Evaluation of dynamic spinal alignment changes and compensation using three-dimensional gait motion analysis for dropped head syndrome

Abstract

Background context: Dynamic kinematic evaluation of spino-pelvic alignment during gait using three-dimensional (3D) motion analysis has been proposed for adult spinal thoracolumbar deformity. That is because conventional full-spine radiographs cannot be used to evaluate dynamic factors. However, dynamic changes in spino-pelvic alignment during gait for dropped head syndrome (DHS) have not been studied using this approach.

Purpose: This study aimed to assess the dynamic changes in spinal-pelvic alignment during gait in patients with DHS using 3D motion analysis.

Study design: Retrospective review of collected radiographic and kinematic data.

Patient sample: Nineteen DHS patients with neck pain and/or anterior gaze disturbance.

Outcome measures: Static spino-pelvic radiological alignment, dynamic spino-pelvic kinematic parameters and electromyogram (EMG) data.

Methods: Center of gravity of the head - C7 sagittal vertical axis (CGH-C7 SVA), C2-C7 SVA, T1 slope; cervical lordosis (CL), C7SVA, thoracic kyphosis (TK), lumbar lordosis (LL), pelvic tilt (PT) and pelvic incidence (PI) were assessed using full-spine radiographs in a standing position to assess static spino-pelvic alignment. The 3D gait motion analysis was conducted during gait. Dynamic kinematic parameters were divided into spinal segments: cervical (C-), thoracic (T-), lumbar (L-) and pelvis (P-). Each spinal segment coronal angle to the pelvic angle, each spinal segment sagittal angle to the pelvic angle and pelvic sagittal angle to the horizontal axis were assessed as dynamic spino-pelvic kinematic parameters. Trunk and lower limb muscle activity during gait were assessed using wireless surface EMG analysis. Dynamic spino-pelvic kinematic variables and muscle activity were compared between the first walking lap and the final lap during gait analysis. The change in dynamic kinematic parameters was correlated with static radiological alignment and electromyographic muscular activity change.

Results: Cervical and thoracic anterior tilt increased significantly after an extended period of walking, indicating that dropped head worsened during gait. An increase of cervical anterior tilt during walking was significantly associated with decreased muscle activity in the cervical paraspinal muscles (r=-0.463, P<.05) and latissimus dorsi (r=-0.763, p<.01). Furthermore, significant correlations were found between a change in thoracic sagittal angle to pelvic angle and C7SVA (r=0.683, p<.01) and LL (r=-0.475, p<.05). This means that a larger C7SVA and smaller LL were associated with increased thoracic anterior tilt during gait.

Conclusions: The 3D motion analysis for DHS showed that cervical and thoracic anterior tilt significantly increased after extended walking, resulting in worsening of dropped head. Decreased muscle activity of the neck extensor muscles during gait suggests insufficient neck extensor muscle endurance, which was associated with increased cervical anterior tilt. A greater increase in the thoracic anterior tilt during gait was found in DHS patients with a larger C7SVA and smaller LL due to insufficient thoracolumbar compensation for the dropped head. Correction of the cervical spine alone would not be sufficient to improve dropped head in cases with increased thoracic anterior tilt during gait. The results suggest that C7SVA and LL are crucial parameters in the surgical strategy for DHS.

Keywords: Dropped head syndrome; Electromyogram; Gait analysis; Radiographic analysis; Spino-pelvic alignment; Three-dimensional motion analysis.