A femoral triangle block (FTB) effectively anesthetizes the anterior group of nerves innervating the knee (infrapatellar branch of the saphenous nerve, the medial femoral cutaneous nerve and the terminal branch of the medial vastus muscle nerve). However, the posterior group of nerves innervating the knee joint is not covered with an FTB, and therefore most patients complain of significant, opioid-requiring pain despite a successful FTB.~The posterior group consists of the popliteal plexus, which is derived from the tibial nerve and the posterior branch of the obturator nerve. The popliteal plexus is located in the popliteal fossa, where it entwines the popliteal artery and vein. Recent cadaver studies have suggested that an injection into the distal part of the adductor canal will spread to the popliteal fossa (PubMed Identifier (ID): 28937534; PubMed ID: 27442773).~This study aims to assess the analgesic effect of the popliteal plexus block (PPB) as a supplement to a femoral triangle block (FTB) after total knee arthroplasty (TKA).~In the study all patients will receive an FTB with 10 ml bupivacaine-epinephrine (0.5%-1:200,000) with the addition of 0.5 ml Dexamethasone (4 mg/ml).~All patients are postoperatively observed for the development of significant pain (NRS > 3) in the primary observation period (POP) defined as: a 3-hour observation period starting at the return of completely normal cutaneous sensation (lateral thigh and lateral side of the lower leg) after spinal anesthesia. If the patient reports pain (NRS > 3) in the POP, the patient will be randomized to the study treatment - a PPB with 10 ml bupivacaine-epinephrine or 10 ml saline.
This study aims to assess the analgesic effect of the popliteal plexus block as a supplement to a femoral triangle block in patients undergoing total knee arthroplasty