the expandable chamber  1706  can be inflated so the first surface  1708  of the expandable chamber  1706  engages a portion of the outer surface of the solid core  1702  and the second surface  1710  of the expandable chamber  1706  engages a portion of the annulus fibrosis  1804 . Further, portions of the outer surface  1710  of the expandable chamber  1706  can engage the superior vertebra  1900  and an inferior vertebra  1902 . Moreover, when the expandable chamber  1706  is expanded, or otherwise inflated, the expandable chamber  1706  at least partially surrounds the solid core  1702 . As depicted in  FIG. 18 , the core  1702  may be placed between the arms of the U formed by the chamber  1706 . 
     The nucleus implant  1700  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 solid core  1702  of the nucleus implant  1700  is greater than or equal to the hardness of the material used to inflate the expandable chamber  1706 , i.e., after that material is cured. Also, the overall height of the solid core  1702  can be greater than or equal to the overall height of the expandable chamber  1706  when inflated. As shown in  FIG. 19 , the solid core  1702  and the expandable chamber  1706  of the nucleus implant  1700  can be configured to provide proper support and spacing between the superior vertebra  1900  and the inferior vertebra  1902 . 
     In a particular embodiment, the expandable chamber  1706  of the nucleus implant  1700  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 chamber  1706  of the nucleus implant  1700  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  1700  can be installed using a posterior surgical approach, as shown. Further, the nucleus implant  1700  can be installed through a posterior incision  1806  made within the annulus fibrosus  1804  of the intervertebral disc  1800 . Alternatively, the nucleus implant  1700  can be installed using an anterior surgical approach, a lateral surgical approach, or any other surgical approach well known in the art. 
     Description of an Embodiment of a Method of Installing a Nucleus Implant 
     Referring to  FIG. 20 , an exemplary, non-limiting embodiment of a method of installing a nucleus implant is shown and commences at block  2000 . At block  2000 , 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  2002 , the location of the affected disc is marked on the patient, e.g., with the aid of fluoroscopy. At block  2004 , the surgical area along spinal column is exposed. Further, at block  2006 , 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  2008 , the annulus fibrosus of the affected disc is incised to expose the nucleus pulposus. Further, at block  2010 , the nucleus pulposus is removed to create an intervertebral disc space within the annulus fibrosus. At block  2012 , the nucleus implant is inserted within the intervertebral disc space of the annulus fibrosus. Further, at block  2014 , the expandable chamber is inflated, or otherwise expanded, around the core, thereby positioning and retaining the core. At block  2016 , the core holder is removed. Further, at block  2018 , the injection tube can be removed. 
     Continuing to block  2020 , the expandable chamber is sealed—if the expandable chamber is not self-sealing, e.g., with a self-sealing valve. At block  2022 , the material used to inflate, or expand, 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  2024 , the annulus fibrosus is sutured. At block  2026 , the intervertebral space can be irrigated. Further, at block  2028 , the retractor system can be removed. At block  2030 , a drainage, e.g., a retroperitoneal drainage, can be inserted into the wound. Additionally, at block  2032 , 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  2034 , postoperative care can be initiated. The method ends at state  2036 . 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.