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 having distal and proximal ends defining a longitudinal axis extending therebetween;   a carriage slideably coupled to the frame and having at least one ramped surface, said carriage further including a threaded portion;   an actuator screw threadably engaged with said frame, said actuator screw configured to bear against said carriage to cause said carriage to slideably move within said frame when said actuator screw is rotated;   a first endplate configured to engage a first bone of the joint, and having at least one surface mateable with said at least one carriage ramped surface, whereby when said carriage is slideably moveable by rotation of said actuator screw, said at least one endplate ramped surface slides against said at least one carriage ramped surface to cause said first endplate to move along an axis transverse to said longitudinal axis to increase a height of the spacer; and   a second endplate configured to engage a second bone of the joint.   
     
     
         2 . The joint spacer of  claim 1 , wherein said carriage includes at least two ramped surfaces, and said second endplate includes at least one ramped surface mateable with at least one of said at least two ramped surfaces of said carriage, whereby when said carriage is slideably moved by rotation of said actuator screw, said at least one second endplate ramped surface slides against said at least one additional carriage ramped surface to cause said second endplate to move along an axis transverse to said longitudinal axis to increase a height of the spacer. 
     
     
         3 . The joint spacer of  claim 1 , wherein said first endplate includes at least one aperture through which a fastener may pass to secure said first endplate to a bone of the joint. 
     
     
         4 . The joint spacer of  claim 4 , further including a blocking mechanism to prevent backing out of a fastener passed through said first endplate. 
     
     
         5 . The joint spacer of  claim 1 , wherein at least one of said first and second endplates is composed of two interconnected portions of dissimilar materials. 
     
     
         6 . The joint spacer of  claim 5 , wherein one dissimilar material is polymeric, and another dissimilar material is metallic. 
     
     
         7 . The joint spacer of  claim 1 , further including a polymeric material configured to press against said actuator screw to reduce a potential for unintended rotation of said actuator screw. 
     
     
         8 . The joint spacer of  claim 1 , further including a plate having at least one aperture sized and dimensioned to receive an elongated fastener for fastening the spacer to bone of the joint, said plate being releasably detachable from said spacer to reduce an profile of the spacer during insertion of the spacer into the body, said plate attached to the spacer inside the body. 
     
     
         9 . The spacer of  claim 1 , wherein said at least one carriage ramp is disposed upon at least one cam, said cam rotatable to bear said at least one carriage ramp against said at least one surface of said first endplate. 
     
     
         10 . The spacer of  claim 1 , wherein said first endplate includes a rotatable portion having first and second transverse axes of different lengths. 
     
     
         11 . The spacer of  claim 10 , wherein said rotatable portion is passable through an interior of the spacer. 
     
     
         12 . The spacer of  claim 1 , wherein said first endplate includes an aperture sized and dimensioned to receive an elongated fastener operable to pass through said aperture to affix the spacer to bone of the joint, said aperture movable with said first endplate as said first endplate is moved along said axis transverse to said longitudinal axis. 
     
     
         13 . The joint spacer of  claim 1 , further including at least one rotatable plate having an aperture through which a fastener may pass to secure said spacer to a bone of the joint, said rotatable plate rotatable after the spacer has been implanted within the body, to overlie said aperture with bone of the joint. 
     
     
         14 . The joint spacer of  claim 1 , at least one of said carriage ramped surfaces operates to push a piercing element through an aperture in said first endplate, said piercing element operative to pierce bone of the joint to secure the spacer within the body. 
     
     
         15 . The joint spacer of  claim 1 , further including a bone screw having bone engaging threads and gear teeth; and
 said actuator screw including gear teeth engageable with said gear teeth of said bone screw, said actuator screw thereby rotated when said bone screw is threaded into bone of the joint.   
     
     
         16 . The joint spacer of  claim 1 , further including:
 at least one elongate rotatable deployer pivotally connected to said frame;   at least one piercing element connected to said deployer, said at least one piercing element operable to pierce bone of the joint when said rotatable deployer is rotated within the body.   
     
     
         17 . A joint spacer for therapeutically maintaining a separation of bones of a joint, comprising:
 a frame having distal and proximal ends defining a longitudinal axis extending therebetween;   a carriage slideably retained within said frame and having at least one ramped surface, said carriage further including a flange;   an actuator screw threadably engaged with said frame, said actuator screw including a flange rotatably mateable with said carriage flange, whereby said carriage is slideably moved when said actuator screw is rotated;   a first endplate configured to engage a first bone of the joint, and having at least one ramped surface mateable with said at least one carriage ramped surface, whereby when said carriage is slideably moved by rotation of said actuator screw in a first direction, said at least one endplate ramped surface slides against said at least one carriage ramped surface to cause said first endplate to move along an axis transverse to said longitudinal axis to increase a height of the spacer; and   a second endplate configured to engage a second bone of the joint.   
     
     
         18 . The spacer of  claim 17 , wherein when said actuator screw is rotated in an opposite, second direction, said at least one endplate ramped surface is slideable against said at least one carriage ramped surface to cause said first endplate to move along an axis transverse to said longitudinal axis to decrease a height of the spacer. 
     
     
         19 . The spacer of  claim 17 , wherein said first endplate includes a metallic portion having an aperture through which a fastener may be passed for connecting the implant to body tissue, the first endplate further having a polymeric portion connected to said metallic portion, the polymeric portion sized and dimensioned to support a bone of the joint. 
     
     
         20 . A method for therapeutically maintaining a separation of bones of a joint, comprising:
 inserting a spacer between bones of the joint, the spacer including:
 a frame having distal and proximal ends defining a longitudinal axis extending therebetween; 
 a carriage slideably retained within said frame and having at least one ramped surface, said carriage further including a flange; 
 an actuator screw threadably engaged with said frame, said actuator screw including a flange rotatably mateable with said carriage flange, whereby said carriage is slideably moved when said actuator screw is rotated; 
 a first endplate configured to engage a first bone of the joint, and having at least one ramped surface mateable with said at least one carriage ramped surface, whereby when said carriage is slideably moved by rotation of said actuator screw in a first direction, said at least one endplate ramped surface slides against said at least one carriage ramped surface to cause said first endplate to move along an axis transverse to said longitudinal axis to increase a height of the spacer; and 
 a second endplate configured to engage a second bone of the joint; 
 the spacer inserted when said first endplate is positioned proximate said frame; and 
   slideably moving, by rotation of said actuator screw, said at least one endplate ramped surface against said at least one carriage ramped surface to cause said first endplate to move along an axis transverse to said longitudinal axis to increase a height of the spacer to maintain a separation of bones of the joint.