Adductor canal block performed 20 hours after total knee arthroplasty to improve postoperative analgesia and functional recovery: a double-blind randomized controlled clinical trial.

Background: The goal of postoperative pain protocols in total knee arthroplasty (TKA) is to get pain free patients throughout severe pain period without impairing walking ability. The aim of the study was to investigate if an adductor canal block performed 20 hours after TKA, in patients treated with systemic analgesia and intraoperative local infiltration anesthesia (LIA), improves postoperative pain and functional outcomes.

Methods: A prospective randomized, double-blinded controlled study was conducted. One hundred eighty-three patients undergoing primary TKA were randomized to receive either a sham block or an adductor canal block with 20 mL of ropivacaine 0.5%. The primary outcome was resting and dynamic pain scores using the Numerical Pain Rating Scale (NPRS). Secondary outcomes included opioid rescue requirements, quadriceps and adductor muscle strength, patient ability for ambulation and complications.

Results: Two hours after the block, in adductor canal block group NPRS was significantly lower at rest (1 [0-2] vs. 3 [2-5], P<0.001) and with mobilization (5 [3-6] vs. 6 [5-8], P<0.001), and quadriceps strength was significantly higher (3.7 [2.7-6] vs. 3 (1.7-4.9), P=0.023). The differences were not maintained beyond 24 hours post-block. In the first 24 hours the percentage of patients with tramadol requirements was lower in the adductor canal block group (36 [38.3] vs. 52 [58.4], P=0.006). Other secondary outcomes were similar between groups. There were no patient falls.

Conclusions: An adductor canal block done 20 hours after total knee arthroplasty reduces pain and opioid requirements without increasing the risk of falls. An optimal pain control, especially at movement was not achieved.