Lateral internal sphincterotomy is a minor operation which can be carried out under either local or general anaesthesia; a report in 1981 showed that general anaesthesia is preferable due to high rates of fissure recurrence in patients treated under local anaesthesia [REF].
the closed technique or subcutaneous technique involves making a small incision at the intersphincteric groove, inserting a scalpel with the blade parallel to the internal sphincter and advancing it along the intersphincteric groove, and then rotating the scalpel towards the internal sphincter and dividing it.