Popliteal plexus block in total knee arthroplasty: a single-center randomized controlled double-blinded trial.

Introduction: Whether a popliteal plexus block improves postoperative pain following total knee arthroplasty remains debated. This randomized trial tested if adding a popliteal plexus block to a continuous femoral nerve block decreases postoperative opioid requirement.

Methods: We included 66 patients undergoing total knee arthroplasty. 32 received continuous femoral nerve block and popliteal plexus block (intervention), and 34 received continuous femoral nerve block alone (control). The primary endpoint was the 12-hour postoperative morphine-equivalent consumption (mg). Secondary outcomes included opioid consumption, Visual Analog Pain Score (0-10), and sensorimotor extension of the block in postanesthesia care unit, at 12 hours, 24 hours and 48 hours postoperatively.

Results: 66 patients with a median body mass index of 28.7 (IQR 26.3-33.8) were included in the study. In an intention-to-treat analysis, the median 12-hour morphine-equivalent consumption was lower in the intervention group (6.1 mg (0.5-14.5) vs 10 mg (5.0-17.3); one-sided Wilcoxon test (p=0.04)). The average pain intensity experienced in postanesthesia care unit was lower in the intervention group (median: 3.0 (3.0-5.0) vs 2.0 (1.0-4.0), two-sided Wilcoxon p=0.01) and fewer patients reported lateroposterior pain of the knee (11 (34.4%) vs 21 (61.8%) p=0.03). These benefits disappeared after 24 hours. The median duration of the popliteal plexus block procedure was 5.0 min (2.0-5.0).

Conclusions: Adding a popliteal plexus block to a continuous femoral nerve block decreases 12-hour opioid utilization, but the effect size is small, calling into question its clinical relevance.

Trial registration number: NCT04048889.