Enhancing functional recovery after ACL injury. A Protocol for a Randomized Control Trial of Transcranial Direct Current Stimulation Over the Motor Cortex

Juan Vicente-Mampel¹Josep Lopez-Soler¹Pablo Sevilla-López¹Javier Ferrer-Torregrosa²Julio Martín-Ruiz³Eloy Jaenada-Carrilero¹Natalia Castillo-Dutor⁴Andrés Pascual-Leone⁵Nicolás Pascual-Leone⁶Luis Baraja-Vegas^1*Alvaro Pascual-Leone^7,8Jose Maria Tormos⁴

• ¹Department of Physiotherapy. School of Medicine and Health Science., Catholic University of Valencia San Vicente Mártir, Valencia, Spain
• ²Department of Podiatry. School of Medicine and Health Science., Catholic University of Valencia San Vicente Mártir, Valencia, Spain
• ³. Department of Health and Functional Assessment. Faculty of Sciences of Physical Activity and Sport, Catholic University of Valencia San Vicente Mártir, Valencia, Spain
• ⁴Department of Medicine. School of Medicine and Health Science., Catholic University of Valencia San Vicente Mártir, Valencia, Spain
• ⁵Vagelos College of Physicians and Surgeons, Columbia University, New York, United States
• ⁶Hospital for Special Surgery, New York, United States
• ⁷Marcus Institute for Aging Research and Wolk Center for Memory Health, Hebrew SeniorLife, Boston, United States
• ⁸Department of Neurology, Harvard Medical School, Boston, United States

Introduction: Anterior cruciate ligament (ACL) tears are common in athletic and nonathletic populations, often resulting from activities involving rapid directional changes that place stress on the knee. Although advances in surgery and rehabilitation have improved recovery, many patients still struggle to regain pre-injury performance and face increased risk of re-injury. We hypothesize that combining standard rehabilitation with transcranial direct current stimulation (tDCS) may accelerate recovery, improve neuromuscular control, and strengthen key muscles like the hamstrings and hip abductors, reducing reinjury risk. Methods/Materials: This randomized controlled trial protocol, approved by the Ethics Committee of the Catholic University of Valencia, follows a double-blind, comparative, longitudinal design per SPIRIT guidelines. Elite athletes will be randomized 1:1 into two age- and sex-matched groups: non-invasive brain stimulation (NIBS) + rehabilitation (ProtocolRHB) or sham NIBS + ProtocolRHB. The NIBS intervention uses tDCS to deliver low-intensity direct current to modulate cortical excitability. Data collection spans April 2025 to December 2027 with outcomes assessed at four postsurgical time points. The primary outcome is electromyographic (EMG) activity to evaluate muscle activation, crucial for restoring knee stability and function. Secondary outcomes include knee function (Lysholm Scale) and ACL-specific quality of life. EEG and TMS will assess cortical excitability and plasticity during voluntary muscle contraction. Impact Statement: This study integrates neurophysiology with rehabilitation, offering a novel approach to enhance functional recovery and lower reinjury risk post-ACL reconstruction, potentially informing future evidence-based sports medicine and neurorehabilitation strategies.