Index of Plantar Pressure Alters with Prolonged Diabetes Duration

Diabetic foot ulcers develop with deviations in the distribution of plantar pressure. It is difficult to interpret any alteration in plantar pressure under different conditions of type 2 diabetes mellitus (T2DM). The aim of this study was to gain a better insight into the variations in plantar pressure with increased duration of diabetes.

Plantar pressure was examined in 1196 participants with or without T2DM. Subjects with normal glucose tolerance (NGT) and impaired glucose tolerance (IGT) were assigned to control groups, and those with T2DM were divided into five groups according to diabetes duration (< 2 years, 2-5 years, 5-10 years, 10-15 years, and > 15 years). The clinical characteristics, plantar peak pressure, and pressure-time integral (PTI) were compared among the seven study groups, and factors associated with peak pressure and the PTI were analyzed.

At the hallux, peak pressure exhibited an upward trend in patients with T2DM within 5 years of diabetes duration, followed by a distinct downward slope with further progression of the disease (trend analysis, p  < 0.05). An uneven distribution of peak pressure was found at other locations, but this unevenness was ultimately lower than that in the two control groups (p  < 0.05). No obvious trend was noted for PTI among patients with different diabetes duration; however, those with diabetes for > 10 years manifested a significantly sharper increase in the PTI at the metatarsus (11.63 Ns/cm², p  < 0.05) and heel (14.12 Ns/cm², p  < 0.05) than at the hallux (8.76 Ns/cm²). A fluctuation in the PTI was also detected at the hallux and midfoot of diabetes patients, which was broadly flat when compared with that of the two control groups. The stepwise multiple regression analysis revealed that the variation in plantar pressure was independently associated with age, body mass index, and vibration perception threshold (VPT) (p  < 0.05).

There would appear to be an association between longer diabetes duration and decreased peak pressure for the hallux, suggesting that individuals with diabetes for > 10 years will have an increased PTI for the metatarsus and heel. The reduced pressure on the hallux is believed to be transferred to the metatarsus. Age, BMI, and VPT are distinct risk factors of abnormal plantar pressure.