gms | German Medical Science

Objectives: The percutaneous placement of iliosacral screws (ISS) is an established technique for the fixation of posterior pelvic ring injuries. The anatomy of the sacrum is complex and the landmarks may be difficult to identify with conventional fluoroscopy, particular in osteoporotic bone or in the presence of interfering bowel gas. Malpositioning of ISS is a complication with potential injury to adjacent neurovascular structures. Thus, computer navigated screw insertion has gained increasing popularity. It was the aim of this study to evaluate the quality of conventional fluoroscopy-guided percutaneous placement of ISS.

Methods: In 2017, the surgical procedure was standardized following a step by step technique using conventional intraoperative fluoroscopy. All procedures between 01/2017 and 12/2018 were included. All patients underwent computed tomography (CT) for fracture analysis and preoperative planning. Surgery was performed percutaneously in supine position. Following the standardized procedure, a postoperative CT was performed to confirm proper screw position. The screw position was defined to be either correct or with tangential involvement or true hit of the neuroforamina or spinal canal, or with anterior or superior bone perforation. Postoperative complications and revision surgeries were recorded as well.

Results and conclusion: Median age was 78 years (range 16-91 years). In total, 50 ISS were inserted in 26 patients, 32 ISS into S1 and 18 into S2, respectively. In a 16 year old patient, 2x6.5 cannulated screws were used, all other patients received 7.3 cannulated screws. One planned procedure had to be aborted before skin incision due to insufficient visualization of the radiological landmarks. Regarding S1, malposition was observed for 2 ISS (6%), of these, 1 (3%) with tangential involvement of the spinal canal and 1 (3%) anterior bone penetration. For S2, tangential involvement of the spinal canal was seen for 3 (17%) ISS. Screw malposition did not cause any neurovascular complications. Early migration resulted in screw exchange in 1 case (2%) and another 2 ISS had to be removed prematurely due to symptomatic loosening (4%).

Following a standardized step by step surgical technique, conventional ISS placement is reliable and safe. Due to the smaller dimensions, ISS malposition was more frequently observed in S2 than in S1. However, only tangential involvement of the spinal canal occurred and no neurovascular complications were seen.