Introduction

Age-at-death estimation in adults remains one of the most debated and methodologically complex issues in forensic anthropology. In real forensic contexts, age estimation contributes directly to personal identification, narrowing of missing persons lists, disaster victim identification, and judicial investigations. For forensic practitioners, the value of a method lies not only in statistical correlation with chronological age, but also in its reproducibility, transparency, and practical usefulness when applied to individual cases.

Several methods for estimating the age at death have been proposed, such as the analysis of the state of fusion of the cranial sutures, the analysis of symphyseal changes in the pubic bone [1, 2], and microscopic evaluation of intracortical remodelling in the long bones [3].

In the 1980s, Iscan and colleagues proposed a new method for assessing age at death based on the morphological study of the sternal end of the fourth right rib [4]. The choice of the fourth rib was purely conventional, being a bone fragment easily found during routine autopsy. This method involves the macroscopic examination of three structural components of the sternal end of the fourth rib, such as pit depth, pit shape, and rim and wall configurations. Initially, the method was applied to a sample of 118 white male subjects [5], and the fragments of the ribs belonging to this sample were divided into nine phases (from phase 0 to phase 8) corresponding to as many age ranges. Later, the same method was applied to a sample of fragments of the sternal end of the fourth right rib of 86 white women [6], for which nine new phases were created, taking into account the sexual dimorphism of the skeleton. Despite its historical importance and continued application, the Iscan method presents well-documented limitations: broad and overlapping age intervals, reliance on subjective morphological interpretation, and population-dependent variability. In practice, these features reduce its discriminative power, particularly in middle and advanced adult ages where phase overlap becomes substantial.

For this reason, in 2010, Hartnett [7] proposed a revision of the Iscan method by incorporating bone quality and density and reducing the number of phases (from phase 1 to phase 7). Although this revision narrowed certain age ranges, it did not fully resolve problems of overlap and has shown variable performance in older individuals. Thus, rib-based age estimation continues to face a structural limitation: the tension between reproducibility of phase assignment and the forensic utility of the resulting age intervals.

An innovative approach in anthropology known as “virtual anthropology” [8], based on computed tomography (CT) research, has been developed in recent years.

CT imaging offers a non-destructive, non-invasive and fast method of data collection and analysis, representing a perfect technique for visualizing bones not only with 2D reconstruction but with 3D volume rendering (VR) imaging, which flawlessly aligns with anthropological analysis [9, 10]. Moreover, it generates standardized digital records that can be repeatedly reviewed, measured and shared among observers, enhancing documentation consistency and reducing variability associated with direct macroscopic handling [8].

Our study aims to assess the reliability of CT imaging for age estimation based on the analysis of the sternal end of the right fourth rib from a contemporary European skeletal sample. The CT was used on dry, isolated bones. This approach serves two methodological purposes: first, to eliminate confounding variables such as soft tissue artifacts and positioning variability, thereby assessing the intrinsic reproducibility of CT-based phase evaluation and second, to explore whether CT visualization of internal bone characteristics provides additional age-related information not captured by traditional surface assessment.

Additionally, we aim to evaluate whether CT-specific parameters can refine age estimation beyond conventional phase assignment.

Therefore, the findings of this study could support forensic professionals by improving reproducibility, enabling standardized digital documentation, facilitating independent expert review, and potentially refining age estimates within overlapping phase ranges, thus improving methodological transparency and defensibility in casework.