Iliosacral screw fixation is an effective and less invasive method that is used widely for the definitive treatment of unstable pelvic ring injuries. On the other hand, fixation failures after iliosacral screw fixation have been reported in vertically unstable pelvic ring injuries. This study examined the surgical outcomes of posterior pelvic fixation using S1 and S2 screws in vertically unstable pelvic ring injuries.

Between January 2011 and April 2016, 17 patients with vertically unstable pelvic ring injuries who met the minimum 1 year follow-up criteria were treated with internal fixation using posterior pelvic S1 and S2 screws. Their mean age was 43.9 years. According to the AO/OTA classification, 10 patients had C1, 6 had C2, and 1 had C3 injuries. Surgical treatments of single or multiple steps, where necessary, were performed by two surgeons. The clinical and radiologic outcomes were assessed retrospectively using radiographs and medical records.

Overall, 16 patients had bone healing without screw loosening; however, one patient could not maintain anterior pelvic fixation because of an open fracture and deep infection in the anterior pelvic ring. Of five patients who complained of neurological symptoms after injury, three had partially recovered from their neurological deficit. At the last follow-up, the clinical outcomes according to the Majeed score were excellent in 5, good in 6, fair in 4, and poor in 2 patients. The postoperative radiologic outcomes by Matta and Tornetta's method were excellent in 5, good in 8, and fair in 4 patients. Malposition of the S2 screw was identified in one case. The mean time to union was 14.6 weeks after surgery.

S1 and S2 screw fixation can be an effective treatment option for posterior pelvic stabilization in vertically unstable pelvic ring injuries when considering the surgical outcomes, such as screw loosening and loss of reduction.