The Analgesic Effect of Combined Nerve Block and Systemic High Dose Glucocorticoid After Total Knee Arthroplasty.

Pain, Peripheral Nerve Block

Peripheral nerve block, Total knee Arthroplasty, Dexamethasone

Purpose: The purpose of this study is to evaluate the postoperative analgesic effect of a combined Saphenous nerve block and Obturator nerve block with local infiltration analgesia in the tissue around the knee after total kneearthroplasty. In the combined nerve blocks we use a mixture of Ropivacaine and Adrenaline combined with high dose systemic dexamethasone and Ketorolac and the mixture for local infiltration consist of Ropivacaine, Adrenaline and Ketoroloc. The investigators hypothesis is that the combined nerve blocks reduces pain and reduces the opioid consumption and thus reduce side effects such as nausea, vomiting and lethargy compared to the current treatment with local infiltration analgesia. Background: Nerve blocks as analgesic treatment after orthopedic surgery is a recognized and proven procedure. The nerve blocks have the disadvantage that not only do they anesthetize the sensory nerve fibers but also the nerve fibers to the muscles of the leg. The Saphenous nerve block causes only stunning of sensory nerves to the knee region. The Obturator nerve block causes both stunning of the sensory nerves to the knee region and the thighs inward leading muscles, and does not affect the patient's mobilization capacity. Both blocks are known to be a good addition to the analgesic treatment. Ropivacaine is a well-known local anesthetic. Adrenaline have also been used in other studies, in addition to the local anesthetic agent, and has been shown to prolong the effect of the nerve block. Saphenous and Obturator nerve block with all four drugs Ropivacaine and Adrenaline combined with high dose systemic Dexamethasone has not been systematically investigated in knee replacement surgery, and it is not known whether this method will provide better pain treatment. Method The patient can receive one of two treatments, determined randomly: * A. Saphenous and Obturator nerve block with active anesthetics (Ropivacaine, Adrenaline) combined with systemic ketoroloc and high dose Dexamethasone and local infiltration around the knee joint with placebo medicine (normal saline). * B. Both blocks with placebo medicine (normal saline) and local infiltration around the knee joint with activ local anesthetic. Neither patient, investigator or staff around the patient will have knowledge of which treatment the patient has received. The blocks will be placed before the operation and local infiltration around the knee joint will be given by the surgeon during the operation.