Saturday, September 29, 2018 9:00 am–10:00 am Impact of Adult Deformity Correction: 262. The effect of surgical alignment on gait complexity in adult deformity patients: a neuromuscular synergy approach

Abstract

BACKGROUND CONTEXT Adult degenerative scoliosis (ADS) patients frequently suffer from impairments in mobility. Surgical intervention for ADS mostly improves gait, balance and other health-related quality of life scores. Previous literature demonstrates that the central nervous system (CNS) might use an organization of muscle synergies to control a wide range of activities, for example walking. Instead of controlling each muscle individually, the CNS groups the muscles and activates many them with a single control signal. Hence, neuromuscular synergies may indicate the ability of the CNS in generating independent control signals. Less number of muscle synergies during walking emphasizes inability of the CNS to generate as many independent control signals. The higher number of synergies represents the higher gait complexity since more number of control inputs are required to achieve the same task. PURPOSE To compare number of walking muscle synergies in ADS patients both before and 3 months postsurgery. STUDY DESIGN/SETTING A prospective concurrent control cohort study. PATIENT SAMPLE A total of 13 ADS patients. OUTCOME MEASURES Gait complexity by number of muscle synergies. METHODS Clinical gait analysis was performed one week prior and 3 months postsurgery. Five walking trials were performed at comfort speed. Surface electromyography (EMG) electrodes were placed and recorded bilaterally from 16 trunk and lower extremity muscles: external oblique, gluteus maximus, multifidus, erector spinae, rectus femoris, semitendinosus, tibialis anterior, medial gastrocnemius. EMG data was collected at 2,000 Hz, filtered, rectified, and normalized. The processed EMG was mathematically broken into synergies and their activation ratio (from 100%). The higher number of synergies always reduces the residual error between the reconstructed EMG and the original EMG. The required number of synergies were defined as the minimum number of synergies that could reconstruct EMG signals with subtracting 5% error ([EMGoriginal -EMGreconstructed] = e, e/EMGoriginal RESULTS Clinical gait analysis was performed one week prior and 3 months postsurgery. Five walking trials were performed at comfort speed. Surface electromyography (EMG) electrodes were placed and recorded bilaterally from 16 trunk and lower extremity muscles: external oblique, gluteus maximus, multifidus, erector spinae, rectus femoris, semitendinosus, tibialis anterior and medial gastrocnemius. EMG data was collected at 2,000 Hz, filtered, rectified and normalized. The processed EMG was mathematically broken into synergies and their activation ratio (from 100%). The higher number of synergies always reduces the residual error between the reconstructed EMG and the original EMG. The required number of synergies were defined as the minimum number of synergies that could reconstruct EMG signals with subtracting 5% error {(EMGoriginal -EMGreconstructed) = e, e/EMGoriginal CONCLUSIONS This study shows an increase in gait complexity by increase in number of synergies following a surgical alignment in ADS patients. More number of synergies postsurgery shows a more elaborate gait pattern since more number of synergies (modules) are required to rebuild the EMG signals, in addition to improvements in ability of the CNS in generating more number of independent or rich control signals. As an example, inability of poststroke patients in generating independent control signals for gait makes their CNS to activate numerous muscles with a single signal (at the same time), causing unwanted co-contractions that hinders their normal gait. We recommend that spine care providers use gait analysis as part of their clinical evaluation to provide an objective measure of function and to better understand the effects of the disease and its treatment on their patients’ gait, function, and, ultimately, quality of life. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.