A spinal treatment system includes a constraint device having an upper tether portion, a lower tether portion and a compliance member coupled therebetween. The upper tether portion is coupled with a superior spinous process of a spinal segment in a patient and the lower tether portion is coupled with an inferior spinous process or sacrum of the spinal segment. The length or tension in the constraint device is adjustable so that the construct of the tether portions and the compliance member provides a force resistant to flexion of the spinal segment. The system also includes a first prosthesis coupled with the spinal segment, wherein the constraint device modulates loads borne by the prosthesis or by tissue adjacent thereto.