## 4 Discussion
Intervention in the humerothoracic joint should be carried out and particular attention should be paid to the scapulothoracic motion. MIMUs seem able to measure the scapular angles and the scapulohumeral rhythm quickly and reliably, contributing to the study of the kinematics of the shoulder complex quickly, reliably, and objectively and revealing possible changes based on the therapeutic intervention. Of course, an EMG of the muscles responsible for scapular dyskinesia could be of interest. Different findings have been reported on this issue, but there are still conflicting conclusions due to heterogenous muscle impairment in stroke patients (spasticity/flaccidity, impingement, etc.) [3]. The electromyographic evaluation of the scapular muscles should be performed in association with a kinematics assessment to investigate scapula dyskinesia to identify spastic muscles [36]. The significant reduction in the anterior-posterior tilt at a 60\({}^{\circ}\) and 90\({}^{\circ}\) arm abduction and at maximum arm flexion (versus the non-paretic and control from the literature [29]) that we report likely reflects an increase in the scapular anterior tilt. It is possible that increased scapular anterior tilt during abduction and flexion could be a consequence of increased muscular recruitment of the trapezius [37]. [PERSON] et al. found that during maximum flexion, there is an altered activation of the lower trapezius and infraspinatus to compensate for the altered activation of the serratus anterior and to correct the scapulothoracic movement [9]. During abduction, the middle deltoid and upper trapezius of stroke patients also have an altered pattern [4]. This has been interpreted as compensation for reduced deltoid force [38] during active glenohumeral abduction. In the literature, it was reported that impaired muscle recruitment of the trapezius, serratus anterior, and rhomboids in stroke patients [3; 39] could lead to greater scapular internal rotation (in particular, in the anterior serratus and the middle and lower trapezius) and greater scapular anterior tilt (in particular, in the upper trapezius) [8; 37]. As a consequence, scapular malalignment is responsible for alterations in biomechanics with reduced active and passive glenohumeral RoM [40]. scapular movements in other directions did not seem to differ between the paretic and non-paretic sides, even if the small number of subjects in this study must be taken into account. Additionally, pain can explain possible scapular dyskinesia and abnormal shoulder motion, as previously demonstrated [12; 13]. In the current study, only one patient reported shoulder pain, although without particular restriction of movement. Therefore, it was not possible to form a conclusion. Our results might have clinical relevance since, while the FMA gives a general overview of upper limb mobility, the instrumental assessment with the protocol used can provide specific information on scapular movement, which has the greatest impact on the altered humeral rhythm so as to provide indications for specific rehabilitation. In stroke patients, alteration of recruitment and control of the periscapular muscles (rhomboid muscles, serratus anterior, trapezius, pectoralis muscles, levator scapulae, and lattissimus dorsi) lead to changes in the position and movement of the scapula, which are defined as dyskinesia [41]. It is involved in the onset of instability and pain of the hemiplegic shoulder (incidence 16-84%) [42]. Preventing or reducing shoulder dysfunction is very important for rehabilitation. This can be attained via an instrumental assessment. The value of the present pilot study in stroke patients is in the feasibility of the use of a validated and reliable wearable system and software to test shoulder scapulothoracic and glenohumeral 3D kinematics, including SHR assessment. The small sample of patients, the lack of a matched control group, and the missing data on scapulothoracic and scapulohumeral value at rest are limitations of this study, making these findings non-generalizable.