This is the final piece in our series entitled The Change Ahead, which was designed to capture some of the regulatory changes on the horizon under the new Horseracing Integrity and Safety Authority. The first racetrack safety rules went into effect on July 2 of this year.
Find Part 1 in this series, on hair testing out-of-competition, here; Part 2 on void claim rules here; Part 3 on jockey safety protocols here; and Part 4 on pre-race veterinary exams here.
Like it or not, when the calendar ticked over to July 2, the first regulations promulgated by the Horseracing Integrity and Safety Authority went into effect. While the start of the Authority's regulation marked the beginning of new regulations, it also signaled the beginning of the end of an old practice – pin firing.
Rule 2271 outlining Prohibited Practices includes “thermocautery, including but not limited to pin firing and freeze firing, or application of any substance to cause vesiculation or blistering of the skin, or a counter-irritant effect.”
The rule will first apply to foals born in 2022.
Discussions of pin firing have flared tempers in the veterinary community in recent years as practitioners have debated its usefulness and ethical implications in a changing culture.
Pin firing or thermocautery involves the application of a tool with metal points to a horse's leg, typically the shins. The points are heated and the tool burns through the skin and touches the periosteum, which is the thin membrane that covers the bone. An iodine-based paint is then applied daily to the site to ease skin discomfort for 10 or 11 days before the horse begins returning to training. Horses are also rested prior to firing to calm down some of the acute inflammation. The overall process has the horse out of training for several weeks.
The practice of thermocautery was actually adapted from a technique that was once used in human medicine. The principle was that the irritation from the hot iron would increase circulation and bone remodeling, with the goal of speeding the body's natural repair process. In racehorses, it has been used on soft tissues, but much more commonly on bone, and is classically associated with bucked shins. Young horses may develop shin soreness (similar to shin splints in human runners) when the pace of their training program progresses more quickly than their cannon bones can adapt to it. For many decades, the irritation left behind by pin firing was believed to cause a surge in bone repair at the point of application.
“The old timers, the people in this industry for a long time, have said you can do that and put the horse back in training and those horses tend not to have a problem with [shins] again,” said Dr. Kevin Dunlavy, racetrack veterinarian in Kentucky. “You wouldn't have to look very far in a literature search to find out there's not a lot of science that supports this.
“Therein lies the problem. I don't think it's taught in a vet school anywhere. They look at it, for lack of a better term, as witchcraft.”
In more recent years, however, some practitioners have questioned whether the practice is actually effective. Many veterinarians believe the amount of time a horse is out of training – from the “cooling out” period prior to firing to the down time after – is probably what makes the difference because it allows the bone to catch up to itself.
For top orthopedic surgeon and Rood and Riddle Equine Hospital partner Dr. Larry Bramlage, the other issue with pin firing is appearances. In reality, he's not sure a horse suffers discomfort much greater or much longer after pin firing than they do after certain types of orthopedic surgery. But try telling that to someone who's not familiar with the practice.
“In our current era, where we're dealing with the social license to conduct racing, it's a thing that would probably hurt our case in the public forum,” said Bramlage, who is a member of the Authority's advisory council. “Weighing all things in risk versus benefit, I think giving it up is safer than trying to defend it.”
Bramlage said pin firing formerly was used to address splints and curbs, but he's not convinced it's effective for either of those problems, either.
Dunlavy said the practice has fallen out of favor with many veterinarians, especially younger vets – so much so, it has gotten harder to purchase the equipment needed to do the firing. While he has pin fired horses himself, Dunlavy also believes he has other treatment options for shins that are equally or more effective. Also, trainers are getting better at recognizing when a horse is developing bucked shins and may be able to pause training before an issue actually develops.
Freeze firing, however, is a little bit of a different animal for Bramlage. First of all, he said, the practice is terribly named. It sounds as though it should be similar to pin firing, but it doesn't involve any kind of burn. Instead, it bears resemblance to the freezing of warts or skin conditions in humans. Liquid nitrogen is used to apply extremely cold temperatures to a targeted area, which creates a mild numbing effect. While some horsemen may turn to freezing in search of a similar counterirritant effect to the one they get from pin firing, Bramlage thinks its usefulness is probably more in localized pain relief than directly changing bone development. He doesn't consider it to be a helpful therapy for shins, but does think it's useful for splints.
Bramlage broke down the most common splint bone injuries in young racehorse into two different groups: Lumps and bumps that occur up high on the cannon bone, just below the knee, and those that are about halfway down the length of the cannon bone.
Splint bones sit on either side of the cannon bone and are somewhat triangular in shape. They're thicker at the top, where they come away from the knee, and thinner toward the bottom approaching the fetlock joint. They're attached to the horse's cannon bones by a ligament and gradually fuse to the cannon bone as horses age. When a horse gets a splint injury up high, it's usually an overload injury, resulting from conformation and/or training stress. As bone remodeling activity increases around that wider portion of the splint bone, that part of the splint tends to fuse to the cannon bone as new bone is laid down to repair the inflammation. That stabilizes the splint bone and usually prevents the same injury from recurring.
For popped splints farther down the leg though, there's a bit of a leverage problem. In young horses, the attachment of the splint to the cannon is tighter at the bottom, where the splint bone is thinner, than it is at the top. If the smaller, pointy end of the splint bone is attached to the cannon but the wider part above still moves, the bone suffers micro-fractures at the junction of the differential stiffness. This causes the lump and the pain and will fuse the bone to the cannon bone like the more proximal splint occurrences if the horse rests. But when the horse returns to work there will still be motion at the top of the splint and not at the bottom of the splint where the lump further fused the splint to the cannon bone. The same differential stiffness occurs between the mobile splint above and the immobile part below. That differential motion repeats the process and prompts a new splint injury.
When a horse has a popped splint lower down in the leg like this, Bramlage wants to keep stimulating the bone until its healing and fusing process continues up the length of the splint, so that everything will be stable. Since bone forms and adapts in response to use and concussion, the way to do this is to allow the horse to remain in light work, which will continue to stimulate the bone. Freezing can be helpful because it can desensitize the area that's inflamed, allowing the horse to keep using the leg in reduced training while the healing process continues until the reaction fully fuses the splint to the cannon bone similar to the splints that occur up high.
“I think freezing of splints is easy to defend,” he said. “Freezing is not offensive because people get freezing. It's not painful, it's actually slightly numbing, and it doesn't really cause any long-term effect except it turns the hair white where you do it.”
An update sent out by the Authority on June 22 clarified that the prohibition on pin firing and freeze firing would only apply to shins, while other areas of application would not be prohibited. The characteristic dot patterns of white hair left behind by pin firing or freezing typically remain the same after the treatment, so it would be hard for a regulator to look at a pin fired horse and know whether the firing had occurred before or after the July 1 implementation.
As for why the pin firing issue is such an emotional one for veterinarians and trainers, Dunlavy and Bramlage said they usually see the debate fall along age-related lines. Those in support of the continued use of pin firing tend to be older and those in favor of phasing it out tend to be younger. For some people, Dunlavy said, it feels like the last straw, like one more tool that's being taken away from them by people who don't walk in their shoes every day. But he's not sure that's the right approach.
“If you don't have science that can back up your stance on it … in racing, we have enough things where we need to show we're acting in the best interest of the horse,” he said. “This isn't the hill I want to die on.”
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