Assessment of Trabecular Bones Microarchitectures and Crystal Structure of Hydroxyapatite in Bone Osteoporosis with Application of the Rietveld Method

Abstract

The term crystal structure is understood as a set of atoms periodically distributed in space, forming a lattice. The composit e material, bone, contains an organic part consisted of collagen and an inorganic part consisted predominantly of hydroxyapatite crystals, having the molecular formula Ca10(PO4)6(OH)2 in its unit cell. The crystal structure of hydroxyapatite can indicate the trabecular bone quality, by the identification of crystallite size, microhardness, microstrain and ratio of calcium and phosphorus in bones of three types: normal, osteopenic or osteoporotic. Osteoporosis is defined by the National Institute of Health as a skeletal disorder characterized by compromised bone strength and increased risk of fracture. Dried trabecular bones of vertebrae L1 columns of nine human cadavers from the São Paulo City Morgue were used. Before sample collection, they were pre-divided into three groups: normal, osteopenic or osteoporotic, through quantitative ultrasound of the calcaneus. The characterization of the three types of bones was made by electron microscopy scanning, microanalysis by energy dispersive spectrometry, microhardness and powder X-ray diffraction with application of the Rietveld method. The results showed a decrease of the crystallite size, hardness, ratio of calcium and phosphorus, trabecular number and bone density and an increase in microstrai n values suggesting greater fragility and disruption in the crystalline structure of hydroxyapatite in osteopenic and osteoporotic bone. Microstructural characterization of hydroxyapatite crystals in dry trabecular bone could differentiate the three types of bones (normal, osteopenic and osteoporotic) and supplement assessment of osteoporosis, with an emphasis on bone quality.

Obtaining hydroxyapatite with different precursors for application as a biomaterial

“…Some studies [31,71] showed that increasing the calcination temperature results in an increase in the size of the crystallite; however, the results showed that for the same calcination temperature (800 °C), the crystallite size was larger for the sample 1, obtained from the precursor of biological origin. The sizes of crystallites were calculated indicating that the larger crystallite sizes are associated with normal bone [72]. In the samples synthesized in this work we verified this larger size in sample 1, synthesized from the biological precursor.…”

“…In the samples synthesized in this work we verified this larger size in sample 1, synthesized from the biological precursor. Rollo et al [72] showed that the crystal structure of hydroxyapatite may indicate the quality of the trabecular bones, by identifying the size of the crystallite, microhardness, microstrain and calcium and phosphorus ratio in bones of three types: normal, osteopenic or osteoporotic. That means that Rietveld analysis should be a practical tool to evaluate the health of individuals through the diffraction study of their skeletal remains.…”

Classification of fracture and non-fracture groups by analysis of coherent X-ray scatter

“…This is entirely consistent with the observations of this study and indicates possible specific differences in apatite chemistry between the fracture and non-fracture groups. Disorder within the apatite lattice, as introduced by such lattice site modifications, has been proposed as a fundamental contributor to bone mechanical compromise for more than three decades 23 and evidence for this hypothesis continues to be reported 24 . Consequently, the chemical composition of bone apatite through its influence on crystallite dimensions and subsequently micro-architecture is a significant determinant of bone mechanical performance.…”

Burden of disease and clinical targets in adult patients with X-linked hypophosphatemia. A comprehensive review

“…Along with calcium, inorganic (i) phosphate (Pi) is the main constituent of hydroxyapatite, the bone mineral that strengthens the mechanical resistance of the organic matrix. Of note, in human adult body, about 90% of total phosphorus is stored in the bone as hydroxyapatite (calcium-phosphate) crystals whose structure is indicative of trabecular bone quality [5,6]. Regulation of phosphate balance relies on a fine-tuning Prof. Maria Luisa Bianchi passed away prior manuscript submission.…”