Femoral nerve blockade versus local infiltration analgesia for primary knee arthroplasty. Randomised controlled trial

Introduction
Total knee arthroplasty (TKA) is associated with severe postoperative pain and significant chronification. The lengthy debate is on-going regarding the best balance between pain management, safety, and functional rehabilitation.

Material and methods
Fifty adult patients scheduled for primary unilateral TKA were randomly divided into 2 groups: continuous femoral nerve blockade (FNB; n = 25) and local infiltration analgesia (LIA; n = 25). We compared FNB and LIA in terms of function (primary outcome; number of steps, recorded using a step-tracking watch), pain scores using the visual analogue scale (VAS), opioid consumption (morphine equivalents), muscle strength (Janda Score), side effects, and complications until postoperative day 5. The results are presented as (mean ± SD).

Results
After excluding one patient, 49 were analysed (25 FNB, 24 LIA). There were no differences between the groups in the primary outcome. The VAS score (day 0: 23 ± 17.7 vs. 32.8 ± 21.5; P = 0.101; day 1: 31.0 ± 22.3 vs. 41.7 ± 25.3; P = 0.112) and mean opioid consumption (day 0: 0.39 ± 0.17 vs. 0.50 ± 0.38; P = 0.655; day 1: 0.60 ± 0.27 vs. 0.71 ± 0.38; P = 0.406) did not differ significantly between the groups. Muscle strength was significantly lower in the FNB group on days 0 (3.05 ± 1.67 vs. 4.35 ± 0.91; P = 0.009) and 1 (2.71 ± 1.57 vs. 3.67 ± 1.18; P = 0.030). Side effects and complications had a similarly low incidence in both groups, and except for constipation (FNB < LIA) no difference was seen.

Conclusions
Based on the results of this study, both FNB and LIA are associated with similar outcomes, and one cannot be recommended over the other.