Area Ossification Ratio: A New Parameter for Quantitative Assessment of Adolescent Bone Age by Conventional Ultrasonography

Objective To research on area ossification ratio (AOR), a novel parameter for quantitatively assessing adolescent bone age by conventional ultrasonography, and evaluate the correlation between AOR and radiographic bone age.

Methods The study selected healthy adolescents from a middle school in Shandong Province in June 2023. Ultrasonic images were collected from five anatomical sites (the styloid process of the ulna, the styloid process of the radius, the lateral epicondyle of the femur, the medial condyle of the tibia, and the posterior median sagittal plane of the tibia). The second ossification center and epiphyseal area on these 2D ultrasound images were delineated to calculate AOR. This ratio was then compared with radiographic bone age measured by Greulich-Pyle (GP) atlas. Inter- and intra-observer consistency was evaluated using intraclass correlation coefficient (ICC) and the Bland-Altman method.

Results A total of 179 healthy adolescents (109 males and 70 females) were included. For both genders, AOR of each site exhibited a significant to high correlation with radiological bone age (r=0.60~0.91). The sum of the AORs of the five sites showed a high correlation with radiological bone age (males: r=0.95, females: r=0.87). Measurements of AOR by different doctors and the same doctor at different times demonstrated high repeatability (inter-observer: ICC=0.926, P < 0.001, intra-observer: ICC=0.954, P < 0.001).

Conclusions The sum of AORs in adolescents is highly correlated with radiographic bone age, and the measurement method shows high repeatability. The AOR is a reliable parameter for the ultrasonic quantitative assessment of bone age in adolescents.