Continuous saphenous nerve block as supplement to single-dose local infiltration analgesia for postoperative pain management after total knee arthroplasty.

BACKGROUND AND OBJECTIVES

Local infiltration analgesia (LIA) reduces pain after total knee arthroplasty without the motor blockade associated with epidural analgesia or femoral nerve block. However, the duration and efficacy of LIA are not sufficient. A saphenous nerve block, in addition to single-dose LIA, may improve analgesia without interfering with early mobilization.

METHODS

Forty patients were included in this double-blind randomized controlled trial. All patients received spinal anesthesia for surgery and single-dose LIA during the operation. An ultrasound-guided saphenous nerve catheter was placed postoperatively in the adductor canal at midthigh level. Patients were randomized into 2 groups to receive 15-mL boluses of either ropivacaine 7.5 mg/mL or saline twice daily for 2 postoperative days.

RESULTS

Worst pain scores during movement on the day of surgery were significantly lower in the ropivacaine group (median [range] visual analog scale, 3 [0-7] vs 5.5 [0-10]; P < 0.050), as well as pain at rest (visual analog scale, 2 [0-8] vs 4 [0-8]; P = 0.032). Breakthrough pain occurred later in the ropivacaine group (10.5 [range, 0.5-48] hours vs 3.4 [range, 0.5-24] hours; P = 0.011). All patients in the ropivacaine group were able to ambulate on the day of surgery versus 13 patients in the control group (P = 0.004). Fewer patients had sleep disturbance on the first postoperative night in the ropivacaine group (P = 0.038). We found no differences in morphine consumption.

CONCLUSIONS

The combination of a saphenous nerve block with single-dose LIA offered better pain relief on the day of surgery than LIA alone.