## 1 Introduction
Management of axial postural abnormalities in PD generally failed to show consistent, long-lasting improvements [14]. Considering the reversibility of these conditions, their management could be highly relevant to improving gait and balance. Indeed, a number of previous studies in the body of evidence have focused on the improvement in these parameters by targeting camptocormia and anterior trunk flexion in static conditions with several pharmacological and nonpharmacological interventions [18; 23; 24; 25; 26; 27; 28]. These included dopaminergic therapy [18], lidocaine injections [23], deep brain stimulation (DBS) [18; 24; 25], physical therapy [26; 27; 28]. Corsets and orthoses are commonly cited among the management strategies for postural abnormalities of PD, but only a few studies, with limited sample sizes and heterogeneous measurements, investigated the impact of orthoses with inconsistent results [27; 29; 30; 31; 32]. Posture can be quantitatively evaluated by different instrumental methods. To facilitate clinical application and standardize the calculation of posture degrees, the MDSTask Force Consensus recommended photograph analysis using the NeuroPostureApp, a freeware software-based measurement tool or wall goniometers [13]. Moreover, the recommendation of how to calculate the sagittal angles was provided for higher and lower postural abnormalities [12; 33]. Besides photographic analysis, other instrumental evaluations of posture are available. In particular, baropodometry allows the quantification of any postural elements, such as postural stability [9], feet morphology, and symmetry in load distribution [34]. Furthermore, X-rays and 3D stereophotogrammetry are the gold standards for the evaluation of sagittal parameters and whole-body posture in static conditions [5] and for kinematic parameters of the entire body during walking in both the healthy and neurological population [6; 35]. Several studies quantitatively evaluated the postural instability of PD patients using baropodometry [29; 36] or force plates [37; 38] in static and dynamic conditions and other ones have used X-rays and/or 3D optoelectronic system for evaluation of sagittal posture during standing [39; 40]. Other studies have investigated the typical kinematic patterns in subjects with PD [19; 41; 42; 43; 44] via 3D motion analysis. This evidence underlined the fundamental role of quantitative posture and gait evaluation to aid in diagnosis and to encourage symptom monitoring, therapy management, rehabilitation, and fall risk assessment and prevention in PD patients [42]. Regarding the use of instrumental evaluation to assess treatment efficacy, a previous study assessed the standing posture and balance of PD patients with DBS and postural abnormalities on the sagittal plane after lidocaine injection in combination with physical therapy [23]. Another study examined the effect of a back active correction keeper on balance parameters in a small sample of people with PD showing an improvement in static and dynamic balance parameters [29]. Finally, one study investigated the effect of a spinal kypho-orthosis on gait and trunk flexion reporting a short-term effect for gait performance, particularly during turning and erect posture [32]. Nevertheless, to the best of our knowledge, no study instrumentally assessed whole-body sagittal alignment in both static and dynamic conditions before and after the treatment with a spinal orthosis in PD patients with postural abnormalities on the sagittal plane as defined by the recent MDS Task Force Consensus. Therefore, the aims of the present study are the following: I) to evaluate the sagittal misalignment of PD patients in upright standing and during walking using 3D motion analysis with a specific whole-body marker set (DB-Total protocol); II) to assess the short- and long-term effects of the K1 Posture Keeper shirt on sagittal posture during static and dynamic conditions.