Effectiveness of continuous versus single injection femoral nerve block for total knee arthroplasty: A double blinded, randomized trial.

BACKGROUND: Effective analgesia following total knee arthroplasty (TKA) is important for maximizing patient satisfaction, early participation in physical therapy and reducing the hospital stay. This trial compared continuous catheter femoral nerve block (cFNB) to single injection femoral nerve block (sFNB) in terms of analgesia, opioid consumption, and participation in physical therapy and associated side effects.

METHODS: This randomized, double blinded trial was conducted in a non-university hospital setting, without major changes to anesthesia or surgical clinical pathways. A total of 85 patients scheduled for primary TKA were randomized to receive either cFNB (n=44) or sFNB (n=41). All patients had FNB with 0.5% ropivacaine bolus followed by subarachnoid block for surgery. Postoperatively, 0.2% ropivacaine infusion was commenced in cFNB group and a sham catheter was taped to the skin in sFNB group. All patients received a structured multimodal analgesia regimen throughout hospital stay. The primary outcomes were peak resting visual analogue scale (VAS) scores and morphine consumption at 48h postoperatively.

RESULTS: VAS scores (Mean difference 0.25, 95% Confidence Interval (CI) -0.56 to 1.06; [P=0.196]) and morphine consumption (Mean difference 0.95mg, 95% CI -9.99 to 11.89; [P=0.863]) were not significantly different among patients who received cFNB versus sFNB at 48h. There was no difference in hospital stay (P=0.517) or long-term functional recovery between the two groups (P=0.385).

CONCLUSIONS: sFNB block provides equal pain relief compared with cFNB, after TKA with no significant difference in opioid consumption, hospital stay, physical therapy outcomes or associated side effects.