Transitioning To Advanced Therapies For DFUs: Are Four Weeks And 50 Percent The Magic Numbers?

Chanel Houston, DPM, Samirah Mohammed, DPM, and Peter A. Blume, DPM, FACFAS

   Various authors have reported on treatment options for diabetic foot ulcers. These modalities include advanced moist wound therapy; periodic wound debridement to remove bacterial biofilm and hyperkeratosis; bioengineered tissue or skin substitutes; growth factors; electric stimulation; and negative pressure wound therapy (NPWT).6-14 Many factors can influence the outcome of treatment. These factors include the nature of the ulcer, the presence of infection, patient adherence, appropriate offloading and the mechanisms of action of the therapy. Even with all appropriate measures, some wounds still fail to heal.

What The Literature Reveals About The Prognostic Value Of The Percentage Of Wound Area Reduction At Four Weeks

Due to the complexity of diabetic foot ulcers and the difficulty it takes to heal them, some studies have reported that an area reduction greater than or equal to 50 percent at four weeks of treatment is a good prognostic indicator about an ulcer’s ability to heal at 12 or 20 weeks.

   In particular, Sheehan and his colleagues published a study describing that diabetic foot wounds that do not heal by at least 50 percent in the first four weeks of treatment have less than a 10 percent chance of closing by week 12.15 They studied the healing rate of 203 patients with chronic diabetic foot ulcers receiving standard wound care therapies. They also looked at the healing ability of ulcers as a direct correlation with their percent area of reduction.

   This large prospective study from 2003 has been widely cited in the recent literature because it revealed that patients who did not reduce their wound area by approximately 50 percent at the four-week average had a very low probability of healing. The study authors further concluded that physicians need to re-evaluate diabetic foot wounds on a regular basis so they can redirect treatment if a wound is not healing as expected.

   Boulton and colleagues also noted that the failure to reduce the size of an ulcer after four weeks, even with appropriate debridement and pressure reduction, should prompt consideration of adjunctive therapy. They noted this in 2004 when they developed a clinical practice article for neuropathic diabetic foot ulcers, which was published in The New England Journal of Medicine.16 The authors reviewed literature about the general management of diabetic foot ulcers and treatment options such as infection management, offloading, routine debridement, glycemic control, and the use of growth factors and tissue-engineered skin. Boulton and co-authors recommend the use of adjunctive treatment options such as tissue-engineered skin when a patient has not had a 50 percent decrease in wound size at four weeks.

   Snyder and colleagues did a post-hoc analysis about percent area reduction and an ulcer’s ability to heal at four weeks in 2010.17 The study looked at two previously conducted studies consisting of patients with type 1 diabetes and patients with type 2 diabetes. Both groups (study A and study B) received debridement, a saline-moistened gauze dressing covered with dry gauze (wet to dry) and adhesive fixation sheets. Both groups also utilized therapeutic footwear and received offloading instructions.

   For study A, 133 patients had a pre-trial standard of care treatment for two weeks and had a full thickness DFU on the heel or plantar foot greater than 1 cm2. The ulcer was essentially the same size during the two-week pre-trial period. There were 117 patients in study B but they did not receive standard of care treatment prior to the study.

   In study A, 57 percent (39 out of 69) of patients with a diabetic foot ulcer had a percent area reduction greater than or equal to 50 percent by week four. Fifty-two percent (38 out of 73) of patients with diabetic foot ulcers in study B healed by 12 weeks. Five percent of diabetic foot ulcers in study A and 2 percent in study B healed at 12 weeks with a percent area reduction of less than 50 percent at four weeks.

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