Lower microhardness along with less heterogeneous mineralization in the femoral neck of individuals with type 2 diabetes mellitus indicates higher fracture risk

There is still limited understanding of the microstructural reasons for the higher susceptibility to fractures in individuals with type 2 diabetes mellitus (T2DM). In this study, we examined bone mineralization, osteocyte lacunar parameters, and microhardness of the femoral neck trabeculae in 18 individuals with T2DM who sustained low-energy fracture (T2DMFx: 78 ± 7 years, 15 women and 3 men) and 20 controls (74 ± 7 years, 16 women and 4 men). Femoral necks of the T2DMFx subjects were obtained at a tertiary orthopedic hospital, while those of the controls were collected at autopsy. T2DMFx individuals had lower trabecular microhardness (p = 0.023) and mineralization heterogeneity (p = 0.001), and a tendency to a lower bone area with mineralization above 95th percentile (p = 0.058) than the controls. There were no significant intergroup differences in the numbers of osteocyte lacunae per bone area, mineralized lacunae per bone area, and total lacunae per bone area (each p > 0.05). After dividing the T2DMFx group based on the presence of vascular complications (VD) to T2DMFxVD (VD present) and T2DMFxNVD (VD absent), we observed that microhardness was particularly reduced in the T2DMFxVD group (vs. control group, p = 0.02), while mineralization heterogeneity was significantly reduced in both T2DMFx subgroups (T2DMFxNVD vs. control, p = 0.002; T2DMFxVD vs. control, p = 0.038). The observed changes in mineralization and microhardness may contribute to the increased hip fracture susceptibility in individuals with T2DM.