Disclosed is an orthopedic implant and methods of implantation for fixing adjacent bones. In an embodiment, the implant includes a locking mechanism that is adapted to be advanced by a locking instrument, wherein advancement of the locking mechanism in a first direction produces rotation of a first rigid abutment surface from a first orientation to a second orientation, and continued advancement of the locking mechanism produces advancement of the first rigid abutment surface towards a second rigid abutment surface and placement of a compressive load onto and sufficient to immobilize the implant relative to the first bony surface and the second bony surface.