Comparison of two pixelated insoles using in-shoe pressure sensors to determine percent offloading: case studies

Abstract

Objective: The gold standard for offloading neuropathic forefoot and midfoot wounds is the total contact cast (TCC). However, in practice TCC is rarely used and is contraindicated in patients with fluctuating oedema, poor perfusion, lack of adequate tissue oxygenation and morbid obesity. It can also be too restrictive for patients, inevitably resulting in treatment rejection and delayed healing. This paper examines the role of shoe-based offloading devices as an alternative in reducing plantar pressure and optimising the healing of neuropathic ulcers. Method: Healthy subjects were recruited and fitted for two types of pixelated insoles: PegAssist (PA) insole system (Darco International, US) and FORS-15 (FORS) offloading insole (Saluber, Italy). An area of discreet, elevated high pressure was created by adding a 1/4-inch-thick felt pad to the plantar skin under the first metatarsal head. Subjects walked barefoot in surgical shoes with standard insoles (Condition 1), barefoot in pixelated insoles (Condition 2), barefoot with pixels removed (Condition 3). Dynamic plantar pressures were measured using F-Scan and the results were analysed to determine plantar pressure changes in each condition. Results: Using PA, the percentage reduction of plantar pressure (kPa) under the first metatarsal between Condition 1 and Condition 2 was 10.54±15.81% (p=0.022), between Condition 2 and Condition 3 was 40.13±11.11% (p<0.001), and between Condition 1 and Condition 3 was 46.67±12.95 % (p<0.001). Using FORS, the percentage reduction between Condition 1 and Condition 2 was 24.25±23.33% (p=0.0029), between Condition 2 and Condition 3 was 23.61±19.45% (p<0.001), and between Condition 1 and Condition 3 was 43.39±18.70% (p<0.001). A notable difference in the findings between the two insoles was the presence of a significant edge effect associated with PA, indicating that the offloading was not entirely successful. No edge effect was detected with FORS. Conclusion: Our current analysis shows that pixelated insoles exhibit potential for supplemental offloading in surgical shoes. These devices could provide an alternative way for physicians to offload plantar wounds and expedite closure for patients that cannot tolerate a TCC or other restrictive devices.

The effect of calcaneus and metatarsal head offloading insoles on healthy subjects’ gait kinematics, kinetics, asymmetry, and the implications for plantar pressure management: A pilot study

“…To the authors knowledge, it is the first time to jointly measure gait kinematics and plantar pressure changes caused by offloading insoles which offload high-risk regions by removing insole material. The results demonstrate that the offloading insoles can decrease the high-risk region plantar pressure, which correlates with other studies [9,10], if the offloading aperture centre is collocated with the subjects' peak high plantar pressure point. But the offloading insoles reveal a negative effect on the kinematics including an increase in heel strike and toe-off velocity, which could cause plantar pressure increases, and an increase of walking asymmetry of width.…”

“…Specially designed insoles can be part of an effective DFU prevention strategy which includes maintaining mobility and physical activity as part of a holistic management package [7,8]. These include insoles which offload the high-risk region of the foot, reducing plantar pressure and therefore the risk of DFU [9,10]. Significantly higher peak forefoot pressures are observed in diabetic subjects, for example researchers report 608 kPa and 373 kPa in diabetics with severe and moderate neuropathic, compared to294 kPa and 323 kPa in the mild neuropathic and nonneuropathic diabetic groups (P < 0.0001), suggesting an important role in the etiology of the diabetic foot condition [11].…”

“…Although offloading insoles can effectively decrease pressure at high-risk regions, it is important to consider the pressure increase surrounding the offloading area. Penny et al [10] measured normal plantar pressure of healthy subjects wearing the PegAssist insole system (Darco International, US) and FORS-15 offloading insole (Saluber, Italy) using F-Scan in-shoe pressure measuring system (TekScan, US), and their results demonstrated that the pixelated insole can offload a forefoot wound by up to 40.1%. Penny et al [10] found the pressure increased around the offloading aperture edge was found but they did not investigate the pressure in detail.…”

“…Penny et al [10] measured normal plantar pressure of healthy subjects wearing the PegAssist insole system (Darco International, US) and FORS-15 offloading insole (Saluber, Italy) using F-Scan in-shoe pressure measuring system (TekScan, US), and their results demonstrated that the pixelated insole can offload a forefoot wound by up to 40.1%. Penny et al [10] found the pressure increased around the offloading aperture edge was found but they did not investigate the pressure in detail. When applying aperture below the high-risk region, the normal pressure at the region periphery will increase, which is known as "edge-effect" [13].…”

“…When applying aperture below the high-risk region, the normal pressure at the region periphery will increase, which is known as "edge-effect" [13]. Although the measurements were conducted on healthy subject, it showed the feasibility of protecting high risk region using offloading insoles [10]. Shaulian et al [14] tested a graded stiffness offloading insole on healthy subjects and the result showed that the insole could improve edge effect problems.…”