Methods for Deploying Spinal Motion Preservation Assemblies

Abstract

Spinal motion preservation assemblies adapted for use in a spinal motion segment are disclosed including the process for delivering and assembling the spinal motion preservation assemblies in the spinal motion segment via an axial channel created with a trans-sacral approach. The spinal motion preservation assemblies make use of a dual pivot. A number of different embodiments of spinal motion preservation assemblies are disclosed which include at least one component adapted for elastic deformation under compressive loads. The disclosed mobility preservation assemblies provide for dynamic stabilization (DS) of the spinal motion segment.

1 . A method for deploying a spinal motion preservation assembly in a motion segment accessed by an axial trans-sacral approach, the implanted spinal motion preservation assembly comprising a distal component and a proximal component both with external threads, an implant subassembly extending between the distal and proximal components which comprises a pivot adapted for unconstrained engagement by means of dual pivot ends within both the distal component and the proximal component, and an expandable membrane which is expanded with a prosthetic nucleus material, the method comprising:
 rotating a driver which simultaneously deploys the distal component and the proximal component to engage the distal component with a distal vertebral body and to engage the proximal component with a proximal vertebral body while maintaining a predetermined separation distance between the distal component and the proximal component and without cross threading the thread path cut into the proximal vertebral body;   inserting a distal end of the pivot into the proximal end of the distal implant device assembly; and   selectively advancing a portion of the proximal implant device assembly to push the pivot against the distal implant device assembly to change the distribution of loading between A) the prosthetic nucleus and B) the external threads on the proximal component and the external threads on the distal component.   
   
   
       2 . The method of  claim 1  further comprising the step of engaging the distal component with at least one component adapted to elastically deform under compressive load. 
   
   
       3 . The method of  claim 1  further comprising the step of engaging the proximal component with at least one component adapted to elastically deform under compressive load. 
   
   
       4 . The method of  claim 3  further comprising the step of engaging the distal component with at least one component adapted to elastically deform under compressive load. 
   
   
       5 . A method of providing dynamic stabilization to a motion segment in a spine, the method comprising;
 deploying into the motion segment by an axial channel created with a trans-sacral approach a spinal motion stabilization assembly with a pair of unconstrained pivot points and at least one component capable of elastic deformation such that motion segment after receipt of the spinal motion stabilization assembly can undergo motion that enables the normal range of motion in all six degrees of freedom.   
   
   
       6 . The method of  claim 5  further comprising the steps of:
 expanding a membrane connected to the spinal motion stabilization assembly with prosthetic nucleus material to form a prosthetic nucleus; and   selectively varying the loading between the prosthetic nucleus and sets of threads on the spinal motion stabilization assembly engaged with vertebral bodies on the superior and inferior ends of the motion segment.   
   
   
       7 . The method of  claim 6  wherein prosthetic nucleus material is provided to the membrane through a distractor/injector tool after distraction of the motion segment and before removal of the distractor/injector tool.