1. Department of Trauma Surgery and Orthopaedics, Reconstructive and Hand Surgery and Burn Medicine, German Armed Forces Central Hospital Koblenz , Koblenz , Germany
2. Department of Trauma, Hand and Reconstructive Surgery, Universitätsklinikum des Saarlandes , Homburg , Germany
3. Department of Procto-Surgery and Pilonidal Sinus, St. Marienhospital Vechta, Academic Teaching Hospital of the MHH Hannover , Vechta , Germany