Osteonal Microcracking Pattern: A Potential Vitality Marker in Human Bone Trauma

SIMPLE SUMMARY: When recovered skeletal remains reveal fractures, one of the main challenges is to determine the timing of the trauma. In particular, fractures that are related to death are of high forensic relevance. The common macroscopic criteria used in forensic anthropology may make it possible to determine whether a fracture occurred in a fresh or in a dry bone. Whilst dry bone fractures clearly occurred after death, fresh bone fractures are not always vital fractures. This is one of the biggest issues for forensic anthropologists. Depending on the period of time and surrounding conditions after death, bones can retain their fresh properties due to the preservation of water and organic components. The aim of this study is to test whether the histological assessment of microcracking patterns assists in determining the vitality of a fresh fracture. As we hypothesized after a previous study, our results further support that vital fractures exhibit a higher ratio of osteonal/interstitial microcracks than non-vital fractures. Moreover, we found that axial bone compression may be used to simulate intra vitam conditions in fracture experiments. Our results show that the osteonal microcracking pattern can potentially be used as a marker of vital trauma, thereby improving the probative value of forensic anthropological investigations. ABSTRACT: In forensic anthropology, the differential diagnosis between peri- and postmortem bone fractures is mainly based on macroscopic criteria. In contrast, studies focusing on bone histology are very scarce. In a recent publication, we showed that (perimortem) fractures in fresh human bones exhibit a different osteonal microcracking pattern than (postmortem) damage in dry bones. In the current work, we explored whether this osteonal microcracking pattern is distinctive of the vitality of (perimortem) fresh bone fractures. To this end, we compared the number, length and structural distribution of microcracks in vital humeral fractures from forensic autopsy cases with experimentally reproduced, three point-bending fractures in fresh and dry human humeri. Half of the fresh experimental bones were fractured whilst applying axial compression, i.e., attempting to simulate intra vitam conditions more accurately. The results showed a similar osteonal microcracking pattern between vital fractures and experimental fractures of fresh humeri subjected to axial compression. Interestingly, this pattern was significantly different from the one observed in the experimental fractures of fresh humeri without axial compression and dry humeri. This supports our hypothesis that the osteonal microcracking pattern can potentially be used as a marker for vital perimortem trauma, providing a histomorphometric tool for fracture timing.