Cryoanalgesia Helps Patients Recover in Comfort

Cryoanalgesia is emerging as a compelling option for managing the immense pain of total knee replacements. Its specific application for total knee pain management is gaining interest and proponents in the orthopedic community like Joshua A. Urban, MD. Since 2018, Dr. Urban, an orthopedic surgeon who performs total hip and knee replacements with OrthoNebraska in Omaha, and his physician assistant have performed almost 1,200 cryo procedures. 

He performs the treatment two to three weeks before knee replacement surgery, and it essentially mutes the nerves that send pain signals to the brain, while sparing the nerves that regulate motor function. The block lasts up to four months — including the majority of the typically excruciating pain period post-surgery.

“Total knees have a well-earned reputation of being barbarically painful,” says Dr. Urban. Postoperatively, an immediate concern for patients is ensuring that the knee doesn’t stiffen and muscles don’t atrophy. “As soon as patients wake up, we tell them to start moving their knee, and it’s akin to doing a big hernia surgery and having them do crunches right away,” he says. 

Surgeons have traditionally prescribed opioids to help their patients cope with the immense pain. But as the industry continues to phase out opioids whenever possible, the idea of an extremely long-term block that removes pain but doesn’t affect the patient’s ability to ambulate is appealing to surgeons and patients alike.

“A nerve block is the best way to control pain because you just shut the message down,” says Dr. Urban. Although perioperative blocks placed by anesthesia work well, they are short-lived. “If you use liposomal bupivacaine, it’s two or three days tops, and then the pain comes,” he says.

By freezing the knee’s sensory nerves at minus-88 degrees Celsius, cryoanalgesia essentially kills them, and they then grow back over time. “If you’re blocking the patient’s nerve mid-thigh, and it has to regenerate down the whole thigh back to the knee, you’re buying the patient three to four months of that nerve being shut off,” says Dr. Urban, who also employs Enhanced Recovery After Surgery (ERAS) and multimodal techniques to manage his total knee patients.

Getting patients to accept the treatment isn’t an issue, says Dr. Urban, but explaining it to them is vital. Dr. Urban avoids using technical terms and explains the process in an easy-to-understand manner: “We’re going to stick a probe under ultrasound to the nerve and freeze it without putting you under. We’re going to do this by making little holes, but we anesthetize you so you don’t feel it. You’re going to have numbness at the top of your knee for about three to four months — and no pain.”

Dr. Urban usually freezes five sensory nerves — three in the thigh, two down by the knee. “We put lidocaine around the nerve, which needs to marinate for a minute per nerve,” he says. “We want the patient awake to give us feedback about where they are feeling the sensations, which helps us dictate where we go next. When they walk out after treating those five nerves, I want the front half of the knee to be numb.” Timewise, he has the process down to about a half-hour, and patients can even drive themselves home afterward.

Total knees have a well-earned reputation of being barbarically painful.
— Joshua A. Urban, MD

Patient selection isn’t a huge issue, although one population does require caution. “Many total knee patients are older and on blood-thinning medication,” says Dr. Urban. “When you start sticking needles in them, you can cause some bruising,” says Dr. Urban. This can lead to big problems if the surgeon doesn’t provide the treatment. “Most total knee surgeons aren’t performing cryo procedures themselves,” he says. “Somebody is doing it on their behalf, like a PA, nurse practitioner, anesthesiologist, pain specialist or interventional radiologist.” As such, if a bruised patient presents on the day of surgery, a surprised provider might cancel the procedure.

To avoid these rare situations, Dr. Urban extends the preoperative period to two to three weeks, which usually gives any bruising enough time to heal. He also refined his technique to prevent bruising in the first place. “The tip of the needle gets frozen, so if you don’t bury enough of the needle, you’re going to get an eraser-sized area of frostbite for about two to three weeks,” says Dr. Urban.

Another technique-dependent issue is making sure the nerve is fully frozen, which can be a particular problem if it’s unusually large. Patients with partially frozen nerves feel good at first but will become dissatisfied when they feel throbbing and burning two or three days later. “Our threshold is 2.5 millimeters in diameter,” says Dr. Urban. “If we see a nerve that’s anywhere near that, we treat it twice, above and below.” 

All told, out of more than 1,000 patients over four years, Dr. Urban estimates that only a couple had bruising issues, and about a dozen dealt with partially frozen nerves. As an early adopter of the nerve-freezing technology, he became a consultant for the original manufacturer of a cryo device and has continued in that role for the company’s current owner.