The aim of this study was to evaluate the applicability of using the growth of the body of C4 vertebra for the estimation of age in children and young adolescents. We used the fact that the proportions between the radiologic projections of the posterior and anterior sides of the C4 vertebral body, which forms a trapezoidal shape, differ with age: in younger individuals, the posterior side is higher, whereas in older individuals, the projections of the sides of the vertebral body form a rectangular shape with the two sides equal or with the anterior side slightly higher. Cephalograms of 444 Italian subjects (214 female and 230 male individuals) aged between 5 and 15 years and with no obvious development abnormalities were analyzed. The projections of the anterior side (a) and of the posterior side (b) of each C4 body were measured, and their ratio (Vba), as a value of the C4 body development, was used for age estimation. Distribution of the Vba suggested that it does not change after 13 years in female and 14 years in male subjects. Consequently, we restricted our analysis of the Vba growing model until 14 years in both sexes. We used a Bayesian calibration method to estimate chronological age as function of Vba as a predicting variable. The intra- and inter-observer agreement was satisfactory, using intra-class correlation coefficient of Vba on 30 randomly selected cephalograms. The mean absolute errors were 1.34 years (standard deviation 0.95) and 1.01 years (standard deviation 0.71), and the mean inter-quartile ranges of the calibrating distribution were 2.32 years (standard deviation 0.25) in male and 1.72 years (standard deviation 0.39) in female individuals, respectively. The slopes of the regression of the estimated age error to chronological age were 0.02 in male and 0.06 in female individuals, where both values did not result significantly different from 0 (p > 0.12). In conclusion, although our Bayesian calibration method might not really outperform the classical regression models in the precision of its estimates, it appears to be more robust, to greatly reduce the typical bias inherent in the regression model approach, and to have the ability to incorporate multiple predictors.

Radiological analysis of the epiphyses of the knee joint provides new valuable information, which may be used in combination with these well-established techniques in order to maximise the accuracy in the assessment of age of 18 years. A total of 215 antero-posterior radiographs of the knee was reviewed retrospectively in patients aged between 14 and 24 years old (99 boys, 116 girls). Fusion was scored as stage 1, epiphysis not fused; stage 2, epiphysis is fully ossified and epiphyseal scar is visible; and stage 3, epiphysis is fully ossified and epiphyseal scar is not visible. Scores of 0, 1 and 2 were assigned to stages 1, 2 and 3, respectively. Lastly, the score related to epiphyseal fusion at the knee joint was obtained by adding the three scores of the distal femur, proximal tibia and proximal fibula. Age distribution gradually increased with each score, for both genders. The mean age (±standard error) in each score category varied between genders, but the differences were not significant (p > 0.11). Five tests were performed to discriminate between individuals who were or were not at age 18 years or more, according to the receiver operating curve. For boys, the highest value of accuracy was obtained with score 3, with high sensitivity (Se = 93.33 %) and specificity (Sp = 89.29 %). For girls, it was obtained with score 4, with high accuracy (Acc = 85.86 %). These results indicate that radiographic analysis of the knee is a valuable alternative as a non-invasive method of estimation of 18 years of age.

Nowadays, due to the global increase in migration movements, forensic age estimation of living young adults has become an important focus of interest. Minors often have no identification documents providing their correct birth dates. Establishing the age of majority is therefore fundamental in order to determine whether juvenile penal systems or penal systems in force for adults are to be applied. Radiological examination of the clavicles is one of the methods recommended by the Study Group on Forensic Age Diagnostics. In this retrospective study, a sample of chest radiographs of 274 subjects, aged between 12 and 25 years, was studied according to Schmeling's method in order to examine the ossification of both medial clavicular epiphyses. All stage classifications were evaluated by five examiners. Intra- and inter-examiner reliability was analysed by Cohen's K statistic. Intra-examiner agreement was insufficient for two of the experts. Inter-examiner agreement, among the other three operators, was moderate (K = 0.509). Study of reliability highlighted difficulties in interpretation, the need to select qualified personnel and choice of the best radiographic image in order to reduce any anatomic overlaps. Although ossification of the medial clavicular epiphyses is recommended to assess whether an individual has already reached the age of majority or not, these results suggested that it is very difficult to clearly identify the five stages of ossification by using conventional chest radiography.

Important aspects of forensic practice are age estimation and discrimination of individuals of unknown age as adults and minors. The developing knee joint was recognized as a potential site for age examination in late adolescence. We analyzed a sample of anteroposterior x-rays of the knee joints from 446 living individuals from Umbria, Italy (234 males and 212 females), aged between 12 and 26 years. We evaluated the ossification of the distal femoral (DF), proximal tibial (PT), and proximal fibular (PF) epiphyses. We took into account possible persistence of the epiphyseal scars in the ossified epiphyses by the adopted stages of those previously introduced by Cameriere et al. (2012). We also used measurements from all three epiphyses to calculate the total score of maturation for the knee joint (SKJ). Cohen Kappa coefficients of intrarater agreement for staging the DF, PT, and PF epiphyses were 0.839, 0.894, and 0.907, while interrater agreement was 0.919, 0.791, and 0.907, respectively. The resulting receiver operating characteristic (ROC) curves of SKJ show better discriminatory power than those for DF, PT, and PF epiphyses in predicting that the participant, either male or female, was an adult or a minor. The areas under the curves for SKJ were 0.991 and 0.968 vs. 0.944, 0.962, 0.974 and 0.891, 0.910, 0.918 for males and females, respectively. The results of the 2 by 2 contingency tables showed that SKJ score of 4 in males and SKJ score of 5 in females were the most suitable cut-off value in discriminating between adults and minors. Principally, the sensitivity test for males was 0.94, with 95 % confidence interval (95 % CI) 0.90 to 0.97 and specificity was 0.96 (95 % CI 0.91 to 0.98). The proportion of correctly classified individuals was 0.95 (95 % CI 0.91 to 0.97). For females, the sensitivity test was 0.89 (95 % CI 0.84 to 0.92) and specificity was 0.92 (95 % CI 0.87 to 0.96), the proportion of correctly classified individuals was 0.90 (95 % CI 0.85 to 0.94). These results indicate that the SKJ method may give valuable supporting information in forensic procedures for discriminating individuals of legal adult age of 18 years. Further studies should address the usefulness of the SKJ method in different populations.