Abstract: A partial endoprosthesis device preserves the motion of a vertebral joint for implant into a spinal segment and includes an articular portion having a thickness that increases in the direction of introduction between the articular facets. The articular portion is elongated along a longitudinal axis with a opposite first and second faces. The first face has a central protrusion that is configured so that, by implanting the device with the articular portion inserted between an upper articular facet of a lower vertebra and a corresponding lower articular facet of upper vertebra adjacent to the lower vertebra, and with the first face in contact with either the upper or lower articular facet, and with the second face in contact with the other articular facet, the articular portion, with the first face, pushes against the first articular facet and finally becomes integral by osteointegration with the lower articular facet.

Abstract: A partial endoprosthesis device preserves the motion of a vertebral joint for implant into a spinal segment and includes an articular portion having a thickness that increases in the direction of introduction between the articular facets. The articular portion is elongated along a longitudinal axis with a opposite first and second faces. The first face has a central protrusion that is configured so that, by implanting the device with the articular portion inserted between an upper articular facet of a lower vertebra and a corresponding lower articular facet of upper vertebra adjacent to the lower vertebra, and with the first face in contact with either the upper or lower articular facet, and with the second face in contact with the other articular facet, the articular portion, with the first face, pushes against the first articular facet and finally becomes integral by osteointegration with the lower articular facet.