A method and apparatus for repairing a damaged intervertebral disc nucleus in a minimally invasive manner utilizes a modular disc prosthesis. The modular disc prosthesis preferably comprises at least three modular segments. In one embodiment, each modular segment includes an inner core and an outer shell. The modular segments are selectively interlockable in situ with each other. The modular segments form an implanted unitary device that closely mimics the geometry of the disc nucleus cavity.