A nucleus replacement mimics a native annulus in shape and function for use in partial disc arthroplasty. The nucleus replacement includes a jacket having a compartment, a first anchoring limb on one side of the compartment, and a second anchoring limb on an opposite side of the compartment. The jacket is insertable into a disc space through an operating channel in at least one of the vertebral pedicle and the vertebral body. A shock absorbing material is injectable into the compartment after installing the jacket into the disc space. The shock absorbing material has characteristics that absorb loads on the replacement.
