**5. Conclusions**

RSA is a very good and reliable treatment option with low complication rates for proximal humerus head-split fractures in the older patient population. Patients who sustain a head-split fracture due to high-impact trauma have greater biological and regenerative potential that can lead to more promising outcomes. Comminution or multifragmentation of the articular face presents as a prognostic indicator for significantly poorer outcome.

**Author Contributions:** Conceptualization, J.-P.I., U.B. and M.S.; methodology, J.-P.I., U.B. and M.S.; formal analysis, T.I.; investigation, J.-P.I.; data curation, M.S., U.B.; writing—original draft preparation, J.-P.I.; writing—review and editing, U.B., F.F., D.E., M.S.; visualization, J.-P.I., T.I.; supervision, M.S. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research received no external funding. **Institutional Review Board Statement:** The study was conducted according to the guidelines of the Declaration of Helsinki and approved by the Institutional Review Board (or Ethics Committee) of Charité—Universitaetsmedicine Berlin (EA1/167/18; date of approval: 11 November 2018) and Ludwig-Maximilians-Universitaet Muenchen (22-0178; date of approval: 6 April 2022).

**Informed Consent Statement:** Informed consent was obtained from all subjects involved in the study.

**Data Availability Statement:** Data available on request due to ethical restrictions. The data presented in this study are available on request from the corresponding author. The data are not publicly available.

**Acknowledgments:** The authors thank M. Wilhelmi, (medical writer at Schulthess Clinic) for manuscript proofreading.

**Conflicts of Interest:** J.-P.I., T.I., F.F. and D.E. declare no conflict of interest. M.S. and U.B. are consultants for Stryker Corporation.
