Author contributions
PD
FW participated in the design of the study, performed surgery, carried out data collection and abstraction, and drafted the manuscript. LE participated in the design of the study, performed surgery, carried out data abstraction and helped to draft the manuscript. RK performed statistical analysis. PD and TK conceived the study and participated in its design and coordination, performed surgery, acquired the funding, and helped to draft the manuscript. PD, YA and EW coordinated the data collection in the different centers, carried out data abstraction, and helped to draft the manuscript. JGK participated in the study design, and helped to draft the manuscript. All authors read and approved the final manuscript.