Summary

Intraoperative adductor canal block is the gold standard for postoperative nerve blocks in TKA. Recent description of an intraoperative technique has proven to be safe but not been tested compared to the standard ultrasound guided block. In a randomized blinded control trial we found no difference regarding pain management and motor activity between both techniques.

Abstract

Introduction

Total knee arthroplasty (TKA) is a successful alternative to treat late-stage knee osteoarthritis (OA). Adductor canal blocks (ACB) have been proposed as an alternative of reducing opioid consumption and decreasing postoperative pain. Standard ACB block is performed under ultrasound guidance after surgery completion, still in the operating room (OR). Recent literature has shown the anatomic feasibility of intraoperative ACB via blunt suprapatellar dissection in standard medial parapatellar TKA approach. We sought to determine the effectiveness of standard ultrasound guidance ACB compared with intraoperative ACB following TKA.

Materials And Methods

Randomized controlled trial, recorded in Clinical Trials. Inclusion criteria were (I) age older than 50 years; (II) primary, unilateral TKA; and (III) indication of TKA due to late-stage OA. Sequence of randomization was blinded and we generated a closed envelop for each patient. The OR nurse prepared two seemingly identical syringes, giving one to the surgeon for intraoperative nerve block and the other to the anesthetist for post-operative ultrasound guided nerve block. Patients could be randomly determined to two groups: intraoperative nerve block with bupivacaine (15 ml of 0.25% bupivacaine), and post-operative ultrasound saline solution (15ml of 0,9% NaCl) injection (intraoperative group); or intraoperative saline solution injection (15ml of 0,9% NaCl) and post-operative ultrasound guided bupivacaine (15 ml of 0.25% bupivacaine) nerve block (ultrasound group).
We measured pain using a visual analog scale every 4 hours during the first 24 hours, PCA requests during the first 24 hours, length of stay and time up and go results at 24 hours post-surgery. Normally distributed data is expressed as mean (and standard deviation), while non-parametric data is shown as median (and interquartile range). We studied the association of group assignment with all demographic data and outcome variables using chi-square or Fisher's exact test in categorical variables, and Student’s T test or Wilcoxon’s ranked test for continuous outcomes.

Results

We prospectively enrolled 80 patients, 40 in the intraoperative group and 40 in the ultrasound-guided group. We found no difference regarding sex (76% vs 86% females respectively, p 0.24), age (68.6 vs 67.6 years old respectively, p 0.54) nor time of surgery (104 vs 101.2 minutes respectively, p 0.57). Regarding our main outcome, morphine consumption did not differ between both groups, with a mean consumption of 11.5mg in 24 hours in the intraoperative group, and 12.9mg in 24 hours in the ultrasound-guided group (p=0.72). Additionally, patients did not report a difference in postoperative pain, as the area under the VAS pain scale did not differ between both groups (32.5 vs 35.9 respectively, p 0.67; figure 2B and 2C). The measurement of physical therapy performance using the time and go measurement found no differences among both groups (median of 79 vs 70 seconds; p 0.73).

Conclusions

ACB has proven to deliver optimal analgesia for patients following TKA. The development of an intraoperative alternative could lead to a breakthrough for health centers that do not have access to this kind of procedure.