A chisel with U.V-shaped, saw tooth or other shaped opposing blades is used to form channels in adjacent vertebrae. The chisel has a projection extending from at least one of the top and bottom surfaces to limit depth of penetration into the vertebrae. A guide member may be attached to the forward tip...http://www.google.de/patents/US7988693?utm_source=gb-gplus-sharePatent US7988693 - Chisels and procedure for insertion of spinal implant in a spinal disc space
