Expandable vertebral implant

Abstract

A joint spacer therapeutically maintains separation of bones of a joint. A carriage is slideably retained within the frame and has at least one ramped surface. An actuator screw is threadably engaged with the frame, and rotatably connected to the carriage, to cause the carriage to slideably move within the frame when the actuator screw is rotated. First and second endplates engage the bones of the joint, and each has at least one ramped surface that is mateable with the ramped surface of the carriage, whereby when the carriage is slideably moved by rotation of the actuator screw, the endplates ramped surface slides against the carriage ramped surface to cause the endplates to move along an axis transverse to the longitudinal axis of the frame, to increase the height of the spacer. Piercing elements are connected to the carriage to pierce bone of the joint when the carriage is moved.

What is claimed is: 
     
         1 . A spacer for maintaining a separation of bones of a joint, comprising:
 a frame;   a carriage slideably coupled to the frame and having distal and proximal ends defining a longitudinal axis extending therebetween, the carriage having at least one ramped surface;   a first endplate configured to engage a first bone of the joint, and having at least one first surface mateable with the at least one ramped surface; and   a second endplate configured to engage a second bone of the joint;   an expansion cam disposed between the first and second endplates;   a shaft coupled to the frame and the expansion cam such that rotation of the shaft causes the expansion cam to rotate, which in turn causes the first endplate to move along an axis transverse to the longitudinal axis to increase a height between the first and second endplates while the first endplate is being guided by the at least one first surface mated with the at least one carriage ramped surface.   
     
     
         2 . The spacer of  claim 1 , wherein the carriage includes at least two ramped surfaces, and the second endplate includes at least one second surface mateable with at least one of the two ramped surfaces of the carriage, whereby when the shaft rotates the expansion cam, the second surface slides against the at least one of the two ramped surfaces. 
     
     
         3 . The spacer of  claim 1 , wherein the first endplate includes a first proximal wall extending laterally to the longitudinal axis, the first proximal wall including at least one aperture through which a fastener may pass to secure the first endplate to a bone of the joint. 
     
     
         4 . The spacer of  claim 3 , wherein the proximal further includes a blocker that prevents backing out of a fastener passed through the first endplate. 
     
     
         5 . The spacer of  claim 1 , wherein the first endplate is composed of two interconnected portions of dissimilar materials. 
     
     
         6 . The spacer of  claim 5 , wherein one dissimilar material is polymeric, and another dissimilar material is metallic. 
     
     
         7 . The spacer of  claim 1 , further including a plate extending laterally to the longitudinal axis and having at least one aperture sized and dimensioned to receive an elongated fastener for fastening the plate to bone of the joint, the plate being releaseably detachable from the frame to reduce a profile of the spacer during insertion of the spacer into the body, the plate adapted to attach to the frame inside the body. 
     
     
         8 . The spacer of  claim 1 , wherein the first endplate includes a rotatable portion having first and second transverse axes of different lengths. 
     
     
         9 . The spacer of  claim 8 , wherein the rotatable portion is passable through an interior of the spacer. 
     
     
         10 . The spacer of  claim 1 , wherein the first endplate includes an aperture sized and dimensioned to receive an elongated fastener operable to pass through the aperture to affix the endplate to bone of the joint, the aperture movable with the first endplate as the first endplate is moved along the axis transverse to the longitudinal axis. 
     
     
         11 . The spacer of  claim 1 , further including at least one rotatable plate having an aperture through which a fastener may pass to secure the spacer to a bone of the joint, the rotatable plate rotatable after the spacer has been implanted within the body, to overlie the aperture with bone of the joint. 
     
     
         12 . The spacer of  claim 1 , wherein the at least one ramped surface is adapted to push a piercing element through an aperture in the first endplate, the piercing element operative to pierce a bone to secure the spacer within the body. 
     
     
         13 . The spacer of  claim 1 , further comprising:
 at least one elongate rotatable deployer pivotally connected to the frame;   at least one piercing element connected to the deployer, the at least one piercing element operable to pierce bone of the joint when the rotatable deployer is rotated within the body.   
     
     
         14 . A spacer for maintaining a separation of bones of a joint, comprising:
 a frame;   a carriage slideably coupled to the frame and having distal and proximal ends defining a longitudinal axis extending therebetween, the carriage having at least one ramped surface;   a first endplate configured to engage a first bone of the joint and having a first proximal wall extending laterally to the longitudinal axis from a proximal end of the first endplate, the first endplate having at least one first surface mateable with the at least one ramped surface, the first proximal wall including at least one aperture through which a fastener may pass to secure the first endplate to a bone of the joint;   a second endplate configured to engage a second bone of the joint;   an expansion cam disposed between the first and second endplates;   a shaft coupled to the frame and the expansion cam such that rotation of the shaft causes the expansion cam to rotate, which in turn causes the first endplate to move along an axis transverse to the longitudinal axis to increase a height between the first and second endplates while the first endplate is being guided by the at least one first surface mated with the at least one carriage ramped surface.   
     
     
         15 . The spacer of  claim 14 , wherein the first proximal wall is a metallic portion and a portion extending longitudinally along the longitudinal axis is a polymeric portion attached to the metallic portion via a screw. 
     
     
         16 . The spacer of  claim 14 , wherein the first endplate includes a rotatable portion having first and second transverse axes of different lengths. 
     
     
         17 . The spacer of  claim 16 , wherein the rotatable portion is passable through an interior of the spacer. 
     
     
         18 . The spacer of  claim 14 , wherein the at least one ramped surface is adapted to push a piercing element through an aperture in the first endplate, the piercing element operative to pierce a bone to secure the spacer within the body. 
     
     
         19 . The spacer of  claim 14 , further comprising:
 at least one elongate rotatable deployer pivotally connected to the frame;   at least one piercing element connected to the deployer, the at least one piercing element operable to pierce bone of the joint when the rotatable deployer is rotated within the body.