The main muscles in the abdominal wall are called the Rectus Abdominus muscles. These muscles run from the rib cage to the pubic bone and define the contour of the abdomen. The muscles are segmental and in thin, athletic individuals they are seen through the skin as the classic “six pack”.
These muscles run together in the center of the abdominal wall and are surrounded by a tissue layer called the Rectus Fascia. This is a fibrous structure which holds the muscles in place and maintains the integrity of the abdominal cavity. The central location of these muscles not only maintains the foundation of the abdomen but helps in maintaining balance with the opposing muscles of the back.
During pregnancy the expansion of the abdominal wall causes the rectus muscles to move away from the midline. Although the muscle has the ability to stretch, it is the fascia or strength layer which does the majority of the stretching. This fascia is weakened by the process and does not return to its original position. The rectus muscles remain separated most noticeably above the belly button. No amount of exercise will restore the muscles to the midline position. Building muscle strength is always beneficial but the rounded appearance of the abdomen can not be obtained through exercise alone. The fascia must be surgically tightened to bring the muscles back into their original alignment.
Rectus diastasis must be differentiated from hernia. A hernia is a weakness in the abdominal wall, rectus fascia, which allows abdominal contents such as the intestines or omentum to come through the fascia and lie beneath the skin. In rectus diastasis the fascia is thin but intact and so there is no danger of developing the types of complications seen with hernias.
Surgical repair of the rectus diastasis is a routine part of the abdominoplasty or tummy tuck procedures. When the abdominal skin is elevated the borders of the rectus muscle are obvious through the rectus fascia. Sutures are used to bring the rectus muscles back into their appropriate anatomic alignment for optima function and aesthetic appearance.