Effects of Felted Foam on Plantar Pressures in the Treatment of Neuropathic Diabetic Foot Ulcers

It is generally accepted that (besides infection control and revascularization, when necessary) pressure relief is the most important measure in the treatment of diabetic foot ulcers. The use of felted foam dressings is a promising but not yet well-standardized technique for the treatment of neuropathic diabetic foot ulcers and may have some advantage over total contact casting (1,2,3,4). We aimed to assess the effects of felted foam on plantar pressure reduction during the therapy of neuropathic foot ulcers and to define the optimal time course for renewal of the felted foam according to the plantar pressure. Using felted foam dressings, plantar pressure reduction and wound healing was determined in 9 type 1 and 19 type 2 diabetic patients (15 men and 13 women, aged 61.0 ± 13.6 years) with neuropathic foot ulcers up to a Wagner grade 2. Physical examination included the inspection of the foot and the palpation of the peripheral pulses. Peripheral diabetic neuropathy was evaluated by measuring the vibration perception threshold with the calibrated Rydell-Seiffer tuning fork. Patients with neuroischemic or ischemic diabetic foot ulcers were excluded from the study.

The felted foam (i.e., a combination of 0.635-cm thick rubber foam with a 0.158-cm layer of felt adhered, fixed by rubber glue) was measured exactly to fit the plantar aspect of the foot. Using a scalpel, an aperture was cut from the felted foam at the exact location of the ulcer, allowing clear visualization of the ulcer. Gauze was then wrapped around the foot and the felted foam pad to secure the pad. The wound was covered with a saline-soaked sponge, which was cut according to the size of the ulcer and changed every day. The felted foam was kept dry at all times. A compress was placed over the wet sponge and fixed with Peha-haft. The felted foam dressing was exclusively used for plantar ulcerations. Foot pressure was measured using the FastScan system, as described elsewhere (5,6). Recordings of the plantar pressures were first done without any dressings and then with the attached felted foam dressing every day from the beginning of the study (day 0) to day 4. The plantar pressures were measured by selecting the area of interest under the foot, within an area of 25 × 25 mm² in the center of the ulceration. A mean of all pressures measured in each walk (three steps per walk and two walks per test) was calculated for each patient. Differences between the plantar pressures at each day were compared by analysis of variance; P < 0.05 was considered significant.

The mean ulcer area in the patients studied was 159.9 ± 102.6 mm². By the application of the felted foam dressing, the mean peak plantar pressures at the ulceration site was significantly reduced, from 297.3 ± 120.0 kPa before to 90.3 ± 38.2 kPa immediately after the application (P < 0.0001). In the following period, over at least 4 days with the mounted felted foam dressing, the plantar load in the area of interest significantly increased, from 93.6 ± 39.6 kPa the day after the application to 222.6 ± 97.8 kPa at day 4 (P < 0.0001, Fig. 1). On days 2 and 3, the plantar pressures at the ulceration site varied, from 113.8 ± 47.6 to 137.5 ± 63.9 kPa, without significant day-to-day changes. However, from day 3 to day 4 there was a clear-cut increase of the plantar pressure in the area of interest, from 137.5 ± 63.9 to 222.6 ± 97.8 kPa (P = 0.0001).

Because the relief of the plantar load at the ulceration site is one of the most important factors in the outcome of neuropathic foot ulcerations, the application of the felted foam appears to be useful to reduce the peak plantar pressures at the site of ulceration. We have shown that the pressure relief from attaching the felted foam dressing at the ulceration site lasts up to 3 days after its application. Taking into account the distinct increase in plantar pressure on the fourth day, we recommend changing the felted foam each 3rd to 4th day. Interestingly, we did not observe the development of callosity at the ulceration site, which underlines the efficacy of the felted foam technique for pressure relief. In contrast to other methods for pressure relief, such as total contact cast, felted foam also enables daily dressing changes and can be used in patients with smaller infections (7,8).

We conclude that in diabetic patients with neuropathic foot ulcerations, the felted foam technique effectively reduces the pressure load at the ulceration site. This pressure relief persists for 3 days, and we therefore recommend renewing the felted foam after each 3–4 days of treatment.