The procedure helps by lowering the resting pressure of the internal anal sphincter, which improves blood supply to the fissure and allows faster healing.
[1] The procedure has been shown to be very effective, with 96% of fissures healing at a median of 3 weeks in one trial.
[2] Lateral internal sphincterotomy is the preferred method of surgery for persons with chronic anal fissures, and is generally used when medical therapy has failed.
[1] It is associated with a lower rate of side effects than older techniques such as posterior internal sphincterotomy and anoplasty,[3] and has also been shown to be superior to topical glyceryl trinitrate (GTN 0.2% ointment) in long term healing of fissures, with no difference in fecal continence.
It can be performed with either "open" or "closed" techniques:[6] In both techniques the lower one third to one half of the internal sphincter is divided, to lower the resting pressure without destroying the effect of the sphincter.