Adult spinal deformity is associated with reduced muscle synergies.

Abstract

This study aimed to investigate differences in muscle synergies during gait between individuals with adult spinal deformity (ASD) and healthy controls and to assess whether fear of falling influences this. Muscle synergies represent modular neural strategies by which the central nervous system simplifies motor control through combinations of basic muscle activation patterns. A reduction in synergies may indicate decreased neuromuscular adaptability and has been linked with impaired gait. 59 individuals with ASD and 17 age- and sex-matched controls were recruited. Surface electromyography of four bilateral trunk and three bilateral lower-limb muscles was recorded. Muscle synergies were extracted via non-negative matrix factorization at a threshold of 95% variance accounted for. Fear of falling was evaluated using the Falls Efficacy Scale-International. Participants were stratified into deformity subgroups using radiographic criteria (decompensated sagittal, compensated sagittal, and coronal malalignment). Ordinal logistic regression assessed the fear of falling, BMI, pain, and subgroups in relation to synergy count. ASD participants exhibited fewer synergies (χ² = 14.08, p < 0.001) compared to controls. Regression analysis revealed that BMI and deformity subgroups were significantly associated with synergy count, while fear of falling was not, potentially due to its correlation with BMI. Participants with decompensated sagittal alignment had significantly fewer synergies than both those with coronal malalignment and healthy controls. ASD participants had higher FES-I scores than controls (p < 0.001). Individuals with ASD demonstrate a simplified neuromuscular control during gait. The deformity subgroups and BMI were associated with synergy count. The elevated fear of falling underscores the need for targeted fall-related interventions in this population.