Abstract
BACKGROUND:
Postoperative pain control is an important factor in determining recovery in total knee arthroplasty (TKA).The aim of the study was to assess the efficacy of 4 sessions of transcranial direct current stimulation (tDCS) over primary motor cortex (M1) in patients undergoing unilateral TKA.

MATERIALS:
Fifty patients undergoing TKA were included in the study. They were divided randomly into two groups (25 patients for each, using closed envelopes): real tDCS (2 mA, 20 min, with anodal stimulation applied over M1 postoperative for 4 consecutive days) and sham tDCS. Opioid consumption was titrated by an anaesthesiologist during the study period and was used as primary outcome. As a secondary outcome, patients were evaluated using Visual Analogue Scale (VAS) and Leeds Assessment of Neuropathic Symptoms and Signs Pain Scale (LANSS) at baseline, then the 1st, 2nd, 3rd and 4th days after operation.

RESULTS:
There was no significant difference between real and sham tDCS in any rating scales at baseline. The opioid consumption and LANSS scores decreased more in patients who received real tDCS over the course of the treatment than sham tDCS. Real tDCS was associated with 59% reduction in the titrated analgesia. There was no significant difference between groups (time × groups interaction) in the VAS.

CONCLUSION:
Since the VAS was constant, repeated sessions of anodal tDCS over M1 with an extra-cephalic cathodal electrode can achieve the same degree of analgesia with less opioid consumption over the postoperative days after TKA. Thus, tDCS is a promising tool in the field of postoperative analgesia.

SIGNIFICANCE:
The data of the present study suggest that four sessions of transcranial direct current brain stimulation over motor cortex could reduce morphine consumption and pain perception during the postoperative period in total knee arthroplasty.

TRIAL REGISTRATION:
ClinicalTrials.gov NCT02704182.