This invention relates generally to spinal stabilization and, in particular, to a spinal implant placed across a facet joint via opener microsurgical techniques that allows for either dynamic (motion preserving) or static (no motion) stabilization.
Various facet fixation techniques are known to those of skill in the art. The universal cannulated screw system of Medtronics includes a translaminar cannulated screw that is placed by guide wire across the facet joint from an entry point at the spinous process/laminate junction. This is opposite the actual facet joint, closing through the lamina and facet joint proper. The system provides only for static stabilization using a translaminar, open approach, with significant dissection. The fixation is non-locking.
The Nuvasive facet fixation system is a non-translaminar approach utilizing a single screw through the facet joint and trajectory down into the pedicle. The screw pathway is oblique to the joint surface. Although open or micro techniques may be used, the system is non-locking and limited to static fixation.
The Dynasys system from Zimmer, which is a dynamic pedicle fixation device, utilizes pedicle screws attached to an elastic-type “rod” covered in a silicone spacer. The system is dynamic only and must use an open technique. The facet joint is not involved.
This invention resides in a facet fixation system that facilitates dynamic or static stabilization with few exposed components. A first anchor component is adapted for implantation through a facet joint and into intra-pedicle bone, and a second anchor component is adapted for fixation to the outer surface of the facet joint. A connector component connects the first and second anchor components. The connector component may be at least partially elastic, facilitating a dynamic stabilization of a facet joint, or rigid, facilitating a static stabilization of a facet joint.
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Although the system just described is dynamic in nature, a static system may be created by substituting the anchor 110 and elastic cord with a fixed, solid shaft and distal anchor. A separate, low-profile top tightening nut attaches to the outer threads of the thick shaft, causing static compression across the facet joint. Indeed, according to the invention, a dynamic system may be revised to become static, if necessary.
This application claims priority from U.S. Provisional Patent Application Ser. No. 60/776,451, filed on Feb. 24, 2006, the entire content of which is incorporated herein by reference.
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60776451 | Feb 2006 | US |