Prevention of incisional hernia with prophylactic onlay and sublay mesh reinforcement vs. primary suture only in midline laparotomies (PRIMA): long-term outcomes of a multicentre, double-blind, randomised controlled trial

Background: Incisional hernia occurs approximately in 40% of high-risk patients after midline laparotomy. Prophylactic mesh placement has shown promising results, but long-term outcomes are needed. The present study aimed to assess the long-term incisional hernia rates of the previously conducted PRIMA trial with radiological follow-up. Methods: In the PRIMA trial, patients with increased risk of incisional hernia formation (AAA or BMI ≥27 kg/m²) were randomised in a 1:2:2 ratio to primary suture, onlay mesh or sublay mesh closure in three different countries in eleven institutions. Incisional hernia during follow-up was diagnosed by any of: CT, ultrasound and physical examination, or during surgery. Assessors and patients were blinded until 2-year follow-up. Time-to-event analysis according to intention-to-treat principle was performed with the Kaplan–Meier method and Cox proportional hazard models. Trial registration: NCT00761475 (ClinicalTrials.gov). Findings: Between 2009 and 2012, 480 patients were randomized: 107 primary suture, 188 onlay mesh and 185 sublay mesh. Five-year incisional hernia rates were 53.4% (95% CI: 40.4–64.8), 24.7% (95% CI: 12.7–38.8), 29.8% (95% CI: 17.9–42.6), respectively. Compared to primary suture, onlay mesh (HR: 0.390, 95% CI: 0.248–0.614, p < 0.001) and sublay mesh (HR: 0.485, 95% CI: 0.309–0.761, p = 0.002) were associated with a significantly lower risk of incisional hernia development. Interpretation: Prophylactic mesh placement remained effective in reducing incisional hernia occurrence after midline laparotomy in high-risk patients during long-term follow-up. Hernia rates in the primary suture group were higher than previously anticipated. Funding: B. Braun.