To the Editor,
We read with great interest the article authored by Eraydin and Avsar1 in the March/April 2018 issue of your journal on the effect of foot exercises on wound healing in type 2 diabetic patients with foot ulcer. We think that this study addresses an important aspect of nursing care for diabetic foot ulcers (DFUs). However, we wish to point out some limitations of the study.
The Diabetic Foot Ulcer Wagner classification system was used to target the eligible subjects. Although the relevance of this classification is well established in the assessment of DFU, it focuses exclusively on wound depth.2 The eligibility of participants was based on this criterion, with no consideration for the wound surface area, which is one of the primary outcomes used in this study to evaluate wound healing through repeated measurements over a 12-week interval. The significant variation (P < .05) between groups observed in the mean DFU area at baseline indicates a significant intergroup difference, for this variable, prior to the intervention. The average DFU area calculated in the control group at baseline is almost twice as large compared to the one calculated in the experimental group. Previous studies3,4 have emphasized the impact of wound size on the healing process, particularly on the initial response to treatment and the rate of healing. This significant baseline difference between groups on the wound surface area could explain the differences in ulcer healing measured at the 4th, 8th, and 12th weeks. With this limitation in mind, we cannot conclude on the relationship between exercises and ulcer healing. The favorable effects observed in the experimental group for this outcome should therefore be interpreted with caution. We believe that the authors should have considered using a foot ulcer classification system that includes wound surface area or adding a criterion that takes into account this variable to ensure that both groups were comparable after randomization.5 Because of the major impact of this limitation on the study validity, we believe the authors should have reconsidered the randomization process or at least addressed this flaw in the discussion.
Furthermore, the authors provide very little detail on the procedure used to measure the wound surface area and depth. It is well-known in the literature6,7 that the techniques used to measure wound size present important variations in terms of accuracy and consistency. A clear justification should have been provided on why the authors chose to use tracing rather than digital planimetry for wound measurement, since pros and cons have been identified for these 2 techniques.6 Due care should have been taken in addressing the validity and reliability of the instruments used to measure wound size. Besides, no mention is made of who performed the assessment or whether any related training was provided.
Finally, although no significant differences are reported between the characteristics of the control and experimental groups, the authors do not address the use of offloading devices among the participants. These devices are one of the most acknowledged and widespread recommendations for preventing and treating DFU and are commonly used in diabetic patients who previously have had foot ulcers.8,9 The use of offloading methods itself could have contributed to the healing of the ulcer and therefore interfere with the association between the foot exercises and the measured outcomes. As 70% of the patients included in the sample (42/60) had a history of DFU, the use of offloading methods should have been documented in the participants' characteristics and discussed as a confounding factor that can impact wound healing.
We believe this study emphasizes potential benefits but would need revision in its present form to be considered valid to evaluate the effect of incorporating foot exercises into the routine care of diabetic patients with a foot ulcer.
Sincerely,
Emilie Dufour, RN, MSN
Arnaud Duhoux, PhD
Montreal, Canada
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