Prosthetic intervertebral discs assemblies having compressible core elements with enhanced torque transmission

Abstract

This description deals with a medical device, specifically a prosthetic intervertebral disc having a compressible core that is mechanically interactive with the prosthetic disc's end plates thereby providing excellent torque or twisting transmission between the end plates.

1 . A prosthetic intervertebral disc comprising:
 a first end plate affixable, directly or indirectly, to a vertebral bone in a spine,   a second end plate affixable, directly or indirectly, to an adjacent vertebral bone in a spine,   a unitary compressible core member comprising a polymeric material, the core member having an axis, said axis also passing through the first end plate and the second end plate, said member being operational to interlock with said first and second end plates such that when a twisting force is imparted to one of said end plates about that axis, the compressible core member transmits the twisting force from that end plate to the other end plate.   
     
     
         2 . The prosthetic intervertebral disc of  claim 1  wherein said first and second end plates each include openings for accepting one or more protrusions extending from the compressible core member and thereby interlocking the compressible core with the first and second end plates and wherein the compressible core member comprises the one or more protrusions, the protrusions being operable to engage the first and second endplate openings. 
     
     
         3 . The prosthetic intervertebral disc of  claim 1  wherein said first and second end plates each further include a rounded spring that does not substantially rotate with respect to said end plates, each said spring including openings for accepting protrusions from the compressible core member and wherein the compressible core member comprises the one or more protrusions, the protrusions being operable to engage the first and second endplate rounded spring openings. 
     
     
         4 . The prosthetic intervertebral disc of  claim 1  wherein said first and second end plates each further includes an inner end plate having a periphery, the periphery having outer notches for accepting protrusions from the compressible core member and thereby interlocking the compressible core member with each of the first and second end plates and wherein the compressible core member includes a plurality of arms ending in protrusions operable to interlock with the first and second end plates. 
     
     
         5 . The prosthetic intervertebral disc of  claim 1  further comprising fixation elements for directly affixing the first and second end plates to vertebral bone. 
     
     
         6 . The prosthetic intervertebral disc of  claim 1  further comprising one or more stress elements. 
     
     
         7 . The prosthetic intervertebral disc of  claim 1  wherein said first and second end plates each further comprises an outer end plate and a spider, each spider comprising a spider extension configured to be affixed to the outer end plate and comprising a plurality of spider arms extending from the spider extension adjacent the outer end plate, each spider thereby providing open regions between the spider arms, the open regions operable for accepting protrusions from the compressible core member and interlocking the compressible core member with each of the first and second end plates and wherein the compressible core member comprises the one or more protrusions, the protrusions operable to engage the first and second endplate in the open regions between the spider arms. 
     
     
         8 . The prosthetic intervertebral disc of  claim 7  wherein each spider extension is welded to an outer end plate and the spider arms comprise a spring material and are configured to act as cantilever springs. 
     
     
         9 . A prosthetic intervertebral disc comprising:
 a first end plate affixable, directly or indirectly, to a vertebral bone in a spine,   a second end plate affixable, directly or indirectly, to an adjacent vertebral bone in a spine,   a compressible core member consisting essentially of thermoplastic elastomer or silicone, the core member having an axis, said axis also passing through the first end plate and the second end plate, said member being operational to interlock with said first and second end plates such that when a twisting force is imparted to one of said end plates about that axis, the compressible core member transmits the twisting force from that end plate to the other end plate.   
     
     
         10 . The prosthetic intervertebral disc of  claim 9  wherein said first and second end plates each include openings for accepting one or more protrusions extending from the compressible core member and thereby interlocking the compressible core member with the first and second end plates and wherein the compressible core member comprises the one or more protrusions, the protrusions being operable to engage the first and second endplate openings. 
     
     
         11 . The prosthetic intervertebral disc of  claim 9  wherein the compressible core member comprises a plurality of core elements. 
     
     
         12 . The prosthetic intervertebral disc of  claim 11  wherein said first and second end plates each include openings for accepting one or more protrusions extending from the compressible core member and thereby interlocking the compressible core member with the first and second end plates and wherein the compressible core member comprises the one or more protrusions, the protrusions being operable to engage the first and second endplate openings. 
     
     
         13 . The prosthetic intervertebral disc of  claim 12  wherein each of the plurality of core elements extends into said first and second end plate openings. 
     
     
         14 . The prosthetic intervertebral disc of  claim 9  wherein said first and second end plates each further includes a hemispherical spring that does not substantially rotate with respect to said end plates, each said spring including openings for accepting one or more protrusions extending from the compressible core member and thereby interlocking the compressible core member with the first and second end plates and wherein the compressible core member comprises the one or more protrusions, the protrusions being operable to engage the openings in the first and second endplate hemispherical springs. 
     
     
         15 . The prosthetic intervertebral disc of  claim 9  wherein said first and second end plates each further includes an inner end plate having a periphery, the periphery having outer notches operable to accept protrusions from the compressible core member and operable to interlock the compressible core member and each of the first and second end plates and wherein the compressible core member includes a plurality of arms ending in protrusions operable to enter respectively between the first and second end plates and their respective inner end plates. 
     
     
         16 . The prosthetic intervertebral disc of  claim 9  wherein the first and second end plates each comprises an outer end plate and a spider, each spider comprising a spider extension member operable to be affixed to the respective outer end plate and further comprising a plurality of spider arms extending from the spider extension, each spider thereby providing open regions between the arms operable for accepting protrusions from the compressible core member and thereby interlocking the compressible core member with each of the first and second end plates and wherein the compressible core member comprises the one or more protrusions, the protrusions operable to engage the open regions between the spider arms of the first and second endplates. 
     
     
         17 . The prosthetic intervertebral disc of  claim 16  wherein each spider extension is welded to an outer end plate and the spider arms comprise a spring material and are operable to act as cantilever springs. 
     
     
         18 . The prosthetic intervertebral disc of  claim 9  further comprising fixation elements for directly affixing the first and second end plates to vertebral bone. 
     
     
         19 . The prosthetic intervertebral disc of  claim 9  further comprising one or more stress elements. 
     
     
         20 . A prosthetic intervertebral disc comprising:
 a first end plate affixable, directly or indirectly, to a vertebral bone in a spine,   a second end plate affixable, directly or indirectly, to an adjacent vertebral bone in a spine,   a compressible composite core member consisting essentially of a thermoplastic elastomer or silicone covering surrounding a hydrogel center, the core member having an axis, said axis also passing through the first end plate and the second end plate, said member being operational to interlock with said first and second end plates such that when a twisting force is imparted to one of said end plates about that axis, the compressible core member transmits the twisting force from that end plate to the other end plate.   
     
     
         21 . The prosthetic intervertebral disc of  claim 20  wherein said first and second end plates each include openings for accepting one or more protrusions extending from the compressible core member and thereby interlocking the compressible core member with the first and second end plates and wherein the compressible core member comprises the one or more protrusions, the protrusions being operable to engage the first and second endplate openings. 
     
     
         22 . The prosthetic intervertebral disc of  claim 20  wherein the compressible core member comprises a plurality of core elements. 
     
     
         23 . The prosthetic intervertebral disc of  claim 22  wherein said first and second end plates each include openings for accepting one or more protrusions extending from the compressible core member and thereby interlocking the compressible core member with the first and second end plates and wherein the compressible core member comprises the one or more protrusions, the protrusions being operable to engage the first and second endplate openings. 
     
     
         24 . The prosthetic intervertebral disc of  claim 23  wherein each of the plurality of core elements extends into said first and second end plate openings. 
     
     
         25 . The prosthetic intervertebral disc of  claim 20  wherein said first and second end plates each further includes a hemispherical spring that does not substantially rotate with respect to said end plates, each said spring including openings for accepting one or more protrusions extending from the compressible core member and thereby interlocking the compressible core member with the first and second end plates and wherein the compressible core member comprises the one or more protrusions, the protrusions being operable to engage the openings in the first and second endplate hemispherical springs. 
     
     
         26 . The prosthetic intervertebral disc of  claim 20  wherein said first and second end plates each further includes an inner end plate having a periphery, the periphery having outer notches operable to accept protrusions from the compressible core member and operable to interlock the compressible core member and each of the first and second end plates and wherein the compressible core member includes a plurality of arms ending in protrusions operable to enter respectively between the first and second end plates and their respective inner end plates. 
     
     
         27 . The prosthetic intervertebral disc of  claim 20  wherein the first and second end plates each comprises an outer end plate and a spider, each spider comprising a spider extension member operable to be affixed to the respective outer end plate and further comprising a plurality of spider arms extending from the spider extension, each spider thereby providing open regions between the arms operable for accepting protrusions from the compressible core member and thereby interlocking the compressible core member with each of the first and second end plates and wherein the compressible core member comprises the one or more protrusions, the protrusions operable to engage the open regions between the spider arms of the first and second endplates. 
     
     
         28 . The prosthetic intervertebral disc of  claim 27  wherein each spider extension is welded to an outer end plate and the spider arms comprise a spring material and are operable to act as cantilever springs. 
     
     
         29 . The prosthetic intervertebral disc of  claim 20  further comprising fixation elements for directly affixing the first and second end plates to vertebral bone. 
     
     
         30 . The prosthetic intervertebral disc of  claim 20  further comprising one or more stress elements.