## 4 Discussion  
Our study showed an excellent overall correlation of BAA using the model between both hands, refuting the findings of Roche [23]. Considering that approximately 10% of the population is assumed to be left-handed [28], it can be concluded that the dominant hand appears to mature at the same rate as the non-dominant hand, and that the right-hand BAA can be used as a validation tool. Among the total participants, 59 (7.8%) showed an ADBH model score of >0.5 years, with higher MAD values (left: 0.409, right: 0.424) compared to previous studies using the same model (0.39 and 0.37, respectively) [11; 24]; their highest values were 1.75 years for the left hand and 1.33 years for the right hand. Although this result does not mean that a higher ADBH model score indicates a measurement error, it could serve as a cue for manual supervision. \begin{table}
\begin{tabular}{l c c c} \hline \hline
**Variables** & **ADBH Model \(\leq\) 0.5 Year** & **ADBH Model \textgreater{} 0.5 Year** & \\  & **(_n = 698_)** & **(_n = 59_)** & **\(p\) Value** \\ \hline Age, years a ** & 8.77 \(\pm\) 2.66 & 8.55 \(\pm\) 2.73 & 0.555 \\ Male-to-female ratio & 295:403 & 26:33 & 0.788 \\ Left-hand BAA a  & 9.18 \(\pm\) 3.21 & 8.78 \(\pm\) 2.27 & 0.356 \\ Right-hand BAA a  & 9.22 \(\pm\) 3.22 & 9.00 \(\pm\) 3.39 & 0.620 \\ ADBH model b  & 0.198 \(\pm\) 0.145 & 0.667 \(\pm\) 0.109 & \textless{}0.001 \\  & (0.187, 0.209) & (0.638, 0.695) & \\ \hline Developmental stage & & & 0.025 \\ Pre-puberty & 201/698 (28.2\%) & 26/59 (44.1\%) & 0.018 \\ Early and mid-puberty & 462/698 (66.2\%) & 29/59 (49.2\%) & 0.010 \\ Late puberty & 28/698 (4.0\%) & 2/59 (3.4\%) & 1.000 \\ Post puberty & 7/698 (1.0\%) & 2/59 (3.4\%) & 0.151 \\ \hline \hline \end{tabular} Unless otherwise indicated, the data are presented as the number of patients, with percentages in parentheses. ADBH model, the absolute difference between each hand’s bone age assessment. BAA, bone age assessment.  
* The data are presented as the means \(\pm\) standard deviation. b The data are shown as the means \(\pm\) standard deviation, with the 95% confidence interval in parentheses.  
\end{table} 
Table 2: A comparison of the characteristics of the study population. \begin{table}
\begin{tabular}{l c c c} \hline \hline  & **Left Hand** & **Right Hand** & **\(p\) Value** \\ \hline Automatic bone age assessment by the model & 8.78 \(\pm\) 3.27 & 9.00 \(\pm\) 3.39 & 0.011 \\ Reference standard bone age reference by & 8.93 \(\pm\) 3.29 & 8.89 \(\pm\) 3.33 & 0.157 \\ two reviewers & & & \\ Mean absolute difference a  & 0.409 \(\pm\) 0.335 (0.322, 0.467) & 0.424 \(\pm\) 0.329 (0.339, 0.510) & 0.809 \\ Median & 0.354 & 0.330 & \\ Range & 0–1.75 & 0–1.33 & \\ \hline \hline \end{tabular} Unless otherwise indicated, the data are shown as the means \(\pm\) standard deviation. a The data are shown as the means \(\pm\) standard deviation, with the 95% confidence intervals in parentheses.  
\end{table} 
Table 3: A comparison of the bone age assessment by the model and the reference standard. Since the early 1990s, researchers have attempted to automate BAA using computers. In 1992, the computer-assisted skeletal age score (CASAS) was presented, a semi-automatic method that required a significant amount of manual labor [29]. In 1997, the automated computer-aided skeletal maturation assessment system (CASMAS) was also presented, which was reported to automatically analyze 90% of films but required a manual rating of 10% [30]. Fully automated BAA has been routinely used in clinical practice since 2009, when BoneXpert (Visiana Aps, Holte, Denmark; [[http://www.boneexpert.com](http://www.boneexpert.com)]([http://www.boneexpert.com](http://www.boneexpert.com)), accesses on 15 June 2024) was introduced [31]. Since then, various automatic and deep learning methods for BAA have been proposed, which have demonstrated high accuracy, reproducibility, and time efficiency [9; 10; 11; 12]. Despite these advantages, AI-based methods are still not suitable for clinical use due to the risk of large measurement errors.