Is bone analysis with µCT useful for short postmortem interval estimation?

ABSTRACT

The evaluation of the postmortem interval (PMI) is an important consideration in forensic medicine. The time between death and the discovery thereof is extremely important, not only in terms of the legal process, but also for the course of the investigation. At the time of the discovery of human bones, the evaluation of the PMI is extremely difficult. To date, there is no really effective tool for this evaluation. The objective of our study is to characterize the architectural modifications of human bones using micro-tomography (µCT) in the postmortem period. Ten bone samples were extracted from a single fresh human cranial vault (no freezing, no embalming) from a body donation. The samples were conserved in a controlled environment (a laboratory hood at 20 °C with 60% humidity) for 10 weeks. Every 2 weeks after the death and the sample extraction from the vault, the samples were analyzed with µCT (resolution 10 µm, Bruker HR1172 ®). The 3D analysis focused on general 3D data related to the trabeculae the total volume (TV), the bone volume (BV), and the bone surface (BS), as well as specific trabeculae data; namely the number of trabeculae (TbN), trabecular thickness (TbTh), the average distance between the trabeculae (TbSp), and the trabecular pattern factor (TbPf). Each sample was observed separately and compared to itself over time; no comparisons among samples were made. We used a linear mixed model for repeated measures (an unstructured covariance pattern model) and post hoc comparisons between each consecutive time using linear contrast with an SAS software package, release 9.3 (SAS Institute, Cary, NC). We showed a statistical difference for BS/BV (p = 0.046) over time, with a significant decrease during the first 2 weeks (p = 0.003; mean decrease, - 0.99, 95% CI [- 1.61; - 0.36]), while TbSp (p < 0.0001) showed a significant increase during the first 2 weeks (p < 0.0001; mean increase, 0.022, 95% CI, [- 0.016; - 0.028]).Our study highlighted architectural trabecular modifications on postmortem bones using the µCT. These modifications occurred at an early stage, during the first 2 weeks of conservation. Complementary work will need to be performed to allow for better understanding of the biological phenomena observed and to create databases of osseous taphonomy, starting with various individuals, mediums of conservation, types of bone, and with varying techniques for analysis.