A spinal fixation procedure and system are provided for fixing the spacing of an inferior vertebra relative to a superior vertebra. The procedure for implanting a spinous process spacer can comprise decorticating and/or forming a notch in adjacent spinous processes, measuring the distance between the notches formed in the spinous processes, and inserting an interspinous process implant such that the implant is fitted into the notches of the spinous processes. Other fixation devices, such as bone screws, can also be used for fixing the position of the vertebrae and to create facet fusion.