The relationship between spinal alignment and activity of paravertebral muscle during gait in patients with adult spinal deformity: a retrospective study

Abstract

Background: Spinal alignment in patients with adult spinal deformity (ASD) changes between rest and during gait. However, it remains unclear at which point the compensated walking posture breaks down and how muscles respond. This study used time-synchronized electromyography (EMG) to investigate the relationship between dynamic spinal alignment and muscle activity during maximum walking duration to reveal compensation mechanisms.

Methods: This study collected preoperative three-dimensional gait analysis data from patients who were candidates for corrective surgery for ASD from April 2015 to May 2019. We preoperatively obtained dynamic spinal alignment parameters from initiation to cessation of gait using a motion capture system with time-synchronized surface integrated EMG (iEMG). We compared chronological changes in dynamic spinal alignment parameters and iEMG values 1) immediately after gait initiation (first trial), 2) half of the distance walked (half trial), and 3) immediately before cessation (last trial).

Results: This study included 26 patients (22 women, four men) with ASD. Spinal sagittal vertical axis distance during gait (SpSVA) increased over time (first vs. half vs. last, 172.4 ± 74.8 mm vs. 179.9 ± 76.8 mm vs. 201.6 ± 83.1 mm; P < 0.001). Cervical paravertebral muscle (PVM) and gluteus maximus activity significantly increased (P < 0.01), but thoracic and lumbar PVM activity did not change. Dynamic spinal alignment showed significant correlation with all muscle activity (cervical PVM, r = 0.41-0.54; thoracic PVM, r = 0.49-0.66; gluteus maximus, r = 0.54-0.69; quadriceps, r = 0.46-0.55) except lumbar PVM activity.

Conclusion: Spinal balance exacerbation occurred continuously in patients with ASD over maximum walking distance and not at specific points. To maintain horizontal gaze, cervical PVM and gluteus maximus were activated to compensate for a dynamic spinal alignment change. All muscle activities, except lumbar PVM, increased to compensate for the spinal malalignment over time.

Keywords: Adult spinal deformity; Dynamic spinal parameters; Gait analysis; Integrated EMG; Paravertebral muscle.

Fig. 1

Reflective markers (white circle), electrodes (shaded squares) placement, and oval-shaped course. a) Markers and electrodes in the front. Electrodes: a, Quad. b) Markers and electrodes in the back. Electrodes: b, cervical PVM; c, trapezius m.; d, thoracic PVM; e, lumbar PVM; f, Gmax. c) Oval-shaped course. Gait analysis was conducted only for the straight part of the course. Quad quadriceps muscle, PVM paravertebral muscle, Gmax gluteal maximum muscle

Fig. 2

a. SpSVA was defined as the distance between the plumb lines (dotted lines) from C7 and S1 markers. b. SpSA was defined as the angle between the plumb line from the S1 marker (the dotted line) and the line connecting C7 and S1 markers (the green line). c. SpPSA was measured as the angle between the plumb line (the orange line) to the pelvic surface (the white solid line) and the line connecting C7 and S1 markers (the green line). The pelvic surface was created by bilaterally connecting the ASIS and the PSIS. All angles were projected from three-dimensional angles to a 2D sagittal surface. SpSVA spinal sagittal vertical axis distance, SpSA spinal sagittal angle, SpSVA spinal sagittal vertical axis distance, ASIS anterior superior iliac spine, PSIS posterior superior iliac spine

Fig. 3

a. SpSVA increased significantly over time during walking. b. SpSA increased significantly over time during walking. c. SpPSA increased significantly between half and last trials. SpSVA spinal sagittal vertical axis distance, SpSA spinal sagittal angle, SpSVA spinal sagittal vertical axis distance. *; P < 0.001 in repeated-measure ANOVA analysis between first, half and last trial. **; P < 0.001 in post hoc analysis between each group. ***; P < 0.05 in post hoc analysis between each group

Fig. 4

These figures indicate each muscle’s iEMG change over time during walking. The red line indicates the right side (R), and the green line indicates the left side (L). a. Cervical PVM. b. Trapezius muscle. c. Thoracic PVM. d. Lumbar PVM. e. Gmax. f. Quad. iEMG integrated electromyography, PVM paravertebral muscle, Gmax gluteus maximus, Quad quadriceps. †; P < 0.05 in repeated-measure ANOVA analysis between first, half, and last trials. ††; P < 0.05 in repeated-measure ANOVA analysis for iEMG of the right Gmax

Fig. 5

The correlation coefficients between SpSVA and each muscle at first, half, and last trials. Cervical PVM, thoracic PVM, Gmax, and Quad showed moderate correlations with SpSVA. SpSVA spinal sagittal vertical axis distance, PVM paravertebral muscle, C cervical PVM, T thoracic PVM, L lumbar PVM, Gmax gluteus maximus muscle, Quad quadriceps muscle, n.s. not significant indicating P > 0.05 in Pearson correlation coefficients

Fig. 6

The correlation coefficients between SpSA and each muscle at first, half, and last trials. Cervical PVM, thoracic PVM, Gmax, and Quad showed moderate correlations with SpSA. SpSA spinal sagittal angle, PVM paravertebral muscle, C cervical PVM, T thoracic PVM, L lumbar PVM, Gmax gluteus maximus muscle, Quad quadriceps muscle, n.s. not significant indicating P > 0.05 in Pearson correlation coefficients

Fig. 7

The correlation coefficients between SpPSA and each muscle at first and half trials. Cervical PVM, thoracic PVM, Gmax, and Quad showed moderate correlations with SpPSA, but the correlation between Quad and SpPSA was not significant in the last trial. SpPSA spinal-pelvic sagittal angle, C Cervical PVM, T Thoracic PVM, L Lumbar PVM, Gmax gluteus maximus muscle, Quad quadriceps muscle, n.s. not significant indicating P > 0.05 in Pearson correlation coefficients