Effects of extracorporeal shock wave therapy (ESWT) for the healing of distal limb wounds in horses
This study is an investigation of the effects of ESWT on the healing of distal limb wounds in horses. The objective of the study is to verify whether shock wave treated wounds heal differently than wounds receiving only a bandage. We hypothesized that ESWT would accelerate healing time, alter the inflammatory response, and reduce the formation ofexuberant granulation tissue of equine distal limb wounds. Five 6.25cm2 wounds were created on both 3rd metacarpi of six horses. Forelimbs were randomly assigned to treatment (ESWT) or control (sham therapy) groups. An electro-hydraulic shockwave device was used to apply 625 pulses per wound of the treatment group, while the control wounds received sham therapy by applying the ESWT probe over the wounds without emitting the waves. Clinical evaluation of the wounds was performed weekly and the general wound appearance was scored and classified as clinically normal or clinically inflamed. The exuberant granulation tissue was subjectively scored based on the amount of protruding granulation tissue. Standardized digital photographs were taken to determine area of neoepithelialization and absolute wound area. One biopsy was taken from one randomly selected wound of each group every week for 6 weeks. Each wound was biopsied once during the trial. Biopsy samples were used to evaluate epithelialization, neovascularization, inflammation and fibroplasia via histological examination. Immunohistochemistry was performed to assess myofibroblast differentiation and organization via staining of a smooth muscle actin. Results of the clinical evaluation of the wounds showed that control wounds were 1.9 times more likely to be classified as clinically inflamed and had significantly higher scores for exuberant granulation tissue than the ESWT wounds. Measurements obtained from digital pictures revealed that ESWT affected neither absolute wound area nor area of neoepithelialization at any time during the study. No significant statistical difference was found for any of the histological or immunohistochemical parameters between the study groups. In conclusion, defocused ESWT did not accelerate the healing of equine distal limb wounds, however shock wave treated wounds had less inflamed appearance and reduced formation of exuberant granulation tissue.