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Base de datos Cochrane de Revisiones Sistemáticas Protocolo - Intervención

Lightweight versus Heavyweight mesh for laparoscopic repair of inguinal hernia

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Versión publicada: 07 diciembre 2011 Historial de versiones

https://doi.org/10.1002/14651858.CD009475

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Abstract

This is a protocol for a Cochrane Review (Intervention). The objectives are as follows:

The objective of this review is to systematically analyse the randomised controlled trials on the use of LWM versus HWM in patients undergoing LIHR by both trans‐abdominal pre‐peritoneal (TAPP) and total extra‐peritoneal (TEP) approach.

Background

Description of the condition

Open and laparoscopic inguinal hernia repair (LIHR) with mesh has become a gold surgical procedure for an estimated 16% symptomatic groin hernias in general surgical patients (Kingsnorth 2000; McCormack 2003; Payne 1994; Rosch 2003; Sarosi 2011; Scott 2001; Thompson 2008; Zieren 1998). Approximately 20 millions laparoscopic and open inguinal hernias are repaired each year worldwide, over 17000 operations in Sweden, over 12000 in Finland, over 80,000 in England and over 800,000 in the USA (Cheek 1998; Heikkinen 1998; Rutkow 2003).

Description of the intervention

The most frequently used biomaterial in all forms of hernia repair is polypropylene which offers maximum mechanical stability at hernial defect resulting in stiff and non‐flexible greatest scar formation to ensure a resilient hernia repair once mesh biomaterial is incorporated in abdominal wall. However, it produces a segment of abdominal wall with excessive tensile strength that is not adapted to local tissue leading to stiffness and foreign body sensations. Polymers of biomaterial used to construct mesh are considered physically and chemically inert, non‐immunogenic and non‐toxic but they can still trigger locally an extensive inflammatory adverse reaction called foreign body reaction (Bhardwaj 1997; Klosterhalfen 2005). If this reaction is too strong and unremitting, it could together with hazards of bio‐incompatibility and mis‐matched tensile strength of the mesh play a key role in the development of chronic groin pain (Poobalan 2001; Poobalan 2003). Additionally, mesh biomaterial is direct in contact with vas deferens and testicular vessels during LIHR, widespread regional fibrosis could leads to dysfunction of these structures, resulting in fertility problems and testicular pain (Ridgway 2002; Shin 2005). In view of the fact that inflammatory reaction to biomaterial of heavyweight mesh (HWM) correlates with the weight of mesh (amount of polymer expressed as gm/m2) and pore size of the material inserted, the concept of lightweight mesh (LWM) was developed to minimize the content of non‐absorbable foreign material with pore size of more than 1 mm (Klosterhalfen 1998).

How the intervention might work

The strategies to avoid long‐term complications of LIHR resulting from exaggerated foreign‐body reaction induced by HWM have been adequately implemented and reported with variable outcomes. One of the suggested solutions is to limit the amount of heavyweight component in HWM to use a low‐density Polypropylene mesh reinforced by an absorbable biomaterial that will provide initial strength but that will soon be absorbed, hence, limiting local inflammation and foreign‐body reaction. The first mesh that is partially absorbable and that has been commercialised consists of non‐absorbable Polypropylene and absorbable polyglactin 910 fibres, with a density of 83 gm/m2 in total, with 32 gm/m2 of Polypropylene and 51 gm/m2 of Polyglactin (Di Vita 2010; Junge 2002; Krause 2006; Rosch 2003). Increased bio‐compatibility and reduced incidence of chronic groin pain has already been reported after insertion of   new generations of LWM such as lightweight Polypropylene, Polypropylene‐Polyglactin, beta‐D‐glucan, titanium‐coated Polypropylene and Polypropylene‐Poliglecapron (Akolekar 2008; Hollinsky 2008; Khan 2006; Scheidbach 2004; Schopf 2011).

Why it is important to do this review

By analysing published randomised controlled trials (RTCs) comparing the effectiveness of LWM versus HWM according to the principles of meta‐analysis, authors will attempt to reach a conclusion and recommend the routine use of LWM in LIHR in order to avoid long‐term complications such as chronic groin pain, foreign body sensations and sperm dysmotility in men.

Objectives

The objective of this review is to systematically analyse the randomised controlled trials on the use of LWM versus HWM in patients undergoing LIHR by both trans‐abdominal pre‐peritoneal (TAPP) and total extra‐peritoneal (TEP) approach.

Methods

Criteria for considering studies for this review

Types of studies

We will analyse randomised controlled trials comparing the effectiveness of LWM versus HWM in LIHR

Types of participants

We will include randomised controlled trials on patients of any age, any gender, on both elective and emergency LIHR whatever the indication is i.e. groin lump, groin pain, inguinoscrotal lump, unilateral, bilateral, recurrent hernia.
We will consider inclusion of trials in English language of publication, regardless of number of patients recruited and whether hernia is acute in origin or chronic.

Types of interventions

We intend to compare the short‐term outcomes and long‐term outcomes following the use of LWM versus HWM in patients undergoing LIHR with TEP or TAPP approach.

Types of outcome measures

We will attempt to analyse following variables

Primary outcomes

  • Recurrence

  • Chronic groin pain

  • Post‐operative complications

  • Mortality

  • Return to work time

Secondary outcomes

  • Postoperaitve pain

  • Postoperaitve mortality

  • Postoperaitve morbidity

  • Foreign body sensations and stiffness in groin

Search methods for identification of studies

Electronic searches

Will will search the following electronic databases:

  • The Cochrane Colorectal Cancer Group (CCCG) Group Controlled Trials Register, the Cochrane Central Register of Controlled Trials (Appendix 1) on The Cochrane Library (Issue 1, 2011),

  • MEDLINE (until June 2011) Appendix 2 ,

  • EMBASE (The Intelligent Gateway to Biomedical & Pharmacological Information until June 2011) Appendix 3,

A filter for identifying relevant studies recommended by the Cochrane Collaboration (Higgins 2002; Higgins 2008) will be used to filter out irrelevant studies in Medline and Embase

Searching other resources

The references of the included studies will be searched to identify further trials. The 'related article' function of Medline will also be searched thoroughly in order to identify additional studies. Websites responsible for the registration of the randomised controlled trials will be searched to find out if there is recent trial running or ready to publish on this subject. We will attempt to gather information on all published, unpublished and ongoing trials from all possible data sources. If necessary, a personal communication by authors will be made to author for correspondence in published trials for further information on data or clarification. In addition, colorectal and hernia experts, specialist surgeons and pharmaceutical companies involved in provision of necessary equipment may be contacted and asked to provide details of outstanding clinical trials or any relevant unpublished materials. The international societies of colorectal surgery and hernia surgery will also be contacted and asked to provide information on any unpublished studies.

Data collection and analysis

Data will be collected using a data extraction form (Excel spread sheet) individually by three authors (MSS, CL, PS) and it will be further confirmed by the fourth author (MKB). The conflict will be resolved by mutual agreement among three authors. We will conduct the systematic review according to this presented protocol and the recommendations by the Cochrane Reviewers' Handbook (Higgins 2008; Review Manager 2011). The statistical analysis will be performed by MSS and will be further confirmed by CL and PS. The software package RevMan 5.1.1 (Review Manager 2011), provided by the Cochrane Collaboration, will be used for analysis. The risk ratio (RR) with a 95 percent confidence interval (CI) will be calculated for binary data variables, and the mean difference (MD) with a 95 per cent CI for continuous data variables will be calculated. If the mean values are not available for continuous outcomes, median values will be used for the purpose of meta‐analysis. If the standard deviation is not available, it will be calculated according to the guidelines of The Cochrane Collaboration (Higgins 2008). This will involve the assumptions that both groups had the same variance, which may not be true. The random‐effects model (DerSimonian 1986) and the fixed‐effect model (DeMets 1987) will be used to calculate the combined outcome in both binary and continuous variables. The Mantel‐Haenszel method will be used for the calculation of RR under the fixed effect model, and the DerSimonian/Laird method will be used for the calculation of RR under the random effect model (Egger 2006).  In a sensitivity analysis, 0.5 will be added to each cell frequency for trials in which no event occurred in either the treatment or control group, according to the method recommended (Deeks 2001). The estimate of the difference between both techniques will be pooled, depending upon the affect weights in results determined by each trial estimate variance. The forest plot will be used for the graphical display of results from the meta‐analysis. The square around the estimate will stand for the accuracy of the estimation (sample size) and the horizontal line will represent the 95% CI. Extraction of data. We will record the inclusion and exclusion criteria in each trial that fulfils our criteria for inclusion. In order to check is adequacy and quality of included trials we will score them according to published guide lines of Scottish inter‐collegiate Guidelines Network and Rangel et al (Rangel 2003; SIGN 2011)

Following details on methods will be extracted:

  • LIHR technique

  • Use of prophylactic antibiotics

  • Type of meshes used

  • Peri‐operative untoward events

  • Post‐operative untoward events

  • Measuring scales of different variables

The following data on randomisation and blinding procedure will be extracted:

  • Number of randomised patients.

  • Number of patients not randomised and reasons for non‐randomisation.

  • Exclusion after randomisation.

  • Drop‐outs.

  • Blinding of patients and observers.

  • Intention‐to‐treat' analysis.

  • Internal validity

  • External validity

  • Power calculations

Selection of studies

Studies will be selected according to predefined inclusion criteria. We will analyse randomised controlled trials comparing the effectiveness of LWM versus HWM in LIHR.

Data extraction and management

Data will be collected on the data extraction form (Microsoft Excel spread sheet) separately by three authors (MSS, CL, PS) and it will be further confirmed/re‐checked by the fourth author (MKB). Any conflict will be resolved by mutual agreement among all authors.

Assessment of risk of bias in included studies

We will define the methodological quality as the confidence that the design and report restrict bias in the intervention comparison (Higgins 2008; Moher 1998; Rangel 2003) and four important parameters (randomisation technique, allocation concealment, blinding, intention to treat analysis) for a high quality randomised controlled trial are clearly described in the reported study. We will also look for power calculation and strength of the trial in order to score it precisely and accurately. Due to the risk of overestimation of intervention effects in randomised trials with inadequate methodological quality (Higgins 2008; Kjaergard 2001; Moher 1998; Rangel 2003; Schulz 1995), we will assess the influence of methodological quality as follows.

Generation of the allocation sequence

Low, if the allocation sequence was generated by a computer or random number table.
Adequate, If methods are drawing of lots, tossing of a coin, shuffling of cards, or throwing dice, and if a person who was not otherwise involved in the recruitment of participants performed the procedure.
Unclear, if the trial was described as randomised, but the method used for the allocation sequence generation was not described.
Inadequate, if a system involving dates, names, or admittance numbers were used for the allocation of patients. These studies are known as quasi‐randomised and will be excluded from the present review when assessing beneficial effects.

Allocation concealment

Low, if the allocation of patients involved a central independent unit, on‐site locked computer, or sealed envelopes. Unclear, if the trial was described as randomised, but the method used to conceal the allocation was not described. High, if the allocation sequence was known to the investigators who assigned participants or if the study was quasi‐randomised.

Double/ blinding or masking

Low, if the trial was described as double blind and the method of blinding was described.
Unclear, if the trial was described as double blind, but the method of blinding was not described.
Not performed, if there was no blinding at all.

Follow‐up/intention to treat analysis

Low, if the numbers and reasons for dropouts and withdrawals in all intervention groups were described or if it was specified that there were no dropouts or withdrawals.
Unclear, if the report gave the impression that there had been no dropouts or withdrawals, but this was not specifically stated.
High, if the number or reasons for dropouts and withdrawals were not described.

Measures of treatment effect

We will score each study according to methods recommended by Cochrane Group, SIGN and Rangel et al (Higgins 2008; Rangel 2003SIGN 2011) in order to define risk of bias, power of the study, presence or absence of blinding and calculations based on the intention to treat analysis. Each trial will be a scored as follows: score A (adequate), score B (unclear), score C (not concealed) and score D (not done). Trials scoring A and B will be included and trials scoring C and D will be excluded.

Unit of analysis issues

The risk ratio (RR) with 95 % confidence interval (CI) will be calculated for binary data variables, and the mean difference (MD) with 95 % CI for continuous data variables will be calculated. If the mean values are not available for continuous outcomes, median values will be used for the purpose of meta‐analysis. If the standard deviation is not available, it will be calculated according to the guidelines of the Cochrane Collaboration (Higgins 2008). This will involve the assumptions that both groups had the same variance, which may not be true. The random‐effects model (DerSimonian 1986) and the fixed‐effect model (DeMets 1987) will be used to calculate the combined outcome in both binary and continuous variables. The Mantel‐Haenszel method will be used for the calculation of OR under the fixed effect model, and the DerSimonian/Laired method will be used for the calculation of OR under the random effect model (Egger 2006).  In a sensitivity analysis, 0.5 will be added to each cell frequency for trials in which no event occurred in either the treatment or control group, according to the method recommended (Deeks 2001). The estimate of the difference between both techniques will be pooled, depending upon the affect weights in results determined by each trial estimate variance. The Forest plot will be used for the graphical display of results from the meta‐analysis. The square around the estimate will stand for the accuracy of the estimation (sample size) and the horizontal line will represent the 95% CI.

Dealing with missing data

We will contact the first author via personal communication in order to get missing data. If further information are required from any source we will contact every relevant person involved in running of the published trial. If missing data could not be achieved and that particular trial does not score according to our inclusion criteria we will exclude that trial and explain it in the table giving details about excluded trials.

Assessment of heterogeneity

In case of heterogeneity, only the results of the random‐effects model will be reported. Heterogeneity will be explored using the Chi2 test, with significance set at P < 0.05, and it will be quantified (Higgins 2002) using I2 statistic, with a maximum value of 30 percent identifying low heterogeneity (Higgins 2008).

Assessment of reporting biases

We will define the methodological quality as the confidence that the design and report restrict bias in the intervention comparison (Higgins 2008; Kjaergard 2001; Moher 1998; Rangel 2003) and four important parameters (randomisation technique, allocation concealment, blinding, intention to treat analysis) for a high quality randomised controlled trial are clearly described in the reported study. We will also look for power calculation and strength of the trial in order to score it precisely and accurately. Due to the risk of overestimation of intervention effects in randomised trials with inadequate methodological quality (Higgins 2008; Kjaergard 2001; Moher 1998; Rangel 2003;Schulz 1995), we will assess the influence of methodological quality.

Data synthesis

Data of all primary and secondary outcomes will be synthesised on the Revman 5 (Review Manager 2011) in order to achieve a summative outcome.

Subgroup analysis and investigation of heterogeneity

We will attempt to study if some difference exists between trials with short‐term follow up (year of less than a year) and long‐term follow up (more than a year.  In addition we will also attempt to analyse trials according to approach adopted for LIHR i.e. TEP versus TAPP. We will perform a sensitivity analysis in order to compare the intervention effect in trials with high methodological quality (i.e. trials with adequate generation of the allocation sequence, allocation concealment, and blinding) to that of trials with low methodological quality (i.e., trials not having one or more adequate component). We will attempt to analyse if some difference exists between various groups of patients having primary inguinal hernia, unilateral hernia, bilateral hernia and recurrent inguinal hernia. Furthermore, we will explore causes of heterogeneity (defined as the presence of statistical heterogeneity by Chi2 test with significance set at P value less than 0.10 and measure the quantities of heterogeneity by I2 statistic (Higgins 2002) by comparing different groups of trials stratified according to patient risk factors, level of experience of the surgeon, and other factors that may explain heterogeneity. Clinical and methodological causes of the heterogeneity will be searched in reported trials and it will be clearly documented in this review.

Sensitivity analysis

Sensitivity analysis will be attempted by using funnel plot in order to determine potential bias in the reported trial and isolate the outliers.