A method for replacing a spinal disc between first and second vertebrae including determining a reference point on the spinal column. A marker is connected to a vertebrae at a reference point. The marker is engaged with a guide assembly for guiding insertion of a surgical instrument between the first and second vertebrae. The apparatus is inserted between the first and second vertebrae. An outer surface of the apparatus is engageable with the first vertebrae and a rail extending from the outer surface is engageable with the first vertebrae to connect the apparatus to the first vertebrae. First and second projections extend from the outer surface and each projection is engageable with the first vertebrae to connect the apparatus to the first vertebrae. The first projection extends from the outer surface a first distance. The second projection extends from the outer surface a second distance greater than the first distance.
