Methods and apparatus for coupling a prosthesis to a spinal segment

A system for restricting flexion of a spinal segment in a spine of a patient, said system comprising:

• a tether structure adapted to be coupled with the spinal segment or the spine;
• a first compliance element coupled with the tether structure and configured to elastically elongate as tension is applied through the tether structure;
• and
• a first constraining tool releasably coupled with the first compliance element so as to hold the first compliance element in a first desired position and allow a first predetermined amount of elastic elongation of the first compliance element as tension is applied to the first compliance element through the tether structure.