Bone quality assessment techniques: geometric, compositional, and mechanical characterization from macroscale to nanoscale

Abstract

This review presents an overview of the characterization techniques available to experimentally evaluate bone quality, defined as the geometric and material factors that contribute to fracture resistance independently of areal bone mineral density (aBMD) assessed by dual energy x-ray absorptiometry. The methods available for characterization of the geometric, compositional, and mechanical properties of bone across multiple length scales are summarized, along with their outcomes and their advantages and disadvantages. Examples of how each technique is used are discussed, as well as practical concerns such as sample preparation and whether or not each testing method is destructive. Techniques that can be used in vivo and those that have been recently improved or developed are emphasized, including high resolution peripheral quantitative computed tomography to evaluate geometric properties and reference point indentation to evaluate material properties. Because no single method can completely characterize bone quality, we provide a framework for how multiple characterization methods can be used together to generate a more comprehensive analysis of bone quality to complement aBMD in fracture risk assessment.

Keywords: Fourier transform infrared imaging; Raman imaging; computed tomography; electron microscopy; mechanical testing; microindentation; nanoindentation; one quality; reference point indentation; vibrational spectroscopy.

Figure 1

Bone quality measurement techniques are depicted on a logarithmic scale of the hierarchical structure of bone. Along the top from left to right, representative images of bone using the imaging techniques of HRpQCT (adapted with permission from [135]), qBEI (adapted with permission from [136]), FTIRI of crystallinity (adapted with permission from [137]), and AFM (adapted with permission from [138]) are shown. The field of view of the representative images corresponds with the scale bar. Along the bottom, each characterization technique is categorized as geometric, compositional, or mechanical and is depicted by a bar showing the approximate range of resolutions currently achievable. Abbreviations: AFM = atomic force microscopy; FTIR = Fourier transform infrared; HPLC = high-performance liquid chromatography; HRMRI = high-resolution magnetic resonance imaging; HRpQCT = high-resolution peripheral quantitative computed tomography; Micro-CT = micro-computed tomography; NMR = nuclear magnetic resonance imaging; qBEI = quantitative backscattered electron imaging; QCT = quantitative computed tomography; RPI = reference point indentation; SAXS = small-angle x-ray scattering; SEM = scanning electron microscopy; TGA = thermogravimetric analysis; XRD = x-ray diffraction.