Diagnostic Accuracy of Point-of-Care Ultrasound for Acute Pediatric Ankle Injuries

The aim of this study was to determine test performance characteristics of point-of-care ultrasound (POCUS) in the diagnosis of pediatric ankle fractures compared with ankle x-rays. Secondary objectives were to determine if POCUS can reduce the number of x-rays, analyze diagnostic errors, compare the Ottawa Ankle Rules (OAR) with POCUS, and determine if the outcome of the ultrasound results is affected by the musculoskeletal ultrasound experience of the pediatric emergency physicians.

This was a prospective study of children aged 6 to 18 years who presented to the emergency department with ankle injuries with no prior x-rays. The physicians received a 2-hour training session, performed an ultrasound with a standardized protocol, and documented the POCUS results as positive or negative for fracture. The reference standard was the radiologist's x-ray interpretation.

We enrolled 118 patients with a median age of 12 years (interquartile range, 10 to 14 years). There were 17 fractures among 15 patients; 8 were clinically significant. Overall, POCUS would reduce x-rays by 105 (89%), but miss 6 fractures, including 1 clinically significant fracture. For detecting all ankle fractures, POCUS yielded a sensitivity of 60% (95% CI, 32.3-83.7), a specificity of 96% (95% CI, 90.4-98.9), a positive predictive value of 69.2 (95% CI, 44.2-86.5), and a negative predictive value of 94.3 (95% CI, 89.9-96.9). For the detection of clinically significant fractures, POCUS yielded a sensitivity of 87.5% (95% CI, 47.4-99.7), a specificity of 94.6% (95% CI, 88.5-97.9), a positive predictive value of 53.9 (95% CI, 33.9-72.6), and a negative predictive value of 99.1 (95% CI, 94.3-99.9). The sensitivity of POCUS + OAR and OAR alone was 90% (95% CI, 55.5-99.8), but the specificity was 0% (95% CI not computed).

POCUS alone or combined with OAR is an inadequate screening tool to detect pediatric ankle fractures.