A prosthesis system replaces facet joints on adjoining vertebral bodies. The prosthesis system employs a caudal prosthesis for fixation to a first vertebral body and a cephalad prosthesis for fixation to the second vertebral body. The caudal and cephalad prostheses have, respectively a first artificial caudal facet joint structure and an artificial cephalad facet joint structure, to replace all or a portion of, respectively a caudal and cephalad portions of the natural facet joint (i.e., superior and inferior articular processes, respectively) between the adjoining first and second vertebral bodies. The prosthesis system further employs a second artificial caudal facet joint structure fixed superior to the artificial cephalad facet joint structure on the second vertebral body. The second artificial caudal facet joint structure replaces all or a portion of a caudal portion of a natural facet joint (i.e., a superior articular process) between the second vertebral body and an adjoining third vertebral body superior to the second vertebral body.