Flexed Truncal Posture in Parkinson Disease: Measurement Reliability and Relationship With Physical and Cognitive Impairments, Mobility, and Balance.

BACKGROUND AND PURPOSE: Flexed truncal posture is common in people with Parkinson disease (PD); however, little is known about the mechanisms responsible or its effect on physical performance. This cross-sectional study aimed to establish the reliability of a truncal posture measurement and explore relationships between PD impairments and truncal posture, as well as truncal posture and balance and mobility.

METHODS: A total of 82 people with PD participated. Truncal posture was measured in standing as the distance between vertebra C7 and a wall. Univariate and multivariate regression analyses were performed with truncal posture and impairments, including global axial symptoms, tremor, bradykinesia, rigidity, freezing of gait (FOG), reactive stepping and executive function, as well as truncal posture with balance and mobility measures.

RESULTS: The truncal posture measure had excellent test-retest reliability (ICC3,1 0.79, 95% CI 0.60-0.89, P < 0.001). Global axial symptoms had the strongest association with truncal posture (adjusted R = 0.08, P = 0.01), although the majority of the variance remains unexplained. Post hoc analysis revealed that several impairments were associated with truncal posture only in those who did not report FOG. Flexed truncal posture was associated with poorer performance of most balance and mobility tasks after adjustment for age, gender, disease severity, and duration (adjusted R = 0.24-0.33, P < 0.001-0.03).

DISCUSSION AND CONCLUSIONS: The C7 to wall measurement is highly reliable in people with PD. Global axial symptoms were independently associated with truncal posture. Greater flexed truncal posture was associated with poorer balance and mobility. Further studies are required to elucidate the mechanisms responsible for flexed truncal posture and the impact on activity.Video Abstract available for more insights from the authors (see Video, Supplemental Digital Content 1, https://links.lww.com/JNPT/A164).