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The abdominal wall is frequently manipulated in a variety of reconstructive procedures, and its anatomy is well described. The authors’ clinical observations, however, contradict the standard depiction of the components of the abdominal wall at various levels—particularly regarding the course of the transversus abdominis muscle. Therefore, the authors sought to characterize the components of the rectus sheath at various surgical landmarks to define anatomic points important to abdominal wall repair.The authors analyzed the abdominal computed tomographic studies of 100 healthy, young (age, 18 to 35 years; body mass index, 20 to 40 kg/m2) patients with suspected renal calculi. Coordinates of key landmarks were recorded at vertebral levels T12 to L5 using a specially designed computer program that scaled all values and calculated distances between various points.All subjects had significant presence of the transversus abdominis within the rectus sheath (the overlap between the abdominis rectus and transversus abdominis muscles) at the costal margin plane (T12-L1, 4.2 cm). Ninety-nine percent had transversus abdominis presence within the rectus sheath at L1-L2 (3.2 cm), 86 percent at the level of the twelfth rib (L2-L3, 1.4 cm), 36 percent at the umbilicus (L3-L4), and 2 percent slightly above the posterosuperior iliac spine (L5-S1).These findings contradict classic teachings of abdominal wall structure and highlight the need for a cautious revisiting of the various permutations of component separation, particularly posterior component release. Furthermore, these anatomical landmarks may help predict the development or recurrence of ventral hernias, thus guiding patient selection and informing surgical technique.