Prosthetic joint and nucleus supplement

The present disclosure provides improved prosthetic facet joints (20) and a nucleus supplement device (50) for a spinal disc without violating its annulus fibrosus. In one example, a prosthetic facet joint includes: a tip (34) adapted for mating against a superior articular process of an inferior vertebra, and the tip acts as at least a spacer between the superior articular process and an inferior articular process of a superior vertebra; and an body (38) for mating against a hole in the superior vertebra, and the body comprises a surface that is uneven along its entire length. The prosthetic facet joint may comprise a cavity (36) used for delivering a substance to the articular capsule or joint space. In another example, a nucleus supplement device (50) is provided, having the same structure, but larger body. The nucleus supplement device is to be inserted into a vertebral body (V3) so that the tip penetrates the endplate and the substance (72) in the cavity is used to re-pressurize the nucleus pulposus of the spinal disc (74).