Offloading Often Not Adequate in Custom-Made Footwear of Patients With Diabetes and Foot Deformity

Patients with diabetic neuropathy and foot deformity who wore custom-made footwear showed the highest offloading success rates at known high-risk locations, such as previous ulcer sites and in those with Charcot foot. However, the lowest success rates were found in forefoot deformities, according to a recently published study.

“In the Netherlands and also in our own clinic, the Academic Medical Center in Amsterdam, we see a large population of diabetic patients with neuropathy, foot deformity and foot ulcers. Prevention of ulcers is important because these ulcers can lead to infection and amputation of the foot. Offloading at-risk foot regions with custom-made therapeutic footwear should lead to less recurrent ulcers, but there is yet not much evidence for successful ulcer prevention with such shoes, which are assumed to reduce mechanical pressure under the foot,” Mark L.J. Arts, MSc, of the department of rehabilitation at the Academic Medical Center in
Amsterdam, told O&P Business News. “We therefore performed this study to investigate what the offloading efficacy of therapeutic footwear actually is and to eventually show possibilities for improvement. To do so, we used a measurement system with flexible insoles with which we could objectively assess pressure under the foot inside the shoes.”

Results of offloading

Researchers measured plantar pressures in 171 patients with diabetic neuropathy with foot deformity and a recently healed plantar foot ulcer. Patients walked barefoot and inside new custom-made footwear. Researchers compared in-shoe pressures of non-deformed feet at the previous ulcer location and at locations of highest barefoot pressure attributable to the deformity. When in-shoe peak pressure was less than 200 kPa in the previous ulcer location and locations of highest barefoot pressure, the footwear was considered effective in offloading.

In feet with forefoot deformity, mean in-shoe peak pressures ranged between 211 kPa and 308 kPa vs. 191 kPa to 222 kPa in non-deformed feet. Mean in-shoe peak pressures ranged from 140 kPa to 187 kPa in feet with midfoot deformity vs. 112 kPa in non-deformed feet. According to study results, offloading was effective in 61% of all feet with deformity, 81% of feet with midfoot deformity, 44% of feet with forefoot deformity and 62% of feet with previous ulcer locations. Researchers found a large inter-subject variability in measured in-shoe plantar pressure.

“The results surprisingly showed that feet with severe deformity, like Charcot feet and feet with amputations, were offloaded better than feet with less severe deformity, like claw toes or hallux valgus. This was against our expectations because severely deformed feet, for example Charcot feet or feet with forefoot amputation, showed extremely high barefoot pressures,” Arts said. “We concluded that offloading effectiveness of individual footwear is insufficient in many individual cases, which should be evaluated and improved before final delivery.”

DIAFOS trial

This study was part of the DIAbetic Foot Orthopedic Shoe (DIAFOS) trial, a randomized controlled trial conducted to demonstrate adequate offloading leads to less recurrent foot ulcers. Performed in cooperation with 10 diabetic foot clinics in the Netherlands, the researchers compared two groups of diabetic patients who have neuropathy and had a previous foot ulcer. Both groups received custom-made therapeutic shoes before assessment.

Customized footwear was optimized, guided by plantar pressure assessment and monitored in the experimental group, while researchers only monitored pressure in the shoes in the control group. The researchers evaluated the number of recurrent ulcers in both groups for a follow-up of 18 months, with assessments every 3 months. The results of this trial are now being analyzed.

In previous studies, the researchers have shown that footwear offloading properties can be successfully improved when modifications to the footwear are guided by plantar pressure assessment. They also investigated the role of other important factors in ulcer prevention and footwear biomechanics, such as footwear adherence and perceived usability of footwear.

“We found that feet are often not adequately offloaded. That means that identification of high pressure location is essential, because these locations are at highest risk for ulcer development,” Arts said. “There are several objective measurement systems available for measuring mechanical pressure under the foot. Such systems are useful to identify foot regions with high pressure. When identified, these regions can be targeted for further offloading by modifying the footwear.” — by Casey Murphy

For more information:

Arts MLJ. Diabet Med. 2012;10.1111/j.1464-5491.2012.03770.x.

Disclosure: Arts has no relevant financial disclosures. The DIAFOS trial was supported by project grants from the Dutch Diabetes Research Foundation, the Dutch Branch Organization of Shoe Technicians and the Dutch Organization for Health Research and Development.

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