Dynamic Alignment Changes of the Spine, Pelvis, and Lower Limbs during Gait Analyzed Using Inertial Motion Capture in Patients with Adult Spinal Deformity

Introduction: Patients with adult spinal deformity (ASD) lean forward with their trunks when walking, even if they can remain upright during static standing. However, it remains unclear which part of the spinal column is involved in forward trunk tilt and the details of the relationships between sagittal alignment during static standing and changes in dynamic parameters during walking. Therefore, this study aimed to clarify the above by analyzing the walking motion of ASD patients using inertial measurement units (IMUs). Methods: Preoperative ASD patients were included in this study. Dynamic parameters during gait were measured by IMUs attached on the skin at the T1, T12, and S1 spinous processes, thigh, and lower leg. Walking data were divided into three phases of 10 s each (initial, middle, and final), and the average dynamic parameters at each phase were statistically compared. The relationships between the standing radiographic and dynamic parameters in the final phase were evaluated by linear regression analyses. Results: A total of 34 patients were included in this study. Their mean age was 72 years. The inclination of IMUs on the T1, T12, and S1 and the flexion angle of T12-S1 IMUs significantly increased over time. Pelvic tilt (PT) of standing radiography was positively correlated with the inclination angles of T12 (r2=0.22, p=0.0048) and S1 (r2=0.16, p=0.0178) and the flexion angle of T12-S1 IMUs (r2=0.29, p=0.0011). Conclusions: This study showed that anteversion of the trunk in patients with ASD is due to an increase in lumbar forward bending and anterior tilt of the pelvis. Lumbar forward bending was significantly correlated with PT on standing radiography. It is important to consider the presence of poorer posture during gait than during standing when we evaluate patients with high PT.