The study is a double-blinded randomized trial, comparing the widely recommended midline laparotomy closure using a running slowly absorbable suture to closure with the aid of a permanent sub-lay mesh (Parietex Progrip), in patients undergoing midline laparotomy for clean-contaminated surgery. From January 2016 to June 2018, a series of 200 patients were included. All patients were operated in a single surgical Unit, located in Lacco Ameno (Naples) at the only Hospital of the island. All patients undergoing 'open' midline laparotomy for abdominal surgery in clean-contaminated fields were included. All patients subscribed informed consent. Authorization was requested from the local regional Ethics Committee. Exclusion criteria were: age \< 18 years; life expectancy \< 24 months (as estimated by the operating surgeon), pregnancy, immunosuppressant therapy within 2 weeks before surgery, clean, contaminated and dirty wounds, wound length\<10 cm. Patients were randomized in two groups (Group A, receiving primary closure; Group B, receiving mesh supported closure in a Sublay fashion). Randomization was obtained just before abdominal wall closure through number (1 to 200) extraction by Operative room nurse (Even: Group A vs Odd: Group B). All patients enrolled in the study were followed up sending a letter to their General Practitioner. Outpatient clinic controls were done by surgeons/surgical residents/General Practitioner blinded for the procedure.

Technical details Group A. Primary closure of midline laparotomy. The midline fascia is closed using a double layer running slowly absorbable suture. Above arcuate line, the posterior layer was performed suturing peritoneum and posterior rectus sheath; below arcuate line posterior layer was performed suturing peritoneum and trasversalis fascia. Anterior layer was performed suturing anterior rectus sheath. Suture length to wound length ratio of 4:1 as recommended (not routinely measured). Subcutaneous tissue and skin are closed according to the first surgeon's preference.

Group B. Sub-lay mesh supported closure A 4 cm space is created between posterior rectus sheath and rectus muscle, widening 2 cm at each side of midline. Both posterior rectus sheath edges are sutured using a running slowly absorbable suture. Above the arcuate line, the posterior layer was performed suturing peritoneum and posterior rectus sheath; below the arcuate line, the posterior layer was performed suturing peritoneum and trasversalis fascia. The anterior layer was performed suturing anterior rectus sheath. A suture length to wound length ratio of 4:1 is recommended (not routinely measured). A 4-cm Parietex Progrip Mesh strip was placed between the posterior rectus sheath and rectus muscle with an overlap of at least 2 cm at each side, sutureless. The not gripping face of the mesh was positioned on the posterior rectal sheat to allow the muscle to become in contact with the grips. In laparotomies \>20 cm two stripes of 15 cm each were designed. The midline anterior rectus sheath was closed using a running slowly absorbable suture covering the mesh. A suture length to wound length ratio of 4:1 is recommended (not routinely measured). Subcutaneous tissue and skin closure were up to the surgeon preference.

Endpoints Primary endpoint was Incisional Hernia rate. Patients were postoperatively examined at 3, 6, 12 and 24 months. Both clinical examination and ultrasound imaging were performed in all patients at follow-up. Physicians were blind about which Group (A or B) the patients had been placed. Incisional Hernia was clinically defined as any visible or palpable ''blowout'' in the midline abdominal scar. At 3, 6, 12 and 24 months ultrasound imaging was performed to examine the midline for all patients with symptomatic or asymptomatic, providing any valuable information about Incisional Hernia onset. Size and location of all ultrasound detected Incisional Hernia were registered, as well as any other patient's complaint. The ultrasonic criteria of Incisional Hernia were a visible gap within the abdominal wall and/or ''tissue moving through the abdominal wall by Valsalva manoeuvre'' and/or a detectable ''blowout''. Incisional Hernia was diagnosed if clinical criteria and/or ultrasound criteria were fulfilled. The study was not designed to discriminate single or multiple defects. The study will be completed at 2 years' follow up. Secondary endpoints included the incidence of wound events. Wound events were classified as surgical site infections according to Clavien Dindo criteria (superficial, deep or organ space). Surgical site events were reported according to the Ventral Hernia Working Group definitions. Actions for wound events were categorized as follows: antibiotics only, bedside wound interventions, percutaneous manoeuvres or surgical debridement.

Blinding Process

Patients, care providers, staff collecting data, and those assessing the endpoints were all blinded to treatment allocation. Patients were blinded to the surgical procedure performed until the final assessment of the study endpoints. Because the blinding of the operating surgeons was not feasible, they were not involved in the data collection and outcome assessment. Physicians in charge of patients' management were not involved in the operating room and were blinded to the intervention. The data were collected and analyzed by physicians who were not involved in the patient's management during the whole Randomized trial.