Healing by primary versus secondary intention after surgical treatment for pilonidal sinus
Abstract
This is a protocol for a Cochrane Review (Intervention). The objectives are as follows:
The aim of this systematic review is to determine the relative effects of open versus closed surgical treatment for pilonidal sinus on the outcomes of time to healing, infection and recurrence rate.
Background
The term pilonidal sinus, 'pilus' meaning hair and 'nidal' meaning nest, was first used by Hodges in 1880 to describe an abnormal chronic tract between the buttocks (Chinn 2003). Pilonidal disease was termed 'jeep disease' during World War II because many military drivers were found to have the condition (Chinn 2003).
Pilonidal sinus is a disease that arises in the hair follicles of the natal cleft of the sacrococcygeal area (i.e. in the buttock cleft at the end of the backbone). It is a common disease with an estimated incidence of 26 per 100,000, affecting males twice as often as females (2.2 to 1.0 male to female ratio)(Sondeena 1995). The mean age of presentation is 21 and 19 years in males and females respectively (Notaro 2003). Many, but not all patients are hirsute, and an excess incidence has been reported in moderately obese patients (Notaro 2003).
Originally thought to be a congenital condition, recent studies suggest that pilonidal sinus is an acquired disease that results from one or other of two aetiological mechanisms (causes)(Al‐Naami 2005). Firstly, obstruction of the hair follicles can lead to follicle enlargement and rupture into the subcutaneous tissues causing abscess ‐ and ultimately chronic sinus ‐ formation. Secondly, broken hair can become inserted abnormally into the skin at the natal cleft, provoking a foreign‐body reaction where the subsequent infection results in cyst formation or sinus disease (Al‐Naami 2005).
Patients with pilonidal sinus often present with an acute painful swelling in the natal cleft associated with an abscess with, or without, the drainage of bloody purulent material (pus) from the sinus opening. Alternatively, patients may present with a chronically discharging, and often painful, sinus tract. Irrespective of the mode of presentation, the painful nature of the condition causes significant morbidity and, although many patients tolerate symptoms for up to one year before seeking treatment, there is often a protracted loss of normal activity for these patients.
The 'ideal' therapy would be a quick cure that allowed patients to return to normal activity as soon as possible, with minimal pain and a low risk of complications such as recurrence or persistence of the sinus, and ongoing infection. The treatment of a pilonidal sinus‐related acute abscess is well established and consists of immediate drainage of the abscess followed by the slow process of healing by granulation (formation of new tissue in the sinus void). However, management of chronic pilonidal disease is variable, contentious and problematic. The principles of treatment require the eradication of the sinus tract, complete healing of the overlying skin and prevention of a recurrence. Non‐surgical treatments include the application of phenol, regular shaving and cryosurgery.
Surgical techniques are based on either incision, usually of an acute abscess, or excision of a chronic sinus tract. The surgical wound may be left to heal by secondary intention, that is, left open, packed and allowed to heal. Advocates of this technique think that this reduces both wound tension and wound infection, as free drainage can occur.
Alternatively, the wound is closed (healing by primary intention) either immediately (primary wound closure) after surgical treatment, or after a delay. The best method of closure is a matter of conjecture. Methods can be broadly categorised as either midline closure techniques (with the wound lying within the natal cleft), or other techniques (where the wound is placed outwith the midline, or the defect e.g. skin grafts, tissue flaps). Advocates of this approach think that healing is improved by eliminating the rolling actions of the buttocks over one another, which is achieved by flattening the gluteal crest. Variations in current practice reflect the literature which describes a wide spectrum in the outcomes reported for different open and closed surgical techniques for the treatment of pilonidal sinus.
The aim of this systematic review is to determine the relative effects of open versus closed surgical treatment for pilonidal sinus. This will assist clinicians in managing this common problem and identify where further research is required.
Objectives
The aim of this systematic review is to determine the relative effects of open versus closed surgical treatment for pilonidal sinus on the outcomes of time to healing, infection and recurrence rate.
Methods
Criteria for considering studies for this review
Types of studies
Randomised controlled trials comparing two or more surgical techniques that include healing by primary (closed wounds) or secondary intention (open wounds) for the treatment of non‐infected pilonidal sinus. Non randomised studies will be excluded.
Types of participants
Adult patients (over 14 years of age) undergoing surgery for pilonidal sinus disease. No distinction will be made between new (initial presentation of the disease) and recurrent presentation of pilonidal sinus. Patients presenting with an abscess will be excluded. Studies will be included if they include patients treated for pilonidal abscess, only if results can be analysed separately for patients with abscess and pilonidal sinus without abscess
Types of interventions
Any surgical intervention (open or closed) for treatment of pilonidal sinus will be included where it has been compared against another surgical intervention. Interventions will be assigned to the closed group if primary closure has been used to complete the procedure. This will include studies comparing different types of surgical closures, e.g. midline versus alternative closure techniques. The secondary intention healing (open) group will include wounds that have been left open to heal by secondary intention. Trials comparing surgery with non‐surgical interventions will be excluded.
Types of outcome measures
The primary and secondary outcomes (where available) will include:
Primary outcome measures
(a) Time to wound healing.
(b) Rate of surgical site infection (SSI)/proportion of wounds that become infected postoperatively.
(c) Recurrence rate or reoperation rate (there may be differences between how these are reported).
Secondary outcome measures
(a) Time to return to work.
(b) Other complications and morbidity.
(c) Patient satisfaction.
(d) Cost.
(e) Length of hospital stay.
(f) Pain.
(g) Quality of life.
(h) Rate of change of wound volume
Search methods for identification of studies
In order to identify studies to be considered for this review the following databases will be searched.
(a) The Wounds Group Specialised Register.
(b) The Cochrane Central Register of Controlled Trials (CENTRAL)(latest issue).
(c) MEDLINE 1966‐2006.
(d) EMBASE 1980 ‐2006.
The following search strategy will be used for CENTRAL. This has been developed in collaboration with the Cochrane Wounds Group.
1. exp pilonidal sinus/
2. pilonidal.tw
3. (pilonidal adj3 sinus$).mp
4. pilonidal adj3 fistula$).mp
5. (pilonidal ajd3 cyst$).mp
6. pilonidal adj3 disease$).mp
7. (pilonidal adj3 abscess$).mp
8. natal cleft.mp
9. or/1‐8
This strategy will be amended for other databases as appropriate.
Handsearching of journals
Handsearching of journals is deemed unnecessary, as all likely high‐yield publications are either included within the above search strategy or have already been hand searched and included in the Wounds Group Specialised Register.
Contact with experts in the field
Once the initial search has been completed, we will contact the authors of included randomised controlled trials (RCTs) to ask for information on ongoing studies or unpublished data.
Language restrictions
There will be no language restrictions. We will endeavour to translate any non‐English language papers using the resources of the Cochrane Wounds Group.
Bibliography Searching
The bibliography of all included studies will be searched in order to identify other potentially suitable studies.
Data collection and analysis
Selection of trials
Titles of papers will be identified using the search strategy set out above. Titles and abstracts will be read by two authors (IM and JB) to decide which should be included in the review (the inclusion/exclusion criteria are listed below). Any disagreements over inclusion or exclusion of abstracts will be resolved by obtaining the full paper for assessment. Duplicate citations will be removed, although duplicate publications reporting data from one study in two or more papers will be obtained for full consideration.
Inclusion criteria for abstracts
Inclusion:
(a) Randomised controlled trial.
(b) Adult population (over 14 years of age).
(c) Pilonidal sinus without abscess
Exclusion:
(a) Non‐randomised studies.
(b) Children (less than 14 years).
(c) Comparison of non‐surgical interventions.
(d) Pilonidal Abscess
The resulting list of included papers will then be subject to full critical appraisal and data extraction.
Assessment of study quality
Study quality will be assessed, particularly for risk of selection, performance, attrition and detection biases.
Randomisation .
Was the method of the randomisation appropriate e.g. computer generated, random number tables, coin toss. Method of randomisation will be recorded as yes, no, or unclear.
Concealment of allocation .
Was a randomisation method described that would not allow investigator/participant to know or influence the intervention group before an eligible participant was entered in the study? Was allocation concealment adequate? This will be recorded as: adequate, unclear, inadequate or not used.
Level of blinding.
Were participants and assessors blind to the intervention? Were differential co‐interventions avoided? These will each be recorded as yes, no, unclear, or not possible.
Completeness of follow‐up.
Were withdrawals described and reported by treatment group with reasons given? Were all randomised participants analysed in the groups to which they were originally randomised (intention‐to‐treat)? We will record whether or not there was a clear explanation for withdrawals and drop‐outs in each treatment group. Follow‐up of more than 80% will be recorded as yes, no or not clear and any evidence of differential loss to follow up noted. Intention‐to‐treat analysis will be recorded as yes, no or not clear.
Data extraction
A data extraction form has been developed to record these data. It has been piloted on three RCT papers, by two independent investigators (IM and JB). Full data extraction of included papers will be done by two authors independently (IM and JB). Disagreements will be resolved by a third person (PMK). The study quality items listed above will be presented in a table of quality assessment. Consideration will be given to the categorisation of low, medium or high risk of bias according to the Cochrane Handbook (grading A, B or C).
Data Analysis
Data will be entered into RevMan for analysis. Results will be presented with 95% confidence intervals. Estimates for dichotomous outcomes will be reported as relative risks. Continuous data will be converted to the standardised mean difference (or a weighted mean difference, when plausible) and overall effect size (with 95% confidence intervals) will be calculated. Time to wound healing and time to return to work will be analysed as survival (time to event) outcomes, using the appropriate analytical method e.g. hazard ratios (as per the Cochrane Reviewers' Handbook version 4.2.5).
Given the type and format of data extracted from primary studies, we intend to statistically combine results of similar studies statistically where possible using RevMan software. Weighted averages will be used to account for differences in sample sizes and event rates.
Heterogeneity of included studies
We will investigate the following factors as potential causes of heterogeneity using the framework below:
Clinical diversity
For example study location and setting, full characteristics of participants (e.g. age/sex/social class), co‐morbidity and treatments that participants may be receiving on entry to the trial. We will assess how outcomes were measured, definition of outcomes and the outcomes recorded. Depending upon how diverse these factors are across studies, these may be analysed separately (or, as described below, a narrative approach may be used).
Methodological diversity
For example assessment of randomisation process, study quality and analytical method (intention‐to‐treat versus treated).
Statistical diversity
This will be explored initially by looking at the estimates of treatment effect of included studies and considering whether we are confident that a combined estimate will give a meaningful description. This will be conducted using forest plots generated with the Revman software. We will also consider using the I‐squared statistic within RevMan, which examines the percentage of total variation across studies due to heterogeneity rather than due to chance (Higgins 2003). A value of greater than 50% may be considered substantial heterogeneity (Higgins 2005). If the data are too diverse for combining effect sizes in a meaningful or valid manner, we will use a narrative approach to summarising the findings.
The decision about whether to use fixed effect or random effect models will be taken after study assessment and data extraction have been completed. We intend to liaise with the Wounds Group to consider the most appropriate statistical method for the data obtained. We have access to statistical support within the Department of Public Health at the University of Aberdeen.
Subgroup analyses
We intend to analyse studies by three closure methods: open, closed midline and closed other. Closed 'other' will include closures techniques off the midline, including all plastic and advancement techniques (e.g. flaps, marsupialisation) where the surgical wound lies off the midline.
Analysis will be as follows:
open vs. closed (all)
open vs. closed (mid line)
open vs closed (other)
closed (midline) vs. closed (other)
