Technik der perkutanen SI-Verschraubung mit Unterstützung durch konventionellen C-Bogen

Abstract

During percutaneous iliosacral screw fixation, fluoroscopy with a conventional C-arm X-ray unit is still the standard procedure for intraoperative orientation. Lateral sacral images in combination with the inlet and outlet view are always necessary. Nevertheless, the complex pelvic anatomy makes it difficult to prevent malpositioning of screws. Defining the correct entry into the bone is the decisive step for ideal screw placement. The better this is defined, the larger safety margins will be concerning cortical perforation by the screws. In the lateral view, an entry ventral to the sacral canal has to be avoided as well as an entry into the cranial half of the first sacral vertebra. To improve the surgeon's three-dimensional orientation with the help of his personal experience and two-dimensional images, it is recommended to place the tip of the screws in the center of the sacrum (in AP view) whenever possible. Routinely performed postoperative CT imaging of 24 screws, consecutively implanted according to the standards described, revealed no case of malpositioning. Standard X-ray views in combination with standardized aiming of screw entry position and final screw thread position enable the surgeon to find the "safe zone" for iliosacral screw insertion and to prevent iliosacral screw malpositioning with high accuracy.