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Background Incisional hernias occur after up to 40 per cent of laparotomies. Recent RCTs have demonstrated the role of prophylactic mesh placement in reducing the risk of developing an incisional hernia. An onlay approach is relatively straightforward; however, a variety of techniques have been described for mesh fixation. The biomechanical properties have not been interrogated extensively to date. Methods This ex vivo randomized controlled trial using porcine abdominal wall investigated the biomechanical properties of three techniques for prophylactic onlay mesh placement at laparotomy closure. A classical onlay, anchoring onlay, and novel bifid onlay approach were compared with small-bite primary closure. A biomechanical abdominal wall model and ball burst test were used to assess transverse stretch, bursting force, and loading characteristics. Results Mesh placement took an additional 7–15 min compared with standard primary closure. All techniques performed similarly, with no clearly superior approach. The minimum burst force was 493 N, and the maximum 1053 N. The classical approach had the highest mean burst force (mean(s.d.) 853(152) N). Failure patterns fell into either suture-line or tissue failures. Classical and anchoring techniques provided a second line of defence in the event of primary suture failure, whereas the bifid method demonstrated a more compliant loading curve. All mesh approaches held up at extreme quasistatic loads. Conclusion Subtle differences in biomechanical properties highlight the strengths of each closure type and suggest possible uses. The failure mechanisms seen here support the known hypotheses for early fascial dehiscence. The influence of dynamic loading needs to be investigated further in future studies.

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