This study evaluated the applicability of the Vieth staging system for forensic age estimation using MRI of the distal radial epiphysis in the Turkish population, a methodology previously applied in the German population by Ottow et al. [19]. The findings align with previous research demonstrating the reliability of MRI-based methods in assessing bone age, reinforcing the potential of MRI as a non-invasive, radiation-free, and accurate tool for forensic age estimation [1, 2, 5, 10, 19, 21]. The application of the Vieth staging system in wrist MRI scans is strongly supported by high intra- and inter-observer agreement values (κ = 0.974 and κ = 0.961) for the distal radius epiphysis. Ottow et al. [19] also reported high observer agreement values in their study. However, it should be noted that the current methodologies for age estimation and the specific assessments for age estimation may be influenced by the experience of the observers. It should be taken into account that the observers in this study, as well as those in the study by Ottow et al., had extensive prior experience with multiple MRI methods for age estimation. As Wittschieber et al. [21] previously emphasized, observer experience plays a significant role in the application of forensic age estimation methods. Indeed, as this method is a combination of different MRI weightings and introducing “band” and “line” definitions in its classification, the results may be more affected by observer experience then other methods. The lack of a clear distinction between these two definitions appears to be a limitation of the Vieth method. On the other hand, this study and other studies where the Vieth method was applied to the knee and shoulder also demonstrated high concordance, reducing concerns about the method’s applicability [10, 22,23,24]. Future studies that classify the number of studies and the experience of practitioners could provide valuable insights into the applicability and reproducibility of the Vieth method.

In the study by Ottow et al. [19], the minimum ages for the distal radial epiphysis were reported as 12.05, 13.69, 15.35, 16.59, and 19.19 years for males and 12.11, 12.30, 14.44, 15.94, and 18.86 years for females. When these results are compared with the findings of the current study, both consistencies and differences are observed. In this study, the minimum ages for males were found to be slightly higher in stages 2, 3, and 4, while the ages for stages 5 and 6 were more closely aligned. For females, the minimum ages in stages 2, 3, and 4 were found to be comparable, but stages 5 and 6 were marginally higher. The comparative minimum age values are presented in Table 4.

The differences in observed minimum ages can be attributed to sample size, population differences, and MR-specific methodological variations. The sample in this study was larger and potentially provided a broader age range and variability. Although this introduces a bias regarding the average values of the stages, as highlighted in the Ottow et al. study, it does not offer an additional advantage for the use of the minimum age concept in forensic age estimation. This is because the minimum age concept is based on identifying the lowest observed age for a specific stage of ossification, and it supports that there are no individuals younger than this in the studied cohort. For readers unfamiliar with the concept, the minimum age is used to determine whether an individual has reached a certain developmental stage, helping to establish forensic age thresholds with certainty.

This study was conducted retrospectively, and it was not possible to obtain socioeconomic or ethnicity data for the study population. Additionally, while the differences between ethnic origins is not considered an effective factor, low socioeconomic status may be associated with delayed ossification [25, 26]. Although the extent to which the study results were affected by socioeconomic status was not directly determined, the delayed ossification ages observed in comparison to the Ottow et al. study might be related to the fact that this study was conducted in a Turkish population with a lower Human Development Index. According to the Human Development Index published by the United Nations in 2023, Turkey is ranked 45th, and Germany is ranked 4th, highlighting a significant difference between the countries where the studies were conducted [27].

Other factors that could influence the study results include the different MRI weightings and magnetic field strengths used. The Vieth method, which relies on hyperintensity and image continuity, might be particularly sensitive to these variations. In this study, a 1.5 Tesla magnetic field was used. The higher magnetic field strength of 3 Tesla MRI scanners might lead to better image quality compared to 1.5 Tesla scanners, potentially offering a higher signal-to-noise ratio and improved spatial resolution. This could enhance the accuracy of ossification stage assessments in forensic age estimation.One of the factors that might influence the differences observed in minimum age values is the MRI sequences used. While Ottow et al. utilized the T2 TSE SPIR sequence, the current study employed the FSE PD sequence. The differences between the T2 TSE SPIR sequence and the FSE PD sequence can play a significant role in age estimation, particularly in terms of image quality and the clarity of bone structures. Indeed, the T2 TSE SPIR sequence, with its fat suppression feature, can provide higher contrast for soft tissues and water-based components, making the epiphyseal-diaphyseal fusion more visible. On the other hand, the FSE PD sequence, which focuses on proton density-weighted imaging, allows for more detailed examination of bone and cartilage structures, potentially offering an advantage in evaluating bone structures for age estimation [28, 29]. These differences suggest that each sequence could yield different results when used for age estimation, with each method potentially offering advantages in specific scenarios.

The results of this study can be compared with previous studies that evaluated the distal radial epiphysis using T1 TSE and FSE PD MRI in a cohort from the Turkish population [18, 30]. Similarly, Timme et al. [31] in a Germany-based study also assessed the distal radius epiphysis using the T1 TSE sequence. They reported minimum age thresholds of 17 years for stages 4 and 4a males and 18 years for stage 4b males using T1-weighted MRI. Ekizoglu et al. [18] found the minimum ages for the distal radius using the FSE PD sequence to be 15–17 years for males and 14–16 years for females. Serin et al. [32], using T1-SE MRI, reported the lowest ages as 15 years for females and 16 years for males. Studies by De Tobel et al. [17], Tomei et al. [14], and Serinelli et al. [15] which used T1-weighted MRI, found significant correlations between chronological age and epiphyseal development but did not specify minimum age thresholds. Among all past studies using T1, T2, and FSE PD sequences for evaluating the distal radius epiphysis, only the staging methodology of Timme et al. [31]., reported a minimum age threshold of 18 years for males at stage 4b. The established minimum ages of 18.2 and 18.6 years require caution due to the low margin. Compared to the results of other methodologies, Ottow et al. [19] reported minimum ages of 18.86 years for females and 19.19 years for males, whereas our current study found minimum ages of 18.42 years for females and 20.00 years for males, providing a safer age margin for determining the age of 18 years at stage 6.

Future research could focus on increasing the sample size and diversity to enhance the generalizability of the findings. Additionally, the development of automated MRI analysis and machine learning methods could reduce observer-dependent errors.

In conclusion, the application of the Vieth staging system to the distal radial epiphysis in the living using MRI can provide critical age estimations for legal and civil proceedings. The high intra- and inter-observer agreement values support the use of this method in forensic applications, contributing to the proven potential of MRI as a non-invasive, radiation-free and accurate tool for age estimation. Future studies should aim to refine these methods and explore their applicability across different populations, ultimately working towards the development of standardized, non-invasive protocols for forensic age estimation.