Surgical anatomy of transversus abdominis muscle for transversus abdominis release.

Transversus abdominis release (TAR) is a myofascial release technique which helps in surgical repair of large ventral abdominal wall defects. In this procedure, the medial margin of muscular part of transversus abdominis (TA) is of great importance. Hence, the authors sought to describe the extent of medial margin of TA muscle. The surgical steps of TAR were performed in 10 formalin-fixed cadavers and distance between medial margin of TA muscle, lateral margin of rectus abdominis, to linea alba at five anatomical levels were documented respectively. The distance between the inferior epigastric vessels and the medial border of TA muscle was also noted. The TA muscle was within the posterior rectus sheath in all cadavers, at the xiphisternum (R, 61.6 mm; L, 58.9 mm), and at midway between xiphisternum and umbilicus (R, 25.4 mm; L, 27.1 mm). The TA muscle exited the posterior rectus sheath between this point and the umbilicus. The mean incongruity at the next three levels were -24.6 mm, -24.9 mm, and -22.9 mm respectively on the right and -21.4 mm, -19.9 mm, and -18.9 mm respectively on the left. The mean distance between the medial border of TA and inferior epigastric vessels was 18.9 mm on the right and 17.2 mm on the left. The muscular part of TA was incorporated within the posterior rectus sheath above the umbilicus, and it completely exited the rectus sheath at the umbilicus. This is contrary to the traditional understanding of posterior rectus sheath formation.