After laparotomy, treating large incisional hernias (width \>= 10cm) proves challenging due to the progressive retraction of lateral abdominal muscles and the separation of rectus muscles. This width is a significant risk factor for repair failure and recurrence. High rates of severe postoperative morbidity, up to 50%, are reported, linked to dissection extent, increased muscular tension, and abdominal pressure. Reconstructing normal anatomy by bringing muscles together may be impossible, leading to the use of complex procedures like component separation techniques (CST), involving large aponeurotomy for muscle relaxation. Intramuscular injection of botulinum toxin A (BTA) induces reversible flaccid paralysis, with potential benefits in hernia closure, known as chemical CST. Retrospective studies suggest reduced muscle retraction and facilitated closure without specific morbidity. Prehabilitation with BTA aims to reduce surgical morbidity compared to repair and CST. The prospective evaluation of BTA's clinical benefits, including reduced postoperative morbidity, pain, successful abdominal closure, and decreased IH recurrence risk, is lacking. A prospective randomized double-blind placebo-controlled trial is proposed to demonstrate BTA's efficacy. The hypothesis is that BTA injection before IH repair is more effective than a placebo in reducing postoperative morbimortality. Secondary expectations include a significant reduction in complete closure of the abdominal wall without CST.