Neuroplasticity Associated With Anterior Cruciate Ligament Injury

Whereas three percent of amateur athletes injure their anterior cruciate ligament (ACL) each year, this percentage can be as high as 15% in elite athletes. Because the ACL contains mechanoreceptors it directly influences the neuromuscular control of the knee. ACL deficiency leads to partial deafferentiation which, in turn, alters spinal and supraspinal motor control.

Return to sports following ACL injuries is mostly decided based on time since surgery; however, this decision process produces unsuccessful outcomes; e.g. high re-injury rates or athletes not being able to return to their pre-injury sport levels. The rate of return to preinjury play levels for non-professional pivoting athletes for example is 65%. A recent evidence-based clinical update revealed that it is currently unclear whether there is a benefit of supervised physical therapy rehabilitation compared to home-based rehabilitation or no rehabilitation at all, and comparisons between 19-week with 32-week rehabilitation programmes show no differences in terms of laxity, range of motion, knee function, or measures of leg muscle strength. Evidence-based guidelines suggest practitioners should generally follow a moderate recommendation, which means that the benefits of treatment exceed the potential harm; however, the quality/applicability of the supporting evidence is not as strong. Many rehabilitation programs currently target biomechanical factors; e.g. muscle strength, balance and plyometric function, and consider to a rather lesser extend cognitive or neurological components.

Brain activation for knee flexion/extension motion alters following ACL reconstruction. The brain activation profile following ACL reconstruction may indicate a shift toward a visual-motor strategy as opposed to a sensory-motor strategy to engage in knee movement. This recent research evidence suggests that rehabilitation protocols for ACL reconstruction should additionally be considering neurocognition and its role in movement, neuromuscular control, and injury risk to help improve intervention effectiveness.

However, there is a lack of evidence concerning the feasibility of implementing neurocognitive exercise interventions in a primary rehabilitation program aimed at restoring function following ACL injury. New treatments usually have to go through a series of phases to test whether they are safe and effective before larger scale studies and application in clinical practice are to be considered. The aim of this pilot study was to perform a phase II trial according the model for complex interventions advocated by the British Medical Research Council to test the feasibility and effects of a conventional ACL injury rehabilitation program with added neurocognitive training in a group of ACL injured individuals. This study aims to: (1) compare ACL injured individuals with non-injured individuals, (2) develop an exercise intervention based on research literature theory and to deliver it to ACL injured individuals, (3) evaluate the feasibility of the intervention and the ability to recruit and retain ACL injured individuals, and (4) assess whether the treatment has some effect on neural drive and physical performance.

The inclusion criteria for the cross-sectional study part are:

• 18- to 55-year-old subjects
• healthy or in the subacute phase (from 7 to 21 days) or in the chronic phase (≥ one year) after unilateral surgical reconstruction of complete ACL rupture, confirmed by MRI in the medical record and by the surgical procedure.

The exclusion criteria for the cross-sectional study part are:

• not healthy
• bilaterally previous diagnoses in the medical record, such as neuropathic pain in the lower limb, lumbosacral radiculopathy, saphenous nerve entrapment, meralgia paresthetica, fractures, rheumatoid or systemic conditions, other surgeries, post-surgery complications (i.e., thrombosis or osteomyelitis), belonephobia, legs length difference in the lower limb (>0.5 cm) [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5413255/].

The inclusion criteria for the longitudinal study part are:

• 18- to 55-year-old subjects, in the subacute phase (from 7 to 21 days) after unilateral surgical reconstruction of complete ACL rupture, confirmed by MRI in the medical record and by the surgical procedure.

The exclusion criteria for the longitudinal study part are:

• bilaterally previous diagnoses in the medical record, such as neuropathic pain in the lower limb, lumbosacral radiculopathy, saphenous nerve entrapment, meralgia paresthetica, fractures, rheumatoid or systemic conditions, other surgeries, post-surgery complications (i.e., thrombosis or osteomyelitis), belonephobia, legs length difference in the lower limb (>0.5 cm) [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5413255/].