Ultrasound-guided genicular nerve blocks following total knee arthroplasty: a randomized, double-blind, placebo-controlled trial

Introduction Local anesthetic blockade of the genicular nerves, known targets of radiofrequency ablative techniques for knee pain, has not previously been studied in a randomized controlled trial evaluating acute pain after knee arthroplasty. We hypothesized that genicular nerve blockade added to an existing block regimen in total knee arthroplasty would result in a reduction in 24 hours opioid consumption. Methods Patients (American Society of Anesthesiologists 1-3, aged 18-85 years) undergoing primary total knee arthroplasty were randomized to receive single-injection nerve blocks of the superolateral, superomedial, and inferomedial genicular nerves with injectate (15 mL 0.25% bupivacaine and 2 mg dexamethasone or 15 mL saline placebo). All subjects received a standard oral analgesic regimen, spinal anesthetic with 12.5 mg isobaric bupivacaine, infiltration between the popliteal artery and capsule of the knee with 0.2% ropivacaine, and postoperative adductor canal perineural infusion with 0.2% ropivacaine. The primary outcome was 24 hours opioid consumption (measured in morphine milliequivalents). Results Forty (40) subjects were enrolled. Opioid consumption at 24 hours was significantly lower in the BLOCK group compared with the SHAM group (23 +/- 20 vs 58 +/- 35, p<0.001), and this difference remained significant at 48 hours (50 +/- 40 vs 98 +/- 56, p=0.004). Pain scores were reduced in the BLOCK group at time 6 hours (2.6 +/- 1.9 vs 4.3 +/- 2.2, p=0.012), but were otherwise similar at remaining time points. Patient satisfaction at 24 hours and 20 m walk test times were similar between groups. Discussion Genicular nerve blockade was associated with a reduction in opioid consumption at 24 hours in primary total knee arthroplasty patients.