Prosthetic Disc Assembly Having Natural Biomechanical Movement

A prosthetic intervertebral disc comprising:

• a first end structure attachable to a first vertebrae,
• a second end structure attachable to a second vertebrae,
• a core structure comprising at least a portion in compression with relation to the first end structure and the second end structure, said core member comprising at least a portion in tension with relation both to the first end structure and to the second end structure, having a bulk compressibility of 737 Nmm+/−885 Nmm, and positioned with respect to and interacting with the first end structure and with the second end structure such that, when measured with 150 Nm axial preloading, provides:
• a nonlinear torsional response to relational movement between the first end structure and with the second end structure when a torsional moment is applied to at least one of the first end structure and the second end structure of the form in FIG. 5, and,
• a nonlinear side-to-side bending response to relational movement between the first end structure and the second end structure when a side-to-side bending moment is applied to at least one of the first end structure and the second end structure of the form in FIG. 5, and,
• a nonlinear flexion-extension to relational movement between the first end structure and the second end structure when a flexion-extension moment is applied to at least one of the first end structure and the second end structure of the form in FIG. 5, and,
• and wherein each of the first end structure and the second end structure defines an IAR and wherein the IAR's of each of the first end structure and the second end structure, when a moment is applied to said end structure, is determined by the compression and tension of the core structure