Robot-assisted S2 screw fixation for posterior pelvic ring injury

Percutaneous sacroiliac screw is one of the main methods to treat unstable posterior pelvic ring injury. However, complexity of pelvic anatomical structure increases the difficulty and risk with freehand operation. Besides, S2 screw fixation began to receive attention. The purpose of the current study was to evaluate the safety, accuracy, efficiency and clinical outcome of robot-assisted S2 screw fixation for posterior pelvic ring injury.We reviewed 128 cases of unstable posterior pelvic ring injury treated by percutaneous sacroiliac screw fixation in our hospital from January 2016 to January 2020. All cases were divided into robot-assisted S1 group (RAS1), robot-assisted S2 group (RAS2), freehand group S1 group (FHS1) and freehand group S2 group (FHS2). The mean times of fluoroscopy per screw and adjustment per guide wire were used to evaluate radiation exposure and the efficiency of screw placement, respectively. The final position of the screw was evaluated with postoperative CT to illustrate security and accuracy. 108 patients (84.38%) were followed up for 5~24 months and the Majeed scores were compared among groups.A total of 180 screws were inserted. In comparison of the mean times of fluoroscopy per screw and adjustment per guide wire, RA group was significant less than FH group, further comparison revealed that freehand S2 placement need more fluoroscopy and adjustment times compared with freehand S1 placement, but for robot-assisted procedure, there was no difference between placing S1 and S2. Screw penetration was found in the FHS1(3/48) and FHS2(2/14) and none in RAS1 or RAS2, which means robot-assisted groups were more safety and accurate (P<0.001). The mean Majeed score in RAS1 (83.33±13.47) and RAS2 (82.32±11.42) was higher than in FHS1 (80.43±12.25) and FHS2 (75.08±18.47), but this difference failed to reach significant.Compared with the freehand operation, TiRobot increased the safety and accuracy, reduced radiation exposure, and improved the efficiency. TiRobot could reduce the risk of S2 placement and provide a safe and feasible way for clinical practice.