Hierarchical multimodal structural and material analysis of bone in diabetes

Diabetic neuropathy and Charcot neuroarthropathy (CN) may compromise lower limb skeletal integrity. We performed a comprehensive comparative assessment of foot bone across multiple hierarchical parameters at nano, meso and micro scale orders.

Calcaneal bone specimens obtained from individuals with CN (Group A; n = 12), diabetic neuropathy (Group B; n = 21), and healthy controls (Group C; n = 18). Trabecular microarchitecture was assessed using micro-computed tomography (micro-CT), mechanical strength through uniaxial compression, biochemical composition by infrared spectroscopy (FTIR), crystal dimensions with X-ray diffraction (XRD), tissue-level mechanical behaviour by nanoindentation and quantiative organic and mineral content of bone matrix by thermogravimetric analysis (TGA).

Micro-CT revealed 35.9 % reduced trabecular thickness (0.25 ± 0.11 mm vs 0.39 ± 0.14 mm, p = 0.016), 57 % lower maximum load tolerance (218.85 ± 18.84 N vs 508.15 ± 100.98 N, p < 0.001) and 55 % reduced stiffness (51.62 ± 4.89 N/mm vs. 114.63 ± 13.74 N/mm, p < 0.001) in Group A compared to Group C, respectively. Mineral-to-matrix ratio (3.17 ± 0.68 vs. 4.75 ± 1.47, p < 0.001), collagen maturity index (1.25± 0.29 vs. 1.74 ± 0.50, p < 0.001) and organic fraction (44.95 ± 5.15 % vs 50.91 ± 4.85 %;p = 0.005) were lower in Group A compared to group C, respectively. The elastic modulus (8.13 ± 1.57 GPa vs. 18. 12± 1.96 GPa) and hardness (0.34 ± 0.07 GPa vs. 0.71 ± 0.13 GPa) were significantly reduced in group A compared to Group C (p < 0.001 for both), confirming compromised tissue-level mechanics of foot bones in CN. Bone samples from Group B showed intermediate values compared to either group A and C, respectively.

Charcot neuroarthropathy of foot is characterised by severe, multiscale impairments in bone architecture, composition, and mechanical function that contribute to heightened skeletal fragility and underscore the need for targeted interventions addressing bone quality.