The efficacy of a removable vacuum-cushioned cast replacement system in reducing plantar forefoot pressures in diabetic patients

Abstract

Background The purpose of this study was to determine the plantar forefoot offloading efficacy of a new prefabricated vacuum-cushioned cast replacement system designed for foot ulcer treatment in neuropathic diabetic patients. Methods Fifteen diabetic subjects with peripheral neuropathy underwent in-shoe plantar pressure assessment while walking in five different footwear types: a standard vacuum-cushioned system with instantly moldable vacuum cushion and roller outsole, two modified vacuum-cushioned systems, one with flat surface vacuum cushion and one with flat outsole, a forefoot offloading shoe, and a control shoe. Regional peak pressures, pressure–time integrals, and inter-regional load transfers were calculated to determine the mechanical action of the footwear. Perceived walking comfort was tested using a 10-point visual analogue scale. Findings Forefoot peak pressures and pressure–time integrals were significantly lower (by 41–56%) in the vacuum-cushioned system compared to control. Compared to the forefoot offloading shoe, the vacuum-cushioned system showed significantly higher metatarsal head peak pressures, similar metatarsal head pressure–time integrals, and significantly lower hallux peak pressures and pressure–time integrals. A major transfer of forefoot load to the midfoot explained the offloading efficacy of the vacuum-cushioned system. Few significant differences were present between the modified and standard vacuum-cushioned systems. Perceived walking comfort was significantly higher in the vacuum-cushioned system (score 6.6) than in the forefoot offloading shoe (score 3.4). Interpretation The results showed that the vacuum-cushioned cast replacement system was effective in offloading the plantar forefoot of diabetic patients at risk for ulceration, although the contribution of the instantly moldable vacuum cushion and roller outsole were relatively small. The combined peak pressure, pressure–time integral and walking comfort results indicate that the vacuum-cushioned system may be a useful alternative for the forefoot offloading shoe in offloading the plantar diabetic forefoot.