Cryoneurolysis for Acute Postoperative Pain Following Total Knee Arthroplasty

Local anesthesia is injected in the skin. The superficial genicular nerves, more specifically the ISN and the AFCN, are visualized. A nerve stimulator is used to verify the visualized nerves., 2-3 ml of ropivacaine 5 mg/ml is injected around the nerves. After 5-15 minutes the effect is evaluated by assessing pain in the surgical area and asking the patient whether there is a pain relief. Following this evaluation, cryoneurolysis (Cryo-S, Metrum Cryoflex, Blizne Laszczynskiego, Poland) is performed unilaterally along a treatment line, the location of which was guided by visualization and palpation of anatomic landmarks. The ISN treatment line is located along the line that connects a point located 5 cm medial to the lower pole of the patella and a point located 5 cm medial to the tibial tubercle. The AFCN treatment line is located at one-third the length of the distance from the center of the patella to the top of the femur, with a width equal to the width of the patella.

The exact same procedure as in the cryo-group is performed, except that the nerves are not frozen with the cryoneurolysis apparatus. Sound effects from the machine are replicated to give the patient the same experience as in the active intervention group.