Abstract:
A spine disc prosthesis mimics a natural human spine disc through use of a structure that duplicates a natural Annulus Fibrosis of the disc to provide translation, extension, flexion, and axial support in like manner to a natural disc. The present spine disc prosthesis achieves this through the use of a first and second disk connected to one another via a flexible annulus fibrosis structure. The flexible annulus fibrosis structure or core is characterized by a plurality of compressible (pliant) strands that are affixed to and extend between the first and second disks. The strands are preferably, but not necessarily, situated on and extend about an outer perimeter of inside surfaces of the two end disks so as to mimic natural contours of an annulus fibrosis of a natural spinal disc. The strands may be formed by various types of biocompatible fibers, braids, cords, bundles or the like and may have a hollow core or a solid core (e.g. PEEK [polyetheretherketone] cores/core strands may also be used). The strands may be situated on the vertical, crossed or in other configurations. The end disks may be formed as to promote fusion with adjoining vertebrae when implanted. The end plate may also include a keel and/or installation structure to allow for implanting the spine disc prosthesis.

Description:
RELATED APPLICATIONS 
     This patent application claims the benefit of and/or priority to U.S. Provisional Patent Application Ser. No. 60/925,039 filed Apr. 18, 2007, entitled “Spinal Disc Prostheses” the entire contents of which is specifically incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to spinal disc prostheses to replace a damaged, degenerated or otherwise defective spinal disc in a spinal column of a human. 
     2. Background 
     The prior art is replete with various types of prosthetic or artificial spinal discs designed to replicate a spinal disc and thus replace a damaged, degenerated or otherwise defective spinal disc in a spinal column of a human. U.S. Pat. Nos. 5,071,437 and 5,534,030 disclose spinal disc prostheses that are typical of the prior art. The discs disclosed in these US patents include a pair of rigid plates adhered to opposite surfaces of a body of elastomeric material. Many other variations have since been developed. 
     The disc prosthesis when in use is positioned between adjacent vertebrae. The rigid plates may have bone in-growth material for enabling bone to adhere or fuse to the rigid plates. The disc prosthesis is subject to forces that act in the spine including compression forces due to loads on the spine, shear forces due to bending of the spine, and torsion forces due to twisting of the spine. These application forces may cause disc component failure. For example, such application forces may cause the rigid plates to separate from the body of elastomeric material in the disc prostheses of the &#39;437 and &#39;030 patents. Such separation would be detrimental to the proper functioning of the disc prosthesis. Moreover, these application forces have a tendency to squeeze the elastomeric body out from between the two plates. This, again, is detrimental to the proper functioning of the disc prosthesis. 
     When a visco-elastic material is used for the prosthetic disc body between two plates, the application forces and their attendant problems are especially true. Particularly, such spine application forces can compress a portion or more of a visco-elastic spinal disc prosthesis body from between the two plates thereof. Moreover, the application forces tend to rotate the disc body. Excess rotation can cause stress on the disc body. Such stress can lead to disc body failure in all types of prior art discs. 
     It is apparent from the above that prior art spinal disc prostheses fall short of providing a reliable artificial disc. 
     In view of the above, it is desirable to provide spinal disc prostheses that alleviate the shortcomings of the prior art. 
     SUMMARY OF THE INVENTION 
     Spine disc prostheses are presented that imitate the Annulus Fibrosis of a natural spine disc and so provide natural translation, extension, flexion and axial support within an artificial spine disc. The present spine disc prosthesis has first and second disks that are connected to one another via a flexible core. The flexible core is characterized by a plurality of compressible and/or flexible (pliant) strands extending between the upper and lower plates. The flexible core preferably, but not necessarily, extends from annular peripheries or perimeters of adjacent sides of the first and second disks in like relationship as the Annulus Fibrosis of a natural spine disc is to adjacent vertebrae of a spine. The strands may be formed as a mesh, a web, in rows, or in other configurations. 
     In one form, the pliant strands extend substantially perpendicular to the first and second disks. In another form, the pliant strands extend skew to the first and second disks. In this form, the pliant strands may be crisscrossed or skewed according to any number of manners or patterns. The strands are formed of a compressible and/or flexible, biocompatible material. Moreover, the strands forming the flexible core may all be of the same type or may consist of two or more types of strands as appropriate. 
     The pliant strands are preferably, but not necessarily, situated on and extend from the periphery of an upper side of the second disk and a lower side of the first disk. In one form, the strands are situated in a single row about the disk geometry. The disk geometry preferably mimics natural contours of a human spinal disc. The strands may be formed by various types of biocompatible fibers, braids, cords, bundles or the like and may have a hollow core or a solid core. PEEK (polyetheretherketone) cores/core strands may also be used. The strands may be situated on the vertical, crossed or in other configurations. 
     The end disks are preferably, but not necessarily, formed to promote fusion with adjoining vertebrae when implanted. In one form, the end disks have oval or annular frames supporting a grill or grillwork. Strands of the grillwork extend across the frame and provide openings that allow for fusion between the grillwork/frame and an adjacent vertebra when implanted. In another form, the end disks have plates shaped preferably, but not necessarily, like spine discs. Ports or openings in the end plates allow for fusion between the end plate and an adjacent vertebra when implanted. The ports, being for bone growth, may be either blind or blind with undercut. The end plate may also include a keel and/or installation structure to allow for implanting the spine disc prosthesis. 
     In all cases, the spinal disc prostheses may be formed in various sizes as well as be sized for lateral introduction (implantation) into a spine. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing and other features of the present invention will become more apparent to one skilled in the art upon also reading the following description of embodiments of the invention with reference to the accompanying drawings wherein: 
         FIG. 1  is a first upper side perspective view of an embodiment of a spinal disc prosthesis fashioned in accordance with the present principles; 
         FIG. 2  is a second upper side perspective view of the spinal disc prosthesis of  FIG. 1 ; 
         FIG. 3  is a top view of the spinal disc prosthesis of  FIG. 1 ; 
         FIG. 4  is a lateral side view of the spinal disc prosthesis of  FIG. 1  as taken along line  4 - 4  of  FIG. 5 ; 
         FIG. 5  is an anterior/posterior side view of the spinal disc prosthesis of  FIG. 1  as taken along line  5 - 5  of  FIG. 3 ; 
         FIG. 6  is an enlarged view of a portion of the spinal disc prosthesis of  FIG. 1  as taken along encircling  6 - 6  of  FIG. 5 ; 
         FIG. 7  is a first upper perspective view of another embodiment of a spinal disc prosthesis fashioned in accordance with the present principles; 
         FIG. 8  is a second upper perspective view of the spinal disc prosthesis of  FIG. 7 ; 
         FIG. 9  is an anterior side view of the spinal disc prosthesis of  FIG. 7 ; 
         FIG. 10  is a lateral side view of the spinal disc prosthesis of  FIG. 7  as taken along line  10 - 10  of  FIG. 9 ; 
         FIG. 11  is a top view of the spinal disc prosthesis of  FIG. 7 ; 
         FIG. 12  is a sectional view of the spinal disc prosthesis of  FIG. 7  as taken along line  12 - 12  of  FIG. 11 ; 
         FIG. 13  is a sectional view of the spinal disc prosthesis of  FIG. 7  as taken along line  13 - 13  of  FIG. 11 ; 
         FIG. 14  is an enlarged view of a portion of the spinal disc prosthesis of  FIG. 7  as taken along encircling  14 - 14  of  FIG. 13 ; 
         FIG. 15  is an anterior/posterior side view of another embodiment of a spinal disc prosthesis fashioned in accordance with the present principles; 
         FIG. 16  is an enlarged view of a portion of the spinal disc prosthesis of  FIG. 15  as taken along encircling  15 - 15  thereof; 
         FIG. 17A  is a diagrammatic cross-sectional representation of an exemplary strand as may be utilized in the spinal disc prostheses of the present invention; 
         FIG. 17B  is a diagrammatic cross-sectional representation of another exemplary strand for the present spinal disc/disc prostheses; 
         FIG. 17C  is a diagrammatic cross-sectional representation of another exemplary strand as may be utilized in the spinal disc prostheses of the present invention; 
         FIG. 17D  is a diagrammatic cross-sectional representation of another exemplary strand as may be utilized in the spinal disc prostheses of the present invention; 
         FIG. 17E  is a diagrammatic cross-sectional representation of another exemplary strand as may be utilized in the spinal disc prostheses of the present invention; 
         FIG. 17F  is a diagrammatic cross-sectional representation of another exemplary strand as may be utilized in the spinal disc prostheses of the present invention; 
         FIG. 17G  is a diagrammatic cross-sectional representation of another exemplary strand as may be utilized in the spinal disc prostheses of the present invention; 
         FIG. 17H  is a diagrammatic cross-sectional representation of another exemplary strand as may be utilized in the spinal disc prostheses of the present invention; 
         FIG. 17I  is a diagrammatic cross-sectional representation of another exemplary strand as may be utilized in the spinal disc prostheses of the present invention; and 
         FIG. 17J  is a diagrammatic cross-sectional representation of another exemplary strand as may be utilized in the spinal disc prostheses of the present invention. 
     
    
    
     Corresponding reference characters indicate corresponding parts throughout the several views. Although the drawings represent embodiments of the invention, the drawings are not necessarily to scale and certain features may be exaggerated in order to better illustrate and explain the present invention. The exemplifications set out herein illustrate several embodiments of the invention, but the exemplifications are not to be construed as limiting the scope of the invention in any manner. 
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention provides artificial or prosthetic spinal or spine discs (collectively, spinal disc prostheses) such as to replace damaged, degenerated, or otherwise defective or undesirable spinal discs in a spinal column of a human.  FIGS. 1-6  illustrate an exemplary embodiment of a spinal disc prosthesis, i.e. spinal disc  10 . The spinal disc  10  is fashioned from suitable biocompatible materials such as are known in the art. The disc  10  comprises a first end  12 , a second end  14  and a middle or core  16 . The nomenclature first and second is arbitrary. The first end  12  may be considered a first vertebral contacting portion while the second end  14  may be considered a second vertebral contacting portion. The core  16  may be considered an annulus fibrosis portion or hub of the spinal disc  10 . The first vertebral contacting portion  12 , the second vertebral contacting portion  14  and the core  16  simulates, duplicates or mimics a vertebral disc and especially the annulus fibrosis portion preferably, but not necessarily, without the nucleus pulposus (nucleus) of a disc. The first vertebral contacting portion  12  provides disc annulus fibrosis emulation and thus functions and/or provides for contact or abutment with a surface of a vertebra. The second vertebral contacting portion  14  provides disc core emulation and thus functions and/or provides for contact or abutment with a surface of an adjacent vertebra. The core  16  thus provides disc core emulation and thus functions and/or provides cushioning between the adjacent vertebrae. 
     The first vertebral contacting portion  12  is characterized by a preferably, but not necessarily, elliptical, oval or ovoid end, ring, frame, disk or body  20  defining an upper surface  21 , an inner surface  22  and a curved lower surface  23 . The elliptical body  20  supports and/or incorporates a grill, grillwork or grill structure  24  that allows for the disk top to fuse into an adjacent vertebral body (i.e. vertebra—not shown). The grill structure  24  is formed of a plurality of rods  26 . The rods  26  extend between sides of the inner elliptical surface  22  of the ring  20  and therethrough (see, e.g.  FIGS. 1 and 2 ). 
     The second vertebral contacting portion  14  is characterized by a preferably, but not necessarily, elliptical, oval or ovoid end, ring, frame, disk or body  30  defining a lower surface  31 , an inner surface (not seen in the figures but like inner surface  22  of body  20 ) and a curved upper surface  33 . The elliptical body  30  supports and/or incorporates a grill, grillwork or grill structure  34  (not seen in the figures but like grill structure  24  of the first end  12 ) that allows for the disc top to fuse into an adjacent vertebral body (i.e. vertebra—not shown). The grill structure is formed of a plurality of rods (not seen in the figures but like grill rods  26  of the grill structure  24  of the first end  12 ). The rods extend between sides of the inner elliptical surface of the body  30  and therethrough (see, e.g.  FIGS. 1 and 2 ). 
     The middle, annulus fibrosis portion or core  16  has a plurality of strands, cords, braids, rope or the like (akin in one form to carpet strands)  36  that connect and extend between inner surfaces of the ends  12 ,  24 . The end  12  or frame  20  has an elliptical opening  28 . In like manner, the end  14  or frame  30  has an elliptical opening  38 . The strands  36  extend about an inner periphery or diameter of the first and second rings  20 ,  30  of the first and second ends  12 ,  14 . As best seen in  FIG. 6 , the strands  36  are preferably formed of twisted filaments, fibers or individual smaller strands  38  of the same. The number of strands and their thickness may be varied, both relative to other sizes of discs  10  or with respect to other strands of the same disc  10 . The strands  36  function and/or act like a natural disc. Various exemplary strands are shown in  FIGS. 17A-J  encompassing strand portions  200 ,  300 ,  400 ,  500 ,  600 ,  700 ,  800 ,  900 ,  1000  and  1100 . 
     The strands  36  are shown oriented essentially vertical, perpendicular or transverse to the ends  12 ,  14 . It should be appreciated that the strands  36  may be oriented differently than shown. For instance, the strands  36  may be oriented in a slant or askew from one body  20  to the other body  30 . Each strand may be slanted in the same direction or one or more strands may be slanted differently. Various patterns may be used. The strands may also be formed as a mesh, web or the like. 
     Referring now to  FIGS. 7-14 , there is depicted another exemplary embodiment of a spinal disc prosthesis, i.e. spinal disc  50 . The spinal disc  50  is fashioned from suitable biocompatible materials such as are known in the art. The disc  50  comprises a first end  52 , a second end  54  and a middle or core  56 . The nomenclature first and second is arbitrary. The first end  52  may be considered a first vertebral contacting portion while the second end  54  may be considered a second vertebral contacting portion. The core  56  may be considered a annular fibrosis portion or hub of the spinal disc. The first vertebral contacting portion  52 , the second vertebral contacting portion  54  and the core  56  simulates a vertebral disc and especially portions of the annulus fibrosis and nucleus pulposus (nucleus) of a disc. Particularly, the first vertebral contacting portion  52  provides disc annulus fibrosis emulation and thus functions and/or provides for contact or abutment with a surface of a vertebra. The second vertebral contacting portion  54  provides disc annulus fibrosis emulation and thus functions and/or provides for contact or abutment with a surface of an adjacent vertebra. The core  56  provides nucleus emulation and thus functions and/or provides cushioning between the adjacent vertebrae. 
     The first vertebral contacting portion  52  is characterized by an essentially D-shaped or spinal disc-shaped plate, body or end (or other shapes to accommodate MIS insertion) or body  60  defining an upper surface  61 , a lower surface  63  and a curved peripheral or transition surface (periphery)  62 . The plate  60  has a plurality of ports, holes or bores  64  formed in the upper surface  61 . The ports  64  are for bone growth. A protuberance in the form of a keel or keel structure  66  extends from the upper surface  61  of the plate  60 . The keel structure  66  is defined by a keel or keel body  68 . The keel body  68  has a longitudinal axis about a centerline of the disc  50  (anterior-posterior axis). The posterior side has an angled or tapered surface  69  that extends from the upper surface  61  of the plate  60 , in the posterior direction, and terminates at a plurality of ridges, teeth, serrations of the like  70  at the apex of the keel body  68 . The front face  71  of the keel body  68  has a bore  72  that angles downwardly (see, e.g.  FIG. 12 ). The keel  66  may take other forms, shapes or configurations but which is preferably configured as depicted in the figures. 
     The second vertebral contacting portion  54  is characterized by an essentially D-shaped or spinal disc-shaped (or other shapes to accommodate MIS insertion) plate, body or end  76  defining a lower surface  77 , an upper surface  79  and a curved peripheral or transition surface (periphery)  78 . The plate  76  has a plurality of ports, holes or bores  80  formed in the lower surface  77 . The ports  80  are for bone growth. A protuberance in the form of a keel or keel structure  82  extends from the lower surface  77  of the plate  76 . The keel structure  82  is defined by a keel or keel body  84 . The keel body  84  has a longitudinal axis about a centerline of the disc  50  (anterior-posterior axis). The posterior side has an angled or tapered surface  85  that extends from the lower surface  77  of the plate  76 , in the posterior direction, and terminates at a plurality of ridges, teeth, serrations of the like  86  at the apex of the keel body  84 . The front face  87  of the keel body  84  has a bore  88  that angles downwardly (see, e.g.  FIG. 12 ). The keel  82  may take other forms, shapes or configurations but which is preferably configured as depicted in the figures. 
     The middle, annulus portion or core  56  has a plurality of strands, fibers, cords, braids, rope or the like (akin to carpet strands)  92  that connect and extend between inner edges, diameters or peripheries of the plates  60  and  76 . The strands  92  extend about the inner diameter of the plates  60 ,  76  of the first and second ends  52 ,  54  with the exception of area  90  (see, e.g.  FIGS. 10 ,  12  and  13 ) that provides an overhang of the plates  60 ,  76  in which the strands  92  are inward of the periphery. In like manner to the strands  36 , the strands  92  are preferably formed of twisted filaments, fibers or individual smaller strands (see, e.g.  FIG. 6 ) of the same. The number of strands and their thickness may be varied, both relative to other sizes of discs  50  or with respect to other strands of the same disc  50 . The strands  92  function and/or act like a natural disc core of a natural spine disc. 
     The strands  92  are shown oriented essentially vertical or perpendicular to the ends  52 ,  54 . It should be appreciated that the strands  92  may be oriented differently than shown. For instance, the strands  92  may be oriented in a slant from one plate  60  to the other plate  76 . Each strand may be slanted in the same direction or one or more strands may be slanted differently. Various patterns may be used. Meshes, webs or weaves may be fashioned via the strands. Various exemplary strands are shown in  FIGS. 17A-J  encompassing strand portions  200 ,  300 ,  400 ,  500 ,  600 ,  700 ,  800 ,  900 ,  1000  and  1100 . 
       FIG. 14  presents an enlarged view of a portion of the spinal disc  50  particularly illustrating ports  80  of the end  76 . As the ports  80  are for bone in-growth, they may be fashioned as either blind or with an undercut. Port  80   L  on the left side of  FIG. 14  is a blind port. Port  80   R  on the right side of  FIG. 14 , is a port with an undercut  89 . It should be appreciated that undercuts may be provided in any, some or all of the ports  80  of the plate  76  and the ports  64  of the plate  60 . 
       FIGS. 15 and 16  depict another exemplary embodiment of a spinal disc prosthesis, i.e. spinal disc  100 . The spinal disc  100  is fashioned from suitable biocompatible materials such as are known in the art. The disc  100  comprises a first end  102 , a second end  104  and a middle or core  106 . The nomenclature first and second is arbitrary. The first end  102  may be considered a first vertebral contacting portion while the second end  104  may be considered a second vertebral contacting portion. The middle or core  106  may be considered an annulus fibrosis portion with or without the nucleus portion. The first vertebral contacting portion  102 , the second vertebral contacting portion  104  and the core  106  simulates a vertebral disc and especially portions of the annulus fibrosis of a disc. Particularly, the first vertebral contacting portion  102  provides disc annulus fibrosis emulation and thus functions and/or provides for contact or abutment with a surface of a vertebra. The second vertebral contacting portion  104  provides 
     disc annulus fibrosis emulation and thus functions and/or provides for contact or abutment with a surface of an adjacent vertebra. The core  106  provides nucleus emulation and thus functions and/or provides cushioning between the adjacent vertebrae. 
     The first vertebral contacting portion  102  is characterized by a preferably, but not necessarily elliptical, oval or ovoid body, end or plate  110  defining an upper surface  111  and a curved lower surface  113 . The elliptical body  110  supports and/or incorporates a grill, grillwork or grill structure (not seen but see, e.g., grill structure  24  of disc  10 ) that allows for the disc top to fuse into an adjacent vertebral body (i.e. vertebra). The grill structure is formed of a plurality of rods  116  the ends of which can be seen in  FIG. 15 . The rods  116  extend between sides of the inner elliptical surface of the body  110  and therethrough. 
     The second vertebral contacting portion  104  is characterized by a preferably, but not necessarily, elliptical, oval or ovoid body, end or plate  120  defining a lower surface  121  and a curved upper surface  123 . The elliptical body  120  supports and/or incorporates a grill, grillwork or grill structure (not seen but see, e.g., grill structure  24  of disc  10 ) that allows for the disc top to fuse into an adjacent vertebral body (i.e. vertebra). The grill structure is formed of a plurality of rods  126  the ends of which can be seen in  FIG. 15 . The rods  126  extend between sides of the inner elliptical surface of the body  120  and therethrough. 
     The middle, hub, annulus fibrosis portion or core  106  has a plurality of strands or the like  130  that connect and extend between the bodies  110  and  120 . The strands  106  extend about an inner periphery, perimeter or diameter of the first and second bodies  110 ,  120  of the first and second ends  102 ,  104 . As best seen in  FIG. 16 , the strands  130  are preferably formed of twisted lines, filaments, threads or individual smaller strands  132 . The number of strands and their thickness may be varied, both relative to other sizes of discs  100  or with respect to other strands of the same disc  100 . The strands  130  function and/or act like a natural disc. The strands  130  are shown oriented in an X (criss-cross pattern) with respect to the ends  102 ,  104 . Such a pattern may form a web or mesh. 
       FIGS. 17A-J  are diagrammatic cross-sectional representations of the geometry, configuration and/or structure of various strands that may be used in the present various exemplary spinal disc/disc prostheses.  FIG. 17A  provides a representation of a 1×7 disc prosthesis strand  300 . The strand  300  is characterized by a single middle fiber or filament and six surrounding fibers or filaments. The strand  300  is a bundled or collective braid of seven fibers so as to have or be considered as having a core. The 1×7 strand  300  may be twisted (helical) or straight. Similar to the 1×7 strand,  FIG. 17B  provides a representation of a 1×19 disc prosthesis strand  400  that is characterized by a single middle fiber or filament and eighteen surrounding fibers or filaments. The strand  400  is a bundled or collective braid or 20 fibers so as to have or be considered as having a core. The 1×19 strand  400  may be twisted (helical) or straight. Various 1×# combinations may be used.  FIG. 17C  provides a representation of a 3×7 disc prosthesis strand  500  that is characterized by three triangularly-arranged strands, each strand having seven fibers or filaments bundled or arranged or collected so as to have or be considered as having a hollow core. Variations are contemplated. 
     The 6×42 strand  600  of  FIG. 17D  has a PEEK core and thus is a solid core strand. The 6×42 strand  600  is a variation of the 1×7 strand  300  ( FIG. 17A ) wherein a central core ( 1 ) is surrounded by six (6) strands (hence a 1×7 strand), each surrounding strand being a 1×7 strand. The cores of the surrounding 1×7 strands may or may not be PEEK. The 6×42 strand may be twisted (helical) or straight. The 6×19 strand  700  of  FIG. 17E  and the 6×37 strand  800  of  FIG. 17F  provide variations of stranded strands (and cored). 
       FIG. 17G  depicts a 7×3 strand  900  with a core as a further example of a stranded strand that is usable in the various disc prostheses presented herein.  FIG. 17H  depicts a 7×7 strand  100  with a core as a yet further example of a stranded strand that is usable in the various disc prostheses presented herein. A 19×7 strand  1000  and a 7×19 strand  1100  is depicted in  FIGS. 17I and 17J  respectively as yet further examples of stranded strands usable in the various disc prostheses presented herein.