ENVELOP: Wound Care Following Pilonidal Sinus Surgery

Pilonidal sinus disease (PSD) is a chronic inflammatory condition of the skin and subcutaneous tissues arising from hair follicles in the natal cleft. The definitive aetiology of the condition is unknown, however, it is theorised that it is the result of either the obstruction and subsequent inflammation of hair follicles or secondary to hair penetrating through the skin into the subcutaneous tissue. This results in infection, abscess formation, chronic discharge and pain. PSD is a common condition affecting 26 per 10,000 population, with the prevalence reaching 1.1% in young adult males.

PSD causes a significant burden on healthcare services due to high rates of recurrence and readmission following surgery, together with negative impacts on patients' quality of life and self-image. An effective management strategy for the disease is necessary to ensure that post-operative outcomes are optimised and patient-reported outcomes are satisfactory in those whose PSD requires surgery.

The objective of this multicentre, national RCT is to prospectively investigate the effect of negative pressure wound therapy compared to leaving open with standard wound care on time to wound healing following surgical excision of chronic PSD.

• Negative Pressure Wound Therapy (Device): Following elective excision of chronic pilonidal sinus disease with the wound left open, NPWT is applied in theatre using a polyurethane foam-based system (e.g. VAC, Renasys-GO, Prevena or equivalent) cut to fit the wound cavity, sealed with an adhesive drape and connected to a portable pump at -125 mmHg continuous pressure. Dressings are changed every 48-72 hours in clinic until granulation reaches skin level, followed by standard dressings until epithelialisation.
• Standard wound care (Other): Standard wound care

Primary outcomes

• Time to complete wound healing [Up to 6 months post surgery]: Number of days to complete epithelialisation or closure of the wound without any discharge, drainage, scab, and/or the requirement for further dressing.

Secondary outcomes

• Measure of post operative pain [Day of surgery, 28 days post surgery & 3 months post surgery]: Pain measured by visual analogue pain scale (0 = no pain, 10 = worst pain) at rest, on walking and on sitting
• Measure of post operative complications [6 months post surgery]: Post-operative complications, including surgical site infection (CDC criteria), seroma, abscess, readmission and return to theatre.
• To compare recurrence rates [6 months post surgery]: To compare the 6-month recurrence rates (recurrence being defined as the development of a new sinus or abscess within the natal cleft occurring after wound healing had been achieved) between the NPWT and SWC Groups
• Cost-effectiveness [6 months post surgery]: Within-trial cost-utility analysis from health-system and patient perspectives, expressed as incremental cost per QALY gained (QALYs from EQ-5D-5L, area under the curve). Resource use includes hospital and community contacts, dressing changes, complications, readmissions and returns to theatre, valued at Irish unit costs; patient costs and productivity losses via CoPaQ.
• Health-related quality of life with the EuroQol-5 dimensions five level index questionnaire (EQ-5D-5L) [Baseline, 1 month, 3 months & 6 months]: The questionnaire covers five dimensions of health: mobility, self-care, usual activities, pain or discomfort, and anxiety or depression. Each dimension has 5 levels: no problems (1), slight problems (2), moderate problems (3), severe problems (4) and extreme problems (5). The patient is asked to indicate his/her health state by ticking the box next to the most appropriate statement in each of the five dimensions. Index values derived using the EQ-5D-5L value set specified in the Statistical Analysis Plan (Irish value set where available).
• Scar assessment - using the Patient and Observer Scar Assessment Scale (POSAS) [28 days, 3 months, 6 months]: The POSAS is made up of two scales: the patient and observer scales each comprise six items scored 1 to 10; each scale is summed (6 = normal, 60 = worst) and reported separately.
• Health-related out-of- Pocket Costs assessed using the Costs for Patients Questionnaire (CoPaQ) [28 days, 3 months, 6 months]: The CoPaQ measures patient and caregivers out-of-pocket expenses (direct and indirect) associated with a health condition

Sex: All, ages: 18 Years to any

Inclusion Criteria:

i) They are aged 18 years or older

ii) They are undergoing elective pilonidal sinus excision without primary closure

Exclusion Criteria:

i) They are unable to adhere to protocol requirements e.g. questionnaire completion

ii) They are undergoing emergency drainage for a pilonidal abscess

iii) They are undergoing surgery for pilonidal sinus disease in locations other than the natal cleft

iv) They have underlying osteomyelitis

v) They have underlying fistulating disease e.g. Crohn's

• Sean T Martin, Principal investigator, St. James's Hospital, Ireland