Ex vivo penetration of low-level laser light through equine skin and flexor tendons.

The research investigates the penetration efficiency of low-level laser light through the skin of horses and its absorption by their flexor tendons. It finds the effectiveness of such energy is heavily influenced by factors like skin and hair color, thickness, preparation and the applied wavelength.

Methodology

• The researchers used therapeutic lasers with 800 and 970 nm wavelength capabilities.
• The study sample included skin and flexor tendons (superficial [SDFT] and deep [DDFT]) from 19 equine cadavers.
• The percentage of energy penetration through skin both before and after hair removal, through shaved skin over tendons, and through skin, SDFTs, and DDFTs in their anatomically correct positions was determined.
• The influence of hair and skin color, preparation methods, thickness, and applied wavelength on energy penetration were evaluated.

Findings

• Energy penetration was found to be highest for light-colored hair and lowest for dark-colored hair.
• Energy penetration improved when the skin was clipped or shaved.
• The 800-nm wavelength had the greatest penetration through light-colored skin, whereas the 970-nm wavelength was more successful with medium- and dark-colored skin.
• Energy penetration decreased as skin thickness increased. In regards to the absorption by tendons, only 1% – 20% and 0.1% – 4% of energy was absorbed by SDFTs and DDFTs respectively. This amount varied based on skin color, thickness, and the applied wavelength.

Conclusions and Relevance

• Most of the laser energy directed through equine skin was either absorbed or scattered by the skin rather than being absorbed by the tendons.
• In order to efficiently deliver energy doses to equine SDFTs and DDFTs—doses known to impact cells positively in a laboratory setting— considerations about the horse’s skin color, skin thickness, preparation process, and wavelength must be factored into the equation.