Femora from adults with type 1 or type 2 diabetes have lower bone strength and smaller hip geometry

The increased hip fracture risk in individuals with type 1 (T1D) and type 2 (T2D) diabetes is not explained by areal bone mineral density (aBMD), indicating that diabetes increases fracture risk through mechanisms independent of aBMD. To investigate, we used quantitative computed tomography to compare femoral strength, volumetric BMD (vBMD), and geometry in cadaveric femora from older adults with T1D (n = 23; 13 female) and T2D (n = 21; 11 female) to controls of similar age, sex, and race (n = 19; 11 female). While aBMD and vBMD measures were similar across groups, femoral strength was lower in the diabetic groups compared to controls. Geometric strength, based on external bone shape, was lower in T1D (-15%, p = 0.001) and T2D (-12%, p = 0.014) compared to controls. When combining geometry and density, femoral strength was significantly lower in T1D (-19%, p = 0.044). The strength-to-density ratio was also lower in T1D and T2D (p ≤ 0.013), indicating greater skeletal fragility in the diabetic groups beyond what is predicted by BMD. Diabetic groups had smaller bone size, including lower femoral neck volume (-8%, p ≤ 0.030), neck cross-sectional area (-8%, p ≤ 0.030), and trochanter cross-sectional area (-7%, p ≤ 0.010). These findings suggest that lower femoral strength and smaller geometry contribute to elevated fracture risk in diabetes, warranting further study in larger populations.