Development and Validation of a Shorthand Knee MRI Atlas for Bone Age Estimation in the Korean Population

Background: Estimating skeletal maturity is crucial for treating pediatric knee conditions. Recently, a knee bone age atlas based on the magnetic resonance imaging (MRI) data of pediatric and adolescent population in Southern California (the San Diego atlas) was published. However, its accuracy in other populations has not been verified.Purpose: To (1) validate the San Diego atlas in a South Korean pediatric and adolescent population and (2) create and validate a shorthand knee MRI atlas for bone age estimation tailored to South Korean pediatric and adolescent population (the Korean shorthand atlas).Study Design: Cohort study (diagnosis); Level of evidence, 2.Methods: We retrospectively analyzed the data of 695 participants aged <= 18 years with normal knee MRI findings between 2000 and 2019. To create the Korean shorthand atlas, age-specific features based on the San Diego atlas that appeared on the evaluated MRI scans (n = 417) were modified to reduce the standard deviation of age. In a separate data set (n = 278), the accuracy of both the San Diego and the Korean shorthand atlases was validated by comparing the knee bone age with the chronological age and determining the correlation between bone age and chronological age.Results: In the overall study population, the mean bone age based on the San Diego atlas did not differ from the mean chronological age, and a very strong correlation was observed between them (rS = 0.95). However, the mean bone age based on the San Diego atlas significantly differed from the mean chronological age in female participants aged 7 to 12.9 years (0.6 years younger; P = .003) and in male participants aged 14.0 to 18.0 years (0.4 years older; P = .045). The mean bone age assessed based on the Korean shorthand atlas did not significantly differ from the mean chronological age in any age or sex subgroup and was also very strongly correlated with the mean chronological age (rS = 0.94) in the overall population.Conclusion: The San Diego atlas was accurate in estimating bone age in Korean pediatric and adolescent population except for certain age ranges. The Korean shorthand atlas was an accurate tool for estimating bone age in the Korean pediatric and adolescent population at any age range.