Motion analysis of axial rotation and gait stability during turning in people with Parkinson's disease

• People with Parkinson's disease rotate the axial segments simultaneously during turning.
• The disrupted axial coordination suggests an excessive trunk rigidity.
• Axial rigidity in turning may slow forward progression and rise lateral instability.
• Reduced progression and increased instability contribute to turning difficulty.

BackgroundAxial rigidity and postural instability in people with Parkinson's disease (PD) may contribute to turning difficulty. This study examined the rotation of axial segments and gait instability during turning in people with PD.MethodsThirteen PD and twelve age-matched healthy adults were recruited. Participants performed the timed Up-and-Go test and were recorded by a 3D motion capture system. Axial rotation was evaluated by the rotation onset of the head, thorax and pelvis. Gait stability was evaluated by the center of mass and center of pressure inclination angle. Turning performance was evaluated by turning time and turning steps.ResultsDuring turning, PD adults rotated the head, thorax and pelvis simultaneously, whereas healthy adults rotated in a cranial to caudal sequence. Further, PD adults had a smaller sagittal inclination angle (p < 0.001) but larger frontal inclination angle (p = 0.006) than healthy adults. PD adults also turned slower (p = 0.002) with a greater number of steps (p < 0.001) than healthy adults. Last, PD adults showed a significant correlation between the sagittal inclination angle and turning steps (Spearman's ρ = −0.63), while healthy adults showed a significant correlation between frontal inclination angle and turning steps (Spearman's ρ = −0.67).ConclusionThis study demonstrated the axial rigidity in PD adults during turning may reduce forward progression and increase lateral instability. The reduced progression is associated with extra turning steps and the increased lateral instability may result in great fall risk.