INTRODUCTION: up to the present time, both open and closed lateral internal sphincterotomy (LIS) are considered by surgeons as fully comparable methods for eliminating the spasm of the internal sphincter in patients with chronic anal fissure. However, each method has a number of advantages and disadvantages. AIM: determination of an effective and safe method of lateral subcutaneous sphincterotomy.MATERIALS AND METHODS: a systematic overview and meta-analysis of studies, which compare the results of treatment after an open and closed lateral sphincterotomy was performed. The following has been evaluated: the incidence of fissure epithelialization, the postoperative morbidity, the recurrence rate, the incidence of anal incontinence (AI). Statistical processing has been carried out in the Review Manager 5.3 program.RESULTS: the meta-analysis included 9 studies with the results of treatment of 452 patients after an open lateral sphincterotomy and 443 after a closed one. The groups were comparable in frequency of epithelialization of fissures (OR = 0.87; CI = 0.30; 2.53; p = 0.8), in terms of the number of postoperative complications (OR = 0.52; CI = 0.15; 1.76; p = 0.29), as well as the number of relapses of the disease (OR = 0.5; CI = 0.19; 1.31; p = 0.16). At the same time, the implementation of an open lateral sphincterotomy leads to the development of AI 2.05 times more often than the closed method (OR = 2.05; CI = 1.01; 4.16; p = 0.05).CONCLUSION: during the treatment of the chronic anal fissure, in order to eliminate the spasm of the internal sphincter, it is advisable to use a closed method, in which the chance of AI is 2.05 times lower.