Top Equine Surgery Studies of 2013

Two of the studies Fortier described evaluated colic surgery; one evaluated horses' return to use rates after surgery, while the other examined racehorses' performance after colic surgery.

Photo: Anne M. Eberhardt/The Horse

The ever-popular Kester News Hour was once again well-attended at the 2013 American Association of Equine Practitioners' Convention, held Dec. 7-11 in Nashville, Tenn. This quick-fire presentation is designed to bring busy equine practitioners up to speed on some of the most important and influential studies in different fields.

Lisa Fortier, DVM, PhD, Dipl. ACVS, professor of Large Animal Surgery at Cornell University’s College of Veterinary Medicine, in Ithaca, N.Y., shared her picks for the top surgery- and lameness-related studies with attendees during the news hour.

Upper Airway Issues

The first study Fortier described introduced the prevalence and features of a recently identified upper respiratory condition called ventrorostral displacement of the dorsal laryngeal mucosa (or VRDDLM). She explained that the condition occurs when the mucosa on top of the arytenoids (flappers) progressively obscures the airway during exercise. The researchers who performed the study identified the condition in 12 of 600 racehorses with presenting complaints of poor performance and/or abnormal respiratory noise. Most of the affected horses also had another concurrent respiratory issue, Fortier said. The condition's etiology remains unclear, and treatment isn't immediately necessary, she said.

"Six of the horses' conditions resolved in six to nine weeks, suggesting transient airway instability may be related to the level of training, immaturity, and airway disease of young Thoroughbred racehorses," she said.

Next, Fortier described a study evaluating 41 horses that had previously undergone tie-back surgery (a procedure used to treat roaring, or recurrent laryngeal neuropathy, which involves placing one or more sutures to permanently abduct the arytenoid cartilage) using video endoscopy during exercise under saddle. The researchers sought to evaluate arytenoid abduction and stability, diagnose any concurrent upper airway problems, and correlate these with the owners' perception of surgery success, she said.

Although 93% of owners thought the surgery was beneficial and 90% believed they saw improved performance post-surgery, the researchers found that 79% of horses still had respiratory abnormalities at exercise and identified multiple abnormalities in 41% of the horses, Fortier said.

"When investigating cases of ongoing respiratory noise and/or poor performance after tie-back surgery, exercising endoscopy should be performed (to ensure there's not another respiratory problem present) before consideration is given to tie-back revision or retirement of the horse," Fortier concluded.

Moving forward, Fortier described a study in which researchers evaluated 98 horses presenting with poor performance to garner a better understanding of the clinical and diagnostic features of lower inflammatory airway disease (IAD).

"The objectives of this retrospective study … were to identify differences in age, career, season of admission, and upper airway endoscopic, and cytological finding between horses with mixed airway inflammation compared with noninflammatory bronchoalveolar lavage fluid (or BALF)," Fortier said.

The researchers reviewed the results of the horses' standardized high-speed treadmill tests, lameness evaluations, cardiac evaluations, and post-exercise bronchoalveolar lavages (BAL), but ultimately found that post-exercise BAL isn't very informative when it comes to evaluating poor performance. Fortier suggested veterinarians consider evaluating BAL or serum cytokine profiles instead.


Lameness Issues

Fortier described a study in which researchers compared two methods for injection, or centesis (sampling the synovial fluid in the coffin joint, navicular bursa, and digital tendon sheath), of the digital flexor tendon sheath: the basilar sesamoidean approach (BSA) and the axial sesamoidean approach (ASA).

The team found that the BSA was faster to inject, 100% successful for injection, and six times more successful when performing centesis than the ASA approach. Thus, Fortier suggested practitioners consider using the BSA approach with an 18-gauge needle.

She then presented a study in which researchers evaluated techniques to inject diagnostic analgesia into the lateral femorotibial stifle joint (the lower outside joint of the three stifles joints). Fortier said the traditional method can be challenging, so a team of veterinary students tested whether they could accomplish the same effects by injecting the joint through the long digital extensor tendon (LDE).

Fortier said the team achieved a 100% success rate in administering diagnostic analgesia through the LDE, while the success rate for other traditional approaches averaged less. She concluded that this approach has good anatomic landmarks for veterinarians to work with, avoids injury to the cartilage and meniscus, and is a reliable technique even for inexperienced vets.

The next study Fortier described evaluated the outcome of fusing pastern joints using intra-articular ethyl alcohol. The team evaluated 34 horses over a six year span and noted that 50% became sound and lameness had improved in another 40%. "Importantly, none got worse," Fortier said. Horses required an average of three injections, she said, and six developed mild and transient complications that resolved with phenylbutazone administration and wrapping.

"Although surgery likely remains the treatment of choice because it is 80% successful, some owners can't afford it," Fortier said. "Alcohol fusion started in the hocks and there are anecdotal reports of its use in pasterns, so it's good to see this paper with some data."

Then, Fortier shifted gears and described a study in which researchers evaluated the pharmacokinetic and pharmacodynamic variables and local tolerance at injection site of the antibiotic marbofloxacin administered via regional intravenous limb perfusion (RIVLP) to treat infections and bacterial issues.

"We would love the ability to use a fluorquinoloe (a class of antibiotic) for efficacy against many gram-negative and many Staph bacteria," Fortier said. However, researchers have previously found that 70% of horses treated with the cousin drug, enrofloxacin, via IVRLP developed vasculitis (inflammation of blood vessels). So the research team on the current study tested marbofloxAcin's efficacy instead.

They found that none of the horses tested developed vasculitis, and the synovial fluid concentrations were well above the level required to combat enterobacteria and Staphylococcus aureus. Fortier cautioned that marbofloxacin might treat some strains of Streptococcus, but won't combat all of them. She also noted that the drug currently has low availability in the United States.


Surgery Issues

Fortier described a study of castration complications. "Castrations are probably the most commonly performed surgery in equine practice and result in the most common cause of malpractice claims against equine practitioners in North America," she explained.

Researchers retrospectively evaluated 324 equid castrations and found the overall complication rate was about 10%, most of which were mild in nature (including mild swelling, seroma [fluid accumulation in the tissues that can become bone infection], infection, and fever). Fortier noted that complications were five times more likely when veterinarians used a semiclosed castration technique versus a closed technique, and complications were more likely when additional anesthetic was administered—essentially when the horses were under general anesthesia for longer periods of time.

From castrations to colic, Fortier next described a study evaluating return to use rates after exploratory celiotomy, or colic surgery. "Most other reports detail patient-specific details such as hematocrit levels, duration of colic, and return to performance," she said. "This one looked at surgical data and had six- and 12-month follow-ups, and they sorted success based on return to use and return to performance."

The team found that 77% of the 195 study horses returned to use as athletes. The team determined that horses that developed hernias were seven times less likely to return to function, those that developed laminitis were nine times less likely to return to function, and those that required colic surgery while on stall rest for a musculoskeletal injury were 11 times less likely to return to function. Fortier said the latter was likely related to recurrence of the lameness issue.

She ultimately concluded that horses that undergo colic surgery have a good chance to return to performance, but stressed that veterinarians should educate the owner about potential risks, especially relating to lameness.

Along similar lines, Fortier described a study evaluating 85 racehorses' performance after colic surgery. She said researchers found that 70% of horses that underwent colic surgery returned to racing compared to 73% of controls, suggesting that colic surgery had no significant effect on race performance, including number of starts and earnings.

She noted that six horses did not return to racing due to surgical complications, including repeated colic, laminitis, and hernia.


Bone and Joint Issues

Fortier began her final segment by describing a study that evaluated the risk of infection after 16,624 intra-articular injections in 1,103 Thoroughbred racehorses. Ultimately, 0.0008% of joints developed infections after injections, she said.

Risk factors included the veterinarian administering the injections and methylprednisolone (or Depo-Medrol) use compared to triamcinolone use (0.003% compared to 0.0002%, respectively). She noted the researchers reported no infections after amikacin injection, but the drug was used in only 5% of the injections.

Next, Fortier described a study in which researchers evaluated whether early or increased intensity of training and racing would lead to palmar/plantar osteochondral disease (POD) in Thoroughbreds. "POD is a degenerative condition affecting the distal (lower) condyles of the distal cannon bones and is common in Thoroughbred racehorses," she said. "The condition is believed to be due to injury of subchondral bone associated with repetitive high strains and strain rate in bone during high-speed racing and training."

Based on their review of 1,288 condyles, the team found that POD severity was associated with an increased number of lifetime starts, increased gallops in one training session, if the horse raced for more than one season, and the race interval. Essentially, she said, horses that run too hard, too frequently are more likely to develop POD. The team found no association between POD severity and age and first race, age at first work, earnings and performance, weight, or the use of aquatic therapy.

She concluded that "cumulative racing exposure may be more important than age at first exercise" when it comes to POD severity. She said the trainer and training surface's influence are still unknown.

Finally, Fortier presented a study designed to describe cases that block to the basi-sesamoid (at the base of the proximal sesamoid bones), but had pathology proximal to the block site. Essentially, the researchers evaluated instances in which diagnostic analgesia administered in the basi-sesamoid area spread to areas above, or proximal to, the injection site.

By using MRI, the team confirmed that basi-sesamoid blocks can desensitize the suspensory branches, the distal aspect of the cannon bone, proximal long pastern bone, and the proximal sesamoid bones.


About the Author

Erica Larson, News Editor

Erica Larson, news editor, holds a degree in journalism with an external specialty in equine science from Michigan State University in East Lansing. A Massachusetts native, she grew up in the saddle and has dabbled in a variety of disciplines including foxhunting, saddle seat, and mounted games. Currently, Erica competes in eventing with her OTTB, Dorado.

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