the present disclosure concerns implants to at least partially replace the nucleus of a spinal disc . in one embodiment , a prosthetic structure is provided which includes a bag operable to contain at least one internal implant within the bag . in another embodiment , a sinusoidal - shaped structure made of a flexible material is provided with various unique configurations to act as the internal implant and once released from a stretched or compressed configuration resumes nearly its original shape . in one embodiment , for delivery , a sinusoidal - shaped structure may be in a reduced amplitude state . in another embodiment , a sinusoidal - shaped structure is alternately woven from one end to the other with a second sinusoidal - shaped structure .