Bone mineral properties and 3D orientation of human lamellar bone around cement lines and the Haversian system

Abstract

Bone is a complex, biological tissue made up primarily of collagen fibrils and biomineral nanoparticles. The importance of hierarchical organization in bone was realized early on, but the actual interplay between structural features and the properties on the nanostructural and crystallographic level is still a matter of intense discussion. Bone is the only mineralized tissue that can be remodeled and, at the start of the formation of new bone during this process, a structure called a cement line is formed on which regular bone grows. Here, the orientational relationship of nanostructural and crystallographic constituents as well as the structural properties of both nanostructural and crystallographic constituents around cement lines and the Haversian system in human lamellar bone are investigated. A combination of small- and wide-angle X-ray scattering tensor tomography is employed together with diffraction tomography and synchrotron computed tomography to generate a multi-modal image of the sample. This work shows that the mineral properties vary as a function of the distance to the Haversian canal and, importantly, shows that the cement line has differing mineral properties from the surrounding lamellar bone, in particular with respect to crystallite size and degree of orientation. Cement lines make up a significant portion of the bone matrix despite their small size, hence the reported findings on an altered mineral structure, together with the spatial modulation around the Haversian canal, have implications for the formation and mechanics of bone.

Mineralized Collagen Fibrils: An Essential Component in Determining the Mechanical Behavior of Cortical Bone

“…Some evidence suggests that the cement line is hypermineralized, although not necessarily in the form of mature hydroxyapatite and collagen deficient with respect to surrounding bone. , By contrast, other evidence suggests that the cement line is hypomineralized and may contain sulfated mucosubstances and provide a ductile interface with surrounding the bone matrix. , More interestingly, the mineral properties of the cement line seem to be significantly different from the surrounding lamellar bone. The crystal in the cement line is shorter than that in the surrounding bone and also has broadened distribution . When viewed under polarized light, osteons predominately composed of oblique orientated MCFs appear bright, while osteons predominately composed of MCFs parallel to the osteon axis appear dark. , …”

“…The crystal in the cement line is shorter than that in the surrounding bone and also has broadened distribution. 76 When viewed under polarized light, osteons predominately composed of oblique orientated MCFs appear bright, while osteons predominately composed of MCFs parallel to the osteon axis appear dark. 77,78 As the basic component of microscale bone structure, MCFs are actively involved in microscopic bone deformation, crack initiation, and crack propagation.…”

Recent developments in X-ray diffraction/scattering computed tomography for materials science

“…1-100 nm) structures. WAXS is thus used to characterize the d-spacing of crystalline materials while SAXS can be used to characterize samples with larger-scale structure such as colloids [42], nanoparticles [43], proteins [44], DNA assemblies [45], soft tissue [46] and bone [47][48][49][50] among others.…”

“…Across a reasonably large 3 × 3 × 3 mm 3 FOV, HAp was to orient their c-axis towards the ossification front despite lower resolution and signal-to-noise [151]. Most recently, Grünewald et al [50] used SAXS/XRD-TT to investigate Haversian canals in lamellar bone, showing that cement lines have different material properties including crystallite size and orientation compared with the rest of the bone matrix.…”

Molecularly Imprinted Polymers: Shaping the Future of Early-Stage Bone Loss Detection─A Review

“…5,6 These collagen fibrils orient themselves into sheets called lamellar sheets. These lamellar sheets are further organized into osteons, which are structures that contain blood vessels surrounded by concentric layers of lamellar sheets, 6 and these osteons are densely packed to form the cortical bone as shown in Figure 1. Bone tissues are of two types: cortical bone and cancellous bone.…”