Background and Objectives Adductor canal blocks (ACBs) are associated with improved analgesia, preserved quadriceps strength, and decreased length of hospitalization after total knee arthroplasty (TKA). However, controversy remains regarding the ideal location of a continuous block within the adductor canal, and it remains unclear whether similar clinical benefits are obtained irrespective of block location. In this randomized, double-blind, noninferiority study, we hypothesized that a continuous proximal ACB provides postoperative analgesia that is no worse than a continuous distal ACB.
Methods Subjects presenting for unilateral TKA were randomized in a 1:1 ratio to either a continuous proximal or distal ACB group. The primary outcome of this noninferiority study was opioid consumption within the first 24 hours following surgery. Secondary outcomes included quadriceps strength, pain scores, distance ambulated, and patient satisfaction.
Results Seventy-three subjects, 36 from the proximal group and 37 from the distal group, completed the study per protocol. The intention-to-treat analysis demonstrated a cumulative mean intravenous morphine equivalent consumption difference between the proximal and distal groups of −7.2 mg (95% confidence interval, −14.8 to 0.4; P < 0.001), demonstrating noninferiority of the proximal approach. The per-protocol analysis yielded similar results: −6.2 mg (95% confidence interval, −14.1 to 1.6; P < 0.001). No secondary outcomes showed statistically significant differences between the proximal and distal groups.
Conclusions This study demonstrates that a continuous proximal ACB offers noninferior postoperative analgesia compared with a distal continuous ACB in the first 24 hours after TKA.
Clinical Trial Registration ClinicalTrials.gov (NCT02701114).
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Author Contributions: A.W.M. helped design the study, conduct the study, analyze the data, and write the manuscript. D.B.A. helped design the study, conduct the study, analyze the data, and write the manuscript. S.C.Y. helped conduct the study, analyze the data, and write the manuscript. S.L. helped conduct the study, analyze the data, and write the manuscript. J.M.F. helped conduct the study, analyze the data and write the manuscript. N.A.H. helped design the study, conduct the study, analyze the data, and write the manuscript.
This research was supported by the Department of Anesthesiology at Virginia Mason Medical Center (Seattle, WA) and the Wilske Center for Translational Research (Benaroya Research Institute, Seattle, WA).
D.B.A. has received research funding and honoraria from SonoSite and honoraria from Halyard Health, but this funding was in no way related to the research presented here. The other authors declare no conflict of interest.