Patent ID: 7942904

Claim:
A screw based spinal stabilization device, comprising: a superior screw; an inferior screw; a spacer coupled to the superior screw and inferior screw, the spacer allows compression and expansion of vertebral bodies and comprises an elastic portion to allow relative movement between the superior screw and the inferior screw that dampens compression and expansion of the spacer to provide a relatively gentle stop to motion; and a sheath of substantially inelastic material comprising a degradable material abutting the spacer to inhibit relative motion between the superior screw and the inferior screw for a period of time, a first configuration of the sheath of substantially inelastic material, during the period of time and prior to degradation, inhibiting relative motion between the screws so as to promote fusion of the superior screw and the inferior screw to the vertebral bodies, and a second configuration of the sheath of substantially inelastic material, after the period of time and degradation, allowing relative motion between the screws.