Anodal transcranial direct current stimulation (tDCS) modulates quadriceps motor cortex inhibition and facilitation during rehabilitation following anterior cruciate ligament (ACL) reconstruction: a triple-blind, randomised controlled proof of concept trial

OBJECTIVES: Following anterior cruciate ligament reconstruction (ACLR), maladaptive changes occur in the motor cortex representation of the quadriceps, evidenced by increases in intracortical inhibition and facilitation. The primary objective of this proof-of-concept study was to determine if anodal transcranial direct current stimulation (tDCS) can alter quadriceps intracortical inhibition and facilitation in an early-ACLR population after 6 weeks of application during exercise.

METHODS: We performed a randomised, triple-blind controlled trial for proof of concept comparing anodal-tDCS to sham-tDCS following ACLR. Anodal-tDCS or sham-tDCS was delivered to the primary motor cortex for 20 min, three times per week, for 6 weeks from week 2 post ACLR. Transcranial magnetic stimulation quantified quadriceps short-interval intracortical inhibition (SICI), long-interval intracortical inhibition (LICI) and short-interval intracortical facilitation (SICF). Significance at p<0.05.

RESULTS: Participants were randomised to anodal (n=11) or sham (n=10) tDCS. Participants were predominantly male (n=13) and had a mean (SD) age of 24.4 (4.7) years. For SICI, there was a group-by-time effect for anodal-tDCS (β=0.519, 95% CI 0.057 to 0.981, p=0.028) and an effect for time (β=-1.421, 95% CI -1.919 to -0.923, p<0.001). For LICI, there was no group-by-time (β=-0.217, 95% CI -0.916 to 0.482, p=0.543) or time effect (β=0.039, 95% CI -0.815 to -0.893, p=0.928). For SICF, there was a group-by-time effect for anodal-tDCS (β=-0.764, 95%CI -1.407 to -0.120, p=0.020) but not time (β=0.504, 95% CI -0.627 to 1.635, p=0.383).

CONCLUSION: This study provided proof of the efficacy of anodal-tDCS post ACLR in reducing maladaptive quadriceps inhibition and facilitation. We demonstrated anodal-tDCS improved facilitation and inhibition post ACLR, which are drivers of arthrogenic muscle inhibition.