Corticospinal and intracortical excitability in individuals with anterior cruciate ligament injury and ligament reconstruction: a meta-analysis

ABSTRACT

Background

Primary motor cortex (M1) organization and quadriceps femoris excitability may change after anterior cruciate ligament injury (ACLi) and anterior cruciate ligament reconstruction (ACLr), as demonstrated by transcranial magnetic stimulation (TMS) studies.

Objective

To systematically review studies evaluating changes in quadriceps femoris corticospinal and intracortical excitability in subjects with ACLi and ACLr.

Methods

Database searches were conducted in PubMed, Embase, Scopus, and ScienceDirect, with the last search performed on November 23, 2023. Newcastle-Ottawa Scale and a specific checklist for evaluating descriptions in studies using TMS assessment were used. Continuous variables were expressed as mean and standard deviation and represented by the estimated difference from the mean and 95% confidence interval (CI). Heterogeneity was assessed by Chi² and I² and the level of statistical significance was 5%.

Results

Fourteen studies, comprising 381 individuals, using TMS were identified. Meta-analysis results showed significantly higher motor threshold (MT) in ACLi/ACLr individuals compared to healthy controls (p < .01, mean difference 6.72). Additionally, MTs were significantly higher on the uninjured side compared to healthy controls (p < .0001, mean difference 3.82). Motor-evoked potentials (MEP) amplitude was significantly higher on the uninjured side compared to the injured side (p < .00001, mean difference 0.01). Short-interval intracortical inhibition (SICI) amplitude was significantly lesser on the injured limb compared to the uninjured side (p < .00001, mean difference 0.50).

Conclusion

Quadriceps MT and SICI are altered in ACLi and ACLr populations, and minor alterations were identified in MEP, demonstrating brain changes related to anterior cruciate ligament injury and/or reconstruction.

KEYWORDS:

• Transcranial magnetic stimulation
• cortical excitability
• intracortical inhibition
• anterior cruciate ligament injuries
• anterior cruciate ligament reconstruction

Acknowledgments

AFB received a scholarship level 2 from CNPq (305539/2021-3). We thank Dr. APQC for assistance with study selection.

Disclosure statement

The authors declare that this work is not associated with any financial or other relationships that might lead to conflict of interest. All authors have participated in relevant aspects of this study. This is the first submission of this study, Abrahão Fontes Baptista (corresponding author) and it is not under simultaneous consideration by another journal.

Additional information

Funding

The author(s) reported that there is no funding associated with the work featured in this article. AFB receives a scholarship for scientific productivity from CNPq (305539/2021-3).