Prophylactic mesh reinforcement at emergency midline laparotomy: a systematic review and meta-analysis with pre-specified subgroup analysis of contaminated and dirty abdominal wounds (CDC Class III–IV)

PURPOSE: To evaluate the efficacy and safety of prophylactic mesh reinforcement (PMR) at the closure of emergency midline laparotomy (EML), with a pre-specified subgroup analysis of contaminated and dirty wounds (CDC class III-IV). METHODS: PRISMA 2020-compliant review (PROSPERO CRD420261324766; OSF 10.17605/OSF.IO/ZX2BG; amendments registered before data extraction). PubMed/MEDLINE, Embase, Cochrane CENTRAL, Scopus and Web of Science were searched (January 2015-March 2026). RCTs and comparative cohort studies reporting incisional hernia (IH) at ≥ 12 months were eligible; bias was assessed with ROB-2/ROBINS-I. Random-effects meta-analysis used the REML estimator with Hartung-Knapp-Sidik-Jonkman correction. A pre-specified Borenstein interaction test compared CDC class I-II with III-IV; trial sequential analysis (TSA) and GRADE were applied. RESULTS: Five studies (4 RCTs; 1 cohort; n = 617) were included. PMR was associated with a reduction in IH (pooled OR 0.221, 95% CI 0.122-0.402 [Knapp-Hartung]; 0.101-0.483 under the conservative truncated variant; I2 = 0%); because control-arm event rates exceeded 10%, this corresponds to an approximate RR of ~ 0.36 (0.28-0.38). The RCT-only analysis was concordant (OR 0.179, 95% CI 0.074-0.435). TSA gave an accrued information size of 617 versus a required ~ 151 (409%), interpreted only as numerical sufficiency, not firm evidence. The CDC interaction was non-significant and underpowered (z = 0.327, p = 0.743). Seroma was significantly increased (k = 4; OR 3.980, 95% CI 1.924-8.234; 1.06-14.94 under the conservative variant), whereas deep SSI was non-significant and underpowered (OR 0.991). GRADE: LOW to VERY LOW. CONCLUSION: PMR at EML closure was associated with a consistent IH reduction across CDC classes; however, contaminated-wound evidence is sparse, the subgroup interaction is exploratory, non-significant and underpowered, and the safety profile - particularly deep SSI - remains uncharacterized. Seroma was significantly increased. Given LOW-VERY LOW certainty, these hypothesis-generating findings should not change practice and support an adequately powered multicentre RCT in CDC class III-IV wounds. TRIAL REGISTRATION: PROSPERO CRD420261324766 (registered 23 February 2026); OSF Registries https://doi.org/10.17605/OSF.IO/ZX2BG .