Computed tomography to visualize and quantify the plantar aponeurosis and flexor hallucis longus tendon in the diabetic foot

Background. The purposes of this report were to describe a three-dimensional computed tomography based method to visualize and quantify the thickness of the plantar aponeurosis and flexor hallucis longus tendon and determine the reliability of thickness measures. Given reliable measures, a secondary purpose was to compare plantar aponeurosis and flexor hallucis longus thickness in subjects with diabetes mellitus and peripheral neuropathy to an age and weight matched group without diabetes. Methods. CT data from 16 people with diabetes mellitus and peripheral neuropathy (mean age 55.2 (SD 10.5), 4 female, 12 male, body mass index 31.7 (SD 7.6)) and 10 people without diabetes mellitus (mean age 53.8 (SD 9.1), 2 female, 8 male, body mass index 37.0 (SD 8.6)) were analyzed. Length and thickness of the plantar aponeurosis and flexor hallucis longus tendon were measured twice for five subjects from each group in a blinded single observer reliability study. Findings. The average mean difference of the linear measurements was 0.12 mm (average SD = 1.00 mm). Significant differences for measures of plantar aponeurosis thickness (p = 0.044) were found between diabetic, 4.2 mm (SD 0.9), and control groups, 3.6 mm (SD 0.8), and approached significance for tendon thickness measured at the midfoot (diabetic group 4.8 mm (SD 0.8), control group 4.3 mm (SD 0.8), p = 0.051). Interpretation. CT was shown to be a reliable imaging technique for visualizing and quantifying soft tissue structures in diabetic feet. The methods and the quantitative description of the plantar aponeurosis and tendon thickness reported in this paper may be useful to those developing three-dimensional computational models of the foot.