Abstract
BackgroundPrinciples of brain plasticity is used in the treatment of patients with functional limitations to improve sensorimotor function. Training is included in the treatment of knee injury to improve both patient-reported function and sensorimotor function. However, impairment in sensorimotor function often persists despite training. Therefore, it was suggested that training programs need to be more effective to improve sensorimotor function after knee injury. The aim of the current study was to investigate if principles of brain plasticity that have been successfully used on the hand and foot to improve sensorimotor function can be applied on the knee. We hypothesized that temporary anesthesia of the skin area above and below the knee would improve sensorimotor function of the ipsilateral knee and leg.MethodsIn this first double-blind exploratory study, 28 uninjured subjects (mean age 26 years, range 19–34, 50% women) were randomized to temporary local cutaneous application of anesthetic (EMLA®) (n = 14) or placebo cream (n = 14). Fifty grams of EMLA, or placebo, was applied on the leg 10 cm above and 10 cm below the center of patella, leaving the area around the knee without cream. Measures of sensory function (perception of touch, vibration sense, knee kinesthesia) and motor function (knee muscle strength, hop test) were assessed before and after 90 minutes of treatment with EMLA or placebo. The paired t-test was used for comparisons within groups and the independent t-test for comparisons between groups. The number of subjects needed was determined by an a priori sample size calculation.ResultsNo statistically significant or clinically relevant differences were seen over time (before vs. after) in the measures of sensory or motor functions in the EMLA group or in the placebo group. There were no differences between the groups due to treatment effect (EMLA vs. placebo).ConclusionWe found no effect of temporary cutaneous anesthesia on sensorimotor function of the ipsilateral knee and leg in uninjured subjects. The principles used in this study remain to be tested in subjects with knee injury.
Highlights
Principles of brain plasticity is used in the treatment of patients with functional limitations to improve sensorimotor function
Sensory function before and after treatment with EMLA or placebo No differences were found between assessments for perception of touch, vibration sense, or kinesthesia in the EMLA group
There were no differences between the groups in effects of treatment for the measures of sensory function (Table 2)
Summary
Principles of brain plasticity is used in the treatment of patients with functional limitations to improve sensorimotor function. Longitudinal, prospective studies show that poor muscle function, such as muscle weakness, is a predictor of OA development [9,10,11] In this perspective, treatment leading to improved sensorimotor function would be of value for patients with knee injury or OA in the short and long term. One of the most interesting questions in neuroscience concerns the manner in which the nervous system can modify its organization and its function throughout an individual's lifetime based on sensory input, experience, learning and injury[12,13] This phenomenon is often referred to as brain plasticity [14,15]. Long-term changes are typically seen weeks or months after an injury or intervention and are based on increase or decrease in synaptic transmission or axonal and dendritic sprouting. Plasticity changes include changes in nerve signal amplitude and activation of additional cortical areas [14,15]
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