I routinely prescribe cryotherapy approximately every four hours in hospitalized TPLO patients. I don’t actually know why this time interval is chosen, and I was therefore immediately interested when a colleague sent me this publication from Frontiers in Veterinary Science.
The study describes the skin temperature around the surgical site as a result of cryotherapy after TPLO in 17 dogs. The benefits of cryotherapy are well documented and include vasoconstriction and hence less bleeding, reduced enzymatic tissue damage, decreased cell metabolism, less swelling and a good analgesic effect. Although some of these benefits will persist even after the area is rewarmed, analgesia will not. Normal nerve conduction will resume after the area is rewarmed and give rice to nociception and pain. But how long does it take for an operated area to warm up after cold treatment?
Two surgeons performed TPLO surgery in 17 dogs, after which a wound dressing and a Robert Jones bandage were applied overnight. The following day, the bandage was removed and the dogs received cryotherapy using a bag of crushed ice, for a total of 20 minutes. An infrared heat camera (thermography) was used to measure the 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 the same value as before cryotherapy. The results showed that the skin temperature dropped by as much as 7.4 degrees Celsius on the medial side; i.e. in the area of the incision, while it decreased 8.9 and 6.5 degrees on the lateral and cranial side of the bone, respectively. On the medial side, the skin returned to its original temperature after 45 minutes (mean), whereas the temperatures on the lateral and cranial side were back to their initial value after 60 minutes.
Compared to previous studies on non-operated stifles, the time to rewarming after cryotherapy was shorter. This can probably be explained by the inflammation that occurs in tissue subjected to surgery, and one can imagine that the inflammatory process is more pronounced on the operated medial side compared to the other sides of the leg. The degree of inflammation is related to the degree of tissue damage, so this comes as no surprise.
We as veterinarians have often been told to avoid cryotherapy directly over the implant because cold transfer to the bone may occur. But does it really matter where you place the icepack? I am not aware of any studies that describe this phenomenon, but the current study may indicate that you should actually cool down the medial side if the dogs allow it.
After a surgical procedure some years ago, I was advised to put an icepack on the operated area every hour for the first 24 hours, except when I was sleeping. It goes without saying that veterinarians cannot always recommend this frequent use of cryotherapy for various reasons, such as our patients not necessarily cooperating, and/or due to the time expenditure involved. But perhaps we should recommend slightly more frequent intervals for cryotherapy, at least in the most pronounced inflammatory phase (during the first couple of days)? Looking at the results from this study, perhaps we should.
The image is borrowed from the publication, which you can find here: https://www.frontiersin.org/articles/10.3389/fvets.2022.784327/full
