[S2 iliosacral screw insertion technique].

OBJECTIVE: To introduce a technique pertaining to S2 iliosacral screw insertion. METHODS: The screw pathway was first measured on the preoperative pelvic CT scan or the standard sacral lateral radiograph to make sure the existence of the "safe zone" in the S2 segment for screw insertion. Under general anesthesia, patients were positioned supine or prone, depending on the injury pattern of pelvic ring or associated injuries requiring concomitant operation. The operation field was routinely sterilized using iodine and subsequent alcohol solution and draped. The tip of a guide wire was inserted through a stab wound to the posterior outer iliac table, manipulated in the "safe zone" being enclosed by the anterior aspect of the S2 nerve root tunnel, the anterior aspect of the sacral vertebrae, and the inferior aspect of the S1 foramen under the guidance of the standard sacral lateral fluoroscopy, and then the tip was hammered one to two millimeters into the iliac cortex. The guide wire progressed along the trajectory between the inferior aspect of the S1 foramen and the superior aspect of the S2 foramen on the pelvic outlet fluoroscopic view, and then along the posterior to the anterior aspect of the S2 sacral vertebrae and alae on the pelvic inlet fluoroscopic view with a predetermined length. At that moment, in order to ensure the safety, another standard sacral lateral view was imaged to detect the guide wire's tip which should locate posterior to the anterior aspect of the sacral vertebrae and anterior to the anterior aspect of the S2 nerve root tunnel. Subsequently, the depth was measured, the trajectory was drilled and tapped, and the screw was inserted. Following the removal of the guide wire, the wound was irrigated and sutured. RESULTS: Utilizing this insertion technique, there were 30 S2 iliosacral screws in total being placed to stabilize the injured and unstable posterior pelvic ring in 27 patients. Each S2 screw was accompanied by an ipsilateral S1 screw. The S2 screw location was completely intraosseous in all patients, which was verified by postoperative pelvic outlet and inlet radiographs and CT scans. The insertion accuracy was 100 percent in the present series. CONCLUSION: The S2 iliosacral screw insertion technique is safe and reproducible to guide the placement of the S2 screw, enhancing the stability for the compromised posterior pelvic ring.