title: Yin-Yang flaps: the mathematics of two keystone island  flaps for reconstructing increasingly large defects.
authors.forename: Felix C
authors.initials: FC
authors.lastname: Behan
authors.forename: Warren M
authors.initials: WM
authors.lastname: Rozen
authors.forename: Stephanie
authors.initials: S
authors.lastname: Tan
mesh_terms: D006801:Humans; D008297:Male; D010864:Pilonidal Sinus / Q000601:surgery; D019651:Plastic Surgery Procedures / Q000379:methods*; D012008:Recurrence; D013524:Surgical Flaps