Introduction

One of the most common surgical procedures performed worldwide is Inguinal Hernia (IH) repair surgery [1]. A technique introduced by Lichtenstein, open Lichtenstein repair (OLR), in 1984 is to this day performed extensively [2]. However, a significant drawback of this technique is greater percentage of recurrence and complexity in treating them as a result of dissecting through the fibrotic tissue and taking out and replacing the anchoring mesh [3].

Moreover, in recent years, a different method known as the laparoscopic trans-abdominal pre-peritoneal (TAPP) technique has gained an increasing amount of attention [4,5,6]. According to Claus et al., latest research talks about TAPP procedure to be minimally invasive and be advantageous to patients causing prompt recovery with decreased intensity of pain [1].

However, very few studies report data on the laparoscopic advantages of bilateral inguinal hernia (BIH) repair over the open approach, where the benefits are anticipated to be even greater since both hernias are repaired using a single access point. Therefore, we conducted this systematic review and meta-analysis to compare the outcomes of OLR and TAPP repair for BIH. As per our knowledge, this is the first study of this kind in the literature for BIH.

Methodology

Data search and literature review strategy

This meta-analysis was established based on the Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA) guidelines (Fig. 1) [7]. It was conducted within the framework laid out by the Cochrane collaboration. A literature search of PubMed, Scopus, and Google Scholar for comparative studies between TAPP versus OLR for BIH groups was performed from inception till December 31, 2023. The complete search strategies used in each database are given in Table 1. No time or sample size restrictions were applied. In addition, bibliographies of relevant review articles, clinicaltrials.gov, and databases of unpublished literature were searched to ensure that no relevant studies from white or gray literature were omitted.

Fig. 1
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PRISMA flowchart

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Table 1 Detailed search strategy used in each database
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Selection criteria

Articles retrieved from the literature search were transferred to Endnote X9 (Clarivate Analytics, US) where duplicates were identified and removed [8]. Two independent reviewers carefully evaluated and selected the remaining articles based on their relevance to the criteria mentioned below. All articles were initially selected based on title and abstract, after which the full text was comprehensively reviewed. In case of any disagreement, a third reviewer was consulted. The inclusion criteria were set as follows: (1) English literature; (2) comparative studies including TAPP and OLR repair groups for BIH with full-text descriptions; (3) randomized-controlled trials (RCTs); (4) studies assessing at least one primary or secondary outcome. The exclusion criteria included conference abstracts, letters, reviews, case reports and laboratory studies, non-comparative studies, inadequate original data for further analysis, and studies from the same institute or authors or sharing the same database.

Data extraction and quality assessment

The six authors independently searched for relevant articles using a standardized search string. After addressing all the related controversies and doubts, the selected articles’ main text and supplementary were thoroughly read and data were extracted for all possible outcomes.

The data were allocated for demographics, baseline characteristics, and outcomes, and were assorted in tabular form in a spreadsheet labeled as TAPP and OLR group. All the outcomes that could have been extracted and of value were reported, along with that we extracted baselines and demographics such as BMI, Age, Gender, Country, ASA score, hernia size, and known comorbidities if given were listed in their respective areas.

Additional Outcomes such as (1) Quality of life, (2) Time taken to return to daily activities and work, and (3) Complications in patients with BMI more than 25 were extracted, but they could not be reported, since quality of life, despite being reported by 3 of the 4 studies, was reported using a different scaling criteria and the remaining two outcomes had less than three studies reporting them.

The primary outcomes (1) Operative Time, (2) Duration of post-operative stay, (3) Pain score on VAS (Visual Analog Scales) Criteria Day 1, and (4) Pain score on VAS Criteria Day 7 were reported in all the studies and were extracted. The secondary outcomes included (1) Recurrence and (2) Complications.

The Risk-of-Bias (ROBS) assessment for all the included studies was done by MS and checked for (1) Selection Bias, (2) Attrition Bias, (3) Reporting Bias, (4) Performance Bias, (5) Detection Bias, and (6) Allocation Bias using the Cochrane Risk-of-Bias Assessment tool [9].

Data synthesis and analysis

Analysis was done using RevMan Version 5.4, in which a comparison between the OLR and TAPP groups was made [10]. The data were analyzed irrespective of the demographics, ESA score and ASA score.

The data for our primary outcomes were reported as a continuous outcome, and hence, we applied ‘Inverse Variance’ as the analysis method with a confidence interval (CI) of 95%, and ‘Random effects’ as the analysis model. The values were entered for the given ‘Mean’ along with its ‘Standard Deviation (SD)’ and total population for both the groups. The results of the analysis were reported as ‘Mean Difference (MD)’. We did not note any disparity for which we had to use external calculators, converters, or graphs.

The analysis of the secondary outcomes was reported as dichotomous, so we applied ‘Mantel–Haenszel’ as the analysis method with a CI of 95%, and ‘Random effects’ as the analysis model. The values for the events that occurred along with their total population of the groups were entered and the desired outcomes were analyzed. The results of the analysis were reported as Risk Ratio (RR).

Results

Study characteristics

The characteristics of the studies included in this systemic review and meta-analysis are listed in Table 2. All four included studies were RCTs. They belonged to two countries, Egypt [11] and Spain [12,13,14]. The age group included in these studies range from 18 to 80 years, with a male dominant participant in all the studies. The population enrolled in the studies had a BIH of EHS grade I to grade III. The reported hernia size in TAPP groups was 2 cm, while in the OLR group it was 2.3 cm. The duration of studies ranged from 2 to 3 years.

Table 2 Patient demographics in the included studies
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Risk-of-bias assessment

All the studies showed Selection bias, Allocation bias, Performance bias, and Detection bias which was adequate (Fig. 2). However, apart from El-Messiry et al. [11], all the remaining studies showed an unclear risk for Attrition bias.

Fig. 2
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Quality assessment of included studies

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Primary outcomes

Duration of post-operative hospital stay

The post-operative hospital stay was reported in all four studies [11,12,13,14] in our meta-analysis. The MD was reported as – 0.40 [CI at 95% was (– 0.51 to – 0.29)] with a p value of < 0.00001 and a heterogeneity of 33%, hence showing a significantly reduced duration of post-operative hospital stay in the TAPP group (Fig. 3).

Fig. 3
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Comparison of duration of post-operative hospital stay between the OLR and TAPP groups

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Operative time

The time consumed during the operative procedure was reported in all four studies [11,12,13,14]. The MD was reported as 5.85 [CI at 95% was (2.11–9.60)] with a p value of 0.002 and a heterogeneity of 66% (Fig. 4). The analysis showed a significantly decreased operative time in the OLR group as compared to the TAPP group.

Fig. 4
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Comparison of operative time between the OLR and TAPP groups

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Pain score on VAS criteria day 1

Post-operative pain on day 1 assessed by VAS score was calculated in all four studies [11,12,13,14]. The MD reported was – 2.02 [CI at 95% (-2.20—-1.83)] with a p value of < 0.00001 and a heterogeneity of 0% (Fig. 5). The result showed a significant decrease in the pain score on VAS criteria on post-operative Day 1 in the TAPP group.

Fig. 5
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Comparison of pain score on VAS criteria day 1 between the OLR and TAPP groups

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Pain score on VAS criteria day 7

Post-operative pain on day 7 assessed by VAS score was calculated in all four studies [11,12,13,14]. The MD reported was – 1.41 [CI at 95% (– 1.58 to – 1.24)] with a p value of < 0.00001 and a heterogeneity of 0% (Fig. 6). The result showed a significant decrease in the pain score on VAS criteria on post-operative Day 7 in the TAPP group.

Fig. 6
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Comparison of pain score on VAS criteria day 7 between the OLR and TAPP groups

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Secondary outcomes

Recurrence

Recurrence was reported in all four of the included studies [11,12,13,14]. The RR reported was 1.45 [CI at 95% (0.71–2.96)] with a p value of 0.31 and a heterogeneity of 0% (Fig. 7). The result showed an insignificant difference between the two groups.

Fig. 7
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Comparison of recurrence between the OLR and TAPP groups

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Complications

All the post-operative surgical complications were pooled and analyzed for both groups in all four studies [11,12,13,14]. The RR calculated was 0.32 [CI at 95% (0.20–0.51)] with a p value of < 0.00001 and a heterogeneity of 0% (Fig. 8). The result showed a significantly reduced complication rate in the TAPP group.

Fig. 8
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Comparison of complications between the OLR and TAPP groups

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Sensitivity analysis

A sensitivity analysis was conducted using the leave-one-out method for (a) Operative Time. After leaving out El-Messiry et al. [11], the heterogeneity dropped from 66 to 0% (Fig. 9).

Fig. 9
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Sensitivity analysis of operative time

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Discussion

With an incidence of 1–5% occurrence in the general population, inguinal hernia and its repair is the most frequently performed procedure in general surgery [15]. RCTs comparing TAPP with OLR for BIHs have been less frequently conducted and present with limited patients. Data on quality of life of OLR vs. TAPP procedures are still limited and almost unknown in BIH repair. Therefore, this meta-analysis was performed by identifying appropriate studies to gauge a better understanding of the relative merits of various outcomes in each surgical technique.

This meta-analysis included 4 studies randomizing 573 patients comparing the TAPP and OLR approaches for BIH repair. With frequent advancements in laparoscopic approaches, techniques that are minimally invasive are now given more importance [16]. In our study, the minimally invasive technique stated was TAPP.

Our meta-analysis focused mainly on six outcomes. With regards to the post-operative hospital stay, our study noted that OLR required a longer hospital stay compared to the TAPP technique (p < 0.00001) and favored the TAPP approach over Lichtenstein. Second, OLR requires two incisions as opposed to TAPP (where usually one incision is required), leading to greater discomfort and pain and hence probably being the reason for the increased pain score on the VAS criteria. However, several surgeons employ the three-port approach in TAPP, which could theoretically cause more pain but our analysis reports otherwise. Furthermore, increased pain requires pain management, which is also another reason for a longer hospital stay. However, the mean operative time for TAPP was greater than for OLR (p = 0.002) and showed statistical significance favoring the OLR approach.

Decreased post-operative pain and shorter hospital stay duration are two advantages that are greatly apparent in BIHs treated by the TAPP approach. Nonetheless, in addition to a shorter mean operative time, another benefit of OLR technique is that 60% of them are performed as day-cases [17]. Keeping in mind the different outcomes that favored TAPP, it is imperative to consider its disadvantage of increased operative time when making a decision on which technique to use.

Apart from age and hernia recurrence, pre-operative pain and early post-operative pain seem to be risk factors for chronic inguinal pain syndrome following a hernia repair. Notably, most studies lack assessment of inguinal pain either in the pre-operative or the post-operative phases. Furthermore, the severity of pain along with the request for pain medication in the post-operative course is poorly documented [18]. Based on the data extracted, by comparing data of VAS on post-operative day 7, the TAPP group exhibits a favorable pain score compared to OLR with a MD of -1.41 and most importantly no heterogeneity (0%). The lower pain scores associated with TAPP repair offer a potential advantage in overall patient comfort and facilitate a quicker return to normal activities.

Our study’s secondary outcomes encompassed both post-operative surgical results and recurrence rates, with a focus on inguinal hernia (IH) repair, where recurrence risk is of utmost importance. Our meta-analysis indicated that neither TAPP nor the OLR approach portrayed a statistically significant difference in recurrence rate (p value of 0.31) alongside a homogenous distribution of results across the studies (0% heterogeneity). Despite observing a trend suggesting a lower risk of recurrence with OLR technique, lack of statistical authenticity prompts caution in interpreting its clinical superiority over TAPP. Therefore, while recurrence reduction appears promising with OLR, clinical significance warrants careful consideration in treatment decision making.

Post-operative surgical outcomes are feared complications of any procedure, and they were accumulated and analyzed in all the four studies. According to Ielpo et al. (2018), common early complications occurring in the OLR approach include seroma, hematoma formation, and superficial surgical site infection, which are likely to occur in the inguinal area rather than in various other abdominal areas, as compared to the TAPP approach [14]. Our analysis revealed that the TAPP approach was less likely, than the OLR approach, to result in post-operative surgical problems (p value < 0.00001). This result also showed no evidence of heterogeneity (0%). According to these results, TAPP might be a less risky choice in terms of surgical complications, but still other outcomes need to be analyzed before following a particular surgical intervention.

Two important variables affecting the results of TAPP hernia repair are surgeon experience and the learning curve. Literature has shown that when surgeons become more proficient and familiar with TAPP, they frequently obtain shorter operating times and better results, as with all laparoscopic procedures [19]. For example, in comparison to their more experienced colleagues, less-experienced surgeons usually need more time to finish TAPP and may have higher rates of complications. Moreover, the learning curve associated with TAPP has the potential to have a vital impact on post-operative pain and recovery in addition to operating time [20]. Thus, surgeons and researchers planning to conduct further studies in the future are highly encouraged to account for surgeon experience in their analysis of outcomes for TAPP.

To sum up, this meta-analysis offers insightful information about the relative merits of OLR versus TAPP for BIH repair. The findings draw attention to crucial factors that patients and healthcare professionals should consider when selecting the best surgical strategy. It is crucial to understand that each approach has benefits and drawbacks, and clinical judgment calls for a thorough evaluation of the patient's features, the surgical objectives, and the resources available, and the absence of heterogeneity in certain results enhances the validity of our conclusions. However, to confirm and build upon these findings, more investigations and larger studies are necessary.

Several limitations are associated with our meta-analysis. First, the inclusion of only four studies can reduce the consistency and reliability of our results. Therefore, to overcome this, an increased number of studies would provide a thorough, comprehensive analysis. Another limitation in our analysis is the fact that the included studies are predominantly from two countries (Egypt and Spain), which may hinder the applicability of the results to other demographics or medical environments. Hence, studies from a wider range of nations might offer a broader perspective on the effectiveness and safety of the two surgical techniques. The assessment of risk of bias in our meta-analysis reveals that three out of the four included studies exhibit potential attrition bias. This bias can impact the validity and reliability of the results and should be taken into consideration when interpreting our findings. However, other biases such as performance bias and detection bias were found to be adequate as outlined in methodology.

Moreover, some outcomes, such as quality of life, time taken to return to daily activities and work, and complications in patients with a BMI over 25, were extracted but not reported due to the limited number of studies reporting these criteria. The lack of complete reporting for these outcomes may restrict the overall conclusions drawn from our meta-analysis. Our manuscript lacked an in-depth discussion of how varying patient characteristics may effect the outcome and more thorough research work on patients’ characteristics is required. Furthermore, our meta-analysis did not account for important variables such surgeon experience, surgical technique discrepancies, or patient comorbidities; making it imperative that future studies include assessments of surgeon experience to provide a clearer understanding on how it effects the results. These factors may influence the outcomes and introduce bias into the results Therefore, it is crucial to acknowledge these limitations when interpreting the results of our meta-analysis and drawing conclusions regarding the efficacy, safety, and time duration of laparoscopic TAPP versus OLR for patients with BIH. To address these limitations, further research incorporating larger sample sizes and well-designed studies is warranted.

Conclusion

Our meta-analysis found that TAPP has multiple advantages over the OLR approach, including a statistically significant shorter duration of hospital stay post-operatively, reduced pain scores on the VAS criteria, and a decreased complication rate. OLR, on the other hand, was only statistically superior in terms of operative time. However, there was no significant difference in the recurrence rates between the two approaches. Since most clinically relevant outcomes favored the TAPP approach over OLR, larger randomized studies might possibly lead toward a more solid understanding of the risks and benefits of both techniques, hence increasing the possibility of formation of international clinical guidelines for BIH repair.