The research hypothesis for this study is to possibly reduce the incidence of incisional hernia 2 years postoperatively after midline laparotomy for treatment of aortic aneurysm from 25% to 5% by mesh augmentation during closure of the laparotomy. The study is designed as a prospective randomised multi-centre trial, randomising patients in 2 groups concerning the surgical technique of the closure of the abdominal wall.