LAUSR

A complex perianal fistula can be managed conservatively by the insertion of a loose seton fixed in place by some kind of knot. In 2014 the first seton with a closure mechanism with a barbed hook, the Comfort Drain (CD), was introduced to prevent local irritation and discomfort caused by a knot [1]. The CD proved to be superior in terms of quality of life and perianal comfort compared with a conventional loose seton [2]. However, some potential problems were identified, especially regarding the closure mechanism. Furthermore, we experienced that closure can be technically difficult and time‐consuming given that a barbed hook has to be inserted in a small opening with a diameter of 0.3 mm. Recently, another knot-free seton with closure mechanism with two barbed hooks has been introduced, the SuperSeton (SS). Because no comparative studies have been performed, we tested 10 CD and 10 SS to compare the ease of use, expressed by time to attach the seton, and the strength of the closure mechanism of the knot-free setons. We also determined assembling time and ultimate tensile strength of 10 conventional loose setons in order to obtain reference values. The different types of setons were attached alternatingly by two EBSQ certified colorectal surgeons (DKW, DDEZ), both very experienced with placing knot-free setons. Although no significant difference was found in median time needed to fully attach the knot-free setons (p = 0.50), we did find that attachment of both types of knot-free setons took less time than assembling the conventional loose seton (p < 0.001). It must be noted that the controlled environment in which the seton closure was performed is not considered representative of clinical circumstances in which setons are closed when routed through a fistulous tract. Application times may therefore increase. The attachment rod of one CD and one SS kinked during attachment of the seton, making it far more difficult and timeconsuming to fully attach the seton. Neither of our surgeons succeeded in closing the remaining gap in the silicone tubing of the SS after kinking of the attachment rod. The second barbed hook of the SS possibly complicates closing the remaining gap in the silicone tubing. A calibrated force meter was developed by our medical technician (AS) to measure ultimate tensile strength. Median ultimate tensile strength of the SS was 16% higher compared to the CD (p = 0.004). This increase in tensile strength might be explained by the presence of a second barbed hook of the closure mechanism. However, when compared to the conventional loose seton, median ultimate tensile strength of the SS was still more than two and a half times smaller (p < 0.001). Although statistically significant we think that this subtle difference in tensile strength between the CD and SS is most likely clinically irrelevant. Especially when compared to the conventional loose seton. Other factors like price and availability should be taken into consideration when choosing between different knot-free setons. We recently showed that the incidence of seton loss in patients with complex perianal fistula is more than twice as high in patients treated with a knot-free seton compared to patients treated with a conventional loose seton [3]. Our current findings suggest that this difference can be explained by the far higher ultimate tensile strength of the conventional loose seton, implicating that improvement of the connection point of the knot-free seton can prevent seton loss. Further research should therefore be focused on optimizing the closure mechanism of knot-free setons to increase tensile strength and improve durability. * D. D. E. Zimmerman [email protected]