An artificial disc having a pair of opposing plates for seating against opposing
vertebral bone surfaces, separated by at least one spring mechanism. The preferred
spring mechanism is at least one spirally slotted belleville washer, and in some
embodiments the belleville washer is also radially thinning or thickening. Various
illustrated embodiments use two washers or one washer. For double washer embodiments,
the wide ends of the washers seat against respective opposing plates, in some embodiments
each being maintained thereagainst by a retaining wall and ring or a circular recess
and retaining shield. For single washer embodiments, the narrow end of the washer
can be modified to have a curvate socket for rotatably mounting onto a semispherical
protuberance extending from one of the plates.
