US Patent 7740659 Insert for nucleus implant

Methods and devices are provided for replacing a nucleus of a spinal disc, and in particular for preventing nucleus disc replacement expulsion. The nucleus of a spinal disc can be removed from the annulus by forming a small opening in the annulus. Once the nucleus is removed, one or more insert devices can be implanted within the annulus of a spinal disc and they can be mated to one or both endplates of the adjacent vertebrae. The insert(s) is configured to interact with a nucleus disc replacement implant to prevent expulsion of the implant from the annulus.