Methods and systems for increasing the bending stiffness and constraining the spreading of a spinal segment

Abstract

A system for restricting spinal flexion includes superior and inferior tether structures joined by a pair of compliance members. Compliance members comprise tension members which apply a relatively low elastic tension on the tether structures. By placing the tether structures on or over adjacent spinous processes, flexion of a spinal segment can be controlled in order to reduce pain.

1 . A method for relieving symptoms of lumbar pain associated with flexion of a spinal segment of a patient, said method comprising:
 increasing the bending stiffness of the spinal segment by an amount in the range from 0.1 Nm/deg to 2 Nm/deg.   
     
     
         2 . A method as in  claim 1 , wherein the bending stiffness is increased by coupling an elastic constraint between a superior spinous process and an inferior spinous process or between an L 5  spinous process and a sacrum. 
     
     
         3 . A method as in  claim 2 , wherein the elastic constraint has an elastic stiffness in the range from 7.5 N/mm to 40 N/mm and the constraint is positioned at a lateral distance in the range from 25 mm to 75 mm in a posterior direction from a center of rotation of the spinal segment. 
     
     
         4 . A method as in  claim 2 , further comprising adjusting the elastic constraint so that it is taut but not stretched over the spinous processes or L 5  spinous process and sacrum when the spinal segment is in its neutral position. 
     
     
         5 . A method as in  claim 4 , wherein adjusting comprises changing the length of the elastic constraint after it has been coupled to the spinous processes or L 5  spinous process and sacrum. 
     
     
         6 . A method as in  claim 1 , wherein the bending stiffness is increased over at least a portion of the full flexion range of motion of the spinal segment. 
     
     
         7 . A method as in  claim 7 , wherein the bending stiffness is increased over the entire full flexion range of motion of the spinal segment. 
     
     
         8 . A method for relieving symptoms of lumbar pain associated with flexion of spinal segment, said method comprising:
 constraining spreading of the spinous processes of the spinal segment to a maximum distance in the range from 1 mm to 10 mm from a neutral position of the segment.   
     
     
         9 . A method as in  claim 8 , wherein spreading is constrained to a maximum distance in the range from 2 mm to 8 mm. 
     
     
         10 . A method as in  claim 8 , wherein constraining comprises coupling an elastic constraint between a superior spinous process and an inferior spinous process or between a spinous process and a sacrum of the spinal segment. 
     
     
         11 . A compliance member for attaching inelastic tethers circumscribing spinal processes, said compliance member comprising:
 a body having a first tether attachment element and a second tether attachment element, said body defining an axial tension spring between said attachments;   wherein the body has a maximum axial length of 38 mm, a maximum depth in an anterior-posterior direction of 18 mm, and a maximum width in a direction normal to the depth of 15 mm.   
     
     
         12 . A compliance member as in  claim 11 , wherein at least the first tether attachment element releasably secures the tether. 
     
     
         13 . A compliance member as in  claim 11 , wherein at least the first tether attachment element allows bidirectional axial displacement of the tether relative to the body. 
     
     
         14 . A compliance member as in  claim 13 , wherein the at least first tether attachment comprises a mechanism selected from the group consisting of rollers and ratchets. 
     
     
         15 . A system for elastically constraining a spinal segment of a patient, said system comprising:
 first and second compliance members as in  claim 9 ;   a first inelastic tether adapted to attach to the first tether attachment element of the first compliance member and to the second tether attachment element of the second compliance member; and   a second inelastic tether adapted to attach to the first tether attachment element of the second compliance member and to the second tether attachment element of the first compliance member;   wherein the inelastic tethers have a central region adapted to be received over the spinous processes, said central region having a thickness no greater than 2 mm and a width in the range from 3 mm to 10 mm.