But ulcer severity may be decreased
By Jordana Bieze Foster
In a Dutch randomized controlled trial of 171 high-risk diabetic patients, using plantar pressure measurements to confirm offloading below 200 kPa did not result in lower rates of ulcer recurrence over 18 months compared to standard custom shoes.
The Dutch research team, from the University of Amsterdam in the Netherlands, is only the latest group to be frustrated by the ongoing efforts to link therapeutic footwear to positive diabetic foot ulcer outcomes. However, the recent RCT findings do suggest that footwear customized using plantar pressure data may result in fewer complicated ulcers than standard custom footwear.
“We found no clinical benefit of improving offloading with custom footwear by approximately twenty percent, but it does seem to decrease ulcer severity,” said Sicco Bus, PhD, senior investigator and head of the Human Performance Laboratory at the university’s Department of Rehabilitation, who presented the results at the i-FAB congress. The findings were subsequently e-published on April 30 by Diabetes Medicine.
All patients in the trial had diabetic peripheral neuropathy and a history of a healed ulcer within the 18 months prior to enrollment. Eighty five patients were randomized to the test intervention, in which footwear customization was specifically designed to offload any areas where plantar pressure exceeded 200 kPa during a baseline measurement. The remaining 86 patients received standard therapeutic footwear, which in the Netherlands is still custom-made but not based on pressure data.
After 18 months, ulcer recurrence had been documented in 39% of patients in the intervention group and 44% of those in the control group, a difference that was not statistically significant. However, complicated ulcers developed in six patients in the control group but none in the intervention group, a difference that was statistically significant.
Multiple studies have documented the ability of therapeutic footwear to significantly reduce plantar pressures, including a July 2011 study from the same Dutch group that was published in Diabetes Care (see “Pressure-based diabetic footwear modifications reduce plantar loads”). But researchers have been stymied in their efforts to demonstrate that those pressure reductions lead to a reduced risk of ulceration. As Bus and colleagues detailed in a 2008 review article in Diabetes Metabolism Research and Reviews, several previous studies have found no effect of footwear on ulceration rates but have been criticized for methodological shortcomings; two oft-cited RCTs in particular did not measure plantar pressures.
The threshold level of 200 kPa used for pressure reduction by the Dutch researchers is based on the findings of a Swedish study published in Diabetes Medicine in 2009 that did not track ulceration outcomes. It is possible that greater levels of offloading may be required to significantly affect ulceration recurrence rates in high-risk patients, Bus said.
Differences between patient groups in terms of adherence and activity levels also may have influenced the results. Patients in the intervention group had lower levels of at-home compliance and higher levels of activity, especially while at home, than those in the control group.
“Future studies should focus on more comprehensive analyses in which footwear offloading is one integral part,” Bus said.
Waaijman R, Arts ML, Haspels R, et al. Pressure-reduction and preservation in custom-made footwear of patients with diabetes and a history of plantar ulceration. Diabet Med 2012 Apr 30 [Epub ahead of print]
Bus SA, Haspels R, Busch-Westbroek TE. Evaluation and optimization of therapeutic footwear for neuropathic diabetic foot patients using in-shoe pressure analysis. Diabetes Care 2011;34(7):1595-1600.
Bus SA, Valk GD, van Deursen RW, et al. The effectiveness of footwear and offloading interventions to prevent and heal foot ulcers and reduce plantar pressure in diabetes: a systematic review. Diabetes Metab Res Rev 2008;24(Suppl 1):S162-S180.
Owings TM, Apelqvist J, Stenstrom A, et al. Plantar pressures in diabetic patients with foot ulcers which have remained healed. Diabet Med 2009;26(11):1141-1146.