I routinely prescribe cold therapy (cryotherapy) approximately every four hours for patients hospitalized after TPLO surgery. I am actually unsure of the rationale behind this specific time interval, which is why I was immediately interested when a colleague sent me a publication from Frontiers in Veterinary Science. The study describes the skin temperature around the surgical site following cold therapy after TPLO in 17 dogs.
The benefits of cryotherapy are increasingly well-documented and include vasoconstriction, reduced enzymatic tissue damage, decreased cellular metabolism, reduced swelling, and a good analgesic effect. While some of these benefits will persist even after the treated area warms up, this does not apply to analgesia—nerve conduction resumes as normal once the area has rewarmed. However, how long does it take for a surgical site to rewarm after cold therapy?
Two surgeons performed standard TPLO procedures on a total of 17 dogs, after which the dogs were fitted with a dressing and a Robert Jones bandage overnight. The following day, the bandage was applied, and the dogs received cold therapy using a crushed ice pack for a total of 20 minutes. An infrared thermal camera (thermography) was used to measure skin temperature before cryotherapy, immediately after, and then every 15 minutes for the first hour, and every 30 minutes thereafter, until the skin temperature returned to its pre-treatment value.
The results showed that skin temperature decreased by a significant 7.4 degrees on the medial side, i.e., in the incision area, while it decreased by 8.9 and 6.5 degrees on the lateral and cranial sides of the leg, respectively. On the medial side, the skin returned to its original temperature after an average of 45 minutes, whereas the temperature on the lateral and cranial sides returned to baseline after 60 minutes.
Compared to previous studies on non-operated stifles, the rewarming time after cold therapy was shorter. This can likely be explained by the inflammation that occurs in a surgical area, and it is reasonable to assume that the inflammatory process is more intense on the operated medial side than on the other sides of the leg. Where tissue damage is greater, inflammation naturally becomes more severe.
It has often been advised to avoid cold therapy directly over implants due to concerns about cold transfer to the bone. However, is this truly a significant concern? I am not aware of any studies that specifically address this, but this particular study may indicate that cooling the affected area should indeed be considered if the dogs tolerate it.
After my own surgery, I was advised to ice the operated area every hour during the first 24 hours, except when sleeping. It occurs to me that for various reasons, we as veterinarians cannot recommend such frequent use of cold therapy, partly because our patients do not necessarily tolerate lying still with the pack on, and/or because owners may not have the time to implement such a regimen. However, should we recommend somewhat more frequent intervals for cold therapy, at least during the phase when inflammation is most severe, i.e., the first two days? Based on this study, it is likely that we should.
The image is sourced from the article, which can be found here:
https://www.frontiersin.org/articles/10.3389/fvets.2022.784327/full