To measure the scapulohumeral rhythm (SHR) in outpatient settings, the motion analysis protocol named ISEO (INAIL Shoulder and Elbow Outpatient protocol) was developed, based on inertial and magnetic sensors. To complete the sensor-to-segment calibration, ISEO requires the involvement of an operator for sensor placement and for positioning the patient’s arm in a predefined posture. Since this can affect the measure, this study aimed at quantifying ISEO intra- and inter-operator agreement. Forty subjects were considered, together with two operators, A and B. Three measurement sessions were
completed for each subject: two by A and one by B. In each session, the humerus and scapula rotations were measured during sagittal and scapular plane elevation movements. ISEO intra- and inter operator agreement were assessed by computing, between sessions, the: (1) similarity of the scapulohumeral patterns through the Coefficient of Multiple Correlation (CMC2), both considering and excluding the difference of the initial value of the scapula rotations between two sessions (inter-session offset); (2) 95% Smallest Detectable Difference (SDD95) in scapula range of motion. Results for CMC2 showed that the intra- and inter-operator agreement is acceptable (median 0.85, lower-whisker 0.75) for most of the scapula rotations, independently from the movement and the inter-session offset. The only exception is the agreement for scapula protraction–retraction and for scapula medio-lateral rotation during abduction (inter-operator), which is acceptable only if the intersession
offset is removed. SDD95 values ranged from 4.48 to 8.68 for the inter-operator and between 4.98 and 8.58 for the intra-operator agreement. In conclusion, ISEO presents a high intra- and inter-operator agreement, particularly with the scapula inter-session offset removed.
