US Patent 9445845 Dynamic stabilization systems and devices for a spine

A dynamic stabilization device is disclosed. The device includes a dual spring member comprising an outer spring and an inner spring that have approximately equal working lengths. The dynamic stabilization device is also configured so that the dual spring member does not undergo stresses greater than an effective fatigue limit that is related to a fatigue limit of the spring. Methods for treating a deformity of a spine using a dynamic stabilization device are also disclosed.