Forensic age estimation by magnetic resonance imaging of the knee: the definite relevance in bony fusion of the distal femoral- and the proximal tibial epiphyses using closest-to-bone T1 TSE sequence.

OBJECTIVES: To clarify the relevance of the bony fusion of the distal femoral and the proximal tibial epiphyses by means of magnetic resonance imaging (MRI), a prospective cross-sectional cohort study was performed with a special focus on a reliable determination of the 14th, 16th and 18th years of life.

METHODS: We scanned 658 German volunteers in the age bracket 12-24 years using a 3.0 T MR-scanner and utilising a T1 turbo spin-echo sequence representing true bone anatomy. Minimum, maximum, mean ± standard deviation and median with lower and upper quartiles were defined. Intra- and interobserver agreements were determined (Cohen's kappa). The statistical relevance of sex-related differences was analysed (Mann-Whitney U test, p < 0.05, exact, two-sided).

RESULTS: The bony fusion took place before the 18th year of life in both epiphyses. The Mann-Whitney U test results imply significant sex-related differences for most stages. For both epiphyses, the intra observer (κ femur 0.961; tibia 0.971) and interobserver (κ femur 0.941; tibia 0.951) agreement levels were very good.

CONCLUSION: The 14th and the 16th years of life can be determined in both sexes, but the completion of the 18th year of life cannot solely be determined by the bony fusion, as depicted by closest-to-bone MRI.

KEY POINTS: • Forensic age estimation by means of MRI of the knee is feasible. • MRI provides data about the ossification process without using ionising radiation. • The method allows the determination of the 14th and 16th years of life. • The bony fusion is not suitable as the sole indicator of majority. • The chosen classification is easy to use for specially trained professional personnel.