Comparison Between Ultrasonography and Radiography in the Detection of Epiphyseal Ossification Centers of the Knee in Infants With Permanent Congenital Hypothyroidism.

Objective: To demonstrate the usefulness of ultrasonography in detecting knee ossification centers in infants with permanent congenital hypothyroidism (PCH).

Methods: From 2011 to 2021, all infants with PCH referred for thyroid ultrasound also underwent left knee ultrasound and radiography on the same day. Knee radiographs were compared with knee sonograms. Two pediatric radiologists reviewed the consensus knee radiographs and sonograms to identify femoral and tibial epiphyseal ossification centers (presence/absence). The concordance between ultrasonography and radiography was assessed. Another radiologist conducted a second late review to evaluate interobserver agreement.

Results: We identified 125 patients (65 girls, 60 boys) with a mean age of 24 days (5 days-5 months). On scintigraphy, the thyroid was in place in 66.4%, ectopic in 24%, and absent in 9.6% of patients. The femoral center was observed in 108 patients (86.4%) via sonography and 106 patients (84.8%) via radiography. The tibial center was observed in 84 patients (67.2%) via sonography and radiography. Both femoral and tibial centers were present on sonography and radiography in 84 patients (67.2%). A single nucleus was present in 24 patients (19.2%) on sonography and 22 patients (17.6%) on radiography; it corresponded to the femoral center in all patients. The concordance between ultrasonography and radiography was 99% and 100%, respectively, for the detection of the femoral and tibial centers. Interobserver agreement was substantial to almost perfect for both ultrasonography and radiography.

Conclusion: Ultrasonography is as effective as radiography in detecting knee ossification centers in PCH. It can be performed at the same time as thyroid examination, in place of radiography.