Patent ID: 8206419

Claim:
A bone anchor-based spinal dynamic stabilization system, comprising: a. a first bone anchor assembly engageable with a first vertebra; b. a second bone anchor assembly engageable with a second vertebra; c. a first articulation element attachable to the first bone anchor assembly, the first articulation element comprising: i. an end portion for attachment to the first bone anchor assembly; ii. a first articulation surface; and iii. a resilient element disposed between the end portion and the first articulation surface; iv. a connector engaging the first articulation surface and extending from the first articulation surface disposed through a first passage in the resilient element and through a second passage in the end portion to terminate in the end portion, the connector adapted to connect the first articulation surface to the end portion; and d. a second articulation element attachable to the second bone anchor assembly and having a second articulation surface configured to engage the first articulation surface; wherein the first articulation surface is configured to be separably engageable with the second articulation surface and is positioned between the end portion of the first articulation element and the second articulation surface; and wherein the resilient element is configured to resiliently resist movement of the first bone anchor assembly and the second bone anchor assembly towards each other when the first articulation surface and the second articulation surface are engaged with each other and the first articulation element and the second articulation element are attached to the first bone anchor assembly and the second bone anchor assembly, respectively; wherein the system is configured to provide no resistance to movement of the first bone anchor assembly and the second bone anchor assembly away from each other.