The Use of Amnion in Equine Wound Healing

Objective: To assess the safety and efficacy of lyophilized milled human amnion as a wound dressing of experimentally created equine distal limb wounds.

Animals: Four clinically normal adult horses (3 Thoroughbred and 1 Paint, median age 11 years) obtained via donation.

Procedures: One forelimb of each horse was randomly assigned to the treatment group, and the contralateral limb was assigned as the control. Full-thickness skin wounds were created on each metacarpus. Treatment limb wounds were dressed with lyophilized, milled, human-derived amnion material delivered under triple antibiotic ointment. Control wounds were dressed with triple antibiotic ointment. All wounds were covered in non-adherent dressings and distal limb bandages were applied. Digital photographs were taken of the wounds at each bandage change, performed every 2-4 days throughout a 98-day study period. Biopsies were collected at days 7, 21, 35, and 84.

Results: One horse developed unilateral cellulitis that resolved with additional treatment. All treatment limbs exhibited an inflammatory response characterized by focal edema and discharge from the wounds. Wounds were completely epithelialized in control limbs sooner than treatment limbs in all horses, although there was no statistical difference between control (mean 46.8 days) and treatment (mean 51.8 days) wounds. Histologic scores were better in control wounds than in amnion-treated wounds at all time points.

Conclusions and Clinical Relevance: Because wounds treated with amnion material in this study exhibited an inappropriate inflammatory response that resulted in delayed time to wound closure, human lyophilized milled amnion is not recommended for use in equine wound management.