Adjustable spinal stabilization system

Abstract

An adjustable spinal stabilization system having a flexible connection unit for non-rigid stabilization of the spinal column. In one embodiment, the spinal stabilization system includes a flexible connection unit having a tether running through a hollow portion of the flexible connection unit, wherein the tether limits bending of the flexible connection unit. In a further embodiment the tether is pre-tensioned. In a further embodiment, the tension upon or compression of the tether is adjustable.

1 . A connection unit for use in a spinal stabilization device comprising a longitudinal member having first and second ends that are configured to be secured to a patient's spine using at least two securing members, a flexible section in between the first and second ends, and at least one tether that is fixed to the longitudinal member at the first and second ends, the at least one tether having enough slack to allow bending or extension of the longitudinal member up to a point that the tether becomes taught, thereby resisting further bending or extension. 
     
     
         2 . The connection unit of  claim 1  wherein the longitudinal member is configured in the shape of a cylindrical rod. 
     
     
         3 . The connection unit of  claim 1  wherein the longitudinal member is hollow. 
     
     
         4 . The connection unit of  claim 3  wherein a cavity of the hollow longitudinal member includes the at least one tether that is fixed to the longitudinal member at the first and second ends. 
     
     
         5 . The connection unit of  claim 1  wherein the longitudinal member comprises a material that is selected from at least one of a group of known, bio-compatible materials consisting of metals, metal alloys, organic polymers, natural resins, synthetic resins, thermoplastics, elastomers and composite materials. 
     
     
         6 . The connection unit of  claim 1  wherein the at least one tether comprises a material that is selected from at least one of a group of known flexible, materials consisting of metals, metal alloys, organic polymers, natural resins, synthetic resins, thermoplastics, elastomers and composite materials. 
     
     
         7 . The connection unit of  claim 1  wherein the at least one tether comprises a structure that is selected from a group of known structures consisting of fibers, multi-fiber bundles, wires, multi-wire bundles, ribbons, multi-ribbon bundles, rods, and multi-rod bundles. 
     
     
         8 . The connection unit of  claim 1  wherein the at least one tether is pre-tensioned to a desired degree of tautness in at least one orientation relative to the longitudinal axis of the connection unit. 
     
     
         9 . The connection unit of  claim 1  wherein the longitudinal member is hollow and the at least one tether is mounted offset from a longitudinal center axis of the hollow longitudinal member to allow for different ranges of bending of the hollow longitudinal member in different directions of bending. 
     
     
         10 . The connection unit of  claim 9  wherein the at least one tether is pre-tensioned to make the hollow longitudinal member bend in the absence of external bending forces. 
     
     
         11 . A connection unit for use in a spinal stabilization device comprising a hollow longitudinal member having first and second ends that are configured to be secured to a patient's spine using at least two securing members, a flexible section in between the first and second ends, and at least one tether positioned within a cavity of the longitudinal member, wherein a first end of the at least one tether is coupled to an adjustable coupling member at the first end of the longitudinal member, and a second end of the at least one tether is coupled to the second end of the longitudinal member. 
     
     
         12 . The connection unit of  claim 11  wherein the longitudinal member is configured in the shape of a cylindrical rod. 
     
     
         13 . The connection unit of  claim 11  wherein the adjustable coupling member is an externally threaded screw member configured to mate with an internally threaded section of the first end of the hollow longitudinal member, the screw member being capable of rotation to adjust its position along a longitudinal axis of the hollow longitudinal member, thereby adjusting an axially directed tension on the at least one tether. 
     
     
         14 . The connection unit of  claim 13  wherein the screw member is coupled to the at least one tether with a slip joint that allows axial rotation of the screw member without rotating the at least one tether and maintains the axially directed tension on the tether by the screw member. 
     
     
         15 . The connection unit of  claim 13  wherein the screw member is rigidly fixed to the first end of the at least one tether, and the second end of the at least one tether is coupled to a slip joint located at the second end of the longitudinal member such that the slip joint allows rotation of the at least one tether while maintaining the axially directed tension on the at least one tether. 
     
     
         16 . The connection unit of  claim 11  wherein the adjustable coupling member comprises a material that is selected from at least one of a group of known, bio-compatible materials consisting of metals, metal alloys, organic polymers, natural resins, synthetic resins, thermoplastics, elastomers and composite materials. 
     
     
         17 . The connection unit of  claim 11  wherein the hollow longitudinal member comprises a material that is selected from at least one of a group of known, bio-compatible materials consisting of metals, metal alloys, organic polymers, natural resins, synthetic resins, thermoplastics, elastomers and composite materials. 
     
     
         18 . The connection unit of  claim 11  wherein the at least one tether comprises a material that is selected from at least one of a group of known flexible, materials having controlled extensibility responsive to tensile stress consisting of metals, metal alloys, organic polymers, natural resins, synthetic resins, thermoplastics, elastomers and composite materials. 
     
     
         19 . The connection unit of  claim 11  wherein the at least one tether comprises a structure that is selected from a group of known structures consisting of fibers, multi-fiber strands, wires, multi-wire strands, ribbons, multi-ribbon strands, rods, and multi-rod bundles. 
     
     
         20 . The connection unit of  claim 11  wherein the at least one tether is mounted offset from a longitudinal center axis of the hollow longitudinal member to allow for different ranges of bending of the hollow longitudinal member in different directions of bending.