German Congress of Orthopaedics and Traumatology (DKOU 2025)
Analysis of eligibility of the S1 corridor for the trans-sacral screw placement in a geriatric population
2CHUV: Centre hospitalier universitaire vaudois, Lausanne, Schweiz
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Objectives and questions: Trans-sacral screw (TSS) placement represents a popular method of fixation for Fragility Fractures of the Pelvis (FFP), with variable sacral anatomy representing the main challenge. Little is known about the variability of sacral anatomy in the geriatric population and the effect of osteoporosis on the S1 corridor morphology. We aimed to examine the prevalence of a narrow S1 corridor for the TSS placement in the geriatric population and to analyze what sacral dysmorphism signs might serve as predictors for a narrow S1 corridor.
Material and methods: We analyzed the S1 corridor in pelvic CT scans of 107 geriatric patients without a history of pelvic pathology or fracture. First, the eligibility for the TSS placement was determined by measuring the width and the height at the narrowest point of the corridor. Corridors < 12 mm were defined as critical, the ones under 8 mm as impossible for the TSS placement. Then, sacra were examined for dysmorphism signs. The correlation of these signs with narrow S1 corridors was analyzed.
Results: In our population with an average age of 79.55 8.79 years (male : female 0.88) 41.1% of S1 corridors were critical and 24.3% impossible for the TSS placement. In both groups, the height was shown to be a more significant limiting dimension than the width (p<0.05). Mamillary processes, not recessed upper sacrum and irregular neural foramina were present in 38.3%, 34.6%, and 26.2% respectively, and all demonstrated a significant correlation with a critical or impossible S1 corridor (p<0.05).
Discussion and conclusions: The geriatric population showed a high prevalence of narrow S1 corridors, making TSS placement risky or impossible. The height of the S1 corridor represented the main limiting factor with dysmorphism signs of a not recessed upper sacrum, irregular neural foramina, and mamillary processes being significant predictors for a narrow corridor.
