SLR - April 2021 - Patrick M. Bik

Re-Evaluating the Safety and Effectiveness of the 0.9 Ankle-Brachial Index Threshold in Penetrating Lower Extremity Trauma

Reference: Hemingway J, Adjei E, Desikan S, Gross J, Tran N, Singh N, Starnes B, Quiroga E. Re-Evaluating the Safety and Effectiveness of the 0.9 Ankle-Brachial Index Threshold in Penetrating Lower Extremity Trauma. J Vasc Surg. 2020 Oct;72(4):1305-1311.

Level of Evidence: Level III

Scientific Literature Review 

Reviewed By: Patrick M. Bik, DPM
Residency Program: Temple University Hospital – Philadelphia, PA

Podiatric Relevance: Penetrating lower extremity trauma is often encountered by the podiatric surgeon at a level I trauma center. The primary aim of this study was to evaluate the ABI threshold in detecting vascular injuries in penetrating lower extremity trauma and, as such, the need for computed tomography angiography (CTA). The authors hypothesized that a lower ABI threshold can safely be applied to patients with penetrating mechanisms of lower extremity trauma to reduce unnecessary imaging when compared to the standard 0.9 ABI threshold. 

Methods: This was a retrospective cohort study of 47 patients with a total of 49 limbs who presented to a single level I trauma center between January 2015 to December 2017. Patients were excluded if CTA was performed for non-diagnostic purposes or if ABIs were not documented. Baseline demographics, clinical features of presentation, interventions performed, and outcomes were recorded. ABIs were performed in the emergency department at the initial time of the patient’s presentation in a standard published protocol. The primary outcome was to determine if an ABI value of 0.9 is the most sensitive and specific threshold for detection of vascular injuries requiring repair following penetrating lower extremity trauma. 

Results: The patients in this study were divided into two groups based on intervention: group one required revascularization (six patients) and group two did not require revascularization (41 patients). The most common mechanism of injury was a gunshot wound (92 percent of all penetrating injuries). Other mechanisms of injury included stab wounds (6 percent) and boat propeller injuries (2 percent). Of the 17 limbs (36 percent) with an identified vascular abnormality on CTA, only six (35 percent) required an intervention. The distribution of ABIs in injured limbs requiring revascularization was significantly lower (P = .006) than in those who did not require intervention. An ABI threshold of ≤0.7 had the highest combined sensitivity (83 percent) and specificity (91 percent), with a 98 percent negative predictive value in detecting vascular injuries requiring repair in penetrating lower extremity trauma. 

Conclusions: The ABI remains a reliable tool in distinguishing between limbs with and without vascular injury that require revascularization after penetrating lower extremity trauma. 51 percent of CTA studies would have been avoided if a lower ABI threshold of ≤0.7 were used. Therefore, the authors conclude that an ABI threshold of ≤0.7 can be used to identify limbs requiring revascularization  reducing unnecessary imaging after penetrating lower extremity trauma. It is important for the podiatric surgeon to be familiar with the ankle-brachial index (ABI) threshold in penetrating lower extremity trauma to assist with diagnosis and management, including when to order advanced imaging and consult vascular surgery.

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