The Prolonged Analgesic Efficacy of an Ultrasound-Guided Single-Shot Adductor Canal Block in Patients Undergoing Total Knee Arthroplasty

In this prospective, randomized, placebo-controlled study, the authors compared the analgesic efficacy of the single-shot adductor canal block (SS-ACB) vs the continuous adductor canal block (C-ACB) with intermittent boluses during the 72-hour postoperative period. Seventy-five patients randomly received the following: a single shot of 20 mL of 0.5% ropivacaine preoperatively followed by intermittent saline boluses at 12 hours and 24 hours postoperatively (SS-ACB group); 20 mL of 0.5% ropivacaine preoperatively and 12 hours and 24 hours postoperatively (C-ACB group); or saline preoperatively and postoperatively (control group). The primary outcome was visual analog scale pain scores with movement on postoperative day 1. The dynamic pain scores of the 2 ACB groups were equivalent and were lower than those of the control group on postoperative day 1. Compared with the control group, the 2 ACB groups were less likely to use opioids on the operative day and the first 2 postoperative days. The patients in the control group and the C-ACB group exhibited less quadriceps muscle strength than those in the SS-ACB group on postoperative day 1. The time required for an SS-ACB was markedly shorter than that required for an indwelling adductor canal catheter. Further, each adductor canal catheter cost $80. Patients who received a single block reported more satisfaction with their pain-relief treatment. Given the similar analgesic effect but better quadriceps muscle strength, easier execution, and higher patient satisfaction, the SS-ACB may be more suitable for total knee arthroplasty patients than the C-ACB.