Continuous Adductor Canal versus Continuous Femoral Nerve Blocks:Relative Effects on Discharge-Readiness following Unicompartment Knee Arthroplasty
Sztain JF, Machi AT, Kormylo JN,, Abramson WB, Madison SJ, Monahan AM, Khatibi B, Nakanote KA, Sessler DI, Ball ST, Gonzales FB, Mascha EJ, You J, and Ilfeld BM. From the University of California at San Diego
Following unicompartment knee arthroplasty, a continuous femoral nerve block affords analgesia, but also weakens the quadriceps femoris muscle and is associated with an increased falling risk [1,2]. A continuous adductor canal block induces less quadriceps weakness . Yet, remaining unknown is its relative effects on readiness-for-discharge criteria such as the ability to ambulate independently.
Material and methods
Subjects were randomized to either an adductor canal or femoral perineural catheter (2-day ropivacaine 0.2% infusion). The primary outcome was the time to attain four discharge criteria: (1) adequate analgesia; (2) independence from intravenous opioids; (3) ability to independently stand, walk 3 meters, return and sit down; and (4) independently ambulate 30 meters.
Subjects with an adductor canal catheter (n=15) reached all four criteria in a median [interquartile] of 35 [24-43] hours, compared with 40 [27-69] hours for those with a femoral catheter (Wilcoxon rank sum test: P=0.46; Log-rank test: P = 0.16). However, the percentages of subjects (adductor canal : femoral) who reached the two mobilization criteria were 27%:0% on POD 0, 93%:53% on POD 1, and 100%:73% on POD 2 (Fig. 1). In contrast, femoral catheters provided superior analgesia at rest during POD 0 and 1 (Fig. 2.). Relatedly, subjects with femoral catheters required less supplemental opioid analgesics within the post-anesthesia care unit, although there was little difference between groups for this criterion following recovery room discharge (Fig. 2). Due to the large advantages in mobilization and relatively smaller analgesia-related disadvantages, 100% of subjects with adductor canal catheters met all four discharge criteria by POD 2 vs. only 73% with a femoral catheter. Actual hospitalization duration was also shortened, with 60% of the adductor canal group being discharged home by the second postoperative day versus only 46% of the femoral group.
Following unicompartment knee arthroplasty, a continuous adductor canal block decreased the time to achieve adequate mobilization for discharge. In contrast, a continuous femoral nerve block decreased the time to achieve adequate analgesia. However, because the advantage in mobilization for adductor canal infusions was far greater than the analgesic benefits of femoral infusions, a higher percentage of subjects with an adductor canal catheter met all four discharge criteria by POD 2. Due to the limited sample size of this pilot study, all results must be considered preliminary and require confirmation with a subsequent clinical trial.
1. Ilfeld. Pain 2010;150:477
2. Ilfeld. A&A 2010;111:1552
3. Jaeger. RAPM 2013;38:526