Superelastic spinal stabilization system and method

Abstract

An apparatus for treatment of the spine including a stabilization device at least partially formed of a material capable of exhibiting superelastic characteristics at about body temperature. The stabilization device includes a longitudinal portion positionable across at least one intervertebral space, a first anchor portion engagable with a first vertebral body, and a second anchor portion engagable with a second vertebral body. The stabilization device is reformed from an initial configuration to a different configuration in response to an imposition of stress caused by relative displacement between the first and second vertebral bodies.

What is claimed is:  
     
         1 . An apparatus for treatment of the spine, comprising: 
 a stabilization device at least partially formed of a material capable of exhibiting superelastic characteristics at about body temperature, said stabilization device comprising: 
 a longitudinal portion positionable across at least one intervertebral space;  
 a first anchor portion engagable with a first vertebral body; and  
 a second anchor portion engagable with a second vertebral body; and  
   wherein said stabilization device is reformed from an initial configuration to a different configuration in response to an imposition of stress caused by relative displacement between the first and second vertebral bodies.    
     
     
         2 . The apparatus of  claim 1  wherein said material comprises a shape-memory material.  
     
     
         3 . The apparatus of  claim 2  wherein said shape-memory material comprises a polymer.  
     
     
         4 . The apparatus of  claim 2  wherein said shape-memory material comprises a metallic alloy.  
     
     
         5 . The apparatus of  claim 1  wherein said imposition of stress causes at least a portion of said material to form reversible stress-induced martensite, and wherein a reduction of said stress causes at least a portion of said material to reform into austenite.  
     
     
         6 . The apparatus of  claim 5  wherein said stabilization device is reformed from said different configuration back toward said initial configuration in response to said reduction in said stress.  
     
     
         7 . The apparatus of  claim 1  wherein said material is in an austenitic state when said stabilization device is in said initial configuration and in a stress-induced martensitic state when said stabilization device is in said different configuration.  
     
     
         8 . The apparatus of  claim 1  wherein said longitudinal portion has an initial length corresponding to said initial configuration and a different length corresponding to said different configuration.  
     
     
         9 . The apparatus of  claim 1  wherein said stabilization device has an initial shape corresponding to said initial configuration and a different shape corresponding to said different configuration.  
     
     
         10 . The apparatus of  claim 1  wherein said first and second anchor portions extend transversely from said longitudinal portion.  
     
     
         11 . The apparatus of  claim 1  wherein said longitudinal portion comprises a rod.  
     
     
         12 . The apparatus of  claim 1  wherein said longitudinal portion comprises a plate.  
     
     
         13 . The apparatus of  claim 1  wherein said first and second anchor portions comprise screws.  
     
     
         14 . The apparatus of  claim 1  wherein said first and second anchor portions comprise hooks.  
     
     
         15 . An apparatus for treatment of the spine, comprising: 
 a plurality of stabilization devices at least partially formed of a material capable of exhibiting superelastic characteristics at about body temperature, each of said stabilization devices comprising: 
 a longitudinal portion positionable across at least one intervertebral space;  
 a first anchor portion engagable with a first vertebral body; and  
 a second anchor portion engagable with a second vertebral body; and  
   wherein each of said stabilization devices is reformed from an initial configuration to a different configuration in response to an imposition of stress caused by relative displacement between corresponding ones of the first and second vertebral bodies.    
     
     
         16 . The apparatus of  claim 15  wherein said material comprises a shape-memory material.  
     
     
         17 . The apparatus of  claim 15  wherein said imposition of stress causes at least a portion of said material to form reversible stress-induced martensite, and wherein a reduction of said stress causes at least a portion of said material to reform into austenite.  
     
     
         18 . The apparatus of  claim 15  wherein said material is in an austenitic state when said stabilization device is in said initial configuration and in a stress-induced martensitic state when said stabilization device is in said different configuration.  
     
     
         19 . The apparatus of  claim 15  wherein each of said stabilization devices has an initial shape corresponding to said initial configuration and a different shape corresponding to said different configuration.  
     
     
         20 . A method for treatment of the spine, comprising: 
 providing a plurality of stabilization devices at least partially formed of a material exhibiting superelastic characteristics at about body temperature; and    engaging each of the plurality of stabilization devices to a corresponding pair of vertebral bodies.    
     
     
         21 . The method of  claim 20  further comprising transforming at least a portion of the material into reversible stress-induced martensite as a result of imposition of stress caused by relative movement between the corresponding pair of vertebral bodies.  
     
     
         22 . The method of  claim 21  wherein the relative movement between the corresponding pair of vertebral bodies comprises at least one of flexional and extensional movement.  
     
     
         23 . The method of  claim 21  wherein the relative movement between the corresponding pair of vertebral bodies comprises torsional movement.  
     
     
         24 . The method of  claim 21  wherein the transforming is accompanied by a corresponding change in length of the stabilization device.  
     
     
         25 . The method of  claim 21  wherein the transforming is accompanied by a corresponding change in shape of the stabilization device.  
     
     
         26 . The method of  claim 21  further comprising reforming at least a portion of the reversible stress-induced martensite into austenite by reducing the stress.  
     
     
         27 . The method of  claim 20  wherein the engaging comprises anchoring the plurality of stabilization devices across multiple vertebral levels.  
     
     
         28 . The method of  claim 20  wherein the engaging comprises anchoring the plurality of stabilization devices to a cervical region of the spine.  
     
     
         29 . The method of  claim 20  wherein the material comprises a shape-memory material having a stress-induced martensitic state and an unstressed austenitic state, the engaging occurring while the shape-memory material is in the unstressed austenitic state.  
     
     
         30 . The method of  claim 20  wherein the plurality of stabilization devices stabilize the portion of the spine being treated while providing substantially normal biomechanical motion thereto.