Cryoneurolysis Prior to Total Knee Arthroplasty for the Management of Postoperative Pain; A Randomized, Sham-controlled, Trial

INTRODUCTION In Denmark and the rest of Europe, 20% of all chronic pain conditions is related to osteoarthritis (OA) and the incidence of this pathology is likely to increase significantly. The treatment of knee OA typically focuses on pain relief, however the effects of current conservative treatment options remain small to moderate and most are associated with side effects. In many cases patients alternatively may be subjected to partial/total knee arthroplasty (TKA). The number of TKA procedures, in the U.S., is projected to grow by 85% (1.26 million procedures) by 2030. TKA is considered to be an effective treatment for end-stage knee osteoarthritis, however the period post-surgery is characterized by moderate to severe pain. Postoperative pain inhibits early ambulation, motivation and range of motion, compromising rehabilitation, patient satisfaction, and overall outcomes. In this regard, more than 20% of patients have been shown to experience persistent and unchanged pain post-surgery. In an attempt to attenuate postoperative pain, many multimodal approaches have been proposed and implemented, with mixed results however an optimal strategy of postoperative pain treatment after TKA has not yet been established.

Reviewing these results, focus should be on low-risk, minimally invasive pain management. Novel advances in the ability to target the genicular nerves are in that respect promising. Cryoneurolysis has made it possible to apply low temperatures [-20°C ; -100°C] to a target percutaneous peripheral nerve, causing Wallerian degeneration. This disrupts nerve function while structural elements of the nerve bundle remain intact allowing for complete regeneration and functional recovery of the nerve over time. Cryoneurolysis on peripheral nerves has been shown to provide pain relief in a variety of chronic pain conditions such as lumbar facet joint pain, plantar fasciitis, occipital neuralgia, post thoracotomy pain syndrome, and Morton's neuroma.

Recently, our research center and others have shown that is possible to target the superficial genicular nerves with cryoneurolysis and studies have observed a statistically significant reduction in hospital stay, a decrease in prescribed opioids, and less knee symptoms after TKA when cryoneurolysis was provided prior to operation. These results suggest a potential for cryoneurolysis to significantly improve rehabilitation and overall outcomes. Nevertheless, these studies lack adequate power and a control group to confirm its efficacy and safety. In addition, the optimal freezing protocol for cryoneurolysis remains to be outlined. This involves number of cycles, duration, intensity and thaw time which also depends on crucial factors such as nerve target identification, probe placement and anatomical location of the target tissue.

The present study is the first to utilize methodology, that allows for accurate control of the ablation zone in relation to the target genicular nerves. The nerves are identified using electrical nerve stimulation and ultra-sound, which allows for the identification of nerve structures specific for each patient, independent of the inherent variation of neural structures, and also, from a patient security point of view, considers adjacent neurovascular structures and variations in anatomical structures. We have in our center performed 500+ ablations, using the framework, without any serious adverse events.

If cryoneurolysis successfully attenuates postoperative pain, and as a results opioid use, earlier ambulation, improved rehabilitation and overall outcomes - it would have massive socioeconomic implications. Finally, developing and establishing an efficacious and safe protocol for the treatment of pain with cryoneurolysis, is an initial step for its implementation in a much broader context within the field of pain medicine and cryoanalgesia.