Aim: Loss of seton (LOS) occurs frequently in patients treated with a knot- free seton. Seton reinsertion after LOS is usually performed in the operating room (OR), necessitating daycare hospitalisation and locoregional or general anesthesia. An additonal seton made of a thin braided non-absorbable suture might enable seton reinsertion. In an outpatient setting. Aim of the present study was to assess the usefulness of inserting an additional seton. Method: Consecutive patients treated for complex perianal fistulas who underwent insertion of a knot-free seton at a single institution between January 2017 and December 2021 were included. Since 2020 a seton made of a thin braided non-absorbable suture was in-serted in addition to a knot-free seton. Incidence of surgical rein-tervention, defined as reinsertion of a seton performed in the OR after LOS, was compared for knot-free setons with and without an additional seton. Results: A total of 282 knot-free setons were placed in 184 pa-tients. Of the 282 knot-free setons, 106 were placed with an ad-ditional seton. The incidence of LOS was 33% for knot-free setons without an additional seton and 24% for knot-free setons with an additional seton (p = 0.10). Forty-eight percent of all lost knot-free setons were reinserted (p = 1.00). Surgical reintervention was significantly lower for knot-free setons with an additional seton (p < 0.01). Conclusion: This study confirms frequent LOS in patients with knot-free setons. Placement of an additional seton results in less surgical reinterventions.Disclosure of Interest: None declared.