Prospective, Double-Blind, Randomized Study to Evaluate Single-Injection Adductor Canal Nerve Block Versus Femoral Nerve Block: Postoperative Functional Outcomes After Total Knee Arthroplasty.

BACKGROUND AND OBJECTIVES: Despite multiple clinical trials comparing the adductor canal block (ACB) with femoral nerve block (FNB) for total knee arthroplasty, none looked at the aforementioned nerve blocks from early functional results to up to 6 months after surgery.

METHODS: For this prospective, double-blind, randomized, single-center trial, we enrolled 98 patients set to undergo total knee arthroplasty. The patients were randomized, with 93 patients included in the intention-to-treat analysis. Subjects received injections of both ACB and an FNB, with 1 containing 30 mL of saline (placebo) and the other 30 mL of local anesthetic (treatment) depending on randomization. Adductor canal block and FNB were compared using percentage of baseline maximum voluntary isovolumetric contraction (MVIC) of the quadriceps muscle retained at 6 (primary endpoint), 24, and 48 hours and 6 months postoperatively. Secondary endpoints also included Timed Up and Go, range of motion, 6-minute walking test, pain score, and postoperative pain medication use.

RESULTS: Percent MVIC retained was significantly higher in ACB patients at 6 (P < 0.0001) and 24 hours (P < 0.0001). Comparing Timed Up and Go results yielded significant difference between treatment groups at 6 hours (P = 0.0213) and 24 hours (P = 0.0424). Pain scores, pain medication intake, range of motion, and 6-minute walking test were not significantly different between the treatment groups. A linear relationship exists between the change in quadriceps MVIC and pain score in the ACB group, with increasing pain leading to a decreased MVIC (P = 0.0039).

CONCLUSIONS: The ACB showed better preservation of quadriceps muscle strength and improved ambulation in the first 24 hours postoperatively without compromising pain control.