Validation of the İşcan method in clinical MSCT scans specific to an Australian population

The transposition of traditional biological profiling methods to virtual skeletal reconstructions represents a relatively novel practice that is proving to be versatile in a variety of forensic contexts. Widespread acknowledgement of the disadvantages associated with archaeological and/or other non-contemporary skeletal collections has prompted an increase in the use of medical imaging modalities for the purposes of formulating population-specific reference standards used to estimate characteristics such as chronological age. The primary aim of the present study is to statistically evaluate the reproducibility of assessment and thereafter develop age estimation standards based on the morphoscopic evaluation of the fourth right sternal rib following the phase ageing method developed as reported by İşcan et al. (J Forensic Sci 29:1094–1104, 1984, J Forensic Sci 30:853–863, 1985) in clinical multi-slice computed tomography (MSCT) scans. A total of 335 MSCT scans representing Western Australian individuals between 10 and 80 years of age (179 male and 156 female) were retrospectively reconstructed and analysed in OsiriX following the İşcan et al. sex-specific standards (J Forensic Sci 29:1094–1104, 1984, J Forensic Sci 30:853–863, 1985) for the fourth right rib. Regression and transition analyses are employed to generate standards for the estimation of chronological age and modelling of thoracic senescence, respectively. The method was also applied to right ribs three and five to evaluate intercostal variance in age-related metamorphosis. Intra- and inter-observer accordance is ‘substantial’ (K = 0.76) and ‘almost perfect’ (K = 0.825), respectively. Intercostal variances between ribs three to five were observed in the male sample only. Multiple regression using phase scores from all three ribs produced models with the highest predictive accuracy (± 10.04 years for males and ± 9.81 years for females). The transition analyses demonstrate comparable levels of age-related morphological change across ribs and male and female samples. This study presents a novel set of reference standards for a contemporary Australian population and further demonstrates the utility of virtual analysis in forensic anthropology.