Pilonidal sinus disease (PSD) is a common condition, with an incidence rate of 26/100,000, typically affecting young men (1,2). PSD manifests in the sacrococcygeal region as either an acute abscess or chronic inflammation of the sinus tract (3-5). Multiple factors have been associated with PSD, including obesity, poor hygiene, prolonged sitting, hairiness, and deep natal cleft (5,6). Treatment options range from minimally invasive procedures, such as laser treatment and phenolization, to surgical excision combined with midline closure or flap reconstruction (5-7). While surgical methods have traditionally been the primary choice, recent studies have shown promising results for minimally invasive approaches, providing faster recovery and low post-operative complication rates (8-11).

Pilonidal disease is a frequently recurring condition, with a recurrence rate of up to 40% within a 5-year follow-up, and significant variation across different treatment modalities (12,13). In the literature, higher recurrence rates have been associated with surgical excision combined with midline closure, whereas off-midline techniques, such as Limberg flap and Bascom cleft, lift have been linked to lower recurrence rates (4,12-16). However, patient-related factors (13,16) and follow-up times (6,12) should also be considered when evaluating the recurrence rates. Recurrent PSD can be managed using primary case treatment modalities (16-18). The most effective approach remains debated despite the various treatment options available (15,16,18-20). Additionally, there is a shortage of published literature addressing the management of recurrent disease. This study aims to present the results of re-operations in our patient cohort and discuss the factors contributing to the recurrence of pilonidal disease to inform future decisions based on previous experiences and knowledge.

Our observations indicate that factors leading to recurrence and re-operation vary depending on the selected treatment method. Patients who underwent laser treatment as their primary operation exhibited more residual and recurrence when compared to those treated with other surgical techniques, and there was also a statistical difference between the groups. In our experience, laser treatment provides favorable results for relatively superficial pilonidal sinus. However, residual disease is more common when it affects deeper tissues of the sacrococcyx area. To address this, we perform a magnetic resonance imaging (MRI) scan to assess the extent of pilonidal sinuses if residuals are detected after the second laser treatment. While laser treatment has yielded promising results with fewer complications than open surgical methods (12,15,23), some studies have reported high recurrence rates over extended follow-up periods (11,12). Nevertheless, comprehensive long-term data on laser treatment are still limited. Differentiating recurrence from residual disease may also be challenging without close post-operative monitoring, thus potentially influencing the accuracy of recurrence rates.

The most common complication after direct closure was dehiscence, likely due to this technique resulting in tension and traction of the suture lines (2,5,16). Technical factors in suturing can also influence dehiscence. Factors leading to re-operation seemed more varied after primary flap reconstruction. Patients in the flap group experienced less dehiscence than those in the direct closure group, but hematoma was more prevalent. Flap techniques aim to reduce tension and traction by flattening the natal cleft and placing sutures away from the midline, decreasing the risk of dehiscence (2,5,16). However, flap reconstruction techniques require detaching the soft tissue from a wider area, resulting in a higher risk of postoperative hematoma, which may explain our findings.

Infection rates were similar between the groups, possibly affected by the location of the pilonidal sinus, which can increase the risk of bacterial contamination. Additionally, PSD often appears as an infected sinus before surgery (2,5,17). However, factors like poor hygiene and inadequate wound care may also influence infection rates (24). Other studies have shown significant differences in postoperative infection rates, with the highest risk usually linked to the direct closure method (6,10).

The re-operation method was individually selected for each patient, considering the primary operation. In most cases, patients were re-operated using the same treatment modality as in their initial procedure, apart from flap reconstruction, which was typically followed by direct closure. By mobilizing the flap during re-operative surgery, direct closure can be performed without causing tension on the suture lines, eliminating the need for new reconstruction. Re-operation with laser treatment was rare after direct closure or flap reconstruction, as most of these surgeries were conducted before the introduction of laser treatment to our clinic. Multiple re-operations were frequently required after primary direct closure, suggesting that this method may not be optimal for treating pilonidal disease, a conclusion also reached by other studies (2,4,7,12). Re-operation with laser is recommended in cases with minor residual disease in the operation area. Laser is also a safe and effective option for recurrent pilonidal disease (25).

The typical characteristics of pilonidal disease patients (male gender, age, and overweight) were well represented in our patient cohort. However, significant variation was found between the groups. Patients who underwent flap reconstruction were older and had higher BMIs. Additionally, both the flap reconstruction and direct closure groups had significantly more smokers compared to the laser group, possibly reflecting the increased emphasis on smoking cessation in recent years. Smoking and obesity are associated with a higher risk of complications and inadequate healing, potentially influencing the complication rates of the groups. Smoking and high BMI could also contribute to the need for re-operation rate. Data on poor personal hygiene, sacrococcygeal hair density, sitting time, tight clothing usage, and microbiological data were not collected because the information was unavailable.

Laser treatment is a minimally invasive procedure performed in an outpatient clinic under local anesthesia, requiring little post-operative care and minimal sick leave. In contrast, flap reconstruction and direct closure are more extensive procedures, requiring postoperative wound care, sitting limitations, and longer sick leave for optimal healing (9-11). These differences present a challenge when comparing the complication rates of the groups. The follow-up time after laser treatment was significantly shorter after direct closure and flap reconstruction. Patients in these groups underwent treatment at different periods, so the follow-up times are not directly comparable. As laser treatment is a relatively new method in our clinic, extensive long-term data on its outcomes are yet to be acquired.

While this study provides valuable insights, its limitations include a retrospective design and a relatively small patient cohort. Additionally, comparing laser treatment and excision, combined with direct closure or flap reconstruction, presents challenges due to their distinct natures. Furthermore, variations in patient characteristics between the groups and the notably shorter follow-up time after laser treatment may impact the results. Multivariable analysis was not performed due to the small number of patients in the data. Different techniques used in various periods may lead to selection bias. The Flap group, for example, may include more complex cases. Larger studies with longer follow-up periods are required to determine the optimal treatment method for PSD. In the study, we did not evaluate the quality of life assessment, including pain and return to work, which is a limitation of the operative results. Only pairwise Mann-Whitney U tests were used, increasing the risk of type I error, therefore results should be interpreted with caution to avoid overinterpretation. Despite these limitations, the study benefits from a lengthy, continuous period during which the treatment of pilonidal disease has improved and shifted towards a minimally invasive approach. This improvement is reflected in the post-operative results, with fewer complications associated with laser treatment than other modalities. Additionally, the extended follow-up of patients in the flap and direct closure groups provides valuable insight into the recurrence rates associated with these methods.

In conclusion, the risk of recurrent pilonidal sinus disease remains significant, yet most patients typically require only one re-operation. Laser treatment emerges as a promising approach for both primary and recurrent cases. However, long-term outcomes are necessary to confirm the matter.