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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32 TheHorse.com THE HORSE February 2016 back of the foot, and in blood circula- tion. Sometimes these cartilages ossify, or harden, which veterinarians know can increase a horse's risk of injuring the nearby collateral ligament and other structures, along with predisposing the horse to injury due to a reduced ability to dissipate ground reaction energy. But, all told, they haven't known just how impor- tant ossified cartilages are to a horse's risk for future lameness and injury. Sue Dyson, MA, VetMB, PhD, DEO, FRCVS, head of clinical orthopaedics at Newmarket's Animal Health Trust Centre for Equine Studies, in England, presented the results of a study to determine if ossi- fied ungular cartilages are a clinically sig- nificant finding in horses—in other words, she and her colleagues wanted to find out if these structures cause lameness. Dyson and Laura Jones, BVSc MRCVS, a junior clinician at the Centre, reviewed radiographs of 1,255 front feet and nar- rowed the study field to 386 hooves in 271 horses. All the included feet had un- gular cartilages that scored 2 or higher on a 0 to 5 scale (with 0 being no ossification and 5 being the most severe). During their evaluation, Dyson and Jones determined the shape of the ossified cartilage, as well as which radiographic views were best for evaluating them and any other abnormal- ities. They also noted any significant as- sociations between the ungular cartilages and lameness and other abnormalities. They determined that: ■ 42 horses had injury causing lameness directly related to the ungular cartilag- es (seen with scintigraphy or MRI), and 27 (64%) of these ossified cartilages were Grades 4 or 5; ■ 32/131 horses (24.4%) that underwent MRI had Grade 4 or 5 ossification of an ungular cartilage, but the primary cause of lameness was related to other lesions; ■ Fractures were most common in Grade 4 or 5 ossified cartilages; ■ Feet with Grades 4 or 5 were more likely to have additional bone model- ing (the process in which bone adds to itself) and other adaptive changes than those with Grades 2 or 3; ■ Feet with abnormally shaped cartilages were more likely to have bone modeling and other adaptive changes than those with normally shaped cartilages; and ■ Bone modeling and adaptive changes were often associated with lameness caused by bone trauma or fracture. The team determined that horses with extensive ossification, together with bone modeling and adaptive changes, were at risk for lameness associated with injury to either of the ossified ungular cartilages or the coffin bone. Dyson also briefly reviewed diagnostics. She explained that ossified cartilages are firm to palpate on affected horses (in con- trast to healthy cartilages, which yield to gentle pressure) and affected horses can appear lame; however, many horses with ossified cartilage injuries often don't show significant signs of a problem. Affected horses have a variety of hoof conforma- tions, and lameness is usually mild even when cartilages fracture. Lameness is gen- erally most visible on a circle, and in some cases horses are only lame when ridden. She said veterinarians should use nerve blocks to localize pain and then radiograph the affected area using several views. "Ossified ungular cartilages can be of clinical significance," Dyson said. "Valuable information about the ossified ungular cartilages, such as a fracture at the base, may be missed without oblique images of a flexed foot," meaning the vet- erinarian should include projections tak- en on a slanting plane (neither from the front nor the side) in their radiographic studies to gain the most information. Tips for Managing Acute Laminitis A horse with acute laminitis is gener- ally exceedingly painful—think about the classic, rocked-back laminitic horse that is reluctant to move—and it's up to the veterinarian and farrier to help control that pain and start the animal on his road to recovery. Steve O'Grady, DVM, MRCVS, a veterinarian, farrier, and the owner of Virginia Therapeutic Farriery, in Keswick, reviewed how to handle such cases. He first described how laminitis follows a sequence of stages: ■ The developmental stage, when the internal damage to the lamellae (inter- locking leaflike tissues attaching the hoof to the coffin bone) occurs, ending with the onset of clinical signs, such as pain, an increased digital pulse, and a laminitic stance; ■ The acute stage, which generally af- fords the horse's caretakers a small window—24 to 72 hours or until the coffin bone begins to displace from its normal position in the hoof capsule—to intervene, halt, and/or reverse the inter- nal damage; and ■ The chronic stage, which usually begins within 72 hours after the acute stage starts and during which time the coffin bone continues to move within the hoof capsule and clinical signs continue. Despite this relatively uniform series of events that takes place with all laminitis cases, they are challenging to manage. "There is no proven or consistent treat- ment for laminitis," O'Grady said. All treatments focus on controlling the horse's pain and minimizing damage to the lamellae, and they should begin as soon as possible during the acute phase for the best chance of recovery. Establish Submerging acutely laminitic horses' lower limbs and feet in an ice water slurry can help prevent further damage to the lamellae. ERICA LARSON