Top Surgery Studies of 2015

Photo: The Horse Staff

Each year scientific journals publish thousands of horse health studies to help keep veterinarians apprised of the latest research that can help them diagnose, treat, and care for their patients better. And each year at the annual American Association of Equine Practitioners convention, a panel of three veterinarians presents research highlights to attendees during the ever-popular Kester News Hour.

At the 2015 convention, held Dec. 5-9 in Las Vegas, Elizabeth Santschi, DVM, Dipl. ACVS, took her first turn on the Kester panel. A professor of equine surgery at Kansas State University’s College of Veterinary Medicine, in Manhattan, Santschi shared her picks for the top equine surgery-related studies of the year.

Cryptorchidectomy Complications

In the first study Santschi described, researchers reviewed 604 equids that had undergone cryptorchidectomies to remove a retained testicle at a referral hospital. In this retrospective study, the researchers evaluated factors including breed, location of retained testes, surgical technique, and postoperative complications.

Santschi said the team found that 15% of the study population had undergone previous castration attempts, which made locating the hidden testicle more difficult. She said this was because the dropped testicle had been removed, so it wasn’t clear what side the retained one was on, and because scarring made the approach more difficult. Further, they determined that in 60% of horses the retained testicles were located in the abdomen, while the remainder were in the inguinal (groin) region. The researchers determined that surgical technique—standard, noninvasive, invasive, or laparoscopic—had no impact on success or complication rates.

The team determined that mild complications, such as short-term fevers, were more common (43%) than major postoperative complications, which were quite rare (3% of horses). Fatal complications were very rare (0.05%). Many surgical techniques for removing cryptorchid testicles are safe and effective.

Hartman R et al. Cryptorchidectomy in equids: 604 cases (1977-2010). J Am Vet Med Assoc. 2015 Apr 1;246(7):777-84. 

Pastern Arthrodesis Outcomes

Next, Santschi described a retrospective study in which researchers evaluated the outcome of proximal interphalangeal joint arthrodesis, or surgical fusion of the pastern joint, in 82 horses. Of those, 51 were Quarter Horses involved in Western performance disciplines and 31 were Warmbloods or Thoroughbreds used for showing, show jumping, and dressage. Surgeons carried out the procedure using one of three methods: three transarticular cortical bone screws (screws that cross a joint to stabilize or, ideally, compress it), a dynamic compression plate (a standard bone plate that compresses the fracture) with two transarticular screws, or a locking compression plate (a plate with threaded holes so screws “lock” into the plate as well as the bone; this increases stiffness of the construct) with two transarticular bone screws.

Santschi said the team found that:

  • Osteoarthritis was the most common presenting condition (reason for the surgery);
  • 45% of horses returned to competition, while 37% were considered to have a successful outcome and were sound for riding at a lower level;
  • The surgical technique used had no effect on the outcome;
  • Horses with osteoarthritis were less likely to be sound following surgery; and
  • Horses undergoing hind limb arthrodesis were significantly more likely to return to successful competition (73%) than those with forelimb arthrodesis (25%).

Ultimately, Santschi said, the team determined that pastern arthrodesis results in a favorable outcome, although the procedure has more success when performed in the hind limbs.

Herthel TD et al. Retrospective analysis of factors associated with outcome of proximal interphalangeal joint arthrodesis in 82 horses including Warmblood and Thoroughbred sport horses and Quarter Horses (1992-2014). Equine Vet J. 2015 Aug 19. doi: 10.1111/evj.12503. [Epub ahead of print] 

Critical vs. Noncritical Colic Cases

With critical colic cases, as with many conditions, the earlier the diagnosis the better. But how do veterinarians distinguish between critical and noncritical cases on the farm, when it’s early in the game? Santschi shared the results of one recent study on the topic.

The team assessed information about 1,060 horses with colic submitted by 167 veterinary practitioners in the U.K. Of those, 76.4% of the cases were deemed noncritical and 23.6% were considered critical (resulting in intensive medical treatment, surgery, or euthanasia). The team found significant association of pain level, heart rate, gastrointestinal borborygmi (gut sounds), and simple indicators of hypovolemia (low blood volume) during the first examination with critical cases.

Santschi noted that of the 194 critical cases, 136 were euthanized following the initial visit. She said this indicates a need for continuing owner education on the signs of colic and when to contact a veterinarian for help.

Curtis L et al. Prospective study of the primary evaluation of 1016 horses with clinical signs of abdominal pain by veterinary practitioners, and the differentiation of critical and non-critical cases. Acta Vet Scand. 2015 Oct 6;57:69. 

Contamination Following Joint Injections

With joint injections for intra-articular injury comes the risk of joint contamination with tissue and hair debris, which can lead to problems potentially more serious than the issue being treated. Santschi described a study in which researchers took a closer look at whether factors including needle brand, needle bevel grind, and silicone lubrication have an impact on contamination risk.

She said they found 19-gauge nonlubricated needles were more likely to lead to joint contamination than 19-gauge lubricated needles, and that use of both types were more likely to result in contamination than use of 20-gauge needles. All other needle types tested posed similar risks for contamination.

Santschi cautioned that it’s important to consider these results with perspective: Post-injection septic arthritis is rare, with reports suggesting a prevalence of about 0.078%. However, a septic joint after injection is a serious complication, and it’s important to provide veterinarians relevant, valuable information to help them avoid infection.

Waxman SJ et al. Effect of needle brand, needle bevel grind, and silicone lubrication on contamination of joints with tissue and hair debris after arthrocentesis. Vet Surg. 2015 Apr;44(3):373-8. 

Stifle and Hock OCD Treatments

If your Thoroughbred foal has stifle or hock osteochondrosis dissecans (OCD), will the condition—and how you elect to treat it—impact his future racing performance? The results of the next study Santschi described suggest that it could.

Through their retrospective case control study a research team recently determined that:

  • Horses with stifle OCD treated arthroscopically had lower total earnings, fewer starts, and fewer wins than age-matched controls;
  • Horses with hock OCD treated arthroscopically had fewer starts than age-matched controls; and
  • Both a younger age at surgery and a less experienced surgeon had a deleterious effect on stifle OCD but not hock OCD outcomes.

Because the team measured many racing outcomes, they considered a reduction in only one outcome (as was found in the hock OCD cases, starts) to be relatively unimportant. However, the reduction in several racing outcomes for the horses with stifle OCD indicates that owners can expect reduced performance after surgery. Also, the researchers suggested owners delay any OCD surgery until the horse is about a year old.

Clarke KL et al. Treatment of osteochondrosis dissecans in the stifle and tarsus of juvenile thoroughbred horses. Vet Surg. 2015 Apr;44(3):297-303. 

Long-Term Results of Three-Tract Arthrodesis Technique

It’s always smart to double-check your work, and one research team recently took a look at the long-term effects of a surgical procedure they’d developed several years prior. Santschi described the group’s findings when it evaluated the long-term effects of a three-drill-tract arthrodesis technique for treating carpometacarpal (the lower joint space in the horse’s knee) osteoarthritis. In theory, this surgery is designed to advance joint fusion and, thus, decrease pain and lameness. Using a more invasive technique, researchers had found a long-term 83% success rate, but significant postoperative lameness, and they developed the three-drill-tract technique in response to reduce post-operative pain.

In the recent study, the research team evaluated nine procedures performed on six horses (three bilateral, or on both legs, and three unilateral procedures). While there were no surgical complications, the team found mild postoperative pain in two horses, moderate in three horses, and severe in one horse. Long-term pain relief was not achieved in three horses (one was euthanized) but improvement was reported in the other three.

With a success rate reduced to 50% from 83%, with no significant reduction in postoperative pain, the team concluded that the three-drill-tract technique is not useful for advancing joint fusion in horses with carpometacarpal osteoarthritis. Still, Santschi applauded the research team for following up on the technique and reporting that it was inferior to other available treatment options.

Hillberry E et al. Long-Term Follow-Up Information of a Three-Tract Arthrodesis Technique for Treatment of Carpometacarpal Osteoarthritis. J Equine Vet Sci. 2015 Sept;35(9):773-8. 

Standing Laryngoplasty

The saying goes, “If it ain’t broke, don’t fix it.” True, but can it hurt to improve an already-effective procedure by making it safer and more precise? That’s just what a team of researchers did in the next study Santschi shared.

Researchers found that laryngoplasty has fewer risks and is less expensive if it’s performed in a standing horse.

Photo: Courtesy Fabrice Rossignol, PhD, DVM, Dipl. ECVS

Equine surgeons typically perform laryngoplasty, a surgery that repositions paralyzed laryngeal cartilage (sometimes referred to as tie-back surgery) and often removes the laryngeal ventricle and vocal fold, under general anesthesia, in horses that have poor performance because of this condition, or “roar.” However, researchers recently determined that veterinarians can also perform the procedure in a standing, sedated horse with the assistance of local anesthesia.

After performing the procedure in 71 horses (with a unilateral or bilateral ventriculectomy or ventriculocordectomy in 61 horses) the team confirmed that all patients tolerated the standing laryngoplasty well. Santschi said two horses had incisional swelling that resolved with drainage, and a total of 68 horses were considered to have satisfactory improvement of the condition.

She noted that the researchers said everything falls into its correct anatomical position when the horse is standing, making the procedure more precise and allowing for easier adjustments during surgery. It also eliminates the cost and risks associated with general anesthesia, she said.

Rossignol F et al. Laryngoplasty in Standing Horses. Vet Surg. 2014 Nov 7. doi: 10.1111/j.1532-950X.2014.12307. [Epub ahead of print] 

Short-Term Colic Complications in Senior vs. Mature Horses

Finally, Santschi presented a retrospective study in which researchers compared short-term complications and outcomes associated with colic surgery in 78 geriatric (20-year-olds and older) and 156 mature (4- to 15-year-old) horses.

The team determined that older horses were more likely to have strangulating lesions than mature horses. Santschi added that a higher proportion of geriatric horses had postoperative reflux and inappetence, but there was no difference in the proportion of senior and adult horses with both small intestinal strangulating lesions and postoperative reflux. Further, she noted, the short-term outcomes were similar between the two age groups.

These results reinforce the fact that age should not be the sole deciding factor in determining prognoses or treatment options for colic, Santschi said.

Gazzerro DM et al. Short-term complications after colic surgery in geriatric versus mature non-geriatric horses. Vet Surg. 2015 Feb;44(2):256-64. 

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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