Pilonidal Sinus PS is a prevalent disease in young patients. There is currently no consensus on the surgical treatment of choice. Each method is associated with different advantages and disadvantages, as well as different recurrence rates. The ideal treatment should reduce morbidity, be associated with a short hospital stay (outpatient surgery), promote rapid healing, early return to work, and have a low recurrence rate. To date, no technique meets all these criteria. However, the NPT could meet them. The use of NPT in PS could decrease healing time, achieving an early return to work. In addition, it would avoid the need for daily dressings, which would mean lower hospital costs. However, the location of the wound (sacrum) and its proximity to the anal margin mean that its use cannot be generalized.

Although two retrospective series have recently reported good results with the use of NPT in PS, a prospective, randomized study is needed to compare healing time, recurrence rates, hospital costs, and assess quality of life for determine if this could be the treatment of choice.

Although NPT is commonly used in clinical practice (being useful in closing complex wounds, with devitalized tissues, burns and wounds with exposed tendons), to date there is not enough evidence to support its use after flattening the PS and it is for this reason that we conducted this study.

In this project there is a total absence of commercial interest in the proposal. No project related to the proposed one is currently being carried out.

The study population will be made up of all patients with PS admitted to the General and Digestive Surgery service of the Hospital Universitari de Bellvitge from the start of the trial until the end of recruitment, and who meet the inclusion criteria.

Once the patients belonging to the population of interest have been identified, they will propose to participate in the clinical trial, providing complete information, as well as an information sheet with the details of the study. If you agree, the informed consent document will be provided for your signature and randomization will proceed.

Bitter et al. observed in a prospective study that the use of NTP did not reduce healing time compared to conventional closure 84 days (34-349) vs 93 days (43-264); p=0.44. However, the duration of NPT application of only 2 weeks might have been too short to see an adequate effect. Also, the small sample size could have influenced the results. On the other hand, recent publications on the use of TPN in the treatment of pilonidal sinus have shown a significant reduction in healing time (28 days) with minimal complications and adequate patient satisfaction. Taking into account the scarce evidence of the studies cited, we have decided to adopt a conservative criterion, assuming a smaller difference in time to healing between the two treatments (35 days).

To calculate the sample size, the time variable has been transformed into a logarithm. Accepting an alpha risk of 0.05 and a beta risk of 0.20 in a bilateral contrast, 94 patients, 47 subjects in the control group and 47 in the experimental group, are needed to detect a difference of 0.77. A common standard deviation of 1.26 is assumed. A rate of loss to follow-up of 10% has been estimated.

Randomization 1:1 will be performed using a statistical program at the baseline visit in outpatient clinics 48 hours after surgery, after assessing the dimensions of the wound, checking whether the participant meets the inclusion/exclusion criteria and has signed the informed consent.

For the purposes of the study and in order not to influence the type of surgery performed on patients with PS, only those patients who have undergone a flattening will be included. The 1st cure will be performed 24 hours later in the area outpatient clinic and will consist of removing the dressing, washing with physiological serum and placing a dry dressing.

48 hours after surgery, patients will be evaluated in outpatient clinics at our hospital. The dressing will be removed from the wound and after washing with serum, it will be checked if the patient meets the inclusion criteria. If you meet them, you will be offered to participate in the study and once you have signed the informed consent, randomization will proceed.

The patients will be monitored in person in outpatient clinics (CEX) by two members of the research team, made up of a nurse specialized in cures and a doctor specialized in surgery.

During the follow-up visits, a conventional dressing will be performed or the negative pressure system will be changed. Symptomatology and quality of life data will be collected through validated surveys.

Inclusion Criteria:

• All patients diagnosed with SP (recurrence or not), who have undergone surgery.
• Minimum depth of the wound 1.5 cm.

Exclusion Criteria:

• Inferior margin of the surgical wound is located less than 3 cm from the anus
• Patients under 16 years of age
• Unable to track
• Diagnosed psychiatric illness
• Patients diagnosed with hidradenitis
• Uncontrolled diabetics
• Immunocompromised (kidney or liver transplant, chronic treatment with corticosteroids, haematological disease, neoplastic disease undergoing chemotherapy)