Combining Neurocognitive and Functional Tests to Improve Return-to-Sport Decisions Following ACL Reconstruction

Abstract

SYNOPSIS: Neuroplasticity after anterior cruciate ligament (ACL) injury alters how the nervous system generates movement and maintains dynamic joint stability. The postinjury neuroplasticity can cause neural compensations that increase reliance on neurocognition. Return-to-sport testing quantifies physical function but fails to detect important neural compensations. To assess for neural compensations in a clinical setting, we recommend evaluating athletes' neurocognitive reliance by augmenting return-to-sport testing with combined neurocognitive and motor dual-task challenges. In this Viewpoint, we (1) share the latest evidence related to ACL injury neuroplasticity and (2) share simple principles and new assessments with preliminary data to improve return-to-sport decisions following ACL reconstruction. J Orthop Sports Phys Ther 2023;53(8):1-5. Epub: 16 May 2023. doi:10.2519/jospt.2023.11489.

Keywords: ACL; fMRI; functional magnetic resonance imaging; knee; motor control/learning; neural control; neuroimaging; neuroscience.

FIGURE 1.

Cognitive and motor reserve modulates neural compensation. Postinjury neuroplasticity and associated neural compensations may not directly cause neurocognitive reliance but be mediated through the athlete’s cognitive and motor reserve. Bottom left figure: Healthy brain activity for knee motor control prior to ACL injury (left side: sensorimotor control regions) and post-ACLR (right side: cognitive and cross-modal neural activity) to represent neural compensation. Top figure: We hypothesize that recovery and observed neurocognitive reliance is contingent on the available cognitive and motor reserves for each athlete (variable due to individual capability). Athlete 1 has less cognitive and motor reserve than Athlete 2 (yellow bar shading). Thus, the influence of neural compensation (red bar shading) would more readily manifest as higher neurocognitive reliance in Athlete 1 relative to Athlete 2 with more reserves and able to accommodate for the neural compensations associated with injury. Bottom right figure: We propose that clinicians evaluate the degree of neurocognitive reliance via integrated neurocognitive and motor assessments (eg, dual-task cost [DTC] with >10% performance decrease). High neurocognitive reliance may indicate lingering effects of neural compensation that may be a liability upon return to sport.

FIGURE 2.

Progressive neurocognitive return-to-sport criteria. Progress RTS testing to capture physical capacity, patient-reported function, and neurocognitive reliance. Once a patient achieves symmetry or sufficient performance on standard physical measures, they are progressed to similar tests under a neurocognitive challenge (calculating dual-task cost). The same approach to adding neurocognitive demand applies for on-the-field and sport-specific testing once an athlete is in later stages of rehabilitation. Athletes who perform poorly during the added neurocognitive challenges may be sufficiently recovered and ready to return to sport. Abbreviations: ACL-RSI, Anterior Cruciate Ligament Return to Sport Index; COD, change of direction; IKDC, International Knee Documentation Committee patient-reported outcome; RSI, reactive strength index; SLHD, single-leg hop distance.

FIGURE 3.

Neurocognitive testing battery. Exemplar tests with evidence supporting reliability and psychometric properties.^,,, While research is ongoing to validate for RTS assessment to reduce secondary injury risk or improve patient outcomes, their addition carries little additional risk and provides additional sport readiness information. Tests build on previously established functional performance tests to provide a meaningful dual-task cost in addition to metrics of neurocognitive ability (reaction or response time, online working memory, gaze control, visual-spatial attention).