Wounds located on a horse’s lower (distal) limb can be extremely challenging to treat due to the small amount of “extra” soft tissue in the area (to suture, for example) and the propensity for excessive proud flesh to form, which prolongs rehabilitation. Over the years, veterinarians have tried multiple techniques to improve tissue healing in the lower limbs with limited success, but according to Canadian researchers extracorporeal shock wave therapy (ESWT) looks like a promising tool for treating these difficult wounds.

“ESWT is currently used in equine medicine to treat a wide variety of disorders such as bowed tendons and bucked shins,” said lead author Judith Koenig, DrVetMed, DVSc, from the Department of Clinical Sciences at the Ontario Veterinary College, in Guelph.

Despite being already a common tool, exactly how ESWT works remains a mystery.

“ESWT appears to be capable of altering the expression of growth factors such as transforming growth factor-β1 (TGF-β1), which plays a role in the production of proud flesh,” Koenig added. “If we could determine the role of ESWT in wound healing we would be able to develop treatment protocols and potentially reduce healing time and improve outcomes.”

To help build on previous research in this field, Koenig and colleagues performed ESWT on eight horses with either surgically created skin wounds or on normal intact skin. Researchers created five wounds in each foreleg in six horses; they treated one limb with ESWT while the other limb remained untreated. The other two horses had no wounds. The team subsequently collected biopsy samples from all sites and measured the levels of five different inflammation mediators (cytokines) believed to play a negative role in wound healing. These mediators included fibroblast growth factor-7, TGF-β1, insulinlike growth factor-1, platelet-derived growth factor-A, and vascular endothelial growth factor-A.

“The most impressive finding in this study was that a significant reduction in TGF-β1 was noted in the wounds that had been treated with ESWT compared to untreated wounds over the entire 35-day study period,” Koenig summarized.

No changes in any of the measured mediators occurred in intact skin.

“This study adds additional evidence that ESWT can modulate the expression of various mediators that play a role in wound healing such as TGF-β1,” Koenig concluded. “Additional studies examining a ‘profile’ of cytokine expression in various anatomic locations would be an interesting next study because considerable differences in healing characteristics exist at different sites in the horse.”

According to the study authors, veterinarians can treat wounds prone to developing proud flesh with ESWT weekly with 100 pulses/cm² of wound area at a medium energy setting, ideally with a unfocused or soft focused shock wave head.

The study, “Effect of unfocused extracorporeal shock wave therapy on growth factor gene expression in wounds and intact skin of horses,” was published in the February 2013 edition of the American Journal of Veterinary Research.