Sacral tether anchor and methods of use

Abstract

A system for restricting flexion of a spinal segment in a patient comprises a constraint device having a tether structure and a compliance member coupled with the tether structure. The tether structure is adapted to be coupled with a superior spinous process and a sacrum. The system also includes an anchor member that is anchored to the sacrum. The anchor member has an attachment feature that is adapted to couple with the constraint device.

What is claimed is: 
     
         1 . A method for restricting flexion of a spinal segment of a patient, said method comprising:
 providing a constraint device having a tether structure, the tether structure comprising an upper portion and a lower portion, the tether structure configured to restrict flexion of the spinal segment while allowing substantially unrestricted spinal extension;   coupling the upper portion of the tether structure to a spinous process of a superior vertebra in the spinal segment;   anchoring an anchor element to a sacrum of the patient inferior to the superior vertebra, wherein the anchor element comprises a plate having a plurality of protrusions, the plurality of protrusions configured to penetrate the sacrum,   wherein anchoring the anchor element comprises anchoring the anchor element to the sacrum without using screws, and   wherein anchoring the plurality of protrusions only penetrates cortical bone on a dorsal surface of the sacrum; and   coupling the lower portion of the tether structure to an attachment feature on the anchor element.   
     
     
         2 . The method of  claim 1 , wherein anchoring the anchor element comprises nailing the plurality of protrusions into the sacrum. 
     
     
         3 . The method of  claim 1 , wherein anchoring the anchor element comprises hammering the plurality of protrusions into the sacrum with a mallet. 
     
     
         4 . The method of  claim 1 , wherein the plurality of protrusions comprise a plurality of nail-like protrusions. 
     
     
         5 . The method of  claim 1 , wherein the plurality of nail-like protrusions are inclined relative to a surface of the plate. 
     
     
         6 . The method of  claim 1 , wherein the attachment feature on the anchor element comprises an aperture for receiving the lower portion of the tether structure. 
     
     
         7 . The method of  claim 1 , wherein the attachment feature on the anchor element comprises a hook for hooking the lower portion of the tether structure. 
     
     
         8 . The method of  claim 1 , wherein the constraint device further comprises a compliance member disposed between the upper and lower portions of the tether. 
     
     
         9 . The method of  claim 1 , further comprising inserting the anchor element through a minimally invasive incision. 
     
     
         10 . The method of  claim 1 , further comprising moving the anchoring element cranially or caudally. 
     
     
         11 . The method of  claim 1 , further comprising passing a free end of the upper portion or a free end of the lower portion through a locking mechanism. 
     
     
         12 . The method of  claim 1 , further comprising adjusting length or tension in the tether structure. 
     
     
         13 . The method of  claim 1 , further comprising promoting osseointegration of the anchor element with the spinal segment.