This randomized controlled trial was conducted at the Department of Surgery, Hayatabad Medical Complex, Peshawar. Eligible patients with incisional hernia were randomized into two parallel groups: sublay mesh repair and onlay mesh repair. Procedures were performed by a single experienced general surgeon. Postoperative complications were assessed by an independent surgeon blinded to the type of procedure. Patients were followed for a period of three months to evaluate safety and recurrence outcomes.

Incisional hernia is a frequent postoperative complication following abdominal surgery and represents a significant source of morbidity due to discomfort, impaired quality of life, and risk of recurrence. Mesh reinforcement has become the standard approach for incisional hernia repair; however, the optimal anatomical position of mesh placement remains debated. Among the commonly used techniques, onlay mesh repair involves placement of mesh over the anterior rectus sheath, while sublay mesh repair places the mesh in the retromuscular preperitoneal plane. Each technique differs in operative dissection, tissue handling, and potential risk of postoperative complications.

This randomized controlled trial was conducted at the Department of Surgery, Hayatabad Medical Complex, Peshawar, to compare postoperative outcomes of onlay versus sublay mesh repair in patients undergoing elective incisional hernia repair. Adult patients aged 18 to 60 years presenting with incisional hernia and meeting predefined eligibility criteria were enrolled after providing written informed consent. Patients with recurrent, strangulated, or obstructed hernias, severe comorbid conditions, high anesthetic risk, or morbid obesity were excluded to minimize confounding factors.

Eligible participants were randomly allocated into two parallel groups using a lottery method. Patients assigned to Group A underwent sublay mesh repair, while those in Group B received onlay mesh repair. All surgical procedures were performed by a single experienced general surgeon to ensure procedural consistency. Standardized perioperative care protocols were followed for all patients.

Postoperatively, patients were monitored during hospital admission and followed in outpatient clinics for a period of three months. Assessment of postoperative complications, including wound infection, seroma, hematoma, and hernia recurrence, was carried out by an independent surgeon who was blinded to the surgical technique used. This masking approach was adopted to reduce assessment bias.

The primary objective of the study was to compare the overall postoperative complication rates between the two mesh placement techniques. Secondary objectives included evaluation of individual complication rates and recurrence during the follow-up period. Data were collected using a structured proforma and analyzed using standard statistical methods to determine differences between groups.

The findings of this study aim to provide evidence-based guidance regarding the safety and effectiveness of mesh placement techniques in incisional hernia repair and to assist surgeons in selecting an optimal approach that minimizes postoperative complications and recurrence.

Inclusion Criteria:

• Adults aged 18-60 years.
• Patients diagnosed with primary incisional hernia on clinical examination.
• Hernia suitable for open surgical repair with mesh.
• Both male and female patients.
• Patients able and willing to provide written informed consent.

Exclusion Criteria:

• Obstructed or strangulated hernia on presentation.
• Recurrent incisional hernia.
• Patients with BMI > 40.
• Patients with debilitating chronic diseases, including:
• Chronic liver disease
• Chronic renal impairment
• Chronic cardiac disease
• Chronic pulmonary disease
• Patients with American Society of Anesthesiologists (ASA) physical status ≥ 3.
• Patients unfit for general anesthesia.
• Patients unable or unwilling to follow up for postoperative assessment.

The decision to share individual participant data (IPD) from this study has not yet been finalized. Considerations regarding patient privacy, data de-identification, and institutional policies on data sharing are still under review. Once these factors are addressed, a detailed plan for data sharing may be developed in compliance with ethical guidelines and institutional requirements.

This was an open-label study. Due to the nature of the surgical interventions, neither participants nor healthcare providers nor outcome assessors were blinded to the assigned intervention.