Estimation of risk for plantar foot ulceration in diabetic patients with neuropathy

The main risk factors for plantar forefoot ulcers are loss of protective sensation due to sensory neuropathy and increased mechanical stress on the sole of the foot. The aim of this study was to find a better parameter than the plantar pressure to explain the occurrence of plantar ulcers under the metatarsalheads (MTHs). Twenty diabetic patients (3 Type 1 and 17 Type 2) each with 1 plantar ulcer and 23 Type 2 diabetic patients without plantar ulceration (controls), were investigated. The parameters of plantar pressure, length of contact time and pressure-time integral (PTI) were determined by pedography at defined foot regions. PTI represents the duration of mechanical stress on the foot. Based on the distribution of ulcers, the ratio of stress on the MTHs to that on the big toe was calculated. In diabetic patients with ulcers the difference of PTI between MTHs and hallux was higher at 153% and hence 3.2 times greater than the difference in plantar pressure between MTHs and hallux of 47.3%. In the control group the ratio of difference had a factor of 2 only because the corresponding difference in PTI was 85.1% and the difference in plantar pressure was 43.1%. These results may indicate that increased stress at the MTHs is responsible for the occurrence of planar ulcers compared with other regions of the sole. Diabetic patients with elevated PTI ratio are at risk of developing foot ulcers and therefore have to be provided with orthopaedic shoes to prevent foot ulceration.