Skin temperature during cutaneous wound healing in an equine model of cutaneous fibroproliferative disorder: kinetics and anatomic-site differences.

OBJECTIVE: To map skin temperature kinetics, and by extension skin blood flow throughout normal or abnormal repair of full-thickness cutaneous wounds created on the horse body and limb, using infrared thermography. STUDY DESIGN: Experimental. ANIMALS: Standardbreds (n = 6), aged 3-4 years. METHODS: Three cutaneous wounds were created on the dorsolateral surface of each metacarpus and on the lateral thoracic wall. Thoracic skin wounds and those on 1 randomly chosen forelimb healed by second intention without a bandage, whereas contralateral limb wounds were bandaged to induce formation of exuberant granulation tissue (EGT). Thermal data were collected from all planned wound sites before the surgical procedure (baseline), and at 24, 48, 96 hours, 1, 2, and 4 weeks after wounding. Data were analyzed using repeated measures ANOVA and a priori contrasts submitted to Bonferroni sequential correction. Level of significance was P < .05. RESULTS: Cutaneous wound temperature (CWT) increased temporally from preoperative period to week 1 postwounding, independently of anatomic location (P < .0001). CWT of limb wounds was significantly less than that of body wounds throughout healing (P < .01). CWT of limb wounds managed with bandages and developing EGT was significantly less than that of unbandaged limb wounds, which did not develop EGT (P ≤ .01). CONCLUSIONS: CWT varied with anatomic location and throughout healing. CWT of wounds developing EGT was significantly less than that of wounds without EGT.

Regional differences in wound oxygenation during normal healing in an equine model of cutaneous fibroproliferative disorder.

Wound repair in horse limbs is often complicated by the development of exuberant granulation tissue (EGT) and excessive scarring while body wounds tend to repair uneventfully. EGT resembles the human keloid. While the events leading to keloid formation are not fully elucidated, tissue hypoxia has been proposed as a major contributing factor. The objective of this study was to investigate tissue oxygen saturation in healing full-thickness wounds created on the horse limb and body, using near-infrared spectroscopy. Spectroscopic reflectance data were collected from both anatomic sites at specific times following wounding. The oxygen saturation values of limb wounds were significantly inferior to those of body wounds during the early period of healing, indicating a temporary, relative state of hypoxia in the former during the inflammatory phase of repair. Horses present a weak, persistent inflammatory response to wounding, especially at the limb level. The relative hypoxia present acutely in limb wounds of horses may promote a feeble yet prolonged inflammatory response, which could interfere with and retard the subsequent phases of healing. Ongoing low-grade inflammation in horse wounds is accompanied by up-regulation of various inflammatory and profibrotic mediators, which might ultimately promote the development of fibroproliferative disorders such as EGT.

Effect of a silicone-containing dressing on exuberant granulation tissue formation and wound repair in horses.

OBJECTIVE: To determine the effect of a silicone dressing on the rate and quality of repair of limb wounds and compare microvascular occlusion and apoptosis in wounds treated with the silicone dressing and those treated with a conventional dressing in horses. ANIMALS: 5 horses. PROCEDURE: Horses received two 6.25-cm2 wounds on each metacarpus. Ten wounds were treated with a silicone dressing; the other 10 were treated with a control dressing. Quality of repair and wound size were evaluated at each bandage change. Time to healing and the number of excisions of exuberant granulation tissue were recorded. Biopsy specimens taken from healed wounds were evaluated semiquantitatively via histologic examination, p53 immunohistochemical analysis, terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling (TUNEL) to quantify apoptosis, and electron microscopic examination to measure microvessel luminal diameters. RESULTS: The silicone dressing surpassed the conventional dressing in preventing formation of exuberant granulation tissue and improving tissue quality. Microvessels were occluded significantly more often in wounds dressed with the silicone gel, which also diminished the expression of mutant p53, an indirect inhibitor of apoptosis, although greater apoptosis was not confirmed quantitatively by use of TUNEL. CONCLUSIONS AND CLINICAL RELEVANCE: Because the silicone dressing inhibited the formation of exuberant granulation tissue, it may be integrated in a management strategy designed to improve the repair of limb wounds in horses.

Management of equine hoof injuries.

Hoof injuries are common in horses. Some wounds can pose diagnostic and treatment challenges because of the rigid nature of horn,the tissue involved, the deeper underlying structures eventually invaded, or the pattern of healing. By combining knowledge about the anatomy and biomechanical properties of the foot and healing characteristics of the hoof with adapted general principles of wound management, satisfactory clinical outcomes usually result.