Risk Factors for Mesh Infection After Abdominal Wall Reconstruction

Design and setting. A prospective, single-centre observational cohort study conducted at a tertiary referral hernia and abdominal wall surgery unit (Department of Surgery, Faculty of Medicine, Minia University, Egypt). Consecutive eligible adults undergoing AWR with mesh are enrolled at the time of surgery and followed prospectively. No study-specific intervention is imposed; surgical and perioperative management follow routine unit practice, and exposures (candidate risk factors) are observed rather than assigned.

Study period. The study runs for 24 months in total, from 15 August 2026 to 15 August 2028. Consecutive enrolment takes place over the first 12 months (15 August 2026 - 15 August 2027); each participant is then followed for 12 months, so that the last enrolled participant completes follow-up at the end of month 24. The 90-day primary-outcome window closes for the final participant in November 2027.

Objectives. The primary objective is to identify the independent risk factors associated with mesh-related infection within 90 days of AWR. Secondary objectives are to estimate the cumulative incidence and timing of mesh infection; to characterise its microbiology and the proportion managed by mesh salvage versus partial or complete explantation; to describe surgical site occurrence (SSO) and SSO requiring procedural intervention (SSOPI); to derive an exploratory, prespecified risk-stratification model and assess its discrimination and calibration; and to evaluate the association of mesh infection with hernia recurrence and reoperation at 12 months.

Primary outcome. Mesh-related infection within 90 days, confirmed by at least one of: purulent drainage from a peri-mesh space in contact with the prosthesis; positive microbiological culture from peri-mesh fluid, explanted mesh or an image-guided/operative peri-mesh specimen; cross-sectional imaging (preferably contrast-enhanced CT) demonstrating a peri-mesh collection or abscess with clinical signs of infection; or the need for operative or percutaneous intervention directed at infected mesh. Superficial incisional infection without mesh involvement is recorded separately, and deep or organ/space infection is coded using CDC/NHSN criteria.

Candidate predictors. Up to 18 prespecified variables across four domains - patient (age, sex, BMI/obesity, active smoking, diabetes and HbA1c, serum albumin, ASA class, immunosuppression, COPD), defect (defect width by EHS grouping, recurrent hernia, loss of domain, CDC wound class, VHWG grade, stoma/parastomal defect), operative (mesh type and position, component separation including transversus abdominis release, operative time, concomitant bowel procedure, estimated blood loss, drain use) and perioperative (antibiotic-prophylaxis appropriateness, intraoperative normothermia and glycaemia, transfusion, early SSO).

Follow-up. Participants are reviewed at baseline/operation and at 7-10 days, 30 days, 90 days (primary outcome), 6 months and 12 months. Outcome events are adjudicated against the prespecified definitions by two investigators, with disagreements resolved by consensus.

Sample size and analysis. Target enrolment is 420 participants (≈380 evaluable after ≈10% attrition; ≈53 expected events), sized to support a stable multivariable logistic regression model (events-per-variable ≥10) and precise estimation of infection incidence. Candidate predictors are analysed by univariable tests and multivariable logistic regression with adjusted odds ratios and 95% confidence intervals; Firth penalised likelihood or LASSO is used where events are limited. Model discrimination (c-statistic) and calibration (Hosmer-Lemeshow test, calibration plot) are assessed with optimism-corrected internal validation by bootstrapping. Prespecified secondary and sensitivity analyses include time-to-event modelling and subgroup analyses by mesh type, mesh position and wound contamination class.