Ageing bone fractures: The case of a ductile to brittle transition that shifts with age

Abstract

Human bone becomes increasingly brittle with ageing. Bones also fracture differently under slow and fast loadings, being ductile and brittle, respectively. The effects of a combination of these two factors have never been examined before. Here we show that cortical bone is most fracture-resistant at the physiologically prevalent intermediate strain rates of 10 -3 s -1 to 10 -2 s -1 such as they occur in walking or running, slightly weaker at slower quasistatic and much weaker at fast impact loading rates. In young cortical bone (15 years of age) the ductile-to-brittle transition (DBT) occurs at strain rates of 10 -2 s -1 , in old cortical bone (85 yrs) at speeds lower by a factor of 10 to 40. Other research has shown that the energy required to break bone (per unit of fracture surface) drops as much as 60% between these two ages. Therefore, DBT seems to compound the well-known phenomenon of 'brittle old bones'. Old bones can only cope with slow movement, young ones with both slow and fast movement. These observed material characteristics of (i) a shift of the DBT and (ii) a reduced energy absorption capacity appear to contribute at least as much to the loss of bone quality as the various quantity based (lowered bone density and mineral content) explanations of the past. They also provide a new powerful paradigm, which allows us to demonstrate mechanically, and uniquely, how human bone becomes increasingly brittle with age.

Penetration of Energized Metal Fragments to Porcine Thoracic Tissues

“…The difference in contact between the FSPs and the rib bone, due to their different nose shape, contributes to more cracks observed in the rib bone after impact with the spherical FSP. As both FSPs were not pointy (flat and hemispherical nose shape) and the bone target was a semibrittle material, which experienced brittle-to-ductile transition during fracture [53], the mechanism of perforation could have involved initial compression, formation of radial cracks, ductile hole, and plugging [54][55][56][57][58]. The sharper edge of the cylindrical FSP may have resulted in shearing of the periosteum, which cushioned the impact during the initial moment [57] and created adiabatic shear bands in the bone earlier [56]; thus, only a few cracks were generated.…”

A review on experimental and numerical investigations of cortical bone fracture

“…Therefore, several researchers have studied the influence of age on the K C of cortical bone and concluded a substantial decline in the K C of cortical bone with age. 18,32,33,44,108,110–117 The influence of age on fracture toughness of cortical bone is presented in Figure 5. Specifically, aging has been related to amplified mineralization 115 and lowered collagen network bonding and strength, 113 resulting in a decrease in K C and elasticity.…”

“…6,18,116 One of the researchers stated that human cortical bone becomes brittle with aging and K C , and the W f decrease as the age increases. 117 Gustafsson et al 118 explored the effect of aging on crack propagation in cortical bone and stated that bone quality reduces as age increases, and the crack path and mechanical responses were affected by age.…”

A Review on Multiscale Bone Damage: From the Clinical to the Research Perspective

“…This evident increment is strongly related to the increase in the average age of population. Indeed, with the aging process, human bone becomes more brittle and more prone to fracture [ 2 , 3 ]. Age-related bone fractures can be mainly caused either by a traumatic accident or by a pathology.…”