Percutaneous Robot-Assisted versus Freehand S₂ Iliosacral Screw Fixation in Unstable Posterior Pelvic Ring Fracture

Objectives To assess the efficiency, safety, and accuracy of S-2 (IS) screw fixation using a robot-assisted method compared with a freehand method. Methods This is a retrospective clinical study. We analyzed the patients treated with S-2 IS screw fixation for unstable pelvic fractures from January 2016 to January 2019 in our institution. Sixty-three patients (17 men and 46 women) aged between 21 and 55 years (with an average age of 39.22 +/- 9.28) were included in this study. According to the Tile classification, there were 26 (41.3%) type B fractures and 37 (58.7%) type C fractures. All patients were divided into robot-assisted (RA) group (38 patients) or the traditional freehand (FH) group (25 patients). In RA group, the S-2 IS screws were implanted with a robot-assisted technique. And S-2 IS screws were implanted with a traditional freehand technique in FH group. The screw-related complications were recorded during and after the surgery. The position of all screws and fracture reduction was assessed by postoperative CT scans according to the Gras classification. The number of guide wire attempts and the radiation exposure for S-2 screw implantation during operation were also recorded. Finally, the Matta standard was used to evaluate the fracture reduction of the IS joint. Results A total of 89 IS screws were implanted into S2 iliosacral joint. Fifty-four screws were placed by RA (38 patients) and 35 screws were by FH (25 patients). There was no difference between the two groups with respect to demographic data. There was no screw-related complications or revision surgery in any group. In terms of screw placement, the excellent and good rate was 100% in the RA group, better than that in the FH group where it was only 85.7% (P < 0.001). The fluoroscopy time was 8.06 +/- 3.54 s in RA group, which was much less than that in the FH group (27.37 +/- 8.82 s, P < 0.001). The guide wire attempts in the RA group (0.685 +/- 0.820) were much less than those in the FH group (5.77 +/- 3.34) (P < 0.001). Both the fluoroscopy time per screw and the number of guide wire attempts in the RA group were much less than those in the FH group (P < 0.001). The overall postoperative excellent and good rate of Matta standard in RA and FH groups were 86.8% (34/4) and 90.0% (23/25), respectively (P = 0.750), and there was no statistical difference. Conclusion The robot-assisted surgery is an accurate and minimally invasive technique. S-2 IS screw implantation assisted by TiRobot to treat the posterior pelvic ring fractures, have a high success rate than the freehand technique. Percutaneous RA S-2 IS screw fixation for unstable posterior pelvic ring injuries is safe and clinically feasible and has great clinical application value.