Objective To investigate the effect of preoperative botulinum toxin A injection on abdominal muscle morphology in patients with incisional ventral hernia repair.

Methods The retrospective and descriptive study was conducted. The clinical data of 26 patients with incisional ventral hernia who underwent botulinum toxin A injection before repair at Affiliated Hangzhou First People′s Hospital, School of Medicine, Westlake University from August 2017 to October 2025 were collected. There were 19 males and 7 females, aged (64±15) years. Observation indicators: (1) treatment conditions; (2) changes of the incisional hernia; (3) morphological changes of the abdo-minal wall muscles; (4) morphological changes of the incisional hernia and abdominal wall muscles in patients with different hernia defect width. Comparison of measurement data with normal distri-bution before and after treatment was conducted using the independent sample t test. Comparison of measurement data with skewed distribution before and after treatment was conducted using the Mann‑Whitney U nonparametric test.

Results (1) Treatment conditions: the interval from incisional hernia detection on computed tomography (CT) to botulinum toxin A injection was 12(6,24) months, and the time from botulinum toxin A injection to CT reexamination was (26±3) days. No patient developed botulism‑related toxicity after botulinum toxin A injection, and all 26 patients subsequently underwent open incisional hernia repair, including 19 cases using component separation technique with transversus abdominis release and 5 cases using component separation technique alone. Within postoperative 30 days, 7 patients had complications, of which 1 case died of pulmonary infection, 1 case developed enterocutaneous fistula and was recovered after secondary intestinal resection, 2 cases developed incisional infection complicated by seroma and achieved healing after dressing changes and symptomatic management, 3 cases developed seroma and were resolved spontaneously without surgical intervention. Within 1 year of follow‑up, none of 25 patients had hernia recurrence. (2) Changes of the incisional hernia: CT scans of 26 patients before and after botulinum toxin A injection showed that the hernia sac width changed from (13.7±3.3) cm to (12.1±3.0) cm, the hernia defect width from (13.6±3.3) cm to (12.0±2.9) cm, and the ratio of hernia defect width to transverse abdominal diameter from 54.0%(47.0%,58.8%) to 45.7%(39.0%,48.7%), showing significant differences before and after injection (t=8.63, 8.08, Z=-3.11, P<0.05). (3) Morphological changes of the abdo-minal wall muscles: CT scans of 26 patients before and after botulinum toxin A injection showed that the transverse abdominal diameter changed from (26±3) cm to (27±3) cm, the length of the lateral abdominal wall muscles from (16±4) cm to (18±4) cm, the thickness of the lateral abdominal wall muscles from (1.9±0.3) cm to (1.7±0.3) cm, and the psoas major muscle density from (42±9) HU to (43±9) HU, showing significant differences before and after injection (t=-5.26, -11.44, 7.26, -2.44, P<0.05).(4) Morphological changes of the incisional hernia and abdominal wall muscles in patients with different hernia defect width: in 22 patients of giant incisional hernia with hernia defect width ≥10 cm, the abdominal wall muscle length increased 1.63(0.91,2.07) cm, the abdominal wall muscle thickness decreased 0.22(0.20,0.36) cm, and the hernia sac volume ratio decreased 1.33%(0.38%,3.82%) after botulinum toxin A injection. In 4 patients of small and medium incisional hernia with hernia defect width <10 cm, the above indicators were 1.78(1.43,2.32) cm, 0.14(0.08,0.27) cm, and 1.31%(0.61%,4.73%), respectively, showing no significant difference between them (Z=-0.64, -1.43, 0.14, P>0.05).

Conclusions Injection of botulinum toxin A before incisional ventral hernia repair can safely and effectively induce abdominal wall muscle relaxation, leading to significant reductions in hernia defect width and the ratio of hernia defect width to abdominal transverse diameter.