Hyaluronic Acid-Based Biomaterial to Enhance Leg Wound Healing (AAEP 2010)

Managing equine wounds--particularly on the legs-- is often costly both in time and resources. Linda Dahlgren, DVM, PhD, Dipl. AVCS, assistant professor of large animal surgery at the Virginia-Maryland Regional College of Veterinary Medicine, spoke at the 2010 American Association of Equine Practitioners Convention, held Dec. 4-8 in Baltimore, Md., on the use of a hyaluronic acid-based biomaterial (CMHA) in several application methods to facilitate wound healing.

In her study Dahlgren and colleagues examined the use of the CMHA biomaterial to see if it could accelerate wound healing and decrease scar tissue formation in equine lower limb wounds. The investigators created full-thickness skin wounds on the front of all four cannon bones in eight horses. One randomized leg on each horse served as a control with no CMHA treatment, and then each of the other three limbs on each horse underwent one of three other treatments: a) CMHA gel applied once; b) CMHA gel applied multiple times at each bandage change; or c) CMHA film on a gauze backing applied multiple times at each bandage change. The gel and film are similar forms of hyaluronan cross-linked in a slightly different way.

The team performed bandage changes every four days for seven weeks. They trimmed exuberant granulation tissue (proud flesh) as needed to prevent it from inhibiting wound healing, and they weighed all trimmed tissue. At each bandage change wounds were photographed so wound size and epithelialization (migration of skin tissue) could be analyzed later.

While differences between treatment groups regarding number of times or amount of granulation tissue trimmed were not statistically significant, both frequency and amount were greater in the multiple-gel group, suggesting increased production of granulation tissue. All wounds retracted equally during the initial three to 11 days. Dahlgren reported that wounds treated with multiple applications of CMHA film were significantly smaller than controls on Days 19 and 31, and these returned more quickly to half the original wound size as compared to the other two treatment groups or the control. By Day 47 wounds in the multiple-film group were covered with smooth, adherent epithelium. These also had a flatter profile than the other groups, consistent with less inflammation and less scar tissue formation.

In summary, Dahlgren reported that wounds treated with CMHA films healed faster and with higher quality and less fragile epithelium, compared to the other treatment groups or controls. She noted that repeated applications of CMHA gel stimulated granulation tissue formation, which could help in handling deep injuries where it is advantageous for granulation tissue to quickly fill in a wound defect.

About the Author

Nancy S. Loving, DVM

Nancy S. Loving, DVM, owns Loving Equine Clinic in Boulder, Colorado, and has a special interest in managing the care of sport horses. Her recent book, All Horse Systems Go, is a comprehensive veterinary care and conditioning resource in full color that covers all facets of horse care (available at Shop.TheHorse.com or by calling 800/582-5604). She has also authored the books Go the Distance as a resource for endurance horse owners, Conformation and Performance, and First Aid for Horse and Rider in addition to many veterinary articles for both horse owner and professional audiences.

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