Increased foot strike variability during turning in Parkinson's disease patients with freezing of gait

Background: Turning is a common trigger for freezing episodes in patients with Parkinson's disease (PD). Freezing during turning can lead to falls and fractures and decreased quality of life.

Research question: Does foot-strike contact variability also increase during turning, as previously reported in straight gait in PD patients with Freezing of Gait (FOG)?

Methods: Subjects were instructed to walk on a gait mat, making "normal pivot" (180°) turns at each end. ProtoKinetics Movement Analysis Software (PKMAS) software was used for analysis. Video recordings and foot-pressure-prints were studied to identify and define turn segments. Spatiotemporal gait and turn measures were then determined only for the turn segments. A movement disorders neurologist determined clinical freezes.

Results: 100 subjects (28 controls, 38 noFOG and 34 FOG) were included. Compared to non-freezers (noFOG), FOG subjects had a smaller foot-strike during turning (a measure of completeness of foot contact with the mat) and increased foot-strike variability. FOG subjects also had a shorter stride-length, slower stride-velocity, and greater swing phase time and percentage during turns. After adjusting for turn direction, inner/outer leg dynamics showed heavier inner leg footsteps in FOG subjects. 38% of FOG subjects experienced freezes during turning. 69% of freezes occurred during the middle third of the turn. Turn-freezers had more severe spatiotemporal gait deficits.

Significance: Developing targeted therapies to retrain subjects to plant their whole foot on the ground with more consistency could help decrease episodes of freezing of gait.