Which screw corridors can be used for bilateral fragility fractures of the pelvis with a transverse fracture component (FFP IVb)?

Background: Fragility fractures of the pelvis are becoming increasingly important in an ageing society. However, they are under-represented in the current research literature. In particular, unstable bilateral fragility fractures of the sacrum (FFP IVb) benefit from surgical treatment, but individual fracture patterns need to be considered in the surgical decision. This study describes the sacral anatomy in patients with FFP IVb pelvic fractures, with particular emphasis on the identification and evaluation of possible trans-sacral screw corridors, with particular emphasis on the transverse fracture components. Methods: Design: Retrospective clinical study. Setting: Level 1 trauma center. Patient Selection Criteria: The study reviewed 100 patients admitted for bilateral FFP with a transverse fracture between 01 / 2013 and 11 / 2023 that had a preoperative computed tomography (CT) of the pelvis including the fifth vertebra, treated with FFP IVb using preoperative multiplanar CT scans to analyze sacral anatomy. Outcome Measures and Comparisons: Sacral types and transitional abnormalities were classified, and corridor dimensions for S1 and S2 were measured, including estimated bone density using Hounsfield units. Bone corridors >= 8 mm were considered adequate. In addition, possible trans-sacral screw corridors were evaluated, taking into account the transverse fracture component. Results: While large trans-sacral screw corridors (>= 8 mm) for S1 and S2 were identifiable in most cases, the actual feasibility for screw placement was limited due to the transverse fracture component's location, resulting in meaningful corridors in only 80 % for S1 and 47 % for S2. Additionally, in 4 % of patients without an S1 corridor, trans-sacral screw fixation was deemed inadequate due to the fracture line passing through S2. Conclusions: These results indicate that not all FFP IVb fractures can be effectively stabilized using trans-sacral screw or bar fixation, necessitating alternative techniques for some cases. Furthermore, precise preoperative planning is essential for the management of these fractures due to complexity of anatomy. To identify the most suitable treatment approaches, further clinical studies are required. Level of evidence: III