For patients with first ray amputations resulting from diabetic complications, ulcerations caused by limited joint mobility and gait abnormalities frequently cause higher levels of amputation. However, a total contact insole can significantly reduce plantar pressures and mitigate the risk for subsequent amputation, according to study results published in the journal Foot.

Insole testing

“Many specially designed total contact insoles are currently used to reduce the high plantar pressure in diabetic patients,” the authors wrote in the study. “However, the design of total contact insoles is mostly empirical and little scientific evidence is available to provide a guideline for persons who prescribe such insoles.”

To investigate this further, the researchers evaluated how different insoles affect peak pressure distribution in people with partial first ray amputations. The study included 20 patients with diabetes with a mean age of 60 years who had partial first ray amputations of one foot. They were admitted to the study 3 months after the amputation.

“The purpose of this study was to investigate the efficacy of pressure reduction and redistribution of a conforming total contact insole with different material combinations as compared with those of a regular flat insole used as a baseline condition in diabetic patients with partial ray amputations,” the authors wrote.

Plantar pressure assessment was conducted using Matscan in three conditions: using a standard diabetic shoe without an insole, using the same shoe and a recommended custom-made total contact insole and using the same shoe with regular flat insoles. Both insoles were fabricated with the same material to avoid any variance between materials.

Readings were taken in static conditions, while the patients were standing, and dynamic conditions, as the patients took one step on the Matscan; and conditions were repeated five times. Plantar pressures were determined at the five metatarsal areas, mid-foot area and medial and lateral heel areas.

“Our purpose was to design a personalized insole that would solely conform on the patient’s foot, redistributing the pressure,” the authors wrote. “We designed the insole to adequately conform to the irregularities of the foot, to create again a fully contacted area on the ground, creating a larger surface area receiving the force therefore diminishing localized pressures.”

The patients were then asked to wear the total contact insoles for 6 months and were followed up monthly for a clinical foot assessment by a surgeon.

Pressure reduction

“Our results show that patients with partial first ray amputations tend to have a supinated foot, with pressures shifting to the lateral side of the foot,” the authors wrote. “After surgery, patients lose the pivoting effect of the hallux and first toe, with diminished support area, shifting the weight onto the mid-metatarsal area and mid-foot area that are physically not designed to withstand increased pressures with the defective gait patterns likely to be present.”

But the researchers found that these pressures were reduced when patients walked with the total contact insole.

“We found that an insole could significantly affect the plantar pressure distribution by reducing local peak pressures as compared with the shoe-only condition,” the authors wrote. “Following the application of the total contact insole, the small change that occurred in pressure relative to the other areas gave us the impression that these small changes came from the pressure relieving material of the insole and, in fact, there was a more equal distribution of pressures in all areas.”

Additionally, the researchers found that the risk of subsequent ulceration was mitigated.

“Over the 6 months follow-up, none of the patients developed any foot hazards that included ulceration or recurrent amputations,” the authors wrote. — by Megan Gilbride

For more information:
El-Hilaly R. Foot. 2012. doi: 10.1016/j.foot.2012.10.002.

Disclosure: The authors have no relevant financial disclosures.

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