The surgical options for pilonidal sinus disease (PNS) have seen marked development over the last decade, with a shift farther and farther away from the vigorous and morbid traditional procedures to the more conservative and anatomically respectful methods. In cases of chronic or recurrent disease, large excision extending deep into the postsacral fascia, followed either by primary closure or by some flap reconstruction, was traditionally considered to be the treatment of choice [1]. Due to their larger size, however, these procedures were always at a higher risk for wound problems, taking longer in healing and affecting the early normal activity. Off-lateral closure of wounds became popular in recent years as a means of merely moving the suture line laterally away from the deep intergluteal cleft, thus drastically reducing the rates of recurrence and wound dehiscence compared to midline closure [2-3]. Among the different off-midline flap techniques, the Karydakis, Bascom cleft lift, Limberg, and V-Y advancement plasty have had variable outcomes [4-7]. Comparing [8-10] these with other methods of flap closure or even with simpler closures [11-13] has shown that selection of the flap according to the defect size, chronicity, and surgeon  experience  is  truly  important  in assuring the best possible outcomes postoperatively. Despite their present record of success, the more formalized excision and closure methods require hospital admission and either general or regional anesthesia, and sometimes, drains are inserted and antibiotic therapy started; all these factors add to the duration of a patient's convalescence. Reported rates of recurrence have varied widely because of many reasons, including those pertinent to patient selection, extent of disease, and duration of follow-up predisposition in individual studies. Interestingly, meta-analysis [14-15] favored less rates of recurrence for the open secondary healing techniques when compared to the closed technique. Lord and Millar [16] initiated the minimally invasive techniques of pit picking and limited debridement, and Bascom [17] later elaborated and refined this concept. The concept was further adjusted by Gips et al. [18], who reported prompt wound healing and minimal recurrence during intermediate- and long-term follow-ups. Gips et al. [19] laid the foundation for day-case (ambulatory) surgery under local anesthesia, thus reducing morbidity but giving the patients excellent healing results. Other teams substantiated these results with a similar approach of localized sinusectomy or a style of limited excision of pilonidal pits and associated fistulous tracts using skin trephines [20-21], thus confirming the usefulness of minimally invasive management in a selected group of patients. Based on these techniques, contemporary reconstructive procedures like the Keystone perforator flap and Bascom cleft lift aim for tension-free closure, flatting of the natal cleft, good vascularity, and low recurrence. Because of the limited local data in Iraq, the present study was done at Al-Kindy Teaching Hospital to assess the outcomes of healing and postoperative complications between the two techniques--Keystone flap and Bascom operation--on 200 patients treated from 2022 to 2025.      

This retrospective observational study was conducted in the Department of General Surgery, Al-Kindy Teaching Hospital Baghdad, Iraq, from January 2022 to June 2025. The study aimed to evaluate, analyze, and compare the clinical and surgical outcomes of two operative measures-the Keystone perforator flap and the Bascom cleft-lift operation-for the treatment of chronic and recurrent pilonidal sinus disease (PNS). Two hundred patients were selected after screening for inclusion criteria and were further equally randomized into both groups. In Group A, 100 patients were managed by the Keystone perforator flap, whereas in Group B, 100 patients underwent a Bascom cleft-lift operation.

Patients were eligible for inclusion if they were between 16 and 45 years of age with a diagnosis of either primary or recurrent PNS confirmed clinically and medically fit for spinal or general anesthesia. Patients presenting with acute pilonidal abscesses needing only simple incision and drainage, immunocompromised individuals, patients with uncontrolled diabetes mellitus, those with incomplete clinical records, or defaulters to postoperative follow-up visits were excluded from the study.

All surgical procedures were undertaken with spinal anesthesia by senior consultant surgeons of comparable experience in colorectal and reconstructive surgery to assure consistency of technique and minimize operator bias. The ellipse excision of the Keystone was performed, carefully encompassing all sinus tracts and granulation tissue. The Keystone flap was designed as a double-opposing V–Y advancement flap, with its blood supply coming from the perforating vessels in the gluteal region. Dissection was carried out at the subfascial level, and the flap was then advanced medially to cover the defect adequately without tension. Meticulous hemostasis was secured, and wound closure was performed with absorbable sutures in the subcutaneous layer and interrupted nylon sutures on the skin. When required, a small suction drain was placed and removed within 24-48 hours after surgery.

This procedure consisted of an incision on the lateral side parallel to the midline, excising the sinus tract and surrounding infected tissues. The wound bed was irrigated, and the redundant tissue in the natal cleft was undermined to flatten the deep midline groove so as to prevent hair trapping and moisture retention. The wound was closed off the midline toward the lateral side so that the suture line had less tension, hence less chance for recurrence. The wound was closed in layers with interrupted sutures. Where depending on the findings during the operation, a suction drain was placed or not.

Postoperative care was standardized for both groups and consisted of intravenous broad-spectrum antibiotic administration for five days, analgesia, and daily wound dressing. Patients were educated to ensure adequate local hygiene and were discouraged from prolonged sitting during the early recovery period. Follow-ups were held on days one under anesthesia, at the end of the first week, third week, and sixth week of the postoperative period. In each visit, all patients were assessed for the duration of wound healing (in days to full epithelialization), risk of wound infection, formation of seroma or dehiscence, incidence of recurrence at six weeks, and one year post-surgery, as well as a measure of patient satisfaction. Patient satisfaction was then assessed through a structured questionnaire that consisted of questions relating to postoperative pain, cosmetic satisfaction, and the return to normal daily activities.

The key outcome under consideration was the total time elapsed before the wound had closed completely. Secondary measurements examined complications occurring after surgery, including infection, seroma, and incision secessions, besides the recurrence rate, days of hospitalization, and patient satisfaction scores.

Data analysis was run in the SPSS software, version 26.0, IBM Corp., Armonk, NY, USA. The continuous variables are presented as Mean±SD. The categorical variables were presented as frequencies and percentages. For statistical comparison, we performed the Chi-square test for categorical variables and Student’s t-test for continuous variables. A p-value less than 0.05 was considered significant. Ethical approval was obtained from the Scientific and Ethical Committee of Al-Kindy Teaching Hospital, keeping strict confidentiality of patient data during this research.

Table 1 presents the baseline demographic data of the 200 patients included in the study. The mean age of participants was 25.3±4.7 years in the Keystone flap group and 26.1±5.1 years in the Bascom operation group, with no statistically significant difference (p = 0.41). The male predominance observed in both groups (82% and 79%, respectively) aligns with the known epidemiological pattern of pilonidal sinus disease, which occurs more commonly among young adult males with dense body hair and sedentary lifestyles. The proportion of patients with a body mass index (BMI) greater than 25 kg/m² was comparable between groups (63% vs. 60%), suggesting that overweight and obesity were prevalent contributing factors across the study population. Additionally, recurrent disease was reported in 20% of Keystone flap patients and 18% of those treated with the Bascom operation, indicating that both techniques were applied in similar case profiles without selection bias.

Table 1: Demographic characteristics of patients

Table 2 summarizes the intraoperative characteristics and technical aspects of both surgical procedures. The mean operative time was significantly longer in the Keystone flap group (55±10 min) compared with the Bascom operation (45±8 min) (p = 0.001), reflecting the more complex dissection and flap design required in perforator-based reconstruction. Despite this, the intraoperative blood loss was modest in both groups, though statistically greater in the Keystone flap group (40±15 mL vs. 30±10 mL; p = 0.02), which can be attributed to the wider tissue undermining and flap mobilization. Interestingly, the use of surgical drains was significantly lower in the Keystone flap group (25%) than in the Bascom operation group (40%) (p = 0.03), likely due to the tension-free closure and superior hemostasis achieved with the well-vascularized flap design. Overall, these findings indicate that while the Keystone flap procedure requires slightly longer operative time and marginally higher blood loss, it provides a more stable and secure wound environment, reducing the postoperative need for drainage.

Table 2: Intraoperative parameters

Table 3 outlines the incidence of early postoperative complications observed in both surgical groups. The overall complication rate was low, with no statistically significant differences between the Keystone flap and Bascom operation groups. Wound infection occurred in 5% of Keystone cases compared to 9% in the Bascom group (p = 0.18), suggesting a trend toward better infection control in the flap group, possibly due to its enhanced perfusion and tension-free closure. Seroma formation was slightly more common in the Bascom operation (10%) than in the Keystone flap (4%), likely reflecting greater dead space following lateral undermining, although the difference did not reach statistical significance (p = 0.07). Similarly, wound dehiscence occurred in 3% of Keystone flap cases and 8% of Bascom operations (p = 0.11), while hematoma formation remained minimal in both groups (2% vs. 5%; p = 0.25). Collectively, these results indicate that both techniques are safe and well tolerated, with the Keystone flap demonstrating a modestly lower rate of postoperative wound complications, attributable to its robust vascularity and reduced tension across the closure line.

Table 3: Early postoperative complications

Table 4 compares the postoperative recovery outcomes between the two surgical techniques.  The faster wound healing in the Keystone flap group is evident from the results, with epithelialization being complete in 21±3 days, while the Bascom operation took 42±6 days (p<0.001). Such a decrease in healing time is due to the advantage provided by the strong vascularization of the Keystone flap; a tensionless wound closure; and a good flattening of the natal cleft to encourage tissue regeneration. Similarly, patients treated with the Keystone flap had a shorter hospital stay (2.1±0.6 days) as opposed to patients undergoing Bascom procedure (3.8±1.2 days) (p<0.001). This certainly means that the Keystone flap not only promotes wound healing but also quicker mobilization and discharge, hence decreasing the utilization of healthcare resources. Overall, this evidence highlights the higher performance and faster recovery of the Keystone flap approach, actively appealing to patients, as well as surgeons, given the favorable post-operative outcomes.

Table 4: Healing time and hospital stay

Table 5 illustrates the late postoperative results, focusing on recurrence, persistent pain, and patient satisfaction one year after surgery.  It is interesting to note that the recurrence rate in the Keystone flap was less than 2% compared with Bascom operation, in which it was 7% (P = 0.09). This trend actually indicates thus suggesting that the Keystone technique offers a better closure of the wound due to better perfusion of the flap and the removal of the deep natal cleft-which factors reduce recurrence. Patients having the Keystone flap experienced less persistent pain, though, with 5% and 12% of patients with the Bascom operation reporting dull postprocedural pain (P = 0.05). Less pain may be related to the design of the off-midline flap, which reduces tension along the suture line and avoids irritation during sitting and movement. For scar cosmetic satisfaction, patients were considerably more satisfied with their Keystone flap scar compared with their Bascom scar-that is, 92% versus 80% (p = 0.02). The smooth contour and lateral scar concealment probable greatly aided this perception: together, these findings show that the Keystone flap provides better long-term comfort, recurrence tendency, and cosmetic results and, as such, a dependable reconstructed modality for chronic pilonidal sinus disease.

Table 5: Late postoperative outcomes

Table 6 demonstrates a clear difference between the two surgical approaches in terms of functional recovery and return to normal daily activities.  The patients treated by the Keystone flap method went back to work much earlier, with a mean recovery period of 15±4 days, as against 28±6 days in those treated by the Bascom method (p<0.001). This huge decrease in downtime gives proof that the healing in these patients is much quicker and that there is hardly any postoperative morbidity with the Keystone technique. Likewise, the duration of trouble with sitting was much lower for patients of the Keystone flap group (10±3 days) as against the Bascom group (22±5 days) (p<0.001). The possibility lies in the fact that the Keystone becomes more comfortable and mobilizes sooner due to the flatter postoperative contour and tension-free off-midline closure.

Table 6: Return to normal activity

Patient satisfaction Table 7 shows the comparison between the Keystone flap and Bascom operation groups. Generally, satisfaction was far greater among patients who had the Keystone flap, implying that these patients had a more comfortable postoperative period and better cosmetical results. More of the Keystone flap patients reported an easy recovery (85%) as opposed to 70% in the Bascom group, which agrees with reduced tissue tension and better flap perfusion with the Keystone design. A slight 92% of the patients in the Keystone group were satisfied with the cosmetic aspect compared to 80% of the Bascom group. The aesthetic superiority may be attributed to a smooth contour to the gluteal region and lateral scar placement, which makes it less visible and thus less discomforting within the natal cleft.

Table 7: Patient satisfaction survey (n = 200)

Comparison of principal advantages and indications for both surgical techniques is seen in Table 8. It is indisputably better in several key aspects: healing time of 3 weeks or so, shorter hospital stay, which are direct derivatives of good vascularized support of the flap and tension-free closure. The recurrence of Keystone flap reconstruction is very rare; however, occasional cases of recurrence have been noted after the Bascom operation, thereby testifying to the long-term sustainability of the Keystone flap in difficult or recurrent cases. In terms of aesthetic results, the Keystone flap presented an excellent postoperative appearance  because  of  off-midline  suture placement and flattening of the natal cleft, thus reducing scar visibility and scar-related discomfort. Technically speaking, the Keystone flap is moderately difficult to perform and requires higher surgical skills, while the Bascom operation is simpler surgically and is thus suitable for less extensive or primary pilonidal sinus disease. In brief, this summary again confirms that the Keystone flap provides fastest recovery, best cosmetic results, and least chances of recurrence in cases of large, recurrent, or complex pilonidal sinus. The role of the Bascom operation is retained for the smaller or primary category, and this is especially true in limited-resource or outpatient surgical practice.

Table 8: Summary of major advantages

This study offers a thorough comparison of the Keystone perforator flap and Bascom cleft-lift operations for chronic and recurrent pilonidal sinus (PNS) in a cohort of 200 patients treated at Al-Kindy Teaching Hospital between 2022 and 2025. Both procedures were considered to be safe and effective, but better results were noted with the Keystone flap in almost all variables measured, including wound healing, postoperative morbidity, recurrence rate, and patient satisfaction. With regard to the demographics provided in Table 1, the two groups considered to be statistically comparable in their respect to age, gender distribution, BMI, and recurrence pattern, and thus, there is an elimination of selection bias. This was concurrent with the literature reporting PNS as a disease predominantly affecting young adult males with an average age ranging between 20 and 30 years and with an incidence that is higher in obese people who prefer a sedentary lifestyle [22-24]. On the other hand, intraoperative data in Table 2 showed that slightly longer operative times and marginally greater blood loss occurred during Keystone flap surgery, similar to the study of Arslan et al. [4] and Guner et al. [10] who attributed such differences to the technical accuracy required in designing a perforator-based flap. However, despite longer operative time for the Keystone flap, the need for drains was lower along with secure coverage; this may well be due to the wide advancement and tension-free closure provided by the Keystone flap [25-27]. Early postoperative complications in Table 3 indicated a lower but insignificant risk of wound infection, seroma, and wound dehiscence in the Keystone group compared to the Bascom group, agreeing with previous findings by Petersen et al. [2], Mahdy [11], and Can et al. [9], which confirmed that off-midline flaps reduce dead space and tension with infection risk compared to midline closure. Table 4 displayed a remarkable reduction in healing time (21±3 vs. 42±6 days, p<0.001) and hospital stay (2.1±0.6 vs. 3.8±1.2 days) of patients treated with Keystone flaps, consistent with McCallum et al. [14] and Al-Khamis et al. [15], in which off-midline closures have been associated with faster epithelialization and early discharge compared with open healing or midline repair. Late outcomes in Table 5 showed a lower recurrence rate (2% vs. 7%) and significantly better cosmetic satisfaction (92% vs. 80%) in the Keystone group than in the Bascom group, aligned well with one set of results by Bascom and Bascom [24] and another by Abdelrazeq et al. [27] and Guner et al. [26], who recorded recurrence below 5% after off-midline or flap reconstruction. The small recurrence observed in this series is because of effective flattening of the natal cleft and lateral positioning of the scars minimizing hair collection and friction, an anatomical correction repeatedly stressed in the literature (5–7, 25). Postoperative pain persisting in patients was also lower in the Keystone flap group (5% vs. 12%, p = 0.05), supporting the works of Mahdy [11] and Nursal et al. [12] stating that tension-free flap closure significantly reduces pain levels during sitting and ambulation. Functional recovery parameters found in Table 6 indicated that the mean days to resume work were shorter for patients treated with Keystone flap (15±4) than for those treated with Bascom (28±6) (p<0.001), which is in agreement with the findings of Arslan et al. [4] and Guner et al. [10] in that off-midline procedures speed up the resumption of activity by minimizing postoperative pain and wound tension. Also, sitting pain persisted for 10±3 days in the Keystone group versus 22±5 days in the Bascom group, confirming the benefit of lateral suture lines to patient comfort and shallow cleft geometry [18,9,13]. Patient-reported outcomes outlined in Table 7 further supported the supremacy of the Keystone flap since 85% of patients reported pain-free recovery; 92% were satisfied with cosmetic outcomes; and 95% would recommend the procedure to others, versus 70%, 80%, and 82%, respectively, for the Bascom group. These results are similar to the conclusions reached by the Limberg and Karydakis series [5,8,25], where patient satisfaction was directly correlated with scar placement and a reduced rate of recurrence. The overall comparative summary in Table 8 shows that the Keystone flap was followed by faster healing (3 weeks vs. 6 weeks), shorter hospital stay, and less recurrence than the Bascom procedure, all while retaining excellent cosmetic results. Although it requires moderate technical skills, the versatility and robust perfusion of the Keystone flap render it exceptionally suited to larger or recurrent defects, also supported by Dylek and Bekerecioglu [7] and Kitchen [25]. These findings coincide well with the broad consensus reached by meta-analyses [1,14,15] and observational studies [17-20,22,23,28-30], which unanimously emphasize that off-midline reconstruction, particularly with tension-free and well-vascularized flaps, has the lowest recurrence and highest patient satisfaction during chronic PNS. Thus, these results establish the Keystone perforator flap as a better reconstructive choice with speedy recovery, low morbidity, good cosmesis, and lasting results, while Bascom cleft-lifts are still very good and technically simpler options for smaller or primary lesions.

The Keystone perforator flap provides superior outcomes compared to the Bascom operation, including faster healing, reduced morbidity, lower recurrence, and enhanced cosmetic and functional recovery. It represents a reliable reconstructive option, especially for large or recurrent PNS cases, while the Bascom operation remains a valuable alternative for smaller or primary lesions.

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