Custom-made footwear for diabetes patients must offload pressure if it is to be effective at preventing ulceration, Dutch researchers emphasize.
Effective offloading, defined as an in-shoe pressure of below 200 kPa at site of deformity, was achieved in 61% of 336 feet in a group of 171 patients with diabetic neuropathy attending 10 rehabilitation centers. Just 24% of feet achieved this level of pressure offloading across the entire foot.
In addition, only 62% of 147 previous ulcer locations were successfully offloaded, reports the team from the University of Amsterdam.
Offloading was successful for patients with midfoot deformity, with an average in-shoe pressure of 140-187 kPa versus 112 kPa in nondeformed feet. But for feet with forefoot deformity, the average peak in-shoe pressure was 211-308 kPa compared with 191-222 kPa in healthy feet.
"These outcomes suggest that improvement in footwear design is required and should focus most on those deformities that affect pressure in the metatarsal region," write M Arts et al in Diabetic Medicine.
Highlighting the lack of evidence-based recommendations for prescription and design of custom-made footwear, they add: "These outcomes emphasize the need for such guidelines, as well as quantitative evaluation approaches, to better identify increased pressure locations in individual feet and to assure sufficient offloading in high-risk patients."
The researchers acknowledge the difficulty in predicting the success of footwear offloading, noting that multivariate analysis showed only small but significant relationships between success and treatment center (odds ratio [OR]=0.87) and barefoot peak pressure (OR=0.81 per 100 kPa), after adjusting for vibration perception, body mass index, type of deformity, walking speed, and type of footwear.
Arts et al therefore recommend the use of in-shoe plantar pressure measurements to guide footwear design and reduce the variability in outcome.
Nevertheless, they concede: "Whether the use of these methods prevents ulceration in the diabetic foot remains to be investigated and is a focus of interest in our own [DIAbetic Foot Orthopedic Shoe] trial."
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