Abstract
Diabetes mellitus (DM) results in several complications, and of those, diabetic foot ulcers (DFUs) are the most severe and frequently lead to lower-limb amputation and a subsequent reduction in quality of life (QOL). The management of DFUs involves a multidisciplinary team of healthcare professionals, of which podiatrists play a key role. Podiatric management may include wound debridement, wound dressing, antimicrobial management when necessary, offloading mechanisms for pressure redistributions and overall diabetic foot care, and footwear education. In most cases, DFUs take prolonged periods of time to heal due to complex pathophysiological mechanisms, often advancing into chronic wounds which can take several months and even years to heal. Due to the challenging nature of managing and treating DFUs, advanced treatment modalities are being researched, and among those, photobiomodulation (PBM) has been suggested. PBM is the non-invasive application of low-powered focused light, typically in the red and near infrared (NIR) electromagnetic spectrum, to stimulate various biological systems. PBM is used to encourage tissue repair, reduce inflammation, and induce analgesia.
Studies conducted on photobiomodulation therapy (PBMT) and wound management have shown that PBMT improves the healing rate of DFUs in conjunction with conventional treatment modalities. Home-use PBM devices are being marketed for their therapeutic purposes. Patients benefit from these devices because they reduce the need for frequent clinical visits for treatment. During PBMT, the light (photon) energy must be absorbed by the skin and reach subcutaneous tissue. Absorption of this photon energy may be affected by skin tone, and treatment protocols may need to be adjusted accordingly. It has been suggested that PBMT takes skin tone into consideration, however there are limited studies on the use of PBMT on the management of DFUs in darker skin tones.
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This study aimed to evaluate the effectiveness of home-use PBMT as an adjunct to standard care for the treatment of lower limb ulcers in diabetic patients with Fitzpatrick skin types IV (moderate brown), V (dark brown) and VI (deeply pigmented dark brown to black). In order to achieve this, this study made use of a double-blind, randomised, placebo-controlled study design. Adult diabetic patients with Fitzpatrick skin types IV, V, and VI presenting with chronic foot ulcers graded <IIIA according to the University of Texas Wound Classification System (UTWCS) of at least 2 cm2 located in the ankle area, or below, that had persisted for a minimum of 4 weeks were recruited from five local clinics and hospitals during the period 2021-2023. This study included up to 9 clinic visits: a screening visit, baseline visit (which was combined with the screening visit), and 7 follow-up visits at 2, 4, 6, 8, 10, and 12 weeks, and 3 months (12 weeks) after the last visit/wound closure.
Consenting participants randomly selected either an active or sham home-use PBM device (B-Cure laser pro) to self-treat the wound margins, wound bed, inguinal and popliteal lymph nodes, and arteries (dorsalis, medial, lateral, and plantar) supplying the foot at home with every dressing change. Wound dressing replacement took place every 1-2 days (by participants and/or caregivers), not less than five times a week, and included cleansing the wound with saline and sterile gauze. The active PBM device emitted laser light in the NIR range (808 nm) over an area of 1 x 4.5 cm2 with a power output of 250 mW (55.55 mW/cm2), and an energy dose (fluence) of 1 J/cm2. The treatment dose and number of applications per treatment was dependant on the wound size. Wounds were assessed and measured and treated with standard podiatric care at the baseline visit and every 2 weeks up to 3 months or wound closure, whichever came first.
Ulcer evaluations included digital photography and thermal imaging of the wounds to analyse the healing process and temperature changes in the wound. A life quality questionnaire using the Diabetic Foot Ulcer Scale - Short Form (DFS-SF), and subjective satisfaction was carried out at the screening / baseline visit (visit 1) and on
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visits 4 (6 weeks), 7 (12 weeks), and 8 (3 months post primary endpoint, respectively). To evaluate changes in nerve conduction, the monofilament test was conducted at the screening / baseline visit (visit 1), and follow-up visits 3 (at 4 weeks), 5 (at 8 weeks), 7 (at 12 weeks), and 8 (3 months after the last treatment).
Due to a low participation rate, this study was only conducted on five participants and is reported on as a case series. After the initial screening visit, five participants (skin types V and VI) with five diabetic ulcers located on the ankle area and below voluntarily consented and participated in the study. Participants randomly picked a home-use PBM device which was either a sham-PBM (control) or an active-PBM (experimental group) medical device. The control group had three participants and the experimental group had two participants. The participants in this study had ulcers graded IIA and IIB according to the UTWCS.
Changes in wound area and parameters were observed in both groups over the 12-week period. None of the three wounds in the control group reached full closure by week 12, however significant closure was noted. One wound in the experimental group reached full closure by week 8 (skin tone V), while the other wound had not fully closed by week 12 (skin tone VI) however, significant wound closure was noted. Lower limb sensory sensations were tested using the 10 g monofilament test; at the initial visit all participants could not detect all the 10 points for the 10 g monofilament test, and thus were classified as having peripheral neuropathy. At the primary endpoint of the study (12 weeks), all 3 control participants could detect the 10 g monofilament, and only 1 participant in the experiment group could perceive the 10 g monofilament test. The DFS-SF scores were calculated, and the participants showed improvement in QOL. No adverse effects (AEs) were reported by participants, and overall, all participants were satisfied with the treatments.
The study findings suggest that when home-use PBM and podiatric conservative wound management are combined, DFU reduction rate is improved, and more
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importantly so is the QOL. The treatment protocol used in this study using a wavelength of 808 nm and a power output of 250 mW appeared to be safe for use in darker skin tones. Home-use PBM did not have any adverse effect on darker skin tones, and DFU healing rate was faster. More clinical trials of increased magnitudes must be conducted on the effect of PBM on DFUs, particularly on darker skin tones.