The Horse

MAR 2019

The Horse:Your Guide To Equine Health Care provides monthly equine health care information to horse owners, breeders, veterinarians, barn/farm managers, trainer/riding instructors, and others involved in the hands-on care of the horse.

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YOUR GUIDE TO THE 2018 AAEP CONVENTION A19 The Horse | AAEP Wrap-Up March 2019 ERICA LARSON New Gel Arthritis Treatment Tested There's no cure for equine osteoar- thritis (OA), one of the most common causes of lameness, so vets must man- age associated pain and clinical signs. Scott McClure, DVM, PhD, Dipl. ACVS, ACVSMR, owner of Midwest Equine Sur- gery & Sports Medicine, in Boone, Iowa, recently determined that a synthetic joint lubricant called polyacrylamide hydrogel has promise as a treatment approach. Polyacrylamide hydrogel is a nonde- gradable synthetic viscous gel shown to decrease knee OA symptoms in people. There's less research in horses, so McClure and team evaluated the 4% polyacryl- amide hydrogel (available in the U.S. as Noltrex Vet, he said). In one study they looked at its effects in six healthy horses' fetlock joints, assessing joint fluid seven, 28, and 56 days after intra-articular (IA, in the joint) injection and analyzing cartilage and synovial membrane (joint capsule lin- ing) samples microscopically. He said the polyacrylamide was vis- ible on the synovial membrane on Day 7 post-administration, and it was present between synovial membrane cells Days 28 and 56. They noted no adverse effects. Then they studied the gel's impact on 28 horses with naturally occurring OA, administering IA polyacrylamide hydrogel and evaluating horses 45 and 90 days lat- er. They defined success as improvement by at least one lameness grade or reduced pain scores, improved range of motion, and reduced joint swelling, and found: ■ Average lameness scores decreased significantly, from 2.34 to 0.87; ■ 23 horses (82%) showed improvement at Day 45 post-injection; and ■ 21 horses (75%) still met the criteria for improvement at Day 90. They also found no adverse effects and concluded that the hydrogel decreased lameness long-term in these horses. "This is an exciting new therapy for managing horses with OA," McClure said. "It adds another viable treatment to the veterinarian's options. We will continue to learn more about (it) and how to improve the horse's soundness as we proceed." Healing Tendon Injuries: Hot and Cold Your doctor might recommend a hot and cold application cycle—called con- trast therapy—after a soft-tissue injury. Ice can help reduce pain and inflammation, and heat can increase tissue metabolism and collagen extensibility—all important to healing. Logic says this could benefit horses, but effectively applying ice and heat to their injuries can be tough, much less quickly switching between them. Kevin Haussler, DVM, DC, PhD, Dipl. ACVSMR, of the Equine Orthopaedic Research Center at Colorado State Uni- versity's College of Veterinary Medicine & Biomedical Sciences, said human athletes report that subjecting tissues to tempera- ture fluctuations from above 40 degrees C (104 degrees F) to below 15 degrees C (59 degrees F) in quick succession can: ■ Help with post-exercise recovery; ■ Help treat acute soft-tissue injuries; and ■ Improve neurologic recovery. Haussler said some horses don't toler- ate cold therapy well. And, improperly applied, heat can increase inflammation. So he and colleagues tested a pneumat- ic sleeve designed for applying contrast therapy to horses' lower limbs. They selected four horses with no previous ten- don issues and placed temperature probes in four limb locations. They alternated between hot and cold settings every 15 minutes for two hours, recording tem- peratures every 15 seconds, finding that: ■ The sleeve successfully produced temperatures needed for therapeutic purposes, Haussler said—greater than 40 and less than 15 degrees C; ■ The skin, under the skin, and under the superficial digital flexor tendon reached the desired temperatures, but under the deep digital flexor tendon did not; and ■ Horses appeared to tolerate the con- trast therapy well, and none sustained any injuries because of it. "These results help define the physi- ologic responses of combined tissue heat- ing and cooling within the equine distal (lower) limb," Haussler said. Contrast treatments in humans usually end with cold and last 20 to 30 minutes, twice daily. More research is needed to de- scribe protocols in horses, he said, includ- ing which injuries benefit most; effective temperature ranges; hot/cold timing; and ideal treatment duration and frequency. In equine rehab "we often reach for cold therapies to treat acute injuries and heating modalities for addressing more chronic or fibrotic issues like joint capsule thickening and associated stiffness," Haussler said. "It's likely that applying alternating hot and cold can tap into addi- tional mechanisms to help manage injuries in horses … between these two extremes." BIANCA MCCARTY Diagnosing & Treating Lameness

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