181EMF Prospective Evaluation of Novice-Acquired 3D Ultrasound for Identification of Upper Extremity Fractures

Abstract

The initial imaging modality recommended by the American College of Radiology for suspected hand and wrist fractures is radiography. As there are radiation exposure risks associated with radiography, 2D ultrasound (2DUS) has also been investigated for diagnosis of these injuries. While sensitive and specific, 2DUS is operator dependent, requiring expertise to acquire and interpret images. 3DUS by novices is little studied in orthopedic evaluation. We aimed to determine whether novice-acquired 3DUS with expert or novice readers can identify hand and wrist fractures. We hypothesized that expert and novice interpretations of novice-acquired 3DUS of orthopedic injuries would show high agreement with each other and with the reference standard. The STARD criteria for studies of diagnostic tests were applied. Following IRB approval and informed consent, we prospectively enrolled subjects at a tertiary care academic medical center and an associated orthopedic clinic. We estimated a sample size of 70 subjects for an intraclass correlation coefficient (ICC) 0.7 (with alpha of 0.5 and power 0.8) and to detect kappa of 0.8. A single novice operator third-year medical student (MS3) performed all image acquisitions without any specific effort to identify anatomy or injuries during acquisition. 2D B mode US images were acquired using a Philips Lumify L12-4 transducer connected to a smartphone, and paired to an inertial measurement unit. All scans were reconstructed in volume rendering mode and displayed in 3DSlicer, an open-source visualization tool. Scans were interpreted by three groups of readers: 2 MS3s (novice), 3 emergency physicians with US fellowship training, and 2 board certified radiologists with musculoskeletal fellowship training (expert). The reference standard was board-certified radiologist interpretation of x-rays obtained during routine clinical care. Readers were blinded to all clinical data and x-ray diagnosis and rated 3DUS volumes for the presence or absence of fracture, fracture characteristics when present, and additional findings. Agreement between novices and experts in 3DUS interpretation and between 3DUS and x-ray findings are reported (kappa/ICC). Sensitivity/specificity/LR+/LR- with 95% CI were calculated. Time to perform and interpret 3DUS were reported. 22 subjects were enrolled before the study was suspended due to the COVID-19 pandemic, with 90 3DUS volumes available for interpretation. Analysis is ongoing as results continue to be submitted, precluding calculation of kappa/ICC at this time. Expert 1 had sensitivity 0.8 (0.28, 0.99), specificity 0.69 (0.39, 0.91), LR+ 2.58 (1.03, 6.49), and LR- 0.29 (0.05, 1.73). Novice 1 had sensitivity 0.4 (0.05, 0.85), specificity 0.31 (0.09, 0.61), LR+ 0.58 (0.19, 1.79), and LR- 1.94 (0.66, 5.70). Interpretation times declined by over 50% for both novice and expert readers with an increasing number of scans interpreted. Mean acquisition time was 97 seconds per volume (median 97, IQR 57.75) with a mean of 2.5 volumes acquired per subject (median 2, IQR 1.25). Novice-acquired 3DUS by augmentation of 2DUS was rapid, and interpretation times decreased rapidly with experience. Preliminary results show a promising LR+ when scans are interpreted by an expert reader.