Is S3 a Viable Osseous Fixation Pathway?

Objectives: To report the incidence of patients with a third sacral segment (S3) osseous fixation pathway (OFP) that could accommodate a transiliac-transsacral screw. Design: Retrospective case series. Setting: Regional Level 1 Trauma Center. Patients/Participants: A total of 250 patients without pelvic trauma from January 2017 to February 2017 were included. Intervention: The axial and sagittal reconstruction images of each patient's computed abdomen and pelvis tomography (CT) scans were reviewed. Main Outcome Measurements: Each CT was evaluated for the presence of sacral dysmorphism and whether an S3 OFP that could accommodate an intraosseous transiliac-transsacral screw exists. Results: There were 130 of the 250 patients (52%) with sacral dysmorphism. Overall, 38 of the 250 patients (15.2%) had an S3 OFP that could accommodate a 7.0-mm transiliac-transsacral style screw. When narrowed to patients who had an S3 OFP, 38 of 153 patients (24.8%) could accommodate a 7.0-mm transiliac-transsacral screw. Specific to the 38 patients with an adequate S3 OFP, 34 of 38 patients (89.5%) were noted to have sacral dysmorphism. Conclusions: Our study demonstrates that 15.2% of patients have an S3 OFP large enough to accommodate an intraosseous implant. Patients who have sacral dysmorphism are more likely to have an adequate S3 OFP. Additional studies are needed to quantify the S3 OFP, understand the bone quality of the S3 segment and accompanying biomechanical implications, and investigate the anatomical concerns associated with S3 screw placement. Level of Evidence: Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.