Article last updated: April 1, 2021
Standing a horse in a cold creek was an old horseman’s remedy. Times have changed since this early iteration of cryotherapy, as today we have advanced products to provide the same treatment in clinical and field settings through more controlled and effective processes. Researchers also are continually advancing our understanding of this practice, moving it far beyond an anecdotal remedy.
One area of cryotherapy in need of greater understanding with horses is whether it provides an analgesic effect. Recently, researchers undertook a study to non-invasively measure whether it reduces pain associated with lameness. Dr. Vivian Quam of Ohio State University (OSU) and one of the researchers, presented their findings at the 2019 American Association of Equine Professionals Convention in Denver this past December.
Methods and Treatment
Quam credits the genesis of this study was prompted by questions raised by Dr. James Belknap throughout his career. Now faculty emeritus at OSU, the Hall of Fame veterinarian also is one of the research paper’s authors, and this study was funded by OSU and the Ohio State Racing Commission.
Cryotherapy is well known for its therapeutic benefit in the prevention and treatment of laminitis. Evidence shows that it decreases inflammation and can prevent tissue injury in that disease process. Research in other species has shown cryotherapy to be beneficial as an analgesic. The researchers set out to see whether analgesic effects could be monitored in the horse. For this project, they would give a horse 60 minutes of cryotherapy in an ice water slurry after inducing lameness. Lameness Locator was used to measure this.
Ten mature horses were selected from the OSU research herd for this study. Before separating into a control or test group, each horse received an examination and negligible degree of observed lameness when trotting these horses in a straight line.
Each horse was assigned to a cryotherapy or controlled group during the first treatment period. The horses acted as both cryotherapy and control subjects, and have a 2-week washout period before being moved to the other group.
One week prior to the first treatment period, a certified journeyman farrier applied steel keg shoes to both forefeet. The medial and lateral branches of these shoes had been drilled and tapped for lameness induction. The shoes were left on the horses for the study’s duration. The model of lameness induction used in this study produced a limited amount of inflammation.
“This indication model was selected on purpose,” notes Quam. “We already know that ice has an anti-inflammatory effect. We wanted to parse out analgesia from anti-inflammation. In horses presenting pain associated with inflammation, the analgesic effect of cryotherapy will likely differ, and may even be greater.”
In horses presenting pain associated with inflammation, the analgesic effect of cryotherapy will likely differ …
In the first stage of lameness induction, horses were trotted about 100 meters in a straight line on the same grass surface. The grass surface was selected to prevent excessive pressure from concussion placed on the screw.
Quam notes that the group would select the forelimb with the least sign of lameness based on the examination after placing the screw. The lateral or medial heel would be selected as the screw location based on the best likelihood of contact and heel.
The screw would be tightened or loosened as needed until a consistent grade 3/5 lameness on the AAEP scale was achieved. This level of lameness is defined as “Lameness is consistently observable at a trot under all circumstances.” The lameness would be recorded with the Lameness Locator.
Next, these horses would receive 60 minutes of treatment or controlled conditions. The distal limb would be maintained in an ice water slurry below 6 degrees Celsius (43 degrees Fahrenheit) if the horse was in the cryotherapy group, or at ambient temperature if in the controlled group.
While in the cryotherapy group, the horse’s lame forelimb bathes in the slurry, and the contralateral limb rests in a Soft Ride Comfort Boot with Gel Orthotic. In the controlled group, both forefeet wear the boot and insert.
After the hour of treatment, the lameness would be assessed and recorded at 5, 10, 15, 20, 30, 45 and 60 minutes. The screw was removed from the shoe after the 60-minute assessment. Lameness would again be assessed once the screw was removed.
“This was to ensure that the method of lameness induction was not causing excessive pressure and pain that would persist after removal,” says Quam.
The Findings
Both treatment groups were maintained in stocks without difficulty for the duration of the hour. Measurements showed a success in the lameness induction, and that the degree of lameness induced did not differ between the cryotherapy and controlled groups.
“Lameness induction was successful, and both groups had the same degrees of lameness before and after lameness induction,” she says. “The efficacy of our method of lameness induction was further substantiated by the lameness improvement score immediately following the removal of the screw.”
The cryotherapy group had a statistically significant lameness improvement at 5 and 10 minutes after the treatment, indicating that the degree of lameness lowers at these time points. There was statistical improvement at 5 minutes post treatment for the controlled group.
The researchers concluded that horses in the cryotherapy treatment groups had a longer duration of lameness improvement of 10 vs. 5 minutes. Furthermore, a degree in lameness improvement was detectable between the two groups, but only at 15 minutes after treatment.
“Additional research would be needed to determine the ideal method, duration and temperature for provision of analgesia,” Quam says. “This project is a first step of understanding the analgesic effect of cryotherapy in the horse, the ultimate objective is how to best utilize cryotherapy as a tool for analgesia in our horses, and as a tool for safely managing the sport horse in competition.
Ice Water Slurry Most Effective In Distal Limb Cooling
Based at the University of Pennsylvania’s New Bolton Center in Kennett Square, Pa., Dr. Andrew van Eps is a leading researcher on the effectiveness of distal limb cooling when addressing acute laminitis. Among the varied methods of treatment, he finds that submerging the distal limb to about mid-cannon bone remains the most effective. Other methods such as wrapping ice packs or an ice bag tied off at the coronary band to cool the regions are helpful, but didn’t prove to be effective, nor didn’t function as well.
In the study of effective methods, van Eps says that it is important to remember that during treatment the temperature of the hoof wall may not represent the same temperature as the internal tissue temperature.
“Depending on the type of method you are using to cool this can be deceptive,” he says. “The temperature in the tissue depends on the blood entering it and whether that blood has cooled and dependent on what is coming through the hoof as well.”
In humans, there are adverse effect from constant low temperature application, especially when moisture is involved. But van Eps notes that horses don’t suffer the same issues for a variety of reasons.
“Below 10 degrees Celsius (50 degrees Fahrenheit), people can’t tolerate that temperature as there is a lot of pain associated with it,” he says. “Horses don’t suffer the same uncomfortable effects.”
Horses can experience frost bite in a cryotherapeutic application, but that is extremely rare and associated with more extreme circumstances (van Epps recalls one case from hundreds per year at New Bolton). Other effects like skin damage, are more common. Usually this occurs from direct application of ice to skin, rather than using a slurry.
“The key to a water-ice interface is that you never reach below 0 degrees Celsius (32 degrees Fahrenheit) because of the water’s effect,” he notes.
Regarding timing and duration of the application for treating acute laminitis, it is best applied during the development phase prior to the clinical signs of laminitis, which isn’t always possible. Horses can sustain the continuous application for longer than 5 days, but van Eps finds that there are diminishing returns after that term.
“I think anything longer than 5 days in an acute case, you are probably wasting time,” he says.
“Cryotherapy’s Role in Helping Lame Horses” originally was published in the March 2020 issue of American Farriers Journal.
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It used to mean simply standing a lame horse in the cold-running creek out back to soothe legs and feet and alleviate signs of lameness. Cryotherapy has come a long way since then in terms of what it’s used for and the tools to administer it, but the method’s safety makes it a therapy to rely on. Now, research is confirming that cryotherapy can also have application in the early stages of laminitis.
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