Telescoping interspinous fixation device and method of use

Abstract

The present invention provides spinous process implants and associated methods. In one aspect of the invention, the implant includes a first extension and a second extension. The first extension has a spacer extending from a medial facing side along a longitudinal axis. The second extension has an aperture that slidingly receives the spacer. Accordingly, the second extension is moveable relative to the spacer along the longitudinal axis. The second extension includes a threaded bore in communication with the aperture. A set screw is threadably received in the threaded bore of the second extension. The set screw can be tightened against an outer surface of the spacer to lock the second extension in place relative to the longitudinal axis.

What is claimed is: 
     
         1 . An implant having a portion adapted to be placed between spinous processes of adjacent vertebrae of a spine, the implant comprising:
 a first extension having a lateral facing side and a medial facing side, the medial facing side adapted to reside proximate to at least one of the spinous processes, the first extension defining a longitudinal axis that extends substantially perpendicular to the medial facing side;   a spacer extending from the medial facing side of the first extension along the longitudinal axis;   the spacer including a first end adjacent the medial facing side of the first extension and a second end opposite the first end;   the spacer having an outer surface that extends between the first and second ends;   a second extension having a lateral facing side and a medial facing side, the medial facing side adapted to reside proximate to at least one of the spinous processes, the second extension defining an aperture that slidingly receives the spacer such that the second extension is moveable relative to the spacer along the longitudinal axis;   the second extension having a threaded bore in communication with the aperture; and   a set screw threadably received in the threaded bore of the second extension that is adapted to be tightened against the outer surface of the spacer to lock the second extension in place relative to the longitudinal axis,   wherein the aperture of the second extension is larger than the outer surface of the spacer by a predetermined amount in order to permit a pre-determined amount of angular adjustment between the first extension and the second extension and wherein the threaded bore of the second extension is transverse to the longitudinal axis allowing the second extension to pivot about the set-screw.   
     
     
         2 . The implant of  claim 1 , wherein the arrangement of the threaded bore relative to the longitudinal axis and the size of the aperture relative to the outer surface of the spacer allow the first and second extensions to be set in a non-parallel relationship. 
     
     
         3 . The implant of  claim 1 , wherein the outer surface of the spacer includes a posterior side, the threaded bore of the second extension being open to the posterior side of the spacer such that the set screw is adapted to move into contact with the posterior side of the spacer. 
     
     
         4 . The implant of  claim 3 , wherein the spacer has first and second anterior chamfers disposed at the first and second ends of the spacer opposite the posterior side, the first and second anterior chamfers providing clearance for posteriorly facing structures of the adjacent vertebrae of the spine. 
     
     
         5 . The implant of  claim 3 , wherein the posterior side of the spacer has surface texturing adapted to cooperatively engage a leading edge of the set screw. 
     
     
         6 . The implant of  claim 1 , wherein the spacer has an inner surface defining a hollow interior adapted to receive a bone growth promoting substance for facilitating fusion between the implant and the adjacent vertebrae of the spine. 
     
     
         7 . The implant of  claim 1 , wherein the first and second extensions define a midline plane that bisects the first and second extensions and that runs parallel to the longitudinal axis. 
     
     
         8 . The implant of  claim 7 , wherein the first and second extensions each have a superior lobe that is offset to one side of the midline plane and an inferior lobe that is offset to another side of the midline plane. 
     
     
         9 . The implant of  claim 8 , wherein each of the superior lobes and each of the inferior lobes of the first and second extensions include at least one fastener extending from the medial facing sides of the first and second extensions for securing the first and second extensions to the adjacent vertebrae of the spine. 
     
     
         10 . The implant of  claim 7 , wherein the spacer is centered about the longitudinal axis and the longitudinal axis is offset from and anterior to the midline plane. 
     
     
         11 . An implant having a portion adapted to be placed between spinous processes of adjacent vertebrae of a spine, the implant comprising:
 a first extension having a lateral facing side and a medial facing side, the medial facing side adapted to reside proximate to at least one of the spinous processes, the first extension defining a longitudinal axis that extends substantially perpendicular to the medial facing side;   a spacer extending from the medial facing side of the first extension along the longitudinal axis;   the spacer including a first end adjacent the medial facing side of the first extension and a second end opposite the first end;   the spacer having a posterior side, a superior outer surface, and an inferior outer surface each extending between the first and second ends, the posterior side disposed between the superior and inferior outer surfaces;   a second extension having a lateral facing side and a medial facing side, the medial facing side adapted to reside proximate to at least one of the spinous processes, the second extension defining an aperture that slidingly receives a portion of the spacer such that the second extension is moveable relative to the spacer along the longitudinal axis;   the second extension having a threaded bore in communication with the aperture; and   a set screw threadably received in the threaded bore of the second extension that is adapted to be tightened against the posterior side of the spacer to fix the second extension in place relative to the longitudinal axis,   wherein the superior and inferior outer surfaces of the spacer each has an elongated slot disposed therein and the second extension has first and second tabs extending inwardly into the aperture that are received by and arranged in sliding engagement with the elongated slots in the superior and inferior outer surfaces.   
     
     
         12 . The implant of  claim 11 , wherein the first and second tabs are directed toward the posterior side of the spacer. 
     
     
         13 . The implant of  claim 12 , wherein the first and second tabs are angled toward the posterior side of the spacer. 
     
     
         14 . The implant of  claim 12 , wherein the first and second tabs are hooked toward the posterior side of the spacer. 
     
     
         15 . The implant of  claim 11 , wherein the elongated slots have sides and the first and second tabs are pressed against the sides of the elongated slots when the set screw is tightened against the posterior side of the spacer in order to lock the second extension in place at a finite location along the spacer. 
     
     
         16 . The implant of  claim 11 , wherein the elongated slots in the superior and inferior outer surfaces extend linearly and are parallel to the longitudinal axis. 
     
     
         17 . The implant of  claim 11 , wherein the elongated slots in the superior and inferior outer surfaces are closed at the first end of the spacer and are open at the second end of the spacer. 
     
     
         18 . The implant of  claim 11 , wherein the spacer has an inner surface defining a hollow interior and the elongated slots in the superior and inferior outer surfaces open into the hollow interior of the spacer. 
     
     
         19 . The implant of  claim 11 , wherein the aperture of the second extension includes complementary surfaces that face the superior outer surface, the inferior outer surface, and the posterior side of the spacer and wherein the aperture is open between the first and second tabs such that the second extension has a “C” shaped cross-section adjacent the aperture. 
     
     
         20 . The implant of  claim 11 , wherein the second extension extends completely about the aperture and the portion of the spacer that is received in the aperture.