Is the cervical bone a biological marker for bone age assessment?

Age assessment is essential in forensic practice when the chronological age of living individuals is unknown, particularly in legal, civil, migration, and asylum contexts requiring the judicial determination of age-related rights and responsibilities. This study aimed to evaluate the performance of two cervical vertebral methods in a Portuguese reference subadult population (6-23 years), ethnically homogeneous, using the analysis of the fourth cervical vertebra (C4) on lateral cephalometric radiographs. Two approaches were applied: Baccetti's qualitative morphological staging of C2-C4 and Cameriere's morphometric ratio of C4. A total of 528 lateral cephalometric radiographs, balanced by age and sex, were analysed independently by trained observers. Intra- and inter-observer reliability were evaluated using Intraclass Correlation Coefficient (ICC) and weighted Cohen's kappa (κ). Statistical procedures included correlation analyses, multiple linear regression, Classification Trees (CT), and Receiver Operating Characteristic (ROC) curves to assess performance at legally relevant thresholds (12, 14, 16, 18 years). Baccetti's method explained 75.3% (coefficient of determination R²=0.753) of chronological age variability, with a mean error of approximately two years and high accuracy for thresholds of 12-16 years. Cameriere's ratio showed lower explanatory capacity (R²=0.568) and a mean error of 2.7 years, although its ROC curves demonstrated good discriminatory performance across all age cut-offs. The combination of both methods showed a slight increase in predictive performance (R²=0.784), although this combined approach was not formally evaluated as an independent model. Females reached skeletal maturity earlier, although error rates were similar between sexes. Reliability was excellent across methods. Both approaches proved applicable for forensic age assessment, offering complementary advantages: Baccetti's method provides broader morphological interpretation, whereas Cameriere's morphometric ratio offers objectivity and reproducibility. These population-specific reference data support the forensic use of cervical vertebral analysis as part of a multimodal age estimation framework.