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• Not all bilateral fragility fractures with a transsacral fracture component (FFP 4b) can be fixed with transsacral screw fixation. • Patients with a transitional anomaly were more likely to have no corridor in S1. • All patients without an adequate S1 corridor had an ascending sacral type, whereas all patients with a descending or horizontal type had a feasible corridor. • The transverse component of the fracture was most frequently located in S2 (42 %). • Considering the specific fracture patterns, an S1 screw was only possible in 80 % of cases. Similarly, an S2 screw was only possible in 47 % of cases. 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. 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. 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. 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. III [ABSTRACT FROM AUTHOR]

Background: Iliosacral screw fixation is safe and effective but can be complicated by loss of fixation, particularly in patients with osteopenic bone. Sacral morphology dictates where iliosacral screws may be placed when stabilizing pelvic ring injuries. In dysmorphic sacra, the safe osseous corridor of the upper sacral segment (S1) is smaller and lacks a transsacral corridor, increasing the need for fixation in the second sacral segment (S2). Previous evidence suggests that S2 is less dense than S1. The aim of this cross-sectional study is to further evaluate bone mineral density (BMD) of the S1 and S2 iliosacral osseous pathways through morphology stratification into normal and dysmorphic sacra.Materials and Methods: Pelvic computed tomography scans of 50 consecutive trauma patients, aged 18 to 50 years, from a level 1 trauma center were analyzed prospectively. Five radiographic features (upper sacral segment not recessed in the pelvis, mammillary bodies, acute alar slope, residual S1 disk, and misshapen sacral foramen) were used to identify dysmorphic characteristics, and sacra with four or five features were classified as dysmorphic. Hounsfield unit values were used to estimate the regional BMD of S1 and S2. Student's t-test was utilized to compare the mean values at each segment, with statistical significance being set at p < 0.05. No change in clinical management occurred as a result of inclusion in this study.Results: A statistical difference in BMD was appreciated between S1 and S2 in both normal and dysmorphic sacra (p < 0.0001), with 28.4% lower density in S2 than S1. Further, S1 in dysmorphic sacra tended to be 4% less dense than S1 in normal sacra (p = 0.047). No difference in density was appreciated at S2 based on morphology.Conclusions: Our results would indicate that, based on BMD alone, fixation should be maximized in S1 prior to fixation in S2. In cases where S2 fixation is required, we recommend that transsacral fixation should be strongly considered if possible to bypass the S2 body and achieve fixation in the cortical bone of the ilium and sacrum.Level Of Evidence: Level III. [ABSTRACT FROM AUTHOR]

ABSTRACT Variations in sacral segmentation may preclude safe placement of transsacral screws for posterior pelvis fixation. We developed a novel automated 3D technique to determine the safe zone size for transsacral screws in the upper two sacral segments in 526 adult pelvis computed tomography scans. Safe zone sizes were then compared by gender and sacral segmentation variations (number of neuroforamen and the presence/absence of lumbosacral transitional vertebrae, ±LSTV). Ten millimeters was used as the safety threshold for a large screw. 3 (0.6%), 366 (70%), and 157 (30%) sacra had 3, 4, or 5 neuroforamen, respectively. Eighty-eight (17%) were +LSTV. Safe zone size depended on gender, number of neuroforamen in −LSTV sacra and presence of LSTV ( p < 0.001) but not on the uni- or bilateral nature of the LSTV. 17% of −LSTV sacra were below the safety threshold in S1, 27% in S2, whereas 3% of +LSTV sacra were below in S1, 74% in S2. Of −LSTV sacra that cannot take an S1 screw safely, 77% can do so in S2, leaving only 4% of sacra that cannot accommodate a screw safely in either upper segment. The results demonstrate a predictable pattern of safe zone size based on gender and sacral segmentation variations. © 2014 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 33:277-282, 2015. [ABSTRACT FROM AUTHOR]

Background: Exact knowledge of the sacral anatomy is crucial for the percutaneous insertion of iliosacral screws. However, dysplastic anatomical patterns are common. In addition to a preoperative computed tomography (CT) analysis, conventional radiographic measures may help to identify upper sacral dysplasia and to avoid damage to surrounding structures. Aiming to further increase safety in percutaneous iliosacral screw placement in the presence of sacral dysmorphism, this study examined the prevalence of previously established radiographic signs and, in addition, defined the "critical SI angle" as a new radiographic criterion. Methods: Pelvic CT scans of 98 consecutive trauma patients were analysed. Next to assessment of established signs indicating upper sacral dysplasia, the critical sacroiliac (SI) angle was defined in standardized pelvic outlet views. Results: The critical SI angle significantly correlates with the presence of mammillary bodies and an intraarticular vacuum phenomenon. With a cut-off value of − 14.2°, the critical SI angle detects the feasibility of a safe iliosacral screw insertion in pelvic outlet views with a sensitivity of 85.9% and a specificity of 85.7%. Conclusions: The critical SI angle can support the decision-making when planning iliosacral screw fixation. The clinical value of the established signs of upper sacral dysplasia remains uncertain. [ABSTRACT FROM AUTHOR]