Structural basis of increased bone fragility in aged individuals: Multi-scale perspective

Abstract

Numerous epidemiological studies have shown that increased bone fragility and a higher risk of fractures are present in the aged, which reduces their quality of life and represents a significant socio-economic burden for the healthcare system. However, morphological and structural determinants underlying increased bone fragility have yet to be fully explained. This paper aimed to provide an overview of modern studies that dealt with determinants of increased bone fragility, analyzing different hierarchical levels of bone tissue organization (macro-, micro-, and nano-levels) in aged individuals and individuals with chronic comorbidities (mainly in individuals with chronic liver disease, renal disorders, and type 2 diabetes mellitus). Also, variable frequency of fractures at different skeletal sites in aged persons and individuals with chronic diseases was shown, indicating that aging-related bone loss is not a uniform process. A complete understanding of the spatial pattern of impaired bone quality can aid in the targeted evaluation of individualized fracture risk. Establishing a firm connection between the results of the clinical assessment of bone status and the analysis of numerous structural and mechanical bone properties (on various hierarchical levels) can represent a solid base for developing adequate guidelines and algorithms for prevention and treatment of increased bone fragility in aged individuals and individuals with chronic diseases.