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Objective: To explore how intramuscular injection of botulinum toxin A (BTA) affects the lateral abdominal wall (LAW) musculature, abdominal- and hernia dimensions, and muscle structure on computed tomography (CT) in patients scheduled for complex abdominal wall reconstruction (CAWR)., Methods: Retrospective analysis of prospectively registered patients who received bilateral intramuscular BTA injections into all three muscles of the LAW. Only patients for which a CT was available before and 3-6 weeks after BTA treatment prior to surgery were analyzed., Results: Fifty-two patients were analyzed. Median hernia width in all patients decreased with 0.4 cm (IQR - 2.1;0.6) (p = 0.023). Median intra-abdominal transverse diameter increased with 0.9 cm (IQR - 0.2;3.3) (p = 0.001) and the intra-abdominal anterior-posterior diameter decreased with 0.5 cm (IQR - 1.3;0.5) (p = 0.017), making the abdomen more oval. Median LAW muscle length increased with 0.9 cm (IQR 0.0;2.4) per side (p < 0.001), muscle thickness decreased with 0.5 cm (IQR - 0.8;- 0.2) (- 25.0%) per side (p < 0.001), and muscle mass decreased with 3.9 cm 2 (IQR - 6.4;-1.5) (- 15.8%) per side (p < 0.001). Median HU of the psoas muscles (density) increased with 4.8 HU (IQR 0.4;9.7) (10.3%) per side (p < 0.001). Effects of BTA were more pronounced in patients with a loss of domain (LoD) ≥ 20%., Conclusions: The main effect of BTA injections is elongation and thinning of the LAW muscles, more than a decrease in hernia width. Concomitantly, the abdomen becomes more oval. An increase of psoas muscles density is seen, associated with offloading of the LAW muscles. Patients with large LoD have a proportionally higher effect of BTA., (© 2022. The Author(s).)

Purpose: To systematically review technical aspects and treatment regimens of botulinum toxin A (BTA) injections in the lateral abdominal wall musculature. We also investigated the effect of BTA on abdominal muscle- and hernia dimensions, and clinical outcome., Methods: PubMed, EMBASE, CENTRAL, and CINAHL were searched for studies that investigate the injection of BTA in the lateral abdominal wall muscles. Study characteristics, BTA treatment regimens, surgical procedures, and clinical outcomes are presented descriptively. The effect of BTA on muscle- and hernia dimensions is analyzed using random-effects meta-analyses, and exclusively for studies that investigate ventral incisional hernia patients., Results: We identified 23 studies, comprising 995 patients. Generally, either 500 units of Dysport ® or 200-300 units of Botox ® are injected at 3-5 locations bilaterally in all three muscles of the lateral abdominal wall, about 4 weeks prior to surgery. No major procedural complications are reported. Meta-analyses show that BTA provides significant elongation of the lateral abdominal wall of 3.2 cm per side (95% CI 2.0-4.3, I 2  = 0%, p < 0.001); 6.3 cm total elongation, and a significant but heterogeneous decrease in transverse hernia width (95% CI 0.2-6.8, I 2  = 94%, p = 0.04). Furthermore, meta-analysis shows that BTA pretreatment in ventral hernia patients significantly increases the fascial closure rate [RR 1.08 (95% CI 1.02-1.16, I 2  = 0%, p = 0.02)]., Conclusion: The injection technique and treatment regimens of botulinum toxin A as well as patient selection require standardization. Bilateral pretreatment in hernia patients significantly elongates the lateral abdominal wall muscles, making fascial closure during surgical hernia repair more likely., Study Registration: A review protocol for this meta-analysis was registered at PROSPERO (CRD42020198246)., (© 2021. The Author(s).)