Abstract
Introduction
Due to a lack of evidence, the use of slit meshes in laparo-endoscopic hernia repair is a topic of controversial debate. Therefore, further studies are needed on this key question.
Methods
This retrospective analysis of prospectively recorded data from the Herniamed Registry compared the perioperative and 1-year follow-up outcomes after laparo-endoscopic inguinal hernia repair with slit mesh versus non-slit mesh. Matching was performed for 1,028 pairs.
Results
A significant difference was identified in the recurrence rate on 1-year follow-up in favor of the slit mesh (0.6% vs 1.8%; p = 0.023). No such systematic difference was found for any of the other outcome variables (intraoperative complications, general complications, postoperative complications, complication-related reoperations, pain at rest, pain on exertion, and pain requiring treatment on 1-year follow-up).
Conclusion
The use of a slit mesh versus a non-slit mesh in laparo-endoscopic inguinal hernia repair is associated with a significantly lower recurrence rate. There is no relation with any other outcome criteria. Since the use of a slit mesh in laparo-endoscopic inguinal hernia repair seems to influence the outcome, this topic should be further investigated.
Keywords: Inguinal hernia, TEP, TAPP, Slit mesh, Non-slit mesh, Recurrence
Introduction
In the international guidelines for the treatment of inguinal hernias, the laparo-endoscopic techniques TEP and TAPP are recommended for primary unilateral inguinal hernia in men and women and for primary bilateral inguinal hernia in men and women if adequate resources and expertise are available [1–5].
The laparo-endoscopic techniques have a faster recovery time, lower risk of chronic pain and are cost effective [1–5].
For women TEP and TAPP offer the advantage of better diagnosis and treatment of femoral hernias, which occur more often in women [1–5]. In bilateral inguinal hernias both sides can be operated on using identical access routes [1–5]. The mesh recommended for TEP and TAPP is a simple flat mesh measuring at least 10 × 15 cm [1–5]. The mesh should not be fixed or only fixed with fibrin glue [1–5].
Due to a lack of evidence, the use of slit meshes is a topic of controversial debate [6]. Some surgeons believe that a slit mesh wrapped around the cord, fashioning a new internal ring, could prevent hernia recurrence [6]. However, the slit mesh could cause circumferential scarring with subsequent postoperative pain [6]. There is no evidence in the literature linking the use of slit meshes to spermatic cord injury or to a reduction in the recurrence rate [6–15]. Therefore, the use of slit meshes in laparo-endoscopic inguinal hernia repair is also not recommended in the guidelines [1–5].
Two recent studies compared patients who had undergone laparo-endoscopic inguinal hernia repair with non-slit mesh vs patients treated with a slit mesh [16]. In this way it was possible to identify the influence exerted by slit meshes on the recurrence rate or the chronic pain rate. This means that there could be a relationship between the use of slit meshes vs non-slit meshes in laparo-endoscopic (TEP, TAPP) inguinal hernia repair with regard to the recurrence rate and/or the rate of chronic pain. Therefore, this retrospective analysis of prospective data from the Herniamed Registry now presented below aims to explore this key question using propensity score matching [18, 19].
Methods
Registry design
Herniamed is an internet-based hernia registry in which hospitals and office-based surgeons in Germany, Austria and Switzerland can voluntarily enter data on their routine hernia repairs [18, 19]. A cooperation contract is made with the participating hospitals and surgical centers/practices where the participating hospitals and office-based surgeons commit to entering data completely and correctly into the Herniamed Registry on all hernia operations. As a prerequisite for documentation in the Herniamed Registry, all patients must sign a separate consent form agreeing to their data being documented and processed in the Herniamed Registry. As part of the information provided to patients regarding their participation in the Herniamed Registry, they are told to inform the treating hospital or practice about all special events occurring in the early and late postoperative course. If a problem occurs the patient should present to the treating hospital or the treating surgeon. The hospital or surgeon should then conduct appropriate clinical examination.
All perioperative complications are documented for up to 30 days after the operation. To ensure that all postoperative complications are documented, patients are asked once again about these on 1-year follow-up. On 1-year follow-up patients and the general practitioner are sent a questionnaire asking about chronic pain and/or a suspected recurrence.
If the patient reports inguinal pain or a protrusion again in the surgical area or any postoperative problems, they are requested by the treating hospital or treating surgeon to attend for clinical examination. Studies have attested to the effectiveness of follow-up based on questionnaires addressed to patients and/or the treating general practitioner as well as selective clinical examination [20]. The findings reported by the patients in the questionnaires returned to the treating hospital/practice are entered into the Herniamed Registry database where they can be used for retrospective analysis of prospectively collected data.
Aim of analysis
The analysis presented here aimed to compare the outcomes of laparo-endoscopic repair (TEP, TAPP) of primary unilateral inguinal hernias using comparable meshes with and without a slit. To that effect, matched pair analysis was performed to compare the meshes Covidien/Medtronic Parietex multifilament, folding slit mesh (slit mesh) with Covidien/Medtronic Parietex multifilament, anatomical folding mesh (non-slit mesh) (Fig. 1a, b, c). After checking plausibility and inclusion criteria, univariate analysis was then performed for the mesh group with regard to the matching parameters; this was followed by pairwise matching for the mesh groups and presentation of the analysis results of the outcome parameters for the corresponding mesh comparison based on matched pairs.
Fig. 1.
a Slit mesh, b Non-slit mesh, c Slit mesh in situ
Inclusion criteria for analysis
From 717,133 inguinal hernia repairs recorded from January 5, 2009 to January 4, 2023, 3,098 procedures met the inclusion criteria for this analysis (Fig. 2). The inclusion criteria were: patients with minimum valid age of 16 years who underwent primary elective unilateral inguinal laparoscopic (TEP or TAPP) hernia repair. Patients had hernia repair performed with the use of slit mesh or non-slit mesh. The surgeries had to be fully documented, and patients had to have 1-year follow-up.
Fig. 2.
Flowchart of patient inclusion
Methodology
All analyses were performed with the software SAS 9.4 (SAS Institute Inc.Cary, NC, USA) and intentionally calculated to a full significance level of 5%, i.e. they were not corrected in respect of multiple tests.
Operative complications included intraoperative complications, general complications, postoperative complications, and complication-related reoperations. On 1-year follow-up, recorded outcomes included recurrence, pain on exertion, pain at rest, and pain requiring treatment.
For unadjusted homogeneity tests of mesh groups, the chi-square test was used for categorical variables and the robust t test (Satterthwaite) for continuous variables. Analyses of non-normal distributed data (duration of operation and mesh size) were conducted on log-transformed values.
Pairs of slit mesh and non-slit mesh hernia repairs were matched in a 1:1 propensity score matching using the robust Greedy algorithm and a caliper of 0.2 standard deviations of the logit of the propensity score. The variables used for matching were as follows: age, American Society of Anesthesiologist classification (ASA), defect size, body mass index (BMI), EHS classification, fixation, preoperative pain, risk factors as well as fixed variable: sex, in which no variability was allowed between matched pairs.
Balancing of matching parameters before and after matching was quantified via standardized differences.
After propensity score matching, McNemar test was performed to assess whether the mesh groups deviate significantly from another for an outcome variable.
Results
In total, 3,098 patients were included in the analysis (Fig. 2), with 1,470 patients receiving a slit mesh and 1,628 patients a non-slit mesh. Slit meshes were used only by seven hospitals/office-based surgeons with very varying frequency of use. Two hospitals performed 392 and 627 repairs, respectively, with a slit mesh, one hospital/practice three repairs, two hospitals/practices two repairs and two hospitals/practices one repair. The 1,028 repairs with a non-slit mesh were carried out in 46 hospitals/practices with a mean of 22.3 repairs performed. The 1,028 repairs with a slit mesh were conducted by 34 surgeons and the 1,028 repairs with a non-slit mesh by 176 surgeons. The average number of surgeons per hospital/practice was 3.8 for the non-slit mesh and 4.8 for the slit mesh. The level of training of the surgeons could be determined for 1,019 matched pairs with slit mesh. These operations were performed by 29 different surgeons, 10 of whom were experienced hernia surgeons and 19 of whom were residents.
Unadjusted comparison of the patient and operation characteristics before matching (Table 1 and Table 2) showed significant differences between slit mesh and non-slit mesh patients for age, BMI, duration of operation, surgical technique, defect size, ASA, preoperative pain, fixation (p < 0.001, each), and EHS classification (p = 0.005). Table 3 presents the unadjusted analysis of outcome parameters before matching. After one year of follow-up, significant differences were found between slit mesh and non-slit mesh patients in the postoperative complications (p = 0.009) and recurrence rates (p = 0.002).
Table 1.
Presentation of ranges and unadjusted analysis results for homogeneity between slit and non-slit meshes for age, BMI, duration of operation and mesh size * Logarithmic transformation: Presentation of the back-transformed mean values and ranges (mean value ± SD)
| Slit mesh | Non-slit mesh | p | ||
|---|---|---|---|---|
| Age [years] | N/Mean ± SD | 1470/58.6 ± 16.0 | 1628/56.2 ± 14.6 | <.001 |
| BMI [kg/m2] | N/Mean ± SD | 1465/25.3 ± 3.6 | 1621/25.9 ± 3.7 | <.001 |
| Duration of operation [min]* | N/Mean [Range of dispersion] | 1459/39.1 [37.7; 40.5] | 1603/44.8 [43.3; 46.2] | <.001 |
| Mesh size [cm2]* | N/Mean [Range of dispersion] | 1470/149.9 [148.8; 150.9] | 1628/149.5 [148.4; 150.6] | 0.341 |
Table 2.
Presentation of descriptive statistics and unadjusted analysis results for homogeneity between slit and non-slit meshes for categorical matching variables # Data are available since update of Herniamed February 2022
| Slit mesh | Non-slit mesh | p | ||||
|---|---|---|---|---|---|---|
| n | % | n | % | |||
| Sex | Male | 1305 | 88.8 | 1441 | 88.5 | 0.819 |
| Female | 165 | 11.2 | 187 | 11.5 | ||
| Surgical technique | TEP | 1431 | 97.3 | 953 | 58.5 | <.001 |
| TAPP | 39 | 2.7 | 675 | 41.5 | ||
| Defect size | I (< 1.5 cm) | 265 | 18.0 | 441 | 27.1 | <.001 |
| II (1.5–3 cm) | 904 | 61.5 | 936 | 57.5 | ||
| III (> 3 cm) | 301 | 20.5 | 251 | 15.4 | ||
| EHS classification | Medial | 204 | 13.9 | 300 | 18.4 | 0.005 |
| Lateral | 1040 | 70.7 | 1076 | 66.1 | ||
| Femoral | 23 | 1.6 | 28 | 1.7 | ||
| Scrotal | 13 | 0.9 | 7 | 0.4 | ||
| Combined | 190 | 12.9 | 217 | 13.3 | ||
| ASA | I | 652 | 44.4 | 593 | 36.4 | <.001 |
| II | 722 | 49.1 | 900 | 55.3 | ||
| III/IV | 96 | 6.5 | 135 | 8.3 | ||
| Preoperative pain | no | 713 | 48.5 | 323 | 19.8 | <.001 |
| yes | 742 | 50.5 | 1228 | 75.4 | ||
| unknown | 15 | 1.0 | 77 | 4.7 | ||
| Fixation | No Mesh Fixation | 1136 | 77.3 | 1398 | 85.9 | <.001 |
| Tacks | 227 | 15.4 | 190 | 11.7 | ||
| Glue | 101 | 6.9 | 23 | 1.4 | ||
| Combined | 6 | 0.4 | 17 | 1.0 | ||
| Risk factors—total | yes | 436 | 29.7 | 458 | 28.1 | 0.349 |
| no | 1034 | 70.3 | 1170 | 71.9 | ||
| - COPD | yes | 84 | 5.7 | 89 | 5.5 | 0.765 |
| no | 1386 | 94.3 | 1539 | 94.5 | ||
| - Diabetes | yes | 80 | 5.4 | 71 | 4.4 | 0.163 |
| no | 1390 | 94.6 | 1557 | 95.6 | ||
| - Aortic aneurysm | yes | 9 | 0.6 | 2 | 0.1 | 0.022 |
| no | 1461 | 99.4 | 1626 | 99.9 | ||
| - Immunosuppression | yes | 11 | 0.7 | 8 | 0.5 | 0.360 |
| no | 1459 | 99.3 | 1620 | 99.5 | ||
| - Corticoids | yes | 12 | 0.8 | 16 | 1.0 | 0.625 |
| no | 1458 | 99.2 | 1612 | 99.0 | ||
| - Smoking | yes | 188 | 12.8 | 211 | 13.0 | 0.887 |
| no | 1282 | 87.2 | 1417 | 87.0 | ||
| - Coagulopathy | yes | 14 | 1.0 | 23 | 1.4 | 0.239 |
| no | 1456 | 99.0 | 1605 | 98.6 | ||
| - Antithrombotic medication | yes | 127 | 8.6 | 107 | 6.6 | 0.030 |
| no | 1343 | 91.4 | 1521 | 93.4 | ||
| - Anticoagulant medication | yes | 19 | 1.3 | 26 | 1.6 | 0.479 |
| no | 1451 | 98.7 | 1602 | 98.4 | ||
| - Liver cirrhosis‡ | yes | 0 | 0 | 0 | 0 | 1.000 |
| no | 23 | 100 | 13 | 100 | ||
| - Anticoagulants‡ | yes | 0 | 0 | 1 | 7.7 | 0.177 |
| no | 23 | 100 | 12 | 92.3 | ||
Table 3.
Presentation of descriptive and unadjusted analysis results for homogeneity between slit mesh and non-slit mesh for outcome variables
| Slit mesh | Non-slit mesh | p | ||||
|---|---|---|---|---|---|---|
| n | % | n | % | |||
| Intraoperative complications—total | yes | 18 | 1.2 | 18 | 1.1 | 0.758 |
| no | 1452 | 98.8 | 1610 | 98.9 | ||
| General complications—total | yes | 4 | 0.3 | 10 | 0.6 | 0.156 |
| no | 1466 | 99.7 | 1618 | 99.4 | ||
| Postoperative complications—total | yes | 4 | 0.3 | 17 | 1.0 | 0.009 |
| no | 1466 | 99.7 | 1611 | 99.0 | ||
| Complication-related reoperations | yes | 2 | 0.1 | 7 | 0.4 | 0.129 |
| no | 1468 | 99.9 | 1621 | 99.6 | ||
| Recurrence on 1-year follow-up | yes | 7 | 0.5 | 26 | 1.6 | 0.002 |
| no | 1463 | 99.5 | 1602 | 98.4 | ||
| Pain on exertion on 1-year follow-up | yes | 135 | 9.2 | 156 | 9.6 | 0.704 |
| no | 1335 | 90.8 | 1472 | 90.4 | ||
| Pain at rest on 1-year follow-up | yes | 73 | 5.0 | 90 | 5.5 | 0.484 |
| no | 1397 | 95.0 | 1538 | 94.5 | ||
| Pain requiring treatment on 1-year follow-up | yes | 50 | 3.4 | 55 | 3.4 | 0.972 |
| no | 1420 | 96.6 | 1573 | 96.6 | ||
Propensity score matching was performed for 1,470 patients with slit mesh to 1,628 patients with non-slit mesh, resulting in 1,028 matched pairs. Figure 3 shows the standardized differences between the matching variables both before (original sample) and after (matched sample) matching. Standardized differences were well below 10% for all matching variables, attesting to a good balance for those variables between the groups for matched-pair comparison Table 4.
Fig. 3.
Scatter plot of standardized differences before and after matching
Table 4.
Standardized differences for categorical matching variables before and after matching * for gender this characteristic was enforced within a matched pair
| Slit Mesh | ||||||
|---|---|---|---|---|---|---|
| n | Yes | n | No | Stand. Diff | ||
| % | % | Matched sample | Original sample | |||
| Male* | 912 | 88.7 | 912 | 88.7 | 0.000 | 0.008 |
| Defect size I (< 1.5 cm) | 229 | 22.3 | 209 | 20.3 | 0.048 | 0.218 |
| Defect size II (1.5—3 cm) | 603 | 58.7 | 614 | 59.7 | 0.022 | 0.082 |
| Defect size III (> 3 cm) | 196 | 19.1 | 205 | 19.9 | 0.022 | 0.132 |
| ASA score I | 438 | 42.6 | 435 | 42.3 | 0.006 | 0.162 |
| ASA score II | 522 | 50.8 | 527 | 51.3 | 0.010 | 0.124 |
| ASA score III-IV | 68 | 6.6 | 66 | 6.4 | 0.008 | 0.067 |
| EHS medial | 275 | 26.8 | 267 | 26.0 | 0.018 | 0.113 |
| EHS lateral | 845 | 82.2 | 850 | 82.7 | 0.013 | 0.113 |
| EHS femoral | 36 | 3.5 | 32 | 3.1 | 0.022 | 0.021 |
| EHS scrotal | 11 | 1.1 | 14 | 1.4 | 0.027 | 0.023 |
| No Mesh Fixation | 846 | 82.3 | 847 | 82.4 | 0.003 | 0.223 |
| Tacks | 149 | 14.5 | 152 | 14.8 | 0.008 | 0.110 |
| Glue | 27 | 2.6 | 23 | 2.2 | 0.025 | 0.277 |
| Combined | 6 | 0.6 | 6 | 0.6 | 0.000 | 0.075 |
| Preoperative pain | 691 | 67.2 | 687 | 66.8 | 0.008 | 0.535 |
| Unknown preoperative pain | 15 | 1.5 | 22 | 2.1 | 0.051 | 0.223 |
| No preoperative pain | 322 | 31.3 | 319 | 31.0 | 0.006 | 0.634 |
| Risk factors | 299 | 29.1 | 296 | 28.8 | 0.006 | 0.034 |
The standardized differences between the matching variables both before (original sample) and after (matched sample) matching are shown below. Table 5 presents the standardized differences for the continuous matching variables and Table 4 for the categorical matching variables. For all matching variables this difference was less than 10%, attesting to a good balance for the variables included in the model.
Table 5.
Standardized differences for continuous matching parameters before and after matching
| Slit Mesh | Stand. Diff | ||||
|---|---|---|---|---|---|
| Yes | No | Matched sample | Original sample | ||
| Age [years] | Mean ± SD | 57.1 ± 16.0 | 56.9 ± 14.8 | 0.010 | 0.157 |
| BMI [kg/m2] | Mean ± SD | 25.4 ± 3.8 | 25.4 ± 3.4 | 0.026 | 0.153 |
Table 6 demonstrates differences between slit mesh and non-slit mesh patients after matching. For recurrence, there is a significant disadvantage for non-slit mesh patients. Here, 0.6% of slit mesh patients and 1.8% of non-slit mesh patients reported recurrence, whereas their matched patient reported no recurrence (no concordant cases). This corresponds to a systematic deviation (p = 0.023). No significant difference was found between slit mesh and non-slit mesh patients for any of the other outcome parameters (Fig. 4).
Table 6.
Analysis of systematic differences in the perioperative and 1-year follow-up outcomes between slit mesh and non-slit mesh (matched pair analysis including odds ratios and corresponding 95% confidence intervals)
| Concordant cases [%] | Disadvantageous cases [%] | p-Value | OR for matched samples | ||||
|---|---|---|---|---|---|---|---|
| Slit mesh | Non-slit mesh | OR | Lower limit | Upper limit | |||
| Intraoperative complications | 0.00 | 1.26 | 1.36 | 1.000 | 0.929 | 0.402 | 2.130 |
| General complications | 0.00 | 0.29 | 0.68 | 0.344 | 0.429 | 0.072 | 1.877 |
| Postoperative complications | 0.00 | 0.39 | 0.97 | 0.180 | 0.400 | 0.092 | 1.387 |
| Complication-related reoperations | 0.00 | 0.19 | 0.39 | 0.687 | 0.500 | 0.045 | 3.489 |
| Recurrence on 1-year follow-up | 0.00 | 0.58 | 1.75 | 0.023 | 0.333 | 0.108 | 0.877 |
| Pain on exertion on 1-year follow-up | 1.65 | 9.24 | 7.98 | 0.367 | 1.159 | 0.853 | 1.576 |
| Pain at rest on 1-year follow-up | 0.49 | 5.25 | 4.47 | 0.484 | 1.174 | 0.777 | 1.779 |
| Pain requiring treatment on 1-year follow-up | 0.10 | 4.18 | 3.02 | 0.201 | 1.387 | 0.854 | 2.277 |
Fig. 4.
Forest plot of adjusted odds ratio (OR) including confidence intervals for perioperative and 1-year follow-up outcomes comparing slit mesh versus non-slit mesh
Figure 5 shows the results of the standardized differences for patients with (n = 3,098) and without (n = 1,287) follow-up information. Standardized differences above a value of 10% were found for age, TEP and TAPP as well as ASA I and ASA II. The patients in the analysis population were on average 5.2 years older and had been operated on more often with the TEP technique. As regards the ASA scores, the proportion of group I scores was lower in the analysis population but the proportion of group II scores was somewhat higher. Standardized differences of less than 0.1 were found for all other variables, including the perioperative complication rates, and are thus not suggestive of any bias in patient selection due to available follow-up information.
Fig. 5.
Scatter plot of standardized differences between patients with and without follow-up information
Discussion
The double mesh technique represents a preliminary stage in the development of the surgical technique with slit meshes investigated in this study.
In 1993, Felix et al. [21] reported on a series with 85 laparoscopic hernia operations in which a double mesh technique was used for the first time. A medially slit mesh was placed and fixed laterally around the spermatic cord before a second, non-slit, mesh was placed on top of it. Variations of the slit configuration and mesh sizes were used in further studies [8, 22, 23].
B. Detruit [24] was the first to implant the mesh used in this present study in 322 patients between December 1997 and December 2001. The recurrence rate after one year was 0.44%, and the chronic pain rate was 0.89%.
Witzig et al. [25] also implanted the same mesh in 247 patients between 2000 and 2003. With a follow-up rate of 94%, they did not detect any recurrence during the first year.
In addition to higher recurrence rates, it was feared that the additionally needed dissection of the spermatic cord would increase the testicular atrophy rate, even causing necrosis and chronic pain.
Celik et al. [7] demonstrated in 40 patients, who had been treated in two similarly sized groups with slit or non-slit mesh, that there was no statistically significant difference in terms of the preoperative, 5-day postoperative or 6-month follow-up testicular volume.
Skawran et al. [26] also demonstrated in their case series with 59 patients that bilateral repair of an inguinal hernia in slit double mesh technique and requisite mobilization of the spermatic cord did not impact testicular function.
The use of a slit mesh in laparo-endoscopic inguinal hernia repair continues to trigger controversial debate. No evidence was found in the guidelines or literature reviews [3, 6] of an advantage for the use of slit meshes in laparo-endoscopic inguinal hernia repair.
In 2018, a comparative retrospective study was then published in which 149 TEP repairs with a slit mesh were compared with 154 repairs with a non-slit mesh [17]. This study did not find any difference in the recurrence rate or the complications, but did identify better postoperative and chronic pain results for the repairs with non-slit meshes [17].
The last study published involving propensity score matching of 353 laparoscopic inguinal hernia repairs without slit mesh and 258 repairs with a slit mesh [16] pointed to a lower probability of recurrence for the use of a slit mesh [16]. There was no evidence of an influence on chronic pain or complications [16].
This analysis of prospective data from the Herniamed Registry reported on here presents a retrospective comparison of laparo-endoscopic inguinal hernia repair performed with a slit mesh versus non-slit mesh. Only patients with primary unilateral inguinal hernia were included in analysis. Propensity score matching was chosen as a statistical model. To assure the greatest possible degree of mesh comparability, the Parietex multifilament, folding slit mesh (slit mesh) or the Parietex multifilament, anatomical folding mesh (non-slit mesh) was used.
Based on 1,028 matched pairs of laparo-endoscopic inguinal hernia repairs performed with a slit mesh versus non-slit mesh, it can be demonstrated that the recurrence rate on 1-year follow-up was significantly lower when using slit meshes. No significant differences were found for any of the other outcome variables (perioperative complications, complication-related reoperations, pain at rest, pain on exertion, or chronic pain requiring treatment on 1-year follow-up).
The most recently published data on this key question and our own findings suggest there is reason to critically rethink the hitherto recommendations and conduct further studies. In particular, it must be clarified whether the use of slit meshes does indeed lead to more chronic pain, as noted in one study [17], or tends to influence the recurrence rate, and in a positive sense at that, as seen in the study by Chue et al. [16] and in our own analysis. Noteworthy is that the two studies that used propensity score matching as a statistical model drew similar conclusions. The current data situation should act as an incentive to conduct further comparative studies (RCTs, studies with propensity score matching) with a longer follow-up.
Registry analyses have limitations. Missing or incorrect data can negatively impact the findings. All responsible surgeons participating in Herniamed sign a cooperation contract in which they commit to ensuring that all the necessary data are completely and correctly entered. The registry software will indicate any missing data. In the follow-up questionnaire sent after one year, patients and their general practitioner are asked once again about any perioperative complications. At the time of certification as a hernia center, the auditor can again check data entries for completeness and correctness. No 1-year follow-up data are available for a relevant proportion of patients. However, calculation of the standardized differences between patients with and without follow-up does not point to any selection bias.
The fact that far fewer hospitals/practices and surgeons used a slit mesh compared with a non-slit mesh in laparo-endoscopic inguinal hernia repair may represent a certain bias in the results. The average number of surgeons per institution in the slit mesh group (4.8) was higher than in the non-slit mesh group (3.8). Furthermore, in 1019 matched pairs in the slit mesh group, the operations were performed by 29 different surgeons, the majority of whom were still in training. The experience of the surgeon does not appear to have any demonstrable influence on the results.
In summary, this present analysis of the use of a slit mesh versus a non-slit mesh in laparo-endoscopic inguinal hernia repair demonstrates a significantly lower recurrence rate and no negative association between the slit meshes and the chronic pain rate. This has been confirmed by one other recent study.
One possible explanation for the significantly lower rate is that surgeon-related mesh placement variation is marked less for the slit mesh than the flat mesh, because mesh positioning is specified due to the configuration of the slit. Another possible explanation is that, taking into account the possible pathways for recurrence, the slit mesh technique reduces the probability of caudal recurrence (Fig. 1c).
Due to the existing limitations of the studies, the key question should be investigated in further comparative studies. An ideal approach would be a prospective study with bilateral hernias, with one side repaired using a slit mesh and the other side with a flat mesh. Data analysis of 5-year follow-up is already in the planning stage.
Data availability
The data that support the findings of this study are available from the corresponding author upon reasonable request.
Declarations
Ethical approval
Only cases of routine hernia surgery were documented in the Herniamed Registry and all patients have signed a special informed consent declaration agreeing to participate.
The Herniamed Registry has ethical approval (BASEC No. 2016—00.123, 287/2017BO2).
Human and animal rights
This article does not contain any Study with animals performed by any of the authors.
Conflict of interest
Ferdinand Köckerling reports grants to fund Herniamed from Johnson&Johnson, Norderstedt, Karl Storz, Tuttlingen, MenkeMed, Munich, DB Karlsruhe and personal fees from BD Karlsruhe.
Konstantinos Zarras, Joseph Kankam, Jens Plambeck, Martin Hukauf have nothing to disclose.
Informed consent
All patients with routine hernia surgery documented in Herniamed Registry have signed an informed consent declaration agreeing to participate.
Footnotes
Publisher's Note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
References
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Associated Data
This section collects any data citations, data availability statements, or supplementary materials included in this article.
Data Availability Statement
The data that support the findings of this study are available from the corresponding author upon reasonable request.