Ottawa Ankle Rule as a Tool for Reducing Radiation Exposure in Pregnant Trauma Patients

Abstract

Background Ionising-radiation‐based imaging is avoided whenever possible in pregnancy, yet ankle injuries remain common after falls or vehicular collisions. The Ottawa Ankle Rule (OAR) reliably rules out fracture in the general population, reducing unnecessary radiographs. Its impact on maternal–fetal radiation exposure in pregnant trauma patients has not been formally quantified.

Methods We performed a prospective cohort study (January 2019 – December 2024) at a level-1 trauma centre. Consecutive pregnant women (gestational age ≥ 6 weeks) presenting with ankle trauma were assessed by emergency physicians trained in the OAR. Primary outcomes were (i) diagnostic performance of OAR versus reference-standard radiography or CT and (ii) cumulative effective fetal radiation dose avoided. Secondary outcomes included emergency department (ED) length-of-stay and 30-day missed-fracture rate.

Results Two-hundred-and-twenty participants (mean age 28.7 ± 4.8 years; median gestation 22 weeks) were enrolled. OAR was positive in 94 (42.7 %) and negative in 126 (57.3 %). Forty-four fractures were confirmed, all in the OAR-positive group (sensitivity 100 %, 95 % CI 92–100 %; specificity 43 %, 95 % CI 36–51 %). Application of OAR reduced radiographs from 220 theoretical to 98 actual exams, yielding a 55.4 % reduction and an estimated fetal dose saving of 5.9 mSv (median 0.03 mSv per patient). No fractures were missed at 30 days. ED stay was shorter in the OAR-negative group (mean difference −41 min, p < 0.001).

Conclusion OAR maintains 100 % sensitivity in pregnant trauma patients and more than halves ionising-radiation exposure. Incorporating OAR into obstetric trauma protocols is a simple, evidence-based measure aligned with ALARA principles. Keywords: Ottawa Ankle Rule; pregnancy; radiation dose; trauma; diagnostic decision rule; ankle fracture.