# Comparative X-ray Diffraction Analysis of the Hydroxyapatite Crystal Structure in Developing and Mature Lumbar Vertebrae

## TL;DR

This study compares the crystal structure of hydroxyapatite in newborn and adult vertebrae, revealing significant differences in crystallite size and lattice parameters that may explain age-related changes in bone properties.

## Contribution

The study provides new empirical evidence on the maturation of bone mineral structure through comparative X-ray diffraction analysis of hydroxyapatite in developing and mature vertebrae.

## Key findings

- Adult vertebrae showed significantly larger hydroxyapatite crystallite sizes compared to newborn samples.
- Mature bone exhibited increased lattice parameters in both the a-axis and c-axis of the hexagonal unit cell.
- Trends toward greater crystallinity in adult bone were observed, though not statistically significant.

## Abstract

The ultrastructural characteristics of bone mineral composition during vertebral development remain incompletely understood. This study investigated the crystallographic parameters of hydroxyapatite in L3 vertebrae, comparing samples from newborn (n = 12) and adult (n = 12) specimens. X-ray diffraction analysis was performed using a DRON-3 diffractometer with copper Kα radiation (λ = 0.15433 nm) operating at 30 kV and 20 mA. Diffraction patterns were recorded from 2° to 37° at 1°/min, focusing on the characteristic hydroxyapatite peaks in the 30-34° range. Unit cell parameters were calculated using the (211), (112), and (300) reflections, while crystallite sizes were determined using the Scherrer method. Results revealed significant differences in crystallographic parameters between age groups, with adult samples showing larger crystallite sizes (18.12 ± 0.87 nm vs. 8.92 ± 0.25 nm, p < 0.001) and more defined diffraction peaks. The hexagonal unit cell parameters also differed significantly, with mature bone exhibiting increased lattice parameters in both the a-axis (9.451 ± 0.014 Å vs. 9.391 ± 0.014 Å, p < 0.001) and c-axis length (6.891 ± 0.010 Å vs. 6.860 ± 0.017 Å, p < 0.001) compared to developing bone. While adult specimens showed trends toward greater crystallinity with lower amorphous calcium (-10.76 wt%) and higher crystalline calcium (+2.60 wt%), these differences did not reach statistical significance. These findings provide new insights into the maturation process of bone mineral structure and may contribute to understanding age-related changes in bone mechanical properties.