This study was designed as a retrospective multicenter case series combined with a structured expert consensus analysis. Participating abdominal wall surgery centers contributed cases of complex abdominal wall reconstruction in which a reinforced tissue matrix (RTM) mesh (OviTex®, Tela Bio Inc., Malvern, PA, USA) had been implanted.

Clinical data were entered into a standardized database and included patient demographics, comorbidities, abdominal wall defect characteristics, operative details, perioperative findings, and postoperative outcomes. Recorded variables included age, sex, body mass index (BMI), ASA classification, comorbidities associated with surgical site occurrence (SSO) or recurrence risk, defect type and size, contamination status, operative technique, mesh type and size, postoperative complications, recurrence, mortality, and follow-up duration.

Contamination status was classified according to the Centers for Disease Control and Prevention (CDC) surgical wound classification. Class I was considered clean, class II clean-contaminated, class III contaminated, and class IV dirty/infected. For descriptive analyses, the term ‘contaminated or potentially contaminated’ encompassed CDC classes II–IV.

Mesh infection/colonization was defined as a clinically suspected mesh-associated infection with local signs of infection and/or microbiological evidence of microbial colonization involving the mesh or the mesh-containing wound.

Cases were categorized according to established abdominal wall complexity criteria described in the literature [1, 3]. Complexity determinants were grouped into four domains: defect size and location, contamination or soft tissue condition, patient-related risk factors, and clinical scenario or surgical history. Individual cases were assessed based on documented operative and clinical findings.

Large fascial defects and true loss of abdominal wall substance were considered distinct morphological complexity features. However, for the indication analysis, these scenarios were grouped when they resulted in a residual abdominal wall defect that could not be closed primarily despite appropriate reconstructive measures and therefore required mesh-based reconstruction or bridging. Thus, the combined indication category reflects the reconstructive problem rather than implying morphological equivalence between a large fascial defect and true tissue loss.

Open abdomen-related reconstruction comprised two distinct clinical scenarios [1]: definitive reconstruction during an ongoing open abdomen treatment episode when primary fascial closure could not be achieved, resulting in a residual ventral abdominal wall defect requiring RTM bridging; and [2] secondary abdominal wall reconstruction of a planned ventral hernia resulting from previous open abdomen treatment. Accordingly, a history of open abdomen treatment was not considered an indication for RTM use per se, but represented a complexity feature when associated with a residual abdominal wall defect requiring subsequent reconstruction.

Seven experienced abdominal wall surgeons independently reviewed all cases and evaluated the appropriateness of RTM implantation. All panel members had contributed cases to the study cohort and had clinical experience with RTM implantation. Each expert evaluated the complete case series, including cases contributed by their own institution. Accordingly, the assessment represents a structured evaluation among surgeons experienced with RTM rather than an independent external validation of its indications.

For the consensus assessment, each case was presented to the expert panel using a standardized case summary including relevant patient characteristics, comorbidities, abdominal wall defect characteristics, contamination status, previous abdominal wall surgery and mesh-related complications, and the operative/reconstructive setting. The experts were asked to assess retrospectively whether, based on the clinical information available for each case, the use of an RTM represented a reasonable reconstructive option. Importantly, the assessment did not address whether RTM was superior to alternative mesh materials, but whether its use was considered justifiable within the respective clinical scenario.

Ratings were recorded as binary variables (0 = no indication, 1 = indication for RTM use). Non-binary or incomplete responses were excluded from analysis. Consensus was predefined as agreement among at least 70% of raters (five of seven) either supporting or opposing RTM implantation. In addition, cases were stratified according to the primary documented indication for RTM use to assess indication-specific consensus patterns.

The primary outcome was expert agreement regarding the appropriateness of RTM use within the respective clinical scenario. Additional descriptive outcomes included surgical site infection (SSI), mesh infection, hernia recurrence, reoperation, mortality, operative strategies, contamination status, and complexity criteria associated with RTM implantation.

Follow-up was based on routine clinical care and was therefore not standardized across participating centers. Patients attending clinical follow-up underwent physical examination and generally abdominal wall ultrasonography. In some patients, follow-up information was obtained by telephone; patients reporting symptoms suggestive of recurrence were invited for further clinical assessment. Hernia recurrence was defined as a clinically or radiologically detected recurrent abdominal wall defect at the site of the index reconstruction. Systematic imaging at predefined intervals was not mandated.

Statistical analyses were performed using Microsoft Excel, SPSS version 26 (IBM Corp., Armonk, NY, USA), and R (R Foundation for Statistical Computing, Vienna, Austria). Continuous variables were assessed for normality using the Shapiro–Wilk test and are presented as mean ± standard deviation (SD) or median with range, as appropriate. Categorical variables are reported as absolute numbers and percentages.

Interrater agreement among expert raters was assessed using Fleiss’ kappa statistic for multiple raters. Kappa values were interpreted according to the Landis and Koch classification.

The study involving human participants was reviewed and approved by the Ethics Committee of the University of Regensburg (reference no. 26-4640-104). The study was performed in accordance with the ethical standards of the Declaration of Helsinki and its later amendments. Due to the retrospective nature of the study and the use of anonymized clinical data, the requirement for written informed consent was waived by the Ethics Committee.

A total of 74 patients were included (Table 1). Mean age was 63.9 ± 12.0 years, and median body mass index (BMI) was 30.2 kg/m² (range 17.0–54.0). The cohort consisted of 41 women (55.4%) and 33 men (44.6%). Overall, 76.7% of patients presented with at least one risk factor associated with surgical site occurrence or recurrence. The most common comorbidities were obesity (30.1%), diabetes mellitus (28.8%), nicotine abuse (27.4%), and chronic obstructive pulmonary disease (19.2%). Most patients were classified as ASA II (52.7%) or ASA III (40.5%).

The primary indication for surgery was hernia repair in 82.4% of cases, followed by open abdomen closure in 12.2%. According to CDC wound classification, 50.0% of procedures were classified as clean (class I), 31.1% as clean-contaminated (class II), 14.9% as contaminated (class III), and 4.1% as dirty/infected (class IV).

Based on the European Hernia Society classification, midline hernias were present in 86.5% and lateral hernias in 20.3% of cases. Median hernia width was 11 cm (range 0–30 cm), and median defect area was 129 cm² (range 0–900 cm²). Among patients with available width classification, 56.9% were classified as W3 defects.

Recurrent hernias were present in 20.3%, frequently after previous mesh repair. Additional complex scenarios included loss of domain, prior open abdomen treatment, mesh infection, enterocutaneous fistula, and incarcerated hernia with bowel obstruction. Overall, most patients fulfilled multiple complexity criteria across several domains of the abdominal wall complexity framework, particularly defect size, contamination-related conditions, and previous surgical repair history (Table 2).

The most commonly used implant was OviTex 2S (60.8%), followed by OviTex LPR (20.3%). Mesh sizes ranged from 10 × 12 cm to 45 × 25 cm.

The documented indications for RTM implantation are summarized in Table 3. The most frequent indication was large fascial defects or tissue loss (40.5%), followed by contaminated or potentially contaminated operative fields (31.1%). Additional indications included high-risk patient profiles (16.2%), previous mesh implantation or recurrent hernia (14.9%), bridging situations or loss of domain (9.5%), and open abdomen or laparostoma reconstruction (8.1%).

Intraperitoneal onlay mesh (IPOM) repair was the most frequently performed technique (46.6%), followed by retromuscular reconstruction (20.5%). Bridging repair was required in 12.3% of patients. Advanced reconstructive strategies including transversus abdominis release (TAR), component separation, fascial traction, botulinum toxin application, and staged reconstruction using negative pressure wound therapy were performed in 16.4% of cases.

Table 4 summarized the outcome findings. Median hospital stay was 8 days (range 2–83 days). In-hospital mortality was 4.1%. Surgical site infection occurred in 20.3% of patients with available follow-up.

Mesh infection/colonization was observed in 5/64 patients (7.8%). All infections were managed without operative revision or mesh explantation using local wound management, including partial wound opening and drainage where required. In one patient with a nearby urostomy, Candida colonization/infection involving the mesh was microbiologically confirmed and successfully treated with an eight-week course of fluconazole without subsequent mesh explantation.

Major complications (Clavien–Dindo ≥ IIIb) occurred in 38.3% of patients with available complication data.

Complete follow-up data were available for 65 of 74 patients (87.8%), with a median follow-up duration of 12 months (range 1–36 months). Hernia recurrence occurred in 12.3% of patients, including 3.1% requiring reoperation.

A total of 511 valid ratings from seven expert surgeons were analyzed (Table 5). Seven individual ratings were unavailable or incomplete and were excluded according to the predefined analysis rules. Overall, 68.9% of ratings supported RTM implantation. Using the predefined threshold of ≥70% agreement, consensus supporting RTM use was reached in 37 cases (50.0%), whereas 34 cases (45.9%) showed no clear consensus. Consensus against RTM implantation was reached in 3 cases (4.1%).

Agreement was highest in cases involving infection or contamination, particularly when combined with large fascial defects. In contrast, augmentation or bridging without infection demonstrated substantially lower consensus rates. Overall interrater agreement was fair (Fleiss’ κ = 0.34). The fair interrater agreement should be interpreted in the context of a heterogeneous real-world cohort and likely reflects indication-dependent decision making rather than a uniformly applied RTM indication algorithm.

Several limitations of this study should be acknowledged. First, the analysis is based on a retrospective multicenter case collection and therefore reflects selected clinical scenarios rather than a consecutive patient cohort. Second, surgical techniques and reconstructive strategies were heterogeneous, reflecting real-world decision-making in complex abdominal wall reconstruction but limiting direct comparison between approaches. Third, follow-up duration was variable and relatively limited in some patients, which may underestimate long-term recurrence rates. In addition, the absence of a comparative control group precludes conclusions regarding superiority or equivalence compared with alternative reconstructive materials. Finally, the expert consensus analysis reflects the judgment of a limited number of abdominal wall surgeons and is inherently susceptible to expert-selection and preference bias. Individual experience with RTM, biologic, biosynthetic, and permanent synthetic meshes, as well as different institutional approaches to mesh use in contaminated fields, may have influenced the ratings. Moreover, all experts had contributed cases to the study and also assessed cases originating from their own institutions, introducing a potential confirmation bias. The consensus assessment should therefore not be interpreted as an objective validation of RTM indications, but as an exploratory assessment of current expert perception.

Furthermore, follow-up assessment was not standardized and did not include systematic imaging in all patients. Therefore, asymptomatic or occult recurrences may have remained undetected, and the reported recurrence rate should primarily be interpreted as reflecting clinically detected recurrence. The relatively short median follow-up of 12 months also limits assessment of late recurrence and late mesh-related infection.