Effect of wound location and the use of topical collagen gel on exuberant granulation tissue formation and wound healing in the horse and pony
Bertone, A.L.; Sullins, K.E.; Stashak, T.S.; Norrdin, R.W.
American Journal of Veterinary Research 46(7): 1438-1444
1985
ISSN/ISBN: 0002-9645 PMID: 4026023 Document Number: 247644
Preformed collagen gel was topically applied to cutaneous wounds of the equine dorsal fetlock (thoracic limb) and metatarsal regions to evaluate the effect on exuberant granulation tissue production and wound healing. In 6 horses and 3 ponies (< 140 cm high at the withers and < 365 kg), 36 standardized cutaneous limb wounds were surgically induced (4 wounds/animal); 18 wounds were treated topically with collagen gel, and 18 wounds were not treated (controls). Collagen gel was initially applied to the wound at 0, 2, or 7 days after wound formation (groups 1, 2, and 3, respectively). Four measurements were regularly made: amount of wound contraction and the size of the granulation bed, epithelial covering, and total wound. Sequential skin and wound biopsies were evaluated histologically to assess wound healing. Using a computer, data were analyzed for differences in the 4 measurements between treated and control wounds, between fetlock wounds and metatarsal wounds, and among groups 1, 2, and 3. Analyses were performed on days 15 and 45 of wound healing and on the final day of healing. A significant difference (P > 0.05) in the production of exuberant granulation tissue, rate of epithelialization, or degree of wound contraction was not detected between the collagen-treated and control wounds. Total hearing time and final scar size were similar. Wound healing patterns were significantly different (P < 0.05) in the fetlock wounds and metatarsal wounds. All wounds enlarged up to day 15 with fetlock wounds enlarging significantly more than did the metatarsal wounds. Fetlock wounds had a faster rate of contraction than did the metatarsal wounds at day 45; but, due to their smaller size, metatarsal wounds healed significantly faster than did fetlock wounds. The resulting scar size of fetlock and metatarsal wounds was similar. Metatarsal wounds required more resection of exuberant granulation tissue than did fetlock wounds. Propensity to develop exuberant granulation tissue and the rate of healing were directly correlated to body size of the horse. Larger horses required more frequent resection of the granulating wound bed and healed more slowly, despite the relatively smaller wound size as compared with their larger limb size. Ponies (< 140 cm high at the withers and < 365 kg of body weight) healed faster than horses; wounds of the ponies also healed without exuberant granulation tissue formation. Therefore, ponies are not adequate models of wound healing for horses.