Forward gait instability in patients with Parkinson's disease with freezing of gait

Freezing of gait (FOG) appears to be associated with increased risk of forward falls in patients with Parkinson's disease (PD). This study aimed to experimentally validate forward gait instability in PD patients with FOG (PD + FOG). Eleven PD + FOG patients, 9 PD patients without FOG (PD - FOG), and 13 healthy controls participated. Self-selected paced gait was analyzed by a three-dimensional motion-capture analysis system. We assessed the distance between the center of mass and the base of support (COM-BOS distance) and the margin of stability (MOS), considering the position and velocity of the COM as gait stability parameters, spatiotemporal gait parameters and kinematic parameters. The anteroposterior COM-BOS distance was smaller in PD + FOG patients than in PD-FOG patients and controls. Anteroposterior MOS was larger in PD + FOG and PD - FOG patients than controls (p < 0.05). PD + FOG patients showed smaller anteroposterior MOS than PD - FOG patients, when adjusting for disease severity (p < 0.05). Only in the PD + FOG group, when adjusting for disease severity, step length was positively correlated with the anteroposterior COM-BOS distance (p < 0.05), and cadence was negatively correlated with the anteroposterior MOS (p < 0.05). These results indicated that PD patients with FOG have forward gait instability and suggested that such instability may be associated with reduced step length and increased cadence.