Pediatric reference Raman data for material characteristics of iliac trabecular bone

Bone material characteristics are important contributors in the determination of bone strength. Raman spectroscopic analysis provides information on mineral/matrix ratio, mineral maturity/crystallinity, relative pyridinoline (Pyd) collagen cross-link content, relative proteoglycan content and relative lipid content. However, published reference data are available only for adults. The purpose of the present study was to establish reference data of Raman outcomes pertaining to bone quality in trabecular bone for children and young adults. To this end, tissue age defined Raman microspectroscopic analysis was performed on bone samples from 54 individuals between 1.5 and 23 years with no metabolic bone disease, which have been previously used to establish histomorphometric and bone mineralization density distribution reference values. Four distinct tissue ages, three well defined by the fluorescent double labels representing early stages of bone formation and tissue maturation (days 3, 12, 20 of tissue mineralization) and a fourth representing old mature tissue at the geometrical center of the trabeculae, were analyzed. In general, significant dependencies of the measured parameters on tissue age were found, while at any given tissue age, sex and subject age were not confounders. Specifically, mineral/matrix ratio, mineral maturity/crystallinity index and relative pyridinoline collagen cross-link content index increased by 485%, 20% and 14%, respectively between days 3 and 20. The relative proteoglycan content index was unchanged between days 3 and 20 but was elevated in the old tissue compared to young tissue by 121%. The relative lipid content decreased within days 3 to 20 by -22%. Thus, the method allows not only the monitoring of material characteristics at a specific tissue age but also the kinetics of tissue maturation as well. The established reference Raman database will serve as sensitive tool to diagnose disturbances in material characteristics of pediatric bone biopsy samples.