CT-based application of the Iscan method on isolated ribs: reliability, accuracy, and the role of joint fossa sclerosis in age estimation on a contemporary European skeletal sample

This study evaluates the applicability of the Iscan method to Post-Mortem Computed Tomography (PMCT) for age estimation through morphological analysis of the sternal end of the fourth right rib. Employing a double-blind design, two observers independently assessed a sample of 112 fragments of fourth ribs from individuals of European origin, isolated and processed before CT imaging. The findings indicate that Iscan's method applied via CT scans demonstrates strong reproducibility and substantial inter-operator reliability, as shown by weighted Cohen's kappa values ranging from 0.75 (inter-operator) to 0.92-0.98 (intra-operator). The method exhibited higher accuracy and consistency for middle-aged and older individuals, particularly in phases 3 to 5, whereas younger and elderly age groups showed lower reliability, with phase 8 requiring further refinement due to significant variability. Furthermore, the study introduced and evaluated a new CT-specific parameter-joint fossa sclerosis-to enhance age-at-death predictions. Regression analysis incorporating this parameter demonstrated improved accuracy and refined age-range estimations, particularly highlighting sex-specific variations: in males, sclerosis tended to shift estimates toward higher age phases, while in females, it primarily improved precision within established phase limits without significantly altering phase assignments. These observations underscore potential sex-based differences in bone remodeling dynamics that influence the Iscan phase classification. This research paves the way for future identification, introduction, and refinement of additional morphological parameters aimed at enhancing predictive accuracy. The substantial age-range overlaps inherent to Iscan's traditional method significantly limit its practical forensic applicability, emphasizing the need for methodological advancements to ensure reliable and accurate age estimation in forensic settings.