Comparison of Adductor Canal Block Before Versus After Total Knee Arthroplasty in Terms of Pain, Stress, and Functional Outcomes: A Double-Blinded Randomized Controlled Trial.

Background: Whether an adductor canal block (ACB) is more effective when administered before or after total knee arthroplasty (TKA) is unclear. This study compared pain, stress, and functional outcomes between patients who received the block before surgery and those who received the block after surgery.

Methods: In this double-blinded trial, 100 patients at our hospital were randomized to receive an ACB at either 30 minutes before general anesthesia or postoperatively in the post-anesthesia care unit (PACU). All patients received periarticular local infiltration analgesia during surgery. The 2 groups were compared with respect to the primary outcome, the postoperative consumption of morphine as rescue analgesia, and in terms of the secondary outcomes, including the time from the end of surgery to the first rescue analgesia or discharge, intraoperative and postoperative stress, postoperative pain, functional recovery, the incidence of chronic pain, and complications.

Results: All included patients were Asian (Chinese) in race/ethnicity. The 2 groups had similar demographic information. Compared with the postoperative ACB, the preoperative ACB was associated with significantly lower morphine consumption within the first 24 hours postoperatively and lower total morphine consumption. It was also associated with a longer time until the first rescue analgesia, lower intraoperative consumption of opioids and inhaled anesthetic, fewer episodes of hypertension during surgery, a lower rate of rescue analgesia in the PACU, lower levels of cortisol and adrenocorticotropic hormone in serum on the morning of postoperative day 1, lower pain on a visual analog scale while at rest or during motion within 12 hours postoperatively, better range of knee motion on postoperative day 1, and a lower incidence of chronic pain at 3 months postoperatively. The 2 groups did not differ significantly with respect to postoperative ambulation distance, time until discharge, or complication rates.

Conclusions: Administering an ACB before rather than after TKA may lead to lower opioid consumption during hospitalization, lower intraoperative and postoperative stress responses, better pain relief during hospitalization, and a lower incidence of chronic pain at 3 months postoperatively.

Level of evidence: Therapeutic Level I. See Instructions for Authors for a complete description of levels of evidence.