BACKGROUNDLateral internal sphincterotomy is still the approach of choice for the treatment of chronic anal fissure (CAF) with internal anal sphincter (IAS) hypertonia, but it is burdened by high-risk postoperative faecal incontinence (FI). Sphincter saving procedures have recently been reconsidered as treatments to overcome this risk. The most employed procedure is fissurectomy with anoplasty, eventually associated with pharmacological sphincterotomy. AIMTo evaluate whether fissurectomy and anoplasty with botulinum toxin injection improves the results of fissurectomy and anoplasty alone.METHODSWe conducted a case-control study involving 30 male patients affected by CAF with hypertonic IAS who underwent fissurectomy and anoplasty with V-Y cutaneous flap advancement. The patients were divided into two groups: Those in group I underwent surgery alone, and those in group II underwent surgery and a botulinum toxin injection directly into the IAS. They were followed up for at least 2 years. The goals were to achieve complete healing of the patient and to assess the FI and recurrence rate along with manometry parameters.RESULTSThe intensity and duration of post-defecatory pain decreased significantly in both groups of patients starting with the first defecation, and this reduction was higher in group II. Forty days after surgery, we achieved complete wound healing in all the patients in group II but only in 80% of the patients in group I (P < 0.032). We recorded 2 cases of recurrence, one in each group, and both healed with conservative therapy. We recorded one temporary and low-grade postoperative case of “de novo” FI. Manometry parameters reverted to the normal range earlier for group II patients.CONCLUSIONThe injection of botulinum toxin A in association with fissurectomy and anoplasty with a V-Y advancement flap improves the results of surgery alone in patients affected by CAF with IAS hypertonia.