“Every racehorse that dies on the track is a tragedy,” said Laura Kennedy, DVM, Dipl. ACVP. But each of those horses, she said, is an opportunity to learn, collect data, and educate about what happened.

As part of the Kentucky Horse Racing Commission’s (KHRC) Necropsy Program, Kennedy, an assistant professor and veterinary pathologist at the University of Kentucky (UK) Veterinary Diagnostic Laboratory (VDL), in Lexington, examines every racehorse that dies or is euthanized at any KHRC-regulated property. During each necropsy, she records detailed information about each horse with the hope that she and her colleagues can, eventually, eliminate catastrophic injuries from racing. And while the end goal remains a long way off, Kennedy and her coworkers have made substantial progress in understanding catastrophic fractures and why they happen. She presented an update on the program and her work Oct. 13 at UK’s Gluck Equine Research Center, also in Lexington.

Program History

Kennedy said the KHRC’s necropsy program is largely based on the California Horse Racing Board’s “flagship program,” which aimed to study the nature of the fatal injuries, determine the reasons behind them, and eventually develop preventive strategies.

The KHRC’s necropsy program was launched in January of 2009 for two reasons, Kennedy said. One reason was that a number of high-profile racehorses, including Barbaro and Eight Belles, had suffered catastrophic injuries in recent years. But the main catalyst behind it, she said, was a higher-than-normal number of breakdowns at Turfway Park, in Northern Kentucky, in December 2008.

“Eight horses died in four weeks,” she said. “But today, Turfway Park is consistently among the safest racetracks in the United States.”

Prior to 2009, fatal racehorse injuries were simply documented. From 2009 to 2012, all horses that suffered fatal injuries during races underwent necropsies, during which the pathologist documented the nature of the injury in detail and examined the contralateral limb (the one opposite the injured limb; so, the left forelimb is the contralateral limb when the right fore is injured).

In 2012, the program expanded to include any horse that died or was euthanized, regardless of the reason, at any KHRC property. Additionally, Kennedy and her coworkers began performing extensive examinations on the contralateral limb and documented the structure in detail. This procedure remains in place; the only change is that Kennedy developed a 0 to 3 scoring system for pre-existing pathology identified in the contralateral limb, which she began using in 2015. A score of 0 represents little to no anomalies, and a 3 reflects serious pre-existing pathology.

How It Works

Kennedy said the necropsy program actually begins before races. The KHRC staff reviews each horse’s past performances and watches workouts. They note any anomalies they identify and take special care to examine those horses closely even before the pre-race exam all competitors must undergo.

“In most cases, those horses are cleared to race and do so uneventfully,” she said.

Any horse that does die on KHRC property, regardless of cause, immediately becomes property of the KHRC, Kennedy said. This isn’t to take the owner out of the picture, she said, but to ensure each body is handled and each necropsy is conducted in the same manner.

Kennedy said control horses—those that die from non-musculoskeletal causes such as colic, laminitis, or illness—are just as important as the horses with catastrophic injuries. Such horses lived and trained in the same general environment, she said, but did not suffer catastrophic injury.

Once the body is assigned a unique identifier, Kennedy and her small team conduct a routine necropsy, then collect the injured and contralateral limbs, removing them from the body above the hock or knee. The team takes radiographs of each limb to compare to their findings when they dissect and examine each limb closely.

“Sobering” is how Kennedy described the differences between what’s typically visible on radiographs and the damage actually present in the limb. Radiographs don’t generally appear abnormal until there’s very serious damage to the bony and soft-tissue structures, she said.

After the KHRC finalizes their mortality review, Kennedy said they review the findings with the horse’s connections with a focus on education rather than reprimand.

The “Bad Step” Myth

For years, many racing industry members have believed in the so-called “bad step” myth—that a completely healthy horse can take a single bad step and suffer a catastrophic injury.

“It sort of excused us from responsibility and lent credence to the belief that racing injuries were inevitable,” Kennedy said. “But in the vast majority of cases, it’s just not true.”

She and her colleagues have confirmed that catastrophic fractures occur in consistent sites in consistent patterns and that everything is bilaterally symmetrical—the contralateral limb will have pre-existing pathology in the same location that the fracture occurred.

Fracture Findings

Since the necropsy program began in 2009, Kennedy estimates she’s examined more than 300 horses. In that time, she and her colleagues have observed a number of fracture-related trends. She said horses that suffered catastrophic injury aren’t the only ones with pre-existing pathology in their bones and joints—control horses generally do, as well. This, of course, leads to more questions.

“What’s normal wear and tear, and what’s abnormal? Where do you draw the line?” Kennedy said. “Some control horses have more significant damage than fracture horses. Is that damage pathology or normal adaptation?”

Sesamoid fractures—Fractures of the small bones on the back of the fetlock are the most common, but also the least rewarding, Kennedy said.

“They’re the least understood, there’s the least research on them (of any fracture type), and they’re the most confusing—they’re a total enigma,” she said.

Kennedy said there appear to be two types of sesamoid fractures: ones that result from suspensory ligament (which runs behind the sesamoids and supports the limb) failure and those that have primary sesamoid bone pathology. However, it’s still challenging to differentiate between the two, she added.

Common pre-existing pathology include cartilage loss and marginal (bone edge) remodeling.

Condylar fractures—Condylar fractures occur at the bottom of the cannon where the bulbous end of the bone meets the fetlock joint. Lateral condylar fractures (those that occur on the outer half of the bone) are much more common than medial fractures (which occur on the inner side of the leg), Kennedy said.

Lateral fractures don’t cross the bone’s midline, but travel up about 8 to 12 centimeters, on average, and exit on the same lateral side as the fracture.

Medial fractures, on the other hand, tend to spiral, Kennedy said. They typically originate in the parasagittal groove (a depression on either side of the ridge in the fetlock joint), cross the midline of the bone within about 2 centimeters of the origin, and travel up the bone to the knee. The carpal (knee) joint generally isn’t involved in these fractures, she said.

With both types of condylar fracture, there’s typically pre-existing damage to the parasagittal grooves, she said.

“We know the pathology is bilateral and symmetric, but we still aren’t sure which limb is more severely affected,” Kennedy said. “Is it the limb that fractured? Or is it the contralateral limb, and the horses are overloading the limb that ultimately fractures?”

Common pre-existing pathology includes flattening of the normally round condyles, damage to the subchondral bone (located just under the cartilage), cartilage loss, and parasagittal groove scoring (most horses will have mild lines at the groove).

Pastern fractures—Long pastern fractures aren’t as common as sesamoid or condyle injures, Kennedy said. “Conditions evaluated in the first phalanx (the long pastern bone) include thickening of the joint capsule, fibrosis (scarring) of the soft tissues surrounding the fetlock, and palmar arthrosis—damage to the cartilage of the first phalanx, which may or may not include abnormal proliferation of bone along the front of the fetlock joint,” she said.

Combination fractures—Kennedy says she also sees a combination fractures of the sesamoids, condyles, and/or pasterns.

Diaphyseal metacarpal fractures (cannon fractures)—These fractures occur in the middle of the shaft of the bone and do not impact the fetlock or knee. Kennedy said these result from bucked shins, a common condition that she said isn’t always treated as seriously as it should be.

“They’re microfractures of the bone,” Kennedy said, adding they need to be taken seriously and the horse should be treated appropriately.

She said horses with diaphyseal metacarpal fractures almost always have evidence of unhealed bucked shins on the contralateral leg.

Other fractures—Less common injuries include fractures of the carpus, humerus, scapula, and pelvis, Kennedy said.

Case Studies

Kennedy closed her presentation with two examples of cases the KHRC has investigated with the necropsy program.

Case 1 involved a 6-year-old gelding that began race training in the summer of his 5-year-old year. He won his first start in January of his 6-year-old year and suffered a fatal diaphyseal metacarpal fracture in his second start.

The necropsy revealed that the key in this case was the horse’s age when he started training.

“A 5-year-old horse’s bones aren’t able to adapt to race training,” Kennedy said, emphasizing the importance of starting training young so bones can effectively remodel and become stronger.

The horse’s trainer was unaware of the risk posed by the horse’s history, she added, so the KHRC educated the individual on how to ensure such a case doesn’t happen in the future.

Case 2 involved a 4-year-old mare that was a homebred for her owner. She started race training at the appropriate time and raced regularly with some success. Eventually, she suffered a carpal fracture.

In this case, the KHRC investigators determined that the mare, as part of her routine care, received phenylbutazone, a step her trainer always took because it’s what he’d been taught was acceptable when administered at “safe” doses and not within the recommended withdrawal times before races. As a result, the mare’s lameness exams were compromised and she was declared sound when, in fact, an underlying injury had developed.

The trainer, devastated by the loss, learned about the dangers of long-term medication administration masking injuries from the commission.

Take-Home Message

While there’s still much work to be done, Kennedy and her colleagues are making steady progress toward understanding catastrophic fractures and, ultimately, how to prevent them.

In closing, Kennedy shared that one of her colleagues believes it’s a good thing such injuries don’t occur out of the blue: “If their legs just (broke), what would we do? It’s good news that we have a problem we can solve. We have something to make better.”