Spine kinematics in patients with Parkinson's disease with and without Freezing of Gait

Abstract

Despite the importance of spine and upper limb movements in walking, most of previous studies on human locomotion focused exclusively on lower limbs [1]. Patients with Parkinson’s disease (PD) are characterized by trunk postural alterations and reduced limb movements [2,3]. It is still unclear to what extent postural alterations in PD concur to, or counteract, poor balance [3]. Specifically, their contribution to the occurrence of freezing of gait (FoG), an episodic failure of forward stepping exposing patients to high risk of falls, is yet to be fully elucidated. We aimed at characterizing spine kinematics in PD patients with and without FoG during walking and standing. We investigated linear gait in a cohort of 14 patients with PD. They were grouped into patients with (PDF, N=6, Unified Parkinson Disease Rating Scale part III [UPDRS-III]: 35(23-49)) and without FoG (PDNF, N=7, UPDRS-III: 31(12-48)), based on their clinical history. All patients performed the experimental protocol after overnight suspension of all dopaminergic drugs (meds-off). They were instructed to perform at least three trials of barefoot walking at self-selected speed on a walkway of 8 meters. A session of quiet standing of about 60 s ended the experiment. Kinematics was monitored by means of a full body marker protocol [4]. Three markers placed on the seventh cervical vertebrae (C7), the maximum kyphosis, and a virtual marker reconstructed in correspondence of the coccyx served as reference points for the calculation of the lordosis and kyphosis spine angles. Specifically, the coccyx was reconstructed in the pelvis reference system based on previous radiography studies [5]. The distance between the C7 and the middle point between the posterior-superior iliac spines (MID-PSIS) was used to estimate the rachis length. Height of the C7 and MID-PSIS were also computed. Trunk inclination was defined as the angle between the vertical axis of the laboratory and the line connecting C7 and MID-PSIS. The shoulder-pelvis angle was computed as the angle between the line connecting the two acromion and the line connecting the anterior superior iliac spines and projected to the frontal and horizontal planes of the pelvis reference system. For the walking sessions, all variables were computed and averaged across gait cycles at steady-state velocity. For the standing sessions, variables were averaged over time. A Kruskal–Wallis test identified differences between groups for each condition (i.e., walking and standing). A Wilcoxon matched-pair test was used to compare standing and walking conditions inside each group. Threshold for statistical significance was set at 0.05. No differences between groups were found in the spine variables during standing and walking. PDF showed higher values of the shoulder-pelvis angles in the frontal plane only during the standing condition. During walking, the average height of the MID-PSIS decreased with respect to standing in both groups, while C7 height decreased selectively in the PDNF group, despite a trend was present also in the PDF group. Only PDNF patients showed increased trunk inclination during walking with respect to standing. Our analyses did not show a clear difference in the spine kinematics during gait and standing between PDF and PDNF patients. We speculate that trunk postural alterations may not be at the basis of the occurrence of FoG, but rather be compensatory (ineffective) attempts to overcome this symptom. Considering the small sample size employed in our study, further analyses on larger cohorts are warranted to confirm these preliminary results.