spine in order to cover the entire section of the spine to be treated moreover in order to achieve dynamic spinal stabilization between some vertebrae some rigidity of the rod may be needed between those vertebrae and this would be missing if two separate sections of rods were to be used in such situations some sections of the rod structure have to remain more flexible such as in locations where the disc is still functional while other sections of the rod have to maintain their stiffness to assist in providing complete fusion in order to achieve this structure at those locations of the patient 39 s spine where some flexibility is desired the rods can then be provided with thinned sections between the pedicle screw locations the thinning of the rod can be achieved either by shaving or machining off some of the material of the rod in the region where increased flexibility is desired or by using the same plungers to generate one or more dimples in the surface of the rod to reduce its thickness and hence to increase its compliance at that point this can be achieved by actuating two opposing plungers operating against each other to thin the rod down in the space between the plungers this thinning process may be applied either to a pair of rods on either side of the spine or on a single rod positioned on one side of the spine the latter procedure is often used in minimally invasive cases where the use of one rod minimizes the number of skin incisions also if a given compliance between non fused vertebra is to be maintained in dynamic stabilization then only.