Adjustable spinal prosthesis

Apparatus comprising:

• a first spinal prosthetic member attachable to a first spinal structure;
• and
• a second spinal prosthetic member attachable to a second spinal structure, said first and second spinal prosthetic members being movably attached to one another with a fastening device, said fastening device having a non-tightened position which permits spatial movement of said first and second spinal prosthetic members with respect to one another at a desired orientation, and a tightened position which fixes said first and second spinal prosthetic members at the desired orientation;
• wherein said first and second spinal prosthetic members are pivotable with respect to one another about a first pivot axis to define an angle between said first and second spinal prosthetic members that corresponds to a lordotic angle between the first and second spinal structures, and
• wherein said first and second spinal prosthetic members articulate with respect to one another along non-straight surfaces thereof and said fastening device, in its tightened position, fixes said first and second spinal prosthetic members at a desired orientation along the non-straight surfaces, said fastening device comprising a threaded fastener and a spacer member, said spacer member having a non-straight surface that interfaces with and is tightened by said threaded fastener against the non-straight surfaces of said first and second spinal prosthetic members.