An implantable stabilization apparatus stabilizes a portion of a skeletal structure of a living patient. The implantable stabilization apparatus includes an elongated fixation rod that includes a plurality of different rod regions having different cross-sectional dimensions are aligned along a longitudinal axis of the fixation rod. A transition region integrally formed as part of a common monolithic structure with the different rod regions is tapered, and separates the different rod regions from each other along the longitudinal axis of the fixation rod. A fastener system couples the elongated fixation rod to the skeletal structure. The fastener system includes an anchor that is to be secured to the skeletal structure, a saddle coupled to the anchor, and a locking member that maintains cooperation between the saddle and the portion of at least one of the different rod regions interfere with separation of the fixation rod from the fastener system.
