Over the last decade there have been major changes in the treatment of anal fissures. We know that high anal pressures cause poor healing and chronicity in fissures and the pharmacological agents effecting a chemical sphincterotomy are the mainstay of therapy. Nevertheless, some fissures do not respond and surgery has to be considered to aid resolution of the disease.
The aim of surgery in anal fissure has until recently concentrated on weakening the sphincter, thereby dropping anal pressure and resolving the hypoxic wound. The two main techniques used have been manual dilatation of the anus, and lateral anal sphincterotomy. Damaging the integrity of the sphincter has however been associated with incontinence. In the early 90's surgeons were already recognising that manual dilatation carried a significant risk of this complication. Figures of 10 - 50 % have been reported. Much depended on the technique. The original description of a 4 finger stretch held for 4 minutes seems to have the highest rates of incontinence, but the technique, however practiced is hard to standardise and the risk of incontinence has meant this technique has largely fallen into disrepute and it is rarely practiced now for this indication. There has however been some recent resurgence of interest, with some examining the used of standard dilatational techniques, mostly using endoscopic type fixed diameter balloon dilators. It may be, if complications can be minimised that a role for this will re-emerge, but this seems unlikely.
Lateral anal sphincterotomy as a means of controlled destruction of sphincter integrity is more appealing. The procedure has been described using both open and closed techniques. The former through an intersphincteric incision, involves dissection either side of the internal sphincter to ensure the correct muscle is cut. The IAS is then cut up to the level of the dentate line under vision. The wound may be sutured closed or left open to allow any haematoma to drain. The closed technique was originally described with a sphincterotomy knife, but an 11 or 15 blade suffices. This is stabbed into the intersphincteric groove with the blade parallel to the muscles, and when the blade tip reaches the dentate line the blade is turned medially, and withdrawn to cut the IAS only. Success rates for fissure healing are in the order of 80 - 90% as with all surgical treatments.
Incontinence rates for LAS is quoted around 5 - 15 %, but only 1 - 2 % are said to have true faecal incontinence, the remainder having trouble with only wind or truly liquid stool. LAS remains a useful tool in very resistant fissures as opposed to dilatation, mainly because of the theoretical possibility of a sphincter repair in those made incontinent. The multi-site disruption of a stretch means reconstruction is almost impossible. The results of anal sphincter repair are known to be rather disappointing for EAS disruption, it seems unlikely IAS repairs fare better, and almost certainly fare worse, as dissecting the edges of a muscle 2mm across is difficuilt to say the least, and often impossible. In addition, it is difficult to get sutures to catch and not cut. Smooth muscle has little fibrous tissue and therefore poor holding properties.
Fissures are however chronic granulating wounds, and surgeons have traditionally treated these sorts of wound with re-excision of the wound edges and closure. There are reports of fissurectomy, with or without wound closure but the results have been disappointing. This is perhaps not too surprising, since the underlying pathophysiology is not really that of an over-granulating wound, but of poor tissue healing caused by hypoxia. The underlying cause remains therefore untreated.
There has however been a resurgence of interest, mostly as yet unreported with this technique, because of the low risk of incontinence as a complication of such surgery. This new approach combines fissurectomy with a chemical sphincterotomy. GTN has been suggested, but the use of Botox (60 - 80 iu) injected into the IAS in the base of the fissure with the overlying wound being cleaned and closed has significant attractions (even allowing for the possible chemical temporary incontinence). No significant series have been reported, but having used this technique successfully for the last 8 operations for difficult fissures, there are attractions to this technique.
Finally hypoxic wounds can be healed by introducing new vascularised tissues to the area to overcome the hypoxic effects. This attractive technique does still suffer from the fact that the tissue flap is introduced into a high pressure region and this is probably responsible for a failure rate reported for the various techniques or 10 - 40%. A quick search of reconstructive surgical literature will yield a vast array of flap techniques for reconstructing open wounds. The two major approaches used in fissure surgery, have been advancement and rotational flaps. Not only do both techniques introduce tissue vascularised from outwith the anal canal, but they minimise the risk of incontinence due to anal dilatation during the surgery. There remains a small (but real) risk of incontinence due to the surgery, to which the patient should be alerted. This seems to be in the order of 1 - 2%, and mainly only gas incontinence has been reported.
The first approach reported used the principle of advancement flaps. Eliptical or 'House' flaps were cut from the skin external to the fissure. The skin was divided all round the flap, which was maintained on its deep blood supply. The edges of the fissure were freshened and the flap then advanced into the fissure and secured into position. The residual defect was then directly closed. No combined flap and chemical techniques were reported.. Success rates are reported between 70 and 90%. The main complication is breakdown of the donor site that occurs in up to 80% of cases and has lead to the suggestion the donor site should be left to heal without closure. This leaves an open wound with the potential for prolonged healing. The results available do however suggest that donor site breakdown does not affect the long term success of the procedure regarding resolution of the fissure.
To address the problem of the donor site breakdown, rotational flaps have been tried and used successfully. Any plastic surgical text will describe the technique in detail, but in essence after the edges of the fissure have been freshened, one edge is extended from the anal canal as a curved incision, and the opposite edge is extended round the anal canal. The point of the curved incision is then rotated into the fissure and secured. The remaining incision lines are sutured. In our series of 21 patients there was no change in levels of continence, 20 had a satisfactory result and one failed. The fissure was healed in 19. The donor site broke down and was infected in 2, which healed by secondary intention.
In summary destructive procedures on the anal sphincters should be avoided, there are good low risk, highly effective surgical alternatives. Currently the surgical approach of choice is probably a rotation flap. An alternative to consider is a fissurectomy combined with a chemical sphincterotomy with Botox.