Axially compressible artificial intervertebral disc having limited rotation using a captured ball and socket joint with a solid ball and retaining cap

An intervertebral spacer device, comprising:

• a first baseplate, having an outwardly facing surface and an inwardly facing surface, the inwardly facing surface having a central post secured thereto, the post having a longitudinal axis and a ball at a head end of the post that is inwardly directed toward the second baseplate, the ball defining a spherical contour and having a curvate recess;
• a second baseplate, having an outwardly facing surface and an inwardly facing surface, the second baseplate including a convex structure integral therewith and a cap secured thereto, the convex structure and the cap together establishing a curvate socket communicating with a central bore through the convex structure, the curvate socket defining a spherical contour, the convex structure further having a protrusion extending into the curvate socket;
• wherein
• the ball is capturable in the curvate socket, with the curvate socket's spherical contour accommodating the ball's spherical contour for rotation and angulation of the ball in the curvate socket about a central portion of the ball;
• with the ball's curvate recess accommodating the convex structure's protrusion to limit rotation of the ball in the curvate socket;
• and
• with the central bore accommodating the post for rotation in the central bore about the longitudinal axis as the ball rotates in the curvate socket, and accommodating the post for angulation in the central bore about the ball's central portion as the ball angulates in the curvate socket;
• and further comprising
• a spring member housed by the cap such that a compressive load applied to the outwardly facing surfaces of the baseplates is borne by the spring member.

An artificial intervertebral disc, comprising:

• a first baseplate, having an outwardly facing surface and an inwardly facing surface, the inwardly facing surface having a central hole;
• a second baseplate, having an outwardly facing surface and an inwardly facing surface;
• an inwardly directed convex structure integral with the second baseplate, the convex structure forming a curvate pocket having a semispherical contour on the second baseplate's outwardly facing surface, the convex structure further having a protrusion adjacent the convex structure's curvate pocket, the convex structure further having a bore aligned with the central hole and passing from the convex structure's curvate pocket to the second baseplate's inwardly facing surface;
• a ball at a head end of a post, the ball having a curvate recess having boundaries, the ball being seatable in the convex structure's curvate pocket with the post disposed through the bore, the post having a tail end securable in the central hole;
• and
• a cap forming a curvate pocket having a semispherical contour, the cap being securable to the second baseplate with the cap's curvate pocket opposing the convex structure's curvate pocket to form a curvate socket within which the ball is rotatable and angulatable about a central portion of the ball, the cap housing a spring member such that a compressive load applied to the outwardly facing surfaces of the baseplates is borne by the spring member;
• wherein
• the ball is seatable in the convex structure's curvate pocket with the ball's curvate recess accommodating the convex structure's protrusion such that the ball's curvate recess's boundaries define limits of rotation of the ball within the curvate socket in that the ball's rotation within the curvate socket is limited by interference between the protrusion and the boundaries, and such that the boundaries accommodate angulation of the ball within the curvate socket.