Estimation of Forensic Age from Bony Fusion of Distal Femoral and Proximal Tibial Epiphyses by MRI of the Knee

To test the relevance of bony fusion of distal femoral and proximal tibial epiphysis by means of Magnetic Resonance Imaging (MRI), a cross-sectional study was performed to determine the reliability of 16 and 18 years of life. Methodology: We scanned 140 Indian (Bengali) subjects in the age bracket of 3 and 35 using 1.5 T MR-scanner utilising T1 turbo spin-echo sequence representing true bone anatomy, in the Indian Bengali population. Minimum, maximum, mean and standard deviation were defined. Bony fusion took place before the 18 year of life. Intraand interobserver agreements were determined by calculating the kappa coefficients. Bony fusion of distal femoral and proximal tibial epiphyses in 1.5 Tesla MRI is useful only to a certain extent in determining age 16 to 17 years of life in both sexes, but completion of 18 year of life cannot be solely determined by MRI from bony fusion of knee.


Introduction
Applied forensic age diagnostics can be used for the process of forensic identification.
Age interval is of importance as it contains several relevant age thresholds in medicolegal cases including the 16 th , 18 th and 21 st years of life 1,2 . For example, to deal with child sexual abuse cases (that regards any sexual activity with a child below 18 years a crime), in some countries like India there is a special law, The Protection of Children from Sexual Offences (POCSO) Act, 2012 3,4 .
Victims who seek justice for child sexual abuse cases face a lot of difficulties if they don't have a proper birth certificate or other authentic documents to prove their age. 186 Brazilian Journal of Forensic Sciences, Medical Law and Bioethics 9(2): 185-194 (2020) S. Chowdhuri et al. Proof of age of a person is needed for legal purposes. Several studies have been published on this topic by using traditional method of anthropology and by studying bones of the dead [5][6][7][8] . However, advanced methods involving X-Ray and CT scan is seen to produce better results because of their high-quality images. In this context, study of age-related progression of epiphyseal-metaphyseal bony fusion and epiphyseal ossification proved to be useful in populations across the globe 9,10 . Growth rate of body is diverse for different ethnic groups and for this reason in this study we have attempted to determine age by studying the MRI images of the bony fusion of the distal femoral epiphysis and the proximal tibial epiphysis in the Indian Bengali population. The aim of the present study is to determine how strongly the chronological age relates to ossification of the knee when a 5-stage grading system was used.
Objective of this study was to determine age of study subjects, aged between 3 and 35 years, by studying the MRI images of the bony fusion of the distal femoral epiphysis and the proximal tibial epiphysis

Study participants
Study was conducted on the 140 selected Indian Bengali patients (by simple random sampling) 11 , aged between 3 and 35 years, brought for MRI examination of knee for various reasons at Calcutta National Medical College digital MRI centre, using 1.5 T MRI. 6 months was the study period. The ages of study subjects were verified from unique identification card issued by Govt. of India (Aadhar Card) and cards issued by State Govt for free cashless treatment in hospitals (Swasthya Sathi Card). Those subjects whose ages could not be verified were excluded from this study. Proper informed consent was taken from patient/next of kin. Ethical Clearance (CM/CNMC/1993) for this study was taken from Ethics Committee of Calcutta National Medical College.

MRI analysis
All our scans were performed with same scanner in same sequence. All MRI images were transferred to a commercially available workstation. On the workstation, the images were studied using RadiAnt DICOM Viewer software and ossification stages were noted under the supervision of the Radiologist of that centre. In order to define the different ossification stages, the established classification of Schmeling et al. 12 was used.

Exclusion criteria for the study are:
1. Subjects with congenital, endocrine or other serious diseases were excluded 2. Overlapping or unclear MRI scans were excluded 3. Subjects whose ages could not be verified The images were first evaluated by an examiner with experience in MRI diagnostics with a re-evaluation of 55 randomly chosen cases after a lapse of 1 month.
A second qualified examiner with profound expertise in musculoskeletal radiology also evaluated the same group of 55 cases without knowledge of the previously determined stages. The evaluations were also performed without knowledge of the sex and age of the examined volunteers. Intra-and interobserver agreements were determined by calculating the kappa coefficients.

Statistical analysis
All data was collected, compiled and subjected to suitable statistical analysis using appropriate methods in SPSS software (v. 20). Minimum, maximum, mean and standard deviation were defined.  Table 2), we found that in case of males; grade 2 was achieved in between 5 to 19 years with the mean age for achieving this grade being 13.93 years. In case of females, grade 2 was achieved in between 3 to 15 years with the mean age of achieving this grade being 10.40 years.

Of
In case of males; grade 3 was achieved in between 16 to 19 years with the mean age for achieving this grade being 17.86 years. In case of females, grade 3 was achieved between 17 to 18 years with the mean age of achieving this grade being 17.50 years.
In case of males; grade 4 was achieved in between 17 to 34 years with the mean age for achieving this grade being 23.54 years. In case of females, grade 4 was achieved in between 16 to 27 years with the mean age of achieving this grade being 21.07 years.
In case of males; grade 5 was achieved in between 16 to 30 years with the mean age for achieving this grade being 26.37 years. In case of females, grade 5 was achieved in between 21 to 34 years with the mean age of achieving this grade being 26.25 years.
The correlation between age and stage of ossification was found to be significant by Chi-Square Test (p<0.05). The inter-observer variability for the assessing the stages of ossification was in the range of 0.88 to 0.99, which indicates a very high reliability.    19 with our method was difficult. The classification of Schmeling et al. 12 is well recognised and used by specially trained examiners. Other pre-existing MRI staging systems for long bone epiphyses like that of Devorak et al. 23 were not chosen for our study as they include absolute measurements within the acquired images. The classification provided by Jopp et al. 24 and consequently the results are partially comparable.

Conclusion
We can conclude that bony fusion of distal femoral and proximal tibial epiphyses in 1.5 Tesla MRI can be used in determination of Forensic Age in conjunction with other methods. However, forensic age estimation in living individuals by MRI of knee is feasible and this modality provides data about the individual skeletal age without the use of ionizing radiation. The used classification is for practical use for trained professionals with high intra and inter observer agreement. It is also a fact that has been shown from the unreliability of determination of grade 5 in females compared to males that only 1.5 Tesla MRI is not suitable as a sole indicator of maturity in majority in either sex in compliance with criteria for forensic age estimation. It can be useful only to a certain extent in determining age 16 to 17 years of life in both sexes.