Unilateral Lumbo-Pelvic Fixation for Denis Type I Unilateral Sacral Fracture: A Finite Element Analysis.

Background: Unilateral sacral fractures with posterior ring instability represent a prevalent type of posterior pelvic ring fracture. While lumbo-pelvic fixation is recognized as a highly stable method, the sufficiency of unilateral lumbo-pelvic fixation (ULF) for such fractures remains under debate. Purpose: This study aims to assess the biomechanical stability of ULF compared to traditional bilateral lumbo-pelvic fixation (BLF) and triangular osteosynthesis (TO), incorporating clinical observations, and previous biomechanical data. Methods: We developed a three-dimensional spine-pelvis model to simulate a unilateral sacral fracture with posterior ring instability. The model was used to compare the stability of ULF with BLF and TO, utilizing both newly generated data and ULF models reported in existing literature. Results: Our findings indicate that BLF and TO provide greater stability than ULF, with BLF emerging as the most stable model. While ULF may be insufficient for immediate postoperative weight-bearing, TO also demonstrated potential risks of instability during rotational and lateral bending movements toward the fracture side. Conclusion: Despite its application in clinical settings, ULF may not adequately support early postoperative mobility. This study underscores the need for cautious application of ULF and suggests that enhancements such as additional fixation points may be necessary. The results also highlight the importance of tailored postoperative rehabilitation strategies for patients undergoing TO, especially in managing movements that could destabilize the fracture site.