a system and method for performing spinal fusion using vertebral connecting rods constructed of a shape memory material , such as shape memory alloy . the connecting rod is cooled below its phase transition temperature , which is chosen to be just below body temperature , and is inserted through a curved guide tube previously inserted into the back of the patient . the guide tube is located so as to deliver the connecting rod at its desired location between the preinserted pedicle screw heads . the rod , being in its flexible state below the transition temperature , negotiates the curve and exits the guide tube in a straight form and parallel to the patient &# 39 ; s spine . as it heats up to body temperature , it regains its original straight shape and its original rigidity , and is ready for connecting its associated vertebrae to each other .