Complex anal fistulas are responsible for pain, faecal incontinence and impaired quality of life. The rectal mucosa advancement flap (RMAF) procedure to cover the internal opening of the fistula remains a strategy of choice. However, a new procedure for closing anal fistulas is now available with the use of a nitinol closure clip (OTSC Proctology, OVESCO), which should ensure a better healing rate. This procedure is currently becoming more widespread, though without robust scientific validation, and it is therefore essential to carry out a prospective evaluation in order to determine the efficacy and safety of this new medical device for complex anal fistulas.