Structures and methods for constraining spinal processes with single connector

Abstract

Spinous process constraint structures include a first attachment element for placement over a first spinous process and a second attachment element for placement over a second spinous process. The attachment elements are joined by a single connector which may optionally include a compliance member for providing controlled elasticity between the spinous processes.

1 . A spinous process constraint structure for restricting flexion of a spinal segment, said constraint structure comprising:
 a first attachment element adapted to be coupled to a first spinous process;   a second attachment element adapted to be coupled to a second spinous process or a sacrum; and   at least one connector joining the first attachment element and the second attachment element, said at least one connector lying laterally beside the sides of the spinous processes and providing a connection between said attachment elements having an elastic stiffness in tension that resists flexion of the spinal segment without resisting extension thereof.   
     
     
         2 . A constraint structure as in  claim 1 , wherein the elastic stiffness in tension is in the range from 7.5 N/mm to 50 N/mm. 
     
     
         3 . A constraint structure as in  claim 1 , wherein the elastic stiffness in tension is in the range from 10 N/mm to 25 N/mm. 
     
     
         4 . A constraint structure as in  claim 1 , wherein the elastic stiffness in tension is in the range from 10 N/mm to 15 N/mm. 
     
     
         5 . A constraint structure as in  claim 1 , wherein said connector further provides an elastic stiffness in compression below 3 N/mm. 
     
     
         6 . A constraint structure as in  claim 5 , wherein said elastic stiffness in compression is below 0.5 N/mm. 
     
     
         7 . A constraint structure as in  claim 1 , wherein the at least one connector comprises an axial member positioned to lie parallel to the sides of the spinous processes. 
     
     
         8 . A constraint structure as in  claim 1 , further comprising at least one compliance member on the at least one connector, wherein the at least one connector has a superior segment above the at least one compliance member and an inferior segment below the at least one compliance member. 
     
     
         9 . A constraint structure as in  claim 1 , wherein the single connector comprises an elastomeric body positionable beside the supraspinous ligament. 
     
     
         10 . A constraint structure as in  claim 1 , wherein at least one of the first and second attachment structures is adapted to be fixedly attached to the spinous process. 
     
     
         11 . A constraint structure as in  claim 10 , wherein the first attachment structure is adapted to be fixedly attached to a superior spinous process and the second attachment structure is adapted to be fixedly attached to an inferior spinous process. 
     
     
         12 . A constraint structure as in  claim 10 , wherein the first attachment structure is adapted to be fixedly attached to a spinous process and the second attachment structure is adapted to be fixedly secured to a sacrum. 
     
     
         13 . A constraint structure as in  claim 1 , wherein at least one of the first attachment element and the second attachment element comprise a clamp which is securable over a posterior face of the spinous process. 
     
     
         14 . A constraint structure as in  claim 1 , wherein at least one of the first attachment element and the second attachment element comprise a pin which can be secured laterally through the spinous process. 
     
     
         15 . A constraint structure as in  claim 1 , wherein at least one of the first attachment element and the second attachment element is adapted to be placed around the spinous process without fixed attachment. 
     
     
         16 . A constraint structure as in  claim 15 , wherein the first attachment element is adapted to be placed over a superior surface of a superior spinous process and the second attachment element is adapted to be placed under an inferior surface of the interior spinous process. 
     
     
         17 . A constraint structure as in  claim 15 , wherein the first attachment element is adapted to be placed over a spinous process and the second attachment element is adapted to fixedly secured to a sacrum. 
     
     
         18 . A constraint structure as in  claim 16 , wherein the first attachment element and the second attachment element are open hook structures. 
     
     
         19 . A constraint structure as in  claim 18 , wherein the hook structures are pivotally attached to the at least one connector to allow closure of the hook over the spinous process after the at least one connector has been aligned beside the spinous processes. 
     
     
         20 . A constraint structure as in  claim 18 , wherein the at least one connector comprises an axial member joining the hooks in a C-pattern. 
     
     
         21 . A constraint structure as in  claim 1 , wherein the at least one connector comprises a flexible element that extends at least partly between the two attachment members, wherein the flexible member collapses under compression. 
     
     
         22 . A constraint structure as in  claim 21 , wherein the flexible member is compliant to provide said elastic stiffness in tension. 
     
     
         23 . A constraint structure as in  claim 21 , wherein the flexible member is non-compliant under tension and located in series with a compliance member that provides the elastic stiffness in tension. 
     
     
         24 . A method for restricting flexion of a spinal segment, said method comprising:
 positioning a first attachment element on a first spinous process; and   positioning a second attachment element on a second spinous process or a sacrum;   wherein the attachment elements are joined with at least one connector extending therebetween and lying laterally beside the sides of the spinous processes, said at least one connector providing a connection between said attachment elements having an elastic stiffness in tension that resists flexion of the spinal segment without resisting extension thereof.   
     
     
         25 . A method as in  claim 24 , wherein the at least one connector provides an elastic stiffness in tension between said attachment elements in the range from 7.5 N/mm to 50 N/mm. 
     
     
         26 . A method as in  claim 24 , wherein the elastic stiffness is in the range from 10 N/mm to 25 N/mm. 
     
     
         27 . A method as in  claim 24 , wherein the elastic stiffness is in the range from 10 N/mm to 15 N/mm. 
     
     
         28 . A method as in  claim 24 , wherein the single connector provides an elastic stiffness in compression between said elements below 3 N/mm. 
     
     
         29 . A method as in  claim 28 , wherein said elastic stiffness in compression is below 0.5 N/mm. 
     
     
         30 . A method as in  claim 24 , further comprising attaching the attachment members to the spinous process and/or the sacrum. 
     
     
         31 . A method as in  claim 24 , wherein the attachment elements and elastic member are introduced percutaneously. 
     
     
         32 . A method as in  claim 31 , wherein the attachment elements and elastic member are introduced laterally from one side of the spinal midline 
     
     
         33 . A method as in  claim 31 , wherein the attachment elements and member are introduced from a posterior approach from one side of the spinal midline. 
     
     
         34 . A method as in  claim 24 , wherein at least one of the first attachment element and the second attachment element comprise a clamp positioning comprises securing the clamp over a posterior face of the spinous process. 
     
     
         35 . A method as in  claim 24 , wherein at least one of the first attachment element and the second attachment element comprise a pin and positioning comprises securing the pin laterally through the spinous process. 
     
     
         36 . A method as in  claim 24 , wherein the attachment elements comprise hooks and positioning comprises introducing the hooks in a retracted configuration and pivoting the hooks relative to the at least one connector to capture the spinous processes after the at least one connector is positioned adjacent the spinous processes. 
     
     
         37 . A method as in  claim 36 , wherein a superior hook is pivoted over a superior surface of a superior spinous process and an inferior hook is pivoted over an inferior surface of an inferior spinous process. 
     
     
         38 . A method as in  claim 24 , further comprising reinforcing the at least one connector to limit deformation under axial load. 
     
     
         39 . A method as in  claim 38 , wherein reinforcing comprises placing a reinforcement sleeve over the single connector. 
     
     
         40 . A method as in  claim 38 , wherein the at least one connector includes a compliance member and reinforcing comprises placing a slide assembly adjacent to the compliance member, said slide assembly aligning superior and inferior segments of the single connector.