Subclassification of Vieth stage 4 in MRI of the proximal tibial epiphysis: a pilot study for forensic age estimation

The MRI-based staging system introduced by Vieth et al. has been successfully validated for assessment of the proximal tibial epiphysis. Our previous validation study suggested that additional information regarding completion of the 16th or 18th year of life might be obtained by applying a more fine-grained subclassification of Vieth stage 4. Therefore, the present pilot study investigated the feasibility and potential forensic value of a subclassification of Vieth stage 4. The study cohort comprised 57 T1-weighted MRI examinations of the proximal tibial epiphysis (24 males and 33 females) previously assigned to Vieth stage 4. All examinations were re-assessed using newly defined morphological criteria, allowing Vieth stage 4 to be further subdivided into three novel substages (4a-4c). All cases could be assigned to one of the proposed substages, although substage 4a occurred in only five individuals. Minimum ages in males were 15.45, 15.68, and 15.23 years for substages 4a, 4b, and 4c, while the minimum ages in females were 12.64, 12.57, and 13.18 years. Intra- and interobserver agreement were good (κ = 0.751 and κ = 0.663, respectively). The findings demonstrate that a morphological subclassification of Vieth stage 4 at the proximal tibial epiphysis is feasible. The proposed substages may assist in verifying completion of the 14th year of life but did not permit reliable verification of completion of the 16th or 18th year of life. Although the proposed subclassification is currently not suitable for routine forensic age estimation, it may nevertheless contribute to a more detailed understanding of skeletal maturation at the proximal tibial epiphysis and serve as a basis for future validation studies.