Meta-analysis of glue versus sutured mesh fixation for Lichtenstein inguinal hernia repair

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1 Meta-analysis Meta-analysis of glue versus sutured mesh fixation for Lichtenstein inguinal hernia repair B. de Goede 1,4, P. J. Klitsie 1, B. J. H. van Kempen 2, L. Timmermans 1, J. Jeekel 3, G. Kazemier 4 andj.f.lange 1 Departments of 1 Surgery, 2 Epidemiology and Radiology and 3 Neuroscience, Erasmus University Medical Centre, Rotterdam, and 4 Department of Surgery, VU University Medical Centre, Amsterdam, The Netherlands Correspondence to: Mr B. de Goede, Department of Surgery, Erasmus University Medical Centre Rotterdam, PO Box 2040, 3000 CA Rotterdam, The Netherlands ( b.degoede@erasmusmc.nl) Background: Chronic pain remains a frequent complication after Lichtenstein inguinal hernia repair. As a consequence, mesh fixation using glue instead of sutures has become popular. This meta-analysis aimed to clarify which fixation technique is to be preferred for elective Lichtenstein inguinal hernia repair. Methods: A meta-analysis was conducted according to the PRISMA guidelines. Articles published between January 1990 and April 2012 were searched for in MEDLINE, Embase and the Cochrane Library. Randomized controlled trials (RCTs) comparing glue and sutured mesh fixation in elective Lichtenstein repair for unilateral inguinal hernia were included. The quality of the RCTs and the potential risk of bias were assessed using the Cochrane risk of bias tool. Results: Of 254 papers found in the initial search, a meta-analysis was conducted of seven RCTs comprising 1185 patients. With the use of glue mesh fixation, the duration of operation was shorter (mean difference 2 57 (95 per cent confidence interval (c.i.) 4 88 to 0 26) min; P = 0 03), patients had lower visual analogue scores for postoperative pain (mean difference 0 75 ( 1 18 to 0 33); P = 0 001), early chronic pain occurred less often (risk ratio 0 52, 95 per cent c.i to 0 87; P = 0 01), and time to return to daily activities was shorter (mean difference 1 17 ( 2 30 to 0 03) days; P = 0 04). The hernia recurrence rate did not differ significantly. Conclusion: Elective Lichtenstein repair for inguinal hernia using glue mesh fixation compared with sutures is faster and less painful, with comparable hernia recurrence rates. Paper accepted 18 December 2012 Published online 22 February 2013 in Wiley Online Library ( DOI: /bjs.9072 Introduction Lichtenstein repair for inguinal hernia, described for the first time in 1989, has become a widely accepted surgical procedure which combines safety, effectiveness and a low hernia recurrence rate 1 3. However, chronic pain after inguinal hernia repair remains a frequent complication, with a reported incidence of up to 63 per cent 4,5. This chronic pain is thought to be associated with an inflammatory reaction to the mesh, nerve severance, suture-related nerve entrapment or suture-induced nerve irritation 6,7. In the original description, Lichtenstein and colleagues 3 reported the use of non-absorbable sutures for mesh fixation. However, in an attempt to reduce chronic pain induced by sutures, several methods of mesh fixation have been developed over time, including absorbable sutures, self-adhering meshes and glue fixation 7,8. The latter two are presumed to prevent inguinal nerve entrapment and direct trauma to the nerves 8,9. Use of cyanoacrylate glue appeared to be promising for mesh fixation in Lichtenstein inguinal hernia repair, with recurrence rates comparable with those of sutured mesh fixation, and without adhesive-related complications 9.However, concerns about toxicity and presumed inflammatory reactions to this chemical adhesive have hampered its widespread use 10,11. Because of these concerns, N-butyl- 2-cyanoacrylate (NBCA) was developed, and has been reported to have reduced toxicity and fewer inflammatory reactions 10,12,13. Fibrin glue, which is based on humanderived coagulation cascade proteins, was also found to be a more effective and better tolerated alternative to 2013 British Journal of Surgery Society Ltd British Journal of Surgery 2013; 100:

2 736 B. de Goede, P. J. Klitsie, B. J. H. van Kempen, L. Timmermans, J. Jeekel, G. Kazemier and J. F. Lange cyanoacrylate glue; the results were comparable with those of NBCA for non-mechanical mesh fixation during inguinal hernia repair 8,11,14. Early worries about possible high hernia recurrence rates after glue fixation appear unwarranted 8. The use of fibrin glue for mesh fixation in a porcine model showed comparable results for graft motion and tensile strength, and several clinical studies have reported excellent results with respect to hernia recurrence 13,15,16. The efficacy of glue compared with sutures for Lichtenstein inguinal hernia repair is still subject to debate, because the power of many of the studies was limited and data on the potential benefit for chronic pain are sparse. To clarify which technique for mesh fixation is preferred during elective Lichtenstein repair for inguinal hernia, a systematic review of the literature and meta-analysis were performed. Methods A systematic search of MEDLINE, Embase and the Cochrane Library was undertaken for articles published between January 1990 and April All aspects of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement were followed 17. Manual reference checks of accepted papers in recent reviews and included papers were performed to supplement the electronic searches. The search syntax included keywords corresponding to the target population (adults), interventions (elective Lichtenstein inguinal hernia repair) and target condition (unilateral inguinal hernia/groin hernia). Details of the search syntax are listed in Appendix S1 (supporting information). The initial search was restricted to randomized controlled trials (RCTs). Language restrictions were not used for the initial search in order to investigate potential language bias. Subsequently, the exclusion criteria of non-english language, article type (non-randomized) and non-adult participants were applied and duplicates were removed. Studies were evaluated for inclusion independently by two reviewers based on title and abstract, and finally were evaluated independently based on the full text. Studies were included if they met the following criteria: participants were adults with unilateral inguinal/groin hernia; interventions were elective Lichtenstein inguinal hernia repairs with glue or sutured mesh fixation; outcome measures were duration of operation, acute postoperative pain (in the first 24 h) measured by means of a visual analogue scale (VAS), early chronic pain (within 3 6 months after surgery), late chronic pain (at 12 months), time to return to daily activities, hernia recurrence or need for analgesics in the first 24 h, and RCT. Any discrepancies regarding inclusion were resolved by discussion between the reviewers and the senior author. Data extraction and management Two reviewers extracted all required data from each study independently using a standard form that covered: study characteristics (study design, year of publication, study location, study interval and level of evidence); baseline characteristics (type of intervention, number of patients, age, sex, body mass index, type of suture, type of glue, type of anaesthesia, use of local infiltration and duration of follow-up); type of intervention (Lichtenstein inguinal hernia repair with mesh fixation: glue versus sutures); and surgery-related factors (acute postoperative pain and chronic pain, hernia recurrence and postoperative complications). Disagreements were resolved by consensus. Assessment of study quality The level of evidence of each paper was established according to the Oxford Centre for Evidence-based Medicine levels of evidence 18. The methodological quality of the RCTs and the potential risk of bias were assessed using the Cochrane Collaboration s tool for assessing risk of bias 19. Statistical analysis To pool data and calculate a pooled mean for each patientlevel outcome, the Mantel-Haenszel random-effects model was used, which takes into account the variance between studies and the variance within a study 20. Risk ratios (RRs) or mean differences with 95 per cent confidence intervals (c.i.) were calculated to evaluate the statistical difference between outcomes following mesh fixation by glue or sutures. Statistical heterogeneity was assessed for duration of operation, acute postoperative pain, early and late chronic pain, time to return to daily activities, hernia recurrence and need for analgesics by calculating the Q statistics and the I 2 statistic. Selective dissemination of evidence was assessed by plotting each outcome measure of each study against precision (1/standard error) in a plot with P-valuecontours. Funnel plot asymmetry, specifically with an apparent lack of studies in high P-value areas of the plot, can be indicative of publication bias 21. In addition, the individual study effects on the results were examined by removing the studies one at a time to determine whether removing a particular study would change the significance of the pooled effect. Twosided P was considered statistically significant.

3 Mesh fixation for Lichtenstein hernia repair 737 Citations identified (search date 30 April 2012) n = 314 MEDLINE n = 169 Embase n = 136 Cochrane Library n = 9 Titles and abstracts reviewed n = 254 Duplicates n = 60 Full text reviewed n = 14 RCTs included in meta-analysis n = 7 Studies excluded n = 240 Title irrelevant n = 153 Abstract irrelevant n = 87 Studies excluded from meta-analysis n = 7 Non-randomized n = 2 Multiple publications n = 2 Irrelevant n = 3 Fig. 1 PRISMA flow diagram for the review. RCT, randomized controlled trial Table 1 Baseline characteristics of studies included in the meta-analysis Arslani et al. 22 (2010) (2012) (2012) Nowobilski et al. 24 (2004) Paajanen et al. 25 (2011) Shen et al. 26 (2012) Torcivia et al. 27 (2011) Oxford Type of CEBM Intervention n Age (years)* Men (%) Type of sutures Type of mesh Type of glue 2b Total Sutures (13 9) 98 Prolene 3-0 Prolene TachoSil (DCFM) Glue 52 1b Total (47 65) 100 Polypropylene Polypropylene Tissucol / Sutures (48 66) 2-0 (heavyweight) Tisseel Glue (46 65) 1b Total (25 85) 100 PDS 2-0 VIPRO II Histoacryl Sutures (25 83) (NBCA) Glue (28 85) 2b Total Dexon 3 0 Polypropylene Indermil Sutures (20 78) Glue (30 76) 1b Total 302 Dexon 3-0 Optilene Sutures (15) 89 4 (lightweight) Glue (15) b Total Prolene 2-0 ProLite Sutures 55 60(12) 86 Glue 55 63(10) 82 Ultra (lightweight) (NBCA) Glubran (NBCA) Type of anaesthesia Length of Local follow-up infiltration (months) General 24 Local, regional, general Local, spinal/ epidural, general Yes 12 Yes 60 Local Yes 3 Local 12 NBCA Regional 15 2b Total (18 80) 87 Prolene 2-0 Prolene Glucamesh General Yes 1 Sutures Glue *Values are mean(s.d.) unless indicated otherwise; values are median (interquartile range) and median (range). CEBM, Centre for Evidence-Based Medicine levels of evidence; DCFM, dual-component fibrin mesh; NBCA, N-butyl-2-cyanoacrylate. Prolene and PDS (Ethicon, Johnson & Johnson, Somerville, New Jersey, USA); TachoSil (Takeda Pharmaceuticals International, Zurich, Switzerland); Tissucol /Tisseel (Baxter Healthcare, Westlake Village, California, USA); VIPRO II (Ethicon, Johnson & Johnson Medical Products, Vienna, Austria); Histoacryl (Braun Medical, Sempach, Switzerland); Dexon (Covidien, Mansfield, Massachusetts, USA); Indermil (Henkel, Düsseldorf, Germany); Optilene (B. Braun, Melsungen, Germany); Glubran (GEM, Viareggio, Italy); ProLite Ultra (Atrium, Hudson, New Hampshire, USA); Glucamesh (Brennen Medical, Saint Paul, Minnesota, USA).

4 738 B. de Goede, P. J. Klitsie, B. J. H. van Kempen, L. Timmermans, J. Jeekel, G. Kazemier and J. F. Lange Table 2 Summary of risk of bias assessment Random sequence generation (selection bias) Allocation concealment (selection bias) Blinding of participants and personnel (performance bias) Blinding of outcome assessment (detection bias) Incomplete outcome data (attrition bias) Selective reporting (reporting bias) Other bias Arslani et al. 22????? ? + + +? Nowobilski et al. 24????? Paajanen et al. 25? Shen et al. 26 +? + +? Torcivia et al. 27? +? Glue Sutures Time (min)* n Time (min)* n Weight (%) Mean difference (min) Mean difference (min) Nowobilski et al (10 5) 73(10 8) (9 1) 79(12 4) ( 7 60, 3 80) 6 00 ( 8 80, 3 20) Torcivia et al (15 4) (15 4) (0 39, 18 01) Shen et al (6) 55 43(6) ( 6 24, 1 76) Paajanen et al (12) (13) ( 4 82, 0 82) 39 8(12 1) (11 9) ( 4 38, 0 98) Total ( 4 88, 0 26) Heterogeneity: τ 2 = 4 80; χ 2 = 14 03, 5 d.f., P = 0 02; I 2 = 64% Test for overall effect: Z = 2 18, P = Favours glue Favours sutures Fig. 2 Forest plot showing mean difference in duration of operation between glue and sutured mesh fixation for Lichtenstein inguinal hernia repair. An inverse variance random-effects model was used for meta-analysis. *Values are mean(s.d.). Mean differences are shown with 95 per cent confidence intervals Early chronic pain Glue Sutures Weight (%) Risk ratio Risk ratio Arslani et al of 52 3 of of of (0 01, 2 34) 0 52 (0 24, 1 13) 13 of of (0 33, 1 20) Shen et al of 55 6 of (0 00, 1 33) Total 22 of of (0 31, 0 87) Heterogeneity: τ 2 = 0 01; χ 2 = 3 12, 3 d.f., P = 0 37; I 2 = 4% Test for overall effect: Z = 2 52, P = Favours glue Favours sutures Fig. 3 Forest plot showing risk ratio (RR) for early chronic pain (within 3 6 months) after glue and sutured mesh fixation for Lichtenstein inguinal hernia repair. A Mantel Haenszel random-effects model was used for meta-analysis. RRs are shown with 95 per cent confidence intervals Analyses were performed using Review Manager software (RevMan ; The Nordic Cochrane Centre, Copenhagen, Denmark). Results Of 254 papers found in the initial search, seven fell within the scope of the study (Fig. 1) 1, Four of the included studies provided level 1b evidence (Table 1). No studies were excluded after assessing the quality of the papers included. The summary of risk of bias assessment is presented in Table 2. The meta-analysis was performed using these seven RCTs comprising 1185 patients. No postoperative death related to the Lichtenstein procedure was reported in any of these studies. Study characteristics and

5 Mesh fixation for Lichtenstein hernia repair 739 Late chronic pain Glue Sutures Weight (%) Risk ratio Risk ratio Paajanen et al of of of of of of (0 47, 1 26) 0 51 (0 20, 1 31) 1 30 (0 79, 2 15) Total 58 of of (0 54, 1 42) Heterogeneity: τ 2 = 0 09; χ 2 = 3 82, 2 d.f., P = 0 15; I 2 = 48% Test for overall effect: Z = 0 53, P = Favours glue Favours sutures Fig. 4 Forest plot showing risk ratio (RR) for late chronic pain (at 12 months) after glue and sutured mesh fixation for Lichtenstein inguinal hernia repair. A Mantel Haenszel random-effects model was used for meta-analysis. RRs are shown with 95 per cent confidence intervals Recurrence Nowobilski et al. 24 Arslani et al. 22 Paajanen et al. 25 Shen et al. 26 Glue Sutures Weight (%) Risk ratio Risk ratio 0 of 22 0 of 24 Not estimable 0 of 52 1 of (0 01, 6 93) 8 of 71 5 of (0 66, 5 60) 2 of of (0 14, 6 90) 0 of 55 0 of 55 Not estimable 1 of of (0 05, 5 67) Total 11 of of (0 54, 2 92) Heterogeneity: τ 2 = 0 00; χ 2 = 2 01, 3 d.f., P = 0 57; I 2 = 0% Test for overall effect: Z = 0 54, P = Favours glue Favours sutures Fig. 5 Forest plot showing risk ratio (RR) for hernia recurrence after glue and sutured mesh fixation for Lichtenstein inguinal hernia repair. A Mantel Haenszel random-effects model was used for meta-analysis. RRs are shown with 95 per cent confidence intervals baseline characteristics of patients are summarized in Table 1. Six studies (1077 patients) investigated pooled duration of operation and were included in the meta-analysis 1, The operating time was significantly shorter when glue was used for mesh fixation: mean difference 2 57 (95 per cent c.i to 0 26) min (I 2 = 64 per cent; P = 0 03) (Fig. 2). Four studies (505 patients) investigated the pooled VAS for pain in the first 24 h after surgery and were included in the meta-analysis Patients in the group treated with glue had significantly lower VAS scores, indicating that they experienced less pain: mean difference 0 75 ( 1 18 to 0 33) (I 2 = 77 per cent; P = 0 001). Two studies (348 patients) investigating the pooled need for analgesics within 24 h after operation were included in the meta-analysis 24,25. There was no statistically significant difference in need for analgesics between glue and sutured mesh fixation groups: RR 0 90 (95 per cent c.i to 1 37) (I 2 = 69 per cent; P = 0 63). Four studies (772 patients) investigating pooled early chronic pain after 3 6 months were included in the metaanalysis 1,22,23,26. Early chronic pain occurred significantly less often with glue mesh fixation: RR 0 52 (0 31 to 0 87) (I 2 = 4 per cent; P = 0 01) (Fig. 3). Three studies (852 patients) investigated pooled late chronic pain at 12 months and were included in the meta-analysis 1,23,25. There was no statistically significant difference in late chronic pain between glue and sutured mesh fixation: RR 0 88 (0 54 to 1 42) (I 2 = 48 per cent; P = 0 60) (Fig. 4). Two studies (354 patients) investigated pooled time to return to daily activities and were included in the metaanalysis 23,24. The time to return to daily activities was significantly shorter when glue mesh fixation was used: mean difference 1 17 ( 2 30 to 0 03) days (I 2 = 0per cent; P = 0 04). Six studies (1003 patients) investigated pooled inguinal hernia recurrence and were included in the metaanalysis 1, There was no statistically significant

6 740 B. de Goede, P. J. Klitsie, B. J. H. van Kempen, L. Timmermans, J. Jeekel, G. Kazemier and J. F. Lange difference in recurrence between glue and sutured mesh fixation: RR 1 26 (0 54 to 2 92) (I 2 = 0 per cent; P = 0 59) (Fig. 5). Owing to the limited number of studies, no formal tests of funnel plot asymmetry were possible; visual inspection revealed no indications of publication bias, except for duration of operation and chronic pain after 3 6 months. For duration of operation, the asymmetry in the funnel plot stemmed primarily from the paper by Torcivia and colleagues 27 ; removal of this study did not influence the significance of the pooled effect. Similarly, removal of the two smaller studies with reported larger effect sizes for chronic pain after 3 6 months 22,26 did not change the significance. Further sensitivity analyses were performed for all outcomes by removing each study with the lowest risk of bias scores separately; they did not change the significance level of any of the mean differences. Discussion This study suggests that mesh fixation using glue for Lichtenstein inguinal hernia repair is associated with a significantly shorter operating time, less acute postoperative pain and less early chronic pain, a shorter time to return to daily activities and leads to comparable hernia recurrence rates. No significant differences were observed in the need for postoperative analgesics and late chronic pain. The meta-analysis included several RCTs with level of evidence 1b on the Oxford level of evidence scale and overall moderate quality in risk of bias assessment, which permits solid conclusions. These are relevant findings because inguinal hernia repair is common; in 2003, approximately inguinal hernia repairs were done in the USA alone 15,28. Early chronic pain has been reported in up to 63 per cent of patients after inguinal hernia repair, which leads to prolonged convalescence 4,5. Although effects on acute postoperative pain and duration of operation were significantly in favour of glue fixation, the observed differences for these outcomes were small, which obviously reduces their clinical relevance. However, the reduction in early chronic pain through mesh fixation with glue appears more relevant clinically. Glue fixation may affect acute postoperative pain by avoiding suture-related nerve entrapment or suture-induced nerve irritation 6,7,29. As the intensity of acute postoperative pain correlates with the risk of developing chronic pain, only a proportion of patients with nerve damage during inguinal hernia repair progress 30. Neuropathic pain, suggested as the main cause of postoperative pain, is caused by neuroplastic changes in the central nervous system following nerve damage in the inguinal region, which seem to disappear over time 30,31. To minimize the risk of chronic postoperative pain, all three nerves (ilioinguinal and iliohypogastric nerves, and the genital branch of the genitofemoral nerve) should be identified and preserved during inguinal hernia repair Other reviews of the literature have been performed. In 2012, a systematic review focusing on the use of fibrin glue (Tissucol, also marketed as Tisseel ; Baxter Healthcare, Westlake Village, California, USA) for hernia repair was conducted by Fortelny and colleagues 8. They included studies of patients with inguinal and other abdominal wall hernias; fibrin glue was compared with mechanical mesh fixation during open, endoscopic or laparoscopic repair. Although the conclusions from that study support the data from the present meta-analysis, it focused only on fibrin glue. Furthermore, only one RCT comparing techniques for mesh fixation in Lichtenstein inguinal hernia repair was included, and the study population was heterogeneous, comprising patients with all kinds of abdominal wall defect. A meta-analysis comparing staples and fibrin glue mesh fixation for laparoscopic total extraperitoneal (TEP) inguinal hernia repair was conducted by Kaul and coworkers 11. Their conclusion was that the incidence of chronic pain is reduced after fibrin glue mesh fixation, with no significant difference in hernia recurrence rates. The present study had several shortcomings, which included the quality of the studies in the meta-analysis. The included studies lacked complete data reporting on postoperative complications by fixation technique on a patient level. Therefore, patient-level data on postoperative complications could not be pooled and compared for the two fixation techniques. Second, various types of glue (chemical and biological), sutures (absorbable and non-absorbable) and meshes were used; this restricts the comparability of the studies. Third, outcomes were scored differently in the various studies, particularly with respect to pain. Not all outcomes were investigated in all studies, nor were definitions of outcomes in the studies comparable as different endpoints were used. There was little information on hernia size in the studies; included trials provided no information on whether glue was used differently according to hernia size. No information was given on the limitations of glue mesh fixation in repair of larger hernias. Finally, follow-up was short; only one RCT by Kim-Fuchs and colleagues 1 reported data on recurrence rates after 5 years. The risk of hernia recurrence requiring reoperation, however, is approximately 5 per cent after 30 months, and even after 5 years new recurrence may occur 35.

7 Mesh fixation for Lichtenstein hernia repair 741 Another important topic is the cost benefit consideration for use of glue during Lichtenstein inguinal hernia repair. None of the included studies reported a cost benefit analysis. As medical glue is far more expensive than sutures, this might prevent large-scale use of glue fixation of mesh in inguinal hernia repair. The cost of glue should be balanced against a shorter operating time, shorter time to return to daily activities and potentially reduced convalescence owing to less early postoperative pain. Keeping these limitations in mind, this meta-analysis suggests that glue fixation of the mesh during Lichtenstein inguinal hernia repair is preferred over fixation using sutures. Future studies should standardize the assessment of acute postoperative pain and chronic pain, and should focus on long-term outcomes. Acknowledgements B.d.G. and P.J.K. contributed equally to this manuscript. 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8 742 B. de Goede, P. J. Klitsie, B. J. H. van Kempen, L. Timmermans, J. Jeekel, G. Kazemier and J. F. Lange undergoing Lichtenstein technique for primary inguinal hernia repair: results of the TIMELI trial. Ann Surg 2012; 255: Nowobilski W, Dobosz M, Wojciechowicz T, Mionskowska L. Lichtenstein inguinal hernioplasty using butyl-2-cyanoacrylate versus sutures: preliminary experience of a prospective randomized trial. Eur Surg Res 2004; 36: Paajanen H, Kossi J, Silvasti S, Hulmi T, Hakala T. Randomized clinical trial of tissue glue versus absorbable sutures for mesh fixation in local anaesthetic Lichtenstein hernia repair. Br J Surg 2011; 98: Shen YM, Sun WB, Chen J, Liu SJ, Wang MG. NBCA medical adhesive (n-butyl-2-cyanoacrylate) versus suture for patch fixation in Lichtenstein inguinal herniorrhaphy: a randomized controlled trial. Surgery 2012; 151: Torcivia A, Vons C, Barrat C, Dufour F, Champault G. Influence of mesh type on the quality of early outcomes after inguinal hernia repair in ambulatory setting controlled study: Glucamesh vs Polypropylene. Langenbecks Arch Surg 2011; 396: Rutkow IM. Demographic and socioeconomic aspects of hernia repair in the United States in Surg Clin North Am 2003; 83: , v vi. 29 Amid PK. Radiologic images of meshoma: a new phenomenon causing chronic pain after prosthetic repair of abdominal wall hernias. Arch Surg 2004; 139: Kehlet H, Jensen TS, Woolf CJ. Persistent postsurgical pain: risk factors and prevention. Lancet 2006; 367: van Veen RN, Wijsmuller AR, Vrijland WW, Hop WC, Lange JF, Jeekel J. Randomized clinical trial of mesh versus non-mesh primary inguinal hernia repair: long-term chronic pain at 10 years. Surgery 2007; 142: Wijsmuller AR, van Veen RN, Bosch JL, Lange JF, Kleinrensink GJ, Jeekel J et al. Nerve management during open hernia repair. Br J Surg 2007; 94: Alfieri S, Amid PK, Campanelli G, Izard G, Kehlet H, Wijsmuller AR et al. International guidelines for prevention and management of post-operative chronic pain following inguinal hernia surgery. Hernia 2011; 15: Alfieri S, Rotondi F, Di Giorgio A, Fumagalli U, Salzano A, Di Miceli D et al. Influence of preservation versus division of ilioinguinal, iliohypogastric, and genital nerves during open mesh herniorrhaphy: prospective multicentric study of chronic pain. Ann Surg 2006; 243: Bisgaard T, Bay-Nielsen M, Christensen IJ, Kehlet H. Risk of recurrence 5 years or more after primary Lichtenstein mesh and sutured inguinal hernia repair. Br J Surg 2007; 94: Supporting information Additional supporting information may be found in the online version of this article: Appendix S1 Search strategy