Soft stabilization assemblies with pretensioned cords

Abstract

A soft dynamic stabilization assembly includes a core, typically in the form of a tensioned cord, at least one pair of bone anchors, a spacer surrounding the core located between the bone anchors, typically, at least one elastic bumper and at least one fixing or blocking member. The core is slidable with respect to at least one of the bone anchors and cooperating spacer.

What is claimed and desired to be secured by Letters Patent is as follows: 
     
         1 . A longitudinal connecting member assembly having at least first and second bone anchors spanning between at least a pair of vertebrae, the assembly comprising:
 a) a soft core portion in continuous tension and having a steady state length, the core portion being in slideable relation with at least one of the first and second bone anchors.   
     
     
         2 . The assembly of  claim 1  further comprising a stiff end structure fixed to the soft core portion, the stiff end structure positioned entirely outside of the at least one of the first and second bone anchors. 
     
     
         3 . The assembly of  claim 2  further comprising an elastic bumper in slidable relation with the core portion, the elastic bumper positioned between the stiff end structure and one of the first and second bone anchors. 
     
     
         4 . The assembly of  claim 3  wherein the stiff end structure is a first stiff end structure and further comprising an opposing second stiff end structure also positioned entirely outside of the at least first and second bone anchors, the soft core portion being in slideable relation with both the first and second bone anchors. 
     
     
         5 . The assembly of  claim 4  wherein the elastic bumper is a first elastic bumper and further comprising a second elastic bumper, the second elastic bumper positioned between the second end structure and one of the first and second bone anchors. 
     
     
         6 . The assembly of  claim 2  wherein the stiff end structure has a through bore for receiving the soft core portion and walls that are crimpable toward the soft core portion, fixing the core portion within the through bore. 
     
     
         7 . The assembly of  claim 2  wherein the stiff end structure has a through bore for receiving the soft core portion and a threaded bore disposed perpendicular to the through bore, the threaded bore matable with a set screw, the set screw pressing against the soft core portion and fixing the soft core portion against the stiff end structure within the through bore. 
     
     
         8 . The assembly of  claim 2  wherein the stiff end structure is a plate having at least two holes and the soft core portion is a cord, the cord being looped through the holes, fixing the cord to the plate. 
     
     
         9 . The assembly of  claim 2  wherein the stiff end structure further comprises a rod. 
     
     
         10 . The assembly of  claim 2  wherein the stiff end structure is fixable to a rod. 
     
     
         11 . The assembly of  claim 10  wherein the stiff end structure has a first through bore for receiving the soft core portion and two threaded bores disposed perpendicular to the first through bore, each of the threaded bores matable with a set screw, one of the set screws pressing against the soft core portion and fixing the soft core portion against the stiff end structure within the first through bore, the other of the set screws pressing against the rod and fixing the rod against the stiff end structure within the first through bore. 
     
     
         12 . The assembly of  claim 1  further comprising a spacer located between the first and second bone anchors, the spacer having a through bore that slidingly receives the core portion therethrough. 
     
     
         13 . The assembly of  claim 12  wherein the spacer is compressible. 
     
     
         14 . The assembly of  claim 12  wherein the spacer is elastic. 
     
     
         15 . The assembly of  claim 12  wherein the spacer is substantially tubular and the spacer through bore runs along a central axis thereof. 
     
     
         16 . The assembly of  claim 12  wherein the spacer has a width and a height, the height running from a top surface to a bottom surface, the height being greater than the width and the through bore being located closer to the top surface than to the bottom surface. 
     
     
         17 . The assembly of  claim 1  wherein at least one of the first and second bone anchors has a closure top, one of the bone anchor and the closure top having a stop, the stop prohibiting the closure top from pressing on the soft core portion. 
     
     
         18 . The assembly of  claim 17  wherein the stop is a surface of the bone anchor partially defining a run-out feature of a guide and advancement structure for receiving the closure top. 
     
     
         19 . The assembly of  claim 1  wherein at least one of the first and second bone anchors has an elongate threaded shank and a head, the shank having a central axis, the head having a central bore running there through, the bore disposed perpendicular to the shank central axis, the core portion being slidingly received in the bore, the head having an upper opening for receiving a set screw. 
     
     
         20 . The assembly of  claim 1  wherein at least one of the first and second bone anchors is a polyaxial screw, the screw having a shank, a receiver for holding the soft core portion, and a closure top, the receiver being pivotable with respect to the shank, the closure top capturing the soft core portion within the receiver, the closure top being spaced from the soft core portion when the closure top is locked onto the receiver.