Objective: The S2-alar-iliac (S2AI) screws have been described as an alternative method for lumbosacropelvic fixation in place of iliac screws. However, the clinical effect of the short-segment S2AI screw fixation technique in the treatment of unstable posterior pelvic ring injuries remains unclear. In this study, we report the preliminary clinical results of the internal fixation connecting a S2-alar-iliac screw and a S1 pedicle screw (i.e., S2AI-S1 fixation) in the treatment of unstable pelvic posterior ring injuries.

Methods: Twenty-five patients with unstable posterior pelvic ring injury were treated with S2AI-S1 fixation from February 2019 to June 2020. The incision length, surgical time, blood loss, frequency of intraoperative fluoroscopy, quality of reduction, complications, and functional outcome were analyzed.

Results: A total of 29 groups of S2AI-S1 fixation were used in 25 patients. The mean incision length was 8.3 (6.2 - 10.3) cm, mean operative time was 86.4 (60 - 142) minutes, mean frequency of intraoperative fluoroscopy was 7.9 (4 - 12) times, and mean blood loss was 148 (50 - 500) mL. The mean postoperative follow-up time was 17.8 (10 - 26) months. The satisfaction rate of pelvic reduction quality was 25/29, and the satisfactory rate of functional outcome was 23/25. There were no obvious signs of screw prominence, screw loosening, or implant failure.

Conclusions: The case series presented in this study show the successful use of S2AI-S1 fixation to treat unstable posterior pelvic ring injuries. The S2AI-S1 fixation, not including the lumbar spine in the fixation range, is a simple, safe, and effective fixation method.