Sub-calcaneal plantar fat pad assessment using dual-energy computed tomography: First experience in the diabetic foot

Background: This study assessed the use of dual-energy computed tomography (CT) to evaluate sub-calcaneal plantar fat pad changes in people with diabetic neuropathy. Methods: Dual-energy CT scans of people with diabetic neuropathy and non-diabetic controls were retrospectively included. Average CT values (in Hounsfield Units) and thickness (in centimeters) of the sub-calcaneal plantar fat pad were measured in mono-energetic images at two energy levels (40 keV and 70 keV). The CT values measured in patients with diabetic neuropathy were correlated to barefoot plantar pressure measurements performed during walking in a clinical setting. Findings: Forty-five dual-energy CT scans of people with diabetic neuropathy and eleven DECT scans of non-diabetic controls were included. Mean sub-calcaneal plantar fat pad thickness did not significantly differ between groups (diabetes group 1.20 ± 0.34 cm vs. control group 1.21 ± 0.28 cm, P = 0.585). CT values at both 40 keV (−34.7 ± 48.7 HU vs. −76.0 ± 42.8 HU, P = 0.013) and 70 keV (−11.2 ± 30.8 HU vs. -36.3 ± 27.2 HU, P = 0.017) were significantly higher in the diabetes group compared to controls, thus contained less fatty tissue. This elevation was most apparent in patients with Type 1 diabetes. CT values positively correlated with the mean peak plantar pressure. Interpretation: Dual-energy CT was able to detect changes in the plantar fat pad of people with diabetic neuropathy.