|Year : 2012 | Volume
| Issue : 4 | Page : 111-117
Analysing the benefits of laparoscopic hernia repair compared to open repair: A meta-analysis of observational studies
Sarah A Salvilla1, Sundeep Thusu2, Sukhmeet S Panesar3
1 Department of General Surgery, Charing Cross Hospital, Imperial College NHS Trust, London, Fulham Palace Road, London, W6 8RF, United Kingdom
2 Department of General Surgery, Whittington Hospital NHS Trust, Magdala Avenue, London, United Kingdom
3 Department of General Surgery, National Patient Safety Agency, 4-8 Maple Street, London, United Kingdom
|Date of Submission||05-Nov-2010|
|Date of Acceptance||21-Nov-2012|
|Date of Web Publication||2-Nov-2012|
Sarah A Salvilla
Charing Cross Hospital, Imperial College NHS Trust, Fulham Palace Road, London W6 8RF
Source of Support: None, Conflict of Interest: None
Background: The purpose of this study is to compare the difference of incidence of post-operative complications, operative time, length of stay and recurrence of patients undergoing laparoscopic or open repair of their ventral/incisional hernia a meta-analytic technique for observational studies. Materials and Methods: A literature search was performed using Medline, PubMed, Embase and Cochrane databases for studies reported between 1998 and 2009 comparing laparoscopic and open surgery for the treatment of ventral (incisional) hernia. This meta-analysis of all the observational studies compared the post-operative complications recurrence rate and length of stay. The random effects model was used. Sensitivity and heterogeneity were analysed. Results: Analysis of 15 observational studies comprising 2452 patients qualified for meta-analysis according to the study's inclusion criteria. Laparoscopic surgery was attempted in 1067 out of 2452. The results showed that the length of stay (odds ratio [OR], − 1.00; 95% confidence interval [CI], − 1.09 to − 0.91; P < 0.00001) and operative time (OR, 59.33; 95% CI, 58.55 to 60.11; P < 0.00001) was significantly lower in the laparoscopic group. The results also showed that there was a significant reduction in the formation of abscesses (OR, 0.38; 95% CI, 0.16 to 0.92; P = 0.03) and wound infections (OR, 0.49; 95% CI, 0.29 to 0.82; P = 0.007) post-operatively. There is a trend which indicates that the recurrence of the hernia using laparoscopic repair versus open repair was overall lower with the laparoscopic repair (OR, 0.48; 95% CI, 0.22 to 1.04; P = 0.06), however, this was not significant. Conclusion: Laparoscopic incisional hernia repair was associated with a reduced length of stay, operative time and lower incidence of abscess and wound infection post-operatively. This study also highlights the benefit of using observational studies as a form of research and its value as a tool in answering questions where large sample sizes of patient groups would be impossible to accumulate in a reasonable length of time.
Keywords: Incisional hernia, laparoscopic surgery, meta-analysis, observational, ventral hernia
|How to cite this article:|
Salvilla SA, Thusu S, Panesar SS. Analysing the benefits of laparoscopic hernia repair compared to open repair: A meta-analysis of observational studies. J Min Access Surg 2012;8:111-7
|How to cite this URL:|
Salvilla SA, Thusu S, Panesar SS. Analysing the benefits of laparoscopic hernia repair compared to open repair: A meta-analysis of observational studies. J Min Access Surg [serial online] 2012 [cited 2019 Aug 18];8:111-7. Available from: http://www.journalofmas.com/text.asp?2012/8/4/111/103107
| ¤ Introduction|| |
The majority of surgical research is based on case reports and case series from which many of the routinely performed interventions are justified. This raises the question about the strength of evidence to adopt a new technique or justify the study. In cases where trials have been performed, these have often been small and poorly designed, leading to concerns about interpreting findings as their design affords them unwarranted credibility.  Randomised Controlled Trials (RCTs) and systematic reviews of homogeneous RCTs constitute the most robust form of clinical evidence. ,, Most studies of operations have historically been retrospective case series, with RCTs accounting for less than 10% of the total. 
Meta-analysis and literature reviews combat the limited availability of RCTs. These publications have been used to inform clinical practice, to aid teaching, direct health policy, guide future research and to serve as a foundation for practice guidelines.  Accordingly, systemic reviews and meta-analyses of high-quality primary studies are the highest level of evidence for issues of prevention and treatment in evidence-based medicine.  Indeed, the Oxford Centre for Evidence-Based Medicine ranks meta-analyses as level 1a evidence.
Meta-analysis is a systematic approach to identifying, appraising, synthesizing and combining the results of relevant studies to arrive at conclusions about a body of research. This technique is applied with increasing frequency compared to RCTs, which are considered to provide the strongest evidence regarding an intervention. 
However, in many situations RCTs are not feasible and only data from observational studies are available. Observational designs may lack the experimental element of a random allocation to an intervention and rely on studies of association between changes or differences in one characteristic (e.g., an exposure or intervention) and changes of differences in an outcome of interest. These designs have been used in the evaluation of exposures that might cause disease or injury. Studies of risk factors generally cannot be randomised because they relate to inherent human characteristics or practices and exposing subjects to harmful risk factors is unethical. 
Despite these recommendations the use of observational data for meta-analysis is often dismissed to being inferior in quality to data from RCTs. However, as has been commented upon already, from a surgical stand point data from RCTs is less reported and the proliferation of observational studies means that an appreciable methodology should be sought to validate the use of observational data.
The aim of this article is to use the data collected regarding the surgical management of ventral (incisional) hernias and to undertake a robust meta-analysis. Ventral hernias are defects in the abdominal wall and can be either congenital in nature, such as umbilical or para-umbilical or they may be acquired such as incisional. The gold standard in the treatment of ventral/incisional hernia repair involves the use of a prosthetic mesh in a tension-free repair.  This method can now be utilised by the open repair of a hernia or with the laparoscopic approach as an alternative.
This is a suitable subject area as there are two distinct interventions that are used - open versus laparoscopic and it has a large volume of data. There have also been two meta-analyses examining this subject matter one of which only commented on data from RCTs.
The article has three aims, which include the assessment of:
- A difference in the incidence of post-operative complications between the two techniques?
- A difference in the reduction of recurrence, length of stay and operative time between the laparoscopic and open technique
- The benefit in the use of only observational studies for this meta-analysis.
| ¤ Materials and Methods|| |
A literature search was performed using Medline, Pubmed, Embase and Cochrane databases for studies reported between 1998 and 2009 on laparoscopic and open surgery for the treatment of ventral (incisional) hernia. The following MeSH search headings were used: 'laparoscopy', 'ventral hernia', 'comparative study' and 'treatment outcome'. The following text searches and search headings and their combinations were used: 'laparoscopic', 'incisional hernia' and 'ventral hernia'. The 'related articles' function was used to broaden the search and all abstracts, studies and citations reviewed. The references from collected articles were also manually searched. Language was restricted to original English studies only. This is shown in [Figure 1].
The study was performed in line with the recommendations of the proposal for reporting meta-analysis of observational studies in epidemiology.  The quality of the non-randomised studies was assessed by using a modified Newcastle-Ottawa Scale.  The quality of the studies was evaluated by examining three items: patient selection, comparability of OPCAB and CPB groups and assessment of outcomes. For the comparability between the two groups, we focused on variables that are shown to have an effect on the outcome of hernia repair. 
A single reviewer (ST) performed the search which was independently verified by a second reviewer (SSP). Data from each study was reviewed and extracted according to pre-specified protocol: data were collected concerning first author, year of publication, study population characteristics, study design, inclusion and extraction criteria, and number of subjects and length of follow-up.
In order to be included in the analysis, studies had to compare laparoscopic and open surgery for ventral (incisional) hernia repair and report on at least one of the outcomes measures mentioned below. If the same institution reported two or more studies, then either the one of better quality, the one containing the greatest number of patients or the most recent publication was included unless the study outcomes were mutually exclusive or measured at different time intervals.
Only observational studies were included. The definition of an observational study is an etiological or effectiveness study using data from an existing database, a cross-sectional study, a case series, a case-control design, a design with historical controls or a cohort design. 
Studies were excluded from the analysis if:
Outcomes of Interest and Definitions
- The outcomes of interest were not reported for the two techniques or it was impossible to calculate them from the published results
- When the standard deviation of the mean or the range for continuous outcomes of interest was not reported
- When a zero cell was displayed for one of the outcomes of interest for both the laparoscopic and open surgery groups, then the study was excluded from the analysis of those outcomes
The following outcomes were used to compare the two operative techniques:
- Treatment details - included operative time, operative blood loss, length of post-operative hospital stay and cost of treatment
- Short-term adverse events (early post-operative complications) - included intra-operative enterotomy, wound infection, seroma or haematoma formation, pneumonia, post-operative, ileus, deep vein thrombosis, pulmonary embolus and post-operative urinary retention.
- Long-term outcomes - included hernia recurrence.
The group where open surgery was performed was regarded as the reference group and that in which laparoscopic surgery was used, the treatment group. For a particular outcome to be meta-analysed, the outcome should have been reported by at least three studies. The Mantel-Haenszel method was used to combine the OR for the outcomes of interest. We used both fixed and random effect models.
Three strategies were used to quantitatively assess heterogeneity. First, the data were reanalysed by using both fixed and random effect models. Second, graphical exploration with funnel plots was used to evaluate publication bias.  Third, sensitivity analysis was undertaken by using subgroup analysis. To do this, the following variables were evaluated: (a) all studies; (b) study size (>50 patients in each arm); and (c) higher quality studies (score > 7).
To translate these results into benefits to clinical outcome of the laparoscopic technique, we calculated the absolute risk reduction and the number needed to treat (NNT). Data were analysed by using the statistical software SPSS V.12.0 for Windows (SPSS Inc, Chicago, IL, USA), Intercooled Stata V.7.0 for Windows (StataCorp, College Station, TX, USA), RevMan V.4.2 (The Cochrane Collaboration, http://www.cc-ims.net/RevMan ) and the Sample Power V. 2.0 (SPSS Inc) for power analysis calculations.
The qualities of the selected studies were assessed by using the Newcastle-Ottawa Scale (NOS), with some modifications to match the needs of this study. 
| ¤ Results|| |
A total of 682 trials were identified as satisfying the inclusion criteria of comparing outcomes between laparoscopic and open surgery for ventral (incisional) hernia repair. Six hundred and sixty-five studies were excluded as they were not observational studies and a further 2 were excluded as they were duplicated publications of the same trial. Therefore, 15 observational trials with 2452 patients qualified for meta-analysis according to the study's inclusion criteria. ,,,,,,,,,,,,,,
There was a significant difference in the operative time between an open repair and a laparoscopic repair (OR, 59.33; 95% CI, 58.55 to 60.11; P < 0.00001) which showed a shorter operative time with the open approach, the heterogeneity amongst the trail remained (χ2 , 201.23; P < 0.00001). This is shown in [Figure 2].
|Figure 2: Forest plot illustrating overall meta-analysis of operative time, length of stay, early complications|
Click here to view
Length of stay
The analysis of the results showed that laparoscopic repair was associated with a significantly shorter hospital stay (OR, −1.00; 95% CI, −1.09 to −0.91; P < 0.00001). However, a significant heterogeneity among the trials (χ2 , 71.08; P < 0.00001) was also noted. This is shown in [Figure 2].
Early post-operative complications
The analysis of the composite variable of early post-operative complications which included the various outcomes below indicated that the incidence of early post-operative complications was lower in the laparoscopic repair of a hernia, there were significant benefits with certain outcomes such as the formation of abscesses and wound infection but this was not echoed in other post-operative outcomes examined. This is shown in [Figure 2].
The overall incidence of the formation of an abscess as an early post-operative complication was significantly lower in the laparoscopic repair group (OR, 0.38; 95% CI, 0.16 to 0.92; P = 0.03) with no significant heterogeneity (χ2 1.79; P = 0.94) between the trials.
The results would indicate that overall the incidence of an early post-operative wound infection was significantly lower in the laparoscopic group (OR, 0.49; 95% CI, 0.29 to 0.82; P = 0.007) with no significant heterogeneity between the trials (χ2 8.54; P = 0.74). This is shown in [Figure 3].
There was no significant heterogeneity among the trials (χ2 17.80; P = 0.09). Analysis of the results showed that there was no significant difference in post-operative formation of seroma/haematoma between laparoscopic versus open repair (OR, 1.37; 95% CI, 0.87 to 2.15; P = 0.18).
With regards to looking the incidence of pneumonia post-operatively again there was no significant heterogeneity among the trials (χ2 , 5.72; P = 0.77). The results showed that there was no significant difference in the occurrence of pneumonia post-operatively between laparoscopic versus open repair (OR, 0.72; 95% CI, 0.28 to 1.88; P = 0.51). This is shown in [Figure 4].
Looking at the rate of post-operative ileus this also showed that there was no significant heterogeneity among the trials (χ2 5.14; P = 0.82). The analysis of the results showed that there was no significant difference in the recurrence of an ileus postoperatively between laparoscopic versus open repair (OR, 0.57; 95% CI, 0.29 to 1.11; P = 0.10).
The analysis of the results looking at the incidence of post-operative pulmonary embolus showed that there was no significant difference in the recurrence post-operatively between laparoscopic versus open repair (OR, 1.93; 95% CI, 0.33 to 11.28; P = 0.47). There was no significant heterogeneity among the trials (χ2 , 1.35; P = 0.51).
There was no significant heterogeneity among the trials (χ2 , 1.25; P = 0.53). The analysis of the results showed that there was no significant difference in the recurrence postoperative urinary retention between laparoscopic versus open repair (OR, 0.85; 95% CI, 0.18 to 3.92; P = 0.83). This is shown in [Figure 4].
There is a trend which indicates that the recurrence of the hernia using laparoscopic repair versus open repair was overall lower with the laparoscopic repair (OR, 0.48; 95% CI, 0.22 to 1.04; P = 0.06), the significant heterogeneity still remained (χ2 , 34.19; P < 0.0002).
The subgroup of larger studies (>50 patients) also showed a trend towards laparoscopic surgery in terms of recurrence rate (OR, 0.37; 95% CI, 0.14 to 1.02; P = 0.06) but significant heterogeneity remained (χ2 , 32.37; P < 0.001). The subgroups of slightly smaller studies (<50 patients) also showed a similar trend towards the laparoscopic surgery with regard to recurrence (OR, 0.84; 95% CI, 0.32 to 2.22; P = 0.72) and was not associated with a significant heterogeneity between studies (χ2 , 1.85; P = 0.60). This is shown in [Figure 3] and [Figure 4].
| ¤ Discussion|| |
A meta-analysis goes beyond a literature review, in which the results of the various studies are discussed, compared and perhaps tabulated, since it synthesises the results of the individual studies into a new result. Meta-analysis has the potential to resolve controversies within the literature and ultimately shape surgical practice. 
Although meta-analysis restricted to RCTs is usually preferred to meta-analyses of observational studies, the number of published meta-analyses concerning observational studies in health has increased substantially during the past 5 decades (678 in 1955-1992; 525 in 1992-1995; >900 1995-2005).  To aid the recent profusion of surgical publications researchers have used meta-analysis of observational studies to assess the suitability of the data. In fact meta-analysis of observational studies is as common as meta-analysis of controlled trials. The application of formal meta-analysis methods to observational studies has been controversial. It is understood that confounding and selection bias often distort the findings from observational studies and there is the danger that this brings about spurious results. A study to examine concerns regarding the reporting of Meta-analysis of Observational Studies in Epidemiology (MOOSE)  found that if bias is a problem then using broader inclusion criteria for studies and then to perform analyses relating suspected sources of bias and variability to study findings. More is gained by carefully examining possible sources of heterogeneity between the results from observational studies.
The laparoscopic approach is now fast becoming an established technique in the repair of most types of hernia.  This present meta-analysis has shown that there is significant benefit with laparoscopic repair with regard to recurrence rates, operative time and reduced post-operative wound complication compared to the open repair of hernias.
The use of meta-analytical techniques allowed inclusion of a total of 2452 patients - 1067 (43.5%) undergoing laparoscopic surgery and 1385 (56.5%) undergoing open surgery. A sample group of this size would otherwise be impossible to accumulate in a reasonable length of time in an RCT. The NNT for post-operative complications are 1/0.01 = 100. Similarly for recurrence, the NNT = 1/0.05 = 20.
The findings are consistent with results published in a recent meta-analyses looking at RCTs of laparoscopic versus open repair which as part of its outcomes analysed surgical time, hospital stay and recurrence rate. 
The findings of the present study with regard to hospital length of stay are also consistent with results published in earlier meta-analyses of laparoscopic versus primary ventral hernia repair  and inguinal hernia repair. 
The increased length of stay may in part be due to the open technique, in which there is a need to dissect soft tissue in order to isolate and the hernia. This in turn can lead to an increased morbidity and length of time taken for convalescence post-operatively.
Surgical time in this present article has shown that the laparoscopic repair is statistically significant in the length of time compared with the open approach despite two previous meta-analyses finding that there is no significant difference. , The increase in operative time during a laparoscopic procedure could partly be because the laparoscopic approach is very heavily influenced by the experience of the surgeon performing it. Indeed as with all surgical procedures different surgeons are on different points on the learning curve but as laparoscopic hernia repair is only recently becoming more readily accessible to trainees, there are more trainees who have performed much less laparoscopic repairs compared with open. ,
With regard to the recurrence of a hernia after repair, this present study has found that there may indeed be a trend which indicates a lower recurrence of the hernia if a laparoscopic approach is utilised despite the result having only just found to be not statistically significant (P = 0.06). Indeed previous meta-analysis  was still undetermined with regard to this subject due to a limited number of studies and hence patient number.
A previous meta-analysis focused on early post-operative complications and found that there was no difference in short term adverse events, including wound infection, seroma/haematoma, pneumonia, ileus and urinary retention.  The result of our study has shown that there postoperative wound infection and abscess formation is significantly reduced with the laparoscopic approach compared with the open repair. This result has been shown in a group of trails with no statistically significant heterogeneity. In fact, several trails have compared some postoperative wound complications which found that the minimally invasive approach reduced the incidence of these complications, this was most highlighted in a most recent meta-analysis by Hwang et al., which showed that a wound infection was significantly reduced with laparoscopic mesh repair versus open where the P = 0.001. ,,,
Limitations of the study
The findings of this meta-analysis must be interpreted with caution. First, the design of the study may lack the experimental element of a random allocation to laparoscopic or open repair, and only a few studies included in the meta-analysis reported the criteria considered by the individual surgeons to allocate patients to either group. Selection bias can also be related to the fact that different surgeons performed the two techniques (laparoscopic or open) without any adjustment for surgeon-related morbidity, learning curve and different variations of each technique. Second, the two groups were not comparable for all the factors that can alter the outcome of interest and confounding factors cannot be excluded. 
Publication bias can exist when a meta-analysis relies on previously published studies, because positive results are more likely to be published than negative results. 
Apart from the post-operative complications there was significant heterogeneity among the trails when we analysed operative time, recurrence rate and length of stay of patients. One possible cause of the heterogeneity is that the studies we included in this meta-analysis are observational; therefore, there is researcher and patient bias as these trials are not performed under double-blind condition.
Confounding factors are also a possible cause of heterogeneity, as different patients may present with different sizes of hernias, pre-morbid conditions, variable surgical risks (different ASA grade) and different laparoscopic techniques and mesh placements.
| ¤ Conclusion|| |
This study highlights the benefits of using observational studies as a form of research which not only helps to consolidate the findings in previous meta-analyses, but also it is a valuable tool in answering questions where large sample sizes of patient groups would be impossible to be accumulated in a reasonable length of time.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4]
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