Comparison of the Effect of High-Intensity Laser Therapy (HILT) on Skin Surface Temperature and Vein Diameter in Pigmented and Non-Pigmented Skin in Healthy Racehorses.

Paulina Zielińska,Krzysztof Dudek,Weronika Hildebrand,Kevin Howell,Maria Godlewska,Maria Soroko

doi:10.3390/ani11071965

Abstract

Simple SummaryHigh-intensity laser therapy (HILT) is used in the treatment of horses, but little is known about the differences in the impact of HILT performed on pigmented and non-pigmented skin. The aim of this study was to assess differences in the influence of HILT on skin surface temperature and vein diameter in a group of healthy racehorses with pigmented and non-pigmented skin in the treatment area. The hypothesis was that HILT would cause a greater increase in skin surface temperature and vein diameter in horses with pigmented skin compared to non-pigmented skin. Ten Thoroughbreds with pigmented skin and ten Thoroughbreds with non-pigmented skin in the treatment area received HILT. Changes in the vein diameter and skin surface temperature of the irradiated area were measured before and after HILT. The HILT treatment caused an increase in the pigmented skin surface temperature and a decrease in the non-pigmented skin surface temperature, while the vein diameter increased in both groups. In conclusion, melanin content in the epidermis plays an important role in light energy absorption and photothermal effects. Determining the physiological and clinical effects of HILT performed on pigmented and non-pigmented skin will help clinicians choose appropriate HILT parameters.The aim of the study was to assess differences in the influence of high-intensity laser therapy (HILT) on the skin surface temperature and vein diameter of the lateral fetlock joint region in a group of racehorses with pigmented and non-pigmented skin in the treatment area. Twenty Thoroughbreds were divided into two equal groups: pigmented and non-pigmented skin groups. Each horse received the same HILT treatment. Just before and immediately after HILT, thermographic examination was performed to measure the skin surface temperature and ultrasonographic examination assessed the lateral digital palmar vein diameter. After HILT, the pigmented skin surface temperature increased, while the non-pigmented skin surface temperature decreased, and the difference between both groups was significant (p < 0.001). The vein diameter increased after HILT in horses with pigmented and non-pigmented skin, but the difference between both groups was not significant (p = 0.14). In conclusion, melanin content in the epidermis plays an important role in light energy absorption and photothermal effects. The vein diameter changes after HILT application indicated that the increase in vessel diameter may partly depend on photothermal mechanisms occurring in irradiated tissue. Further research is necessary to describe the physiological and clinical effects of HILT performed on pigmented and non-pigmented skin.

Highlights

Light amplification by stimulated emission of radiation (LASER) describes coherent beams of single wavelengths in the ultraviolet–visible to infrared spectrum that can be emitted in a continuous wave or pulsed mode [1]
No statistically significant differences were found between group A and group B in the skin surface temperature of the lateral aspect of fetlock joint and diameter of the lateral palmar digital vein before high-intensity laser therapy (HILT) application
In our previous study on racing Thoroughbreds, we found a significant increase in temperature of the dorsal skin surface overlying the tarsal joint after HILT application, but the study did not control for skin pigmentation in the treatment area [28]

Summary

Introduction

Light amplification by stimulated emission of radiation (LASER) describes coherent beams of single wavelengths in the ultraviolet–visible to infrared spectrum that can be emitted in a continuous wave or pulsed mode [1]. Laser therapy with class IIIb lasers with an average power not exceeding 500 mW (classified by the Center for Devices and Radiological Health (CDRH)) is called low-level laser therapy (LLLT). Therapeutic laser devices with a much higher power (classified by CDRH as class IV lasers) are used in high-intensity laser therapy (HILT). HILT is successfully used in the rehabilitation of many orthopedic injuries and disorders [4,5,6]. This relatively novel treatment has been recently introduced in equine veterinary medicine. A few studies have evaluated the impact of HILT in the treatment of orthopaedic disorders in horses and are mainly focused on the management of tendon injuries. Promising results have been presented in our previous randomized controlled non-blind study, which focused on 26 horses with 29 cases of superficial digital flexor tendon (SDFT), deep digital flexor tendon (DDFT) and suspensory ligament (SL)

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