Validity and reliability of the XSENSOR in-shoe pressure measurement system

Abstract

Background In-shoe pressure measurement systems are used in research and clinical practice to quantify areas and levels of pressure underfoot whilst shod. Their validity and reliability across different pressures, durations of load and contact areas determine their appropriateness to address different research questions or clinical assessments. XSENSOR is a relatively new pressure measurement device and warrants assessment. Research question Does the XSENSOR in-shoe pressure measurement device have sufficient validity and reliability for clinical assessments in diabetes? Methods Two XSENSOR insoles were examined across two days with two lab-based protocols to assess regional and whole insole loading. The whole insole protocol applied 50–600 kPa of pressure across the insole surface for 30 seconds and measured at 0, 2, 10 and 30 seconds. The regional protocol used two (3.14 and 15.9 cm2 surface area) cylinders to apply pressures of 50, 110 and 200 kPa to each insole. Three trials of all conditions were averaged. The validity (% difference and Root Mean Square Error: RMSE) and repeatability (Bland Altman, Intra-Class Correlation Coefficient: ICC) of the target pressures (whole insole) and contact area (regional) were outcome variables. Results Regional results demonstrated mean contact area errors of less than 1 cm2 for both insoles and high repeatability (≥0.939). Whole insole measurement error was higher at higher pressures but resulted in average peak and mean pressures error < 10%. Reliability error was 3–10% for peak pressure, within the 15% defined as an analytical goal. Significance Errors associated with the quantification of pressure are low enough that they are unlikely to influence the assessments of interventions or screening of the at-risk-foot considering clinically relevant thresholds. Contact area is accurate due to a high spatial resolution and the repeatability of the XSENSOR system likely makes it appropriate for clinical applications that require multiple assessments.

A Wearable Insole System to Measure Plantar Pressure and Shear for People with Diabetes

“…Low linearity errors of up to 3% were revealed in both pressure and shear measurement. The accuracy error (up to 5% of full scale in both pressure and shear) of the insole system reported in this study is equivalent to a recently reported SLIPS system [ 17 ], as well as a commercial pressure-only system [ 30 ].…”

“…The incorporation of the sensor within the insole resulted in −9%, −41%, −16% and −11% group mean percentage difference in peak pressure during walking at the heel, 5MH, 1MH and hallux, respectively. The 5MH region may also be affected by the raised lateral border of the XSENSOR measurement insole [ 30 ]. Due to the slight padding of the sensorised insole’s middle EVA layer, some reduction in pressure was observed across regions.…”

Wireless pressure insoles for measuring ground reaction forces and trajectories of the centre of pressure during functional activities

“…Although direct comparisons with previous literature are difficult due to previously mentioned methodological differences between studies, current findings seem to be in accordance with previous literature investigating other similar systems in healthy adults. In the only study available to date assessing the reliability of the X4 insoles, Parker et al demonstrated high between-day reliability and low area errors for average peak pressure and mean pressure 14 . However, the study used a calibration device, therefore authors suggested that reliability of the system should be explored in humans.…”

“…Recently, Parker et al, used a pressurised bladder to apply an even load to the X4 insole surface at a range of pressures. They demonstrated high validity and reliability of the insoles for measuring contact area, mean pressure and peak pressure 14 . To our knowledge, a thorough analysis of the validity and repeatability of this insole system in humans is lacking.…”

“…Insoles with capacitive sensors for instance, may be subject to creep when exposed to prolonged periods of loading 13 , potentially making them less effective when assessing static tasks. Such devices may also be used due to their capacity to detect small changes in plantar pressure in response to orthotic or footwear intervention, when reducing the risk of foot ulceration in people with diabetes 14 . Commercial wireless insoles are increasingly available, to name a few: Moticon GmbH®, Medilogic®, eSHOE ®, F-Scan®, Pedar®.…”