Pelvic incidence-guided reduction in transverse parts of U-shaped sacral fractures: Technical recommendations

Objective The purpose of this study is to present a surgical technique that simultaneously reduces and fixates the transverse parts of U-shaped sacral fractures. Methods The sacral fracture was exposed through a posterior median approach. In a flexion injury, the rotation of the lower sacral segment is reduced by distraction along a pre-curved rod. Then, lordotic restoration is performed with a Weber clamp placed at the lower sacral segment through dragging. In an extension injury, longitudinal distraction is performed along the spinopelvic rod to reduce the vertical displacement. Next, the transverse displacement is reduced by a dissector placed between the upper and lower sacral segments through levering. The sagittal reduction on the lateral pelvic view was judged by PI. A regression analysis of Oswestry disability index (ODI) with Z-scores of PI, lumbar lordosis (LL), sacral slope (SS), and pelvic tilt (PT) was performed. Results At the 1-year follow-up, the average PI, LL, SS, and PT values were 51.6 (range: 43.1–76.0), 44.8 (34.6 – 60.1), 35.4 (18.1 – 48.0), and 16.7 (2.2–35.4) degrees, respectively. All patients were able to maintain an upright stance. The average ODI was 27.6% (2–72%). Surprisingly, the regression analysis demonstrated a significant linear relationship between ODI and LL ( R 2 = 0.367, p = .048) but not between ODI and PI (R 2 = 0.227, p = .138). Conclusions Using PI as guidance, the surgical procedures were helpful to reduce the PI of transverse sacral fractures into the normal range. However, the relationship between PI and the prognosis remains to be evaluated by future researches.