Diagnostic Value of Joint Effusion and the FAT-PAD Sign in Pediatric Elbow Trauma: A Systematic Review

The objective was to analyze the evidence regarding the diagnostic value of joint effusion and the anterior and posterior fat pad signs for identifying fractures—particularly radiographically occult fractures—in pediatric patients with acute elbow trauma. A systematic review was conducted following the recommendations of the PRISMA 2020 statement. The search was conducted in PubMed/MEDLINE, Scopus, Web of Science, Embase, and the Cochrane Library. Primary diagnostic evaluation studies and synthesis publications that analyzed the signs under study using conventional radiography or ultrasound were included. Following the identification, screening, and eligibility process, 12 publications were included in the qualitative synthesis. The results showed that the presence of a positive fat pad sign is associated with a significant proportion of occult fractures, predominantly supracondylar humeral lesions, followed by fractures of the proximal ulna, proximal radius, and lateral humeral condyle. The posterior fat pad showed greater specificity than the anterior fat pad as an isolated sign, whilst the combined ultrasound assessment of effusion, lipohaemarthrosis and cortical abnormalities demonstrated high sensitivity and high negative predictive values. It is concluded that joint effusion and the fat pad sign constitute relevant indirect findings for suspecting an occult fracture in paediatric elbow trauma. Ultrasound is a useful complementary diagnostic tool, although the heterogeneity of confirmation criteria and methods limits direct comparison between studies.