1. Institute for Quality and Efficiency in Health Care; Department of Non-Drug Interventions; Dillenburger Str. 27 Cologne Germany 51105
2. University of Witten/Herdecke; Institute for Research in Operative Medicine; Ostmerheimer Str. 200 Cologne Germany 51109
3. University of Witten/Herdecke; Institute for Research in Operative Medicine, Medical Faculty; Ostmerheimer Str.200 Cologne-Merheim Germany 51109