A method for guiding a bone removal device to form a socket in the human spine and for inserting a cortical bone implant into the socket. The method includes placing a guard against the posterior aspect of the spine, the guard having a passage therethrough, inserting the bone removal device into the passage, removing a portion of a facet joint with the bone removal device to create the socket having a maximum height, and inserting the cortical bone implant into the socket. The cortical bone implant has a leading end, a trailing end, a mid-longitudinal axis through the ends, and a height transverse to the mid-longitudinal axis, the height of the cortical bone implant being greater than the maximum height of the socket.