Significantly Earlier Ambulation and Reduced Risk of Near-Falls with Continuous Infusion Nerve Blocks: A Retrospective Pilot Study of Adductor Canal Block Compared to Femoral Nerve Block in Total Knee Arthroplasty

Background: One option in total knee arthroplasty (TKA) perioperative pain management is femoral nerve block (FNB). Its association with quadriceps weakness has led to a focus on adductor canal block (ACB), with the aim of avoiding weakness in adjacent muscles. This study reviewed cases at our institution. Methods: In this pilot non-blinded study, nerve block (FNB or ACB) was performed under ultrasonic guidance after induction of general anesthesia, with an initial bolus followed by continuous levobupivacaine infusion into the perineurium as needed until postoperative day (POD) 2 or 3. Pain levels and falls/near-falls with knee-buckling were monitored from POD 1 to POD 3. The score on the manual muscle test, MMT (0 to 5, 5 being normal), of the patients who had been able to ambulate on POD 1, was investigated. Results: A total of 73 TKA cases, 37 FNB and 36 ACB, met the inclusion criteria. Episodes of near-falls in the form of knee-buckling were witnessed in 14 (38%) cases in the FNB group and in 4 (11%) in the ACB group (p = 0.0068). In the ACB group, 81.1% of patients were able to ambulate with parallel bars on POD 1, while only 44.4% of FNB patients could do so (p = 0.0019). The quadriceps MMT values of patients able to ambulate with parallel bars on POD 1 in the ACB group was 2.82, significantly higher than 1.97 in the FNB group (p = 0.0035). There were no significant differences in pain as measured with a numerical rating scale (NRS) through POD 3. Conclusion: Compared to FNB, ACB was associated with significantly less knee-buckling and earlier initiation of ambulation post-TKA, with better quadriceps muscle strength. These findings support the use of ACB as the anesthesia method of choice for TKA.