Forensic age estimation by MRI of the knee - comparison of two classifications for ossification stages in a German population

Abstract

Aim and objectives: In forensic age estimation e.g. for judicial proceedings surpassed age thresholds can be legally relevant. To examine age related differences in skeletal development the recommendations by the Study Group on Forensic Age Diagnostics (AGFAD) are based on ionizing radiation (among others orthopantomograms, plain x-rays of the hand). Vieth et al. and Ottow et al. proposed MRI-classifications for the epiphyseal-diaphyseal fusion of the knee joint to define different age groups in healthy volunteers. The aim of the present study was to directly compare these two classifications in a large German patient population.

Materials and methods: MRI of the knee joint of 900 patients (405 female, 495 male) from 10 to 28 years of age were retrospectively analyzed. Acquired T1-weighted turbo spin-echo sequence (TSE) and T2-weighted sequence with fat suppression by turbo inversion recovery magnitude (TIRM) were analyzed for the two classifications. The different bony fusion stages of the two classifications were determined and the corresponding chronological ages assigned. Differences between the sexes were analyzed. Intra- and inter-observer agreements were determined using Cohen's kappa.

Results: With the classification of Ottow et al. it was possible to determine completion of the 18th and 21st year of life in both sexes. With the classification of Vieth et al. completion of the 18th year of life for female patients and the 14th and 21st year of life in both sexes could be determined. The intra- and inter-observer agreement levels were very good (κ > 0.82).

Conclusion: In the large German patient cohort of this study it was possible to determine the 18th year of life with for both sexes with the classification of Ottow et al. and for female patients with the classification of Vieth et al. It was also possible to determine the 21st year of life for all bones with the classification of Ottow et al. and for the distal femur with the classification of Vieth et al.

Keywords: Bone age; Forensic age estimation; Knee MRI; Ossification stages.

Fig. 1

Coronary MRI images in T1-TSE sequence. a: Distal femur and proximal tibia of a 10-year-old female patient in stage 2. b: Distal femur and proximal tibia of a 14-year-old-female patient. c: Distal femur and proximal tibia of a 17-year-old male patient in stage 3b. d: Distal femur and proximal tibia of a 21-year-old male patient in stage 4. MRI: Magnetic Resonance Imaging, TSE: Turbo Spin Echo

Fig. 2

Coronary MRI images in T1-TSE sequence (first row) and T2-TIRM sequence (second row). a: distal femur and proximal tibia in in stage 2 of a 10-year-old male patient; b: distal femur and proximal tibia of a 14-year-old male patient in stage 3; c: distal femur and proximal tibia of a 14-year-old female patient in stage 4; d: distal femur and proximal tibia of a 17-year-old female patient in stage 5; e: distal femur and proximal tibia of a 24-year-old female patient in stage 6; MRI: Magnetic Resonance Imaging, TSE: Turbo Spin Echo, TIRM: Turbo Inversion Recovery Magnitude

Fig. 3

Classification of MRI images of the knees (n = 900) into stages 2c to 5 according to the classification system according to Ottow et al. The graph illustrates the distribution of the stages of the distal femur over age. the “x” indicates the excluded examinations. The red lines indicate the forensically relevant age limits. Stage 5 was not assigned to the female patients in any MRI Scan for the distal femur, so the box plot is missing at the corresponding location. The white dots indicate statistically deviating values. MRI images of the knees of patients aged 10 to 28 years. MRI: Magnetic Resonance Imaging, n: number

Fig. 4

Classification of MRI images of the knees (n = 900) into stages 2c to 5 according to the classification system according to Ottow et al. The graph illustrates the age distribution for each stage and long bone. The “X” indicates the excluded examinations. MRI images of the knees of patients aged 10 to 28 years. MRI: Magnetic Resonance Imaging, n: number

Fig. 5

Classification of MRI images of the knees (n = 900) into stages 2 to 6 according to the classification system according to Vieth et al. The graph illustrates the distribution of the stages of the distal femur over age. The “x” indicates the excluded examinations. The red lines indicate the forensically relevant age limits. MRI images of the knees of patients aged 10 to 28 years. MRI: Magnetic Resonance Imaging, n: number

Fig. 6

Classification of MRI images of the knees (n = 900) into stages 2 to 6 according to the classification system according to Vieth et al. The graph illustrates the age distribution for each stage and long bone. The “X” indicates the excluded examinations. The white dots indicate statistically deviating values. MRI images of the knees of patients aged 10 to 28 years. MRI: Magnetic Resonance Imaging, n: number