Tethered restraint of vertebral bodies
Methods and devices for the tailored restraint of two separate bones, in which the bones are generally permitted to rotate relative to one another, or move toward each other, but are restrained from separating beyond a predetermined, fixed distance. In some embodiments, the restraint is provided by compressing a tether into a notched groove.
1. An apparatus for tethered connection between bones, comprising:
a bone screw having a shaft with threads;
a cap having a through aperture sized to accept therethrough the shaft, said cap including a wedging surface; and
a tethering restraint member having a first channel between first opposing converging walls, said member defining a through aperture sized to accept therethrough the shaft, the first channel including a first region wherein the width of the channel between the first converging walls is a minimum;
wherein placement of said screw through both the cap aperture and the member aperture and attachment of said screw to a bone aligns the wedging surface relative to one of the converging walls to create a second channel between the wedging surface and the one wall.
2. The apparatus of claim 1 wherein the wedging surface and the one wall converge toward each other.
3. The apparatus of claim 1 wherein the region of the first channel includes a vertex between the converging walls.
4. The apparatus of claim 1 wherein the first opposing walls and the wedging surface form a triangular region adapted and configured to compress a tether therein.
5. The apparatus of claim 1 wherein the first channel includes a pathway for a tether in a direction generally perpendicular to the axis of said bone screw.
6. The apparatus of claim 1 wherein the first channel includes a pathway for a tether, each of the first opposing walls of the pathway including at least one groove that is not perpendicular to the channel and is not parallel to the channel.
7. The apparatus of claim 1 wherein each of the first opposing walls includes at least one groove of a plurality of respective grooves, and wherein the respective grooves converge in a direction toward the first region.