Diagnostic accuracy of pubic symphysis ultrasound in the detection of unstable pelvis in polytrauma patients during e-FAST: the value of FAST-PLUS protocol. A preliminary experience.

BACKGROUND: Extended focused abdominal sonography for trauma (e-FAST) is part of the primary survey in patients with high-energy trauma. However, it does not identify patients with retroperitoneal haemorrhage associated with significant pelvic trauma. A traumatic diastasis of pubic symphysis, as well as an 'open book' (OB) pelvic injury, is a diagnostic clue to recognize unstable pelvis with higher risk of bleeding. FAST-PLUS (FAST-PL pleural -US ultrasound of symphysis) protocol is an addendum to the e-FAST, which takes into account the study of the pubic symphysis in a single transverse scan after the traditional focused evaluation of the abdomen and thorax.

OBJECTIVES: The aim of this study is to determine the value of FAST-PLUS protocol in the evaluation of pubic symphysis injuries and the identification of 'open book' (OB) unstable pelvic fractures.

METHODS: Between January 2018 and December 2019, we retrospectively reviewed 67 polytraumatised patients with clinical suspicion of pelvic instability and with known anteroposterior pelvis compression injuries who underwent e-FAST with an additional transverse scan of the pubic symphysis, named the FAST-PLUS protocol and computed tomography (CT) exam in order to assess the correlation between them in defining the presence or absence of pubic symphyseal widening (SW). A cutoff value of 2.5 cm in transverse diameter was used to diagnose OB unstable pelvic injury. The results were analysed using Cohen's test, which uses the Kappa value as the reference index.

RESULTS: The analysis carried out to assess the degree of agreement between FAST-PLUS and CT showed 5/67 patients (7.5%) with a critical pubic SW (> 2.5 cm transverse diameter) suggestive of unstable OB pelvic injury and 62/67 (92,5%) without any signs of SW at FAST-PLUS. At CT, findings of unstable OB pelvic fracture were confirmed in all patients with positive results at FAST-PLUS. Similarly, all patients with negative results for critical pubic SW (< 2.5 cm in transverse diameter) at FAST-PLUS were found to be negative at CT exam. The level of correlation between the two methods was high (Kappa value = 1) CONCLUSION: The FAST-PLUS protocol shows a high correlation with CT exam, which is the gold standard for the detection of unstable pubic SW, as well as OB pelvic injury, in polytraumatised patients. Inclusion of FAST-PLUS in patient management in the shock room may lead to a quicker identification of patients with unstable pelvis and to faster therapeutic work-up.