Exploring age-related trends in cortical and trabecular bone in an elderly Scottish sample: a pilot study on the clavicle

The human lifespan is increasing globally, increasing the need for further research on age-related changes inthe bone of elderly individuals. Microscopic assessment of the skeletal system can provide information aboutthe composition, mechanical, and functional properties of bone. The aim of this study is to combine 2D and3D approaches examining cortical and trabecular bone to explore histological age-related changes in theclavicles of an elderly Scottish population.The medial portion of 30 left clavicles was collected from Scottish donors from the Centre of Anatomy andHuman Identification. The sample had a mean age of 83 years, with a sex distribution of 15 males and 15females. Histomorphometric variables from the trabecular and cortical bone were collected. Five trabecularparameters were assessed using micro-CT scanning on two volumes of interest (VOI-superior and inferiorsampling locations on the medial clavicular end). On the cortical bone, fourteen parameters were evaluatedusing traditional histological techniques. Cortical area related parameters were assessed on the whole crosssection, while osteon frequency related variables were measured on 8 sampling areas targeting keyanatomical locations on the periosteal section of the clavicle.Intra-observer error was assessed using intra-class correlation coefficient. The two VOIs were compared forstatistical differences using paired t-test or Wilcoxon signed-rank test. Pearson and Spearman correlationcoefficients were calculated, and age group comparisons were conducted for all parameters on the entiresample, the sample divided by decades (70s, 80s, and 90s), and the sample divided into two age groups(over/under 85 years). Sex differences were explored using an independent t-test and Mann-Whitney test.Lastly, stepwise regression analysis was used to test the optimal combination of parameters that couldexplain the highest variation in age.Intra-observer error demonstrated overall good reliability for most parameters. Only bone volume fractiondid not differ between VOIs, with all other trabecular parameters showing statistically significant differences.Cortical area parameters (cortical area and relative cortical area), intact osteon number, and both VOIs fortrabecular connectivity density were statistically significantly correlated to age. When the sample was splitinto decades, no significant changes were observed over the three decadesfor cortical bone parameters (70s,80s, and 90s). However, trabecular thickness and bone volume fraction differed statistically betweenindividuals in their 70s and 80s. When the over/under 85 years groups were compared, only relative corticalarea was statistically different between the two groups. Sex differences were found for cortical area relatedparameters (total area, endosteal area, and cortical area). Stepwise multiple linear regression showed thatrelative cortical area and inferior trabecular connectivity accounted for 30% of the variation in age.This research showed that combining both cortical and trabecular bone using histomorphometric parameterscan provide valuable information about age-related changes, suggesting also that other factors such as sexor age-related pathologies might have an impact on the changes observed in the two bone tissue types. Whilefurther research is necessary, this study adds to the growing research on bone histology using differentpopulations and exploring the ageing patterns of an elderly population.