Ultrasound findings of the elbow posterior fat pad in children with radial head subluxation

OBJECTIVE The aim of this study was to determine whether elbow ultrasound findings of the posterior fat pad (PFP) are present in patients with diagnosis of radial head subluxation (RHS). METHODS This was a prospective study of children presenting to an urban pediatric emergency department diagnosed clinically with RHS. Physicians received a 1-hour training session on musculoskeletal ultrasound including the elbow. Before performing reduction for RHS, the physicians performed a brief, point-of-care elbow ultrasound using a high-frequency linear transducer probe in both longitudinal and transverse views to evaluate for PFP elevation and lipohemarthrosis (LH). Successful clinical reduction with spontaneous movement of injured extremity served as the criterion standard for RHS. Clinical telephone follow-up was performed to ascertain outcomes. RESULTS Forty-two patients were enrolled with a mean age of 22.3 (11.8) months. The mean time to presentation was 7 (9.2) hours, and 9/42 (21%) children had previous history of RHS. The majority of patients (35/42, 83%; 95% confidence interval (CI), 69%-92%) had a normal elbow ultrasound. Of 42 patients, 6 (14%; 95% CI 6%-28%) had an elevated PFP and 2 (5%; 95% CI, 0.5%-17%) had LH. Clinical reduction was successful in 100% of patients, and there were no complications reported on follow-up. CONCLUSIONS The majority of children with RHS have a normal PFP on elbow ultrasound, but elevated PFP and LH are possible findings. Reduction maneuvers for RHS may be attempted in patients with a normal elbow ultrasound when the diagnosis of RHS or elbow fracture is uncertain.