Patent ID: 8257443

Claim:
A prosthesis for stabilizing and maintaining space between adjacent bones for promotion of fusion by retained graft material, the prosthesis comprising: a spacer body having a top surface, a bottom surface and a perimeter surface joining said top surface and bottom surface, said spacer body further comprising at least one lateral channel extending into said spacer body from said perimeter surface; and at least one internally threaded longitudinal channel extending from said upper surface or said lower surface and intersecting said lateral channel; a drive screw having a head and a first externally threaded surface, said drive screw rotatably mounted in said at least one lateral channel, said head accessible at said perimeter surface so as to be engageable by an externally applied tool for rotation thereof; a pin retained in said at least one longitudinal channel, said pin having a pointed distal end and an external surface comprising a plurality of teeth projecting radially there from, said plurality of teeth simultaneously defining a first helical thread engaging said externally threaded surface of said drive screw and a second helical thread engaging said internal threading of said longitudinal channel, whereby on rotation of said drive screw within said lateral channel, engagement of said first helical thread of said pin with said first externally threaded surface of said drive screw causes said pin to rotate in said longitudinal channel whereby engagement of said second helical thread of said pin with said internally threaded surface of said longitudinal channel causes said pointed distal end of said pin to be advanced out of said longitudinal channel.