Background: Periarticular injections (PAIs) and adductor canal blocks (ACBs) are widely accepted pain management strategies for total knee arthroplasty (TKA); however, the optimal anesthetic concentration to provide adequate pain relief while avoiding toxicity remains controversial. The purpose of this study is to evaluate the efficacy of different anesthetic concentrations for PAI alone and in combination with ACB.
Methods: This retrospective cohort study of patients undergoing primary TKAs between January 2019 and November 2020 included 3 groups: 0.25% PAI (50 cc of 0.25% bupivacaine PAI diluted with 50 cc of saline and ketorolac), 0.5% PAI (50 cc of 0.5% bupivacaine with 50 cc of saline and ketorolac), and PAI + ACB (ultrasound-guided preoperative anesthesiologist-administered ACB and 0.25% PAI).
Results: In total, 368 TKAs were analyzed (123 0.25%, 132 0.5%, and 113 PAI + ACB). Total overall hospital narcotic usage in oral morphine equivalents (OME) was significantly lower for the 0.5% group (120.09 vs 165.26 and 175.75) compared to the 0.25% and PAI + ACB groups, respectively (P < .0001). Cumulative OME for the first 3 shifts was also lower for 0.5% (68.7 vs 83.7 and 76.4) compared to the 0.25% and PAI + ACB groups, respectively (P = .030). Total postoperative narcotics in OME were significantly lower for 0.5% (617.9 vs 825.2 and 1047.6) than 0.25% and PAI + ACB, respectively (P = .0003). Number of prescriptions within 6 weeks postoperatively were also significantly lower for 0.5% (1.7) than 0.25% (2.1) and PAI + ACB (2.4) (P = .0003).
Conclusion: Patients receiving 0.5% PAI had lower narcotic usage compared to 0.25% PAI or PAI + ACB. ACB may be eliminated without compromising pain control if the dose of local anesthetic in the PAI is sufficiently high.
Keywords: adductor canal block; narcotic usage; pain control; periarticular injection; total knee arthroplasty (TKA).
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