Microscopic characteristics of peri- and postmortem fracture surfaces

Area of Science:

• Forensic Anthropology
• Biomaterials Science
• Materials Science

Background:

• Determining the postmortem interval (PMI) is crucial in forensic investigations.
• Bone elasticity changes significantly after death, influencing fracture characteristics.
• Macroscopic fracture analysis has limitations in accurately estimating PMI.

Purpose of the Study:

• To investigate the efficacy of microscopic surface features in determining fracture timing.
• To assess if microscopic fracture characteristics can reliably differentiate perimortem and postmortem events.
• To correlate bone microstructure changes with postmortem interval (PMI) and bone elasticity.

Main Methods:

• Human femoral bone samples were fractured at simulated postmortem intervals (PMI) using a drop test frame and three-point bending.
• Scanning electron microscopy (SEM) was used to analyze microscopic fracture features (delamination, osteon pullout, microcracks).
• Multiple linear regression analyzed the relationship between microscopic features, bone properties, and accumulated degree hours (ADH).

Main Results:

• Microscopic fracture surface features, especially osteon pullout, are strong predictors of ADH (R-squared up to 0.92).
• Water loss is the primary factor affecting bone elasticity at lower ADH.
• Collagen fibers remain largely intact until approximately 40,000 ADH.

Conclusions:

• Microscopic fracture surface analysis provides a more reliable and sensitive method for estimating PMI than macroscopic analysis.
• SEM analysis of bone microstructure can elucidate perimortem and postmortem events.
• Osteon pullout is identified as the most significant predictor of postmortem interval.