**3. Proprioception after shoulder arthroplasty**

By reason that the shoulder joint is balanced and centered by the rotator cuff and the glenohumeral ligaments, it can be postulated that proprioception plays an important role in the postoperative outcome and rehabilitation. However, to date there are only three studies analyzing proprioception after shoulder replacement [6, 12, 16]. Two of these studies [6, 12] have a short follow-up period, in both cases six months. Cuomo et al. [6] performed a passive and guided angle-reproduction test in 20 patients with shoulder osteoarthritis before and six months after total shoulder arthroplasty (TSA) with only one degree of freedom at a time and reported improvement of proprioception [6]. Kasten et al. [12] found out, six months after shoulder arthroplasty, proprioception remained unchanged or deteriorated, as assessed by an active and unlimited angle-reproduction test with 3D motion analysis [12]. It was assumed that this finding was most likely attributable to the relatively short rehabilitation period of six months. Therefore, the purpose of the third study by Maier et al. [16] was to examine the patients from the study described by Kasten et al. [12, 14] again three years postoperatively to find out whether proprioception changes after a longer rehabilitation period of three years. In the present study, the same active and unlimited angle-reproduction test with 3D motion analysis was used as described before [12]. The present study firstly describes the results of proprioception development in a cohort of different shoulder arthroplasties, including patients with reverse prosthesis.
