1. Department of Procto-Surgery , St. Marienhospital Vechta, Academic Teaching Hospital of the MHH Hannover , Vechta , Germany
2. Pilonidal Research Group , Vechta , Germany
3. Department of General and Visceral Surgery , Asklepios Klinikum Hamburg-Altona , Hamburg , Germany
4. Department of Visceral Surgery and Medicine , Inselspital, Bern University Hospital, University of Bern , Bern , Switzerland
5. Department of Anaesthesiology and Pain Medicine , Inselspital, Bern University Hospital, University of Bern , Bern , Switzerland