Abstract:[Objective] To compare the clinical efficacy of Tianji Orthopedics robot-assisted sacroiliac cannulated screw fixation ver-sus traditional freehand counterpart for posterior pelvic ring injury. [Methods] A retrospective study was done on a total of 74 patients whounderwent surgical treatment for the posterior pelvic ring injury from March 2019 to March 2021. According to preoperative doctor-patientcommunication, the surgical techniques used of percutaneous sacroiliac cannulated screw placement was selected, including 16 patients inthe robotic-assistance in the early-stage (RAE) group, 16 cases in the robotic-assistance in the late-stage group (RAL), and 42 cases inthe traditional group. Perioperative, follow-up and imaging data were compared among the three groups. [Results] All patients in the threegroups were successfully operated on without serious complications. Compared with that in the traditional group, the RAE group consumedsignificantly longer time for screw placement, while the RAL group took significantly shorter time with statistically significant differenceamong the 3 groups [(78.6±4.8) min vs (66.4±7.1) min vs (70.3±6.5) min, P＜0.001]. In addition, the RAE group and RAL group proved sig-nificantly superior to the traditional group in terms of intraoperative blood loss [(14.8±2.4) ml vs (13.7±1.7) ml vs (18.5±2.9) ml, P＜0.001],intraoperative fluoroscopy times [(10.4±1.3) times vs (9.5±0.7) times vs (12.5±1.4) times, P＜0.001] and the number of screw setting adjust-ments [(0.6±0.6) times vs (0.3±0.5) times vs (1.1±0.7) times, P＜0.001]. However, there were no significant differences in incision healinggrade, postoperative ambulation time and hospital stay among the three groups (P＞0.05). All patients were followed up for more than 12months, and the RAE group and RAL group resumed full weight-bearing activities significantly earlier than the traditional group [(90.5±4.8) days vs (89.1±6.0) days vs (95.8±6.4) days, P＜0.001]. The VAS score for pain decreased significantly, while Majeed scores increased significantly in all the 3 groups over time (P＜0.05). and the RAE group and RAL group were significantly better than the traditional groupin Majeed scores 3 months after surgery [(85.4±5.2) vs (85.7±3.9) vs (80.5±6.1), P＜0.001]. Regarding imaging, the RAE group and RALgroup were significantly better than the traditional group in term of accuracy of screw placement [excellent/good/poor, (14/2/0) vs (15/1/0) vs(28/13/1), P=0.048], but there was no statistically significant difference in Matta grade of fracture reduction among the three groups (P＞0.05). By the last follow-up, all patients in the 3 groups got fractures healed without loosening of internal fixation implants. [Conclusion]The Tianji robot assisted percutaneous sacroiliac cannulated screw internal fixation has the advantages of high accuracy, safety and mini-mally invasive surgery despite of a learning curve.