Introduction: During aging and osteoporosis, the cortical bone becomes more porous, making it more fragile and susceptible to fractures. The aim of this study was to investigate the intracortical compression-induced strain energy distribution, and determine whether the intracortical pores associated with high strain energy density (SED) in the surrounding bone have a different morphology, distribution and remodeling history than pores with low SED.
Methods: The study was conducted on fibula diaphysis specimens from 20 patients undergoing a jaw reconstruction (age range 41-75 years, 18 men and 8 women). Specimens were plastic embedded, µCT-scanned and sectioned for histology. Threedimensional micro-finite element models of each specimen were tested in compression using a linearly elastic analysis, and the SED of the bone immediately surrounding the pores was calculated within a plane of interest corresponding to the histological sections. The statistical distribution of the SED of all pores, per sample, was used to identify high SED pores (SED > 1.5 times the interquartile range from the 75th percentile) and the remaining low SED pores.
Results: Pores with high SED were larger (p ≤ 0.0001), less circular (p ≤ 0.0001), and were located closer to the endosteal edge of the cortex (p ≤ 0.0001) than low SED pores (Figure 1A-C). A detailed histological analysis of the remodeling events generating the pores revealed that the high SED pores compared to low SED pores had a 13.3-fold higher odds of being a resorptive (70%) or formative (11%) pore rather than a completely remodeled pore (p ≤ 0.0001). The resorption space associated with the 91% of high SED pores overlapped with the pore of a preexisting remodeling event (osteon) (5.9-fold higher odds).
Conclusions: Collectively, these data show that the high SED pores are preferentially enlarged irregular pores positioned closer to the endosteal surface of the cortex, and that these pores tend to be resorptive pores that overlap with the pore of a preexisting parent osteon, suggesting that pores may originate from resorption within preexisting pores rather than from penetrative resorptions generating new pores. Overall, the study demonstrates a strong relationship between cortical bone mechanics and the pores morphology, distribution and remodeling history in the human fibula.
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