The first description of the rectal advancement flap in 1902 is attributed to Noble [1]. Noble's technique was modified by Elting in 1912 and Laird in 1948 and also used for anal fistulas [2, 3]. In 1985, Aguilar et al. reported a recurrence rate of only 1.5% in 198 patients [4]. Girona's observations on the etiology and pathogenesis of anal fistulas treated with an advancement flap were published in 1987 [5]. Only 6% of the 330 patients, of whom 74% had previous surgeries, showed recurrences. The average follow-up duration was 5 years.
The following flaps are distinguished:
- Submucosal-Mucosal Flap
- Mucosal-Muscle Flap (Full-thickness flap, RAF = Rectal-Advancement-Flap)
- Mucosal Flap with portions of the internal anal sphincter (partial flap)
The anodermal flap, where the internal fistula opening is covered by an advancement flap from perianal, plays a minor role today. The last publication on this was in 2007.
It is difficult to define quality criteria for evaluating different procedures, among other things, these depend on patient selection, the etiology of the fistula, and the follow-up duration [6]. Relevant randomized studies are still rare, meaning that the evidence generally remains sparse [7].
A review and meta-analysis by Balciscueta et al. from 2017 report on experiences with various flap techniques in complex cryptoglandular fistulas [8]. Among the 5575 studies published between 1985 and 2015, the authors found 26 relevant studies with a total of 1655 patients, of which only 5 were prospective. Of the 26 investigations, 6 concerned a mucosal flap, 13 a partial flap, and 3 a RAF. One study combined different flap thicknesses and 3 studies compared different flap techniques. The patients had a total of 663 mucosal flaps, 768 partial flaps, and 224 RAF. The average follow-up was 30.3 months (3 to 93.6 months). In twelve studies, a fistulectomy was performed, in seven a curettage, and in three studies both procedures were combined. In four studies, no information on the procedure was given. The overall recurrence rate was 21% (7.4% for the RAF, 22.9% for the partial, and 26.7% for the mucosal flap). Regarding the comparison of fistulectomy and/or curettage, there were no differences in the recurrence rate (19% vs. 21%). The pre- and postoperative continence of 622 patients was determined in 12 studies with various scores. Overall, the incontinence rate was 13.3% (0-51%), with 10.3% for the mucosal flap, 14.1% for the partial flap, and 20.4% for RAF. The authors conclude that no clear conclusions can be drawn due to the predominantly retrospective nature of the studies, the small case numbers, and the heterogeneity of the results.
Boenicke et al. investigated whether there are risk factors for recurrence development after the use of an advancement flap [9]. A previous abscess drainage, a suprasphincteric course, and an increased body mass index were identified as risks in a multivariate analysis of 65 patients. In contrast, van Onkelen et al. found in 252 patients with high transsphincteric fistulas that a horseshoe-shaped fistula course reduces recurrences [10].
Comparison with Other Surgical Methods
In a meta-analysis comparing plug and flap, Lin et al. found 11 studies with 810 patients [11]. There were no differences in short-term outcomes regarding healing, complications, postoperative pain, and quality of life. Only four studies reported on long-term outcomes (follow-up > 12 months). In terms of recurrences, the RAFs achieved significantly better results compared to the plug, leading the authors to conclude that the plug should not be used as a primary therapy method. No figures were found for postoperative incontinence.
In a meta-analysis by Stellingwerf et al. with 30 studies, of which 11 were prospective, with 1295 patients, the "Ligation of the intersphincteric fistula tract" (LIFT) was compared with the RAF [12]. The results showed comparable outcomes regarding healing and recurrence rate for RAF and LIFT (74.6% vs. 69.1% and 25.6% vs. 21.9%).
In a retrospective study from Italy with 21 patients, who were treated either with Permacol (collagen implant) or a RAF, a recurrence rate of 48% vs. 35% was determined [13].
The large number of different surgical techniques for treating anal fistulas indicates that there is currently no ideal procedure, as confirmed by various analyses [7, 14 - 17]. In their meta-analysis, Göttkens et al. found that there is no "best" technique, but the advancement flap is the most studied procedure [16].
In 28 patients, Borremann et al. combined a RAF with a plug [18]. In 75% of cases, healing was achieved after the first operation and in 86% of cases after a second intervention with minimal continence disturbance.
Technical Variants and Innovations
Two methods were investigated to avoid ischemia problems in the construction of the full-thickness flap [19, 20]. A platelet-rich plasma was added to the flap by Göttkens et al. [19]. 83% of the fistulas were healed after 27 months. Turner et al. applied fluorescence angiography during surgery on six patients with seven fistulas [20]. In all cases, the postoperative course was uneventful.
The traditionally rhomboid advancement flap was compared with an elliptically configured one in another retrospective study [21]. In 71 patients, 37 of whom had the elliptical flap, no difference was observed after a 14-month follow-up, with healing of 64% and 62%, respectively.
Podetta et al. demonstrated in a study with 121 patients that the RAF procedure is repeatable with good results [22]. The healing rate after the first intervention was 73.6%, after a second 94%, and after another 100%.
A study from France by Bessi et al. shows the importance of the length of follow-up [23]. The recurrence rate of the RAF flap in 87 patients was 16% after 3 months, 23% after 6 months, 32% after 12 months, and 41% after 24 months.
Conclusion
- The advancement flap technique is more than 100 years old, shows good results, is widespread worldwide, and thus still relevant.
- The advancement flap techniques include full-thickness, partial, and mucosal.
- The results are comparable to those of other sphincter-preserving procedures.
- In contrast to LIFT, incontinence is slightly more frequent with the same recurrence rate.
- To improve results, the TAMIS technique, intraoperative fluorescence angiography, platelet enrichment, and the combination of flap & plug are being investigated.