Mesh versus non‐mesh for emergency groin hernia repair

Objectives

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

Main objective

To assess the benefits and harms of mesh compared with non‐mesh in emergency groin hernia repair in adult patients with an inguinal or femoral hernia.

Secondary objective

To assess whether the effects of mesh versus non‐mesh in emergency groin hernia repair differ according to the degree of contamination.

Background

Description of the condition

Groin hernia is a collective name for inguinal and femoral hernias (Brooks 2021). Around 5% of inguinal hernias and 37% of femoral hernias present acutely with incarceration or strangulation of the hernia sac content and require emergency treatment due to the risk of reduced supply of blood and thus oxygen to the bowel (bowel ischaemia) (Nilsson 2007; Reinke 2020). In incarcerated hernias, the sac content cannot be pushed back into its original compartment (Brooks 2021). Strangulation occurs when an incarcerated hernia compromises arterial supply to the content of the hernia sac, resulting in ischaemia and eventually death of body tissue, or necrosis (Brooks 2021). Emergency groin hernia repair is associated with higher morbidity and mortality compared with elective repair (Kjaergaard 2010; Malek 2004; Nilsson 2007).

Femoral hernias are associated with an increased risk of incarceration or strangulation (Dahlstrand 2009; Hernández‐Irizarry 2012). A previous study estimated the cumulative probability of strangulation in femoral hernias to be 22% and 45% at one month and 21 months, respectively (Gallegos 1991). In comparison, the same study estimated the cumulative probability of strangulation in inguinal hernias to be 2.8% at three months and 4.5% at 24 months. Other risk factors for incarceration and the need for emergency groin hernia repair are advanced age, female sex, hernia‐related hospitalisation in the year preceding hernia repair, and recurrent hernia (Dahlstrand 2009; Abi‐Haidar 2011; Primatesta 1996). 

Description of the intervention

Surgical repair is the only definitive treatment for emergency groin hernias (Brooks 2021). This procedure must be performed immediately after diagnosis due to the risk of strangulation and bowel necrosis (Reinke 2020). However, since there is no evidence supporting an optimal surgical approach, current guidelines suggest a tailored approach for adult patients presenting with acutely incarcerated or strangulated groin hernias (HerniaSurge Group 2018). Hernia repair, in general, may involve the use of mesh, or sutures only. In mesh repair, the surgeon covers the hernia defect with a prosthesis that is typically made from a synthetic polymer like polypropylene or polyester (Lockhart 2018). This procedure can be performed using an open surgical approach or a minimally invasive laparoscopic approach (McCormack 2003), whereas non‐mesh procedures are always open. In elective groin hernia repair, open or laparoscopic mesh repair is recommended as standard, to decrease the risk of recurrence (HerniaSurge Group 2018). Incarcerated or strangulated groin hernias are usually repaired with an open approach, but a laparoscopic approach may also be feasible in experienced hands (Karatepe 2008). 

Surgical site infections are the most common kind of nosocomial infections (hospital‐acquired infections) following surgery; they lead to longer hospitalisations, higher mortality, more intensive care unit transfers, and more readmissions (Kirkland 1999). Bacteria colonise all surgical wounds, but not all contaminations lead to infection (Birindelli 2017). An expert panel of the World Society of Emergency Surgery (WSES) approved the following classification to define recommendations for emergency repair of abdominal wall hernias; it is based on the Centre for Disease Control and Prevention wound classification that stratifies wounds according to the likelihood and degree of contamination (Birindelli 2017).

• Clean surgical field: no signs of strangulation and no bowel resection

• Clean‐contaminated surgical field: complicated hernia with strangulation, or bowel resection without gross enteric spillage

• Contaminated surgical field: strangulation with bowel necrosis, or gross spillage during intestinal resection

• Dirty surgical field: peritonitis from a bowel perforation

Implantation of a foreign body, such as a mesh, may increase the risk of postoperative surgical site infection. However, several studies have reported that synthetic mesh placement is feasible in emergency groin hernia repair (Sakamoto 2022; Venara 2014), specifically in clean surgical fields (Elsebae 2008), or in clean‐contaminated surgical fields, even with concurrent bowel resection (Atila 2010; Sawayama 2014; Ueda 2012; Papaziogas 2005; Bessa 2015; Sakamoto 2022). Some studies have found mesh use to be feasible in contaminated and dirty hernias (Pandey 2018; Kelly 2002), and a recent RCT assessing mesh use for contaminated ventral hernias found no mesh‐related reoperations after 6 months (Rosen 2022). However, in general, the use of mesh in emergency groin hernia repair in a contaminated surgical field is still controversial due to the potential risk of surgical site infections following mesh implantation. This risk precludes the laparoscopic approach in these circumstances, as it always requires the use of mesh. To date, no comprehensive systematic review has been carried out to assess whether the use of mesh is feasible in emergency groin hernia repair in all surgical fields (clean, clean‐contaminated, contaminated, and dirty). 

How the intervention might work

Reinforcing the abdominal wall with a prosthetic mesh during groin hernia repair reduces the risk of hernia recurrence compared with non‐mesh repair (Lockhart 2018). However, surgeons typically avoid mesh placement in contaminated surgical fields to minimise the risk of infection. Furthermore, mesh infections can be more complicated to treat: patients may need another surgical procedure to have the mesh removed and the hernia repaired again, or may need a prolonged course of antimicrobial treatment. Hence, mesh infections are associated with higher costs than simple surgical site infections without mesh. 

Why it is important to do this review

Emergency groin hernia repair is one of the most frequently performed emergency surgical procedures worldwide. While mesh repair is the standard treatment for elective hernia repair, the optimal surgical approach to treat emergency groin hernia remains controversial. Elective and emergency groin hernia repairs are performed under very different clinical circumstances, which might not be comparable in research. There are several published Cochrane Reviews on elective groin hernia repairs (Lockhart 2018; Scott 2001; Sun 2017), but none has examined emergency groin hernia repair. In addition, there is no consensus on the use of mesh in acute contaminated or clean‐contaminated fields due to the potential risk of infection. Therefore, this Cochrane Review aims to synthesise the evidence of all the relevant literature to assess whether the use of mesh in emergency groin hernia repair is associated with an increased risk of surgical site infections, postoperative morbidity, and mortality.

Objectives

Main objective

To assess the benefits and harms of mesh compared with non‐mesh in emergency groin hernia repair in adult patients with an inguinal or femoral hernia.

Secondary objective

To assess whether the effects of mesh versus non‐mesh in emergency groin hernia repair differ according to the degree of contamination.

Methods

Criteria for considering studies for this review

Types of studies

We will include all randomised controlled trials (RCTs) that compare the use of mesh with non‐mesh for emergency groin hernia repair. There will be no limitation on the number of randomised participants in trials.

We will apply no publication status or language restrictions.

Types of participants

• We will include all adult patients (aged 18 and over) with an inguinal or femoral hernia undergoing emergency groin hernia repair.

• We will exclude studies with a paediatric population (aged less than 18 years) if the data on the adult population cannot be extracted separately.

Types of interventions

We will include studies that compare the use of mesh with the use of sutures only (non‐mesh) in emergency groin hernia repair. We will consider the procedure 'emergency surgery' when the authors define it as such or when it is performed within 24 hours. 

As the intervention of interest is mesh use, we have chosen to pool all mesh‐based and non‐mesh repairs into two groups. 

Any technique for surgical repair of a groin hernia with mesh implantation will be accepted. Open techniques include, but are not limited to:

• Lichtenstein repair;

• mesh plug repair;

• plug and patch;

• bilayer repair; and

• preperitoneal repair.

Laparoscopic techniques include:

• transabdominal preperitoneal repair (TAPP);

• totally extraperitoneal repair (TEP);

• robotic‐assisted laparoscopic repair; and

• single‐incision laparoscopic surgery (SILS).

Any type of mesh may be used (e.g. absorbable, synthetic, biological).

For open non‐mesh approaches, we will accept both tension and tension‐free repairs techniques, including:

• Marcy;

• Bassini;

• McVay;

• Shouldice; and

• Desarda.

Any type of sutures may be used (absorbable or non‐absorbable).

Types of outcome measures

All studies fulfilling the study, participant, and intervention criteria will be included irrespective of reported outcomes. We will focus on short‐term outcomes that are relevant to an emergency surgical setting.

If the following outcome measures are not reported in the studies, we will contact study authors to request the missing data. If we do not receive a response, we will send a follow‐up email two weeks later. The study will be included irrespective of response.

Primary outcomes

• Surgical site infections (as defined by the included studies) within 30 days of repair

• Mortality (defined as all‐cause mortality) within 30 days of repair

Secondary outcomes

• Surgical site infections (as defined by the included studies) within 90 days of repair

• Complications, classified by The Clavien‐Dindo Classification (Dindo 2004), within 30 days of repair

  • Clavien‐Dindo Classification grade 5 is excluded, as this complication is covered in the primary outcome of 30‐day mortality

• Clinical recurrence or reoperation for recurrence within 30 days of repair and within one year of repair

• Reoperation due to complications (e.g. infection, seroma, bleeding) within 30 days of repair

• Mesh removal within 30 days of repair

• Mesh removal within 90 days of repair

Search methods for identification of studies

In collaboration with a professional Cochrane‐affiliated research librarian, we developed a search strategy for Ovid MEDLINE, which we then adapted to the other databases. There will be no restrictions on language or publication date.

Electronic searches

We will conduct a comprehensive literature search to identify all published and unpublished RCTs.

The search will be run separately in the following databases.

• Cochrane Central Register of Controlled Trials (CENTRAL; 2022) in The Cochrane Library 

• MEDLINE Ovid (1946 to date of search)

• Embase Ovid (1974 to date of search)

The search strategies are presented in Appendix 1, Appendix 2, and Appendix 3, respectively.

Searching other resources

We will search the World Health Organization International Clinical Trials Registry Platform (ICTRP; apps.who.int/trialsearch) and the US National Institutes of Health Ongoing Trials Register (clinicaltrials.gov) for completed and ongoing studies. The search terms to be used for searching trial registries can be found in Appendix 4. 

To complete the search for relevant studies, we will review the reference lists of all included articles (Greenhalgh 2005), and the reference lists of relevant systematic reviews (those identified in the reference lists of the included articles). We will also perform a forward citation search of the included articles using Google Scholar (scholar.google.com). 

If we find unpublished relevant studies in the registries, we will contact the authors to enquire about unpublished data and results. 

Data collection and analysis

Selection of studies

Two review authors will independently screen the titles and abstracts of the included studies using Covidence, then retrieve and assess the full texts of all records considered potentially eligible. Any discrepancies will be resolved by discussion within the review author group.

Data extraction and management

Two authors will independently extract data into piloted forms in Covidence. We will cross‐check all data for accuracy in Covidence before entering them into Review Manager Web (RevMan Web 2020). We will use RevMan Web 2020 to perform all data analysis. Any discrepancies will be resolved by discussion within the author group. 

We will collect information on study design and setting, patient characteristics (including race, smoking status, comorbidities, etc.), the authors' definition of emergency groin hernia repair, intervention characteristics (including surgical approach and contamination grade), outcomes assessed, source of funding, and any conflicts of interest stated by the study authors.  

Should we require any additional data, we will contact the study authors by email, following up with one further email two weeks later in case of no response. Missing data will be addressed with worst‐case and best‐case scenarios (see below).

Assessment of risk of bias in included studies

Two independent reviewers will conduct the risk of bias assessment in RCTs using the Cochrane risk of bias tool (RoB 2; Sterne 2019). Any discrepancies will be resolved by discussion within the author group. 

We will apply the risk of bias tool to the following outcomes and time points. 

• Surgical site infections within 30 days of repair

• Mortality within 30 days of repair

• Complications within 30 days of repair

• Clinical recurrence or reoperation for recurrence within 30 days of repair and within one year of repair

• Reoperation due to complications (e.g. infection, seroma, bleeding) within 30 days of repair

• Mesh removal within 30 days of repair

We intend to assess the effect of allocation to the intervention through an intention‐to‐treat analysis. We will assess risk of bias arising from the following domains.

• The randomisation process

• Deviations from intended interventions

• Missing outcome data

• Measurement of outcome

• Selection of the reported results

Based on the answers to a series of signalling questions, we will make a risk of bias judgement for each domain (low risk of bias, some concerns, or high risk of bias). We will use the Excel tool provided by riskofbias.info for the assessment.

The overall risk of bias for an outcome will be the highest individual risk from the five domains. This means we will only consider an outcome to be at low risk of bias when we have judged all five domains to be at low risk. This information will be presented in the review and included in the analysis and conclusion.  

Measures of treatment effect

We will analyse data using RevMan Web 2020. 

Dichotomous outcomes will be expressed as risk ratios (RRs) or risk differences (RDs) with 95% confidence intervals (CIs). The Clavien‐Dindo‐classified complications are the only categorical outcomes with more than two categories. They will be dichotomised for analyses into grades 1‐2 and grades 3‐4.

None of our outcomes are continuous.

Unit of analysis issues

The unit of analysis will be the participant (not the hernia). 

If we include any multi‐arm studies, we will combine the different arms into one group if they can be regarded as subtypes of the same intervention. If the arms cannot be combined in this way, we will treat the specific arms as separate studies and split the shared participants (either the intervention or control group) between the specific arms to avoid double counting (Higgins 2022)

Dealing with missing data

We will deal with missing data as follows. 

• We will contact the authors to request supplementary data (e.g. dropouts, loss to follow‐up, or when a study only is published as an abstract). 

  • If we obtain any additional data, we will include them in the analysis. 

• If the study does not report means and standard deviations, we will attempt to calculate these statistics from the available reported data. If data are not reported numerically but graphically, we will extract data from the figures. 

• If some participants have missing data, we will only include the available data in the primary analysis. 

• We will perform sensitivity analyses using a best‐case scenario (participants with missing data in the intervention arm developed events for desirable outcomes and participants with missing data in the control arm did not) and a worst‐case scenario (participants with missing data in the intervention arm developed events for undesirable outcomes and participants with missing data in the control arm did not).

• We will address the potential impact of the missing data in the discussion section. 

Assessment of heterogeneity

We will assess clinical, methodological, and statistical heterogeneity. For clinical heterogeneity, we will consider differences in participant characteristics (e.g. American Society of Anesthesiology (ASA) score, age, sex), intervention, outcome, and length of follow‐up. For methodological heterogeneity, we will consider study design (e.g. type of follow‐up) and risk of bias. We will assess statistical heterogeneity using the I² statistic (Higgins 2003), interpreting the results as follows (Deeks 2022).

• 0% to 40%: might not be important

• 30% to 60%: may represent moderate heterogeneity

• 50% to 90%: may represent substantial heterogeneity

• 75% to 100%: considerable heterogeneity

 

Assessment of reporting biases

If we identify more than ten studies, we will assess the risk of reporting bias visually using a funnel plot. Funnel plot asymmetry may indicate substantial publication bias and overestimation of the intervention effect (Page 2021).

Data synthesis

We will pool dichotomous outcomes in a meta‐analysis if clinical, methodological, and statistical heterogeneity is sufficiently low.

We will adopt a random‐effects model for data synthesis, as we expect some heterogeneity among the populations, study designs, and definitions of emergency groin hernia repair. All results will be presented with 95% CIs. We will generate forest plots with RevMan Web 2020. If I² is above 75%, we will not present the pooled estimate in the forest plots (Burcharth 2015). If a meta‐analysis is not possible, we intend to use non‐statistical methods to synthesise findings across studies, visually displaying the results and summarising the effect estimates with the range and distribution of the observed effects (McKenzie 2021).

Subgroup analysis and investigation of heterogeneity

If clinical heterogeneity is suspected and there is a sufficient number of patients, we will perform subgroup analyses based on the following characteristics.

• Patient characteristics (sex, age, BMI, ASA score, diabetes, smoking, and race)

• Hernia type: 

  • Femoral hernia 

  • Inguinal hernia

• Contamination according to the WSES classification (Birindelli 2017):

  • Clean surgical field: no signs of strangulation and no bowel resection

  • Clean‐contaminated surgical field: complicated hernia with strangulation, or bowel resection without gross enteric spillage

  • Contaminated surgical field: strangulation with bowel necrosis, or gross spillage during intestinal resection

  • Dirty surgical field: peritonitis from a bowel perforation

• Mesh type:

  • Absorbable mesh, synthetic mesh, and biological mesh

• Type of surgery 

  • Bowel resection

  • No bowel resection

• Use of antibiotics preoperatively at index surgery.

We will use the I² statistic to examine subgroup differences (Higgins 2003).

Sensitivity analysis

Sensitivity analysis will be performed by excluding studies with a low methodological quality (overall high risk of bias).

As explained in Dealing with missing data, if some data are missing from the included studies, we will perform sensitivity analyses using a best‐case scenario (participants with missing data in the intervention arm developed events for desirable outcomes and participants with missing data in the control arm did not) and a worst‐case scenario (participants with missing data in the intervention arm developed events for undesirable outcomes and participants with missing data in the control arm did not). 

Summary of findings and assessment of the certainty of the evidence

We will use GRADEpro GDT to create a summary of findings table for the following outcomes.

1. Surgical site infections within 30 days of repair

2. Mortality within 30 days of repair

3. Complications within 30 days of repair

4. Clinical recurrence or reoperation for recurrence within 30 days of repair and within one year of repair

5. Reoperation due to complications (e.g. infection, seroma, bleeding) within 30 days of repair

6. Mesh removal within 30 days of repair

Two authors will independently carry out a certainty of evidence assessment for each of the above outcomes using the GRADE approach. Any disagreements will be resolved by discussion. Evidence from randomised controlled trials will be considered high at the beginning, but may be downgraded for limitations related to risk of bias, inconsistency, imprecision, indirectness, or publication bias, according to the GRADE recommendations (Schünemann 2021).

As risk of bias is one of the five GRADE domains, we will summarise risk of bias data before downgrading the certainty of the evidence (Schünemann 2021). The three possible categories are: 

• low risk of bias (most information for the outcome is generated from studies at low risk of bias);

• moderate risk of bias (most information is from studies at low risk of bias or studies with some concerns); and

• high risk of bias (the proportion of information from studies at high risk of bias is sufficient to affect the interpretation of results).

The findings and certainty of evidence will be phrased according to the informative statement guidance (Santesso 2020).

Appendices

Appendix 1. CENTRAL search strategy

#1 MeSH descriptor: [Hernia, Inguinal] explode all trees 

#2 MeSH descriptor: [Hernia, Femoral] explode all trees 

#3 (herni*):ti,ab,kw                 

#4 (inguina* or femoral or groin* or pantaloon or medial or lateral or indirect or direct or internal):ti,ab,kw            

#5 (#3 and #4)      

#6 (#1 or #2 or #5)             

#7 MeSH descriptor: [Acute Disease] explode all trees     

#8 MeSH descriptor: [Emergencies] explode all trees     

#9 (acute or emergen* or urgent* or strangu* or incarc* or obstru*):ti,ab,kw         

#10 (#7 or #8 or #9)                    

#11 (#6 and #10)    

 

Appendix 2. Ovid MEDLINE search strategy

Ovid MEDLINE(R) ALL

1. exp Hernia, Inguinal/                       

2. exp Hernia, Femoral/                             

3. ((Inguina* or femoral or groin* or pantaloon or direct or indirect or medial or lateral or internal) and herni*).mp.                                 

4. 1 or 2 or 3                                            

5. exp Acute Disease/

6. exp Emergencies/

7. (acute or emergen* or urgent* or strangu* or incarc* or obstru*).mp.     

8. 5 or 6 or 7   

9. randomized controlled trial.pt.               

10. controlled clinical trial.pt.  

11. randomi?ed.ab.                

12. placebo.ab.    

13. drug therapy.fs.             

14. randomly.ab. 

15. trial.ab.        

16. groups.ab.    

17. 9 or 10 or 11 or 12 or 13 or 14 or 15 or 16                

18. exp animals/ not humans.sh.                  

19. 17 not 18       

20. 4 and 8 and 19                                             

                                         

               

 

Appendix 3. Ovid EMBASE search strategy

1. exp inguinal hernia/      

2. exp femoral hernia/   

3. ((Inguina* or femoral or groin* or pantaloon or direct or indirect or medial or lateral or internal) and herni*).mp.          

4. 1 or 2 or 3    

5. exp acute disease/         

6. exp emergency/              

7. (acute or emergen* or urgent* or strangu* or incarc* or obstru*).mp.            

8. 5 or 6 or 7   

9. (randomized controlled trial/ or controlled clinical study/ or random$.ti,ab. or randomization/ or intermethod comparison/ or placebo.ti,ab. or (compare or compared or comparison).ti. or ((evaluated or evaluate or evaluating or assessed or assess) and (compare or compared or comparing or comparison)).ab. or (open adj label).ti,ab. or ((double or single or doubly or singly) adj (blind or blinded or blindly)).ti,ab. or double blind procedure/ or parallel group$1.ti,ab. or (crossover or cross over).ti,ab. or ((assign$ or match or matched or allocation) adj5 (alternate or group$1 or intervention$1 or patient$1 or subject$1 or participant$1)).ti,ab. or (assigned or allocated).ti,ab. or (controlled adj7 (study or design or trial)).ti,ab. or (volunteer or volunteers).ti,ab. or human experiment/ or trial.ti.) not (((random$ adj sampl$ adj7 (cross section$ or questionnaire$1 or survey$ or database$1)).ti,ab. not (comparative study/ or controlled study/ or randomi?ed controlled.ti,ab. or randomly assigned.ti,ab.)) or (cross‐sectional study/ not (randomized controlled trial/ or controlled clinical study/ or controlled study/ or randomi?ed controlled.ti,ab. or control group$1.ti,ab.)) or (((case adj control$) and random$) not randomi?ed controlled).ti,ab. or (Systematic review not (trial or study)).ti. or (nonrandom$ not random$).ti,ab. or Random field$.ti,ab. or (random cluster adj3 sampl$).ti,ab. or ((review.ab. and review.pt.) not trial.ti.) or (we searched.ab. and (review.ti. or review.pt.)) or update review.ab. or (databases adj4 searched).ab. or ((rat or rats or mouse or mice or swine or porcine or murine or sheep or lambs or pigs or piglets or rabbit or rabbits or cat or cats or dog or dogs or cattle or bovine or monkey or monkeys or trout or marmoset$1).ti. and animal experiment/) or (Animal experiment/ not (human experiment/ or human/)))             

10. 4 and 8 and 9                    

Appendix 4. Search terms in trial registries

emergency AND hernia

incarcerated AND hernia

strangulated AND hernia

mesh AND hernia

Contributions of authors

• Ann Hou Sæter: corresponding author and guarantor of this review, protocol drafting, search strategy development, final approval of the manuscript

• Siv Fonnes: protocol drafting, final approval of the manuscript

• Jacob Rosenberg: protocol drafting, final approval of the manuscript

• Kristoffer Andresen: protocol drafting, final approval of the manuscript

Sources of support

Internal sources

• No internal sources of support, Other

  No internal sources of support

External sources

• No external sources of support, Other

  No external sources of support

Declarations of interest

The authors Kristoffer Andresen, Siv Fonnes, and Jacob Rosenberg are part of Cochrane Colorectal group editorial team but were not involved in the editorial process.

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