A surgical instrument and instrumentation are suggested, with which expansion of the vertebral canal of vertebrae is possible with less stress for the patient than with operating procedures customary up to now, this instrument having proximally a gripping part and distally two branches which can be moved relative to one another with tool elements held thereon as well as a lever mechanism arranged between the gripping part and the branches, wherein the tool elements are held with the lever mechanism so as to be movable relative to one another from a closed rest position into an open spread position (distraction position).
