Subcutaneous Pedicle Advancement Flap Anoplasty with Pivot Point Medialization for Anal Stenosis: A Single-center Retrospective Study

Abstract

Objectives:

Severe anal stenosis, particularly Whitehead deformity, presents a significant reconstructive challenge. This study reports the clinical outcomes of a modified subcutaneous pedicle advancement flap anoplasty emphasizing pivot point medialization, developed in collaboration with plastic surgeons.

Methods:

We retrospectively analyzed data from 52 consecutive patients (aged 32–97 years; median, 67) treated between April 2021 and June 2025. The etiologies included postsurgical cicatricial stenosis (65.4%) and chronic anal fissure (34.6%). The technique involves establishing the pivot point—defined in this study as the biomechanical anchoring point at the deep subcutaneous fat layer—allowing tension-free advancement of the flap medially without rotation while preserving blood flow through the subcutaneous pedicle. Forty-nine patients completed the 6-month follow-up. Bougie examination at 6 months was performed without anesthesia during outpatient visits.

Results:

Surgical success, defined as bougie passage of ≥22 mm (#9), was achieved in 48 of 49 patients (98.0%), with a median operative time of 24 min (range, 14–35 min). No flap necrosis occurred (0%). Complications included wound dehiscence in nine patients (17.3%), which healed conservatively within a median of 4 weeks, and rectal prolapse in one patient (1.9%). One patient (2.0%) showed insufficient dilation at 6 months and required reoperation at 12 months. No fecal incontinence was observed. Patient satisfaction at 3 months was high (very satisfied 63.5%, satisfied 21.2%, unchanged 15.4%, dissatisfied 0%).

Conclusion:

This technique, utilizing pivot point medialization and straight advancement without rotation, may offer a safe and effective option for severe anal stenosis.

Introduction

Anal stenosis is defined as a condition in which the extensibility of the anal canal is reduced because of scarring or organic changes, resulting in anatomical narrowing[1]. The main causes are postsurgical cicatricial stenosis and stenosis due to chronic anal fissure, and symptoms, such as difficulty in defecation, pain during defecation, and bleeding, significantly impairing patients' quality of life[2,3].

Surgical treatment for anal stenosis in Japan has developed uniquely. The sliding skin graft (SSG) method, reported by Sumikoshi et al.[4] in the 1950s, has become widely adopted because of its simplicity and is considered the standard treatment. The effectiveness of SSG has been demonstrated in multiple reports, with particularly good outcomes reported for stenosis associated with chronic anal fissure[5-7]. However, SSG has structural limitations. Given that it involves only skin-level mobilization, part of the relaxing incision remains as an open wound, and scarring during secondary healing can lead to restenosis, particularly in cases with severe cicatricial stenosis[8]. Takahashi et al.[9] reported recurrence rates of 15–20% in a 5-year follow-up study.

In contrast, advancement flap anoplasty has been established as the standard treatment in Western countries[10-12]. This technique is based on the fundamental principles of plastic surgery, which emphasize preserving the subcutaneous tissue as a pedicle and mobilizing the flap while maintaining blood flow. Representative flap designs include the V-Y advancement flap and House flap (rectangular advancement flap)[13-16]. A key concept common to these techniques is the pivot point, which refers to the fulcrum around which the flap advances. Appropriate positioning of the pivot point enables tension-free flap fixation while maintaining blood flow through the subcutaneous pedicle[17]. Gallo et al.[18] systematically reviewed 29 studies encompassing 556 patients and identified 14 anoplasty techniques. Notably, this review highlighted significant heterogeneity in outcome measures across studies, making direct comparisons difficult. The review concluded that House flap achieved better results in terms of clinical improvement and satisfaction compared with Y-V or rhomboid flaps and called for better-designed multicenter studies with standardized outcome measures.

In collaboration with plastic surgery specialists, we introduced subcutaneous pedicle advancement flap anoplasty, emphasizing the concept of pivot point medialization, in 2021. Previous reports have provided limited detail regarding pivot point positioning; therefore, we focused on this aspect. In our technique, the pivot point was established at the deep subcutaneous fat layer, and the flap was advanced straight medially without rotation. This enabled both blood flow maintenance through the subcutaneous pedicle and tension-free suturing between the medial flap edge and rectal mucosa. The purpose of this study was to report the clinical outcomes of subcutaneous pedicle advancement flap anoplasty with pivot point medialization and to evaluate its utility.

Materials and Methods

Participants

The study included 52 consecutive patients with anal stenosis who underwent subcutaneous pedicle advancement flap anoplasty at our institution between April 2021 and June 2025. The cohort comprised 30 men (57.7%) and 22 women (42.3%), with a median age of 67 years (range: 32–97 years). The etiologies of stenosis included postsurgical cicatricial stenosis (34 cases, 65.4%) and chronic anal fissure (18 cases, 34.6%). Among the postsurgical cases, 16 followed hemorrhoidectomies, and 18 were associated with Whitehead deformity. Stenosis severity was assessed preoperatively using bougie examination, with passage limited to bougie sizes #3–5 (diameter 13–16 mm) in all cases.

Inclusion and Exclusion Criteria

The inclusion criteria were moderate-to-severe anal stenosis with preoperative bougie passage limited to #3–5, refractory to conservative management, and surgery performed at our institution between April 2021 and June 2025. The exclusion criteria were stenosis associated with inflammatory bowel disease, radiation-induced stenosis, stenosis associated with malignancy, and stenosis associated with anal fistula.

Ethical Considerations

This study was conducted in accordance with the Declaration of Helsinki and was approved by the Ethics Committee of Medical Corporation Kokikai (approval no. 24000098). Informed consent was obtained from all patients regarding the surgical procedure and the use of their data for research purposes through opt-out methodology.

Collaboration with Plastic Surgery

All procedures were performed collaboratively by colorectal surgeons and plastic surgery specialists. The flap design was determined intraoperatively after assessing the stenosis condition, with the House flap or V-Y flap selected according to individual case requirements. This collaborative approach facilitated the application of fundamental plastic surgery principles to colorectal surgery.

Surgical Technique

The surgery was performed in the jack-knife (prone) position under spinal anesthesia (39 cases, 75.0%) or local anesthesia (13 cases, 25.0%). The technical details are as follows (Figures 1 and 2).

Figure 1.

Schematic illustration of a subcutaneous pedicle advancement flap anoplasty (surgeon’s view from above in the jack-knife position). (A) Preoperative condition showing severe circumferential anal stenosis (Whitehead deformity). (B) After releasing the stenosis at the 3 o’clock position, a blue House flap is designed laterally to the defect. The white arrow indicates the direction of the straight medial advancement. The pivot point (biomechanical anchoring point) is established in the deep subcutaneous fat layer through a deep medial incision, allowing advancement without rotation. (C) The flap is advanced medially to cover the defect, and the donor site is closed primarily in a Y-shape. All wounds are closed by primary intention.

Figure 2.

Intraoperative photographs of the modified House advancement flap. (A) Flap design. Stenosis was released at the 3 o’clock position, and a House-shaped flap was designed laterally to the defect after intraoperative assessment. (B) Flap elevation. The flap was elevated with the subcutaneous pedicle (15–20 mm width) preserved. (C) Flap advancement. The flap was advanced straight medially without rotation, using the anchoring point at the deep subcutaneous fat layer as a reference. (D) Final suturing. The flap was sutured without tension using 3-0 absorbable sutures, covering the defect with well-vascularized tissue.

First, the location of the stenosis was confirmed by intraoperative bougie examination, and the incision line was placed at the most scarred area (avoiding the anterior-posterior midline). Second, the scarred area was adequately incised from the anal verge toward the dentate line to release the stenosis, creating a web-shaped defect. Third, the flap type was determined intraoperatively after assessing the stenosis condition. A flap was designed lateral to the stenosis release wound, matching the width of the defect. Single-flap repair was performed in 45 cases (86.5%), and double-flap repair (at two locations) was performed in 7 cases (13.5%).

The key technical feature of this procedure was positioning the pivot point in the deep subcutaneous fat layer. In this study, we defined the pivot point not as a classical rotational fulcrum, but as a biomechanical anchoring point that served as both a reference for flap advancement and a vascular preservation landmark. The medial edge of the flap (closer to the anal canal) was incised deeply into the subcutaneous fat layer, and the pivot point was established at this deep level. Medialization of this anchoring point—positioning it closer to the anal canal than in conventional techniques—provides several functional advantages: (1) preservation of adequate pedicle length to prevent vascular compromise, (2) reduction of tension and shear forces during flap advancement, (3) avoidance of torsional stress by enabling straight advancement without rotation, and (4) maintenance of vascular integrity through the subdermal plexus. Using this anchoring point as a reference, the flap was advanced straight medially to cover the defect.

Finally, the medial flap edge was sutured to the rectal mucosa without tension using 3-0 absorbable sutures. The flap margins were similarly sutured to the surrounding skin, and the donor site was closed primarily in a Y-shape. Passage of bougie #9–10 (diameter 22–23 mm) was confirmed postoperatively. Bleeding was negligible.

Postoperative Management and Outcome Measures

After surgery, laxatives were administered to maintain soft stools. The wounds were left open, and the patients were instructed to wash the anal area after defecation. The median hospital stay was 5 days (range: 3–7 days).

The primary outcome was the surgical success rate, defined as bougie passage ≥22 mm (#9) without additional surgery at 6 months postoperatively. Bougie examination at 6 months was performed without anesthesia during outpatient visits. We adopted this criterion because bougie #9 (22 mm) represents an adequate anal caliber comparable to the normal anal canal diameter, whereas smaller calibers may indicate residual functional stenosis. The primary endpoint was 6 months postoperatively, based on plastic surgery principles, when wound healing and scar maturation are typically stabilized.

Secondary outcomes included the complication rate (flap necrosis, wound dehiscence, infection, and rectovaginal fistula), reoperation rate, and patient satisfaction at 3 months.

Patient satisfaction was assessed at 3 months postoperatively using a 10-point numeric rating scale (0–10) comparing symptoms to the preoperative status. To minimize bias, assessments were conducted by nursing staff not directly involved in the surgical procedures. Responses were categorized into four groups: very satisfied (9 or 10), satisfied (6–8), unchanged (3–5), and dissatisfied (0–2).

Statistical Analysis

Continuous variables are presented as medians (interquartile range [IQR] or range), and categorical variables as n (%). Statistical analyses were performed using descriptive statistics.

Results

Patient characteristics and surgical outcomes are summarized in Table 1. Of the 52 patients who underwent surgery, 49 completed the 6-month follow-up assessment. The median follow-up period was 18 months (IQR 12–30, range 3–55 months). The surgical success rate at 6 months, defined as bougie passage ≥22 mm (#9), was 98.0% (48/49 cases). The median operative time was 24 min (range: 14–35 min). Bleeding was negligible. Immediate postoperative bougie passage of 22–23 mm (#9–10) was confirmed in all cases.

Table 1.

Patient Characteristics and Surgical Outcomes.

Parameter	Value
Demographics (n=52)
Age (years), median (range)	67 (32-97)
Sex, male / female	30 (57.7%) / 22 (42.3%)
Etiology
Postsurgical cicatricial stenosis	34 (65.4%)
-Post-hemorrhoidectomy	16
-Whitehead deformity	18
Chronic anal fissure	18 (34.6%)
Surgical details
Anesthesia, spinal / local	39 (75.0%) /13 (25.0%)
Flap repair, single / double	45 (86.5%) /7 (13.5%)
Operative time (min), median (range)	24 (14-35)
Hospital stay (days), median (range)	5 (3-7)
Outcomes (n=49 with 6-month follow-up)
Follow-up (months), median (range)	18 (3-55)
Surgical success rate (bougie ≥22 mm) †	48/49 (98.0%)
Flap necrosis	0 (0%)
Wound dehiscence	9 (17.3%)
Reoperation	1 (2.0%)
Fecal incontinence	0 (0%)
Patient satisfaction at 3 months
Very satisfied (score 9-10)	33 (63.5%)
Satisfied (score 6-8)	11 (21.2%)
Unchanged (score 3-5)	8 (15.4%)
Dissatisfied (score 0-2)	0 (0%)

†Surgical success was defined as bougie passage ≥22 mm (#9) without additional surgery at 6 months post operatively, assessed without anesthesia during outpatient visits.

No cases of flap necrosis were observed (0%). Minor complications included wound dehiscence in nine patients (17.3%). All dehiscences occurred at 2–3 weeks postoperatively when the absorbable sutures dissolved, with a median dehiscence length of 8 mm (range, 5–15 mm). All patients healed conservatively by secondary intention within a median of 4 weeks (range, 2–6 weeks). Severe complications included rectal prolapse in one patient (1.9%), which was successfully treated with the Gant–Miwa–Thiersch procedure. No cases of fecal incontinence were observed despite the anal dilation achieved by surgery.

One patient (2.0%) with severe Whitehead deformity showed insufficient dilation (bougie #6, 18 mm) at the 6-month follow-up, despite initial double-flap repair at the 3 and 7 o'clock positions. Owing to the rigid scar tissue, a larger flap was subsequently created at the 5 o'clock position at 12 months postoperatively, with favorable outcomes at 4 months after the reoperation.

At 3 months postoperatively, 33 patients (63.5%) reported being very satisfied (score 9 or 10), 11 (21.2%) were satisfied (score 6–8), 8 (15.4%) were unchanged (score 3–5), and 0 (0%) were dissatisfied (score 0–2). The total satisfaction rate (very satisfied and satisfied) was 84.6%.

Figure 3 illustrates a representative case with a 3-year follow-up, showing favorable cosmetic and functional outcomes with a wide patent anal canal (bougie passage 22 mm) and good tissue elasticity.

Figure 3.

Long-term postoperative outcome (3-year follow-up). (A) Preoperative view showing severe anal stenosis with bougie passage limited to 13–16 mm diameter. (B) Three years postoperatively, the anal canal remained widely patent with bougie passage of 22 mm (#9), demonstrating good tissue elasticity and well-integrated flap without evidence of contracture or restenosis.

Discussion

This study demonstrated that subcutaneous pedicle advancement flap anoplasty with pivot point medialization achieved favorable outcomes in the management of anal stenosis, with a surgical success rate of 98.0% and a flap necrosis rate of 0%. These results are consistent with those of previous reports on advancement flap techniques.

Gallo et al.[18] highlighted significant heterogeneity in outcome measures across studies, a critical issue in the anal stenosis literature. The review identified 14 anoplasty techniques but noted that the lack of standardized outcome definitions makes direct comparisons challenging. Our study addresses this gap by clearly defining surgical success as bougie passage ≥22 mm (#9) at 6 months without additional surgery, assessed without anesthesia during outpatient visits. We adopted this stricter criterion because bougie #9 (22 mm) represents an adequate anal caliber comparable to the normal anal canal diameter, whereas smaller calibers may indicate residual functional stenosis. Future studies should incorporate internationally validated instruments, such as defecation disorder scores and anal manometry, to enable more meaningful comparisons across centers.

The absence of flap necrosis (0%) in our series warrants detailed discussion. We believe that collaboration with plastic surgery specialists was key to achieving this favorable outcome. The perianal region is richly vascularized by perforating branches from the internal pudendal artery, which provides an inherently robust blood supply to the area[19]. By designing the flap to include deep subcutaneous tissue, we ensured that the subdermal vascular plexus was incorporated within the flap. Furthermore, medialization of the anchoring point at the deep subcutaneous fat layer allows the flap to advance straight medially without rotation, thereby avoiding torsional stress on the pedicle and maintaining reliable blood flow. Our plastic surgery colleagues have extensive experience with gluteal fold flaps for reconstruction following oncologic surgery, and this expertise contributed significantly to the consistent preservation of flap vascularity in our series.

The concept of pivot point positioning requires clarification in the context of our technique. In classical flap surgery, the pivot point typically refers to a rotational fulcrum around which the flap rotates. However, in our straight advancement technique, we used the term to describe a biomechanical anchoring point—the deepest point of dissection at the medial flap edge—that served dual functions: as a reference landmark for flap advancement and as a critical point for vascular preservation. Medialization of this anchoring point, positioning it closer to the anal canal through deep medial incision, provided the functional advantages described above. This approach differs from conventional techniques in which the dissection plane remains relatively superficial. We acknowledge that our primary technical contribution may be better characterized as a comprehensive pedicle-preserving advancement strategy that incorporated: (1) preservation of a sufficiently wide subcutaneous pedicle (15–20 mm), (2) deep-layer dissection to enhance flap mobility, and (3) straight advancement without rotation. The medialized anchoring point facilitated these elements by ensuring adequate pedicle length and preventing vascular compromise during advancement.

Our results are consistent with published outcomes from centers using advancement flap techniques. The only randomized controlled trial comparing anoplasty techniques, by Farid et al.[20], demonstrated that the House flap achieved superior clinical improvement (95%) and quality of life scores compared with rhomboid flap (80%) and Y-V anoplasty (65%) at 1 year. Sentovich et al.[11] reported a 94% success rate with House advancement anoplasty in 16 patients. Perez-Legaspi et al.[21] achieved a 96% success rate with House flap in 25 patients. The systematic review by Gallo et al.[18] found pooled complication rates of 10.2% for Y-V flaps and 11.5% for rhomboid/diamond flaps, with House flaps showing lower complication and recurrence rates. The 0% flap necrosis rate in our series compares favorably with previous reports; Maria et al.[3] reported partial flap necrosis in 4% of cases, and other series have reported necrosis rates of 2–8%[10,12]. We attribute our favorable flap survival to the consistent preservation of a wide subcutaneous pedicle (15–20 mm) and straight advancement without rotation.

Wound dehiscence occurred in 17.3% of the cases, which warrants discussion. As noted by Grossi[22] in a recent expert commentary, dehiscence is the most common complication following anoplasty, and dehiscence on the internal aspect of the anus can be more challenging than distal dehiscences. All dehiscences in our series occurred at 2–3 weeks postoperatively, coinciding with the dissolution of absorbable sutures. The anal canal is subject to significant mechanical stress during defecation, and this timing suggests that suture dissolution before complete wound maturation may be a contributing factor. However, all dehiscences healed conservatively within a median of 4 weeks without specific intervention, and importantly, no case of wound dehiscence resulted in treatment failure. We interpret these findings as evidence that the robust blood supply through the subcutaneous pedicle may promote effective wound healing even when primary intention healing is not achieved.

Despite achieving substantial anal dilation from bougie #3–5 (13–16 mm) preoperatively to #9 (22 mm) postoperatively, no cases of fecal incontinence were observed in our series. This finding is reassuring regarding the safety of this technique with respect to sphincter function. However, objective assessment of anal sphincter function was not performed in this study. Future studies should incorporate anal manometry to objectively evaluate the impact of this procedure on sphincter function and to ensure that adequate dilation does not compromise continence.

Patient satisfaction was high, with 84.6% reporting satisfaction at 3 months postoperatively. The management of Whitehead deformity, which results from circumferential cicatricial stenosis, has historically been one of the most challenging problems in proctology[23]. When stenosis develops, it typically involves the entire circumference, creating a constriction ring effect. The subcutaneous pedicle advancement flap may provide robust vascularized tissue that effectively interrupts this circumferential scarring. In our series, 18 cases were Whitehead deformity, and all but one achieved successful outcomes with this approach.

Collaboration with plastic surgery specialists was essential for introducing this technique into our colorectal surgery practice. The application of fundamental plastic surgery principles, including the optimization of flap design based on defect geometry, principles of blood flow maintenance through pedicle preservation, and tension-free suturing techniques, enabled safe and effective surgery. The learning curve for this technique was approximately 10 cases based on our experience, after which consistent outcomes were achieved. We recommend that colorectal surgeons seeking to adopt this technique establish collaborative relationships with plastic surgery colleagues.

From a clinical perspective, a comparison between SSG and subcutaneous pedicle advancement flap anoplasty may be of interest to readers. SSG involves skin-level mobilization with a relaxing incision that heals by secondary intention, whereas the advancement flap preserves the subcutaneous pedicle for primary closure of all wounds. The theoretical advantages of the advancement flap include (1) primary wound healing without secondary intention, potentially reducing restenosis risk; (2) introduction of well-vascularized subcutaneous tissue into the stenotic area; and (3) greater tissue volume for severe cicatricial stenosis. Conversely, SSG offers simplicity and shorter operative time. In our experience, SSG remains effective for mild-to-moderate stenosis, particularly those associated with chronic anal fissure. However, for severe postsurgical cicatricial stenosis and Whitehead deformity, where the scar extends deep into the subcutaneous layer, the advancement flap may provide more durable results by addressing the pathology at the appropriate tissue depth. A prospective comparative study between these techniques would be valuable. However, such a comparison within a single institution may be challenging given the fundamental differences in surgical philosophy and patient selection criteria.

This study has some limitations. First, as a retrospective observational study from a single institution, selection bias is possible, which may limit the generalizability of the results to all practice settings. Second, this study lacked a direct comparison with other techniques, as discussed above. Third, the observation period (median 18 months) was relatively short, and long-term outcomes beyond 5 years require future investigation. Fourth, the study did not include objective functional assessments, such as anal manometry or validated quality-of-life questionnaires, such as the Gastrointestinal Quality of Life Index used by Farid et al.[20]. Future studies should incorporate these standardized outcome measures, including anal manometry to assess sphincter function, to facilitate international comparisons and ensure comprehensive evaluation of surgical outcomes.

Conclusions

Subcutaneous pedicle advancement flap anoplasty with pivot point medialization, developed in collaboration with plastic surgery specialists, demonstrated favorable outcomes for the treatment of anal stenosis, with a 98.0% success rate and 0% flap necrosis rate. This technique, based on established plastic surgery principles of pedicle preservation and optimized anchoring point positioning, may offer a viable surgical option for anal stenosis, particularly for postsurgical cicatricial stenosis and Whitehead deformity. We encourage colorectal surgeons to establish collaborative relationships with plastic surgery colleagues to facilitate adoption of this technique.

Author Contributions

Naoki Yago conceived and designed the study, collected the data, and drafted the manuscript. Masami Saito provided expertise as a Board-Certified Plastic Surgeon, collaborated on the surgical procedures and flap design, and critically reviewed the manuscript. Hiroki Yago participated in the research, data analysis, and assisted in study coordination.

Conflict of Interest

The authors declare that there are no conflicts of interest.

Ethical Approval

This study was approved by the Ethics Committee of Medical Corporation Kokikai (approval no. 24000098).

Supplementary Files

Supplementary file 1.