A novel summary kinematic index for postural characterization in subjects with Parkinson's disease

Parkinson's disease (PD) is a progressive neurological disorder characterized, among other symptoms, by a significant modified posture. Although a detailed assessment of postural abnormalities can be performed using quantitative movement analysis, the output of such procedure might be not suitable for a routine clinical use due to its intrinsic complexity. However, synthetic measures may facilitate the interpretation of kinematic data for physicians and thus make such tools fully exploitable in daily practice.

According to these considerations, the aim of the present study is to propose a new summary index, the Postural Profile Score (PPS, together with its constituent variables: Postural Variable Scores [PVSs]), which can characterize the postural kinematic biomechanical profile of an individual; this approach was then applied to a cohort of individuals with PD.

Controlled observational study.

Movement Analysis Laboratory of Hospital.

Forty-five individuals with PD in mild to severe disability stage, of mean age 65.9 (SD 8.3) years and 21 healthy control age-matched (CG) were tested using an optoelectronic system during bipedal quiet standing.

Twelve joint angles of trunk and of lower limbs, considered representative of the whole-body posture according to Davis protocol, were acquired and the root mean square (RMS) difference between them and those of the unaffected participants (PVSs) were computed. Then, the PPS was calculated as a combination of the selected PVSs. The existence of possible differences between people with PD and controls for PPS and PVSs was assessed using MANOVA test. UPDRS III score was also considered in order to assess existence of correlation between synthetic indexes and Clinical scales values.

Significant differences in PPS were detected between PD and CG (8.59° vs. 6.11°, P<0.001) and in some of the considered PVS (Trunk Sagittal, Trunk Frontal, Trunk Transversal, Hip flexion-extension, Hip abdo-adduction and Knee flexion-extension). Significant positive correlations were found between Clinical scales Vs trunk and ankle orientation.

PPS could represent a reliable summary index of global postural abnormalities in people with PD, and in particular some PVSs appear more suitable to describe the deviation from a physiologic postural pattern. The results demonstrate that the posture in the patient with PD is modified compared to the control group. In particular, the trunk is the body district which mainly characterizes the alteration of the posture as documented by its PVSs values and their correlation with clinical evaluation scales. In conclusion, this study evidences the interest to measure the position of the trunk in order to characterize the postural kinematic position in individuals with PD.

PPS could be a useful tool for the characterization of postural phenotype in subjects with Parkinson's disease and could provide indications for specific rehabilitation protocols.