A tissue splitter for creating a subcutaneous cut is disclosed. The tissue splitter includes a retractable blade located at the distal end. The tissue splitter is configured to be insertable into a slotted cannula that is placed via an incision to a location proximate a patient's spine. An actuator at the proximal end of the instrument projects the blade located at the distal end from its retracted state through the slot of the cannula to an extracted state to subcutaneously cut tissue at a location outside the cannula. The instrument is configured such that the blade is movable inside the slot of the cannula by a distance such that the cut created by the blade remains subcutaneous and does not puncture the skin of the patient. The distance is adjustable for the size and depth of the cut and is limited by an adjustment collar. The tissue splitter is ideally suited for creating a pathway for the subcutaneous insertion and implantation of a spinal stabilization rod between two bone anchors placed in vertebral bodies.