Patent ID: 9445845
Filing Date: 2016-09-20
CPC Classification: A61B

Claim Text:
1. A dynamic stabilization device configured for implantation into a spine, comprising: an outer coil spring; an inner coil spring inside the outer coil spring; a first rod; and a second rod, wherein the outer coil spring has a first working length; wherein the first working length is a length through which the outer coil spring extends through turns along a free portion of the outer coil spring over which the outer coil spring is free to bend or compress; wherein the outer coil spring has a first end portion and a second end portion opposite to the first end portion of the outer coil spring, the free portion of the outer coil spring disposed between the first and second end portions of the outer coil spring; wherein the first and second end portions of the outer coil spring are attached to the first and second rods, respectively, such that the outer coil spring undergoes compression under compressive loading between the first and second rods and tension under tensile loading between the first and second rods; wherein the inner coil spring has a second working length; wherein the second working length is a length through which the inner coil spring extends through turns along a free portion of the inner coil spring over which the inner coil spring is free to bend or compress; wherein the inner coil spring has a first end portion and a second end portion opposite to the first end portion of the inner coil spring, the free portion of the inner coil spring disposed between the first and second end portions of the inner coil spring; wherein the first and second end portions of the inner coil spring are attached to the first and second rods, respectively, such that the inner coil spring undergoes compression under compressive loading between the first and second rods and tension under tensile loading between the first and second rods; and wherein the first working length is substantially equal to the second working length.