Authors’ contributions
B.M., T.W., S.K., and J.K. are responsible for the study design, the definition of the endpoints, and the preparation of the protocol. A.K. and E.T. are the study’s statisticians and are responsible for the sample size calculation and statistical design of the study. J.W., as the head of the surgical department, provided general support from a clinical perspective and support concerning technical aspects. All authors revised the manuscript critically and read and approved the final manuscript. As all authors are planned to substantially contribute to the conduction, data collection and interpretation of the trial, they will all be considered for authorship of the final publication with the addition of substantial contributors at the specific centres. No professional writer will be used for the final publication.