A Quantitative Kinematic Evaluation of Postural Response in Parkinson's Disease Subtypes

This study aimed to develop a practical and objective measure of postural instability in movement disorder patients using kinematic measurements of the pull test. This study focused on patients with Parkinson's disease (PD) without postural instability (PI) compared with PD patients with postural instability (classified as PIGD (Postural Instability Gait Disorder)), and control subjects. Inertial measurement units were used to capture kinematic data during pull tests performed by a trained clinician. The kinematic data obtained from each pull test were analyzed and aggregated. The center of mass profile was found to effectively differentiate between patient groups. The patients with postural instability exhibited an increase in center of mass and number of steps and a decrease in step length. The groups could be differentiated based on the relationship between step length, center of mass and number of steps. This suggests that a quantitative pull test can provide kinematic metrics that are useful for measuring PI in patients with PD. In summary, this study demonstrated the potential of using kinematic measurements from a purposefully varied pull test as quantitative biomarkers for diagnosing, monitoring, and assessing the therapeutic outcomes of postural instability in patients with movement disorders.