Summary

Preoperative adductor canal block improves immediate postoperative pain in ACL reconstruction patients but offers no long-term benefit for pain control or opioid consumption beyond 24 hours.

Abstract

Introduction

There are no consensus guidelines for perioperative pain management in anterior cruciate ligament reconstruction (ACLR) surgery. The adductor canal block (ACB) is a motor-sparing alternative to femoral nerve block, with studies showing no difference in postoperative opioid consumption or pain. Few randomized studies have assessed its efficacy beyond the immediate postoperative period. The aim of this study was to compare the efficacy of a single preoperative ACB versus no block on postoperative pain control following ACLR. We hypothesized that ACB would reduce pain and opioid use without affecting functional outcomes.

Methods

This was a prospective, randomized controlled trial of all adult patients undergoing primary ACLR at a single academic institution from 2018-2024. Patients were randomized to receive either ACB or no block (NB) preoperatively. All patients received a standardized preoperative regimen (400mg celecoxib, 300mg gabapentin, and 1000mg acetaminophen). The surgical team was blinded to the treatment intervention. Patients given hydromorphone were excluded from the study. All patients completed the Brief Resilience Scale (BRS) the day of surgery and scores were stratified into low, normal, or high resilience groups. Intraoperative fentanyl morphine equivalent doses (MED), postoperative visual analogue scale (VAS) pain level and MEDs were assessed in the post-anesthesia care unit (PACU) after 15 minutes and daily through 10 days postoperatively. Knee Injury and Osteoarthritis Outcomes Scores (KOOS) were completed at 6 and 12 weeks postoperatively.

Results

50 patients were analyzed (ACB, n=25; NB, n=25), with no differences in demographics or surgical characteristics. The cohort consisted of a young patient population (ACB mean age = 24.6, NB mean age = 23.6, p=0.39). The ACB group had a lower mean BRS (3.70 vs 4.11, p=0.02), though both groups remained within the “normal resilience” range. Intraoperative fentanyl MEDs were similar (2.48 vs 2.45, p=0.91). PACU VAS scores were significantly lower in the ACB group at 15 minutes postoperatively (3.40 vs 5.62, p<0.01), but no difference was noted from the time of discharge onwards (3.64 vs 4.24, p=0.24). VAS scores remained comparably low at 5 days (3.49 vs 3.70, p=0.70) and 10 days (3.06 vs 3.22, p=0.80) in both groups. No differences were seen in MED requirements in the PACU (18.08 vs 28.70, p=0.04), at 24 hours (33.28 vs 43.18, p=0.20), 5 days (58.16 vs 87.86, p=0.08), or 10 days (64.25 vs 84.10, p=0.28) postoperatively. No differences were observed in KOOS at 6 or 12 weeks.

Conclusions

The addition of a preoperative ACB to a multimodal, non-opioid pain medication regimen improved immediate postoperative pain in ACLR patients, but these effects dissipated by 24 hours, offering no long-term benefit for pain control or opioid consumption.