Hernia (2022) 26:1459–1471 https://doi.org/10.1007/s10029-022-02668-w REVIEW Ventral hernia repair in high‑risk patients and contaminated fields using a single mesh: proportional meta‑analysis S. Morales‑Conde1 · P. Hernández‑Granados2 · L. Tallón‑Aguilar3 · M. Verdaguer‑Tremolosa4 · M. López‑Cano4 Received: 13 March 2022 / Accepted: 25 August 2022 / Published online: 13 September 2022 © The Author(s) 2022, corrected publication 2022 Abstract Purpose The use of mesh is a common practice in ventral hernia repair (VHR). Lack of consensus on which prosthetic material works better in different settings remains. This meta-analysis aims to summarize the available evidence on hernia recurrence and complications after repair with synthetic, biologic, or biosynthetic/bioabsorbable meshes in hernias grade 2–3 of the Ventral Hernia Working Group modified classification. Methods A literature search was conducted in January 2021 using Web of Science (WoS), Scopus, and MEDLINE (via PubMed) databases. Randomized Controlled Trials (RCTs) and observational studies with adult patients undergoing VHR with either synthetic, biologic, or biosynthetic/bioabsorbable mesh were included. Outcomes were hernia recurrence, Surgical Site Occurrence (SSO), Surgical Site Infection (SSI), 30 days re-intervention, and infected mesh removal. Random-effects meta-analyses of pooled proportions were performed. Quality of the studies was assessed, and heterogeneity was explored through sensitivity analyses. Results 25 articles were eligible for inclusion. Mean age ranged from 47 to 64 years and participants’ follow-up ranged from 1 to 36 months. Biosynthetic/bioabsorbable mesh reported a 9% (95% CI 2–19%) rate of hernia recurrence, lower than synthetic and biologic meshes. Biosynthetic/bioabsorbable mesh repair also showed a lower incidence of SSI, with a 14% (95% CI 6–24%) rate, and there was no evidence of infected mesh removal. Rates of seroma were similar for the different materials. Conclusions This meta-analysis did not show meaningful differences among materials. However, the best proportions towards lower recurrence and complication rates after grade 2–3 VHR were after using biosynthetic/slowly absorbable mesh reinforce- ment. These results should be taken with caution, as head-to-head comparative studies between biosynthetic and synthetic/ biologic meshes are lacking. Although, biosynthetic/bioabsorbable materials could be considered an alternative to synthetic and biologic mesh reinforcement in these settings. Keywords Ventral hernia · Mesh · Biosynthetic mesh · Synthetic mesh · Biologic mesh Introduction * L. Tallón‑Aguilar Incisional ventral hernia repair is a common surgical prac- ltallona@hotmail.com tice. The use of mesh reinforcement has become a reference 1 Unit of Innovation in Minimally Invasive Surgery, to prevent hernia recurrence [1, 2]. However, the variety of Department of General Surgery, University Hospital Virgen devices—with over 150 mesh products on the market—and del Rocío, University of Sevilla, Seville, Spain surgical techniques make it difficult to evaluate prostheses 2 General Surgery Unit, Fundación Alcorcón University performance [3, 4]. Lack of consensus remains regarding Hospital, Rey Juan Carlos University, Alcorcón, Spain the best practices for ventral hernia repair (VHR) in the 3 Abdominal Wall Surgery Unit, Department of General setting of a contaminated surgical field [2]. Permanent Surgery, Hospital Universitario Virgen del Rocío, synthetic meshes are made of non-absorbable materials c/ Asuncion 26, 2ºA, 41011 Seville, Spain such as polyester, polypropylene, polyvinylidene fluoride, 4 Abdominal Wall Surgery Unit, Department of General or polytetrafluoroethylene (PTFE). Although longer used, Surgery, Hospital Universitari Vall d’Hebron, Universitat these prostheses are associated with a risk of postoperative Autónoma de Barcelona, Barcelona, Spain 13 Vol.:(0123456789) 1460 Hernia (2022) 26:1459–1471 infection and subsequent complications in contaminated or Epidemiology guidelines [16]. The review was registered clean-contaminated settings [1, 5–7]. This previous context in the Prospective Register of Systematic Reviews led to the development of biologic implants, as an alternative (CRD42021265235). to synthetic meshes [7, 8]. However, concerns about their possible advantages remain [8–10]. Search strategy Biosynthetic/slowly absorbable meshes have recently been introduced as a potential alternative to biological A literature search was conducted in January 2021. The implants in contaminated abdominal wall reconstruction [6]. search only considered those studies published from 2000 The absorption rates of these meshes may vary according to to 2021, written in English or Spanish, with the last search their composition: 6 months for polyglycolic acid (PGA): update on January 27. Search strategy was performed by an trimethylene carbonate materials (TMC), 12–18 months expert documentalist using the following databases: Web for poly-4-hydroxybutyrate (P4HB) component, and of Science (WoS), Scopus and MEDLINE (via PubMed). 12–36 months for a mixture of copolymer fibers of The search strategy included a combination of keywords polyglycolide, polylactide, and polytrimethylene carbonate and MeSH terms about hernia and mesh-related terms and fibers of polylactide and polytrimethylene carbonate, (see Supplementary file 1 for searching strategies in each respectively, in comparison to classical glycolide and lactide database). Two independent reviewers (SMC and MLC) mesh, which resorbs in less than two months [1, 11]. assessed the title and abstract of each record for inclusion The Ventral Hernia Working Group (VHWG) 2010 clas- and exclusion criteria. After preliminary screening, the sification system [5] stratifies patients with ventral hernia selected publications were scanned in full text by the authors according to their risk for postoperative Surgical Site Occur- for eligibility. Discrepancies were solved after a discussion rence (SSO), depending on the patient and wound character- between reviewers. istics, such as smoker, obese, diabetic, immunosuppressed, chronic obstructive pulmonary disease (COPD), or history of Study selection, data extraction and quality wound infection and hernia defects. Thus, it suggests the use assessment of synthetic mesh, based on surgeon preference, for low-risk (grade 1) and the use of biologic mesh for increased risk and We established the inclusion criteria for study selection co-morbid patients (grade 2) as well as for contaminated or according to observational studies, as well as randomized infected wounds (grades 3 and 4). However, the higher costs control trials (RCTs) of any design, with adult patients of biologic implants could have limited their use, even for (≥ 18 years of age) undergoing grade 2–3 complex VHR high-risk patients [12]. In 2012 the VHWG classification was with prosthetic reinforcement, either with synthetic, modified [13] stratifying patients as grade 1 (clean cases; biologic, or biosynthetic/slowly absorbable mesh. Hernia low risk of complications), grade 2 (clean cases; co-mor- grade was defined according to the modified VHWG bidity, history of infection), or grade 3 (clean-contaminated, grading system [13]. Publications reporting on at least one contaminated, and dirty wounds). In the setting of complex of the following primary outcomes were included: hernia VHR, newly developed biosynthetic/slowly absorbable recurrence, SSO, as described by the VHWG including meshes have shown promising results for hernia recurrence infection, wound dehiscence, seroma, or development of and other postoperative complications [14]. an enterocutaneous fistula [13] and Surgical Site Infection In the previous context and given the lack of consensus (SSI), according to the Center for Disease Control (CDC) on the most appropriate material for hernia repair in clean- [17] definition. Secondary outcomes of interest were 30 days contaminated and contaminated wounds, the present work re-intervention and infected mesh removal. aims to review the existing literature and gather evidence Exclusion criteria included no reported clinical outcomes of postoperative outcomes of synthetic, biologic, and bio- of interest, preclinical studies and/or review articles, synthetic/slowly absorbable meshes in patients undergoing editorials, data from registries, articles with non-full text modified VHWG (2012) grade 2–3 complex ventral hernias. available or comments to a study, single case reports, studies related to parastomal, inguinal, or hiatal hernia repair, repair using either no mesh or two different meshes, as well as prophylactic mesh insertion. For duplicate data reported by Methods the same author(s), the article with the longest follow-up period was selected [18, 19]. A systematic review and meta-analysis were conducted Data were extracted by two independent reviewers following the PRISMA (Preferred Reporting Items for using a Microsoft®Excel (Microsoft® Corporation 2016) Systematic Reviews and Meta-Analyses) 2020 statement data extraction form. Predefined variables such as year of [15] and the Meta-analysis of Observational Studies in publication, study design, follow-up period and number 13 Hernia (2022) 26:1459–1471 1461 of patients were retrieved. Results reported in the studies across the studies. Heterogeneity was considered high if I2 were recorded according to mesh type. In addition, patient was > 50% [24]. Heterogeneity was explored with sensitiv- characteristics and comorbidities associated with increased ity analyses to reflect the influence of several subgroups on risk for postoperative infection were extracted, including the pooled proportions adjusted by mesh type. The variables age, sex, Diabetes Mellitus (DM), obesity (Body Mass explored in the subgroup analysis were based on a time hori- Index > 30 kg/m2), Chronic Obstructive Pulmonary Disease zon of outcomes (studies with only long-term complications), (COPD), active smoker, and history of wound infection. population characteristics (studies with a patient with mean Hernia characteristics and operative details were extracted BMI ≥ 30 and mean BMI < 30, studies with a proportion of as well: CDC wound classification [17], VHWG hernia smokers ≥ 25% and smokers < 25%), study design (prospec- grade [13], mesh type, setting of intervention (emergency tive vs retrospective) and risk of study bias (low vs moderate). or elective), repair technique and mesh placement location. The possibility of publication bias was examined using In terms of postoperative complications, data on hernia the Doi plot and Luis Furuya-Kanamori asymmetry index recurrence, SSO, seroma, and SSI, as well as 30 days (LFK index) [25] by a subgroup of mesh type. This approach re-intervention, mesh removal and length of hospital stay has been suggested to be more robust for meta-analyses that were detailed. Those articles in which VHWG grade was not include less than 10 studies. In the presence of symmetry, explicitly reported but had a cohort of patients with one or one can conclude as no publication bias but in the absence of more of the comorbid conditions mentioned above, which symmetry, one can expect publication bias. This publication allowed for a definition of VHWG grade, were selected and bias was measured by the asymmetry index (LFK index). An included in the review (classified as grade ≥ 2). Articles with LFK index within ± 1, out of ± 1 but within ± 2, and >± 2 is grade 1–3 hernias for which outcomes were disaggregated to mean no asymmetry, minor asymmetry, and major asym- by hernia grade were included in the analysis only collecting metry, respectively. The influence of potential publication data for grade 2–3 outcomes. Discrepancies in data bias on results was explored by using the trim-and-fill pro- extraction were solved by the team of authors involved. cedure [25]. P < 0.05 was considered statistically significant Bias of the included studies has been assessed using the in all analyses. These were conducted using STATA (16.1, Cochrane RoB 2 Tool for RCT [20] and robvis tool to cre- StataCorp LLC, College Station, TX). ate risk-of-bias plots [21]. The appropriate adaptations of the Newcastle–Ottawa scale were used for cohort or cross- sectional studies [22, 23]. This scale is based on a cumulative Results score in three categories: selection of study groups, compa- rability of their cases and controls and ascertainment of the Study selection outcome/exposure. There are two versions of the scale, one for cohort studies and one for case–control studies, and other A total of 2793 articles were identified in the primary lit- version adapted from cross-sectional studies. If the assessed erature search (Fig. 1). After the removal of duplicates, the study includes criteria for an item, a score of one point is allo- literature search identified 1331 publications. Following the cated to the selection and ascertainment of outcome/exposure screening of the title and abstract, 62 articles were assessed category; two points can be allocated to the comparability for full-text review. 25 articles met the inclusion criteria and category, resulting in a maximum of 9 points. We considered qualified for the study. The main reasons for exclusion after studies that received a score of 9–7 to have a low risk of bias, full-text assessment were existing systematic reviews, lack studies with 4–6 points as medium risk of bias, and studies of information on hernia characteristics (VHWG grade 2–3), with 0–3 points as a high risk of bias. lack of information on patient comorbidities and contamina- Two authors evaluated the articles’ methodological qual- tion to define hernia grade if missing, and lack of results for ity, and any discrepancies were solved through discussion outcomes of interest. A subsequent article with the same with a third investigator. data from the same authors but with a longer follow-up replaced the publication with a shorter follow-up. Data synthesis and statistical analysis Study characteristics The meta-analyses were carried out considering one effect size per each study included, regardless of the type of mesh. A Of the 25 publications that met the inclusion criteria, only random-effects model was fitted to estimate pooled weighted two were RCTs [8, 26]; 17 were observational retrospective proportions with corresponding 95% confidence intervals studies [12, 14, 27–41] and six were observational (CIs). CIs 95% excluding 0 were considered significant. Sta- prospective studies [1, 3, 6, 9, 19, 42]. Thirteen studies tistical heterogeneity was assessed using the χ2 and I2 sta- compared permanent synthetic to biologic mesh [8, 12, tistics to analyse the extent of inconsistency and variation 26–32, 34–36, 38]; one publication compared synthetic to 13 1462 Hernia (2022) 26:1459–1471 Fig. 1  PRISMA flow diagram Databased searching Identification 2793 records identified 1025 in Web of Science 1462 duplicate records 992 in Scopus removed before screening 776 in PubMed 1331 records screened 1269 records excluded Screening 37 excluded: 62 articles assessed for - 23 Systematic Review: n = eligibility. - 11 No grade 2 - 3 VHWG - 2 No outcomes data - 1 Same data, follow-up 25 studies included in qualitative synthesis Included 25 studies included in quantitative synthesis biosynthetic/slowly absorbable mesh [40]; two compared The 25 selected studies included a total of 3771 patients. biosynthetic/slowly absorbable to biologic implant [14, Mean age ranged from 47 to 64 years and participants’ 41] and, 9 articles presented outcomes of biosynthetic/ follow-up ranged from 1 to 36 months. A clear description slowly absorbable meshes [1, 3, 6, 9, 14, 19, 33, 39, 42] of the VHWG hernia grade was reported in 13 studies [1, 3, (six for P4HB mesh, two publications referred to PGA: 9, 26, 29–31, 33, 34, 37–40], although the remaining articles TMC mesh, and one referred to both P4HB and PGA: presented data on comorbid conditions which allowed for TMC meshes. Among the studies using synthetic mesh, a definition of VHWG grade if patients had one or more polypropylene was the most common material [8, 12, 26, of the listed comorbidities (hernias classified as grade ≥ 2) 27, 29, 30, 32, 34, 35, 38, 40]. For biologic prosthetics, [6, 8, 12, 14, 27, 32, 35, 36, 41, 42]. Two articles reported nine articles described porcine dermis meshes [8, 14, 26, on “high risk” patients, as those immunosuppressed and 28, 32, 34, 35, 38, 41], whereas one article mentioned both comorbid [19, 28]. In three studies with grade 1 hernias, porcine and human dermis prosthetics [29]. operative outcomes were disaggregated by hernia grade, so 13 Hernia (2022) 26:1459–1471 1463 only data on operative outcomes fulfilling the hernia grade biosynthetic/slowly absorbable mesh was 0% (95% CI 0–2%) criteria (grades 2 and 3) were derived separately [1, 33, with a very low heterogeneity (I2 = 0%) among 4 studies, 37]. Regarding wound contamination, most of the studies compared with the subgroup of biologic and synthetic mesh, reported on CDC wound class [1, 6, 8, 9, 12, 19, 26, 27, 29, with pooled estimations of 2% (95% CI 0–7%) and 9% (95% 30, 33–37, 39–42]. Surgical characteristics and outcomes CI 0–25%), respectively, and high heterogeneity among 5 are shown in Supplementary file 2. Only one article did studies (I2 = 64.60% and 92.33%). not report any information on mesh location [27]. For the outcomes of interest, two studies lacked information on Hernia recurrence hernia recurrence [29, 40]; three articles did not present results on SSI [1, 28, 30]; 12 articles did not report on SSO Meta-analysis showed that the rate of hernia recurrence [3, 14, 19, 26–32, 38, 41] while only five articles did not was lower for biosynthetic/slowly absorbable mesh when report on seroma [1, 14, 27, 30, 32]. Regarding operative compared to synthetic and biologic meshes. Ten studies technique, 12 studies reported on component separation on biosynthetic/slowly absorbable meshes reported an techniques (CST) [1, 6, 9, 12, 29, 30, 33–38] (Table 1). incidence of 9% (95% CI 2–19%), versus 12 studies on synthetic mesh, with a recurrence rate of 13% (95% CI Quality assessment 8–19%) and a hernia recurrence of 20% (95% CI 14–25%) obtained for the 14 studies on a biologic mesh. The I2 The 2 RCT studies included in the review have an overall statistic reported substantial heterogeneity among the low risk of bias in the evaluation of methodological quality studies (93.32%, 77.59% and 69.53% for biosynthetic/ (Fig. 2). For the cohort studies, eleven obtained a high score bioabsorbable, synthetic, and biologic mesh, respectively). and twelve a moderate score. The most frequent risks of bias were related to the risk of comparability based on the design Re‑intervention or analysis (Table 2). 30 days re-invention was reported in 5 studies for synthetic Meta‑analysis findings mesh and 7 studies for biologic and biosynthetic/slowly absorbable each. Meta-analysis resulted in a pooled Seroma re-intervention estimation of 8% (5–12%) for biosynthetic/ slowly absorbable and 11% (95% CI 8–12%) for biologic. Rates of seroma are reported in 20 studies; however, only Heterogeneity was low-moderate I2 = 37.40% and I2 = 3.38%. 13 articles reported in SSO rates. For this reason, only the former was included in the pooled analysis. 10 studies Sensitivity analysis reported rates of seroma for biosynthetic/slowly absorbable meshes of 8% (95% CI 4–13%). A similar rate of 9% (95% For the sensitivity analysis, we first analysed the subgroup CI 5–13%) was obtained from 11 studies on biologic mesh, of studies reporting results on long-term complications. In as well as from the 11 articles on synthetic meshes, with a this sense, only 3 studies [9, 29, 40] reported short-term 9% rate of seroma (95% CI 5–13%). Heterogeneity ranged complication outcomes of seroma, SSI, and reintervention from I2 = 56.72% to I2 = 71.37% (Table 3). derived from the use of biosynthetic and synthetic meshes. The two studies with short-term complications of synthetic Surgical site infection mesh [29, 40] had a seroma rate of 0% (95% CI 0–14%) [29] and 4% (95% CI 2–8%) [40], SSI rate of 21% (95% CI Ten studies reported on SSI rates for biosynthetic/slowly 9–40%) [29] and 11% (95% CI 7–16%) [40], and reoperation absorbable meshes. The pooled estimation showed lower rate of 0% (95% CI 0–14%) [29] and 4% (95% CI 2–18%) SSI rates than biologic and synthetic mesh: 14% (95% CI [40]. Similarly, studies reporting short-term complications 6–24%), compared to 18% (14–24%) for synthetic meshes of biosynthetic mesh reported a seroma rate of 2% (95% CI (12 studies) and a higher rate of 27% (95% CI 17–38%) 0–9%) [40] and 8% (95% CI 4–16%) [9], SSI of 22% (95% obtained from 13 articles reporting on biologic prothesis. CI 14–35%) [40] and 13% (95% CI 7–22%) [9] and reop- There was high heterogeneity among studies (I2 statistics eration rate of 14% (95% CI 7–25%) [40]. After removing values between 68.93 and 89.91%; Fig. 3). these 3 articles, we pooled subgroup analysis only for studies with long-term complications of meshes. Results are shown Infected mesh removal in Supplementary file 4. We can observe a few differences with respect to the results of the total pooled sample by mesh Infected meshes were reported in 9 studies with a total type. Seroma and SSI rates increase slightly in synthetic and of 79 events. The pooled estimation in the subgroup of biosynthetic mesh [from 9 to 11% (95% CI 6–17%] and from 13 1464 Hernia (2022) 26:1459–1471 Table 1  Summary of study characteristics References Study design Sample size (n) Follow-up VHWG grade CDC Mean age Type of mesh, Mesh material months (± SD (± SD or range) n or range) Finch et al. [33] Retrospective 56 21 (4–54) I–IIIa (2012) 1–3 63 (25–84) Biosynthetic PGA: TMC (Gore® Bio- A®) Rosen et al. [6] Prospective 104 24 () – 2–3 58 (27–91) Biosynthetic PGA: TMC (Gore® Bio- A®) Messa et al. Retrospective 70 24 (12.2–41) I–IIIb (2012) 1–4 58.6 (23.2–81) Biosynthetic P4HB (Phasix™) [37] Pakula et al. Retrospective 20 21.1 (5–50) / II–III (2010) 1–3 47 (13) Biosynthetic P4HB (Phasix™) [39] 16.5 () Plymale et al. Prospective 31 24 () – 1–2 52 (44–62) Biosynthetic P4HB (Phasix™) [42] Rognoni et al. Prospective 75 26.4 (6.4) II–III (2010) – 59 (30–87) Biosynthetic P4HB (Phasix™) [3] Roth et al. [19] Prospective 82 36 () High-risk 1 54.7 (12) Biosynthetic P4HB (Phasix™) van Rooijen Prospective 84 3 (2.8–3.3) III (2010) 1–3 62.5 (12.4) Biosynthetic P4HB (Phasix™) et al. [9] Vauclair et al. Prospective 29 12 () I–IIIc (2012) 1–4 61 (13.3) Biosynthetic P4HB (Phasix™) [1] Sahoo et al. Retrospective 438 1 () II–III 2–3 64 (53–69) Synthetic Polypropylene [40] (380) (macroporous) 25.5 (14.5) 61 (51–70) Biosynthetic P4HB (Phasix™), (58) PGA: TMC (Gore Bio-A®) Buell et al. [14] Retrospective 73 – – – 52.5 Biosynthetic P4HB (Phasix™) (31) 56.9 Biologic (42) Porcine (Strat- tice™) de Vries et al. Retrospective 254 36 (0–153) III (2012) 2–4 58 (13.6) Synthetic (36) Polypropylene [30] (Vypro®, Ultrapro®, Physiomesh™ Proceed®, Dualmesh®, Prolene®) Biologic (69) Porcine (Strat- tice™), Surgi- sis® Harris et al. [8] RCT​ 165 27.3 (15.6) – 1–4 55.5 (11.1) Synthetic (83) Polypropylene (Ventralight™ ST) 25.5 (14.5) 55.0 (11.5) Biologic (82) Porcine (Strat- tice™) Renard et al. Retrospective 81 28.8 (15.7– – 3–4 65 (56–76) Absorbable Polyglactin (Vic- [41] 47.6) (57) ryl®) 27.7 (24.5– 63 (57–69) Biologic (24) Porcine (Strat- 33.1) tice®) 13 Hernia (2022) 26:1459–1471 1465 Table 1  (continued) References Study design Sample size (n) Follow-up VHWG grade CDC Mean age Type of mesh, Mesh material months (± SD (± SD or range) n or range) Chamieh et al. Retrospective 58 7.9 () III–IV 2–4 – Synthetic (24) Polypropylene [29] (2010) (lightweight and heavyweight) 11.3 () Biologic (34) Human dermis (FlexHD®), porcine submu- cosa-derived (Biodesign®), porcine dermis (XenMatrix ™, XCM®, Fortiva®, Strat- tice™) Brescia et al. Retrospective 64 24 (7–36) High-riskd – 59.13 (4.4) Synthetic (32) Synthetic (NR) [28] 58.63 (4.8) Biologic (32) Porcine (For- tiva®) Koscielny et al. Retrospective 187 27.3 (4.3) – 1–3 60 (9.9) Synthetic (24) Polypropylene [35] (Ultrapro®, Vypro®) 23.5 (3.7) 58 (9.3) Biologic (24) Porcine submu- cosa-derived (Biodesign®) Nockolds et al. Retrospective 23 17 (2–48) III–IV (2010) – 57 (20–76) Synthetic (6) Polypropylene [38] (Ultrapro®, Proceed®) Biologic (17) Porcine submu- cosa-derived (Biodesign®) Bondre et al. Retrospective 761 15 (1–50) – 1–4 49.4 (12.7) Synthetic Polypropylene [27] (303) (lightweight and/ or mid-weight) Biologic (167) Non-cross-linked biologic DeNoto et al. Retrospective 744 18 () III–IV (2010) – 57.0 (12.4) Synthetic Synthetic (NR) [31] (268) 55.2 (12.1– Biologic (177) Acellular xeno- 12.6) graft implant Majumder et al. Retrospective 126 18.4 (9.6) – 2–3 59.2 (12.3) Synthetic (57) Polypropylene [12] (midweight, macroporous design) 21.5 (10.5) 59.6 (11.7) Biologic (69) Porcine acellular dermal xeno- grafts Fischer et al. Retrospective 72 12.1 (1.6–38.6) II 1 52.6 (12.0) Synthetic (45) Polypropylene [34] (2010) (Marlex®) 54.2 (11.2) Biologic (27) Acellular Dermal Matrix Olavarria et al. RCT​ 87 12.4 (11.4– II–IV (2010) 2–4 51 (12.1) Synthetic (43) Polypropylene [26] 12.8) (medium-den- sity, macropo- rous) 51 (9.9) Biologic (44) Porcine Acellular Dermal Matrix 13 1466 Hernia (2022) 26:1459–1471 Table 1  (continued) References Study design Sample size (n) Follow-up VHWG grade CDC Mean age Type of mesh, Mesh material months (± SD (± SD or range) n or range) El-Gazzaz et al. Retrospective 25 32.9 (38.2) – – 50.1 (13.1) Synthetic (15) Polytetrafluoroeth- [32] ylene, Polypro- pylene (NR) 51.8 (12.7) Biologic (10) Porcine dermal collagen López-Cano Retrospective 62 22.2 (13.6) – 2–3 62.8 (12) Synthetic (48) Non absorbable et al. [36] 33.9 (20.8) Biologic (14) (NR) RCT​ randomized clinical trial, VHWG Ventral Hernia Working group, CDC Center for Disease Control wound classification, SD Standard Deviation, P4HB poly-4-hydroxybutyrate, PGA: TMC polyglycolic acid: trimethylene carbonate, NR not reported a Data on SSI is for 2–3 grade hernias b Data disaggregated by hernia grade; grade 1 is not considered c Outcome of interest, hernia recurrence, is only for grade 3 d High risk: those immunosuppressed and co-morbid (≥ grade 2) [28] Fig. 2  Assessment of risk for randomized controlled trials [18 to 20% (95% CI 15–25%)], for the respective long-term significant heterogeneity and wide confidence intervals, complications. In contrast, the long-term reintervention rates which shows that differences among complication rates in for synthetic mesh increase from 6 to 10% (95% CI 7–13%) patient subgroups are not significant. Similar results are and remain unchanged for biosynthetic mesh. obtained in sensitivity analyses for study design and risk To explore risk factors, two subgroups were analysed, of bias. There were only eight studies with a prospective considering the main patient characteristics influencing design: six out of them were single-arm studies assessing the outcomes of interest. Results are shown in Supple- results on biosynthetic/slowly absorbable mesh use and, mentary file 4. In the subgroup of studies whose patients the remaining were RCTs that compared biologic to syn- had an average BMI ≥ 30, there is a higher rate of her- thetic mesh. Outcomes of biosynthetic/slowly absorbable nia recurrence, infected mesh, and SSI for biologic mesh. mesh in the prospective studies, which represented a larger However, complication rates are lower for synthetic mesh, sample of studies, although not significant, show a lower apart from seroma. For biosynthetic/slowly absorbable rate for seroma, SSI, and recurrence. Finally, the subgroup mesh, there is a trend towards lower rates of SSI, infected analysis that classified studies according to low risk and mesh removal and hernia recurrence, although this per- medium risk of bias showed that studies with lower risk centage remains higher for the re-intervention variable. had a higher rate of SSI, hernia recurrence and re-inter- The subgroup of studies with, at least, 25% of smokers, vention for biosynthetic/slowly absorbable and biologic presented higher rates of seroma, infected mesh, and mesh. Again, these results are not significant. re-intervention, independently of mesh type, although lower rates are observed for hernia recurrence if com- Publication bias pared to the subgroup smoker < 25%. For the subgroups analysed (BMI ≥ 30, smoker ≥ 25%) mesh type does not There was evidence of major publication bias regarding the seem to influence the outcomes. These analyses present proportion of seroma for each type of mesh, SSI for biologic, 13 Hernia (2022) 26:1459–1471 1467 Table 2  Methodological quality evaluation for cohort/cross-sectional Table 3  Summary of meta-analysis results according to type of mesh studies and clinical outcome Studies Selection Comparability Results/ Total No. Sample size Events Pooled I2 (%) Exposition studies proportion (95% CI) Fischer 2014 **** ** *** 9 Renard 2020 **** ** *** 9 Seroma López-Cano 2017 **** * *** 8 Synthetic 11 804 66 9% (5–13%) 71.37 Majumder 2016 **** * *** 8 Biologic 11 544 44 9% (5–13%) 56.72 Bondre 2016 *** ** *** 8 Biosynthetic 10 666 58 8% (4–13%) 73.09 Brescia 2016 **** ** *** 8 SSI Buell 2016 **** * *** 8 Synthetic 12 1090 214 18% 68.93 (14–24%) Sahoo 2017 **** * ** 7 Biologic 13 731 178 27% 87.71 de Vries 2020 *** * *** 7 (17–38%) Koscielny 2018 *** * *** 7 Biosynthetic 10 697 121 14% (6–24%) 89.91 El-Gazzaz 2012 *** * *** 7 Infected Mesh Finch 2021 *** – *** 6 Synthetic 5 428 70 9% (0–25%) 92.33 DeNoto 2013 **** * ** 6 Biologic 5 327 8 2% (0–7%) 64.60 Rognoni 2020 *** – *** 6 Biosynthetic 4 222 1 0% (0–2%) 0 Rosen 2017 *** – *** 6 Hernia Recurrence Roth 2021 *** – *** 6 Synthetic 12 940 151 13% (8–19%) 77.59 Messa et al 2019 *** – *** 6 Biologic 14 792 165 20% 69.53 van Rooijen 2020 *** – *** 6 (14–25%) Nockolds 2014 ** – *** 5 Biosynthetic 10 668 86 9% (2–19%) 93.32 Pakula 2020 ** – *** 5 Re-interven- Plymale 2018 ** – *** 5 tion Vauclair 2021 ** – *** 5 Synthetic 5 559 45 6% (2–11%) 66.01 Chamieh 2017 *** – * 4 Biologic 7 348 43 11% (8–15%) 3.38 Biosynthetic 7 451 42 8% (5–12%) 37.40 infected mesh for synthetic and biologic as indicated by the SSI surgical site infection, IC confidence interval LFK index. The obtained LFK index and Doi plot based on the outcome by a subgroup of mesh type is presented in Supplementary file 3. The ‘‘trim and fill’’ procedure did not repair alone without mesh placement. Reported hernia recur- find any possible “missing” study. rence was higher in this study as grade 2 hernias were ruled out: recurrence rate was 21% for non-absorbable synthetic mesh and 28.5% for biologic materials. Pooled estimation Discussion for SSI also showed a trend towards lower rates for bio- synthetic/slowly absorbable mesh repair, with a 14% rate, Based on meta-analysis findings, the rate of hernia recur- compared to 18% for synthetic meshes and a higher rate rence seems lower after biosynthetic/slowly absorbable of 27% for biologic repair. In the same systematic review, mesh, with a pooled proportion of 9% recurrence as opposed Mellia et al. [43] reported a 6.8% rate for SSI. This differ- to synthetic and biologic repair, with a recurrence of 13% ence might come from the percentage of grade 1 hernias and 20%, respectively. Mellia et al. [43] reviewed clinical included in their analysis, associated with a lower risk of outcomes of P4HB biosynthetic mesh and reported a similar postoperative complications and recurrence, with no comor- recurrence of 9.1%. By contrast, the study by Renard et al. bidities or previously infected wounds. They suggest that [41] compared the efficacy of rapidly absorbable polyglactin anti-microbial properties of P4HB for the repair of contami- mesh versus biologic implant and reported a 68% recurrence nated wounds might explain the lower incidence of SSI in for the former. This variability among the results might their study. In addition, available data for seroma revealed come from grouping different prosthetic materials within a rate of 8% for biosynthetic/slowly absorbable mesh, simi- the same mesh category, as their behaviour and health out- lar to the 9% reported for synthetic and biologic materials. comes may differ. Hodgkinson et al. [44] also stratified their In the present analysis, no infected meshes were removed analysis by repair method, although they included suture after repair with biosynthetic/slowly absorbable mesh, with 13 1468 Hernia (2022) 26:1459–1471 Fig. 3  Estimation of infected mesh and hernia recurrence rates by mesh type. a Infected mesh rates by mesh type, b Hernia recurrence rates by mesh type very low heterogeneity (I2 = 0%) among the studies, whereas studies using biological implants in open VHR and ana- rates of 2% and 9% were estimated for biologic and syn- lyzed reporting data on early complications, late complica- thetic meshes, respectively, with high heterogeneity. How- tions, and recurrences. Thus, reasons for the heterogene- ever, this result should be interpreted with caution, given the ity might come from other demographic characteristics small number of studies reporting on the infected mesh. Re- of the patients, different methodologies, repair strategies, intervention resulted in an 8% rate for biosynthetic/slowly and prosthetic materials used in the studies, which lim- absorbable mesh and 11% for biologics. its the comparison of variables between the articles and This analysis, however, presents several limitations. makes it difficult to derive sound conclusions. However, Data have been reported as a percentage of complications as other authors stated, we must bear in mind that “…in (in absolute terms) derived from each mesh, rather than proportional meta-analysis, I2 is usually high. This can be relative odds ratios from studies comparing one mesh ver- due to the nature of proportional data, where little vari- sus another. The reason is the lack of comparative studies ance is observed even in studies with small sample size. of biosynthetic/slowly absorbable mesh with other materi- Moreover, true heterogeneity is expected in prevalence als (most of them are single-arm studies). Only two RCTs and incidence estimates due to differences in the time and [8, 26] were included in the review, although their qual- place where included studies were conducted. Therefore, ity assessment reported a low risk of bias. Most of the high ­I2 in the context of proportional meta-analysis does retrieved publications were retrospective observational not necessarily mean that data is inconsistent. As such, the studies with a moderate risk of bias because of a lack results of this test should be interpreted conservatively” of comparability of the cases, their design, or the type [46]. of analysis. In addition, the I2 statistic reported substan- Moreover, a clear description of the VHWG hernia tial heterogeneity among the studies for the outcomes of grade was only reported in 13 studies [1, 3, 9, 26, 29–31, interest. Sensitivity analyses performed to assess hetero- 33, 34, 37–40]. Thus, the grade had to be derived by the geneity have shown that patient characteristics are not a reviewers from the patient and wound characteristics. In source of this heterogeneity. Similar results are reported our search of literature, we sought to select comparative in the review by Samson et al. [45]. This review included studies for synthetic meshes and biologic implants. On 13 Hernia (2022) 26:1459–1471 1469 the other hand, for biosynthetic/slowly absorbable meshes, Declarations given the lack of comparative publications, we allowed for the inclusion of single-arm studies. The inclusion of these Conflict of interest This work received financial support from the articles could lead to a higher heterogeneity in the results. Spanish Association of Surgeons (AEC). The authors declare that they have the following conflicts of interest: S. Morales-Conde has In addition, there is no universal acceptance of the VHWG received honoraria for consultancy, lectures, support for travels and grading scale [13]. participation in review activities from BD-Bard, Medtronic, Johnson Also, a recent review includes 274 studies with 28,868 & Johnson, Gore, BBraun, Dipro, Baxter, Olympus, Stryker and Storz. patients to describe till 63 individual predictors for M. López-Cano has received honoraria for consultancy, lectures, sup- port for travels and participation in review activities from BD-Bard, hernia recurrence [47], but we have only considered in Medtronic, Gore and Abex. P. Hernández-Granados has received our methodology 5 selected items (seroma formation, honoraria for consultancy and lectures from BD and BBraun. M. Ver- wound infection, mesh removal, hernia recurrence and daguer does not report conflicts of interest. L. Tallón-Aguilar has re- ceived honoraria for lectures and support for travels from Medtronic, re-intervention), in our opinion most important and Johnson & Johnson, Gore, Dynamesh, Vifor Pharma, Rovi and Abex. appropriate to reach our goal. Finally, our study does not include an analysis of Human and animal rights, and Informed consent Since it is a propor- data on preclinical testing and animal studies, which tional meta-analysis, we consider that it does not require an ethical approval, human and animal rights or informed consent. We do not could supplement the scientific evidence for safety and use confidential information, only public information collected in the effectiveness. articles included in the review. In conclusion, meta-analysis did not show meaningful differences among materials; although, it seems to be a Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, trend towards lower recurrence and complication rates after adaptation, distribution and reproduction in any medium or format, grade 2–3 VHR using biosynthetic/slowly absorbable mesh as long as you give appropriate credit to the original author(s) and the reinforcement. Therefore, biosynthetic/slowly absorbable source, provide a link to the Creative Commons licence, and indicate mesh could be an interesting option as an alternative to if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless synthetic meshes and biologic implants in 2–3 grades. Also, indicated otherwise in a credit line to the material. If material is not these results should be interpreted with caution because of included in the article's Creative Commons licence and your intended the lack of direct comparisons between biosynthetic/slowly use is not permitted by statutory regulation or exceeds the permitted absorbable versus synthetic meshes and/or biological use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://​creat​iveco​mmons.​ implants. Differences in patient characteristics and the org/​licen​ses/​by/4.​0/. selection bias in single-arm observational studies make it difficult to have conclusive results. Future research should focus on randomized controlled trials with defined control groups to allow for head-to- References head comparisons among the different mesh materials like 1. Vauclair E, Bert M, Facy O, Cheynel N, Rat P, Ortega-Deballon COMpACT-BIO study (RCT NCT04597840, clinicaltrials. 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