Assessment of movement workspace
Although the used movement workspace in the tested device has the shape of a cube instead of the anatomical spherical shape the findings were found to be related to clinical outcomes. Klopčar et al. [22] and Robinson et al. [23] describe the clinical relevance of the movement workspace when assessing shoulder function. Klopčar et al. documented the rehabilitation progress of a subject with a frozen shoulder with a 3D arm-reachable workspace [22]. Robinson objectively quantified a three-dimensional
reachable workspace of subjects with tetraplegia using an eight camera opto-electronic system [23]. The workspace volume can be easily calculated from the data provided by the Armeo device and be followed over time to document changes during the course of rehabilitation.
The movement workspace is a multiple joint measure and does not assess the maximal shoulder movement capacity in a single direction as assessed in a single joint range-of-motion measurement. However, the reliability information from this more functional movement seems to be very good compared to, for example, single joint goniometry measurements of the shoulder. Reliability studies for goniometry measurements in the shoulder have a large intra- and inter-rater variability in results. Hayes et al. [27] tested 17 subjects with shoulder pathology with different methods. The inter-rater reliability for the shoulder goniometry was ICC = 0.64-0.69 and for the intra-rater reliability ICC = 0.53-0.65. Better results were found in healthy subjects which had an ICC = 0.83-0.96 (inter-rater) and ICC = 0.74-0.94 (intra-rater) [28] and in a group with subjects with and without shoulder pathology, who had an ICC = 0.36-0.91 (inter-rater) and ICC = 0.76-0.94 (intra-rater) [29]. In these studies the reliability of goniometry measurements was also largely dependent on the specific movement direction.