Transabdominal pre‐peritoneal (TAPP) versus totally extraperitoneal (TEP) laparoscopic techniques for inguinal hernia repair

Abstract

Background

An inguinal hernia occurs when part of the intestine protrudes through the abdominal muscles. In adults, this common condition is much more likely in men than in women. Inguinal hernia can be monitored by 'watchful waiting', but if symptoms persist or worsen, surgery is usually required, which can be open or laparoscopic. Laparoscopic (keyhole) repair of inguinal hernias in adults is generally performed using either the transabdominal preperitoneal (TAPP) or the totally extraperitoneal (TEP) method. Both methods include the use of mesh placed in front of the peritoneal lining of the abdominal wall, but for the TAPP technique, the abdominal cavity needs to be entered to place the mesh, and for the TEP technique, the whole procedure is done on the outside of the peritoneal lining of the abdominall wall. Whether one method is superior to the other has not been established, and there is debate about their relative benefits and harms. An advantage of TEP is its avoidance of the abdominal cavity; the downside is that it requires a steeper learning curve for clinicians. TAPP is considered simpler and makes it possible to inspect the contralateral side, but TAPP may have a higher risk of visceral injury compared to TEP.

This is an update of a Cochrane review first published in 2005.

Objectives

To compare the benefits and harms of laparoscopic TAPP technique versus laparoscopic TEP technique for inguinal hernia repair in adults.

Search methods

On 25 October 2022, the authors searched the Cochrane Central Register of Controlled Trials (CENTRAL) in the Cochrane Library; Ovid MEDLINE(R) Epub Ahead of Print, In‐Process & Other Non‐Indexed Citations, Ovid MEDLINE(R) Daily, and Ovid MEDLINE(R); and Ovid Embase, for published randomised controlled trials. To identify studies in progress, we searched ClinicalTrials.gov and the WHO International Clinical Trial Registry Platform (ICTRP).

Selection criteria

All prospective randomised, quasi‐randomised, and cluster‐randomised trials that compared the laparoscopic TAPP technique with the laparoscopic TEP technique for inguinal hernia repair in adults were eligible for inclusion. We included studies that involved a mix of different types of groin hernia if we could extract data for the inguinal hernias. Studies may have also included a group of participants receiving hernia repair by open surgery, but these groups were not included in our review.

Data collection and analysis

Both review authors independently evaluated trial eligibility, extracted data from included studies, and assessed the risk of bias in the included studies. The review's primary outcomes were serious adverse events, chronic pain (persisting for at least six months after surgery), and hernia recurrence. We also assessed a variety of secondary outcomes at perioperative, early postoperative, and late postoperative time points. We performed statistical analyses using the random‐effects model, and expressed the results as odds ratios (ORs) for dichotomous outcomes and mean differences (MDs) for continuous outcomes, with their respective 95% confidence intervals (CIs). We used GRADE to assess the certainty of evidence for key outcomes as high, moderate, low or very low.

Main results

We included 23 studies in this review update, which randomised 1156 people to TAPP and 1110 people to TEP, all requiring repair of inguinal hernias. Study sample sizes varied from 40 to 316 participants. The vast majority of study participants were male. We judged most studies to be at 'high' or 'unclear' risk of bias. Our judgements of the certainty of the evidence were low or very low for all outcomes we assessed.

There may be little to no difference between TAPP and TEP laparoscopic techniques for serious adverse events (0.4% versus 0.7%; OR 0.58, 95% CI 0.15 to 2.32, P = 0.45, I² = 0%; 19 studies, 1735 participants; low certainty of evidence); and hernia recurrence (1.2% versus 1.1%; OR 1.14, 95% CI 0.49 to 2.62, P = 0.97, I² = 0%; 17 studies, 1712 participants; low certainty of evidence). The evidence is very uncertain about the effects of TAPP versus TEP techniques on chronic pain (OR 0.62, 95% CI 0.20 to 1.97, P = 0.68, I² = 0%; 6 studies, 860 participants; very low certainty of evidence).

In terms of secondary outcomes, the evidence is very uncertain for TAPP versus TEP techniques for perioperative visceral and vascular injury (15 studies, 1523 participants; very low certainty of evidence), and for haematoma or seroma during the early (≤ 30 days) postoperative phase (OR 0.86, 95% CI 0.54 to 1.37, P = 0.3861, I² = 0%; 15 studies, 1423 participants; very low certainty of evidence). TEP technique may carry a higher risk of conversion to another hernia repair method (either TAPP technique or open surgery) when compared to TAPP (2.5% versus 0.7%; OR 0.28, 95% CI 0.09 to 0.84, P = 0.02, I² = 0%; 13 studies, 1178 participants; low certainty of evidence). Only two studies (474 participants) reported quality of life in the late (> 30 days) postoperative phase; overall, there was an improvement in quality of life from the pre‐ to post‐operative assessment, but the evidence suggests little to no difference between the techniques (low certainty of evidence).

Authors' conclusions

This review update found that there may be little to no difference between the TAPP and TEP techniques for serious adverse events, hernia recurrence, or chronic pain (low‐ to very‐low‐certainty evidence). Decisions about which method to use will most likely reflect surgeon and patient preference until high‐certainty evidence becomes available. There may be a higher risk of needing to convert from TEP to TAPP or open surgery when compared to the risk of needing to convert from TAPP to open surgery (low‐certainty evidence). If surgeons opt for TEP as their standard laparoscopic method, they could consider having a strategy for how to handle the potential need for conversion. This might include proficiency in the TAPP approach or having informed the patient about the risk of conversion to open surgery. For surgeons or surgical departments, the choice of a laparoscopic technique should involve shared decision‐making with patients and their families or carers. Future research could focus on patient‐reported outcomes, such as quality of life.

Plain language summary

Transabdominal pre‐peritoneal technique (TAPP) versus totally extraperitoneal (TEP) technique: which keyhole surgery method is better for repairing groin hernias in adults?

Key messages

‐ There may be little to no difference between the transabdominal pre‐peritoneal (TAPP) or totally extraperitoneal (TEP) techniques of groin hernia repair in terms of serious complications, chronic pain, or hernia recurrence.

‐ If the TEP technique is used, there may be a higher risk of having to change to another surgical method during the procedure.

‐ Future studies should investigate quality of life for people undergoing TAPP or TEP for groin hernia repair.

What is groin hernia?

A groin hernia is a weakness or defect in the wall of the abdominal cavity that is large enough to allow soft body tissue or internal organ(s) to poke out. It can appear as a lump in the groin. For some people, it causes pain and discomfort, and limits daily activities and the ability to work. If the bowel gets trapped in the hernia in such a way that it cannot be pushed back, it is at risk of having its blood supply cut off, which can be potentially life‐threatening.

How is groin hernia treated?

Groin hernias are often treated with surgery, though not all hernias require treatment. In some instances, if a groin hernia has no or few symptoms, patients can, together with their surgeon, decide to wait and see if symptoms requiring surgery should occur in the future. This is known as the 'watchful waiting' approach. If the patient and the surgeon do decide on surgical treatment, several different surgical approaches are available.

Current guidelines for groin hernia repair in adults recommend repairing the hernia defect using a synthetic mesh. The repair of the hernia and placement of the mesh can be done by open surgery or keyhole (laparoscopic) surgery. There are two main laparoscopic techniques: a transabdominal preperitoneal (TAPP) repair or a totally extraperitoneal (TEP) repair. With both methods, the mesh, which is made from synthetic material such as polypropylene, is placed behind the muscles of the abdominal wall and in front of the peritoneum (a membrane that lines the inside of the abdomen and pelvis, and covers many of the organs inside). In TAPP repair, the surgeon makes a cut in the peritoneum and enters the peritoneal cavity to place the mesh; in TEP repair, the peritoneal cavity is not entered, but the mesh is positioned in the same place: behind the muscles of the abdominal wall and in front of the peritoneum.

What did we want to find out?

We wanted to find out how two types of keyhole surgical techniques for groin hernia repair compare with each other in terms of serious complications, chronic pain (i.e. pain lasting beyond six months after surgery), and recurrence of the hernia. We wanted to know whether there was any difference between the techniques for abdominal injuries during surgery or the need to change the surgical repair method. We were also interested in whether there was any difference between the techniques in the occurrence of haematoma or serotoma (blood or fluid in the wound) in the 30 days after surgery, or in longer‐term quality of life.

What did we do?

Using online databases and reference lists, we searched for studies known as 'randomised controlled trials' that randomly allocated adults with groin hernia to either surgery using the TAPP technique or surgery using the TEP technique. We combined the results of these studies, and we assessed the risk of bias in the studies. We judged whether our certainty about the evidence could be considered high, moderate, low or very low.

What did we find?

We included 23 studies in the review, which involved a total of 2266 participants with groin hernias. The studies varied in length, with the shortest lasting one week and the longest lasting several years. All studies were conducted in hospital settings. Most studies did not report how they were funded. Most participants in the studies were male, with the average age in the studies ranging from 24 to 60 years.

The evidence suggests there may be little to no difference between the TAPP and TEP techniques for serious complications, hernia recurrence, and quality of life. The evidence suggests that the risk of needing to change to another hernia repair method may be higher with the TEP method. We do not know if there are any differences between TAPP and TEP in terms of chronic pain, abdominal injuries during surgery, and collection of blood or fluid in the wound, as the evidence is very uncertain.

What are the limitations of the evidence?

We have little to no confidence in the evidence because of concerns about the way the studies were carried out, the variety of ways that the studies measured the outcomes, and the relatively rare occurrence of adverse events.

How up to date is this evidence?

This review updates a previous review. The evidence is current to October 2022.

Summary of findings

Summary of findings 1. Summary of findings table ‐ Transabdominal pre‐peritoneal (TAPP) compared to totally extraperitoneal (TEP) laparoscopic techniques for inguinal hernia repair.

Transabdominal pre‐peritoneal (TAPP) compared to totally extraperitoneal (TEP) laparoscopic techniques for inguinal hernia repair
Patient or population: inguinal hernia repair Setting: surgical departments providing laparoscopic inguinal hernia surgery Intervention: transabdominal pre‐peritoneal (TAPP) Comparison: totally extraperitoneal (TEP) laparoscopic techniques
Outcomes	Anticipated absolute effects* (95% CI)		Relative effect (95% CI)	№ of participants (studies)	Certainty of the evidence (GRADE)	Comments
	Risk with totally extraperitoneal (TEP) laparoscopic techniques	Risk with transabdominal pre‐peritoneal (TAPP)
Serious adverse events, Clavien Dindo grade III or higher (within the first 3 months of the postoperative phase)	7 per 1000	4 per 1000 (1 to 16)	OR 0.58 (0.15 to 2.32)	1735 (19 RCTs)	⊕⊕⊝⊝ Lowa	The evidence suggests that there may be little to no difference between TAPP and TEP for the risk of serious adverse events within 3 months of the postoperative phase.
Chronic pain (follow‐up: 6 months to 3 years)	15 per 1000	9 per 1000 (3 to 29)	OR 0.62 (0.20 to 1.97)	860 (6 RCTs)	⊕⊝⊝⊝ Very lowb	The evidence is very uncertain about the effect of TAPP versus TEP in chronic pain.
Hernia recurrence at last clinical follow‐up (follow‐up: 1 month to 7 years)	11 per 1000	12 per 1000 (5 to 28)	OR 1.14 (0.49 to 2.62)	1712 (17 RCTs)	⊕⊕⊝⊝ Lowc	The evidence suggests that TAPP may result in little to no difference in hernia recurrence.
Conversion to another hernia repair method (perioperative phase)	25 per 1000	7 per 1000 (2 to 21)	OR 0.28 (0.09 to 0.84)	1178 (13 RCTs)	⊕⊕⊝⊝ Lowd	The evidence suggests that TEP may have a higher risk of the need to convert to another hernia repair method (to either TAPP or open surgery).
Visceral and vascular injury (perioperative phase)	Two injuries to the urinary bladder were reported among 1513 participants from 15 studies. One participant was operated on with the TAPP technique and one participant was operated on with the TEP technique.			(15 RCTs)	⊕⊝⊝⊝ Very lowe	The evidence is very uncertain about the effect of TAPP versus TEP on perioperative visceral and vascular injury.
Haematoma or seroma within 30 days from surgery (early postoperative phase)	66 per 1000	57 per 1000 (37 to 88)	OR 0.86 (0.54 to 1.37)	1423 (15 RCTs)	⊕⊝⊝⊝ Very lowf	The evidence is very uncertain about the effect of TAPP versus TEP on haematoma or seroma within 30 days of hernia repair.
Quality of life (late postoperative phase)	Two studies reported on quality of life 12 months after surgery, however, different scales were used. In general, participants had an improved quality of life, when comparing preoperative assessments with postoperative assessments. No difference between TAPP and TEP was found in the studies.			474 (2 RCTs)	⊕⊕⊝⊝ Lowg	The evidence suggests that there may be little to no difference between TAPP and TEP in quality of life.
*The risk in the intervention group (and its 95% confidence interval) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI). CI: confidence interval; OR: odds ratio
GRADE Working Group grades of evidence High certainty: we are very confident that the true effect lies close to that of the estimate of the effect. Moderate certainty: we are moderately confident in the effect estimate: the true effect is likely to be close to the estimate of the effect, but there is a possibility that it is substantially different. Low certainty: our confidence in the effect estimate is limited: the true effect may be substantially different from the estimate of the effect. Very low certainty: we have very little confidence in the effect estimate: the true effect is likely to be substantially different from the estimate of effect.
See interactive version of this table: https://gdt.gradepro.org/presentations/#/isof/isof_question_revman_web_429918348384378249.

^a Downgraded 2 levels due to imprecision and study limitations (risk of bias). Imprecision: few events resulting in wide CI including both appreciable benefit and harm. Risk of bias: several included studies had most domains judged as 'unclear' or 'high' risk of bias.
^b Downgraded 3 levels due to indirectness, imprecision, and risk of bias. Indirectness: the assessment tools for chronic pain varied between studies ‐ visual analogue scale, numeric rating scale, and "clinical assessment". Imprecision: very few events resulting in wide CI including both appreciable benefit and harm. Risk of bias: high risk of bias in multiple domains for 2 studies, including selection bias, perfomance bias, detection bias, and attrition bias.
^c Downgraded 2 levels due to imprecision and indirectness. Imprecision: due to few events, the CI is wide and includes appreciable benefit and harm. Indirectness: the assessment method of hernia recurrence varied across studies. Hernia recurrence was only downgraded two levels since risk of bias was judged to not influence the certainty of this outcome.
^d Downgraded 2 levels due to imprecision and risk of bias. Imprecision: few events resulting in wide CI including both a large reduction in the risk of conversion and a small reduction in the risk of conversion. Risk of bias: high risk of selection bias and detection bias.
^e Downgraded 3 levels due to risk of bias, indirectness, and imprecision. Risk of bias: high risk of attrition bias. Indirectness: unclear from study reports if visceral/vascular injury was systematically recorded and if minor peroperative visceral injuries were also recorded. Imprecision: due to only 2 events, it was not possible to conduct a meta‐analysis.
^f Downgraded 3 levels due to indirectness, imprecision, and risk of bias. Indirectness: method of assessment for haematoma/seroma often not described, meaning that some have been identified clinically and some might have been identified by imaging. Imprecision: due to few events, the CI is wide including both appreciable benefit and harm. Risk of bias: high risk in several risk‐of‐bias domains: selection bias, performance bias, detection bias, and attrition bias.
^g Downgraded 2 levels due to indirectness and imprecision. Indirectness: only 2 of the included studies reported quality of life, however, different tools were used for the assessment of quality of life. Imprecision: no difference between TAPP and TEP was demonstrated in the 2 studies, however, it is not possible to provide a CI due to the inability to conduct a meta‐analysis. One study used the Short Form–36 version 2 and one study used the WHO‐QOL BREF.

Background

Description of the condition

An inguinal hernia, the most common type of groin hernia, is a defect or opening in the muscular layer of the abdominal wall of sufficient size to allow the protrusion of intraperitoneal or preperitoneal contents into the groin (Fitzgibbons 2015). Femoral hernias are a rarer groin hernia; they occur lower down, in the femoral canal. Inguinal hernias usually present as a lump, with or without discomfort, which may limit daily activities and the ability to work (Shakil 2020). Inguinal hernias can be primary or recurrent, with subtypes known as direct or indirect depending on their location (Miserez 2007).

Inguinal hernias can be managed conservatively by monitoring, so‐called 'watchful waiting', if patients have few or no symptoms. However, the patient needs to be aware and able to react appropriately if the hernia becomes irreducible (i.e. cannot be pushed back in) and painful, as inguinal hernias can occasionally be life‐threatening if the bowel strangulates or becomes obstructed (Sæter 2022). A systematic review of the watchful waiting strategy showed that a third of participants crossed over to surgery within three years and that 70% of participants were operated on after seven years (Reistrup 2020).

The lifetime risk of groin hernia repair is 27% for men and 3% for women (Primatesta 1996). It is estimated that 20 million repairs are conducted annually worldwide, with about 100,000 in the UK and 500,000 in the US every year (Kingsnorth 2003). In Denmark, the prevalence of groin hernia repair peaks at 4% for 75‐ to 80‐year‐old men (Burcharth 2013).

Description of the intervention

The most commonly used repair for inguinal hernia is the open surgical technique using a mesh prosthesis to repair the hernia defect (Fitzgibbons 2015). However, the number of laparoscopic procedures performed continues to increase. In 2000, an audit of the NHS in Scotland found that 4% of inguinal hernia repairs were carried out using laparoscopic surgery (Hair 2000); by 2013, the laparoscopic approach was used in one‐third of inguinal hernia operations in Scotland (O'Neill 2015). In Denmark, the use of laparoscopic repair has also increased and has now reached almost 60% (Andresen 2021).

The standardised laparoscopic techniques for inguinal hernia repair are transabdominal preperitoneal (TAPP) repair and totally extraperitoneal (TEP) repair (Bittner 2015). The main difference between the TAPP and TEP repairs is whether the abdominal cavity is entered or not. TAPP repair requires access to the peritoneal cavity with the placement of a mesh through a peritoneal incision. This mesh is placed in the preperitoneal space covering all potential hernia defects in the inguinal region. The peritoneal incision is then closed, leaving the mesh between the preperitoneal tissues and the abdominal wall, where it becomes incorporated by fibrous tissue ingrowth. In a TEP repair, the mesh is placed in the same plane, the preperitoneal space. However, the peritoneum is not incised during a TEP repair. For the TAPP technique, it is common to use either a self‐fixating mesh or some kind of fixation device such as tacks, glue, or sutures (Andresen 2017). In the TEP technique, the mesh can also be fixated, but is sometimes not (Novik 2022). The mesh for inguinal hernia repair is usually made of polypropylene or polyester and should be of sufficient size to cover the hernia. Futhermore, a heavy weight mesh (> 70 g/m²) is recommended for laparoscopic groin hernia repair. Guidelines indicate there is still insufficient evidence to draw firm conclusions regarding fixation method (Stabilini 2023). The vast majority of inguinal hernia repair is done electively, but both TAPP and TEP can also be used for emergency surgery (Stabilini 2023).

How the intervention might work

Both laparoscopic techniques aim to repair the hernia defect while minimising the risks of complications. Clinical guidelines have concluded that both are effective (Bittner 2015; HerniaSurge Group 2018).

The main difference between the laparoscopic surgical techniques is whether the peritoneal (abdominal) cavity is entered or not. In the TEP repair, the surgeon places the laparoscope and instruments in the preperitoneal cavity, thus avoiding entering the abdominal cavity. In theory, this could result in a lower risk of injury to intra‐abdominal organs, since neither the laparoscope nor the instruments should be able to come in contact with the intra‐abdominal organs. However, proponents of the TAPP technique might argue that the TAPP technique provides easier operative access since the access is similar to other laparoscopic techniques. Furthermore, the TAPP technique allows for inspection of intra‐abdominal organs as well as the contralateral groin. For the TEP procedure, incision in the peritoneum is avoided, whereas the peritoneum needs to be incised for the TAPP technique.

Why it is important to do this review

There is uncertainty about whether the two laparoscopic techniques differ in terms of hernia recurrence, chronic pain, and other relevant clinical outcomes, and, to date, there has been insufficient evidence to recommend one technique over the other (HerniaSurge Group 2018). Advocates of the TAPP technique may focus on studies that have found a shorter operation duration (Gass 2012) and a lower risk of seroma (Bansal 2013) with TAPP. However, advocates of the TEP technique may focus on studies that have found a shorter postoperative stay after the TEP repair (Bracale 2012) and a shorter operation duration for TEP (Bansal 2013).

This is an update of a Cochrane review published in 2005 (Wake 2005). Since 2005, several randomised trials have been published and the review is therefore in need of an update. The question remains which laparoscopic method of repairing an inguinal hernia is superior. Therefore, it is important to do this review to provide evidence for patients and clinicians, and guide the choice of repair. If the methods are truly similar, then this information will support the continued use of both TAPP and TEP.

Objectives

To compare the benefits and harms of laparoscopic TAPP technique versus laparoscopic TEP technique for inguinal hernia repair in adults.

Methods

Criteria for considering studies for this review

Types of studies

All prospective randomised controlled trials (RCTs), quasi‐RCTs, and cluster‐RCTs comparing the laparoscopic TAPP technique with the laparoscopic TEP technique were eligible for inclusion. We included trials irrespective of the language in which they were reported. There were no restrictions by publication status.

Quasi‐randomised and cluster‐randomised clinical trials were also eligible for inclusion. We define quasi‐randomised studies as controlled studies using inappropriate methods to allocate participants to interventions, such as even and uneven date of first visit, or allocation of alternate participants to intervention or control (Reeves 2021).

Types of participants

Participants who were 18 years of age or over and required surgery for repair of an inguinal hernia were eligible for inclusion. We included all subtypes of inguinal hernias, such as direct, indirect, and mixed (pantaloon hernia). We also included studies involving participants with femoral hernias.

We did not include children and adolescents (under the age of 18 years) since the vast majority are operated on without the use of mesh (Bisgaard 2014), and therefore the TAPP and TEP techniques are not used for children or adolescents.

We included studies with only a subset of eligible participants when it was possible to extract relevant data on that subset, either from the study report or from personal communication with the study authors.

The review did not evaluate open versus laparoscopic surgery; it only compared the TAPP versus TEP techniques. Therefore, studies had to include at least one TAPP group and one TEP group. The comparison of open and laparoscopic surgery was covered in a previous Cochrane review (McCormack 2003).

Types of interventions

Laparoscopic repair of inguinal hernia:

• laparoscopic TAPP technique;

• laparoscopic TEP technique.

The surgical procedure had to involve the use of permanent mesh; we accepted all fixation methods.

Types of outcome measures

Primary outcomes

• Serious adverse events (number of participants with complications that were graded III or higher on the Clavien‐Dindo classification; Dindo 2004) within the first three months of the postoperative phase*

• Chronic pain (number of participants with pain persisting for a minimum of six months after surgery, measured with a validated assessment tool; Alfieri 2010). If a study used more than one type of measurement tool, we extracted all the data in order to allow for meta‐analysis.*

• Hernia recurrences (number of recurrences, as well as number of recurrences requiring reoperation), identified during clinical follow‐up*

^*We presented these primary outcomes in Table 1.

Perioperative outcomes

• Bleeding, measured in mL or measured as the number of participants with perioperative bleeding

• Duration of hernia repair procedure (minutes)

• Conversion to another hernia repair method, from laparoscopy (TAPP or TEP) to open surgery, or from TEP laparoscopic technique to TAPP laparoscopic technique*

  • At the beginning of a TAPP procedure, the peritoneal cavity is entered laparoscopically, and an incision is made in the peritoneum. This means that the surgeon cannot convert from a TAPP to a TEP procedure unless the incision in the peritoneum is closed, which would prolong the procedure without any benefit and is therefore not practised in real‐world settings.

  • In most cases, a requirement of the TEP technique is an intact peritoneum. If the peritoneum is accidentally perforated during a TEP procedure, the surgeon attempts to suture the defect(s) and continue the TEP procedure. However, in some cases, the surgeon will have to convert from TEP to TAPP or to an open surgical procedure instead.

  • Both TAPP and TEP laparoscopic techniques can be converted to open surgery.

• Visceral and vascular injury*

Early postoperative outcomes (≤ 30 days after procedure)

• Return to activities of daily living or return to work (days)

• Early postoperative pain (number of participants with pain up to and including 30 days after surgery), measured using a validated assessment tool. We extracted data at all time points (e.g. 12 hours postoperative, 1st postoperative day, 7th postoperative day).

• Haematoma or seroma. We pooled data on the number of participants with haematomas or seromas, or both, since they are difficult to distinguish clinically.*

Late postoperative outcomes (> 30 days after procedure)

• Quality of life, measured with a validated assessment tool, either disease‐specific or general*

^*We presented these secondary outcomes in Table 1.

Search methods for identification of studies

This is an update of a Cochrane review published in 2005 (Wake 2005).

Electronic searches

We conducted a comprehensive literature search to identify all published and unpublished randomised controlled trials with no language restrictions. The search string was developed by an information specialist. We searched the following electronic databases.

• Cochrane Central Register of Controlled Trials (CENTRAL; The Cochrane Library, Issue 2) (25 October 2022) (Appendix 1)

• Ovid MEDLINE (Epub ahead of print, in‐process & other non‐indexed citations, 1946 to 25 October 2022) (Appendix 2)

• Ovid Embase (1974 to 25 October 2022) (Appendix 3)

• ClinicalTrials.gov (25 October 2022)

• WHO International Clinical Trial Registry Platform (25 October 2022)

Searching other resources

We searched reference lists of included studies for relevant reports, a so‐called "snowball search" (Greenhalgh 2005).

We searched the WHO International Clinical Trial Registry Platform and ClinicalTrials.gov for recently finalised randomised trials, and we contacted investigators in order to obtain data for inclusion in the review.

Data collection and analysis

Selection of studies

Two review authors (KA, JR) independently assessed the relevance of all records identified by the above search strategies. Working in parallel, the two review authors retrieved full texts of potentially eligible studies and unclear abstracts for further assessment according to the predefined inclusion criteria. We excluded studies not meeting the inclusion criteria and listed reasons for their exclusion. We included all eligible studies irrespective of the outcomes reported. Any discrepancies were resolved by discussion. We used the online screening and data extraction tool Covidence for screening of abstracts and full‐ text manuscripts (www.Covidence.org) (Covidence 2016).

Data extraction and management

We developed and piloted a data extraction form to record details of study design, participants, setting and timing, interventions, participant characteristics, and outcomes. Two review authors (KA, JR) independently performed data extraction. Where a difference of opinion existed, we consulted a colleague not otherwise associated with the review. We entered data into Review Manager for analysis (RevMan Web 2020). Where possible, we extracted only data on participants over 18 years of age and with inguinal hernias.

Assessment of risk of bias in included studies

We assessed the risk of bias in all included studies. Two review authors (KA, JR) assessed this independently, using the Cochrane risk of bias tool (RoB1) as described in the Cochrane Handbook for Systematic Reviews of Interventions (Higgins 2011). We assessed the following domains for each study.

• Random sequence generation

• Allocation concealment

• Blinding of participants and personnel

• Blinding of outcome assessment

• Incomplete outcome data

• Selective reporting bias

• Other potential sources of bias

We judged each domain as high risk, low risk, or unclear risk of bias, according to the criteria used in the Cochrane risk of bias tool (see Appendix 4) (Higgins 2011). We presented the results of the risk of bias assessment in two figures. We used the approach suggested by Higgins 2011 to determine the risk of bias within a study as well as overall risk of bias across studies (see Appendix 5). We focused on the primary outcomes when assessing the risk of bias in the studies.

We judged quasi‐randomised studies to have a high risk of selection bias. Had we included cluster‐randomised studies, we would also, by default, have given them a high risk of bias judgement regarding randomisation.

Measures of treatment effect

We handled and analysed data using Cochrane's Review Manager (RevMan Web 2020).

For continuous outcomes, we calculated mean differences (MD) with 95% confidence intervals (CIs). Had different scales been used, where possible, we would have used standardised mean differences (SMD) instead, with corresponding 95% CIs. For dichotomous outcomes, we calculated Mantel‐Haenszel odds ratios (OR) with 95% CIs. We used the Peto OR method where the event rate was less than 10 per cent.

Unit of analysis issues

The primary analysis was performed per participant in the studies. We did not extract data from study arms that did not receive laparoscopic repair of their inguinal hernias.

In future updates of the review, if we identify cluster‐randomised studies, we plan to analyse the results according to recommendations in the Cochrane Handbookfor Systematic Reviews of Interventions (Higgins 2023). The analysis needs to account for clustering in order to avoid a unit‐of‐analysis error. We plan to do this by calculating the 'design effect', using the formula: 1+(M‐1)xICC, where ICC is the intraclass correlation and M is the average cluster size. The design effect will then be used to calculate the effective sample size for the intervention and control group, respectively, as well as the number of events in each group. Then the results can be entered into the meta‐analysis. If the intraclass correlation is not reported in included cluster‐RCTs, then we will use an external estimate, i.e. 0.029, which is based on Cook 2012.

Dealing with missing data

When data were missing from study reports, we contacted the trialists to obtain relevant data. We sent a maximum of three emails: two to the corresponding author with an interval of two weeks and one to the contact address of their institution if we could find it.

Assessment of heterogeneity

We assessed clinical and methodological heterogeneity across the included studies, focusing on variations in intervention (e.g. mesh, fixation), participants, and outcome assessment.

Thereafter, we assessed statistical heterogeneity using the Chi² test, with significance set at a P value of 0.10 (Deeks 2022). We used the I² statistic to quantify heterogeneity. We followed the recommendations set out by the Cochrane Handbook for Systematic Reviews of Interventions to interpret heterogeneity (Deeks 2022). These are:

• 0% to 40% might not be important;

• 30% to 60% may represent moderate heterogeneity;

• 50% to 90% may represent substantial heterogeneity;

• 75% to 100% is considerable heterogeneity.

We explored possible sources of heterogeneity in subgroup analyses if I² was more than 50% (Subgroup analysis and investigation of heterogeneity). If considerable heterogeneity (I² > 75%) was present and could not be explained or corrected for, we omitted meta‐analysis.

Assessment of reporting biases

As asymmetry can be a sign of publication bias or selective reporting, or both, we generated funnel plots in order to conduct a visual inspection of symmetry, for outcomes reported in at least 10 studies, as recommended and described in the Cochrane Handbook for Systematic Reviews of Intervention (Deeks 2022). Had any asymmetry been found, conclusions and the section on implications for practice would have been moderated to reflect this.

Data synthesis

We performed meta‐analyses using Review Manager (RevMan Web 2020). Even though the TAPP and TEP procedures are standardised, there can be variations from centre to centre in the exact application and conduct of the technique. Furthermore, we expected to identify small‐scale studies. Therefore, we used the random‐effects model.

Subgroup analysis and investigation of heterogeneity

We planned the following subgroup analyses in order to investigate if different types of meshes and different types of groin hernias impacted the results (Deeks 2022).

• Type, size, and fixation of mesh

• Type of hernia: primary or recurrent, and direct, indirect, or mixed

Type, size, and fixation of mesh as well as the type of hernia may impact clinical outcomes and clinical guidelines recommend considering these factors when choosing mesh and fixation (Stabilini 2023).

Sensitivity analysis

We performed sensitivity analyses to determine the impact of the following characteristics, to determine whether the findings were robust (Deeks 2022).

• Exclusion of studies with a high risk of bias overall (see Appendix 5)

• Exclusion of studies with imputed data

• Exclusion of studies initiated before 2000, when the techniques might not have been properly established

Summary of findings and assessment of the certainty of the evidence

We evaluated the certainty of evidence using the GRADE approach (Schünemann 2009) for the outcomes that we considered to be the most important for decision‐makers (see Primary outcomes; Secondary outcomes).

1. Serious adverse events within 3 months of the postoperative phase

2. Chronic pain (persisting for a minimum of 6 months after surgery)

3. Hernia recurrence at clinical follow‐up

4. Conversion to another hernia repair method in the perioperative period

5. Visceral and vascular injury in the perioperative period

6. Haematoma or seroma in the early (< 30 days) postoperative period

7. Quality of life in the late (≥ 30 days) postoperative period

We created summary of findings tables in GRADEpro GDT. The certainty of evidence can be downgraded by one (serious concern) or two levels (very serious concerns) for the following reasons: risk of bias, inconsistency (unexplained heterogeneity, inconsistency of results), indirectness (indirect population, intervention, control, or outcomes), imprecision (wide confidence interval, single trial), and publication bias.

Results

Description of studies

We included a total of 23 studies in this review update (see Characteristics of included studies). We excluded 10 studies after full‐text screening (see Characteristics of excluded studies). We identified five ongoing studies (see Characteristics of ongoing studies).

Results of the search

Searches in electronic databases (CENTRAL, Ovid MEDLINE, Ovid Embase) were conducted on 25 October 2022 and identified 1450 records for the title and abstract screening. Searching trials registers for ongoing trials identified 118 records from ClinicalTrials.gov and 79 records from WHO International Clinical Trials Registry Platform. We also identified an additional record through screening of relevant systematic reviews. After de‐duplication, we rejected a total of 1431 irrelevant records during the screening of the titles and abstracts, and we excluded 10 records during the full‐text screening (Figure 1). We have identified five studies that are ongoing (CTRI/2022/09/045456; NCT04114344; NCT02920307; NCT00687375; NCT02928146).

1.

Study flow diagram

* One study was identified as an abstract only, without enough information to be included in meta‐analysis.

Included studies

This review included 23 RCTs reported in 37 reports (Asuri 2021; Bansal 2013; Bansal 2017; Butler 2007; Chitrambalam 2021; Dedemadi 2006; Elheny 2018; Gong 2011; Gunal 2007; Gupta 2020; Hamza 2010; Jeelani 2015; Liu 2020; Mesci 2012; Nawaz 2017; Pokorny 2008; Rhoda 2022; Saurabh 2018; Schrenk 1996; Sharma 2015; Triantafyllidis 2013; Wang 2013; Zhu 2009). Most studies had two arms and randomised participants to TAPP or TEP procedures. Some studies had more than two arms, and included a group receiving an open surgery repair, such as Lichtenstein, Bassini, or Shouldice; we did not include these groups in the review.

The largest study had 314 participants (Bansal 2013), while the smallest had 40 participants (Zhu 2009). A total of 1156 participants were randomised to the TAPP technique and 1100 participants to the TEP technique. The studies included predominantly male participants, with a mean age in each study between 30 and 60 years, other than for one study that had a mean age of 24 years (Gunal 2007). Most participants had primary unilateral hernias; however, we also included studies with a subset of participants with bilateral, femoral, and recurrent hernias. For details regarding the country, setting, and inclusion and exclusion criteria of each study, see Characteristics of included studies.

Six studies explicitly stated that no funding was received (Asuri 2021; Elheny 2018; Gupta 2020; Liu 2020; Rhoda 2022; Sharma 2015). Fourteen studies did not report if any funding was received (Bansal 2013; Bansal 2017; Chitrambalam 2021; Dedemadi 2006; Gong 2011; Gunal 2007; Jeelani 2015; Mesci 2012; Nawaz 2017; Pokorny 2008; Saurabh 2018; Triantafyllidis 2013; Wang 2013; Zhu 2009). One study obtained funding from the navy (Butler 2007), one study received funding from a university (Hamza 2010), and one study received a grant for statistical analysis from a private company (Auto Suture Austria) (Schrenk 1996).

Excluded studies

We excluded 10 reports during full‐text screening: six did not compare the TAPP technique with the TEP technique (DeSaxce 2007; Heikkinen 2004; CTRI2018/10/015964; Millat 2007; Rieger 2017; NCT03563092); two were cohort studies (Fitzgibbons Jr 1995; Van Hee 1998); and two were commentaries rather than studies (Negro 1997; Schafer 2010). See Characteristics of excluded studies.

Risk of bias in included studies

The results of our risk of bias assessment are shown in Figure 2.

2.

Risk of bias summary: review authors' judgements about each risk of bias item for each included study

We also examined the risk of publication bias by visual inspection of funnel plots (not shown) for the outcomes "duration of operation" and "haematoma or seroma", since these were the only analyses with more than 10 studies contributing to the estimate. The funnel plots did not show signs of publication bias.

Overall, a 'low risk of bias' judgement was most common for the selective reporting domain. Random sequence generation and allocation concealment were the two domains with the highest proportion of unclear risk of bias due to lack of information in the reports. None of the studies were at low risk of bias overall. Twelve studies had at least one domain at high risk of bias (Asuri 2021; Chitrambalam 2021; Dedemadi 2006; Gunal 2007; Jeelani 2015; Liu 2020; Mesci 2012; Nawaz 2017; Pokorny 2008; Saurabh 2018; Schrenk 1996; Sharma 2015), and the remaining 13 had at least one domain that was unclear. See Figure 3.

3.

Summary of risk of bias judgements

Allocation

All included studies were randomised trials, however, only nine studies described a method of random sequence generation that we deemed adequate to ensure a low risk of bias, and only eight studies described an adequate method of concealment. We judged six studies to have a low risk of selection bias (Asuri 2021; Bansal 2013; Bansal 2017; Gupta 2020; Pokorny 2008; Rhoda 2022).

Blinding

Several studies implemented some kind of blinding, either blinding of outcome assessors or blinding of researchers during analysis of data. Because of the nature of the interventions, the surgeons cannot be blinded.

It would likely be possible to blind participants regarding which intervention they received as the visible scars are similar between the TAPP and the TEP approaches, however, this was not done.

Lack of blinding could introduce bias if it result in deviations from intended interventions or variations in other parts of patient care (e.g. earlier or later discharge).

We judged one study to be at high risk of performance bias (Pokorny 2008), five at low risk (Butler 2007; Hamza 2010; Liu 2020; Rhoda 2022; Sharma 2015), and the remaining 17 studies as unclear. For detection bias, we judged two to be at high risk (Pokorny 2008; Sharma 2015), five at low risk (Bansal 2013; Butler 2007; Gupta 2020; Hamza 2010; Liu 2020), and 16 as unclear.

Incomplete outcome data

We judged two studies to be at high risk of attrition bias since details were not reported regarding dropouts and exclusion of participants (Gunal 2007; Pokorny 2008). We judged 11 studies to be at low risk of attrition bias, since the studies had no or very few dropouts, with explanations given. The remaining studies were unclear.

Selective reporting

Only two studies did not report all prespecified outcomes (Asuri 2021; Liu 2020). However, for some studies, a protocol or trial registration was not available and therefore reporting bias was judged as unclear.

Other potential sources of bias

We based our assessment of other potential sources of bias on the funding of the studies and the declarations of interest by the study authors. Eight studies had an unclear risk of bias due to lack of either funding information or declaration of interests. Eight studies had a high risk of other bias due to lack of information about both funding and conflicts of interest. We judged seven studies to have a low risk of other bias as they stated that no funding was received for the studies and the trial authors had no conflicts of interest.

Effects of interventions

See: Table 1

See Table 1 for comparisons of outcomes between the TAPP technique and the TEP technique.

Primary outcomes

For the three primary outcomes (serious adverse events, chronic pain, and hernia recurrence), we found no difference between the TAPP and the TEP techniques. The number of events was low.

Serious adverse events

Nineteen studies, including a total of 1735 participants, explicitly mentioned the presence or absence of serious adverse events or mentioned minor adverse events only (Bansal 2013; Butler 2007; Chitrambalam 2021; Dedemadi 2006; Elheny 2018; Gong 2011; Gunal 2007; Gupta 2020; Hamza 2010; Jeelani 2015; Liu 2020; Mesci 2012; Nawaz 2017; Pokorny 2008; Rhoda 2022; Schrenk 1996; Sharma 2015; Wang 2013; Zhu 2009). The other four studies did not explicitly mention the presence or absence of adverse events (Asuri 2021; Bansal 2017; Saurabh 2018; Triantafyllidis 2013). Several studies had zero serious adverse events in both groups. In total, 3 of 893 participants in the TAPP groups and 6 of 842 participants in the TEP groups experienced serious adverse events. The serious adverse events reported in the TAPP group were: one participant requiring seroma aspiration (Bansal 2013), one participant with mesh infection requiring surgical removal of the mesh (Nawaz 2017), and one participant developing intestinal obstruction four months after surgery due to recurrence (Rhoda 2022). The serious adverse events in the TEP group were: five participants needing seroma aspiration (Bansal 2013; Mesci 2012), and one participant with mesh infection requiring surgical removal of the mesh (Nawaz 2017).

The evidence suggests that TAPP versus TEP may result in little to no difference in the number of participants experiencing serious adverse events (OR 0.58, 95% CI 0.15 to 2.32; P = 0.45, I² = 0%; 19 studies, 1735 participants; low certainty of evidence; Analysis 1.1; Table 1).

1.1. Analysis.

Comparison 1: TAPP versus TEP ‐ primary outcomes, Outcome 1: Serious adverse events

Chronic pain

Six studies (860 participants) reported the number of participants with chronic pain (pain that persisted for a minimum of 6 months) (Bansal 2013; Chitrambalam 2021; Elheny 2018; Gupta 2020; Pokorny 2008; Wang 2013). A seventh study, Bansal 2017, did not report the number of participants with chronic pain, but reported the mean pain score for the TAPP and the TEP groups, and found no significant difference between the groups. The definition of chronic pain and its assessment method differed across studies. Five studies used a visual analogue scale (VAS) or numeric rating scale (NRS) (Bansal 2013; Bansal 2017; Chitrambalam 2021; Wang 2013); one study used clinical examination (Pokorny 2008); and two studies did not report the method of pain assessment (Elheny 2018; Gupta 2020).

A total of 6 of 456 participants in the TAPP groups and 6 of 404 in the TEP groups had chronic pain. Three of the studies had zero events in both arms. The evidence is very uncertain about the effect of using TAPP versus TEP on chronic pain (OR 0.62, 95% CI 0.20 to 1.97; P = 0.42, I² = 0%; 6 studies, 860 participants; very low certainty of evidence; Analysis 1.2; Table 1).

1.2. Analysis.

Comparison 1: TAPP versus TEP ‐ primary outcomes, Outcome 2: Chronic pain (persisting for > 6 months after surgery)

Hernia recurrence

Seventeen of the included studies (1712 participants) reported data on hernia recurrence (Bansal 2013; Butler 2007; Chitrambalam 2021; Dedemadi 2006; Elheny 2018; Gong 2011; Gunal 2007; Gupta 2020; Hamza 2010; Jeelani 2015; Nawaz 2017; Pokorny 2008; Rhoda 2022; Schrenk 1996; Sharma 2015; Triantafyllidis 2013; Wang 2013). A total of 22 recurrences were reported. Several studies had zero events in one or both arms. Follow‐up varied from one month (Sharma 2015) to more than seven years (Gunal 2007). There may be little to no difference between TAPP and TEP for recurrence (OR 1.14, 95% CI 0.49 to 2.62; P = 0.97, I² = 0%; 17 studies, 1712 participants; low certainty of evidence; Analysis 1.3; Table 1).

1.3. Analysis.

Comparison 1: TAPP versus TEP ‐ primary outcomes, Outcome 3: Hernia recurrence

Secondary outcomes

Perioperative outcomes

Bleeding

Fifteen studies reported perioperative bleeding amongst 1448 participants (Bansal 2013; Bansal 2017; Butler 2007; Chitrambalam 2021; Dedemadi 2006; Gong 2011; Gunal 2007; Gupta 2020; Jeelani 2015; Liu 2020; Rhoda 2022; Schrenk 1996; Sharma 2015; Wang 2013; Zhu 2009). Several studies had zero events in one or both arms. Only one study reported the amount of bleeding, and found no difference between TAPP and TEP (mean 19 (SD 7) ml and 19 (SD 9) ml, respectively) (Gong 2011). The remaining studies reported bleeding as an "injury to" or "drop of" the epigastric artery. We conducted a meta‐analysis, which demonstrated little to no difference between the two techniques in the number of participants with bleeding (OR 1.04, 95% CI 0.33 to 3.28, P = 0.94, I² = 0%; 15 studies, 1448 participants; Analysis 2.1).

2.1. Analysis.

Comparison 2: TAPP versus TEP ‐ perioperative secondary outcomes, Outcome 1: Bleeding

One study reported that bleeding was the most frequently observed intraoperative complication, but the number of participants with perioperative bleeding could not be extracted from the study report since data for this complication were combined with other intraoperative complications (Pokorny 2008).

Duration of hernia repair procedure

Twenty studies reported on the duration of the procedure (Bansal 2013; Bansal 2017; Butler 2007; Chitrambalam 2021; Dedemadi 2006; Elheny 2018; Gong 2011; Gunal 2007; Hamza 2010; Liu 2020; Mesci 2012; Nawaz 2017; Pokorny 2008; Rhoda 2022; Schrenk 1996; Sharma 2015; Wang 2013; Zhu 2009; Triantafyllidis 2013; Jeelani 2015). One study reported that the duration of surgery was shorter in the TEP group, but no numerical data were provided (Triantafyllidis 2013). Three studies did not provide SDs for the mean duration of surgery (Mesci 2012; Pokorny 2008; Rhoda 2022). For the remaining 16 studies, SDs were provided. However, since we were unable to explain or correct the considerable heterogeneity noted (I² = 99%), we did not present a meta‐analysis.

Overall, nine studies showed little to no difference between the TAPP and the TEP techniques regarding the duration of surgery (Bansal 2013; Bansal 2017; Dedemadi 2006; Gong 2011; Hamza 2010; Jeelani 2015; Schrenk 1996; Wang 2013; Zhu 2009), whereas five studies favoured the TEP approach (Chitrambalam 2021; Elheny 2018; Gunal 2007; Liu 2020; Nawaz 2017), and two studies favoured the TAPP approach (Butler 2007; Sharma 2015). See Table 2 for the reported mean duration of surgery in the studies.

1. Duration of laparoscopic techniques in included studies.

Study ID	Duration in minutes
	TAPP		TEP
	Mean (SD)	n	Mean (SD)	n
Bansal 2013	68.6 (23.8)	154	62.4 (21.5)	160
Bansal 2017	49.7 (22)	80	48.7 (12.3)	80
Butler 2007	60 (10)	22	94 (10)	22
Chitrambalam 2021	42.26 (2.6)	35	31.03 (1.9)	35
Dedemadi 2006	55 (12)	24	56 (9)	26
Elheny 2018	66.9 (17.5)	49	52.7 (16.5)	49
Gong 2011	76 (16)	50	79 (13)	52
Gunal 2007	104.49 (8.1)	39	57.37 (3.84)	40
Hamza 2010	96.12 (22.5)	25	77.4 (43.21)	25
Liu 2020	46.9 (11.46)	50	41 (7.53)	50
Mesci 2012	62.4 (NR)	25	76 (NR)	25
Nawaz 2017	70 (6.01)	60	45.1 (3.54)	60
Pokorny 2008	66 (NR)	93	72 (NR)	36
Schrenk 1996	46 (9.2)	28	52.3 (13.9)	24
Sharma 2015	108.16 (16.1)	30	120.89 (29.28)	30
Wang 2013	47.22 (16.59)	84	50.52 (14.1)	84
Zhu 2009	34.5 (9.3)	20	32.6 (9.9)	20

TAP: transabdominal pre‐peritoneal; TEP: totally extraperitoneal

Conversion to another hernia repair method

There were two types of conversions reported in the studies: (i) from a laparoscopic technique (TAPP or TEP) to open surgery, and (ii) from the TEP to the TAPP technique. Thirteen studies reported 17 conversions amongst 1178 included participants (Bansal 2013; Butler 2007; Chitrambalam 2021; Dedemadi 2006; Gupta 2020; Hamza 2010; Jeelani 2015; Nawaz 2017; Rhoda 2022; Schrenk 1996; Sharma 2015; Wang 2013; Zhu 2009).

Three of the 587 participants who underwent the TAPP technique were converted to open surgery (Chitrambalam 2021; Hamza 2010). Amongst the 591 participants assigned to the TEP technique, 12 were converted to open surgery (Butler 2007; Chitrambalam 2021; Jeelani 2015; Nawaz 2017; Sharma 2015). Furthermore, TEP was converted to the TAPP technique in three participants from three studies (Bansal 2013; Hamza 2010; Sharma 2015).

Meta‐analysis demonstrated a benefit from the TAPP approach when analysing the risk of conversion to another repair method (TEP to TAPP, or laparoscopic to open surgery), with TEP having a higher risk of the need to convert to either TAPP laparoscopic technique or open surgery (OR 0.28, 95% CI 0.09 to 0.84; P = 0.02, I² = 0%; 13 studies, 1178 participants; low certainty of evidence; Analysis 2.2). When analysing the conversion from laparoscopic technique to open surgery, we found no evidence of a difference between groups (OR 0.33, 95% CI 0.10 to 1.09; P = 0.07, I = 0%; 13 studies, 1178 participants; Analysis 2.3).

2.2. Analysis.

Comparison 2: TAPP versus TEP ‐ perioperative secondary outcomes, Outcome 2: Conversion to another hernia repair method

2.3. Analysis.

Comparison 2: TAPP versus TEP ‐ perioperative secondary outcomes, Outcome 3: Conversion from laparoscopic technique to open surgery

One study reported the exclusion of two participants because the peritoneal lining was breached during TEP procedures, but it is unclear why these participants were excluded and not included in follow‐up (Liu 2020). One study reported a total of 11 participants who did not undergo the assigned method of repair due to technical reasons perioperatively or participants' preference, but did not report to which method of surgery they were originally assigned (Pokorny 2008).

Visceral and vascular injury

Fifteen studies reported visceral or vascular injury or reported no perioperative complications amongst 1513 participants (Bansal 2013; Bansal 2017; Dedemadi 2006; Gong 2011; Gunal 2007; Gupta 2020; Hamza 2010; Jeelani 2015; Liu 2020; Pokorny 2008; Rhoda 2022; Schrenk 1996; Sharma 2015; Wang 2013; Zhu 2009).

The evidence is very uncertain about the effect on visceral injury. Two cases of injury to the urinary bladder were reported, one during a TAPP procedure and one during a TEP procedure (Bansal 2017; Rhoda 2022). No other visceral injuries were reported. One study simply reported that there were fewer early complications in the TEP group, without stating the type of complications or numbers (Triantafyllidis 2013). See Table 1.

Vascular injuries are described in the section above on perioperative bleeding.

Early postoperative (≤ 30 days) outcomes

Return to activities of daily living or work

Twelve studies with 1137 participants reported the time to recovery after surgery. However, several measures were used, such as time to return to work, time to return to leisure activities, and "recovery time" (Bansal 2013; Butler 2007; Dedemadi 2006; Gong 2011; Hamza 2010; Jeelani 2015; Mesci 2012; Nawaz 2017; Rhoda 2022; Schrenk 1996; Sharma 2015; Triantafyllidis 2013).

Time to return to work in days was reported by eight studies with similar results between the TAPP and the TEP techniques (Bansal 2013; Butler 2007; Dedemadi 2006; Hamza 2010; Jeelani 2015; Mesci 2012; Schrenk 1996; Sharma 2015). Two studies did not report SD, CI, interquartile range, or other measures to estimate SD and were therefore not included in the meta‐analysis (Butler 2007; Mesci 2012). There was no evidence of a difference between the TAPP and the TEP approaches in return to work (MD 0.33, 95% CI ‐1.11 to 1.77; P = 0.65, I² = 66%; 6 studies, 586 participants; Analysis 3.1).

3.1. Analysis.

Comparison 3: TAPP versus TEP ‐ early postoperative (≤ 30 days) secondary outcomes, Outcome 1: Return to work (days)

One study reported days or weeks to return to walking, running, climbing, driving a car, sexual intercourse, bicycling, sports, and time off work. No significant differences were found between the TAPP and the TEP approaches (Schrenk 1996).

One study reported that in the TAPP group, participants had a quicker return to "normal activities" (Triantafyllidis 2013), but did not state which activities or provide any data on the number of days or weeks.

Early postoperative pain

A total of 20 studies reported on early postoperative pain (Bansal 2013; Bansal 2017; Butler 2007; Chitrambalam 2021; Dedemadi 2006; Elheny 2018; Gong 2011; Gunal 2007; Hamza 2010; Jeelani 2015; Liu 2020; Mesci 2012; Nawaz 2017; Rhoda 2022; Saurabh 2018; Schrenk 1996; Sharma 2015; Triantafyllidis 2013; Wang 2013; Zhu 2009). Early postoperative pain was measured at multiple time points in the postoperative phase, from hourly on the first day to a few times during the first 30 days (see below for details regarding time of assessment). For meta‐analysis regarding early postoperative pain, all pain scores measured by NRS or VAS were converted to a scale of 0 to 10. Fifteen studies used the VAS for assessing early postoperative pain (Bansal 2013; Bansal 2017; Butler 2007; Chitrambalam 2021; Dedemadi 2006; Gunal 2007; Hamza 2010; Jeelani 2015; Mesci 2012; Nawaz 2017; Rhoda 2022; Saurabh 2018; Schrenk 1996; Sharma 2015; Zhu 2009); one study used NRS (Gong 2011); three studies did not report the tool used or specific time or assessment (Liu 2020; Triantafyllidis 2013; Wang 2013); and one study also did not report the method of assessment but did state that the pain was assessed at 30 days postoperatively (Elheny 2018).

6 hours postoperative

Seven studies measured pain at 6 hours postoperatively, using the VAS (Bansal 2013; Bansal 2017; Dedemadi 2006; Gunal 2007; Hamza 2010; Jeelani 2015; Rhoda 2022). Only one study showed a difference, which was in favour of the TAPP approach (Rhoda 2022). Two studies did not report the SD (Dedemadi 2006; Rhoda 2022) and we imputed the missing SDs based on the other studies to be 1.5. The meta‐analysis showed no difference between TAPP and TEP (MD 0.08, 95% CI ‐0.29 to 0.45, P = 0.67, I² = 71%; 7 studies, 781 participants; Analysis 3.2). We conducted a sensitivity analysis excluding the two studies where the SD was imputed (Dedemadi 2006; Rhoda 2022). This did not change the estimate, but heterogeneity was slightly reduced (I² = 66%; analysis not shown).

3.2. Analysis.

Comparison 3: TAPP versus TEP ‐ early postoperative (≤ 30 days) secondary outcomes, Outcome 2: Early postoperative pain (6 hours postoperative)

12 hours postoperative

Three studies reported pain 12 hours after surgery (Chitrambalam 2021; Dedemadi 2006; Jeelani 2015). One study reported a difference between TAPP and TEP, in favour of the TEP approach (MD 1, 95% CI 0.44 to 1.56, on a scale from 0 to 10) (Chitrambalam 2021). Two studies found no difference between the groups (Dedemadi 2006; Jeelani 2015). A meta‐analysis of the three studies showed no difference between TAPP and TEP (MD 0.47, 95% CI ‐0.07 to 1.00, P = 0.09, I² = 63%; 3 studies, 180 participants; Analysis 3.3). The SD for Dedemadi 2006 was estimated to be 1.5; excluding this study in a sensitivity analysis did not change the overall effect estimate.

3.3. Analysis.

Comparison 3: TAPP versus TEP ‐ early postoperative (≤ 30 days) secondary outcomes, Outcome 3: Early postoperative pain (12 hours postoperative)

Day 1 postoperative

For the first postoperative day, 10 studies reported pain scores using the VAS (Bansal 2013; Bansal 2017; Butler 2007; Chitrambalam 2021; Dedemadi 2006; Gong 2011; Hamza 2010; Mesci 2012; Nawaz 2017; Schrenk 1996). Two studies favoured the TAPP approach (Rhoda 2022; Schrenk 1996), two studies favoured the TEP approach (Bansal 2017; Chitrambalam 2021), and the remaining studies showed no difference between groups. One study simply reported less pain following TEP repairs (Saurabh 2018). We noted substantial heterogeneity (I² = 89%) that could not be explained or corrected and thus omitted the meta‐analysis.

Day 7 postoperative

On the seventh postoperative day, seven studies reported pain (Bansal 2013; Bansal 2017; Butler 2007; Chitrambalam 2021; Dedemadi 2006; Gong 2011; Rhoda 2022), with most showing no difference between TAPP and TEP. Two studies found a difference in favour of the TEP approach (Bansal 2017; Chitrambalam 2021); one study found a difference in favour of the TAPP approach (Rhoda 2022); one study reported less pain following the TEP procedure (Saurabh 2018). We observed substantial heterogeneity (I² = 90%) that could not be explained or corrected and thus omitted the meta‐analysis.

Day 30 postoperative

On the thirtieth postoperative day, three studies reported pain using a VAS (Bansal 2017; Chitrambalam 2021; Schrenk 1996). The meta‐analysis demonstrated no difference between the TAPP and TEP procedures (MD 0.18, 95% CI ‐0.08 to 0.44, I² = 45%, P = 0.17; 3 studies; 282 participants; Analysis 3.4). One study reported that 4/49 participants in the TAPP group and 5/49 participants in the TEP group had pain at 30 days postoperatively (Elheny 2018).

3.4. Analysis.

Comparison 3: TAPP versus TEP ‐ early postoperative (≤ 30 days) secondary outcomes, Outcome 4: Early postoperative pain (30th postoperative day)

Haematoma or seroma

Fifteen studies reported the occurrence of haematoma and/or seroma in a total of 1475 participants (Bansal 2013; Chitrambalam 2021; Dedemadi 2006; Elheny 2018; Gong 2011; Gunal 2007; Gupta 2020; Hamza 2010; Jeelani 2015; Mesci 2012; Pokorny 2008; Rhoda 2022; Schrenk 1996; Sharma 2015; Wang 2013). Some studies reported seroma and haematoma separately, and some studies combined them into the occurrence of 'seroma or haematoma'. Since seroma and haematoma can be difficult to distinguish clinically, we decided to combine data for either or both. In total, 44/739 participants in the TAPP group had postoperative seroma or haematoma versus 45/684 in the TEP group. Only one study clearly defined when seroma was diagnosed, reporting that 25/154 in the TAPP group and 52/160 in the TEP group had seroma or haematoma on the seventh postoperative day (Bansal 2013). However, this number dropped to 3 from 154 participants and 6 from 160 participants on postoperative day 30.

The evidence is very uncertain about the effect of TAPP versus TEP on the occurrence of haematoma or seroma (OR 0.86, 95% CI 0.54 to 1.37; P = 0.52, I² = 0%; 15 studies; 1423 participants; very low certainty of evidence; Analysis 3.5; Table 1).

3.5. Analysis.

Comparison 3: TAPP versus TEP ‐ early postoperative (≤ 30 days) secondary outcomes, Outcome 5: Haematoma or seroma

Late postoperative (> 30 days) outcomes

Quality of life

Two studies with 474 participants reported generic quality of life following surgery, one study used the Short Form (36) health survery (SF‐36) (Bansal 2013) and one study used the The World Health Organization Quality of Life – BREF (WHO‐QOL BREF) (Bansal 2017) for assessment. No studies used a disease (hernia) specific quality of life questionnaire.

In both Bansal 2013 and Bansal 2017, there was no evidence of a difference between the TAPP and the TEP approaches in late postoperative quality of life; however, both studies reported improvements in quality of life when comparing preoperative and postoperative assessments for both groups. We judged the certainty of evidence to be low. See Table 1.

Missing data

Missing data in the included studies were not easily identified. For all studies, there was at least one of the prespecified outcomes for this review that were not reported. All included studies reported on the outcomes specified in their individual method sections. We contacted trial authors in order to obtain further information on missing data but without success.

Subgroup and sensitivity analyses

Due to the lack of information in the included studies, it was not possible to conduct the subgroup analyses we had planned: type, size, and fixation of mesh; and type of hernia (primary and recurrent hernia; and direct, indirect, and mixed).

For sensitivity analysis, we planned to exclude studies initiated before the 2000s, since the techniques might not have been properly established at that time. Only one study was conducted before 2000 (Schrenk 1996). The exclusion of Schrenk 1996 did not result in any significant change in the estimates. We conducted sensitivity analyses where SD was estimated, which did not change the effect estimates. We did not conduct the sensitivity analysis we had planned for studies with an overall high risk of bias since all of the studies were either at high or unclear risk of bias overall.

Discussion

Summary of main results

In this review update, we included a total of 23 randomised clinical trials involving 1156 participants randomised to TAPP procedures and 1110 participants randomised to TEP procedures for laparoscopic inguinal hernia repair.

We assessed three primary outcomes: serious adverse events, chronic pain, and hernia recurrence. The available evidence suggests there may be little to no difference between TAPP and TEP in the number of patients having serious adverse events, with the most studies reporting zero participants experiencing any serious adverse events. The evidence is very uncertain about the effect of TAPP versus TEP on chronic pain, with the same number of participants experiencing pain and the same levels of pain reported for the two repair methods. TAPP may result in little to no difference in hernia recurrence as compared to TEP.

We also assessed a number of secondary outcomes, including perioperative, early postoperative, and late postoperative outcomes. The available evidence suggests that TEP may have a higher risk of conversion to either the TAPP technique or open surgery when compared to the risk of the TAPP technique requiring conversion to open surgery. The evidence is very uncertain for perioperative visceral and vascular injury, and for early postoperative haematoma or seroma. There may be little to no difference in late postoperative quality of life based on limited evidence (two studies) of low certainty.

Overall completeness and applicability of evidence

The included studies provide relevant evidence for our review question about the clinical effectiveness of laparoscopic TAPP and TEP repair for inguinal hernia. In order to avoid confounding by indication, we included only randomised clinical trials. The external validity may be debatable, since randomised studies are conducted on selected populations and therefore might not represent "standard" patients with inguinal hernia. Most studies included mainly male participants with primary unilateral inguinal hernia; however, some of the studies also enrolled participants with bilateral hernias or recurrent hernias, or both, thereby increasing the review's external validity to some extent.

Quality of the evidence

We assessed the certainty of evidence as per the GRADE approach. We included seven outcomes in a 'Summary of findings' table. For serious adverse events, hernia recurrence, conversion to another repair method, and quality of life, we graded the certainty of evidence as low. One reason for this was the wide confidence intervals ‐ due to few events in each arm ‐ that included both appreciable harm and appreciable benefit. For serious adverse events, most studies had no events in either arm, meaning that these studies did not contribute to the meta‐analysis. Other reasons for downgrading the certainty of evidence included the risk of bias in the studies and heterogeneity in the assessment methods of the outcomes. We judged the certainty of evidence for quality of life as low since it was not possible to conduct a meta‐analysis, and since only two studies reported quality of life, which was measured by different tools. However, both studies found no difference in quality of life when comparing the TAPP and the TEP techniques.

For the outcomes of chronic pain, visceral and vascular injury, and haematoma or seroma, we graded the certainty of evidence as very low. We downgraded the evidence due to risk of bias, imprecision, and indirectness. For visceral and vascular injury, only two events were reported and it was not possible to conduct a meta‐analysis. For chronic pain, three different tools were used for the assessment (VAS, NRS, and clinical examination).

Potential biases in the review process

The extensive search in several databases is likely to have identified all relevant publications of randomised clinical trials investigating TAPP and TEP. Besides searching the bibliographic databases, we also searched trial registries with the aim of identifying planned, ongoing, or studies that have finalised inclusion of participants but not yet published results. We identified five ongoing studies (CTRI/2022/09/045456; NCT04114344; NCT02920307; NCT00687375; NCT02928146); when the results of these studies become available and are incorporated in a future update of this review, some effect estimates might change, and the certainty of the evidence may increase from its current level of low to very low.

A limitation of the review could be our choice to only include randomised and quasi‐randomised trials. In hernia surgery, considerable evidence is based on data from large national registers such as the Danish Hernia Database (Friis‐Andersen 2016). A limitation of the studies from the database is the risk of confounding by indication, which is why we chose to include only trials where participant allocation to treatment was random or quasi‐random and was not based on surgeon or participant choice.

Agreements and disagreements with other studies or reviews

The results of our review update are in accordance with other reviews and guidelines. The World Guidelines for Inguinal Hernia Surgery also concluded that "...TAPP and TEP have comparable outcomes..." (HerniaSurge Group 2018). Another review with meta‐analysis did not find any differences between TAPP and TEP; however, the authors recommended TAPP because "...TEP is a modified and more complex procedure than TAPP" (Wei 2015). In a study of recurrent inguinal hernia, no clinically meaningful differences were found when comparing TAPP and TEP (Gass 2016). A recent network meta‐analysis concluded that TAPP and TEP seem comparable, though the risk of conversion was not an outcome in the review (Aiolfi 2021a). A meta‐analysis including trial sequential analysis concluded that "TAPP and TEP seem comparable in terms of postoperative hernia recurrence and chronic pain" (Aiolfi 2021b); the authors also proposed that future trials and meta‐analyses are unlikely to identify any notable differences between the two laparoscopic techniques, so they should be avoided, with resources focused instead on clinically important subgroups, such as high‐risk patients. We cannot make recommendations about which hernia repair method might be better based on their procedural complexity and learning curve as these were not assessed in this review.

Authors' conclusions

Implications for practice.

This review demonstrated that there may be little to no difference in clinical outcomes between the transabdominal pre‐peritoneal (TAPP) and the totally extraperitoneal (TEP) laparoscopic procedures for inguinal hernia repair, other than the TEP procedure may have a higher risk of requiring conversion convert to another surgical method (either TAPP repair or open surgery). Surgical departments and surgeons using TEP could consider having a strategy for handling repair method conversions, including being proficient in the TAPP technique and informing patients about the risk of conversion to open surgery. The choice of which laparoscopic method to use should be driven by a shared decision‐making process between surgeons and patients and their families or carers.

Implications for research.

There is no clear evidence that one laparoscopic method is superior to the other for the repair of inguinal hernias. The two techniques seem to have very similar clinical outcomes. Future studies could consider investigating learning curves and implications for training since some argue that TAPP is a less complex procedure. If one technique is simpler to learn and implement, this could be a reason to make it the standard choice; however, studies on this issue are lacking.

Future research should also focus on planning and conducting clinical trials that routinely assess patient‐reported outcomes, such as quality of life, using standardised validated questionnaires. Two of the five ongoing studies listed in our review plan to measure quality of life.

What's new

Date	Event	Description
4 July 2024	New search has been performed	We updated the review with new searches performed in October 2022; we modified the PICO (participants, interventions, comparators, outcomes) framework where required to reflect the current state of the field and current Cochrane methods. Since the last publication of the review in 2005, the number of included trials has increased from 1 to 23.
4 July 2024	New citation required and conclusions have changed	A new author team conducted the update of this review, which included one study when it was last published in 2005. The conclusions have changed as a larger number of studies (23) are now included.

History

Protocol first published: Issue 2, 2004
Review first published: Issue 1, 2005

Date	Event	Description
5 August 2008	Amended	Converted to new review format
9 November 2004	New citation required and conclusions have changed	Substantive amendment

Appendices

Appendix 1. CENTRAL search strategy

Cochrane Central Register of Controlled Trials (CENTRAL; The Cochrane Library Issue 2)

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

#2. ((inguinal* or groin) near/3 hernia):ti,ab,kw

#3. #1 or #2

#4. MeSH descriptor: [Laparoscopy] explode all trees

#5. ((laparoscop* or minimal* invasiv*) near/3 (repair or technique* or procedure* or intervent* or approach*)):ti,ab,kw

#6. ((transabdominal NEXT (preperitoneal or pre‐peritoneal or pro‐peritoneal)) or TAPP):ti,ab,kw

#7. ((totally NEXT (extraperitoneal or extra‐peritoneal)) or TEP):ti,ab,kw

#8. #4 or #5 or #6 or #7

#9. #3 and #8

Appendix 2. MEDLINE search strategy

Ovid MEDLINE (Epub Ahead of print, In‐Process & Other Non‐Indexed Citations, Daily and 1946 to date of search)

1. Exp Hernia, Inguinal/

2. ((inguinal* or groin) adj4 hernia).mp.

3. 1 or 2

4. Exp Laparoscopy/

5. ((laparoscop* or minimal* invasiv*) adj4 (repair or technique* or procedure* or intervent* or approach*)).mp.

6. ((transabdominal adj (preperitoneal or pre‐peritoneal or pro‐peritoneal)) or TAPP).tw,kf.

7. ((totally adj (extraperitoneal or extra‐peritoneal)) or TEP).tw,kf.

8. Or/ 4‐7

9. 3 and 8

10. Randomized controlled trial.pt.

11. Controlled clinical trial.pt.

12. Randomized.ab.

13. Placebo.ab.

14. Clinical trials as topic.sh.

15. Randomly.ab.

16. Trial.ti.

17. Or/10‐16

18. Exp animals/ not humans.sh.

19. 17 not 18

20. 9 and 19

Appendix 3. Embase search strategy

Ovid Embase (1974 to date of search)

1. Exp Inguinal hernia/

2. ((inguinal* or groin) adj4 hernia).mp.

3. 1 or 2

4. Exp Laparoscopy/

5. ((laparoscop* or minimal* invasiv*) adj4 (repair or technique* or procedure* or intervent* or approach*)).mp.

6. ((transabdominal adj (preperitoneal or pre‐peritoneal or pro‐peritoneal)) or TAPP).tw,kw.

7. ((totally adj (extraperitoneal or extra‐peritoneal)) or TEP).tw,kw.

8. Or/4‐7

9. 3 and 8

10. CROSSOVER PROCEDURE.sh.

11. DOUBLE‐BLIND PROCEDURE.sh.

12. SINGLE‐BLIND PROCEDURE.sh.

13. (crossover* or cross over*).ti,ab.

14. Placebo*.ti,ab.

15. (doubl* adj blind*).ti,ab.

16. allocat*.ti,ab.

17. trial.ti.

18. RANDOMIZED CONTROLLED TRIAL.sh.

19. random*.ti,ab.

20. Or/10‐19

21. (exp animal/ or exp invertebrate/ or animal.hw. or nonhuman/) not (exp human/ or human cell/ or (human or humans or man or men or wom?n).ti.)

22. 20 not 21

23. 9 and 22

Appendix 4. Cochrane risk of bias assessment tool

RANDOM SEQUENCE GENERATION Selection bias (biased allocation to interventions) due to inadequate generation of a randomised sequence.
Criteria for a judgement of ‘low risk’ of bias	The investigators describe a random component in the sequence generation process such as: · referring to a random number table; · using a computer random number generator; · coin tossing; · shuffling cards or envelopes; · throwing dice; · drawing lots; · minimisation*. *Minimisation may be implemented without a random element, and this is considered to be equivalent to being random.
Criteria for the judgement of ‘high risk’ of bias	The investigators describe a non‐random component in the sequence generation process. Usually, the description would involve some systematic, non‐random approach, for example: · sequence generated by odd or even date of birth; · sequence generated by some rule based on date (or day) of admission; · sequence generated by some rule based on hospital or clinic record number. Other non‐random approaches happen much less frequently than the systematic approaches mentioned above and tend to be obvious. They usually involve judgement or some method of non‐random categorisation of participants, for example: · allocation by judgement of the clinician; · allocation by preference of the participant; · allocation based on the results of a laboratory test or a series of tests; or · allocation by availability of the intervention.
Criteria for the judgement of ‘unclear risk’ of bias	Insufficient information about the sequence generation process to permit judgement of ‘low risk’ or ‘high risk’.
ALLOCATION CONCEALMENT Selection bias (biased allocation to interventions) due to inadequate concealment of allocations prior to assignment.
Criteria for a judgement of ‘low risk’ of bias	Participants and investigators enrolling participants could not foresee assignment because one of the following, or an equivalent method, was used to conceal allocation: · Central allocation (including telephone, web‐based and pharmacy‐controlled randomization); · Sequentially numbered drug containers of identical appearance; · Sequentially numbered, opaque, sealed envelopes.
Criteria for the judgement of ‘high risk’ of bias	Participants or investigators enrolling participants could possibly foresee assignments and thus introduce selection bias, such as allocation based on: · Using an open random allocation schedule (e.g. a list of random numbers); · Assignment envelopes were used without appropriate safeguards (e.g. if envelopes were unsealed or non­opaque or not sequentially numbered); · Alternation or rotation; · Date of birth; · Case record number; · Any other explicitly unconcealed procedure.
Criteria for the judgement of ‘unclear risk’ of bias	Insufficient information to permit judgement of ‘Low risk’ or ‘High risk’. This is usually the case if the method of concealment is not described or not described in sufficient detail to allow a definite judgement – for example if the use of assignment envelopes is described, but it remains unclear whether envelopes were sequentially numbered, opaque and sealed.
BLINDING OF PARTICIPANTS AND PERSONNEL Performance bias due to knowledge of the allocated interventions by participants and personnel during the study.
Criteria for a judgement of ‘low risk’ of bias	Any one of the following: · No blinding or incomplete blinding, but the review authors judge that the outcome is not likely to be influenced by lack of blinding; · Blinding of participants and key study personnel ensured, and unlikely that the blinding could have been broken.
Criteria for the judgement of ‘high risk’ of bias	Any one of the following: · No blinding or incomplete blinding, and the outcome is likely to be influenced by lack of blinding; · Blinding of key study participants and personnel attempted, but likely that the blinding could have been broken, and the outcome is likely to be influenced by lack of blinding.
Criteria for the judgement of ‘unclear risk’ of bias	Any one of the following: · Insufficient information to permit judgement of ‘Low risk’ or ‘High risk’; · The study did not address this outcome.
BLINDING OF OUTCOME ASSESSMENT Detection bias due to knowledge of the allocated interventions by outcome assessors.
Criteria for a judgement of ‘low risk’ of bias	Any one of the following: · No blinding of outcome assessment, but the review authors judge that the outcome measurement is not likely to be influenced by lack of blinding; · Blinding of outcome assessment ensured, and unlikely that the blinding could have been broken.
Criteria for the judgement of ‘high risk’ of bias	Any one of the following: · No blinding of outcome assessment, and the outcome measurement is likely to be influenced by lack of blinding; · Blinding of outcome assessment, but likely that the blinding could have been broken, and the outcome measurement is likely to be influenced by lack of blinding.
Criteria for the judgement of ‘unclear risk’ of bias	Any one of the following: · Insufficient information to permit judgement of ‘Low risk’ or ‘High risk’; · The study did not address this outcome.
INCOMPLETE OUTCOME DATA Attrition bias due to amount, nature or handling of incomplete outcome data
Criteria for a judgement of ‘low risk’ of bias	Any one of the following: · No missing outcome data; · Reasons for missing outcome data unlikely to be related to true outcome (for survival data, censoring unlikely to be introducing bias); · Missing outcome data balanced in numbers across intervention groups, with similar reasons for missing data across groups; · For dichotomous outcome data, the proportion of missing outcomes compared with observed event risk not enough to have a clinically relevant impact on the intervention effect estimate; · For continuous outcome data, plausible effect size (difference in means or standardized difference in means) among missing outcomes not enough to have a clinically relevant impact on observed effect size; · Missing data have been imputed using appropriate methods.
Criteria for the judgement of ‘high risk’ of bias	Any one of the following: · Reason for missing outcome data likely to be related to true outcome, with either imbalance in numbers or reasons for missing data across intervention groups; · For dichotomous outcome data, the proportion of missing outcomes compared with observed event risk enough to induce clinically relevant bias in intervention effect estimate; · For continuous outcome data, plausible effect size (difference in means or standardized difference in means) among missing outcomes enough to induce clinically relevant bias in observed effect size; · ‘As‐treated’ analysis done with substantial departure of the intervention received from that assigned at randomization; · Potentially inappropriate application of simple imputation.
Criteria for the judgement of ‘unclear risk’ of bias	Any one of the following: · insufficient reporting of attrition/exclusions to permit judgement of ‘low risk’ or ‘high risk’ (e.g. number randomised not stated, no reasons for missing data provided); or · the study did not address this outcome.
SELECTIVE REPORTING Reporting bias due to selective outcome reporting
Criteria for a judgement of ‘low risk’ of bias	Any of the following: · the study protocol is available and all of the study’s prespecified (primary and secondary) outcomes that are of interest in the review have been reported in the prespecified way; or · the study protocol is not available, but it is clear that the published reports include all expected outcomes, including those that were prespecified (convincing text of this nature may be uncommon).
Criteria for the judgement of ‘high risk’ of bias	Any one of the following: · not all of the study’s prespecified primary outcomes have been reported; · one or more primary outcomes is reported using measurements, analysis methods or subsets of the data (e.g. subscales) that were not prespecified; · one or more reported primary outcomes were not prespecified (unless clear justification for their reporting is provided, such as an unexpected adverse effect); · one or more outcomes of interest in the review are reported incompletely so that they cannot be entered in a meta‐analysis; or · the study report fails to include results for a key outcome that would be expected to have been reported for such a study.
Criteria for the judgement of ‘unclear risk’ of bias	Insufficient information to permit judgement of ‘low risk’ or ‘high risk’. It is likely that the majority of studies will fall into this category.
OTHER BIAS Bias due to problems not covered elsewhere in the table
Criteria for a judgement of ‘low risk’ of bias	The study appears to be free of other sources of bias.
Criteria for the judgement of ‘high risk’ of bias	There is at least one important risk of bias. For example, the study: ·had a potential source of bias related to the specific study design used; or · has been claimed to have been fraudulent; or · had some other problem.
Criteria for the judgement of ‘unclear risk’ of bias	There may be a risk of bias, but there is either: · insufficient information to assess whether an important risk of bias exists; or · insufficient rationale or evidence that an identified problem will introduce bias.

Appendix 5. Approach to risk of bias summary assessments

Risk of bias	Interpretation	Within a study	Across studies
Low risk of bias	Plausible bias unlikely to seriously alter the results	Low risk of bias for all key domains	Most information is from studies at low risk of bias.
Unclear risk of bias	Plausible bias that raises some doubt about the results	Unclear risk of bias for one or more key domains	Most information is from studies at low or unclear risk of bias.
High risk of bias	Plausible bias that seriously weakens confidence in the results	High risk of bias for one or more key domains	The proportion of information from studies at high risk of bias is sufficient to affect the interpretation of results.

From Higgins 2011

Appendix 6. Trial registry search

Search on clinicaltrials.gov

Condition or disease: Inguinal hernia

Intervention/treatment: Laparoscopic OR TAPP OR TEP OR (Transabdominal preperitoneal) OR (Totally Extraperitoneal)

Applied filters: interventional, Adult, Older Adult

WHO International Clinical Trials Registry Platform

Condition: (inguinal hernia) OR (hernia, inguinal) OR (groin hernia)

Intervention: laparos* OR endosc*

Appendix 7. GRADE system classification

The GRADE system classifies the quality of evidence in one of four grades.

Grade	Definition
High	Further research is very unlikely to change our confidence in the estimate of effect.
Moderate	Further research is likely to have an impact on our confidence in the estimate of effect and may change the estimate.
Low	Further research is very likely to have an important impact on our confidence on the estimate of effect and is likely to change the estimate.
Very low	Any estimate of effect is very uncertain.

A summary of the GRADE approach to rating the quality of evidence, addressing five possible reasons for downgrading, and three possible reasons for upgrading.

Downgrades the evidence*	Upgrades the evidence
Study limitation	Large magnitude of effect
Inconsistency of results	All plausible confounding would reduce the demonstrated effect
Indirectness of evidence	Dose‐response gradient
Imprecision
Publication bias

*If there are very serious concerns (e.g. if most information is from studies at high risk of bias), the evidence would be downgraded by two levels.

Data and analyses

Comparison 1. TAPP versus TEP ‐ primary outcomes.

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
1.1 Serious adverse events	19	1735	Odds Ratio (M‐H, Random, 95% CI)	0.58 [0.15, 2.32]
1.2 Chronic pain (persisting for > 6 months after surgery)	6	860	Odds Ratio (M‐H, Random, 95% CI)	0.62 [0.20, 1.97]
1.3 Hernia recurrence	17	1712	Odds Ratio (M‐H, Random, 95% CI)	1.14 [0.49, 2.62]

Comparison 2. TAPP versus TEP ‐ perioperative secondary outcomes.

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
2.1 Bleeding	15	1448	Odds Ratio (M‐H, Random, 95% CI)	1.04 [0.33, 3.28]
2.2 Conversion to another hernia repair method	13	1178	Odds Ratio (M‐H, Random, 95% CI)	0.28 [0.09, 0.84]
2.3 Conversion from laparoscopic technique to open surgery	13	1178	Odds Ratio (M‐H, Random, 95% CI)	0.33 [0.10, 1.09]

Comparison 3. TAPP versus TEP ‐ early postoperative (≤ 30 days) secondary outcomes.

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
3.1 Return to work (days)	6	586	Mean Difference (IV, Random, 95% CI)	0.33 [‐1.11, 1.77]
3.2 Early postoperative pain (6 hours postoperative)	7	781	Mean Difference (IV, Random, 95% CI)	0.08 [‐0.29, 0.45]
3.3 Early postoperative pain (12 hours postoperative)	3	180	Mean Difference (IV, Random, 95% CI)	0.47 [‐0.07, 1.00]
3.4 Early postoperative pain (30th postoperative day)	3	282	Mean Difference (IV, Random, 95% CI)	0.18 [‐0.08, 0.44]
3.5 Haematoma or seroma	15	1423	Odds Ratio (M‐H, Random, 95% CI)	0.86 [0.54, 1.37]

Characteristics of studies

Characteristics of included studies [ordered by study ID]

Asuri 2021.

Study characteristics
Methods	Randomised clinical trial Enrolment: from December 2016
Participants	Inclusion criteria: adult male patients aged 25 to 50 yrs with primary uncomplicated, unilateral/bilateral inguinal hernia Exclusion criteria: female, male < 25 yrs, > 50 yrs, history of previous surgery in inguinoscrotal region, recurrent inguinal hernia, complicated hernia (irreducible, obstructed, strangulated), hydrocele, epididymitis, history of orchidectomy TAPP Male: 73 Female: 0 Age mean (SD): 36.4 yrs (7.5) BMI mean (SD): 22.4 (1.5) Direct: 23 Indirect: 50 Femoral: 0 Bilateral: 8 Primary: 73 Recurrent: 0 TEP Male: 72 Female: 0 Age mean (SD): 37 yrs (8.4) BMI mean (SD): 22.2 (1.7) Direct: 27 Indirect: 45 Femoral: 0 Bilateral: 15 Primary: 72 Recurrent: 0
Interventions	73 TAPP repairs 72 TEP repairs
Outcomes	The study's primary outcomes included comparison of sexual function using BMFSI, qualitative semen analysis, and ASA levels. None of the main outcomes of interest in the review were measured in the study.
Notes	Country: India Setting: tertiary care hospital Funding: "no funding received from any source" Conflicts of interest: "all authors declare that they have no conflict of interest"
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Computer‐generated random numbers, using www.randomization.com
Allocation concealment (selection bias)	Low risk	Sealed envelopes
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	No information on blinding of participants and personnel
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	No information on blinding of outcome assessment
Incomplete outcome data (attrition bias) All outcomes	Low risk	No dropouts
Selective reporting (reporting bias)	High risk	Not all outcomes specified in trial registration (CTRI/2018/05/013621) were reported.
Other bias	Unclear risk	None of the outcomes of interest in the review were reported in the study.

Bansal 2013.

Study characteristics
Methods	Randomised clinical trial Enrolment: May 2007 to April 2012
Participants	Inclusion criteria: clinically diagnosed, non‐recurrent, uncomplicated symptomatic inguinal hernia Exclusion criteria: significant comorbidity, such as hypertension, bronchial asthma, diabetes, or any other systemic disease; unfit for general anaesthesia; complicated (irreducible, obstructed, or strangulated) hernias, or history of previous abdominal surgery (pelvic surgeries, including prostatectomy, appendectomy, etc); previous groin hernia repair on either side (either laparoscopic or open technique with or without prosthetic material); recurrent hernia; uncorrectable coagulopathy; suspected intra‐abdominal or pelvic malignancy TAPP Male: NR Female: NR Age mean (SD): 43.4 yrs (16.4) BMI mean (SD): 24.03 (3.1) Direct: NR Indirect: NR Femoral: NR Bilateral: NR Primary: 154 Recurrent: 0 TEP Male: NR Female: NR Age mean (SD): 50.5 yrs (17.3) BMI mean (SD): 23.8 (2.6) Direct: NR Indirect: NR Femoral: NR Bilateral: NR Primary: 160 Recurrent: 0
Interventions	154 TAPP repairs 160 TEP repairs
Outcomes	Primary outcome: pain (unspecified) All main outcomes of interest in the review were measured in the study. Recurrence was assessed with a median follow‐up of 36.5 months.
Notes	Country: India Setting: tertiary care centre Funding: NR Conflicts of interest: "Authors have no competing interest or financial ties to disclose"
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: "Randomization was performed using computer‐generated random numbers with sealed envelopes for concealed allocation and block randomizations in blocks of eight."
Allocation concealment (selection bias)	Low risk	Quote: "Randomization was performed using computer‐generated random numbers with sealed envelopes for concealed allocation and block randomisation in blocks of eight."
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	Blinding of participants and personnel not mentioned in the study report.
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Quote: "An independent observer blinded to the technique of surgery recorded the pain scores on the Visual Analogue Scale (VAS)."
Incomplete outcome data (attrition bias) All outcomes	Low risk	Of 314 treated, 314 were analysed according to figure 1 in the paper.
Selective reporting (reporting bias)	Low risk	Specified outcomes are reported.
Other bias	Unclear risk	Funding not reported

Bansal 2017.

Study characteristics
Methods	Randomised clinical trial Enrolment: April 2012 to October 2014
Participants	Inclusion criteria: 18 to 60 yrs old, primary, uncomplicated unilateral or bilateral inguinal hernia Exclusion criteria: female; previous surgery in the inguinoscrotal region; recurrent hernia; complicated hernia: irreducible, obstructed, strangulated; orchiectomy; significant comorbidities like coronary artery disease, uncontrolled hypertension and diabetes mellitus, chronic bronchitis, renal and hepatic failure; unfit for general anaesthesia; uncontrolled coagulopathies; not giving consent TAPP Male: 80 Female: 0 Age mean (SD): 40.9 yrs (12.3) BMI mean (SD): 24.1 (2) Direct: NR Indirect: NR Femoral: NR Bilateral: 22 Primary: 80 Recurrent: 0 TEP Male: 80 Female: 0 Age mean (SD): 40 yrs (12.5) BMI mean (SD): 24 (2) Direct: NR Indirect: NR Femoral: NR Bilateral: 34 Primary: 80 Recurrent: 0
Interventions	80 TAPP repairs 80 TEP repairs
Outcomes	Primary outcome: equivalence trial to see overall effect on sexual functions following laparoscopic inguinal hernia repair by TEP and TAPP Reported on pain, both early (< 30 days) and late (6 and 12 months), and quality of life Did not report on serious adverse events, recurrence, conversion rate, return to activities of daily living, haematoma/seroma
Notes	Country: India Setting: tertiary care centre Funding: NR Conflicts of interest: "Authors have no conflicts of interest or financial ties to disclose."
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: "Randomization was done using computer‐generated random numbers with sealed opaque envelopes to ensure concealed allocation with block randomization."
Allocation concealment (selection bias)	Low risk	Quote: "Randomization was done using computer‐generated random numbers with sealed opaque envelopes to ensure concealed allocation with block randomization."
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	No information available regarding blinding
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	No information available regarding blinding
Incomplete outcome data (attrition bias) All outcomes	Low risk	Of 160 participants randomised, 160 were analysed according to figure 1 in the paper.
Selective reporting (reporting bias)	Low risk	Specified outcomes are reported.
Other bias	Unclear risk	Funding not reported

Butler 2007.

Study characteristics
Methods	Randomised clinical trial 3 arms: TAPP, TEP, open repair. Open repair not included in the review Enrolment: dates NR
Participants	Inclusion criteria: clinical diagnosis of primary, unilateral hernia Exclusion criteria: NR TAPP Male: 22 Female: 0 Age mean (SD): NR BMI mean (SD): NR Direct: NR Indirect: NR Femoral: NR Bilateral: 0 Primary: 22 Recurrent: 0 TEP Male: 22 Female: 0 Age mean (SD): NR BMI mean (SD): NR Direct: NR Indirect: NR Femoral: NR Bilateral: NR Primary: 22 Recurrent: 0
Interventions	22 TAPP repairs 22 TEP repairs
Outcomes	Primary outcome: pain measured on VAS day 1 to 7 Reported the following outcomes of interest in the review: serious adverse events, recurrence (follow‐up unknown), duration of surgery, conversion rate, return to activities of daily living, early postoperative pain (< 7 days)
Notes	Country: USA Setting: Department of Surgery, Naval Medical Center Funding: "This study was sponsored by the Chief, Navy Bureau of Medicine and Surgery, Washington, DC, Clinical Investigation Program (CIP #P01‐0019)." Conflicts of interest: not reported
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Not reported
Allocation concealment (selection bias)	Unclear risk	Not reported
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Quote: "The operative team caring for the patient postoperatively was blinded to the surgical approach used, and the patient was blinded to the operative approach by the placement of a large dressing covering the abdomen, which was not removed until postoperative day 3."
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Quote: "The patients were interviewed during their postoperative visits by an investigator blinded to the operative approach, who questioned them regarding their ability to return to work and their pain levels."
Incomplete outcome data (attrition bias) All outcomes	Low risk	No dropouts reported
Selective reporting (reporting bias)	Low risk	Specified outcomes are reported.
Other bias	Unclear risk	Conflicts of interest not reported

Chitrambalam 2021.

Study characteristics
Methods	Quasi‐randomised trial. Single‐centre, prospective, interventional cohort study using "simple randomisation". 70 people with inguinal hernia were divided into two groups of 35, one for TAPP repair and one for TEP repair. Enrolment: April 2018 to October 2020
Participants	Inclusion criteria: unilateral uncomplicated inguinal hernias undergoing laparoscopic hernioplasty and willing for regular follow‐up Exclusion criteria: complicated hernias, bilateral hernias, recurrent hernias, requiring concomitant abdominal procedures, connective tissue disorders, on steroid therapy TAPP Male: NR Female: NR Age mean (SD): NR BMI mean (SD): NR Direct: NR Indirect: NR Femoral: NR Bilateral: 0 Primary: 35 Recurrent: 0 TEP Male: NR Female: NR Age mean (SD): NR BMI mean (SD): NR Direct: NR Indirect: NR Femoral: NR Bilateral: 0 Primary: 35 Recurrent: 0
Interventions	35 TAPP repairs 35 TEP repairs
Outcomes	Aim: to compare the outcomes for TEP and TAPP approaches in laparoscopic inguinal hernia surgery in terms of operative time consumed, postoperative pain, duration of hospital stay, complications and recurrence rate when performed by a single surgeon Reported many of the outcomes of interest in the review. Recurrence was assessed at 1 year. Did not report on visceral/vascular injury, return to activities of daily living, or quality of life
Notes	Country: India Setting: hospital Funding: none reported Conflicts of interests: authors report no conflicts of interests
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	High risk	Randomisation done by selecting every alternate patient for TAPP and TEP. Quote: "Simple randomisation was done by selecting every alternate patient for TAPP and TEP".
Allocation concealment (selection bias)	High risk	Allocation was by selecting every alternate patient for TAPP and TEP. No description of concealment methods
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	No reporting of blinding
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	No reporting of blinding.
Incomplete outcome data (attrition bias) All outcomes	Low risk	All participants analysed at 6‐month follow‐up.
Selective reporting (reporting bias)	Unclear risk	No protocol or trial registration was identified for this study.
Other bias	Low risk	No conflicts of interest and no funding

Dedemadi 2006.

Study characteristics
Methods	Randomised clinical trial 3 arms: TAPP, TEP, Lichtenstein. Lichtenstein not included in the review Enrolment: February 2009 to November 2004
Participants	Inclusion criteria: recurrent inguinal hernia Exclusion criteria: personal preference for one procedure, ASA > III, coagulation disorder, previous abdominal or pelvic surgery, irreducible hernia, ascites, refuse randomisation TAPP Male: 24 Female: 0 Age mean (SD): NR BMI mean (SD): NR Direct: 10 Indirect: 14 Femoral: 1 Bilateral: 1 Primary: 0 Recurrent: 24 TEP Male: 26 Female: 0 Age mean (SD): NR BMI mean (SD): NR Direct: 10 Indirect: 16 Femoral: 0 Bilateral: 1 Primary: 0 Recurrent: 26
Interventions	24 TAPP repairs 26 TEP repairs
Outcomes	Primary outcome: postoperative pain, estimated as amount of analgesics consumed and the number of days until the participant returned to full ordinary and professional activities Most of the main outcomes of interest in the review were measured in the study. Quality of life was not assessed. Recurrence was assessed at 3 years.
Notes	Country: Greece Setting: Department of Surgery Funding: NR Conflicts of interest: NR
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Not reported
Allocation concealment (selection bias)	Low risk	Quote: "The patients were randomly assigned (...) by opening of sealed envelopes on the day before surgery."
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	Not reported
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Not reported
Incomplete outcome data (attrition bias) All outcomes	Low risk	2 participants were not followed up and analysed; reason given.
Selective reporting (reporting bias)	Low risk	Specified outcomes are reported.
Other bias	High risk	Funding and conflicts of interest not reported

Elheny 2018.

Study characteristics
Methods	Randomised clinical trial Enrolment: November 2016 to July 2017
Participants	Inclusion criteria: patients with inguinal hernias admitted to the surgery department of Minia University Hospital. Informed consent was taken. Exclusion criteria: not mentioned TAPP Male: 49 Female: 0 Age mean (SD): 42.87 yrs (15.02) BMI mean (SD): NR Direct: 17 Indirect: 37 Femoral: NR Bilateral: 5 Primary: NR Recurrent: NR TEP Male: 48 Female: 1 Age mean (SD): 36.3 yrs (15.18) BMI mean (SD): NR Direct: 13 Indirect: 38 Femoral: NR Bilateral: 2 Primary: NR Recurrent: NR
Interventions	49 TAPP repairs 49 TEP repairs
Outcomes	Aim: to evaluate the impact of age, type of hernia, size of the mesh used, and fixation of the mesh on the competence of laparoscopic repair of inguinal hernia Follow‐up for recurrence was 6 months. Did not report all outcomes of interest in the review. Perioperative bleeding, conversion rate, visceral/vascular injury, return to activities of daily living, quality of life, and early (< 7 days) pain were not reported.
Notes	Country: Egypt Setting: surgical department Funding: "Source of support: Nil" Conflicts of interest: "None"
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Method of randomization not reported
Allocation concealment (selection bias)	Unclear risk	Method of allocation concealment not reported
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	No blinding mentioned
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	No blinding mentioned
Incomplete outcome data (attrition bias) All outcomes	Low risk	All participants analyzed at six months follow‐up
Selective reporting (reporting bias)	Unclear risk	No protocol or trial registration identified, no pre‐specification of outcomes reported in study report
Other bias	Low risk	No funding and no conflicts of interest

Gong 2011.

Study characteristics
Methods	Randomised clinical trial Enrolment: February 2006 to February 2009
Participants	Inclusion criteria: 30 to 70 yrs old, ASA I or II, primary inguinal hernia Exclusion criteria: irreducible hernia, emergency surgery, previous major surgery in lower abdomen TAPP Male: 50 Female: 0 Age mean (SD): 56 yrs (10) BMI mean (SD): NR Direct: 9 Indirect: 35 Pantaloon: 6 Femoral: 0 Bilateral:0 Primary: 50 Recurrent: 0 TEP: Male: 52 Female: 0 Age mean (SD): 57 yrs (9) BMI mean (SD): NR Direct: 11 Indirect: 37 Pantaloon: 4 Femoral: 0 Bilateral: 0 Primary: 52 Recurrent: 0
Interventions	50 TAPP repairs 52 TEP repairs
Outcomes	Primary outcome: not specified. Outcomes: postoperative complications, recurrence, operating time, operative bleeding, postoperative pain at 24 h and 1 week, hospital stay after surgery, time until resumption of normal activities, cost Conversion rate, haematoma/seroma, and quality of life were not reported. The remaining main outcomes of interest in the review were measured in the study. Recurrence was assessed at mean of 15 months.
Notes	Country: China Setting: Department of Surgery Funding: NR Conflicts of interest: "authors have no conflicts of interest or financial ties to disclose."
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Quote: "We randomly divided the patients into three groups based on treatment, namely, open tension‐free mesh‐plug and patch hernia repair, TAPP, or TEP."
Allocation concealment (selection bias)	Unclear risk	Qote: "We randomly divided the patients into three groups based on treatment, namely, open tension‐free mesh‐plug and patch hernia repair, TAPP, or TEP."
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	Not reported
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Not reported
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Comment: no flow diagram and no reports of dropout
Selective reporting (reporting bias)	Unclear risk	Comment: specified outcomes are reported, but no trial registration or protocol identified
Other bias	Unclear risk	Funding not reported, but authors declare no conflicts of interest

Gunal 2007.

Study characteristics
Methods	Randomised clinical trial 3 arms: TAPP, TEP, open repair. Open repair not included in this review Enrolment: February 1997 to February 2001
Participants	Inclusion criteria: primary, unilateral hernia, ASA I or II Exclusion criteria: NR TAPP Male: NR Female: NR Age mean (SD): 25.72 yrs (1.09) BMI mean (SD): NR Direct: NR Indirect: NR Femoral: 0 Bilateral: 0 Primary: 39 Recurrent: 0 TEP Male: NR Female: NR Age mean (SD): 22.38 yrs (0.65) BMI mean (SD): NR Direct: NR Indirect: NR Femoral: 0 Bilateral: 0 Primary: 40 Recurrent: 0
Interventions	39 TAPP repairs 40 TEP repairs
Outcomes	Primary outcome: not specified. Outcomes: level of tumour necrosis factor‐a (TNF‐a) and interleukin‐6 (IL‐6), VAS scores at 6 and 48 h, complications, recurrence rates Recurrence was assessed at mean of 87 months. Persisting pain, conversion rate, return to activities of daily living, quality of life, and pain > 48 h postoperatively were not reported.
Notes	Country: Turkey Setting: Department of Surgery Funding: NR Conflicts of interest: NR
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Quote: "One hundred sixty patients were randomly assigned..." Comment: method not reported
Allocation concealment (selection bias)	Unclear risk	Quote: "One hundred sixty patients were randomly assigned..." Comment: method not reported
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	Not reported
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Not reported
Incomplete outcome data (attrition bias) All outcomes	High risk	Comment: no flow diagram and no report on number of included, excluded and lost to follow‐up participants Quote: "Patients that have unsatisfactory data or those that could not be reached at their last follow‐up call were removed from the study."
Selective reporting (reporting bias)	Low risk	Specified outcomes are reported.
Other bias	High risk	Funding and conflicts of interest not reported

Gupta 2020.

Study characteristics
Methods	Randomised clinical trial 3 arms: TAPP, TEP, Lichtenstein. Lichtenstein not included in this review Enrolment: July 2017 to March 2019
Participants	Inclusion criteria: consecutive adult male patients in the age group of 25 to 50 yrs with primary, uncomplicated, unilateral/bilateral inguinal hernia Exclusion criteria: female, male < 25 yrs and > 50 yrs, history of previous surgery in the inguinoscrotal region, recurrent inguinal hernia, complicated hernia (irreducible, obstructed, strangulated), hydrocele, epididymitis, history of orchidectomy, significant comorbidities like coronary artery disease, uncontrolled hypertension and diabetes mellitus, chronic bronchitis, renal and hepatic failure, unfit for general anaesthesia (ASA 3 or 4), uncontrolled coagulopathy, refusal to give consent TAPP Male: 41 Female: 0 Age mean (SD): 36.5 yrs (9.29 BMI mean (SD): 22.4 (1.5) Direct: 10 Indirect: 30 Pantaloon: 1 Bilateral: 8 Primary/recurrent: 41 TEP Male: 40 Female: 0 Age mean (SD): 36.9 yrs (8.6) BMI mean (SD): 22.2 (1.7) Direct: 13 Indirect: 27 Bilateral: 8 Primary/recurrent: 40
Interventions	41 TAPP 40 TEP 40 Lichtenstein (not included in this review)
Outcomes	Primary outcome: sexual function 3 months after surgery Duration of surgery, return to activities of daily living, quality of life, and early postoperative pain were not reported. Remaining main outcomes of interest in the review were measured in the study. Recurrence assessed at 18 months
Notes	Country: India Setting: hospital Conflicts of interests: reported no conflicts of interests Funding: no funding received
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Randomization was done using computer generated random numbers (www.randomization.com) with sealed envelopes to ensure concealed allocation with block randomization.
Allocation concealment (selection bias)	Low risk	Randomization was done using computer generated random numbers (www.randomization.com) with sealed envelopes to ensure concealed allocation with block randomization.
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	Blinding of participants or personnel not mentioned
Blinding of outcome assessment (detection bias) All outcomes	Low risk	The statistician and assessors of fertility indices and sexual function scores were blinded to the procedure.
Incomplete outcome data (attrition bias) All outcomes	Low risk	No dropouts
Selective reporting (reporting bias)	Low risk	Outcomes registered on trial registration is reported
Other bias	Low risk	No funding and no conflicts of interest among the autohrs

Hamza 2010.

Study characteristics
Methods	Randomised clinical trial 4 arms: TAPP, TEP, open pre‐peritoneal, and Lichtenstein. Only TAPP and TEP included in this review. Enrolment: dates NR
Participants	Inclusion criteria: adult male patients Exclusion criteria: recurrent, irreducible/obstructed hernia, previous lower abdominal surgery(besides appendectomy), coagulopathies, obstructive airway disease, constipation, obstructive uropathy TAPP Male: 25 Female: 0 Age mean (SD): 36.37 yrs (12.06) BMI mean (SD): 22.4 (1.242) Direct: 0 Indirect: 25 Femoral: 0 Bilateral: 0 Primary: 25 Recurrent: 0 TEP Male: 25 Female: 0 Age mean (SD): 34.91 yrs (13) BMI mean (SD): 23.2 (5.3) Direct: 0 Indirect: 25 Femoral: 0 Bilateral: 0 Primary: 25 Recurrent: 0
Interventions	25 TAPP repairs 25 TEP repairs
Outcomes	Primary outcome: not specified. Outcomes: duration of surgery, postoperative pain (VAS) 6 h postoperative and day after Persisting pain, perioperative bleeding, quality of life, and pain > 7 days after surgery were not reported. The remaining main outcomes of interest in the review were measured in the study. Recurrence was assessed at 24 weeks postoperatively.
Notes	Country: Egypt Setting: Department of Surgery Funding: "The research is funded by the University of Alexandria." Conflicts of interest: "None declared."
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: "Patients were randomised into four groups by random number allocation, twenty‐five patients each."
Allocation concealment (selection bias)	Unclear risk	Not reported
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Quote: "This double blinded prospective randomised trial was conducted on 100 consecutive male patients." Comment: Since it is impossible to blind the surgeon to which surgical method that is being used, it is unclear exactly who was blinded.
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Quote: "The results of the trial were recorded by a medical officer who was not involved in the surgery."
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	100 participants were randomised and no report of any missing data/participants at follow‐up. No flow diagram presented.
Selective reporting (reporting bias)	Low risk	Specified outcomes are reported.
Other bias	Low risk	Funded by a university and authors declare no conflicts of interest

Jeelani 2015.

Study characteristics
Methods	Randomised clinical trial Enrolment: dates NR
Participants	Inclusion criteria: either sex, above 18 yrs of age, admitted for surgical correction of groin hernia Exclusion criteria: NR TAPP Male: 29 Female: 1 Age mean (SD): 48.2 yrs (13.3) BMI mean (SD): NR Direct: 7 Indirect: 27 Femoral: 0 Bilateral: 4 Primary: NR Recurrent: NR TEP Male: 30 Female: 0 Age mean (SD): 46.76 yrs (13) BMI mean (SD): NR Direct: 9 Indirect: 24 Femoral: 0 Bilateral: 3 Primary: NR Recurrent: NR
Interventions	30 TAPP repairs 30 TEP repairs
Outcomes	Primary outcome: not specified Persisting pain and quality of life were not reported. The remaining main outcomes of interest in the review were measured in the study. Recurrence assessed at 2 years.
Notes	Country: India Setting: hospital Funding: NR Conflicts of interests: NR
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	No information on sequence generation
Allocation concealment (selection bias)	Unclear risk	No information on concealment
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	No information on blinding
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	No information on blinding
Incomplete outcome data (attrition bias) All outcomes	Low risk	All included are reported as analysed
Selective reporting (reporting bias)	Unclear risk	No protocol available
Other bias	High risk	Funding and conflicts of interest not reported

Liu 2020.

Study characteristics
Methods	Randomised clinical trial Enrolment: June 2019 to November 2019
Participants	Inclusion criteria: age 18 to 80 yrs, both sexes; no dysfunction of the heart, lung, liver, kidney or other important organ; no contraindications to surgery; written informed consent for inclusion from patients or family members Exclusion criteria: incarcerated or recurrent inguinal hernia; presence of respiratory diseases, abnormal blood gas analysis or lung function preoperatively; presence of chronic kidney disease or renal insufficiency; enroled in other clinical research within the last 3 months TAPP Male: 46 Female: 4 Age mean (SD): 57.8 yrs (15.45) BMI mean (SD): NR Direct: 1 Indirect: 33 Femoral: 3 Bilateral: 10 Primary: 50 Recurrent: 0 TEP: Male: 47 Female: 3 Age mean (SD): 58.0 yrs (14.82) BMI mean (SD): NR Direct: 15 Indirect: 33 Femoral: 2 Bilateral: 7 Primary: 50 Recurrent: 0
Interventions	50 TAPP repairs 50 TEP repairs
Outcomes	Primary outcome: CO2 (carbon dioxide) metabolism before, during, and after repair. Perioperative bleeding, duration of surgery, visceral/vascular injury, and early postoperative pain were the only outcomes of interest in the review that were measured in the study.
Notes	Country: China Setting: hospital Conflicts of interests: authors declare they have no conflicts of interest. Funding: none
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Randomization was performed by a computer‐generated random sequence, patients being assigned to either Group A (TAPP) or Group E (TEP) in equal proportions.
Allocation concealment (selection bias)	Unclear risk	Allocation concealment not described
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Unlikely that knowledge of allocation would affect carbon dioxide measures
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Blinding during data analysis
Incomplete outcome data (attrition bias) All outcomes	Low risk	No dropouts
Selective reporting (reporting bias)	High risk	Not all outcomes specified in trial registration is reported.
Other bias	Low risk	No funding and authors desclare no conflicts of interest

Mesci 2012.

Study characteristics
Methods	Randomised clinical trial 3 arms: TAPP, TEP, open repair. Open repair not included in this review Enrolment: March 2005 to January 2008
Participants	Inclusion criteria: age 18 to 70 yrs Exclusion criteria: severe heart failure, rheumatoid arthritis or similar joint diseases, severe hypertension, hip or knee prosthesis, and neurological sequelae TAPP Male: NR Female: NR Age mean (SD): 48.2 yrs (NR) BMI mean (SD): NR Direct: 13 Indirect: 17 Pantaloon: 5 Femoral: 0 Bilateral: 4 Primary: 20 Recurrent: 5 TEP Male: NR Female: NR Age mean (SD): 48.4 yrs (NR) BMI mean (SD): NR Direct: 13 Indirect: 18 Pantaloon: 6 Femoral: 0 Bilateral: 4 Primary: 20 Recurrent: 5
Interventions	25 TAPP repairs 25 TEP repairs 25 prolene mesh graft repairs (not included in this review)
Outcomes	Primary outcome: muscle function in lower extremities Serious adverse events, duration of surgery, return to activities of daily living, early postoperative pain, haematoma/seroma, and early pain (< 24 hours) were the only main outcomes of interest in the review that were measured in the study.
Notes	Country: Turkey Setting: University Medical School, General Surgery Department Funding: NR Conflicts of interest: NR
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Not reported
Allocation concealment (selection bias)	Unclear risk	Not reported
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	Not reported
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Not reported
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	No dropouts reported, but no flow diagram
Selective reporting (reporting bias)	Low risk	Specified outcomes are reported.
Other bias	High risk	Funding and conflicts of interest not reported

Nawaz 2017.

Study characteristics
Methods	Randomised clinical trial Enrolment: January 2010 to December 2012
Participants	Inclusion criteria: male patients aged 20 to 50 yrs with inguinal hernia confined to inguinal canal (bubonocele), with no other comorbidity or previous surgery, and without any other general contraindication for laparoscopic surgery Exclusion criteria: NR TAPP Male: 60 Female: 0 Age mean (SD): NR BMI mean (SD): NR Direct: NR Indirect: NR Femoral: NR Bilateral: NR Primary: 60 Recurrent: 0 TEP Male: 60 Female: 0 Age mean (SD): NR BMI mean (SD): NR Direct: NR Indirect: NR Femoral: NR Bilateral: NR Primary: 60 Recurrent: 0
Interventions	60 TAPP repairs 60 TEP repairs
Outcomes	Primary outcomes: pain at 24 hours and recurrence at 1 year Persisting pain, perioperative bleeding, visceral/vascular injury, haematoma/seroma, and quality of life were not reported. The remaining main outcomes of interest in the review were measured in the study. Recurrence was assessed at 1 year.
Notes	Country: Pakistan Setting: Hospital Funding: NR Conflicts of interests: NR
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Not reported
Allocation concealment (selection bias)	Unclear risk	Not reported
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	Not reported
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Not reported
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Not reported
Selective reporting (reporting bias)	Unclear risk	Not reported
Other bias	High risk	Funding or conflicts of interest not reported

Pokorny 2008.

Study characteristics
Methods	Randomised clinical trial 5 arms: TAPP, TEP, Shouldice, Bassini, and Lichtenstein. Only TAPP and TEP were included in this review. Enrolment: 1998 to 2002
Participants	Inclusion criteria: 19 to 85 yrs of age, unilateral primary inguinal hernia Exclusion criteria: incarcerated, recurrent, bilateral, or femoral hernias, unfit for general anaesthesia TAPP Male: 86 Female: 7 Age mean (range): 49 yrs (21 to 78) BMI mean (range): 25 (17 to 35) Direct: NR Indirect: NR Femoral: NR Bilateral: 0 Primary: 93 Recurrent: 0 TEP Male: 35 Female: 1 Age mean (range): 48 yrs (17 to 73) BMI mean (range): 25 (21 to 30) Direct: NR Indirect: NR Femoral: NR Bilateral: 0 Primary: 36 Recurrent: 0
Interventions	93 TAPP repairs 36 TEP repairs
Outcomes	Primary outcome: recurrence of hernia within 3 years Recurrence, persisting pain, duration of surgery, visceral/vascular injury, early postoperative pain, and haematoma/seroma were the only main outcomes of interest in the review that were measured in the study. Recurrence was assessed at up to 3 years.
Notes	Country: Austria Setting: general surgical clinics Funding: NR Conflicts of interest: NR
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	The study used a biometric department to randomise participants.
Allocation concealment (selection bias)	Low risk	Quote: "Allocation concealment was warranted, as the external biometric department was only contacted via the Internet, once a patient was to be randomised"
Blinding of participants and personnel (performance bias) All outcomes	High risk	Quote: "The patients were informed of their treatment assignment directly after the randomisation."
Blinding of outcome assessment (detection bias) All outcomes	High risk	Quote: "...by a surgeon who had not been involved in that patient’s operation." A surgeon will likely be able to distinguish between surgical wounds and is therefore not blinded.
Incomplete outcome data (attrition bias) All outcomes	High risk	2 dropouts in the TEP group and 8 dropouts in the TAPP group, but no reason given.
Selective reporting (reporting bias)	Low risk	Specified outcomes are reported.
Other bias	High risk	Funding and conflicts of interest not reported

Rhoda 2022.

Study characteristics
Methods	Randomised clinical trial Enrolment: November 2018 to March 2020
Participants	Inclusion criteria: 18 to 90 yrs of age. Male. Uncomplicated unilateral inguinal hernia undergoing elective laparoscopic hernia repair (TEP or TAPP) Exclusion criteria: not willing to participate in study, complicated inguinal hernia, recurrent inguinal hernia, not fit for GA, coagulopathy, bilateral inguinal hernia, female, previous lower abdominal surgery TAPP Male: 34 Female: 0 Age mean (SD): 49 yrs (NR) BMI mean (SD): NR Direct: 15 Indirect: 19 Femoral: 0 Bilateral: 0 Primary: 34 Recurrent: 0 TEP Male: 34 Female: 0 Age mean (SD): 51 yrs (NR) BMI mean (SD): NR Direct: 6 Indirect: 28 Femoral: 0 Bilateral: 0 Primary: 34 Recurrent: 0
Interventions	34 TAPP repairs 34 TEP repair
Outcomes	Primary outcome: comparison of postoperative pain between the TAPP and TEP groups All main outcomes of interest in the review were measured in the study, other than persisting pain and quality of life. Recurrence assessed at 3 months.
Notes	Country: India Setting: hospital Funding: did not receive funding Conflicts of interests: authors declare no conflicts of interests
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	An independent statistician, who was not involved in patient care, generated the randomization sequence via a computer‐generated random number.
Allocation concealment (selection bias)	Low risk	The randomisation code was contained in opaque, sealed envelopes
Blinding of participants and personnel (performance bias) All outcomes	Low risk	The participant was unaware of the assigned treatment group.
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Not reported
Incomplete outcome data (attrition bias) All outcomes	Low risk	None lost to follow‐up
Selective reporting (reporting bias)	Low risk	Reporting in accordance with trial registration
Other bias	Low risk	Did not recieve funding and authors declare no conflicts of interest

Saurabh 2018.

Study characteristics
Methods	Randomised clinical trial Enrolment: dates NR
Participants	Inclusion criteria: patients above 18 yrs of age with unilateral inguinal hernia undergoing laparoscopic TEP and TAPP repair Exclusion criteria: NR TAPP Male: 30 Female: 0 Age mean (SD): 40.23 yrs (NR) BMI mean (SD): NR Direct: NR Indirect: NR Femoral: NR Bilateral: 0 Primary: NR Recurrent: NR TEP Male: 30 Female: 0 Age mean (SD): 43.33 yrs (NR) BMI mean (SD): NR Direct: NR Indirect: NR Femoral: NR Bilateral: 0 Primary: NR Recurrent: NR
Interventions	30 TAPP repairs 30 TEP repairs
Outcomes	This study was conducted to compare the changes in systemic inflammatory response after laparoscopic total extra peritoneal (TEP) and laparoscopic transabdominal preperitoneal (TAPP) repair for inguinal hernia, and to compare postoperative pain in both groups on a VAS. The only main outcome of interest in the review that was reported in the study was pain at 24 hours and 7 days.
Notes	Country: India Setting: Hospital Funding: NR Conflicts of interests: NR
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Not reported
Allocation concealment (selection bias)	Unclear risk	Not reported
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	Not reported
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Not reported
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Not reported
Selective reporting (reporting bias)	Unclear risk	Not reported
Other bias	High risk	Funding and conflicts of interest not reported

Schrenk 1996.

Study characteristics
Methods	Randomised clinical trial 3 arms: TEP, TAPP and Shouldice. Shouldice not included in this review Enrolment: dates NR
Participants	Inclusion criteria: patients having elective unilateral inguinal hernia repair Exclusion criteria: recurrent or incarcerated hernia TAPP Male: 24 Female: 4 Age mean (SD): 39.1 (14.3) BMI mean (SD): NR Direct: 9 Indirect: 19 Femoral: 0 Bilateral: 0 Primary: 28 Recurrent: 0 TEP Male: 22 Female: 2 Age mean (SD): 42.3 (11.9) BMI mean (SD): NR Direct: 6 Indirect: 18 Femoral: 0 Bilateral: 0 Primary: 24 Recurrent: 0
Interventions	28 TAPP repairs 24 TEP repairs 34 Shouldice repairs (not included in this review)
Outcomes	Postoperative pain and return to pain‐free activities Recurrence, perioperative bleeding, duration of surgery, conversion, visceral/vascular injury, return to activities of daily living, early postoperative pain, and haematoma/seroma were outcomes of interest in the review that were reported in the study. Recurrence was assessed at 3 months.
Notes	Country: Austria Setting: NR Funding: "Statistical analysis was supported by a grant from Auto Suture Austria" Conflicts of interest: NR
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Not reported
Allocation concealment (selection bias)	Low risk	Quote: "Randomization was done immediately before surgery in the anaesthetic room by use of sealed envelopes."
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	Not reported
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Not reported
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	No dropouts reported, but no flow diagram
Selective reporting (reporting bias)	Low risk	Specified outcomes are reported.
Other bias	High risk	Funded by private company and conflicts of interest not reported

Sharma 2015.

Study characteristics
Methods	Randomised clinical trial Enrolment: January 2010 to December 2013
Participants	Inclusion criteria: clinically diagnosed bilateral inguinal hernia Exclusion criteria: unfit for general anaesthesia; age > 70 yrs; previous lower abdominal surgery; pregnancy; past history of malignancy; complicated hernia; severe lower urinary tract symptoms; morbid obesity; uncorrected coagulopathy TAPP Male: NR Female: NR Age mean (SD): 49.4 yrs (NR) BMI mean (SD): NR Direct: 27 Indirect: 33 Femoral: 0 Bilateral: 30 Primary: 30 Recurrent: 0 TEP Male: NR Female: NR Age mean (SD): 49 yrs (NR) BMI mean (SD): NR Direct: 32 Indirect: 28 Femoral: 0 Bilateral: 30 Primary: 30 Recurrent: 0
Interventions	30 TAPP repairs 30 TEP repairs
Outcomes	Primary outcome: intraoperative complications Early pain, persisting pain, and quality of life were not reported. The remaining main outcomes of interest in the review were measured in the study. Recurrence was assessed at 30 days.
Notes	Country: India Setting: tertiary centre Funding: "None" Conflicts of interest: "None"
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: "Patients were randomised into TAPP (Group I) or the TEP (Group II) group using computer generated random numbers."
Allocation concealment (selection bias)	Unclear risk	Not reported
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Quote: "Patients were blinded to the operative procedure."
Blinding of outcome assessment (detection bias) All outcomes	High risk	Authors state that it is a single blind study, where participants are blinded to the allocation.
Incomplete outcome data (attrition bias) All outcomes	Low risk	Quote: "We followed all our patients for only 30 days for this study; however all the patients are still under follow up."
Selective reporting (reporting bias)	Low risk	Specified outcomes are reported.
Other bias	Low risk	No funding and authors declare no conflicts of interest

Triantafyllidis 2013.

Study characteristics
Methods	Randomised trial 3 arms: TAPP, TEP, mesh repair (open surgery). Open surgery not included in this review. Enrolment: unclear start date to January 2012
Participants	Inclusion criteria: NR Exclusion criteria: NR TAPP Male: NR Female: NR Age mean (SD): NR BMI mean (SD): NR Direct: NR Indirect: NR Femoral: NR Bilateral: NR Primary: NR Recurrent: NR TEP Male: NR Female: NR Age mean (SD): NR BMI mean (SD): NR Direct: NR Indirect: NR Femoral: NR Bilateral: NR Primary: NR Recurrent: NR
Interventions	81 TAPP repairs 86 TEP repairs 88 mesh plug repair (open surgery) (not included in review)
Outcomes	Primary outcome not specified Outcomes only reported in an abstract with no numerical results.
Notes	Country: Greece Setting: hospital Funding: NR Conflicts of interests: NR Only reported in abstract with no numbers. Authors have been contacted several times but have not replied.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Not reported (abstract only)
Allocation concealment (selection bias)	Unclear risk	Not reported (abstract only)
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	Not reported (abstract only)
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Not reported (abstract only)
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Not reported (abstract only)
Selective reporting (reporting bias)	Unclear risk	Not reported (abstract only)
Other bias	Unclear risk	Too little information in report to make a judgement

Wang 2013.

Study characteristics
Methods	Randomised clinical trial 3 arms: TAPP, TEP, Lichtenstein. Lichtenstein not included in this review Enrolment: March 2005 to March 2010
Participants	Inclusion criteria: inguinal hernia Exclusion criteria: NR TAPP Male: 70 Female: 14 Age mean (SD): 48.23 yrs (13.2) BMI mean (SD): NR Direct: 6 Indirect: 77 Femoral: 1 Bilateral: NR Primary: NR Recurrent: NR TEP Male: 71 Female: 13 Age mean (SD): 48.25 yrs (17.09) BMI mean (SD): NR Direct: 8 Indirect: 73 Femoral: 3 Bilateral: NR Primary: NR Recurrent: NR
Interventions	84 TAPP repairs 84 TEP repairs
Outcomes	Primary outcome: not specified. Outcomes: operating time, postoperative hospital stay, intraoperative and postoperative complications, postoperative pain scores, postoperative analgesic administration, postoperative local dysthesia, postoperative chronic pain, postoperative long‐term hernia recurrence The participants were followed up for 3 to 32 months, with an average of 16 months.
Notes	Country: China Setting: hospital Funding: not reported Conflicts of interest: "No competing financial interests exist"
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Not reported
Allocation concealment (selection bias)	Unclear risk	Not reported
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	Not reported
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Not reported
Incomplete outcome data (attrition bias) All outcomes	Low risk	Quote: "...3 patients in the TAPP group, 2 patients in the TEP group...were lost to follow‐up"
Selective reporting (reporting bias)	Low risk	Specified outcomes are reported.
Other bias	Unclear risk	Funding not reported, but authors declare no conflicts of interest

Zhu 2009.

Study characteristics
Methods	Randomised clinical trial Enrolment: dates NR
Participants	Inclusion criteria: inguinal hernia, scheduled for laparoscopic hernioplasty Exclusion criteria: recurrent or bilateral hernia; previous history of low abdominal surgery; coexisting severe cardiovascular or pulmonary diseases; any other contraindications for laparoscopic surgery TAPP Male: 19 Female: 1 Age mean (SD): 63.3 yrs (12.3) BMI mean (SD): 23.6 (1.8) Direct: NR Indirect: NR Femoral: NR Bilateral: 0 Primary: 20 Recurrent: 0 TEP Male: 20 Female: 0 Age mean (SD): 60.2 yrs (9.7) BMI mean (SD): 23.5 (2) Direct: NR Indirect: NR Femoral: NR Bilateral: 0 Primary: 20 Recurrent: 0
Interventions	20 TAPP repairs 20 TEP repairs
Outcomes	Primary outcome: not specified. Outcomes: operation time, length of stay, VAS score, blood gases, such as pH (potential of hydrogen ‐ acidity), HCO3 (bicarbonate), and PaCO2 (partial pressure of carbon dioxide), heart rate, blood pressure, end‐tidal CO2 (level of carbon dioxide released at the end of an exhaled breath) Only reported on perioperative measures during admission (3.5 days): duration of surgery, conversion, visceral/vascular injury, and postoperative pain. Time of assessment was not reported for pain.
Notes	Country: China Setting: surgical department, hospital Funding: not reported Conflicts of interest: "No competing financial interests exist"
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Not reported
Allocation concealment (selection bias)	Unclear risk	Not reported
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	Not reported
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Not reported
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Not reported
Selective reporting (reporting bias)	Low risk	Specified outcomes are reported.
Other bias	Unclear risk	Funding not reported, but authors desclare no conflicts of interest

ASA: American Society of Anaesthesiologists; BMFSI: brief male sexual function inventory; h: hours; NR: not reported; SD: standard deviation; VAS: visual analogue scale; yrs: years

Characteristics of excluded studies [ordered by study ID]

Study	Reason for exclusion
CTRI2018/10/015964	Not comparing TAPP with TEP
DeSaxce 2007	Not comparing TAPP with TEP
Fitzgibbons Jr 1995	Cohort study
Heikkinen 2004	Not comparing TAPP with TEP
Millat 2007	Not comparing TAPP with TEP
NCT03563092	Did not randomise to TAPP or TEP
Negro 1997	A commentary, not a study
Rieger 2017	Not comparing TAPP with TEP
Schafer 2010	A commentary, not a study
Van Hee 1998	Cohort study

Characteristics of ongoing studies [ordered by study ID]

CTRI/2022/09/045456.

Study name	A randomized trial comparing pain threshold using quantitative sensory testing in patients with primary groin hernia following laparoscopic groin hernia repair and Lichtenstein open mesh repair
Methods	Randomised clinical trial
Participants	Inclusion criteria 18 to 75 years of age Both sexes Uncomplicated primary groin hernia, fit to undergo either laparoscopic groin hernia repair or Lichtenstein open mesh repair Exclusion criteria Age < 18 years or > 75 years Complicated, i.e. strangulated or obstructed hernia Recurrent inguinal hernia History of previous pelvic or lower abdominal surgery History of hernia repair either on same or contralateral side History of chronic systemic or mental illness Diabetes mellitus and chronic kidney disease Chronic analgesic or opioid abuse Unfit for general anesthesia Coagulopathies
Interventions	TEP or TAPP
Outcomes	Primary Preoperative and postoperative pain threshold at 6 weeks and 3 months, via Quantitative Sensory Testing, using non‐invasive thermal stimulus Secondary Correlation of pain threshold with postoperative pain scores measured on a VAS Correlation of pain threshold and pain scores with hernia‐related quality of life, using Carolinas Comfort Scale and World Health Organization Quality Of Life instrument (WHOQOL‐BREF Questionnaire) Risk factors for early postoperative and chronic groin pain following groin hernia repair
Starting date	15 September 2022
Contact information	drvkbansal@gmail.com
Notes	We emailed authors regarding status of the trial, but no response has been received.

NCT00687375.

Study name	A randomized controlled trial of laparoscopic inguinal hernia repair ‐ transabdominal preperitoneal (TAPP) versus totally extra peritoneal (TEP) approach
Methods	Randomised clinical trial
Participants	Inclusion criteria All consecutive patients with uncomplicated symptomatic inguinal hernia attending the outpatient department of surgery at the All India Institute of Medical Sciences The diagnosis of inguinal hernia will be made clinically. Exclusion criteria Comorbid conditions making the patients unfit for general anaesthesia Complicated hernia Uncorrectable coagulopathy Morbid obesity (BMI > 30) Suspected intra‐abdominal or pelvic malignancy
Interventions	TAPP versus TEP
Outcomes	Primary Operating time (in minutes) Cost of the procedure Secondary Conversion rate Recurrence Major complications
Starting date	April 2007
Contact information	Dr. Subodh Kumar, All India Institute of Medical Sciences, New Delhi‐29, India
Notes	No contact email provided and therefore trial authors not contacted.

NCT02920307.

Study name	Prospective, randomized and controlled study comparing fixation versus no fixation of mesh in laparoscopic inguinal hernia repair
Methods	Randomised clinical trial
Participants	Inclusion criteria Unilateral hernia Uncomplicated hernia Medical fitness for general anesthesia Exclusion criteria Unfit for general anaesthesia Complicated hernia Uncorrectable coagulopathy BMI > 35 Concomitant pathologies requiring simultaneous surgery Bilateral hernia
Interventions	TAPP or TEP, with or without fixation
Outcomes	Primary Postoperative pain 1 week to 2 years after surgery Secondary Total hospital costs Conversion rate Recurrence rate Rate of minor and major complications
Starting date	September 2016
Contact information	Mehmet Kaplan, Principal Investigator, Medical Park Gaziantep Hospital
Notes	No contact email provided and therefore trial authors not contacted.

NCT02928146.

Study name	Comparison of Lichtenstein versus TAPP and TEP techniques for inguinal hernia repair
Methods	Randomised clinical trial
Participants	Inclusion criteria Male Age 18 to 65 yrs Planned inguinal hernia repair using synthetic implant BMI range: 20 to 35 kg/m2 Written informed consent Exclusion criteria Prior midline laparotomy Contraindications for general anaesthesia ASA > IV Cirrhosis (Child B or C) or ascites Active treatment with use of chemotherapy Incarcerated hernia
Interventions	TAPP versus TEP (Lichtenstein group not relevant for this review)
Outcomes	Primary Postoperative complications associated with wound Secondary Frequency of conversions (from laparoscopic to open approach) Severity of pain according to VAS Quality of life
Starting date	January 2017
Contact information	Contact: Miroslaw Szura, MD, PhD, msszura@gmail.com; Artur Pasternak, MD, PhD, artur.pasternak@uj.edu.pl
Notes	We emailed both authors regarding status of the trial, but no response has been received.

NCT04114344.

Study name	Clinical trial to compare TAPP (transabdominal preperitoneal) vs TEP (totally extraperitoneal) y approach for Women's Inguinal Hernia on an Outpatient Basis (WOLAP)
Methods	Randomised clinical trial
Participants	Inclusion criteria Inguinofemoral hernia, EHS classification Over 18 years old Signed informed consent form Female Meeting of outpatient discharge criteria, determined by Aldrete's test Exclusion criteria Loss of domain Abdominal skin grafts Previous preperitoneal (open or laparoscopic) prosthetic mesh Incarcerated hernia Previous complications such as infection, fistulae, etc Not candidate for ambulatory surgery Pregnancy or desire for pregnancy in the first postoperative year Sample size: 78
Interventions	TAPP or TEP repair
Outcomes	Primary Postoperative pain Recurrence Complications Secondary Operative time Length of hospital stay
Starting date	May 2019 Estimated primary completion date: October 2022
Contact information	José Tinoco González, Principal Investigator, Fundación Pública Andaluza para la gestión de la Investigación en Sevilla
Notes	Country: Spain No contact email provided and therefore trial authors not contacted.

ASA: American Society of Anesthesiologists; BMI: bosy mass index; EHS: European Hernia Society; TAPP; transabdominal pre‐peritoneal; TEP: totally extraperitoneal; VAS: visual analogue scale

Differences between protocol and review

This review is an update of one first published in 2005 (Wake 2005). Since several randomised studies have been published since the original review, we have made changes to the methodology, resulting in differences between this update and the protocol (Wake 2004). Furthermore, Cochrane policies regarding conduct and reporting of reviews have also changed, resulting in differences between the protocol and review. Below we detail the differences between the protocol and the current version of the review.

Criteria for selecting studies for inclusion in the review

Type of studies: we decided not to include non‐randomised studies, since several randomised studies have been conducted.

Type of participants: we decided to set the age limit at 18 years of age, since laparoscopic TAPP or TEP is seldom done for children or adolescents. As TAPP and TEP can be done for both inguinal and femoral hernias, we chose to include studies involving people with femoral hernias, in case some studies involved a mixed population.

Types of outcome measures: we made some changes to the secondary outcomes as below.

• We changed "opposite method initiated" and "conversion" to "conversion to other laparoscopic method or open procedure".

• We combined "haematoma" and "seroma" into one outcome.

• We listed "wound/superficial infection" and "mesh/deep infection" as serious adverse events.

• We omitted "port site hernia", "length of hospital stay", and "health service resource use and costs".

We made a post hoc decision to analyse early postoperative pain as a continuous variable because most of the included studies reported mean pain scores as opposed to number of participants with pain. Furthermore, because the time point of assessment varied across studies, we decided to present and analyse data at 6 hours, 12 hours, 1st postoperative day, 7th postoperative day and 30th postoperative day.

Data collection and analysis

We chose a random‐effects model for meta‐analysis because of the inherent heterogeneity in surgical procedures, even for standardised methods such as TAPP and TEP. We chose the odds ratio, mean difference, and standardised mean difference as effect measures with corresponding 95% confidence intervals. See Measures of treatment effect for details.

Contributions of authors

Kristoffer Andresen contributed to the conception and design of the review, and the analysis and interpretation of data. He drafted the review and approved the final document to be published.

Jacob Rosenberg contributed to the conception and design of the review, and the analysis and interpretation of data. He commented on the review critically for intellectual content and approved the final document to be published.

Sources of support

Internal sources

• No sources of support provided

External sources

• No sources of support provided

Declarations of interest

KA: no relevant interests. KA is a surgical resident at Herlev Hospital, Denmark, and Managing Editor of Cochrane Colorectal, but he was not involved in the editorial processing of this review update.

JR: no relevant interests. JR is a surgeon at Herlev Hospital, Denmark, and Co‐ordinating Editor of Cochrane Colorectal, but he was not involved in the editorial processing of this review update.

New search for studies and content updated (conclusions changed)