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 2017 AAEP CONVENTION SPONSORED BY A22 TheHorse.com/AAEP2017 AAEP Wrap-Up THE HORSE March 2018 ERICA LARSON The Latest on Supporting-Limb Laminitis S ince Kentucky Derby winner Bar- baro's death due to supporting-limb laminitis (SLL) more than a decade ago, researchers have made great strides in understanding laminitis (inflammation of the horse's laminae, which suspend the coffin bone within the hoof), why it develops, how to treat it, and more. An- drew van Eps, BVSc, PhD, MACVSc, Dipl. ACVIM, an associate professor of equine musculoskeletal research at the Universi- ty of Pennsylvania's School of Veterinary Medicine, in Kennett Square, reviewed veterinarians' current understanding of SLL and what remains to be learned. "Despite significant recent advances in our ability to treat complicated fractures and other painful limb conditions in horses, supporting-limb laminitis remains a primary limiting factor to treating these cases," he said. "Although the severity and duration of lameness are considered risk factors, the development of SLL is still unpredictable, both in terms of timing and also with respect to which cases will succumb to it." Possible mechanisms for SLL develop- ment, he said, include: ■ Mechanical overload of the lamellar tissue. This theory is "hard to swal- low," however, because the limbs are subjected to substantial forces when the horse moves, said van Eps. In theory, however, lamellar remodeling in response to prolonged stress could play a role in structural failure, he said. ■ Lack of blood supply (ischemia) . "When a foot is bearing weight, as it would be with an injured leg on the opposite side, there's an interruption in perfusion (blood flow)," van Eps said. The degree of interruption varies between horses. Additionally, blood flow in the palmar digital artery decreases during weight- bearing, he said. This lack of blood flow could also lead to structural failure. Further, researchers know that the lamellae require a substantial amount of glucose to function properly. An inadequate blood glucose supply could lead to failure due to lack of energy. Van Eps said more research is needed to fully understand the relationship between limb-load and perfusion, but researchers have recently revealed that the limb-loading cycle—weight-shifting or walking—increases lamellar blood flow significantly. Vasodilators (drugs that dilate vessels and increase blood flow) don't appear to have the same effects, he added. "These studies showed that the act of walking had a marked positive effect on lamellar perfusion and interstitial (within the tissues) glucose concentrations," van Eps said, "more so than just repeated unloading of the limb in a standing horse, indicating that the weight-bearing phase itself—and perhaps the movement of the limb associated with breakover (at the toe when the heel lifts off the ground)— may play an important role in lamellar perfusion." Overall, he said, recent research is providing additional evidence suggesting ischemia plays a role in SLL development. SLL Prevention "It seems that cyclic loading and unloading of the feet play an essential role" in keeping the hoof func- tioning properly, van Eps said. A fitness tracker with an accelerometer (e.g., a Fitbit) might be useful for moni- toring limb-loading cycles, he said. Encouraging patients to walk could help promote limb-loading in cases that aren't too painful. Using a sling to reduce the load on the opposite limb could be effective with the development of newer dynamic sling technology; traditional slings have not been useful for this purpose. Researchers have also explored forced recumbency (creating a lowered ceiling to keep the horse lying down) to unload the opposite limb. This approach should be used carefully, however. Research has shown that horses that are recumbent for long periods can develop complications. While cryotherapy (icing the feet) has been shown to benefit horses at risk of developing sepsis-related laminitis, van Eps said he hasn't yet studied whether it could help prevent SLL, "but it would be an interesting area to look at." PAULA DA SILVA Laminitis: We're Still Learning Megan Tracy Petty @meganmarysia #HotTopics today. Horse owners should be very proud of the veterinarians on their team. These folks are brilliant. Well done