Horse vets learn about surgery research
Part one of two…
Equine practitioners are undeniably busy individuals, making farm calls, caring for patients, and evaluating test results on a daily basis. To help veterinarians keep up to date on the most recent and relevant research, three veterinarians review the top studies in the fields of surgery, medicine, and reproduction at the annual American Association of Equine Practitioners’ convention. This ever-popular session, called the Kester News Hour, kicked off the 2012 convention, held Dec. 1-5, in Anaheim, CA.
Lisa A. Fortier, DVM, PhD, Dipl. ACVS, associate professor of Large Animal Surgery at Cornell University’s College of Veterinary Medicine in Ithaca, NY, highlighted the year’s top equine surgery-related studies.
Upper Respiratory Topics
Fortier began by discussing some of the first published studies in which researchers examined the use of dynamic videoendoscopy (in which the horse undergoes the exam while exercising on a high speed treadmill or working under saddle) to evaluate equine upper respiratory issues. In one study researchers used the relatively new technology to evaluate 129 performance horses presented for evaluation of exercise noise or decreased performance; researchers fitted the horses with a videoendscope before exercise riders put the animals through their normal routines. Study results showed that 91 percent of horses presenting with exercise noise and 71 percent of those presenting with poor performance were diagnosed with some type of dynamic airway obstruction (such as structural collapse; axial deviation of the aryepiglottic fold; and dorsal displacement of the soft palate, or DDSP). What’s more, Fortier said, the obstructions – with the exception of DDSP – worsened during times of “increased rider intervention,” such as head flexion, spurring, circling, or jumping. Additionally, Fortier said, all of the dynamic airway obstructions identified via videoendoscopy were associated with both upper and lower airway inflammation. Fortier stressed that veterinarians should treat underlying airway inflammation in these cases.
Dynamic videoendoscopy might provide a new way for veterinarians to evaluate the respiratory tract, but does the instrument itself impact horses’ performance? The researchers conducting the next study Fortier described asked just that. The team examined Standardbred horses in sanctioned harness races using videoendoscopy and confirmed they could detect the presence of upper airway disorders without disrupting performance.
“This study further supports the use of dynamic endoscopy to understand what is happening in the upper respiratory tract during exercise with the horse in its natural environment as opposed to during a treadmill exam,” she said. However, if a treadmill exam is the only option, then veterinarians should incorporate the study of head flexion into the research, she relayed, so they can evaluate the horse’s airway in the normal circumstances in which the animal works.
Finally, Fortier discussed a study in which researchers evaluated how three degrees of soft palate dysfunction – mild, moderate, and severe – affected respiratory parameters. The team evaluated 40 Thoroughbred racehorses in training presented for recurrent palate instability (movement of the soft palate without displacement of its caudal border) and found that even abnormalities considered mild or moderate yielded negative effects on respiratory parameters. Specifically, Fortier said, affected horses had “decreased end tidal carbon dioxide and oxygen levels,” indicating these obstructions impeded the horses’ breathing.
“These results indicate that respiratory parameters should be considered along with subjective endoscopic observations to fully understand the clinical ramifications of observations that are subjectively judged as mild or moderate,” she concluded.
Van Erck E. Dynamic respiratory videoendoscopy in ridden sport horses: Effect of head flexion, riding and airway inflammation in 129 cases. Equine Vet J 2011; 43(40):18-24.
Priest DT, Cheetham J, Regner AL, et al. Dynamic respiratory endoscopy of Standardbred racehorses during qualifying races. Equine Vet J 2012; 44:529-534.
Allen K, Franklin S. The effect of palatal dysfunction on measures of ventilation and gas exchange in Thoroughbred racehorses during high intensity exercise. Equine Vet J 2012 Jul 10. doi: 10.1111/j.2042-3306.2012.00627.x. [Epub ahead of print].
Fortier then shifted focus and discussed several studies pertaining to orthopedic treatments, the first of which involved distal (lower) hock arthritis. She said this was the first prospective study in which researchers evaluated the safety and efficacy of alcohol-facilitated ankylosis (joint fusion) in arthritic lower hock joints; “proof of concept” studies have previously been carried out on healthy horses, she noted. In the current study, the team performed ankylosis (with 70 percent alcohol) on 21 horses with confirmed hock arthritis. The study revealed that 85 percent of the horses were not lame after three months, and 90 percent were sound at one year post-procedure. Fortier cautioned that about 30 percent of the time, researchers could not enter the distal intertarsal joint (DIT, one of the four joints in the hock) to perform the injection, and that 45 percent of injected DIT joints “communicated” with the proximal intertarsal joint (another joint in the hock) and tibiotarsal joint (the major motion joint of the hock). This means that veterinarians should use caution when considering alcohol injections because leakage of alcohol into the tibiotarsal joint could lead to ankylosis there, as well, which would be detrimental to the horse.
The results of a second study
Fortier discussed, in which researchers investigated alcohol for fusion of the lower hock joints, showed that 52 percent of osteoarthritic horses that had not responded to corticosteroid treatment improved in the short term after injection; however, the condition of 19 percent of those animals deteriorated significantly six to nine months post-ankylosis. Study researchers believe this occurred because the horses were more clinically challenged (i.e., bilateral cases of arthritis or more cases of advanced
disease than in other studies).
Referring to both alcohol-facilitated ankylosis studies, Fortier cautioned that while the procedure is effective in fusing joints, it also poses drawbacks and should not be used as a first-line treatment option, given the complications highlighted by these studies. In addition, veterinarians should perform contrast arthrography (joint evaluation) before each injection and, perhaps, they should only inject the tarsometatarsal joint to minimize alcohol leaking into the main hock joint.
Finally, Fortier discussed a study in which practitioners evaluated alternative routes for administering mesenchymal stem cell (MSC). In some cases in which clinicians desire a greater distribution of stem cells – for example, where there isn’t a core lesion (single obvious injury) or where there is a diffuse lesion (injury that is spread out over an area) – they need to establish a regional delivery route of MSCs. The research team administered stem cells labeled for tracking purposes via intravenous (IV) and intra-arterial injection in six horses, using regional limb perfusion. They found that both IV and intra-arterial injections had good distribution in the carpus (knee) and metacarpus (cannon bone), and that the intra-arterial approach was more effective for distributing MSCs to the pastern and hoof than the IV approach. She cautioned that intra-arterial injections resulted in “severe thrombosis” (blood clotting in the veins) in one horse.
“This suggests that IV delivery of stem cells is the safer route of administration and that, perhaps, if delivery of stem cells to the pastern or foot is desired, then the cells should be delivered more closely to the target via IV injection below the carpus,” she concluded.
Carmalt JL, Bell CD, Panizi L, et al. Alcohol-facilitate ankylosis of the distal intertarsal and tarsometatarsal joint in horses with osteoarthritis. J Am Vet Med Assoc 2012; 240:199-204.
Lamas LP, Hodge JE, Zamora-vera L, et al. Use of ethanol in the treatment of distal tarsal joint osteoarthritis; 24 cases. Equine Vet J 2012; 44:399-403.
Sole A, Spriet M, Galuppo LD, et al. Scintigraphic evaluation of intra-arterial and intravenous regional limb perfusion of allogeneic bone marrow-derived mesenchymal stem cells in the normal equine distal limb using 99mTc-HMPAO. Equine Vet J 2012; 44:594-599. F
…Watch next week for part two.
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As a routine management matter, the Teddy Roosevelt National Park plans to remove a few horses from its herd.