A cephalad prosthesis (330) for replacing all or a portion of a cephalad portion of a natural facet joint on a vertebral body is described. The prosthesis comprises: a prosthesis body (310) for accommodating fixation to the vertebral body at or near a pedicle (14) and without support by a lamina, and an artificial cephalad facet joint structure carried by the prosthesis body which is adapted and configured to replace all or a portion of a cephalad portion of a natural facet joint.