[Femoral nerve block for total knee arthroplasty]

Femoral nerve block and sciatic nerve block are used to provide intraoperative and postoperative analgesia for total knee arthroplasty. Sciatic nerve block is contraindicated in our hospital, because orthopedists want to assess peroneal nerve function after the surgery. We retrospectively assessed postoperative analgesic effect and complications of the continuous femoral nerve block for total knee arthroplasty.

We included 19 cases in 17 patients scheduled to undergo total knee arthroplasty under femoral nerve block combined with general anesthesia. Ultrasound-guided femoral nerve block was performed before the surgery. The ultrasound linear probe was used to visualize the femoral nerve. A 22 gauge needle attached to a nerve stimulator, was inserted with in-plane method. Five percent glucose solution was injected through the needle to encircle the femoral nerve. Then, the 22 gauge needle was withdrawn and an 18 gauge needle was inserted with out-of-plane method. Five percent glucose solution was injected through the needle to confirm the needle tip and perineural catheter was inserted through the needle. To achieve femoral nerve block, 0.375% ropivacaine 20 ml was injected through the needle. Perineural infusion with 0.15% ropivacaine at 4 ml x hr(-1) was initiated at the end of the surgery. Intravenous patient-controlled analgesia (IV-PCA) was also conducted postoperatively. We assessed pain at rest with a verbal numeric pain rating score (0-10) including pain on moving, and nausea as well as vomiting.

Patients with numeric pain scores at 3 or less were 14 out of 19. Two patients complained of severe pain. There were 4 cases suffering pain on moving.

Femoral nerve separation with 5% glucose solution using in-palne method and catheter placement with out-of-plane method could be useful for perineural catheter placement. Perineural infusion of 0.15% ropivacaine at 4 ml x hr(-1) combined with IV-PCA provided a good postoperative analgesia in patients receiving total knee arthroplasty.