US Patent 8025681 Dynamic motion spinal stabilization system

Provided is a system for dynamically stabilizing a spine. In one example, the system includes a first bone anchor coupled to a first polyaxial head and a second bone anchor coupled to a second polyaxial head. An axis passing through a center of each polyaxial head is aligned with a center of rotation. A first member has a first end movably coupled to the first polyaxial head and a second end. A second member has a third end coupled to the second polyaxial head and a fourth end moveably coupled to the second end. The first and second members are configured to maintain the alignment of the axes with the center of rotation during three dimensional movement of the first member relative to the second member.