Shear strength and toughness of trabecular bone are more sensitive to density than damage

Abstract

Microdamage occurs in trabecular bone under normal loading, which impairs the mechanical properties. Architectural degradation associated with osteoporosis increases damage susceptibility, resulting in a cumulative negative effect on the mechanical properties. Treatments for osteoporosis could be targeted toward increased bone mineral density, improved architecture, or repair and prevention of microdamage. Delineating the relative roles of damage and architectural degradation on trabecular bone strength will provide insight into the most beneficial targets. In this study, damage was induced in bovine trabecular bone samples by axial compression, and the effects on the mechanical properties in shear were assessed. The damaged shear modulus, shear yield stress, ultimate shear stress, and energy to failure all depended on induced damage and decreased as the architecture became more rod-like. The changes in ultimate shear strength and toughness were proportional to the decrease in shear modulus, consistent with an effective decrease in the cross-section of trabeculae based on cellular solid analysis. For typical ranges of bone volume fraction in human bone, the strength and toughness were much more sensitive to decreased volume fraction than to induced mechanical damage. While ultimately repairing or avoiding damage to the bone structure and increasing bone density both improve mechanical properties, increasing bone density is the more important contributor to bone strength.

Comparative Study of Locational Variation in Shear and Transverse Elastic Modulus of Buffalo Cortical Bone

“…Bone is considered to be stronger in compression and weakest in tension or shear. Most of the earlier studies have been focused on the determination of shear properties of trabecular bone [4][5][6] whereas in very limited studies shear behavior of cortical bone have been discussed based on torsional and three point bending methods [7][8]. Turner et al [9] observed that torsion often causes spiral fracture plane that corresponds to tensile rather than shear failure.…”

Fortifying the Bone-Implant Interface Part 2: An In Vivo Evaluation of 3D-Printed and TPS-Coated Triangular Implants

“…While the ultimate shear strength of sheep cancellous bone has yet to be reported, the ultimate shear strength of bovine femoral cancellous bone has been measured at 6.57±2.46 MPa. 33 Looking to Figure 5A, it can be seen that the majority of the tested sample's ultimate shear strengths were within the range of cancellous bone. Unlike the TPS implants, the bone-implant interface of all the AM groups remained intact after ≥ 2500N of force; this indicates that the bone-implant interface is stronger that than the surrounding cancellous bone.…”

The relative influence of damage versus density on trabecular bone mechanical behavior

“…In the previously mentioned study by Garrison et al , 5 damage was first induced in bovine trabecular bone specimens by either low or high amounts of compressive overloading (2.5 or 4.5 % strain, respectively). Specimens were then tested to failure by shear loading to simulate the unusual loading pattern that may occur in a fall.…”

“…Importantly, multiple regression analyses indicated that bone toughness was more sensitive to BV / TV than to damage quantity. Thus, Garrison et al 5 Commentary net beneficial effect on bone. The results concur with their prior work showing that bone density and microarchitecture have a greater influence than microdamage on the toughness of bovine trabecular bone specimens tested in compression.…”

“…5 As mentioned earlier, clinicians are increasingly concerned that microdamage accumulation may outweigh the beneficial effects of antiresorptive treatments on bone mineral density and microarchitecture. Garrison et al show that bone quantity influences trabecular bone toughness to a greater extent than microdamage.…”