Reliability of the Schmeling method for bone age estimation using the clavicle: Systematic review and meta-analysis

Clavicular ossification is widely used in forensic age estimation, particularly in late adolescence and early adulthood. However, the reliability of the Schmeling method when applied to conventional radiography (CR) remains uncertain. Therefore, this study aimed to evaluate the applicability of the Schmeling method in CR through a systematic review and meta-analysis. Searches were performed in Embase, LILACS, PubMed/MEDLINE, SciELO, Scopus, and Web of Science. Studies evaluating medial clavicular ossification using the Schmeling method based on CR were included. Risk of bias was assessed using the Joanna Briggs Institute checklist. Mean ages were pooled for each ossification stage, while heterogeneity was assessed using Cochran's Q and the I² statistic. In addition, outliers were investigated through Baujat plots and sensitivity analyses. A total of nine studies were included, of which five were eligible for meta-analysis. Mean age increased progressively across ossification stages. Nevertheless, substantial heterogeneity was observed in all analyses (I² ≥ 79.4%), with particularly high variability in advanced stages. Prediction intervals were wide, indicating considerable differences between studies. Furthermore, sensitivity analyses showed that heterogeneity persisted in later stages even after the removal of influential cases. Although the Schmeling method applied to CR reflects general patterns of skeletal maturation, its reliability is limited by substantial inter-study heterogeneity. Therefore, it should not be used in isolation for forensic age estimation. Greater methodological standardization and more consistent reporting in future studies are required to improve its applicability in forensic practice.