Intervertebral motion disc with helical shock absorber

1. A motion disc comprising:

a) a first prosthetic vertebral endplate comprising:

i) a first outer surface adapted to mate with a first vertebral body,

ii) a first inner surface comprising an first peripheral surface and a first articulation surface,

iii) a body portion connecting the first inner and outer surfaces,

b) a second prosthetic vertebral endplate comprising:

i) a second outer surface adapted to mate with a second vertebral body, and

ii) a second inner surface comprising a second peripheral surface and a second articulation surface,

iii) a body portion connecting the second inner and outer surfaces,

c) an articulating core member comprising:

i) a first articulation surface adapted for articulation with the first articulation surface of the first endplate, and

ii) a second articulation surface adapted for articulation with the first articulation surface of the second endplate,

d) a peripheral, helical shock-absorbing component comprising:

i) a first end portion contacting the first endplate, and

ii) a second end portion contacting the second endplate, and

iii) an axial channel,

wherein the core member is disposed within the axial channel of the helical shock-absorbing component and oriented therein to produce a first articulation interface between the first articulation surface of the first endplate and the first articulation surface of the core member, and a second articulation interface between the first articulation surface of the second endplate and the second articulation surface of the core member,

further comprising a sheath adapted to at least partially enclose the articulation surfaces, wherein the sheath is located between the core and the peripheral, helical shock-absorbing component.