Funding for this research was provided by:
AO Foundation (No. AR2011_4)
Received: 6 February 2018
Accepted: 10 May 2018
First Online: 21 May 2018
Ethics approval and consent to participate
: The study was approved by the independent ethical committee of the medical council of Saxony-Anhalt, Germany, and confirmed under approval no. 63/17.
: All patients involved in this study gave their consent for the anonymized data to be used for scientific purposes and published in a scientific journal. The signed consent forms are stored at the database of the AO Research Institute, Davos.
: The authors declare that they have no competing interests.
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