TITLE: A Prospective Study Comparing Onlay with Retrorectus Mesh Placement in Ventral Hernia Repair at the Lagos University Teaching Hospital BACKGROUND: A hernia is an abnormal protrusion of a whole or part of an organ or tissue through a defect, weakness or potential weakness in the wall surrounding it. Although hernias do occur at various sites of the body, these defects most commonly involve the abdominal wall. A ventral hernia therefore is a protrusion through the anterior abdominal wall fascia and the estimated incidence is 15-20% of the population. Ventral hernia incidence has been on a rising trend in our environment with attendant complications that usually require emergency surgeries, resulting in increased cost of management and morbidity. Mesh hernioplasty has been shown to be very crucial in the management of ventral hernias and also has been confirmed to be superior to tissue repair, however there has been poor documentation of the optimal position of mesh during repair in our environment. The aim of this study was to determine the pattern of distribution and predisposing factors, then compare the outcome of onlay with retrorectus mesh placement for ventral hernia repair in our patients with appropriate recommendations. AIM AND OBJECTIVES: This study aims to compare the outcome of onlay and retrorectus placement of prosthetic mesh in ventral hernia repair PATIENTS, MATERIALS AND METHOD: This was a prospective comparative interventional study involving patients with ventral hernia that presented to the General Surgery Unit (clinics, emergency, referrals) of The Lagos University Teaching Hospital (LUTH). Approval for the study was issued by LUTH Health Research Ethics Committee with approval number ADM/DCST/HREC/APP/2806 and written informed consent was obtained from participants before progression of study. Inclusion criteria were all patients with uncomplicated ventral hernias xv with >3cm fascial defect and aged 18years and above. Exclusion criteria included pregnancy, complicated hernias, ongoing sepsis, inability to undergo general anaesthesia and non-consent. Potential participants were approached and study explained to them with benefits and possible complications outlined. Willing participants were subsequently recruited to the study. Estimating the sample size (N) with a known standard deviation at 95% confidence interval and type one error of 0.05, total number of participants required was 98 patients and were randomized into 2 groups A and B of 49 participants each.. A study proforma for data capturing was used. Data obtained were analyzed with Statistical Package for Social Sciences version 22 for Windows and results were presented in tables and charts. Categorical variables were expressed in frequency and percentage and displayed in table and charts while quantitative variables were expressed with mean, median and mode as appropriate. RESULTS: A total of 98 study participants were analyzed (49 participants were in group A (Onlay) and 49 participants in group B (Retro-rectus).). The study consisted of 62 (63.2%) females and 36 (36.7%) males. The mean age of the participants were 44.71 ± 16.27 years for group A compared with 42.08 ± 12.68 years for group B, which was not statistically significant at p-value of 0.348. Across the groups, the distribution of the hernia according to types were incisional 66 patients (67%) and primary 32 patients (33%). Of the patients with incisional hernia, 4 (6.0%) had recurrent hernia and a greater proportion 41 (41.8%), were from previous midline laparotomy. Previous abdominal surgery accounted for 73.5% of cases and was an absolute factor for incisional hernia. There was statistically significant difference in the drain effluents between the participants with Onlay and Retro-rectus repair (p = <0.001). The median perception of pain was higher in Onlay group compared with recto-rectus participants, 8.0/10.0 (6.0 – 8.0) versus 5.0/10.0 (4.0 – 5.0) at p-value 0.001. There was significant difference in time to ambulation post operatively between Onlay group and Retro-rectus group 24.0 (15.0 – 27.0) versus 48.0 (36.0 – 48.0) hours (p xvi = <0.001). The mean duration of admission in the hospital was also observed to show statistically significant difference between groups A and B, with an average of 9.5 ± 2.9 days for group A as compared to 5.6 ± 1.5 days for group B (p = <0.001). Furthermore, the time to return to normal daily activities were also statistically significant between the two groups, with an average of 12.0 weeks (8.0 – 12.0) for A and 4.0 weeks (4.0 – 6.0) for B (p = <0.001). The most common complication reported was seroma which was seen in 44 (44.9%) participants, among which 43 (43.9%) participants had onlay and only 1 (1.0%) participant had retrorectus mesh placement (p = <0.001). There was also a better wound outcome among retrorectus group with majority having a Southampton class 0 wound (73.5%) compared to onlay with Southampton class IIA (26.5%) (p = <0.001)