The Effect of Compositional and Physicochemical Heterogeneity on Age-Related Fragility of Human Cortical Bone
Year: 2006
Type: article
Abstract: The progressive loss of bone with age very commonly leads to osteoporosis, a condition characterized by increased skeletal fragility.Osteoporosis and its consequences are significant causes of frailty, morbidity, and even mortality.While reduced bone mass, currently used in estimating fragility, enhances risk of fracture, low bone mass alone is not a sufficient explanation for osteoporotic or elderly fractures.This is exemplified by substantial overlap in bone density between normal individuals and patients who sustain hip and other osteoporotic fractures.A new perspective, in addition to bone mass, is needed that broadens the conceptual basis of skeletal integrity.Bone is studied at various levels starting from ultrastructural and chemical to histological and structural properties with the ultimate goal being prediction of bone strength accurately.Researchers used photon absorptiometry and CT scan techniques to predict fractures in elderly people believing bone mineral density is a major determinant of bone strength.However, later many researchers are convinced that other factors, such as bone quality, also contribute significantly to bone strength.Consequently, the proposed study investigated heterogeneity of compositional, physicochemical and micro-structural properties, and related them to mechanical properties.Raman spectroscopy was used to characterize distribution of mineralization, crystallinity and carbonation from gage regions of tensile specimens, which were bio-mechanically tested afterwards.Using linear polarized light, collagen fiber orientation and microstructures were determined from sections close to the fracture surface.Results indicated that distribution of mineralization became more uniform with age, which benefited stiffness and strength at the expense of deformation of bone.Moreover, fatigue life was improved and modulus degradation rate was decreased.Volume fractions of highly mineralized locations increased and spacing between them were reduced with age, which improved monotonic properties but proved unfavorable with respect to fatigue properties.Bigger osteons, porosity and transversely oriented collagen fibers largely found in elderly individuals considerably reduced strength of bone.Transverse collagen fiber orientation also decreased fatigue life.In conclusion, ultra and micro level changes in bone can be supplementary to BMD measures for better clinical assessment of age-related bone's fragility; however, their predictive power is limited and depends on anatomical location.
Author: Janardhan Yerramshetty
Institution: University of Toledo
Language: English
Subfield: Orthopedics and Sports Medicine
Field: Medicine
Domain: Health Sciences
Open Access status: green
Funders: Purdue University, University of Toledo
OpenAlex ID: W1202683965