Lowering the Ankle-Brachial Index Threshold in Blunt Lower Extremity Trauma May Prevent Unnecessary Imaging

Current algorithms for the management of blunt lower extremity trauma recommend additional imaging in patients presenting with soft signs of vascular injury and an ankle-brachial index (ABI) less than 0.9. The aim of this study is to analyze lower extremity computed tomography angiographies (CTAs) to determine the incidence and characteristics of patients sustaining vascular injury from blunt lower extremity trauma. We hypothesized that a lower ABI threshold can avoid unnecessary imaging without missing clinically significant vascular injury.

A single-center, retrospective review of all consecutive patients who presented to a level 1 trauma center with blunt lower extremity trauma and underwent a CTA from January 2015 to December 2017 was conducted. Baseline demographics, clinical features, and outcomes were recorded. Patients without documented ABIs were excluded. A receiver operating characteristic curve was used to define the ABI threshold.

One hundred twenty-five patients (133 injured limbs) met inclusion criteria. The mean age was 44 years (range 9-96), and 74% of the patients were male. A vascular abnormality was identified on CTA in 65 limbs (48.9%), of which only 8 (12%) required intervention. The ABIs in these 8 injured limbs were between 0 and 0.6. An ABI threshold of 0.6 maximized the balance between sensitivity (100%) and specificity (87%) and missed no injuries requiring revascularization.

The ABI remains useful in evaluating blunt lower extremity trauma. A lower ABI threshold in patients presenting with soft signs of vascular injury after blunt trauma may avoid unnecessary imaging without missing vascular injuries requiring intervention. Further prospective studies are needed to validate the safety and effectiveness of a lower ABI threshold.