Introduction: Posterior component separation herniorrhaphy via transversus abdominis release (TAR) permits midline reapproximation of large fascial defects. To date, no report delineates the reduction in tensile force to reapproximate midline fascia following TAR. We hypothesized that open and laparoscopic TAR would provide similar reductions in midline reapproximation forces in a porcine model. Methods: Under general anesthesia, a 20-cm midline laparotomy was created and bilateral lipocutaneous flaps were raised to expose the anterior rectus sheath. Five stainless steel hooks were placed at 1-cm intervals lateral to the midline at three locations: 5 cm above, at, and 5 cm below the umbilicus bilaterally. Baseline force measurements were taken by pulling each lateral point to midline. Laparoscopic TAR was performed unilaterally by incising the parietal peritoneum and transversus muscle lateral to the linea semilunaris. Open TAR was performed contralaterally, and force measurements were repeated. Comparisons were made to baseline and between the groups. Results: Following laparoscopic TAR, 87 % (13/15) of points showed significant reduction compared to baseline forces, whereas only 20 % (3/15) of open TAR points had significant force reductions. Compared to open TAR, three locations favored the laparoscopic approach [1 cm lateral to midline, 5 cm above the umbilicus (p = 0.04; 95 % CI 0.78–1.00), 2 cm lateral to midline at the umbilicus (p = 0.04; 95 % CI 0.80–1.00), and 1 cm lateral to midline 5 cm below the umbilicus (p = 0.05; 95 % CI 0.79–1.00)]. The mean length of TAR was longer for laparoscopic than open at 27.29 versus 19.55 cm (p < 0.0001; 95 % CI 6.46–9.02). Conclusions: Open TAR reduced midline tensile force at few locations, suggesting that the mechanism by which TAR facilitates herniorraphy may not solely be through reductions in linea alba tensile forces. At specific locations, laparoscopic TAR provides superior reduction in midline closure force compared to open TAR, likely as a result of a longer muscle release.
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