Summation of Ossification Ratios of Radius, Ulna and Femur: A New Parameter to Evaluate Bone Age by Ultrasound

Radiographic bone age (BA) assessment is reviewer dependent or time consuming. We aimed to clarify the correlation between sonographic ossification ratios (ORs, the ratio of ossification center and epiphysis diameters) of bones and radiographic BA and then to develop a repeatable parameter for BA assessment by ultrasound. The distal ends of the radius and ulna, medial epicondyle of the femur, medial tibial condyle, medial malleolus and lateral malleolus in 271 consecutive patients (132 boys and 139 girls) aged 0.1–19.0 y were imaged by ultrasound. The ORs of these bones were measured sonographically. The highest Pearson correlation r was that between the sum of the ORs of radius, ulna and femur (RUF) calculated from ultrasound images and the radiographic BA (0.97 in boys and 0.96 in girls). The entire process of collecting data and calculating the ORs of RUF took 2.6 ± 0.6 min. The ORs of RUF obtained with ultrasound have potential as an easy-to-perform and efficient quantitative assessment of BA.