Correct positioning of the calcar screw leads to superior results in proximal humerus fractures treated with carbon-fibre-reinforced polyetheretherketone plate osteosynthesis with polyaxial locking screws.

"Declarations Ethics approval and consent to participateThe study was approved by the local ethics committee of the University of Mannheim/Heidelberg, Germany. Written informed consent was obtained from all patients. The ethics approval number is 2019-755N. The conducted experiments respect the ethical standards in the Helsinki Declaration of 1975, as revised in 2000, as well as the national law. Consent for publicationAll subjects have been informed about the open access publication of this work. A declaration of informed consent to publication was signed by each subject. Competing interestsLars-Johannes Lehmann and Christian Gerhardt are consultants for Arthrex and DJO. Michael Kimmeyer, Jonas Schmalzl, Verena Rentschler and Arno Macken have no competing interest to disclose. The research foundation received financial payments from Fa. Arthrex (Munich, Germany) for the conduct of this study. Competing interests Lars-Johannes Lehmann and Christian Gerhardt are consultants for Arthrex and DJO. Michael Kimmeyer, Jonas Schmalzl, Verena Rentschler and Arno Macken have no competing interest to disclose. The research foundation received financial payments from Fa. Arthrex (Munich, Germany) for the conduct of this study."

"Funding The research foundation received financial payments from Fa. Arthrex (Munich, Germany) for the conduct of this study. The authors and their immediate families did not receive any financial payments or other benefits from any commercial entity related to the subject of this article."