Intervertebral nucleus prosthesis and surgical procedure for implanting the same

There is provided an intervertebral-nucleus prosthesis characterized by comprising at least one bi-directionally movable, in particular spherical, body (8) of a solid, non-oxidizing, biocompatible material and having one adapted to the biological nucleus Diameter, which is freely rotatably and immovably mounted in a cage (7) about its center and which protrudes on both opposite sides in the form of a spherical cap from the cage. This nucleus prosthesis can spontaneously assume its own position in the anatomical environment, so that all natural movements between two vertebral bodies can be restored (lateral inclination, inclination forwards and backwards, rotation).