Dynamic fusion mechanostat devices

Abstract

A dynamic bone fusion device for facilitating fusion between bone sections, particularly vertebrae, is selected having certain stiffness to induce specific strain conditions associated with high success rates in bone fusion. Temporary stiffeners that are absorbable by the body may be implemented with the fusion device.

9 . (New) A dynamic fusion device, which comprises: 
 a spring mechanism positionable between adjacent bone structures, the spring mechanism having a spring constant to maintain a natural spacing between the bone structure and to simulate a strain condition in response to compressive forces on the bone structures sufficient to initiate and sustain fusion and healing thereof.    
     
     
         10 . (New) The dynamic fusion device according to  claim 9  wherein the spring mechanism has a spring constant adapted to create a strain range between the bone structures ranging from about 0.5 to 15%.  
     
     
         11 . (New) The dynamic fusion device according to  claim 9  wherein the spring mechanism has a spring constant adapted to create a strain range between the bone structures ranging from about 2 to 10%.  
     
     
         12 . (New) The dynamic fusion device according to  claim 9  wherein the spring mechanism has a spring constant adapted to create a strain range between the bone structures ranging from about 4 to 8%.  
     
     
         13 . (New) The dynamic fusion device according to  claim 9  wherein the spring mechanism includes a stiffening element adapted to increase stiffness in the direction of the compressive force, the stiffening element comprising a bioabsorbable material.  
     
     
         14 . (New) The dynamic fusion device according to  claim 13  wherein the bioabsorbable material comprises a bioabsorbable polymeric material.  
     
     
         15 . (New) The dynamic fusion device according to  claim 9  wherein the spring mechanism is dimensioned to support adjacent vertebrae in spaced relation.  
     
     
         16 . (New) A method for facilitating healing of adjacent bone structures comprising the steps of: 
 accessing an open space between adjacent bone structures; and    positioning a bone fusion device within the open space, the bone fusion device including a spring mechanism having a spring constant sufficient to support the adjacent bone structures in spaced relation and creating a strain condition in response to forces exerted on the bone structures sufficient to initiate and sustain ossification and fusion thereof.    
     
     
         17 . (New) The method for facilitating healing of adjacent bone structures according to  claim 16  wherein the spring mechanism defines a spring constant which creates a strain condition having a strain range ranging from about 4% to 8%.  
     
     
         18 . (New) The method for facilitating healing of adjacent bone structures according to  claim 16  wherein the spring mechanism includes a bioabsorbable stiffening member, and further including the step of permitting the bioabsorbable member to absorb over time to gradually increase a load exerted on the spring mechanism.  
     
     
         19 . (New) The method for facilitating healing of adjacent bone structures according to  claim 16  wherein the spring mechanism includes a stiffening member comprising a bioabsorbable polymeric material, and further including the step of permitting the bioabsorbable member to absorb over time to gradually increase a load exerted on the spring mechanism.  
     
     
         20 . (New) A bone fusion device, which comprises: 
 a spring element positionable relative to adjacent bone structures, the spring element having a spring constant sufficient to maintain the bone structures in spaced relation during healing; and    a bioabsorbable stiffening element associated with the spring element, the stiffening element adapted to resist compressive forces exerted on the bone structures, the stiffening element being absorbable to increase a load on the spring element over a predetermined period of time.    
     
     
         21 . (New) The bone fusion device according to claim  20  wherein the stiffening element comprises a bioabsorbable polymeric material.