Objective assessment of postural instability in Parkinson’s disease under dynamic conditions

Abstract Postural instability is considered one of the most incapacitating motor symptoms and a primary cause of falls in Parkinson’s disease (PD), compromising the autonomy and well-being of people suffering from this condition. Usually, the clinical examination used to evaluate this symptom is the pull test since it does not require any instruments and is easy to perform. However, this test is difficult to standardize and is not sensitive to subtle but significant changes. Recent studies have shown that inertial measurement units constitute a portable and cost-effective solution to measure postural sway, which provides metrics sensitive to balance disorders as postural instability. Further studies are required to monitor patients’ postural conditions and implement an adequate treatment to improve postural stability, it is crucial to quantify balance under dynamic conditions. Hence, the proposed research focused on investigating the hypothesis of whether it is possible to differentiate between all the scores of the pull test through postural and gait metrics extracted from raw acceleration and angular velocity signals from the center of mass of patients with PD acquired while performing basic day-to-day tasks. A cross-sectional study was followed, including 23 patients, and the achieved results showed that most of the estimated metrics can differentiate the pull test scores (ρ-value≤0.048, R 2 ≥0.513). Overall, satisfactory results were achieved as the statistical analysis revealed gait and postural metrics estimated under dynamic conditions were considered relevant to distinguish between the scores of the pull test.