Plantar fat-pad displacement in neuropathic diabetic patients with toe deformity: a magnetic resonance imaging study

The aim of this study was to quantify the association between claw/hammer toe deformity and changes in submetatarsal head (sub-MTH) fat-pad geometry in diabetic neuropathic feet.

Thirteen neuropathic diabetic subjects (mean age 56.2 years) with toe deformity, 13 age- and sex-matched neuropathic diabetic control subjects without deformity, and 13 age- and sex-matched healthy control subjects without deformity were examined. From high-resolution sagittal plane magnetic resonance images of the second and third ray of the foot, toe angle (a measure of deformity), sub-MTH fat-pad thickness, and subphalangeal fat-pad thickness were measured. The ratio of these thicknesses was used to indicate fat-pad displacement.

Sub-MTH fat pads were significantly thinner (2.5 +/- 1.3 vs. 6.0 +/- 1.4 mm, P < 0.001) and subphalangeal fat pads significantly thicker (9.1 +/- 1.9 vs. 7.6 +/- 1.2 mm, P < 0.005) in the neuropathic group with deformity compared with neuropathic control subjects. As a result, thickness ratio was substantially smaller in the deformity group: 0.28 +/- 0.14 vs. 0.79 +/- 0.14 in neuropathic control subjects (P < 0.001). A significant correlation of 0.85 was present between toe angle and thickness ratio (P < 0.001). No significant differences were found between neuropathic and healthy control subjects.

This study shows a distal displacement and subsequent thinning of the sub-MTH fat pads in neuropathic diabetic patients with toe deformity and suggests that, as a result, the capacity of the tissue in this region to reduce focal plantar pressure is severely compromised. This condition is likely to increase the risk of plantar ulceration in these patients.