Background: Diabetic foot ulcers are a major clinical problem. The first line of treatment according to international guidelines consists of offloading these ulcers to reduce pressure with a non-removable knee-high device rather than a removable knee-high or ankle-high device, although the latter are more easy to use. However, the superiority of knee-high devices in reducing plantar pressure has not been proven directly within the same patients. The aim of this study was to assess the efficacy of different offloading devices with exact similar plantar characteristics in a within-subject design.

Methods: In-device plantar pressures were measured during walking in three offloading devices (non-removable knee high (TCC), removable knee high (BTCC), removable below the ankle (cast shoe)) in eleven participants with a diabetic foot ulcer (history). Dynamic in-device peak pressure and force-time integral were calculated. Perceived walking comfort was measured using a visual analogue scale (VAS).

Results: Peak plantar pressures were significantly lower at the total foot, metatarsal heads (MTH), hallux, lesser toes and (previous) ulcer location in TCC (21.3-68.8%) and BTCC (17.9-46.5%) compared with cast shoe. Peak plantar pressure was significantly lower at midfoot, lesser toes and hallux in TCC (34.6-47.7%) compared with BTCC. Force-time integral was significantly lower at the total foot, midfoot, MTH2-5, hallux and lesser toes in TCC compared with BTCC (11.9-43.6%) and cast shoe (19.4-57.1%). Force-time integral was significantly lower at MTH2-5, hallux, lesser toes and (previous) ulcer location in BTCC (23.7-34.3%) compared with cast shoe. Perceived walking comfort was significantly lower in TCC (VAS 5.7) compared with BTCC (VAS 7.0) and cast shoe (VAS 6.7). All p-values were <0.05.

Conclusions: Knee-high devices are more effective in offloading than ankle-high devices, pointing at considerable offloading by the shaft of these devices. Within knee-high devices, a non-removable device reduces walking comfort.