A spinal stabilization rod includes a first rod portion having a proximal end and a distal end and having a first cross-sectional area. The second rod portion extends from the distal end of the first rod portion and has a second minimum cross-sectional area smaller than the first cross-sectional area....http://www.google.fr/patents/US20090275983?utm_source=gb-gplus-shareBrevet US20090275983 - DYNAMIC STABILIZATION ROD
