Full bilateral TAR was performed to restore medial compliance and rebalance abnormal lateral traction [1,2,3,4]. Posterior rectus sheaths were opened, retromuscular planes were developed bilaterally, and the transversus abdominis muscle was divided under direct vision. This enabled controlled medialization of the rectus muscles and creation of an extensive retromuscular space.

A 40 × 40 cm macroporous polypropylene mesh was positioned in the retromuscular space, providing wide overlap and tension-free midline reconstruction [2, 5,6,7]. Reconstruction was accomplished anatomically. However, the lateral compartments stayed notably tight.

In this setting, BTA was not used to achieve fascial closure, which had already been surgically secured, but to protect the reconstruction during the early postoperative period. A total of 125 units of botulinum toxin A were injected intraoperatively into six predefined sites within the internal and external oblique muscle sheaths (three per side). Injection sites were distributed longitudinally along the lateral abdominal wall under direct anatomical guidance (Fig. 1).

Schematic and intraoperative views of the abdominal wall reconstruction. a Schematic illustration of six intraoperative botulinum toxin A injection sites within the internal and external oblique muscle sheaths. The diagram shows the anatomy of the lateral abdominal wall, the distribution of injections, and the retromuscular space created for mesh placement. b Intraoperative photograph showing bilateral transversus abdominis release, demonstrating the fully developed retromuscular space and placement of the macroporous polypropylene mesh before midline fascial closure

Given the delayed onset of BTA action, chemical modulation of lateral muscle tone was designed to decrease traction forces during the critical 7–14-day healing period, when the risk of recurrent dehiscence is highest [8, 9].

Preoperative administration is a more established use of BTA in elective complex ventral hernia repair, where the goal is to facilitate fascial closure by gradually elongating lateral muscles over several days to weeks. In this case, this approach was not feasible because reconstruction was performed in an urgent salvage setting after repeated postoperative failures, without a preoperative window for chemical component separation. Therefore, intraoperative BTA was not intended to support immediate closure but rather to enable delayed reduction of lateral wall tone during the early, vulnerable healing phase. We acknowledge that the pharmacodynamic effect is not immediate and that the benefit in this setting remains theoretical and hypothesis generating.

Postoperative management included hemodynamic stabilization, targeted antibiotic therapy for extended-spectrum beta-lactamase (ESBL)-producing Klebsiella pneumoniae and high-level aminoglycoside-resistant (HLAR) Enterococcus faecalis, nutritional optimization, and routine use of an abdominal binder. Drains were removed on postoperative day 6. The patient was discharged with an intact midline reconstruction and satisfactory wound healing. At 6‑month follow-up, there was no recurrence, bulging, or chronic pain.

This scenario emphasizes several practical principles. Repeated primary midline reapproximation in the presence of ongoing lateral contracture may actually worsen biomechanical failure rather than fix it. In this situation, TAR was used as a salvage maneuver to restore medial compliance despite the significant risks of reconstruction in a recently contaminated field. Intraoperative BTA might be considered a protective adjunct rather than a facilitative tool, intended to decrease early postoperative tension rather than enable closure. This approach should only be considered in highly selected cases and be performed by experienced reconstructive surgeons. Potential risks include longer operative times, mesh-related infections in contaminated fields, and excessive muscle relaxation; careful patient selection and a meticulous technique are essential.

The reconstructive choice in this case involved balancing significant competing risks. Using a retromuscular permanent synthetic mesh in a patient with recent contamination, multidrug-resistant infection, and major physiological frailty clearly presents a notable risk of surgical-site morbidity and mesh-related infection. Similarly, extensive layer separation increases the potential impact of any subsequent deep infection. However, during the fourth laparotomy, the main issue was deemed to be progressive biomechanical failure with fixed lateral retraction and repeated failure of primary midline reapproximation. In this context, a bridging solution was considered less favorable because it would not restore native abdominal wall continuity or address the pathological lateral traction forces that seemed to drive recurrence. The chosen strategy was therefore implemented as a salvage, anatomy-restoring procedure in an exceptional situation, not as a standard approach for contaminated abdominal wall failure.