• Cynthia A Gravel, Alex Q Lynn, Megan Hannon, Andrew F Miller, Jeffrey T Neal, Mark I Neuman, and Rebecca L Vieira.
• Division of Emergency Medicine, Boston Children's Hospital Harvard Medical School, Boston, Massachusetts.
• J Emerg Med. 2021 Oct 1; 61 (4): 376-380.

BackgroundChildren with limp or hip pain often undergo radiographs and ultrasound as part of their initial evaluation. Previous research suggests that hip radiography may have limited utility, and early use of ultrasound may safely reduce the use of radiographs.ObjectivesWe sought to assess the utility of radiography in addition to ultrasound by evaluating the rate of bony abnormalities present on hip radiographs among children with and without effusion on ultrasound. We also assessed the agreement of point-of-care and Radiology-performed ultrasounds for the detection of effusion.MethodsThis is a retrospective cohort study of children presenting to a pediatric emergency department with acute atraumatic limp or hip pain. Data from patients who received both hip ultrasound and hip radiography as part of their evaluation were analyzed. We included both point-of-care and Radiology-performed hip ultrasounds.ResultsWe identified 134 patients who received both hip ultrasound and hip radiographs. Sixty-eight patients (51%) had a hip effusion present on ultrasound and none of these had bony abnormalities on radiography (0%, 95% confidence interval 0-5.3%). Of the 66 patients (49%) who had no effusion on hip ultrasound, 2 patients were found to have a bony abnormality (3%, 95% confidence interval 0.4-10.5%). For patients who received both point-of-care and Radiology-performed ultrasound, the overall agreement for diagnosis of effusion was 92.6% (kappa = 0.82).ConclusionsWe observed that no children with an effusion on ultrasound had bony pathology on plain radiography, suggesting that the routine performance of hip radiography may not be indicated in all children. Future studies are needed to evaluate the negative predictive value of effusion in larger numbers of patients with known bony abnormalities.Copyright © 2021 Elsevier Inc. All rights reserved.

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