Anatomical considerations for surgery of the anterolateral abdominal wall. 
Closure of large incisional hernias with the Components Separation Method (CSM) could be explained by medial-caudal rotation of the internal and transverse oblique muscles around their centres of origin.  In eight human cadavers, the CSM was performed, and translation of the rectus abdominis muscle was measured.  Mean unilateral translation of the rectus abdominis in the lateral-medial direction measured 2.2, 3.7, and 3.5 cm.  This was 2.7, 4.5, and 4.0 cm after release of the posterior rectus sheath.  Mean translation in a caudal direction was 0.5 cm, but seven cadavers showed a mean translation of 1 cm of the uppermost measuring point in a cranial direction.  The hypothesis that rotation of separate tissue layers of the abdominal wall largely accounts for the translation effect of the CSM must be rejected.  Release of the external oblique muscle produces more benefit to abdominal wall closure than release of the posterior rectus sheath.