Device-dependent variability of plantar pressure thresholds: Consequences for clinical decision-making in diabetic...

Plantar pressure measurement is used to identify areas of high mechanical loading in people at risk of diabetic foot ulceration. Fixed thresholds, such as 200 kPa for in-shoe and 600 kPa for barefoot measurements, are commonly reported in the literature and applied in clinical decision-making in diabetic foot care. However, the validity of these thresholds across different measurement systems remains uncertain.

Fifteen healthy adults walked under controlled conditions while plantar pressures were recorded using three platform systems and two in-shoe systems. Peak pressures were extracted for heel, midfoot, and forefoot regions. Analyses examined the frequency of exceeding 200 and 600 kPa thresholds, agreement across devices, the reliability of derived measures, including the rearfoot-forefoot ratio and identification of the region of maximum loading.

The 200 kPa threshold was exceeded in 99.3 % of heel and forefoot data, but distributions of values differed significantly across devices (p < 0.05). Agreement, defined as all devices classifying the same participant, foot, and region as either above or below 600 kPa, was low overall (5.4 %), higher in the heel than the forefoot, and differed significantly between platform systems (p < 0.05). In-shoe devices consistently reported values below 600 kPa. Limited reliability was observed with the rearfoot-forefoot ratio achieving only 53.6 % agreement across devices, and agreement in the most loaded in just 6.7 % of cases.

Absolute thresholds such as 200 and 600 kPa are unreliable across commercial systems and foot regions. Common derived measures are also device dependent. Clinical guidelines should move beyond fixed thresholds and adopt device-specific or multidimensional approaches for risk assessment in diabetic foot care.