Postoperative quadriceps strength of continuous or patient-controlled femoral nerve block: a prospective, randomized double-blind trial after total knee arthroplasty

INTERVENTION: Postoperative continuous femoral infusion of levobupivacaine 0.08% 6mL/h for 24 hours. After 24 hours of continuous infusion, switch to patient‐contorolled bolus infusion of levobupivacaine 0.08% 3mL/bolus for additional 24 hours. Postoperative continuous femoral infusion of levobupivacaine 0.08% 6mL/h for 48 hours, using dummy PCA botton. CONDITION: Patients scheduled for elective unilateral total knee arthroplasty under general anesthesia and peripheral nerve block PRIMARY OUTCOME: The primary endpoint is the difference in maximum voluntary isometric contraction (MVIC) of the quadriceps 48 hours after surgery compared with the preoperative MVIC, expressed as a real amount of reduction and a percentage of the preoperative MVIC. SECONDARY OUTCOME: Secondary endpoints included postoperative knee range‐of‐motion, ambulatory ability, Knee Society Score, pain scores(Visual Analog Scale) at rest and during knee movement, and the consumption of additional analgesics. INCLUSION CRITERIA: 1.Patients scheduled unilateral total knee arthroplasty at Osaka University Medical Hospital 2.Adults (>=20 years) with American Society of Anaesthesiologists Physical Status Classification I‐III 3.Participants were scheduled for primary unilateral TKA for osteoarthritis or rheumatoid arthritis 4.Written informed consent is provided