This article originally appeared in the Fall 2024 issue of EquiManagement. Sign up here for a FREE subscription to EquiManagement’s quarterly digital or print magazine and any special issues.
Most equine practitioners are well-acquainted with the frustrations of managing chronic, nonhealing wounds. Despite myriad wound care efforts—debridement, topical and systemic antibiotics, regional limb perfusion (RLP), intrasynovial injection where needed, and constant bandage changes—they don’t always achieve the expected results. Allison Stewart, DVM, Dipl. ACVS, of Tennessee Equine Hospital, in Thompson’s Station, proposes absorbable antibiotic-impregnated beads (AAIB) as an adjunct therapy to improve healing for wounds with heavy contamination, severe tissue trauma, devitalized tissue and compromised blood supply, fibrinous exudate, and/or the presence of biofilms.
Absorbable Antibiotic-Impregnated Beads (AAIB)
The therapy involves placing absorbable antibiotic-impregnated beads directly into or around a wound. The technique is similar to the use of 3-millimeter cisplatin beads for sarcoids or tumors. The antibiotic-impregnated beads are available commercially (Kerrier), and the excess can be gas-sterilized with ethylene oxide, double packaged, and stored for immediate use. In a clean, dry environment, they should last at least three to six months.
The absorbable beads provide one to two weeks of broad-spectrum or narrowly defined antibiotic treatment within the tissues, depending on the bacteria the veterinarian is targeting. Prolonged antibiotic release is especially valuable in cases where owners have financial constraints and difficulty affording regional limb perfusion every other day for five treatments. Bead formulations typically include amikacin and penicillin or meropenem. Beads come in 3- or 5-millimeter sizes—3-millimeter beads are easy to insert into a stab incision expanded with mosquito hemostats. The practitioner can place about 10-20 of the 3-millimeter beads in a moderate wound, creating a 20- to 30-millimeter zone of inhibition. The bead therapy is especially useful for unmanageable horses that won’t tolerate frequent treatment or bandage changes. Beads can be replaced every 10 days (give or take) as needed.
Case Study: AAIB Therapy for Equine Infections
Stewart recently co-authored a retrospective case study of 55 horses with severe infections, all treated with traditional broad-spectrum antimicrobials and, in the case of synovial involvement, lavage of the affected joint. This treatment approach was unsuccessful in about 50% of these difficult cases. In addition to traditional care, the horses were treated with implanted beads, which were replaced in the wounds one to five times. Of the 55 patients:
- Wound sepsis resolved in 48 horses (87%).
- 69% returned to their previous level of performance (38/55).
- 15% were pasture sound (8/55).
- One horse was confined to stall rest due to laminitis.
- 13% died or were euthanized due to laminitis of the opposite foot (4), colic (1), loss of performance per owner request, even though the horse would have been pasture-sound (1), and clostridial myositis (1).
Outcomes for Horses Treated With AAIB
Stewart reports that most of these cases had some degree of synovial involvement, yet resolution of infection was high with the AAIB regardless of synovial or bone involvement. The worst outcomes were wounds involving the foot, with 67% resolution of infection but 50% lost due to laminitis—four in the affected limb and two in the contralateral limb. She said counterpressure on the frog is important to improve these outcomes.
Lacerations had the best outcome, with 86% resolution and return to performance. Draining tracts, particularly in the inguinal area, had lower resolution rates. Hematogenous spread, especially to foal growth plates, resulted in 75% resolution. In general, 72% of cases returned to performance, but only 59% of those with osseous involvement returned to performance. Those with chronic draining tracts of the foot had the lowest rate of return to performance (33%), while 60% developed laminitis.
Overall, only 50% of horses with wounds treated using traditional therapy reached resolution compared to 87% of horses treated adjunctively with the beads. This is a relatively easy and inexpensive treatment modality that can yield improved results for challenging injuries, said Stewart.
Related Reading
- Antimicrobial Stewardship With Honey
- Maggot Debridement Therapy for Horses
- Electrostimulation Bandages
Stay in the know! Sign up for EquiManagement’s FREE weekly newsletters to get the latest equine research, disease alerts, and vet practice updates delivered straight to your inbox.
