Ultrasound Evaluation of Soft Tissue Foreign Bodies by U.S. Army Medics

Background: Ultrasound (US) represents an ideal imaging modality to evaluate for various types of soft tissue foreign bodies (FBs) due to its accuracy, cost, and lack of ionizing radiation exposure to patients. Portability of... [ view full abstract ]

Background: Ultrasound (US) represents an ideal imaging modality to evaluate for various types of soft tissue foreign bodies (FBs) due to its accuracy, cost, and lack of ionizing radiation exposure to patients. Portability of machines have allowed ultrasound to be utilized increasingly at the point of care, however, ultrasound remains an operator-dependent diagnostic adjunct. The objective of this study was to determine US-naïve personnel’s accuracy in detecting radiolucent foreign bodies using bedside ultrasound in soft tissue hand models. Secondary objectives were to assess US stand-off pad effects on soft tissue FB detection rates and assess the established FB detectable lower limit size of 2 mm.
Methods: This was a prospective, single blinded, observational study. US Army medics naïve to ultrasound recruited as voluntary participants for this study underwent a two hour block of didactic and hands-on instruction on using ultrasound for evaluating soft tissue. Wooden foreign bodies ranging from 1 to 3mm were embedded in 8 of 20 chicken thigh models which were then randomized. Participants’ abilities to detect FB utilizing a SonoSite®M-Turbo US and 13-6 MHz linear probe, with and without stand-off pad, were assessed.
Results: Twenty-eight medics had an overall sensitivity and specificity of 73% and 78% respectively in detecting 1 to 3mm FBs utilizing standard US equipment. The medics’ sensitivity and specificity detecting radiolucent FBs 2mm and larger were both 78% without a stand-off pad. The sensitivity and specificity decreased to 48%, 62% and 67% when utilizing the stand-off pad to detect 1, 2 and 3mm soft tissue FBs. Sub-2mm detection rates decreased from 82% for 2mm FB to 64% for 1mm FBs without utilizing a stand-off pad.
Conclusion: Army medics with minimal US experience successfully identified FBs embedded in chicken thigh models with accuracies similar to more experienced medical professionals that have been previously studied. Sensitivity and specificity decreased in US-naive Army medics utilizing stand-off pads to detect radiolucent FBs. Additionally, this study reconfirmed the lower limit of FB detection rates at 2 mm. These results support Army medics’ utilization of US to evaluate for soft tissue FBs.