*Article* **Continuous Shoulder Activity Tracking after Open Reduction and Internal Fixation of Proximal Humerus Fractures**

**Michiel Herteleer 1 , Armin Runer 2,3 , Magdalena Remppis 4 , Jonas Brouwers 1 , Friedemann Schneider 2 , Vasiliki C. Panagiotopoulou 4 , Bernd Grimm <sup>5</sup> , Clemens Hengg 2 , Rohit Arora 2 , Stefaan Nijs 1,6 and Peter Varga 4, \***


**Abstract:** Postoperative shoulder activity after proximal humerus fracture treatment could influence the outcomes of osteosynthesis and may depend on the rehabilitation protocol. This multi-centric prospective study aimed at evaluating the feasibility of continuous shoulder activity monitoring over the first six postoperative weeks, investigating potential differences between two different rehabilitation protocols. Shoulder activity was assessed with pairs of accelerometer-based trackers during the first six postoperative weeks in thirteen elderly patients having a complex proximal humerus fracture treated with a locking plate. Shoulder angles and elevation events were evaluated over time and compared between the two centers utilizing different standard rehabilitation protocols. The overall mean shoulder angle ranged from 11 ◦ to 23 ◦ , and the number of daily elevation events was between 547 and 5756. Average angles showed longitudinal change <5 ◦ over 31 ± 10 days. The number of events increased by 300% on average. Results of the two clinics exhibited no characteristic differences for shoulder angle, but the number of events increased only for the site utilizing immediate mobilization. In addition to considerable inter-patient variation, not the mean shoulder angle but the number of elevations events increased markedly over time. Differences between the two sites in number of daily events may be associated with the different rehabilitation protocols.

**Keywords:** shoulder activity; sensor; rehabilitation protocol; proximal humerus fracture
