ObjectiveTo investigate the long-term efficacy of intersphincter approach combined with virtual solid and hanging line in the treatment of posterior high complex anal fistulas and risk factors for recurrence. Methods A total of 167 patients with posterior high complex anal fistula treated in our hospital from April 2020 to June 2023 were retrospectively included. According to different treatment methods, the patients were divided into observation group (n=88) and control group (n=79). The observation group was treated with the combination of virtual solid and hanging line via intersphincter approach, while the control group was treated with cutting and wire hanging drainage. The general clinical data, the height of the internal fistula opening and the anorectal pressure before and after 1, 2 and 3 months were compared between the two groups. The patients were divided into recurrence group (n=50) and non-recurrence group (n=117) according to the recurrence situation during the follow-up period. Univariate and multivariate logistic regression were used to analyze the risk factors of postoperative anal fistula recurrence, and Kaplan-Meier method was ued to draw relapse-free curve. ResultsCompared with the control group, the observation group had longer operative time, shorter wound healing time and shorter hospital stay (P<0.05). At 1, 2 and 3 months after operation, the anal resting pressure and maximum anal retraction pressure in the observation group were significantly increased, while the height of the inner mouth was significantly decreased, with statistical significance (P<0.05). There were statistically significant differences in age, body mass index, gender, regular dressing change to hospital after discharge, history of anal fistula surgery, clarity of internal opening and treatment methods between the recurrence group and the non-recurrence group (P<0.05). The results of multivariate logistic regression analysis showed that the independent risk factors for postoperative recurrence of patients with posterior high complicated anal fistula were that they didn’t regularly go to the hospital for dressing change after discharge, had a history of anal fistula operation, had unclear internal orifice and underwent thread-drawing drainage (P<0.05). The cumulative relapse-free rate of patients in the observation group and the control group was 84.58% and 67.73% respectively, and the difference was statistically significant (P<0.05). ConclusionsThe treatment of posterior high complex anal fistulas by intersphincter approach combined with virtual solid and hanging line has a good effect in protecting anal function and promoting wound healing. After discharge, the factors affecting postoperative recurrence in patients with posterior high complex anal fistula are not regularly changed dressing, history of anal fistula surgery, unclear internal mouth, cutting and wire hanging drainage, which should be paid attention to.