Local anesthetics after total knee arthroplasty: intraarticular or extraarticular administration? A randomized, double-blind, placebo-controlled study.

BACKGROUND: High-volume local infiltration analgesia with additional intraarticular and wound administration of local anesthetic has been shown to be effective after knee replacement, but the optimum site of administration of the local anesthetic (i.e. intraarticular or extraarticular) has not been evaluated.

PATIENTS AND METHODS: 32 patients undergoing total knee replacement with high-volume (170 mL) 0.2% ropivacaine infiltration analgesia were randomized to receive injection of 20 mL ropivacaine (0.2%) intraarticularly plus 30 mL saline in the extraarticular wound space 24 hours postoperatively or to receive 20 mL ropivacaine (0.2%) intraarticularly plus 30 mL ropivacaine (0.2%) in the extraarticular wound space 24 hours postoperatively. Pain intensity at rest and with mobilization was recorded for 4 hours after administration of additional local anesthetics.

RESULTS: Intensity of pain at rest, during flexion, or straight leg lift was not statistically significantly different between the two groups, but there was a tendency of improved analgesia with administration of additional local anesthetic in the extraarticular wound space.

INTERPRETATION: The optimal site of administration of local anesthetic in total knee arthroplasty cannot be determined from the present study. However, the insignificant analgesic effect from additional administration of extraarticular local anaesthetic may have been due to the relatively low pain scores observed 24 h postoperatively, confirming the efficiency of the high-volume infiltration analgesia technique. Further studies are required to define the optimal site of administration of local anesthetic following knee replacement surgery.