European Radiology

Assessment of Rapidly Advancing Bone Age during Puberty on Elbow Radiographs using a Deep Neural Network Model

  • Jun. 2021
  • by Kyung-Sik Ahn and Byeonguk Bae et. al.


Bone age is considered an indicator for the diagnosis of precocious or delayed puberty and a predictor of adult height. We aimed to evaluate the performance of a deep neural network model in assessing rapidly advancing bone age during puberty using elbow radiographs.


In all, 4437 anteroposterior and lateral pairs of elbow radiographs were obtained from pubertal individuals from two institutions to implement and validate a deep neural network model. The reference standard bone age was established by five trained researchers using the Sauvegrain method, a scoring system based on the shapes of the lateral condyle, trochlea, olecranon apophysis, and proximal radial epiphysis. A test set (n = 141) was obtained from an external institution. The differences between the assessment of the model and that of reviewers were compared.


The mean absolute difference (MAD) in bone age estimation between the model and reviewers was 0.15 years on internal validation. In the test set, the MAD between the model and the five experts ranged from 0.19 to 0.30 years. Compared with the reference standard, the MAD was 0.22 years. Interobserver agreement was excellent among reviewers (ICC: 0.99) and between the model and the reviewers (ICC: 0.98). In the subpart analysis, the olecranon apophysis exhibited the highest accuracy (74.5%), followed by the trochlea (73.7%), lateral condyle (73.7%), and radial epiphysis (63.1%).


Assessment of rapidly advancing bone age during puberty on elbow radiographs using our deep neural network model was similar to that of experts.

Key Points

• Bone age during puberty is particularly important for patients with scoliosis or limb-length discrepancy to determine the phase of the disease, which influences the timing and method of surgery.

• The commonly used hand radiographs–based methods have limitations in assessing bone age during puberty due to the less prominent morphological changes of the hand and wrist bones in this period.

• A deep neural network model trained with elbow radiographs exhibited similar performance to human experts on estimating rapidly advancing bone age during puberty.


Kyung-Sik Ahn, Byeonguk Bae, Woo Young Jang, Jin Hyuck Lee, Saelin Oh, Baek Hyun Kim, Si Wook Lee, Hae Woon Jung, Jae Won Lee, Jinkyeong Sung, Kyu-Hwan Jung, Chang Ho Kang, and Soon Hyuck Lee

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