Return to Play After an Anterior Cruciate Ligament Injury: Prioritizing Neurological and Psychological Factors of the Decision-Making Algorithm

The reorganization that results in movement planning, transitioning from subcortical levels to cortical levels, is a phenomenon that researchers believe can lead to deficiencies even as the athlete has returned to sport. Grooms et al⁷²revealed in a case report that a subject with an ACLR showed higher levels of activity in the crus region of the cerebellum. This area contains corticobulbar and corticospinal tracts that transmit neural input to maintain balance and coordination.⁷³ These changes in the cerebellum, combined with increased motor cortex activity, are thought to be indicative of a global neural strategy that uses higher levels of the CNS, as opposed to subcortical processing.⁷²

The current research makes a clear and compelling argument for the importance of CNS reorganization after an ACL injury, placing increased reliance on higher cortical levels of control, as well as the visual system to coordinate balance and movement. It is thought that this reorganized method of neural transmission can then become imprinted within the CNS, if not corrected.^35,74 If this is the case, then traditional strength programs may not be sufficient to restore these connections to their pre-injury level. If the CNS has the ability to reorganize based on the aberrant input that it receives from the periphery, then it also certainly has the potential to adapt to more specific structured input via the ascending afferent pathways.^41,45 The rehabilitation program, however, needs to be structured specifically to target the reorganized regions of the brain. There needs to be an emphasis on rehabilitating not only the peripheral neuromotor structures but also the CNS.⁷⁵

CENTRAL NERVOUS SYSTEM REHABILITATION PRINCIPLES

For a neurological rehabilitation to be successful, the interventions need to be repetitive and task-specific, involve learning, employ whole and part practice, and transition from using an internal to an external focus of control.⁷⁶Movements that are repetitive, but which lack structured learning and skill, have been shown to have no effect on inducing neuroplastic changes in the primary motor cortex.^77,78 However, using neurological rehabilitation techniques that facilitate the acquisition of new motor skills by the CNS have been shown to cause neuroplastic adaptation in the motor cortex.^79-85 This occurs because neuroplasticity is determined by experience and practice.⁷⁸ The CNS operates on cues received in the ascending tracts by mechanoreceptors in the joint. If a new movement pattern is being learned by the athlete, then this new afferent input received from the periphery will start to initiate reorganization in the higher learning centers. If this occurs with optimal repetition and precision, then a positive reorganization can take place within the CNS that results in a higher percentage of motor planning and control being filtered down to a subcortical level. Essentially, the movements become instinctive, which is crucial in athletics, where attention in higher cortical areas is frequently diverted to external aspects of the competition and not solely used to focus on movement.

This is why shifting neurological rehabilitation from an internal focus of control to an external focus of control is paramount. While using an internal focus of control is required early in rehabilitation to enable the athlete to understand the specific tasks required in a composite movement, a gradual transition to an external focus of control is necessary as the athlete begins to perform tasks that are more soccer-specific. This autonomous stage of motor learning is crucial because it transfers the burden of motor planning from higher to lower levels of the CNS and frees up the pre-SMA and primary motor cortex to handle more complex patterns.^58,86-88

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